Abstract
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.
Highlights
The intestinal microbiota is the collection of microbes that reside in the gastrointestinal (GI) tract and is comprised of over 1000 different species that contributes 3.3 million unique microbial genes in the GI tract of humans [1,2]
Mice lacking toll-like receptor (TLR)5, a transmembrane protein expressed in the intestinal mucosa that binds bacterial flagella, develop metabolic syndrome associated with dysbiosis and low-grade inflammation which was worsened following a high-fat diet [86]
The GI microbiota was first considered as a factor contributing to Type 1 diabetes (T1D) when it was observed that penetrance of diabetes in non-obese diabetic (NOD) mice was dependent on the animal facility that the mice were housed in [91]
Summary
The intestinal microbiota is the collection of microbes that reside in the gastrointestinal (GI) tract and is comprised of over 1000 different species that contributes 3.3 million unique microbial genes in the GI tract of humans [1,2] This intricate microbial system includes bacteria which live in a symbiotic relationship with their host and some microbes which have potentially pathogenic characteristics. Initial colonization of the intestine does not appear to be random [13] but instead, pre-programmed This was initially shown by Rawls et al (2006) who performed reciprocal microbiota transplants in zebrafish and mice, which have similar microbiota at the division level, but different composition at the species level [14]. While host genetics can predict microbial composition to an extent, several extrinsic factors contribute to the development of an individual’s unique microbial fingerprint and as a result, susceptibility to several diseases
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