Pathological mechanisms and treatment of sporadic Parkinson's disease: past, present, and future.

For a special issue, we review studies on the pathogenesis of nigral cell death and the treatment of sporadic Parkinson's disease (sPD) over the past few decades, with a focus on the studies performed by Prof. Mizuno and our group. Prof. Mizuno proposed the initial concept that mitochondrial function may be impaired in sPD. When working at Jichi Medical School, he found a decrease in complex I of the mitochondrial electron transfer complex in the substantia nigra of patients with Parkinson's disease (PD) and MPTP models. After moving to Juntendo University as a professor and chairman, he continued to study the mechanisms of cell death in the substantia nigra of patients with sPD. Under his supervision, I studied the relationships between PD and apoptosis, PD and iron involvement, mitochondrial dysfunction and apoptosis, and PD and neuroinflammation. Moving to Kitasato University, we focused on PD and the cytotoxicity of alpha synuclein (αSyn) as well as brain neuropathology. Eventually, I moved to Osaka University, where I continued working on PD and αSyn projects to promote therapeutic research. In this paper, we present the details of these studies in the following order: past, present, and future.

Deciphering social traits and pathophysiological conditions from natural behaviors in common marmosets.

Nonhuman primates (NHPs) are indispensable animal models by virtue of the continuity of behavioral repertoires across primates, including humans. However, behavioral assessment at the laboratory level has so far been limited. Employing the application of three-dimensional (3D) pose estimation and the optimal integration of subsequent analytic methodologies, we demonstrate that our artificial intelligence (AI)-based approach has successfully deciphered the ethological, cognitive, and pathological traits of common marmosets from their natural behaviors. By applying multiple deep neural networks trained with large-scale datasets, we established an evaluation system that could reconstruct and estimate the 3D poses of the marmosets, a small NHP that is suitable for analyzing complex natural behaviors in laboratory setups. We further developed downstream analytic methodologies to quantify a variety of behavioral parameters beyond motion kinematics. We revealed the distinct parental roles of male and female marmosets through automated detections of food-sharing behaviors using a spatial-temporal filter on 3D poses. Employing a recurrent neural network to analyze 3D pose time series data during social interactions, we additionally discovered that marmosets adjusted their behaviors based on others' internal state, which is not directly observable but can be inferred from the sequence of others' actions. Moreover, a fully unsupervised approach enabled us to detect progressively appearing symptomatic behaviors over a year in a Parkinson's disease model. The high-throughput and versatile nature of an AI-driven approach to analyze natural behaviors will open a new avenue for neuroscience research dealing with big-data analyses of social and pathophysiological behaviors in NHPs.

Switching disease-modifying therapies from sphingosine-1-phosphate receptor modulators to natalizumab or dimethyl fumarate restores immune responses after SARS-CoV-2 mRNA vaccination in patients with multiple sclerosis.

OBJECTIVES: This study aimed to evaluate whether switching disease-modifying therapies (DMTs) from sphingosine-1 phosphate (S1P) receptor modulators to either natalizumab (NTZ) or dimethyl fumarate (DMF) could restore the effectiveness of SARS-CoV-2 mRNA vaccination in patients with multiple sclerosis (MS). METHODS: This study included 9 controls and 33 patients with MS: 7 patients treated with DMF, 7 patients treated with NTZ, 9 patients treated with S1P receptor modulators, and 10 patients who had switched DMTs from S1P receptor modulators to DMF or NTZ by the second vaccine dose. The patients who had switched DMTs were classified into two groups, based on whether their lymphocyte counts were above or below 1000/µL at the time of vaccination. In addition, relapses within 6 months after switching DMTs were also evaluated in these patients. Six months after the second dose of the vaccination, anti-SARS-CoV-2 spike antibodies were evaluated in all participants, and spike specific CD4+ T cells were also assessed in patients who had switched DMTs from S1P receptor modulators. RESULTS: Patients treated with S1P receptor modulators had lower levels of anti-SARS-CoV-2 spike antibodies than the controls and patients treated with DMF and NTZ. On the other hand, in patients who had switched DMTs from S1P receptor modulators, a recovery of lymphocyte counts above 1000/µL resulted in restored humoral and cellular immune responses to the vaccination. There were no neurological relapses in patients who had switched DMTs from S1P receptor modulators to NTZ. CONCLUSION: SARS-CoV-2 mRNA vaccination is expected to be effective in patients whose lymphocyte counts have recovered due to switching DMTs from S1P receptor modulators. Switching DMTs from S1P receptor modulators to NTZ before vaccination may be beneficial in achieving efficacy for SARS-CoV-2 mRNA vaccination, with a reduced risk of relapse.

