The effect of intake of whole grain and whole grain components on type 2 diabetes in rats.

Abstract

Consumption of whole grains has been associated with reduced risk of type 2 diabetes epidemiologically. However, studies of the effect of individual whole grains on the development of type 2 diabetes are lacking. The objective of this research was to examine the effect of consumption of whole grains and a processed whole grain component on type 2 diabetes in diabetic rats. The first study was designed to investigate the effect of various whole grains consumption on diabetic control and progression in an animal model of type II diabetes, the Goto-Kakisaki (GK) rat. In this study, whole grain consumption showed only slight improvements in glucose control and insulin resistance early in the progression of diabetes, improvements which were lost with time, and no improvement in a marker of oxidative stress. The slight effect of whole grain consumption on slowing the progression of type 2 diabetes may be due to poor bioavailability of nutrients and phytochemicals. Thus, it was hypothesized that consumption of a processed whole grain ingredient with increased bioavailability of nutrients and phytochemicals might improve the diabetic state. The purpose of the second study was to examine the effect of processed wheat bran consumption on metabolic parameters related to diabetes and obesity in an animal model of type 2 diabetes with obesity, the Zucker diabetic fatty (ZDF) rat. The consumption of processed wheat bran had highly beneficial effects on the diabetic state, including decreasing the insulin response after a meal, decreasing visceral fat pad weight, insulin resistance, and plasma and liver cholesterol, and increasing bile acid excretion. The finding of correlations between ferulic acid, the major phenolic in wheat, in plasma and urine and metabolic parameters related to diabetes suggests that increased bioavailability of ferulic acid is responsible for the improvements seen in these parameters. In conclusion, whole grain intake provided a modestly beneficial effect on the development of type 2 diabetes. However, processing of a whole grain component, wheat bran, to increase the bioavailability of active compounds in the bran resulted in highly significant improvements in the diabetic state in an animal model of type 2 diabetes with obesity.