title: The expression of androgen-regulated genes before and after a resistance exercise bout in younger and older men.
abstract: This cross-sectional study examined aging and resistance exercise-related changes in intramuscular gene expression in younger (21.3 +/- 0.6 years, 84.8 +/- 6.0 kg, 26.6 +/- 2.1 kg x m(-2); n = 11) and older men (67.6 +/- 1.3 years, 88.7 +/- 4.8 kg, 28.6 +/- 1.4 kg x m(-2); n = 13) surrounding a single bout of resistance exercise. Participants completed 3 x 10 repetitions at 80% of their 1 repetition maximum for Smith squat, leg press, and leg extension. Muscle biopsies were obtained before and 24 hours after exercise, whereas venous blood was collected before, immediately after and 24 hours after exercise. Free testosterone levels were greater in younger participants at all time points (p < 0.05), in addition to a greater increase in the younger men immediately post exercise (p < 0.01). Preexercise human growth hormone levels between age groups were similar (p > 0.05). Human growth hormone increased immediately post exercise in both groups (p < 0.05) with a greater response occurring in the younger (p < 0.001) men. Older men expressed greater levels of androgen receptor (AR) at rest (p = 0.02). A significant correlation existed between preexercise free testosterone levels basal AR gene expression (r = -0.59, p < 0.01). These data suggest that AR expression patterns may be related to circulating free testosterone levels. Although these findings do not fully unveil the genomic effects of androgen signaling and its relationship to muscle wasting conditions, these results provide a platform for future researchers seeking to employ gene therapy to remedy muscle loss.
authors.affiliation: Applied Biochemistry and Molecular Physiology Laboratory, Health and Exercise Science Department, University of Oklahoma, Norman, Oklahoma, USA.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Roberts
authors.forename: Vincent J
authors.initials: VJ
authors.lastname: Dalbo
authors.forename: Scott E
authors.initials: SE
authors.lastname: Hassell
authors.forename: Chad M
authors.initials: CM
authors.lastname: Kerksick
mesh_terms: D000368:Aged; D000375:Aging / Q000097:blood / Q000235:genetics / Q000378:metabolism*; D015415:Biomarkers / Q000097:blood; D001706:Biopsy; D003430:Cross-Sectional Studies; D015444:Exercise / Q000502:physiology*; D015870:Gene Expression; D019382:Human Growth Hormone / Q000097:blood*; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D011944:Receptors, Androgen / Q000235:genetics / Q000378:metabolism*; D013739:Testosterone / Q000097:blood*; D055815:Young Adult
chemical_list: D015415:Biomarkers; D011944:Receptors, Androgen; D019382:Human Growth Hormone; D013739:Testosterone