Adiponectin, insulin resistance and clinical expression of the metabolic syndrome in patients with Type 2 diabetes

Background: Obesity and the metabolic syndrome have emerged as clinical and public health crises in many populations, but not all obese patients have the syndrome. As adipocytes produce several adipokines that modulate insulin action as well as glucose and lipid metabolism, we postulate that estimation of adipokines may be useful addition to the criteria used to identify obese individuals with the metabolic syndrome. Objective: To evaluate the determinants and associations of plasma adiponectin in relation to the metabolic syndrome in patients with Type 2 diabetes. Design: Cross-sectional study. Setting: General Teaching Hospital. Patients: One hundred and thirty five (57 M, 78 F) patients with Type 2 diabetes mellitus. Measurements: Adiponectin, leptin, high-sensitivity C-reactive protein (hs-CRP), fasting plasma insulin, glucose, glycated hemoglobin and full lipid profile. Patients were classified on the basis of the degree of adiposity, insulin resistance (IR) (homeostasis model assessment of insulin resistance (HOMA-IR)) and the number of the American Heart Association and the National Heart, Lung and Blood Institute criteria of the metabolic syndrome. Results: Adiponectin levels were inversely correlated with age, indices of obesity, IR and hs-CRP. Overweight/obese and non-obese insulin-sensitive patients had significantly higher (P<0.05) adiponectin levels than those with IR despite similar body mass index and waist circumference. Therefore, within each category of obesity stratification, lower adiponectin levels were associated with IR. Adiponectin showed stepwise decrease with increasing number of the criteria for diagnosis of the metabolic syndrome. Using multiple logistic regression, the odds ratio of the metabolic syndrome as predicted by adiponectin was 0.73 (95% confidence interval 0.53-0.96; P=0.04). At cutoff point of 18 ng/ml, the diagnostic sensitivity and specificity of adiponectin for the metabolic syndrome were 83 and 65%, respectively, in male patients and 92 and 41%, respectively, in female patients. Receiver operating characteristic analysis showed that adiponectin had significantly higher area under the curve compared with leptin, leptin:adiponectin ratio and triglycerides for the detection of the metabolic syndrome. Conclusions: In patients with Type 2 diabetes, adiponectin concentrations are closely related to IR and the components of the metabolic syndrome. Adiponectin concentration may be a useful addition to the criteria used for identifying obese subjects with the metabolic syndrome.