Drosatos K, etal., Circ Res. 2016 Jan 22;118(2):241-53. doi: 10.1161/CIRCRESAHA.115.306383. Epub 2015 Nov 16.
RATIONALE: Fatty acid oxidation is transcriptionally regulated by peroxisome proliferator-activated receptor (PPAR)alpha and under normal conditions accounts for 70% of cardiac ATP content. Reduced Ppara expression during sepsis and heart failure leads to redu
ced fatty acid oxidation and myocardial energy deficiency. Many of the transcriptional regulators of Ppara are unknown. OBJECTIVE: To determine the role of Kruppel-like factor 5 (KLF5) in transcriptional regulation of Ppara. METHODS AND RESULTS: We discovered that KLF5 activates Ppara gene expression via direct promoter binding. This is blocked in hearts of septic mice by c-Jun, which binds an overlapping site on the Ppara promoter and reduces transcription. We generated cardiac myocyte-specific Klf5 knockout mice that showed reduced expression of cardiac Ppara and its downstream fatty acid metabolism-related targets. These changes were associated with reduced cardiac fatty acid oxidation, ATP levels, increased triglyceride accumulation, and cardiac dysfunction. Diabetic mice showed parallel changes in cardiac Klf5 and Ppara expression levels. CONCLUSIONS: Cardiac myocyte KLF5 is a transcriptional regulator of Ppara and cardiac energetics.
Pyrazinamide (PZA) causes serious hepatotoxicity, but little is known about the exact mechanism by which PZA induced liver injury. The peroxisome proliferator-activated receptors alpha (PPARα) is highly expressed in the liver and modulates the intracellular lipidmetabolism. So far, the role of
Depressive disorders cause a substantial burden for the individual and the society. Key depressive symptoms can be modeled in animals and enable the development of novel therapeutic interventions. Chronic unavoidable stress disrupts rats' competence to escape noxious stimuli and self-administer sucr
ose, configuring a depression model characterized by escape deficit and motivational anhedonia associated to impaired dopaminergic responses to sucrose in the nucleus accumbens shell (NAcS). Repeated treatments that restore these responses also relieve behavioral symptoms. Ventral tegmental area (VTA) dopamine neurons encode reward and motivation and are implicated in the neuropathology of depressive-like behaviors. Peroxisome proliferator-activated receptors type-α (PPARα) acutely regulate VTA dopamine neuron firing via ß2 subunit-containing nicotinic acetylcholine receptors (ß2*nAChRs) through phosphorylation and this effect is predictive of antidepressant-like effects. Here, by combining behavioral, electrophysiological and biochemical techniques, we studied the effects of repeated PPARα stimulation by fenofibrate on mesolimbic dopamine system. We found decreased ß2*nAChRs phosphorylation levels and a switch from tonic to phasic activity of dopamine cells in the VTA, and increased phosphorylation of dopamine and cAMP-regulated phosphoprotein Mr 32,000 (DARPP-32) in the NAcS. We then investigated whether long-term fenofibrate administration to stressed rats reinstated the decreased DARPP-32 response to sucrose and whether this effect translated into antidepressant-like properties. Fenofibrate restored dopaminergic responses to appetitive stimuli, reactivity to aversive stimuli and motivation to self-administer sucrose. Overall, this study suggests PPARα as new targets for antidepressant therapies endowed with motivational anti-anhedonic properties, further supporting the role of an unbalanced mesolimbic dopamine system in pathophysiology of depressive disorders.
Tai ES, etal., Arterioscler Thromb Vasc Biol. 2002 May 1;22(5):805-10.
Peroxisome proliferator activated receptor (PPAR) alpha is a member of the nuclear receptor superfamily that regulates key proteins involved in fatty acid oxidation, extracellular lipid metabolism, hemostasis, and inflammation. A L162V polymorphism at the PPARA
locus has been associated with alterations in lipid and apolipoprotein concentrations. We studied the association among lipids, lipoproteins, and apolipoproteins and the presence of the L162V polymorphism in 2373 participants (1128 men and 1244 women) in the Framingham Offspring Study. The frequency of the less common allele (V162) was 0.069. The V162 allele was associated with increased serum concentrations of total and LDL cholesterol in men (P=0.0012 and P=0.0004, respectively) and apolipoprotein B in men (P=0.009) and women (P=0.03 after adjustment for age, body mass index, smoking, and use of beta-blockers, diuretics or estrogens). Apolipoprotein (apo) C-III concentrations were higher in carriers of the V162 allele. The association of the L162V polymorphism on LDL cholesterol concentration was greatest in those who also carried the E2 allele at the APOE locus and the G allele at the APOC3 3238C>G polymorphism. This suggests that alterations in triglyceride-rich lipoprotein metabolism may be involved in the generation of the increase in LDL cholesterol observed with the L162V PPARA polymorphism.
BACKGROUND: Atherosclerosis is the most important cause of coronary artery disease (CAD). Genetic predisposition to CAD is related to polymorphisms of genes encoding products functionally involved in pathogenesis of atherosclerosis. Polymorphisms of genes participating in monocyte adhesion and diape
desis, lipid metabolism and fibrinolysis regulation may be partially responsible for this process. The aim of our study was to assess the polymorphic variants frequencies of ICAM1, APOE, PPARA and PAI-1 genes in CAD patients and healthy blood donors and to find specific arrangement of polymorphic variants which would differentiate both groups. METHODS: We studied 146 CAD patients and 121 healthy blood donors. Polymorphisms in analyzed genes were examined using PCR-RFLP analysis. RESULTS: We found significantly higher frequency of 5G allele of PAI-1 gene in patients than in control subjects (p = 0.038, OR = 1.44). We observed also a considerably higher frequency of contemporaneous carriers of two or three "proatherosclerotic" variants: 1) PPARA and PAI-1, 2) APOE and ICAM1 and 3) PPARA, ICAM1 and PAI-1 in CAD group comparing to control subjects. The number of "proatherosclerotic" variants carriers differentiate studied groups also independently of specific genotype arrangement. CONCLUSION: In conclusion, contemporaneous carrier-state of two or three polymorphic variants within analyzed genes is associated with CAD.
Administration of dehydroepiandrosterone (DHEA), a precursor of sex steroid hormones, reduces total and visceral fat mass and elevates adipocytic adiponectin gene expression. The aim of this study is to investigate whether levels of peroxisome proliferator-activated receptors (PPARs) in muscle and t
ranscription of PPAR target genes are affected by long-term DHEA administration or exercise training, and whether altered PPAR levels are associated with circulating adiponectin level in obese rats. After 14 weeks on a high-sucrose diet, obese male Wistar rats were assigned randomly to one of 3 groups: control, DHEA administration (1 mg/kg body weight), or exercise training (treadmill running for 1¿h, 25¿m/min, 5 days/week) for 6 weeks (n=7 for each group). Plasma DHEA and total adiponectin levels in the DHEA-treated and exercise-training groups were significantly higher than those in the obese control group. Additionally, DHEA administration and exercise training significantly increased muscular PPARa and PPARd protein levels, with a concomitant increase in mRNA expression of 3ß-hydroxyacyl-CoA dehydrogenase and cytochrome c oxidase IV, which are target genes of PPARa and PPARd respectively. Moreover, DHEA administration increased these protein and mRNA levels to the same degree as exercise training. Circulating adiponectin level was positively correlated with plasma DHEA and with muscle levels of PPARa and PPARd. These results suggest that in obese rats, secretion of adiponectin due to chronic DHEA administration and exercise training may contribute to an increase in the transcription of genes encoding lipid metabolic enzymes, mediated via elevated expression of PPARa and PPARd in muscle.
BACKGROUND: Danqi pill (DQP) is one of the most widely prescribed formulas and has been shown to have remarkable protective effect on coronary heart disease (CHD). However, its regulatory effects on lipid metabolism disorders haven't been comprehensively studied so far. We aimed to explor
e the effects of DQP on Peroxisome Proliferator activated receptors α (PPARα), lipid uptake-transportation-metabolism pathway and arachidonic acid (AA)-mediated inflammation pathway in rats with CHD. METHODS: 80 Sprague-Dawley (SD) Rats were randomly divided into sham group, model group, positive control group and DQP group. Rat model of CHD was induced by ligation of left ventricle anterior descending artery and fed with high fat diet in all but the sham group. Rats in sham group only underwent thoracotomy. After surgery, rats in the positive control and DQP group received daily treatments of pravastatin and DQP respectively. At 28 days after surgery, rats were sacrificed and plasma lipids were evaluated by plasma biochemical detection. Western blot and PCR were applied to evaluate the expressions of PPARα, proteins involved in lipid metabolism and AA pathways. RESULTS: Twenty eight days after surgery, dyslipidemia developed in CHD model rats, as illustrated by elevated plasma lipid levels. Expressions of apolipoprotein A-I (ApoA-I), cluster of differentiation 36 (CD36) and fatty acid binding protein (FABP) in the heart tissues of model group were down-regulated compared with those in sham group. Expressions of carnitine palmitoyl transferase I (CPT-1A) and lipoproteinlipase (LPL) were also reduced significantly. In addition, levels of phospholipase A2 (PLA2) and cyclooxygenase 2 (COX-2) were up-regulated. Expressions of Nuclear factor-κB (NF- κB) and signal transducer and activator of transcription 3 (STAT3) also increased. Furthermore, Expression of PPARα decreased in the model group. DQP significantly up-regulated expressions of ApoA-I and FABP, as well as the expressions of CPT-1A and CD36. In addition, DQP down-regulated expressions of PLA2, COX-2 and NF-κB in inflammation pathway. Levels of STAT3 and LPL were not affected by DQP treatment. In particular, DQP up-regulated PPARα level significantly. CONCLUSIONS: DQP could effectively regulate lipid uptake-transportation-metabolism process in CHD model rats, and the effect is achieved mainly by activating ApoA-I-CD36-CPT-1A molecules. Interestingly, DQP can up-regulate expression of PPARα significantly. The anti-inflammatory effect of DQP is partly exerted by inhibiting expressions of PLA2-COX2 -NF-κB pathway.
Peroxisome proliferator-activated receptor alpha (PPARalpha) is a member of the steroid hormone receptor super family involved in the control of cellular lipid utilization. This makes PPARalpha a candidate gene for type 2 diabetes and dyslipidemia. The aim of this study was to investigate whether ge
netic variation in the human PPARalpha gene can influence the risk of type 2 diabetes and dyslipidemia among French Canadians. We therefore first determined the genomic structure of human PPARalpha, and then designed intronic primers to sequence the coding region and the exon-intron boundaries of the gene in 12 patients with type 2 diabetes and in 2 nondiabetic subjects. Sequence analysis revealed the presence of a L162V missense mutation in exon 5 of one diabetic patient. Leucine 162 is contained within the DNA binding domain of the human PPARalpha gene, and is conserved among humans, mice, rats, and guinea pigs. We subsequently screened a sample of 121 patients newly diagnosed with type 2 diabetes and their age and sex-matched nondiabetic controls, recruited from the Saguenay-Lac-St-Jean region of Northeastern Quebec, for the presence of the L162V mutation by a PCR-RFLP based method. There was no difference in L162 homozygote or V162 carrier frequencies between diabetics and nondiabetics. However, whether diabetic or not, carriers of the V162 allele had higher plasma apolipoprotein B levels compared to noncarriers (P 5 0.05). To further this association, we screened another sample of 193 nondiabetic subjects recruited in the greater Quebec City area. Carriers of the V162 allele compared with homozygotes of the L162 allele had significantly higher concentrations of plasma total and LDL-apolipoprotein B as well as LDL cholesterol (P
Lunde I, etal., Eur J Clin Pharmacol. 2014 Jun;70(6):685-93.
