Effect of Vitamin D on Urinary Angiotensinogen Level in Early Diabetic Nephropathy

Urinary angiotensinogen (UAGT) is supposed to be a marker of activation of the intrarenal renin- angiotensin system (RAS) system in early diabetic nnephropathy (EDN). Vitamin D has been studied as a negative regulator of the circulating and tissue RAS activity, so its supplementation may prevent the progression of diabetic nephropathy (DN). This study was planned to assess the RAS activation and effect of vitamin D supplementation in EDN progression by estimating the UAGT level.

A total of 103 EDN subjects were randomized in two groups to receive either cholecalciferol (54) or matching placebo (49) in a double-blind manner. All were subjected to routine investigations, urinary albumin-to-creatinine ratio (UACR), UAGT, vitamin D, and intact parathyroid hormone (iPTH) at the 0 and 6 months. A total 40 healthy controls were also included for assessment of the same investigations at 0 month.

Significant reduction of UACR, UAGT, and iPTH level were corroborated with an increase in 25(OH) vitamin D level from 0 to 6 months (all four P < 0.001). After 6 months, the median [interquartile range (IQR)] of UAGT and UACR levels was significantly lower in the cholecalciferol group as compared to placebo group (p < 0.001 and P = 0.04, respectively). The median UAGT level was significantly higher in patients with EDN (cholecalciferol & placebo Group) than control group at 0 month (p = 0.001).

Significantly higher UAGT levels in EDN supports the role of intrarenal RAS activation. A significant decrease in UAGT level in the cholecalciferol group supports the beneficial role of vitamin D supplementation in the progression of EDN.