Serum αKlotho as a Predictor of Graft Dysfunction After Kidney Transplantation

To improve the long-term survival rate after kidney transplantation (KTx), allograft injury should be identified as soon as possible. Regardless of aggressive immunosuppressive therapies, recipients of kidney transplants still have a significant risk of graft failure. No specific predictor for the progression of chronic kidney disease (CKD) after KTx has yet been found. Aberrant molecular mechanisms involving the αKlotho-fibroblast growth factor (FGF) 23 axis may be a useful determinant of renal impairment and graft failure over time.

Plasma and spot urine samples were collected from 47 patients 1 year after KTx. Evaluation of renal function after KTx was performed using levels of biomarkers including serum intact FGF23, soluble αKlotho, 25(OH) vitamin D (25(OH)D), and the difference in the estimated glomerular filtration rate (eGFR) between the first and third year after KTx (ΔeGFR).

The median serum αKlotho, intact FGF23, and 25(OH)D were 516.3 pg/mL, 58.7 pg/mL, and 5.7 ng/mL, respectively. No marked changes in the standard biomarkers that regulate phosphate homeostasis were found. Serum αKlotho levels were associated with ΔeGFR. Multivariate regression analysis revealed that serum αKlotho levels significantly predicted a decrease in eGFR in the graft kidney 2 years after KTx, but serum 25(OH)D and FGF23 levels were not significant. Serum αKlotho levels showed an inverse correlation with fractional excretion of magnesium, which reflects tubular injury in the early stage of CKD.

Measurement of serum αKlotho may serve as a useful predictor of KTx patients who require initiation of pre-emptive medication.