Vitamin D, 1,25-Dihydroxyvitamin D, FGF23, and graft function after renal transplantation

Abstract

Vitamin-D has immuno-modulatory properties besides its role in mineral and bone disorder (MBD) and could have a role in allograft outcome. Fifty-two chronic kidney disease patients on dialysis going for transplantation were prospectively studied before and after renal transplantation. FGF23, 25(OH) vitamin D, 1,25-Dihydroxyvitamin D, PTH, serum Ca, serum PO4, and e-GFR status were evaluated. Vitamin D deficiency was seen in 25.0% of recipients before transplant (26.09 ± 12.19 ng/mL) and in 48.1% at 6 months post-transplant (23.36 ± 15.11 ng/mL). 1,25-(OH) 2 D levels before transplant were 102.37 ± 108.44 pmol/L, which were less than control (143.30 ± 108.0 pmol/L) and decreased further to 46.20 ± 42.11 pmol/mL at 3 months and started increasing to 78.37 ± 60.12 pmol/mL at 6 months post-transplantation without vitamin D supplementation. The prevalence of hypophosphatemia after transplantation was 32.0%, hyperkalemia was 12.0%, elevated intact PTH levels at 3 and 6 months after transplant were seen in 66.7% and 30.8% patients, respectively. FGF-23 levels were high in 72.5% of patients before transplant (495.94 ± 690.68 pg/mL) and decreased to normal levels at 3 months post-transplant (31.63 ± 14.17 pg/m) (control 32.07 ± 9.78 pg/mL). Serum intact PTH levels were 379.54 ± 281.27 pg/mL before transplant and came down to 103.96 ± 68.34 at 3 months and 69.87 ± 116.03 at 6 months post-transplantation. There was trend of higher e-GFR at 1 year post-transplant in patients without vitamin D deficiency (levels ≥30 ng/mL). The dysregulated mineral metabolism continues in post-transplant despite improvement in renal function and normalization of FGF-23.

Klotho and Fibroblast Growth Factor 23 Are Independent of Vitamin D, and Unlike Vitamin D, Are Not Associated With Graft- and Patient Survival After Kidney Transplantation

“… 39 One study including 52 kidney transplant recipients found that FGF23 levels were elevated before transplantation but decreased to normal levels within 3 mo posttransplant as eGFR normalized. 40 Another study reported elevated FGF23 levels 3 mo posttransplant, 41 and others have shown persistently elevated FGF23 levels in transplant recipients 1 y posttransplant. 42 Even in kidney transplant recipients with a well-functioning graft >10 y posttransplant, the levels of FGF23 were found to be increased compared with normal controls.…”