Regulation of triglyceride metabolism. IV. Hormonal regulation of lipolysis in adipose tissue.

Triacylglycerol (TAG) stored in adipose tissue can be rapidly mobilized by the hydrolytic action of lipases, with the release of fatty acids (FA) that are used by other tissues during times of energy deprivation. Unlike synthesis of TAG, which occurs not only in adipose tissue but also in other tissues such as liver for very-low-density lipoprotein formation, hydrolysis of TAG, lipolysis, predominantly occurs in adipose tissue. Until recently, hormone-sensitive lipase was considered to be the key rate-limiting enzyme responsible for regulating TAG mobilization. However, recent studies on hormone-sensitive lipase-null mice have challenged such a concept. A novel lipase named desnutrin/ATGL has been recently discovered to play a key role in lipolysis in adipocytes. Lipolysis is under tight hormonal regulation. Although opposing regulation of lipolysis in adipose tissue by insulin and catecholamines is well understood, autocrine/paracrine factors may also participate in its regulation. Intricate cooperation of these endocrine and autocrine/paracrine factors leads to a fine regulation of lipolysis in adipocytes, needed for energy homeostasis. In this review, we summarize and discuss the recent progress made in the regulation of adipocyte lipolysis.