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. 2014 Feb;2(1):14-21.
doi: 10.1177/2050640613505279.

Fructose transporters GLUT5 and GLUT2 expression in adult patients with fructose intolerance

Clive H Wilder-Smith  1 , Xinhua Li  2 , Sherry Sy Ho  3 , Sai Mun Leong  2 , Reuben K Wong  2 , Evelyn Sc Koay  4 , Ronaldo P Ferraris  5
Affiliations

Fructose transporters GLUT5 and GLUT2 expression in adult patients with fructose intolerance

Clive H Wilder-Smith et al. United European Gastroenterol J. 2014 Feb.

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.

Keywords: FODMAP; GLUT2; GLUT5; fructose intolerance; fructose transporters; irritable bowel syndrome; malabsorption; visceral pain.

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Figures

Figure 1.
Figure 1.
GLUT5 (a) and GLUT2 (b) mRNA expression in 11 patients with fructose intolerance compared to 15 controls, normalized to beta-actin B. The box-Whisker plots show medians (central horizontal line), interquartile ranges (upper and lower ends of boxes), and absolute ranges of values (ends of whiskers). The expression of GLUT5 and GLUT2 mRNA was similar between patients and controls.
Figure 2.
Figure 2.
Western immunoblots of GLUT5 and GLUT2 showing the control protein, alpha-tubulin, and total protein (Ponceau S staining) in 10 patients with fructose intolerance compared to 14 controls.
Figure 3.
Figure 3.
GLUT5 (a) and GLUT2 (b) protein expression in 11 patients with fructose intolerance compared to 15 controls, normalized to alpha-tubulin. The box-whisker plots show medians (central horizontal line), interquartile ranges (upper and lower ends of boxes), and absolute ranges of values (ends of whiskers). The expression of GLUT5 and GLUT2 protein was similar between patients and controls.
See this image and copyright information in PMC

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