The Gut Microbiota and Inflammation: An Overview

Abstract

The gut microbiota encompasses a diverse community of bacteria that carry out various functions influencing the overall health of the host. These comprise nutrient metabolism, immune system regulation and natural defence against infection. The presence of certain bacteria is associated with inflammatory molecules that may bring about inflammation in various body tissues. Inflammation underlies many chronic multisystem conditions including obesity, atherosclerosis, type 2 diabetes mellitus and inflammatory bowel disease. Inflammation may be triggered by structural components of the bacteria which can result in a cascade of inflammatory pathways involving interleukins and other cytokines. Similarly, by-products of metabolic processes in bacteria, including some short-chain fatty acids, can play a role in inhibiting inflammatory processes. In this review, we aimed to provide an overview of the relationship between the gut microbiota and inflammatory molecules and to highlight relevant knowledge gaps in this field. Based on the current literature, it appears that as the gut microbiota composition differs between individuals and is contingent on a variety of factors like diet and genetics, some individuals may possess bacteria associated with pro-inflammatory effects whilst others may harbour those with anti-inflammatory effects. Recent technological advancements have allowed for better methods of characterising the gut microbiota. Further research to continually improve our understanding of the inflammatory pathways that interact with bacteria may elucidate reasons behind varying presentations of the same disease and varied responses to the same treatment in different individuals. Furthermore, it can inform clinical practice as anti-inflammatory microbes can be employed in probiotic therapies or used to identify suitable prebiotic therapies.

The Immunopathogenesis of Alzheimer’s Disease Is Related to the Composition of Gut Microbiota

“…Gut microbiota comprise a community of microorganisms which have many important functions for the health of their host (see other reviews [ 19 ]): they defeat invading pathogens, metabolize nutrients, produce neurotransmitters and regulate the immune system. During recent years, the crucial role of intestinal microbiota for the development of different diseases like infections, metabolic, autoimmune and mental diseases has been recognized [ 20 ].…”

“…Actually, recent studies showed an association of the development of neurodegenerative diseases like AD with alterations of the gut microbiota [ 19 , 21 ]. In fact, studies with AD patients and healthy controls conducted at the Alzheimer´s disease Research Center showed significant differences regarding the composition of the intestinal microbiome [ 22 ].…”

“…While this strategy of the immune system is necessary and very effective in acute situations, chronic (persistent) inflammatory reactions of the gut mucosa can overcharge the immune system and lead to a chronic, over-active, but ineffective immune response. They are supposed to go along with the development of many chronic diseases, like inflammatory bowel disease, diabetes, atherosclerosis, and also neurodegenerative diseases [ 19 ]. Chronic microbial translocation can also drive distant organ failure and injury [ 28 ].…”

“…Typically, human microbiota remain stable during longer periods of time [ 98 , 133 ], but changes in diet as well as antibiotic treatment can result in dysbiosis [ 134 , 135 ]. Standard Western diet (WD) with its high intake of refined sugars/grains, red and processed meat, saturated fats and a high consumption of sugared beverages goes along with substantial and fundamental changes of the gut microbiota (see also reviews by Noble et al and Al Bander et al [ 19 , 21 ]). The high contents of animal protein in WD appears to provide an optimal environment for anaerobic microorganisms and specific genera including Bacteroides and Bilophila [ 136 ].…”

The association of child maltreatment and systemic inflammation in adulthood: A systematic review

“…Low-grade inflammation has been associated with a range of physical health conditions such as cardiovascular disease and diabetes [10,11]. Notably, a large body of work has associated low-grade elevations in CRP with cardiovascular events -however subsequent work has questioned the direction of causality in this relationship [12].…”