Subclinical Cardiac Microdamage, Motor Severity, and Cognition in Parkinson's Disease

How should we be using biomarkers in trials of disease modification in Parkinson's disease?

The recent validation of the α-synuclein seed amplification assay as a biomarker with high sensitivity and specificity for the diagnosis of Parkinson's disease has formed the backbone for a proposed staging system for incorporation in Parkinson's disease clinical studies and trials. The routine use of this biomarker should greatly aid in the accuracy of diagnosis during recruitment of Parkinson's disease patients into trials (as distinct from patients with non-Parkinson's disease parkinsonism or non-Parkinson's disease tremors). There remain, however, further challenges in the pursuit of biomarkers for clinical trials of disease modifying agents in Parkinson's disease, namely: optimizing the distinction between different α-synucleinopathies; the selection of subgroups most likely to benefit from a candidate disease modifying agent; a sensitive means of confirming target engagement; and the early prediction of longer-term clinical benefit. For example, levels of CSF proteins such as the lysosomal enzyme β-glucocerebrosidase may assist in prognostication or allow enrichment of appropriate patients into disease modifying trials of agents with this enzyme as the target; the presence of coexisting Alzheimer's disease-like pathology (detectable through CSF levels of amyloid-β42 and tau) can predict subsequent cognitive decline; imaging techniques such as free-water or neuromelanin MRI may objectively track decline in Parkinson's disease even in its later stages. The exploitation of additional biomarkers to the α-synuclein seed amplification assay will, therefore, greatly add to our ability to plan trials and assess the disease modifying properties of interventions. The choice of which biomarker(s) to use in the context of disease modifying clinical trials will depend on the intervention, the stage (at risk, premotor, motor, complex) of the population recruited and the aims of the trial. The progress already made lends hope that panels of fluid biomarkers in tandem with structural or functional imaging may provide sensitive and objective methods of confirming that an intervention is modifying a key pathophysiological process of Parkinson's disease. However, correlation with clinical progression does not necessarily equate to causation, and the ongoing validation of quantitative biomarkers will depend on insightful clinical-genetic-pathophysiological comparisons incorporating longitudinal biomarker changes from those at genetic risk with evidence of onset of the pathophysiology and those at each stage of manifest clinical Parkinson's disease.

Blood neurofilament light chain in Parkinson's disease

Blood neurofilament light chain (NfL) is an easily accessible, highly sensitive and reliable biomarker for neuroaxonal damage. Currently, its role in Parkinson's disease (PD) remains unclear. Here, we demonstrate that blood NfL can distinguish idiopathic PD from atypical parkinsonian syndromes (APS) with high sensitivity and specificity. In cross-sectional studies, some found significant correlations between blood NfL with motor and cognitive function, whereas others did not. In contrast, prospective studies reported very consistent associations between baseline blood NfL with motor progression and cognitive worsening. Amongst PD subtypes, especially postural instability and gait disorder (PIGD) subtype, symptoms and scores are reliably linked with blood NfL. Different non-motor PD comorbidities have also been associated with high blood NfL levels suggesting that the neuroaxonal damage of the autonomic nervous system as well as serotonergic, cholinergic and noradrenergic neurons is quantifiable. Numerous absolute NfL cutoff levels have been suggested in different cohort studies; however, validation across cohorts remains weak. However, age-adjusted percentiles and intra-individual blood NfL changes might represent more valid and consistent parameters compared with absolute NfL concentrations. In summary, blood NfL has the potential as biomarker in PD patients to be used in clinical practice for prediction of disease severity and especially progression.

Blood-based biomarker in Parkinson's disease: potential for future applications in clinical research and practice

The clinical presentation of Parkinson's disease (PD) is both complex and heterogeneous, and its precise classification often requires an intensive work-up. The differential diagnosis, assessment of disease progression, evaluation of therapeutic responses, or identification of PD subtypes frequently remains uncertain from a clinical point of view. Various tissue- and fluid-based biomarkers are currently being investigated to improve the description of PD. From a clinician's perspective, signatures from blood that are relatively easy to obtain would have great potential for use in clinical practice if they fulfill the necessary requirements as PD biomarker. In this review article, we summarize the knowledge on blood-based PD biomarkers and present both a researcher's and a clinician's perspective on recent developments and potential future applications.

Diabetes, Glycated Hemoglobin (HbA1c), and Neuroaxonal Damage in Parkinson's Disease (MARK-PD Study)

BACKGROUND

Diabetes is associated with incidence and prevalence of Parkinson's disease (PD). Furthermore, glycated hemoglobin (HbA1c) levels have been linked with motor function and progression.

OBJECTIVES

We evaluated the relationship between prevalent diabetes and HbA1c levels with serum neurofilament light chain (NfL) levels as marker of neuroaxonal damage.

