Skeletal muscle lipid droplets are resynthesized before being coated with perilipin proteins following prolonged exercise in elite male triathletes

摘要

The location of intramuscular triglyceride (IMTG)-contain-ing lipid droplets (LD) in close proximity to mitochondria underpins the importance of IMTG as a fuel source during prolonged moderate-intensity exercise in trained individuals, particularly in type I muscle fibers (36). Indeed, many studies report a decrease in IMTG content during exercise (16, 35), but to date there has been much less focus on postexercise IMTG resynthesis. This is in contrast to the large body of research that has focused on glycogen use during exercise and dietary strategies to optimize glycogen repletion following exercise (5). High carbohydrate (CHO) diets, however, are reciprocally low in fat (typically 2-25% of total energy intake) and markedly reduce IMTG storage (9, 15, 33). Indeed, postexercise IMTG resynthesis is suppressed up to 48 h following 3 h moderate-intensity cycling when consuming a high CHO diet (containing 24% fat) (36). More recently though, postexercise nutritional strategies have shifted toward CHO or calorie restriction in an attempt to augment specific training adaptations in human skeletal muscle. In this respect, limiting CHO or energy intake following glycogen-depleting exercise has been shown to enhance the activation of intracellular signaling pathways compatible with mitochondrial biogenesis (reviewed in 13). Typically, in these studies, CHO or energy provision is limited throughout exercise as well as during the first few hours following exercise, after which habitual energy and macronu-trient intake are resumed. Whether this nutritional strategy, designed to augment skeletal muscle training adaptations, can also accelerate postexercise IMTG resynthesis is yet to be investigated.