Gene-environment interactions and the diabetes epidemic in India

The prevalence of diabetes is rising rapidly in all developing countries and India already has the largest number of people with diabetes. Evidence for the rising prevalence of diabetes in India comes from recent population-based studies such as the Chennai Urban Population Study (n = 1,262) and the Chennai Urban Rural Epidemiology Study (n = 26,001). These two studies revealed that the current age-standardized prevalence of diabetes in Chennai in adults >/=20 years of age is 14.3%, which is 70% higher than that seen in the year 1989 (8.3%). In the Chennai Urban Population Study, we observed that the higher-income group who consumed excess fat and calorie-rich food had an increased prevalence of diabetes compared to the lowerincome group. There was also a linear increase in the prevalence of diabetes with an increase in visible fat consumption. In addition, we observed that visible fat consumption and physical inactivity showed a cumulative effect on increasing the prevalence of diabetes. We carried out gene-diet interaction studies, which revealed that the adiponectin gene polymorphism (+10211T - G) contributed to insulin resistance and diabetes and this was exaggerated in those consuming diets with higher glycemic loads. These subjects also had an increased risk for hypoadiponectinemia. Similarly, the Ala54Thr polymorphism of the fatty acid-binding protein 2 gene showed a synergistic effect with a high glycemic load increasing the risk for hypertriglyceridemia. These studies indicate that gene-diet interactions could play a major role in increasing the risk for diabetes. However, given the imprecision in measuring dietary intake, very large sample sizes would be needed for meaningful conclusions to be drawn.