FASTING INCREASES PLASMA-MEMBRANE FATTY-ACID-BINDING PROTEIN (FABP(PM)) IN RED SKELETAL-MUSCLE

The present study was designed to investigate the presence of the fatt y acid-binding protein (FABP(PM)) in the plasma membranes of skeletal muscles with different oxidative capacities for free fatty acid (FFA) oxidation during conditions of normal (fed) or increased (fasted) FFA utilization in the rat. Female Sprague-Dawley rats were either fed or fasted for 12, 24, or 48 h and, plasma membranes (PM) fractions from r ed and white skeletal muscles were isolated. Short-term fasting signif icantly decreased body weight by 11% and blood glucose concentration b y 42% (6.6+/-0.2-3.8+/-0.4 mmol/l) and increased plasma FFA concentrat ion by 5-fold (133+/-14-793+/-81 mu mol/l). Immunoblotting of PM fract ions showed that FABP(PM) protein content was 83+/-18% higher in red t han in white skeletal muscle and correlated with oxidative capacity as measured by succinate dehydrogenase activity (r=0.78, p<0.05). Short- term fasting significantly increased FABP(PM) protein content by 60+/- 8% in red skeletal muscle but no change was measured in white skeletal muscle. These results show that FABP(PM) protein content in skeletal muscle is related to oxidative potential and can be increased during a physiological condition known to be associated with an increase in FF A utilization, suggesting that cellular expression of FABP(PM) may pla y a role in the regulation of FFA metabolism in skeletal muscle.