CONCENTRATIONS OF ADIPSIN IN BLOOD AND RATES OF ADIPSIN SECRETION BY ADIPOSE-TISSUE IN HUMANS WITH NORMAL, ELEVATED AND DIMINISHED ADIPOSE-TISSUE MASS

Adipsin, which is identical to complement factor D, is synthesized by fat cells, circulates in the bloodstream and is profoundly deficient i n mice with genetic and hypothalamic obesity. With the recent cloning of human adipsin, a quantitative human immunoassay has been developed. In the present study, we measured adipsin blood concentrations in hum ans with increased and decreased adipose stores as well as adipsin sec retion by adipose tissue obtained from lean and obese individuals. The results demonstrate that adipsin is released by human adipose tissue fragments as has previously been shown in mice, and that, in contrast to obese mice, blood adipsin concentrations were not reduced in the ob ese humans tested in this study. We also observed that blood adipsin c oncentrations can vary as a function of feeding or adiposity, in that they tend to be mildly elevated in obese individuals or mildly reduced in individuals with total lipo-atrophy, cachexia related to AIDS and anorexia nervosa. Thus, the circulating concentration of adipsin tends to correlate positively with degree of adiposity. Clearly, no deficie ncy in blood adipsin concentrations or adipsin secretion by adipose ti ssue was observed in the obese individuals studied.