Non-Motor Features of Parkinson's Disease in Women

Keeping an eye on Parkinson's disease: color vision and outer retinal thickness as simple and non-invasive biomarkers

Over the last two decades, visual symptoms and retinal changes in Parkinson's disease (PD) have emerged as important biomarkers. Color vision deficiency, which begins in the outer retina, has been increasingly investigated, but a focused review of these papers has not recently been conducted. Similarly, thinning of the outer retina as measured using optical coherence tomography (OCT) holds potential as a screening marker for PD, particularly as these devices are already commonplace in community and hospital settings. Moreover, outer retinal thinning may be more specific for Parkinson's disease as inner retinal changes also occur in more common neurodegenerative diseases like glaucoma and Alzheimer's disease. This review summarizes contemporary evidence on two outer retina focused measures, color vision and outer retinal thickness, which can be readily quantified using non-invasive approaches and thus examines their potential as biomarkers for screening, detection, and progression in PD.

Eugenia uniflora Effects on the Depressive-like Behavior of MPTP-Exposed Female Rats: Apoptosis and α-Synuclein Modulation

Background: Parkinson's disease (PD) is a neurodegenerative disorder marked by motor deficits and non-motor symptoms, such as depression, which are associated with dopaminergic loss and α-synuclein aggregation in the brain. Objectives: This study investigated the neuroprotective effects of a hydroalcoholic extract of the purple fruit of Eugenia uniflora (PFEU) on motor ability and depressive-like behaviors in a PD model induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in female Wistar rats. Methods: Rats received intranasal administration of MPTP or vehicle, followed by 14 days of oral administration of PFEU (300 or 2000 mg/kg, administered once daily) or vehicle. Depressive-like behavior was assessed using the splash and forced swimming tests, while motor ability was evaluated using the rotarod and open field tests. On day 15, hippocampal tissue was collected for immunoreactivity analysis. Results: MPTP treatment induced depressive-like behavior, which was significantly reversed by PFEU, as evidenced by increased grooming and decreased immobility. No motor coordination or locomotion deficits were observed. Furthermore, PFEU treatment prevented the MPTP-induced increase in hippocampal α-synuclein, p-p53, and Bax while restoring Bcl-2 levels, suggesting neuroprotective effects through the modulation of apoptotic pathways and α-synuclein. Conclusions: These findings support PFEU's potential as a neuroprotective agent for MPTP-induced depressive-like behavior in female rats, highlighting its molecular mechanisms.

Metagenomics of the Gut Microbiome in Parkinson's Disease: Prodromal Changes

OBJECTIVE

Prior studies on the gut microbiome in Parkinson's disease (PD) have yielded conflicting results, and few studies have focused on prodromal (premotor) PD or used shotgun metagenomic profiling to assess microbial functional potential. We conducted a nested case-control study within 2 large epidemiological cohorts to examine the role of the gut microbiome in PD.

METHODS

We profiled the fecal metagenomes of 420 participants in the Nurses' Health Study and the Health Professionals Follow-up Study with recent onset PD (N = 75), with features of prodromal PD (N = 101), controls with constipation (N = 113), and healthy controls (N = 131) to identify microbial taxonomic and functional features associated with PD and features suggestive of prodromal PD. Omnibus and feature-wise analyses identified bacterial species and pathways associated with prodromal and recently onset PD.

RESULTS

We observed depletion of several strict anaerobes associated with reduced inflammation among participants with PD or features of prodromal PD. A microbiome-based classifier had moderate accuracy (area under the curve [AUC] = 0.76 for species and 0.74 for pathways) to discriminate between recently onset PD cases and controls. These taxonomic shifts corresponded with functional shifts indicative of carbohydrate source preference. Similar, but less marked, changes were observed in participants with features of prodromal PD, in both microbial features and functions.

INTERPRETATION

PD and features of prodromal PD were associated with similar changes in the gut microbiome. These findings suggest that changes in the microbiome could represent novel biomarkers for the earliest phases of PD. ANN NEUROL 2023;94:486-501.

Subjective Cognitive Decline in Women with Features Suggestive of Prodromal Parkinson's Disease

BACKGROUND

Cognitive deficits can be present in the prodromal phase of Parkinson's disease (PD). Subjective cognitive decline (SCD) may contribute to identifying individuals with prodromal PD.

OBJECTIVE

The objective of this study was to examine whether SCD is more likely to be present in women with features suggestive of prodromal PD compared with women without these features.

METHODS

The study population comprised 12,427 women from the Nurses' Health Study selected to investigate prodromal PD. Prodromal and risk markers of PD were assessed via self-administered questionnaires. We evaluated the association of hyposmia, constipation, and probable rapid eye movement sleep behavior disorder, three major features of prodromal PD, with SCD, adjusting for age, education, body mass index, physical activity, smoking, alcohol, caffeine intake, and depression. We also explored whether SCD was associated with the probability of prodromal PD and conducted additional analyses using data from neurocognitive tests.