METHODS

NfL concentrations were analyzed with Simoa in serum of 195 PD patients with available HbA1c values. Motor (MDS-UPDRS III, Hoehn & Yahr [H&Y]) and cognitive (Montreal Cognitive Assessment [MoCA]) function was assessed and vascular comorbidities were documented from medical records.

RESULTS

PD patients with prevalent diabetes had higher serum NfL levels and lower MoCA scores independent of age, body mass index (BMI), and vascular risk factors. Furthermore, diabetes was associated with higher H&Y stages in unadjusted and age/BMI-adjusted models. Higher HbA1c levels were associated with increased NfL in unadjusted and age/BMI-adjusted models.

CONCLUSIONS

In PD patients, diabetes and high HbA1c are associated with increased neuroaxonal damage and cognitive impairment. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson Movement Disorder Society.

Serum neurofilament light chain and postural instability/gait difficulty (PIGD) subtypes of Parkinson’s disease in the MARK-PD study

The PIGD (postural instability / gait difficulty) subtype of Parkinson´s disease (PD) is associated with faster cognitive and motor decline. So far, there are no quantifiable biomarkers to aid clinical subtyping. Neurofilament light chain (NfL) is a highly specific marker of neuro-axonal damage and can be assessed in blood. Here, we investigated if serum NfL concentrations are associated with PIGD subtype and PIGD scores in PD patients at advanced disease stages. Furthermore, we evaluated if serum NfL is associated with motor and cognitive function assessed with MDS-UPDRS part III and Montreal cognitive assessment (MoCA). Serum NfL levels were analyzed with Single Molecule Assays (Simoa) in blood of 223 PD patients from the bioMARKers in Parkinson’s Disease (MARK-PD) study. Serum NfL concentrations were higher in PIGD patients independent of age, sex and disease duration. In linear regression analysis, serum NfL levels were associated with MoCA, MDS-UPDRS III and PIGD scores in unadjusted models, but remained significant after adjustment only with PIGD scores. In conclusion, increased serum NfL levels were associated with PIGD subtype and PIGD scores in patients with advanced PD.

Cardiac Troponin, Cognitive Function, and Dementia: A Systematic Review

Elevated cardiac troponin, a biomarker of myocardial injury, has been found in individuals with brain damage and lower cognitive function. We conducted a systematic review to examine the association of troponin with cognitive function, incidence of dementia and dementia-related outcomes. PubMed, Web of Science and EMBASE were searched from inception to August 2022. Inclusion criteria were: (i) population-based cohort studies; (ii) troponin measured as determinant; and (iii) cognitive function in any metric or diagnosis of any type of dementia or dementia-related measures as outcomes. Fourteen studies were identified and included, with a combined total of 38,286 participants. Of these studies, four examined dementia-related outcomes, eight studies examined cognitive function, and two studies examined both dementia-related outcomes and cognitive function. Studies report higher troponin to be associated with higher prevalence of cognitive impairment (n=1), incident dementia (n=1), increased risk of dementia hospitalization (specifically due to vascular dementia) (n=1), but not with incident Alzheimer's Disease (n=2). Majority of studies on cognitive function found elevated troponin also associated with worse global cognitive function (n=3), attention (n=2), reaction time (n=1) and visuomotor speed (n=1), both cross-sectionally and prospectively. Evidence regarding the association between higher troponin and memory, executive function, processing speed, language and visuospatial function was mixed. This was the first systematic review on the association between troponin, cognitive function, and dementia. Higher troponin is associated with subclinical cerebrovascular damage and might act as a risk-marker of cognitive vulnerability.

Serum neurofilament is associated with motor function, cognitive decline and subclinical cardiac damage in advanced Parkinson's disease (MARK-PD)

INTRODUCTION

Serum neurofilament light chain (NfL) levels are associated with disease severity in early Parkinson's disease (PD). We assessed the association of serum NfL with motor and cognitive function and decline in advanced PD patients.

METHODS

NfL concentrations were analyzed with single molecule array (Simoa) assay in serum of 289 PD patients with advanced disease from the single-center prospective observational biobank study Biomarkers in Parkinson's disease (MARK-PD). Motor and cognitive symptoms were assessed with MDS-UPDRS III, Hoehn&Yahr stages and Montreal Cognitive Assessment (MoCA) at baseline and during 520 [364, 674] days of follow-up.

RESULTS

Serum NfL concentrations were associated with Hoehn&Yahr stages. During follow-up, baseline NfL levels were associated with time to cognitive decline in adjusted Cox regression models (hazard ratio: 3.23; 95% CI [1.16, 9.00], P < 0.025). Serum NfL was associated with NT-proBNP in adjusted models linking neuronal and cardiac damage in advanced PD patients.

