Estimation of PMI depends on the changes in ATP and its degradation products

[Characteristics of histochemical, molecular genetic and radiation-induced liver changes depending on the postmortem interval]

The aim of this study is to analyze literature data on postmortem changes in the liver and their use in determination of postmortem interval. Biological death expectedly causes the development of postmortem disorders not only in the liver structure, but also changes in its biochemical and histochemical parameters. Literature data about changes of histochemical, immunohistochemical and biomolecular characteristics of liver tissue, as well as bacterial migration to the liver depending on the duration of postmortem period, are presented. The effectiveness of radiology for visualization of postmortem changes and, accordingly, for determining the postmortem interval is noted.

In Vitro Animal Model for Estimating the Time since Death with Attention to Early Postmortem Stage

Estimating the postmortem interval (PMI) has remained the subject of investigations in forensic medicine for many years. Every kind of death results in changes in metabolites in body tissues and fluids due to lack of oxygen, altered circulation, enzymatic reactions, cellular degradation, and cessation of anabolic production of metabolites. Metabolic changes may provide markers determining the time since death, which is challenging in current analytical and observation-based methods. The study includes metabolomics analysis of blood with the use of an animal model to determine the biochemical changes following death. LC-MS is used to fingerprint postmortem porcine blood. Metabolites, significantly changing in blood after death, are selected and identified using univariate statistics. Fifty-one significant metabolites are found to help estimate the time since death in the early postmortem stage. Hypoxanthine, lactic acid, histidine, and lysophosphatidic acids are found as the most promising markers in estimating an early postmortem stage. Selected lysophosphatidylcholines are also found as significantly increased in blood with postmortal time, but their practical utility as PMI indicators can be limited due to a relatively low increasing rate. The findings demonstrate the great potential of LC-MS-based metabolomics in determining the PMI due to sudden death and provide an experimental basis for applying this attitude in investigating various mechanisms of death. As we assume, our study is also one of the first in which the porcine animal model is used to establish PMI metabolomics biomarkers.

Early postmortem biochemical, histological, and immunohistochemical alterations in skeletal muscles of rats exposed to boldenone undecylenate: Forensic implication

This study investigated the biochemical and histopathological alterations along with the immunoexpression pattern of heat shock protein 27 (Hsp27) within 6 h postmortem (PM) in skeletal muscle of boldenone (BOL)-treated rats. Forty-eight male rats were divided into two groups; a control group received sesame oil (0.25 mL/kg bwt), and BOL group received 5 mg/kg bwt BOL. Both treatments were intramuscularly injected once a week for eight weeks. Rats were euthanized by cervical dislocation, and the skeletal muscle specimens were collected at zero-time, 2, 4, and 6 h PM for biochemical and histopathological evaluations. The results revealed that BOL treatment significantly increased pH, MDA, ATP, ADP, glycogen, and hydroxyproline values. Still, it decreased the GPX, GST, and lactic acid levels, and Hsp27 immunoexpression compared to the control group. With increasing postmortem interval (PMI), whether control or BOL-treated, a significant reduction in pH value, markers of muscular antioxidant status, ATP, ADP, glycogen, hydroxyproline levels, as well as Hsp27 immunoexpression but a significant increase in lipid peroxidation and lactic acid content were recorded. Of note, the interaction between BOL treatment and PMI had a significant effect on ATP, ADP, lactic acid, hydroxyproline, GST, MDA, and TAC levels. Conclusively, these findings signify BOL exposure's modifying effect on the energy content, oxidative status, and histological architecture of skeletal muscles in the early PMI that reflected in delaying the onset of rigor mortis. For forensic practitioners, these findings should be highly considered at estimating PMI in athletic, AAS-treated patients, and fattening animals.

Applications of Metabolomics in Forensic Toxicology and Forensic Medicine

Forensic toxicology and forensic medicine are unique among all other medical fields because of their essential legal impact, especially in civil and criminal cases. New high-throughput technologies, borrowed from chemistry and physics, have proven that metabolomics, the youngest of the “omics sciences”, could be one of the most powerful tools for monitoring changes in forensic disciplines. Metabolomics is a particular method that allows for the measurement of metabolic changes in a multicellular system using two different approaches: targeted and untargeted. Targeted studies are focused on a known number of defined metabolites. Untargeted metabolomics aims to capture all metabolites present in a sample. Different statistical approaches (e.g., uni- or multivariate statistics, machine learning) can be applied to extract useful and important information in both cases. This review aims to describe the role of metabolomics in forensic toxicology and in forensic medicine.

