Diet-Induced Dysbiosis of the Intestinal Microbiota and the Effects on Immunity and Disease

The gastrointestinal (GI) microbiota is the collection of microbes which reside in the GI tract and represents the largest source of non-self antigens in the human body. The GI tract functions as a major immunological organ as it must maintain tolerance to commensal and dietary antigens while remaining responsive to pathogenic stimuli. If this balance is disrupted, inappropriate inflammatory processes can result, leading to host cell damage and/or autoimmunity. Evidence suggests that the composition of the intestinal microbiota can influence susceptibility to chronic disease of the intestinal tract including ulcerative colitis, Crohn’s disease, celiac disease and irritable bowel syndrome, as well as more systemic diseases such as obesity, type 1 diabetes and type 2 diabetes. Interestingly, a considerable shift in diet has coincided with increased incidence of many of these inflammatory diseases. It was originally believed that the composition of the intestinal microbiota was relatively stable from early childhood; however, recent evidence suggests that diet can cause dysbiosis, an alteration in the composition of the microbiota, which could lead to aberrant immune responses. The role of the microbiota and the potential for diet-induced dysbiosis in inflammatory conditions of the GI tract and systemic diseases will be discussed.     

Nutritional management of gut health in pigs around weaning

Early weaning of piglets is often accompanied by a severe growth check and diarrhoea. It is well established that this process is multi-factorial and that post-weaning anorexia and undernutrition are major aetiological factors. Gastrointestinal disturbances include alterations in small intestine architecture and enzyme activities. Recent data indicate transiently-increased mucosal permeability, disturbed absorptive-secretory electrolyte balance and altered local inflammatory cytokine patterns after weaning. These responses appear to operate according to two distinct temporal patterns, an acute response followed by a long-lasting adaptation response. Pigs coexist with a diverse and dense commensal microbiota in their gastrointestinal tract. Most of these microbes are beneficial, providing necessary nutrients or protection against harmful pathogens for the host. The microbial colonisation of the porcine intestine begins at birth and follows a rapid succession during the neonatal and weaning period. Following the withdrawal of sow's milk the young piglets are highly susceptible to enteric diseases partly as a result of the altered balance between developing beneficial microbiota and the establishment of intestinal bacterial pathogens. The intestinal immune system of the newborn piglet is poorly developed at birth and undergoes a rapid period of expansion and specialisation that is not achieved before early (commercial) weaning. Here, new insights on the interactions between feed components, the commensal microbiota and the physiology and immunology of the host gastrointestinal tract are highlighted, and some novel dietary strategies are outlined that are focused on improving gut health. Prebiotics and probiotics are clear nutritional options, while convincing evidence is still lacking for other bioactive substances of vegetable origin.     

Cesarean delivery may affect the early biodiversity of intestinal bacteria

The gastrointestinal tract of neonates becomes colonized immediately after birth with environmental microorganisms, mainly from the mother; strong evidence suggests that the early composition of the microbiota of neonates plays an important role for the postnatal development of the immune system. The present study was designed to evaluate by means of a molecular biology approach the relation between the intestinal ecosystem of the newborn and the mode of delivery. The intestinal bacterial composition on d 3 of life was investigated in 23 infants born by vaginal delivery and in 23 infants delivered by cesarean section. PCR-denaturing gradient gel electrophoresis and PCR-temperature gradient gel electrophoresis have been utilized, together with the specific amplifications for 10 Bifidobacterium species, 3 Ruminococcus species, and Bacteroides. The intestinal microbiota of neonates delivered by cesarean delivery appears to be less diverse, in terms of bacteria species, than the microbiota of vaginally delivered infants. The intestinal microbiota after cesarean delivery is characterized by an absence of Bifidobacteria species. Vaginally delivered neonates, even if they showed individual microbial profiles, were characterized by predominant groups such as B. longum and B. catenulatum. Our data demonstrate that the mode of delivery has a deep impact on the composition of the intestinal microbiota at the very beginning of human life. This study opens the path to further investigations to confirm the link between microbiota composition and immune system development and to identify tools for the modulation of the intestinal microbiota of cesarean-delivered neonates. Additionally, we underline the importance of adequate microbiological tools used to support clinically relevant trials, if intestinal microbiota is considered as a study outcome.     

Perinatal and Neonatal Manipulation of the Intestinal Microbiome: A Note of Caution

As we learn more about interactions between microbes and the developing gastrointestinal (GI) tract, it is becoming clear that the establishment of the intestinal "microbiome" shortly after birth plays a critical role in the early origins of health and disease. Nutrition, mode of delivery, the use of maternal or postnatal antibiotics, and pre- and probiotics are factors that may alter the microbial ecology and affect lifelong gene expression. Because the neonatal period is a critical period of development when microbes become established in the GI tract, the long-term effects of manipulations of the GI microbial ecology during this time are more amplified than the effects of later manipulations. In this paper, recent research findings are reviewed with the intent of providing information about the benefits of early manipulation of the GI microbiome, but also to give a warning about its indiscriminant manipulation during the perinatal and neonatal time periods.     

