The role of growth hormone/insulin-like growth factors in adipocyte differentiation

Growth of the adipose tissue results from both the enlargement of mature adipocytes and the formation of new adipocytes from adipocyte precursor cells. The differentiation process of adipocyte precursor cells is controlled by a variety of hormones. Clinical observations indicate that growth hormone (GH) and insulin-like growth factor I (IGF-I) are able to influence the growth of the adipose organ. Recent in vitro studies using cultures of clonal and primary adipocyte precursor cells have elucidated the role of GH and IGF-I in adipocyte differentiation. From the studies it can be concluded that GH is able to enlarge the pool of adipocyte precursor cells capable of differentiating into mature adipocytes, which occurs under the control of other adipogenic hormones. However, due to its metabolic action, GH is also able to reduce the volume of mature adipocytes and thus the net result of its biological action is aimed at reducing body fat. IGF-I stimulates the differentiation process by inducing critical cell divisions of adipocyte precursor cells necessary for their differentiation. IGF-I, which is known to be regulated by GH and several nutritional factors, may exert its effects in the adipose tissue in an autocrine/paracrine and endocrine way. This review summarizes the results of recent studies investigating the role of GH and IGF-I in adipocyte differentiation.