Lipolysis and lipases in white adipose tissue – An update

Abstract

Lipolysis is defined as the sequential hydrolysis of triacylglycerol (TAG) stored in cell lipid droplets. For many years, it was believed that hormone-sensitive lipase (HSL) and monoacylglycerol lipase (MGL) were the main enzymes catalyzing lipolysis in the white adipose tissue. Since the discovery of adipose triglyceride lipase (ATGL) in 2004, many studies were performed to investigate and characterize the actions of this lipase, as well as of other proteins and possible regulatory mechanisms involved, which reformulated the concept of lipolysis. Novel findings from these studies include the identification of lipolytic products as signaling molecules regulating important metabolic processes in many non-adipose tissues, unveiling a previously underestimated aspect of lipolysis. Thus, we present here an updated review of concepts and regulation of white adipocyte lipolysis with a special emphasis in its role in metabolism homeostasis and as a source of important signaling molecules. Metab. 2015;59(4):335-42 Arch Endocrinol

Exercise‐induced α‐ketoglutaric acid stimulates muscle hypertrophy and fat loss through OXGR1‐dependent adrenal activation

“…As we observed in chow‐fed mice, AKG increased BAT expression of thermogenic genes including UCP1, Dio2, and Cidea, suggesting upregulation of BAT thermogenesis. Similar AKG‐induced WAT lipolysis was also indicated by upregulated RER and increased expression of ATGL and p‐HSL, the main enzymes catalyzing lipolysis in WAT (Bolsoni‐Lopes & Alonso‐Vale, ). These results suggest that the water supplement of AKG prevents DIO by increasing BAT thermogenesis and WAT lipolysis.…”

The herbicide quinclorac as potent lipase inhibitor: Discovery via virtual screening and in vitro/in vivo validation

“…Quinclorac was tested in vitro against the lipase activity of rat epididymal fat pads (which essentially resemble MGL and HSL lipase activities (Bolsoni‐Lopes & Alonso‐Vale, )). Rat HSL and MGL are homologous to human HSL and MGL with 83% and 84.2% sequence identities, respectively (Langin, Laurell, Holst, Belfrage, & Holm, ; Scalvini et al., ), and can therefore be adequately used as models of human lipases (Taha et al., ).…”

“…On the other hand, the remaining less toxic compounds (namely, quinmerac, tetrafluoron, dichlormate, and karbutilate) were not tested because they are significantly inferior vis-à-vis their docking/scoring values compared to quinclorac. Quinclorac was tested in vitro against the lipase activity of rat epididymal fat pads (which essentially resemble MGL and HSL lipase activities (Bolsoni-Lopes & Alonso-Vale, 2015)). Rat HSL and MGL are homologous to human HSL and MGL with 83% and 84.2% sequence identities, respectively (Langin, Laurell, Holst, Belfrage, & Holm, 1993;Scalvini et al, 2016), and can therefore be adequately used as models of human lipases (Taha et al, 2008).…”

“…Elevated level of circulating free fatty acids (FFA) is linked to insulin resistance, type II diabetes mellitus, and neuroinflammation (Arner & Langin, 2014). FFA are released from adipose triglyceride stores into the circulation by lipolytic process which is tightly controlled by hormone-sensitive lipase (HSL) and monoglyceride lipase (MGL) (Bolsoni-Lopes & Alonso-Vale, 2015). Hormone-sensitive lipase catalyzes the hydrolysis of triglycerides and diglycerides, whereas MGL is required for complete hydrolysis of monoglycerides (Bolsoni-Lopes & Alonso-Vale, 2015;Lass, Zimmermann, Oberer, & Zechner, 2011).…”

“…FFA are released from adipose triglyceride stores into the circulation by lipolytic process which is tightly controlled by hormone-sensitive lipase (HSL) and monoglyceride lipase (MGL) (Bolsoni-Lopes & Alonso-Vale, 2015). Hormone-sensitive lipase catalyzes the hydrolysis of triglycerides and diglycerides, whereas MGL is required for complete hydrolysis of monoglycerides (Bolsoni-Lopes & Alonso-Vale, 2015;Lass, Zimmermann, Oberer, & Zechner, 2011). Therefore, the combined action of HSL and MGL is essential to accomplish complete degradation of the stored triglyceride to FFA and glycerol (Bolsoni-Lopes & Alonso-Vale, 2015;Fredrikson, Tornqvist, & Belfrage, 1986).…”