Good morning gut lovers!! I am back in the New York fall after a deeply inspiring, though totally exhausting, trip to sunny San Diego for the annual Society for Neuroscience (SFN) conference. The residents of SD must still be reeling after some 32,000 neuroscientists (and their poster tubes) descended on their city to indulge in a week of hard science, even harder socializing, and all the fish tacos they could throw at us.
The brain-gut axis was heavily featured at the conference, and was extremely well-attended. So much so that the “Microbiome and Brain-Gut Axis” symposium required a bouncer to be positioned at the door to control the crowd. The Brain-Gut love is spreading, people!!!
Here are some conference highlights:
A poster from Alex Carlson of the Knickmeyer Lab at South Carolina Chapel Hill showed us how bacterial communities in the guts of 1 year old children can already be stratified into patterns (or ‘enterostates’) that look very similar to what we typically see in adults. What’s more, these enterostates can predict cognitive functioning 12 months later, and are associated with grey matter differences in various brain regions.
The symposium entitled “Food for thought: How Diet Influences Cognitive Functioning and Emotion” had many speakers talking about the link between diet and inflammation. Aniko Korosi of the University of Amsterdam demonstrated how exposure to early stress in the rodent is associated with a reduction of methionine (needed for turning on and off genes in response to the environment) in the pup plasma and hippocampus, as well as impaired memory on a task that requires the hippocampus. Supplementing the diet of the mother with methyl donors rescues the pups methionine levels and their behavior. Sarah Spencer from the Royal Melbourne Institute of Technology University in Australia (representing my mother land!) showed how male rats overfed as infants had a higher hormonal stress responses, made more errors on a cognitive learning task, and had stronger fear memories. They also had more microglia (which are the immune regulators in the brain). Ruth Barrientos from the University of Colorado Boulder also showed that high fat diets were sufficient to potentiate an inflammatory response to an immune challenge in the hippocampus of rats. Take home message from this symposium, cut down on the Big Daddy Nachos; and my favorite thing – this symposium was all women!
I also saw a poster by Chris Mcmurran from the Cambridge Stem Cell Institute, who demonstrated that antibiotic exposure slowed down remyelination in the brain – maybe there is a future for probiotic treatments in slowing down the progression of demyelinating diseases like multiple sclerosis?
In my favorite symposium at the meeting – “Microbiome and the Brain-Gut Axis” (the one that was so popular a neuroscience bouncer was required!), we heard from researchers who were studying the microbiome in rodents and even one who was studying the human microbiome in rodents!! Elizabeth Perez Guzman from McMaster University demonstrated that you can transfer the microbiome of humans with generalized anxiety disorders to mice through a fecal transplant (literally putting the human poop in the mouse stomach). What happens? Well, it changes their behavior. Mice given the anxiety microbiome begin to exhibit anxious behaviors, while those given the microbiome of the non-anxious person remain the same, non-anxious. The poop transplant also changed their brains, less BDNF (a growth factor) in the hippocampus of anxious-poop transplants. Mind. Officially. Blown.
Tamar Gur from Ohio State University busted the ‘sterile fetus’ myth by showing that maternal stress in rats altered the placental microbiome, increasing levels of pro-inflammatory markers, which crossed the placental barrier. Offspring born of those same stressed mothers had changes in their own microbiome, altered behavior on cognitive tasks, and decreased levels of BDNF in the brain.
Aadil Bharwani from the Forsythe Lab at McMaster University used a rodent model to demonstrate that stress-associated changes to inflammation makers, social behavior, and anxiety, were rescued by treatment with Lactobacillus. But bacteria treatment didn’t actually restore the stress-induced microbiome changes. So how is the bacteria causing these changes to brain and behavior? I guess we’ll have to wait until SFN 2017. Excited!
Berkley Luk from Baylor College of Medicine colonized germ-free infant rodents with bifidobacterium and then looked at their brains at postnatal day 4 (infant), 10 (toddler), and 20 (late childhood). She found that bifidobacterium treatment increased the expression of numerous plasticity regulators (e.g., synaptophysin, GABA, Serotonin) at all ages. But most amazingly, the treatment caused a 13-fold increase in GABA at postnatal day 20! Did I hear someone say ‘critical period regulator’?
Also, Jiah Pearson-Leary of the Children’s Hospital of Philadelphia demonstrated how the microbiome of rats was altered by stress-exposure in different ways depending on whether the rat was stress-resilient or stress-vulnerable.
But the story wasn’t all clear cut and green grass. Javier Bravo from Pontificia Universidad Catolica de Valparaiso demonstrated some anxiety producing effects of probiotics and prebiotics (things that microbes eat – like fiber) in the young rat, reminding us to not just jump on the closest probiotic train and to pay close attention to the data as it rolls in.
And what about the old vagus nerve, the ‘essential conduit’ for brain-gut cross-talk? Not important under all conditions, it would seem. Lori Driscoll from Colorado College demonstrated that probiotics worked to reduce anxiety in male rats only when the vagus nerve was intact, but not when it was cut, suggesting the vagus is essential for brain-gut communication in males. In females, however, probiotics were effective whether or not the vagus was intact, suggesting that other mechanisms are at play.
Cannot wait to see some of this research come out in publications soon!
Until next time Brain-Gut Lovers!