Abstract
Parkinson's disease (PD) is an age-related neurodegenerative disorder which is assessed based on the motor symptoms. A number of microRNAs (miRNAs) are dysregulated and involved in the pathogenesis or development of PD. However, no confirmed markers are used for the early detection of PD. The present study aimed to elucidate the potential two miRNAs (miR-132-3p and miR-146-5p) as novel markers for early PD diagnosis. In the present study, the expression levels of miR-132-3p and miR-146-5p in serum samples from 82 patients with PD and 44 healthy volunteers were measured by reverse transcription-quantitative polymerase chain reaction. Furthermore, the correlation analysis was performed between aberrant miRNAs and Braak staging, Part V of the Unified Parkinson's Disease Rating Scale (UPDRS-V; the modified Hoehn and Yahr staging of PD) and Part III of the UPDRS-III. Subsequently, the receiver-operating characteristic (ROC) curve results of miR-132-3p and miR-146-5p from healthy volunteers for PD prediction and from severe PD patients were assessed. From the results it was observed that miR-132-3p and miR-146a-5p expressions were significantly decreased in the serum samples of patients with PD compared to those in the healthy volunteers. Moreover, the expressions of miR-132-3p and miR-146a-5p showed a dramatic decrease in severe PD patients as compared to the normal PD patients. Meanwhile, miR-132-3p and miR-146-5p expressions were negatively correlated with Braak staging (r = -0.45, P < 0.0001; r = -0.51, P < 0.0001), UPDRS-III (r = -0.55, P < 0.0001; r = -0.51, P < 0.0001) and UPDRS-V scores (r = - 0.46, P < 0.0001; r = -0.45, P < 0.0001) in PD patients. The area under the curve (AUC) results of miR-132-3p and miR-146a-5p in discriminating PD patients from the healthy controls were 0.7325 (95% CI = 0.6400-0.8251) and 0.7295 (95% CI = 0.3658-0.8232). Moreover, the AUC results of miR-132-3p and miR-146-5p concerning discriminating severe PD patients from normal PD patients were 0.8175 (95% CI = 0.7229-0.9121) and 0.7921 (95% CI = 0.6937-0.8905). In other words, both miR-132-3p and miR-146a-5p may function as promising biomarkers for early diagnosis of PD.