Determinants of Diabetes Mellitus in the Pima Indians

OBJECTIVE: To review the research findings on the determinants of diabetes mellitus in Pima Indians. RESEARCH DESIGN AND METHODS: Pima Indians in Arizona have participated in a longitudinal diabetes study that has provided data on and hypotheses about the development of NIDDM. Findings from this study are reviewed and updated. RESULTS: Frequency distributions of plasma glucose and HbA1 are bimodal in Pima adults, and substantial risk of the specific vascular complications of diabetes is confined to those in the higher components of these distributions. These findings contributed to the adoption of internationally recognized criteria for classification of glucose tolerance. Diabetes in the Pimas is strongly familial, and probably of genetic origin, although the precise nature of the gene or genes involved remains unknown. Obesity, which is at least in part environmentally determined, is a major factor interacting with the presumed genetic susceptibility to result in diabetes. The incidence of diabetes in the Pimas has increased during the last several decades, providing further evidence for environmental-genetic interaction. Longitudinal studies suggest that the progression from normal to diabetes can be considered to involve two stages. The first, primarily attributable to insulin resistance, leads to impaired glucose tolerance, and the second, which depends on insulin secretory failure, leads to worsening hyperglycemia and overt diabetes. CONCLUSIONS: The Pimas and many other American Indian populations suffer from a high incidence of diabetes and its characteristic disabling or fatal complications, and would benefit from continued research on the pathogenesis and prevention of the disease.