Polyneuropathy in levodopa-treated Parkinson's patients

Metabolomic Footprint of Disrupted Energetics and Amino Acid Metabolism in Neurodegenerative Diseases: Perspectives for Early Diagnosis and Monitoring of Therapy

The prevalence of neurodegenerative diseases (NDs) is increasing due to the aging population and improved longevity. They are characterized by a range of pathological hallmarks, including protein aggregation, mitochondrial dysfunction, and oxidative stress. The aim of this review is to summarize the alterations in brain energy and amino acid metabolism in Alzheimer’s disease (AD), Parkinson’s disease (PD), and Huntington’s disease (HD). Based on our findings, we proposed a group of selected metabolites related to disturbed energy or mitochondrial metabolism as potential indicators or predictors of disease. We also discussed the hidden challenges of metabolomics studies in NDs and proposed future directions in this field. We concluded that biochemical parameters of brain energy metabolism disruption (obtained with metabolomics) may have potential application as a diagnostic tool for the diagnosis, prediction, and monitoring of the effectiveness of therapies for NDs. However, more studies are needed to determine the sensitivity of the proposed candidates. We suggested that the most valuable biomarkers for NDs studies could be groups of metabolites combined with other neuroimaging or molecular techniques. To attain clinically applicable results, the integration of metabolomics with other “omic” techniques might be required.

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.

Peripheral neuropathy in Parkinson's disease: prevalence and functional impact on gait and balance

Peripheral neuropathy is a common problem in patients with Parkinson's disease. Peripheral neuropathy's prevalence in Parkinson's disease varies between 4.8-55%, compared with 9% in the general population. It remains unclear whether peripheral neuropathy leads to decreased motor performance in Parkinson's disease, resulting in impaired mobility and increased balance deficits. We aimed to determine the prevalence and type of peripheral neuropathy in Parkinson's disease patients and evaluate its functional impact on gait and balance. A cohort of consecutive Parkinson's disease patients assessed by movement disorders specialists based on the UK Brain Bank criteria underwent clinical, neurophysiological (nerve conduction studies and quantitative sensory testing) and neuropathological (intraepidermal nerve fibre density in skin biopsy punches) evaluation to characterize the peripheral neuropathy type and aetiology using a cross-sectional design. Gait and balance were characterized using wearable health-technology in OFF and ON medication states, and the main parameters were extracted using validated algorithms. A total of 99 Parkinson's disease participants with a mean age of 67.2 (±10) years and mean disease duration of 6.5 (±5) years were assessed. Based on a comprehensive clinical, neurophysiological and neuropathological evaluation, we found that 40.4% of Parkinson's disease patients presented peripheral neuropathy, with a predominance of small fibre neuropathy (70% of the group). In the OFF state, the presence of peripheral neuropathy was significantly associated with shorter stride length (P = 0.029), slower gait speed (P = 0.005) and smaller toe-off angles (P = 0.002) during straight walking; significantly slower speed (P = 0.019) and smaller toe-off angles (P = 0.007) were also observed during circular walking. In the ON state, the above effects remained, albeit moderately reduced. With regard to balance, significant differences between Parkinson's disease patients with and without peripheral neuropathy were observed in the OFF medication state during stance with closed eyes on a foam surface. In the ON states, these differences were no longer observable. We showed that peripheral neuropathy is common in Parkinson's disease and influences gait and balance parameters, as measured with mobile health-technology. Our study supports that peripheral neuropathy recognition and directed treatment should be pursued in order to improve gait in Parkinson's disease patients and minimize balance-related disability, targeting individualized medical care.

Emerging Pharmacotherapies for Motor Symptoms in Parkinson's Disease

Parkinson's disease (PD) is the second commonest neurodegenerative disorder in the older adult and is characterized by progressive disabling motor symptoms of bradykinesia, tremor, rigidity, postural instability and also non motor symptoms that affect quality of life. The pharmacotherapy of PD consists of oral, transdermal, and subcutaneous medications, as well as invasive advanced therapies at later stages of the disease. PD medications are often started as monotherapy but with the progression of the illness often there is a need to add more medications and frequently comprises of a challenging polypharmacotherapy. Adverse effects of pharmacotherapy often add to the problems of adequate treatment. Patients and physicians have to prioritize treatment goals on the most disabling symptoms and the safest and most effective treatments. Almost every year newer medications and modes of delivery continue to be researched and added to the therapeutic armamentarium. This review article outlines existing and emerging pharmacotherapies for motor symptoms in PD.

