lipolytic

Lipolytic is an adjective describing processes, enzymes, or substances that promote lipolysis, the hydrolysis of stored fats (triglycerides) into glycerol and free fatty acids. Lipolysis primarily occurs in adipose tissue but also takes place in muscle and liver, providing substrates for energy production during fasting or stress.

In adipocytes, triglycerides are broken down by a sequence of lipases: adipose triglyceride lipase (ATGL) initiates the reaction to diglycerides, hormone-sensitive lipase (HSL) converts diglycerides to monoglycerides, and monoacylglycerol lipase (MGL) yields glycerol and free fatty acids. Hormonal regulation includes catecholamines (epinephrine and norepinephrine) and glucagon, which raise intracellular cAMP and activate protein kinase A (PKA) to phosphorylate and activate HSL and promote lipolysis. Perilipin A phosphorylation facilitates access of lipases to the lipid droplet. Insulin inhibits lipolysis by lowering cAMP and activating phosphodiesterases; cortisol and thyroid hormones can modulate the rate of lipolysis in response to energy demands.

Lipolytic effects can arise from endogenous mediators or pharmacologic agents, including beta-adrenergic agonists or compounds that increase cellular cAMP in adipocytes. The fatty acids released are transported in the bloodstream bound to albumin and used by tissues for beta-oxidation, while glycerol is largely taken up by the liver for gluconeogenesis or glycerolysis. In clinical and cosmetic contexts, various lipolytic agents are marketed to reduce fat or cellulite, though efficacy and safety vary and should be evaluated critically.