Altered profiles of intestinal microbiota and organic acids may be the origin of symptoms in irritable bowel syndrome Original paper

What was studied?

This study investigated the profiles of intestinal microbiota and organic acids in patients diagnosed with Irritable Bowel Syndrome (IBS) compared to healthy controls. The researchers hypothesized that the gut microbiota of IBS patients is disrupted, contributing to elevated levels of organic acids, which may be linked to the manifestation of gastrointestinal (GI) symptoms. To evaluate this, the study analyzed fecal samples for microbial populations using quantitative real-time PCR and culture methods, as well as organic acid concentrations through high-performance liquid chromatography (HPLC). Abdominal gas was also measured via X-ray imaging to determine if microbial fermentation contributed to bloating and discomfort commonly reported by IBS patients.

Who was studied?

The study involved 26 patients diagnosed with IBS according to the Rome II criteria, further confirmed by the Rome III modular questionnaire. The cohort was composed of 11 patients with constipation-predominant IBS (IBS-C), 8 with diarrhea-predominant IBS (IBS-D), and 7 with mixed IBS (IBS-M). Twenty-six age- and sex-matched healthy controls were also included for comparison. All participants underwent comprehensive medical evaluations, including physical exams, lab tests, and radiological assessments to exclude any organic GI diseases or systemic health issues.

What were the most important findings?

IBS patients demonstrated significant alterations in their gut microbiota and organic acid levels compared to healthy controls. Notably, the study found higher counts of Veillonella (p = 0.046) and Lactobacillus (p = 0.031) in IBS patients, two bacterial groups known for their role in organic acid production. Correspondingly, fecal analysis revealed that IBS patients exhibited significantly elevated levels of acetic acid (p = 0.049), propionic acid (p = 0.025), and total organic acids (p = 0.014). These organic acids are byproducts of microbial fermentation and have been implicated in gut motility and sensory processing.

Importantly, patients with high levels of acetic or propionic acid experienced more severe GI symptoms, poorer quality of life (QOL), and greater levels of negative emotions compared to those with lower acid concentrations. This correlation suggests that microbial shifts favoring Veillonella and Lactobacillus may drive acid production, which in turn exacerbates abdominal discomfort and impacts psychological well-being. Interestingly, despite the elevated organic acid levels, there were no significant differences in abdominal gas volume between IBS patients and controls, indicating that symptom severity may be driven more by microbial metabolites than gas accumulation.

What are the greatest implications of this study?

The study’s findings provide compelling evidence that microbial imbalances and organic acid overproduction are critical components of IBS symptomatology. Elevated levels of Veillonella and Lactobacillus are linked to increased acetic and propionic acid production, which correlates with symptom severity, reduced QOL, and heightened negative emotional states. These findings support the concept that IBS may not be merely a functional disorder but is mechanistically influenced by microbial fermentation and its metabolic byproducts. Understanding these microbial and metabolic interactions opens the door for targeted probiotic, prebiotic, or dietary interventions aimed at modulating organic acid production, potentially offering novel therapeutic avenues for IBS management.