Effects of Folic Acid Supplementation on Proteinuria in Type 2 Diabetic Patients with Overt Proteinuria

Objective: An association between high homocysteine levels and proteinuria in diabetic nephropathy has been shown. On the other hand, supplementation with folic acid lowers homocysteine concentration. We have studied the effects of folic acid supplementation on proteinuria in type 2 diabetic patients with overt proteinuria. Materials and Methods: Forty five (29 men and 16 women) type 2 diabetic patients with overt proteinuria were randomized into 2 groups. One group was treated with folic acid for 6 months (22 patients), and the other was not (control group, 23 patients). Twenty-four hours proteinuria, creatinine clearance, and serum homocysteine were measured at baseline and 6 months of treatment. Results: In the treatment group, baseline proteinuria was 2927 ± 2858 mg/day, and after 6 months of folic acid treatment, there was a significant decrease in proteinuria to 2049 ± 1641 mg/day (P < 0.05). For the control group, there was no change of proteinuria after 6 months of follow-up ( P = 0.9). Serum homocysteine levels were significantly decreased in subjects treated with folic acid, from 19.2 ± 9.46 µmol/L to 16 ± 5.6 µmol/L; P < 0.05). There were no significant differences in creatinine clearance at the end of the study comparing the two groups. Conclusion: Supplementation with folic acid decreases proteinuria in type 2 diabetic patients with overt proteinuria and that this action may be mediated through reduced concentrations of serum homocysteine. However, for evaluation of the effect of folic acid on renal function, further studies with longer follow-up are needed.