X-Linked Parkinsonism: Phenotypic and Genetic Heterogeneity

Association of Terazosin, Doxazosin, or Alfuzosin Use and Risk of Dementia With Lewy Bodies in Men

BACKGROUND AND OBJECTIVES

Terazosin, doxazosin, and alfuzosin (Tz/Dz/Az) are α-1 adrenergic receptor antagonists that also bind to and activate a key adenosine triphosphate (ATP)-producing enzyme in glycolysis. It is hypothesized that the increase in energy availability in the brain may slow or prevent neurodegeneration, potentially by reducing the accumulation of alpha-synuclein. Recent work has suggested a potentially neuroprotective effect of the use of Tz/Dz/Az in Parkinson disease in both animal and human studies. We investigated the neuroprotective effects of Tz/Dz/Az in a closely related disease, dementia with Lewy bodies (DLB).

METHODS

We used a new-user active comparator design in the Merative Marketscan database to identify men with no history of DLB who were newly started on Tz/Dz/Az or 2 comparator medications. Our comparator medications were other drugs commonly used to treat benign prostatic hyperplasia that do not increase ATP: the α-1 adrenergic receptor antagonist tamsulosin or 5α-reductase inhibitor (5ARI). We matched the cohorts on propensity scores and duration of follow-up. We followed up the matched cohorts forward to estimate the hazard of developing DLB using Cox proportional hazards regression.

RESULTS

Men who were newly started on Tz/Dz/Az had a lower hazard of developing DLB than matched men taking tamsulosin (n = 242,716, 728,256 person-years, hazard ratio [HR] 0.60, 95% CI 0.50-0.71) or 5ARI (n = 130,872, 399,316 person-years, HR 0.73, 95% CI 0.57-0.93). while the hazard in men taking tamsulosin was similar to that of men taking 5ARI (n = 159,596, 482,280 person-years, HR 1.17, 95% CI 0.96-1.42). These results were robust to several sensitivity analyses.

DISCUSSION

We find an association in men who are taking Tz/Dz/Az and a lower hazard of DLB compared with similar men taking other medications. When combined with the literature of Tz/Dz/Az on Parkinson disease, our findings suggest that glycolysis-enhancing drugs may be broadly protective in neurodegenerative synucleinopathies. A future randomized trial is required to assess these associations for causality.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that Tz/Dz/Az use reduces the rate of developing DLB in adult men.

A pilot dose-finding study of Terazosin in humans

Background

Parkinson's disease (PD) is a prevalent neurodegenerative disorder where progressive neuron loss is driven by impaired brain bioenergetics, particularly mitochondrial dysfunction and disrupted cellular respiration. Terazosin (TZ), an α-1 adrenergic receptor antagonist with a known efficacy in treating benign prostatic hypertrophy and hypertension, has shown potential in addressing energy metabolism deficits associated with PD due to its action on phosphoglycerate kinase 1 (PGK1). This study aimed to investigate the safety, tolerability, bioenergetic target engagement, and optimal dose of TZ in neurologically healthy subjects.

Methods

Eighteen healthy men and women (60 - 85 years old) were stratified into two cohorts based on maximum TZ dosages (5 mg and 10 mg daily). Methods included plasma and cerebrospinal fluid TZ concentration measurements, whole blood ATP levels, 31 Phosphorous magnetic resonance spectroscopy for brain ATP levels, 18 F-FDG PET imaging for cerebral metabolic activity, and plasma metabolomics.

Results

Our results indicated that a 5 mg/day dose of TZ significantly increased whole blood ATP levels and reduced global cerebral 18 F-FDG PET uptake without significant side effects or orthostatic hypotension. These effects were consistent across sexes. Higher doses did not result in additional benefits and showed a potential biphasic dose-response.

Conclusions

TZ at a dosage of 5 mg/day engages its metabolic targets effectively in both sexes without inducing significant adverse effects and provides a promising therapeutic avenue for mitigating energetic deficiencies. Further investigation via clinical trials to validate TZ's efficacy and safety in neurodegenerative (i.e., PD) contexts is warranted.

X-Linked Levodopa-Responsive Parkinsonism-Epilepsy Syndrome: A Novel PGK1 Mutation and Literature Review

BACKGROUND

Genetic underpinnings in Parkinson's disease (PD) and parkinsonian syndromes are challenging, and recent discoveries regarding their genetic pathways have led to potential gene-specific treatment trials.

CASES

We report 3 X-linked levodopa (l-dopa)-responsive parkinsonism-epilepsy syndrome cases due to a hemizygous variant in the phosphoglycerate kinase 1 (PGK1) gene. The likely pathogenic variant NM_000291.4 (PGK1):c.950G > A;p.(Gly317Asp) was identified in a hemizygous state.

