Nitric oxide formation in the metabolism of nitrates in the oral cavity

Abstract

Nowadays, nitric oxide is recognized as a regulator of important vascular and metabolic functions. Nitric oxide is formed in the endothelium by converting essential amino acid L-arginine to L-citrulline with the participation of constitutional endothelial nitric oxide synthase. In addition to endogenous pathway of formation, dietary nitrate contributes to the nitric oxide generation through the successive stages (NO 3 -NO 2 -NO) mediated by salivary glands and bacteria of the oral cavity. Purpose of the research – to demonstrate modern scientific data focused on a role of salivary glands and bacteria in nitrates metabolism and maintenance of nitric oxide homeostasis. Results of the studies show that in the oral cavity, there are synanthropic facultative anaerobic bacteria which possess nitrate reductase enzymes and reduce nitrates to nitrites. In the acidic environment of the stomach, nitrites undergo non-enzymatic disproportionation, followed by the formation of nitric oxide and other nitrogen compounds which are involved in the regulation of important biological functions. Dietary nitrites and nitrates can be rapidly absorbed from the upper gastrointestinal tract into the systemic bloodstream and serve as effective donors of nitric oxide in a case of physiological hypoxia. This mechanism of nitric oxide formation is called “enterosalivary nitrate-nitrite-nitric oxide pathway”. The review presents a cardioprotective effect of regular consumption of dietary nitrate-rich products. Diagnostic markers of nitric oxide metabolism in the oral fluid are shown. Comclusions. Based on the scientific data, it was concluded that dietary nitrate and bacteria of the oral cavity play a significant role in the synthesis of NO by enzymatic conversion. Regular intake of dietary nitrate-rich products is able to provide a systemic and local vasodilating effect through enterosalivary pathway and conversion of nitrite to nitric oxide.