The Gut Microbiota and Immune System Relationship in Human Graft-versus-Host Disease

Baseline gut microbiota profiles affect treatment response in patients with depression

The role of the gut microbiota in the pathophysiology of depression has been explored in numerous studies, which have confirmed that the baseline gut microbial profiles of patients with depression differ from those of healthy individuals. The gut microbiome affects metabolic activity in the immune and central nervous systems and regulates intestinal ecology through the neuroendocrine system. Additionally, baseline changes in the gut microbiota differed among patients with depression who demonstrated varying treatment response. Currently, probiotics are an emerging treatment for depression; however, the efficacy of modulating the gut microbiota in the treatment of depression remains uncertain. Additionally, the mechanisms by which changes in the gut microbiota affect treatment response in patients with depression remain unclear. In this review, we aimed to summarize the differences in the baseline gut microbiota between the remission and non-remission groups after antidepressant therapy. Additionally, we summarized the possible mechanisms that may contribute to antidepressant resistance through the effects of the gut microbiome on the immune and nervous systems, various enzymes, bioaccumulation, and blood-brain barrier, and provide a basis for treating depression by targeting the gut microbiota.

Organoids in gastrointestinal diseases: from bench to clinic

The etiology of gastrointestinal (GI) diseases is intricate and multifactorial, encompassing complex interactions between genetic predisposition and gut microbiota. The cell fate change, immune function regulation, and microenvironment composition in diseased tissues are governed by microorganisms and mutated genes either independently or through synergistic interactions. A comprehensive understanding of GI disease etiology is imperative for developing precise prevention and treatment strategies. However, the existing models used for studying the microenvironment in GI diseases-whether cancer cell lines or mouse models-exhibit significant limitations, which leads to the prosperity of organoids models. This review first describes the development history of organoids models, followed by a detailed demonstration of organoids application from bench to clinic. As for bench utilization, we present a layer-by-layer elucidation of organoid simulation on host-microbial interactions, as well as the application in molecular mechanism analysis. As for clinical adhibition, we provide a generalized interpretation of organoid application in GI disease simulation from inflammatory disorders to malignancy diseases, as well as in GI disease treatment including drug screening, immunotherapy, and microbial-targeting and screening treatment. This review draws a comprehensive and systematical depiction of organoids models, providing a novel insight into the utilization of organoids models from bench to clinic.

Microbiota and Gut-Liver Axis: An Unbreakable Bond?

The gut microbiota, amounting to approximately 100 trillion (1014) microbes represents a genetic repertoire that is bigger than the human genome itself. Evidence on bidirectional interplay between human and microbial genes is mounting. Microbiota probably play vital roles in diverse aspects of normal human metabolism, such as digestion, immune modulation, and gut endocrine function, as well as in the genesis and progression of many human diseases. Indeed, the gut microbiota has been most closely linked to various chronic ailments affecting the liver, although concrete scientific data are sparse. In this narrative review, we initially discuss the basic epidemiology of gut microbiota and the factors influencing their initial formation in the gut. Subsequently, we delve into the gut-liver axis and the evidence regarding the link between gut microbiota and the genesis or progression of various liver diseases. Finally, we summarise the recent research on plausible ways to modulate the gut microbiota to alter the natural history of liver disease.

Co-Supplementation of Baobab Fiber and Arabic Gum Synergistically Modulates the In Vitro Human Gut Microbiome Revealing Complementary and Promising Prebiotic Properties

Arabic gum, a high molecular weight heteropolysaccharide, is a promising prebiotic candidate as its fermentation occurs more distally in the colon, which is the region where most chronic colonic diseases originate. Baobab fiber could be complementary due to its relatively simple structure, facilitating breakdown in the proximal colon. Therefore, the current study aimed to gain insight into how the human gut microbiota was affected in response to long-term baobab fiber and Arabic gum supplementation when tested individually or as a combination of both, allowing the identification of potential complementary and/or synergetic effects. The validated Simulator of the Human Intestinal Microbial Ecosystem (SHIME®), an in vitro gut model simulating the entire human gastrointestinal tract, was used. The microbial metabolic activity was examined, and quantitative 16S-targeted Illumina sequencing was used to monitor the gut microbial composition. Moreover, the effect on the gut microbial metabolome was quantitatively analyzed. Repeated administration of baobab fiber, Arabic gum, and their combination had a significant effect on the metabolic activity, diversity index, and community composition of the microbiome present in the simulated proximal and distal colon with specific impacts on Bifidobacteriaceae and Faecalibacterium prausnitzii. Despite the lower dosage strategy (2.5 g/day), co-supplementation of both compounds resulted in some specific synergistic prebiotic effects, including a biological activity throughout the entire colon, SCFA synthesis including a synergy on propionate, specifically increasing abundance of Akkermansiaceae and Christensenellaceae in the distal colon region, and enhancing levels of spermidine and other metabolites of interest (such as serotonin and ProBetaine).

Enterococcus faecalis: implications for host health

The microbiota represents a crucial area of research in maintaining human health due to its potential for uncovering novel biomarkers, therapies, and molecular mechanisms relevant to population identification and experimental model characterization. Among these microorganisms, Enterococcus faecalis, a Gram-positive bacterium found in the gastrointestinal tract of humans and animals, holds particular significance. Strains of this bacterial species have sparked considerable debate in the literature due to their dual nature; they can either be utilized as probiotics in the food industry or demonstrate resistance to antibiotics, potentially leading to severe illness, disability, and death. Given the diverse characteristics of Enterococcus faecalis strains, this review aims to provide a comprehensive understanding of their impact on various systems within the host, including the immunological, cardiovascular, metabolic, and nervous systems. Furthermore, we summarize the bacterium-host interaction characteristics and molecular effects to highlight their targets, features, and overall impact on microbial communities and host health.

Impact of Transgenerational Nutrition on Nonalcoholic Fatty Liver Disease Development: Interplay between Gut Microbiota, Epigenetics and Immunity

Nonalcoholic fatty liver disease (NAFLD) has emerged as the most prevalent pediatric liver disorder, primarily attributed to dietary shifts in recent years. NAFLD is characterized by the accumulation of lipid species in hepatocytes, leading to liver inflammation that can progress to steatohepatitis, fibrosis, and cirrhosis. Risk factors contributing to NAFLD encompass genetic variations and metabolic disorders such as obesity, diabetes, and insulin resistance. Moreover, transgenerational influences, resulting in an imbalance of gut microbial composition, epigenetic modifications, and dysregulated hepatic immune responses in offspring, play a pivotal role in pediatric NAFLD development. Maternal nutrition shapes the profile of microbiota-derived metabolites in offspring, exerting significant influence on immune system regulation and the development of metabolic syndrome in offspring. In this review, we summarize recent evidence elucidating the intricate interplay between gut microbiota, epigenetics, and immunity in fetuses exposed to maternal nutrition, and its impact on the onset of NAFLD in offspring. Furthermore, potential therapeutic strategies targeting this network are also discussed.

