2 D gel based analysis of biological variability of the human plasma proteome

Human blood plasma is a valuable specimen for the biomarker discovery process, since it is easily accessible and contains proteins that are synthesised, secreted or lost from cells and tissue. In this way, changes in plasma proteome reflect the current state of the organism. The analysis of plasma proteome is yet challenging due to the huge dynamic range of protein abundance. When evaluating a potential biomarker, stable basal level of the protein is needed before it can be considered a functional biomarker. However, basal level differences of plasma proteins are naturally occurring between individuals and within an individual changes will also happen over time (e.g. after meal intake). Thus, the aim of the present study was to examine the inter-individual variability of plasma protein levels in humans after meal intake. Five subjects consumed three single meals in a randomised order separated by one-week interval. Blood samples were drawn before the meal intake and five times during 24 hours for proteome analysis. Plasma was fractionated by use of IgY-12 spin column depleting the 12 highly abundant proteins and further processed for two-dimensional gel electrophoresis. The plasma proteome profiling was visualized by silver staining and analysed by the software Samespots. The inter-individual variability of the plasma proteome was demonstrated by multivariate data analysis (principal component analysis and partial least squares reression) on normalised spot volumes.