Impact of a 12-week structured exercise program on motor function and exosomal alpha-synuclein levels in Parkinson's disease: A prospective analysis

Abstract

Objectives: This study aimed to determine whether exercise reduced alpha-synuclein aggregation and ultimately improved symptoms of Parkinson’s disease (PD).

Patients and methods: The prospective study was conducted with 26 PD patients (14 males, 12 females; mean age: 58.5±11.3 years; range, 38 to 79 years) between October 2019 and January 2020. A 12-week combined exercise program, including respiratory training, spinal stabilization, and stretching, was performed by the patients. Detailed clinical assessments were conducted, along with alpha-synuclein quantification, before and after the intervention.

Results: The data revealed notable improvements in motor, cognitive, and nonmotor realms (p<0.05). However, alpha-synuclein levels remained consistent (p>0.05).

Conclusion: While the exercise regimen aids symptom mitigation in PD, it does not alter alpha-synuclein concentrations, emphasizing the need to further investigate the mechanisms behind the exercise-related benefits.

Introduction

Idiopathic Parkinson's disease (PD) is a complex neurodegenerative disorder characterized by the loss of dopamine-producing neurons within the substantia nigra. This neuronal loss gives rise to the formation of Lewy bodies, aggregates primarily composed of the protein alpha-synuclein.[1-3] These molecular changes precipitate a cascade of motor disturbances, such as tremors, rigidity, and bradykinesia, as well as cognitive deficits that significantly impact the quality of life.[4-6] Although pharmaceutical interventions provide some relief by enhancing dopamine signaling, they often offer only partial and temporary alleviation of symptoms. As a result, there has been a growing interest in exploring alternative therapeutic strategies that target not only the motor symptoms but also the underlying pathophysiological mechanisms of PD. Among these strategies, aerobic exercise has emerged as a promising avenue due to its potential to stimulate neurogenesis, improve balance, enhance gait, and even counter cognitive decline.[7-10]

The benefits of aerobic exercise extend beyond the realm of physical fitness. Accumulating evidence suggests that these exercises possess the capacity to modulate neuroinflammatory processes within the brain, potentially curbing the chronic inflammation that contributes to the progressive degeneration in PD. Furthermore, emerging research hints at exercise's ability to influence protein misfolding, a phenomenon central to the aggregation of alpha-synuclein and the formation of Lewy bodies.[11-13] Although the notion of engaging in a 12-week combined exercise training (CET) regimen has gained traction in recent years as a nonpharmacological intervention for PD, the outcomes are inconsistent across various studies.[14,15] Differing methodologies, participant characteristics, and exercise protocols have all contributed to a diverse range of results, leaving a need for further investigation and a clearer understanding of the effects of CET on PD symptoms.[14,16]

Given the paramount role of alpha-synuclein in the pathogenesis of PD,[2,17] this study sought to investigate the effects of CET on the molecular pathways associated with alpha-synuclein. By focusing on these pathways, we aimed to elucidate whether exercise reduced alpha-synuclein aggregation and ultimately improved PD symptoms. In doing so, we hope to contribute to the growing body of knowledge that bridges the gap between physical activity, neurodegeneration, and novel therapeutic strategies for PD.

Material and Methods

The prospective study was conducted with 26 PD patients (14 males, 12 females; mean age: 58.5±11.3 years; range, 38 to 79 years) at the Bezmialem Vakıf University Faculty of Medicine, Department of Neurology between October 2019 and January 2020. In the study, patients with PD were consecutively selected based on the UK Parkinson’s Disease Society Brain Bank diagnostic criteria.[18] The patients who presented to the hospital between February 2019 and August 2019 were included in the study. The inclusion criteria were as follows: literacy, diagnosis of PD with Stages 1-3, a Mini-Mental State Examination (MMSE) score ≥24,[19] and stable treatment for at least six months prior to the study. Following the initial selection phase, all eligible cases were subjected to the study activities between October 2019 and January 2020. This comprehensive timeframe was carefully chosen to minimize selection bias and ensure a clear temporal context, thus enhancing the relevance and accuracy of our findings. Patients were rigorously assessed for eligibility to maintain the integrity and validity of outcomes. Exclusion criteria included recent physical activity or any conditions that prevented physical activity to ensure a homogenous participant group.

Patients undertook a 12-week CET with weekly supervised sessions and home exercises.[20,21] Clinic sessions lasted 60 min and covered various exercises, and the intensity was monitored for some exercises. Home routines, done thrice weekly for 45 min, included diverse activities.[14,16] Adherence was tracked via an exercise diary. Levodopa equivalent daily dose was also calculated.

