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

Once potential biomarkers of a disease are discovered, it is important that they are 'validated' in a group of patients and controls different from the group in which the biomarker was initially discovered.

In this study, the researchers test for the presence of 10 candidate biomarkers (discovered in previous work) in the blood of patients very recently diagnosed with PD and controls.

A particular strength of this study is that the newly diagnosed patients had not yet been prescribed any treatments for Parkinson's. This removes the possibility that PD medications might be having an effect on the biomarker levels and suggests that the biomarkers are reflective of the underlying diseas process.

The researchers makes use of samples from the Parkinson's Progression Markers Initiative (PPMI) demonstrating, how large collaborative projects can help accelerate biomarker discovery.


Santiago JA, & Potashkin JA (2015). Blood Biomarkers Associated with Cognitive Decline in Early Stage and Drug-Naive Parkinson's Disease Patients. PloS one, 10 (11) PMID: 26566043

Abstract

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.