Role of intestinal microbiota and metabolites on gut homeostasis and human diseases

Abstract

BackgroundA vast diversity of microbes colonizes in the human gastrointestinal tract, referred to intestinal microbiota. Microbiota and products thereof are indispensable for shaping the development and function of host innate immune system, thereby exerting multifaceted impacts in gut health.MethodsThis paper reviews the effects on immunity of gut microbe-derived nucleic acids, and gut microbial metabolites, as well as the involvement of commensals in the gut homeostasis. We focus on the recent findings with an intention to illuminate the mechanisms by which the microbiota and products thereof are interacting with host immunity, as well as to scrutinize imbalanced gut microbiota (dysbiosis) which lead to autoimmune disorders including inflammatory bowel disease (IBD), Type 1 diabetes (T1D) and systemic immune syndromes such as rheumatoid arthritis (RA).ResultsIn addition to their well-recognized benefits in the gut such as occupation of ecological niches and competition with pathogens, commensal bacteria have been shown to strengthen the gut barrier and to exert immunomodulatory actions within the gut and beyond. It has been realized that impaired intestinal microbiota not only contribute to gut diseases but also are inextricably linked to metabolic disorders and even brain dysfunction.ConclusionsA better understanding of the mutual interactions of the microbiota and host immune system, would shed light on our endeavors of disease prevention and broaden the path to our discovery of immune intervention targets for disease treatment.

Probiotics in Gut-Bone Signaling

“…Through co-evolution, humans not only tolerated the presence of the intestinal microbiota but also evolved to use the colonization of commensal microbes for immune development and function, intestinal barrier integrity, and overall health [49]. Commensal microbes comprise the resident bacteria that live on the human body and in the intestine amount to over 500 different strains including probiotic strains.…”

“…In the intestine, the balance of beneficial bacteria with neutral or inflammatory bacteria is critical. Thus, intestinal dysbiosis (microbe imbalance) leads to a reduction in the beneficial commensal microbes and can contribute to disease [49]. Probiotic intake can help restore commensal microbe balance.…”

The role of inflammation in temporal shifts in the inflammatory bowel disease mucosal microbiome

“…1-3 As no single microorganism has been identified as the cause of IBD, the focus of current research has shifted to studying the characteristic “dysbiosis” 4-6 (an abnormal or unbalanced microbiome) and developing therapies to correct it. 7 , 8 This is based on the assumption that it is the dysbiosis that leads to the uncontrolled inflammation characteristic of IBD, either directly, or by interfering with mucosal protective mechanisms.…”

Dynamic relationships among tumor, immune response, and microbiota

“…Gut microbiota and human beings are co-evolutionary, in a win-win symbiosis [5][6][7] . Recently, there have been many studies and much research on the relationships between the gut microbiota and human disease [8][9][10][11] . Gut microbiota seem to be strongly correlated with various kinds of disease, such as inflammatory bowel disease (IBD) [12][13][14][15] , diabetes mellitus (DM) [16][17][18] , central nervous disorder (CND) [19][20][21][22][23][24] , allergic diseases [25][26][27][28][29] , and infectious diseases [30] .…”