This summer, our colleagues published an article in the American Journal of Physiology-Endocrinology and Metabolism with the title: “Post-exercise changes in myocellular lipid droplet characteristics of young lean individuals are affected by circulatory non-esterified fatty acids”. Acute exercise affects intramyocellular lipid (IMCL) storage during exercise and recorvery, particularly in type I muscle fibers, in the subsarcolemmal region and in the presence of PLIN5. Moreover, the effects of exercise on IMCL content are affected by plasma non-esterified fatty acid levels.
The full article can be found here: https://doi.org/10.1152/ajpendo.00654.2020
Read the abstract below:
Intramyocellular lipid (IMCL) content is an energy source during acute exercise. Non-esterified fatty acid (NEFA) levels can compete with IMCL utilization during exercise. IMCL content is stored as lipid droplets (LDs) that vary in size, number, subcellular distribution and in coating with LD protein PLIN5. Little is known about how these factors are affected during exercise and recovery. Here, we aimed to investigate the effects of acute exercise with and without elevated NEFA levels on intramyocellular LD size and number, intracellular distribution and PLIN5 coating, using high-resolution confocal microscopy. In a cross-over study, 9 healthy lean young men performed a 2h moderate intensity cycling protocol in the fasted (high NEFA levels) and glucose-fed state (low NEFA levels). IMCL and LD parameters were measured at baseline, directly after exercise and 4h post-exercise. We found that total IMCL content was not changed directly after exercise (irrespectively of condition), but IMCL increased 4h post-exercise in the fasting condition, which was due to an increased number of LDs rather than changes in size. The effects were predominantly detected in type I muscle fibers and in LDs coated with PLIN5. Interestingly, subsarcolemmal, but not intermyofibrillar IMCL content, was decreased directly after exercise in the fasting condition and was replenished during the 4h recovery period. In conclusion, acute exercise affects IMCL storage during exercise and recovery, particularly in type I muscle fibers, in the subsarcolemmal region and in the presence of PLIN5. Moreover, the effects of exercise on IMCL content are affected by plasma NEFA levels.