A powerful new tool to unveil the communication between gut microbes and the brain

Summary: Researchers are developing a new tool to study the communication of microbes in the gastrointestinal tract and the brain.

Source: Baylor College of Medicine

Over the past decade, researchers have begun to appreciate the importance of a two-way communication that occurs between microbes in the gastrointestinal tract and the brain, known as the gut-brain axis.

These “conversations” can alter how these organs function and involve a complex web of chemical signals derived from microbes and the brain that are difficult for scientists to uncouple in order to better understand.

“Currently, it is difficult to determine which microbial species cause specific brain alterations in a living organism,” said first author Dr. Thomas D. Horvath, instructor of pathology and immunology at Baylor College of Medicine and Texas. Children’s Hospital.

“Here we present a valuable tool that allows investigation of the connections between gut microbes and the brain. Our laboratory protocol allows for the identification and comprehensive evaluation of metabolites – compounds produced by microbes – at the cellular and animal levels. entire.

The gastrointestinal tract is home to a rich and diverse community of beneficial microorganisms known collectively as the gut microbiota. In addition to their role in maintaining the gut environment, gut microbes are increasingly recognized for their influence on other distant organs, including the brain.

“Gut microbes can communicate with the brain through several pathways, for example by producing metabolites, such as short-chain fatty acids and peptidoglycans, neurotransmitters, such as gamma-aminobutyric acid and histamine, and compounds that modulate the immune system as well as others. said co-first author Dr. Melinda A. Engevik, assistant professor of regenerative and cellular medicine at the Medical University of South Carolina.

The role microbes play in central nervous system health is highlighted by links between the gut microbiome and anxiety, obesity, autism, schizophrenia, Parkinson’s disease and Alzheimer’s disease .

“Animal models have played a pivotal role in linking microbes to these fundamental neural processes,” said co-author Dr. Jennifer K. Spinler, assistant professor of pathology and immunology at Baylor and Texas Children’s Hospital. Microbiome Center.

“The current study protocol allows researchers to take steps to unravel the specific involvement of the gut-brain axis in these conditions, as well as its role in health.”

A roadmap to understanding the complex circulation system in the gut-brain axis

One strategy researchers used to better understand how a single type of microbe can influence the gut and brain was to first grow the microbes in the lab, collect the metabolites they produced, and analyze them using mass spectrometry and metabolomics.

Mass spectrometry is a laboratory technique that can be used to identify unknown compounds by determining their molecular weight and to quantify known compounds. Metabolomics is a technique for the large-scale study of metabolites.

This shows a diagram of the study
This protocol gives researchers a roadmap to understand the complex circulation system between the gut and the brain and its effects on health and disease. Credit: Baylor College of Medicine

“The effect of the metabolites was then studied in the mini-gut, a laboratory model of human intestinal cells that retains the properties of the small intestine and is physiologically active,” Engevik said. “In addition, the microbe’s metabolites can be studied in living animals.”

“We can extend our study to a community of microbes,” Spinler said.

“In this way, we study how microbial communities work together, synergize and influence the host. This protocol gives researchers a roadmap to understand the complex circulation system between the gut and the brain and its effects.

“We were able to create this protocol through large interdisciplinary collaborations involving clinicians, behavioral scientists, microbiologists, molecular biology scientists, and metabolomics experts,” Horvath said.

“We hope our approach will help create communities of creators of beneficial microbes that can help maintain a healthy body. Our protocol also offers a way to identify potential solutions when miscommunication between the gut and the brain leads to disease.

Read all the details of this work in Natural protocols.

Other contributors to this work include Sigmund J. Haidacher, Berkley Luck, Wenly Ruan, Faith Ihekweazu, Meghna Bajaj, Kathleen M. Hoch, Numan Oezguen, James Versalovic, and Anthony M. Haag. The authors are affiliated with one or more of the following institutions: Baylor College of Medicine, Texas Children’s Hospital, and Alcorn State University.

Funding: This study was supported by an NIH grant K01 K12319501 and the Global Probiotic Council 2019-19319, grants from the National Institute of Diabetes and Digestive and Kidney Diseases (Grant P30-DK-56338 to Texas Medical Center Digestive Disease Center, Gastrointestinal Experimental Model Systems), NIH grant U01CA170930 and unrestricted research support from BioGaia AB (Stockholm, Sweden).

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About this gut-brain axis research news

Author: Homa Shalchi
Source: Baylor College of Medicine
Contact: Homa Shalchi – Baylor College of Medicine
Picture: Image is credited to Baylor College of Medicine

Original research: Access closed.
“Interrogation of the mammalian gut-brain axis using LC-MS/MS-based targeted metabolomics with in vitro bacterial and organoid cultures and in vivo gnotobiotic mouse models” by Thomas D. Horvath et al . Natural Protocols


Summary

Interrogation of the mammalian gut-brain axis using targeted LC-MS/MS-based metabolomics with in vitro bacterial and organoid cultures and in vivo gnotobiotic mouse models

Interest in the communication between the gastrointestinal tract and the central nervous system, known as the gut-brain axis, has prompted the development of quantitative analytical platforms to analyze signals derived from microbes and host.

This protocol enables investigations of the connections between microbial colonization and intestinal and brain neurotransmitters and contains strategies for the comprehensive assessment of metabolites in in vitro (organoids) and in vivo mouse model systems.

Here we present an optimized workflow that includes procedures to prepare these gut-brain axis model systems: (step 1) growth of microbes in defined media; (step 2) microinjection of intestinal organoids; and (step 3) generation of animal models including germ-free (no microbes), specific pathogen-free (complete gut microbiota) and specific pathogen-free re-conventionalized models (germ-free mice associated with a complete gut microbiota of a mouse without specific pathogen), and Bifidobacterium teeth and Bacteroides ovatus mono-associated mice (germ-free mice colonized by a single gut microbe).

We describe targeted metabolomics methods based on liquid chromatography and tandem mass spectrometry to analyze short-chain fatty acids and neurotransmitters of microbial origin from these samples.

Unlike other protocols that typically only examine stool samples, this protocol includes bacterial cultures, organoid cultures, and in vivo samples, in addition to monitoring the stool samples for metabolite content. The incorporation of three experimental models (microbes, organoids and animals) reinforces the impact of this protocol.

The protocol requires 3 weeks of murine colonization with microbes and ~1-2 weeks for instrumental and quantitative analysis based on liquid and tandem chromatography mass spectrometry, as well as post-processing and sample normalization .

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