title: Evidence for impaired assimilation of protein in chronic renal failure.
abstract: BACKGROUND
  Protein malnutrition is a common finding in chronic renal failure (CRF) and is associated with poor outcome. We hypothesized that besides inadequate dietary protein intake and alterations in metabolism, deficient protein assimilation (digestion and absorption) might contribute to the pathogenesis of protein malnutrition in uremia.
  
  
  METHODS
  Protein assimilation was evaluated in 64 healthy volunteers and 119 CRF patients by means of a 13C protein breath test and/or quantification of p-cresol in a 24-hour urine collection. Both approaches provide reliable information on the efficiency of protein assimilation. Breath test results were expressed as maximum percentage of administered dose of 13C (%max) and cumulative percentage at the end of the test (%cum(end)). Data were stratified according to renal function.
  
  
  RESULTS
  As compared to subjects with glomerular filtration rate (GFR) > or = 60 mL/min/1.73 m2, subjects with GFR < 30 mL/min/1.73 m2 demonstrated significantly lower breath test-derived parameters of protein assimilation (%max 3.97 +/- 0.23 vs. 5.20 +/- 0.23, P=0.0017; %cum(end) 13.91 +/- 0.86 vs. 17.40 +/- 0.80, P= 0.013) and significantly higher urinary output of p-cresol (54.88 mg/24 hours vs. 28.65 mg/24 hours, P= 0.0005). %max (r=0.399, P < 0.0001), %cum(end) (r=0.347, P=0.0007), and urinary p-cresol (r=-0.229, P=0.007) correlated significantly with GFR. Serum albumin correlated significantly with %max (r=0.399, P=0.0002), %cum(end) (r=0.408, P=0.0001), and urinary p-cresol output (r=-0.186, P=0.035).
  
  
  CONCLUSIONS
  Our data provide evidence that protein assimilation is impaired in CRF. This impairment might contribute to protein malnutrition in CRF.
authors: Department of Medicine, Division of Nephrology and Laboratory of Radiopharmaceutical Chemistry, University Hospital Gasthuisberg, Leuven, Belgium.
authors: Bert
authors: B
authors: Bammens
authors: Kristin
authors: K
authors: Verbeke
authors: Yves
authors: Y
authors: Vanrenterghem
authors: Pieter
authors: P
authors: Evenepoel
mesh_terms: D000042:Absorption; D000328:Adult; D000368:Aged; D001944:Breath Tests; D002247:Carbon Isotopes; D003408:Cresols / Q000652:urine; D003430:Cross-Sectional Studies; D004063:Digestion; D004527:Egg Proteins / Q000378:metabolism* / Q000493:pharmacokinetics; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007676:Kidney Failure, Chronic / Q000150:complications / Q000378:metabolism* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011502:Protein-Energy Malnutrition / Q000209:etiology; D012709:Serum Albumin / Q000032:analysis
chemical_list: D002247:Carbon Isotopes; D003408:Cresols; D004527:Egg Proteins; D012709:Serum Albumin; C032538:4-cresol