Premotor symptoms and the risk of Parkinson's disease: A case-control study in Mexican population

Nuclear localization of alpha-synuclein induces anxiety-like behavior in mice by decreasing hippocampal neurogenesis and pathologically affecting amygdala circuits

Fear and anxiety are common in Parkinson's disease (PD) and may be caused by pathologies outside the dopaminergic system. Increasing evidence has shown that alpha-synuclein (α-syn) is involved in the development of anxiety in PD. In this study, we examined the effects of α-syn nuclear translocation on anxiety-like behavior in mice by overexpressing α-syn in the nuclei of the cell in the hippocampus. Our results show that α-syn overexpression in the nuclei increased the excitability of hippocampal neurons and activated NG2 glial cells and promoted the synthesis and release of γ-aminobutyric acid (GABA). And nuclear localization of α-syn led to the loss of neurotrophic factors and decreased neurogenesis. Meanwhile, the hippocampus and amygdala acted synergistically, resulting in pathologic accumulation of α-syn and gliosis in the amygdala and caused loss of interneurons. These events led to the impairments of hippocampus and amygdala function, which ultimately induced anxiety-like behavior in mice. The findings obtained in our present study indicate that excessive nuclear translocation of α-syn in hippocampal neurons and damage to the amygdala circuits may be important in the development of anxiety in PD.

Impact of deep brain stimulation (DBS) on olfaction in Parkinson's disease: Clinical features and functional hypotheses

Deep brain stimulation (DBS) is a surgical therapy typically applied in Parkinson's disease (PD). The efficacity of DBS on the control of motor symptoms in PD is well grounded while the efficacity on non-motor symptoms is more controversial, especially on olfactory disorders (ODs). The present review shows that DBS does not improve hyposmia but can affect positively identification/discrimination scores in PD. The functional hypotheses suggest complex mechanisms in terms of cerebral connectivity and neurogenesis process which could act indirectly on the olfactory bulb and olfactory pathways related to specific cognitive olfactory tasks. The functional hypotheses also suggest complex mechanisms of cholinergic neurotransmitter interactions involved in these pathways. Finally, the impact of DBS on general cognitive functions in PD could also be beneficial to identification/discrimination tasks in PD.

Prodromal depression and subsequent risk of developing Parkinson's disease: a systematic review with meta-analysis

Aim: Parkinson's disease (PD) is a progressive neurological disorder that predominately affects dopaminergic neurons. We believe that this pooling of data will help to better understand the prodromal nature of depression in PD. Materials & methods: We conducted this study in accordance with PRISMA guidelines 2020. Fifteen eligible articles were shortlisted for final analysis. Risk of bias assessment was also conducted Results: The random-effect model revealed that the risk of subsequent Parkinson's disease in patients with prodromal depression was twice as likely (OR, 2.04; 95% CI, 1.02-4.08) as compared with a healthy population. Conclusion: Our meta-analysis concluded that the subsequent risk of PD is significantly higher in patients with depression as compared with healthy individuals.

Impact of Subthalamic Deep Brain Stimulation on Hyposmia in Patients With Parkinson's Disease Is Influenced by Constipation and Dysbiosis of Microbiota

Background: Non-motor symptoms in PD usually arise at very early stage and vary during the whole disease progression. Deep brain stimulation (DBS) is considered as a highly efficient treatment option for PD's motor function. However, the effect of DBS on NMS, especially hyposmia, has not been fully understood and the deep connection between different NMS such as hyposmia and constipation is still unknown. Objective: The objective of this study was to evaluate the therapeutic effect of DBS on hyposmia in PD patients with or without constipation and find potential factors which might influence the efficacy. Methods: A retrospective analysis of 65 PD patients accepted STN-DBS operation in Qilu Hospital during 2019-2020 were conducted to evaluate the exact therapeutic effect of DBS on hyposmia in PD. Sub-group analyses about the relationship between hyposmia and constipation were carried out. Analysis of flora in nasal mucosa was also conducted to evaluate the abundance and variety in different PD groups. Results: Our study showed that DBS had clearly improved olfactory function in Parkinson patients (P = 0.012) and subgroup analysis found that PD patients with constipation have lower olfactory function scores (25.27 ± 3.44 vs. 33.90 ± 6.633, p = 0.014) and worse improvement after DBS operation (ΔTDI 12.11 ± 3.2 vs. 8.78 ± 2.91, p = 0.0072). Analysis of flora indicated the obvious discrepancy on olfactory function scores and degree of improvement might be related to the abundance and dysbiosis of microbiota. Conclusion: In summary, this article presents a study on PD with hyposmia and constipation after DBS operation, explored the relationship between different NMS and offer a potential explanation on why PD patients with constipation usually have worse olfactory function for the less abundance and variety of microbiota.

