Homocysteine is not associated with global motor or cognitive measures in nondemented older Parkinson's disease patients

Nonlinear Relationship Between Homocysteine and Mild Cognitive Impairment in Early Parkinson's Disease: A Cross-Sectional Study

Background

Cognitive impairment, a prevalent non-motor symptom in advanced Parkinson's disease (PD), has been associated with hyperhomocysteinemia, an important risk factor for PD progression and cognitive decline in PD. However, evidence regarding the association between homocysteine (Hcy) and cognitive function during early PD remains insufficient. Therefore, this study aims to examine the correlation between Hcy levels and cognitive function in the early stage of PD.

Methods

The study included 218 individuals in the early stages of PD who were consecutively admitted to the Suining Central Hospital Neurology Department. All the individuals completed the Parkinson's Disease Cognitive Rating Scale (PD-CDR). The Unified Parkinson's Disease Rating Scale part III (UPDRS-III) was employed for measuring the severity of motor symptoms, while the Hoehn-Yahr scale was used to measure the clinical symptom stage. Fasting venous blood samples were also drawn to measure the Hcy concentration, red blood cell folate, and vitamin B12.

Results

In this cross-sectional study, 47 (21.5%) patients with PD showed cognitive dysfunction. The serum Hcy levels were significantly higher in the cognitive impairment PD (PDCI) group compared with the cognitive normal PD group (P<0.001). The Generalized Additive Model (GAM) analysis revealed a nonlinear relationship between Hcy and the risk of PDCI. Multiple logistic regression analyses demonstrated a positive relationship between elevated Hcy and the risk of PDCI in the fully adjusted model ([OR]:3.1, 95% CI, 1.1-8.5, P=0.028). Segmented linear regression analysis showed that when Hcy levels were above 17.7 umol/l, the risk of PDCI increased by 1.6 times for every 1 unit elevated in Hcy (95% CI:1.1-2.2, P=0.008).

Conclusion

This study revealed a nonlinear positive correlation between the risk of PDCI and elevated serum Hcy levels in early PD patients, suggesting hyperhomocysteinemia as one of the treatable factors for cognitive impairment in the early stages of PD.

Association between the risk and severity of Parkinson's disease and plasma homocysteine, vitamin B12 and folate levels: a systematic review and meta-analysis

Background

Parkinson's disease (PD) is recognized as the second most prevalent progressive neurodegenerative disease among the elderly. However, the relationship between PD and plasma homocysteine (Hcy), vitamin B12, and folate has yielded inconsistent results in previous studies. Hence, in order to address this ambiguity, we conducted a meta-analysis to summarize the existing evidence.

Methods

Suitable studies published prior to May 2023 were identified by searching PubMed, EMBASE, Medline, Ovid, and Web of Science. The methodological quality of eligible studies was assessed using the Newcastle-Ottawa Quality Assessment Scale (NOS). Meta-analysis and publication bias were then performed using R version 4.3.1.

Results

The results of our meta-analysis, consisting of case-control and cross-sectional studies, showed that PD patients had lower folate and vitamin B12 levels (SMD [95%CI]: -0.30[-0.39, -0.22], p < 0.001 for Vitamin B12; SMD [95%CI]: -0.20 [-0.28, -0.13], p < 0.001 for folate), but a significant higher Hcy level (SMD [95%CI]: 0.86 [0.59, 1.14], p < 0.001) than healthy people. Meanwhile, PD was significantly related to hyperhomocysteinemia (SMD [95%]: 2.02 [1.26, 2.78], p < 0.001) rather than plasma Hcy below 15 μmol/L (SMD [95%]: -0.31 [-0.62, 0.00], p = 0.05). Subgroup analysis revealed associations between the Hcy level of PD patients and region (p = 0.03), age (p = 0.03), levodopa therapy (p = 0.03), Hoehn and Yahr stage (p < 0.001), and cognitive impairment (p < 0.001). However, gender (p = 0.38) and sample size (p = 0.49) were not associated.

Conclusion

Hcy, vitamin B12, and folic acid potentially predict the onset and development of PD. Additionally, multiple factors were linked to Hcy levels in PD patients. Further studies are needed to comprehend their roles in PD.

Effects of rasagiline combined with levodopa and benserazide hydrochloride on motor function and homocysteine and IGF-1 levels in elderly patients with Parkinson's disease

BACKGROUND

During the course of their illness, people with Parkinson's disease may see changes in their insulin-like growth factor (IGF-1) and serum homocysteine (Hcy) indices. In this study, patients with intermediate to severe Parkinson's disease were examined for how Resagiline and levodopa and benserazide hydrochloride affected their motor performance, serum levels of homocysteine (Hcy), and insulin-like growth factor (IGF-1).

METHODS

From June 2020 to December 2021, a total of 100+ cases of Parkinson's patients over 60 years old in the middle and late stages of Parkinson's were seen in the outpatient and inpatient departments of the Third People's Hospital of Chengdu City and had a detailed observation record, and according to the inclusion criteria, the patients who met the criteria were randomly grouped into a clinical observation group and a control group. The subjects in the control group received only levodopa and benserazide hydrochloride treatment, while the observation group was treated with Resagiline in combination with the clinical control group. The total treatment observation period was 1 year for both groups, and the motor function and serum Hcy and IGF-1 indexes of both groups were compared after the end of treatment.

RESULTS

We randomly and evenly grouped 64 patients who met the requirements of the inclusion criteria into a clinical observation group and a control group, each with 32 patients, from among 168 patients over 60 years of age with detailed observation records in the middle and late stages of Parkinson's. After the 1-year observation period, we found that the total effective rate after treatment in the clinical observation group (93.75%) and significantly higher than that in the control group (68.75%) (P < 0.05); after 1 year of treatment, the UPDRS score decreased in both groups, and the observation group was significantly lower than the control group (P < 0.05); after treatment, serum Hcy decreased and IGF-1 increased in both groups, and the observation group was higher than the control group mean values (P < 0.05).

