Faecal microbiota transplantation in 2013: developing human gut microbiota as a class of therapeutics

Progress in understanding of relationship between duodenal mucosal microecology and hepatitis B virus related acute-on-chronic liver failure

According to statistics, the rate of hepatitis B virus (HBV) infection is still high in China, and the mortality of acute-on-chronic liver failure (ACLF) is also high. In recent years, studies on the fecal flora of patients with HBV related ACLF have found that intestinal microecology affects the occurrence, development, and prognosis of HBV related ACLF. However, fecal flora cannot completely replace the whole intestinal microecology, and duodenal mucosal microecology may be a new research direction. This review discusses the influence of duodenal mucosal flora on the clinical outcome of HBV-ACLF with regard to mechanism, physiology, and anatomical characteristics.

Roles of α‑synuclein in gastrointestinal microbiome dysbiosis‑related Parkinson's disease progression (Review)

Parkinson's disease (PD) is the second most common neurodegenerative disease amongst the middle-aged and elderly populations. Several studies have confirmed that the microbiota-gut-brain axis (MGBA) serves a key role in the pathogenesis of PD. Changes to the gastrointestinal microbiome (GM) cause misfolding and abnormal aggregation of α-synuclein (α-syn) in the intestine. Abnormal α-syn is not eliminated via physiological mechanisms and is transported into the central nervous system (CNS) via the vagus nerve. The abnormal levels of α-syn aggregate in the substantia nigra pars compacta, not only leading to the formation of eosinophilic Lewis Bodies in the cytoplasm and mitochondrial dysfunction in dopaminergic (DA) neurons, but also leading to the stimulation of an inflammatory response in the microglia. These pathological changes result in an increase in oxidative stress (OS), which triggers nerve cell apoptosis, a characteristic of PD. This increase in OS further oxidizes and intensifies abnormal aggregation of α-syn, eventually forming a positive feedback loop. The present review discusses the abnormal accumulation of α-syn in the intestine caused by the GM changes and the increased levels of α-syn transport to the CNS via the MGBA, resulting in the loss of DA neurons and an increase in the inflammatory response of microglial cells in the brain of patients with PD. In addition, relevant clinical therapeutic strategies for improving the GM and reducing α-syn accumulation to relieve the symptoms and progression of PD are described.

Use of the microbiome in the management of children with type 2 diabetes mellitus

PURPOSE OF REVIEW

The purpose of this review is to present recent data that defines our current understanding of the role of the gut microbiome in the development of T2DM.

RECENT FINDINGS

Recent studies focus on the physiology and molecular pathways of the gut microbiome-host interaction. Short-chain fatty acids (SCFAs) derived from the fermentation of plant-based nonsoluble fiber bind to G-protein-coupled receptors (GPR) GPR 41 and GPR 43 to induce enteroendocrine molecules that control appetite, and to upregulate intestinal gluconeogenesis gene expression that controls glucose regulation. "Metabolic endotexemia" reflects a state of low-grade systemic inflammation that results from lipopolysaccharide (LPS) release from the gut into the systemic circulation in response to a high-fat diet. Inflammatory pathways induced by LPS, activation of toll-like receptor-4 (TLR-4), and other inflammatory signaling pathways are mediators of systemic inflammation, insulin resistance and type II diabetes mellitus.

SUMMARY

Recent scientific data support that derangements in the composition of the microbiota, termed "microbiome dysbiosis" is a factor in the development of "metabolic endotoxemia" and T2DM. Therapeutic options that target the gut microbiome in the treatment of T2DM are explored.

Ablation of gut microbiota alleviates obesity-induced hepatic steatosis and glucose intolerance by modulating bile acid metabolism in hamsters

Since metabolic process differs between humans and mice, studies were performed in hamsters, which are generally considered to be a more appropriate animal model for studies of obesity-related metabolic disorders. The modulation of gut microbiota, bile acids and the farnesoid X receptor (FXR) axis is correlated with obesity-induced insulin resistance and hepatic steatosis in mice. However, the interactions among the gut microbiota, bile acids and FXR in metabolic disorders remained largely unexplored in hamsters. In the current study, hamsters fed a 60% high-fat diet (HFD) were administered vehicle or an antibiotic cocktail by gavage twice a week for four weeks. Antibiotic treatment alleviated HFD-induced glucose intolerance, hepatic steatosis and inflammation accompanied with decreased hepatic lipogenesis and elevated thermogenesis in subcutaneous white adipose tissue (sWAT). In the livers of antibiotic-treated hamsters, cytochrome P450 family 7 subfamily B member 1 (CYP7B1) in the alternative bile acid synthesis pathway was upregulated, contributing to a more hydrophilic bile acid profile with increased tauro-β-muricholic acid (TβMCA). The intestinal FXR signaling was suppressed but remained unchanged in the liver. This study is of potential translational significance in determining the role of gut microbiota-mediated bile acid metabolism in modulating diet-induced glucose intolerance and hepatic steatosis in the hamster.

