Blood Sampled Through Dried Blood Spots (DBS) Exhibits DiminishedEx vivo Metabolism Compared to Whole Blood Through Use of a KineticIsotope-Labeling Metabolomics Approach

Blood is the primary matrix for metabolite profiling, providing a means for biomarker identification, pharmacokinetic/ pharmacodynamic analysis and disease monitoring. Conventional methodologies of blood sample collection require blood drawn by venous puncture. However, this technique allows for residual ex vivo metabolic activity of the blood matrix, thus presenting a challenge to capturing a physiologically representative readout of the metabolome. Blood that is not immediately processed is subjected to extended periods of ex vivo metabolism. Even when samples are transported by cold storage, some enzymatic processes remain active. The dried blood spot (DBS) collection technique renders cells metabolically inactive in a short span of time. We demonstrate that whole blood deposited onto a DBS card decreases uptake and metabolism of U13C-glucose after 4 hours, as analyzed by mass spectrometry. The cells also exhibit no further metabolic activity for up to 24 hours, whilst blood stored in a collection tube continue to actively uptake and metabolize U13C-glucose for up to 24 hours post-collection. Given that glycolysis is one of the most active pathways in blood cells, the ability to arrest glucose metabolism in a short amount of time is important to accurately capture the metabolite profile at the time of collection. We assert that this likely extends beyond glucose metabolism, as blood cells are capable of taking up other extracellular nutrients. We believe blood collection using the DBS technique offers an informative readout of the metabolome, compared to conventional blood collection, which is critical for population health and precision medicine applications.