The Role of Prebiotics in Modulating Gut Microbiota: Implications for Human Health

The human gut microbiota, an intricate ecosystem within the gastrointestinal tract, plays a pivotal role in health and disease. Prebiotics, non-digestible food ingredients that beneficially affect the host by selectively stimulating the growth and/or activity of beneficial microorganisms, have emerged as a key modulator of this complex microbial community. This review article explores the evolution of the prebiotic concept, delineates various types of prebiotics, including fructans, galactooligosaccharides, xylooligosaccharides, chitooligosaccharides, lactulose, resistant starch, and polyphenols, and elucidates their impact on the gut microbiota composition. We delve into the mechanisms through which prebiotics exert their effects, particularly focusing on producing short-chain fatty acids and modulating the gut microbiota towards a health-promoting composition. The implications of prebiotics on human health are extensively reviewed, focusing on conditions such as obesity, inflammatory bowel disease, immune function, and mental health. The review further discusses the emerging concept of synbiotics-combinations of prebiotics and probiotics that synergistically enhance gut health-and highlights the market potential of prebiotics in response to a growing demand for functional foods. By consolidating current knowledge and identifying areas for future research, this review aims to enhance understanding of prebiotics' role in health and disease, underscoring their importance in maintaining a healthy gut microbiome and overall well-being.

A guide to germ-free and gnotobiotic mouse technology to study health and disease

The intestinal microbiota has major influence on human physiology and modulates health and disease. Complex host-microbe interactions regulate various homeostatic processes, including metabolism and immune function, while disturbances in microbiota composition (dysbiosis) are associated with a plethora of human diseases and are believed to modulate disease initiation, progression and therapy response. The vast complexity of the human microbiota and its metabolic output represents a great challenge in unraveling the molecular basis of host-microbe interactions in specific physiological contexts. To increase our understanding of these interactions, functional microbiota research using animal models in a reductionistic setting are essential. In the dynamic landscape of gut microbiota research, the use of germ-free and gnotobiotic mouse technology, in which causal disease-driving mechanisms can be dissected, represents a pivotal investigative tool for functional microbiota research in health and disease, in which causal disease-driving mechanisms can be dissected. A better understanding of the health-modulating functions of the microbiota opens perspectives for improved therapies in many diseases. In this review, we discuss practical considerations for the design and execution of germ-free and gnotobiotic experiments, including considerations around germ-free rederivation and housing conditions, route and timing of microbial administration, and dosing protocols. This comprehensive overview aims to provide researchers with valuable insights for improved experimental design in the field of functional microbiota research.

Veillonella faecalis sp. nov., a propionic acid-producing bacterium isolated from the faeces of an infant

A strictly anaerobic, Gram-stain-negative, catalase-negative, cocci-shaped, and propionate-producing bacterial strain, named Ds1651T was isolated from the fecal sample collected from a South Korean infant. Through a comparison of 16S rRNA gene sequences, it was revealed that Ds1651T had the highest phylogenetic affinity with Veillonella nakazawae KCTC 25297 T (99.86%), followed by Veillonella infantium KCTC 25370 T (99.80%), and Veillonella dispar KCTC 25309 T (99.73%) in the family Veillonellaceae. Average nucleotide identity values between Ds1651T and three reference species were 95.48% for Veillonella nakazawae KCTC 25297 T, 94.46% for Veillonella infantium KCTC 25370 T, and 92.81% for Veillonella dispar KCTC 25309 T. The G + C content of Ds1651T was 38.58 mol%. Major fermentation end-products were acetic and propionic acids in Trypticase peptone glucose yeast extract broth with 1% (v/v) sodium lactate. The predominant cellular fatty acids that account for more than 10% were summed in Feature 8 (C17:1 ω8c and/or C17:2) and C13:0. Based on the findings from phylogenetic, genomic, phenotypic, and chemotaxonomic studies, we propose that the type strain Ds1651T (= KCTC 25477 T = GDMCC 1.3707 T) represents a novel bacterial species within the genus Veillonella, with the proposed name Veillonella faecalis sp. nov.

Role of the Gut Microbiome and Bacterial Amyloids in the Development of Synucleinopathies

Less than ten years ago, evidence began to accumulate about association between the changes in the composition of gut microbiota and development of human synucleinopathies, in particular sporadic form of Parkinson's disease. We collected data from more than one hundred and thirty experimental studies that reported similar results and summarized the frequencies of detection of different groups of bacteria in these studies. It is important to note that it is extremely rare that a unidirectional change in the population of one or another group of microorganisms (only an elevation or only a reduction) was detected in the patients with Parkinson's disease. However, we were able to identify several groups of bacteria that were overrepresented in the patients with Parkinson's disease in the analyzed studies. There are various hypotheses about the molecular mechanisms that explain such relationships. Usually, α-synuclein aggregation is associated with the development of inflammatory processes that occur in response to the changes in the microbiome. However, experimental evidence is accumulating on the influence of bacterial proteins, including amyloids (curli), as well as various metabolites, on the α-synuclein aggregation. In the review, we provided up-to-date information about such examples.

Role of gut microbiota in cardiovascular diseases - a comprehensive review

The connection between cardiovascular illnesses and the gut microbiota has drawn more and more attention in recent years. According to research, there are intricate relationships between dietary elements, gut bacteria, and their metabolites that affect cardiovascular health. In this study, the role of gut microbiota in cardiovascular disorders is examined, with an emphasis on the cardiac consequences brought on by changes in gut microbiota. This essay discusses the gut-heart axis in depth and in detail. It talks about clinical research looking at how soy consumption, probiotic supplements, and dietary changes affected gut microbiota and cardiovascular risk variables. Our goal is to clarify the possible pathways that connect gut microbiota to cardiovascular health and the implications for upcoming treatment approaches. The authors examine the composition, roles, and effects of the gut microbiota on cardiovascular health, including their contributions to hypertension, atherosclerosis, lipid metabolism, and heart failure. Endotoxemia, inflammation, immunological dysfunction, and host lipid metabolism are some of the potential processes investigated for how the gut microbiota affects cardiac outcomes. The research emphasizes the need for larger interventional studies and personalized medicine strategies to completely understand the complexity of the gut-heart axis and its implications for the management of cardiovascular disease. The development of novel treatment strategies and cutting-edge diagnostic technologies in cardiovascular medicine may be facilitated by a better understanding of this axis.

In vitro study of potential prebiotic properties of monovarietal extra virgin olive oils

Olive oil, essential ingredient of the Mediterranean diet, is attracting a growing interest due to increasing evidence on its beneficial effects on human health. This study investigated whether extra virgin olive oil (EVOO) possess prebiotic properties. Twenty different monovarietal EVOO samples from 5 Marche region cultivars (Italy) were studied. The prebiotic activity of EVOOs was assessed monitoring the selective stimulation of gut bacterial species and the short chain fatty acids (SCFAs) production, using an in vitro fermentation system. All EVOOs selectively stimulated Lactobacillus spp., with a stronger activity than that observed in the inulin fermentation (positive control). Also, the bifidobacteria population increased; this bifidogenic stimulation was of EVOOs from Raggia cultivar. SCFAs appeared significantly higher after 24 h in all EVOO fermentations than in the control. Acetic and propionic acids production was particularly stimulated. Overall, most of the investigated EVOOs had a potential prebiotic activity, similar or stronger than inulin.

