High Carbohydrate Diet Effects on the Development of Diabetes Mellitus and Modification of Pancreatic Islets in OLETF Rats

Kim, Sung Ki; Hong, Seong Bin; Park, Hwi Ra; Kim, Eun A; Lee, Kyung Wook; Nam, Moon Suk; Kim, Yong Seong

Abstract

BACKGROUND: Diet has long been believed to be an important risk factor for type 2 diabetes. The composition of carbohydrates in the diet was higher in the past, where as now it is considerably reduced in the diet of Korean peoples, which is probably associated with the risk of developing type 2 diabetes. The aim of the present study was to investigate the long-term effect of high carbohydrate/low protein diets on the glucose and lipid metabolism and the pancreatic islet in OLETF(Otsuka Long-Evans Tokushima Fatty) rats, the animal model of type 2 diabetes.
METHODS
Seven week old male OLETF rat were fed a high carbohydrate/low protein diet(carbohydrate 71.0%, fat 14.5%, protein 14.5%) as the experimental group, with an ordinary chow diet(carbohydrate 63.5%, fat 14.5%, protein 22%) fed to the controls. The plasma insulin, lipid profiles, free fatty acid and oral glucose tolerance were analyzed at 16 and 32 weeks. After the glucose tolerance test, the pancreas was excised, and immunohistochemical staining was conducted for the islet morphology and insulin mRNA to quantify the insulin secretory capacity.
RESULTS
The basal glucose levels tended to be higher in the control group, but with no significant statistical difference. There were no differences in the serum insulin, total cholesterol, triglyceride, HDL-cholesterol and plasma free fatty acid levels between the two groups. The pancreatic islets of the control group showed multilobulation, with fibrotic changes; where as those of the experimental group were maintained normal profiles. A higher expression of insulin mRNA was observed in the experimental than in the control group.
CONCLUSION
A high carbohydrate diet induced lower body weight increases, and protected against beta cell injury and decreased the development of abnormal glucose tolerance in OLETF rats. This may explain the growing incidence of diabetes with respect to the change in carbohydrate composition in the diet of Korean peoples. However, whether the protective effect of a high carbohydrate diet, against the development of diabetes in OLETF rats, can be attributed to small weight increases or if the change in food composition itself, or both needs to be determined.