Molecular Medicine Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA.
Clinical Mass Spectrometry Core, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA.
Sci Rep. 2023 Mar 1;13(1):3499. doi: 10.1038/s41598-023-28190-2.
The reduction pathway of nitrate (NO) and nitrite (NO) to nitric oxide (NO) contributes to regulating many physiological processes. To examine the rate and extent of dietary nitrate absorption and its reduction to nitrite, we supplemented rat diets with NaNO-containing water (1 g/L) and collected plasma, urine and several tissue samples. We found that plasma and urine showed 8.8- and 11.7-fold increases respectively in total nitrate concentrations in 1-day supplementation group compared to control. In tissue samples-gluteus, liver and eyes-we found 1.7-, 2.4- and 4.2-fold increases respectively in 1-day supplementation group. These increases remained similar in 3-day supplementation group. LC-MS/MS analysis showed that the augmented nitrate concentrations were primarily from the exogenously provided N-nitrate. Overall nitrite concentrations and percent of N-nitrite were also greatly increased in all samples after nitrate supplementation; eye homogenates showed larger increases compared to gluteus and liver. Moreover, genes related to nitrate transport and reduction (Sialin, CLC and XOR) were upregulated after nitrate supplementation for 3 days in muscle (Sialin 2.3-, CLC1 1.3-, CLC3 2.1-, XOR 2.4-fold) and eye (XOR 1.7-fold) homogenates. These results demonstrate that dietary nitrate is quickly absorbed into circulation and tissues, and it can be reduced to nitrite in tissues (and likely to NO) suggesting that nitrate-enriched diets can be an efficient intervention to enhance nitrite and NO bioavailability.
硝酸盐（NO）和亚硝酸盐（NO）向一氧化氮（NO）的还原途径有助于调节许多生理过程。为了研究膳食硝酸盐的吸收及其还原为亚硝酸盐的速度和程度，我们用含 NaNO 的水（1g/L）补充大鼠饮食，并收集血浆、尿液和几种组织样本。我们发现，与对照组相比，1 天补充组的血浆和尿液中的总硝酸盐浓度分别增加了 8.8 倍和 11.7 倍。在组织样本（臀肌、肝脏和眼睛）中，1 天补充组的硝酸盐浓度分别增加了 1.7 倍、2.4 倍和 4.2 倍。3 天补充组的这些增加仍然相似。LC-MS/MS 分析表明，增加的硝酸盐浓度主要来自外源性提供的 N-硝酸盐。在硝酸盐补充后，所有样本中的亚硝酸盐浓度和 N-亚硝酸盐的百分比也大大增加；与臀肌和肝脏相比，眼睛匀浆显示出更大的增加。此外，在肌肉（Sialin 2.3 倍、CLC1 1.3 倍、CLC3 2.1 倍、XOR 2.4 倍）和眼睛（XOR 1.7 倍）匀浆中，硝酸盐补充 3 天后与硝酸盐转运和还原相关的基因（Sialin、CLC 和 XOR）上调。这些结果表明，膳食硝酸盐很快被吸收到循环和组织中，并且可以在组织中被还原为亚硝酸盐（可能为 NO），这表明富含硝酸盐的饮食可以是一种有效的干预措施，以提高亚硝酸盐和 NO 的生物利用度。
