An update on the role of gut microbiota in chronic inflammatory diseases, and potential therapeutic targets

Can the Evidence-Based Use of Probiotics (Notably Saccharomyces boulardii CNCM I-745 and Lactobacillus rhamnosus GG) Mitigate the Clinical Effects of Antibiotic-Associated Dysbiosis?

Dysbiosis corresponds to the disruption of a formerly stable, functionally complete microbiota. In the gut, this imbalance can lead to adverse health outcomes in both the short and long terms, with a potential increase in the lifetime risks of various noncommunicable diseases and disorders such as atopy (like asthma), inflammatory bowel disease, neurological disorders, and even behavioural and psychological disorders. Although antibiotics are highly effective in reducing morbidity and mortality in infectious diseases, antibiotic-associated diarrhoea is a common, non-negligible clinical sign of gut dysbiosis (and the only visible one). Re-establishment of a normal (functional) gut microbiota is promoted by completion of the clinically indicated course of antibiotics, the removal of any other perturbing external factors, the passage of time (i.e. recovery through the microbiota's natural resilience), appropriate nutritional support, and-in selected cases-the addition of probiotics. Systematic reviews and meta-analyses of clinical trials have confirmed the strain-specific efficacy of some probiotics (notably the yeast Saccharomyces boulardii CNCM I-745 and the bacterium Lactobacillus rhamnosus GG) in the treatment and/or prevention of antibiotic-associated diarrhoea in children and in adults. Unusually for a probiotic, S. boulardii is a eukaryote and is not therefore directly affected by antibiotics-making it suitable for administration in cases of antibiotic-associated diarrhoea. A robust body of evidence from clinical trials and meta-analyses shows that the timely administration of an adequately dosed probiotic (upon initiation of antibiotic treatment or within 48 h) can help to prevent or resolve the consequences of antibiotic-associated dysbiosis (such as diarrhoea) and promote the resilience of the gut microbiota and a return to the pre-antibiotic state. A focus on the prescription of evidence-based, adequately dosed probiotics should help to limit unjustified and potentially ineffective self-medication.

Role of exercise in preventing and restoring gut dysbiosis in patients with inflammatory bowel diseases: A review

Inflammatory bowel diseases (IBD) include a spectrum of chronic inflammatory disorders of the gastrointestinal tract whose pathogenesis is yet to be elucidated. The intestinal microbiome has been studied as a causal component, with certain microbiotic alterations having been observed in subtypes of IBD. Physical exercise is a modulator of the intestinal microbiome, causing shifts in its composition that are partially corrective of those observed in IBD; furthermore, physical exercise may be beneficial in patients with certain IBD subtypes. This review studies the effects of physical exercise on the human gut microbiome while investigating pathophysiologic mechanisms that could explain physical activity’s clinical effects on patients with IBD.

Short chain fatty acids and monocarboxylate transporters in irritable bowel syndrome

BACKGROUND/AIMS

Gut microbiota ferments indigestible food that rests in the colon to produce short-chain fatty acids (SCFAs) acetate, propionate, and butyrate. Colonic SCFA stimulate the synthesis of serotonin which is central in irritable bowel syndrome (IBS) pathophysiology. Reduced SCFA have been linked to specific IBS symptoms like colonic hyperalgesia and hypersensitivity. SCFA enter the colonocyte mainly via 2 energy-dependent monocarboxylate transporters, MCT1 (SLC16A1) and SMCT1 (SLC5A8). We investigated specific gut microbiota, SCFA concentrations, and monocarboxylate transporter mRNA expression in patients with IBS.

MATERIAL AND METHODS

A total of 30 IBS patients-15 constipation-predominant (C-IBS) and 15 diarrhoea-predominant (D-IBS)-and 15 healthy controls were recruited. Bacteroidetes and Bifidobacterium species were analyzed using quantitative polymerase chain reaction (qPCR) on stool samples. SCFA concentrations were determined by gas chromatography/mass spectroscopy of stool samples. Monocarboxylate transporter mRNA was quantified by qPCR on colon biopsy specimens.

RESULTS

Bacteroides was significantly increased in the D-IBS group compared with the C-IBS group and healthy controls. Bifidobacterium was significantly reduced in both IBS groups. SCFA ratios were altered in both IBS groups with a reduction of all 3 measured SCFA in C-IBS and acetic acid in D-IBS. MCT1 and SMCT1 were significantly reduced in C-IBS and D-IBS.

CONCLUSION

In agreement with findings of previous studies, the microbiota assessed were significantly altered inferring dysbiosis in IBS. SCFA and their ratios were significantly altered in both IBS groups. SCFA transporters, MCT1 and SMCT1 were significantly reduced in both IBS groups, suggesting reduced colonocyte SCFA transfer. SCFA availability and transfer into the colonocytes may be important in IBS pathogenesis and should be prospectively studied.

