Mechanism of Increase in Basal Lipolysis of Enlarged Adipocytes in Obese Animals

Abstract

Sonication of rat fat cells caused an increase in lipolysis in the absence of lipolytic hormones (basal lipolysis) and loss of epinephrine responsiveness. Sonication of endogenous lipid droplets from fat cells also induced an increase in lipolysis in the presence of HSL. Addition of phosphatidylcholine to the sonicated lipid droplets reduced the hydrolysis of triglyceride by HSL. These results suggest that the active HSL is already present in the fat cell even in the absence of lipolytic hormone, and phosphatidylcholine on the surface of endogenous lipid droplets causes inhibition toward lipolytic action of HSL. The decrease in the surface phosphatidylcholine concentration in endogenous lipid droplets was proved to cause the increase in basal lipolysis. It is demonstrated that basal lipolysis was elevated in the enlarged fat cells of obese rats by reduction of surface phosphatidylcholine concentration of the endogenous lipid droplets. 1995 North American Association for the Study of Obesity (NAASO)