OXIDATIVE STRESS LEVELS ARE INCREASED IN TYPE 2 DIABETES MELLITUS AND OBESITY

Abstract

Objective: The relationship between obesity, type 2 diabetes mellitus (T2DM) and oxidative stress (OS) is complex and insufficiently studied. Chronic hyperglycemia causes endothelial damage by increasing reactive oxygen species (ROS) production and decreasing the activity of antioxidant enzymes, explaining why OS is a main contributor in T2DM pathogenesis. The adipose tissue is also a source of ROS via low-grade chronic inflammation and deregulation of adipokine secretion. Thus, we aimed to evaluate OS levels in obese T2DM subjects and obese non-T2DM subjects vs. controls. Design and method: OS was measured in 20 T2DM obese patients (mean age 64.85 ± 7.74 years), 20 obese non-T2DM patients (mean age 61.30 ± 10.59 years) and 20 non-obese non-T2DM controls (mean age 64.10 ± 2.26 years). ROS were evaluated via the Free Oxygen Radical Testing (FORT; normal range: < = 2.3 mmol/L H2O2) assay. The total antioxidant capacity was measured by the Free Oxygen Radical Defense (FORD; normal range: 1.07 – 1.53 mmol/L Trolox) test. Results: T2DM obese subjects registered higher FORT (3.33 ± 0.30 vs. 3.10 ± 0.34; p = 0.017) and lower FORD (0.60 ± 0.10 vs. 0.71 ± 0.15; p = 0.008) values compared to their obese non-T2DM counterparts. Both obese T2DM subjects and obese non-T2DM subjects depicted higher FORT and lower FORD values vs. controls (p < 0.001) (Table 1). In obese T2DM subjects, FORT values correlated positively with BMI, LDL-cholesterol, total cholesterol, triglycerides, uric acid and HDL/cholesterol value and negatively with age. FORD values evolved oppositely (Table 2).Conclusions: Obese T2DM subjects recorded higher FORT and lower FORD values vs. obese non-T2DM. In both obese T2DM and obese non-T2DM subjects, OS levels were higher vs. controls. In obese T2DM subjects, ROS levels correlated positively with lipid values, BMI, uric acid and, surprisingly, negatively with age. The total antioxidant capacity evolved oppositely. The negative correlation between age and ROS levels and the positive correlation between FORD and age are paradoxical since the ageing process is associated with higher ROS and lower antioxidant values.