MP33-03 OXALOBACTER FORMIGENES COLONIZATION NORMALIZES OXALATE EXCRETION IN A GASTRIC BYPASS MODEL OF HYPEROXALURIA

Abstract

You have accessJournal of UrologyStone Disease: Basic Research I1 Apr 2015MP33-03 OXALOBACTER FORMIGENES COLONIZATION NORMALIZES OXALATE EXCRETION IN A GASTRIC BYPASS MODEL OF HYPEROXALURIA Benjamin Canales and Marguerite Hatch Benjamin CanalesBenjamin Canales More articles by this author and Marguerite HatchMarguerite Hatch More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2015.02.564AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Compared to obese controls, patients who undergo Roux-en-Y gastric bypass (RYGB) surgery for weight loss have up to 4-fold increase in calcium oxalate stone risk, driven primarily by post-operative hyperoxaluria. The probiotic Oxalobacter formigenes (OF) has been demonstrated to reduce urinary oxalate excretion by degrading intraluminal oxalate in addition to promoting enteric oxalate elimination. The objective of the study was to examine the effect of OF colonization on urinary oxalate excretion and intestinal oxalate transport in an established hyperoxaluric RYGB animal model. METHODS Obese male Sprague Dawley rats underwent sham (n=10) or RYGB (n=18) surgery and were maintained post-operatively on low oxalate (1.5%) and low fat (10%) containing diets. After 10 weeks, half of the animals were randomized to gavage containing OF wild rat strain (OXWR). Urine and stool were collected weekly to determine oxalate and colonization status, respectively. At 20 weeks post-operatively, [14C]-oxalate fluxes and electrical parameters were measured in vitro across isolated distal colon tissue mounted in Ussing chambers. RESULTS All rats gavaged with OXWR were confirmed colonized at the time of flux studies. Urinary oxalate excretion remained low and unchanged in sham animals regardless of colonization status (mean 3.54 ± 0.59 umol/day). RYGB + OXWR animals had significant reductions in their urinary oxalate excretion after gavage (24.94 ± 9.4 vs 6.85 ± 3.0 umol/day, p<0.001) while uncolonized RYGB animals showed no significant difference in urinary oxalate (17.2 ± 4.2 vs 14.0 ± 3.3, p=0.62). Compared to sham, the RYGB procedure increased intestinal tissue permeability of oxalate by 36% and transcellular [14C]-oxalate net secretion more than 2-fold. When compared to non-colonized RYGB, RYGB + OXWR animals had 46% increase in net oxalate efflux with no significant changes in tissue permeability. CONCLUSIONS In our model, RYGB-related hyperoxaluria can be reduced to that of sham controls by OF colonization because of a dual action of the bacteria. OF colonization enhanced net secretion of oxalate across the large intestine. Because intestinal permeability was similar between both RYGB groups, the mechanism for this change in urinary oxalate appears to be primarily due to luminal oxalate degradation by OF resulting in a reduction of passive oxalate absorption across the distal colon. This in vivo study suggests that OF colonization may benefit RYGB patients with hyperoxaluria and warrants a clinical trial in patients. © 2015 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 193Issue 4SApril 2015Page: e373-e374 Advertisement Copyright & Permissions© 2015 by American Urological Association Education and Research, Inc.MetricsAuthor Information Benjamin Canales More articles by this author Marguerite Hatch More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...