Protective roles of inorganic nitrate in health and diseases

Abstract Various beneficial biological activities of inorganic nitrate have been revealed in recent decades. Oral bacteria can reduce nitrate to nitrite, which is further reduced to nitric oxide (NO) in the body; this process is known as the nitrate-nitrite-NO pathway. Sialin is a mammalian membrane nitrate transporter that transports nitrate to the salivary glands and secretes it into the oral cavity through the saliva. Recent studies have indicated that nitrate has a protective effect on the salivary glands and other organs by regulating the expression of sialin and maintaining microbial homeostasis. Through the nitrate-nitrite-NO pathway, nitrate can act as a reservoir of NO in vivo and perform a variety of NO-like bioactivities, such as promoting exercise performance, protecting the digestive system, lowering blood pressure, and assisting in tumor treatment. This paper reviews the sources, functions, and possible mechanisms of inorganic nitrate, and discusses the protective role that nitrate promises to play in health and diseases.