The common genetic variant upstream of INSIG2 gene is not associated with obesity in Indian population

The high incidence of obesity has resulted in increased morbidity and mortality worldwide. Obesity, a common lifestyle disorder, is caused by multiple factors with heredity playing a strong causal role. Recently, a genetic variation upstream of insulin-induced gene 2 (INSIG2) (rs7566605) has been reported to be associated with obesity in four separate cohorts. Because the lifestyle and food preferences of a large proportion of Indian population differ from the rest of the world, we studied the impact of this polymorphism with body mass index (BMI). The study consisted of two cohorts - 1577 healthy individuals from three major linguistic lineages in India and 610 coronary artery disease cases and controls. In the two cohorts studied, no significant association was observed between the polymorphism and BMI. However, frequency of homozygous variant genotype was higher in non-obese individuals as compared with obese individuals in both cohorts although the difference was marginally significant only in the case-control cohort under the assumption of a recessive model. Furthermore, regardless of age and sex, mean BMI did not vary with genotype under the assumptions of recessive model. Thus, in contrast to earlier reports, the variant upstream of INSIG2 is not a determinant of BMI in Indian population.