title: Testosterone modulates gene expression pathways regulating nutrient accumulation, glucose metabolism and protein turnover in mouse skeletal muscle.
abstract: Testosterone regulates energy metabolism and skeletal muscle mass in males, but the molecular mechanisms are not fully understood. This study investigated the response of skeletal muscle to castration and testosterone replacement in 8-week-old male mice. Using microarray analyses of mRNA levels in gastrocnemius muscle, 91 genes were found to be negatively regulated by testosterone and 68 genes were positively regulated. The mRNA levels of the insulin signalling suppressor molecule Grb10 and the glycogen synthesis inhibitors, protein phosphatase inhibitor-1 and phosphorylase kinase-γ, were negatively regulated by testosterone. The insulin-sensitive glucose and amino acid transporters, Glut3 and SAT2, the lipodystrophy gene, Lpin1 and protein targeting to glycogen were positively regulated. These changes would be expected to increase nutrient availability and sensing within skeletal muscle, increase metabolic rate and carbohydrate utilization and promote glycogen accumulation. The observed positive regulation of atrogin-1 (Fbxo32) by testosterone could be explained by the phosphorylation of Akt and Foxo3a, as determined by Western blotting. Testosterone prevented the castration-induced increase in interleukin-1α, the decrease in interferon-γ and the atrophy of the levator ani muscle, which were all correlated with testosterone-regulated gene expression. These findings identify specific mechanisms by which testosterone may regulate skeletal muscle glucose and protein metabolism.
authors.affiliation: Geriatric Research, Education and Clinical Center (GRECC), St Louis Veterans Affairs Medical Center, St Louis, MO 63125, USA.
authors.forename: M T
authors.initials: MT
authors.lastname: Haren
authors.forename: A M
authors.initials: AM
authors.lastname: Siddiqui
authors.forename: H J
authors.initials: HJ
authors.lastname: Armbrecht
authors.forename: R T
authors.initials: RT
authors.lastname: Kevorkian
authors.forename: M J
authors.initials: MJ
authors.lastname: Kim
authors.forename: M J
authors.initials: MJ
authors.lastname: Haas
authors.forename: A
authors.initials: A
authors.lastname: Mazza
authors.forename: Vijaya B
authors.initials: VB
authors.lastname: Kumar
authors.forename: M
authors.initials: M
authors.lastname: Green
authors.forename: W A
authors.initials: WA
authors.lastname: Banks
authors.forename: J E
authors.initials: JE
authors.lastname: Morley
mesh_terms: D000123:Acetyltransferases / Q000235:genetics; D000818:Animals; D051383:GRB10 Adaptor Protein / Q000235:genetics; D015870:Gene Expression; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D005947:Glucose / Q000378:metabolism*; D051274:Glucose Transporter Type 3 / Q000235:genetics; D007371:Interferon-gamma / Q000235:genetics; D053582:Interleukin-1alpha / Q000235:genetics; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics; D008297:Male; D051379:Mice; D009124:Muscle Proteins / Q000235:genetics; D018482:Muscle, Skeletal / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics; D009919:Orchiectomy; D010711:Phosphatidate Phosphatase; D010764:Phosphorylase Kinase / Q000235:genetics; D011506:Proteins / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D011897:Random Allocation; D020133:Reverse Transcriptase Polymerase Chain Reaction; D044843:SKP Cullin F-Box Protein Ligases / Q000235:genetics; D015398:Signal Transduction; D013739:Testosterone / Q000008:administration & dosage* / Q000097:blood; D000099228:Diamine N-Acetyltransferase
chemical_list: D000123:Acetyltransferases; D051383:GRB10 Adaptor Protein; D005947:Glucose; D051274:Glucose Transporter Type 3; D007371:Interferon-gamma; D053582:Interleukin-1alpha; D047908:Intracellular Signaling Peptides and Proteins; D009124:Muscle Proteins; D009687:Nuclear Proteins; D010711:Phosphatidate Phosphatase; D010764:Phosphorylase Kinase; D011506:Proteins; D012333:RNA, Messenger; D044843:SKP Cullin F-Box Protein Ligases; D013739:Testosterone; D000099228:Diamine N-Acetyltransferase; C495689:Slc2a3 protein, mouse; C021042:protein phosphatase inhibitor-1; C486691:Fbxo32 protein, mouse; C418978:Lpin1 protein, mouse