HORMONES AND ADIPOSE-TISSUE DEVELOPMENT

Dormant preadipocytes isolated from adipose tissue are able to differe ntiate into adipocytes in vitro. A few adipogenic hormones (glucocorti coids or prostacyclin, IGF-I and insulin) are sufficient to trigger th e differentiation program. In preadipose and adipose cells, glucocorti coids play a cardinal role by regulating the expression of numerous ge nes and by increasing the production of prostacyclin which acts as an intracrine/autocrine/paracrine effector. Fatty acids and metabolites ( including prostacyclin) enhance adipocyte differentiation via the acti vation of nuclear peroxisome proliferator-activated receptors (PPARs). PPARs then modulate positively the expression of various lipid-relate d genes involved in triacylglycerol accumulation. These in vitro obser vations emphasize the importance of the hypothalamic-pituitary-adrenal axis and provide also a link which may take place in vivo between hig h-fat diets and the excess of adipose tissue development.