Time-course of glycolytic control proteins in urinary extracellular vesicles of deceased donor kidney transplant recipients

Abstract

Aim To measure expression of glycolytic control proteins contained in urinary extracellular vesicles (UEV) as a marker for changes in glycolysis and kidney metabolism following deceased donor kidney transplantation.

Methods In this prospective observational study, urine samples were collected from adult deceased donor kidney transplant recipients prior to transplant (T0) and serially after transplant at days 1-3 (T1), 5-10 (T2) and 70-100 (T3). UEV were separated by differential ultracentrifugation and characterized by expression of CD9, TSG101 and THP. All proteins were analysed by immunoblotting. Glycolytic control proteins PFK-L, PFKFB2, pSer483-PFKFB2, PFKFB3, PFKFB4, PK-L/R, PK-M2 and NGAL were assayed. Densitometry was compared via repeated measures one-way ANOVA.

Results 29 urine samples from 8 participants were included. Three were anuric at baseline. All recipients had functioning grafts at 3 and 12 months. There was increasing detection of CD9 and TSG101 post-transplant (p=0.014, 0.028 respectively). Expression of PFKFB2 and PK-M2 was seen at T1 (100%) and persisted in 7/8 subjects at T3. PK-LR was detected in 4/5 (80%) samples at T0 and not thereafter (p=0.0022). NGAL+ UEV was detected in 4/5 subjects at T0 and in 8/8 recipients at T1-3, with expression measured by densitometry reducing over time (p<0.0001). PFK-L was not detected. There were no statistically significant changes in densitometry expression of PFKFB2 (p=0.30), pSer483-PFKFB2 (p=0.29), PFKFB3 (p=0.41), PFKFB4 (p=0.41) and PK-M2 (p=0.62) over time.

Conclusion We identified changes in the profile of glycolytic control proteins PFKFB2 and PK-M2 immediately post-transplant, which persists over time. PFKFB2 and PK-M2 have been associated with increased glycolysis, including aerobic glycolysis.

Impact The study describes changes in glycolytic control proteins in the early post-transplant period. Future studies will focus on the way that expression of these proteins can be used to non-invasively monitor the health of kidney transplants.