RGD Reference Report - Testosterone signals through mTOR and androgen receptor to induce muscle hypertrophy. - Rat Genome Database

RGD Reference Report - Testosterone signals through mTOR and androgen receptor to induce muscle hypertrophy. - Rat Genome Database

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General

Testosterone signals through mTOR and androgen receptor to induce muscle hypertrophy.
Authors:	Basualto-Alarcon, C Jorquera, G Altamirano, F Jaimovich, E Estrada, M
Citation:	Basualto-Alarcon C, etal., Med Sci Sports Exerc. 2013 Sep;45(9):1712-20. doi: 10.1249/MSS.0b013e31828cf5f3.
RGD ID:	10041029
Pubmed:	PMID:23470307 (View Abstract at PubMed)
DOI:	DOI:10.1249/MSS.0b013e31828cf5f3 (Journal Full-text)
PURPOSE: The anabolic hormone testosterone induces muscle hypertrophy, but the intracellular mechanisms involved are poorly known. We addressed the question whether signal transduction pathways other than the androgen receptor (AR) are necessary to elicit hypertrophy in skeletal muscle myotubes. METHODS: Cultured rat skeletal muscle myotubes were preincubated with inhibitors for ERK1/2 (PD98059), PI3K/Akt (LY294002 and Akt inhibitor VIII) or mTOR/S6K1 (rapamycin), and then stimulated with 100 nM testosterone. The expression of alpha-actin and the phosphorylation levels of ERK1/2, Akt and S6K1 (a downstream target for mTOR) were measured by Western blot. mRNA levels were evaluated by real time RT-PCR. Myotube size and sarcomerization were determined by confocal microscopy. Inhibition of AR was assessed by bicalutamide. RESULTS: Testosterone-induced myotube hypertrophy was assessed as increased myotube cross-sectional area (CSA) and increased alpha-actin mRNA and alpha-actin protein levels, with no changes in mRNA expression of atrogenes (MAFbx and MuRF-1). Morphological development of myotube sarcomeres was evident in testosterone-stimulated myotubes. Known hypertrophy signaling pathways were studied at short times: ERK1/2 and Akt showed an increase in phosphorylation status after testosterone stimulus at 5 and 15 min, respectively. S6K1 was phosphorylated at 60 min. This response was abolished by PI3K/Akt and mTOR inhibition but not by ERK1/2 inhibition. Similarly, the CSA increase at 12 h was abolished by inhibitors of the PI3K/Akt pathway as well as by AR inhibition. CONCLUSIONS: These results suggest a crosstalk between pathways involving fast intracellular signaling and the AR to explain testosterone-induced skeletal muscle hypertrophy.

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Term	Qualifier	Evidence	With	Reference	Notes	Source	Original Reference(s)
positive regulation of skeletal muscle hypertrophy		IMP		10041029		RGD

Objects Annotated

Genes (Rattus norvegicus)

Mtor (mechanistic target of rapamycin kinase)

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