Associations of plasma glucose levels and traits of metabolic syndrome with carotid intima media thickness in nondiabetic elderly subjects. are they mediated by insulin resistance

BACKGROUND: The independent role of insulin resistance (IR) and high fasting blood glucose (FBG) levels within the normal range on vascular diseases is still under debate. This study was designed to explore whether IR, FBG levels, and the traits of metabolic syndrome are associated with increased carotid intima media thickness (IMT), the early marker of subclinical atherosclerosis, independently of each other in nondiabetic elderly subjects. METHODS: Blood analytes and anthropometric measurements were obtained. Carotid IMT was measured by ultrasonography; metabolic syndrome was diagnosed according to National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III) criteria. IR was assessed through homeostasis model assessment of insulin resistance (HOMA-IR). RESULTS: At total of 207 subjects aged 68.2±3.6 years were enrolled. Subjects with increased carotid IMT (50.7%) were older (P=0.001), had a higher prevalence of metabolic syndrome (P<0.0001) and all its traits, impaired fasting glucose (IFG) (P<0.0001), and values of HOMA-IR (P<0.0001) than normal subjects. Increased carotid IMT significantly correlated with metabolic syndrome, its traits, IFG, and HOMA-IR. When multivariable regression models were constructed, central obesity [B=0.392; 95% confidence interval (CI) 0.280-0.505; P<0.0001], high-density lipoprotein cholesterol (HDL-C) (B=-0.007; 95% CI -0.013-0.000; P=0.042], hypertension (B=0.475; 95% CI 0.363-0.587; P<0.0001), and IFG (B=0.230; 95% CI 0.092-0.367; P=0.001) were found to be the independent determinants of increased carotid IMT independently of HOMA-IR, but not FBG (B=0.013; 95% CI 0.000-0.026; P=0.050) and HOMA-IR itself. CONCLUSIONS: Our results suggest that hypertension, low HDL-C, and central obesity are independently associated with increased carotid IMT in nondiabetic elderly subjects. These associations seem to be not affected by IR. The associations of FBG levels within the normal range and IR with carotid IMT should be investigated further.