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A Possible Link Between Gut Bacteria and PTSD

Could bacteria in your gut be used to cure or prevent neurological conditions such as post-traumatic stress disorder (PTSD), anxiety or even depression? Two researchers sponsored by the Office of Naval Research (ONR) think that’s a strong possibility.

Dr. John Bienenstock and Dr. Paul Forsythe–who work in The Brain-Body Institute at McMaster University in Ontario, Canada, are investigating intestinal bacteria and their effect on the human brain and mood.

“This is extremely important work for U.S. warfighters because it suggests that gut microbes play a strong role in the body’s response to stressful situations, as well as in who might be susceptible to conditions like PTSD,” said Dr. Linda Chrisey, a program officer in ONR’s Warfighter Performance Department, which sponsors the research.

The trillions of microbes in the intestinal tract, collectively known as the gut microbiome, profoundly impact human biology; digesting food, regulating the immune system and even transmitting signals to the brain that alter mood and behavior. ONR is supporting research that’s anticipated to increase warfighters’ mental and physical resilience in situations involving dietary changes, sleep loss or disrupted circadian rhythms from shifting time zones or living in submarines.

Through research on laboratory mice, Bienenstock and Forsythe have shown that gut bacteria seriously affect mood and demeanor. They also were able to control the moods of anxious mice by feeding them healthy microbes from fecal material collected from calm mice.

Bienenstock and Forsythe used a “social defeat” scenario in which smaller mice were exposed to larger, more aggressive ones for a couple of minutes daily for 10 consecutive days. The smaller mice showed signs of heightened anxiety and stress–nervous shaking, diminished appetite and less social interaction with other mice. The researchers then collected fecal samples from the stressed mice and compared them to those from calm mice.

“What we found was an imbalance in the gut microbiota of the stressed mice,” said Forsythe. “There was less diversity in the types of bacteria present. The gut and bowels are a very complex ecology. The less diversity, the greater disruption to the body.”

Bienenstock and Forsythe then fed the stressed mice the same probiotics (live bacteria) found in the calm mice and examined the new fecal samples. Through magnetic resonance spectroscopy (MRS), a non-invasive analytical technique using powerful MRI technology, they also studied changes in brain chemistry.

“Not only did the behavior of the mice improve dramatically with the probiotic treatment,” said Bienenstock, “but it continued to get better for several weeks afterward. Also, the MRS technology enabled us to see certain chemical biomarkers in the brain when the mice were stressed and when they were taking the probiotics.”

Image shows microbiota.

The trillions of microbes in the intestinal tract, collectively known as the gut microbiome, profoundly impact human biology—digesting food, regulating the immune system and even transmitting signals to the brain that alter mood and behavior. Image is for illustrative purposes only. Credit: Nicola Fawcett.

Both researchers said stress biomarkers could potentially indicate if someone is suffering from PTSD or risks developing it, allowing for treatment or prevention with probiotics and antibiotics.

Later this year, Bienenstock and Forsythe will perform experiments involving fecal transplants from calm mice to stressed mice. They also hope to secure funding to conduct clinical trials to administer probiotics to human volunteers and use MRS to monitor brain reactions to different stress levels.

Gut microbiology is part of ONR’s program in warfighter performance. ONR also is looking at the use of synthetic biology to enhance the gut microbiome. Synthetic biology creates or re-engineers microbes or other organisms to perform specific tasks like improving health and physical performance. The field was identified as a top ONR priority because of its potential far-ranging impact on warfighter performance and fleet capabilities.

About this PTSD research

Source: Bob Freeman – Office of Naval Research
Image Source: The image is credited to Nicola Fawcett and is licensed CC BY-SA 4.0.
Original Research: Abstract for “Posttraumatic Stress Disorder: Does the Gut Microbiome Hold the Key?” by Sophie Leclercq, Paul Forsythe, and John Bienenstock in Canadian Journal of Psychiatry. Published online February 24 2016 doi:10.1177/0706743716635535


Abstract

Posttraumatic Stress Disorder: Does the Gut Microbiome Hold the Key?

Gut bacteria strongly influence our metabolic, endocrine, immune, and both peripheral and central nervous systems. Microbiota do this directly and indirectly through their components, shed and secreted, ranging from fermented and digested dietary and host products to functionally active neurotransmitters including serotonin, dopamine, and γ-aminobutyric acid. Depression has been associated with enhanced levels of proinflammatory biomarkers and abnormal responses to stress. Posttraumatic stress disorder (PTSD) appears to be marked in addition by low cortisol responses, and these factors seem to predict and predispose individuals to develop PTSD after a traumatic event. Dysregulation of the immune system and of the hypothalamic-pituitary-adrenal axis observed in PTSD may reflect prior trauma exposure, especially early in life. Early life, including the prenatal period, is a critical time in rodents, and may well be for humans, for the functional and structural development of the immune and nervous systems. These, in turn, are likely shaped and programmed by gut and possibly other bacteria. Recent experimental and clinical data converge on the hypothesis that imbalanced gut microbiota in early life may have long-lasting immune and other physiologic effects that make individuals more susceptible to develop PTSD after a traumatic event and contribute to the disorder. This suggests that it may be possible to target abnormalities in these systems by manipulation of certain gut bacterial communities directly through supplementation or indirectly by dietary and other novel approaches.

“Posttraumatic Stress Disorder: Does the Gut Microbiome Hold the Key?” by Sophie Leclercq, Paul Forsythe, and John Bienenstock in Canadian Journal of Psychiatry. Published online February 24 2016 doi:10.1177/0706743716635535

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