The Role of the Gut Microbiome in Hematological Cancers

Humans are in a complex symbiotic relationship with a wide range of microbial organisms, including bacteria, viruses, and fungi. The evolution and composition of the human microbiome can be an indicator of how it may affect human health and susceptibility to diseases. Microbiome alteration, termed as dysbiosis, has been linked to the pathogenesis and progression of hematological cancers. A variety of mechanisms, including epithelial barrier disruption, local chronic inflammation response trigger, antigen dis-sequestration, and molecular mimicry, have been proposed to be associated with gut microbiota. Dysbiosis may be induced or worsened by cancer therapies (such as chemotherapy and/or hematopoietic stem cell transplantation) or infection. The use of antibiotics during treatment may also promote dysbiosis, with possible long-term consequences. The aim of this review is to provide a succinct summary of the current knowledge describing the role of the microbiome in hematological cancers, as well as its influence on their therapies. Modulation of the gut microbiome, involving modifying the composition of the beneficial microorganisms in the management and treatment of hematological cancers is also discussed. Additionally discussed are the latest developments in modeling approaches and tools used for computational analyses, interpretation and better understanding of the gut microbiome data.

Unveiling the Connection between Microbiota and Depressive Disorder through Machine Learning

In the last few years, investigation of the gut-brain axis and the connection between the gut microbiota and the human nervous system and mental health has become one of the most popular topics. Correlations between the taxonomic and functional changes in gut microbiota and major depressive disorder have been shown in several studies. Machine learning provides a promising approach to analyze large-scale metagenomic data and identify biomarkers associated with depression. In this work, machine learning algorithms, such as random forest, elastic net, and You Only Look Once (YOLO), were utilized to detect significant features in microbiome samples and classify individuals based on their disorder status. The analysis was conducted on metagenomic data obtained during the study of gut microbiota of healthy people and patients with major depressive disorder. The YOLO method showed the greatest effectiveness in the analysis of the metagenomic samples and confirmed the experimental results on the critical importance of a reduction in the amount of Faecalibacterium prausnitzii for the manifestation of depression. These findings could contribute to a better understanding of the role of the gut microbiota in major depressive disorder and potentially lead the way for novel diagnostic and therapeutic strategies.

Managing the Skin Microbiome as a New Bacteriotherapy for Inflammatory Atopic Dermatitis

The microbiome, comprising various bacteria, assumes a significant role in the immune system's maturation and maintaining bodily homeostasis. Alterations in the microbial composition can contribute to the initiation and progression of inflammation. Recent studies reveal that changes in microbial composition and function, known as dysbiosis in the skin and gut, have been associated with altered immunological responses and skin barrier disruption. These changes are implicated in the development of several skin diseases, such as atopic dermatitis (AD). This review examines research demonstrating the potential of microbiome repair as a therapeutic approach to reduce the effect of inflammatory processes in the skin during atopic dermatitis. This way, corticosteroids in atopic dermatitis therapy can be reduced or even replaced with treatments focusing on controlling the skin microbiome. This study used scientific literature from recognized platforms, including PubMed, Scopus, Google Scholar, and ScienceDirect, covering publications from 2013 to 2023. The primary aim of this study was to assess the efficacy of skin microbiome management in treating atopic dermatitis. This study concludes that physicians must comprehensively understand the microbiome's involvement in atopic dermatitis, including its pathophysiological implications and its relevance to therapeutic interventions.

Gut Microbiota and Its Role in Anti-aging Phenomenon: Evidence-Based Review

The gut microbiota widely varies from individual to individual, but the variation shows stability over a period of time. The presence of abundant bacterial taxa is a common structure that determines the microbiota of human being. The presence of this microbiota greatly varies from geographic location, sex, food habits and age. Microbiota existing within the gut plays a significant role in nutrient absorption, development of immunity, curing of diseases and various developmental phases. With change in age, chronology diversification and variation of gut microbiota are observed within human being. But it has been observed that with the enhancement of age the richness of the microbial diversity has shown a sharp decline. The enhancement of age also results in the drift of the characteristic of the microbes associated with the microbiota from commensals to pathogenic. Various studies have shown that age associated gut-dysbiosis may result in decrease in tlongevity along with unhealthy aging. The host signalling pathways regulate the presence of the gut microbiota and their longevity. The presence of various nutrients regulates the presence of various microbial species. Innate immunity can be triggered due to the mechanism of gut dysbiosis resulting in the development of various age-related pathological syndromes and early aging. The gut microbiota possesses the ability to communicate with the host system with the help of various types of biomolecules, epigenetic mechanisms and various types of signalling-independent pathways. Drift in this mechanism of communication may affect the life span along with the health of the host. Thus, this review would focus on the use of gut-microbiota in anti-aging and healthy conditions of the host system.

Traditional Chinese medicine for the treatment of Alzheimer's disease: A focus on the microbiota-gut-brain axis

Alzheimer's disease (AD), the most frequent cause of dementia, is a neurodegenerative disorder characterised by a progressive decline in cognitive function that is associated with the formation of amyloid beta plaques and neurofibrillary tangles. Gut microbiota comprises of a complex community of microorganisms residing in the gastrointestinal ecosystem. These microorganisms can participate in gut-brain axis activities, thereby affecting cognitive function and associated behaviours. Increasing evidence has indicated that gut dysbiosis can jeopardise host immune responses and promote inflammation, which may be an initiating factor for the onset and evolution of AD. Traditional Chinese medicine (TCM) is a promising resource which encompasses immense chemical diversity and multiple-target characteristics for the treatment of AD. Many TCMs regulate the gut microbiota during treatment of diseases, indicating that gut microbiota may be an important target for TCM efficacy. In this review, we summarised the role of the microbiota-gut-brain axis in the development of AD and the effects of TCM in treating AD by regulating the gut microbiota. We anticipate that this review will provide novel perspectives and strategies for future AD research and treatments.

Scientific Evidence for the Beneficial Effects of Dietary Blueberries on Gut Health: A Systematic Review

Emerging evidence indicates the association between an unhealthy gut and chronic diseases. A healthy gut comprises an intact gut epithelium and balanced gut microbes. Diet is one of the critical factors that modulate gut health by positively or negatively affecting the intestinal barrier and gut microbes. Blueberries are an excellent source of health-promoting bioactive components, and this systematic review is conducted to evaluate the effect of dietary blueberries on gut health. A literature search is conducted on PubMed/MEDLINE, Scopus, Web of Science, and Embase databases to review relevant studies published between 2011 and 2022 according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The Systematic Review Center for Laboratory Animal Experimentation Risk of Bias (SYRCLE-RoB) tool is used for methodological quality assessments. Sixteen studies included from four countries are reviewed and the results are synthesized narratively. This data analysis indicates that blueberry supplementation improves gut health by improving intestinal morphology, reducing gut permeability, suppressing oxidative stress, ameliorating gut inflammation, and modulating the composition and function of gut microbes. However, there are significant knowledge gaps in this field. These findings indicate that further studies are needed to establish the beneficial effects of blueberries on gut health.

