Adipocyte lipases and lipid droplet-associated proteins: insight from transgenic mouse models.

Adipose tissue lipolysis is the catabolic process whereby stored triacylglycerol (TAG) is broken down by lipases into fatty acids and glycerol. Here, we review recent insights from transgenic mouse models. Genetic manipulations affecting lipases are considered first, followed by transgenic models of lipase co-factors and lastly non-lipase lipid droplet (LD)-associated proteins. The central role of hormone-sensitive lipase (HSL), long considered to be the sole rate-limiting enzyme of TAG hydrolysis, has been revised since the discovery of adipose triglyceride lipase (ATGL). It is now accepted that ATGL initiates TAG breakdown producing diacylglycerol, which is subsequently hydrolyzed by HSL. Furthermore, lipase activities are modulated by co-factors whose deletion causes severe metabolic disturbances. Another major advance has come from the description of the involvement of non-lipase proteins in the regulation of lipolysis. The role of perilipins has been extensively investigated. Other newly discovered LD-associated proteins have also been shown to regulate lipolysis.