Insulin resistance and hypertension: the Insulin Resistance Atherosclerosis study.

The association between insulin resistance and insulinemia and hypertension is controversial. We examined the relation between insulin resistance and hypertension in 564 non-Hispanic whites (NHW), 505 Hispanics (H), and 413 African Americans (AA) who participated in the Insulin Resistance Atherosclerosis Study (IRAS). Insulin sensitivity was measured with a frequently sampled intravenous glucose tolerance test with minimal model analysis. The prevalence of hypertension was 32.5%, 49.4%, and 32.3% in NHW, AA, and H, respectively (P<0.001). When subjects without diabetes in all ethnic groups were combined, age, male sex, race (AA), body mass index (BMI), and insulin resistance, but not fasting insulin, were significantly associated with hypertension. When each ethnic group was analyzed separately, insulin resistance was significantly associated with hypertension in NHW and H, but not AA. After excluding subjects taking antihypertensive medications, male sex, BMI, fasting glucose, and insulin resistance, but not fasting insulin, were significant determinants of blood pressure. When the 3 ethnic groups were analyzed separately, insulin resistance was significantly associated with blood pressure in H, but not NHW, or AA. Neither insulin resistance nor fasting insulin was significantly associated with hypertension or blood pressure in subjects with diabetes of the 3 ethnic groups after adjusting for age, sex, BMI, and waist. In conclusion, insulin resistance, but not insulinemia, was related to hypertension and blood pressure in subjects without diabetes, but ethnic differences in these relations appear to exist. Neither insulin resistance nor insulinemia was related to hypertension or blood pressure in patients with type 2 diabetes in the 3 ethnic groups.

Is insulin sensitivity a causal intermediate in the relationship between alcohol consumption and carotid atherosclerosis?: the insulin resistance and atherosclerosis study.

OBJECTIVE: A J-shaped association has been demonstrated between alcohol consumption and atherosclerosis. Insulin resistance, also a risk factor for atherosclerosis, has been shown to have a similar J-shaped association with alcohol intake. This raises the question of whether insulin sensitivity (S(I)) is a causal intermediate in the alcohol-atherosclerosis relationship. RESEARCH DESIGN AND METHODS: The Insulin Resistance Atherosclerosis Study was a multicenter cohort study designed to investigate relationships among S(I), risk factors for cardiovascular disease, and carotid artery atherosclerosis. Using regression analysis, we tested whether adjustment for S(I) attenuated the alcohol-atherosclerosis relationship observed at baseline. RESULTS: A J-shaped association was observed between alcohol consumption and common carotid artery intimal medial thickness. The protective aspect of the alcohol-atherosclerosis relationship was attenuated by 25% after the adjustment for S(I). However, an interaction was observed between alcohol consumption and glucose tolerance (GT) status. In comparison with never drinkers, all levels of alcohol consumption were associated with less atherosclerosis in participants with normal GT status. Participants with impaired GT status (but not diabetes) demonstrated a J-shaped alcohol-atherosclerosis association. All levels of alcohol consumption were associated with more atherosclerosis in participants with diabetes. CONCLUSIONS: S(I) may be a causal intermediate at protective levels of alcohol intake, but an alcohol-GT interaction precluded a definitive conclusion. Moderate alcohol consumption may increase the risk of atherosclerosis in people with diabetes. These findings contrast with previous reports and do not support current recommendations regarding moderate alcohol consumption in people with diabetes. More research is needed to clarify this issue.