Introduction: FGF-23 has been linked to allograft failure. However, careful serial profiling of FGF-23 has not been done. Therefore, we measured FGF-23 levels in recipients who participated in the ABCAN Trial funded by the NIH.

Methods: This is a post-hoc analysis of the 154 kidney transplant recipients who were randomized to losartan (100 mg daily) vs. placebo shortly after transplantation. Subjects underwent annual iothalamate GFR for 5 years in addition to allograft biopsy at study entry and exit. The primary endpoint of the trial was doubling of cortical interstitium volume expansion from baseline to 5 years or ESRD from IF/TA. The main result showed a modest protective effect with losartan (p = 0.08).

Results: FGF-23 was measured at baseline and year 5. Cross sectional unadjusted analysis of FGF-23 at baseline showed that it was not associated with age, systolic or diastolic blood pressures, urinary protein or fraction of renal cortical volume occupied by interstitium. However, FGF-23 was positively associated with creatinine (r = 0.42, p < 0.0001), uric acid (r = 0.22, p = 0.02) and inversely associated with iothalamate GFR (r = -0.23, p = 0.01). Figure 1 shows a marginal sex*time interaction in FGF-23 (p <0.05) indicating at baseline FGF-23 is higher in females, but at year 5 this difference disappeared (p = 0.50). FGF-23 doubled in the placebo group while it declined with losartan.

Conclusion: FGF-23 levels decline with angiotensin II blockade and its level was inversely associated with iothalamate GFR. Unfortunately, we do not have data on the different components of this axis such as parathyroid hormone and serum calcium and phosphate.

CITATION INFORMATION: Sanchez O, Reule S, Li S, Berglund D, Spong R, Ibrahim H. Angiotensin II Blockade and Fibroblast Growth Factor-23 in Stable Kidney Transplant Recipients. Am J Transplant. 2016;16 (suppl 3).

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