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Altered expression levels of microRNA-132 and Nurr1 in peripheral blood of Parkinson’s disease: a potential disease biomarker Zhaofei Yang, Tianbai Li, Song Li, Min Wei, Hongqian Qi, Bairong Shen, Raymond Chuen-Chung Chang, Fengyuan Piao, and Weidong Le ACS Chem. Neurosci., Just Accepted Manuscript • DOI: 10.1021/acschemneuro.8b00460 • Publication Date (Web): 28 Feb 2019 Downloaded from http://pubs.acs.org on March 1, 2019

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Altered expression levels of microRNA-132 and Nurr1 in peripheral

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blood of Parkinson’s disease: potential disease biomarkers

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Zhaofei Yang,§,†,‡ Tianbai Li,†,‡ Song Li,†,‡ Min Wei,†,‡ Hongqian Qi,†,‡ Bairong

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Shen#, Raymond Chuen-Chung Chang,¶ Fengyuan Piao§,* and Weidong Le,†,‡,*

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§ Department of Occupational and Environmental Health, Dalian Medical University,

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Dalian 116044, China.

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† Center for Clinical Research on Neurological Diseases, the First Affiliated Hospital,

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Dalian Medical University, Dalian 116021, China.

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‡ Liaoning Provincial Key Laboratory for Research on the Pathogenic Mechanisms of

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Neurological Diseases, the First Affiliated Hospital, Dalian Medical University,

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Dalian 116021, China.

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# Institute for Systems Genetics, West China Hospital, Sichuan University, Chengdu

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610041, China.

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¶ Laboratory of Neurodegenerative Diseases, LKS Faculty of Medicine, School of

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Biomedical Sciences, The University of Hong Kong, Hong Kong, China.

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* Corresponding author.

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Email: [email protected] (Weidong Le), [email protected] (Fengyuan Piao)

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ABSTRACT: MicroRNAs (miRNAs) are small and evolutionary conserved

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non-coding RNAs that are involved in post-transcriptional gene regulation.

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Differential expression levels of miRNAs can be used as potential biomarkers of

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disease. Previous animal studies have indicated that the expression level of miR-132

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is negatively correlated with its downstream molecule nuclear receptor related 1

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protein (Nurr1), which is one of the key factors for the maintenance of dopaminergic

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function and is particularly vulnerable in Parkinson’s disease (PD). However, this

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correlation has not been confirmed in human patients with PD. Moreover, the possible

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involvement of miR-132 during the pathogenesis and progression of PD is not fully

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investigated. Therefore, in the present study, we determined the peripheral circulation

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levels of miR-132 and Nurr1 in patients with PD, neurological disease controls

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(NDC) and healthy controls (HC) by reverse transcription real-time quantitative PCR

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(RT-qPCR). Our data clearly demonstrated that the plasma miR-132 level in PD was

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significantly higher than those in HC (178%, p < 0.05) and NDC (188%, p < 0.001).

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When adjusted for gender and age, higher level of miR-132 expression was associated

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with the significantly increased risk for PD in male, and was closely related with the

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disease stages and disease severity. Furthermore, peripheral Nurr1 was significantly

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decreased in PD compared with HC (56%, p < 0.001) and NDC (58%, p < 0.001).

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Much more interestingly, further analysis revealed a negatively correlation between

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the decreased Nurr1 level and the elevated miR-132 level in PD. All these findings

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indicated that the combination of high miR-132 level with its downstream low Nurr1

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level might be a potential biomarker aiding in the diagnosis of PD and monitoring the

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disease progression.

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KEYWORDS: Parkinson’s disease, miR-132, Nurr1, biomarker, peripheral blood

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■ INTRODUCTION

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Parkinson's disease (PD) is the second most common neurodegenerative disease in the

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world,1,2 pathologically characterized by the selective loss of dopaminergic (DAergic)

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neurons in substantia nigra (SN) and the formation of Lewy body (LB).3 Although

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great achievements have been made to clarify the disease pathogenesis and explore

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potent therapeutic strategies against PD for over 200 years, there is still no systematic

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understanding of this disease and the current treatments are mostly symptomatic.4

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Moreover, the current diagnosis of PD is based primarily on subjective clinical rating

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of motor functions. By the time of diagnosis, over 60% of DAergic neurons in the SN

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of PD patients are already lost.5 Since there is no reliable quantitative diagnostic test

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for PD, the objective and measurable molecular biomarkers should be critical to serve

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as potential clinical tool to facilitate PD diagnosis and early intervention.

