Hancox Thomas P M, Skene Debra J, Dallmann Robert, Dunn Warwick B
School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
Chronobiology, Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7XH, UK.
Metabolites. 2021 May 19;11(5):328. doi: 10.3390/metabo11050328.
The past decade has seen a large influx of work investigating time of day variation in different human biofluid and tissue metabolomes. The driver of this daily variation can be endogenous circadian rhythms driven by the central and/or peripheral clocks, or exogenous diurnal rhythms driven by behavioural and environmental cycles, which manifest as regular 24 h cycles of metabolite concentrations. This review, of all published studies to date, establishes the extent of daily variation with regard to the number and identity of 'rhythmic' metabolites observed in blood, saliva, urine, breath, and skeletal muscle. The probable sources driving such variation, in addition to what metabolite classes are most susceptible in adhering to or uncoupling from such cycles is described in addition to a compiled list of common rhythmic metabolites. The reviewed studies show that the metabolome undergoes significant time of day variation, primarily observed for amino acids and multiple lipid classes. Such 24 h rhythms, driven by various factors discussed herein, are an additional source of intra/inter-individual variation and are thus highly pertinent to all studies applying untargeted and targeted metabolomics platforms, particularly for the construction of biomarker panels. The potential implications are discussed alongside proposed minimum reporting criteria suggested to acknowledge time of day variation as a potential influence of results and to facilitate improved reproducibility.
在过去十年中，大量研究致力于探究不同人体生物流体和组织代谢组的日变化规律。这种每日变化的驱动因素可能是由中枢和/或外周生物钟驱动的内源性昼夜节律，也可能是由行为和环境周期驱动的外源性昼夜节律，它们表现为代谢物浓度的规律24小时循环。这篇综述涵盖了迄今为止所有已发表的研究，确定了在血液、唾液、尿液、呼吸和骨骼肌中观察到的“节律性”代谢物的数量和种类方面的每日变化程度。除了列出常见的节律性代谢物清单外，还描述了驱动这种变化的可能来源，以及哪些代谢物类别最容易遵循或脱离这些周期。综述研究表明，代谢组会经历显著的日变化，主要体现在氨基酸和多种脂质类别上。由本文讨论的各种因素驱动的这种24小时节律，是个体内/个体间变异的另一个来源，因此与所有应用非靶向和靶向代谢组学平台的研究高度相关，特别是对于生物标志物面板的构建。文中还讨论了潜在影响，并提出了建议的最低报告标准，以承认日变化是结果的潜在影响因素，并促进提高可重复性。