PURPOSE: Tacrolimus (Tac) and cyclosporine (CsA) are mainly metabolized by CYP3A4 and CYP3A5. Several studies have demonstrated an association between the CYP3A5 genotype and Tac dose requirements. Recently, CYP3A4, PPARA, and POR gene variants have been shown t
o influence CYP3A metabolism. The present study investigated potential associations between CYP3A5*3, CYP3A4*22, PPARA c.209- 1003G>A and c.208+3819A>G, and POR*28 alleles and dose-adjusted concentrations (C/D) of Tac and CsA in 177 renal transplant patients early post-transplant. METHODS: All patients (n=177) were genotyped for CYP3A4*22, CYP3A5*3, POR*28, PPARA c.209-1003G>A, and PPARA c.208+3819A>G using real-time polymerase chain reaction (PCR) and melting curve analysis with allelespecific hybridization probes or PCR restriction fragment length polymorphisms (RFLP) methods. Drug concentrations and administered doses were retrospectively collected from patient charts at Oslo University Hospital, Rikshospitalet, Norway. One steady-state concentration was collected for each patient. RESULTS: We confirmed a significant impact of the CYP3A5*3 allele on Tac exposure. Patients with POR*28 and PPARA variant alleles demonstrated 15 % lower (P=0.04) and 19 % higher (P=0.01) Tac C0/D respectively. CsA C2/D was 53 % higher among CYP3A4*22 carriers (P=0.03). CONCLUSION: The results support the use of pre-transplant CYP3A5 genotyping to improve initial dosing of Tac, and suggest that Tac dosing may be further individualized by additional POR and PPARA genotyping. Furthermore, initial CsA dosing may be improved by pre-transplant CYP3A4*22 determination.
Numerous clinical and population studies have demonstrated that increased serum bilirubin levels protect against cardiovascular and metabolic diseases such as obesity and diabetes. Bilirubin is a potent antioxidant, and the beneficial actions of moderate increases in plasma bilirubin have been thoug
ht to be due to the antioxidant effects of this bile pigment. In the present study, we found that bilirubin has a new function as a ligand for PPARalpha. We show that bilirubin can bind directly to PPARalpha and increase transcriptional activity. When we compared biliverdin, the precursor to bilirubin, on PPARalpha transcriptional activation to known PPARalpha ligands, WY 14,643 and fenofibrate, it showed that fenofibrate and biliverdin have similar activation properties. Treatment of 3T3-L1 adipocytes with biliverdin suppressed lipid accumulation and upregulated PPARalpha target genes. We treated wild-type and PPARalpha KO mice on a high fat diet with fenofibrate or bilirubin for seven days and found that both signal through PPARalpha dependent mechanisms. Furthermore, the effect of bilirubin on lowering glucose and reducing body fat percentage was blunted in PPARalpha KO mice. These data demonstrate a new function for bilirubin as an agonist of PPARalpha, which mediates the protection from adiposity afforded by moderate increases in bilirubin.
Peroxisome proliferator-activated receptor-alpha (PPARalpha), a nuclear receptor, plays an important role in the transcription of genes involved in fatty acid metabolism through heterodimerization with the retinoid x receptor (RXR). The consensus sequence of the PPAR response element (PPRE) is compo
sed of two AGGTCA-like sequences directionally aligned with a single nucleotide spacer. PPARalpha and RXR bind to the 5' and 3' hexad sequences, respectively. However, the precise sequence definition of the PPRE remains obscure, and thus, the consensus sequence currently available remains AGGTCANAGGTCA with unknown redundancy. The vague PPRE sequence definition poses an obstacle to understanding how PPARalpha regulates fatty acid metabolism. Here we show that, rather than the generally accepted 6-bp sequence, PPARalpha actually recognized a 12-bp DNA sequence, of which the preferred binding sequence was WAWVTRGGBBAH. Additionally, the optimized RXRalpha hexad binding sequence was RGKTYA. Thus, the optimal PPARalpha/RXRalpha heterodimer binding sequence was WAWVTRGGBBAHRGKTYA. The single nucleotide substitution, which reduces binding of RXRalpha to DNA, attenuated PPARalpha-induced transcriptional activation, but this is not always true for PPARalpha. Using the definition of the PPRE sequence, novel PPREs were successfully identified. Taken altogether, the provided PPRE sequence definition contributes to the understanding of PPARalpha signaling by identifying PPARalpha direct target genes with functional PPARalpha response elements.
Moran E, etal., Invest Ophthalmol Vis Sci. 2014 May 13;55(7):4568-76. doi: 10.1167/iovs.13-13127.
PURPOSE: Previous studies have demonstrated that peroxisome proliferator-activated receptor-alpha (PPARalpha) agonists have therapeutic effects in diabetic retinopathy, although the mechanism of action remains incompletely understood. The purpose of this study was to evaluate PPARalpha's protective
effects in the ischemic retina, and to delineate its molecular mechanism of action. METHODS: For the oxygen-induced retinopathy (OIR) model, wild-type (WT), and PPARalpha knockout (PPARalpha(-/-)) mice were exposed to 75% O(2) from postnatal day 7 (P7) to P12 and treated with the PPARalpha agonist fenofibric acid (Feno-FA) from P12 to P16. At P17, the effects of Feno-FA on retinal glial fibrillary acidic protein (GFAP) expression, apoptotic DNA cleavage, and TUNEL labeling were analyzed. Cultured retinal cells were exposed to CoCl(2) to induce hypoxia, and TUNEL staining and 5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein dye were used to measure apoptosis and reactive oxygen species (ROS) generation. Western blotting was used to measure GFAP levels and cell signaling. RESULTS: Feno-FA decreased retinal apoptosis and oxidative stress in WT but not PPARalpha(-/-) OIR mice. Peroxisome proliferator-activated receptor-alpha knockout OIR mice showed increased retinal cell death and glial activation in comparison to WT OIR mice. Feno-FA treatment and PPARalpha overexpression protected cultured retinal cells from hypoxic cell death and decreased ROS levels. Nuclear hypoxia-inducible factor-alpha (HIF-1alpha) and nicotine adenine dinucleotide phosphate oxidase-4 (Nox 4) were increased in OIR retinas and downregulated by Feno-FA in WT but not in PPARalpha(-/-) mice. CONCLUSIONS: Peroxisome proliferator-activated receptor-alpha has a potent antiapoptotic effect in the ischemic retina. This protective effect may be mediated in part through downregulation of HIF-1alpha/Nox 4 and consequently alleviation of oxidative stress.
Inflammatory bowel disease (IBD) is characterized by repeated chronic inflammation of the gastrointestinal tract. We have used the complementary model of colonic inflammation to examine the roles of peroxisome proliferator-activated receptor alpha (PPARalpha) in colonic inflammation and thus its pos
sible role in IBD. We characterized an innate immune-mediated model of colitis induced by dextran sulfate sodium (DSS). Mice with DSS-induced colitis were injected with Wy-14643 (2 mg/kg) as a PPARalpha agonist every day from day 0 to day 5. We show that mice given Wy-14643 were less susceptible to experimental acute colitis induced by DSS, and this decreased susceptibility was correlated with decreased production of IFNgamma, IL-1beta, IL-6, and TNF-alpha. Our findings suggest that PPARalpha has a role in controlling colonic inflammation and mucosal tissue homeostasis.
Zhou JY and Zhou SW, Yao Xue Xue Bao. 2007 Dec;42(12):1243-9.
Retinopathy is a major cause of morbidity in diabetes and remains the primary cause of new blindness. Therefore, it is necessary to find new drug to treat diabetic retinopathy. Type 2 diabetes mellitus (T2DM) rats were induced by injection (ip) with streptozotocin (STZ) 35 mg x kg(-1) and fed with a
high-carbohydrate/high-fat diet 2 weeks later. From week 17 to 32, diabetic rats were given different doses of berberine 75, 150, and 300 mg x kg(-1), fenofibrate 100 mg x kg(-1) and rosiglitazone 4 mg x kg(-1), separately. Retinal structure was observed with hematoxylin-eosin staining and peroxisome proliferator-activated receptors (PPARs) alpha/delta/gamma protein expressions were detected by immunohistochemistry. The retina of control rats was thicker than that of other groups, 16 weeks treatment with berberine (150 and 300 mg x kg(-1)) and rosiglitazone 4 mg x kg(-1) thickened the diabetic retina, but no difference existed in retinal structure among groups. Both berberine (150 and 300 mg x kg(-1)) and rosiglitazone 4 mg x kg(-1) significantly decreased PPARy expression in diabetic retina; while berberine (150 and 300 mg x kg(-1)) and fenofibrate 100 mg x kg(-1) obviously increased both PPARalpha and PPARdelta expressions in diabetic retina. Berberine modulates PPARalpha/delta/gamma protein levels in diabetic retina which may contribute to ameliorate retinopathy complication induced by STZ and a high-carbohydrate/high-fat diet. It is expected that berberine might be a more beneficial drug to treat diabetic retinal complication comparing with fenofibrate and rosiglitazone.
Nagai Y, etal., Am J Physiol Endocrinol Metab 2002 May;282(5):E1180-90.
To elucidate molecular mechanisms of high fructose-induced metabolic derangements and the influence of peroxisome proliferator-activated receptor-alpha (PPARalpha) activation on them, we examined the expression of sterol regulatory element binding protein-1 (SREBP-1) and PPARalpha as well as its nuc
lear activation and target gene expressions in the liver of high fructose-fed rats with or without treatment of fenofibrate. After 8-wk feeding of a diet high in fructose, the mRNA contents of PPARalpha protein and its activity and gene expressions of fatty acid oxidation enzymes were reduced. In contrast, the gene expressions of SREBP-1 and lipogenic enzymes in the liver were increased by high fructose feeding. Similar high fructose effects were also found in isolated hepatocytes exposed to 20 mM fructose in the media. The treatment of fenofibrate (30 mg.kg(-1).day(-1)) significantly improved high fructose-induced metabolic derangements such as insulin resistance, hypertension, hyperlipidemia, and fat accumulation in the liver. Consistently, the decreased PPARalpha protein content, its activity, and its target gene expressions found in high fructose-fed rats were all improved by fenofibrate treatment. Furthermore, we also found that the copy number of mitochondrial DNA, the expressions of mitochondrial transcription factor A, ATPase-6 subunit, and uncoupling protein-3 were increased by fenofibrate treatment. These findings suggest that the metabolic syndrome in high fructose-fed rats is reversed by fenofibrate treatment, which is associated with the induction of enzyme expression related to beta-oxidation and the enhancement of mitochondrial gene expression.
Fan LQ, etal., Toxicology. 2004 Oct 15;203(1-3):41-8.
Peroxisome proliferators (PP) are a large class of structurally diverse chemicals that mediate their effects in the liver mainly through the peroxisome proliferator-activated receptor alpha (PPARalpha). Exposure to PP results in down-regulation of CYP2C family members under control of growth hormone
and sex steroids including CYP2C11 and CYP2C12. We hypothesized that PP exposure would also lead to similar changes in CYP2C7, a retinoic acid and testosterone hydroxylase. CYP2C7 gene expression was dramatically down-regulated in the livers of rats treated for 13 weeks by WY-14,643 (WY; 500 ppm) or gemfibrozil (GEM; 8000 ppm). In the same tissues, exposure to WY and GEM and to a lesser extent di-n-butyl phthalate (20,000 ppm) led to decreases in CYP2C7 protein levels in both male and female rats. An examination of the time and dose dependence of CYP2C7 protein changes after PP exposure revealed that CYP2C7 was more sensitive to compound exposure compared to other CYP2C family members. Protein expression was decreased after 1, 5 and 13 weeks of PP treatment. CYP2C7 protein expression was completely abolished at 5 ppm WY, the lowest dose tested. GEM and DBP exhibited dose-dependent decreases in CYP2C7 protein expression, becoming significant at 1000 ppm or 5000 ppm and above, respectively. These results show that PP exposure leads to changes in CYP2C7 mRNA and protein levels. Thus, in addition to known effects on steroid metabolism, exposure to PP may alter retinoic acid metabolism.
Pawlak M, etal., Mol Endocrinol. 2015 Aug;29(8):1134-43. doi: 10.1210/me.2014-1383. Epub 2015 Jun 18.
Acute liver failure (ALF) is a severe and rapid liver injury, often occurring without any preexisting liver disease, which may precipitate multiorgan failure and death. ALF is often associated with impaired beta-oxidation and increased oxidative stress (OS), characterized by elevated levels of hepat
ic reactive oxygen species (ROS) and lipid peroxidation (LPO) products. Peroxisome proliferator-activated receptor (PPAR)alpha has been shown to confer hepatoprotection in acute and chronic liver injury, at least in part, related to its ability to control peroxisomal and mitochondrial beta-oxidation. To study the pathophysiological role of PPARalpha in hepatic response to high OS, we induced a pronounced LPO by treating wild-type and Pparalpha-deficient mice with high doses of fish oil (FO), containing n-3 polyunsaturated fatty acids. FO feeding of Pparalpha-deficient mice, in contrast to control sunflower oil, surprisingly induced coma and death due to ALF as indicated by elevated serum alanine aminotransferase, aspartate aminotransferase, ammonia, and a liver-specific increase of ROS and LPO-derived malondialdehyde. Reconstitution of PPARalpha specifically in the liver using adeno-associated serotype 8 virus-PPARalpha in Pparalpha-deficient mice restored beta-oxidation and ketogenesis and protected mice from FO-induced lipotoxicity and death. Interestingly, administration of the ketone body beta-hydroxybutyrate prevented FO-induced ALF in Pparalpha-deficient mice, and normalized liver ROS and malondialdehyde levels. Therefore, PPARalpha protects the liver from FO-induced OS through its regulatory actions on ketone body levels. beta-Hydroxybutyrate treatment could thus be an option to prevent LPO-induced liver damage.