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MicroRNAs (miRNAs) are a class of ~ 22 nt endogenous RNA molecules.6 Mature

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miRNAs recognize and bind to the 3’ untranslated region of the messenger RNA

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(mRNA) by specific complementary sequence, then affecting the expression of target

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genes.7 Several miRNAs have been found to play important roles in DAergic neuronal

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differentiation, apoptosis and protection of PD.8,9 For instance, miR-133b can regulate

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DAergic function negatively and affect PD pathogenesis by repressing the expression

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of Pitx3 gene, a homeobox transcription factor required for the development and

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mature of DAergic neurons;8 miR-7 protects DAergic neurons against oxidative stress

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damage by altering α-synuclein expression, as well as miR-153;10,11 miR-433 induces

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overexpression of α-synuclein indirectly by binding to the promoter region of

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fibroblast growth factor 20,12 while miR-128 suppresses the accumulation of

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α-synuclein by targeting to transcription factor EB;13 miR-132 dysregulation is

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associated with the changes of momoamine oxidase A (MAO-A), D1- and D2-like

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DA receptor (DRD1 and DRD2) genes in DA receptor signaling in toxoplasma

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gondii-infected mice.14

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Among these above mentioned miRNAs, we were particularly interested in the

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expression of miR-132, a miRNA that was reported to be highly expressed in neurons,

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and significantly altered in various neurodegenerative disorders.15-18 The level of

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mesencephalon miR-132 was found to be significantly increased in rat PD model,

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accompanied by a decreased Nurr1.19 Nurr1 is a transcription factor20-22 that plays

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crucial roles in the differentiation and functional maintenance of midbrain DAergic

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neurons and the microglia-mediated neuroinflammation.23,24 Our previous study

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demonstrated that over-expression of miR-132 repressed embryonic stem (ES) cells

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differentiation into DAergic neurons by directly targeting Nurr1 gene,25 and Nurr1

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expression level was decreased in the patients with PD compared to health

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individuals.26,27 However, miR-132 expression level in PD patients and controls, and

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the possible correlation between peripheral levels of miR-132 and Nurr1 in PD

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patients has not been determined.

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In the present study, we recruited 269 patients with diagnosed PD, 222 healthy

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controls (HC) and 176 patients with various non-PD neurological disorder controls

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(NDC). The main aims of the present study were to determine: (1) whether peripheral

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miR-132 expression level was significantly altered in patients with PD as compared

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with controls; (2) whether there were the effects of age, gender, disease severity and

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medications on miR-132 expression; (3) whether peripheral miR-132 had a negative

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correlation with Nurr1 in PD patients.

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■ RESULTS AND DISCUSSION

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In order to prove our hypothesis, we measured the relative expression level of

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miR-132 in human plasma from patients with PD, non-PD neurodegenerative disease

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and healthy individuals by RT-qPCR. All 667 subjects enrolled in this study were Han

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ethnic Chinese with the male/female ratio at 392/275. Their ages ranged from 40 to 89

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years with a mean of 66.14 ± 0.66 years. The demographic characteristics including

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age and gender of each group were summarized in Table 1. There was no significant

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difference among PD, HC and NDC groups for the distribution of age, gender in each

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group. In addition, 142 PD, 98 HC and 105 NDC were enrolled for the study of Nurr1

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expression in peripheral blood lymphocytes (PBL). There was no significant

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difference in both gender and age among the groups, the demographic characteristics

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of the cohort of subjects selected for the Nurr1 gene expression were summarized in

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Table 2.

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miRNAs have been proposed as putative non-invasive biomarkers in diagnosis,

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prognosis and response to treatment for several diseases, including neurodegenerative

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disorders such as PD.28 In the present study, we aimed to measure the relative

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expression of miR-132 and Nurr1 in human peripheral blood from PD and controls.

