Voluntary running, skeletal muscle gene expression, and signaling inversely regulated by orchidectomy and testosterone replacement.
Declines in skeletal muscle size and strength, often seen with chronic wasting diseases, prolonged or high-dose glucocorticoid therapy, and the natural aging process in mammals, are usually associated with reduced physical activity and testosterone levels. However, it is not clear whether the decline in testosterone and activity are causally related. Using a mouse model, we found that removal of endogenous testosterone by orchidectomy results in an almost complete cessation in voluntary wheel running but only a small decline in muscle mass. Testosterone replacement restored running behavior and muscle mass to normal levels. Orchidectomy also suppressed the IGF-I/Akt pathway, activated the atrophy-inducing E3 ligases MuRF1 and MAFBx, and suppressed several energy metabolism pathways, and all of these effects were reversed by testosterone replacement. The study also delineated a distinct, previously unidentified set of genes that is inversely regulated by orchidectomy and testosterone treatment. These data demonstrate the necessity of testosterone for both speed and endurance of voluntary wheel running in mice and suggest a potential mechanism for declined activity in humans where androgens are deficient.
Department of Musculoskeletal Diseases, Novartis Institutes for Biomedical Research, Cambridge, MA 02139, USA.
Chikwendu
C
Ibebunjo
John K
JK
Eash
Christine
C
Li
QiCheng
Q
Ma
David J
DJ
Glass
D019412:Anatomy, Cross-Sectional; D000818:Animals; D015153:Blotting, Western; D001835:Body Weight / Q000502:physiology; D004435:Eating; D004734:Energy Metabolism / Q000187:drug effects / Q000502:physiology; D015870:Gene Expression / Q000502:physiology*; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis / Q000235:genetics; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D046228:Microarray Analysis; D009043:Motor Activity / Q000502:physiology*; D018485:Muscle Fibers, Skeletal / Q000502:physiology; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000166:cytology / Q000378:metabolism*; D009919:Orchiectomy; D009929:Organ Size / Q000502:physiology; D010807:Physical Endurance / Q000502:physiology; D012313:RNA / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012420:Running / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D013739:Testosterone / Q000097:blood / Q000494:pharmacology*
D013739:Testosterone; D012313:RNA; D007334:Insulin-Like Growth Factor I