CIC bioGUNE researchers show that genetic defects in carbohydrate digestion predispose to irritable bowel syndrome

One in ten people suffer from irritable bowel syndrome (IBS), but therapeutic options are scarce and generally of limited efficacy due to unknown aetiology.

A new study, published in the journal Gut, provides new evidence that genetic defects in carbohydrate-digesting enzymes may contribute to IBS.

Irritable bowel syndrome (IBS) is a highly prevalent gastrointestinal disorder affecting around 10-15% of the world’s population. Common symptoms of IBS include abdominal pain, bloating, diarrhoea and constipation. Although the causes of IBS remain unknown, a significant number of individuals associate the onset of their symptoms with carbohydrate intake, and their elimination or controlled reduction in the diet appears to be beneficial, at least in some patients.

Researchers at CIC bioGUNE, a member of BRTA, have published in the journal Gut that changes in the DNA of genes involved in carbohydrate digestion predispose to IBS.

The international team, led by Ikerbasque Professor Mauro D’Amato from the Gastrointestinal Genetics Research group at CIC bioGUNE and LUM University, studied a number of enzymes responsible for the breakdown of dietary carbohydrates (called CAZymes), and showed that genetic variations in the corresponding genes can affect an individual’s risk of developing IBS. They had previously reported that genetic defects in sucrase-isomaltase (SI, an enzyme that digests sucrose) increase the risk of IBS. Studying lifestyle, genetic and health data on 366,432 individuals from the UK Biobank population-based cohort, they now provide similar evidence for two other CAZymes, the starch-digesting amylases AMY1B and AMY2A.

“Poor digestion of sugars and/or starch due to dysfunctional CAZymes can lead to IBS symptoms due to their accumulation in the lower gut where they are fermented by the gut microbiota causing bloating, gas, abdominal pain and diarrhoea,” explains Professor D’Amato. “The specific genetic make-up of CAZymes genes may also explain why some people experience symptoms after consuming starchy or sucrose-rich foods while others do not,” he adds. This information can be used strategically to try to personalise dietary approaches to IBS management based on patients’ CAZymes genetic profile, the authors conclude in their publication.

The research was supported by research funding for MD’A from: MICIU/AEI-funded grant PCI2021-122064-2A and, by the European Union’s NextGenerationEU/PRTR programme under the Joint European Programming Initiative “A Healthy Diet for a Healthy Life” (JPI HDHL) and the ERA-NET Cofund ERA-HDHL (GA No. 696295 of the EU Horizon 2020 Research and Innovation Programme); and MICIU/AEI-funded grant PID2020-113625RB-I00.