Transcriptional Regulation of the Human Hepatic Lipase Gene: Relation to Glucose and Lipid Metabolism

Abstract

Hepatic Lipase (HL; EC 3.1.1.3) is an extracellular glycoprotein with phospholipase A1 and triacylglycerol hydrolase activity. The human HL protein is encoded by the LIPC gene on chromosome 15q21. Most of this protein is synthesized in the parenchymal cells of the liver and secreted into the space of Disse where it binds to heparin sulfate proteoglycans. Some synthesis of HL was also observed in macrophages. The HL protein is also present in the steroidogenic adrenal glands, ovaries and, in small amounts, in the testes. By using heparin, HL protein is displaced from its binding site. Human HL protein is a homodimer, the monomer has a molecular weight of 65 kDa. In the metabolism of plasma lipoproteins HL plays an important role; it mediates the conversion of high density lipoprotein subfraction 2 (HDL2) to high density lipoprotein subfraction 3 (HDL3), the conversion of intermediate density lipoprotein (IDL) to low density l