Haptoglobin serum levels are independently associated with insulinemia in overweight and obese women

BACKGROUND: Obesity is associated with a chronic low-grade inflammatory condition. Haptoglobin is a glycoprotein involved in the acute-phase response to inflammation, and it is increased in obese subjects. The possibility that hyperinsulinemia and/or insulin resistance may directly increase haptoglobin levels has never been tested. The aim of this study was to investigate the associations of haptoglobin serum levels with anthropometric parameters, insulin levels, insulin resistance and related metabolic variables in overweight and obese women. PATIENTS AND METHODS: This is a cross-sectional study of 194 non-diabetic overweight and obese subjects, aged 18-68 yr. Measurements included body mass index (BMI), central fat accumulation [evaluated by waist circumference (WC)], systolic and diastolic blood pressure, and fasting concentrations of haptoglobin, insulin, glucose, lipids (triglycerides, total cholesterol, and HDL-cholesterol), and insulin resistance as estimated by the homeostasis model assessment (HOMAIR). RESULTS: Haptoglobin serum levels showed a positive association with BMI (p<0.001), WC (p<0.001), HOMAIR (p<0.001), and fasting insulin (p<0.001), triglyceride (p<0.001) and glucose (p<0.05) blood levels. However, only insulin maintained a significant independent association with haptoglobin (p<0.001) when a multiple regression analysis was performed and age, BMI (or WC), blood pressure levels, HOMAIR, and fasting insulin, glucose, and lipid blood concentrations were entered as independent variables. CONCLUSIONS: Higher haptoglobin serum levels seem to be a strong marker of hyperinsulinemia, independently of BMI, body fat distribution, insulin resistance and related parameters.