Composition and function of the human-associated microbiota

The human body is an ecosystem harboring complex site-specific microbial communities. The majority of these human-associated microbes are found in the intestinal tract, where they play important roles in energy uptake, vitamin synthesis, and epithelial and immunity development. Recent molecular studies have characterized the human-associated microbiotas in more detail than conventional culture-dependent techniques, showing a large degree of microbial diversity and differences between anatomical sites and individuals. Investigating the composition and function of microbial symbionts will facilitate better understanding of their roles in human health and disease.     

The physiological relevance of the intestinal microbiota--contributions to human health

The intestinal commensal microbiota is a dynamic mixture of essential microbes that develops under key influences of genetics, environment, diet and disease. Population profiles differ along the gastrointestinal tract, from the lumen to the mucosa, and among individuals. The total microbiota population outnumbers the cells in the human body and accounts for 35-50% of the volume of the colonic content. Key physiological functions of the commensal microbiota include protective effects exerted directly by specific bacterial species, control of epithelial cell proliferation and differentiation, production of essential mucosal nutrients, such as short-chain fatty acids and amino acids, prevention of overgrowth of pathogenic organisms, and stimulation of intestinal immunity. Oral probiotics are living microorganisms that upon ingestion in specific numbers exert health benefits beyond those of inherent basic nutrition. Emerging evidence indicates prophylactic and therapeutic utility for probiotic consumption in gastrointestinal health and disease.     

The Physiological Relevance of the Intestinal Microbiota - Contributions to Human Health

The intestinal commensal microbiota is a dynamic mixture of essential microbes that develops under key influences of genetics, environment, diet and disease. Population profiles differ along the gastrointestinal tract, from the lumen to the mucosa, and among individuals. The total microbiota population outnumbers the cells in the human body and accounts for 35–50% of the volume of the colonic content. Key physiological functions of the commensal microbiota include protective effects exerted directly by specific bacterial species, control of epithelial cell proliferation and differentiation, production of essential mucosal nutrients, such as short-chain fatty acids and amino acids, prevention of overgrowth of pathogenic organisms, and stimulation of intestinal immunity. Oral probiotics are living microorganisms that upon ingestion in specific numbers exert health benefits beyond those of inherent basic nutrition. Emerging evidence indicates prophylactic and therapeutic utility for probiotic consumption in gastrointestinal health and disease.     

Molecular ecological analysis of the gastrointestinal microbiota: a review

The gastrointestinal (GI) microbiota of mammals is characterized by its high population density, wide diversity and complexity of interactions. While all major groups of microbes are represented, bacteria predominate. Importantly, bacterial cells outnumber animal (host) cells by a factor of ten and have a profound influence on nutritional, physiological and immunological processes in the host animal. Our knowledge of the molecular and cellular bases of host-microbe interactions is limited, though critically needed to determine if and how the GI microbiota contributes to various enteric disorders in humans and animals. Traditionally, GI bacteria have been studied via cultivation-based techniques, which are labor intensive and require previous knowledge of individual nutritional and growth requirements. Recently, findings from culture-based methods have been supplemented with molecular ecology techniques that are based on the 16S rRNA gene. These techniques enable characterization and quantification of the microbiota, while also providing a classification scheme to predict phylogenetic relationships. The choice of a particular molecular-based approach depends on the questions being addressed. Clone libraries can be sequenced to identify the composition of the microbiota, often to the species level. Microbial community structure can be analyzed via fingerprinting techniques, while dot blot hybridization or fluorescent in situ hybridization can measure abundance of particular taxa. Emerging approaches, such as those based on functional genes and their expression and the combined use of stable isotopes and biomarkers, are being developed and optimized to study metabolic activities of groups or individual organisms in situ. Here, a critical summary is provided of current molecular ecological approaches for studying the GI microbiota.     