Peroxisome proliferator-activated receptor alpha (PPARalpha) ligands are medications used to treat hyperlipidaemia and atherosclerosis. Increasing evidence suggests that these agents are immunosuppressive. In the following studies we demonstrate that WY14,643, a PPARalpha ligand, attenuates expressi
on of anti-glomerular basement membrane disease (AGBMD). C57BL/6 mice were fed 0.05% WY14,643 or control food and immunized with the non-collagenous domain of the alpha3 chain of Type IV collagen [alpha3(IV) NC1] in complete Freund's adjuvant (CFA). WY14,643 reduced proteinuria and greatly improved glomerular and tubulo-interstitial lesions. However, the PPARalpha ligand did not alter the extent of IgG-binding to the GBM. Immunohistochemical studies revealed that the prominent tubulo-interstitial infiltrates in the control-fed mice consisted predominately of F4/80(+) macrophages and WY14,643-feeding decreased significantly the number of renal macrophages. The synthetic PPARalpha ligand also reduced significantly expression of the chemokine, monocyte chemoattractant protein (MCP)-1/CCL2. Sera from mice immunized with AGBMD were also evaluated for antigen-specific IgGs. There was a significant increase in the IgG1 : IgG2c ratio and a decline in the intrarenal and splenocyte interferon (IFN)-gamma mRNA expression in the WY14,643-fed mice, suggesting that the PPARalpha ligand could skew the immune response to a less inflammatory T helper 2-type of response. These studies suggest that PPARalpha ligands may be a novel treatment for inflammatory renal disease.
The peroxisome proliferator-activated receptor alpha (PPARalpha) is a ligand-activated transcription factor belonging to the nuclear hormone receptor superfamily. PPARalpha plays a key role in lipid and glucose metabolism, inflammatory response and energy homeostasis. The aim of our study was to scr
een the PPARalpha gene for mutations, and to test the genetic contribution of PPARalpha in diabetes and its vascular complications. The first two non coding exons and the coding region of the PPARalpha gene were screened by single strand conformation polymorphism (SSCP) and sequencing in 74 unrelated Type 2 diabetic patients with history of coronary heart disease (CHD) (18 Caucasian and 56 Indian subjects). A total of 7 nucleotide variants were detected: two single amino acid substitutions, a silent mutation, four intron base changes. Association studies were undertaken in two populations of Type 2 diabetic patients from Pondichery and from France, to test the distribution of allelic frequencies for L162V (exon 5) and A268V (exon 7) polymorphisms. No association was found between these PPARalpha variants and diabetes or CHD. However, in the Caucasian diabetic male population with CHD, the Val162 allele carriers showed higher concentrations of total cholesterol and Apo B when compared to non-carriers (p =0.01 and p =0.005, respectively). A trend toward elevated concentrations of total cholesterol and Apo B was also observed in the Caucasian diabetic male patients without CHD carrying Val162 allele. In conclusion, it is likely that PPARalpha gene does not have a major role in diabetes and CHD in our populations, although we can not exclude a minor contribution of the PPARalpha gene to the risk of CHD associated with Type 2 diabetes through a modulation of atherogenic plasma lipids.
Wang Q, etal., Zhongguo Zhong Xi Yi Jie He Za Zhi. 2012 Sep;32(9):1245-8.
OBJECTIVE: To explore the effects of electroacupuncture (EA) at Fenglong (ST40) on blood lipids, mRNA and protein expression of ATP binding cassette transporter A1 (ABCA1) and peroxisome proliferator-activated receptor a (PPARalpha) in hyperlipidemia rats. METHODS: Thirty-two SD
rats of SPF grade were selected to prepare the hyperlipidemia model. After successful modeling, they were randomly divided into the model group, the treatment group, the control group, and the treatment control group, 8 in each group. Another 8 rats were selected as the normal control group. Rats in the treatment group and the treatment control group received EA at Fenglong (ST40), once daily for 30 successive days. Rats in the model group and the treatment group were administered with high fat forage, while rats in the normal control group, the control group, and the treatment control group were administered with common forage. The contents of the total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) were detected in every group. The mRNA and protein expressions of ABCA1 and PPARalpha were detected using RT-PCR and Western blot. RESULTS: The levels of TC and LDL-C increased, and the mRNA and protein expressions of ABCA1 and PPARalpha decreased in the model group when compared with the normal group, showing statistical difference (P<0.01, P<0.05). But there was no obvious change in TG or HDL-C (P>0.05). Compared with the model group, the levels of TC and LDL-C decreased in each intervention group with statistical difference (P<0.01). The mRNA and protein expression of ABCA1 and PPARa in the treatment group and the treatment control group increased. The mRNA and protein expressions of PPARalpha increased in the control group with statistical difference (P<0.01, P<0.05). Compared with the control group, the levels of TC and LDL-C decreased, the mRNA and protein expressions of ABCA1 and PPARa increased in the treatment control group with statistical difference (P<0.01). But there was no obvious change in TG or HDL-C (P>0.05). CONCLUSIONS: EA at ST40 could obviously down-regulate the levels of TC and LDL-C in hyperlipidemia rats, up-regulate the expressions of ABCA1 and PPARalpha, thus promoting counter transport of cholesterol. It had some therapeutic effects on hyperlipidemia.
Lin H, etal., Mol Pharmacol. 2013 Aug;84(2):275-85. doi: 10.1124/mol.112.083964. Epub 2013 May 30.
Adiponectin is a circulating adipose-derived cytokine that may act as an antioxidative and anti-inflammatory protein. Although adiponectin has been reported to exert cytoprotective effects in acute cardiac diseases, its effects on chronic heart failure are less clear. Therefore, we aimed to investig
ate whether adiponectin would have a beneficial effect in iron-induced chronic heart failure and to elucidate its regulation in cardiomyocytes. Mice were first treated with iron dextran for 4 weeks to induce iron-overload cardiomyopathy. They exhibited decreased survival with impaired left ventricle contractility and decreased serum adiponectin levels. In vivo cardiac adiponectin gene (ADIPOQ) overexpression with adenoassociated virus (AAV)-ADIPOQ ameliorated cardiac iron deposition and restored cardiac function in iron-overloaded mice. In addition, AAV-ADIPOQ-treated iron-overload mice had lower expression of inflammatory markers, including myeloperoxidase activity, monocyte chemotactic protein-1, tumor necrosis factor-alpha, interleukin-6, and intercellular adhesion molecule-1, than iron-overloaded mice not treated with AAV-ADIPOQ. Our in vitro study showed that adiponectin induced heme oxygenase-1 (HO-1) expression through the peroxisome proliferator-activated receptor (PPAR)alpha-HO-1 signaling pathway. Furthermore, the adiponectin-mediated beneficial effects were PPARalpha-dependent as the adiponectin-mediated attenuation of iron deposition was abolished in PPARalpha-knockout mice. Finally, PPARalpha-HO-1 signaling involved PPARalpha and peroxisome proliferator-activated receptor gamma coactivator-1 (PGC-1) binding and nuclear translocation, and their levels were increased by adiponectin therapy. Together, these findings suggest that adiponectin acts as an anti-inflammatory signaling molecule and induces the expression of HO-1 through the PPARalpha-PGC-1 complex-dependent pathway in cardiomyocytes, resulting in the attenuation of iron-induced cardiomyopathy. Using adiponectin for adjuvant therapies in iron-overload cardiac dysfunction may be an option in the future.
Kang SA, etal., J Nutr Biochem. 2006 Jun;17(6):419-26. Epub 2005 Sep 23.
Levan or high molecular beta-2,6-linked fructose polymer is produced extracellularly from sucrose-based substrates by bacterial levansucrase. In the present study, to investigate the effect of levan feeding on serum leptin, hepatic lipogenic enzyme and peroxisome proliferation-activated receptor (PP
AR) alpha expression in high-fat diet-induced obese rats, 4-week-old Sprague-Dawley male rats were fed high-fat diet (beef tallow, 40% of calories as fat), and, 6 weeks later, the rats were fed 0%, 1%, 5% or 10% levan-supplemented diets for 4 weeks. Serum leptin and insulin level were dose dependently reduced in levan-supplemented diet-fed rats. The mRNA expressions of hepatic fatty acid synthase and acetyl CoA carboxylase, which are the key enzymes in fatty acid synthesis, were down-regulated by dietary levan. However, dietary levan did not affect the gene expression of hepatic malic enzyme, phosphatidate phosphohydrolase and HMG CoA reductase. Also, the lipogenic enzyme gene expression in the white adipose tissue (WAT) was not affected by the diet treatments. However, hepatic PPARalpha mRNA expression was dose dependently up-regulated by dietary levan, whereas PPARgamma in the WAT was not changed. The results suggest that the in vivo hypolipidemic effect of dietary levan, including anti-obesity and lipid-lowering, may result from the inhibition of lipogenesis and stimulation of lipolysis, accompanied with regulation of hepatic lipogenic enzyme and PPARalpha gene expression.
Fan W, etal., Genet Test Mol Biomarkers. 2015 Jul;19(7):379-86. doi: 10.1089/gtmb.2015.0002. Epub 2015 Jun 22.
AIMS: Elevated low-density lipoprotein-cholesterol (LDL-C) is regarded as one of major risks of cardiovascular diseases and atherosclerotic events. It has been previously reported that peroxisome proliferator-activated receptors (PPARs) play an important role in the regulation of lipid metabolism.
In this study, we aimed to investigate the influence of PPARalpha/delta/gamma gene polymorphisms on LDL-C level. Eight hundred twenty unrelated participants were recruited. Ten single-nucleotide polymorphisms (SNPs) were genotyped to analyze the gene-gene interactions among these polymorphisms using the generalized multifactor dimensionality reduction (GMDR) method. RESULTS: The results of single-locus analyses indicated that the genotypes with minor allele variants at the rs1800206, rs9794, rs1805192, rs709158, and rs3856806 loci are associated with higher LDL-C levels (p<0.05) after adjusting for covariates. In contrast, individuals that were homozygous for the major allele (CC) of rs10865710 had significantly higher LDL-C than those with either one or more minor type alleles (CG+GG, mean difference: -0.21 mM; 95% confidence interval [CI]: -0.37 to -0.04 mM; p=0.013). Significant gene-gene interactions among PPAR gene polymorphisms on LDL-C were identified by a generalized multifactor dimensionality reduction (GMDR) approach in 2- to 8-locus models (p<0.05). CONCLUSION: Our results provide evidence that multiple PPARalpha/delta/gamma gene polymorphisms are individually associated with increased LDL-C, and that interactions, among these alleles result in additional increased risk suggesting that PPAR genes may contribute substantially to the risk of cardiovascular diseases and atherosclerosis.
Second-generation antipsychotics including olanzapine are associated with weight gain, dyslipidemia and other metabolic disorders. Both animal and clinical studies have shown that co-treatment with betahistine (a histamine H1 receptor agonist/H3 receptor antagonist) is effective in controlling olan
zapine-induced weight gain. In the present study, we investigate whether co-treatment with betahistine is able to prevent dyslipidemia induced by chronic olanzapine treatment and the underlying mechanisms. Female rats were orally administered with olanzapine (1 mg/kg, t.i.d.) for 3.5 consecutive weeks and then a 2.5-week drug withdrawal. Then, rats were divided into 4 groups for 5 weeks treatment: (1) vehicle, (2) olanzapine-only (1 mg/kg, t.i.d.), (3) betahistine-only (9.6 mg/kg, t.i.d.), and (4) olanzapine and betahistine (O+B) co-treatment. After completing treatment, hepatic mRNA expression was measured by qRT-PCR, while the protein levels were detected by western blot. In our study, olanzapine-only treatment significantly increased triglyceride accumulation and non-esterified fatty acids (NEFA), and upregulated mRNA expression of sterol regulatory element binding protein 1 (SREBP-1) and its target genes, while these alterations were ameliorated by O+B co-treatment. Hepatic AMP-activated protein kinase alpha (AMPKalpha) was activated in the O+B co-treatment group, with a significant reduction in nuclear SREBP-1 protein expression but an increased expression of peroxisome proliferator-activated receptor-alpha (PPARalpha) and its-responsive molecule(CPT1A), compared with olanzapine-only treatment. In addition, olanzapine significantly increased hepatic histamine H1 receptors, while O+B co-treatment significantly reversed them to normal levels. This study provided the first evidence that betahistine could act on hepatic H1 receptors via modulation of AMPKalpha-SREBP-1 and PPARalpha-dependent pathways to ameliorate olanzapine-induced dyslipidemia in rats.