RESULTS

Women experiencing the three examined nonmotor features had the worst mean SCD score and the highest odds of poor subjective cognition (odds ratio [OR] = 1.78; 95% confidence interval [CI], 1.29-2.47). This association persisted when women with objective cognitive deficits were excluded from analyses. SCD was also more common in women with a probability of prodromal PD ≥0.80, particularly among those aged younger than 75 years (OR of poor subjective cognition = 6.57 [95% CI, 2.43-17.77]). These observations were consistent with the results from analyses using neurocognitive tests, where a worse global cognitive performance was observed among women with three features.

CONCLUSIONS

Our study suggests that self-perceived cognitive decline can be present during the prodromal phase of PD. © 2023 International Parkinson and Movement Disorder Society.

Diet Quality is Associated with Prodromal Parkinson's Disease Features in Chinese Adults

BACKGROUND

The prodromal phase of Parkinson's disease (PD) is a critical window for prevention by modifying lifestyle factors. However, there is limited knowledge on how diet quality is associated with prodromal PD symptoms in Asian populations.

OBJECTIVE

To examine the association between overall diet quality and prodromal PD features.

METHODS

A total of 71,640 Chinese participants who were free of PD were included in this cross-sectional study. Diet quality was assessed using the modified Alternative Healthy Eating Index (mAHEI) and alternate Mediterranean Diet (aMED). Five prodromal features including probable rapid eye movement sleep behavior disorder (pRBD), hyposmia, excessive daytime sleepiness, constipation, and depressive symptom were measured using validated questionnaires. Logistic regression was used to calculate the odds ratio (OR) for having a combination of prodromal PD symptoms (1 and 2+ symptoms vs. 0 symptoms), adjusting for age, sex, lifestyle factors, total energy intake, and other potential confounders.

RESULTS

In the multivariable-adjusted model, the OR for having 2+ versus 0 prodromal PD features was 0.64 (95% confidence interval [CI]: 0.49, 0.85) comparing the highest versus the lowest mAHEI diet quality quartiles with a significant inverse trend (P-trend = 0.003). For individual prodromal PD features, better diet quality, as assessed by the mAHEI, was associated with lower odds of having excessive daytime sleepiness and constipation (P-trend < 0.05 for both). We observed a marginally significant association between aMED and prodromal PD features (adjusted OR comparing the extreme quartiles = 0.74; 95% CI: 0.55, 0.98; P-trend = 0.09).

CONCLUSION

Better diet quality, as assessed by the mAHEI and the aMED, was associated with lower probability of having prodromal PD features in Chinese adults. © 2022 International Parkinson and Movement Disorder Society.

Who to Enroll in Parkinson Disease Prevention Trials? The Case for Composite Prodromal Cohorts

Significant progress has been made in expanding our understanding of prodromal Parkinson disease (PD), particularly for recognition of early motor and nonmotor signs and symptoms. Although identification of these prodromal features may improve our understanding of the earliest stages of PD, they are individually insufficient for early disease detection and enrollment of participants in prevention trials in most cases because of low sensitivity, specificity, and positive predictive value. Composite cohorts, composed of individuals with multiple co-occurring prodromal features, are an important resource for conducting prodromal PD research and eventual prevention trials because they are more representative of the population at risk for PD, allow investigators to evaluate the efficacy of an intervention across individuals with varying prodromal feature patterns, are able to produce larger sample sizes, and capture individuals at different stages of prodromal PD. A key challenge in identifying individuals with prodromal disease for composite cohorts and prevention trial participation is that we know little about the natural history of prodromal PD. To move toward prevention trials, it is critical that we better understand common prodromal feature patterns and be able to predict the probability of progression and phenoconversion. Ongoing research in cohort studies and administrative databases is beginning to address these questions, but further longitudinal analyses in a large population-based sample are necessary to provide a convincing and definitive strategy for identifying individuals to be enrolled in a prevention trial.

Perspective: cell death mechanisms and early diagnosis as precondition for disease modification in Parkinson's disease: are we on the right track?

INTRODUCTION

Current research paradigms on biomarkers for chronic neurodegenerative diseases, such as Parkinson's disease, focus on identification of reliable, easy-to-apply tools for diagnostic screening and progression assessment.

AREAS COVERED

This perspective discusses possible misconceptions of biomarker research in chronic neurodegeneration from a clinician's view based on a not systematic literature search. Multifactorial disease triggers, heterogeneity of symptom and their progression are main reasons for the still missing availability of biomarkers.

EXPERT OPINION

Onset of chronic neurodegenerative disease entities may probably result from a decompensated endogenous repair machinery in the central nervous system, for example the neogenin receptor associated repulsive guidance molecule pathway. Future clinical research is warranted on these repair structures and aim to identify markers for the imbalance between damage and repair, which hypothetically contributes to generation of disease. An assignment to a specific chronic neurodegenerative disease entity probably appears to be secondary. Decryption of probable molecular signals of an impaired repair potential will enable an earlier diagnosis, better monitoring of disease progress and of treatment response. This concept will hopefully provide better preconditions for prevention, cure or therapeutic beneficial disease modification. These unmet therapeutic needs may be achieved for example via antagonism of repulsive guidance molecule A.