婴幼儿肠道菌群的影响因素及其在肠道免疫中的作用

婴幼儿肠道菌群自定植起,随着年龄增长,需历经多次改变才能最终形成微生物稳态。本文主要介绍婴幼儿肠道菌群受分娩阶段、喂养方法、饮食结构、生活环境、疾病因素、药物使用后发生的改变,及其在肠道免疫功能形成中发挥的重要作用。     

婴幼儿肠道菌群的影响因素及其在肠道免疫中的作用

婴幼儿肠道菌群自定植起,随着年龄增长,需历经多次改变才能最终形成微生物稳态。本文主要介绍婴幼儿肠道菌群受分娩阶段、喂养方法、饮食结构、生活环境、疾病因素、药物使用后发生的改变,及其在肠道免疫功能形成中发挥的重要作用。     

肠道微生态研究技术在代谢综合征中的应用

哺乳动物肠道内定居着数量庞大且组分复杂的微生物群,它们共同构成了肠道微生物组。近年来,人们逐渐认识到肠道微生物与一些疾病的发生和发展密切相关,如代谢性疾病、炎症性肠病、肿瘤、免疫系统以及神经系统疾病等,使得肠道微生物成为研究的热点。迅猛发展的微生物研究技术为我们提供了高效有力的技术平台,推动了对肠道微生态的系统认知,也为疾病的诊断及治疗开辟了新思路。本文旨在总结与分析目前常用微生态研究技术的最新进展及其局限性,为进一步的肠道微生物组研究提供参考,并简要介绍肠道微生态与代谢综合征的相关研究成果。     

Microbial modulation of innate defense: goblet cells and the intestinal mucus layer

The gastrointestinal epithelium is covered by a protective mucus gel composed predominantly of mucin glycoproteins that are synthesized and secreted by goblet cells. Changes in goblet cell functions and in the chemical composition of intestinal mucus are detected in response to a broad range of luminal insults, including alterations of the normal microbiota. However, the regulatory networks that mediate goblet cell responses to intestinal insults are poorly defined. The present review summarizes the results of developmental, gnotobiotic, and in vitro studies that showed alterations in mucin gene expression, mucus composition, or mucus secretion in response to intestinal microbes or host-derived inflammatory mediators. The dynamic nature of the mucus layer is shown. Available data indicate that intestinal microbes may affect goblet cell dynamics and the mucus layer directly via the local release of bioactive factors or indirectly via activation of host immune cells. A precise definition of the regulatory networks that interface with goblet cells may have broad biomedical applications because mucus alterations appear to characterize most diseases of mucosal tissues.     

Dysbiotic Events in Gut Microbiota: Impact on Human Health

The human body is colonized by a large number of microbes coexisting peacefully with their host. The most colonized site is the gastrointestinal tract (GIT). More than 70% of all the microbes in the human body are in the colon. The microorganism population is 10 times larger of the total number of our somatic and germ cells. Two bacterial phyla, accounting for more than 90% of the bacterial cells, dominate the healthy adult intestine: Firmicutes and Bacteroidetes. Considerable variability in the microbiota compositions between people is found when we look at the taxonomic level of species, and strains within species. It is possible to assert that the human microbiota could be compared to a fingerprint. The microbiota acts as a barrier from pathogens, exerts important metabolic functions, and regulates inflammatory response by stimulating the immune system. Gut microbial imbalance (dysbiosis), has been linked to important human diseases such as inflammation related disorders. The present review summarizes our knowledge on the gut microbiota in a healthy context, and examines intestinal dysbiosis in inflammatory bowel disease (IBD) patients; the most frequently reported disease proven to be associated with changes in the gut microbiota.     

Probiotics and mucosal barrier in children

PURPOSE OF REVIEW: Colonization by the microbiota plays an important role in intestinal tract maturation of newborn. Once installed, indigenous microbiota maintains this modulation and also protects against infectious aggression. Due to these abilities, gut microbiota can be considered a 'microbial organ' that contributes to health of human host. Factors can affect microbiota colonization as well as its maintenance and ingestion of probiotics is a promissory way to counteract these perturbations. This review discusses recent papers dealing with the use of probiotics and their effects on intestinal barrier in children. RECENT FINDINGS: Data obtained from experiments in animal models or cell cultures as well as from clinical trials suggest that probiotics may prevent infectious and inflammatory diseases in which reduction of mucosal barrier functions is involved. SUMMARY: Recent results suggest that probiotics control maturation and maintenance of the intestinal barrier in children. However, human data are limited and more biological and well controlled clinical trials must be carried out for a more precise understanding of the mechanisms underlying the probiotic action and the balance of the complex gastrointestinal ecosystem with which probiotics are expected to interact.     

