Insulin sensitivity in subjects with type 2 diabetes. Relationship to cardiovascular risk factors: the Insulin Resistance Atherosclerosis Study.

OBJECTIVE: Among nondiabetic subjects, insulin resistance has been associated with increased cardiovascular risk factors, including dyslipidemia, hypertension, impaired fibrinolysis, and coagulation. Less is known about the relationship between insulin resistance and cardiovascular risk factors in subjects with type 2 diabetes.

RESEARCH DESIGN AND METHODS: To examine this issue, we determined insulin sensitivity (SI) in 479 type 2 diabetic subjects by minimal model analyses of frequently sampled intravenous glucose tolerance tests in the Insulin Resistance Atherosclerosis Study (IRAS), a large multicenter study of insulin sensitivity and cardiovascular disease in African-Americans, Hispanics, and non-Hispanic whites. We defined insulin-sensitive subjects as having SI > or = 1.61 x 10(-4) min-1.microU-1.ml-1 (above median in nondiabetic subjects of all ethnic groups in the IRAS). Using this definition, only 37 type 2 diabetic subjects were insulin sensitive, and the remaining 442 were insulin resistant.

RESULTS: After adjustment for age, sex, ethnicity, and clinic, insulin resistance was significantly correlated with total triglycerides, VLDL cholesterol, VLDL triglyceride, fibrinogen, PAI-1, and fasting glucose, and was inversely correlated with HDL cholesterol level and LDL size. Carotid intimal-medial thickness was greater in insulin-resistant than in insulin-sensitive subjects, but this difference was not statistically significant. After further adjustment for waist circumference (marker of visceral adiposity), insulin-resistant subjects continued to have higher plasminogen activator inhibitor 1 and VLDL triglyceride levels, lower HDL cholesterol levels, and smaller LDL particle size than did insulin-sensitive subjects. After further adjustment for fasting glucose levels, these results were very similar.

CONCLUSIONS: We conclude that insulin-resistant type 2 diabetic subjects have more atherogenic cardiovascular risk factor profiles than insulin-sensitive type 2 diabetic subjects and that this is only partially related to increased obesity and an adverse body fat distribution.