Ikeda I, etal., Biochim Biophys Acta. 2006 May;1760(5):800-7. doi: 10.1016/j.bbagen.2006.02.017. Epub 2006 Mar 23.
Dietary campest-5-en-3-one (campestenone), an oxidized derivative of campesterol, significantly reduced visceral fat weight and the concentration of triacylglycerol in serum and liver of rats. Dietary campestenone dramatically increased the activities and the mRNA expressions of mitochondrial and pe
roxisomal enzymes involved in beta-oxidation in the liver. Campestenone activated human peroxisome proliferator-activated receptor (PPAR) alpha as determined using the novel GAL4 ligand-binding domain chimera assay system with coactivator coexpression. In contrast, dietary campestenone reduced the activities and the mRNA expressions of enzymes involved in fatty acid synthesis, except for the malic enzyme. Dietary campestenone decreased the sterol regulatory element binding protein-1 (SREBP-1) mRNA level. Energy expenditure was significantly higher in the feeding of campestenone in rats. Dietary campestenone reduced hepatic cholesterol concentration and increased fecal excretion of neutral steroids originated from cholesterol. Lymphatic absorption of cholesterol was reduced by the coadministration of campestenone in rats cannulated in the thoracic duct. These observations suggest a possibility that campestenone has an ability to prevent coronary heart disease by improving obesity and abnormality of lipid metabolism.
Jing L, etal., Med Sci Monit. 2011 Jan;17(1):BR1-9.
BACKGROUND: Chronic alcohol intake exerts myocardial damage en route to the development of alcoholic cardiomyopathy (ACM), although the precise pathogenesis of ACM is unknown. Carnitine is known to participate in the regulation of metabolism in a number of heart diseases. This study was designed to
examine the interplay between myocardial metabolism and carnitine in the development of ACM. MATERIAL/METHODS: Experimental animals were divided into 3 groups: (i) group A: alcohol-fed. (ii) group B: alcohol/carnitine: (200mg/kg/d, p.o. by mixing carnitine in rat chow). (iii) group C: control. Blood levels of free fatty acid (FFA), total carnitine (TC) and free carnitine (FC) were monitored in rats receiving alcohol with or without carnitine. Mitochondrial adenine nucleotide translocator-1 (ANT1) activity, ATPase activity, high energy phosphate concentration, peroxisome proliferator-activated receptor-alpha (PPARalpha), carnitine-palmitoyl transferase I (CPT-I), medium-chain acyl-coenzyme A dehydrogenase (MCAD), ANT1 and ATPase mRNA and protein expression were also monitored in myocardial tissue. RESULTS: Experimental animals received alcohol with or without carnitine for six 6 months. Our results indicated that FFA increased abruptly. TC and FC were significantly decreased in groups receiving alcohol at 4 months. The concentration of ATP, ADP and AMP in the myocardium decreased following 2 months of alcohol administration. mRNA and protein expression of PPARalpha, CPT-I, MCAD, ANT1 and ATPase expressions were gradually altered in groups following alcohol feeding. CONCLUSIONS: These observations suggest that abnormal metabolism is present in the myocardium during the development of ACM. Carnitine may improve myocardial metabolism by elevating the content of PPARalpha, CPT-I and MCAD.
Li J, etal., J Hepatol. 2015 Dec;63(6):1378-89. doi: 10.1016/j.jhep.2015.07.039. Epub 2015 Aug 15.
BACKGROUND & AIMS: CD147 is a transmembrane glycoprotein which is highly expressed in various human cancers including hepatocellular carcinoma (HCC). A drug Licartin developed with (131)Iodine-labeled antibody against CD147 has been approved by the Chinese Food and Drug Administration (FDA) and ent
ers into clinical use for HCC treatment. Increasing lines of evidence indicate that CD147 is implicated in the metabolism of cancer cells, especially glycolysis. However, the molecular mechanism underlying the relationship between CD147 and aberrant tumor lipid metabolism remains elusive. METHODS: We systematically investigated the role of CD147 in the regulation of lipid metabolism, including de novo lipogenesis and fatty acid beta-oxidation, in HCC cells and explored the underlying molecular mechanisms. RESULTS: Bioinformatic analysis and experimental evidence demonstrated that CD147 significantly contributed to the reprogramming of fatty acid metabolism in HCC cells mainly through two mechanisms. On one hand, CD147 upregulated the expression of sterol regulatory element binding protein 1c (SREBP1c) by activating the Akt/mTOR signaling pathway, which in turn directly activated the transcription of major lipogenic genes FASN and ACC1 to promote de novo lipogenesis. On the other hand, CD147 downregulated peroxisome proliferator-activated receptor alpha (PPARalpha) and its transcriptional target genes CPT1A and ACOX1 by activating the p38 MAPK signaling pathway to inhibit fatty acid beta-oxidation. Moreover, in vitro and in vivo assays indicated that the CD147-mediated reprogramming of fatty acid metabolism played a critical role in the proliferation and metastasis of HCC cells. CONCLUSION: Our findings demonstrate that CD147 is a critical regulator of fatty acid metabolism, which provides a strong line of evidence for this molecule to be used as a drug target in cancer treatment.
Rakhshandehroo M, etal., PPAR Res. 2007;2007:26839. doi: 10.1155/2007/26839.
PPARalpha is a ligand-activated transcription factor involved in the regulation of nutrient metabolism and inflammation. Although much is already known about the function of PPARalpha in hepatic lipid metabolism, many PPARalpha-dependent pathways and genes have yet to be discovered. In order to obta
in an overview of PPARalpha-regulated genes relevant to lipid metabolism, and to probe for novel candidate PPARalpha target genes, livers from several animal studies in which PPARalpha was activated and/or disabled were analyzed by Affymetrix GeneChips. Numerous novel PPARalpha-regulated genes relevant to lipid metabolism were identified. Out of this set of genes, eight genes were singled out for study of PPARalpha-dependent regulation in mouse liver and in mouse, rat, and human primary hepatocytes, including thioredoxin interacting protein (Txnip), electron-transferring-flavoprotein beta polypeptide (Etfb), electron-transferring-flavoprotein dehydrogenase (Etfdh), phosphatidylcholine transfer protein (Pctp), endothelial lipase (EL, Lipg), adipose triglyceride lipase (Pnpla2), hormone-sensitive lipase (HSL, Lipe), and monoglyceride lipase (Mgll). Using an in silico screening approach, one or more PPAR response elements (PPREs) were identified in each of these genes. Regulation of Pnpla2, Lipe, and Mgll, which are involved in triglyceride hydrolysis, was studied under conditions of elevated hepatic lipids. In wild-type mice fed a high fat diet, the decrease in hepatic lipids following treatment with the PPARalpha agonist Wy14643 was paralleled by significant up-regulation of Pnpla2, Lipe, and Mgll, suggesting that induction of triglyceride hydrolysis may contribute to the anti-steatotic role of PPARalpha. Our study illustrates the power of transcriptional profiling to uncover novel PPARalpha-regulated genes and pathways in liver.
Hu XQ, etal., Lipids Health Dis. 2010 Mar 9;9:25. doi: 10.1186/1476-511X-9-25.
BACKGROUND: Nonalcoholic fatty liver disease is the most common chronic liver disease in the world, and is becoming increasingly prevalent. Saponins of sea cucumber (SSC) are proven to exhibit various biological activities. Therefore, the present study was undertaken to examine the effect of saponin
s extracted from sea cucumber (Pearsonothuria graeffei) on the preventive activity of fatty liver in rats. METHODS: Male Wistar rats were randomly divided into five groups, including normal control group, fatty liver model group, SSC-treated group with SSC at levels of 0.01%, 0.03% and 0.05%. Model rats were established by administration with 1% orotic acid (OA). After the experiment period, serum total cholesterol (TC), triglyceride (TG), and hepatic lipid concentrations were determined. To search for a possible mechanism, we examined the changes of key enzymes and transcriptional factors involved in hepatic lipids biosynthesis, fatty acid beta-oxidation. RESULTS: Both 0.03% and 0.05% SSC treatment alleviated hepatic steatosis and reduced serum TG and TC concentration significantly in OA fed rats. Hepatic lipogenic enzymes, such as fatty acid synthase (FAS), malic enzyme (ME), and glucose-6-phosphate dehydrogenase (G6PDH) activities were inhibited by SSC treatment. SSC also decreased the gene expression of FAS, ME, G6PDH and sterol-regulatory element binding protein (SREBP-1c). Otherwise, the rats feeding with SSC showed increased carnitine palmitoyl transferase (CPT) activity in the liver. Hepatic peroxisome proliferator-activated receptor (PPARalpha), together with its target gene CPT and acyl-CoA oxidase (ACO) mRNA expression were also upregulated by SSC. CONCLUSIONS: According to our study, the lipids-lowering effect of dietary SSC may be partly associated with the enhancement of beta-oxidation via PPARalpha activation. In addition, the inhibited SREBP-1c- mediated lipogenesis caused by SSC may also contribute to alleviating fatty liver.
Konig B and Eder K, J Nutr Biochem. 2006 Jun;17(6):410-8. Epub 2005 Sep 23.
In rats, oxidized fats activate the peroxisome proliferator-activated receptor alpha (PPARalpha), leading to reduced triglyceride concentrations in liver, plasma and very low density lipoproteins. Oxidation products of linoleic acid constitute an important portion of oxidized dietary fats. This stud
y was conducted to check whether the primary lipid peroxidation product of linoleic acid, 13-hydroperoxy-9,11-octadecadienoic acid (13-HPODE), might be involved in the PPARalpha-activating effect of oxidized fats. Therefore, we examined the effect of 13-HPODE on the expression of PPARalpha target genes in the rat Fao and the human HepG2 hepatoma cell lines. In Fao cells, 13-HPODE increased the mRNA concentration of the PPARalpha target genes acyl-CoA oxidase (ACO), cytochrome P450 4A1 and carnitine-palmitoyltransferase 1A (CPT1A). Furthermore, the concentration of cellular and secreted triglycerides was reduced in Fao cells treated with 13-HPODE. Because PPARalpha mRNA was not influenced, we conclude that these effects are due to an activation of PPARalpha by 13-HPODE. In contrast, HepG2 cells seemed to be resistant to PPARalpha activation by 13-HPODE because no remarkable induction of the PPARalpha target genes ACO, CPT1A, mitochondrial HMG-CoA synthase and delta9-desaturase was observed. Consequently, cellular and secreted triglyceride levels were not changed after incubation of HepG2 cells with 13-HPODE. In conclusion, this study shows that 13-HPODE activates PPARalpha in rat Fao but not in human HepG2 hepatoma cells.
BACKGROUND: The peroxisome proliferator-activated receptors (PPARs) have been implicated in immune regulation. We determined the transcriptional expression of the three isoforms, PPARalpha, PPARgamma1, and PPARgamma2 in the peritoneal macrophages, CD4- and CD8-positive lymphocytes in non-obese diabe
tic (NOD) mice at 5 and 10 weeks of age as well as at diabetic stage. RESULTS: Compared to the non-obese diabetic resistant (NOR) mice, the peritoneal macrophages of NOD mice expressed increased levels of PPARalpha but reduced levels of PPARgamma2, while PPARgamma1 expression was unchanged in all age groups. CD4-positive lymphocytes expressed low levels of PPARalpha in diabetic NOD mice and greatly reduced expression of PPARgamma2 in all age groups. Unlike peritoneal macrophages and CD4-positive cells, the CD8-positive cells expressed low levels of PPARgamma1 in diabetic NOD mice but no difference in PPARalpha and PPARgamma2 expression was observed compared to NOR mice. CONCLUSION: The current findings may suggest an important regulatory role of PPARs in the pathogenesis of autoimmune diabetes.
Lovekamp-Swan T, etal., Mol Cell Endocrinol. 2003 Mar 28;201(1-2):133-41.
