分析NMR代谢物的验尸变化Provides Accurate and Reliable Time of Death
法医科学是法院中的关键工具；它提供了科学证据，这对于实现定罪或无罪释放至关重要。它可以提供的证据包括指纹识别，DNA分析，血液染色模式分析以及死亡时间或验尸间隔（PMI）。
Of these techniques, the PMI interval is generally performed the most often and can therefore be considered the most important. There are several methods used for the determination of the PMI: the physical changes of the body (including body temperature, muscle stiffness, and hypostasis); DNA degradation; forensic entomology; and carbon dating. Analyzing the physical changes of the body gives accurate and reliable PMI calculations for several hours after death, while the other techniques are most accurate weeks to years after death. There is currently no method that can provide accurate and reliable PMI data for the period in between; from several hours to several weeks.
Metabolomics Shows Promise for PMI Estimation
Recently, metabolomics has shown promise to fill this gap in PMI estimation. The technique can analyze the entire components of a system in an organism, allowing the post-mortem changes of metabolites in bodily fluids to be monitored. Ideally, these changes would occur linearly for a relatively long period of time after death for accurate and reliable data to be obtained. Therefore, research is underway to identify the most promising metabolites in the most suitable bodily fluid that meet these requirements.
许多初步研究已经确定了一系列体液的代谢变化，但最近在动物模型上的工作表明，眼睛流体，水性幽默（AH）和玻璃体幽默（VH）对PMI评估最有益。与其他体液（例如血液）相比，这些液体在解剖学上是分离的，因此对代谢产物的变化较慢，从而使测量更可靠。
Recently, a group of researchers at the International Tomography Center and Novosibirsk Regional Clinical Bureau of Forensic Medicine, in Russia, set out to determine whether these ocular fluids also show promise in human PMI estimation, and to identify the most promising metabolites for use as biomarkers for this analysis.
使用Bruker Avance III NMR光谱仪鉴定代谢物生物标志物
The team collected blood, AH, and VH from human cadavers at different PMIs and processed these samples to obtain blood plasma, protein-free extracts of AH, and lipid-free extracts of VH. Qualitative metabolomic profiling of these samples was performed by nuclear magnetic resonance (NMR) using a Bruker Biospin Avance III HD 700 MHz NMR spectrometer.
From these data, a total of 42 metabolites were identified in all three samples. Of this sample set, six demonstrated strong positive linear correlation with PMI across all bodily fluids: hypoxanthine, choline, creatine, betaine, glutamate, and glycine.
与血液相比，在AH和VH中，代谢物浓度的变化较慢，更光滑，在该血液中，代谢物浓度更随意。这些数据支持先前动物研究的代谢组分分析，因此得出结论，AH和VH更适合PMI。
在两种眼液中，在VH中发现了PMI和代谢物浓度之间最强的正线性相关性。这种趋势被认为是因为VH具有更高的粘度，并且与AH相比，与血管系统更孤立。但是，在AH采样期间，血液污染的风险较低，降低了实验错误的风险，并且样品制备更为简单，因为它含有非常低的蛋白质和脂质。
Multiple Biomarker Analysis Improves the Accuracy of PMI Estimation
迄今为止，该领域的大多数研究出版物都集中在使用一种代谢物作为PMI估计的生物标志物。但是，这项研究确定了有可能用作PMI生物标志物的六个代谢产物。因此，研究人员还使用多个代谢物进行了代谢组学分析。
The metabolites with the strongest positive correlation with PMI were creatine, choline, and betaine for the AH and creatine and betaine for the VH. The combination of these 2–3 biomarkers was able to significantly reduce the errors in the PMI assessment. Interestingly, the use of more than three metabolites was not found to influence further improving the accuracy of PMI estimation.
概括
This research corroborates animal data, indicating that anatomically isolated fluids are more suitable for PMI estimation, in comparison to blood plasma, due to the slower and smoother metabolic changes. Both the AH and the VH provide accurate and reliable information, and while the VH data is more accurate, the AH is easier to prepare with a lower chance of contamination.
Due to several metabolites (hypoxanthine, choline, creatine, betaine, glutamate, and glycine) providing a positive, linear correlation with PMI, the authors propose that several of these biomarkers should be used when performing this analysis to improve accuracy, reliability, and minimize errors for PMI estimation.
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参考
1. Zelentsova，E.，A。等。（2020）。人血清，水性幽默和玻璃体幽默的代谢组谱发生后变化。代谢组学。https://doi.org/10.1007/s11306-020-01700-3。
