The reduction of nitrate to nitrite by the oral microbiota has been proposed to be important for oral health and results in nitric oxide formation that can improve cardiometabolic conditions. Studies of bacterial composition in subgingival plaque suggest that nitrate-reducing bacteria are associated with periodontal health, but the impact of periodontitis on nitrate-reducing capacity (NRC) and, therefore, nitric oxide availability has not been evaluated. The current study aimed to evaluate how periodontitis affects the NRC of the oral microbiota. First, 16S rRNA sequencing data from five different countries were analyzed, revealing that nitrate-reducing bacteria were significantly lower in subgingival plaque of periodontitis patients compared with healthy individuals (P < 0.05 in all five datasets with n = 20–82 samples per dataset). Secondly, subgingival plaque, saliva, and plasma samples were obtained from 42 periodontitis patients before and after periodontal treatment. The oral NRC was determined in vitro by incubating saliva with 8 mmol/L nitrate (a concentration found in saliva after nitrate-rich vegetable intake) and compared with the NRC of 15 healthy individuals. Salivary NRC was found to be diminished in periodontal patients before treatment (P < 0.05) but recovered to healthy levels 90 days post-treatment. Additionally, the subgingival levels of nitrate-reducing bacteria increased after treatment and correlated negatively with periodontitis-associated bacteria (P < 0.01). No significant effect of periodontal treatment on the baseline saliva and plasma nitrate and nitrite levels was found, indicating that differences in the NRC may only be revealed after nitrate intake. Our results suggest that an impaired NRC in periodontitis could limit dietary nitrate-derived nitric oxide levels, and the effect on systemic health should be explored in future studies.

口腔微生物群将硝酸盐还原为亚硝酸盐对于口腔健康很重要，并导致一氧化氮的形成，从而改善心脏代谢状况。对龈下菌斑中细菌组成的研究表明，硝酸盐还原菌与牙周健康有关，但牙周炎对硝酸盐还原能力（NRC）以及一氧化氮可用性的影响尚未得到评估。目前的研究旨在评估牙周炎如何影响口腔微生物群的 NRC。首先，对来自五个不同国家的16S rRNA测序数据进行了分析，结果表明，与健康个体相比，牙周炎患者龈下菌斑中的硝酸盐还原菌含量显着较低（ 所有五个数据集中的P < 0.05，每个数据集n  = 20-82个样本） 。其次，采集了42名牙周炎患者牙周治疗前后的龈下菌斑、唾液和血浆样本。通过将唾液与 8 mmol/L 硝酸盐（摄入富含硝酸盐的蔬菜后在唾液中发现的浓度）一起孵育，在体外测定口腔 NRC，并与 15 名健康个体的 NRC 进行比较。研究发现，牙周患者在治疗前唾液 NRC 有所减少（P  < 0.05），但在治疗后 90 天恢复到健康水平。此外，治疗后龈下硝酸盐还原菌水平升高，且与牙周炎相关细菌呈负相关（P  < 0.01）。没有发现牙周治疗对基线唾液和血浆硝酸盐和亚硝酸盐水平有显着影响，这表明 NRC 的差异可能只有在摄入硝酸盐后才会显现出来。我们的研究结果表明，牙周炎中 NRC 受损可能会限制饮食中硝酸盐衍生的一氧化氮水平，并且应在未来的研究中探讨其对全身健康的影响。