A gut-full of probiotics for your neurological well-being

From the 5 July 2011 Science Daily article

Probiotics, often referred to as ‘good bacteria’, are known to promote a healthy gut, but can they promote a healthy mind? Exploring the new world of neurological probiotics, researchers in BioEssays present new ideas on how neurochemicals delivered directly to the gut, via probiotic intestinal microbiota, exert their beneficial effects in maintaining gastrointestinal health and even psychological well-being.
The research, led by Professor Mark Lyte from Texas Tech University Health Sciences Center, proposes that through a unifying process of microbial endocrinology, neurochemical-producing probiotics could act as a delivery mechanism for neuroactive compounds that could improve a host’s gastrointestinal and psychological health.
“This paper proposes a new field of microbial endocrinology, where microbiology meets neuroscience,” said Lyte. “There is already evidence to suggest that the connection between gut microbes and the nervous system represents a viable route for influencing neurological function. A recent study in mice, for example, showed that the presence of neurochemicals such a serotonin in the bloodstream was due to direct uptake from the gut.”
In his hypothesis Professor Lyte considers the selection of probiotics, such as lactobacilli and bifidobacteria, and how the active uptake of neurochemicals, generated by bacteria in the gut and circulated through a patient’s bloodstream, represents a pathway for probiotics to exert extra-intestinal effects including behavioral changes.

 

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That Anxiety May Be In Your Gut, Not In Your Head

From a 17 May 2011 Medical News Today article

For the first time, researchers at McMaster University have conclusive evidence that bacteria residing in the gut influence brain chemistry and behaviour.

The findings are important because several common types of gastrointestinal disease, including irritable bowel syndrome, are frequently associated withanxiety or depression. In addition there has been speculation that some psychiatric disorders, such as late onset autism, may be associated with an abnormal bacterial content in the gut.

“The exciting results provide stimulus for further investigating a microbial component to the causation of behavioural illnesses,” said Stephen Collins, professor of medicine and associate dean research, Michael G. DeGroote School of Medicine. Collins and Premysl Bercik, assistant professor of medicine, undertook the research in the Farncombe Family Digestive Health Research Institute.

The research appears in the online edition of the journal Gastroenterology. ….

Humans Shown To Have Intestinal Bacteria Groups As Well As Blood Groups

From the 27 April 2011 Medical News Today article

It would appear that in terms of composition, the intestinal bacteria of every individual can be divided into three main groups known as enterotypes. The intestinal bacteria in each enterotype organise themselves into distinct, stable clusters displaying common features. ..

..Three enterotypes

The three enterotypes show various categories of bacteria with a different impact of the gut. Enterotype 1 is dominated by the Bacteroides intestinal bacteria, which together with a few other species of bacteria, forms a distinctive cluster of gut flora. The dominant bacteria in enterotype 2 is Prevotella. And in enterotype 3, Ruminococcus is the main bacteria, along with other species such as Staphylococcus, Gordonibacter and a species discovered in Wageningen previously, Akkermansia. Enterotype 3 is the most common.

Furthermore, every cluster of bacteria has its own way of supplying energy. Enterotype 3, for example, specialises in breaking down mucin, a carbohydrate that enters the gut via our food. This allows the gut to absorb these fragments asnutrition for the body. All three enterotypes also produce vitamins, albeit in varying amounts. Enterotype 1 produces the most vitamin B7 (biotin), B2 (riboflavin) and C (ascorbic acid), and enterotype 2 produces mainly vitamin B1 (thiamin) and folic acid. Every enterotype, with its distinctive clusters of bacteria and functional differences, reflects a distinctive way of generating energy that is closely compatible with its host. It is also possible that the enterotypes may interact with their host on various levels, having an impact on the individual’s health.

In March of last year, the MetaHIT consortium published the first catalogue of genes of human intestinal bacteria (also known as the second genome). These bacteria populations encode 150 times more genes than our own genome. It was shown that from a range of more than a thousand species of bacteria that live in the human gut, every individual is host to several hundred types of bacteria.

The discovery of the enterotypes will influence the fields of biology, medicine and nutrition, making it much easier to analyse an individual’s needs. The research team sees future opportunities for personal and preventive dietary and medicinal advice.

Learning to tolerate our microbial self: Bacteria co-opt human immune cells for mutual benefit

The image depicts symbiotic microbes in the process of colonizing the mucosal surface of the mouse colon. Yellow cells are Escherichia coli; red cells are Bacteroides fragilis. Intestinal tissues are labeled in green with blue nuclei.

(Credit: S. Melanie Lee/Caltech)

From the 21 April 2011 Science Daily article

ScienceDaily (Apr. 22, 2011) — The human gut is filled with 100 trillion symbiotic bacteria — ten times more microbial cells than our own cells — representing close to one thousand different species. “And yet, if you were to eat a piece of chicken with just a few Salmonella, your immune system would mount a potent inflammatory response,” says Sarkis K. Mazmanian, assistant professor of biology at the California Institute of Technology (Caltech).

Salmonella and its pathogenic bacterial kin don’t look that much different from the legion of bacteria in our gut that we blissfully ignore, which raises the question: What decides whether we react or don’t? Researchers have pondered this paradox for decades.

In the case of a common “friendly” gut bacterium, Bacteroides fragilis, Mazmanian and his colleagues have figured out the surprising answer: “The decision is not made by us,” he says. “It’s made by the bacteria. Since we are their home, they hold the key to our immune system.”

What’s more, the bacteria enforce their “decision” by hijacking cells of the immune system, say Mazmanian and his colleagues, who have figured out the mechanism by which the bacteria accomplish this feat — and revealed an explanation for how the immune system distinguishes between beneficial and pathogenic organisms….