Differential expression and significance of miRNAs in plasma extracellular vesicles of patients with Parkinson's disease

OBJECTIVE

To study the feasibility of plasma extracellular vesicles (EVs) miRNAs as diagnostic biomarkers for Parkinson's disease (PD).

METHODS

Plasma EVs were isolated from 30 PD patients and 30 age- and sex-matched healthy controls. Plasma EVs miRNAs were analysed by qRT-PCR. SH-SY5Y cells were induced by different concentrations of 1-Methyl-4-phenil-pyridinium (MPP⁺) to obtain PD cellular model. The levels of miRNAs and α-synuclein (α-syn) in PD cellular model were analysed by qRT-PCR and Western blot. Receiver operating characteristic (ROC) curve analysis was performed to determine the diagnostic usefulness of the miRNAs in plasma EVs for PD. The gene ontology (GO) and KEGG pathways of the target genes of miRNAs were analysed by softwares.

RESULTS

The level of hsa-miR-30c-2-3p in plasma EVs was significantly higher in PD patients than that in controls, and the levels of hsa-miR-15b-5p, hsa-miR-138-5p, hsa-miR-338-3p, hsa-miR-106b-3p and hsa-miR-431-5p in plasma EVs were lower in PD patients than that in controls. When compared with the control group, the area under the curve (AUC) values for hsa-miR-15b-5p, hsa-miR-30c-2-3p, hsa-miR-138-5p, hsa-miR-431-5p, hsa-miR-338-3p and hsa-miR-106b-3p were all greater than 0.6. The target genes of hsa-miR-15b-5p, hsa-miR-30c-2-3p, hsa-miR-138-5p and hsa-miR-338-3p were enriched in dopaminergic synapse and PD pathway.

CONCLUSIONS

The hsa-miR-15b-5p, hsa-miR-30c-2-3p, hsa-miR-138-5p, hsa-miR-106b-3p, hsa-miR-338-3p and hsa-miR-431-5p may be used as potential biomarkers for the diagnosis of PD, and the combined diagnostic accuracy of hsa-miR-15b-5p, hsa-miR-30c-2-3p, hsa-miR-138-5p and hsa-miR-106b-3p was better. The target genes of hsa-miR-15b-5p, hsa-miR-30c-2-3p, hsa-miR-138-5p and hsa-miR-338-3p may regulate the expression of dopamine by dopaminergic synapse and PD pathway.HighlightsIsolation and identification of plasma EVs.The miRNAs in plasma EVs may be used as potential biomarkers for the diagnosis of PD.When SH-SY5Y cells were induced by different concentrations of MPP⁺, the levels of miRNAs and α-syn changed gradually.The target genes of miRNAs were enriched in dopaminergic synapse and PD pathway.The target genes of miRNAs may regulate the expression of dopamine.

Potential use of corneal confocal microscopy in the diagnosis of Parkinson's disease associated neuropathy

Parkinson’s disease (PD) is a chronic, progressive neurodegenerative disease affecting about 2–3% of population above the age of 65. In recent years, Parkinson’s research has mainly focused on motor and non-motor symptoms while there are limited studies on neurodegeneration which is associated with balance problems and increased incidence of falls. Corneal confocal microscopy (CCM) is a real-time, non-invasive, in vivo ophthalmic imaging technique for quantifying nerve damage in peripheral neuropathies and central neurodegenerative disorders. CCM has shown significantly lower corneal nerve fiber density (CNFD) in patients with PD compared to healthy controls. Reduced CNFD is associated with decreased intraepidermal nerve fiber density in PD. This review provides an overview of the ability of CCM to detect nerve damage associated with PD.