CONCLUSIONS

In patients with Parkinson's disease who are in the middle and late stages of the disease, the administration of Resagiline combined with levodopa and benserazide hydrochloride can significantly lower the body's serum Hcy level, significantly raise IGF-1 levels, and significantly improve motor function in patients with Parkinson's disease. It can also have significant therapeutic effects.

Identifying key multi-modal predictors of incipient dementia in Parkinson's disease: a machine learning analysis and Tree SHAP interpretation

Background

Persons with Parkinson's disease (PD) differentially progress to cognitive impairment and dementia. With a 3-year longitudinal sample of initially non-demented PD patients measured on multiple dementia risk factors, we demonstrate that machine learning classifier algorithms can be combined with explainable artificial intelligence methods to identify and interpret leading predictors that discriminate those who later converted to dementia from those who did not.

Method

Participants were 48 well-characterized PD patients (M_{baseline age} = 71.6; SD = 4.8; 44% female). We tested 38 multi-modal predictors from 10 domains (e.g., motor, cognitive) in a computationally competitive context to identify those that best discriminated two unobserved baseline groups, PD No Dementia (PDND), and PD Incipient Dementia (PDID). We used Random Forest (RF) classifier models for the discrimination goal and Tree SHapley Additive exPlanation (Tree SHAP) values for deep interpretation.

Results

An excellent RF model discriminated baseline PDID from PDND (AUC = 0.84; normalized Matthews Correlation Coefficient = 0.76). Tree SHAP showed that ten leading predictors of PDID accounted for 62.5% of the model, as well as their relative importance, direction, and magnitude (risk threshold). These predictors represented the motor (e.g., poorer gait), cognitive (e.g., slower Trail A), molecular (up-regulated metabolite panel), demographic (age), imaging (ventricular volume), and lifestyle (activities of daily living) domains.

Conclusion

Our data-driven protocol integrated RF classifier models and Tree SHAP applications to selectively identify and interpret early dementia risk factors in a well-characterized sample of initially non-demented persons with PD. Results indicate that leading dementia predictors derive from multiple complementary risk domains.

Dementia Risk Prediction in a Longitudinal Geriatric Parkinson's Disease Cohort: Evaluation and Application of the Montreal Parkinson Risk of Dementia Scale

Background

Parkinson's disease (PD) increases risk for dementia and cascading adverse outcomes. The eight-item Montreal Parkinson Risk of Dementia Scale (MoPaRDS) is a rapid, in-office dementia screening tool. We examine predictive validity and other characteristics of the MoPaRDS in a geriatric PD cohort by testing a series of alternative versions and modelling risk score change trajectories.

Methods

Participants were 48 initially non-demented PD patients (Mage = 71.6 years, range = 65-84) from a three-year, three-wave prospective Canadian cohort study. A dementia diagnosis at Wave 3 was used to stratify two baseline groups: PD with Incipient Dementia (PDID) and PD with No Dementia (PDND). We aimed to predict dementia three years prior to diagnosis using baseline data for eight indicators that harmonized with the original report, plus education.

Results

Three MoPaRDS items (age, orthostatic hypotension, mild cognitive impairment [MCI]) discriminated the groups both independently and as a composite three-item scale (area under the curve [AUC] = 0.88). The eight-item MoPaRDS reliably discriminated PDID from PDND (AUC = 0.81). Education did not improve predictive validity (AUC = 0.77). Performance of the eight-item MoPaRDS varied across sex (AUCfemales = 0.91; AUCmales = 0.74), whereas the three-item configuration did not (AUCfemales = 0.88; AUCmales = 0.91). Risk scores of both configurations increased over time.

Conclusions

We report new data on the application of the MoPaRDS as a dementia prediction tool for a geriatric PD cohort. Results support the viability of the full MoPaRDS, and indicate that an empirically determined brief version is a promising complement.

An umbrella review of systematic reviews with meta-analysis on the role of vitamins in Parkinson's disease

INTRODUCTION

This umbrella review aimed to systematically review the available literature and assess the association of dietary intake or serum levels of different vitamins and the risk of PD, to help find out more efficient treatments for PD patients by replenishing the deficiency of vitamins.

METHODS

Pubmed/Medline, Scopus, Google Scholar and hand searching bibliographies of retrieved articles in duplicate, were used to detect all relevant meta-analyses investigating the relationship between vitamins and PD. After study selection, data were extracted from previously published meta-analyses and pooled by Review Manager version 5.4 and CMA software version 2.2.064 to achieve effect sizes. Level of statistical significance was set at P ≤ 0.05.

RESULTS

14 meta-analyses were included in the meta-review. Serum vitamin D and B12 levels were significantly lower in PD (SMD = -0.67 and SMD = -0.40 respectively). Homocysteine (Hcy) levels were significantly higher in PD patients (SMD = 1.26). Also the odds ratio for highest vs. lowest vitamin E intake was 0.73 which was significant. However, there was no significant difference between vitamin A, C and B6 intake or serum levels in PD vs. control groups.

CONCLUSION

Serum vitamin D and B12 levels were significantly lower in PD in comparison to healthy individuals, while Hcy level was significantly higher in PD patients. Also higher vitamin E intake was associated with significantly lower risk of development of PD in comparison to lower vitamin E intake. However, there was no significant difference between risk of PD and higher vitamin A, C and B6 intake or serum levels of folate.

