title: Fructose transporters GLUT5 and GLUT2 expression in adult patients with fructose intolerance.
abstract: BACKGROUND
  Gastrointestinal symptoms and malabsorption following fructose ingestion (fructose intolerance) are common in functional gastrointestinal disorders (FGID). The underlying mechanism is unclear, but is hypothesized to be related an abnormality of intestinal fructose transporter proteins.
  
  
  OBJECTIVE
  To assess the expression of the main intestinal fructose transporter proteins, glucose transport protein 5 (GLUT5) and 2 (GLUT2), in FGID.
  
  
  METHODS
  The expression of GLUT5 and GLUT2 protein and mRNA in small intestinal biopsy tissue was investigated using real-time reverse-transcription PCR and Western immunoblotting in 11 adults with FGID and fructose intolerance ascertained by breath testing and in 15 controls.
  
  
  RESULTS
  Median expression levels of GLUT5 mRNA normalized to beta-actin were 0.18 (interquartile range, IQR, 0.13-0.21) in patients and 0.17 (IQR 0.12-0.19) in controls (p > 0.05). Respective levels of GLUT2 mRNA were 0.26 (IQR 0.20-0.31) and 0.26 (IQR 0.19-0.31) (p > 0.05). Median expression levels of GLUT5 protein normalized to alpha-tubulin were 0.95 (IQR 0.52-1.68) in patients and 0.95 (IQR 0.59-1.15) in controls (p > 0.05). Respective protein expression levels for GLUT2 were 1.56 (IQR 1.06-2.14) and 1.35 (IQR 0.96-1.79) (p > 0.05).
  
  
  CONCLUSIONS
  Human fructose intolerance may not be associated with marked changes in GLUT5 and GLUT2 expression. Replication of these results in a larger subject group, including measures of transporter activation and membrane and subcellular localization, is warranted.
authors.affiliation: Brain-Gut Research Group, Bern, Switzerland ; Neurogastroenterology Unit, Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore.
authors.forename: Clive H
authors.initials: CH
authors.lastname: Wilder-Smith
authors.affiliation: Neurogastroenterology Unit, Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore.
authors.forename: Xinhua
authors.initials: X
authors.lastname: Li
authors.affiliation: Molecular Diagnosis Centre, Department of Laboratory Medicine, National University Hospital, Singapore.
authors.forename: Sherry Sy
authors.initials: SS
authors.lastname: Ho
authors.affiliation: Neurogastroenterology Unit, Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore.
authors.forename: Sai Mun
authors.initials: SM
authors.lastname: Leong
authors.affiliation: Neurogastroenterology Unit, Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore.
authors.forename: Reuben K
authors.initials: RK
authors.lastname: Wong
authors.affiliation: Molecular Diagnosis Centre, Department of Laboratory Medicine, National University Hospital, Singapore ; Department of Pathology, Yong Loo Lin School of Medicine, National University of Singapore.
authors.forename: Evelyn Sc
authors.initials: ES
authors.lastname: Koay
authors.affiliation: Department of Pharmacology & Physiology, UMDNJ - New Jersey Medical School, Newark, USA.
authors.forename: Ronaldo P
authors.initials: RP
authors.lastname: Ferraris
keywords: FODMAP; GLUT2; GLUT5; fructose intolerance; fructose transporters; irritable bowel syndrome; malabsorption; visceral pain