Gut Feelings: New Research Reveals Our Bodies Communicate with Gut Bacteria

There’s definitely something intriguing about instincts, especially when it comes to our gut feelings. Recent research has unveiled that our bodies may have a direct way of sensing and interacting with the bacteria that reside in our digestive system.

A study led by scientists at Duke University, featured in Nature, indicates that nerve cells within our body respond in real time to signals from gut bacteria, including those that help us regulate our appetite. This suggests that our relationship with the microorganisms that share our bodies is even more intricate than previously understood.

We often think about the five basic senses—sight, hearing, touch, smell, and taste—but the researchers point out there’s growing evidence of additional senses specifically attuned to our digestive system, termed the “gut sense.”

Some of the researchers had previously found that specific cells in the gut can detect particular stimuli, communicating directly with neighboring nerve cells that relay signals back to the brain, known as neuropods. They hypothesized that one of the stimuli these cells recognize would be the gut microbiome, which consists of countless usually harmless and often beneficial bacteria and other microbes residing in our bodies.

“We had previously found that neuropod cells in the small intestine sense and quickly respond to nutrients,” explained co-lead author Maya Kaelberer, a sensory neuro-gastroenterologist. “So, it seemed logical that the neuropod cells in the colon would also sense the gut microbiome, which led us to investigate further.”

The research team honed in on an ancient protein called flagellin, found in the flagella of many gut bacteria. It turns out that gut bacteria produce heightened levels of flagellin when we eat, which neuropods detect via a receptor known as the Toll-like receptor 5 (TLR5). Experiments with mice demonstrated that this interaction appears to be crucial in appetite regulation.

For instance, when fasting mice were given flagellin directly into the colon, they consumed less food than usual. However, when the team disabled the TLR5 receptor in neuropods and repeated the experiment, those mice continued eating and gained weight.

The findings indicate that increased levels of bacterial flagellin serve as real-time signals to the brain, telling it to lessen our hunger. Neuropods perceive this signal through the TLR5 receptor and promptly communicate it to the brain through the vagus nerve. If the ability of neuropods to sense nutrients can be viewed as a sixth sense, their sensitivity to gut microbes might suggest a distinct seventh sense, according to the researchers.

“We discovered that our colon has a sense for microbes—the neurobiotic sense,” Kaelberer stated.

While more research is needed to fully understand how this neurobiotic sense functions in humans, the discovery could have significant scientific and medical implications. Health conditions, diet, and environmental factors might impact the interaction among gut bacteria, neuropods, and the brain. There’s a possibility that in the future, we could influence this sense to manage or even prevent certain health issues.

“Imagine a world where everything you see is blue—a blue room, blue cars, blue everything. Then you come home and see a bright orange peach on your table; it would certainly change your experience. With that in mind, could we target this sense for a similar profound effect, even without the peach?” Kaelberer pondered.

This seems to be just the tip of the iceberg for the team’s explorations. Their next steps will hopefully reveal whether neuropods can also detect immune-related signals. Meanwhile, I’ve started to appreciate my gut bacteria a bit more for playing a role in helping me control my cravings—especially when dessert rolls around!