Gut communicates with the entire brain through cross-talking neurons

April 2, 2020

Science Daily/University of Illinois College of Agricultural, Consumer and Environmental Sciences

You know that feeling in your gut? We think of it as an innate intuition that sparks deep in the belly and helps guide our actions, if we let it. It's also a metaphor for what scientists call the "gut-brain axis," a biological reality in which the gut and its microbial inhabitants send signals to the brain, and vice versa.

It's not a surprise that the brain responds to signals in the gut, initiating motor functions involved with digestion. Directed by the brainstem, these types of basic biological actions are largely automatic. But what if the higher brain -- the thinking, emotional centers -- were influenced by signals in the gut, too? New University of Illinois research in rats shows the entire brain responds to the gut, specifically the small intestine, through neuronal connections.

To map the connections, researchers inserted neuron-loving viruses in the rats' small intestines and traced the viruses as they moved from neuron to neuron along the Vagus and spinal nerves and throughout the brain. The idea was virus movement mimicked the movement of normal signals through neurons from the gut to the brain and back.

"We saw a lot of connections in the brainstem and hindbrain regions. We knew these regions are involved in sensing and controlling the organs of the body, so there weren't any big surprises there. But things got more interesting as the viruses moved farther up into parts of the brain that are usually considered emotional centers or learning centers, cognitive places. They have all these multifaceted functions. So thinking about how information from the small intestine might be nudging those processes a little bit is really cool," says Coltan Parker, doctoral student in the Neuroscience Program at Illinois and lead author on a study published in Autonomic Neuroscience: Basic and Clinical.

The study represents the first complete map of neuronal connections between the small intestine -- what Parker and his co-authors call an "underloved" part of the digestive system -- and the entire brain. The involvement of cognitive and emotional centers hints at how the thinking brain sometimes overrides our feeling of being full, provides fodder to explore relationships between depression and digestive troubles, and more.

"Now we're actually finding the neuro-anatomy that might be involved in that 'feeling in your gut,'" says Megan Dailey, study co-author and program administrator in the College of Agricultural, Consumer and Environmental Sciences at Illinois.

In addition to showing just how extensive the connections are between the small intestine and the brain, the study uncovered a rarely documented feature of the neurons themselves.

Scientists have long assumed sensations from the gut, or anywhere in the body, traveled to the brain along one set of neurons (the sensory neurons), with instructions from the brain traveling back along a separate set of neurons (the motor neurons). But in their mapping study, Illinois researchers discovered some of the neurons -- about half -- were transmitting both sensory and motor signals.

They were capable of cross-talk within the same neuron.

"From the cortex to the brainstem, in pretty much every region we investigated, there was that 50% overlap of sensory-motor signals. It was throughout the brain, consistently," says study co-author Elizabeth Davis. Davis is a 2018 graduate of the Illinois Neuroscience Program and is currently studying as a postdoctoral scholar at the University of Southern California.

The same pattern -- 50% of neurons having both sensory and motor signaling capabilities -- had only been shown one other time, in a study mapping neuronal connections between fat tissue and the brain. The researchers point out new evidence of the same crosstalk pattern could suggest a general architecture of neuronal networks between the body and brain.

"This study shows that sensorimotor feedback loops are abundant across all levels of the brain. Up until now, it has really been unknown how information in the small intestine, about nutrients or anything else, can get up to the brain and affect cognitive-emotional processes, and then how those processes can come back down and affect the gut," Parker says. "With more research, we may finally begin to understand how hunger makes us 'hangry,' or how a stressful day becomes an irritable bowel."

https://www.sciencedaily.com/releases/2020/04/200402155733.htm

New study points to another possible correlation between sleep and overall good health

Your gut microbiome and quality sleep are interconnected

October 28, 2019

Science Daily/Nova Southeastern University

As if you didn't already have enough to worry about to keep you up at night, a new study indicates that poor sleep can negatively affect your gut microbiome, which can, in turn, lead to additional health issues.

Great.

That's at the heart -- or gut -- of the study just published in PLoS ONE that involved several researchers from Nova Southeastern University (NSU.) They wanted to see just how much of a connection there is between what is going on in our insides and how that may impact the quality of sleep we experience.

"Given the strong gut-brain bidirectional communication they likely influence each other," said Jaime Tartar, Ph.D., a professor and research director in NSU's College of Psychology who was part of the research team. "Based on previous reports, we think that poor sleep probably exerts a strong negative effect on gut health/microbiome diversity."

What you may be asking yourself right now is: "what in the world is a gut microbiome?" Simply put -- it's all the microorganisms (bacteria, viruses, protozoa and fungi) and their genetic material found in your gastrointestinal (GI) tract. And yes, we all have these in our GI tract, but not all at the same levels (diversity.) As it turns out, it's this diversity that could be the key.

For this study, subjects wore what Tartar called an "Apple Watch on steroids" to bed, which monitored all sorts of vitals. This way the researchers could determine just how well a night's sleep the subjects got, and then they tested the subjects' gut microbiome. What they found was those who slept well had a more diverse -- or "better" -- gut microbiome.

Tartar said that gut microbiome diversity, or lack thereof, is associated with other health issues, such as Parkinson's disease and autoimmune diseases, as well as psychological health (anxiety and depression.) The more diverse someone's gut microbiome is, the likelihood is they will have better overall health.

"We know that sleep is pretty much the 'Swiss Army Knife of health," Tartar said. "Getting a good night's sleep can lead to improved health, and a lack of sleep can have detrimental effects. We've all seen the reports that show not getting proper sleep can lead to short term (stress, psychosocial issues) and long-term (cardiovascular disease, cancer) health problems. We know that the deepest stages of sleep is when the brain 'takes out the trash' since the brain and gut communicate with each other. Quality sleep impacts so many other facets of human health."

Tartar's area of research focuses on the mechanisms and consequences of acute and chronic stress in humans and the impact of normal sleep and sleep deprivation on emotion processing and physiological functioning.

So what determines someone's gut microbiome? According to Robert Smith, Ph.D., an associate professor and research scientist at Nova Southeastern University (NSU) Halmos College of Natural Sciences and Oceanography, who is also a member of the research team, there are a couple of factors that come into play.

One is genetics -- some people are predisposed at a genetic level to have a more diverse gut microbiome than their friends and neighbors. Another factor is drugs -- certain medications, including antibiotics, can have an impact on the diversity of your gut microbiome. He also said that your diet plays a factor as well.

Smith said that their team, which included colleagues from Middle Tennessee State University, examined the association between sleep, the immune system and measures of cognition and emotion. He said understanding how these parts of human physiology work may lead to a better understanding of the "two-way communication" between the person and their gut microbiome, and could lead to novel sleep intervention strategies.

"The preliminary results are promising, but there's still more to learn," Smith said. "But eventually people may be able to take steps to manipulate their gut microbiome in order to help them get a good night's sleep."

https://www.sciencedaily.com/releases/2019/10/191028164311.htm