New contributions to the relationship between sequential changes of ATP-related metabolites and post-mortem interval in rats

In recent years, it has become a new research direction to post-mortem interval (PMI) estimation from the changes in metabolite content generated during the process of cadaver corruption, and lead to more and more attention has been paid to the biochemical changes of muscles after death. The ATP degradation process has long been accepted as a precise manner to estimate freshness of meat products in food science. ATP-related metabolites may also serve as an indicator for PMI estimation of corpses. The purpose of this study was to test this possibility. Firstly, this study optimized the detection method of ATP-related metabolites in skeletal muscles of rat. Moreover, in animal experiment, ATP-related metabolites (ATP, ADP, AMP, IMP, Ino, Hx) in lower hind limb skeletal muscles of sixty rats were measured by RP-HPLC at different PMI for 168 h at 20 °C ± 1 °C, the change of freshness indicators (K value, K1 value, K0 value, H value, P value, G value, IMP ratio) were carefully analyzed, and investigate the relationship between them and PMI. The overall results showed that IMP, AMP, Hx, Total metabolites, K value, K1 value, K0 value, H value, P value, G value, and IMP ratio in skeletal muscles changed significantly with PMI (R2 = 0.864-0.971, all P < 0.01) while ATP, ADP, Ino, IMP precursors and IMP degradants had minor changes during the same period (R2 = 0.171-0.706). Specifically, significant linear positive correlations between H value of skeletal muscles and PMI were found, and the coefficients of their regression functions were R2 = 0.971. The correlation between AMP and PMI was slightly lower (R2 = 0.864), but the scope of PMI estimation was the widest (168 h). It can be concluded that the determination of ATP-related metabolites in skeletal muscle may be a potential tool in the PMI estimation. However, more researches on its influencing factors are needed to facilitate its final use in practice.

Postmortomics: The Potential of Untargeted Metabolomics to Highlight Markers for Time Since Death

The success of forensic investigations involving fatalities very often depends on the establishment of the correct timeline of events. Currently used methods for estimating the postmortem interval (PMI) are mostly dependent on the professional and tacit experience of the investigator, and often with poor reliability in the absence of robust biological markers. The aim of this study was to investigate the potential of metabolomic approaches to highlight molecular markers for PMI. Rat and human muscle tissues, collected at various times postmortem, were analyzed using an untargeted metabolomics approach. Levels of certain metabolites (skatole, xanthine, n-acetylneuraminate, 1-methylnicotinamide, choline phosphate, and uracil) as well as most proteinogenic amino acids increased steadily postmortem. Threonine, tyrosine, and lysine show the most predictable evolution over the postmortem period, and may thus have potential for possible PMI markers in the future. This study demonstrates how a biomarker discovery approach can be extended to forensic investigations using untargeted metabolomics.

Upregulation of AMPK Ameliorates Alzheimer's Disease-Like Tau Pathology and Memory Impairment

The studies have shown that 5'-adenosine monophosphate (AMP)-activated protein kinase (AMPK) is involved in Alzheimer's disease (AD) pathology, but the effects of AMPK on AD-like Tau abnormal phosphorylation and its underlying mechanism remains unclear. Herein, we found that the mRNA expression and activity of AMPK are significantly decreased in the brains of the aging C57 mice and 3 × Tg AD mice when compared with their respective control. Moreover, when downregulation of AMPK with AAV-siAMPK-eGFP in the hippocampus CA3 of 3-month-old C57 mice, the mice display AD-like Tau hyperphosphorylation, fear memory impairment, and glycogen synthase kinase-3β (GSK3β) activity increased. On the other hand, there are also AD-like Tau hyperphosphorylation, impairment of fear memory, and AMPK activity decreased in streptozotocin (STZ) mice. Interestingly, AMPK overexpression could efficiently rescue AD-like Tau phosphorylation and brain impairment in STZ mice. Moreover, the activity of GSK3β and the level of Tau phosphorylation (Ser396 and Thr231 sites) were significantly decreased in HEK293 Tau cells transfected by AMPK plasmid or treated with agonists salicylate (SS), but GSK3β agonists Wortmannin (Wort) could ablate AMPK-mediated Tau dephosphorylation. Taken together, the study indicated that AMPK reduces Tau phosphorylation and improves brain function and inhibits GSK3β in AD-like model. These findings proved that AMPK might be a new target for AD in the future.

UV-Vis and ATR-FTIR spectroscopic investigations of postmortem interval based on the changes in rabbit plasma

Estimating PMI is of great importance in forensic investigations. Although many methods are used to estimate the PMI, a few investigations focus on the postmortem redistribution. In this study, ultraviolet-visible (UV-Vis) measurement combined with visual inspection indicated a regular diffusion of hemoglobin into plasma after death showing the redistribution of postmortem components in blood. Thereafter, attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy was used to confirm the variations caused by this phenomenon. First, full-spectrum partial least-squares (PLS) and genetic algorithm combined with PLS (GA-PLS) models were constructed to predict the PMI. The performance of GA-PLS model was better than that of full-spectrum PLS model based on its root mean square error (RMSE) of cross-validation of 3.46 h (R2 = 0.95) and the RMSE of prediction of 3.46 h (R2 = 0.94). The investigation on the similarity of spectra between blood plasma and formed elements also supported the role of redistribution of components in spectral changes in postmortem plasma. These results demonstrated that ATR-FTIR spectroscopy coupled with the advanced mathematical methods could serve as a convenient and reliable tool to study the redistribution of postmortem components and estimate the PMI.