Homocysteine levels, genetic background, and cognitive impairment in Parkinson's disease

BACKGROUND

Hyperhomocysteinemia is considered an independent risk factor for cognitive impairment.

OBJECTIVE

To study the correlation between homocysteine levels and cognitive impairment in patients with PD.

METHODS

We conducted a case-control study that included 246 patients with PD, of whom 32 were cognitively impaired. The levels of homocysteine, folate, and vitamin B12 were measured in peripheral blood. Multivariate logistic regression analysis was applied to determine differences in homocysteine levels between PD patients with and without cognitive impairment. A meta-analysis was performed to clarify the role of Hcy levels in PD with cognitive decline. Five polymorphisms in genes involved in Hcy metabolism, including MTHFR rs1801133 and rs1801131, COMT rs4680, MTRR rs1801394, and TCN2 rs1801198, were genotyped.

RESULTS

Our case-control study showed that homocysteine levels were associated with cognitive impairment in PD after adjusting for possible confounding factors such as levodopa equivalent daily dose. The results of our meta-analysis further supported the positive association between homocysteine levels and cognition in PD. We found that the MTHFR rs1801133 TT genotype led to higher homocysteine levels in PD patients, whereas the MTHFR rs1801131 CC genotype resulted in higher folate levels. However, the polymorphisms studied were not associated with cognitive impairment in PD.

CONCLUSIONS

Increased homocysteine levels were a risk factor for cognitive decline in PD. However, no association was found between polymorphisms in genes involved in homocysteine metabolism and cognitive impairment in PD. Large-scale studies of ethnically diverse populations are required to definitively assess the relationship between MTHFR and cognitive impairment in PD.

Quantitative and causal analysis for inflammatory genes and the risk of Parkinson's disease

Background

The dysfunction of immune system and inflammation contribute to the Parkinson's disease (PD) pathogenesis. Cytokines, oxidative stress, neurotoxin and metabolism associated enzymes participate in neuroinflammation in PD and the genes involved in them have been reported to be associated with the risk of PD. In our study, we performed a quantitative and causal analysis of the relationship between inflammatory genes and PD risk.

Methods

Standard process was performed for quantitative analysis. Allele model (AM) was used as primary outcome analysis and dominant model (DM) and recessive model (RM) were applied to do the secondary analysis. Then, for those genes significantly associated with the risk of PD, we used the published GWAS summary statistics for Mendelian Randomization (MR) to test the causal analysis between them.

Results

We included 36 variants in 18 genes for final pooled analysis. As a result, IL-6 rs1800795, TNF-α rs1799964, PON1 rs854560, CYP2D6 rs3892097, HLA-DRB rs660895, BST1 rs11931532, CCDC62 rs12817488 polymorphisms were associated with the risk of PD statistically with the ORs ranged from 0.66 to 3.19 while variants in IL-1α, IL-1β, IL-10, MnSOD, NFE2L2, CYP2E1, NOS1, NAT2, ABCB1, HFE and MTHFR were not related to the risk of PD. Besides, we observed that increasing ADP-ribosyl cyclase (coded by BST1) had causal effect on higher PD risk (OR[95%CI] =1.16[1.10-1.22]) while PON1(coded by PON1) shown probably protective effect on PD risk (OR[95%CI] =0.81[0.66-0.99]).

Conclusion

Several polymorphisms from inflammatory genes of IL-6, TNF-α, PON1, CYP2D6, HLA-DRB, BST1, CCDC62 were statistically associated with the susceptibility of PD, and with evidence of causal relationships for ADP-ribosyl cyclase and PON1 on PD risk, which may help understand the mechanisms and pathways underlying PD pathogenesis.

Cognitive and motor correlates of grey and white matter pathology in Parkinson's disease

INTRODUCTION

Previous studies have found associations between grey matter atrophy and white matter hyperintensities (WMH) of vascular origin with cognitive and motor deficits in Parkinson's disease (PD). Here we investigate these relationships in a sample of PD patients and age-matched healthy controls.

METHODS

Data included 50 PD patients and 45 age-matched controls with T1-weighted and FLAIR scans at baseline, 18-months, and 36-months follow-up. Deformation-based morphometry was used to measure grey matter atrophy. SNIPE (Scoring by Nonlocal Image Patch Estimator) was used to measure Alzheimer's disease-like textural patterns in the hippocampi. WMHs were segmented using T1-weighted and FLAIR images. The relationship between MRI features and clinical scores was assessed using mixed-effects models. The motor subscore of the Unified Parkinson's Disease Rating Scale (UPDRSIII), number of steps in a walking trial, and Dementia Rating Scale (DRS) were used respectively as measures of motor function, gait, and cognition.

RESULTS

Substantia nigra atrophy was significantly associated with motor deficits, with a greater impact in PDs (p < 0.05). Hippocampal SNIPE scores were associated with cognitve decline in both PD and controls (p < 0.01). WMH burden was significantly associated with cognitive decline and increased motor deficits in the PD group, and gait deficits in both PD and controls (p < 0.03).

CONCLUSION

While substantia nigra atrophy and WMH burden were significantly associated with additional motor deficits, WMH burden and hippocampal atrophy were associated with cognitive deficits in PD patients. These results suggest an additive contribution of both grey and white matter damage to the motor and cognitive deficits in PD.

