# Clostridioides difficile toxins alter host metabolic pathway and bile acid homeostasis gene expression in colonic epithelium

## TL;DR

This study shows that Clostridioides difficile and its toxins disrupt host metabolism and bile acid regulation in the gut, leading to inflammation and disease.

## Contribution

The study reveals novel insights into how C. difficile toxins alter host metabolic and bile acid pathways in colonic epithelial cells.

## Key findings

- C. difficile infection reduces PPAR signaling and cholesterol metabolism gene expression in mice.
- Toxins TcdA and TcdB alter PPAR-regulated and cholesterol metabolic genes in human cell cultures.
- Farnesoid X receptor pathways are significantly affected by toxin exposure in cell models.

## Abstract

A major risk factor for acquiring Clostridioides difficile is antibiotic usage that disrupts a healthy microbial gut community, facilitating the establishment of infection. Once established, C. difficile secretes exotoxins (TcdA and TcdB) that are internalized into host colonic epithelial cells where they disrupt gut barrier function and induce hyperinflammation resulting in severe diarrhea and possibly leading to death. We employed three different platforms to explore gene expression of cells in the gut when exposed to C. difficile or its toxins, TcdA and TcdB. An antibiotic-treated mouse model of Clostridioides difficile infection (CDI) was used to identify differential gene expression with a NanoString Technologies mouse inflammatory gene panel consisting of 770 genes, including a subset of bile acid (BA) homeostasis and nuclear receptor genes. In the cecal tissue of mice with CDI, reduced expression was observed for genes involved in peroxisome proliferator-activated receptor (PPAR) signaling and cholesterol and glucose metabolism, while a significant increase in expression was observed for IL-17 related inflammatory genes. Similarly, Caco-2 cell culture and primary human colonic epithelial cells (hCE) exposed to toxins for 24 h showed altered expression in several PPAR-regulated and cholesterol metabolic genes similar to those found in mice. These cell culture experiments also revealed significant alterations in gene expression of the Farnesoid X receptor BA regulatory pathway. Together, these data suggest that exposure to C. difficile and its toxins may alter host cholesterol metabolic processes, including BA transport and synthesis.