Adipogenic activity in sera from obese children before and after weight reduction.

The adipogenic and mitogenic potentials of sera obtained from obese children before and after weight reduction and from lean control subjects were studied in clonal 3T3 L1 fibroblasts. The sera from the lean (n = 14) and obese (n = 12) children under habitual diet contained similar adipogenic activity. However, when the obese children underwent a weight-reduction program for 3 wk (600 kcal/d), the potential of their sera to stimulate glycero-phosphate dehydrogenase, an index of adipogenic activity, was significantly reduced by 32% (p less than 0.01). Similarly, the mitogenic activity of these sera decreased significantly (202 +/- 15 vs 231 +/- 27 micrograms per dish, p less than 0.01). Testing pooled sera from the different groups in cultured rat adipocyte precursor cells gave similar results. This study suggests that human childhood-onset obesity is not accompanied by increased circulatory factors involved in the formation of new fat cells. The adipogenic and mitogenic activity of sera from obese children may be influenced by long-term dietary restriction.