A Set of Reliable Samples for the Study of Biomarkers for the Early Diagnosis of Parkinson’s Disease

Abstract Background: The identification of biomarkers for the early diagnosis of Parkinson’s Disease (PD) might improve treatment and avoid complications. However, the search of such biomarkers is a real challenge. The main reason for this is that finding samples for that purpose is not an easy task. In this work, we propose a set of reliable samples for the identification of biomarkers for the early diagnosis of PD. In fact, the original source of these samples can be searched for similar purposes when dealing with other diseases.Materials and methods: Case-control study included 12 plasma samples of subjects that subsequently developed PD and 21 plasma samples of matched healthy controls from the Spanish EPIC-Navarra cohort, part of the European Prospective Investigation into Cancer and Nutrition (EPIC)-Spain study. All the case samples were provided by healthy volunteers who were followed up for a mean of 15.9 (± 4.1) years and developed PD disease later on. Therefore, these sample are ideal for the search of early biomarkers of PD. We used an analytical multiplatform based on liquid chromatography and tandem mass spectrometry in order to find significant differences in the amounts of previously reported metabolites that are altered when the disease has been established and diagnosed. Results: Out of all 40 analytes that were studied, seven significant metabolites were observed. Benzoic acid, palmitic acid, oleic acid, stearic acid, myo-inositol, sorbitol and quinolinic acid were significantly changed in subjects that developed PD. These metabolites are closely related to mitochondrial dysfunction, the oxidative stress and the mechanisms of energy production, which might indicate that these mechanisms are already affected before disease onset.Conclusions: We propose the samples from the EPIC study as reliable and priceless samples for the search of early biomarkers of PD, although many other diseases can be also studied as long as the information stored about the participants recorded such details. As a proof of concept, we showed that these samples were useful for the study of metabolites that may be altered before the participants developed PD. This might also be a starting point in the establishment of a well-founded panel of metabolites that can be used for the early detection of this disease.