Plasma levels of suPAR are inversely associated with absolute renal function and predict long-term outcomes in renal transplant recipients - a pilot study.

BACKGROUND

The effect of renal function on elimination of soluble urokinase-type plasminogen activator receptor (suPAR), has not been properly investigated. Initially we investigated change in suPAR concentration in the same patients before and after kidney transplantation. The primary aim was to assess the association between suPAR concentration and measured glomerular filtration rate (mGFR) in kidney transplant recipients. Secondly, investigate whether suPAR concentration, as a biomarker for inflammation, measured early post-transplant may serve as a biomarker of long-term patient and graft survival.

METHODS

Plasma suPAR concentrations were measured before and 8-weeks after kidney transplantation, absolute mGFR (iohexol serum clearance) was measured 8-weeks post-transplant. Long-term outcomes were obtained from the Norwegian Renal Registry.

RESULTS

suPAR concentrations (n = 121 paired samples) were significantly reduced by a mean of 56% (95% CI: 52-60%) from a mean of 9.7 ± 4.3 µg/L before to 3.9 ± 2.3 µg/L 8-weeks after transplantation p < 0.0001. At 8-weeks, higher suPAR concentrations were moderately associated with lower mGFR (r=-0.398, p < 0.001). Multivariable logistic regression revealed that pre-transplant suPAR concentrations, in addition to mGFR, plasma uric acid and albumin at 8-weeks were significant predictors of suPAR concentrations at 8-weeks. Patients with normal (cut-off: 4.0 µg/L), compared with elevated, suPAR concentrations 8-weeks post-transplantation experienced significantly better patient survival, but not death censored long-term graft survival.

CONCLUSIONS

suPAR concentrations are closely associated with absolute mGFR indicating that renal filtration is a major elimination route for this biomarker. Our results indicate that suPAR concentrations early post-engraftment may be a relevant biomarker to consider for prediction of long-term outcomes after transplantation.