Effects of leucine and its metabolite β‐hydroxy‐β‐methylbutyrate on human skeletal muscle protein metabolism

摘要: Maintenance of skeletal muscle mass is contingent upon the dynamic equilibrium (fasted losses–fed gains) in protein turnover. Of all nutrients, single amino acid leucine (Leu) possesses most marked anabolic characteristics acting as a trigger element for initiation synthesis. While mechanisms by which Leu ‘sensed’ have been subject great scrutiny, branched-chain acid, can be catabolized within muscle, thus posing possibility that metabolites could involved mediating effect(s) Leu. Our objective was to measure anabolism response and its metabolite HMB. Using [1,2-13C2]Leu [2H5]phenylalanine tracers, GC-MS/GC-C-IRMS we studied effect HMB or alone on MPS (by tracer incorporation into myofibrils), also measured proteolysis arteriovenous (A–V) dilution). Orally consumed 3.42 g free-acid (FA-HMB) (providing 2.42 pure HMB) exhibited rapid bioavailability plasma and, similarly Leu, stimulated synthesis (MPS; +70%vs. +110%). both increased signalling (mechanistic target rapamycin; mTOR), this more pronounced with (i.e. p70S6K1 ≤90 min vs. ≤30 HMB). consumption attenuated breakdown (MPB; −57%) an insulin-independent manner. We conclude exogenous induces acute (increased reduced MPB) albeit perhaps via distinct, and/or additional mechanism(s)