03/12/2022
Physiologically, hydrogen gas of approximately 150 cc is produced daily by numerous strains of intestinal bacteria during fermentation of nondigestible carbohydrates primarily in the large intestine and is excreted as a natural component of abdominal gas, exhaled or further metabolized by colonic flora. Exhalation of hydrogen forms the basis for the routinely used hydrogen breath test for gastrointestinal transit and assessment of small intestinal bacterial overgrowth. It is well established that antibiotic treatment can alter results from H2 breath tests by diminishing anaerobe H2 producing microorganisms. In contrast to other gaseous bacterial byproducts in the gastrointestinal tract, hydrogen seems to have motility altering properties. In fact, irritable bowel syndrome (IBS) patients with predominantly methane producing bacteria have a significant decrease in gastrointestinal transit compared with hydrogen producers. Antibiotic eradication of bacterial overgrowth in IBS dominant hydrogen producers results in symptomatic relief from diarrhea suggesting H2 producing bacteria induced hypercontractility. Interestingly, the ability of the colonic flora to metabolize hydrogen has been suggested to be important in preventing the untoward effects during hydreliox diving.
Recently, it has been reported that inhaled hydrogen gas has antioxidant and antiapoptotic properties that can protect the brain and liver against ischemia/reperfusion (I/R) injury by selectively neutralizing hydroxyl radicals. I/R injury of the intestine occurs in a variety of clinical settings such as mesenteric artery occlusion, hypovolemic shock and small intestinal transplantation (SITx)). The ischemic intestine can be a major source of proinflammatory mediators that enhances not only local intestinal injury and dysfunction, but also the systemic inflammatory response leading to multiple organ failure. Although various mechanisms leading to intestinal dysfunction after I/R injury have been proposed, reactive radicals undoubtedly play a key role. Superoxide anion (·O2−) radicals are generated in mitochondria by electron transport chain leakage and produced by metabolic oxidases. The excessive generation of ·O2− radicals drives the production of H2O2 and subsequently hydroxyl radicals (OH·) via the Fenton reaction. OH· are the strongest of the oxidant species and react indiscriminately peroxidizing membrane lipids, oxidizing DNA and denaturing proteins