[Issues of transition support to adulthood and the practices of pediatric-adult healthcare transition in neurological diseases].

A workshop of the Special Committee on Measures for Transition from Pediatric to Adult Health Care, the Japanese Society of Neurology was held to discuss various issues and practices involved in healthcare transition. The following points were addressed: (1) the history of, and issues involved in, promoting support for patients requiring medical care, (2) cooperation between pediatric medical centers and university hospitals, (3) collaboration between pediatrics and neurology in medical and rehabilitation facilities, and (4) a questionnaire survey of members of the Japanese Society of Neurology. The reasons for extreme difficulties in pediatric-adult healthcare transition for patients with neurological diseases, especially those who require continuous intensive medical care over a long period of time, include the difference in the operating systems of pediatric and adult departments, in addition to the difference in the diseases treated during childhood and adulthood. For holistic transition support, it is necessary to strengthen cooperation not only among medical professionals, but also among multiple professions, as well as between local communities and government.

Effects of local reduction of endogenous α-synuclein using antisense oligonucleotides on the fibril-induced propagation of pathology through the neural network in wild-type mice.

In Parkinson's disease and other synucleinopathies, fibrillar forms of α-synuclein (aSyn) are hypothesized to structurally convert and pathologize endogenous aSyn, which then propagates through the neural connections, forming Lewy pathologies and ultimately causing neurodegeneration. Inoculation of mouse-derived aSyn preformed fibrils (PFFs) into the unilateral striatum of wild-type mice causes widespread aSyn pathologies in the brain through the neural network. Here, we used the local injection of antisense oligonucleotides (ASOs) against Snca mRNA to confine the area of endogenous aSyn protein reduction and not to affect the PFFs properties in this model. We then varied the timing and location of ASOs injection to examine their impact on the initiation and propagation of aSyn pathologies in the whole brain and the therapeutic effect using abnormally-phosphorylated aSyn (pSyn) as an indicator. By injecting ASOs before or 0-14 days after the PFFs were inoculated into the same site in the left striatum, the reduction in endogenous aSyn in the striatum leads to the prevention and inhibition of the regional spread of pSyn pathologies to the whole brain including the contralateral right hemisphere. ASO post-injection inhibited extension from neuritic pathologies to somatic ones. Moreover, injection of ASOs into the right striatum prevented the remote regional spread of pSyn pathologies from the left striatum where PFFs were inoculated and no ASO treatment was conducted. This indicated that the reduction in endogenous aSyn protein levels at the propagation destination site can attenuate pSyn pathologies, even if those at the propagation initiation site are not inhibited, which is consistent with the original concept of prion-like propagation that endogenous aSyn is indispensable for this regional spread. Our results demonstrate the importance of recruiting endogenous aSyn in this neural network propagation model and indicate a possible potential for ASO treatment in synucleinopathies.

Arterial Thromboembolism in Japanese Patients With Cancer: Incidence, Predictors, and Survival Impact.

