[Lipid mobilization, physiopathological and pharmacological aspects]

The lipolysis in adipose tissue is controlled by the hormone-sensitive lipase activity which is dependent on the intracellular cAMP level. In human adipose tissue, cAMP level is increased by catecholamines (through beta-adrenoceptor stimulation) or decreased by insulin, catecholamine (through alpha 2-adrenoceptor stimulation), neuropeptide Y, prostaglandins and adenosine. The mobilization of lipids from adipose tissue is an adaptative mechanism in response to starvation or hypocaloric diet, which involves reduction of the antilipolytic effect of insulin and the increase of catecholamine sensitivity. The regulatory pathways of lipolysis and their adaptation to caloric reduction are not defective in obesity state. Pharmacological approaches proposed for the activation of lipolysis are limited; they mainly consist either to stimulate the fat cell beta-adrenoceptors (beta-sympathomimetic drugs) or to indirectly activate the sympathetic nervous system (ephedrine and its derivatives, methylxanthines, alpha 2-antagonists). However, the side effects elicited by these drugs frequently limit their clinical use.