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Itchy Gut Nerves Responsible for Irritable Bowel Syndrome

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Researchers are still struggling to determine the exact cause of irritable bowel syndrome. Getty Images
  • Researchers say a receptor that can cause itchy skin may be a factor in causing irritable bowel syndrome (IBS).
  • They say the receptor is more common in people with IBS, and it may activate neurons in the gut, causing pain.
  • Experts differ on whether this new research will produce new treatments for the painful condition.

Australian researchers say they’ve discovered that the mechanism that causes itchy skin may also be responsible for the pain experienced in people with irritable bowel syndrome (IBS).

Scientists from Flinders University in Australia have identified receptors that can cause itchy skin are also found in the gut.

In their recent study, the researchers theorize that these receptors are more present in people with IBS, resulting in more neurons being activated that result in pain in the gut.

“We know that the nerves in the gut become hyperactive to stimuli in IBS, and this contributes to chronic pain,” Stuart Brierley, PhD, an author of the study and a professor in gastrointestinal neuroscience at Flinders University, told Healthline.

“What isn’t clear is how these nerves get activated in the first place. Here we show that the same receptors that cause itch from the skin (by irritants acting on receptors on nerves in the skin) also cause activation of nerves in the gut. This leads them to signal pain when they shouldn’t, or send increased pain signals,” he said.

Brierley adds that IBS models show these receptors, and this gut-itch mechanism are more common in people with IBS.

“This could be the underlying cause of abdominal discomfort and pain in IBS patients,” he said.

About 11 percent of the global population have IBS. Research estimates between 25 million and 45 million people in the United States live with the condition, and 2 out of 3 people living with IBS are female.

IBS is characterized by a group of symptoms that can occur together, such as stomach pain and irregular bowel habits.

“There seem to be two problems in people with IBS. First, the bowel can become overly sensitive to normal sensation. Second, the motility, or movement of the bowel, can become irregular,” Jesse Stondell, MD, an assistant professor in the department of gastroenterology at the University of California, Davis, told Healthline.

“This can lead to increased movement causing diarrhea, decreased movement causing constipation, or even both at the same time in different places, leading to pressurization of the bowel which causes pain,” he said.

Stondell says the exact cause of IBS is unknown, but researchers have a few theories.

“It’s likely that there are multiple different causes, but there is a lot of interest right now in the concept of dysbiosis, or imbalance in the bacteria that live in the colon,” Stondell said.

“It may be that correcting this imbalance could improve bowel function significantly. There’s also clearly a component of hypersensitivity, which means that for some people, their bowel is much more sensitive to normal stimuli, and the body misinterprets this as pain. Finally, anxiety and depression can significantly worsen IBS but may or may not be a true cause,” he added.

Brierley, who’s also the director of the Visceral Pain Research Group at the South Australian Health and Medical Research Institute, argues that pain experienced by those with IBS happens when itch receptors occur alongside the “wasabi receptor.”

The wasabi receptor, officially called TRPA1, is a protein that exists in sensory nerve cells. When it encounters certain chemicals it activates to protect the body.

Wasabi, mustard, and tear gas are examples of things that can trigger a response from this receptor.

Brierley says the same thing is happening in the gut of someone with IBS.

“The nerves which connect the gut to the brain become activated and remain in an alarmed state, therefore signaling pain when they might not need to. This can also result in the rewiring of pain pathways in the spine and brain,” he said.

Brierley is hopeful this recent research will pave the way for new treatment options for those with IBS.

“Essentially, IBS gut nerves are more sensitive than other people’s, and this is telling your body that you’re in pain. It’s essentially an ongoing false alarm,” Brierley said.

“By understanding these mechanisms, we can target the specific mechanisms which are altered in IBS. We can treat chronic abdominal pain by developing a medication that a patient can take once a day to block those receptors and stop the pain signal from the gut to the brain,” he said.

But Emeran Mayer, PhD, co-director of the CURE: Digestive Diseases Research Center at the University of California, Los Angeles, says the discovery of such itch receptors is unlikely to influence treatment options for IBS.

“Many different receptors have been identified in mouse models of IBS, but findings have never been translatable into human patients,” Mayer told Healthline.

“IBS isn’t caused by the abnormality of a single receptor in the gut but is a complex brain-gut disorder with both central and peripheral abnormalities. So, I don’t believe the identification of the itch receptor will have any significant impact on IBS symptoms,” he said.

Mayer adds he’s been involved in many drug development efforts with major pharmaceutical companies during his 30 years in the field, and all of them have been unsuccessful.

Currently there’s no cure for IBS. Rather, treatment options are aimed at managing symptoms, such as diarrhea and constipation.

A recent study in Norway of fecal microbiota transplantation (FMT) using a “super donor” concluded that FMT was effective for IBS.

The study was unveiled this weekend at the 2019 United European Gastroenterology Week in Barcelona.

The results haven’t been published yet in a peer-reviewed journal.

Experts who spoke with Healthline say FMT isn’t yet appropriate for those with IBS, and further research in larger groups is needed.

“It’s important to note that currently the FDA considers a fecal transplant an ‘investigational new drug,’ and it is illegal for any doctor to do a fecal transplant outside of two situations: one, treatment of a particular infection called C. diff, and two, a research study,” Stondell said.

Stondell says one of the most critical steps in improving IBS is dietary modification.

“I find the FODMAP diet to be particularly effective in treating bloating, abdominal pain, and diarrhea. It can sometimes be very difficult to convince people that a dietary change can significantly improve their symptoms, especially pain.

“I also find that some patients feel there’s nothing to be done and don’t seek care. It’s true that IBS does tend to be a long-term problem, but it’s also true that symptoms can very often be reduced with appropriate care,” Stondell said.


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