Peroxisome proliferator-activated receptors (PPARs) are key regulators of lipid metabolism and cell differentiation. The plasticizer di-(2-ethylhexyl) phthalate is a peroxisome proliferator, and its active metabolite mono-(2-ethylhexyl) phthalate (MEHP) activates PPARalpha and PPARgamma in cell tra
nsactivation assays. MEHP is a female reproductive toxicant and decreases activity, mRNA, and protein levels of aromatase, the rate-limiting enzyme that converts testosterone to estradiol in ovarian granulosa cells. To test the hypothesis that MEHP suppresses aromatase through PPAR pathways, granulosa cells were cultured with MEHP (50 microM) or selective activators of PPARgamma or PPARalpha for 48 h and gene expression was analyzed by real time RT-PCR. Both PPARalpha and PPARgamma activators significantly decreased aromatase mRNA and estradiol production like MEHP. The PPARgamma-selective antagonist GR 259662 partially blocked the suppression of aromatase by MEHP, suggesting that MEHP acts through PPARgamma, but not exclusively. MEHP and the PPARalpha-selective agonist GW 327647 induced expression of 17beta-hydroxysteroid dehydrogenase IV, a known PPARalpha-regulated gene, and induction was maintained with addition of the PPARgamma-selective antagonist. PPARalpha-selective activation also induced expression of aryl hydrocarbon receptor (AhR), CYP1B1, and epoxide hydrolase in the granulosa cell. These data support a model in which MEHP activates both PPARalpha and PPARgamma to suppress aromatase and alter other genes related to metabolism and differentiation in the granulosa cell.
MicroRNA-34a (miR-34a) is thought to be involved in nonalcoholic fatty liver disease (NAFLD). However, the association between altered expression of miR-34a and the pathophysiological features of NAFLD remains unclear. Here, we investigated the mechanisms by which miR-34a influences NAFLD through th
e PPARalpha-related pathway. Real-time quantitative PCR, western blotting and other assays kit were used to investigate the expression and function of miR-34a in an NAFLD model. Cultured cells transfected with miR-34a inhibitor and C57BL/6 mice injected with the miR-34a inhibitor through vein tail were conducted for the effects of miR-34a on its target. MiR-34a levels were significantly upregulated in steatosis-induced hepatocytes and in liver tissues of high-fat diet-fed mice. The upregulation of miR-34a resulted in the downregulation of hepatic PPARalpha and SIRT1 that are the direct targets of miR-34a. Silencing miR-34a led to an initially increased expression of PPARalpha, SIRT1 and PPARalpha's downstream genes. Activation of the central metabolic sensor AMPK was also increased. The miR-34a inhibitor suppressed lipid accumulation and improved the degree of steatosis. Taken together, our data indicated that decreased expression of miR-34a potentially contributes to altered lipid metabolism in NAFLD. Downregulation of miR-34a may be a therapeutic strategy against NAFLD by regulating its target PPARalpha and SIRT1.
Under synchronized conditions daily rhythms run in precise phase relationships. Long lasting shift-work disturbs circadian rhythms and causes metabolism dysfunction. As a result of frequent shifts of the light (L):dark (D) cycle the circadian system has to adjust to a new regimen repeatedly, and org
anism can never achieve complete adjustment of all circadian rhythms. Nuclear receptor PPARalpha is supposed to be a functional interface between circadian clock and metabolism, and its interconnection with rev-erbalpha and pdk4 was proven. The aim of this study was to elucidate responsiveness of the circadian system to the LD cycle mimicking the rotating shift-work with 8-h phase delay every second day. Expression of key clock genes and clock controlled metabolic genes rev-erbalpha, pparalpha, and pdk4 was analyzed in the liver and heart of rats by real time PCR. Control Wistar rats were exposed to the regular LD cycle 12:12. The second group was exposed to the LD regimen mimicking shift-work with 8-h phase delays during period of 10 weeks. Sampling was performed in 4-h intervals during 24-h cycle. Clock gene expression in the heart and liver of shifted rats was rhythmic and phase delayed by 8-9 h compared to control. Expression of metabolic genes was influenced more in the liver than in the heart. Results indicate that frequent shifts of LD cycle may interfere with control of lipid metabolism.
Carlsson L, etal., Am J Physiol Endocrinol Metab. 2001 Oct;281(4):E772-81.
The aim of this study was to investigate the interaction between long-chain fatty acids (LCFA) and growth hormone (GH) in the regulation of liver fatty acid binding protein (LFABP) and peroxisome proliferator-activated receptor-alpha (PPARalpha). Cultured rat hepatocytes were given oleic acid (OA; 5
00 microM) and GH (100 ng/ml) for 3 days. LFABP mRNA increased 3.6-fold by GH and 5.7-fold by OA, and combined incubation with GH and OA increased LFABP mRNA 17.6-fold. PPARalpha mRNA was decreased 50% by GH, but OA had no effect. Hypophysectomized (Hx) female rats were treated with L-thyroxine, cortisol, GH, and dietary fat for 7 days. PPARalpha mRNA levels were three- to fourfold higher in Hx than in normal female rats. GH decreased PPARalpha mRNA 50% in Hx rats. Dietary triglycerides (10% corn oil) increased LFABP mRNA and cytosolic LFABP about twofold but had no effect on PPARalpha mRNA in Hx rats. GH and dietary triglycerides had an additive effect on LFABP expression. Dietary triglycerides increased mitochondrial hydroxymethylglutaryl-CoA synthase mRNA only in the presence of GH. The diet increased serum triglycerides in Hx rats, and GH treatment prevented this increase. Addition of cholesterol to the diet did not influence LFABP levels but mitigated increased hepatic triglyceride content. In summary, these studies show that GH regulates LFABP expression independently of PPARalpha. Moreover, GH has different effects on PPARalpha-responsive genes and does not counteract the effect of LCFA on the expression of these gene products.
Jeong S and Yoon M, Exp Mol Med. 2009 Jun 30;41(6):397-405.
Peroxisome proliferator-activated receptor alpha (PPARalpha) activation in rodents is thought to improve insulin sensitivity by decreasing ectopic lipids in non-adipose tissues. Fenofibrate, a lipid-modifying agent that acts as a PPARalpha agonist, may prevent adipocyte hypertrophy and insulin resis
tance by increasing intracellular lipolysis from adipose tissue. Consistent with this hypothesis, fenofibrate decreased visceral fat mass and adipocyte size in high fat diet-fed obese mice, and concomitantly increased the expression of PPARalpha target genes involved in fatty acid beta-oxidation in both epididymal adipose tissue and differentiated 3T3-L1 adipocytes. However, mRNA levels of adipose marker genes, such as leptin and TNFalpha, were decreased in epididymal adipose tissue by fenofibrate treatment. Fenofibrate not only reduced circulating levels of free fatty acids and triglycerides, but also normalized hyperinsulinemia and hyperglycemia in obese mice. Blood glucose levels of fenofibrate-treated mice were significantly reduced during intraperitoneal glucose tolerance test compared with obese controls. These results suggest that fenofibrate-induced fatty acid beta-oxidation in visceral adipose tissue may be one of the major factors leading to decreased adipocyte size and improved insulin sensitivity.
Zuo N, etal., Int J Clin Exp Pathol. 2015 Sep 1;8(9):10653-61. eCollection 2015.
Albumin-bound fatty acids is the main cause of renal damage, PPARalpha is responsible in the metabolism of fatty acids. Previous study found that PPARalpha played a protective role in fatty acids overload associated tubular injury. The aim of the present study is to investigate whether fenofibrate,
a PPARalpha ligands, could contribute to the renoprotective action in fatty acids overload proximal tubule epithelial cells. We observed in HK-2 cells that fenofibrate significantly inhibited fatty acids bound albumin (FA-BSA) induced up-regulation of MCP-1 and IL-8. Treatment with fenofibrate attenuated renal oxidative stress induced by FA-BSA as evidenced by decreased MDA level, increased SOD activity and catalase, GPx-1 expression. FA-BSA induced apoptosis of HK-2 cells were also obviously prevented by fenofibrate. Furthermore, fenofibrate significantly increased the expression of PPARalpha mRNA and protein in FA-BSA treated cells. Finally, the activation of NF-kB induced by FA-BSA was markedly suppressed by fenofibrate. Taken together, our study describes a renoprotective role of fenofibrate in fatty acids associated tubular toxicity, and the transcriptional activation of PPARalpha and suppression of NF-kB were at least partially involved.
Tong Y, etal., Cerebrovasc Dis. 2016;41(1-2):96-9. doi: 10.1159/000442306. Epub 2015 Dec 16.
BACKGROUND: PPARx03B3; and PPARalpha belong to a receptor family of ligand-activated transcription factors involved in the regulation of inflammation, cellular glucose uptake, protection against atherosclerosis and endothelial cell function. Through these effects, they might be involved with the isc
hemic stroke (IS). METHODS: One thousand two hundred ninety-six subjects from the Chinese Han Population were chosen to assess the nature of the functional polymorphisms of PPARs and any links with IS. Multivariate logistic regression analysis was used to examine the association between PPARx03B3; and PPARalpha genotypes and a diagnosis of IS. RESULTS: Pro/Ala carriage may be associated with the decreased risk of IS in Hans (OR 0.542, 95% CI 0.346-0.850). The 162Val allele frequency at the DNA-binding region of PPARalpha was extremely rare in Chinese Han population. CONCLUSIONS: PPARx03B3; 12Pro/Ala resulting in an amino acid exchange in N-terminal sequence may be an independent protective factor for IS in the Chinese Han population. However, more populations are warranted to validate our findings.
Liu A, etal., Arch Toxicol. 2014 Apr;88(4):983-96. doi: 10.1007/s00204-013-1188-0. Epub 2014 Jan 3.
Gemfibrozil, a ligand of peroxisome proliferator-activated receptor alpha (PPARalpha), is one of the most widely prescribed anti-dyslipidemia fibrate drugs. Among the adverse reactions observed with gemfibrozil are alterations in liver function, cholestatic jaundice, and cholelithiasis. However, the
mechanisms underlying these toxicities are poorly understood. In this study, wild-type and Ppara-null mice were dosed with a gemfibrozil-containing diet for 14 days. Ultra-performance chromatography electrospray ionization quadrupole time-of-flight mass spectrometry-based metabolomics and traditional approaches were used to assess the mechanism of gemfibrozil-induced hepatotoxicity. Unsupervised multivariate data analysis revealed four lysophosphatidylcholine components in wild-type mice that varied more dramatically than those in Ppara-null mice. Targeted metabolomics revealed taurocholic acid and tauro-alpha-muricholic acid/tauro-beta-muricholic acid were significantly increased in wild-type mice, but not in Ppara-null mice. In addition to the above perturbations in metabolite homeostasis, phenotypic alterations in the liver were identified. Hepatic genes involved in metabolism and transportation of lysophosphatidylcholine and bile acid compounds were differentially regulated between wild-type and Ppara-null mice, in agreement with the observed downstream metabolic alterations. These data suggest that PPARalpha mediates gemfibrozil-induced hepatotoxicity in part by disrupting phospholipid and bile acid homeostasis.
In mammals, hepatic lipid catabolism is essential for the newborns to efficiently use milk fat as an energy source. However, it is unclear how this critical trait is acquired and regulated. We demonstrate that under the control of PPARalpha, the genes required for lipid catabolism are transcribed b
efore birth so that the neonatal liver has a prompt capacity to extract energy from milk upon suckling. The mechanism involves a fetal glucocorticoid receptor (GR)-PPARalpha axis in which GR directly regulates the transcriptional activation of PPARalpha by binding to its promoter. Certain PPARalpha target genes such as Fgf21 remain repressed in the fetal liver and become PPARalpha responsive after birth following an epigenetic switch triggered by beta-hydroxybutyrate-mediated inhibition of HDAC3. This study identifies an endocrine developmental axis in which fetal GR primes the activity of PPARalpha in anticipation of the sudden shifts in postnatal nutrient source and metabolic demands.
Ohashi K, etal., Biochem Biophys Res Commun. 2015 Dec 4-11;468(1-2):185-9. doi: 10.1016/j.bbrc.2015.10.134. Epub 2015 Oct 28.
