Joan Rothchild Hardin
Clue to How Gut Bacteria Affect Mood – New Evidence that Gut Bacteria Feed on a Neurotransmitter
If you’ve read that bacteria in our guts influence our moods and have wondered how that works, here’s a new clue towards solving this piece of the recently enlivened mind/body axis puzzle. THE NEUROTRANSMITTERS GABA & GLUTAMATE
The amino acid called GABA (Gamma Aminobutyric Acid) is the principal INHIBITORY neurotransmitter in the mammalian central nervous system, sending chemical messages through the brain and nervous system and helping regulate communication between brain cells.
GABA’s chief role is to reduce the activity of nerve cells. It plays an important role in behavior, cognition, and how we respond to stress. Research suggests that GABA helps control fear and anxiety when neurons become overexcited. Below normal GABA levels in the brain have been linked to depression, anxiety, sleep disorders, and schizophrenia.
Pharmaceuticals called benzodiazepines bind to the same receptors as GABA, mimicking GABA’s natural calming effects. Examples of popular benzodiazepines for anxiety and insomnia are Valium (diazepam) and Ativan (lorazepam). They slow down the body’s central nervous system and cause sleepiness. (Konkel, 2015)
Glutamate (also called L-glutamate or glutamic acid)) is another important amino acid neurotransmitter released by nerve cells in the brain. It is involved in most aspects of normal brain functioning, including cognition, memory and learning. It is the major mediator of EXCITATORY signals in the mammalian central nervous system. (Danbolt, 2001)
GABA & GLUTAMATE IN BALANCE
Calming GAMBA restrains the release of excitatory glutamate. So you can see that a balance between GABA and glutamate production is needed for proper functioning. It’s a Goldilocks situation: The brain needs to release just the right amount of both GABA and glutamate. Too much or too little of one or the other causes problems.
IT TURNS OUT THAT A TYPE OF BACTERIA IN THE GUT LIVES ON GABA
Researchers have now observed gut bacteria consuming the brain chemical GABA. They found that a type of recently discovered gut bacteria, called KLE1738, can survive and reproduce only if it has GABA molecules to feed on. The researchers tried providing KLE1738 with other types of neurotransmitters but the bacteria couldn’t survive on anything but GABA. Without GABA, these bacteria die.
This is an important clue about how our gut bacteria influence our mood. “GABA acts by inhibiting signals from nerve cells, calming down the activity of the brain, so it’s surprising to learn that a gut bacterium needs it to grow and reproduce. Having abnormally low levels of GABA is linked to depression and mood disorders, and this finding adds to growing evidence that our gut bacteria may affect our brains.” (Coghlan, 2016)
An earlier experiment, in 2011, demonstrated that a different type of gut bacteria, Lactobacillus rhamnosus, dramatically altered GABA activity in the brains of mice as well as affected how well they responded to stress.
When the researchers surgically removed the vagus nerve, the communication pathway between the gut and the brain, the effect on the mice disappeared – more evidence on how gut bacteria influence the brain. (Coghlan, 2016)
The research team, led by Philip Strandwitz at Northeastern University in Boston, is now searching for other gut bacteria that consume or even produce GABA. They plan to test their effect on the brains and behavior of animals. Such work may eventually lead to new treatments for mood disorders like depression or anxiety.
“Due to this unique growth requirement, we provisionally name KLE1738 Evtepia gabavorous. Using growth of E. gabalyticus as an indicator, we then identified novel GABA producing bacteria from the gut microbiome. Reduced levels of GABA are associated with depression, and we found fewer GABA producers in a human cohort of depressed individuals. By modulating the level of GABA, microbial producers and consumers of this neurotransmitter may be influencing host behavior.” (Strandwitz et al, 2016)
Researchers are just at the beginning of looking into the many ways the gut microbiome influences, if not regulates, many bodily processes and how unbalance in the gut microbiome eventually leads to poor health.
This finding of a dependence of a type of gut bacteria on the neurotransmitter GABA doesn’t mean you should start yourself on one of the GABA supplements you’ll find for sale online. But do stay tuned! Neurotransmitters and specific microbes may become the treatment of choice for mood disorders – or, even better, for preventing mood disorders in the first place.
Keep your gut microbiome health, keep your body healthy.
Coghlan, A. (2016). Gut bacteria spotted eating brain chemicals for the first time. NewScientist. com. See: https://www.newscientist.com/article/2095769-gut-bacteria-spotted-eating-brain-chemicals-for-the-first-time/
Danbolt, N.C. (2001). Glutamate as a Neurotransmitter – An overview. Center for Molecular Biology & Neuroscience, The Neurotransporter Group – Dynamics of extracellular transmitter amino acids. See: http://neurotransporter.org/glutamate.html
Konkel, G. (2015). What Is GABA? See: http://www.everydayhealth.com/gaba/guide/
Strandwitz et al. (2016). Gaba Modulating Bacteria of the Human Gut Microbiome. American Society for Microbiology 2016, Session 347 – Microbial Mind Control. See: http://www.abstractsonline.com/pp8/#!/4060/presentation/18619 © Copyright 2016. Joan Rothchild Hardin. All Rights Reserved.
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