A single bout of strenuous exercise overcomes lipid-induced anabolic resistance to protein ingestion in overweight, middle-aged men

High-circulating lipid availability attenuates protein feeding–inducedmuscle protein synthesis (MPS). Whether the combined effects of exercise and proteiningestion can rescue this inhibition isunknown. Ina parallelgroups design,middle-aged sedentarymales (n = 28) matched for fat-freemass and bodymass index received a 5-h intravenous infusion of either saline/control (n = 9), 20%intralipid infusion (n = 9), or intralipid with concomitant exercise (n = 10). Two hours into each of these infusions, participants received a primed constant infusion of L-(ring-[13C]6)-phenylalanine.Muscle biopsies were taken immediately after control and lipid infusions, at which time, a 30-g protein beveragewas ingested. Further biopsies were taken 2 and 4 h after protein ingestion. Intralipid increased plasma free fatty acid concentrations from ∼0.4–2 mM, resulting in an attenuated MPS response to protein ingestion, which was prevented by exercise. Intralipid resulted in a lower peak aminoacidemia following protein ingestion that was exacerbated by prior exercise, suggesting efficiency of the working skeletal muscle to utilize amino acid substrate to drive the postprandial anabolic response. We conclude that in the face of highfat availability, exercise preserves the sensitivity of skeletalmuscle to the anabolic properties of aminoacids.