DNA methylation status is affected by environmental factors, including nutrition. Fructose consumption is considered a risk factor for the conditions that make up metabolic syndrome such as dyslipidemia. However, the pathogenetic mechanism by which fructose consumption leads to metabolic syndrome i
s unclear. Based on observations that epigenetic modifications are closely related to induction of metabolic syndrome, we hypothesized that fructose-induced metabolic syndrome is caused by epigenetic alterations. Male SD rats were designated to receive water or 20% fructose solution for 14 weeks. mRNA levels for peroxisome proliferator-activated receptor alpha (PPARalpha) and carnitine palmitoyltransferase 1A (CPT1A) was analyzed using Real-time PCR. Restriction digestion and real-time PCR (qAMP) was used for the analysis of DNA methylation status. Hepatic lipid accumulation was also observed by fructose intake. Fructose feeding also significantly decreased mRNA levels for PPARalpha and CPT1A. qAMP analysis demonstrated the hypermethylation of promoter regions of PPARalpha and CTP1A genes. Fructose-mediated attenuated gene expression may be mediated by alterations of DNA methylation status, and pathogenesis of metabolic syndrome induced by fructose relates to DNA methylation status.
BACKGROUND: The peroxisome proliferator-activated receptor-alpha (PPARalpha) is a lipid-sensing transcriptional factor that has a role in gluco-oxidative stress and lipotoxicity. Forkhead box O (FoxO)s and peroxisome proliferator-activated receptor-gamma coactivator (PGC)-1alpha are also known to re
gulate cell metabolism, cell cycle arrest, apoptosis and oxidative stress during stressful conditions. We evaluated whether PPARalpha-FoxOs-PGC-1alpha signaling in overfed spontaneously hypertensive rats (SHR) has a protective role in the kidney. METHODS: Male SHR and Wistar-Kyoto rats (WKY) fed a high-fat diet (HFD) received treatment with fenofibrate, PPARalpha agonist or tempol, antioxidants for 12 weeks and were evaluated about the PPARalpha-FoxOs-PGC-1alpha pathway. RESULTS: The SHRs with an HFD had an elevated systolic pressure, plasma insulin, free fatty acid (FFA) and triglyceride (TGs) levels, and they had induced glucose intolerance as well as albuminuria, glomerular expansion and renal inflammation. An HFD caused the accumulation of intra-renal FFA and TGs and this was related to a decrease in the PPARalpha expression, the activation of phosphatidylinositol 3-kinase (PI3K)-Akt, phosphorylation of FoxO3a and decreases in the PGC-1alpha and estrogen-related receptor (ERR)-1alpha expressions, which suppressed the superoxide dismutase (SOD2) and Bcl-2 expressions and led to increases in oxidative stress and the number of apoptotic renal cells. Interestingly, administering fenofibrate or tempol to the HFD-induced SHRs reversed all of the renal phenotypes by increasing the PPARalpha expression with concomitant inactivation of the PI3K-Akt pathway, dephosphorylation of FoxO3a and activation of PGC-1alpha-ERR-1alpha signaling, and this all resulted in ameliorating the oxidative stress and apoptotic cell death. CONCLUSION: Our results demonstrated that PPARalpha agonists or antioxidants are associated with improvement of the circulating FFA and TGs levels and this prevents HFD-induced renal lipotoxicity and hypertension by the activation of PPARalpha and its downstream signals of both FoxO3a and PGC-1alpha.
Manea A, etal., Cell Tissue Res. 2015 Aug;361(2):593-604. doi: 10.1007/s00441-015-2120-0. Epub 2015 Feb 27.
High glucose induces vascular smooth muscle cell (SMC) dysfunction by generating oxidative stress attributable, in part, to the up-regulated NADPH oxidases (Nox). We have attempted to elucidate the high-glucose-generated molecular signals that mediate this effect and hypothesize that products of h
igh-glucose-induced lipid peroxidation regulate Nox by activating peroxisome proliferator-activated receptors (PPARs). Human aortic SMCs were exposed to glucose (5.5-25 mM) or 4-hydroxynonenal (1-25 muM, 4-HNE). Lucigenin assay, real-time polymerase chain reaction, western blot, and promoter analyses were employed to investigate Nox. We found that high glucose generated an increase in Nox activity and expression. It also promoted oxidative stress that consequently induced lipid peroxidation, which resulted in the production of 4-HNE. Pharmacological inhibition of Nox activity significantly reduced the formation of high-glucose-induced 4-HNE. Exposure of SMCs to non-cytotoxic concentrations (1-10 muM) of 4-HNE alone mimicked the effect of high glucose incubation, whereas scavenging of 4-HNE by N-acetyl L-cysteine completely abolished both the effects of high glucose and 4-HNE. The latter exerted its effect by activating PPARalpha and PPARbeta/delta, but not PPARgamma, as assessed pharmacologically by the inhibitory effect of selective antagonists and following the silencing of the expression of these receptors. These new data indicate that 4-HNE, generated following Nox activation, functions as an endogenous activator of PPARalpha and PPARbeta/delta. The newly discovered "lipid peroxidation products-PPARs-Nox axis" represents a novel mechanism of Nox regulation and an additional therapeutic target for oxidative stress in diabetes.
Roy A, etal., Cell Metab. 2015 Aug 4;22(2):253-65. doi: 10.1016/j.cmet.2015.05.022. Epub 2015 Jun 25.
Neurotrophins are important for neuronal health and function. Here, statins, inhibitors of HMG-CoA reductase and cholesterol lowering drugs, were found to stimulate expression of neurotrophins in brain cells independent of the mevalonate pathway. Time-resolved fluorescence resonance energy transfer
(FRET) analyses, computer-derived simulation, site-directed mutagenesis, thermal shift assay, and de novo binding followed by electrospray ionization tandem mass spectrometry (ESI-MS) demonstrates that statins serve as ligands of PPARalpha and that Leu331 and Tyr 334 residues of PPARalpha are important for statin binding. Upon binding, statins upregulate neurotrophins via PPARalpha-mediated transcriptional activation of cAMP-response element binding protein (CREB). Accordingly, simvastatin increases CREB and brain-derived neurotrophic factor (BDNF) in the hippocampus of Ppara null mice receiving full-length lentiviral PPARalpha, but not L331M/Y334D statin-binding domain-mutated lentiviral PPARalpha. This study identifies statins as ligands of PPARalpha, describes neurotrophic function of statins via the PPARalpha-CREB pathway, and analyzes the importance of PPARalpha in the therapeutic success of simvastatin in an animal model of Alzheimer's disease.
Breast cancer resistance protein (Bcrp/Abcg2) localized at the blood-brain barrier (BBB) limits permeability into the brain of many xenobiotics, including pharmacological agents. Peroxisome proliferator-activated receptor alpha (Pparalpha), a ligand-activated tr
anscription factor, primarily involved in lipid metabolism, has been shown to regulate the functional expression of Bcrp in human cerebral microvascular endothelial cells (hCMEC/D3). The aim of this study was to investigate ex vivo and in vivo, the regulation of Bcrp by Pparalpha in an intact BBB. Ex vivo quantitative real-time PCR and immunoblot analyses showed significant up-regulation of Abcg2/Bcrp mRNA and protein levels in CD-1 mouse brain capillaries incubated with clofibrate, a Pparalpha ligand. Fluorescence-based transport assays in CD-1 and C57BL/6 brain capillaries showed that exposure to clofibrate significantly increased Bcrp transport activity. This increase was not observed in capillaries isolated from Pparalpha knockout mice. In vivo, we found: i) significant Bcrp protein up-regulation in clofibrate-dosed CD-1 and C57BL/6 capillary lysates, but no effect in Pparalpha knockout capillary lysates, and ii) significantly increased Bcrp transport activity in capillaries isolated from clofibrate-treated mice. These results demonstrate an increase in Bcrp functional expression by Pparalpha in brain capillaries, and suggest that Pparalpha is another nuclear receptor that can contribute to the regulation of membrane efflux transporters and drug permeability at the BBB. We propose the involvement of the following pathways in clofibrate-mediated induction of the drug transporter Abcg2/Bcrp mRNA, protein expression and function by the nuclear receptor Pparalpha, in mouse brain capillary endothelial cells. Upon activation with clofibrate (Pparalpha, ligand), Pparalpha complex translocates from the cytoplasm into the nucleus and further recruits coactivators and transcription machinery which induce the transcription of Abcg2 gene and ultimately results in upregulation of Bcrp protein expression and function. These findings have significant implications since Bcrp is known to play an important role at the BBB in preventing the permeability of several xenobiotics and drugs into the brain.
Yoo SH, etal., Toxicol Lett. 2011 Apr 10;202(1):23-9. Epub 2011 Jan 22.
Peroxisome proliferator-activated receptor-alpha (PPARalpha) has been implicated in a potent anti-inflammatory activity. However, no information is available on whether PPARalpha can affect signal transducers and activator of transcription proteins (STATs) in acute liver damage. Thus, this study was
aimed to investigate the in vivo role of PPARalpha in elevating STATs as well as oxidative/nitrosative stress in a model of lipopolysaccharide (LPS)-induced acute hepatic inflammatory injury. Using age-matched Ppara-null and wild-type (WT) mice, we demonstrate that the deletion of PPARalpha aggravates LPS-mediated liver injury through activating STAT1 and NF-kappaB-p65 accompanied by increased levels of pro-inflammatory cytokines. Furthermore, the activities of key anti-oxidant enzymes and mitochondrial complexes were significantly decreased while lipid peroxidation and protein nitration were elevated in LPS-exposed Ppara-null mice compared to WT. These results indicate that PPARalpha is important in preventing LPS-induced acute liver damage by regulating STAT1 inflammatory signaling pathways and oxidative/nitrosative stress.
Louet JF, etal., Biochem J 2001 Feb 15;354(Pt 1):189-97.
Liver carnitine palmitoyltransferase I (L-CPT I) catalyses the transfer of long-chain fatty acid (LCFA) for translocation across the mitochondrial membrane. Expression of the L-CPT I gene is induced by LCFAs as well as by lipid-lowering compounds such as clofibrate. Previous studies have suggested t
hat the peroxisome-proliferator-activated receptor alpha (PPARalpha) is a common mediator of the transcriptional effects of LCFA and clofibrate. We found that free LCFAs rather than acyl-CoA esters are the signal metabolites responsible for the stimulation of L-CPT I gene expression. Using primary culture of hepatocytes we found that LCFAs failed to stimulate L-CPT I gene expression both in wild-type and PPARalpha-null mice. These results suggest that the PPARalpha-knockout mouse does not represent a suitable model for the regulation of L-CPT I gene expression by LCFAs in the liver. Finally, we determined that clofibrate stimulates L-CPT I through a classical direct repeat 1 (DR1) motif in the promoter of the L-CPT I gene while LCFAs induce L-CPT I via elements in the first intron of the gene. Our results demonstrate that LCFAs can regulate gene expression through PPARalpha-independent pathways and suggest that the regulation of gene expression by dietary lipids is more complex than previously proposed.
Fibrates are hypolipidemic drugs that exert multiple effects on lipid metabolism by activating peroxisome proliferator-activated receptor alpha (PPARalpha) and modulating the expression of many target genes. In order to investigate the link between PPARalpha and cholesterol synthesis, we analysed th
e effect of fibrates on expression of the farnesyl diphosphate synthase (FPP synthase) gene, known to be regulated by sterol regulatory element-binding proteins (SREBPs), in conjunction with HMG-CoA reductase. In wild-type mice, both fenofibrate and WY 14,643 induced FPP synthase gene expression, an effect impaired in PPARalpha-null mice. A three-fold induction was observed in ciprofibrate-treated rat hepatocytes, in primary culture. This effect was decreased in presence of 5,6-dichlorobenzimidazole riboside (DRB) and cycloheximide (CHX), transcription and translation inhibitors, respectively. Acyl-CoA oxidase (AOX), a bona fide PPARalpha target gene, was induced by ciprofibrate but slower and more strongly than FPP synthase. In addition, induction of FPP synthase gene expression was abolished in the presence of 25-hydroxycholesterol (25-OH Chol). Thus, activation of PPARalpha by fibrates induced FPP synthase gene expression in both hepatocytes in culture and in mouse liver. This effect is likely to be dependent on cellular sterol level, possibly through SREBP-mediated transcriptional activation.
Ravnskjaer K, etal., Endocrinology. 2005 Aug;146(8):3266-76. Epub 2005 May 5.
