Elevated fatty acid availability after exercise increases intramyocellular triglyceride content by enhancing capacity for fatty acid flux into skeletal muscle

Abstract

We previously reported a single exercise session protects against fatty acid (FA)‐induced insulin resistance, perhaps via augmented intramyocellular triglyceride (IMTG) synthesis. The aim of this study was to examine the effect of elevated FA availability after exercise on the regulation of IMTG metabolism. After exercise (90min at 65% VO2peak) 7 healthy women (BMI: 23±1 kg/m2) were infused overnight (16h) with either a lipid and heparin solution (LIP; 0.11 g fat/kg/h) or saline (SAL), and we obtained a skeletal muscle sample the next morning. Despite a 4‐fold increase in overnight plasma [FA] during LIP, whole‐body FA oxidation was not elevated (P=0.35). Conversely, IMTG increased by ~30% during LIP vs SAL (49±3 vs 38±3 umol/g dw; P=0.04), accompanied by ~25% greater localization of the FA transporter, CD36 to the muscle membrane (P<0.01) and ~8% increase in the activity of the IMTG synthetic enzyme glycerol‐3‐phosphate acyltransferase (GPAT; P=0.01). We found no difference in GPAT and diacylglycerol acyltransferase (DGAT) protein abundance, or DGAT activity between treatments. Our findings suggest augmented capacity for FA flux into muscle (i.e., via membrane‐bound CD36), perhaps together with a slight, yet significant increase in activity of a key IMTG synthetic enzyme (GPAT) may enhance IMTG storage when FA availability is high after exercise.Supported by NIH Grant #R01 DK071955