Catechol-O-Methyltransferase Enzyme

Therapeutic drug monitoring in Parkinson's disease

A patient-tailored therapy of the heterogeneous, neuropsychiatric disorder of Parkinson's disease (PD) aims to improve dopamine sensitive motor symptoms and associated non-motor features. A repeated, individual adaptation of dopamine substituting compounds is required throughout the disease course due to the progress of neurodegeneration. Therapeutic drug monitoring of dopamine substituting drugs may be an essential tool to optimize drug applications. We suggest plasma determination of levodopa as an initial step. The complex pharmacology of levodopa is influenced by its short elimination half-life and the gastric emptying velocity. Both considerably contribute to the observed variability of plasma concentrations of levodopa and its metabolite 3-O-methyldopa. These amino acids compete with other aromatic amino acids as well as branched chain amino acids on the limited transport capacity in the gastrointestinal tract and the blood brain barrier. However, not much is known about plasma concentrations of levodopa and other drugs/drug combinations in PD. Some examples may illustrate this lack of knowledge: Levodopa measurements may allow further insights in the phenomenon of inappropriate levodopa response. They may result from missing compliance, interactions e.g. with treatments for other mainly age-related disorders, like hypertension, diabetes, hyperlipidaemia, rheumatism or by patients themselves independently taken herbal medicines. Indeed, uncontrolled combination of compounds for accompanying disorders as given above with PD drugs might increase the risk of side effects. Determination of other drugs used to treat PD in plasma such as dopamine receptor agonists, amantadine and inhibitors of catechol-O-methyltransferase or monoamine oxidase B may refine and improve the value of calculations of levodopa equivalents. How COMT-Is change levodopa plasma concentrations? How other dopaminergic and non-dopaminergic drugs influence levodopa levels? Also, delivery of drugs as well as single and repeated dosing and continuous levodopa administrations with a possible accumulation of levodopa, pharmacokinetic behaviour of generic and branded compounds appear to have a marked influence on efficacy of drug treatment and side effect profile. Their increase over time may reflect progression of PD to a certain degree. Therapeutic drug monitoring in PD is considered to improve the therapeutic efficacy in the course of this devastating neurologic disorder and therefore is able to contribute to the patients' precision medicine. State-of-the-art clinical studies are urgently needed to demonstrate the usefulness of TDM for optimizing the treatment of PD.

Effect of Probiotic Bacteria on the Gut Microbiome of Mice with Lipopolysaccharide-Induced Inflammation

The role of lipopolysaccharide (LPS) in the development of diseases is clear, but the specific mechanisms remain poorly understood. This study aimed to investigate the microbiome aberrations in the guts of mice against the background of LPS, as well as the anti-inflammatory effect of probiotic supplementation with Lactobacillus plantarum from the gut, a mix of commercial probiotic lactic acid bacteria, and Weissella confusa isolated from milk using next-generation sequencing. LPS injections were found to induce inflammatory changes in the intestinal mucosa. These morphological changes were accompanied by a shift in the microbiota. We found no significant changes in the microbiome with probiotic supplementation compared to the LPS group. However, when Lactobacillus plantarum and a mix of commercial probiotic lactic acid bacteria were used, the intestinal mucosa was restored. Weissella confusa did not contribute to the morphological changes of the intestinal wall or the microbiome. Changes in the microbiome were observed with probiotic supplementation of Lactobacillus plantarum and a mix of commercial probiotic lactic acid bacteria compared to the control group. In addition, when Lactobacillus plantarum was used, we observed a decrease in the enrichment of the homocysteine and cysteine interconversion pathways with an increase in the L-histidine degradation pathway.

Molecular Mechanisms Provide a Landscape for Biomarker Selection for Schizophrenia and Schizoaffective Psychosis

Research evaluating the role of the 5,10-methylenetetrahydrofolate reductase (MTHFR C677T) gene in schizophrenia has not yet provided an extended understanding of the proximal pathways contributing to the 5-10-methylenetetrahydrofolate reductase (MTHFR) enzyme's activity and the distal pathways being affected by its activity. This review investigates these pathways, describing mechanisms relevant to riboflavin availability, trace mineral interactions, and the 5-methyltetrahydrofolate (5-MTHF) product of the MTHFR enzyme. These factors remotely influence vitamin cofactor activation, histamine metabolism, catecholamine metabolism, serotonin metabolism, the oxidative stress response, DNA methylation, and nicotinamide synthesis. These biochemical components form a broad interactive landscape from which candidate markers can be drawn for research inquiry into schizophrenia and other forms of mental illness. Candidate markers drawn from this functional biochemical background have been found to have biomarker status with greater than 90% specificity and sensitivity for achieving diagnostic certainty in schizophrenia and schizoaffective psychosis. This has implications for achieving targeted treatments for serious mental illness.