Gut Microbiota Composition and Cardiovascular Disease: A Potential New Therapeutic Target?

A great deal of evidence has revealed an important link between gut microbiota and the heart. In particular, the gut microbiota plays a key role in the onset of cardiovascular (CV) disease, including heart failure (HF). In HF, splanchnic hypoperfusion causes intestinal ischemia resulting in the translocation of bacteria and their metabolites into the blood circulation. Among these metabolites, the most important is Trimethylamine N-Oxide (TMAO), which is responsible, through various mechanisms, for pathological processes in different organs and tissues. In this review, we summarise the complex interaction between gut microbiota and CV disease, particularly with respect to HF, and the possible strategies for influencing its composition and function. Finally, we highlight the potential role of TMAO as a novel prognostic marker and a new therapeutic target for HF.

Diets, Gut Microbiota and Metabolites

The gut microbiota refers to the gross collection of microorganisms, estimated trillions of them, which reside within the gut and play crucial roles in the absorption and digestion of dietary nutrients. In the past decades, the new generation 'omics' (metagenomics, transcriptomics, proteomics, and metabolomics) technologies made it possible to precisely identify microbiota and metabolites and describe their variability between individuals, populations and even different time points within the same subjects. With massive efforts made, it is now generally accepted that the gut microbiota is a dynamically changing population, whose composition is influenced by the hosts' health conditions and lifestyles. Diet is one of the major contributors to shaping the gut microbiota. The components in the diets vary in different countries, religions, and populations. Some special diets have been adopted by people for hundreds of years aiming for better health, while the underlying mechanisms remain largely unknown. Recent studies based on volunteers or diet-treated animals demonstrated that diets can greatly and rapidly change the gut microbiota. The unique pattern of the nutrients from the diets and their metabolites produced by the gut microbiota has been linked with the occurrence of diseases, including obesity, diabetes, nonalcoholic fatty liver disease, cardiovascular disease, neural diseases, and more. This review will summarize the recent progress and current understanding of the effects of different dietary patterns on the composition of gut microbiota, bacterial metabolites, and their effects on the host's metabolism.

Intestinal dysbiosis and probiotic use: its place in hepatic encephalopathy in cirrhosis

The gut microbiota, which plays an important role in health and disease processes, is affected by many disease processes, such as cirrhosis, and dysbiosis can lead to the development of numerous liver diseases, including complications of cirrhosis. In this disease group, the intestinal microbiota shifts towards dysbiosis for reasons such as endotoxemia, increased intestinal permeability, and decreased bile acid production. Although weak absorbable antibiotics and lactulose are among the treatment strategies in cirrhosis and its most common complication, hepatic encephalopathy (HE), this may not be the most appropriate treatment option for all patients, in view of its side-effects and high costs. Accordingly, it seems possible that probiotics could be used as an alternative treatment. The use of probiotics in these patient groups has a direct effect on the gut microbiota. Probiotics can also provide treatment with multiple effects through various mechanisms, such as lowering serum ammonia levels, reducing oxidative stress and reducing the intake of other toxins. This review was written to explain the intestinal dysbiosis associated with HE in cirrhotic patients, and the role of probiotics in treatment.

Celiac Disease and Neurological Manifestations: From Gluten to Neuroinflammation

Celiac disease (CD) is a complex multi-organ disease with a high prevalence of extra-intestinal involvement, including neurological and psychiatric manifestations, such as cerebellar ataxia, peripheral neuropathy, epilepsy, headache, cognitive impairment, and depression. However, the mechanisms behind the neurological involvement in CD remain controversial. Recent evidence shows these can be related to gluten-mediated pathogenesis, including antibody cross-reaction, deposition of immune-complex, direct neurotoxicity, and in severe cases, vitamins or nutrients deficiency. Here, we have summarized new evidence related to gut microbiota and the so-called "gut-liver-brain axis" involved in CD-related neurological manifestations. Additionally, there has yet to be an agreement on whether serological or neurophysiological findings can effectively early diagnose and properly monitor CD-associated neurological involvement; notably, most of them can revert to normal with a rigorous gluten-free diet. Moving from a molecular level to a symptom-based approach, clinical, serological, and neurophysiology data might help to disentangle the many-faceted interactions between the gut and brain in CD. Eventually, the identification of multimodal biomarkers might help diagnose, monitor, and improve the quality of life of patients with "neuroCD".

Celiac Disease and Possible Dietary Interventions: From Enzymes and Probiotics to Postbiotics and Viruses

Celiac Disease (CeD) is a chronic small intestinal immune-mediated enteropathy caused by the ingestion of dietary gluten proteins in genetically susceptible individuals. CeD is one of the most common autoimmune diseases, affecting around 1.4% of the population globally. To date, the only acceptable treatment for CeD is strict, lifelong adherence to a gluten-free diet (GFD). However, in some cases, GFD does not alter gluten-induced symptoms. In addition, strict adherence to a GFD reduces patients’ quality of life and is often a socio-economic burden. This narrative review offers an interdisciplinary overview of CeD pathomechanism and the limitations of GFD, focusing on current research on possible dietary interventions. It concentrates on the recent research on the degradation of gluten through enzymes, the modulation of the microbiome, and the different types of “biotics” strategies, from probiotics to the less explored “viromebiotics” as possible beneficial complementary interventions for CeD management. The final aim is to set the context for future research that may consider the role of gluten proteins and the microbiome in nutritional and non-pharmacological interventions for CeD beyond the sole use of the GFD.

Celiac Disease and Possible Dietary Interventions: From Enzymes and Probiotics to Postbiotics and Viruses

Celiac Disease (CeD) is a chronic small intestinal immune-mediated enteropathy caused by the ingestion of dietary gluten proteins in genetically susceptible individuals. CeD is one of the most common autoimmune diseases, affecting around 1.4% of the population globally. To date, the only acceptable treatment for CeD is strict, lifelong adherence to a gluten-free diet (GFD). However, in some cases, GFD does not alter gluten-induced symptoms. In addition, strict adherence to a GFD reduces patients' quality of life and is often a socio-economic burden. This narrative review offers an interdisciplinary overview of CeD pathomechanism and the limitations of GFD, focusing on current research on possible dietary interventions. It concentrates on the recent research on the degradation of gluten through enzymes, the modulation of the microbiome, and the different types of "biotics" strategies, from probiotics to the less explored "viromebiotics" as possible beneficial complementary interventions for CeD management. The final aim is to set the context for future research that may consider the role of gluten proteins and the microbiome in nutritional and non-pharmacological interventions for CeD beyond the sole use of the GFD.

