Dysbiosis in Functional Bowel Disorders

Abstract

Functional bowel disorders (FBD) resemble a group of diseases of the gastrointestinal (GI) tract that are without a clear pathogenesis; the best known is probably the “irritable bowel syndrome” (IBS). Only recently we have been able to explore the role of the gut microbiota in FBD due to progress in microbiological analytic techniques. There are different ways to explore the role of the gut microbiota and its dysbiosis in FBD. Comparison of the microbial composition in a group of patients with FBD, for example, with IBS to a group of healthy volunteers is one way. Studies have shown that the microbiota in FBD is different from that of healthy controls, but the recorded differences are not necessarily specific for FBD, they may also occur in other diseases. Another approach to explore the role of the gut microbiota in FBD is to challenge the existing “flora” with novel bacteria (probiotics) or with nutritional substrates that stimulate bacterial growth (prebiotics). More than 60 such trials including several thousand patients have been performed in IBS. These studies have produced mixed outcome: some probiotics appear to be better than others, and some appear to work only for a part of the IBS symptoms and not for all. An extreme form of this approach is the transfer of an entire microbiota from 1 healthy person to another, called fecal microbiota transplantation. This has rarely been tested in FBD but is not without risk in benign disorders.

Efficacy of faecal microbiota transplantation for patients with irritable bowel syndrome in a randomised, double-blind, placebo-controlled study

“…These improvements were accompanied by changes in the bacterial faecal profile but not in the DI. The clinical relevance of the dysbiosis has been questioned recently 4 23. It is notable that the scores in all IBS-QoL domains except for health worries improved after the patients received FMT.…”

“…The faecal bacteria were analysed with the GA-map Dysbiosis Test using a method described in detail elsewhere 3 4. In brief, the test uses the 16S rRNA gene to determine both the bacterial profile and DI.…”

“…In brief, the test uses the 16S rRNA gene to determine both the bacterial profile and DI. It detects bacteria within five phyla (Firmicutes, Proteobacteria, Bacteroidetes, Tenericutes and Verrucomicrobia) that cover 10 bacterial classes, 36 genera and 32 species,3 which means that the test assesses >300 bacteria at different taxonomic levels 4. The DI is measured on a 5-point scale from 1 to 5 (severe dysbiosis), where DI values>2 indicate the presence of dysbiosis 3…”

“…The aetiology of IBS is not completely understood, and there is no effective treatment for the condition 1. The gut microbiota in patients with IBS differs from that of the healthy subjects, including exhibiting a low bacterial diversity (dysbiosis) 1 3–5. It is believed that microbiota dysbiosis is one of the factors contributing to the aetiology of IBS 1…”

Germ-Free Swiss Webster Mice on a High-Fat Diet Develop Obesity, Hyperglycemia, and Dyslipidemia

“…Increasingly, studies suggest alterations to the intestinal microbiota (IMB) contribute to the development of obesity, MetS, T2DM, CVD, and non-alcoholic fatty liver disease (NAFLD) [17]. The IMB plays an important role in energy harvest and obesity-associated inflammation [11,[18][19][20][21].…”