#5668 PERITONEAL DIALYSIS ADDITIVE REDUCES TRANSPERITONEAL LOSS OF BLOOD MICROPARTICLE AND EXTRACELLULAR MATRIX PROTEINS IN A CONTROLLED CROSSOVER TRIAL
Authors: Eibensteiner Fabian , Herzog Rebecca , Vychytil Andreas , Aufricht Christoph , Kratochwill Klaus 
Published: June 2023

Abstract

Background and Aims
About 11% of patients requiring dialysis worldwide are treated with peritoneal dialysis (PD). With each PD exchange high amounts of protein are removed from the peritoneal cavity stemming from the systemic circulation (reflecting toxin removal, loss of serum proteins, inflammatory processes) and local inflammatory processes. Thereby, the clinically measured peritoneal protein loss (PPL) is the result of transperitoneal serum loss, lymphatic drainage, transmesothelial reabsorption, local production, and cellular components. Although high PPL has been found to be predictive of mortality and cardiovascular morbidity, the pathophysiological concept is still poorly understood.

Method
Peritoneal dialysis effluent (PDE) samples were obtained from peritoneal equilibrium tests during a prospective, multicenter, double-blinded, controlled, randomized, dual-period, 2-treatment, crossover, phase II, proof-of-concept study in Austria. PDE samples were submitted to proteomic analysis by tandem mass tag (TMT) labeling and 2D reversed phase liquid chromatography mass spectrometry. To disentangle transmembrane serum protein loss from local protein production we developed a novel and unique analytical approach. Briefly, partitioning around medoids and proximity in the Euclidean space for between visit (non-treatment visits only) single-protein kinetics was utilized to achieve this separation. A multivariate mixed-effects model was calculated to identify treatment (intraperitoneal alanyl-glutamine administration) effects.

Results
We identified 2,624 different proteins within the PDE of 12 patients across two time-points. A large cluster of proteins with stable abundances in collinearity with well-established clinical characteristics of transperitoneal transport (e.g., dialysate-to-plasma-albumin) in accordance with the three-pore-model was identified. After clustering and separation, the proteins resembling similar time-course kinetics to clinical transperitoneal membrane transport characteristics (one of five clusters) were all identified to be able to theoretically traverse through the small peritoneal pore (&lt; 4-6 nm). Of these 549 proteins lost from the systemic circulation via transperitoneal small pore diffusion, the appearance of 51 in the PD effluent was significantly reduced by intraperitoneal administration of alanyl-glutamine. The affected proteins are mainly involved in extracellular matrix organization, part of extracellular exosome signaling and blood microparticles, e.g. high density lipoprotein (HDL) formation (Apolipoprotein A1).

Conclusion
PPL is an important but poorly understood undesired effect of PD associated with cardiovascular morbidity and mortality. Our novel analytical approach enables us to disentangle the complexity of transperitoneal serum protein loss and local protein production on single-protein level across the peritoneal proteome. Furthermore, we were able to delineate the potential beneficial effects of intraperitoneal alanyl-glutamine treatment on PPL and peritoneal health which might even suggest potential beneficial effects on cardiovascular morbidity (e.g., HDL formation).