The gut microbiome as possible mediator of the beneficial effects of very low calorie ketogenic diet on type 2 diabetes and obesity: a narrative review

Several studies have shown a strong correlation between the different types of diets and gut microbiota composition on glycemia and weight loss. In this direction, low-carbohydrate and ketogenic diets have gained popularity, despite studies published so far leading to controversial results on subjects with diabetes. In this narrative review, firstly, we aimed to analyze the role of very-low-calorie ketogenic diets (VLCKDs) in type 2 diabetes (T2DM) and obesity management. Secondly, in this context, we focused attention on gut microbiota as a function of VLCKD, particularly in T2DM and obesity treatment. Finally, we reported all this evidence to underline the importance of gut microbiota to exalt new nutritional strategies for "tailor-made" management, treatment, and rehabilitation in subjects with T2DM and obesity, even with diabetic complications. In conclusion, this narrative review outlined the beneficial impact of VLCKD on gut microbiota even in subjects with T2DM and obesity, and, despite inner VLCKD short-duration feature allowing no sound-enough provisions for long-term outcomes, witnessed in favor of the short-term safety of VLCKD in those patients.Level of evidence Level V: Opinions of authorities, based on descriptive studies, narrative reviews, clinical experience, or reports of expert committees.

Inborn errors of immunity and related microbiome

Inborn errors of immunity (IEI) are characterized by diverse clinical manifestations that are dominated by atypical, recurrent, chronic, or severe infectious or non-infectious features, including autoimmunity, lymphoproliferative disease, granulomas, and/or malignancy, which contribute substantially to morbidity and mortality. Some data suggest a correlation between clinical manifestations of IEI and altered gut microbiota. Many IEI display microbial dysbiosis resulting from the proliferation of pro-inflammatory bacteria or a decrease in anti-inflammatory bacteria with variations in the composition and function of numerous microbiota. Dysbiosis is considered more established, mainly within common variable immunodeficiency, selective immunoglobulin A deficiency, severe combined immunodeficiency diseases, Wiskott–Aldrich syndrome, Hyper-IgE syndrome, autoimmune polyendocrinopathy–candidiasis–ectodermal-dystrophy (APECED), immune dysregulation, polyendocrinopathy, enteropathy X-linked (IPEX) syndrome, IL-10 receptor deficiency, chronic granulomatous disease, and Kostmann disease. For certain IEIs, the specific predominance of gastrointestinal, respiratory, and cutaneous involvement, which is frequently associated with dysbiosis, justifies the interest for microbiome identification. With the better understanding of the relationship between gut microbiota, host immunity, and infectious diseases, the integration of microbiota modulation as a therapeutic approach or a preventive measure of infection becomes increasingly relevant. Thus, a promising strategy is to develop optimized prebiotics, probiotics, postbiotics, and fecal microbial transplantation to rebalance the intestinal microbiota and thereby attenuate the disease activity of many IEIs.

Intriguing role of Gut-Brain Axis on cognition with emphasis on interaction with Papez circuit

The gut microbiome is a complicated ecosystem of around a hundred billion symbiotic bacteria cells. Bidirectional communication between the gut and the brain is facilitated by the immune system, the enteric nervous system, the vagus nerve, and microbial compounds such as tryptophan metabolites and short-chain fatty acids (SCFAs). The current study emphasises the relationship of the gut-brain axis with cognitive performance and elucidates the underlying biological components, with a focus on neurotransmitters such as serotonin, indole derivatives, and catecholamine. These biological components play important roles in both the digestive and brain systems. Recent research has linked the gut microbiome to a variety of cognitive disorders, including Alzheimer's (AD). The review describes the intriguing role of the gut-brain axis in recognition memory depending on local network connections within the hippocampal as well as other additional hippocampal portions of the Papez circuit. The available data from various research papers show how the gut microbiota might alter brain function and hence psychotic and cognitive illnesses. The role of supplementary probiotics is emphasized for the reduction of brain-related dysfunction as a viable strategy in handling cognitive disorders. Further, the study elucidates the mode of action of probiotics with reported adverse effects.

Microbiota in health and diseases

The role of microbiota in health and diseases is being highlighted by numerous studies since its discovery. Depending on the localized regions, microbiota can be classified into gut, oral, respiratory, and skin microbiota. The microbial communities are in symbiosis with the host, contributing to homeostasis and regulating immune function. However, microbiota dysbiosis can lead to dysregulation of bodily functions and diseases including cardiovascular diseases (CVDs), cancers, respiratory diseases, etc. In this review, we discuss the current knowledge of how microbiota links to host health or pathogenesis. We first summarize the research of microbiota in healthy conditions, including the gut-brain axis, colonization resistance and immune modulation. Then, we highlight the pathogenesis of microbiota dysbiosis in disease development and progression, primarily associated with dysregulation of community composition, modulation of host immune response, and induction of chronic inflammation. Finally, we introduce the clinical approaches that utilize microbiota for disease treatment, such as microbiota modulation and fecal microbial transplantation.

Moxibustion may delay the aging process of Wistar rats by regulating intestinal microbiota

As one of the important treatments of health care and anti-aging in traditional Chinese medicine (TCM), moxibustion has been proved to have the effects of scavenging free radicals, anti-oxidation, reducing inflammatory reaction, regulating immunity and so on. Recent studies have shown that intestinal microbiota affect the process of aging. The relationship between aging, moxibustion and intestinal microbiota is still unclear. In this study, we explored the effects of moxibustion at Guanyuan (RN4) acupoint on intestinal microbiota, short-chain fatty acids and immunological characteristics of young and elder female Wistar rats to explore the relationship between aging, moxibustion and intestinal microbiota. Six 12-week-old female Wistar rats were young group (Y), and twelve 36-week-old female Wistar rats were randomly divided into elder group (C) and moxibustion group (M). The rats in M group were received mild moxibustion at Guanyuan (RN4) acupoint, 20 min/d for 40 days. The rats in Y group and C group were not given any therapeutic intervention. The results showed that moxibustion increased the abundance of intestinal probiotics (mainly Lactobacillus) and the level of short chain fatty acids, the microcirculation blood flow around Guanyuan (RN4) acupoint was also significantly improved in elder rats. In addition, the expression of MyD88, MAPK, TRAF6, NF-κB in intestinal tissue was down-regulated, and the levels of inflammatory cytokines in intestinal were decreased.

Why Are Bifidobacteria Important for Infants?

The presence of Bifidobacterium species in the maternal vaginal and fecal microbiota is arguably an evolutionary trait that allows these organisms to be primary colonizers of the newborn intestinal tract. Their ability to utilize human milk oligosaccharides fosters their establishment as core health-promoting organisms throughout life. A reduction in their abundance in infants has been shown to increase the prevalence of obesity, diabetes, metabolic disorder, and all-cause mortality later in life. Probiotic strains have been developed as supplements for premature babies and to counter some of these ailments as well as to confer a range of health benefits. The ability to modulate the immune response and produce short-chain fatty acids, particularly acetate and butyrate, that strengthen the gut barrier and regulate the gut microbiome, makes Bifidobacterium a core component of a healthy infant through adulthood.

Gut microorganisms and neurological disease perspectives

The gastrointestinal tract of every healthy human consists of a unique set of gut microbiota that collectively harbors a diverse and complex community of over 100 trillion microorganisms, including bacteria, viruses, archaea, protozoa and fungi. Gut microbes have a symbiotic relationship with our body. The composition of the microbiota is shaped early in life by gut maturation, which is influenced by several factors. Intestinal bacteria are crucial in maintaining immune and metabolic homeostasis and protecting against pathogens. Dysbiosis of gut microbiota is associated not only with intestinal disorders but also with extraintestinal diseases such as metabolic and neurological disorders. In this review, the authors examine different studies that have revealed the possible hypotheses and links in the development of neurological disorders associated with the gut microbiome.

