Plasma IL-6 concentration is inversely related to insulin sensitivity, and acute-phase proteins associate with glucose and lipid metabolism in healthy subjects

Aim: It has been shown that atherosclerosis is an inflammatory disease. Recent data suggest that inflammation precedes type 2 diabetes. Hence, we wanted to study the interrelationship between IL-6, insulin sensitivity, lipids and numerous acute-phase proteins. Methods: Twenty-one healthy individuals [16 males/5 females, age 27.9 +/- 1.8 years, body mass index (BMI) 24.1 +/- 0.8 kg/m(2)] participated in the study. Each patient went through a 4-h hyperinsulinaemic (40 mU/m(2)/min) euglycaemic clamp and 4-h saline infusion. Blood samples were taken before and at the end of the infusions. Results: Plasma interleukin (IL)-6 concentration correlated inversely with insulin sensitivity (M-value) (r = -0.49, p < 0.05). Moreover, the plasma levels of IL-6 associated with c-peptide (r = 0.49, p < 0.05), fat% (r = 0.43, p < 0.05) and diastolic blood pressure (r = 0.46, p < 0.05). alpha-1-acid glycoprotein was related to HbA1(c) (r = 0.47, p < 0.05), insulin (r = 0.55, p < 0.01), diastolic blood pressure (r = 0.58, p < 0.01), systolic blood pressure (r = 0.58, p < 0.01) and triglycerides (r = 0.58, p < 0.01). Haptoglobin was correlated with insulin (r = 0.46, p < 0.05), total cholesterol (r = 0.61, p < 0.01), BMI (r = 0.58, p < 0.01), fat% (r = 0.63, p < 0.01) and lipid oxidation during clamp (r = 0.43, p < 0.05). Diastolic blood pressure decreased during the clamp (from 78.3 +/- 1.9 to 72.1 +/- 2.0 mmHg, p = 0.001). Insulin infusion did not affect the serum levels of most acute-phase proteins. Conclusions: Our study suggests that low grade inflammation, as reflected by IL-6, A1GP and haptoglobin contributes to the regulation of insulin sensitivity, lipid metabolism and blood pressure in normal human physiology.