Effects of Long-Term Storage on the Biobanked Neonatal Dried Blood Spot Metabolome

Over 2.5 million neonatal dried blood spots (DBS) are
stored at
the Danish National Biobank. These samples offer extraordinary possibilities
for metabolomics research, including prediction of disease and understanding
of underlying molecular mechanisms of disease development. Nevertheless,
Danish neonatal DBS have been little explored in metabolomics studies.
One question that remains underinvestigated is the long-term stability
of the large number of metabolites typically assessed in untargeted
metabolomics over long time periods of storage. Here, we investigate
temporal trends of metabolites measured in 200 neonatal DBS collected
over a time course of 10 years, using an untargeted liquid chromatography
tandem mass spectrometry (LC-MS/MS) based metabolomics protocol. We
found that a majority (71%) of the metabolome was stable during 10
years of storage at −20 °C. However, we found decreasing
trends for lipid-related metabolites, such as glycerophosphocholines
and acylcarnitines. A few metabolites, including glutathione and methionine,
may be strongly influenced by storage, with changes in metabolite
levels up to 0.1–0.2 standard deviation units per year. Our
findings indicate that untargeted metabolomics of DBS samples, with
long-term storage in biobanks, is suitable for retrospective epidemiological
studies. We identify metabolites whose stability in DBS should be
closely monitored in future studies of DBS samples with long-term
storage.