Purpose of Review
The purposes of this review were as follows: first, to provide an overview of the gut microbiota and its interactions with the gut and the central nervous system (the ...microbiota-gut-brain axis) in health, second, to review the relevance of this axis to the pathogenesis of neurodegenerative diseases, such as Parkinson’s disease, and, finally, to assess the potential for microbiota-targeted therapies.
Recent Findings
Work on animal models has established the microbiota-gut-brain axis as a real phenomenon; to date, the evidence for its operation in man has been limited and has been confronted by considerable logistical challenges. Animal and translational models have incriminated a disturbed gut microbiota in a number of CNS disorders, including Parkinson’s disease; data from human studies is scanty. While a theoretical basis can be developed for the use of microbiota-directed therapies in neurodegenerative disorders, support is yet to come from high-quality clinical trials.
Summary
In theory, a role for the microbiota-gut-brain axis is highly plausible; clinical confirmation is awaited.
In 2019, the International Scientific Association for Probiotics and Prebiotics (ISAPP) convened a panel of experts specializing in nutrition, microbial physiology, gastroenterology, paediatrics, ...food science and microbiology to review the definition and scope of postbiotics. The term 'postbiotics' is increasingly found in the scientific literature and on commercial products, yet is inconsistently used and lacks a clear definition. The purpose of this panel was to consider the scientific, commercial and regulatory parameters encompassing this emerging term, propose a useful definition and thereby establish a foundation for future developments. The panel defined a postbiotic as a "preparation of inanimate microorganisms and/or their components that confers a health benefit on the host". Effective postbiotics must contain inactivated microbial cells or cell components, with or without metabolites, that contribute to observed health benefits. The panel also discussed existing evidence of health-promoting effects of postbiotics, potential mechanisms of action, levels of evidence required to meet the stated definition, safety and implications for stakeholders. The panel determined that a definition of postbiotics is useful so that scientists, clinical triallists, industry, regulators and consumers have common ground for future activity in this area. A generally accepted definition will hopefully lead to regulatory clarity and promote innovation and the development of new postbiotic products.
Summary
Background
Irritable bowel syndrome (IBS) is a chronic functional bowel disorder. Disturbances in the gastrointestinal microbiome may be involved in its aetiology.
Aim
To perform a systematic ...review and meta‐analysis to examine the efficacy of prebiotics, probiotics, synbiotics and antibiotics in IBS.
Methods
MEDLINE, EMBASE, and the Cochrane Controlled Trials Register were searched (up to July 2017). Randomised controlled trials (RCTs) recruiting adults with IBS, comparing prebiotics, probiotics, synbiotics or antibiotics with placebo or no therapy were eligible. Dichotomous symptom data were pooled to obtain a relative risk (RR) of remaining symptomatic after therapy, with a 95% confidence interval (CI). Continuous data were pooled using a standardised mean difference with a 95% CI.
Results
The search identified 4017 citations. Data for prebiotics and synbiotics were sparse. Fifty‐three RCTs of probiotics, involving 5545 patients, were eligible. Particular combinations of probiotics, or specific species and strains, appeared to have beneficial effects on global IBS symptoms and abdominal pain, but it was not possible to draw definitive conclusions about their efficacy. There were five trials of similar design that used rifaximin in non‐constipated IBS patients, which was more effective than placebo (RR of symptoms persisting = 0.84; 95% CI 0.79‐0.90). Adverse events were no more common with probiotics or antibiotics.
Conclusions
Which particular combination, species or strains of probiotics are effective for IBS remains, for the most part, unclear. Rifaximin has modest efficacy in improving symptoms in non‐constipated IBS.
Important metabolic functions have been identified for the gut microbiota in health and disease. Several lines of evidence suggest a role for the gut microbiota in both the etiology of nonalcoholic ...fatty liver disease (NAFLD) and progression to its more advanced state, nonalcoholic steatohepatitis (NASH). Both NAFLD and NASH are strongly linked to obesity, type 2 diabetes mellitus and the metabolic syndrome and, accordingly, have become common worldwide problems. Small intestinal bacterial overgrowth of Gram-negative organisms could promote insulin resistance, increase endogenous ethanol production and induce choline deficiency, all factors implicated in NAFLD. Among the potential mediators of this association, lipopolysaccharide (a component of Gram-negative bacterial cell walls) exerts relevant metabolic and proinflammatory effects. Although the best evidence to support a role for the gut microbiota in NAFLD and NASH comes largely from animal models, data from studies in humans (albeit at times contradictory) is accumulating and could lead to new therapeutic avenues for these highly prevalent conditions.
As the importance of the gut microbiota in health and disease is increasingly recognized interest in interventions that can modulate the microbiota and its interactions with its host has soared. ...Apart from diet, prebiotics and probiotics represent the most commonly used substances taken in an effort to sustain a healthy microbiome or restore balance when it is believed bacterial homeostasis has been disturbed in disease. While a considerable volume of basic science attests to the ability of various prebiotic molecules and probiotic strains to beneficially influence host immune responses, metabolic processes and neuro-endocrine pathways, the evidence base from human studies leaves much to be desired. This translational gap owes much to the manner in which this sector is regulated but also speaks to the challenges that confront the investigator who seeks to explore microbiota modulation in either healthy populations or those who suffer from common digestive ailments. For many products marketed as probiotics, some of the most fundamental issues relating to quality control, such as characterization, formulation, viability safety are scarcely addressed.
