Gender- and disease-specific urinary thioredoxin in chronic kidney disease patients with or without type 2 diabetic nephropathy

Aim: The role of urinary (U-) thioredoxin (Trx), a class of small redox proteins, in physiological and pathological conditions, in addition to its gender specificity, has been insufficiently determined in chronic kidney disease (CKD) patients, especially in diabetes mellitus (DM) nephropathy. Methods: U-Trx was measured cross-sectionally in 110 CKD outpatients with estimated glomerular filtration rate (eGFR) of >15 mL/min per 1.73 m(2), namely, in 57 type 2 DM patients (male: n = 41, female: n = 16) and 53 non-DM patients (M: n = 33, F: n = 20), as well as 30 healthy controls (M: n = 11, F: n = 19). Comparisons were made among controls, DM and non-DM, and between M and F, with clinical parameters compared in each group. In addition, a comparison between average U-Trx level and the changes of renal function during a one-year period was performed. Results: U-Trx was significantly higher in females than in males in controls (P < 0.05) and in non-DM patients (P < 0.05). Multiple regression analysis revealed that urinary protein (UP)/creatinine (Cr) ratio, female sex and HbA1c were independent factors affecting U-Trx among all subjects (adjusted R-2 = 0.468). In DM patients, U-Trx was negatively correlated with eGFR, especially in males, and positively correlated with UP/Cr and NAG in both sexes (all P < 0.01), as well as with systolic blood pressure in all (P < 0.05). Average U-Trx was positively correlated with the rate of annual eGFR decline of male (P < 0.01) but not female DM patients. Conclusion: U-Trx might have a gender-specific physiological and pathological role and be a potent marker of renal damage in DM nephropathy.