# Examination of Postmortem \(\beta\)-Hydrobutyrate Increase in Forensic Autopsy Cases
## 4 Discussion  
The results showed the possibility that BHB values could increase when associated with prolonged PMI. The robustness of these findings is supported by the concordant results of both the [PERSON]'s and [PERSON]'s tests. Additionally, the result of the [PERSON]'s rank sum test of Group 4 revealed that the BHB values in the PMI of the \(>\)1-week group were higher than those in the PMI of the \(\leq\)1-week group. This corroborated with the previous findings, which showed that postmortem BHB values were associated with PMI. On the basis of our results, postmortem production of BHB likely occurs, during the postmortem phase. It is known that ketone bodies are produced by the conversion of  
Figure 1: (**a**) Bar graph of the log-transformed BHB values with an error bar as the result of [PERSON]’s test. The error bar depicts the standard error. (**b**) Boxplot graph of the BHB values as the result of the [PERSON]’s test. Both tests showed the tendency that longer PMI groups result in higher BHB values. The significant differences between Group 1 and Group 3, as well as Group 1 and Group 4, were confirmed by both tests. * means statistical significance (\(p<0.05\)). BHB, \(\beta\)-hydroxybutyrate. Figure 2: Comparison of BHB values between the PMI of \(\leq\)1-week and \(>\)1-week groups. The median values are significantly higher in the PMI of the \(>\)1-week group than in the PMI of the \(\leq\)1-week group. * means statistical significance (\(p<0.05\)). BHB; \(\beta\)-hydroxybutyrate. fatty acids mainly in the mitochondria of the liver [31; 32; 33]. Ketogenesis, the pathway of producing three ketone bodies, is activated in the low energetic state. Carnite palmitoyl-transferase transports fatty acids to the mitochondria, and fatty acids are converted into acetyl-CoA. Thiolase synthesizes two acetyl-CoA into acetoacetyl-CoA. Then, HMG-CoA synthase converts acetoacetyl-CoA into HMG-CoA. Acetoacetate is generated from HMG-CoA by HMG-CoA lyase. In the situations in that D-\(\beta\)-hydroxybutyrate dehydrogenase exists, acetoacetate is converted into BHB. Conversely, if nonenzymatic decarboxylation occurs, acetoacetate converts into acetone [34]. Our bodies can use BHB and acetoacetate as alternative energies. Since they have water solubility, they can be transported to other organs even the brain. In the organs where they arrive, \(\beta\)-hydroxybutyrate dehydrogenase converts BHB into acetoacetate, and \(\beta\)-ketoacyl-CoA converts acetoacetate into acetyl-CoA, respectively. Then, acetyl-CoA is used in the citric acid cycle [34]. The citric acid cycle starts from acetyl-CoA and releases energy [35; 36]. Clinically, death is defined as respiratory, cardiac, or neurologic arrest [37]. However, this does not necessarily mean the death of other organs or tissues. For example, there is a report about skeletal muscle stem cells. In the study, researchers performed a biopsy on cadavers, and they confirmed that some skeletal myogenic cells were alive and functional [38]. Furthermore, researchers succeeded in the culture of brain tissues which they obtained from autopsy cases [39]. Since dead cells cannot be cultured, the result showed a possibility that some of the brain cells were alive at the time of the autopsy. Recently, even the gene that activated after death was examined [40]. This gene keeps active for a few days after organ death. On the basis of these facts, we built a hypothesis that following the arrest of the respiratory and cardiac systems, hepatic cells become severely hypoxic or ischemic, which might result in ketone body production [29]. To the best of our knowledge, only one study has demonstrated postmortem BHB level changes [26]. That study measured BHB levels from the time of death until 49 h and showed an increase in BHB levels with the intragroup analysis. Although a significant difference was confirmed in the prolonged-PMI cases, it was not confirmed in the short-PMI cases of that study. Our results showed the same tendency.