Dietary Carbohydrate Enhances Intestinal Sugar Transport in Diabetic Mice

Abstract

The rate of intestinal absorption of sugars and their site of absorption determine postprandial plasma glucose concentrations. Does chronic consumption of high-carbohydrate, high-fiber, low-fat diets of the type recommended by many diabetes associations induce adaptive changes in transport and metabolism of sugars in the small intestine? Control and STZ-induced diabetic (> 60 days diabetic) mice were fed high-carbohydrate or no-carbohydrate rations for 7 days. Brush-border glucose and fructose uptake per milligram increased 2 times with dietary carbohydrate in both diabetic and control mice; uptake, however, did not differ between diabetic and control mice. Compared with the distal small intestine, glucose uptake per milligram was 2 to 6 times higher in the proximal and middle regions, and enhancement of uptake by diet was limited to these regions. Changes in site density of intestinal glucose transporters as determined by specific phlorizin binding were tightly correlated with changes in brush-border glucose uptake per milligram. There were neither diabetes- nor diet-induced changes in the Kd of specific phlorizin binding, in the amount of glucose absorbed per transporting site, or in passive glucose permeability. Intestinal weights, wt/cm, intestinal length, and mucosal mass increased significantly with diabetes, and sugar transport per centimeter and per small intestine was up to 60% greater in diabetic mice. Dietary carbohydrate stimulated specific sucrase activity in the proximal small intestine of both diabetic and control mice. Chronic diabetes enhances sugar transport by nonspecific increases in intestinal mass.(ABSTRACT TRUNCATED AT 250 WORDS)

α-Glucosidase inhibitors prevent diet-induced increases in intestinal sugar transport in diabetic mice

“…The streptozotocin was administered intraperitoneally in 2 consecutive days: the initial dose was 100 and the second was 25 mg/kg body weight, as previously described [6]. All the mice became hyperglycemic, but only the mice whose glycemia was at least 200 mg/dL 1 week from the first injection were assigned to this study.…”

“…Increases in luminal carbohydrate concentrations such as those arising from a high-carbohydrate diet specifically stimulate sugar transport [8]. We have shown in diabetic mice that diet-induced increases in sugar uptake rate combined with an enlarged absorptive mucosa resulted in much higher rates of total intestinal sugar absorption than those of nondiabetic mice consuming a high-carbohydrate diet [6].…”

“…Diabetes is also thought to cause intestinal hypertrophy and hyperplasia [6,7], thus nonspecifically increasing sugar transport. Increases in luminal carbohydrate concentrations such as those arising from a high-carbohydrate diet specifically stimulate sugar transport [8].…”

“…Because high-carbohydrate diets increase the absorption rate of sugars (see Ref [4]), the carbohydrate-related increase in sugar absorption during diabetes [6] already abnormally high in diabetes. Diabetes is also thought to cause intestinal hypertrophy and hyperplasia [6,7], thus nonspecifically increasing sugar transport.…”

“…We chose mice as a model because they have been used often in studies on regulation of intestinal transport in both normal and diabetic condition [10] and because we have successfully used them in our previous research on intestinal absorption in experimental diabetes [6,10].…”