Mitochondrial DNA oxidation and manganese superoxide dismutase activity in peripheral blood mononuclear cells from type 2 diabetic patients.

Abstract Aim To investigate the balance between parameters of oxidative stress and antioxidant defences in the mitochondria of peripheral blood mononuclear cells (PBMCs) of type 2 diabetic patients with late complications. Methods Ten type 2 diabetic patients with late diabetic complications and 10 age-matched healthy volunteers (controls) were prospectively recruited. Mitochondrial DNA (mtDNA) oxidative damage and mtDNA content were measured as indices of oxidative stress. Manganese superoxide dismutase (MnSOD) activity has been used as an index of mitochondrial antioxidant defence. Mitochondrial respiratory-chain function (cytochrome C oxidase activity) was also assessed. Results Mitochondrial DNA (mtDNA) oxidation was significantly higher in the PBMCs of diabetic patients than in control subjects ( P P =0.01), and was related to mtDNA oxidative damage. No differences in mitochondrial respiratory-chain function were found between diabetic patients and controls. Conclusion PMBCs from type 2 diabetic patients with late diabetic complications exhibit high mtDNA oxidative damage. The degree of mtDNA oxidation was associated with an increase in MnSOD as an adaptive response to oxidative stress. The consequences of mtDNA oxidative damage on PBMC function and the progression of diabetic complications remain to be elucidated.