Effect of high-amylose starch on carbohydrate digestive capability and lipogenesis in epididymal adipose tissue and liver of rats

Abstract

This study was conducted to clarify whether feeding high-amylose cornstarch would delay digestion and absorption of the starch and lead to a decrease in lipogenesis in epididymal adipose tissue and liver. Two groups of five or six male Wistar rats were fed defined diets ad libitum for 14 days. The control group received a diet containing 53.7% standard cornstarch rich in amylopectin (control diet) and the experimental group received a diet containing 53.7% high-amylose cornstarch (70% amylose). Food intake during the experimental period did not differ between the two groups. Feeding the high-amylose diet resulted in significantly lower activities of sucrase, isomaltase, and maltase in the upper jejunum than in the animals fed the control diet. However, in the lower part of small intestine, disaccharidase activities were significantly elevated in the rats fed the high-amylose diet compared with those fed control diet. The activities of lipogenic enzymes, i.e., fatty acid synthetase, malic enzyme, and glucose-6-phosphate dehydrogenase were significantly lower in the liver as well as in the adipose tissue of the animals fed the high-amylose diet compared with the control group. The weights of both epididymal and mesentery adipose tissues were reduced by 30% in rats fed the high amylose diet, and the serum concentration of triglycerides was also reduced in rats fed the high-amylose diet. These results suggest that digestion and absorption of high-amylose starch may be slower than low-amylose starch and feeding a diet rich in amylose might produce lower glycemic response, consequently leading to declined lipogenesis in adipose tissue and liver.