Research progress in the estimation of the postmortem interval by Chinese forensic scholars

The determination of time since death or the postmortem interval (PMI) is one of the most important and frequently asked questions in forensic medicine. Medicolegal scholars and forensic pathologists around the world have studied the estimation of PMI extensively in the past, and many novel methods and advanced technologies have now been applied in the field. For several centuries, Chinese forensic examiners have also worked on the estimation of the PMI, and there are a large number of excellent studies published in Chinese rather than in English, and these are not easily accessible or known internationally. Therefore we have conducted a review of relevant studies published by Chinese forensic scholars in the last few decades. The scope of this review is to provide a concise summary of the current progress in the estimation of PMI by Chinese forensic researchers using molecular biology, spectroscopic technology, entomological methods, energy changes, thanatochemistry and other methods.

The experimental design of postmortem studies: the effect size and statistical power

Purpose

The aim is of this study was to show the poor statistical power of postmortem studies. Further, this study aimed to find an estimate of the effect size for postmortem studies in order to show the importance of this parameter. This can be an aid in performing power analysis to determine a minimal sample size.

Methods

GPower was used to perform calculations on sample size, effect size, and statistical power. The minimal significance (α) and statistical power (1 − β) were set at 0.05 and 0.80 respectively. Calculations were performed for two groups (Student’s t-distribution) and multiple groups (one-way ANOVA; F-distribution).

Results

In this study, an average effect size of 0.46 was found (n = 22; SD = 0.30). Using this value to calculate the statistical power of another group of postmortem studies (n = 5) revealed that the average statistical power of these studies was poor (1 − β < 0.80).

Conclusion

The probability of a type-II error in postmortem studies is considerable. In order to enhance statistical power of postmortem studies, power analysis should be performed in which the effect size found in this study can be used as a guideline.

A preliminary study on postmortem interval estimation of suffocated rats by GC-MS/MS-based plasma metabolic profiling

Estimation of postmortem interval (PMI) is an important goal in judicial autopsy. Although many approaches can estimate PMI through physical findings and biochemical tests, accurate PMI calculation by these conventional methods remains difficult because PMI is readily affected by surrounding conditions, such as ambient temperature and humidity. In this study, Sprague-Dawley (SD) rats (10 weeks) were sacrificed by suffocation, and blood was collected by dissection at various time intervals (0, 3, 6, 12, 24, and 48 h; n = 6) after death. A total of 70 endogenous metabolites were detected in plasma by gas chromatography-tandem mass spectrometry (GC-MS/MS). Each time group was separated from each other on the principal component analysis (PCA) score plot, suggesting that the various endogenous metabolites changed with time after death. To prepare a prediction model of a PMI, a partial least squares (or projection to latent structure, PLS) regression model was constructed using the levels of significantly different metabolites determined by variable importance in the projection (VIP) score and the Kruskal-Wallis test (P < 0.05). Because the constructed PLS regression model could successfully predict each PMI, this model was validated with another validation set (n = 3). In conclusion, plasma metabolic profiling demonstrated its ability to successfully estimate PMI under a certain condition. This result can be considered to be the first step for using the metabolomics method in future forensic casework.

Can early myocardial infarction-related deaths be diagnosed using postmortem urotensin receptor expression levels?

PURPOSE

Myocardial infarction (MI) is one of the most prevalent causes of sudden adult death. It is difficult to diagnose early MI postmortem because there are no typical or characteristic changes in morphology. In this study, changes in the level of the mRNA for the urotensin receptor (UR) were investigated postmortem to determine the suitability of UR as a biomarker for diagnosis of early MI after death.

METHODS

An MI rat model was developed by injecting rats with isoproterenol (ISO) (lethal dose 850 mg/kg) or normal saline (control group). The hearts of rats in the control and ISO-induced MI groups were harvested at 0, 1, 3, 6, 12, 24, 48, and 72 h (h) postmortem. The hearts were then immediately submerged in 1 mL of RNA stabilization solution and stored at 4 °C for <1 week before RNA extraction. Relative UR expression analysis was performed using the StepOne Plus Real Time PCR System with cDNA synthesized from rat heart.

RESULTS

Postmortem UR mRNA expression was higher in the ISO-induced MI group than in the control group, at both 4 and 20 °C, at all of the time points examined except 72 h postmortem (p < 0.0001). The largest increases were observed at ambient temperature and 6 h postmortem.

CONCLUSIONS

Based on our findings, increased postmortem UR expression could serve as a biomarker to aid diagnosis of early MI.