Examining heat treatment for stabilization of the lipidome

Aim: To confidently determine lipid-based biomarkers, it is important to minimize variation introduced during preanalytical steps. We evaluated reducing variation associated with lipid measurements in invertebrate sentinel species using a state-of-the-art heat treatment technique. Materials and Methods: Earthworms (Eisenia fetida), house crickets (Acheta domestica) and ghost shrimp (Palaemonetes paludosus) were euthanized either by flash freezing or heat treatment. For both experiments, samples were either immediately extracted after removal from -80 degrees C storage or incubated on ice for one hour prior to sample weighing and extraction. Lipidomics was performed on resulting extracts using liquid chromatography high resolution tandem mass spectrometry. LipidMatch and LipidSearch were used for lipid identification. Results: Lipid enzymatic products (e.g., phosphatidylmethanols, diglycerides, lysoglycerophospholipids and ether-linked/oxidized lysoglycerophospholipids), were in higher concentrations in flash-frozen samples, when compared with heat-treated samples. Results suggest that heat treatment reduces phospholipase A and phospholipase D activity. Conclusion: Heat treatment reduced enzymatic products and increased precursors of these enzymatic products. We believe heat treatment warrants a closer interrogation for improving the robustness of lipid biomarker research, especially in tissue samples, where enzyme stabilizers are difficult to apply, and for use in field studies, where the stabilization of the collected sample is critical.