Food and Behaviour Research

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The Small Intestine Converts Dietary Fructose into glucose and organic acids

Jang C, Hui S, Lu W, Cowan AJ, Morscher RJ, Lee G, Liu W, Tesz GJ, Birnbaum MJ, Rabinowitz JD (2018) Cell Metab Feb 2018; 27, 2: 351–361.e3, doi.org/10.1016/j.cmet.2017.12.016 

Web URL: Read the research on cell.com here

Abstract:

Excessive consumption of sweets is a risk factor for metabolic syndrome. A major chemical feature of sweets is fructose.

Despite strong ties between fructose and disease, the metabolic fate of fructose in mammals remains incompletely understood. Here we use isotope tracing and mass spectrometry to track the fate of glucose and fructose carbons 
in vivo, finding that dietary fructose is cleared by the small intestine. Clearance requires the fructose-phosphorylating enzyme ketohexokinase.

Low doses of fructose are ∼90% cleared by the intestine, with only trace fructose but extensive fructose-derived glucose, lactate, and glycerate found in the portal blood.

High doses of fructose (≥1 g/kg) overwhelm intestinal fructose absorption and clearance, resulting in fructose reaching both the liver and colonic microbiota. Intestinal fructose clearance is augmented both by prior exposure to fructose and by feeding.

We propose that the small intestine shields the liver from otherwise toxic fructose exposure.

FAB RESEARCH COMMENT:

See the associated news article, which explains the important implications of this finding: