NMR-based metabonomics of bovine blood: an investigation into the effects of long term storage on plasma samples

摘要

Freezers in research institutions often contain a plethora of samples left over from studies performed years or even decades ago. Along with samples stored in biobanks, these could prove to be treasure troves for metabonomic research. Although the influence of sample handling and short to medium term storage on conventionally determined blood parameters has been reported, little is known about the effects of long term storage (years to decades) on plasma samples. The aim of this study was to investigate the influence of long term storage on the metabolite profile and to assess the value of archived samples for metabonomic studies. Heparinised plasma samples of 22 Holstein Friesian heifers that had been stored at -20°C for between 2 and 15 years were analysed using proton NMR spectroscopy and statistical analysis techniques. Lactate accounted for principal component one and explained 79.6% of variance between all spectra, but was not correlated with storage time. The highest correlation with storage time (R2 = 0.474) was found for betaine, with other metabolites (acetoacetate, histidines, glycerol, lipids and glucose) also showing moderate correlation (R2 values between 0.217 and 0.437). Our results indicate that samples stored for extended periods of time can potentially be used in metabolomics studies, if precautions are taken during data analysis.