Background: Thromboembolism is a significant complication for patients with cancer, leading to treatment interruptions and poor outcomes. Objectives: The aim of this study was to investigate the incidence of arterial thromboembolism (ATE) within cancer populations, identify the predictors of ATE, and determine its survival impact. Methods: A retrospective multicenter study was performed using data from the Osaka Cancer Registry linked with administrative data from 2010 to 2015. Patients were monitored for 5 years after cancer diagnosis, and ATE incidence was calculated with death as a competing risk. Fine and Gray competing risk regression models and Cox proportional hazards models were used to evaluate the predictors of ATE and the survival impact. Restricted mean survival time (RMST) was used to assess whether antithrombotic therapy after ATE contributed to improved survival. Results: The cohort comprised 97,448 patients with cancer (42.3% women, median age 70 years). ATE incidence displayed an annual increase, peaking 1 year after cancer diagnosis (1-, 2-, 3-, 4-, and 5-year cumulative incidences were 1.29%, 1.77%, 2.05%, 2.22%, and 2.32%, respectively). Male sex, advanced age, advanced cancer stage, and hematologic malignancies correlated with a high risk for ATE. Patients with ATE had a 2-fold increased risk for mortality compared with those without ATE. The 90-day and 1-year RMST differences for those on antithrombotic therapy were 13.3 days (95% CI: 10.4-16.2 days; P < 0.001) and 57.8 days (95% CI: 43.1-72.5 days; P < 0.001), favoring the antithrombotic therapy group. The RMST differences varied by cancer stage. Conclusions: The risk for ATE varies according to sex, age, and cancer progression and type. Antithrombotic therapy after ATE is associated with improved survival among patients with cancer.

One-year morbidity and mortality in patients treated with standard-dose and low-dose apixaban after acute large vessel occlusion stroke.

Although low-dose direct oral anticoagulants (DOACs) are recommended for patients at high risk of bleeding complications, it remains unclear whether the dose reduction in real-world setting is also appropriate in patients after large-vessel occlusion (LVO) stroke. This study hypothesized that patients with atrial fibrillation (AF) and LVO receiving low-dose DOACs have an increased risk of ischemic and hemorrhagic events. The study aimed to assess 1 year morbidity and mortality in patients treated with standard-dose and low-dose apixaban after LVO stroke. A post hoc analysis was performed using the acute LVO registry data, which enrolled patients with AF and LVO who received apixaban within 14 days of stroke onset. The incidences of ischemic events (ischemic stroke, acute coronary syndrome, acute myocardial infarction, and systemic embolism), major bleeding events, and death from any cause were compared between patients receiving standard- and low-dose apixaban. Of 643 patients diagnosed with LVO, 307 (47.7%) received low-dose apixaban. After adjustment for clinically relevant variables, no significant differences were observed in the incidence of ischemic events (adjusted hazard ratio [aHR]: 2.12, 95% confidence interval [CI] 0.75-6.02), major bleeding events (aHR: 1.17, 95% CI 0.50-2.73), and death from any cause (aHR: 1.95, 95% CI 0.78-4.89) between patients receiving standard- and low-dose apixaban. No significant differences were observed in the incidence of ischemic events, major bleeding events, or death from any cause between patients with AF and LVO receiving standard- and low-dose apixaban.

The gonio scratch study: methodology of a multicenter clinical trial establishing a new minimally invasive glaucoma surgery.

