Biomarker profiling of postmortem blood for diabetes mellitus and discussion of possible applications of metabolomics for forensic casework

Acute metabolic disorders of diabetes mellitus (DM), such as diabetic ketoacidosis, hyperosmolar hyperglycemic state, and hypoglycemia, are life-threatening and difficult to diagnose postmortem owing to lack of macroscopic and microscopic findings, especially when the medical history of the patient is not available before autopsy. Although various biochemical tests, including ketone bodies and hemoglobin A1c, have been used to diagnose diabetes in the postmortem setting, each marker has some limitations. Consequently, it would be helpful in forensic practice to find new biomarkers reflecting the decedent’s history of DM irrespective of whether the DM was being treated. Metabolomics enables the non-targeting analysis of biomarkers, and metabolomics was performed on postmortem blood from decedents with and without a DM history to determine whether a marker reflecting DM could be identified. The statistical analysis, including primary component analysis, presented a potent set of metabolites that could be used for the forensic diagnosis of DM. Qualitative analysis revealed significantly lower sphingomyelin and plasmalogen lipid levels and higher lysophospholipid levels in the DM group. Meanwhile, some discrepancies in the levels of some classes of phospholipids were noted between samples from living and deceased persons. This suggests that further metabolomics using postmortem samples rather than living persons’ samples is required to identify markers that can be used for forensic diagnosis.