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Our results showed that plasma miR-132 expression was significantly higher in PD

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than that in HC (Figure 1, 0.32 ± 0.03 vs. 0.18 ± 0.03, p < 0.05) and in NDC (Figure

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1, 0.32 ± 0.03 vs. 0.17 ± 0.03, p < 0.001), suggesting that plasma miR-132 expression

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level may be specially altered.

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In order to explore the possible impacts of age on the changes of plasma miR-132

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expression level, we analyzed the correlation between miR-132 expression and age in

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both HC and PD groups using Spearman’s correlation analysis. As shown in Figure

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2A, the coefficient (R) results revealed no correlation between miR-132 and age in

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HC (r=0.117, p=0.144) and PD group (r= 0.048, p=0.465), suggesting that age did not

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influence the expression of plasma miR-132. Much more interestingly, we found a

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significantly higher plasma miR-132 level in male PD than that in HC, while there

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was no difference between PD and NDC (Figure 2B). It was reported that miRNAs

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expression profiles were differentially expressed between male and female in SN

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DAergic neurons of PD patients.29 Moreover, the expression levels of miR-132 were

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varied amongst different regions of the brain and presented in a sex-dependent

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manner in mice with chronic toxoplasma gondii infection.30 It is conceivable that the

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significant higher miR-132 expression in male PD than female in our study may

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suggest that gender influence might be involved in miR-132 expression and might

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play a role in different ratio of male/female PD.31

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We further analyzed disease duration and severity (H-Y score) in 269 patients with

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PD. We found that plasma miR-132 expression was associated with the disease

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duration. The Spearman correlation analysis results revealed a positive correlation

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between the relative expression of miR-132 and duration in PD (r=0.187, p=0.006)

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(Figure 3A). Consistently, similar association was also found between miR-132

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expression and H-Y scores (Figure 3B). In our study, we analyzed plasma miR-132

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expression level of 67 PD patients who were of recent-onset and not yet been treated

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with anti-PD medications (“naïve” PD), we found that the miR-132 expression in PD

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was significantly increased in comparison to that in HC (Figure 3C). We also

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analyzed the miR-132 expression in 183 PD patients who were regularly treated with

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first- or second-line anti-PD medications, including DA receptor agonists alone (DR,

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n=16), levodopa alone (L-dopa) (n=69), or the combination of L-dopa and DR (n=98).

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Nineteen PD patients treated irregularly with several other medications were not

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included in the analysis. Interestingly, L-dopa treatment increased the miR-132

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expression level of PD patients compared to HC, but there was no significant

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difference among other four groups (PD, naïve, DR, L-dopa+DR, Figure 3C). Alieva

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et al.32 reported that the level of miR-132 in PBL was increased in 18 L-dopa-treated

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patients with PD compared with non-treated PD (H-Y scores 1-2). We considered that

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the expression levels of miR-132 were also affected by other factors, such as gender,

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duration and severity of disease in addition of medications. Receiver operating

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characteristic (ROC) analysis revealed that the areas under the ROC curve (AUC)

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were 0.72 (95% CI, 0.66–0.78; p < 0.0001) for miR-132 in plasma between PD and

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HC. The AUC of miR-132 were larger than 0.7, which means that miR-132 could be

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considered to have a discriminative value. Certainly, a larger population-based study

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is needed for the validation of this observation.

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To further explore how miR-132 worked in the occurrence and development of PD,

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we measured the PBL expression level of Nurr1, which was reported to be a target

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gene of miR-132.25 Our previous studies had shown that Nurr1 gene expression was

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significantly decreased in PBL of patients with PD as compared with both HC and

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NDC.26,27 Furthermore, Nurr1 mRNA level in PBL of PD was significantly lower than

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that in HC (0.007 ± 0.001 vs 0.017 ± 0.003, p < 0.001), and NDC (0.007 ± 0.001 vs

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0.017 ± 0.002, p < 0.001). There was no difference of Nurr1 expression between HC

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and NDC (Figure 4A), which was in correlation with the changes of plasma miR-132.

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Besides, higher plasma miR-132 expression level in male of PD, we also analyzed

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and found that Nurr1 expression level was significantly decreased in male PD, as

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compared to HC and NDC (Figure 4B). We further documented that Nurr1 was

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significantly decreased in naïve PD comparing to HC (Figure S2).