Before and after CET, patients were evaluated using the Unified Parkinson's Disease Rating Scale (UPDRS), modified Hoehn and Yahr Stage (mHYS),[22] and cognitive tests, such as the Hospital Anxiety and Depression Scale (HADS) and MMSE. The HADS comprises 14 items, each rated from 0 to 3, with higher scores indicating greater anxiety/depression. The anxiety and depression subscales each have seven items and a maximum score of 21.[23] Additionally, the Parkinson’s Disease Questionnaire-39 (PDQ-39) was used to assess the quality of life. The PDQ-39 contains 39 items, each rated from 0 to 4, covering eight domains: mobility, activities of daily living, emotional well-being, stigma, social support, cognition, communication, and bodily discomfort.Mobility metrics included the Tinetti assessment tool and the timed-up-and-go test.[14,18] The Tinetti assessment tool measures an older adult’s gait and balance abilities. A low-performance score is associated with a high fall risk in an individual. The Tinetti assessment tool has been validated as a robust fall risk instrument and predictor of falls in the elderly.[24] The timed-up-and-go test assesses dynamic balance and functional mobility. Subjects were instructed to sit back in a standard armchair and to stand up, walk a marked path of 3 m, turn around, and sit back down in the chair. The cutoff value was set at 12 sec based on the reference value for geriatric adults.[25] All results were documented on a dedicated worksheet. The scoring of all scales were double checked by two clinical researchers.

Quantification of exosomal alpha-synuclein

Blood sampling was synchronized with the CET schedule. On the day designated for the initiation of CET, a preintervention blood specimen was collected. At the conclusion of the three-month CET period, a postintervention blood specimen was procured. These collections were strategically timed to facilitate the comparative analysis of biomarkers before and after the exercise intervention. Venous blood was drawn into tubes containing EDTA and promptly centrifuged at 3500 rpm for 10 min at +4°C for plasma separation. Afterward, the samples were preserved at –80°C until analysis. Exosomal isolation from the plasma was performed employing the Norgen Biotek (NB) Plasma/Serum Exosome Purification Mini Kit (Norgen Biotek Corp., cat.no. 57400, Thorold, ON, Canada) methodology. Following isolation, the plasma was mixed with the specific reagents supplied in the kit and subjected to another centrifugation cycle. The isolated exosomes were then stored at –20°C. Quantitative assessment of alpha-synuclein was conducted using an enzyme-linked immunosorbent assay (ELISA) kit supplied by Elabscience (Elabscience Biotechnology Co., Ltd., cat.no. E-EL-H0983, Wuhan, Hubei, China), with absorbance measured at 450 nm using a MultiSkan Go spectrophotometer (Thermo Scientific, MultiSkan Go Microplate Spectrophotometer, Tokyo, Japan). The assay demonstrated a sensitivity of 9.83 pg/mL across a dynamic range of 15.63 to 1000 pg/mL.

Statistical analysis

Data were analyzed using IBM SPSS version 25.0 software (IBM Corp., Armonk, NY, USA). The statistical approach comprised paired t-tests for comparing mHYS scores before and after CET, alongside the Shapiro-Wilk test for evaluating the normality of data distribution. Nonparametric tests were employed to evaluate nonnormally distributed data. A p-value <0.05 was considered statistically significant. The analysis was designed to elucidate the symptomatic changes related to CET and explore their association with alpha-synuclein level variations. Continuous variables were expressed as mean ± standard deviation (SD) or median values, and categorical variables were expressed as frequencies and percentages. The interplay between clinical traits and alpha-synuclein concentrations were examined by Spearman’s rank correlation coefficient, while the pre- and post-CET alpha-synuclein levels were assessed using the Wilcoxon signed-rank test.

Leveraging insights from Chang et al.,[26] who noted a medium effect size (Cohen’s d) of 0.61 in mHYS score variations, we performed a priori power analysis. This analysis, with an alpha level of 0.05 and a desired power of 0.80, indicated a minimum requisite of 22 participants to confidently detect significant changes in mHYS scores after CET, affirming the adequacy of our sample size for capturing consequential shifts in PD severity due to the intervention.

Results

This program was designed to improve motor, nonmotor, and cognitive functions, the specifics of which are detailed in Table 1. Significant improvements were observed in cognitive functions, with UPDRS Part I scores decreasing from 13 to 7 (p<0.001). Motor symptoms, evaluated by UPDRS Part III, showed notable improvement, with scores reduced from 27 to 20 (p<0.001). Positive changes were also observed in nonmotor symptoms, with Non-Motor Symptoms Questionnaire scores dropping from 10 to 8 (p=0.005). Noteworthy improvements in anxiety and depression levels were measured by the HADS, with scores significantly decreasing (p=0.039 and p=0.008, respectively).

Quality of life, as quantified by the Parkinson’s Disease Questionnaire-39, showed marked progress in social support, cognition, and bodily discomfort (all p<0.01). Furthermore, the Brief Pain Inventory reflected significant improvements in the ability to work and maintain interpersonal relationships (p=0.027). Other cognitive assessments indicated slight enhancements in overall function, with substantial progress in specific cognitive tasks noted (p<0.01); these results are comprehensively summarized in Table 2.

