Ancestral origin of insulin-dependent diabetes in Mexican-Americans

To test the hypothesis that insulin-dependent diabetes mellitus in the Mexican-American population is due to Spanish genetic admixture, we obtained ancestral information on 106 Mexican-American families with an insulin-dependent diabetic index case and 80 Mexican-American control families from 1987 to 1991. The Mexican states of origin were available on 395 grandparents of the insulin-dependent diabetic index cases and 291 grandparents of the controls. Analysis of the individual states of origin revealed that there were significantly more Mexican-American grandparents of diabetic index cases from the states of Jalisco and Michoacan when compared to the control families (31% and 16% diabetic versus 22% and 11% controls respectively, P less than 0.01). The states of Zacatecas and Durango had a lower frequency of diabetic grandparents as compared to controls (6% diabetic versus 12% controls, P less than 0.001). Analysis of the origin by Northern and Southern states of México revealed a significant decrease in the number of grandparents of the insulin-dependent diabetic cases from the Northern regions of México, 19.5%, versus 32% in controls, (P less than 0.001). These data indicate that the grandparents of the insulin-dependent diabetic index cases originate from states and regions of México which were those of the early entry of the Europeans. These data thus support the hypothesis that insulin-dependent diabetes mellitus in the Mexican-American population may be due in significant part to an original genetic contribution from the Spanish-European population.