Fatty acid synthetizing enzymes in adipocytes and stromavascular fraction of hyperthyroid rat adipose tissue

In the rat, hyperthyroidism induced from birth has been shown to increase both adipose cell recruitment and de novo lipogenesis at 6 weeks of age. Since preadipose cells are included into the stromavascular fraction (SVF) of adipose tissue, fatty acid synthetizing enzyme activities were estimated separately in adipocytes and SVF cells of adipose tissue of 6 week-old hyperthyroid rats. Fatty acid synthetase (FAS), malic enzyme (ME), glucose-6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (6PGD) activities were generally increased in adipocytes and in SVF cells when compared to age-matched controls. Among the enzymes studied, ME activity displayed the highest stimulation in SVF cells and was much more stimulated in these cells than in adipocytes (214% and 73% increase, respectively, above control values, P less than 0.001). These results show that, in vivo, SVF cells and adipocytes can respond differently to an hormonal stimulation and raise the question of the role of ME in the adipose conversion.