There are numerous surgical procedures for glaucoma. Minimally invasive glaucoma surgery is becoming popular; however, the disadvantage is the high incidence of anterior chamber hemorrhage. Heavy bleeding can also lead to increased intraocular pressure (IOP) postoperatively. Gonio scratch is a surgical procedure that improves aqueous humor outflow by rubbing off deposits on the trabecular meshwork with a Diamond Dusted Sweeper. As the conjunctiva and trabecular meshwork are not incised, no postoperative bleeding is expected, and the IOP spike will be minimal. We designed this study to determine the efficacy and safety of gonio scratch. This is an on-going multicenter, prospective, clinical trial. Patients who are scheduled for glaucoma surgery with or without cataract surgery are being enrolled. A total of 80 eyes will be recruited in the Hiroshima University Hospital, Miyoshi Eye Clinic, Yokoyama Retina Clinic, and Kusatsu Eye Clinic. All patients will undergo gonio scratch. When combined with cataract surgery, gonio scratch is performed after the intraocular lens is inserted. The primary study endpoint is the change in IOP from baseline to 1 year after surgery. The secondary endpoints are complications, number of glaucoma medications, surgical time, and changes in visual acuity and the visual field. This study protocol was approved by the institutional review board of Hiroshima University. The trial results will be shared with the scientific community at international conferences and by publication in a peer-reviewed journal. Trial registration number is jRCTs062200003.

Higher Frequency of Premature Atrial Contractions Correlates With Atrial Fibrillation Detection after Cryptogenic Stroke.

BACKGROUND: Covert atrial fibrillation (AF) is a major cause of cryptogenic stroke. This study investigated whether a dose-dependent relationship exists between the frequency of premature atrial contractions (PACs) and AF detection in patients with cryptogenic stroke using an insertable cardiac monitor (ICM). METHODS: We enrolled consecutive patients with cryptogenic stroke who underwent ICM implantation between October 2016 and September 2020 at 8 stroke centers in Japan. Patients were divided into 3 groups according to the PAC count on 24-hour Holter ECG: ≤200 (group L), >200 to ≤500 (group M), and >500 (group H). We defined a high AF burden as above the median of the cumulative duration of AF episodes during the entire monitoring period. We evaluated the association of the frequency of PACs with AF detection using log-rank trend test and Cox proportional hazard model and with high AF burden using logistic regression model, adjusting for age, sex, CHADS2 score. RESULTS: Of 417 patients, we analyzed 381 patients with Holter ECG and ICM data. The median age was 70 (interquartile range, 59.5-76.5), 246 patients (65%) were males, and the median duration of ICM recording was 605 days (interquartile range, 397-827 days). The rate of new AF detected by ICM was higher in groups with more frequent PAC (15.5%/y in group L [n=277] versus 44.0%/y in group M [n=42] versus 71.4%/y in group H [n=62]; log-rank trend P<0.01). Compared with group L, the adjusted hazard ratios for AF detection in groups M and H were 2.11 (95% CI, 1.24-3.58) and 3.23 (95% CI, 2.07-5.04), respectively, and the adjusted odds ratio for high AF burden in groups M and H were 2.57 (95% CI, 1.14-5.74) and 4.25 (2.14-8.47), respectively. CONCLUSIONS: The frequency of PACs was dose-dependently associated with AF detection in patients with cryptogenic stroke.

The validation of a Japanese version of the New Freezing of Gait Questionnaire (NFOG-Q).

OBJECTIVE: This study aimed to develop a Japanese version of the New Freezing of Gait Questionnaire (NFOG-Q) and investigate its validity and reliability. METHODS: After translating the NFOG-Q according to a standardised protocol, 56 patients with Parkinson's disease (PD) were administered it. Additionally, the MDS-UPDRS parts II and III, Hoehn and Yahr (H&Y) stage, and number of falls over 1 month were evaluated. Spearman's correlation coefficients (rho) were used to determine construct validity, and Cronbach's alpha (α) was used to examine reliability. RESULTS: The interquartile range of the NFOG-Q scores was 10.0-25.3 (range 0-29). The NFOG-Q scores were strongly correlated with the MDS-UPDRS part II, items 2.12 (walking and balance), 2.13 (freezing), 3.11 (freezing of gait), and 3.12 (postural stability) and the postural instability and gait difficulty score (rho = 0.515-0.669), but only moderately related to the MDS-UPDRS item 3.10 (gait), number of falls, disease duration, H&Y stage, and time of the Timed Up-and-Go test (rho = 0.319-0.434). No significant correlations were observed between age and the time of the 10-m walk test. The internal consistency was excellent (α = 0.96). CONCLUSIONS: The Japanese version of the NFOG-Q is a valid and reliable tool for assessing the severity of freezing in patients with PD.