Large-Fiber Neuropathy in Parkinson's Disease: Clinical, Biological, and Electroneurographic Assessment of a Romanian Cohort

(1) Background: Increased attention has lately been given to polyneuropathy in Parkinson’s Disease (PD). Several papers postulated that large-fiber neuropathy (PNP) in PD is related to vitamin B12 deficiency and L-Dopa exposure. (2) Methods: Using a cross-sectional, observational study, we evaluated 73 PD patients without a previously known cause of PNP using clinical scores (UPDRS II and III and Toronto Clinical Scoring System), biological evaluation of vitamin B12 and folic acid, and nerve conduction studies to assess the prevalence and features of PNP. (3) Results: The prevalence of PNP was 49.3% in the study group. In the L-Dopa group, the frequency of PNP was 67.3% as compared to PNP in the non-L-Dopa group, where one subject had PNP (χ² = 23.41, p < 0.01). PNP was predominantly sensory with mild to moderate axonal loss. Cyanocobalamin correlated with L-Dopa daily dose (r = −0.287, p < 0.05) and L-Dopa duration of administration (r = −0.316, p < 0.05). L-Dopa daily dose correlated with the amplitudes of sensory nerve action potentials of the superficial peroneal and radial nerves (r = −0.312, p < 0.05) (r = −0.336, p < 0.05), respectively. (4) Conclusions: PNP is more frequent in L-Dopa-treated patients than in L-Dopa-naïve patients. The results imply that longer exposure to high doses of L-Dopa may cause vitamin B12 and folate imbalance and PNP, secondarily.

Levodopa-Induced Neuropathy: A Systematic Review

Background

Clinical, neurophysiological, and pathological evidence suggest an association between Parkinson's disease (PD) and peripheral neuropathy (PNP), with a possible causative role of levodopa metabolic products, such as homocysteine and methylmalonic acid.

Methods

We conducted a systematic review of studies reporting cases of PNP in l-dopa-treated PD patients indexed in PubMed between January 1990 and March 2018.

Results

We identified 38 articles reporting cases of PNP in PD patients treated with oral l-dopa or with l-dopa/carbidopa intestinal gel infusion (LCIG). Prevalence of PNP was 30.2% in the former group and 42.1% in the latter. Oral l-dopa was mostly associated with slowly progressive PNP, whereas LCIG showed an acute or subacute onset in 35.7% of cases. In both groups, there was an association between PNP and higher l-dopa doses, as well as with the following biochemical alterations: increased homocysteine; reduced vitamin B12; increased methylmalonic acid; and reduced vitamin B6. A skin biopsy was performed in 181 patients, showing signs of small fibers neuropathy in 169 (93.4%). Positive, yet preliminary, results were observed in patients receiving periodic vitamin supplementation.

Conclusions

Over one third of PD patients in treatment with l-dopa may develop PNP, with a significantly higher prevalence of acute and subacute forms in those receiving LCIG. Pathogenic mechanisms remain unclear, but possibly related to a complex interplay between peripheral neurodegenerative processes and l-dopa neurotoxic metabolites. Prospective, randomized, clinical trials are required to identify factors associated with the onset and progression of PD-associated PNP and clarify the protective role of B-group vitamin supplementation.

Serum amino acid profile in patients with Parkinson's disease

Amino acids play numerous roles in the central nervous system, serving as neurotransmitters, neuromodulators and regulators of energy metabolism. The free amino acid profile in serum of Parkinson's disease (PD) patients may be influenced by neurodegeneration, mitochondrial dysfunction, malabsorption in the gastroenteric tract and received treatment. The aim of our study was the evaluation of the profile of amino acid concentrations against disease progression. We assessed the amino acid profile in the serum of 73 patients divided into groups with early PD, late PD with dyskinesia and late PD without dyskinesia. Serum amino acid analysis was performed by high-pressure liquid chromatography with fluorescence detection. We observed some significant differences amongst the groups with respect to concentrations of alanine, arginine, phenylalanine and threonine, although no significant differences were observed between patients with advanced PD with and without dyskinesia. We conclude that this specific amino acid profile could serve as biochemical marker of PD progression.