Dietary influence on the insulin function in the epididymal fat cell of the Wistar rat. II. Effect of type of carbohydrate.

Abstract

Newly weaned male specific pathogen-free Wistar rats were fed semipurified diets containing sunflowerseed oil or palm oil and various types of carbohydrates, i.e. sucrose, maize starch or potato starch for at least 3-4 weeks. Fat cells were isolated from the epididymal fat pads to study the sensitivity to insulin. The response to insulin of the cells was always higher for sunflowerseed oil than for palm oil. Diets containing polysaccharides were found to induce a higher response as compared to sucrose-containing diets. The changes in insulin response due to the type of carbohydrate were not accompanied by changes in insulin binding to the cells, or in the fatty acid composition of the membrane phospholipids. The fatty acid compositions of the triacylglycerol fractions from the epididymal fat pads reflected very well those of the dietary fats. In addition, the type of dietary carbohydrate had also some effect on this composition. The fecal fatty acid content was low and very similar after diets containing either sucrose or maize starch and sunflowerseed oil or palm oil, indicating that the difference in insulin function between the two dietary fats cannot be caused by a difference in fat absorption in the digestive tract. These findings, as well as the insulin concentrations in the blood samples after the various diets, suggest that the changes in insulin response due to the type of dietary carbohydrate are caused by postreceptor effects.