# Microbiota based mechanisms of post-infection irritable bowel syndrome

> **NIH NIH R01** · MAYO CLINIC ROCHESTER · 2022 · $349,800

## Abstract

ABSTRACT
One in six adults in the U.S. suffers from chronic and often disabling symptoms of irritable bowel syndrome
(IBS). Intestinal infections are an established risk-factor for development of post-infection IBS (PI-IBS). The
intestinal tract contains a variety of proteases, and we have discovered that PI-IBS patients have significantly
higher fecal proteolytic activity (PA) than controls. More importantly, PA associates strongly with loss of
intestinal barrier function and worse symptoms for the patients. We found that patients who develop PI-IBS and
have high PA have a significant loss of microbial diversity that starts soon after the infection. Key microbial
taxa are lost, especially from the Alistipes genus. Using metaproteomics, we found that proteases driving PA in
these patients are of human origin. In order to understand if loss of microbiota could be affecting host
proteases, we used germ-free mice. Colonization of germ-free mice with healthy human microbiota
(humanization) results in a significant decline of PA suggesting commensal microbes inhibit host proteases
and thus have a role in maintaining intestinal health. However, the dysbiotic microbiota from the high PA
patients that are missing specific microbes were unable to suppress PA. We hypothesize that Alistipes and
other missing bacteria play a critical role in suppression of PA. We plan to test the candidate bacteria identified
in the preliminary experiments and inter-species interactions in PA regulation in Aim 1. Next, we determined
how loss of microbes result in poor inhibition of proteases. Unconjugated bilirubin is an inhibitor of serine
proteases and microbial β-glucuronidases deconjugate bilirubin. We found that the PI-IBS patients with high
PA have lower fecal microbial β-glucuronidase enzymatic activity. Additionally, they have lower levels of end
products of bilirubin deconjugation. β-glucuronidases are a large family of microbial enzymes with varying
sources, structures and catalytic efficacies for different substrates. We hypothesize that loss of specific
microbial β-glucuronidases will result in impaired deconjugation of bilirubin. In Aim 2, we will analyze
metagenomics data from our PI-IBS patients with high and low PA for presence of microbial β-glucuronidases
as well as determine the efficacy of these fecal samples for bilirubin deconjugation. Additionally, we will
generate purified β-glucuronidases from Alistipes and other bacterial taxa for assessing bilirubin deconjugation
efficacy in vitro. Next, we have shown that fecal microbiota transfer using an Alistipes enriched low PA
community can suppress PA in high PA humanized mice providing a rationale for using microbiota for protease
suppression and correcting intestinal barrier function. In Aim 3, we will use cohousing strategies to allow
microbiota transfer between humanized high and low PA mice and determine if barrier dysfunction associated
with a high PA state can be reversed. Furthermore, we will determi...

## Key facts

- **NIH application ID:** 10491307
- **Project number:** 5R01DK127998-02
- **Recipient organization:** MAYO CLINIC ROCHESTER
- **Principal Investigator:** Madhusudan Grover
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $349,800
- **Award type:** 5
- **Project period:** 2021-09-21 → 2026-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10491307

## Citation

> US National Institutes of Health, RePORTER application 10491307, Microbiota based mechanisms of post-infection irritable bowel syndrome (5R01DK127998-02). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/10491307. Licensed CC0.

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