Fatty acids (FAs) are known to be important regulators of insulin secretion from pancreatic beta-cells. FA-coenzyme A esters have been shown to directly stimulate the secretion process, whereas long-term exposure of beta-cells to FAs compromises glucose-stimulated insulin secretion (GSIS) by mechani
sms unknown to date. It has been speculated that some of these long-term effects are mediated by members of the peroxisome proliferator-activated receptor (PPAR) family via an induction of uncoupling protein-2 (UCP2). In this study we show that adenoviral coexpression of PPARalpha and retinoid X receptor alpha (RXRalpha) in INS-1E beta-cells synergistically and in a dose- and ligand-dependent manner increases the expression of known PPARalpha target genes and enhances FA uptake and beta-oxidation. In contrast, ectopic expression of PPARgamma/RXRalpha increases FA uptake and deposition as triacylglycerides. Although the expression of PPARalpha/RXRalpha leads to the induction of UCP2 mRNA and protein, this is not accompanied by reduced hyperpolarization of the mitochondrial membrane, indicating that under these conditions, increased UCP2 expression is insufficient for dissipation of the mitochondrial proton gradient. Importantly, whereas expression of PPARgamma/RXRalpha attenuates GSIS, the expression of PPARalpha/RXRalpha potentiates GSIS in rat islets and INS-1E cells without affecting the mitochondrial membrane potential. These results show a strong subtype specificity of the two PPAR subtypes alpha and gamma on lipid partitioning and insulin secretion when systematically compared in a beta-cell context.
Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is expressed at high levels in the hepatocyte, consistent with its role in promoting insulin clearance in liver. CEACAM1 also mediates a negative acute effect of insulin on fatty acid synthase activity. Western blot analysis reveal
s lower hepatic CEACAM1 expression during fasting. Treating of rat hepatoma FAO cells with Wy14,643, an agonist of peroxisome proliferator-activated receptor alpha (PPARalpha), rapidly reduces Ceacam1 mRNA and CEACAM1 protein levels within 1 and 2 h, respectively. Luciferase reporter assay shows a decrease in the promoter activity of both rat and mouse genes by Pparalpha activation, and 5'-deletion and block substitution analyses reveal that the Pparalpha response element between nucleotides -557 and -543 is required for regulation of the mouse promoter activity. Chromatin immunoprecipitation analysis demonstrates binding of liganded Pparalpha toCeacam1promoter in liver lysates ofPparalpha(+/+), but notPparalpha(-/-)mice fed a Wy14,643-supplemented chow diet. Consequently, Wy14,643 feeding reduces hepatic Ceacam1 mRNA and CEACAM1 protein levels, thus decreasing insulin clearance to compensate for compromised insulin secretion and maintain glucose homeostasis and insulin sensitivity in wild-type mice. Together, the data show that the low hepatic CEACAM1 expression at fasting is mediated by Pparalpha-dependent mechanisms. Changes in CEACAM1 expression contribute to the coordination of fatty acid oxidation and insulin action in the fasting-refeeding transition.
Le K, etal., Arch Biochem Biophys. 2012 Feb 1;518(1):71-8. Epub 2011 Dec 16.
Peroxisome proliferator-activated receptor alpha (PPARalpha) has been implicated in the pathogenesis of cardiac hypertrophy, although its mechanism of action remains largely unknown. To determine the effect of PPARalpha activation on endothelin-1 (ET-1)-induced cardiomyocyte hypertrophy and explore
its molecular mechanisms, we evaluated the interaction of PPARalpha with nuclear factor of activated T-cells c4 (NFATc4) in nuclei of cardiomyocytes from neonatal rats in primary culture. In ET-1-stimulated cardiomyocytes, data from electrophoretic mobility-shift assays (EMSA) and co-immunoprecipitation (co-IP) revealed that fenofibrate (Fen), a PPARalpha activator, in a concentration-dependent manner, enhanced the association of NFATc4 with PPARalpha and decreased its interaction with GATA-4, in promoter complexes involved in activation of the rat brain natriuretic peptide (rBNP) gene. Effects of PPARalpha overexpression were similar to those of its activation by Fen. PPARalpha depletion by small interfering RNA abolished inhibitory effects of Fen on NFATc4 binding to GATA-4 and the rBNP DNA. Quantitative RT-PCR and confocal microscopy confirmed inhibitory effects of PPARalpha activation on elevation of rBNP mRNA levels and ET-1-induced cardiomyocyte hypertrophy. Our results suggest that activated PPARalpha can compete with GATA-4 binding to NFATc4, thereby decreasing transactivation of NFATc4, and interfering with ET-1 induced cardiomyocyte hypertrophy.
BACKGROUND & AIMS: Peroxisome proliferator-activated receptors (PPARs) have been implicated in non-alcoholic steatohepatitis (NASH) pathogenesis, mainly based on animal data. Gene expression data in NASH patients are scarce. We studied liver PPARalpha, beta/delta, and gamma expression in a large c
ohort of obese patients assessed for presence of NAFLD at baseline and 1 year follow-up. METHODS: Patients presented to the obesity clinic underwent a hepatic work-up. If NAFLD was suspected, liver biopsy was performed. Gene expression was studied by mRNA quantification. Patients were reassessed after 1 year. RESULTS: 125 patients were consecutively included in the study, of which 85 patients had paired liver biopsy taken at 1 year of follow-up. Liver PPARalpha expression negatively correlated with the presence of NASH (p=0.001) and with severity of steatosis (p=0.003), ballooning (p=0.001), NASH activity score (p=0.008) and fibrosis (p=0.003). PPARalpha expression was positively correlated to adiponectin (R(2)=0.345, p=0.010) and inversely correlated to visceral fat (R(2)=-0.343, p<0.001), HOMA IR (R(2)=-0.411, p<0.001) and CK18 (R(2)=-0.233, p=0.012). Liver PPARbeta/delta and PPARgamma expression did not correlate with any histological feature nor with glucose metabolism or serum lipids. At 1 year, correlation of PPARalpha expression with liver histology was confirmed. In longitudinal analysis, an increase in expression of PPARalpha and its target genes was significantly associated with histological improvement (p=0.008). CONCLUSION: Human liver PPARalpha gene expression negatively correlates with NASH severity, visceral adiposity and insulin resistance and positively with adiponectin. Histological improvement is associated with an increase in expression of PPARalpha and its target genes. These data might suggest that PPARalpha is a potential therapeutic target in NASH.
BACKGROUND AND PURPOSE: Zymosan-induced non-septic shock is a multi-factorial pathology that involves several organs including the kidneys, liver and lungs. Its complexity and diversity presents a continuing therapeutic challenge. Given their pleiotropic effect, statins could be beneficial in non-se
ptic shock. One of the molecular mechanisms underlying the anti-inflammatory effect of statins involves the peroxisome proliferator-activated receptor (PPAR) alpha. We used a zymosan-induced non-septic shock experimental model to investigate the role of PPARalpha in the anti-inflammatory effects of simvastatin. EXPERIMENTAL APPROACH: Effects of simvastatin (5 or 10 mg.kg(-1) i.p.) were analysed in PPARalpha knock-out (KO) and PPARalpha wild type (WT) mice after zymosan or vehicle administration. Organ injury in lung, liver, kidney and intestine was evaluated by immunohistology. PPARalpha mRNA expression and nuclear factor-kappaB activation were evaluated in all experimental groups, 18 h after study onset. Cytokine levels were measured in plasma, and nitrite/nitrate in plasma and peritoneal exudate. Nitric oxide synthase, nitrotyrosine and poly ADP-ribose were localized by immunohistochemical methods. KEY RESULTS: Simvastatin significantly and dose-dependently increased the zymosan-induced expression of PPARalpha levels in all tissues analysed. It also dose-dependently reduced systemic inflammation and the organ injury induced by zymosan in lung, liver, intestine and kidney. These effects were observed in PPARalphaWT mice and in PPARalphaKO mice. CONCLUSIONS AND IMPLICATIONS: Simvastatin protected against the molecular and cellular damage caused by systemic inflammation in our experimental model. Our results also provide new information regarding the role of PPARalpha in the anti-inflammatory effects of statins.
Wang Z, etal., Invest Ophthalmol Vis Sci. 2014 May 20;55(6):3820-32. doi: 10.1167/iovs.13-13396.
PURPOSE: The mechanism for the antiangiogenic activity of peroxisome proliferator-activated receptor alpha (PPARalpha) remains incompletely understood. Endothelial progenitor cells (EPC) are known to participate in neovascularization (NV). The purpose of this study was to investigate whether PPARalp
ha regulates EPC during retinal NV. METHODS: Retinal NV was induced by oxygen-induced retinopathy (OIR). Mice with OIR were injected intraperitoneally with the PPARalpha agonist fenofibric acid (FA) or with adenovirus expressing PPARalpha (Ad-PPARalpha). Flow cytometry was used to quantify circulating and retinal EPC. Serum stromal cell-derived factor 1 (SDF-1) levels were measured by ELISA. Hypoxia was induced in primary human retinal capillary endothelial cells (HRCEC) and mouse brain endothelial cells (MBEC) by CoCl2. Levels of SDF-1 and hypoxia-inducible factor 1 alpha (HIF-1alpha) were measured by Western blotting. RESULTS: Fenofibric acid and overexpression of PPARalpha attenuated the increase of circulating and retinal EPC, correlating with suppressed retinal NV in OIR mice at P17. The PPARalpha knockout enhanced the OIR-induced increase of circulating and retinal EPC. Fenofibric acid decreased retinal HIF-1alpha and SDF-1 levels as well as serum SDF-1 levels in the OIR model. In HRCEC, PPARalpha inhibited HIF-1alpha nuclear translocation and SDF-1 overexpression induced by hypoxia. Further, MBEC from PPARalpha(-/-) mice showed more prominent activation of HIF-1alpha and overexpression of SDF-1 induced by hypoxia, compared with the wild-type (WT) MBEC. PPARalpha failed to block SDF-1 overexpression induced by a constitutively active mutant of HIF-1alpha, suggesting that regulation of SDF-1 by PPARalpha was through blockade of HIF-1alpha activation. CONCLUSIONS: Peroxisome proliferator-activated receptor alpha suppresses ischemia-induced EPC mobilization and homing through inhibition of the HIF-1alpha/SDF-1 pathway. This represents a novel molecular mechanism for PPARalpha's antiangiogenic effects.
Peroxisome proliferator-activated receptor (PPAR) alpha/gamma may control lipid metabolism and inflammatory response by regulating the downstream target genes, and play a crucial role in the process of non-alcoholic steatohepatitis (NASH) formation, but the difference and interaction between PPARalp
ha and PPARgamma are poorly understood. The rat model with NASH was established by orally feeding high-fat and high-sucrose emulsion for 6weeks. The results shown that after the model rats were simultaneously treated with PPARalpha/gamma agonists, the total cholesterol (TC), triglyceride (TG) and inflammatory cytokine levels in serum and hepatic tissue, the hepatic steatosis and inflammatory cellular infiltration were decreased, and were consistent with the results of hepatic lipogenic gene and nuclear factor (NF)-kappaB protein expressions. Conversely, these indexes were increased by PPARalpha/gamma antagonist treatment. Compared with the model group, the serum free fatty acid (FFA) level was increased in the PPARalpha agonist-treated group, decreased in the PPARgamma agonist-treated group, and unchanged in the PPARalpha/gamma agonists-treated group. The hepatic FFA level was low in the PPARalpha/gamma agonists-treated groups, but no significant variation in the PPARalpha/gamma antagonists-treated groups. The increments of hepatic reduced glutathione (GSH) and superoxide dismutase (SOD) contents in the PPARalpha/gamma agonists-treated groups were accompanied by decreased hepatic malondialdehyde (MDA) content. These findings demonstrated that PPARalpha/gamma activation might decrease the hepatic lipid accumulation, oxidative stress and inflammatory cytokine production, and PPARgamma could counterbalance the adverse effect of PPARalpha on circulating FFA. It was concluded that the integrative application of PPARalpha and PPARgamma agonists might exert a synergic inhibitory effect on NASH formation through the modulation of PPARalpha/gamma-mediated lipogenic and inflammatory gene expressions.
