Porcine fatty acid synthase: cloning of a complementary DNA, tissue distribution of its mRNA and suppression of expression by somatotropin and dietary protein.

A cDNA for porcine fatty acid synthase was isolated and used to examine the tissue distribution of fatty acid synthase mRNA within the pig and to determine the impact of recombinant porcine somatotropin (rpSt) and the level of dietary protein on fatty acid synthase mRNA abundance in pig liver and adipose tissue. A 1.5-kb cDNA representing the thioesterase domain of porcine fatty acid synthase was isolated from a lambda gt 11 liver cDNA library. Northern analysis with total RNA extracted from adipose tissue, liver, heart, lung, kidney and intestine revealed a single major fatty acid synthase mRNA species of 8-9 kb. The amount of fatty acid synthase mRNA in hepatic tissue was 25% of the amount in adipose tissue, which suggests that the liver may be a significant site of fatty acid synthesis in the pig. Fatty acid synthase mRNA abundance was significantly reduced in the adipose tissue (P less than 0.01) and the liver (P less than 0.1) by chronic daily administration (60 micrograms/kg) of rpSt. In addition, increasing the amount of dietary protein decreased (P less than 0.1) the abundance of fatty acid synthase mRNA in adipose tissue but had no effect on liver fatty acid synthase expression. In contrast, the abundance of adipose fatty acid binding protein mRNA was unaffected by rpSt or dietary protein. These data indicate that the reduction in the level of fatty acid synthase mRNA is a factor in the pSt-mediated suppression of fatty acid synthesis in porcine adipose tissue.