Fatty acid binding protein 4 in human skeletal muscle.

The mechanisms that regulate intramyocellular triglycerol (IMTG) storage and mobilization are largely unknown. However, during the last decades several intracellular fatty acid binding proteins (FABPs) have been identified. FABP3 is the dominating FABP in skeletal muscle. Expression of additional FABPs is suggested from findings in FABP3-null mutated mice. In the present study, our aims were to investigate if FABP4 is expressed within skeletal muscle fibers and if FABP3 and FABP4 are more abundant in skeletal muscle fibers in endurance-trained than in control subjects. We show that FABP4 protein is expressed within the skeletal muscle fibers and that FABP4 mRNA and protein are more abundant in the endurance trained subjects. Still, FABP4 is markedly less expressed than FABP3, which is the generally accepted dominating FABP in skeletal muscle tissue.