Insulin resistance, cardiovascular risk factors and ultrasonically measured early arterial disease in normotensive Type 2 diabetic subjects

BACKGROUND: The objective of the study was to examine the relationship between serum fasting insulin, insulin sensitivity S(i), cardiovascular risk factors, and asymptomatic early atherosclerosis in normotensive Type 2 diabetic subjects. METHODS: Specific insulin was measured using an enzyme-linked immunosorbent assay (ELISA) and insulin sensitivity was assessed with an insulin-modified frequently sampled intravenous glucose tolerance test (FSIVGTT). Early atherosclerotic change was assessed using carotid intima media thickness (IMT) and an arterial ultrasound score (AUS) measured by high-resolution B-mode ultrasound. RESULTS: On bivariate analysis, there was a positive correlation between S(i) and high density lipoprotein (HDL) cholesterol (r(s)=0.27, p<0.05), and a negative correlation between S(i) and body mass index (BMI) (r(s)=-0.42, p<0.001), HbA(1c) (r(s)=-0.29, p<0.05) and serum triglyceride (r(s)=-0.30, p<0.05). There was a positive correlation between carotid IMT and age (r(s)=0.41, p<0.0005), and a positive association with male sex (p<0.0001) as well as with smoking (p<0.0001). However, we found no correlation between carotid IMT and fasting specific insulin (r(s)=-0.04) or S(i) (r(s)=-0.08). On multiple regression analyses, only age and serum triglycerides appeared to be significant independent variables with respect to carotid IMT whereas age, male sex and smoking emerged jointly significant with respect to AUS. There were no independent associations between carotid IMT or AUS with other variables including using either fasting specific insulin or S(i) as markers on insulin resistance separately. CONCLUSION: Carotid IMT and AUS in Type 2 diabetes are closely associated with age, male sex and smoking. The relationships between serum insulin and insulin resistance with ultrasonically measured early arterial disease in Type 2 diabetes remain unclear.