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Researching on human peripheral blood is common in a clinic study to identify

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disease biomarkers and evaluate disease progression. miRNAs have been reported to

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be encapsulated in microvesicles, which are secreted by circulating blood cells and

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other cells from different tissues.33,34 Kim and his colleagues8 determined

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pre-miR-132 by qPCR for a panel of 224 precursor miRNAs in RNAs samples from

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PD and normal brains. Their results showed that pre-miR-132 was enriched and high

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expressed in the midbrain of PD brains compared to HC. Moreover, it is known that

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Nurr1 is expressed predominantly in the central nervous system (CNS), especially in

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the midbrain and limbic areas.20 And decline of Nurr1-immunoreactive neuronal

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number and optical density had been observed in the SN neurons of PD midbrain.35 In

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addition to the biological effects on CNS, Nurr1 has been reported to be associated

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with pro-inflammatory cytokines in peripheral blood mononuclear cell including PBL

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in patients with PD and type 2 diabetes.36,37 Here, we measured Nurr1 expression in

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PBL and analyzed the correlation between PBL Nurr1 and plasma miR-132, showing

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that there was a negative correlation in PD patients (r=−0.579, p < 0.001) (Figure 5).

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Interestingly, no correlation was found in NDC patients (r=0.082, p=0.411) (Figure

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5), suggesting that miR-132/Nurr1 signaling was specifically involved in PD.

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Moreover, to explore the correlation of miR-132 and Nurr1 in blood, we determined if

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miR-132 can affect the Nurr1 expression in PBL. We transfected with miR-132

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mimic or normalized control (NC) mimic in cultured PBL for 24 hours, and found

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that the Nurr1 level was significantly decreased in PBL transfected with miR-132

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mimic (Figure S2), suggesting miR-132 had a regulative effect on Nurr1 expression in

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PBL. Our previous studies and others have documented that Nurr1 was critical not

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only in the midbrain DAergic neuron differentiation and functional maintenance, but

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also in regulating glia- and lymphocyte-mediated inflammation.24,36,37 Collectively,

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Nurr1 defect might play an important role in PD pathogenesis.

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Recently, growing evidence has shown that miR-132 may be one of promising

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miRNAs in the diagnosis and prognosis of neurological disease. In AD, miR-132 was

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found to be down-regulated in patients’ brains and cerebrospinal fluid,38 whereas it

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was up-regulated in their serum39 and plasma.15 However, these reports did not

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compare miR-132 expression to NDC. In this study, we found that miR-132

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measurement in plasma may help in differentiating PD from various non-PD NDC,

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and the combination of Nurr1 with miR-132 may enhance the sensitivity and

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specificity for differential diagnosis of PD.

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Nevertheless, the results from our present study may merit the attention that

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miR-132 may be associated with PD, as evidenced by the progressive increasing of

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plasma miR-132 level in PD patients in a disease stage- and disease

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severity-dependent manner. In conclusion, our study may provide the following

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information: (1) miR-132 expression level was significantly increased in patients with

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PD compared to both HC and NDC; (2) the changes in plasma miR-132 expression

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level were correlated with disease progression and severity; (3) the difference of

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miR-132 level in male PD vs controls is greater than that in female PD vs controls; (4)

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Nurr1 gene expression is significantly decreased in PBL of PD as compared with HC

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and NDC, showing negative correlation with miR-132 expression level in PD

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patients. Collectively the combined measurements of miR-132 and Nurr1 expression

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levels in blood may help the diagnosis and differential diagnosis of PD, and may also

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assist the monitoring of the disease progression.