婴幼儿肠道菌群初始定植的影响因素

肠道菌群与宿主的健康和疾病有极为密切的关系,多种因素可干扰肠道菌群的构成进而影响宿主的正常生理功能。本文将探讨胎龄、分娩方式、喂养方式、生长环境、抗生素应用、细菌间相互作用和微生态制剂的使用等诸多因素对婴幼儿肠道菌群初始定植的影响。     

Diet–Microbiota Interactions in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic inflammatory disease of the gastrointestinal tract. Although the precise etiology of IBD is largely unknown, it is widely thought that diet contributes to the development of IBD. Diet shapes the composition of the gut microbiota, which plays critical roles in intestinal homeostasis. In contrast, intestinal inflammation induces gut dysbiosis and may affect the use of dietary nutrients by host cells and the gut microbiota. The interaction of diet and the gut microbiota is perturbed in patients with IBD. Herein, we review the current knowledge of diet and gut microbiota interaction in intestinal homeostasis. We also discuss alterations of diet and gut microbiota interaction that influence the outcome and the nutritional treatment of IBD. Understanding the complex relationships between diet and the gut microbiota provides crucial insight into the pathogenesis of IBD and advances the development of new therapeutic approaches.     

食物营养与辅食对肠道菌群的影响

食物是人体和肠道菌群共同的营养物质。不同食物提供的各种营养素不但是身体的需要也会影响肠道微生物的组成和丰度,辅食添加使肠道菌群发生重要的转变,引入新食物并向家庭食物过渡,会增加婴儿肠道菌群的多样性,多种食物的摄入,保持重要的食物结构,对维持肠道有益的微生物种类和数量,对人体近期和远期的健康均有重要影响。     

食物营养与辅食对肠道菌群的影响

食物是人体和肠道菌群共同的营养物质。不同食物提供的各种营养素不但是身体的需要也会影响肠道微生物的组成和丰度,辅食添加使肠道菌群发生重要的转变,引入新食物并向家庭食物过渡,会增加婴儿肠道菌群的多样性,多种食物的摄入,保持重要的食物结构,对维持肠道有益的微生物种类和数量,对人体近期和远期的健康均有重要影响。     

COVID-19 and gut dysbiosis,understanding the role of probiotic supplements in reversing gut dysbiosis and immunity

In December 2019, an outbreak of novel beta-coronavirus started in Wuhan, China, spread globally as coronavirus disease 2019 (COVID-19) pandemic and is still underway. The causative agent for COVID-19 identified as a novel strain of beta coronavirus named nSARS-CoV-2. The nSARS-CoV-2 primarily targets the respiratory tract and results in severe acute respiratory distress (ARDS), leading to the collapse of the respiratory tract. The virus internalizes primarily via ACEII receptor, and many tissues reported a significant level of expression of ACEII receptor including lungs, hearts, kidneys, and gastrointestinal tract. The clinical manifestations of COVID-19 are diverse, but growing evidence suggests that gut dysbiosis is one of them and poses a threat to native immunity. The human microbial ecology plays a vital role in human physiology, including building immunity. The gastrointestinal tract (GIT) habitats trillions of beneficial microbes’ precisely bacterial species synchronize with human physiology and remain symbiotic. On the contrary, harmful microbiota seeks an opportunity to break the equilibrium failure of balance between beneficial and detrimental human gut microbiota results in impaired physiology and immunity. The grown research evidence demonstrated that infection caused by the nSARS-CoV-2 result in moderate to severe diarrheal outcomes. The diarrheal conditions in COVID-19 patients are due to alteration of gut microbial ecology. The management of COVID-19 requires specialized therapeutics along with a series of nutraceuticals. Probiotics remain vital nutrient supplements in COVID-19 management, offer relief in diarrhea and improve/restore immunity. This study uses available data/findings to emphasize an association between COVID-19 and gut dysbiosis. The study also provides a scientific basis of impaired immunity during gut dysbiosis in COVID-19 and how probiotics help restore and improve impaired immunity and diarrhea.     

Gastrointestinal development and meeting the nutritional needs of premature infants

The fear of necrotizing enterocolitis and feeding intolerance are major factors inhibiting the use of the enteral route as the primary means of nourishing premature infants. Parenteral nutrition may help to meet many of the nutritional needs of these infants, but has significant detrimental side effects that include intestinal atrophy, sepsis, and increased susceptibility to inflammatory stimuli and systemic inflammatory responses. Being able to minimize the use of the parenteral route and still maintain appropriate nutrition safely would be a major advance in neonatology. At the basis of our inability to use the enteral route is a poorly understood immature gastrointestinal tract. Approaches such as minimal enteral nutrition or trophic feedings may partially alleviate these problems. However, if we are to progress in greater utilization of the gastrointestinal tract, other factors need to be considered. These include the macronutrient composition of minimal enteral or trophic feedings and the microecology of the intestinal lumen. Some of the developmental aspects of the intestine, which include intestinal growth, motor activity, barrier and other innate immune functions, and the microecology of the developing intestine, are briefly reviewed here. The purpose of this review is to suggest important areas of future research in neonatal and developmental gastroenterology that could affect several conditions that are related to immaturity of the gastrointestinal tract.