Study of insulin resistance in relation to serum IGF-I levels in subjects with different degrees of glucose tolerance

AIM We studied the correlations between fasting and post-lunch serum IGF-I concentrations, and insulin resistance and insulin sensitivity in subjects with various degrees of glucose tolerance. MATERIALS AND METHODS A total of 12 nondiabetic subjects, 09 subjects with impaired glucose tolerance (IGT) and 18 patients with newly diagnosed type-2 diabetes of either sex (mean age, 46 years) were recruited. None of the participants received any drug treatment at the commencement of the study. Fasting as well as post-lunch blood samples were collected from all the subjects and anthropometric and biochemical parameters were analyzed. RESULTS Fasting serum IGF-I concentrations were negatively correlated with fasting serum glucose, insulin, C-peptide, triglycerides, total LDL and VLDL cholesterol, homeostatic model assessment of insulin resistance (HOMA-IR), and age. Fasting serum IGF-I concentrations were positively correlated with fasting blood HDL cholesterol and homeostatic model assessment of insulin sensitivity (HOMA-S) in only diabetic subjects. Post-lunch serum IGF-I concentrations were positively correlated with HDL and LDL cholesterol. Correlations with HOMA-S with these metabolic anthropometric variables were of similar magnitude and direction as that of IGF-I concentrations. IGF-I concentrations were significantly lower in the subjects with World Health Organization-defined metabolic syndrome compared with the subjects without metabolic syndrome (P < 0.0001). CONCLUSIONS Our data indicate that IGF-I could be a useful marker in the insulin resistance syndrome. The post-lunch low-IGF-I levels help in better identification of subjects at risk for type-2 diabetes mellitus and cardiovascular disease.