title: Steatorrhea and hyperoxaluria occur after gastric bypass surgery in obese rats regardless of dietary fat or oxalate.
abstract: OBJECTIVE
  We determined the effect of dietary fat and oxalate on fecal fat excretion and urine parameters in a rat model of Roux-en-Y gastric bypass surgery.
  
  
  METHODS
  Diet induced obese Sprague-Dawley® rats underwent sham surgery as controls (16), or Roux-en-Y gastric bypass surgery (19). After recovery, rats had free access to a normal calcium, high fat (40%) diet with or without 1.5% potassium oxalate for 5 weeks and then a normal (10%) fat diet for 2 weeks. Stool and urine were collected after each period. Fecal fat was determined by gas chromatography and urine metabolites were evaluated by assay spectrophotometry.
  
  
  RESULTS
  Daily fecal fat excretion remained low in controls on either diet. However, Roux-en-Y gastric bypass rats ingested a food quantity similar to that of controls but had eightfold higher fecal fat excretion (p <0.001) and heavier stools (p = 0.02). Compared to controls, gastric bypass rats on the high fat diet with potassium oxalate had a fivefold increase in urine oxalate excretion (p <0.001), while gastric bypass rats without potassium oxalate had a twofold increase in urine calcium (p <0.01). Lowering dietary fat in gastric bypass rats with potassium oxalate led to a 50% decrease in oxalate excretion (p <0.01), a 30% decrease in urine calcium and a 0.3 U increase in urine pH (p <0.001).
  
  
  CONCLUSIONS
  In this Roux-en-Y gastric bypass model high fat feeding resulted in steatorrhea, hyperoxaluria and low urine pH, which were partially reversible by lowering the dietary fat and oxalate content. Roux-en-Y gastric bypass rats on normal fat and no oxalate diets excreted twice as much oxalate as age matched, sham operated controls. Although Roux-en-Y gastric bypass hyperoxaluria appears primarily mediated by gut and diet, secondary causes of oxalogenesis from liver or other mechanisms deserve further exploration.
authors.affiliation: Department of Urology, University of Florida, Gainesville, Florida 32610, USA. benjamin.canales@urology.ufl.edu
authors.forename: Benjamin K
authors.initials: BK
authors.lastname: Canales
authors.forename: Joseph
authors.initials: J
authors.lastname: Ellen
authors.forename: Saeed R
authors.initials: SR
authors.lastname: Khan
authors.forename: Marguerite
authors.initials: M
authors.lastname: Hatch
mesh_terms: D000818:Animals; D004041:Dietary Fats / Q000378:metabolism*; D004195:Disease Models, Animal; D005243:Feces / Q000737:chemistry; D015390:Gastric Bypass / Q000009:adverse effects* / Q000379:methods; D006959:Hyperoxaluria / Q000209:etiology* / Q000503:physiopathology; D008297:Male; D009765:Obesity / Q000150:complications / Q000601:surgery*; D010070:Oxalates / Q000378:metabolism*; D011183:Postoperative Complications / Q000453:epidemiology / Q000503:physiopathology; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values; D018570:Risk Assessment; D045602:Steatorrhea / Q000209:etiology* / Q000503:physiopathology; D016896:Treatment Outcome; D016482:Urinalysis
chemical_list: D004041:Dietary Fats; D010070:Oxalates
keywords: DIO; FM; GI; LBM; Ox; RYGB; Roux-en-Y gastric bypass; calcium oxalate; diet induced obesity; fat mass; gastric bypass; gastrointestinal; lean body mass; morbid; obesity; oxalate; steatorrhea; urinary bladder