Effect of refeeding raw and cooked starches on hepatic enzyme activities of rats

Abstract

1. Responses of hepatic glucose-6-phosphate dehydrogenase (EC 1.1.1.49; G6PD), malic enzyme (EC 1.1.1.40; ME), acetyl-CoA carboxylase (EC 6.4.1.2; ACAC), and fatty acid synthetase (FAS) were studied in male Wistar rats after a period of starvation and refeeding of diets containing 400 g glucose, or raw or cooked starches as the source of carbohydrate/kg. Starches fed included maize, potato, wheat, rice, and tapioca.2. When compared to the responses of rats given the glucose-containing diet, rats given raw maize- or rice-starch-containing diets had a significantly lower ME response, and rats given raw potato starch had significantly lower responses of G6PD, ME, ACAC, and FAS. The enzyme responses of rats given cooked starches were similar to those of glucose-fed rats, except that rats given cooked wheat starch had significantly lower G6PD and ME responses than did glucose-fed rats.3. When the enzyme responses to refeeding of the same starch source in either raw or cooked form were compared, it was found that (a) the FAS response was significantly higher to cooked than to raw maize starch, (b) the G6PD and ACAC responses were significantly higher to cooked than to raw tapioca starch, (c) the G6PD, ME, ACAC, and FAS responses were significantly higher to cooked than to raw potato starch.4. The results suggest that reported differences in the lipogenic enzyme responses between simple sugars and starch may in some instances be magnified because of the use of uncooked starches in experimental diets.