Abstract P237: Alterations In Renal Sodium Handling Proteins Determined By Urinary Extracellular Vesicle Analysis During Dietary Sodium Modulation And In Primary Aldosteronism

Abstract

Sodium handling is altered during extremes in dietary sodium intake or in pathologic conditions such as primary aldosteronism. Urinary extracellular vesicles (uEVs) are excreted by all cell types along the nephron, are enriched for membrane proteins, and could provide insight into renal physiology in humans. We assessed uEV protein excretion of renal epithelial proteins relevant to sodium handling from 54 volunteers with pre-hypertension on high (HS, 200 mmol/d) and low (LS, 10 mmol/d) sodium diet for 5-7 days. To compare pathologic versus physiologic responses to aldosterone excess, samples were collected from 9 patients with primary aldosteronism (PA). uEVs were isolated by ultracentrifugation and trypsin digested proteins were quantified using multiple reaction monitoring mass spectrometry using isotopically labeled standards, normalized to the uEV-specific marker CD9. Wilcoxon signed rank and rank sum tests were used for within-subject and between-subject comparisons, respectively. LS diet altered uEV excretion of pendrin (4.0, expressed as fold-change vs HS), aquaporin-2 (-2.03), TRPV5 (-1.91), NCC (1.51), OSR1 (1.42; P <0.01 for all), and SGLT2 (1.20, P =0.042). In primary aldosteronism, expression of ENaC-α, ENaC-β, and ENaC-γ, NCC, SGLT2, and OSR-1 were increased to a greater extent compared to during LS diet ( P <0.05 for each), whereas AQP2 and TRPV5 were similar to HS diet ( Figure ). Expression of uEV proteins relevant to renal tubular sodium handling are dynamically altered by dietary sodium restriction and aldosterone excess. Further studies could identify patterns specific to pathologic versus physiologic aldosterone responses.