Regulation of lipolytic activity by long-chain acyl-coenzyme A in islets and adipocytes

Intracellular lipolysis is a major pathway of lipid metabolism that has roles, not only in the provision of free fatty acids as energy substrate, but also in intracellular signal transduction. The latter is likely to be particularly important in the regulation of insulin secretion from islet β-cells. The mechanisms by which lipolysis is regulated in different tissues is, therefore, of considerable interest. Here, the effects of long-chain acyl-CoA esters (LC-CoA) on lipase activity in islets and adipocytes were compared. Palmitoyl-CoA (Pal-CoA, 1–10 μM) stimulated lipase activity in islets from both normal and hormone-sensitive lipase (HSL)-null mice and in phosphatase-treated islets, indicating that the stimulatory effect was neither on HSL nor phosphorylation dependent. In contrast, we reproduced the previously published observations showing inhibition of HSL activity by LC-CoA in adipocytes. The inhibitory effect of LC-CoA on adipocyte HSL was dependent on phosphorylation and enhanced by acyl-CoA-bindi...