Association Between MTHFR Genetic Polymorphism and Parkinson's Disease Susceptibility: A Meta-analysis

Folate metabolism plays quite a critical role in Parkinson’s disease (PD). Previous published research works have studied the link existing between the folate metabolism genetic polymorphisms and PD susceptibility; nevertheless, the results continue having controversies and inconclusiveness. Accordingly, we carried out the present meta-analysis for the assessment of the potential link between the folate metabolism genetic polymorphisms and the susceptibility to PD. In addition we carried out a literature search in the PubMed, EMBASE, Cochrane Library, and WanFang databases till November 10, 2018. The odds ratios (ORs) with corresponding 95% credible interval (95%CI) were put to use for evaluating the strength of the association of three folate metabolism genetic polymorphism ( C677T, A1298C, and A2756G) with the susceptibility to PD. Each statistical analysis was carried out with the use of STATA 15.0. An aggregate of twenty-one case-control investigations were retrieved, which involved 3,944 PD patients and 4,412 controls. We discovered the existence of no substantial link between the C677T and A1298C polymorphism and PD risk in any genetic framework comparisons. With regard to A2756G polymorphism, we discovered that there was an association between the A2756G genetic polymorphism and an augmented threat of PD in the co-dominant genetic framework (GG vs. AA: OR=1.86, 95%CI=1.02-3.37, P=0.042) and the recessive genetic model (GG vs. GA+AA: OR=1.90, 95%CI=1.06-3.41, P=0.031). To summarize, our research work indicates that the A2756G polymorphism of the folate metabolism gene had an association with an augmented threat of PD. Also, A1298C polymorphisms is unlikely to significantly contribute towards the susceptibility to PD. Further large-scale case-control studies are still required.

The role of one-carbon metabolism and homocysteine in Parkinson’s disease onset, pathology and mechanisms

Parkinson’s disease (PD) is the second most common neurodegenerative disorder. It is characterised by the progressive degeneration of dopaminergic (DA) neurons. The cause of degeneration is not well understood; however, both genetics and environmental factors, such as nutrition, have been implicated in the disease process. Deficiencies in one-carbon metabolism in particular have been associated with increased risk for PD onset and progression, though the precise relationship is unclear. The aim of the present review is to determine the role of one-carbon metabolism and elevated levels of homocysteine in PD onset and pathology and to identify potential mechanisms involved. A search of PubMed, Google Scholar and Web of Science was undertaken to identify relevant human and animal studies. Case–control, prospective cohort studies, meta-analyses and non-randomised trials were included in the present review. The results from human studies indicate that polymorphisms in one-carbon metabolism may increase risk for PD development. There is an unclear role for dietary B-vitamin intake on PD onset and progression. However, dietary supplementation with B-vitamins may be beneficial for PD-affected individuals, particularly those onl-DOPA (levodopa orl-3,4-dihydroxyphenylalanine) treatment. Additionally, one-carbon metabolism generates methyl groups, and methylation capacity in PD-affected individuals is reduced. This reduced capacity has an impact on expression of disease-specific genes that may be involved in PD progression. During B-vitamin deficiency, animal studies report increased vulnerability of DA cells through increased oxidative stress and altered methylation. Nutrition, especially folates and related B-vitamins, may contribute to the onset and progression of PD by making the brain more vulnerable to damage; however, further investigation is required.

Elevated Serum Homocysteine Levels Have Differential Gender-Specific Associations with Motor and Cognitive States in Parkinson's Disease

Background

Studies attempting to elucidate an association between homocysteine and symptom progression in Parkinson's disease (PD) have had largely discrepant findings. This study aimed to investigate elevated serum homocysteine levels and symptom progression in a cohort of PD patients.

Methods

Serum homocysteine, folate, and vitamin B12 levels were measured in 205 people with PD and 78 age-matched healthy controls. People with Parkinson's disease underwent a battery of clinical assessments to evaluate symptom severity, including motor (MDS-UPDRS) and cognitive (ACE-R) assessments. Multivariate generalised linear models were created, controlling for confounding variables, and were used to determine whether serum markers are associated with various symptom outcome measures.

Results

People with Parkinson's disease displayed significantly elevated homocysteine levels (p < 0.001), but not folate or vitamin B12 levels, when compared to healthy controls. A significant positive correlation between homocysteine and MDS-UPDRS III score was identified in males with Parkinson's disease (r_s = 0.319, p < 0.001), but not in females, whereas a significant negative correlation between homocysteine levels and total ACE-R score was observed in females with Parkinson's disease (r_s = −0.449, p < 0.001), but not in males. Multivariate general linear models confirmed that homocysteine was significantly predictive of MDS-UPDRS III score in male patients (p=0.004) and predictive of total ACE-R score in female patients (p=0.021).

Conclusion

Elevated serum homocysteine levels are associated with a greater motor impairment in males with Parkinson's disease and poorer cognitive performance in females with Parkinson's disease. Our gender-specific findings may help to explain previous discrepancies in the literature surrounding the utility of homocysteine as a biomarker in PD.

MTHFR C677T and A1298C polymorphisms may contribute to the risk of Parkinson's disease: A meta-analysis of 19 studies

The 5,10-methylenetetrahydrofolate reductase (MTHFR) gene has been reported to be a candidate gene for susceptibility to Parkinson's disease (PD), but results of different studies are conflicting. Here, we conducted a meta-analysis of published case-control studies to evaluate the association between MTHFR C677T and A1298C gene polymorphisms with the risk of PD. Electronic search through PubMed, EmBase, ScienceDirect and Cochrane Library was conducted to identify all relevant studies. A total of 19 studies with 2746 cases and 8967 controls were included. No significant association between MTHFR C677T polymorphism and PD risk was found in the overall population in all five genetic models. In the subgroup analysis stratified by ethnicity, a significant association between MTHFR C677T and PD risk was observed in the dominant model in Caucasians (OR=1.175, 95%CI: 1.008-1.369, P=0.040), but not in Asians. Significant association was found between MTHFR A1298C polymorphism and PD risk in the overall population in the dominant (OR=1.168, 95%CI: 1.008-1.353, P=0.039) and heterozygous model (OR=1.172, 95%CI: 1.004-1.367, P=0.044). But in the subgroup analysis, no association was found between MTHFR A1298C and PD neither in Caucasians nor in Asians. Our meta-analysis suggests that MTHFR C677T polymorphism may be associated with increased PD risk in Caucasians and MTHFR A1298C polymorphism may also increase susceptibility to PD.

