Dr. Ron’s Research Review – March 28, 2012

This week’s research review focuses on gut health.

The Common Fund's Human Microbiome Project (HMP) aims to characterize the microbial communities found at several different sites on the human body, including nasal passages, oral cavities, skin, gastrointestinal tract, and urogenital tract, and to analyze the role of these microbes in human health and disease.

A recent article discusses a hidden gem by Arthur I. Kendall, published in the Journal of Biological Chemistry in November 1909, which offers a visionary insight into many of today's hot research questions. (Aziz 2009) (Kendall 1909)

The microorganisms inhabiting the gut lumen interact with the intestinal immune system, supply key nutrients for the major components of the gut wall, and modulate energy metabolism. Host-microbiome interactions can be either beneficial or deleterious, driving gastrointestinal lymphoid tissue activities and shaping gut wall structures. (Stanghellini, Barbara et al. 2010)

The epithelial cells linked by tight junctions not only physically separate the microbiota from the lamina propria, but also secrete pro-inflammatory cytokines and reactive oxygen species in response to pathogen invasion and metabolic stress and serve as a sentinel to the underlying immune cells. (Yu, Wang et al. 2012)

Gut microbiota might be involved in the development of obesity and related disorders such as metabolic syndrome. Dietary composition and caloric intake appear to swiftly regulate intestinal microbial composition and function. (Tilg and Kaser 2011)

Dr. Ron


Articles

A hundred-year-old insight into the gut microbiome!

            (Aziz 2009) Download

As the National Institutes of Health-funded Human Microbiome Project enters its second phase, and as a major part of this project focuses on the human gut microbiome and its effects on human health, it might help us to travel a century back in time and examine how microbiologists dealt with microbiome-related challenges similar to those of the 21st century using the tools of their time. An article by Arthur I. Kendall, published in The Journal of Biological Chemistry in November 1909 (Some observations on the study of the intestinal bacteria J Biol Chem 1909, 6:499-507), offers a visionary insight into many of today's hot research questions.

Some observations on the study of the intestinal bacteria

            (Kendall 1909) Download

The alimentary canal may be regarded from the point of view of bacterial processes within it, as a singularly perfect incubator; an incubator in which there is provided at different levels such a range of reaction and diversity of food that not only are the conditions suitable for the growth of the normal habituated intestinal bacteria but often also for those organisms, capable of developing at body temperature, which are ingested with the food of the host.

Gut microbiota and related diseases: clinical features

            (Stanghellini, Barbara et al. 2010) Download

Intestinal microbiota is essential for gut homeostasis. Specifically, the microorganisms inhabiting the gut lumen interact with the intestinal immune system, supply key nutrients for the major components of the gut wall, and modulate energy metabolism. Host-microbiome interactions can be either beneficial or deleterious, driving gastrointestinal lymphoid tissue activities and shaping gut wall structures. This overview briefly focuses on the potential role played by abnormalities in gut microbiota and relative responses of the gastrointestinal tract in the determination of important pathological conditions such as the irritable bowel syndrome, inflammatory bowel diseases and colorectal cancer.


Gut microbiome, obesity, and metabolic dysfunction

            (Tilg and Kaser 2011) Download

The prevalence of obesity and related disorders such as metabolic syndrome has vastly increased throughout the world. Recent insights have generated an entirely new perspective suggesting that our microbiota might be involved in the development of these disorders. Studies have demonstrated that obesity and metabolic syndrome may be associated with profound microbiotal changes, and the induction of a metabolic syndrome phenotype through fecal transplants corroborates the important role of the microbiota in this disease. Dietary composition and caloric intake appear to swiftly regulate intestinal microbial composition and function. As most findings in this field of research are based on mouse studies, the relevance to human biology requires further investigation.

Host-microbial interactions and regulation of intestinal epithelial barrier function: From physiology to pathology

            (Yu, Wang et al. 2012) Download

The gastrointestinal tract is the largest reservoir of commensal bacteria in the human body, providing nutrients and space for the survival of microbes while concurrently operating mucosal barriers to confine the microbial population. The epithelial cells linked by tight junctions not only physically separate the microbiota from the lamina propria, but also secrete proinflammatory cytokines and reactive oxygen species in response to pathogen invasion and metabolic stress and serve as a sentinel to the underlying immune cells. Accumulating evidence indicates that commensal bacteria are involved in various physiological functions in the gut and microbial imbalances (dysbiosis) may cause pathology. Commensal bacteria are involved in the regulation of intestinal epithelial cell turnover, promotion of epithelial restitution and reorganization of tight junctions, all of which are pivotal for fortifying barrier function. Recent studies indicate that aberrant bacterial lipopolysaccharide-mediated signaling in gut mucosa may be involved in the pathogenesis of chronic inflammation and carcinogenesis. Our perception of enteric commensals has now changed from one of opportunistic pathogens to active participants in maintaining intestinal homeostasis. This review attempts to explain the dynamic interaction between the intestinal epithelium and commensal bacteria in disease and health status.


References

Aziz, R. K. (2009). "A hundred-year-old insight into the gut microbiome!" Gut Pathog 1(1): 21.

Kendall, A. I. (1909). "Some observations on the study of the intestinal bacteria." J Biol Chem 6: 499-507.

Stanghellini, V., G. Barbara, et al. (2010). "Gut microbiota and related diseases: clinical features." Intern Emerg Med 5 Suppl 1: S57-63.

Tilg, H. and A. Kaser (2011). "Gut microbiome, obesity, and metabolic dysfunction." J Clin Invest 121(6): 2126-32.

Yu, L. C., J. T. Wang, et al. (2012). "Host-microbial interactions and regulation of intestinal epithelial barrier function: From physiology to pathology." World J Gastrointest Pathophysiol 3(1): 27-43.