REGULATION OF HEPATIC STEAROYL-COA DESATURASE GENE-1 BY VITAMIN-A

The effect of vitamin A supplementation on stearoyl-CoA desaturase gen e 1 expression in mouse liver was characterized. Normal BALB/c mice we re fed 0.01% and 0.1% retinol palmitate as components of nonpurified d iets. This treatment resulted in a 3-fold and a 7-fold induction of SC D1 mRNA levels, respectively, as determined by RNase protection analys is, Vitamin A-deficient animals were also fed diets containing 0.01% a nd 0.1% retinol palmitate, resulting in a similar pattern, of SCD 1 mR NA induction. Fatty acid synthase and beta-actin mRNA levels did not r espond consistently or significantly to retinoic acid treatment. Dieta ry and hormonal studies were carried out to investigate the role of th e retinoid X receptor in the regulation of SCD1 by type II steroid hor mones, A receptor-saturating dose of thyroid hormone, triiodothyronine , repressed vitamin A-elevated SCD1 mRNA levels in vivo. Peroxisome pr oliferator-elevated SCD1 mRNA levels were unaffected by administration of thyroid hormone. This suggests that the retinoic acid receptor tra nscriptionally regulates SCD1 through a traditional mechanism of heter odimerization with the retinoid X receptor, (C) 1997 Academic Press.