Constipation and diarrhoea are frequent symptoms of gastrointestinal disorders including irritable bowel syndrome (IBS), which affects up to 10% of the global population.

How often people go to the restroom is important for their health and shows how well their gastrointestinal (GI) tract works at digesting and absorbing nutrients while also getting rid of waste products of digestion and toxic substances.

Common gastrointestinal conditions like IBS, which affects up to 10% of the world’s population, often have irregular bowel habits and changes in the way the digestive system moves, which can cause constipation and diarrhea.

The exact mechanisms that control peristalsis (the movement of intestinal muscles that push food and feces along the GI tract), as well as why this is often different in people with IBS, are unknown. They may be in our DNA, it turns out.

The study led by Mauro D’Amato, an Ikerbasque Research Professor at CIC bioGUNE says that people have bowel habits and are more likely to get IBS because of their genes.

It was a study of 167,875 people who were part of population-based cohorts in the UK and the Netherlands, Belgium, Sweden, and the United States. They looked at their genetic makeup and questionnaire data, mostly in relation to a simple question about how many times a person opened their bowels each day (the “stool frequency,” as they called it in the study).

They found that specific DNA mutations were more common in those with higher (or lower) stool frequency than in the general population.

These alterations, discovered in 14 locations of the human genome, affected multiple genes that were investigated further: “We were surprised how much sense these new findings make, highlighting multiple molecules whose role in gut motility was already known from clinical studies, including the communication between the brain and the gut” said Ferdinando Bonfiglio, first author of the study.

Some of the genes identified in the study create neurotransmitters, hormones, and other substances that are particularly active in the brain and nerve cells involved in the control of intestinal peristalsis, and have previously been targeted pharmaceutically to induce bowel motions (like BDNF).

“These results are very exciting and warrant follow-up studies: once more stool frequency genes are unequivocally identified, we may have a battery of new drug targets to be exploited for the treatment of constipation, diarrhoea and common dysmotility syndromes like IBS” explained corresponding author Mauro D’Amato.

The researchers also found evidence of a common genetic background for stool frequency and IBS, and this knowledge could be utilized to identify those who are at higher risk of disease. This was more useful for IBS that was primarily characterized by diarrhoea (IBS-D). The researchers converted their study’s genetic findings into simple numerical values (dubbed “polygenic scores”) in order to predict the likelihood of having altered stool frequency in each individual. Using data from the UK Biobank, they discovered that those with higher polygenic scores were up to five times more likely to have IBS-D than the general population.

“The genetic information and the polygenic scores obtained in this study can be refined and eventually contribute to the classification of patients into different treatment groups, hopefully leading to improved therapeutic precision when aiming to bring gut dysmotility and altered bowel habits back to normal. This would be a major step forward in IBS, a common condition for which there is currently no effective treatment that works for all,” concluded Mauro D’Amato.

Source: 10.1016/j.xgen.2021.100069

Image Credit: Getty

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