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■ METHODS

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Participants and blood sampling. In this study, we recruited a total of 667

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participants including 269 patients with sporadic PD, 222 HC, and 176 various

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non-PD NDC which consist of 38 cerebrovascular disease, 38 epilepsy, 25 peripheral

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neuropathy, 20 essential tremor, 16 myasthenia gravis, 15 migraine, 14 motor neuron

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disease, 10 multiple sclerosis. PD patients were examined and diagnosed by at least

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two experienced neurologists from the First Affiliated Hospital of Dalian Medical

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University, according to the Movement Disorder Society Clinical Diagnostic Criteria

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for Parkinson’s disease.40 Subjects with secondary parkinsonism, neoplastic or

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metabolic disorders, alcoholism were excluded. PD disease severity was assessed by

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Modified Hoehn and Yahr (H-Y) staging. HC group were recruited from the Health

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Examination Center of the First Affiliated Hospital of Dalian Medical University, and

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were either diagnosed without a neurological disorder or with a systemic disease

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without neurological manifestations. All subjects (or their caregivers) recruited to our

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studies provided a written informed consent agreeing to participate the project. This

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study has been granted ethical approval by the Ethics Committee of the First

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Affiliated Hospital of Dalian Medical University (approval number: LCKY2014-29).

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Blood samples used in this study were collected by direct venipuncture at the First

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Affiliated Hospital of Dalian Medical University. Briefly, two milliliters of peripheral

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blood was drawn from cubital vein into a vacuum blood tube with

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ethylenediaminetetraacetic acid (EDTA) and then the plasma was aliquoted (200 µL)

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into sterile tube and stored at -80°C. PBL were separated from gradient Ficoll/Paque

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by centrifugation at 450 g for 20 min at room temperature (20 ± 2°C), resuspended

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with Sample Protector of RNA/DNA (TаKаRа, Dalian, China) and stored at -80 °C

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until RNA extraction.

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Plasma miRNA and PBL RNA extraction and quantification. Total miRNAs

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were extracted from plasma using miRNA isolation system (Tiangen Biotech

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(Beijing) Co., Ltd., Beijing, China). Five microliters of miRNA from plasma was

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reverse transcribed into first strand cDNA by Tiangen miRCute miRNA cDNA

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synthesis kit (Tiangen Biotech (Beijing) Co., Ltd.). Total RNAs from PBL were

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extracted using the mirVana™ miRNA Isolation Kit (Ambion, Carlsbad, CA, USA)

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following the manufacturer’s instructions, and 1 µg RNA from PBL was reverse

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transcribed into first strand cDNA by PrimeScript™ RT reagent Kit with gDNA

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Eraser (TаKаRа, Dalian, China).

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The plasma miR-132 and PBL Nurr1 mRNA levels were determined by RT-qPCR.

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For plasma, considering the lack of suitable internal control for normalization,

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artificial synthetic external miRNA (Tiangen Biotech (Beijing) Co., Ltd., Beijing,

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China) was used for normalization. Besides, the reverse primer of miR-132 was

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provided by the miRcute miRNA qPCR Detection Kit (Tiangen Biotech (Beijing)

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Co., Ltd., Beijing, China). The up-primer targeting plasma miR-132-3p was as

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follows: 5’-GCT AAC AGT CTA CAG CCA TGG TCG-3’. For PBL, human

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GAPDH gene was used as an internal control. The specific primers targeting PBL

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Nurr1 and GAPDH as follows: Nurr1-forward: 5’-TCC AAC GAG GGG CTG TGC

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G-3’, Nurr1-reverse: 5’-CAC TGT GCG CTT AAA GAA GC-3’; GAPDH-forward:

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5’-GAA GGT GAA GGT CGG AGT C-3’, GAPDH-reverse: 5’-GAA GAT GGT

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GAT GGG ATT TC-3’. Relative quantification was performed using the 2−delt

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method. PCR was carried out using ABI 7500 fast real-time PCR system (Applied

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Biosystems, Foster City, CA) in a total volume of 20 μL for each reaction.

Ct

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Statistical analysis. Quantitative data were expressed as mean ± SEM, or median

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depending on the distribution of the data. The chi-square test was used to evaluate the

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statistical differences of gender distribution between PD patients and control subjects.

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The Kruskal-wallis test followed by Dunn’s multiple comparison test as a post hoc

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test using the GraphPad Prism software version 4 (GraphPad Inc., San Diego, CA,

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USA) was used to evaluate the differences in the age distribution and relative miRNA

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expression levels in individuals from each group. Exact 95% confidence intervals

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(CIs) were reported for estimation of sensitivity and specificity. ROC analysis was

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performed using MedCalc software version 17.2 (MedCalc Software Inc.,

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Mariakerke, Belgium), and predictive performance of the putative biomarker

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(miRNA-132 or Nurr1 or both) for the presence of PD was quantified by using AUC.

