Gut feelings can be very real. There are neurons that connect the gut directly to the brain, and this so-called gut-brain axis has a significant influence on the body.
The microbes in the gut can also affect the brain, and researchers are trying to decipher the complex relationship between the brain and microorganisms in the body. Recent work has shown how microbial metabolites can influence brain function. Neurotransmitters can also affect gut physiology. Now scientists have developed a process that can be used by other researchers to develop a deep understanding of how gut microbes impact the brain. The work has been reported in Nature Protocols.
"Currently, it is difficult to determine which microbial species drive specific brain alterations in a living organism," said first study author, Dr. Thomas D. Horvath, an instructor at Baylor College of Medicine and Texas Children's Hospital. "Here we present a valuable tool that enables investigations into connections between gut microbes and the brain."
"Gut microbes can communicate with the brain through several routes, 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," added co-first study author Dr. Melinda A. Engevik, an assistant professor at the Medical University of South Carolina.
Related: Bugs on the Brain - Gut Microbes Affect Neurodegeneration
In this process, the researchers suggest creating a three-stage workflow. First, microbes should be prepared in a defined culture media. Next, intestinal organoids are injected with the microbes. Finally, animal models are used that have either complete gut microbiomes; germ-free mice that lack microbiomes; mice that began as germ-free but were colonized with gut microbiota that carried no pathogens; and mice that started out germ-free but were colonized with individual strains of a gut microbe - Bifidobacterium dentium or Bacteroides ovatus.
The short-chain fatty acids produced by gut microbes can have a physiological impact on the brain, and they can be isolated and analyzed by liquid chromatography–tandem mass spectrometry (LC/MS) along with any neurotransmitters that are derived from microbes.
This methodology is different from research that only assesses material in stool samples, because it encompasses many other things including in vivo models and cell cultures. The study authors estimated that the mouse colonization process requires about three weeks and LC/MS techniques take about another two weeks.
"We can expand our study to a community of microbes," said study co-author Dr. Jennifer K. Spinler, an assistant professor at Baylor and the Texas Children’s Hospital Microbiome Center. "This protocol gives researchers a road map to understand the complex traffic system between the gut and the brain and its effects."
Sources: Baylor College of Medicine, Nature Protocols