Erythromycin for myotonic dystrophy type 1: a multicentre, randomised, double-blind, placebo-controlled, phase 2 trial.

Background: Myotonic dystrophy type 1 (DM1) is a devastating multisystemic disorder caused by a CTG repeat expansion in the DMPK gene, which subsequently triggers toxic RNA expression and dysregulated splicing. In a preclinical study, we demonstrated that erythromycin reduces the toxicity of abnormal RNA and ameliorates the aberrant splicing and motor phenotype in DM1 model mice. Methods: This multicentre, randomised, double-blind, placebo-controlled, phase 2 trial was conducted at three centres in Japan to translate preclinical findings into practical applications in patients with DM1 by evaluating the safety and efficacy of erythromycin. Between Nov 29, 2019, and Jan 20, 2022, a total of 30 adult patients with DM1 were enrolled and randomly assigned in a 1:2:2 ratio to receive either placebo or erythromycin at two daily doses (500 mg or 800 mg) for 24 weeks. The primary outcome included the safety and tolerability of erythromycin. The secondary efficacy measures included splicing biomarkers, 6-min walk test results, muscle strength, and serum creatinine kinase (CK) values. This trial is registered with the Japan Registry of Clinical Trials, jRCT2051190069. Findings: Treatment-related gastrointestinal symptoms occurred more frequently in the erythromycin group, but all adverse events were mild to moderate and resolved spontaneously. No serious safety concerns were identified. The CK levels from baseline to week 24 decreased in the overall erythromycin group compared with the placebo group (mean change of -6.4 U/L [SD 149] vs +182.8 [SD 228]), although this difference was not statistically significant (p = 0.070). Statistically significant improvements in the overall erythromycin treated groups compared to placebo were seen for two of the eleven splicing biomarkers that were each evaluated in half of the trial sample. These were MBNL1 (p = 0.048) and CACNA1S (p = 0.042). Interpretation: Erythromycin demonstrated favourable safety and tolerability profiles in patients with DM1. A well-powered phase 3 trial is needed to evaluate efficacy, building on the preliminary findings from this study. Funding: Japan Agency for Medical Research and Development.

Single-cell transcriptome landscape of circulating CD4+ T cell populations in autoimmune diseases.

CD4+ T cells are key mediators of various autoimmune diseases; however, their role in disease progression remains unclear due to cellular heterogeneity. Here, we evaluated CD4+ T cell subpopulations using decomposition-based transcriptome characterization and canonical clustering strategies. This approach identified 12 independent gene programs governing whole CD4+ T cell heterogeneity, which can explain the ambiguity of canonical clustering. In addition, we performed a meta-analysis using public single-cell datasets of over 1.8 million peripheral CD4+ T cells from 953 individuals by projecting cells onto the reference and cataloging cell frequency and qualitative alterations of the populations in 20 diseases. The analyses revealed that the 12 transcriptional programs were useful in characterizing each autoimmune disease and predicting its clinical status. Moreover, genetic variants associated with autoimmune diseases showed disease-specific enrichment within the 12 gene programs. The results collectively provide a landscape of single-cell transcriptomes of CD4+ T cell subpopulations involved in autoimmune disease.

Dysregulation of stress granule dynamics by DCTN1 deficiency exacerbates TDP-43 pathology in Drosophila models of ALS/FTD.