Homocysteine and cognitive function in Parkinson's disease

INTRODUCTION

Increased plasma homocysteine (HC) is a risk factor for dementia in the general population. Levodopa therapy causes increased plasma HC, but it remains unclear whether elevated plasma HC is associated with cognitive impairment in Parkinson's disease (PD).

METHODS

The study population includes all participants in the Pacific Northwest Udall Center (PANUC) Clinical cohort at the time of the study, consisting of 294 individuals with PD who had a standardized neuropsychological assessment and plasma collection for HC measurement. We tested the hypothesis that elevated plasma HC is inversely related to cognitive function in patients with PD.

RESULTS

As expected, plasma HC was positively associated with age, disease duration, disease severity, and levodopa usage, while cognitive function was associated with age, education, gender, and APOE genotype, so subsequent analyses controlled for these covariates. When plasma HC was dichotomized as normal (<14 μmol/L) or elevated (≥14 μmol/L), subjects with hyper-homocysteinemia had lower scores on Digit Symbol (p = 0.031), Hopkins Verbal Learning Task (HVLT) Delayed Recall (p = 0.004), and semantic verbal fluency (p = 0.049). When examined as a continuous variable, plasma HC was inversely associated with HVLT Delayed Recall (p = 0.009)) and semantic verbal fluency (p = 0.004), but was not significantly related to Digit symbol, Trail-making test, Judgment of Line Orientation, phonemic verbal fluency, MMSE, or MOCA. When analysis was restricted to non-demented subjects (n = 231), the findings were unchanged.

CONCLUSIONS

We conclude that plasma HC is significantly associated with some aspects of cognitive function in PD, and may represent a treatable risk factor for cognitive decline in PD.

The Effect of Hyperhomocysteinemia on Motor Symptoms, Cognitive Status, and Vascular Risk in Patients with Parkinson's Disease

Factors related with hyperhomocysteinemia (HHcy) and the impact of HHcy in Parkinson's disease (PD) are not well understood. We investigated the factors associated with increased levels of homocysteine (Hcy) and the relationship between HHcy and motor symptoms, cognitive status, and vascular risk in patients with Parkinson's disease. Among 60 patients (29 males, 48.3%) with PD, the stage of the disease, the severity of clinical symptoms, and the patients' cognitive status were measured using a modified Hoehn and Yahr Staging Scale (mHY), Unified Parkinson's Disease Rating Scale (UPDRS) II and III, and Mini-Mental State Examination (MMSE), respectively. Patients were also noted for having dyskinesia and hallucinations. Serum vitamin B12, folic acid, and plasma Hcy levels were measured. Furthermore, the presence of vascular risk factors was recorded. Finally, we investigated carotid artery intima-media thickening and stenosis using colour Doppler ultrasonography as well as the presence of ischemic lesions using brain imaging techniques. Plasma Hcy levels were higher with advanced age and in males. In addition, there was an inverse relationship between Hcy and vitamin B12 levels. There was no correlation between HHcy and the stage of the disease, severity of motor symptoms, cognitive status as assessed by the MMSE, vascular risk factors, carotid artery atherosclerotic findings, and ischemic brain lesions. Plasma Hcy levels may rise due to several factors in PD. However, the resulting HHcy has no significant effect on the clinical picture in terms of motor features, cognitive status, and vascular diseases.

Homocysteine and cognition: A systematic review of 111 studies

BACKGROUND

Elevated plasma homocysteine ​​(Hcy) levels have been associated with cognitive dysfunction in a wide range of conditions. The aim of this review is to establish which cognitive domains and populations are the most affected.

METHODS

We systematically review the literature and consider all articles that showed any relationship between plasma Hcy levels and scores achieved on cognitive performance tests in both, the general population and patients suffering from central nervous system disorders and other diseases. When effect sizes were available and combinable, several meta-analyses were performed.

RESULTS

We found 111 pertinent articles. There were 24 cohort studies, 18 randomized trials, 21 case-control studies, and 48 cross-sectional studies. This review reveals a positive trend between cognitive decline and increased plasma Hcy concentrations in general population and in patients with cognitive impairments. Results from the meta-analyses also confirm this trend. Treatment with vitamin supplementation fails to show a reduction in cognitive decline.

DISCUSSION

Further investigations are warranted to clarify this relationship. Earlier detection of the elevated Hcy levels may be an effective intervention to prevent cognitive impairment and dementia.

Homocysteine Levels in Parkinson's Disease: Is Entacapone Effective?

Plasma homocysteine (Hcy) levels may increase in levodopa-treated patients with Parkinson's disease (PD) as a consequence of levodopa methylation via catechol-O-methyltransferase (COMT). Results from previous studies that assessed the effect of COMT inhibitors on levodopa-induced hyperhomocysteinemia are conflicting. We aimed to evaluate the effects of levodopa and entacapone on plasma Hcy levels. A hundred PD patients were enrolled to the study and divided into three treatment groups (group I: levodopa and/or dopamine agonists; group II: levodopa, entacapone, and/or a dopamine agonist; and group III: dopamine agonist alone). We measured the serum B12, folic acid, and Hcy levels in all patients. There were no statistically significant differences between groups in terms of modified Hoehn and Yahr stages, Unified Parkinson's Disease Rating Scale II/III, Standardized Mini-Mental Test scores, and serum vitamin B12 and folic acid levels. Plasma median Hcy levels were found above the normal laboratory values in groups I and II, but they were normal in group III. However, there was no statistically significant difference in plasma Hcy levels between groups. Our results showed that levodopa treatment may cause a slight increase in the Hcy levels in PD compared with dopamine agonists and that COMT inhibitors may not have a significant effect on preventing hyperhomocysteinemia.

