Postmortem Stability Analysis of Lipids and Polar Metabolites in Human, Rat, and Mouse Brains

Lipids and polar metabolites are emerging as promising indicators of the brain's molecular phenotype in both clinical and fundamental research. However, the impact of postmortem delay on these compounds, unavoidable in human brain studies, remains insufficiently understood. In this study, we examined the postmortem stability of lipids and polar metabolites over a 48-h interval in the brains of three species: humans, rats, and mice. We show that the abundance levels of 23% of the 867 studied lipids and 75% of the 104 studied polar metabolites were affected significantly by postmortem delay in at least one species. The postmortem effects correlated positively and significantly among the species, while showing an approximately tenfold slower rate in humans compared to rodents. The only exception to the postmortem rates deceleration was a group of oxidized fatty acids, which accumulated at similar speed in both humans and rodents. These findings provide valuable insights for improving reproducibility and refining the interpretation of human and rodent brain lipidome and metabolome data in future studies.