Assessments of mobility and balance also showed notable improvements. The Tinetti Gait and Balance Scale scores increased from 32 to 34 (p=0.009), and balance scores improved from 23.5 to 25 (p=0.008). The Tinetti Falls Efficacy Scale scores decreased from 13 to 10 (p=0.021), suggesting increased fall efficiency. However, changes in the timed-up-and-go test did not achieve statistical significance (p=0.094), as outlined in Table 3.

Regarding biological markers, alpha-synuclein levels measured before and after the exercise program did not change significantly. Exosomal alpha-synuclein showed a slight decrease from 227 pg/mL to 213 pg/mL (p=0.159), and total plasma alpha-synuclein levels exhibited a minor increase from 4,350 pg/mL to 5,350 pg/mL (p=0.230). These findings are displayed in Table 4.

Discussion

This study highlights the profound effects of a 12-week CET on PD symptoms. Despite marked improvements in motor, nonmotor, cognitive, and movement areas, alpha-synuclein levels remained unchanged, indicating other mechanisms may drive these benefits.

Parkinson’s disease is a multifaceted neurodegenerative disorder with both motor and nonmotor manifestations. Recent focus on exercise as a therapeutic avenue stems from its neuroprotective characteristics. Various modalities, from aerobic exercises to dance therapies, have been investigated for PD management. Dance interventions have shown to enhance movement coordination and cognitive function, likely due to improved sensorimotor coordination and social aspects.[27]

However, the range of CET approaches emphasizes the need for standardized protocols. Different research outcomes could arise from exercise modality variations, differing intensities, or patient demographics. For instance, contrasting findings by Vitório et al.[16] and Hubble et al.[28] might be attributed to methodological differences or patient specifics. Maintaining CET adherence over time is challenging. Innovative strategies, such as app-based reminders, could boost participation. Furthermore, technology-augmented remote CET delivery may increase patient engagement.

Although some debate the extent of exercise's influence on PD severity, our research found notable improvements after CET. This could indicate symptom relief rather than genuine disease regression. Additionally, the depressive aspect of PD, overshadowed by prominent motor symptoms, needs consideration. Group activities, such as dancing, might offer therapeutic effects due to their social and neurochemical components.[27] Sage and Almeida reported that sensory attention focused exercise had a beneficial effect on motor symptoms in PD patients.[29] From a molecular perspective, some hypothesize that exercise benefits in PD are related to decreased alpha-synuclein accumulation and reduced inflammation.[5,30] Preliminary research suggests exercise might deter abnormal protein build-up.[2,3,17,31,32] However, consistent alpha-synuclein levels in our findings necessitate further investigations.

This study is limited by its participant pool and lack of a control group, potentially affecting generalizability.

In conclusion, this study emphasizes the significant role of exercise in PD symptom management. Comprehensive research is essential to validate these findings and understand CET's comprehensive effect on PD.

Cite this article as: Mustafayev N, Tunç A, Elibol B, Eren KU, Terzioglu-Usak S. Impact of a 12-week structured exercise program on motor function and exosomal alpha-synuclein levels in Parkinson’s disease: A prospective analysis. Turk J Neurol 2024;30(2):86-92. doi: 10.55697/tnd.2024.8.

The data that support the findings of this study are available from the corresponding author upon reasonable request.

The study protocol was approved by the Bezmialem Vakıf University Faculty of Medicine Hospital Ethics Committee (date: 09.01.2019, no: 2019-448). The study was conducted in accordance with the principles of the Declaration of Helsinki.

A written informed consent was obtained from each patient.

Author contributions: N.M., A.T., B.E., K.U.E., S.T.U.; Contributed significantly to this study: N.M., A.T., B.E.; Were primarily responsible for the study's conception and design: S.T.U., K.U.E.; Contributed to the data collection and analysis: A.T., N.M., S.T.U.; Assisted with the interpretation of the results and manuscript preparation: N.M., B.E., S.T.U.; Conducted the literature review: N.M., B.E.; Supervised the project and critically reviewed the manuscript: A.T., N.M.; Were responsible for writing the article: N.M.; Ensured the acquisition of funding and resources. All authors reviewed and approved the final manuscript.

The authors declared no conflicts of interest with respect to the authorship and/or publication of this article.

This work was supported by the grant of Bezmialem Foundation University’s Scientific Research Projects Coordination Unit (grant references number: 2.2019/15).

I extend my deepest gratitude to my dear professor, Gulsen Babacan Yıldız, for their invaluable counsel and knowledge throughout my residency. Their patience and understanding have left an indelible impact on my academic development. I am profoundly thankful for their support and convey my utmost respect and appreciation.

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