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Gene Profiling of Testosterone-Regulated Genes in the Skeletal Muscle of Hiv-Infected Men Experiencing Weight Loss

ABSTRACT: Context: Although androgen treatment increases muscle mass in HIV-infected men, the underlying mechanisms are poorly understood. Analysis of genome-wide microarray data obtained from skeletal muscle biopsies can be used to profile androgen-regulated pathways. Objective: To identify genes and pathways associated with testosterone treatment and myogenesis in the context of HIV-infected men using genome-wide microarray analysis of skeletal muscle biopsies. Results: A significant weight gain was observed in subjects treated with testosterone compared to placebo (+2.05 kgs and –1.07 kgs, respectively; P = 0.003) as well as gains in DEXA lean mass (2.93 kgs vs. 0.35 kgs, respectively; P = 0.003). Microarray expression profiles and RTPCR validation of RNA after 14 days of treatment indicated that several gene sets including transcriptional control, myogenesis, adipogenesis, insulin signaling, apoptosis, cell cycle, chromatin remodeling, and stress response genes were differentially expressed with testosterone treatment. Protein expression analysis of myogenic differentiation and protein synthesis markers (MyoD, Myogenin, phosphorylated p38 MAPK and phosphorylated AKT) in muscle biopsies and skeletal muscle cells treated with DHT confirmed that testosterone engages a network of pro-myogenic genes. Conclusions: Testosterone-associated gain in muscle mass in HIV-infected men engaged a network of regulatory pathways involved in broad transcriptional control, myogenesis, insulin signaling, chromatin remodeling, and stress response. Further evaluation of precise signaling intermediates within androgen regulated pathways may help to better define improvements in muscle mass, both in healthy and HIV infected patients. Keywords: Dose Response, Myogenesis

ORGANISM(S): Homo sapiens

PROVIDER: GSE5106 | GEO | 2007/08/29

SECONDARY ACCESSION(S): PRJNA95367

REPOSITORIES: GEO

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Project description:Context: Although androgen treatment increases muscle mass in HIV-infected men, the underlying mechanisms are poorly understood. Analysis of genome-wide microarray data obtained from skeletal muscle biopsies can be used to profile androgen-regulated pathways. Objective: To identify genes and pathways associated with testosterone treatment and myogenesis in the context of HIV-infected men using genome-wide microarray analysis of skeletal muscle biopsies. Results: A significant weight gain was observed in subjects treated with testosterone compared to placebo (+2.05 kgs and â??1.07 kgs, respectively; P = 0.003) as well as gains in DEXA lean; mass (2.93 kgs vs. 0.35 kgs, respectively; P = 0.003). Microarray expression profiles and RTPCR validation of RNA after 14 days of treatment indicated that several gene sets including; transcriptional control, myogenesis, adipogenesis, insulin signaling, apoptosis, cell cycle, chromatin remodeling, and stress response genes were differentially expressed with testosterone treatment. Protein expression analysis of myogenic differentiation and protein synthesis markers (MyoD, Myogenin, phosphorylated p38 MAPK and phosphorylated AKT) in muscle biopsies and skeletal muscle cells treated with DHT confirmed that testosterone engages; a network of pro-myogenic genes. Conclusions: Testosterone-associated gain in muscle mass in HIV-infected men engaged a network of regulatory pathways involved in broad transcriptional control, myogenesis, insulin signaling, chromatin remodeling, and stress response. Further evaluation of precise signaling intermediates within androgen regulated pathways may help to better define improvements in muscle mass, both in healthy and HIV infected patients. Experiment Overall Design: Design, Setting, and Participants: 44 HIV+ men with weight loss were randomized to receive either 300mg testosterone enanthate or placebo injections IM weekly for 16 weeks. Muscle Experiment Overall Design: biopsies were obtained at baseline and on treatment day 14. A random subset of specimens was chosen for microarray analysis; changes in selected genes were confirmed by reverse transcriptase - polymerase chain reaction (RT-PCR), and western blot analysis. Human skeletal Experiment Overall Design: myogenic precursor cells (SkMCs) were cultured in vitro in the presence of dihydrotestosterone (DHT) to evaluate activation of myogenic protein expression. Experiment Overall Design: Main outcome measures: Relative RNA levels in skeletal muscle biopsies were measured by expression profiling with microarrays and expression levels were validated in samples using quantitative RT-PCR. Further confirmation of changes in key myogenic biomarkers was obtained in DHT treated SkMCs.

Project description:Glucocorticoids are a well recognized and common cause of muscle atrophy. Glucocorticoid-induced atrophy can be prevented by testosterone, but the molecular mechanisms underlying such protection have not been described. Thus, the global effects of testosterone on dexamethasone-induced changes in gene expression were evaluated in rat gastrocnemius muscle using Affymetrix 230_2 DNA microarrays. Gene expression was analyzed after 7 days administration of dexamethasone, dexamethasone plus testosterone, or vehicle. Effects of these agents on weights of gastrocnemius muscles from these animals has been reported (1. Zhao W, Pan J, Zhao Z, Wu Y, Bauman WA, and Cardozo CP. Testosterone protects against dexamethasone-induced muscle atrophy, protein degradation and MAFbx upregulation. J Steroid Biochem Mol Biol 110: 125-129, 2008.) Dexamethasone changed expression of 876 probe sets by at least 2-fold, of which 474 probe sets were changed by at least two fold in the opposite direction in the dexamethasone plus testosterone group (genes in opposition). Major biological themes represented by genes in opposition included IGF-1 signaling, protein synthesis, myogenesis and muscle development, and ubiquitin conjugases and ligases. Testosterone blocked increased expression of DDIT4 and eIF4EBP1, FOXO1 and of the p85 regulatory subunit of the IGF-1 receptor, while preventing decreased expression of IRS-1. Testosterone blocked decreased expression of LXR and suppressed upregulation of C/EBP beta and delta. Testosterone prevented increase expression of Cdkn1A (p21) and decrease expression of cyclins B and D, as well as many other changes that would be expected to reduce cell cycle progression. Testosterone prevented increased expression of muscle development factors Csrp3 and Mbn1 and blocked reduced expression of Wnt4. These data suggest that testosterone blocks multiple changes in gene expression that, collectively, would otherwise downregulate molecular signals that promote protein synthesis and muscle hypertrophy and that stimulate muscle protein catabolism. Experiment Overall Design: Rats (250 g males) were administered dexamethasone (0.7 mg/kg/day) alone or with testosterone (20 mg/kg/day) dissolved in vehicle (propylene glycol) by continuous infusion (Alzet pumps) for 7 days. Control animals were administered vehicle only. Gene expression was compared among the 3 groups at 7 days using one chip per animal, 3 animals per group.

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Gene Profiling of Testosterone-Regulated Genes in the Skeletal Muscle of Hiv-Infected Men Experiencing Weight Loss

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