The UC Gardner Neuroscience Institute presented its first Neuroscience Day as part of Research Week 2017. One of the day’s events included neuroscience guest speaker John F. Cryan, PhD, professor and chair, Department of Anatomy and Neuroscience, University College Cork, Ireland.
He is a principal investigator at the APC Microbiome Institute, where his work focuses on the brain-gut-microbiota axis.
Cryan’s talk, “The Microbiome as a Key Regulator of Stress Across the Lifespan,” began with a brief history of the relationship scientists have found between the gut and the brain, dating back to William Beaumont’s gastric observations in 1853, up to the latest research involving designer diets, even fecal transplantation. It was a talk packed with insights and research, all with the recurring theme of the gut-brain connection.
“We personify our emotions in the gut. We talk about gut instincts, butterflies in our tummy, trust our gut…so perhaps not surprising that the gut does play a role?”
Cryan said his lab at the APC Microbiome Institute is focused on how we deal with stress— understanding stress resiliencies and what factors are at play, but what if it’s something else as well, our microbes?
“We are particularly interested in understanding the microbiome’s influence on brain at key time windows across the lifespan. Not only perinatal, but also adolescence and aging.”
Stress is a whole body syndrome, explains Cryan. “It doesn’t just affect a few neurons in the hippocampus, we study them and love them, but it affects our immune system, it affects the gut, it affects our barrier functions, driving pro-inflammatory drive.”
The research to date is primarily from animal models, but there have been some significant findings
“We’ve been interested in animal models of early life stress, including studies of separation at birth that point to a whole body syndrome throughout the lifespan of the animal,” says Cryan. Studies show changes in behavior, endocrine, changes in their gut, abdominal pain. “Wide scale changes going on.”
“It could be due to many things, but it got us on this pathway to try to understand the relationship that this microbiome might have to brain function and behavior in general,” says Cryan.
Our first microbes came from our mothers, variables dependent on gestation, delivery method, and whether breastfed these are a variety of factors determining our microbiome.
The prebiotics— food which bacteria can thrive on—exist in breastmilk, and are shown to be beneficial across many systems in the body, including in the brain. These prebiotics do provide the infant with an energy source that is key for immune development and other functions.
Prebiotics used in animal models reversed chronic stress and “moreover reverse the behavioral effects of chronic stress, in terms of both social behavior, anxiety, depression-related behavior.”
Adolescence is another peak period of vulnerability and change, particularly, in the brain
“There’s a lot of wiring and pruning going on at this stage. It’s also be a time where vulnerability to certain disorders starts to emerge,” noted Cryan.
“What I’d like to reinforce is that while in neuroscience we focus on what stress, drug addiction, poor nutrition and inadequate sleep have on the adolescent brain, but all of these equally have impact on the composition of the microbiome.
“Aging is the third area [we are interested in]. As we age, our brain can go through this inflammation process, but we are seeing there is also a big change in the microbiome as we age.”
Stress can add fuel to the fire and may drive some of the key psychiatric phenotypes we see in aging. In aged mice showing social anxiety, memory deficits, can we correlate any of that to the microbiome? Cryan asks.
He says with this accumulation of information he’s now examining two questions: how can we understand the mechanisms, and can we translate this into humans?
“We also need to add diet into this axis … it’s not just microbiome-gut-brain-axis, it’s a diet-microbiome-gut-brain-axis.”
Designer diets clearly have a lot of hype, Cryan warns, but admits it’s an exciting area to consider: whether diets designed to be better for microbes, can produce and act on specific receptors, phenotypes, maybe feed the microbes that can help our brain develop appropriately. Does eating fermented food help? What about Paleo diets?
Cryan cautions against the media hype, “We have a long way to go in trying to tease this apart,” but there are connections, but more studies, rigorous trials need to be done on probiotic and prebiotic diets.
Ultimately, he believe there are some connections and some merit to what’s newly been coined as “psychobiotics” and that could change how we think about mental health, illness and psychiatry. “Our state of gut will affect our state of mind.”
John F. Cryan is co-author with Scott Anderson of The Psychobiotic Revolution: Mood, Food, and the New Science of the Gut-Brain Connection, to be released in November 2017.
— Alison Sampson