Functional Abdominal Bloating Is Associated With Gut Microbiota Dysbiosis and Altered Intestinal Barrier Function:...

This study aimed to characterize gut microbiota alterations and intestinal barrier markers in patients with functional abdominal bloating (FAB) to explore its underlying biological mechanisms.

Stool samples from 42 adults diagnosed with FAB per Rome IV criteria were analyzed using the intergenic spacer profiling, which profiles the 16S-23S ribosomal DNA intergenic spacer region to enhance species-level resolution. Targeted real-time polymerase chain reaction quantified key bacterial taxa. Microbial diversity, Firmicutes/Bacteroidetes (F/B) ratio, enterotype distribution, and levels of beneficial and pathogenic bacteria were assessed. Gastrointestinal immune and permeability markers (calprotectin, secretory IgA, zonulin, α1-antitrypsin, bile acids, pancreatic elastase) were measured by enzyme-linked immunosorbent assay.

A dysbiosis index ≥15 was observed in 90.5% of patients, indicating significant microbial imbalance. Most showed a low mean F/B ratio (<1.5) and microbial diversity index (<5), reflecting reduced microbiota resilience. Enterotype 1 (Bacteroides-dominant) was predominant (67%), with no detection of Enterotype 3 (Ruminococcus-dominant). Levels of beneficial bacteria, including Faecalibacterium prausnitzii, Akkermansia muciniphila, Bacteroides spp., and Bifidobacterium spp., were markedly decreased in over 80% of individuals. Conversely, Proteobacteria such as Sutterella wadsworthensis and Klebsiella spp. were at elevated levels. Calprotectin and sIgA were increased in >59.5% of cases; zonulin and α1-antitrypsin were elevated in 19% and 16.7%, respectively, suggesting mucosal immune activation and possible barrier dysfunction.

This study demonstrates that FAB is accompanied by profound alterations in gut microbiota composition and mucosal immune responses, indicating that its pathophysiology extends beyond functional disturbances to include measurable biological changes. These findings support the growing clinical relevance of microbiota-informed evaluation and open new avenues for targeted therapeutic strategies.