Introduction

Saliva metabolites are suggested to reflect the health status of an individual in humans. The same could be true with the dog (Canis lupus familiaris), an important animal model of human disease, but its saliva metabolome is unknown. As a non-invasive sample, canine saliva could offer a new alternative material for research to reveal molecular mechanisms of different (patho)physiological stages, and for veterinary medicine to monitor dogs’ health trajectories.

Objectives

To investigate and characterize the metabolite composition of dog and human saliva in a non-targeted manner.

Methods

Stimulated saliva was collected from 13 privately-owned dogs and from 14 human individuals. We used a non-targeted ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-qTOF-MS) method to measure metabolite profiles from saliva samples.

Results

We identified and classified a total of 211 endogenous and exogenous salivary metabolites. The compounds included amino acids, amino acid derivatives, biogenic amines, nucleic acid subunits, lipids, organic acids, small peptides as well as other metabolites, like metabolic waste molecules and other chemicals. Our results reveal a distinct metabolite profile of dog and human saliva as 25 lipid compounds were identified only in canine saliva and eight dipeptides only in human saliva. In addition, we observed large variation in ion abundance within and between the identified saliva metabolites in dog and human.

Conclusion

The results suggest that non-targeted metabolomics approach utilizing UHPLC-qTOF-MS can detect a wide range of small compounds in dog and human saliva with partially overlapping metabolite composition. The identified metabolites indicate that canine saliva is potentially a versatile material for the discovery of biomarkers for dog welfare. However, this profile is not complete, and dog saliva needs to be investigated in the future with other analytical platforms to characterize the whole canine saliva metabolome. Furthermore, the detailed comparison of human and dog saliva composition needs to be conducted with harmonized study design.

中文翻译：

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犬和​​人唾液的代谢组：非靶向代谢组学研究。

介绍

建议唾液代谢物反映人的健康状况。狗（犬天狼疮）是人类疾病的重要动物模型，情况同样如此，但其唾液代谢组未知。犬唾液作为一种非侵入性样本，可以为研究揭示不同（病理）生理阶段的分子机制以及兽医监测狗的健康轨迹提供新的替代材料。

目标

以非靶向方式研究和表征狗和人唾液的代谢产物组成。

方法

从13只私人狗和14个人身上收集受刺激的唾液。我们使用了非目标超高效液相色谱-四极杆飞行时间质谱（UHPLC-qTOF-MS）方法来测量唾液样品中的代谢物谱。

结果

我们鉴定并分类了总共211种内源性和外源性唾液代谢物。这些化合物包括氨基酸，氨基酸衍生物，生物胺，核酸亚基，脂质，有机酸，小肽以及其他代谢产物，例如代谢废物分子和其他化学物质。我们的结果揭示了狗和人唾液的独特代谢产物特征，因为仅在犬唾液中鉴定出25种脂质化合物，仅在人唾液中鉴定出8种二肽。此外，我们观察到狗和人的唾液代谢产物内和之间的离子丰度存在很大差异。

结论

结果表明，利用UHPLC-qTOF-MS进行的非靶向代谢组学方法可以检测出狗和人唾液中部分重叠的代谢物组成的多种小化合物。鉴定出的代谢物表明，犬唾液可能是发现用于狗福利的生物标志物的通用材料。但是，这种情况并不完整，将来需要使用其他分析平台对狗唾液进行研究，以表征整个犬唾液的代谢组。此外，需要通过统一的研究设计对人和狗唾液成分进行详细比较。