MP33-11 CALCIUM IS MORE EFFECTIVE THAN VITAMIN B6 AT REDUCING OXALATE EXCRETION IN A GASTRIC BYPASS MODEL OF HYPEROXALURIA

Abstract

You have accessJournal of UrologyStone Disease: Basic Research I1 Apr 2015MP33-11 CALCIUM IS MORE EFFECTIVE THAN VITAMIN B6 AT REDUCING OXALATE EXCRETION IN A GASTRIC BYPASS MODEL OF HYPEROXALURIA Christopher Monsour, Jesse Gregory, Marguerite Hatch, Saeed Khan, and Benjamin Canales Christopher MonsourChristopher Monsour More articles by this author , Jesse GregoryJesse Gregory More articles by this author , Marguerite HatchMarguerite Hatch More articles by this author , Saeed KhanSaeed Khan More articles by this author , and Benjamin CanalesBenjamin Canales More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2015.02.572AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Patients who develop enteric hyperoxaluria and oxalate stones after Roux-en-Y gastric bypass (RYGB) surgery are encouraged to supplement with calcium or vitamin B6 to lower stone risk. We tested the effect of these therapies on urinary oxalate excretion in an established RYGB animal model of hyperoxaluria. METHODS Obese male Sprague Dawley rats underwent sham (n=7) or RYGB (n=10) surgery. Animals were maintained on low oxalate/fat (LOF), normal calcium (NC) diet and completed a 2-phase crossover metabolic study. In the first 2-week phase, all rats were fed a LOF, high calcium (HC) diet. After a 2-week washout, all rats were fed a LOF/NC diet with supplemented vitamin B6 (1600% of laboratory rodent requirement). Urine was collected and analyzed before and after each intervention. Plasma levels of pyridoxal phosphate and associated metabolic products were measured in both control and RYGB groups twice before supplementation. RESULTS Urinary oxalate excretion remained low and unchanged in shams on each of the 3 diets. RYGB animals on LOF/HC had a 28% decrease in urine oxalate (16.9 ± 1.6 vs 12.2 ± 1.1 µmol/day, p=0.0001) without a significant change in urinary calcium. Prior to B6 supplementation, RYGB and sham animals had similar levels of plasma pyridoxal phosphate and byproducts except for slightly higher plasma homocysteine (hcy) in the RYGB group (5.25 ± 0.5 vs 3.7 ± 0.3 µmol/L, p=0.001). B6 supplementation lowered urinary oxalate excretion 15% (20.2 ± 3.0 vs 17.1 ± 1.7 µmol/day, p=0.055) although not to statistical significance. CONCLUSIONS In our obese RYGB model, increasing dietary calcium lowered urinary oxalate excretion more than B6 supplementation, and neither affected urinary calcium. RYGB animals were B6 sufficient with variations in plasma hcy likely reflective of greater protein turnover and catabolism. Calcium supplementation appears to be a reasonable therapy in hyperoxaluric RYGB patients who already maintain a low fat and low oxalate diet. The value of B6 supplementation is less clear and further study is necessary to determine whether this commonly employed therapy provides a benefit in enteric hyperoxaluria. © 2015 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 193Issue 4SApril 2015Page: e377 Advertisement Copyright & Permissions© 2015 by American Urological Association Education and Research, Inc.MetricsAuthor Information Christopher Monsour More articles by this author Jesse Gregory More articles by this author Marguerite Hatch More articles by this author Saeed Khan More articles by this author Benjamin Canales More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...