Maternal separation in rodents: a journey from gut to brain and nutritional perspectives

The developmental period constitutes a critical window of sensitivity to stress. Indeed, early-life adversity increases the risk to develop psychiatric diseases, but also gastrointestinal disorders such as the irritable bowel syndrome at adulthood. In the past decade, there has been huge interest in the gut-brain axis, especially as regards stress-related emotional behaviours. Animal models of early-life adversity, in particular, maternal separation (MS) in rodents, demonstrate lasting deleterious effects on both the gut and the brain. Here, we review the effects of MS on both systems with a focus on stress-related behaviours. In addition, we discuss more recent findings showing the impact of gut-directed interventions, including nutrition with pre- and probiotics, illustrating the role played by gut microbiota in mediating the long-term effects of MS. Overall, preclinical studies suggest that nutritional approaches with pro- and prebiotics may constitute safe and efficient strategies to attenuate the effects of early-life stress on the gut-brain axis. Further research is required to understand the complex mechanisms underlying gut-brain interaction dysfunctions after early-life stress as well as to determine the beneficial impact of gut-directed strategies in a context of early-life adversity in human subjects.

Functional Gut Microbiota Remodeling Contributes to the Caloric Restriction-Induced Metabolic Improvements

Caloric restriction (CR) stimulates development of functional beige fat and extends healthy lifespan. Here we show that compositional and functional changes in the gut microbiota contribute to a number of CR-induced metabolic improvements and promote fat browning. Mechanistically, these effects are linked to a lower expression of the key bacterial enzymes necessary for the lipid A biosynthesis, a critical lipopolysaccharide (LPS) building component. The decreased LPS dictates the tone of the innate immune response during CR, leading to increased eosinophil infiltration and anti-inflammatory macrophage polarization in fat of the CR animals. Genetic and pharmacological suppression of the LPS-TLR4 pathway or transplantation with Tlr4^-/- bone-marrow-derived hematopoietic cells increases beige fat development and ameliorates diet-induced fatty liver, while Tlr4^-/- or microbiota-depleted mice are resistant to further CR-stimulated metabolic alterations. These data reveal signals critical for our understanding of the microbiota-fat signaling axis during CR and provide potential new anti-obesity therapeutics.

Human Gut Microbiota: Toward an Ecology of Disease

Composed of trillions of individual microbes, the human gut microbiota has adapted to the uniquely diverse environments found in the human intestine. Quickly responding to the variances in the ingested food, the microbiota interacts with the host via reciprocal biochemical signaling to coordinate the exchange of nutrients and proper immune function. Host and microbiota function as a unit which guards its balance against invasion by potential pathogens and which undergoes natural selection. Disturbance of the microbiota composition, or dysbiosis, is often associated with human disease, indicating that, while there seems to be no unique optimal composition of the gut microbiota, a balanced community is crucial for human health. Emerging knowledge of the ecology of the microbiota-host synergy will have an impact on how we implement antibiotic treatment in therapeutics and prophylaxis and how we will consider alternative strategies of global remodeling of the microbiota such as fecal transplants. Here we examine the microbiota-human host relationship from the perspective of the microbial community dynamics.

Gut Microbiota Orchestrates Energy Homeostasis during Cold

Microbial functions in the host physiology are a result of the microbiota-host co-evolution. We show that cold exposure leads to marked shift of the microbiota composition, referred to as cold microbiota. Transplantation of the cold microbiota to germ-free mice is sufficient to increase insulin sensitivity of the host and enable tolerance to cold partly by promoting the white fat browning, leading to increased energy expenditure and fat loss. During prolonged cold, however, the body weight loss is attenuated, caused by adaptive mechanisms maximizing caloric uptake and increasing intestinal, villi, and microvilli lengths. This increased absorptive surface is transferable with the cold microbiota, leading to altered intestinal gene expression promoting tissue remodeling and suppression of apoptosis-the effect diminished by co-transplanting the most cold-downregulated strain Akkermansia muciniphila during the cold microbiota transfer. Our results demonstrate the microbiota as a key factor orchestrating the overall energy homeostasis during increased demand.

Fecal microbiota transplantation for Clostridium difficile infection: back to the future

INTRODUCTION

Clostridium difficile infection (CDI) is a leading cause of diarrhea in the industrialized world. The estimated costs of this infection are impressive: over 3.2 billion dollars annually in the US. The introduction of fecal microbiota transplantation (FMT) to clinical practice can be considered a Copernican Revolution. The rationale of this approach consists of correcting the imbalance of the organisms dwelling in the gut by reintroducing a normal flora.

AREAS COVERED

This review focuses on the indication for FMT in CDI; it examines in-depth the most relevant aspects of the techniques used, and the safety and efficacy of this new 'old' therapy.

EXPERT OPINION

Authoritative guidelines about the management of CDI strongly recommend FMT for multiple recurrent episodes of infection by C. difficile unresponsive to repeated antibiotic treatment. The cure rates are about 90%, with no serious adverse events having been reported. The main concerns are the long-term outcomes, lack of a standardized procedure for the delivery of donor material, and a cultural barrier to the transplantation of fecal microbiota. A promising solution to some of these problems could be the use of a more acceptable administration route of fecal material, namely, oral capsules.

Rural and urban microbiota: To be or not to be?

A multitude of metagenomic studies has brought to light an enormous richness of human gut microbiota compositions. In this space of possible configurations, clinical specialists are trying to mine the markers of healthy microbiota via case-control and longitudinal studies. We have discovered potentially beneficial communities while examining the microbial diversity in rural Russians in comparison with the urban dwellers. In this addendum, we further examine the data by elaborating on some of the less common types and suggesting the possible co-metabolism of their drivers. In the light of the first validated clinically effective bacterial transplantation, we discuss the concept of a reference healthy microbiota, outline the problems encountered on the way to its restoration in the developed world, and speculate if rural communities can serve as a source for its prototype.