Sucrase-Isomaltase Hypomorphic Variants and Response to a Low-FODMAP Diet in Irritable Bowel Syndrome
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Background:
Irritable Bowel Syndrome (IBS) is a common functional gastrointestinal disorder. Emerging research suggests a potential link between hypomorphic (reduced function) variants of the sucrase-isomaltase (SI) enzyme and the advancement of IBS symptoms, particularly in adults. However, it remains unclear whether the presence of thes genetic variants influences how effectively patients respond to dietary interventions like the low-FODMAP diet. SI deficiency,even partial,can lead to malabsorption of sucrose and starches,contributing to gastrointestinal distress.
Aims:
This study aimed to determine the prevalence of sucrase-isomaltase hypomorphic variants in a cohort of IBS patients and to investigate whether these variants are associated with either initial or long-term improvements in symptoms following education on and implementation of a low-FODMAP diet.
Methods:
Researchers retrospectively analyzed clinical data from 72 IBS patients. These patients had previously (mean 7.1 years prior,range 2.5-13.4 years) received dietary education from a gastrointestinal dietitian regarding a low-FODMAP diet. Data collected included current dietary intake (assessed via a Thorough Nutrition Assessment questionnaire) and reported gastrointestinal symptoms obtained through patient interviews. DNA was extracted from blood samples and analyzed using the Illumina Global Screening Array to identify the presence of sucrase-isomaltase hypomorphic variants.
Results:
The study cohort consisted of 72 participants,with 62% being female and a median age of 59 years. Genetic analysis revealed that 54% of participants carried at least one hypomorphic variant of the SI gene. The majority of carriers (85%) were single-carriers,meaning they had one copy of a hypomorphic variant. Statistical analysis (adjusted binary logistic regression) showed no significant association between the presence of SI hypomorphic variants (considering different genotypic groups) and either the initial response to the low-FODMAP diet or long-term symptom control. There were also no differences in the reported intake of sucrose or starch between individuals with and without the variants. Both groups demonstrated a correlation between FODMAP intake and symptom levels,and this relationship was not altered by the presence of SI variants. The findings were consistent in the subgroup of patients with diarrhea-predominant IBS (n=29). Due to the small number of individuals with two copies of a hypomorphic variant (double-carriers, n=6), meaningful conclusions regarding their outcomes could not be drawn.
Conclusions:
This study suggests that carrying a single sucrase-isomaltase hypomorphic variant is relatively common in individuals with IBS.However, in patients who have been educated on and are following a low-FODMAP diet, the presence of these variants does not appear to significantly impact short- or long-term symptom control or dietary habits. This indicates that the low-FODMAP diet might potentially be effective regardless of SI genotype in this population.
Keywords:
FODMAP diet, carbohydrates, dietary intake, irritable bowel syndrome, outcomes, sucrase-isomaltase deficiency, genetics, IBS-D.
Important Considerations & updates (based on current research – 2024/2025):
* SI Deficiency & IBS: While the study found no correlation within a low-FODMAP diet context, it’s important to note that research continues to explore the role of SI deficiency in IBS pathogenesis. Some studies suggest that undiagnosed SI deficiency can hinder the effectiveness of other IBS treatments.
* Genetic Testing: Genetic testing for SI variants is becoming more accessible, but its routine use in IBS diagnosis is still debated.
* FODMAP Diet Limitations: the low-FODMAP diet is