Microbes, Mood and Obesity


In the straightforwardly titled “Mind-altering microorganisms: the impact of the gut microbiota on brain and behaviour” two writers for Nature, John F. Cryan and Timothy G. Dinan, discussed the microbiota-gut-brain axis and the communications that take place there:

A growing body of evidence indicates that microbiota have a role in the normal regulation of behaviour and brain chemistry that are relevant to mood and anxiety. Moreover, they intriguingly suggest that an individual’s microbiota composition may influence their susceptibility to anxiety and depression.

Anxiety and depression are two of the main triggers of disordered eating behavior, so if the gut bugs have anything to do with enabling anxiety and depression, we probably should know about it.

Mark Lyte is one of the people who look into this matter professionally, in a laboratory housed at the Texas Tech University Health Services Center. In search of answers to questions about how the microbiome influences the brain, Lyte studies monkey poo and, through fecal transplant technology, attempts to change the course of neurodevelopment in monkeys.

Journalist Peter Andrey Smith learned from other scientists of Lyte’s reputation as a pioneer and a prophet who believes that specific psychological disorders can be treated by tailored bacteria. A gastroenterologist colleague, Stephen Collins, said of Lyte that he “showed, quite clearly, in elegant studies that are not often cited, that introducing a pathological bacterium into the gut will cause a change in behavior.”

Creatures live inside us and pump out dopamine, serotonin, and GABA, all of which are connected human anxiety and depression, and intestinal disorders. They are making the same chemicals that our neurons use in their communication and mood-regulation systems. Who needs space invaders, when we already have interior armies battling grimly for control of our minds? Smith goes on to say:

Lyte has spent his career trying to prove that gut microbes communicate with the nervous system using some of the same neurochemicals that relay messages in the brain.

“If they make this stuff here, does it have an influence there? Guess what? We make the same stuff. Maybe all this communication has an influence on our behavior.”

Of course, Mark Lyte is not the only expert working in this area. Just to randomly name another, there is California Institute of Technology microbiologist Sarkis Mazmanian, about whom Smith says:

Research has moved beyond the basic neurochemicals to focus on a broader class of molecules called metabolites: small, equally druglike chemicals that are produced by micro-organisms. Using high-powered computational tools, he also hopes to move beyond the suggestive correlations that have typified psychobiotic research to date, and instead make decisive discoveries about the mechanisms by which microbes affect brain function.

The gut bugs literally produce psychoactive compounds that function like psychiatric drugs. In one fanciful way of looking at it, a human is inhabited by zillions of tiny little dope pushers, offering to deal out feel-good molecules in return for our cooperation. Sure, they want to survive and reproduce, just like us, but even if their agenda is totally understandable, what do they want in return for all those little fixes, and what does it cost us?

Your responses and feedback are welcome!

Source: “Mind-altering microorganisms: the impact of the gut microbiota on brain and behaviour,” Nature.com, October 2012
Source: “Can the Bacteria in Your Gut Explain Your Mood?,” NYTimes.com, 06/23/15
Photo credit: Ben Ballard (Relaxdesign Minis) via Visualhunt/CC BY

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