Biomarkers for dementia and mild cognitive impairment in Parkinson's disease

Cognitive decline is one of the most frequent and disabling nonmotor features of Parkinson's disease. Around 30% of patients with Parkinson's disease experience mild cognitive impairment, a well-established risk factor for the development of dementia. However, mild cognitive impairment in patients with Parkinson's disease is a heterogeneous entity that involves different types and extents of cognitive deficits. Because it is not currently known which type of mild cognitive impairment confers a higher risk of progression to dementia, it would be useful to define biomarkers that could identify these patients to better study disease progression and possible interventions. In this sense, the identification among patients with Parkinson's disease and mild cognitive impairment of biomarkers associated with dementia would allow the early detection of this process. This review summarizes studies from the past 25 years that have assessed the potential biomarkers of dementia and mild cognitive impairment in Parkinson's disease patients. Despite the potential importance, no biomarker has as yet been validated. However, features such as low levels of epidermal and insulin-like growth factors or uric acid in plasma/serum and of Aß in CSF, reduction of cerebral cholinergic innervation and metabolism measured by PET mainly in posterior areas, and hippocampal atrophy in MRI might be indicative of distinct deficits with a distinct risk of dementia in subgroups of patients. Longitudinal studies combining the existing techniques and new approaches are needed to identify patients at higher risk of dementia. © 2016 International Parkinson and Movement Disorder Society.

Association of the MTHFR rs1801131 and rs1801133 variants in sporadic Parkinson's disease patients

Parkinson's disease (PD) is a common age-dependent neurodegenerative movement disorder related to multiple factors, and genetic factors play an important role in the pathogenesis of PD. Variants in the methylenetetrahydrofolate reductase gene (MTHFR), a gene encoding a folate-dependent enzyme that is involved in homocysteine metabolism, have been reported to be associated with PD. To explore the role of the MTHFR gene in the development of PD in Chinese Han population, we analyzed two MTHFR variants (rs1801131 and rs1801133) in a patient cohort consisting of 512 patients with PD from mainland China and a control cohort consisting of 512 age, gender and ethnicity matched normal subjects. Statistically significant differences in genotypic and allelic frequencies were detected in the MTHFR variant rs1801133 (P=0.022 and 0.007, respectively; odds ratio=0.780, 95% confidence interval=0.651-0.934). In addition, the A-T haplotype of rs1801131-rs1801133 showed a protective role against PD development (P=0.007, odds ratio=0.779, 95% confidence interval=0.650-0.933). Our results suggested that the T allele of rs1801133 variant and A-T haplotype of rs1801131-rs1801133 in the MTHFR gene may decrease the risk of developing PD in Chinese Han population from mainland China.

Methylenetetrahydrofolate reductase (MTHFR) C677T/A1298C polymorphisms and susceptibility to Parkinson's disease: a meta-analysis

BACKGROUND

The association between the methylenetetrahydrofolate reductase (MTHFR) C677T/A1298C polymorphisms and susceptibility to Parkinson's disease (PD) was controversial in previous studies. The present study was therefore designed to investigate a more reliable estimate.

METHODS

15 studies were identified by a search of PubMed, EBMBASE, PDGENE, Elsevier, Springer Link, CBM (Chinese Biomedical Database), CNKI (Chinese National Knowledge Infrastructure), VIP (Chinese), and Wanfang (Chinese) databases, up to April 2013. Odds ratios (ORs) with corresponding 95% confidence interval (CI) were calculated using fixed effects model or random effects model. The subgroup analyses were made on the ethnicity.

RESULTS

MTHFR C677T polymorphism had a significant association with susceptibility to PD in all genetic models (for T vs. C: OR=1.24, 95% CI=1.11-1.38; for TT+CT vs. CC: OR=1.27, 95% CI=1.10-1.46; for TT vs. CC: OR=1.56, 95% CI=1.22-1.98; for TT vs. CT+CC: OR=1.43, 95% CI=1.14-1.79). Subgroup analyses by ethnicity revealed that the association between the MTHFR C677T polymorphism and PD existed in Caucasian population and Asian population. However, no association was detected between the MTHFR A1298C polymorphism and PD.

CONCLUSIONS

Results from this meta-analysis supported that the MTHFR C677T polymorphism was associated with an increased risk of PD. The MTHFR A1298C polymorphism may not increase the susceptibility to PD. Further studies are required to confirm our findings.

Clinical significance of homocysteine (hcy) on dementia in Parkinson's disease (PD)

Cognitive dysfunction and dementia are common non-motor symptoms of PD. hcy has various neuronal and endothelial cellular toxicities. The clinical relevance of the levodopa associated with elevated hcy level and its effect on the course of cognitive decline in PD are still undetermined. We conducted this study to clarify the clinical significance of elevated hcy in PD associated with dementia in the Korean population. A total of 33 PD patients without dementia (PDwoD) and 28 PD patients with dementia (PDD) who were recruited for this study were compared with 48 HCs to confirm the value of hcy as a contributing factor of dementia associated with PD. PD patients had neuropsychological tests and neurological examinations performed. The plasma hcy level was measured routinely in all patients and HCs. The hcy of PDD showed a higher hcy level than those of PDwoD as well as HCs. In considering each group of PDwoD and PDD, there were no intercorrelations between hcy levels, duration of PD symptoms, duration of PD treatment, or the results of neuropsychological tests. In conclusion, we ascertained that hcy level was related to the cognitive decline of PD patients. However we were unable to confirm a clear pathophysiologic role of hcy in PDD and the relationship between hcy and levodopa, significantly.

