Korean J Gastroenterol.  2013 Oct;62(4):191-205. 10.4166/kjg.2013.62.4.191.

Roles of Enteric Microbial Composition and Metabolism in Health and Diseases

• Kim JM

• KMID: 1792737
• DOI: http://doi.org/10.4166/kjg.2013.62.4.191

Abstract

A complex microbiota colonizes mucosal layers in different regions of the human gut. In the healthy state, the microbial communities provide nutrients and energy to the host via fermentation of non-digestible dietary components in the large intestine. In contrast, they can play roles in inflammation and infection, including gastrointestinal diseases and metabolic syndrome such as obesity. However, because of the complexity of the microbial community, the functional connections between the enteric microbiota and metabolism are less well understood. Nevertheless, major progress has been made in defining dominant bacterial species, community profiles, and systemic characteristics that produce stable microbiota beneficial to health, and in identifying their roles in enteric metabolism. Through studies in both mice and humans, we are recently in a better position to understand what effect the enteric microbiota has on the metabolism by improving energy yield from food and modulating dietary components. Achieving better knowledge of this information may provide insights into new possibilities that reconstitution of enteric microbiota via diet can provide the maintenance of healthy state and therapeutic/preventive strategies against metabolic syndrome such as obesity. This review focuses on enteric microbial composition and metabolism on healthy and diseased states.

Keyword

Diet; Dominant bacterial species; Enteric microbiota; Host metabolism

MeSH Terms

Animals
Bacteria/growth & development/metabolism
Diet
Gastrointestinal Diseases/*microbiology/pathology
Humans
Inflammation/microbiology/pathology
Intestines/microbiology
Metabolic Syndrome X/*microbiology/pathology
*Microbiota
Probiotics

Figure

• 

  Fig. 1. Energy intake and fermentation of non-digestible carbohydrates by intestinal microbiota in large intestine. Each gram of glucose that is directly absorbed from the small intestine contributes approximately 3.9 kcal to energy intake. Non-digestible carbohydrates that are resistant to digestion in the small intestine contribute energy indirectly as a result of microbial fermentation in the colon to produce short-chain fatty acids (SCFA) and gases. This contribution to the body's energy intake is approximately 1.5 kcal/g glucose because of the lower energy content of SCFA and their incomplete absorption from the colon. Fermentability depends primarily on the structure of the substrate. However, it may be influenced by methods of food preparation and storage, by host physiology, by gut transit, and potentially by the density and species composition of the intestinal microbiota. Fermentation of non-dige-stible carbohydrates by anaerobic bacteria in the large intestine enables the recovery of only a fraction of the initial energy content for microbial growth. SCFA such as butyrate, acetate, and propionate are absorbed in the colon and butyrate provides energy for intestinal epithelial cells (IECs). Acetate and propionate reach the liver and peripheral organs where they are substrates for gluconeogenesis and lipogenesis.

Reference

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