November 22, 2016
1 min read

IBS linked to genetic defects in carbohydrate digestion

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Mutations in the gene encoding the enzyme sucrase-isomaltase, responsible for the digestion of small carbohydrates from sugars and starches called disaccharides, are associated with an increased risk for irritable bowel syndrome, according to recent study data.

These gene variants are known to occur in congenital sucrase-isomaltase deficiency, a rare genetic form of disaccharide malabsorption that shares many features of IBS, including diarrhea, abdominal pain and bloating. Thus, this gene “represents an excellent candidate to play a role in IBS predisposition,” researchers wrote.

“A significant decrease in the enzymatic activity of sucrase-isomaltase would be compatible with poor carbohydrate digestion in the intestine, possibly leading to malabsorption and bowel symptoms,” Hassan Naim, PhD, from the department of physiological chemistry at the University of Veterinary Medicine in Hannover, Germany, said in a press release.

Naim and colleagues screened for congenital sucrase-isomaltase deficiency gene variants and a common sucrase-isomaltase polymorphism (15Phe) in a multicenter cohort of 1,887 IBS cases and controls from Sweden, Italy and the U.S. They also analyzed associations between 15Phe and IBS status, stool frequency and fecal microbiota composition in 250 subjects from the general population.

They found that congenital sucrase-isomaltase deficiency gene variants were significantly more common in IBS patients compared with asymptomatic controls (OR = 1.84) and the general population (OR = 1.57). In addition, they found that 15Phe showed reduce enzymatic activity in vitro, and was strongly associated with an increased risk for IBS (OR = 1.36), especially diarrhea-predominant IBS.

Mauro D'Amato, PhD

Mauro D'Amato

“Our studies show that genetic variation in the [sucrase-isomaltase] gene is associated with predisposition to IBS,” the investigators concluded. “We detected a twofold increased risk of IBS in heterozygous carriers of known rare CSID mutations. In addition, we detected genetic risk effects attributable to a common coding variant, 15Phe at SNP rs9290264, which cosegregated with IBS in some affected families, and was associated with increased disease odds in large multinational IBS case–control cohorts and a pilot general population sample.”

“Our results provide rationale for novel nutrigenetic studies in IBS, with potential for personalizing treatment options based on SI genotype,” Mauro D’Amato, PhD, from Karolinska Institutet in Sweden, said in the press release. – by Adam Leitenberger

Disclosures: D’Amato reports an unrestricted grant from Medical Need Europe AB partially funded this study, and several researchers report financial relationships with QOL Medical.