Lipolytic effect of olive leaf extracts and a major component on mature 3T3‐L1 cells

Abstract

The olive, Olea europaea, is a small tree native to the countries adjoining to areas of eastern Mediterranean basin and southern Caspian Sea. Recent studies showed biological activities such as antioxidative, hypoglycemic, antihypertensive, antiatherosclerotic, and antiadipogenic effects from olive leaves. In this study, we evaluated the effect of olive leaf extract (OLE) on lipolysis in mature 3T3‐L1 cells by examining the levels of free glycerol, triacylglycerol, and lipolytic enzymes. OLE increased the release of free glycerol from triacyglycerol in a dose‐dependent manner. The mRNA expression levels of hormonal sensitive lipase (HSL), adipose triglyceride lipase (ATGL) and perilipin showed no significant differences in the presence and absence of OLE. The protein levels of the major lipolytic enzymes, HSL and ATGL, were not affected by OLE treatment. However, OLE increased the level of phosphorylated HSL, an indicator of lipolytic activation, which led to a decrease in the triacylglycerol level. In addition, oleuropein, a major compound in OLE, decreased the level of triacylglycerol and increased the level of free glycerol, like OLE. The protein levels of HSL, p‐HSL, and ATGL are increased by oleuropein treatment. Our data suggest that oleuropein in OLE stimulates lipolysis through activation of HSL in adipocytes.