…bacteria actually live in a unique ecological niche, deep within the crypts of the colon, “and thus in intimate contact with the gut mucosal immune system,” he says.

“The closeness of this association highlights that an active communication is occurring between the bacteria and their host,” says Caltech postdoctoral scholar June L. Round.

From that vantage point, the bacteria are able to orchestrate control over the immune system — and, specifically, over the behavior of immune cells known as regulatory T cells, or Treg cells. …

…”Our immune system arose in the face of commensal colonization and thus likely evolved specialized molecules to recognize good bacteria,” says Round. Mazmanian suspects that genetic mutations in these pathways could be responsible for certain types of immune disorders, including inflammatory bowel disease: “The question is, do patients get sick because they are rejecting bacteria they shouldn’t reject?”

On a more philosophical level, Mazmanian says, the findings suggest that our concept of “self” should be broadened to include our many trillions of microbial residents. “These bacteria live inside us for our entire lives, and they’ve evolved to look and act like us, as part of us,” he says. “As far as our immune system is concerned, the molecules made by gut bacteria should be tolerated similarly to our own molecules. Except in this case, the bacteria ‘teaches’ us to tolerate them, for both our benefit and theirs.”…

Journal Reference:

1. June L. Round, S. Melanie Lee, Jennifer Li, Gloria Tran, Bana Jabri, Talal A. Chatila, and Sarkis K. Mazmanian.The Toll-Like Receptor 2 Pathway Establishes Colonization by a Commensal of the Human Microbiota. Science, 21 April 2011 DOI:10.1126/science.1206095

[Abstract only, for suggestions on how to get this article for free or at low cost, click here]

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• Humans Shown To Have Intestinal Bacteria Groups As Well As Blood Groups

  “The three enterotypes show various categories of bacteria with a different impact of the gut. Enterotype 1 is dominated by the Bacteroides intestinal bacteria, which together with a few other species of bacteria, forms a distinctive cluster of gut flora. The dominant bacteria in enterotype 2 is Prevotella. And in enterotype 3, Ruminococcus is the main bacteria, along with other species such as Staphylococcus, Gordonibacter and a species discovered in Wageningen previously, Akkermansia. Enterotype 3 is the most common.

  Furthermore, every cluster of bacteria has its own way of supplying energy. Enterotype 3, for example, specialises in breaking down mucin, a carbohydrate that enters the gut via our food. This allows the gut to absorb these fragments asnutrition for the body. All three enterotypes also produce vitamins, albeit in varying amounts. Enterotype 1 produces the most vitamin B7 (biotin), B2 (riboflavin) and C (ascorbic acid), and enterotype 2 produces mainly vitamin B1 (thiamin) and folic acid. Every enterotype, with its distinctive clusters of bacteria and functional differences, reflects a distinctive way of generating energy that is closely compatible with its host. It is also possible that the enterotypes may interact with their host on various levels, having an impact on the individual’s health.

  In March of last year, the MetaHIT consortium published the first catalogue of genes of human intestinal bacteria (also known as the second genome). These bacteria populations encode 150 times more genes than our own genome. It was shown that from a range of more than a thousand species of bacteria that live in the human gut, every individual is host to several hundred types of bacteria.

  The discovery of the enterotypes will influence the fields of biology, medicine and nutrition, making it much easier to analyse an individual’s needs. The research team sees future opportunities for personal and preventive dietary and medicinal advice.”

• Learning to tolerate our microbial self: Bacteria co-opt human immune cells for mutual benefit (jflahiff.wordpress.com)
• Deepak Chopra: Weekly Health Tip: You Are Home to Millions of Microbes! (huffingtonpost.com)
• Friendly bacteria fight the flu (nature.com)

Gut bacteria can control organ functions

Gut bacteria can control organ functions

From the Feburary 28 2011 Eureka news alert

Bacteria in the human gut may not just be helping digest food but also could be exerting some level of control over the metabolic functions of other organs, like the liver, according to research published this week in the online journal mBio®. These findings offer new understanding of the symbiotic relationship between humans and their gut microbes and how changes to the microbiota can impact overall health.

“The gut microbiota enhances the host’s metabolic capacity for processing nutrients and drugs and modulates the activities of multiple pathways in a variety of organ systems,” says Sandrine Claus of the Imperial College of London, a researcher on the study.

Claus and her colleagues exposed germ-free mice to bedding that had previously been used by conventional mice with normal microbiota and followed their metabolic profiles for 20 days to observe changes as they became colonized with gut bacteria.

Over the first 5 days after exposure, the mice exhibited a rapid increase in weight (4%). Colonization also triggered a number of processes in the liver in which sugars (glucose) are converted to starch (glycogen) and fat (triglycerides) for short-term and long-term energy storage. Statistical modeling between liver metabolic functions and microbial populations determined that the levels of glucose, glycogen and triglycerides in the liver were strongly associated with a single family of bacteria called Coriobacteriaceae.

“Here we describe the first evidence of an in vivo association between a family of bacteria and hepatic lipid metabolism. These results provide new insights into the fundamental mechanisms that regulate host-gut microbiota interactions and are of wide interest to microbiological, nutrition, metabolic, systems biology and pharmaceutical research communities,” says Claus.

Another important finding in the paper, according to Claus, is that gut colonization strongly stimulated the expression and activity of the cytochrome P450 3A11, an essential enzyme in drug-detoxification pathways.

Although she warns about being careful to extrapolate the specific findings from mice to humans, Claus notes the results of this research will provide a basis to further develop new strategies to beneficially modulate host metabolism by altering microbial communities in the gut.

 

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mBio® is a new open access online journal published by the American Society for Microbiology to make microbiology research broadly accessible. The focus of the journal is on rapid publication of cutting-edge research spanning the entire spectrum of microbiology and related fields. It can be found online at http://mbio.asm.org.

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