The microbiome and inflammatory bowel disease Glassner, Kerri L.; Abraham, Bincy P.; Quigley, Eamonn M.M.
Journal of allergy and clinical immunology,
January 2020, 2020-Jan, 2020-01-00, 20200101, Letnik:
145, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Inflammatory bowel disease (IBD) is a chronic immune-mediated disease affecting the gastrointestinal tract. IBD consists of 2 subtypes: ulcerative colitis and Crohn disease. IBD is thought to develop ...as a result of interactions between environmental, microbial, and immune-mediated factors in a genetically susceptible host. Of late, the potential role of the microbiome in the development, progression, and treatment of IBD has been a subject of considerable interest and enquiry. Indeed, studies in human subjects have shown that the gut microbiome is different in patients with IBD compared with that in healthy control subjects. Other evidence in support of a fundamental role for the microbiome in patients with IBD includes identification of mutations in genes involved in microbiome-immune interactions among patients with IBD and epidemiologic observations implicating such microbiota-modulating risk factors as antibiotic use, cigarette smoking, levels of sanitation, and diet in the pathogenesis of IBD. Consequently, there has been much interest in the possible benefits of microbiome-modulating interventions, such as probiotics, prebiotics, antibiotics, fecal microbiota transplantation, and gene manipulation in the treatment of IBD. In this review we will discuss the role of the gut microbiome in patients with IBD; our focus will be on human studies.
Spurred on by ever-evolving developments in analytical methodology, the microbiome, and the gut microbiome in particular, has become the hot topic in biomedical research. Ingenious experiments in ...animal models have revealed the extent to which the gut microbiota sustains health and how its disruption might contribute to disease pathogenesis. Not surprisingly, associations between the microbiota and disease states in humans have been the subject of considerable interest and many links proposed. However, with rare exceptions, the incrimination of an altered microbiota in disease pathogenesis seems premature at this time given our incomplete understanding of the composition of the gut microbiota in health and the effect of many confounding factors in the interpretation of supposedly abnormal microbial signatures. Future studies must account for these variables and the bidirectionality of host-microorganism interactions in health and disease. In this Perspectives, the status of microbiota signatures in the clinical arena (for facilitating diagnosis or refining prognosis) will be critically assessed and guidance toward future progress provided.
Purpose The objectives of this study were, firstly, to determine the diversity of the host's gut microbiota in irritable bowel syndrome (IBS) using a culture-independent method (DGGE of the 16S rRNA ...gene) and, secondly, to examine mucosal biopsies of IBS patients and compare them to their own fecal microbiota. Methods The diversity of the dominant microbiota in the fecal material of IBS patients was compared to a healthy control group. In addition, we compared the mucosal and fecal microbiota of IBS patients. Results Statistical analysis of the mean similarity data for these groups indicated a significant difference (P < 0.001) between IBS (n = 47) and healthy controls (n = 33) with significantly more variation in the gut microbiota of healthy volunteers than that of IBS patients. The average intra-individual similarity between the mucosa and luminal microbiota was 84%, which indicates that different communities were present at the two sites. This difference, however, is similar to that previously described between these two niches in control subjects. The average inter-individual similarity of the bacterial communities on the mucosa and in the lumen of IBS was not significantly different (P > 0.05). Conclusions IBS impacts equally on both bacterial communities in the IBS host and a significant difference in the gut microbiota exists between fecal samples from IBS patients and healthy controls. The reason for this difference is unclear and various possible explanations are available, but much more work is required to determine the underlying reason for this observation.
Probiotics are derived from traditional fermented foods, from beneficial commensals or from the environment. They act through diverse mechanisms affecting the composition or function of the commensal ...microbiota and by altering host epithelial and immunological responses. Certain probiotic interventions have shown promise in selected clinical conditions where aberrant microbiota have been reported, such as atopic dermatitis, necrotising enterocolitis, pouchitis and possibly irritable bowel syndrome. However, no studies have been conducted that can causally link clinical improvements to probiotic-induced microbiota changes. Whether a disease-prone microbiota pattern can be remodelled to a more robust, resilient and disease-free state by probiotic administration remains a key unanswered question. Progress in this area will be facilitated by: optimising strain, dose and product formulations, including protective commensal species; matching these formulations with selectively responsive subpopulations; and identifying ways to manipulate diet to modify bacterial profiles and metabolism.
As our knowledge of the various roles of the gut microbiota in the maintenance of homeostasis grows and as we learn how a disrupted microbiota may contribute to disease, therapeutic strategies that ...target our microbial fellow‐travellers become ever more attractive. Most appealing are those interventions that seek to modify or supplement our diet through the addition of nutraceuticals. We now know that our diet, whether in the short or long term, is a major modifier of microbiota composition and function. Of the various nutraceuticals, two categories, prebiotics and probiotics, have received the greatest attention in basic research and product development. While our understanding of the impacts of prebiotics and probiotics on the indigenous microbiota and host biology have been described in great detail in vitro and in animal models, the clinical literature leaves much to be desired. While many claims have been made, few are supported by high quality clinical trials.
Linked Articles
This article is part of a themed section on The Pharmacology of Nutraceuticals. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.6/issuetoc
PDF
