# Plasma FGF21 Concentration in Kidney Transplant Patients—Results from Prospective and Cross-Sectional Studies

## TL;DR

This study shows that kidney transplant patients have high FGF21 levels before surgery, which drop significantly after a successful transplant and correlate with kidney function and metabolic health.

## Contribution

The study provides new insights into how kidney function and metabolic factors influence FGF21 levels in long-term kidney transplant recipients.

## Key findings

- Plasma FGF21 levels in CKD patients before transplant were significantly higher than in healthy subjects.
- FGF21 levels decreased significantly after kidney transplantation and remained lower over time.
- Long-term FGF21 levels correlated with kidney function and metabolic markers like BMI and triglycerides.

## Abstract

Background/Objectives: Fibroblast growth factor 21 (FGF21) is a protein hormone involved in physiological conditions in the regulation of energy expenditure and several metabolic processes. The aim of this present study was to analyze the effect of successful kidney transplantations on the plasma FGF21 concentration and to study the factors which may influence plasma FGF21 concentration in patients in long time after kidney transplantation. Methods: This study consisted of two independent parts. The first part was a prospective observation of CKD patients in stage 5 before and then on the 14th and 30th day and 6 months after kidney transplantation. The second part of this study was the cross-sectional study completed in patients at least one year after kidney transplantation and the control group. In CKD patients directly before and during the early period after KTx, plasma FGF21 concentrations were measured four times (immediately before and 14 and 30 days and 6 months after KTx). In patients long time after kidney transplantation and in healthy subjects, plasma FGF21 concentration was measured once. Results: Forty patients with chronic kidney disease (CKD) who were either directly before or within the early period after kidney transplantation (KTx), 184 patients longtime after KTx and 50 healthy subjects were enrolled into this study. In CKD patients at the stage directly before receiving a KTx, the mean plasma FGF21 concentration was significantly higher than in the healthy subjects [1013.0 pg/mL versus 239.5 pg/mL, p < 0.001]. At 14, 30 days, and 6 months after the KTx, a significant decrease of plasma FGF21 was observed, with values of 322.5 pg/mL; 355.0 pg/mL; and 344.0 pg/mL (p < 0.001), respectively]. In patients long time after KTx, a negative correlation was found between the plasma FGF21 concentration and the estimated glomerular filtration rate and a positive correlation was found between the plasma FGF21 concentration and the BMI, the serum concentration of triglycerides, insulin, interleukin-6, CRP, and cystatin C. Conclusions: The plasma FGF21 concentration in patients with end-stage renal disease is higher than in healthy subjects and significantly decreases after a successful KTx. The plasma FGF21 concentration measured by ELISA in patients long time after kidney transplantation seems to be related to the degree of kidney function impairment and their metabolic status. The kidneys appear to be one of the main organs involved in the biodegradation and/or elimination of FGF21.