Alteration of Gut Microbiota in Patients With Epilepsy and the Potential Index as a Biomarker

Objective

To explore the structure and composition of the fecal microbiota of patients with epilepsy.

Methods

Variations in the fecal microbiota between patients with epilepsy and healthy controls (HCs) from the same household were investigated and validated by utilizing 16S ribosomal RNA sequencing in two independent cohorts [exploration cohort (N = 55 patients and N = 46 HCs) and validation cohort (N = 13 patients and N = 10 HCs)].

Results

The alpha diversity indexes of the specimens from patients with epilepsy were much lower than those from the HCs (p < 0.05). The structure and composition of the fecal microbiota differed between patients with different clinical prognoses and between patients and HCs (Adonis: p < 0.05). Microbiome alterations in patients with epilepsy included increases in Actinobacteria and Verrucomicrobia and decreases in Proteobacteria at the phylum level and increases in Prevotella_9, Blautia, Bifidobacterium, and others at the genus level [linear discriminant analysis (LDA): 3.5] Patients with drug-resistant epilepsy showed enrichment of bacterial taxa in Actinobacteria, Verrucomicrobia, and Nitrospirae and the genera Blautia, Bifidobacterium, Subdoligranulum, Dialister, and Anaerostipes (Kruskal-Wallis test: p < 0.05). Analysis of gut microbiome indicated predictive ability for disease diagnosis, with an area under the receiver operating characteristic (ROC) curve (AUC) of 0.97 (95% CI, 0.84-0.98). Applying the model to our validation cohort resulted in an AUC of 0.96 (95% CI, 0.75-0.97). Notably, the model could distinguish drug-resistant from drug-sensitive epilepsy (AUC = 0.85, 95% CI: 0.69-0.94).

Conclusion

Patients with epilepsy exhibit substantial alterations of fecal microbiota composition, and specific gut commensal strains are altered depending on different clinical phenotypes and thus could serve as potential biomarkers for disease diagnosis.

Should we Try to Alleviate Immunosenescence and Inflammaging - Why, How and to What Extent?

With advancing age, immune responses of human beings to external pathogens, i.e., bacteria, viruses, fungi and parasites, and to internal pathogens - malignant neoplasm cells - become less effective. Two major features in the process of aging of the human immune system are immunosenescence and inflammaging. The immune systems of our predecessors co-evolved with pathogens, which led to the occurrence of effective immunity. However, the otherwise beneficial activity may pose problems to the organism of the host and so it has builtin brakes (regulatory immune cells) and - with age - it undergoes adaptations and modifications, examples of which are the mentioned inflammaging and immunosenescence. Here we describe the mechanisms that first created our immune systems, then the consequences of their changes associated with aging, and the mechanisms of inflammaging and immunosenescence. Finally, we discuss to what extent both processes are detrimental and to what extent they might be beneficial and propose some therapeutic approaches for their wise control.

Dynamic changes in gut microbiota under the influence of smoking and TNF-α-blocker in patients with ankylosing spondylitis

OBJECTIVES

This study aimed to investigate the relationship among smoking, TNF-α-blocker therapy, and the dynamic changes in gut microbiota in patients with ankylosing spondylitis (AS).

METHODS

Using a 16S rRNA sequence, 98 fecal samples of 20 AS patients collected after 0, 1, 3 and 6 months of anti-TNF-α treatment and from 20 matched health controls were examined. The variation in composition, abundance, and diversity of gut microbiota was analyzed. The dynamic effects of smoking and treatment on gut microbiota and therapeutic efficacy in AS patients were studied.

RESULTS

The increased relative abundance of microbiota in AS nonsmokers was g_Comamonas and g_Desulfovibrio, while that in AS smokers was g_Actinomyces, g_Collinsella, g_Lachnospiraceae_UCG-008, and g_Paraprevotella. The relative abundance of gut microbiota showed dynamic variation. The improvement rate of ASDAS in AS nonsmokers was higher than that in AS smokers (2.297 vs 1.736) after anti-TNF-α treatment. The β-diversity of gut microbiota in AS smokers was lower than that in AS nonsmokers and improved with treatment.

CONCLUSIONS

Both smoking and TNF-α-blocker had significant effects on the composition, relative abundance, and diversity of gut microbiota in AS patients. The AS smokers characteristically shared g_Collinsella and g_Dorea. The relative abundance of gut microbiota revealed high variability and was in dynamic fluctuation during treatment. The response of gut microbiota to anti-TNF-α treatment was found to be heterogeneous and selective. AS nonsmokers showed a greater improvement rate of ASDAS-CRP with treatment than AS smokers did. The AS smokers showed a lower β-diversity of gut microbiota, and improved after treatment. Key Points • Characterized the dynamic variation in gut microbiota in AS patients classified as smokers and nonsmokers during treatment with anti-TNF-α. • Confirmed the interaction between smoking, anti-TNF-α therapy, and gut microbiota.