Kashyap, Purna C

The intestinal epithelium is exposed to diverse combinations of microbiota-derived compounds; however, the mechanisms by which the host integrates these signals remain poorly defined. Studying two highly abundant microbial metabolites, we identified the purine metabolite hypoxanthine as an effector metabolite that directly drives signaling and the short-chain fatty acid butyrate as a regulatory metabolite that conditions host responsiveness. Specifically, hypoxanthine activates the adenosine A1 receptor–TRPC4 axis in enterochromaffin (EC) cells, triggering calcium influx and serotonin release resulting in accelerated gastrointestinal transit locally and increased platelet activation systemically. In contrast, butyrate epigenetically upregulates specific G protein–coupled receptors and ion channels to enhance response to hypoxanthine and the neurotransmitters norepinephrine and dopamine. These findings define a cooperative signaling framework and highlight the role of EC cells as a distinct epithelial signaling hub that senses and integrates microbial metabolite signals to drive physiological responses. Our findings provide a mechanistic foundation for therapeutic strategies that leverage combinatorial microbial signaling.

AbstractBackgroundThis SRMA reviewed and assessed the changes in the severity of disorders of gut‐brain interaction (DGBI) symptoms during the COVID‐19 pandemic, and evaluated factors associated with symptom severity changes.MethodsElectronic databases were searched until February 2024, for articles reporting on changes in symptom severity in DGBI patients during the COVID‐19 pandemic. The proportion of DGBI patients who reported a change in their symptom severity were pooled using a random‐effects model, and subgroup analyses were conducted to assess the effect of socio‐cultural modifiers on symptom severity in DGBI.Key ResultsTwelve studies including 3610 DGBI patients found that 31.4% (95% CI, 15.9–52.5) of DGBI patients experienced symptom deterioration, while 24.3% (95% CI, 10.2–47.5) experienced improvement. Countries with high gross domestic product (GDP) had a 43.5% (95% CI, 16.3–75.2) likelihood of symptom deterioration, compared to 9.2% (95% CI, 1.4–42.2) in lower GDP countries. Similarly, countries with low COVID fatality rates had a 60.1% (95% CI, 19.7–90.3) likelihood of symptom deterioration, compared to 18.3% (95% CI, 7.8–36.9) in higher fatality rate countries. Countries with lenient COVID policies had a 58.4% (95% CI, 14.1–92.3) likelihood of symptom deterioration, compared to 19% (95% CI, 8.2–38.1) in countries with stricter policies. Patients in high vaccine hesitancy countries had a 51.4% (95% CI, 19.5–82.2) likelihood of symptom deterioration, compared to 10.6% (95% CI, 2.7–33.4) in low vaccine hesitancy countries.Conclusions & InferencesThis meta‐analysis reveals that a significantly higher proportion of DGBI patients experienced deterioration of symptoms during the COVID‐19 pandemic. Various sociocultural, economic and environmental factors potentially modify the effects of the COVID‐19 pandemic on DGBI.

AbstractBackgroundDisorders of gut–brain interaction (DGBI) are characterized by debilitating symptoms not explained by structural or biochemical abnormalities. While functional conditions present with complex, likely heterogeneous pathophysiology, we aimed to investigate if proxy measures of sociocultural and environmental factors are associated with the prevalence of various DGBI in populations across the world.MethodsWe performed an ecological study utilizing peer‐reviewed published datasets reporting for 26 countries prevalence rates of DGBI (Rome Foundation Global Epidemiology Study, RFGES), with six independent variables: Helicobacter pylori prevalence and household size as proxy measures for orofecal infections, gross domestic product per capita (GDP), and median age as a proxy measures for socioeconomic development, density of fast food outlets (FFO) per 100,000 population as proxy measure for processed food exposure, and suicide mortality rate per 100,000 people, and world happiness scores were used as a proxy for psychological stress. The data were retrieved from publicly accessible datasets (United Nations, CIA World Factbook, World Bank, World Happiness Report, commercial/financial reports of a global FFO chain). We used linear regression to assess variables in univariate and multivariate analysis and report standardized β coefficients with 95% confidence intervals (CI).Key ResultsThe regression model revealed that the overall prevalence of DGBI was inversely associated with both GDP per capita (β = −0.57, 95% CI: −0.92, −0.22, p = 0.002) and happiness scores (β = −0.433 95% CI: 0.821, −0.065, p = 0.023), while being positively associated with H. pylori prevalence (β = 0.40, 95% CI: 0.008, 0.81, p = 0.046). The prevalence of functional constipation (FC) was also inversely associated with GDP per capita (β = −0.50, 95% CI: −0.86, −0.13, p = 0.01) and happiness scores (β = −0.497, 95% CI: −0.863, −0.132, p = 0.01), while being positively associated with H. pylori prevalence (β = 0.53, 95% CI: 0.16, 0.91, p = 0.007). The Multivariate model analysis revealed that combining the factors of H. pylori prevalence, suicide rate, household size and happiness scores showed statistically significant association with FC (p = 0.039). Household size (β = −0.43, 95% CI: −0.82, 0.038, p = 0.033) and suicide rates (β = 0.55, 95% CI: 0.19, 0.90, p = 0.004) were statistically significantly associated with functional diarrhea. Irritable bowel syndrome (IBS) was associated with GDP per capita (β = −0.40, 95% CI: −0.79, −0.014, p = 0.043) and happiness scores (β = −0.390, 95% CI: −0.778, −0.003, p = 0.049).Conclusions & InferencesUtilizing publicly available data, the prevalence of DGBI across diverse countries is linked to various socio‐cultural and environmental factors. Collectively, the data suggests that the prevalence of DGBI is increased in less prosperous regions of the world.

Disorders of Gut‐Brain Interaction (DGBI) are widely prevalent and commonly encountered in gastroenterology practice. While several peripheral and central mechanisms have been implicated in the pathogenesis of DGBI, a recent body of work suggests an important role for the gut microbiome. In this review, we highlight how gut microbiota and their metabolites affect physiologic changes underlying symptoms in DGBI, with a particular focus on their mechanistic influence on GI transit, visceral sensitivity, intestinal barrier function and secretion, and CNS processing. This review emphasizes the complexity of local and distant effects of microbial metabolites on physiological function, influenced by factors such as metabolite concentration, duration of metabolite exposure, receptor location, host genetics, and underlying disease state. Large‐scale in vitro work has elucidated interactions between host receptors and the microbial metabolome but there is a need for future research to integrate such preclinical findings with clinical studies. The development of novel, targeted therapeutic strategies for DGBI hinges on a deeper understanding of these metabolite‐host interactions, offering exciting possibilities for the future of treatment of DGBI.

Increased amino acids in the dysbiotic gut influences susceptibility to Clostridioides difficile infection in mice and humans.