Subclinical inflammation is strongly related to insulin resistance but not to impaired insulin secretion in a high risk population for diabetes

Abstract

Subclinical inflammation was shown to be a strong predictor of cardiovascular events and was suggested to be a part of the metabolic syndrome (MS). The aim of the present study was to investigate the relationship of the inflammatory parameters-leukocyte count, C-reactive protein (CRP), and fibrinogen level-to insulin resistance and insulin secretion, as well as to other components of the MS in a population at risk for diabetes. A total of 396 subjects (142 men and 254 women) were analyzed from the follow-up of the Risk Factors in Impaired Glucose tolerance (IGT) for Atherosclerosis and Diabetes (RIAD) study, who were at risk for type 2 diabetes, such as family history of diabetes, obesity, and/or hyper/dyslipoproteinemia. Subjects under lipid-lowering treatment or with acute infections were not eligible. A variety of risk factors within the MS were examined: lipids, glycemic parameters, coagulation, insulin fractions. and microalbuminuria. CRP was determined by a highly sensitive method, using an immunological agglutination test, and fibrinogen was measured by the method of Clauss. Insulin resistance was evaluated by the homeostasis model assessment (HOMA) and insulin secretion by HOMA and by insulin areas under curve in an oral glucose tolerance test (OGTT), insulin increment at 30 mnutes of OGTT, and insulin increment/glucose increment at 30 minutes of OGTT. By univariate analysis, fibrinogen level (r = 0.180, P <.001), leukocyte count (r = 0.162, P =.001), and CRP (r = 0.251, P <.001) were all highly significantly correlated to insulin resistance, but not to insulin secretion. A significant rise was found for the majority of the components of the MS in quartiles of the examined inflammatory parameters. In multivariate analysis of all analyzed metabolic parameters, including age, sex, physical activity, and smoking, body mass index (BMI) was found a strong independent determinant of all inflammatory markers examined. Thus, in a population at risk for type 2 diabetes we demonstrate that subclinical inflammation underlies the metabolic syndrome, through association to one of its primary anomalies-insulin resistance, whereas no association was found to impaired insulin secretion.