Relation of type 2 diabetes to individual admixture and candidate gene polymorphisms in the Hispanic American population of San Luis Valley, Colorado

The prevalence of type 2 diabetes is higher in populations of Native American ancestry, and in Hispanic American populations formed by admixture between Europeans and Native Americans, than in populations of European ancestry.1 One approach to distinguishing between environmental and genetic explanations for this difference is to study the relationship of type 2 diabetes risk to individual admixture proportions (the proportions of an individual’s genome that are of European and Native American ancestry). With only a few markers informative for ancestry, it is possible to estimate the average admixture proportions of any Hispanic American population. In such analyses, it has been possible to demonstrate that the prevalence of type 2 diabetes in Hispanic Americans in the south western United States varies with the average Native American admixture proportion of these populations.2–4 In the Native American population of Gila River, Arizona, USA, European admixture is associated with lower prevalence of type 2 diabetes.5 However, it has not been possible to demonstrate an association of type 2 diabetes with individual admixture proportions within an Hispanic American population. To estimate the admixture proportions of an individual accurately requires a larger panel of markers: at least 40 markers with average frequency differentials of 0.6 are required to estimate the admixture of an individual with a standard error of no more than 0.1.6 It is now possible to identify relatively large numbers of such ancestry informative markers from data accumulating in the public domain. For this study we typed a panel of 21 markers chosen to have large differences in frequency between European, Native American, and West African ancestry. The possible relationship of type 2 diabetes risk to individual admixture proportions within Hispanic American populations complicates the interpretation of associations of type 2 diabetes with candidate gene polymorphisms within these …