Association of COMT, MTHFR, and SLC19A1(RFC-1) polymorphisms with homocysteine blood levels and cognitive impairment in Parkinson's disease

INTRODUCTION

Elevated plasma homocysteine (Hcy) concentration is an independent risk factor for cardiovascular disease, and its involvement in endothelial cell dysfunction is well established. However, the role of Hcy and folate in the pathogenesis of Parkinson's disease (PD) remains controversial.

OBJECTIVES

The study was aimed at evaluating the relationships between Hcy, vitamin B12, and folic acid levels in the blood and cognitive status in PD patients with the genetic polymorphisms of MTHFR (rs1801133: C>T-677C>T, rs1801131: A>C-1298A>C), COMT (rs4680: A>G-Val158Met, rs6269: A>G, rs4633: C>T, rs4818: C>G), or SLC19A1 (rs1051266: G>A-80G>A).

METHODS

A total of 502 participants (248 with PD and 254 age-matched and sex-matched controls) were included in the study. The Unified Parkinson's Disease Rating Scale score, Hoehn-Yahr staging, and the Schwab-England scale were used to assess motor abilities and activity during daily life. Complex psychological examination with a battery of tests was used to classify patients into groups with (PDD) and without (nPDD) dementia. Blood samples were examined for Hcy, vitamin B12, and folic acid levels, as well as polymorphisms in genes related to Hcy metabolism, such as COMT, MTHFR, and SLC19A1(RFC-1).

RESULTS

The frequency of homozygous COMT rs4680G and rs4633C allele carriers was significantly decreased in PD patients in comparison with the controls (P=0.015; odds ratio=0.60; 95% confidence interval 0.41-0.90 and P=0.020; odds ratio=0.619; 95% confidence interval 0.42-0.92, respectively). No significant differences in the distribution of MTHFR 677C>T, 1298A>C, and SLC19A1 80G>A alleles and genotypes between PD patients and the controls were found. Hcy levels were significantly increased in PD patients (18±7.8 μmol/l) as compared with the controls (14.0±9.6 μmol/l, P=10(-8)) and were significantly associated with the MTHFR 677C>T polymorphism both in PD patients and controls, in which T allele carriers were characterized by markedly elevated Hcy plasma concentrations. No association was observed between Hcy plasma level and COMT and SLC19A polymorphisms. The results of multivariate logistic regression analysis revealed age (P=0.0003) and Hcy plasma levels (P=0.07) as independent risk factors predisposing individuals to PD dementia. The studied polymorphisms were not associated with cognitive status in PD patients.

CONCLUSION

The genetic factors studied were not associated with cognitive status in PD patients. Only age and Hcy plasma levels were found to be independent risk factors predisposing individuals to PD dementia. However, COMT: rs4680: A>G and rs4633: C>T polymorphisms were found to significantly affect PD risk, and the MTHFR 677C>T polymorphism helped determine plasma Hcy concentrations.

Serum homocysteine and physical exercise in patients with Parkinson's disease

BACKGROUND

Hyperhomocysteinemia is a major risk factor for cerebral and peripheral vascular diseases, as well as cortical and hippocampal injury, including an increased risk of dementia and cognitive impairment. Elevated serum homocysteine (Hcy) concentrations are common in patients with Parkinson's disease (PD) who have been treated with levodopa; however, physical exercises can help reduce Hcy concentrations. The aim of the present study was to compare serum Hcy levels in patients with PD who partook in regular physical exercises, sedentary PD patients, and healthy controls.

METHODS

Sixty individuals were enrolled in the present study across three groups: (i) 17 patients who did not partake of any type of exercise; (ii) 24 PD patients who exercised regularly; and (iii) 19 healthy individuals who did not exercise regularly. All participants were evaluated by Hoehn and Yahr scale, the Unified Parkinson's Disease Rating Scale (UPDRS) and Schwab and England scale (measure daily functionality). The serum levels of Hcy were analyzed by blood samples collected of each participant. An analysis of variance and a Tukey's post hoc test were applied to compare and to verify differences between groups. Pearson's correlation and stepwise multiple regression analyses were used to consider the association between several variables.

RESULTS

Mean plasma Hcy concentrations in individuals who exercised regularly were similar to those in the healthy controls and significantly lower than those in the group that did not exercise at all (P= 0.000). In addition, patients who did not exercise were receiving significantly higher doses of levodopa than those patients who exercised regularly (P= 0.001). A positive relationship between levodopa dose and Hcy concentrations (R(2) = 0.27; P= 0.03) was observed in patients who did not exercise, but not in those patients who exercised regularly (R(2) = 0.023; P= 0.15).

CONCLUSIONS

The results of the present study suggest that, even with regular levodopa therapy, Hcy concentrations in PD patients who exercise regularly are significantly lower than in patients who do not exercise and are similar Hcy concentrations in healthy controls.

The combination of homocysteine and C-reactive protein predicts the outcomes of Chinese patients with Parkinson's disease and vascular parkinsonism

Background

The elevation of plasma homocysteine (Hcy) and C-reactive protein (CRP) has been correlated to an increased risk of Parkinson's disease (PD) or vascular diseases. The association and clinical relevance of a combined assessment of Hcy and CRP levels in patients with PD and vascular parkinsonism (VP) are unknown.

