Department of Sport and Health Sciences, University of Exeter, Exeter, UNITED KINGDOM.
Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO.
Med Sci Sports Exerc. 2021 Feb 1;53(2):280-294. doi: 10.1249/MSS.0000000000002470.
Nitric oxide (NO) is a gaseous signaling molecule that plays an important role in myriad physiological processes, including the regulation of vascular tone, neurotransmission, mitochondrial respiration, and skeletal muscle contractile function. NO may be produced via the canonical NO synthase-catalyzed oxidation of l-arginine and also by the sequential reduction of nitrate to nitrite and then NO. The body's nitrate stores can be augmented by the ingestion of nitrate-rich foods (primarily green leafy vegetables). NO bioavailability is greatly enhanced by the activity of bacteria residing in the mouth, which reduce nitrate to nitrite, thereby increasing the concentration of circulating nitrite, which can be reduced further to NO in regions of low oxygen availability. Recent investigations have focused on promoting this nitrate-nitrite-NO pathway to positively affect indices of cardiovascular health and exercise tolerance. It has been reported that dietary nitrate supplementation with beetroot juice lowers blood pressure in hypertensive patients, and sodium nitrite supplementation improves vascular endothelial function and reduces the stiffening of large elastic arteries in older humans. Nitrate supplementation has also been shown to enhance skeletal muscle function and to improve exercise performance in some circumstances. Recently, it has been established that nitrate concentration in skeletal muscle is much higher than that in blood and that muscle nitrate stores are exquisitely sensitive to dietary nitrate supplementation and deprivation. In this review, we consider the possibility that nitrate represents an essential storage form of NO and discuss the integrated function of the oral microbiome, circulation, and skeletal muscle in nitrate-nitrite-NO metabolism, as well as the practical relevance for health and performance.
一氧化氮（NO）是一种气态信号分子，在许多生理过程中发挥着重要作用，包括调节血管张力、神经递质传递、线粒体呼吸和骨骼肌收缩功能。NO 可以通过经典的一氧化氮合酶催化氧化 l-精氨酸产生，也可以通过硝酸盐依次还原为亚硝酸盐，然后再还原为 NO。通过摄入富含硝酸盐的食物（主要是绿叶蔬菜）可以增加体内的硝酸盐储存。存在于口腔中的细菌的活性大大增强了 NO 的生物利用度，它们将硝酸盐还原为亚硝酸盐，从而增加了循环中亚硝酸盐的浓度，在低氧供应区域，亚硝酸盐可以进一步还原为 NO。最近的研究集中在促进这种硝酸盐-亚硝酸盐-NO 途径，以积极影响心血管健康和运动耐量的指数。有报道称，甜菜根汁中的膳食硝酸盐补充可降低高血压患者的血压，亚硝酸盐补充可改善血管内皮功能，并减少老年人大动脉的僵硬。硝酸盐补充还被证明可以增强骨骼肌功能，并在某些情况下提高运动表现。最近，已经确定骨骼肌中的硝酸盐浓度远高于血液中的浓度，并且肌肉中的硝酸盐储存对膳食硝酸盐的补充和剥夺非常敏感。在这篇综述中，我们考虑了硝酸盐可能代表 NO 的一种必需储存形式的可能性，并讨论了口腔微生物组、循环和骨骼肌在硝酸盐-亚硝酸盐-NO 代谢中的综合功能，以及对健康和表现的实际意义。
