1.
Irritable Bowel Syndrome Is Not Associated with an Increased Risk of Polyps and Colorectal Cancer: A Systematic Review and Meta-Analysis.
Vichos, T, Rezaie, A, Vichos, P, Cash, B, Pimentel, M
Digestive diseases and sciences. 2023;68(6):2585-2596
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Colorectal cancer (CRC) is one of the most common cancers and adenomatous colorectal polyps (CRP) are a risk factor for developing CRC. The potential role of functional disturbances seen in irritable bowel syndrome (IBS) for the development of CRC are not yet clear. The aim of this systematic review and meta-analysis was to evaluate the occurrence of CRC and CRP in IBS patients. 14 cohort studies with a total of 654,764 IBS patients and 2,277,195 controls and six cross-sectional studies with 26,641 IBS patients and 87,803 controls were included in the review. Based on the pooled data from 5 cross-sectional studies, IBS patients had a significantly lower occurrence of CRP (by 71%). CRC risk was also reduced but this did not reach statistical significance. Only four of the 14 cohort studies were included in the meta-analysis and, again, CRC risk was lower in IBS patients but this was not statistically significant.
Abstract
OBJECTIVES Colorectal cancer (CRC) is the third most common malignancy in the US. Several factors are associated with increased/decreased CRC risk and often linked to adenomatous colorectal polyps (CRP). Recent studies suggest a lower risk of neoplastic lesions among irritable bowel syndrome (IBS) patients. We aimed to systematically assess the occurrence of CRC and CRP in IBS patients. METHODS Searches of the Medline, Cochrane, and EMBASE databases were performed, blindly and independently, by two investigators. Studies of CRC or CRP incidence in IBS patients (diagnosed by Rome or other symptom-based criteria) were eligible for inclusion. CRC and CRP effect estimates were pooled in meta-analyses using random models. RESULTS Of 4941 non-duplicate studies, 14 were included, comprising 654,764 IBS patients and 2,277,195 controls in 8 cohort studies, and 26,641 IBS patients and 87,803 controls in 6 cross-sectional studies. Pooled analysis revealed a significantly decreased prevalence of CRP in IBS subjects vs. controls, with a pooled odds ratio (OR) of 0.29 (95% CI (0.15, 0.54)). There was significant heterogeneity between studies (I2 = 96%, p < 0.01). This finding persisted when studies which did not report pre-cancerous polyps separately were excluded (OR 0.23, 95% CI (0.15, 0.35), I2 = 85%, p < 0.01). CRC prevalence was lower in IBS subjects, but this did not reach statistical significance (OR 0.40, 95% CI (0.09, 1.77]). CONCLUSION Our analyses reveal a decreased incidence of colorectal polyps in IBS, although CRC did not reach significance. Mechanistic studies with detailed genotypic analysis and clinical phenotyping are needed to better elucidate the potentially protective effect of IBS on CRC development.
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Post-Antibiotic Gut Mucosal Microbiome Reconstitution Is Impaired by Probiotics and Improved by Autologous FMT.
Suez, J, Zmora, N, Zilberman-Schapira, G, Mor, U, Dori-Bachash, M, Bashiardes, S, Zur, M, Regev-Lehavi, D, Ben-Zeev Brik, R, Federici, S, et al
Cell. 2018;174(6):1406-1423.e16
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Probiotics are commonly used to reduce the risk of antibiotic associated diarrhoea (AAD). This study, in both mice and humans, investigated the effects of an 11 strain probiotic supplement and autologous faecal microbiome transplantation (aFMT) after antibiotic treatment. (Autologous meaning the person’s own, pre-antibiotic stool was transplanted.) Gut mucosa samples along the digestive tract and stool samples were investigated for microbiome composition and activity (transcriptome). The investigators found that without antibiotics the probiotics did not colonise very well, suggesting that our native microbiome offers resistance. After antibiotics, which would kill off much of our gut bacteria,the probiotics colonise the gut mucosa much better. However, the probiotics appear to then prevent the microbiome to return to its native, pre-antibiotic state. Whilst in those with the aFMT and in those who did nothing (“watchful waiting”) the microbiome returned to pre-antibiotic state fairly quickly, in the probiotic group even after 5 months the microbiome had not returned to its native composition. In vitro experiments suggest that the delay in the probiotic group is due to substances secreted by the probiotic bacteria, in particular Lactobacilli. The authors conclude that the potential benefits in terms of reducing the risk of AAD with probiotics may be offset with a delay in reconstitution of the native microbiome, and call for more research into aFMT and a more personalised approach to probiotic therapy.
Abstract
Probiotics are widely prescribed for prevention of antibiotics-associated dysbiosis and related adverse effects. However, probiotic impact on post-antibiotic reconstitution of the gut mucosal host-microbiome niche remains elusive. We invasively examined the effects of multi-strain probiotics or autologous fecal microbiome transplantation (aFMT) on post-antibiotic reconstitution of the murine and human mucosal microbiome niche. Contrary to homeostasis, antibiotic perturbation enhanced probiotics colonization in the human mucosa but only mildly improved colonization in mice. Compared to spontaneous post-antibiotic recovery, probiotics induced a markedly delayed and persistently incomplete indigenous stool/mucosal microbiome reconstitution and host transcriptome recovery toward homeostatic configuration, while aFMT induced a rapid and near-complete recovery within days of administration. In vitro, Lactobacillus-secreted soluble factors contributed to probiotics-induced microbiome inhibition. Collectively, potential post-antibiotic probiotic benefits may be offset by a compromised gut mucosal recovery, highlighting a need of developing aFMT or personalized probiotic approaches achieving mucosal protection without compromising microbiome recolonization in the antibiotics-perturbed host.
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Personalized Gut Mucosal Colonization Resistance to Empiric Probiotics Is Associated with Unique Host and Microbiome Features.
Zmora, N, Zilberman-Schapira, G, Suez, J, Mor, U, Dori-Bachash, M, Bashiardes, S, Kotler, E, Zur, M, Regev-Lehavi, D, Brik, RB, et al
Cell. 2018;174(6):1388-1405.e21
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Evidence regarding the efficacy of probiotics in colonising the gut mucosa are sparse. The authors investigated whether probiotics colonise the gut mucosa in mice and humans, using both gut mucosa and stool samples. They found that, in both mice and humans, results from stool samples only partially correlate with colonisation of the gut mucosa as determined through gut mucosa samples. Whilst results were fairly uniform in mice, in humans a person-specific resistance to colonisation of the gut mucosa by probiotics was observed. Inter-person variation could be predicted by the composition of the pre-probiotic microbiome and host immune features.
Abstract
Empiric probiotics are commonly consumed by healthy individuals as means of life quality improvement and disease prevention. However, evidence of probiotic gut mucosal colonization efficacy remains sparse and controversial. We metagenomically characterized the murine and human mucosal-associated gastrointestinal microbiome and found it to only partially correlate with stool microbiome. A sequential invasive multi-omics measurement at baseline and during consumption of an 11-strain probiotic combination or placebo demonstrated that probiotics remain viable upon gastrointestinal passage. In colonized, but not germ-free mice, probiotics encountered a marked mucosal colonization resistance. In contrast, humans featured person-, region- and strain-specific mucosal colonization patterns, hallmarked by predictive baseline host and microbiome features, but indistinguishable by probiotics presence in stool. Consequently, probiotics induced a transient, individualized impact on mucosal community structure and gut transcriptome. Collectively, empiric probiotics supplementation may be limited in universally and persistently impacting the gut mucosa, meriting development of new personalized probiotic approaches.