CONCLUSION

In advanced PD patients, serum NfL concentrations are associated with motor function, cognitive decline and subclinical cardiac damage.

Cardiovascular and cerebrovascular risk markers in Parkinson's disease: Results from a case-control study

BACKGROUND

The relationship between Parkinson's disease (PD) and cardiovascular and cerebrovascular disease is not yet well established. Recent data suggest an increased risk of myocardial infarction and stroke in PD patients. Therefore, we designed a study to assess surrogate markers of cardiovascular and cerebrovascular risk in PD.

METHODS

We conducted a case-control study comparing PD patients recruited from a Movement Disorders Unit with controls randomly invited from a primary healthcare center. All participants underwent a detailed clinical evaluation, including medical history, physical assessment, carotid ultrasound, blood and urine analysis, and 24-h ambulatory blood pressure monitoring. The primary outcome was the carotid intima-media thickness (CIMT).

RESULTS

We included 102 participants in each study arm. No significant difference was found in the CIMT among groups (MD: 0.01, 95% CI: -0.02, 0.04). Carotid plaques were more frequent in PD patients (OR: 1.90, 95% CI: 1.02, 3.55), although the lipid profile was more favorable in this group (LDL MD: -18.75; 95% CI: -10.69, -26.81). Nocturnal systolic blood pressure was significantly higher in PD patients (MD: 4.37, 95% CI: 0.27, 8.47) and more than half of the PD patients were non-dippers or reverse dippers (OR: 1.83, 95% CI: 1.04, 3.20).

CONCLUSION

We did not find a difference in CIMT between PD and controls. A higher frequency of carotid plaques and abnormal dipper profile supports the hypothesis that PD patients are not protected from cardiovascular and cerebrovascular disease.

Sphingosine-1-Phosphate, Motor Severity, and Progression in Parkinson's Disease (MARK-PD)

BACKGROUND

Treatment with sphingosine-1-phosphate (S1P) agonists confers neuroprotective effects in animal models of Parkinson's disease (PD).

OBJECTIVES

We assessed the association of serum S1P levels with motor and cognitive symptoms in patients with PD.

METHODS

S1P concentrations were analyzed with liquid chromatography-tandem mass spectrometry (LC-MS/MS) in serum of 196 PD patients and in 196 age- and sex-matched controls. Motor (Unified Parkinson's disease rating scale III [UPDRS III], Hoehn and Yahr) and cognitive (Montreal Cognitive Assessment [MoCA]) function were assessed at baseline. Follow-up data was available from 64 patients (median [interquartile range], 513 [381-677] days).

RESULTS

S1P levels were lower in PD patients compared with controls, that is 1.75 (1.38-2.07) and 1.90 (1.59-2.18) μmol/L, respectively (P = 0.001). In PD patients, lower S1P concentrations were associated with higher UPDRS III scores and Hoehn and Yahr stage. In the follow-up cohort, S1P concentrations below the median were associated with faster motor decline (hazard ratio: 4.78 [95% CI, 1.98, 11.50]), but not with cognitive worsening.

CONCLUSIONS

Our observations reveal an association of S1P with PD. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Association of lipid levels with motor and cognitive function and decline in advanced Parkinson's disease in the Mark-PD study

OBJECTIVES

In prospective cohort studies different blood lipid fractions have been identified as risk factors of Parkinson's disease (PD). However, data relating lipoproteins to disease phenotypes and progression in advanced PD patients are sparse. Therefore, we assessed the most common lipoproteins in a case-control design and evaluated their associations with motor and cognitive function and decline in PD patients.

METHODS

Triglycerides, LDL-cholesterol (LDL-C), HDL-cholesterol (HDL-C), apolipoprotein A1 (ApoA1), apolipoprotein B (ApoB), and lipoprotein a (Lp(a)) were analyzed in 294 PD patients of the MARK-PD study cohort and 588 controls matched for age, sex and cardiovascular risk factors. In PD patients, motor (MDS-UPDRS III, Hoehn-Yahr stage) and cognitive function (MoCA) were examined. In a sub-cohort (n = 98 patients), baseline lipid levels were correlated with motor and cognitive disease progression during a follow-up period of 523 ± 199 days.

RESULTS

At baseline, HDL-C levels were lower in PD patients compared to matched controls after adjustment. We observed a very weak association of Lp(a) levels with UDPRS III scores. In cross-sectional analyses, no other lipid fraction revealed a significant and consistent association with motor or cognitive function. During follow-up, no lipid fraction level was associated with motor or cognitive progression.

CONCLUSION

In advanced PD, there is no strong and consistent association of lipid levels with motor or cognitive function and decline.