Type 2 diabetes starts with insulin resistance in tissues that normally use insulin to facilitate the uptake of glucose from the blood. The American Diabetes Association (ADA) defines prediabetes as a condition with fasting blood glucose between 100 and 125 mg/dl. Values higher than this are characteristic of diabetes, while lower values are normal. Prediabetes is also called impaired glucose tolerance or impaired fasting glucose.
Dr. Tadashi Moriuchi and colleagues at Kanazawa University Graduate School of Medical Science, Japan, performed a study on progression from high blood glucose to diabetes.
As background information, Moriuchi noted that the ADA changed the lower limit of impaired fasting glucose from 110 to 100 mg/dl in 2003. The goal of the study was to investigate the risk for subjects with high blood glucose to develop diabetes. The subjects were 4,165 school teachers who were non-diabetic at baseline. The average (mean) follow-up time was 5.1 years. Moriuchi and colleagues found the following rates for development of diabetes, depending on initial blood glucose levels:
1. Normal blood glucose, less than 100 mg/dl, 0.5 percent.
2. Blood glucose 100 to 109 mg/dl, 6.5 percent.
3. Blood glucose 100 to 125 mg/dl, 28.2 percent.
Once the fasting blood glucose levels reach the diabetic level of 126 mg/dl or higher, the beta cells of the pancreas are at risk for damage. Dr. Hideaki Kaneto and colleagues at Osaka University, Japan, provided a review of the progression from early type 2 diabetes to insulin dependence.
The process of beta cell glucose toxicity decreases insulin secretion and causes apoptosis of the pancreatic beta cells. Reactive oxygen species are also induced under diabetic conditions, and Kaneto concluded that these may be involved in the progression of both insulin resistance and beta cell dysfunction.
“Although at present several clinical trials with antioxidants show only a little effect, if any, on the progression of type 2 diabetes, we think that future therapy with stronger and more appropriate antioxidants would exert some beneficial effects,” Kaneto reported.