Microbiota, Bacterial Carbonic Anhydrases, and Modulators of Their Activity: Links to Human Diseases?

The involvement of the human microbiome is crucial for different host functions such as protection, metabolism, reproduction, and especially immunity. However, both endogenous and exogenous factors can affect the balance of the microbiota, creating a state of dysbiosis, which can start various gastrointestinal or systemic diseases. The challenge of future medicine is to remodel the intestinal microbiota to bring it back to healthy equilibrium (eubiosis) and, thus, counteract its negative role in the diseases' onset. The shaping of the microbiota is currently practiced in different ways ranging from diet (or use of prebiotics, probiotics, and synbiotics) to phage therapy and antibiotics, including microbiota fecal transplantation. Furthermore, because microbiota modulation is a capillary process, and because many microbiota bacteria (both beneficial and pathogenic) have carbonic anhydrases (specifically the four classes α, β, γ, and ι), we believe that the use of CA inhibitors and activators can open up new therapeutic strategies for many diseases associated with microbial dysbiosis, such as the various gastrointestinal disorders and the same colorectal cancer.

Meibomian Gland Dysfunction in Ocular Graft vs. Host Disease: A Need for Pre-Clinical Models and Deeper Insights

Despite decades of experience with hematopoietic stem cell transplantation, we are still faced with the delicate equipoise of achieving stable ocular health post-transplantation. This is because ocular graft-versus-host disease (oGvHD) following hematopoietic stem cell transplantation frequently occurs (≥50%) among transplant patients. To date, our understanding of the pathophysiology of oGvHD especially the involvement of the meibomian gland is still limited as a result of a lack of suitable preclinical models among other. Herein, the current state of the etiology and, pathophysiology of oGvHD based on existing pre-clinical models are reviewed. The need for additional pre-clinical models and knowledge about the involvement of the meibomian glands in oGvHD are emphasized.

New Avenues for Parkinson's Disease Therapeutics: Disease-Modifying Strategies Based on the Gut Microbiota

Parkinson's disease (PD) is a multifactorial neurodegenerative disorder that currently affects 1% of the population over the age of 60 years, and for which no disease-modifying treatments exist. Neurodegeneration and neuropathology in different brain areas are manifested as both motor and non-motor symptoms in patients. Recent interest in the gut-brain axis has led to increasing research into the gut microbiota changes in PD patients and their impact on disease pathophysiology. As evidence is piling up on the effects of gut microbiota in disease development and progression, another front of action has opened up in relation to the potential usage of microbiota-based therapeutic strategies in treating gastrointestinal alterations and possibly also motor symptoms in PD. This review provides status on the different strategies that are in the front line (i.e., antibiotics; probiotics; prebiotics; synbiotics; dietary interventions; fecal microbiota transplantation, live biotherapeutic products), and discusses the opportunities and challenges the field of microbiome research in PD is facing.

Gut Microbiota Influence in Hematological Malignancies: From Genesis to Cure

Hematological malignancies, including multiple myeloma, lymphoma, and leukemia, are a heterogeneous group of neoplasms that affect the blood, bone marrow, and lymph nodes. They originate from uncontrolled growth of hematopoietic and lymphoid cells from different stages in their maturation/differentiation and account for 6.5% of all cancers around the world. During the last decade, it has been proven that the gut microbiota, more specifically the gastrointestinal commensal bacteria, is implicated in the genesis and progression of many diseases. The immune-modulating effects of the human microbiota extend well beyond the gut, mostly through the small molecules they produce. This review aims to summarize the current knowledge of the role of the microbiota in modulating the immune system, its role in hematological malignancies, and its influence on different therapies for these diseases, including autologous and allogeneic stem cell transplantation, chemotherapy, and chimeric antigen receptor T cells.

Exploring the diversity of mechanosensitive channels in bacterial genomes

Mechanosensitive ion channels are responsible for touch sensation and proprioception in higher level organisms such as humans and recovery after osmotic stress in bacteria. Bacterial mechanosensitive channels are homologous to either the mechanosensitive channel of large conductance (MscL) or the mechanosensitive channel of small conductance (MscS). In the E. coli genome there are seven unique mechanosensitive channels, a single MscL homologue, and six MscS homologues. The six MscS homologues are members of the diverse MscS superfamily of ion channels, and these channels show variation on both the N and C termini when compared to E. coli MscS. In bacterial strains with phenotypic analysis of the endogenous mechanosensors, the quantity of MscS superfamily members in the genome range from 2 to 6 and all of the strains contain a copy of MscL. Here, we show an in-depth analysis of over 150 diverse bacterial genomes, encompassing nine phyla, to determine the number of genomes that contain an MscL homologue and the average number of MscS superfamily members per genome. We determined that the average genome contains 4 ± 3 MscS homologues and 67% of bacterial genomes encode for a MscL homologue.

Tyrosine supplement ameliorates murine aGVHD by modulation of gut microbiome and metabolome

BACKGROUND

Microbial communities and their metabolic components in the gut are of vital importance for immune homeostasis and have an influence on the susceptibility of the host to a number of immune-mediated diseases like acute graft-versus-host disease (aGVHD) after allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, little is known about the functional connections between microbiome and metabolome in aGVHD due to the complexity of the gastrointestinal environment.

METHOD

Initially, gut microbiota and fecal metabolic phenotype in aGVHD murine models were unleashed by performing 16S ribosomal DNA gene sequencing and ultra-high-performance liquid chromatography-mass spectrometry (UHPLC-MS)-based metabolomics.

FINDINGS

The group with aGVHD experienced a significant drop in Lachnospiraceae_unclassified but an increase in the relative abundance of Clostridium XI, Clostridium XIVa and Enterococcus. Meanwhile, a lower content of tyrosine was observed in the gut of aGVHD mice. The correlation analysis revealed that tyrosine-related metabolites were inversely correlated with Clostridium XIVa, besides, Blautia and Enterococcus also displayed the negative tendency in aGVHD condition. Apart from exploring the importance and function of tyrosine, different tyrosine diets were offered to mice during transplantation. Additional tyrosine supplements can improve overall survival, ameliorate symptoms at the early stage of aGVHD and change the structure and composition of gut microbiota and fecal metabolic phenotype. In addition, aGVHD mice deprived from tyrosine displayed worse manifestations than the vehicle diet group.

INTERPRETATION

The results demonstrated the roles and mechanisms of gut microbiota, indispensable metabolites and tyrosine in the progression of aGVHD, which can be an underlying biomarker for aGVHD diagnosis and treatment.

FUNDING

This research was funded by the International Cooperation and Exchange Program (81520108002), the National Key R&D Program of China, Stem Cell and Translation Research (2018YFA0109300), National Natural Science Foundation of China (81670169, 81670148, 81870080 and 91949115) and Natural Science Foundation of Zhejiang Province (LQ19H080006).