Adiponectin (APN), a circulating adipose-derived hormone that regulates inflammation and energy metabolism, has beneficial effects on the cardiovascular disorders. Serum APN levels are lower in patients with coronary artery disease and higher in patients with chronic kidney disease. However, the pr
ecise role of APN in acute reno-vascular disease is not clear. Results of the present study show that serum APN concentration decreased after renal ischemia reperfusion (I/R) injury in mice. In addition, I/R-induced renal dysfunction (elevated serum creatinine and urea levels), inflammation (number of infiltrating neutrophils, myeloperoxidase activity), and apoptotic responses (apoptotic cell number and caspase-3 activation) were attenuated in APN-treated compared to control mice. Molecular and biochemical analysis revealed that APN up-regulates heme oxygenase-1 (HO-1) via peroxisome-proliferator-activated-receptor-alpha (PPARalpha) dependent pathway which is mediated through the enhancement of COX-2 and 6-keto PGF1alpha expression. Chromatin immune-precipitation assay demonstrated that APN increases the binding activity of PPARalpha to PPRE region of HO-1 promoter. Furthermore, APN induced HO-1 expression was only found in wild-type but not in PPARalpha gene deleted mice. This provides in vivo evidence that APN mediated HO-1 expression depends on PPARalpha regulation. In conclusion, our results provide a novel APN mediated prostacyclin-PPARalpha-HO-1 signaling pathway in protecting renal I/R injury.
Miyazaki M, etal., J Toxicol Sci. 2010;35(1):131-5.
To investigate peroxisomal proliferator-activated receptor alpha (PPARalpha) signal responses in heart muscle, we performed LC-MS/MS-based proteomics analysis of heart muscle from rats given fenofibrate or clofibrate. Fenofibrate increased the expression of ACAA2, DECR1, and ECH1 consistent with act
ivation of PPARalpha. Fenofibrate and clofibrate reduced the expression of 10 and 12 proteins, respectively with the expression of ACSL1, SLC25A4, A1BG, HADHA, ATP2A2, BDH1, ETFDH, HADHB, and CPT2 being reduced in common with both of fibrate-treated groups. The approach adopted in this study provides an efficient method for monitoring global changes in protein expression.
ABSTRACT: The peroxisome-proliferator activated receptor alpha (PPARalpha) is a member of the nuclear receptor family with many important physiologic roles related to metabolism and inflammation. Previous research in pediatric patients with septic shock revealed that genes corresponding to the PPARa
lpha signaling pathway are significantly downregulated in a subgroup of children with more severe disease. In this study, PPARalpha expression analysis using whole blood derived RNA revealed that PPARalpha expression was decreased in patients with septic shock and that the magnitude of that decrement correlated with the severity of disease. In a mouse model of sepsis, induced by cecal ligation and puncture (CLP), knockout mice lacking PPARalpha had decreased survival compared to wild type animals. Plasma cytokine analysis demonstrated decreased levels of IL-1beta, IL-6, IL-17, KC, MCP-1, MIP-2, and TNFalpha at 24 hours in PPARalpha knockout animals. Cell surface markers of activation on splenic dendritic cells, macrophages, and CD8 T-cells were reduced in PPARalpha null animals and the bacterial load in lung and splenic tissues was increased. These data indicate that reduced or absent PPARalpha expression confers a survival disadvantage in sepsis and that PPARalpha plays a role in maintaining appropriate immune functions during the sepsis response.
BACKGROUND: Therapeutic options for atopic dermatitis mostly address the symptoms but causal therapies are still missing. Peroxisome proliferator activated receptor (PPAR) agonists exert beneficial effects in patients suffering this disease, whereas the stimulation of PPARalpha and gamma seemed most
promising. OBJECTIVES: To elucidate the effects of the PPARalpha specific agonist WY14643, the PPARgamma agonist ciglitazone, and the dual PPARalpha+gamma agonist docosahexaenoic acid (DHA) on the homeostasis and barrier function of filaggrin deficient skin. METHODS: The effects of the PPAR agonists on skin differentiation were evaluated via qPCR, Western blot, histological or immunofluorescence staining. Skin lipid organization was determined by ATR-FTIR and lipid composition was analyzed by HPTLC. Ultimately, the skin barrier function was assessed by skin absorption studies using the radioactively labeled compound testosterone. RESULTS: Significant upregulation of filaggrin after DHA and WY14643 supplementation, but no effect of ciglitazone, on protein and mRNA level was detected. DHA and WY14643, but not ciglitazone, normalized the molar ratio of the main skin barrier lipids to 1:1:1 (free fatty acids:ceramides:cholesterol). Furthermore, DHA and WY14643 supplementation normalized the skin lipid profile in filaggrin deficient skin, but only WY14643 significantly improved the skin barrier function. CONCLUSION: Supplementation particularly with the PPARalpha agonist WY14643 improved the homeostasis and barrier function of filaggrin deficient skin models by normalization of the free fatty acid profile underlining the potential of PPAR agonists for the treatment of filaggrin-associated skin diseases.
Rodriguez-Cruz M, etal., J Lipid Res. 2006 Mar;47(3):553-60. Epub 2005 Dec 6.
The purpose of this work was to study whether rat lactating mammary gland can synthesize PUFAs through the expression of Delta5 and Delta6 desaturases (Delta5D and Delta6D), whether these enzymes are regulated by the transcription factors sterol-regulatory element binding protein 1 (SREBP-1) and per
oxisome proliferator-activated receptor alpha (PPARalpha) and the coactivator peroxisome proliferator-activated receptor gamma coactivator 1beta (PGC-1beta), and whether these desaturases are regulated by the lipid concentration in the diet. The results showed that on day 12 of lactation, approximately 35% of the linoleic acid in the diet, which is the precursor of PUFAs, is transferred to the mammary gland. There was expression of Delta5D and Delta6D in mammary gland, and it was regulated by the corn oil content in the diet. The higher the corn oil content in the diet, the lower the expression of both desaturases. Induction of Delta5D and Delta6D was associated positively with similar changes in SREBP-1 and PGC-1beta. Expression of PPARalpha was barely detected and was not affected by the corn oil content in the diet, whereas PGC-1beta expression increased as the corn oil in the diet increased. These results indicate that the lactating mammary gland has the capacity to synthesize PUFAs and can be regulated by the lipid content in the diet.
Janssen AW, etal., BMC Genomics. 2015 Oct 8;16:760. doi: 10.1186/s12864-015-1969-3.
BACKGROUND: Studies in mice have shown that PPARalpha is an important regulator of lipid metabolism in liver and key transcription factor involved in the adaptive response to fasting. However, much less is known about the role of PPARalpha in human liver. METHODS: Here we set out to study the functi
on of PPARalpha in human liver via analysis of whole genome gene regulation in human liver slices treated with the PPARalpha agonist Wy14643. RESULTS: Quantitative PCR indicated that PPARalpha is well expressed in human liver and human liver slices and that the classical PPARalpha targets PLIN2, VLDLR, ANGPTL4, CPT1A and PDK4 are robustly induced by PPARalpha activation. Transcriptomics analysis indicated that 617 genes were upregulated and 665 genes were downregulated by PPARalpha activation (q value < 0.05). Many genes induced by PPARalpha activation were involved in lipid metabolism (ACSL5, AGPAT9, FADS1, SLC27A4), xenobiotic metabolism (POR, ABCC2, CYP3A5) or the unfolded protein response, whereas most of the downregulated genes were involved in immune-related pathways. Among the most highly repressed genes upon PPARalpha activation were several chemokines (e.g. CXCL9-11, CCL8, CX3CL1, CXCL6), interferon gamma-induced genes (e.g. IFITM1, IFIT1, IFIT2, IFIT3) and numerous other immune-related genes (e.g. TLR3, NOS2, and LCN2). Comparative analysis of gene regulation by Wy14643 between human liver slices and primary human hepatocytes showed that down-regulation of gene expression by PPARalpha is much better captured by liver slices as compared to primary hepatocytes. In particular, PPARalpha activation markedly suppressed immunity/inflammation-related genes in human liver slices but not in primary hepatocytes. Finally, several putative new target genes of PPARalpha were identified that were commonly induced by PPARalpha activation in the two human liver model systems, including TSKU, RHOF, CA12 and VSIG10L. CONCLUSION: Our paper demonstrates the suitability and superiority of human liver slices over primary hepatocytes for studying the functional role of PPARalpha in human liver. Our data underscore the major role of PPARalpha in regulation of hepatic lipid and xenobiotic metabolism in human liver and reveal a marked immuno-suppressive/anti-inflammatory effect of PPARalpha in human liver slices that may be therapeutically relevant for non-alcoholic fatty liver disease.
Li PP, etal., Br J Pharmacol. 2006 Jul;148(5):610-8. Epub 2006 Jun 5.
1. The aim of this study was to investigate the capacity of chiglitazar to improve insulin resistance and dyslipidemia in monosodium L-glutamate (MSG) obese rats and to determine whether its lipid-lowering effect is mediated through its activation of PPARalpha. 2. Chiglitazar is a PPARalpha/gamma du
al agonist. 3. The compound improved impaired insulin and glucose tolerance; decreased plasma insulin level and increased the insulin sensitivity index and decreased HOMA index. Euglycemic hyperinsulinemic clamp studies showed chiglitazar increased the glucose infusion rate in MSG obese rats. 4. Chiglitazar inhibited alanine gluconeogenesis, lowered the hepatic glycogen level in MSG obese rats. Like rosiglitazone, chiglitazar promoted the differentiation of adipocytes and decreased the maximal diameter of adipocytes. In addition, chiglitazar decreased the fibrosis and lipid accumulation in the islets and increased the size of islets. 5. Chiglitazar reduced plasma triglyceride, total cholesterol (TCHO), nonesterified fatty acids (NEFA) and low density lipoprotein-cholesterol levels; lowered hepatic triglyceride and TCHO contents; decreased muscular NEFA level. Unlike rosiglitazone, chiglitazar showed significant increase of mRNA expression of PPARalpha, CPT1, BIFEZ, ACO and CYP4A10 in the liver of MSG obese rats. 6. These data suggest that PPARalpha/gamma coagonist, such as chiglitazar, affect lipid homeostasis with different mechanisms from rosiglitazone, chiglitazar may have better effects on lipid homeostasis in diabetic patients than selective PPARgamma agonists.
Rodriguez JE, etal., Mol Cell Endocrinol. 2015 Sep 15;413:36-48. doi: 10.1016/j.mce.2015.06.008. Epub 2015 Jun 25.
The transcriptional regulation of peroxisome proliferator-activated receptor (PPAR) alpha by post-translational modification, such as ubiquitin, has not been described. We report here for the first time an ubiquitin ligase (muscle ring finger-1/MuRF1) that inhibits fatty acid oxidation by inhibitin
g PPARalpha, but not PPARbeta/delta or PPARgamma in cardiomyocytes in vitro. Similarly, MuRF1 Tg+ hearts showed significant decreases in nuclear PPARalpha activity and acyl-carnitine intermediates, while MuRF1-/- hearts exhibited increased PPARalpha activity and acyl-carnitine intermediates. MuRF1 directly interacts with PPARalpha, mono-ubiquitinates it, and targets it for nuclear export to inhibit fatty acid oxidation in a proteasome independent manner. We then identified a previously undescribed nuclear export sequence in PPARalpha, along with three specific lysines (292, 310, 388) required for MuRF1's targeting of nuclear export. These studies identify the role of ubiquitination in regulating cardiac PPARalpha, including the ubiquitin ligase that may be responsible for this critical regulation of cardiac metabolism in heart failure.
g via peroxisome-proliferator-activated receptor alpha (PPARalpha) is an important component of the mechanism enhancing hepatic and renal PDK4 protein expression. Activation of PPARalpha in gastrocnemius, a predominantly fast glycolytic (FG) muscle, also increases PDK4 expression, an effect that, if extended to all muscles, would be predicted to drastically restrict whole-body glucose disposal. Paradoxically, chronic activation of PPARalpha by WY14,643 treatment improves glucose utilization by muscles of insulin-resistant high-fat-fed rats. In the resting state, oxidative skeletal muscles are quantitatively more important for glucose disposal than FG muscles. We evaluated the participation of PPARalpha in regulating PDK4 protein expression in slow oxidative (SO) skeletal muscle (soleus) and fast oxidative-glycolytic (FOG) skeletal muscle (anterior tibialis) containing a high proportion of oxidative fibres. In the fed state, acute (24 h) activation of PPARalpha by WY14,643 in vivo failed to modify PDK4 protein expression in soleus, but modestly enhanced PDK4 protein expression in anterior tibialis. Starvation enhanced PDK4 protein expression in both muscles, with the greater response in anterior tibialis. WY14,643 treatment in vivo during starvation did not further enhance upregulation of PDK4 protein expression in either muscle type. Enhanced PDK4 protein expression after starvation was retained in SO and FOG skeletal muscles of PPARalpha-deficient mice. Our data indicate that PDK4 protein expression in oxidative skeletal muscle is regulated by a lipid-dependent mechanism that is not obligatorily dependent on signalling via PPARalpha.