LITERATURE REVIEW

Only 8 previous cases have linked this phenotype to PGK1, a gene more commonly associated with hemolytic anemia and myopathy. The unusual association of epilepsy, psychiatric symptoms, action tremor, limb dystonia, cognitive symptoms, and l-dopa-responsive parkinsonism must draw attention to PGK1 mutations, especially because this gene is absent from most commercial hereditary parkinsonism panels.

CONCLUSIONS

This report aims to shed light on an overlooked gene that causes hereditary parkinsonian syndromes. Further research regarding genetic pathways in PD may provide a better understanding of its pathophysiology and open possibilities for new disease-modifying trials, such as SNCA, LRRK2, PRKN, PINK1, and DJ-1 genes.

Dopamine modification of glycolytic enzymes impairs glycolysis: possible implications for Parkinson's disease

BACKGROUND

Parkinson's disease (PD), a chronic and severe neurodegenerative disease, is pathologically characterized by the selective loss of nigrostriatal dopaminergic neurons. Dopamine (DA), the neurotransmitter produced by dopaminergic neurons, and its metabolites can covalently modify proteins, and dysregulation of this process has been implicated in neuronal loss in PD. However, much remains unknown about the protein targets.

METHODS

In the present work, we designed and synthesized a dopamine probe (DA-P) to screen and identify the potential protein targets of DA using activity-based protein profiling (ABPP) technology in combination with liquid chromatography-tandem mass spectrometry (LC-MS/MS). In situ pull-down assays, cellular thermal shift assays (CETSAs) and immunofluorescence were performed to confirm the DA modifications on these hits. To investigate the effects of DA modifications, we measured the enzymatic activities of these target proteins, evaluated glycolytic stress and mitochondrial respiration by Seahorse tests, and systematically analyzed the changes in metabolites with unbiased LC-MS/MS-based non-targeted metabolomics profiling.

RESULTS

We successfully identified three glycolytic proteins, aldolase A, α-enolase and pyruvate kinase M2 (PKM2), as the binding partners of DA. DA bound to Glu166 of α-enolase, Cys49 and Cys424 of PKM2, and Lys230 of aldolase A, inhibiting the enzymatic activities of α-enolase and PKM2 and thereby impairing ATP synthesis, resulting in mitochondrial dysfunction.

CONCLUSIONS

Recent research has revealed that enhancing glycolysis can offer protection against PD. The present study identified that the glycolytic pathway is vulnerable to disruption by DA, suggesting a promising avenue for potential therapeutic interventions. Safeguarding glycolysis against DA-related disruption could be a potential therapeutic intervention for PD.

Endemic parkinsonism: clusters, biology and clinical features

The term 'endemic parkinsonism' refers to diseases that manifest with a dominant parkinsonian syndrome, which can be typical or atypical, and are present only in a particular geographically defined location or population. Ten phenotypes of endemic parkinsonism are currently known: three in the Western Pacific region; two in the Asian-Oceanic region; one in the Caribbean islands of Guadeloupe and Martinique; and four in Europe. Some of these disease entities seem to be disappearing over time and therefore are probably triggered by unique environmental factors. By contrast, other types persist because they are exclusively genetically determined. Given the geographical clustering and potential overlap in biological and clinical features of these exceptionally interesting diseases, this Review provides a historical reference text and offers current perspectives on each of the 10 phenotypes of endemic parkinsonism. Knowledge obtained from the study of these disease entities supports the hypothesis that both genetic and environmental factors contribute to the development of neurodegenerative diseases, not only in endemic parkinsonism but also in general. At the same time, this understanding suggests useful directions for further research in this area.

Dystonia and Parkinson's disease: Do they have a shared biology?

Parkinsonism and dystonia co-occur across many movement disorders and are most encountered in the setting of Parkinson's disease. Here we aim to explore the shared neurobiological underpinnings of dystonia and parkinsonism through the clinical lens of the conditions in which these movement disorders can be seen together. Foregrounding the discussion, we briefly review the circuits of the motor system and the neuroanatomical and neurophysiological aspects of motor control and highlight their relevance to the proposed pathophysiology of parkinsonism and dystonia. Insight into shared biology is then sought from dystonia occurring in PD and other forms of parkinsonism including those disorders in which both can be co-expressed simultaneously. We organize these within a biological schema along with important questions to be addressed in this space.

Parkinson's disease - genetic cause

PURPOSE OF REVIEW

Our knowledge of the genetic architecture underlying Parkinson's disease has vastly improved in the past quarter century. About 5-10% of all patients suffer from a monogenic form of Parkinson's disease.

RECENT FINDINGS

Mutations in autosomal dominant genes (e.g. SNCA, LRRK2, VPS35) or autosomal recessive genes (e.g. PRKN, PINK1, DJ-1) can cause genetic Parkinson's disease. Recessive DNAJC6 mutations can present predominantly as atypical parkinsonism, but also rarely as typical Parkinson's disease. Majority of Parkinson's disease is genetically complex. Mutation in RIC3, a chaperone of neuronal nicotinic acetylcholine receptor subunit α-7 (CHRNA7), provides strong evidence for the role of cholinergic pathway, for the first time, in cause of Parkinson's disease. X-linked parkinsonism manifests at a young age accompanied by many (atypical) features such as intellectual disability, spasticity, seizures, myoclonus, dystonia, and have poor response to levodopa.