Molecular link between dietary fibre, gut microbiota and health

Natural polysaccharides cellulose, hemicelluloses, inulin etc., galactooligosaccharides (GOS), and fructooligosaccharides (FOS) play a significant role in the improvement of gut microbiota balance and human health. These polysaccharides prevent pathogen adhesion that stimulates the immune system and gut barrier function by servicing as fermentable substrates for the gut microbiota. The gut microbiota plays a key role in the fermentation of non-digestible carbohydrates (NDCs) fibres. Moreover, the gut microbiota is responsible for the production of short-chain fatty acids (SCFAs) like acetate, propionate and butyrate. Acetate is the most abundant and it is used by many gut commensals to produce propionate and butyrate in a growth-promoting cross-feeding process. The dietary fibres affect the gut microbiome and play vital roles in signaling pathways. The SCFAs, acetate, butyrate, and propionate have been reported to affect on metabolic activities at the molecular level. Acetate affects the metabolic pathway through the G protein-coupled receptor (GPCR) and free fatty acid receptor 2 (FFAR2/GPR43) while butyrate and propionate transactivate the peroxisome proliferator-activated receptors_γ (PPAR_γ/NR1C3) and regulate the PPAR_γ target gene Angptl4 in colonic cells of the gut. The FFAR2 signaling pathway regulates the insulin-stimulated lipid accumulation in adipocytes and inflammation, however peptide tyrosine-tyrosine (PPY) and glucagon-like peptide 1 regulates appetite. The NDCs via gut microbiota dependent pathway regulate glucose homeostasis, gut integrity and hormone by GPCR, NF-kB, and AMPK-dependent processes.

Hypoxia Inducible Factor-1α: The Curator of Gut Homeostasis

The human gut microbiome is a stratified and resilient ecosystem co-inhabited by a diverse and dynamic pool of microorganisms. Microbial selection, establishment, and colonization are modulated through a complex molecular network of host-microbial interactions. These molecular bioprocesses ensure the taxonomic composition of the mature human gut microbiome. The human gut microbiome plays a vital role in host health; otherwise, any microbial dysbiosis could predispose to the onset of physiological and metabolic disorder/s. Focussed research are being carried out to identify key molecular agents defining gut homeostasis. These molecules hold the potential to develop effective therapeutic solutions for microbial dysbiosis-associated human disorders. Of these, Hypoxia-inducible factor-1α (HIF-1α) is a central player in host-microbial crosstalk to maintain gut homeostasis. Human gut microbial metabolites regulate its cellular stability, which in turn regulates various cellular processes required for the stable gut microbiome. In the present review, an effort has been made to summarize the key role of HIF-1α to maintain gut homeostasis.

Gut Microbiota in Celiac Disease: Is There Any Role for Probiotics?

Celiac disease (CD) is an immune-mediated disorder initiated by the ingestion of gluten in genetically predisposed individuals. Recent data shows that changes in the gut microbiome composition and function are linked with chronic inflammatory diseases; this might also be the case for CD. The main aim of this manuscript is to discuss our present knowledge of the relationships between gut microbiota alterations and CD and to understand if there is any role for probiotics in CD therapy. PubMed was used to search for all of the studies published from November 2009 to November 2019 using key words such as “Celiac Disease” and “Microbiota” (306 articles), “Celiac Disease” and “Gastrointestinal Microbiome” (139), and “Probiotics” and “Celiac Disease” (97 articles). The search was limited to articles published in English that provided evidence-based data. Literature analysis showed that the gut microbiota has a well-established role in gluten metabolism, in modulating the immune response and in regulating the permeability of the intestinal barrier. Promising studies suggest a possible role of probiotics in treating and/or preventing CD. Nevertheless, human trials on the subject are still scarce and lack homogeneity. A possible role was documented for probiotics in improving CD-related symptoms, modulating the peripheral immune response and altering the fecal microbiota, although the results were not consistent in all of the studies. No evidence was found that probiotic administration might prevent CD onset. Knowledge of the role of intestinal bacteria in the development of CD opens new possibilities for its treatment through probiotic administration, even though further studies are needed to better clarify whether probiotics can help treat or prevent the disease and to define which probiotics to use, at what dose and for how long.

The lung microbiome: clinical and therapeutic implications

The human respiratory tract, usually considered sterile, is currently being investigated for human-associated microbial communities. According to Dickson's conceptual model, the lung microbiota (LMt) is a dynamic ecosystem, whose composition, in healthy lungs, is likely to reflect microbial migration, reproduction, and elimination. However, which microbial genera constitutes a "healthy microbiome" per se remains hotly debated. It is now widely accepted that a bi-directional gut-lung axis connects the intestinal with the pulmonary microbiota and that the diet could have a role in modulating both microbiotas as in health as in pathological status. The LMt is altered in numerous respiratory disorders such as obstructive airway diseases, interstitial lung diseases, infections, and lung cancer. Some authors hypothesize that the use of specific bacterial strains, termed "probiotics," with positive effects on the host immunity and/or against pathogens, could have beneficial effects in the treatment of intestinal disorders and pulmonary diseases. In this manuscript, we have reviewed the literature available on the LMt to delineate and discuss the potential relationship between composition alterations of LMt and lung diseases. Finally, we have reported some meaningful clinical studies that used integrated probiotics' treatments to contrast some lung-correlated disorders.

Food Components and Dietary Habits: Keys for a Healthy Gut Microbiota Composition

The gut microbiota is a changing ecosystem, containing trillions of bacteria, continuously shaped by many factors, such as dietary habits, seasonality, lifestyle, stress, antibiotics use, or diseases. A healthy host-microorganisms balance must be respected in order to optimally maintain the intestinal barrier and immune system functions and, consequently, prevent disease development. In the past several decades, the adoption of modern dietary habits has become a growing health concern, as it is strongly associated with obesity and related metabolic diseases, promoting inflammation and both structural and behavioral changes in gut microbiota. In this context, novel dietary strategies are emerging to prevent diseases and maintain health. However, the consequences of these different diets on gut microbiota modulation are still largely unknown, and could potentially lead to alterations of gut microbiota, intestinal barrier, and the immune system. The present review aimed to focus on the impact of single food components (macronutrients and micronutrients), salt, food additives, and different dietary habits (i.e., vegan and vegetarian, gluten-free, ketogenic, high sugar, low FODMAP, Western-type, and Mediterranean diets) on gut microbiota composition in order to define the optimal diet for a healthy modulation of gut microbiota.

