Medizinisches Proteom-Center, Ruhr-University Bochum, Universitaetsstrasse, Bochum, Germany.
Paracelsus-Elena-Klinik, Klinikstraße, Kassel, and University Medical Center Göttingen, Department of Neurology, Göttingen, Germany.
PLoS One. 2018 Nov 29;13(11):e0206478. doi: 10.1371/journal.pone.0206478. eCollection 2018.
Cerebrospinal fluid is investigated in biomarker studies for various neurological disorders of the central nervous system due to its proximity to the brain. Currently, only a limited number of biomarkers have been validated in independent studies. The high variability in the protein composition and protein abundance of cerebrospinal fluid between as well as within individuals might be an important reason for this phenomenon. To evaluate this possibility, we investigated the inter- and intraindividual variability in the cerebrospinal fluid proteome globally, with a specific focus on disease biomarkers described in the literature. Cerebrospinal fluid from a longitudinal study group including 12 healthy control subjects was analyzed by label-free quantification (LFQ) via LC-MS/MS. Data were quantified via MaxQuant. Then, the intra- and interindividual variability and the reference change value were calculated for every protein. We identified and quantified 791 proteins, and 216 of these proteins were abundant in all samples and were selected for further analysis. For these proteins, we found an interindividual coefficient of variation of up to 101.5% and an intraindividual coefficient of variation of up to 29.3%. Remarkably, these values were comparably high for both proteins that were published as disease biomarkers and other proteins. Our results support the hypothesis that natural variability greatly impacts cerebrospinal fluid protein biomarkers because high variability can lead to unreliable results. Thus, we suggest controlling the variability of each protein to distinguish between good and bad biomarker candidates, e.g., by utilizing reference change values to improve the process of evaluating potential biomarkers in future studies.
脑脊液由于其与大脑的接近性，在各种中枢神经系统神经疾病的生物标志物研究中被研究。目前，只有少数生物标志物在独立研究中得到验证。脑脊液中蛋白质组成和蛋白质丰度在个体之间和个体内部的高度可变性可能是造成这种现象的一个重要原因。为了评估这种可能性，我们全面研究了脑脊液蛋白质组的个体内和个体间的变异性，特别关注文献中描述的疾病生物标志物。通过 LC-MS/MS 进行无标记定量 (LFQ) 分析了包括 12 名健康对照者的纵向研究组的脑脊液。通过 MaxQuant 对数据进行定量。然后，计算了每种蛋白质的个体内和个体间变异性以及参考变化值。我们鉴定和定量了 791 种蛋白质，其中 216 种蛋白质在所有样本中都很丰富，被选来进行进一步分析。对于这些蛋白质，我们发现个体间的变异系数高达 101.5%，个体内的变异系数高达 29.3%。值得注意的是，这些值对于作为疾病生物标志物发表的蛋白质和其他蛋白质来说都相当高。我们的结果支持了自然变异性极大地影响脑脊液蛋白质生物标志物的假设，因为高变异性可能导致不可靠的结果。因此，我们建议控制每个蛋白质的变异性，以区分好的和坏的生物标志物候选物，例如，通过利用参考变化值来提高未来研究中评估潜在生物标志物的过程。
