ADIPOCYTE DIFFERENTIATION AND LEPTIN EXPRESSION

Adipose tissue has long been known to house the largest energy reserve s in the animal body. Recent research indicates that in addition to th is role, the adipocyte functions as a global regulator of energy metab olism. Adipose tissue is exquisitely sensitive to a variety of endocri ne and paracrine signals, e.g. insulin, glucagon, glucocorticoids, and tumor necrosis factor (TNF), that combine to control both the secreti on of other regulatory factors and the recruitment and differentiation of new adipocytes. The process of adipocyte differentiation is contro lled by a cascade of transcription factors, most notably those of the C/EBP and PPAR families, which combine to regulate each other and to c ontrol the expression of adipocyte-specific genes. One such gene, i.e. the obese gene, was recently identified and found to encode a hormone , referred to as leptin, that plays a major role in the regulation of energy intake and expenditure. The hormonal and transcriptional contro l of adipocyte differentiation is discussed, as is the role of leptin and other factors secreted by the adipocyte that participate in the re gulation of adipose homeostasis.