SUMMARY

This review article aims to provide a comprehensive overview on Parkinson's disease genetics. MAPT, which encodes the microtubule associated protein tau, TMEM230, LRP10, NUS1 and ARSA are the five new putative disease-causing genes in Parkinson's disease. The validation of novel genes and its association with Parkinson's disease remains extremely challenging, as genetically affected families are sparse and globally widespread. In the near future, genetic discoveries in Parkinson's disease will influence our ability to predict and prognosticate the disease, help in defining etiological subtypes that are critical in implementation of precision medicine.

Mechanisms underlying phenotypic variation in neurogenetic disorders

Neurological diseases associated with pathogenic variants in a specific gene, or even with a specific pathogenic variant, can show profound phenotypic variation with regard to symptom presentation, age at onset and disease course. Highlighting examples from a range of neurogenetic disorders, this Review explores emerging mechanisms that are involved in this variability, including environmental, genetic and epigenetic factors that influence the expressivity and penetrance of pathogenic variants. Environmental factors, some of which can potentially be modified to prevent disease, include trauma, stress and metabolic changes. Dynamic patterns of pathogenic variants might explain some of the phenotypic variations, for example, in the case of disorders caused by DNA repeat expansions such as Huntington disease (HD). An important role for modifier genes has also been identified in some neurogenetic disorders, including HD, spinocerebellar ataxia and X-linked dystonia-parkinsonism. In other disorders, such as spastic paraplegia, the basis for most of the phenotypic variability remains unclear. Epigenetic factors have been implicated in disorders such as SGCE-related myoclonus-dystonia and HD. Knowledge of the mechanisms underlying phenotypic variation is already starting to influence management strategies and clinical trials for neurogenetic disorders.

Genetic Architecture of Parkinson's Disease

Year 2022 marks 25 years since the first mutation in familial autosomal dominant Parkinson's disease was identified. Over the years, our understanding of the role of genetic factors in the pathogenesis of familial and idiopathic forms of Parkinson's disease has expanded significantly - a number of genes for the familial form of the disease have been identified, and DNA markers for an increased risk of developing its sporadic form have been found. But, despite all the success achieved, we are far from an accurate assessment of the contribution of genetic and, even more so, epigenetic factors to the disease development. The review summarizes the information accumulated to date on the genetic architecture of Parkinson's disease and formulates issues that need to be addressed, which are primarily related to the assessment of epigenetic factors in the disease pathogenesis.

Glycolysis: The Next Big Breakthrough in Parkinson's Disease

Parkinson's disease (PD) is a common neurodegenerative disease characterized by the death of dopaminergic neurons. Its pathogenesis comprises defects in the physiological pathway of mitophagy and mutations in the genes involved in this process's regulatory mechanism. PD manifests itself with multiple motor and non-motor symptoms, and currently, there are multiple pharmacological treatments, and unconventional non-drug treatments available. The mainstay of Parkinson's disease treatment has centered around directly manipulating neural mechanisms to retain high dopamine levels, either by exogenous administration, increasing intrinsic production, or inhibiting the breakdown of dopamine. In this review, we highlight a new potential biochemical modality of treatment, treating PD through glycolysis. We highlight how terazosin (TZ), via PGK1, increases ATP levels and how enhanced glycolysis serves a neuroprotective role in PD, and compensates for damage caused by mitophagy. We also discuss the role of quercetin, a bioactive flavonoid, in preventing the development of PD, and reversing mitochondrial dysfunction but only so in diabetic patients. Thus, further research should be conducted on glycolysis as a protective target in PD that can serve to not just prevent, but also alleviate the non-dopaminergic signs and symptoms of PD.

Genetic architecture of Parkinson’s disease subtypes – Review of the literature

The heterogeneity of Parkinson’s disease (PD) has been recognized since its description by James Parkinson over 200 years ago. The complexity of motor and non-motor PD manifestations has led to many attempts of PD subtyping with different prognostic outcomes; however, the pathophysiological foundations of PD heterogeneity remain elusive. Genetic contributions to PD may be informative in understanding the underpinnings of PD subtypes. As such, recognizing genotype-phenotype associations may be crucial for successful gene therapy. We review the state of knowledge on the genetic architecture underlying PD subtypes, discussing the monogenic forms, as well as oligo- and polygenic risk factors associated with various PD subtypes. Based on our review, we argue for the unification of PD subtyping classifications, the dichotomy of studies on genetic factors and genetic modifiers of PD, and replication of results from previous studies.