HIGH-CARBOHYDRATE DIET AND STARVATION REGULATE LIPOGENIC MESSENGER-RNA IN RATS IN A TISSUE-SPECIFIC MANNER

We have previously shown that the effects of a high carbohydrate, fat- free diet and 24-h starvation on fatty acid synthesis in rats are tiss ue specific. In the present study we examined the tissue-specific pret ranslational effects of high carbohydrate feeding, starvation and refe eding a high carbohydrate diet after starvation on the lipogenic pathw ay by measuring the levels of mRNA encoding acetyl-CoA carboxylase (AC C) and fatty acid synthase (FAS) using Northern analysis. Additionally , we measured mRNA S14, a sequence tightly associated with lipogenesis . In rats fed the high carbohydrate diet, hepatic levels of the three mRNA were 3-5 fold higher than in controls. The level of S14 mRNA was doubled in epididymal fat, but other effects of this diet in adipose t issues were not significant. Expression in kidney, heart, lung and bra in was not altered. Starvation significantly reduced the level of thes e mRNA in all tissues examined except brain. In liver, refeeding the h igh carbohydrate diet induced the expression of ACC, FAS and S14 mRNA 20-30 fold compared with the values found in 48-h starved animals. Hyp erinduction of ACC and FAS, but not S14 mRNA expression was also obser ved in adipose tissues. The tissue-specific nature of these effects is consistent with previous measurements of fatty acid synthesis and con firm that this regulation occurs at the pretranslational level.