Blood Biomarkers Associated with Cognitive Decline in Early Stage and Drug-Naive Parkinson's Disease Patients

PLoS One. 2015 Nov 13;10(11):e0142582. doi: 10.1371/journal.pone.0142582. eCollection 2015.


Early diagnosis of Parkinson's disease (PD) continues to be a major challenge in the field. The lack of a robust biomarker to detect early stage PD patients has considerably slowed the progress toward the development of potential therapeutic agents. We have previously evaluated several RNA biomarkers in whole blood from participants enrolled in two independent clinical studies. In these studies, PD patients were medicated, thus, expression of these biomarkers in de novo patients remains unknown. To this end, we tested ten RNA biomarkers in blood samples from 99 untreated PD patients and 101 HC nested in the cross-sectional Parkinson's Progression Markers Initiative by quantitative real-time PCR. One biomarker out of ten, COPZ1 trended toward significance (nominal p = 0.009) when adjusting for age, sex, and educational level. Further, COPZ1, EFTUD2 and PTBP1 mRNAs correlated with clinical features in PD patients including the Hoehn and Yahr scale, Movement Disorder Society revision of Unified Parkinson's Disease Rating Scale (MDS-UPDRS) and Montreal Cognitive Assessment (MoCA) score. Levels of EFTUD2 and PTBP1 were significantly higher in cognitively normal PD patients (PD-CN) compared to cognitively impaired PD patients (PD-MCI). Interestingly, blood glucose levels were significantly higher in PD and PD-MCI patients (≥ 100 mg/dL, pre-diabetes) compared to HC. Collectively, we report the association of three RNA biomarkers, COPZ1, EFTUD2 and PTBP1 with clinical features including cognitive decline in early drug-naïve PD patients. Further, our results show that drug-naïve PD and PD-MCI patients have glucose levels characteristic of pre-diabetes patients, suggesting that impaired glucose metabolism is an early event in PD. Evaluation of these potential biomarkers in a larger longitudinal study is warranted.

Publication types

  • Observational Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Aged
  • Biomarkers / blood
  • Coatomer Protein / genetics
  • Cognition
  • Cognitive Dysfunction / blood*
  • Cognitive Dysfunction / complications
  • Cognitive Dysfunction / diagnosis
  • Cognitive Dysfunction / genetics
  • Cross-Sectional Studies
  • Female
  • Heterogeneous-Nuclear Ribonucleoproteins / genetics
  • Humans
  • Longitudinal Studies
  • Male
  • Middle Aged
  • Parkinson Disease / blood*
  • Parkinson Disease / complications
  • Parkinson Disease / diagnosis
  • Parkinson Disease / genetics
  • Peptide Elongation Factors / genetics
  • Polypyrimidine Tract-Binding Protein / genetics
  • RNA, Messenger / blood*
  • RNA, Messenger / genetics
  • Ribonucleoprotein, U5 Small Nuclear / genetics


  • Biomarkers
  • Coatomer Protein
  • EFTUD2 protein, human
  • Heterogeneous-Nuclear Ribonucleoproteins
  • PTBP1 protein, human
  • Peptide Elongation Factors
  • RNA, Messenger
  • Ribonucleoprotein, U5 Small Nuclear
  • Polypyrimidine Tract-Binding Protein

Grant support

Data used in the preparation of this article were obtained from the Parkinson’s Progression Markers Initiative (PPMI) database ( For up-to-date information on the study, visit PPMI – a public-private partnership – is funded by the Michael J. Fox Foundation for Parkinson’s Research and funding partners, including Abbvie, Avid Radiopharmaceuticals, Biogen Idec, Bristol-Myers Squibb, Covance, GE healthcare, Genentech, GlaxoSmithKline, Lilly, Lundbeck, Merck, Meso Scale Discovery, Pfizer, Piramal, Roche, Servier, and UCB found at This study was also partially funded by the US Army Medical Research and Materiel Command under awards number W81XWH-09-0708 and W81XWH13-1-0025 to JAP. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.