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Correlations were assessed using Spearman’s correlation coefficient. The correlations

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were reported at á level of 0.05. The other statistical analysis in this research was

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performed with the SPSS software version 13.0 (SPSS Inc., Chicago, IL, USA). All

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statistical checks were carried out two-sided and a p-value < 0.05 was considered as

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statistical significance.

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■ ASSOCIATED CONTENT

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Supporting Information

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The effect of miR-132 on Nurr1 expression in cultured PBL, and the medications

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effect on the Nurr1 expression in PBL of PD patients.

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■ AUTHOR INFORMATION

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Corresponding Author

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*E-mail: [email protected] (Weidong Le)

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[email protected] (Fengyuan Piao)

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ORCID

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Weidong Le: 0000-0001-7459-2705

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Author Contributions

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WL and FP designed the project of this manuscript, ZY and TL carried out all the

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experiments. ZY, TL and BS contributed to statistical analyses and results

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interpretation. ZY, TL, SL, MW and BS contributed to drafting of the manuscript.

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ZY, TL, SL, MW, HQ, CRC, WL and FP revised the paper. All authors edited and

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approved the final version of the manuscript.

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Notes

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The authors declare no competing financial interest.

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■ ACKNOWLEDGMENTS

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This work was supported by the National Basic Research Program of China

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(81370470), Key Filed Research and Development Program of Guangdong Province

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(2018B030337001), National Key Research and Development Program of

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China (2016YFC1306603).

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Figure legends

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Figure 1. Scatter plots of miR-132 relative expression in plasma in different study

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groups. Fluorescent reading from real-time PCR reaction was quantitatively analyzed

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by determining the difference of Ct (delta Ct) between Ct of miR-132 and external

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control, and the miR-132 expression was determined by the formation of 2−delta Ct. The

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level of miR-132 expression was significantly increased in patients with PD (n=269)

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as compared with healthy controls (HC, n=222) and neurological disease controls

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(NDC, n=176). Horizontal bar represent median value. The Kruskal-wallis test was

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used to evaluate the differences in the relative miR-132 expression levels in

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individuals from each group. *p < 0.05 vs. HC, ###p < 0.001 vs. NDC.

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Figure 2. Age and gender effects on plasma miR-132 expression levels in PD and

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controls. A. Correlation between plasma miR-132 and age in PD and HC groups. The

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Spearman correlation analysis results revealed no correlation between the relative

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expression of miR-132 and age in HC (r=0.117, p=0.144) and PD group (r=0.048,

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p=0.465). B. The expression levels of miR-132 in male and female of HC, PD and

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NDC groups. The Kruskal-wallis test was used to evaluate the differences in the

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gender distribution in individuals from each group. **p < 0.01 vs. HC.

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Figure 3. The expression levels of miR-132 in PD and HC. The effect of (A) disease

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course, (B) severity and (C) anti-PD medications to the expression levels of miR-132.

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The Spearman correlation analysis revealed a positive correlation between the relative

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expression of miR-132 and duration in PD (r=0.187, p=0.006). The Kruskal-wallis

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test was used to evaluate the differences in the relative miR-132 expression levels in

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individuals from each group. *p < 0.05 vs. HC.

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Figure 4. PBL Nurr1 expression levels in PD and controls (HC, NDC). The

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Kruskal-wallis test was used to evaluate the differences in the relative Nurr1

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expression levels in individuals from each group. *p < 0.05 vs. HC, #p < 0.05 vs.

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NDC, ***p < 0.001 vs. HC, ###p < 0.001 vs. NDC.

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Figure 5. Correlation between plasma miR-132 and PBL Nurr1 levels in the

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peripheral blood of HC (n=98), PD (n=142) and NDC (n=105). The Spearman

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correlation analysis revealed a negative correlation between the relative expression of

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miR-132 and Nurr1. (A) HC group: r=−0.335, p < 0.001; (B) PD group: r=−0.579, p