FAT/CD36 regulates PEPCK expression in adipose tissue.

Fatty acid translocase (FAT)/CD36 has been extensively studied for its role in facilitating fatty acid uptake. Recent findings have also demonstrated that this protein regulates adipocyte lipolysis and may modulate fatty acid reesterification. As FAT/CD36 has been shown to control the expression of genes involved in fatty acid oxidation in adipocytes, we reasoned that this protein might also control the expression of enzymes involved in fatty acid reesterification. In adipose tissue from FAT/CD36 knockout (KO) mice, we found that glycerol and fatty acid release were reduced and this was associated with reductions in adipose triglyceride lipase. Decreases in lipolysis were paralleled by increases in the free fatty acid-to-glycerol ratio and reductions in primary and fractional rates of fatty acid reesterfication in cultured adipose tissue from FAT/CD36 KO mice. Reductions in reesterfication were associated with decreases in the mRNA expression and protein content of phosphoenolpyruvate carboxykinase (PEPCK). To determine if reductions in lipolysis could lead to decreases in PEPCK mRNA expression, we treated cultured mouse adipose tissue with the lipase inhibitor CAY10499 (2 μM) and found that this resulted in an ∼50% reduction in PEPCK mRNA expression. Treatment with hexarelin (10 μM, 12 h), a CD36 agonist, increased PEPCK mRNA expression independent of lipolysis. Collectively, our results provide novel evidence that FAT/CD36 regulates PEPCK in adipose tissue and that this could be secondary to reductions in lipolysis.