Pedersen fetuin contains three adipogenic factors with distinct biochemical characteristics

Crude Pedersen fetuin, derived from fetal bovine serum, contains adipogenic activity. Biochemical characterization was undertaken by following the differentiation of the 1246 adipogenic cell line. The present paper provides evidence that crude fetuin contains distinct proteins with adipogenic activity. By molecular sieve fractionation using Sephacryl S-300, the majority of adipogenic activity eluted in two distinct peaks, FI (molecular weight greater than 669 kDa) and FII (molecular weight ranging from 445 and 232 kDa). In addition a minor activity was found in a third peak, FIII (molecular weight around 69 kDa). Partial purification and biochemical characterization indicate that FI and FII are two distinct factors. FI has a PI higher than 9.4, is destroyed by alkaline treatment, and is stable when treated with acid. FII has a PI lower than 4.0, is alkali stable, but is destroyed completely by treatment with acid. Moreover, our data show that adipogenic factors are distinct from another protein alpha 2 macroglobulin known to be found in crude Pedersen fetuin. These results suggest that serum contains two large molecular weight proteins bearing adipogenic activity which could play an important role in the control of the adipose differentiation process.