ADIPOSE-TISSUE STEAROYL-COA DESATURASE MESSENGER-RNA IS INCREASED BY OBESITY AND DECREASED BY POLYUNSATURATED FATTY-ACIDS

Stearoyl-CoA desaturase (SCD) is a key regulatory enzyme in the synthe sis of unsaturated fatty acids. Although regulation of hepatic SCD by obesity and polyunsaturated fatty acids (PUFA) has been well investiga ted, no studies have addressed whether similar regulation occurs in ad ipose tissue. We addressed these questions by feeding control (12% cor n oil) and high-PUFA (48% corn oil) diets to lean and obese Zucker rat s and analyzing SCD mRNA levels in adipose tissue and liver. We report that SCD mRNA content was dramatically elevated in adipose tissue of obese vs. lean rats on both diets and was significantly decreased by P UFA in both genotypes. Interestingly, we demonstrate that SCD expressi on was directly downregulated in a dose-dependent manner by PUFA in 3T 3-L1 adipocytes. We conclude that 1) obese Zucker rats overexpress the SCD gene in both liver and adipose tissue and 2) PUFA directly suppre ss SCD expression in adipocytes. Further studies will elucidate the me chanisms responsible for obesity- and PUFA-mediated regulation of SCD in adipose cells.