The roles of insulin, obesity, and fat distribution in the elevation of cardiovascular risk factors in impaired glucose tolerance. The San Luis Valley Diabetes Study

Abstract

The objective of this study was to determine whether a less favorable risk factor pattern for cardiovascular disease among persons with impaired glucose tolerance could be explained by fasting insulin, obesity, and/or a central distribution of body fat. Between 1984 and 1988, cardiovascular risk factors were examined cross-sectionally in Hispanic and non-Hispanic white participants in the San Luis Valley Diabetes Study who had either impaired (n = 173) or normal (n = 1,107) glucose tolerance. Sex-specific analysis of covariance models were constructed to adjust risk factor levels for age, age and insulin, and age, insulin, body mass index, and centrality index. Both males and females with impaired glucose tolerance had higher age-adjusted mean diastolic blood pressures, heart rates, uric acid levels, and triglyceride levels and lower levels of high density lipoprotein (HDL) cholesterol and HDL3 cholesterol than normal subjects; differences were significant for all risk factors except HDL cholesterol and HDL3 cholesterol in males. Differences in diastolic blood pressure in males, and differences in heart rate and triglyceride in both sexes, remained significant after adjustment for all covariates. However, differences in uric acid in males and differences in diastolic blood pressure and HDL3 cholesterol in females were attenuated to borderline significance levels. Differences in uric acid and HDL cholesterol in females were diminished to nonsignificant levels, especially after adjustment for obesity-related measures. With few exceptions, fasting insulin did not appear to play a major role in accounting for differences in these risk factors. With adjustment, ethnic differences (Hispanic vs. non-Hispanic white) were smaller and were statistically significant less often than differences observed between impaired and normal glucose tolerant groups. The authors concluded that hyperinsulinemia, obesity, and a central body fat distribution accounted for some, but usually not all, of the less favorable cardiovascular risk factor pattern found in subjects with impaired glucose tolerance.