The Relationship Between Anxiety Disorders and Parkinson's Disease: Clinical and Therapeutic Issues

PURPOSE OF REVIEW

This paper seeks to describe anxiety's different symptomatologic presentations in Parkinson's disease (PD), its longitudinal course and predictors, as well as its motor and non-motor correlates. It also reviews the available screening tools and different treatment modalities.

RECENT FINDINGS

In PD, longitudinal predictors of anxiety are mostly non-motor non-dopaminergic symptoms. The longitudinal course of anxiety is mainly a stable one. The Parkinson Anxiety Scale and the Geriatric Anxiety Scale are the 2 recommended screening tools. A third of PD patients suffer from an anxiety disorder at any time point. It can precede or follow PD motor symptoms. Anxiety is associated with demographic, disease-related motor and non-motor features. There is a lack of studies evaluating psychotropic treatment of anxiety in PD. Adjustment of dopaminergic treatment is indicated when anxiety is associated with motor fluctuations. DBS can be useful as well as CBT and body-mind interventions.

Role of Microgliosis and NLRP3 Inflammasome in Parkinson's Disease Pathogenesis and Therapy

Parkinson's disease (PD) is a neurodegenerative disorder marked primarily by motor symptoms such as rigidity, bradykinesia, postural instability and resting tremor associated with dopaminergic neuronal loss in the Substantia Nigra pars compacta (SNpc) and deficit of dopamine in the basal ganglia. These motor symptoms can be preceded by pre-motor symptoms whose recognition can be useful to apply different strategies to evaluate risk, early diagnosis and prevention of PD progression. Although clinical characteristics of PD are well defined, its pathogenesis is still not completely known, what makes discoveries of therapies capable of curing patients difficult to be reached. Several theories about the cause of idiopathic PD have been investigated and among them, the key role of inflammation, microglia and the inflammasome in the pathogenesis of PD has been considered. In this review, we describe the role and relation of both the inflammasome and microglial activation with the pathogenesis, symptoms, progression and the possibilities for new therapeutic strategies in PD.

Non-motor Symptoms in Parkinson's Disease Patients with Parkin Mutations: More Depression and Less Executive Dysfunction

The purpose of this study was to identify differences between genetically undefined (GU) early-onset Parkinson's disease (EOPD) patients and carriers of Parkin mutations on non-motor symptoms (NMSs). EOPD patients (N = 261) underwent targeted sequencing of Parkinson's disease (PD) related genes. Among them, 53 cases carried homozygous or compound heterozygous Parkin mutations (Parkin group) while 208 did not carry known causative PD mutations or risk factors of GBA or Parkin heterozygous mutations (GU group). NMSs were evaluated by face-to-face interviews, self-completed questionnaires and results on a neuropsychological battery. Linear regression and logistic regression models were applied to assess the predictors of NMSs. Parkin patients had younger ages of onset (AOO) (p < 0.001), longer disease durations (p < 0.001) and lower grades of Hoehn and Yarh (H&Y) (p = 0.007). Results on the neuropsychological battery showed a shorter time in Trail Making Test (TMT) (part B) in Parkin patients (p = 0.034) compared to GU patients. After adjusting for AOO, disease duration, H&Y, and levodopa equivalent daily dose (LEDD), there was a higher depression index on the Beck Depression Inventory (BDI) (p = 0.013) and better performance (p = 0.038) on executive function in the Parkin group compared to the GU group. No significant differences were found for autonomic functions, sleep-wake problems or other domains of cognitive function. Our study showed that the Parkin mutation status might be a good predictor of symptoms of depression without an impact on executive function. While these findings need to be confirmed in larger cohorts, they identify a need to screen for depression. Graphical Abstract Flow chart of genetic tests.

