The Importance of Fatty Acids as Nutrients during Post-Exercise Recovery

Abstract

It is well recognized that whole-body fatty acid (FA) oxidation remains increased for several hours following aerobic endurance exercise, even despite carbohydrate intake. However, the mechanisms involved herein have hitherto not been subject to a thorough evaluation. In immediate and early recovery (0-4 h), plasma FA availability is high, which seems mainly to be a result of hormonal factors and increased adipose tissue blood flow. The increased circulating availability of adipose-derived FA, coupled with FA from lipoprotein lipase (LPL)-derived very-low density lipoprotein (VLDL)-triacylglycerol (TG) hydrolysis in skeletal muscle capillaries and hydrolysis of TG within the muscle together act as substrates for the increased mitochondrial FA oxidation post-exercise. Within the skeletal muscle cells, increased reliance on FA oxidation likely results from enhanced FA uptake into the mitochondria through the carnitine palmitoyltransferase (CPT) 1 reaction, and concomitant AMP-activated protein kinase (AMPK)-mediated pyruvate dehydrogenase (PDH) inhibition of glucose oxidation. Together this allows glucose taken up by the skeletal muscles to be directed towards the resynthesis of glycogen. Besides being oxidized, FAs also seem to be crucial signaling molecules for peroxisome proliferator-activated receptor (PPAR) signaling post-exercise, and thus for induction of the exercise-induced FA oxidative gene adaptation program in skeletal muscle following exercise. Collectively, a high FA turnover in recovery seems essential to regain whole-body substrate homeostasis.

Keywords: AMP-activated protein kinase (AMPK); adipose tissue lipolysis; carnitine palmitoyltransferase I (CPT1); fatty acid oxidation; lipid metabolism; lipoprotein lipase (LPL); molecular mechanism; post-exercise recovery; pyruvate dehydrogenase (PDH); skeletal muscle.

Figure 1

Representative illustration of plasma fatty acid (FA) (A) and glycerol (B) concentrations during moderate-intensity exercise (80 min to 4 h at 40%–70% of maximal oxygen consumption rate (VO₂peak)) and in early recovery in endurance-trained subjects. Subjects remained fasted in recovery. The scatter plots are based on data in references [3,6,12,13,18].