Analyzing Post-Mortem Changes of Metabolites by NMR

分析NMR代谢物的验尸变化提供了准确可靠的死亡时间

Forensic science is a key tool in courts of law; it provides scientific evidence that can be crucial in achieving a conviction or acquittal. The evidence it can provide includes fingerprint identification, DNA profiling, blood stain pattern analysis, and time of death or the post-mortem interval (PMI).
在这些技术中，PMI间隔通常是最常执行的，因此可以被认为是最重要的。有几种用于确定PMI的方法：身体的身体变化（包括体温，肌肉刚度和降低）；DNA降解；法医昆虫学；和碳约会。分析人体的身体变化可在死后几个小时内准确可靠的PMI计算，而其他技术是死亡后数周最准确的。当前没有任何方法可以在两者之间提供准确可靠的PMI数据；从几个小时到几周。

代谢组学显示了PMI估计的希望
最近，代谢组学在PMI估计中表现出了填补这一空白的希望。该技术可以分析有机体中系统的整个组件，从而可以监测体液中代谢产物的后变化。理想情况下，这些变化将在死亡后相对较长的时间内线性发生，以获得准确可靠的数据。因此，正在进行研究，以确定满足这些要求的最合适的体液中最有希望的代谢产物。

Many initial studies have identified metabolic changes in a range of bodily fluids, but recent work on animal models has indicated that eye fluids, the aqueous humor (AH) and vitreous humor (VH), are most beneficial for PMI assessment. These fluids are anatomically isolated compared to other bodily fluids, such as blood, and therefore have slower changes to metabolites, making measurements more reliable.

最近，俄罗斯的国际断层扫描中心和Novosibirsk区域临床医学临床局的一群研究人员着手确定这些眼液在人类PMI估计中是否也表现出希望，并确定最有希望的代谢物作为生物标志物用作生物标志物对于此分析。
Metabolite Biomarkers Were Identified Using a Bruker Avance III NMR Spectrometer
该小组从不同PMI的人尸体中收集了血液，AH和VH，并处理这些样品以获得血浆，无蛋白质的AH蛋白质提取物和VH的无脂肪提取物。这些样品的定性代谢组分析是通过Bruker Biospin Avance III HD 700 MHz NMR光谱仪通过核磁共振（NMR）进行的。

从这些数据中，在所有三个样品中总共确定了42个代谢产物。在该样品集中，有六个表现出与PMI的强阳性线性相关性，其中所有体液：低黄嘌呤，胆碱，肌酸，甜菜碱，谷氨酸和甘氨酸。

The change in metabolite concentration was slower and smoother in the AH and VH compared to the blood, where the metabolite concentrations were more haphazard. These data support the metabolomic analysis of previous animal studies, and therefore, it was concluded that the AH and VH were more suitable for PMI.
Of the two ocular fluids, the strongest positive linear correlation between PMI and metabolite concentration was found in the VH. This trend is thought to be because the VH has a higher viscosity and is more isolated from the vascular system than the AH. However, there is a lower risk of blood contamination during AH sampling, reducing the risk of experimental errors, and sample preparation is more straightforward as it contains very low levels of proteins and lipids.

多个生物标志物分析提高了PMI估计的准确性
To date, the majority of research publications in this area have focused on using one metabolite as the biomarker for PMI estimation. However, this study identified six metabolites that had the potential for use as PMI biomarkers. Therefore, the researchers also performed metabolomic analysis using multiple metabolites.
与PMI具有最强正相关的代谢产物是AH，肌酸和Betaine的VH肌酸，胆碱和甜菜碱。这2-3个生物标志物的组合能够显着减少PMI评估中的错误。有趣的是，没有发现使用三种以上的代谢产物会影响进一步提高PMI估计的准确性。

Summary
这项研究证实了动物数据，表明与血浆相比，由于解剖学上孤立的液体更适合PMI估计，这是由于较慢且更平滑的代谢变化。AH和VH都提供了准确可靠的信息，虽然VH数据更准确，但AH易于污染的机会易于制备。

由于几种代谢产物（低黄嘌呤，胆碱，肌酸，甜菜碱，谷氨酸和甘氨酸）提供与PMI的阳性线性相关性，作者建议在执行此分析时使用这些生物标志物中的几种，以提高准确性，可靠性，并最小化，并最小化并最小化这些生物标志物PMI估计的错误。

法医的全面解决方案投资组合
布鲁克（Bruker）提供了最全面的解决方案组合，用于法医分析。这包括对麻醉品和掺杂剂的识别和量化，化学战代理，爆炸物的特征，食品欺诈的检测，艺术和文件伪造，环境取证，包括废物分析和犯罪现场调查，例如玻璃，纤维和枪支残留物分析。Bruker的技术适用于日常的常规分析，并在本研究中开发和增强新方法。我们使执法能够为法律程序生成连贯和强大的数据的使命将使社会更安全。

References
1. Zelentsova, E., A., et al. (2020). Post-Mortem Changes in Metabolomic Profiles of Human Serum, Aqueous Humor and Vitreous Humor. Metabolomics. https://doi.org/10.1007/s11306-020-01700-3.