The abnormal aggregation of TDP-43 into cytoplasmic inclusions in affected neurons is a major pathological hallmark of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Although TDP-43 is aberrantly accumulated in the neurons of most patients with sporadic ALS/FTD and other TDP-43 proteinopathies, how TDP-43 forms cytoplasmic aggregates remains unknown. In this study, we show that a deficiency in DCTN1, a subunit of the microtubule-associated motor protein complex dynactin, perturbs the dynamics of stress granules and drives the formation of TDP-43 cytoplasmic aggregation in cultured cells, leading to the exacerbation of TDP-43 pathology and neurodegeneration in vivo. We demonstrated using a Drosophila model of ALS/FTD that genetic knockdown of DCTN1 accelerates the formation of ubiquitin-positive cytoplasmic inclusions of TDP-43. Knockdown of components of other microtubule-associated motor protein complexes, including dynein and kinesin, also increased the formation of TDP-43 inclusions, indicating that intracellular transport along microtubules plays a key role in TDP-43 pathology. Notably, DCTN1 knockdown delayed the disassembly of stress granules in stressed cells, leading to an increase in the formation of pathological cytoplasmic inclusions of TDP-43. Our results indicate that a deficiency in DCTN1, as well as disruption of intracellular transport along microtubules, is a modifier that drives the formation of TDP-43 pathology through the dysregulation of stress granule dynamics.

Atrial Fibrillation Detection and Ischemic Stroke Recurrence in Cryptogenic Stroke: A Retrospective, Multicenter, Observational Study.

BACKGROUND: Atrial fibrillation (AF) is known to be a strong risk factor for stroke. However, the risk of stroke recurrence in patients with cryptogenic stroke with AF detected after stroke by an insertable cardiac monitor (ICM) is not well known. We sought to evaluate the risk of ischemic stroke recurrence in patients with cryptogenic stroke with and without ICM-detected AF. METHODS AND RESULTS: We retrospectively reviewed patients with cryptogenic stroke who underwent ICM implantation at 8 stroke centers in Japan. Cox regression models were developed using landmark analysis and time-dependent analysis. We set the target sample size at 300 patients based on our estimate of the annualized incidence of ischemic stroke recurrence to be 3% in patients without AF detection and 9% in patients with AF detection. Of the 370 patients, 121 were found to have AF, and 110 received anticoagulation therapy after AF detection. The incidence of ischemic stroke recurrence was 4.0% in 249 patients without AF detection and 5.8% in 121 patients with AF detection (P=0.45). In a landmark analysis, the risk of ischemic stroke recurrence was not higher in patients with AF detected ≤90 days than in those without (hazard ratio, 1.47 [95% CI, 0.41-5.28]). In a time-dependent analysis, the risk of ischemic stroke recurrence did not increase after AF detection (hazard ratio, 1.77 [95% CI, 0.70-4.47]). CONCLUSIONS: The risk of ischemic stroke recurrence in patients with cryptogenic stroke with ICM-detected AF, 90% of whom were subsequently anticoagulated, was not higher than in those without ICM-detected AF.

Von Willebrand Factor Antigen Levels Predict Poor Outcomes in Patients With Stroke and Cancer: Findings From the Multicenter, Prospective, Observational SCAN Study.

BACKGROUND: Patients with acute ischemic stroke and active cancer have more severe neurological symptoms, elevated risks of stroke recurrence, and death compared with the general population. We examined whether von Willebrand factor (vWF) antigen levels at stroke onset were associated with the poor outcomes of patients with stroke and cancer. METHODS AND RESULTS: Using data from 90 patients with acute ischemic stroke and active cancer who were registered in the SCAN (Ischemic Stroke in Patients With Cancer and Neoplasia) study, a prospective multicenter, observational study in Japan, we divided patients into 2 groups according to their median vWF antigen levels (high, n=46; or low, n=44). The high-vWF group had a significantly higher initial National Institutes of Health Stroke Scale score (median, 7 [interquartile range, 3-11.25] versus 3 [interquartile range, 1-8.5]; P<0.05) and a significantly higher incidence of cryptogenic stroke (32 [70%] versus 16 [36%]; P<0.01) and venous thromboembolism (7 [15%] versus 0 [0%]; P<0.01), as well as multiple lesions (28 [62%] versus 12 [27%]; P<0.001), than the low-vWF group. We observed no significant difference in the rate of stroke recurrence within 1 year between the groups. However, increased vWF levels were an independent predictor of death within 1 year of stroke onset, after adjusting for potential confounders (odds ratio, 6.77 [95% CI, 1.49-30.78]; P<0.05). CONCLUSIONS: Elevated vWF antigen levels were associated with adverse outcomes in patients with cancer-associated stroke and may represent a useful biomarker to guide future therapeutic interventions.

