Evidence from migrant population studies and secular trend data indicates that environmental factors play a role in the etiology of non-insulin-dependent (type II) diabetes. These environmental factors appear to be concomitants of the process whereby traditional populations become "modernized" or "westernized" and include increased intake of total calories, fat, and sucrose, decreased intake of total and complex carbohydrates, including fiber, and decreased physical exercise. There also appears to be a "postmodernization" process, which we have characterized as the "descending limb of the curve." In Mexican Americans in San Antonio, the prevalence of type II diabetes declines with acculturation to the values, attitudes, and behaviors of "postmodernized" American society. However, examination of the dietary and exercise concomitants of this process revealed a mixed picture. There was some suggestion that Mexican-American women, although not men, had entered onto the descending limb of the curve. However, Native American genetic admixture in Mexican Americans also covaried with affluence and acculturation in such a way that the declining prevalence of diabetes could as easily be due to genetic factors as to environmental factors. The "pancreatic exhaustion" theory holds that resistance to insulin action is a principal lesion leading to hypersecretion of insulin, hyperinsulinemia, and eventual islet cell failure and clinical diabetes. This theory predicts that prediabetic subjects will be hyperinsulinemic. In conformity with this theory, we have shown that subgroups of the Mexican-American population, defined on the basis of family history of diabetes, who would be expected a priori to be enriched with prediabetic subjects, are hyperinsulinemic as predicted. Recently, we described a restriction-fragment-length polymorphism of the insulin-receptor gene that appears to be associated with type II diabetes. This polymorphism appears to be unique to Native American populations and hybrid populations such as Mexican Americans. Whether this polymorphism has consequences for insulin-receptor function remains to be determined. Identification of genetic susceptibles to type II diabetes would be useful, because it would permit public health activists to concentrate resources for primary prevention of diabetes on subgroups at high risk.
ASJC Scopus subject areas
- Internal Medicine
- Endocrinology, Diabetes and Metabolism
- Advanced and Specialized Nursing