Fatty acids liberated from high-density lipoprotein phospholipids by endothelial-derived lipase are incorporated into lipids in HepG2 cells.

We previously reported that endothelial-derived lipase (EDL) efficiently hydrolyses high-density-lipoprotein-derived phosphatidycholine (HDL-PC). In the present study, we assessed the ability of EDL to supply HepG2 cells with non-esterified fatty acids (NEFA) liberated from HDL-phospholipids. For this purpose, HepG2 cells infected with adenovirus encoding human EDL (EDL-Ad), or with control beta-galactosidase-expressing adenovirus (LacZ-Ad), were incubated with (14)C-HDL-PC.

Hormone-sensitive lipase deficiency in mice causes diglyceride accumulation in adipose tissue, muscle, and testis.

Hormone-sensitive lipase (HSL) is expressed predominantly in white and brown adipose tissue where it is believed to play a crucial role in the lipolysis of stored triglycerides (TG), thereby providing the body with energy substrate in the form of free fatty acids (FFA). From in vitro assays, HSL is known to hydrolyze TG, diglycerides (DG), cholesteryl esters, and retinyl esters. In the current study we have generated HSL knock-out mice and demonstrate three lines of evidence that HSL is instrumental in the catabolism of DG in vivo.