The therapeutic effect of deep brain stimulation on olfactory functions and clinical scores in Parkinson's disease

Deep brain stimulation (DBS) is still a highly effective treatment option that significantly improves motor function in advanced PD. Moreover, previous findings have shown that Olfactory dysfunction (OD) has been found in a majority of patients with Parkinson's Disease (PD). Despite this, the effect of DBS on the olfactory function is not fully understood. Here we aimed to determine the effect of STN DBS on OD by evaluating the olfactory functions in the preoperative and postoperative early stages (1st and 3rd months) in forty-five PD patients and 40 healthy controls. The therapeutic effect of DBS on the improvement of motor functions was parallelly investigated. We have observed that there was a significant improvement in OI in the 1st month and in all olfactory parameters (OT, ODI, OI, and TDI) in the 3rd month. In evaluating the motor functional scores, we have revealed a statistically significant (p < 0.001) difference between preoperative UPDRS-motor score (23 ± 7.3) and the postoperative 3rd month score (11.1 ± 5.1). Although Beck Depression and Anxiety scores were improved to a certain level in the 3rd month, this improvement was not at a statistically significant level (p > 0.05). As a conclusion, we have shown that STN-DBS improves the smell functions in PD within three months suggesting that the therapeutic effects of DBS might have a wide range of therapeutic spectrum. Despite some limitations (i.e., short follow-up period) our study gives a critical message that future studies are needed to evaluate the functional correlates of STN-DBS treatment in PD patients.

Long-term exposure to air pollution and the incidence of Parkinson's disease: A nested case-control study

BACKGROUND

Previous studies revealed that chronic exposure to air pollution can significantly increase the risk of the development of Parkinson's disease (PD), but this relationship is inconclusive as large-scale prospective studies are limited and the results are inconsistent. Therefore, the purpose of this study was to ascertain the adverse health effects of air pollution exposure in a nationwide population using a longitudinal approach.

MATERIALS AND METHODS

We conducted a nested case-control study using the National Health Insurance Research Dataset (NHIRD), which consisted of 1,000,000 beneficiaries in the National Health Insurance Program (NHI) in the year 2000 and their medical records from 1995 to 2013 and using public data on air pollution concentrations from monitoring stations across Taiwan released from the Environmental Protection Administration to identify people with ages ≥ 40 years living in areas with monitoring stations during 1995-1999 as study subjects. Then, we excluded subjects with PD, dementia, stroke and diabetes diagnosed before Jan. 1, 2000 and obtained 54,524 subjects to follow until Dec. 31, 2013. In this observational period, 1060 newly diagnosed PD cases were identified. 4240 controls were randomly selected from those without PD using a matching strategy for age, sex, the year of PD diagnosis and the year of entering the NHI program at a ratio of 1:4. Ten elements of air pollution were examined, and multiple logistic regression models were used to measure their risks in subsequent PD development.

RESULTS

The incidence of PD in adults aged ≥ 40 years was 1.9%, and the median duration for disease onset was 8.45 years. None of the chemical compounds (SO2, O3, CO, NOx, NO, NO2, THC, CH4, or NMHC) significantly affected the incidence of PD except for particulate matter. PM10 exposure showed significant effects on the likelihood of PD development (T3 level: > 65μg/m3 versus T1 level: ≤ 54μg/m3; OR = 1.35, 95% CI = 1.12-1.62, 0.001 ≤ P < 0.01). In addition, comorbid conditions such as dementia (ORs = 3.53-3.93, Ps < 0.001), stroke (ORs = 2.99-3.01, Ps < 0.001), depression (ORs = 2.51-2.64, Ps < 0.001), head injury (ORs = 1.24-1.29, 0.001 ≤ Ps < 0.01 or 0.01 ≤ Ps < 0.05), sleep disorder (OR = 1.23-1.26, 0.001 ≤ Ps < 0.01), and hypertension (ORs = 1.18-1.19, 0.01 ≤ Ps < 0.05) also significantly increased the risk for PD development.

CONCLUSIONS

Although PM10 plays a significant role in PD development, the associated chemical/metal compounds that are capable of inducing adverse biological mechanisms still warrant further exploration. Because of a link between comorbid conditions and PM exposure, research on the causal relationship between long-term exposure to PM and the development of PD should be considered with caution because other possible modifiers or mediators, comorbid diseases in particular, may be involved.