Glutathione peroxidase activity in obese and nonobese diabetic patients and role of hyperglycemia in oxidative stress

BACKGROUND: Both hyperglycemia and obesity are known to cause oxidative stress, which leads to many complications associated with diabetes mellitus. A large number of diabetic patients are obese. Glutathione peroxidase (GPx) is an important indicator of level of oxidative stress. MATERIALS AND METHODS: In the present study, we assessed GPx levels in 20 healthy controls, obese, and nonobese diabetic patients (n=20 each) and analyzed the effect of insulin treatment for 24 and 48 weeks on GPx activity. GPx activity was measured using biochemical method. The GPx activity was also correlated with glycemic status of obese and nonobese diabetic patients [fasting plasma glucose (FPG) levels] after insulin therapy. Statplus software was used for statistical analysis. RESULTS: We found that there is suppression of GPx activity in diabetic patients as compared to healthy controls (70.9 ± 9.6 U/mg protein) and suppression is more in case of obese (23.4 ± 3.8 U/mg protein) than nonobese diabetics (41.5 ± 3.5 U/mg protein). Both obese (26.05 ± 4.03 U/mg protein) and nonobese (48.7 ± 4.8 U/mg protein) diabetics had increase in GPx activity after 24 weeks of insulin treatment. Further, insulin treatment led to improvement in oxidative stress after 48 weeks in both obese (28.4 ± 6.4) as well as nonobese diabetics (51.8 ± 5.4). The nonobese group showed extremely significant (P<0.001) increase in GPx activity after 24 and 48 weeks both, while obese group showed significant (P value<0.05) increase in GPx activity with insulin treatment only after 48 weeks. A negative correlation was found between postinsulin GPx levels and FPG of obese and nonobese diabetics. The correlation was more strong in case of nonobese than obese diabetics. CONCLUSION: Higher levels of oxidative stress in obese diabetics even after control of hyperglycemia by insulin treatment reflect the importance of obesity in contributing to oxidative stress.