Faculty and research guide

Laboratory of Food and Nutritional Chemistry (Nishimura)

Naomichi Nishimura

It had been believed that the large intestine is an organ whose principal function is only to absorb water and some minerals and only to produce feces. However, numerous types of bacteria in large numbers exists in the large intestine and are superior to the number of human somatic cells and have interdependent relationship with their host. Various gas components such as hydrogen, methane, and short chain fatty acids are produced by these bacteria and affect the host. We are studying the relationship between host’s events induced by fermentation products derived from non-digestible, especially hydrogen molecule, and the prevention of the metabolic syndrome using rat models. Here we will show some of our studies.

1. Study on enhanced colonic H2 production due to non-digestible food components and colonic microbiota
H2 molecule have reducing power and alleviates oxidative stress in the body. H2 is produced solely by colonic bacteria, which ferment dietary components that escape digestion by host enzymes such as dietary fiber, oligosaccharides, resistant starch, etc. We have examined the relationship between non-digestible components and microbiota on colonic H2 production using in vitro fermentation model and in vivo rat model. 

2. Suppressive effect of colonic H2 on oxidative stress
We found that H2 delivery by colonic H2 in the body as well as by inhalation of H2 gas alleviates oxidative stress and then suppresses oxidative damage. We also found that colonic H2 generated from non-digestible saccharides diffuses to the abdominal cavity as well as blood before transferring to abdominal tissues. This shows that colonic H2 would contribute systemically to maintain redox balance. We have examined the effects of colonic H2 on the respective tissues and the mechanism by which colonic H2 causes the alleviation of oxidative stress using rats.

These images show representative liver sections in ischemia-reperfusion (IR)-treated rats fed pectin (Pec), which is a type of soluble dietary fiber. Liver histology reveals hepatic sinusoids that had a normal appearance in the sham-C group, while a degree of occlusion and accumulation of neutrophils around the central vein are observed in the IR-C group. Samples from the IR-Pec group are similar to those in the sham-C group.

These graphs indicate that improved liver histology in the IR-Pec group is dependent on suppressed oxidative stress by colonic H2

This graphs show breath and flatus H2 excretion and portal blood, aorta, abdominal cavity, and tissue H2 concentrations in rats fed diets containing fructooligosaccharides, which are not digested by host digestive enzymes. As you can see in the graph, part of the H2 generated in the large intestine diffuses into the abdominal cavity and is then localized in various tissues, especially the adipose tissues. H2 can pass through colonic tissue and then diffuse into the abdominal cavity because except for helium, which is monomolecular monoatomic molecule, H2 molecule is the smallest molecule known to exist.


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