Relationship between glyco-oxidation, antioxidant status and microalbuminuria in type 2 diabetic patients

This study examined the relationship, if any, between glucose-induced oxidative stress, antioxidant status and microalbuminuria in patients with type 2 diabetes.

The study involved 99 consecutive type 2 diabetic patients (57 men, 42 women). Patients with persistent microalbuminuria were identified and the following variables evaluated: fasting plasma glucose, HbA_1c, malonyldialdehyde (MDA), pentosidine, AGE, the total radical-trapping antioxidant parameter (TRAP), vitamin E, creatinine, estimated GFR and lipid profile.

Patients were divided into two groups, i.e. 37 individuals without microalbuminuria (AER <20 μg/min) and 62 with microalbuminuria (AER ≥20 μg/min). The following variables were significantly higher in patients with microalbuminuria than in those without microalbuminuria (mean ± SD): fasting plasma glucose 9.41 ± 2.88 vs 8.19 ± 1.93 mmol/l, p < 0.05; HbA_1c 7.97 ± 1.51 vs 7.39 ± 1.03%, p < 0.05; MDA 1.18 ± 0.35 vs 1.02 ± 0.29 µmol/l, p < 0.05; pentosidine 98.5 ± 24.6 vs 82.9 ± 20.9 pmol/ml, p < 0.005; and AGE 13.2 ± 4.8 vs 10.6 ± 3.8 µg/mg protein, p < 0.01. However, vitamin E and TRAP did not differ between the two groups. Serum creatinine values and estimated GFR were similar in the two groups. Only in patients with microalbuminuria were significant linear correlations seen between AER and both oxidation (HbA_1c r = 0.33, p < 0.01; MDA r = 0.59, p < 0.001; pentosidine r = 0.48, p < 0.001; and AGE r = 0.44, p < 0.001) and antioxidation variables (vitamin E r = −0.55, p < 0.001; TRAP r = −0.49, p < 0.001). Considering all variables together, multiple regression revealed a correlation between microalbuminuria and vitamin E, TRAP, HbA_1c and MDA, but not pentosidine or AGE.

Our data suggest that microalbuminuria in type 2 diabetic patients might be promoted by an insufficient counter-regulation of the antioxidant system in the event of increased glyco-oxidation/glycation.