HDL-paraoxonase and membrane lipid peroxidation: a comparison between healthy and obese subjects.

High-density lipoproteins (HDLs) play a key role in the protection against oxidative damage. The enzyme paraoxonase-1 (PON1) associated at the surface of HDL modulates the antioxidant and anti-inflammatory role of HDL. Previous studies have demonstrated a decrease of serum PON in obese patients. The aim of this study was to investigate whether modifications of PON1 activity reflect in a different ability to protect and/or repair biological membranes against oxidative damage. Thirty obese patients at different grades of obesity (BMI ranging from 30.4 to 64.0 kg/m(2)) and 62 age-matched control subjects (BMI <25 kg/m(2)) were included in the study. The ability of HDL to protect membranes against oxidative damage was studied using erythrocyte membranes oxidized with 2,2-azobis(2 amidinopropane)dihydrochloride (AAPH) (ox-membrane). The membrane lipid hydroperoxide levels were evaluated after the incubation of ox-membranes in the absence or in the presence of HDL of controls or obese patients. The results confirm that HDL exerts a protective effect against lipid peroxidation. The ability of HDL to repair erythrocyte membranes was positively correlated with HDL-PON activity and negatively correlated with lipid hydroperoxide levels in HDL. These results suggest that PON modulates the HDL repairing ability. HDL from obese patients repaired less efficiently erythrocyte membranes against oxidative damage with respect to HDL from healthy subjects. A negative relationship has been established between BMI of obese patients and the protective effect of HDL. In conclusion, the decrease of HDL-PON activity and the lower HDL protective action against membrane peroxidation in obese patients could contribute to accelerate the cellular oxidative damage and arteriosclerosis in obesity.