Whey Peptides Intake activates mTOR Signaling after Resistance Exercise Independent of Sex and Menstrual Cycle: 2264 Board #100 June 1 9

PURPOSE: Sex differences are evident in human skeletal muscle as the cross-sectional area of individual muscle fibers is greater in men than in women. In addition, the female steroid hormone fluctuates during menstrual cycle phase. We have recently shown that whey peptides intake after resistance exercise stimulates mammalian target of rapamycin (mTOR) signaling related to protein synthesis in young men. Therefore, the purpose of this study was to determine the effects of sex and menstrual cycle on mTOR signaling following resistance exercise and whey peptide intake. METHODS: Young healthy, recreationally active men (n=7) and women (n=16) performed a bout of one- leg isokinetic knee extension exercise (angular degree; 30°/sec, 6 reps. × 4 sets). Immediately after exercise, all subjects took a whey peptide drink (0.19 g/kg). At resting and 1h post-exercise, muscle samples were taken from vastus lateralis using needle biopsy technique. Phosphorylations of mTOR signaling transducers (mTOR, S6K1, 4E-BP1) was analyzed by western blotting. At rest, 30 min and 60 min post-exercise, blood amino acids and insulin concentrations were measured. RESULTS: Peak torques during resistance exercise was significantly greater in men than in women (p<0.05), but the relative value (% MVC) was the same between men and women. Blood amino acids and insulin concentration were significantly increased at 30 min after whey peptide intake (p<0.05), but there was no effect of sex and menstrual cycle. The phosphorylation of mTOR, S6K1 and 4E-BP1 after resistance exercise and whey peptide intake was significantly increased compared with that in the rest (p<0.05), but there was no effect of sex and menstrual cycle. CONCLUSIONS: Our data suggest that sex and menstrual cycle do not affect mTOR signaling in response to whey peptide intake after resistance exercise in human skeletal muscle. Supported by MEXT-Supported Program for the Strategic Research Foundation at Private Universities, 2014-2018.