What is the Healthy Gut Microbiota Composition? A Changing Ecosystem across Age, Environment, Diet, and Diseases

Each individual is provided with a unique gut microbiota profile that plays many specific functions in host nutrient metabolism, maintenance of structural integrity of the gut mucosal barrier, immunomodulation, and protection against pathogens. Gut microbiota are composed of different bacteria species taxonomically classified by genus, family, order, and phyla. Each human's gut microbiota are shaped in early life as their composition depends on infant transitions (birth gestational date, type of delivery, methods of milk feeding, weaning period) and external factors such as antibiotic use. These personal and healthy core native microbiota remain relatively stable in adulthood but differ between individuals due to enterotypes, body mass index (BMI) level, exercise frequency, lifestyle, and cultural and dietary habits. Accordingly, there is not a unique optimal gut microbiota composition since it is different for each individual. However, a healthy host⁻microorganism balance must be respected in order to optimally perform metabolic and immune functions and prevent disease development. This review will provide an overview of the studies that focus on gut microbiota balances in the same individual and between individuals and highlight the close mutualistic relationship between gut microbiota variations and diseases. Indeed, dysbiosis of gut microbiota is associated not only with intestinal disorders but also with numerous extra-intestinal diseases such as metabolic and neurological disorders. Understanding the cause or consequence of these gut microbiota balances in health and disease and how to maintain or restore a healthy gut microbiota composition should be useful in developing promising therapeutic interventions.

The Role of Diet, Micronutrients and the Gut Microbiota in Age-Related Macular Degeneration: New Perspectives from the Gut⁻Retina Axis

Age-related macular degeneration (AMD) is a complex multifactorial disease and the primary cause of legal and irreversible blindness among individuals aged ≥65 years in developed countries. Globally, it affects 30–50 million individuals, with an estimated increase of approximately 200 million by 2020 and approximately 300 million by 2040. Currently, the neovascular form may be able to be treated with the use of anti-VEGF drugs, while no effective treatments are available for the dry form. Many studies, such as the randomized controlled trials (RCTs) Age-Related Eye Disease Study (AREDS) and AREDS 2, have shown a potential role of micronutrient supplementation in lowering the risk of progression of the early stages of AMD. Recently, low-grade inflammation, sustained by dysbiosis and a leaky gut, has been shown to contribute to the development of AMD. Given the ascertained influence of the gut microbiota in systemic low-grade inflammation and its potential modulation by macro- and micro-nutrients, a potential role of diet in AMD has been proposed. This review discusses the role of the gut microbiota in the development of AMD. Using PubMed, Web of Science and Scopus, we searched for recent scientific evidence discussing the impact of dietary habits (high-fat and high-glucose or -fructose diets), micronutrients (vitamins C, E, and D, zinc, beta-carotene, lutein and zeaxanthin) and omega-3 fatty acids on the modulation of the gut microbiota and their relationship with AMD risk and progression.

Gut microbiota injury in allogeneic haematopoietic stem cell transplantation

Allogeneic haematopoietic stem cell transplantation (allo-HSCT) is considered to be the strongest curative immunotherapy for various malignancies (primarily, but not limited to, haematologic malignancies). However, application of allo-HSCT is limited owing to its life-threatening major complications, such as graft-versus-host disease (GVHD), relapse and infections. Recent advances in large-scale DNA sequencing technology have facilitated rapid identification of the microorganisms that make up the microbiota and evaluation of their interactions with host immunity in various diseases, including cancer. This has resulted in renewed interest regarding the role of the intestinal flora in patients with haematopoietic malignancies who have received an allo-HSCT and in whether the microbiota affects clinical outcomes, including GVHD, relapse, infections and transplant-related mortality. In this Review, we discuss the potential role of intestinal microbiota in these major complications after allo-HSCT, summarize clinical trials evaluating the microbiota in patients who have received allo-HSCT and discuss how further studies of the microbiota could inform the development of strategies that improve outcomes of allo-HSCT.

Patients with Treatment-Requiring Chronic Graft versus Host Disease after Allogeneic Stem Cell Transplantation Have Altered Metabolic Profiles due to the Disease and Immunosuppressive Therapy: Potential Implication for Biomarkers

Chronic graft versus host disease (cGVHD) is a common long-term complication after allogeneic hematopoietic stem cell transplantation. The objective of our study was to compare the metabolic profiles for allotransplant recipients and thereby identify metabolic characteristics of patients with treatment-requiring cGVHD. The study included 51 consecutive patients (29 men and 22 women; median age: 44 years, range: 15–66 years) transplanted with peripheral blood stem cells derived from human leukocyte antigen-matched family donors. All serum samples investigated by global metabolomic profiling were collected approximately 1 year posttransplant (median 358 days). Thirty-one of the 51 patients (61%) had cGVHD 1 year posttransplant. The affected organs were (number of patients) liver/bile duct (23), eyes (15), gastrointestinal tract (14), skin (13), mouth (10), lungs (3), and urogenital tract (1). We compared the metabolic profile for patients with and without cGVHD, and a Random Forrest Classification Analysis then resulted in 75% accuracy in differentiating the two groups. The 30 top-ranked metabolites from this comparison included increased levels of bile acids, several metabolites from the cytokine-responsive kynurenine pathway for tryptophan degradation, pro-inflammatory lipid metabolites, phenylalanine and tyrosine metabolites derived from the gut microbial flora, and metabolites reflecting increased oxidative stress. However, nine of these 30 top-ranked metabolites were probably altered due to cyclosporine or steroid treatment, and we therefore did a hierarchical clustering analysis including all 51 patients but only based on the other 21 cGVHD-specific metabolites. This analysis identified three patient subsets: one cluster included mainly patients without cGVHD and had generally low metabolite levels; another cluster included mainly patients with cGVHD (most patients with at least three affected organs) and high metabolite levels, and the last intermediate group including cGVHD patients with limited organ involvement. We conclude that allotransplant recipients with cGVHD have an altered metabolic profile caused both by the disease and its immunosuppressive treatment.

Bacterial Blood Stream Infections Negatively Impact on Outcome of Patients Treated with Allogeneic Stem Cell Transplantation: 6 Years Single-Centre Experience

BACKGROUND

Blood stream infections (BSIs) represent a major complication of allo-SCT and are a major cause of morbidity and mortality during and after bone marrow aplasia.

OBJECTIVES

The objective of this study was to describe the incidence and outcome of BSIs in a cohort of patients submitted to allo-SCT, in order to track changes of the epidemiology and bacteria resistance.

METHODS

We retrospectively analyzed the microbiological data of 162 patients allotransplanted in Brescia University Hospital, over a period of 6 years.

RESULTS

Eighty patients experienced a BSIs for a total of 119 isolates. In 77 cases (65%) a Gram positive bacteria was isolated, being coagulase negative Staphilococci the most frequent species (77% of the cases). In 42 cases (35%) a Gram negative bacteria was isolated (E. coli 57% and P. aeruginosa 24%). Fluoroquinolones resistance was frequent (90% for S. epidermidis, 92% for E. coli, 90% for P. aeruginosa). Methycillin resistance of S. epidermidis was 100%, 76% of E. coli were ESBL positive and among P. aeruginosa resistance to carbapenems was 40%. The 2 years overall survival of patients with BSIs vs patients without BSIs was 46% vs 60% (HR1,48, p=0,07). P. aeruginosa and E. coli were the species with the highest mortality (50% and 33%, respectively).

CONCLUSIONS

These data confirm that BSIs, mainly sustained by Gram positive bacteria, are frequent in allotransplanted patients (50% of the cases) and may influence the outcome of allotransplanted patients, being antibiotics resistance highly frequent among these bacteria.