Association between the controlling nutritional status score and outcomes in ischemic stroke patients with active cancer.

BACKGROUND: The effect of nutritional status on survival in ischemic stroke patients with active cancer remains unclear. METHODS: This study retrospectively evaluated ischemic stroke patients with active cancer admitted to a university hospital in Japan between 2006 and 2016. Patients were followed for 2 years after stroke. The controlling nutritional status (CONUT) score was used to classify undernutrition degree into 4 groups: normal, light, moderate, and severe. Survival rates were compared using the Kaplan-Meier method. Hazard ratio (HR) and 95 % confidence intervals (CIs) for mortality were calculated using Cox regression models. RESULTS: A total of 158 patients (31 % women; median age: 71 years) were analyzed. Of these, 47 % had distant metastasis. The median (interquartile range) National Institute of Health Stroke Scale and CONUT scores were 4 (1-10) and 5 (3-7), respectively. Kaplan-Meier curve indicated that patients with poorer nutritional status had worse outcomes (overall log-rank test, p < 0.001). The univariable Cox regression analysis showed that the HR (95 % CI) for the light, moderate, and severe groups were 1.14 (0.45-2.86), 3.01 (1.27-7.12), and 2.94 (1.10-7.84), respectively. This statistical significance did not persist after adjustment for potential confounders (HR [95 % CI] for the light, moderate, and severe groups were 0.95 [0.36-2.49], 1.56 [0.57-4.28], and 1.34 [0.37-4.92], respectively). Past stroke, distant metastasis, and plasma D-dimer levels on admission were independent predictors of prognosis. CONCLUSIONS: This single-center, retrospective study suggests that nutritional status serves as a prognostic indicator for ischemic stroke patients with active cancer. However, the effect is not statistically independent.

Decreased hepatic enzymes reflect the decreased vitamin B6 levels in Parkinson's disease patients.

The study aims to investigate the vitamin B6 levels in Parkinson's disease (PD) patients and their association with liver enzymes and evaluate how much dysregulation is associated with levodopa dose. Furthermore, to evaluate the effect of Opicapone, a catechol-o-methyl-transferase inhibitor, on vitamin B6 levels by monitoring the AST and ALT levels in patients treated with Levodopa-Carbidopa Intestinal Gel Infusion (LCIG). For these aims, serum vitamin B6 levels were measured (PD, n = 72 and controls, n = 31). The vitamin B6 level was compared with the total levodopa dose, clinical parameters, and blood homocysteine, albumin, and hemoglobin levels in PD patients. Correlations between vitamin B6 levels and AST and ALT levels, as well as the ratio ALT/AST, were analyzed. Changes in the AST and ALT levels and ALT/AST were analyzed in the patients treated with LCIG before and after the therapy (n = 24) and in the patients treated with LCIG + Opicapone before and after Opicapone treatment (n = 12). We found vitamin B6 levels were significantly lower in PD patients. Total levodopa dose and albumin levels were independently associated with vitamin B6 levels. Decreased vitamin B6 levels appeared as lower AST and ALT levels and ALT/AS. Treatment with LCIG decreased the AST and ALT levels and ALT/AST. Adjunctive therapy with Opicapone to LCIG ameliorated the decreased ALT and ALT/AST. We conclude that the ALT and ALT/AST can be useful parameters for monitoring vitamin B6 levels and Opicapone can ameliorate the dysregulated vitamin B6 in PD patients.