DIETARY CARBOHYDRATE ENHANCES INTESTINAL SUGAR-TRANSPORT IN DIABETIC MICE

The rate of intestinal absorption of sugars and their site of absorpti on determine postprandial plasma glucose concentrations. Does chronic consumption of high-carbohydrate, high-fiber, low-fat diets of the typ e recommended by many diabetes associations induce adaptive changes in transport and metabolism of sugars in the small intestine? Control an d STZ-induced diabetic (>60 days diabetic) mice were fed high-carbohyd rate or no-carbohydrate rations for 7 days. Brush-border glucose and f ructose uptake per milligram increased 2 times with dietary carbohydra te in both diabetic and control mice; uptake, however, did not differ between diabetic and control mice. Compared with the distal small inte stine, glucose uptake per milligram was 2 to 6 times higher in the pro ximal and middle regions, and enhancement of uptake by diet was limite d to these regions. Changes in site density of intestinal glucose tran sporters as determined by specific phlorizin binding were tightly corr elated with changes in brush-border glucose uptake per milligram. Ther e were neither diabetes- nor diet-induced changes in the K(d) of speci fic phlorizin binding, in the amount of glucose absorbed per transport ing site, or in passive glucose permeability. Intestinal weights, wt/c m, intestinal length, and mucosal mass increased significantly with di abetes, and sugar transport per centimeter and per small intestine was up to 60% greater in diabetic mice. Dietary carbohydrate stimulated s pecific sucrase activity in the proximal small intestine of both diabe tic and control mice. Chronic diabetes enhances sugar transport by non specific increases in intestinal mass. Dietary carbohydrate further st imulates sugar transport in diabetic mice by specific increases in sit e density of sugar transporters, resulting in dramatic increases in to tal sugar absorptive capacity of the diabetic small intestine.