TRANSFORMING GROWTH-FACTOR BETA(1) INDUCES DIFFERENTIATION-SPECIFIC GENE-EXPRESSION IN FETAL-RAT BROWN ADIPOCYTES

Fetal rat brown adipocytes show a low number of transforming growth fa ctor beta(1) (TGF-beta(1)) binding sites of high affinity, revealing t he presence of type I, II and III TGF-beta(1) receptors acid a minor-l abeled species of approximately 140 kDa. The culture of cells in the p resence of TGF-beta(1) induced the expression of the tissue-specific g ene uncoupling protein in a dose- and time-dependent manner. In additi on, TGF-beta(1) up-regulates the expression of genes involved in adipo genesis such as fatty acid synthase, glycerol 3-phosphate dehydrogenas e, malic enzyme and glucose 6-phosphate dehydrogenase, as well as indu ces the expression of fibronectin (specific target gene for TGF-beta(1 )). Our results suggest that TGF-beta(1) is a major signal involved in initiating and/or maintaining the thermogenic and adipogenic differen tiation of rat fetal brown adipocytes.