We assessed DNA damage in patients with metabolic syndrome (MetS) by performing comet and micronucleus (MN) assays on peripheral blood lymphocyte cultures from study participants. 52 MetS patients and 35 age-matched healthy controls were evaluated for abdominal obesity, body-mass index (BMI), blood pressure, serum triglycerides, HbA1c, HDL-C, and fasting blood glucose levels. In addition, malondialdehyde (MDA) levels and activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were determined. Serum levels of triglycerides, HbA1c, fasting blood glucose and waist circumference, systolic blood pressure, diastolic blood pressure, and BMI of the subjects in the MetS group were significantly higher than those of the control group (for each, p < 0.001). However, the mean level of HDL-C in the MetS group was lower than in the control group (p < 0.001). In the study, the length of comet tails was significantly higher in the MetS patients (10.23 +/- 1.98, range 5.72-15.08) than in the controls (3.12 +/- 1.73, range 0.6-7.1) (p < 0.001). MN frequency was also significantly increased in MetS patients (3.68 +/- 1.27 per 1000 cells) compared to that of the control group (1.81 +/- 0.84 per 1000 cells) (p < 0.001). Micronucleated cell frequency and comet-tail length in subjects showed positive correlations with waist circumference, BMI, and plasma triglyceride levels (p < 0.01) and negative correlations with HDL-C levels (p < 0.01). Among the oxidative stress factors, MDA levels were significantly higher in MetS patients than in the controls. However, SOD and GSH-Px enzyme activities were significantly lower in the MetS group than in the controls. These findings suggest that patients with MetS have increased DNA damage and oxidative stress. (C) 2015 Elsevier B.V. All rights reserved.