Obesity: an independent risk factor for oxidative stress

Abstract

Background: Obesity is increasing in prevalence and presents a serious risk for the development of various disorders like diabetes mellitus, hypertension, heart disease, gall bladder disease and certain forms of cancer. Animal studies have shown that obesity is associated with increased myocardial oxidative stress and increased lipid peroxidation. The objective of this study was to test the hypothesis that obesity per se causes increased plasma lipid peroxidation and decreased erythrocyte cytoprotection.Methods: A prospective randomized study including 300 obese subjects, was conducted in the Department of Medicine and Department of Biochemistry, G. R. Medical College, Gwalior. Age and sex matched 100 subjects having BMI between 19 to 25 kg/m2 were also enrolled. Patients were grouped as Case (n=300) and Control (n=100). Detailed physical examination and laboratory investigations including lipid profile were performed. Venous blood was obtained and used for the estimation of Superoxide dismutase (SOD) and plasma malondialdehyde (MDA). Unpaired t test and analysis of variance (ANOVA) with post-hoc Bonferroni and Tukey test along with Pearson correlation was used to analyze the data using IMB SPSS ver. 20 software. Significance is assessed at 5 % level.Results: Mean age of subjects among Case and Control group was 46.2±2.4 years and 44.5±2.2 years respectively with male predominance in each group. Mean weight, height, BMI, waist, hip, waist to hip ratio, mean blood glucose, total cholesterol, triglyceride, LDL-C, HDL-C and VLDL-C among Cases were91.57±9.8 kg, 161.6±9.3 cm, 36.17± 3.4 kgm2, 114.7±6.2 cm, 114.23±17.12 cm, 0.98±0.22, 87.3±2.6 mg/dl, 196.0±12.6 mg/dl, 253.6±27.3 mg/dl, 135±47.03 mg/dl, 47.1±1.2 mg/dl and 45.8±14.03 mg/dl and among Control group were61±5.2 kg, 163.1±8.7 cm, 21.24±1.88 cm, 21.24±1.88 kg m2, 85.2±1.4 cm, 97.32±9.12 cm, 0.86±0.14, 94.4 ± 3.2 mg/dl, 186.6 ± 6.9 mg/dl, 143.4±15.4 mg/dl, 95.73±27.48 mg/dl, 51.6±1.7 mg/dl and 22.4±10.45mg/dl respectively. Mean MDA level in Case and Control group was 4.68 ± 1.72 and 2.06±0.76 μmol/ml respectively (p< 0.001). Mean SOD level among Case and Control groups was 7.65±1.13 and 12.42±2.18 units/ml respectively (p<0.001). Female obese patients had lower level of SOD. A significant negative correlation of SOD was observed with BMI (n=300, r= -0.045, P<0.001), whereas, MDA was positively correlated with BMI (n=300, r= 0.342, P<0.001).Conclusions: Obesity in humans is an independent risk factor for lipid peroxidation and depletion of cytoprotective enzymes even in the absence of other confounding factors such as diabetes and hyperlipidaemia.