Methodology/Principal Findings

We performed a cross-sectional study of 88 Chinese patients with PD and VP using a clinical interview and the measurement of plasma Hcy and CRP to determine if Hcy and CRP levels in patients may predict the outcomes of the motor status, non-motor symptoms (NMS), disease severity, and cognitive declines. Each patient's NMS, cognitive deficit, disease severity, and motor status were assessed by the Nonmotor Symptoms Scale (NMSS), Mini-Mental State Examination (MMSE), the modified Hoehn and Yahr staging scale (H&Y), and the unified Parkinson's disease rating scale part III (UPDRS III), respectively. We found that 100% of patients with PD and VP presented with NMS. The UPDRS III significantly correlated with CRP (P = 0.011) and NMSS (P = 0.042) in PD patients. The H&Y was also correlated with Hcy (P = 0.002), CRP (P = 0.000), and NMSS (P = 0.023) in PD patients. In VP patients, the UPDRS III and H&Y were not significantly associated with NMSS, Hcy, CRP, or MMSE. Strong correlations were observed between Hcy and NMSS as well as between CRP and NMSS in PD and VP.

Conclusions/Significance

Our findings support the hypothesis that Hcy and CRP play important roles in the pathogenesis of PD. The combination of Hcy and CRP may be used to assess the progression of PD and VP. Whether or not anti-inflammatory medication could be used in the management of PD and VP will produce an interesting topic for further research.

Impaired transmethylation potential in Parkinson's disease patients treated with L-Dopa

Hyperhomocysteinaemia was reported in patients with Parkinson's disease (PD) treated with l-Dopa. The increase in plasma concentration of this sulfur compound arises from the massive methylation of the drug operated by the enzyme catechol-O-methyltransferase (COMT), which acts as a powerful sink of methyl groups. The contemporary occurrence of C677T polymorphism in homozygosity, leading to a temperature-labile variant of the MTHFR enzyme, induces an even more marked increase in tHcy. Here we show that l-Dopa administration in hyperhomocysteinemic PD patients is able to lower intracellular concentration of S-Adenosylmethionine (AdoMet) in erythrocytes (RBC), while the occurrence of hyperhomocysteinaemia causes a significant increase in S-Adenosylhomocysteine (AdoHcy) level. In patients with PD treated with l-Dopa and hyperhomocysteinemic, the remarkable decrease in AdoMet and the concurrent increase in AdoHcy concentration both contribute to significantly lower the transmethylation potential ([AdoMet]/[AdoHcy]), a useful index of the effectiveness of methyl group transfer by methyltransferases. This decrease could indeed contribute to partly attenuate, through a self-limiting kinetic mechanism, the tendency of developing drug resistance, partly mediated in these patients by COMT upregulation. Our results also support the conclusion that COMT inhibitors (entacapone or tolcapone), when administered in PD patients treated with l-Dopa, may potentiate the endogenous AdoHcy-dependent COMT inhibition mechanism already operative in a variable fashion.

Methylenetetrahydrofolate reductase polymorphisms and plasma homocysteine in levodopa-treated and non-treated Parkinson's disease patients

Genetic C677T and A1298C polymorphisms in 5,10-methylenetetrahydrofolate reductase (MTHFR) and levodopa therapy in Parkinson's disease (PD) may increase homocysteine (Hcy) level. We examined whether connecting both polymorphisms influences the effect of levodopa on Hcy. MTHFR genotypes and Hcy, vitamin B(12), and folate levels were determined in 48 levodopa-treated PD patients (PD-L), 28 non-treated PD patients (PD-N) and 110 controls. Hcy was remarkably higher in PD-L than in PD-N and controls (p<0.001); similarly, the differences were seen in different age subgroups and in both genders. Furthermore, Hcy differences between PD-L and PD-N were evident in 677C/T, T/T, C/T + A/A, T/T + A/A (all p<0.05), and 1298A/A (p<0.001), but not in others such as 677C/C, and C/C + A/A. Hcy in PD-N and controls was comparable for all genotypes. In PD-L, Hcy was the highest in 677T/T, then in C/T, and in C/C with a significant difference from T/T (p=0.014), but was not different among A1298C genotypes. Likewise, Hcy was the highest in 677T/T+1298A/A, intermediate in C/T+A/A, and the lowest in C/C+A/A. In PD-N, Hcy was similar among all genotypes. In conclusion, Hcy elevation may be caused by levodopa administration, and further promoted by 677C/T and T/T, but not by A1298C genotypes. The promoting elevation in 1298A/A is attributed to combining the 677T allele. Neither C677T nor A1298C genotypes contribute to elevating Hcy in PD-N.

Hyperhomocysteinemia in patients with Parkinson's disease and relationship to vitamin B level

Background:

Plasma homocysteine (Hcy) levels are increased in patients with Parkinson’s disease (PD) undergoing levodopa treatment. We measured the Hcy levels in PD patients and assessed the relationship between Hcy level and features of PD, cognitive function and vitamin B status.

Methods:

Concentrations of Hcy, vitamin B₁₂ and folate were measured in 33 PD patients and 41 normal control individuals. Mini-mental Status Examination (MMSE) was assessed in all subjects. In PD patients, Hoehn & Yahr stage and Unified Parkinson Disease Rating Scale (UPDRS) motor scores were also examined.

Results:

Plasma Hcy levels were lower in PD patients than in control individuals. Hcy level was inversely correlated with vitamin B₁₂ and folate levels in the PD group but not in control individuals. Age, symptom duration, UPDRS motor scores, MMSE score, levodopa dose and duration of treatment did not differ between patients with Hcy >14 μmol/L and those with Hcy <14 μmol/L.

Conclusions:

Plasma Hcy levels were increased in PD patients with levodopa treatment and were related to vitamin B level. These results indicate that vitamin supplementation may be beneficial in levodopa-treated PD patients, although hyperhomocysteinemia did not affect the motor and cognitive status of PD patients.