Fructose malabsorption in ChREBP-deficient mice disrupts the small intestine immune microenvironment and leads to diarrhea-dominant bowel habit changes.

Background: The mechanism by which incompletely absorbed fructose causes gastrointestinal symptoms is not fully understood. In this study, we investigated the immunological mechanisms of bowel habit changes associated with fructose malabsorption by examining Chrebp-knockout mice exhibiting defective fructose absorption.

Methods: Mice were fed a high-fructose diet (HFrD), and stool parameters were monitored. The gene expression in the small intestine was analyzed by RNA sequencing. Intestinal immune responses were assessed. The microbiota composition was determined by 16S rRNA profiling. Antibiotics were used to assess the relevance of microbes for HFrD-induced bowel habit changes.

Results: Chrebp-knockout (KO) mice fed HFrD showed diarrhea. Small-intestine samples from HFrD-fed Chrebp-KO mice revealed differentially expressed genes involved in the immune pathways, including IgA production. The number of IgA-producing cells in the small intestine decreased in HFrD-fed Chrebp-KO mice. These mice showed signs of increased intestinal permeability. Chrebp-KO mice fed a control diet showed intestinal bacterial imbalance, which the HFrD exaggerated. Bacterial reduction improved diarrhea-associated stool parameters and restored the decreased IgA synthesis induced in HFrD-fed Chrebp-KO mice.

Conclusions: The collective data indicate that gut microbiome imbalance and disrupting homeostatic intestinal immune responses account for the development of gastrointestinal symptoms induced by fructose malabsorption.