[Variability of healthy human proteome]

The purpose of this review is to analyze investigations devoted to characteristic of protein variability and diversity of their posttranslational modifications in healthy humans. The numerous researches have demonstrated that proteomic profile has a considerable both intra- and inter-individual variability, and quite often normal variability of some proteins can be comparable to changes observed in pathological processes. Results obtained by our research group have confirmed high intra-individual variability of serum low-molecular subproteome of healthy volunteers, certified by a special medial committee. Proteins characterized by high variability in normal conditions (e.g. haptoglobin--0-40 mg/ml; lysozyme--0,01-0,1 mg/ml; C-reactive protein--0,01-0,3 mg/ml) should be excluded from the list of potential biomarkers. On the contrary, proteins and peptides characterized by insignificant dispersion in healthy population (such as albumin--coefficient of variation (CV) 9%; transferrin--CV14%; C3c complement--CV 17%, alpha-1 acid glycoprotein--CV 21%, alpha2-macroglobulin--CV 20%; transthyretin fragment--CV 28,3% and beta-chain alpha2-HS-glycoprotein--CV 29,7%) can provide us with important information about state of health. Thus investigations of plasticity in proteomic profiles of healthy humans will help to correct reference intervals used in clinical proteomics.

Remarkable temporal stability of high-abundance human plasma proteins assessed by targeted mass spectrometry

PURPOSE

To examine temporal fluctuations in selected plasma protein levels over a period of nearly 4 months and assess biological variation of these proteins across a healthy population cohort.

EXPERIMENTAL DESIGN

Plasma was collected from ten healthy volunteers over two time-courses: (i) weekly for 4 weeks; (ii) bimonthly over 4 months and depleted of albumin and IgG. SRM MS was used to determine the relative quantitation of 31 plasma proteins commonly observed in biomarker studies over these time courses. Estimates of between-subject and within-subject biological variances determined by SRM were calculated for each protein.

RESULTS

Replicate analysis demonstrated the high precision of SRM assays of plasma proteins. Statistical analysis indicated that none of the measured proteins exhibited significant temporal fluctuations over either time course. Overall, time-based intraindividual quantitative variation of plasma protein levels was considerably lower than biological variation occurring between individual volunteers.

CONCLUSIONS AND CLINICAL RELEVANCE

This study is the first to show robust temporal stability of the plasma proteome in healthy individuals using SRM-based peptide quantitation. This is important as it provides a strong basis for reliable detection of disease/treatment-related changes of these plasma proteins and others using SRM.