S-adenosyl-l-methionine antidepressant-like effects involve activation of 5-HT1A receptors

S-adenosyl-l-methionine (SAMe), a methyl donor, induces antidepressant effects in preclinical and clinical studies of depression. However, the mechanisms behind these effects have been poorly investigated. Since SAMe is involved in monoamine metabolism, this work aimed at 1) testing the effects induced by systemic treatment with SAMe in mice submitted to the forced swimming test (FST) and tail suspension test (TST); 2) investigating the involvement of serotonergic neurotransmission in the behavioral effects induced by SAMe. To do that, male Swiss mice received systemic injections (1 injection/day, 1 or 7 days) of imipramine (30 mg/kg), L-methionine (400, 800, 1600, and 3200 mg/kg), SAMe (10, 25, 50, 100, and 200 mg/kg), or vehicle (10 ml/kg) and were submitted to the FST or TST, 30 min after the last injection. The effect of SAMe (50 mg/kg) was further investigated in independent groups of male Swiss mice pretreated with p-chlorophenylalanine (PCPA, serotonin synthesis inhibitor, 150 mg/kg daily, 4 days) or with WAY100635 (5-HT_1A receptor antagonist, 0.1 mg/kg, 1 injection). One independent group was submitted to the FST and euthanized immediately after for collection of brain samples for neurochemical analyses. Serotonin (5-HT) and noradrenaline (NA) levels were measured in the hippocampus (HPC) and prefrontal cortex (PFC). Furthermore, to investigate if the treatments used could induce any significant exploratory/motor effect which would interfere with the FST results, the animals were also submitted to the open field test (OFT). The administration of imipramine (30 mg/kg), L-methionine (400, 800, 1600, and 3200 mg/kg), and SAMe (10 and 50 mg/kg) reduced the immobility time in the FST, an effect blocked by pretreatment with PCPA and WAY100635. None of the treatments increased the locomotion in the OFT. In conclusion, our results suggest that the antidepressant-like effects induced by SAMe treatment are dependent on serotonin synthesis and 5-HT_1A receptor activation.

Nicotinamide N-Methyltransferase: An Emerging Protagonist in Cancer Macro(r)evolution

Nicotinamide N-methyltransferase (NNMT) has progressed from being considered merely a Phase II metabolic enzyme to one with a central role in cell function and energy metabolism. Over the last three decades, a significant body of evidence has accumulated which clearly demonstrates a central role for NNMT in cancer survival, metastasis, and drug resistance. In this review, we discuss the evidence supporting a role for NNMT in the progression of the cancer phenotype and how it achieves this by driving the activity of pro-oncogenic NAD+-consuming enzymes. We also describe how increased NNMT activity supports the Warburg effect and how it promotes oncogenic changes in gene expression. We discuss the regulation of NNMT activity in cancer cells by both post-translational modification of the enzyme and transcription factor binding to the NNMT gene, and describe for the first time three long non-coding RNAs which may play a role in the regulation of NNMT transcription. We complete the review by discussing the development of novel anti-cancer therapeutics which target NNMT and provide insight into how NNMT-based therapies may be best employed clinically.

Exercise increases striatal Glu reuptake and improves motor dysfunction in 6-OHDA-induced Parkinson's disease rats

The purpose of this study is to clarify that exercise may improve the motor dysfunction of Parkinson's disease (PD) model rats by increasing the reuptake of glutamate (Glu) in the striatum. The neurotoxin 6-hydroxydopamine (6-OHDA) was injected into the medial forebrain bundle (MFB) of the rats' right brain to establish PD model rats with unilateral injury, and the sham operation group was given the same dose of normal saline at the same site as the control group. The reliability of the model was evaluated by apomorphine (APO)-induced rotation test combined with tyrosine hydroxylase (TH) immunohistochemical staining in the substantia nigra and striatum. The exercise group started treadmill training intervention (11 m/min, 30 min/day, 5d/week, and 4 weeks in total) 1 week after the operation. The balance bar test, suspension test, and the tail-lifting handstand test were used to evaluate exercise performance of rats; RT-PCR and western blotting were used to detect protein and mRNA expression of glutamate transporter-1 (GLT-1) and glutamine synthetase (GS) in the striatum; and isotope labeling was used to detect the ability of Glu reuptake in the striatum. (1) Compared with PD group, the number of TH immunoreactive cells in the substantia nigra and the content of TH immunoreactive fibers in the striatum did not change significantly in PD + Ex group. (2) Compared with PD group, the latency and total time of crossing the balance beam were significantly shorter (P < 0.01), the retention time of two forepaws on the metal wire was significantly longer (P < 0.01), the maximum lifting of head and trunk was significantly increased (P < 0.01) in PD + Ex group. (3) Compared with PD group, the ability of Glu reuptake in the striatum was significantly increased (P < 0.05), the expression levels of GLT-1 and GS mRNA in the striatum were significantly increased (P < 0.05), the protein expression of GLT-1 and GS in the striatum was significantly upregulated (P < 0.05) in PD + Ex group. Exercise intervention can significantly improve the motor dysfunction of PD model rats, increase the ability of striatal Glu reuptake significantly, and upregulate the expression levels of GLT-1 and GS protein and GS mRNA significantly. Exercise intervention may increase the protein expression level of GLT-1 and increase the reuptake ability of Glu in the striatum, thereby reducing the excitotoxic effect of excessive Glu on the postsynaptic membrane, and ultimately alleviate the motor dysfunction in PD model rats.

Evidence to Support the Use of S-Adenosylmethionine for Treatment of Post-Concussive Sequelae in the Military

INTRODUCTION

Since the year 2000, over 413,000 service members have sustained traumatic brain injury (TBI) and may present with post-concussive sequelae including headaches, fatigue, irritability, cognitive problems, depression, insomnia, and chronic pain. Although the focus of the article is on military TBI, the usefulness of S-adenosylmethionine (SAMe) would extend to both civilian and military populations. This narrative review examines the preclinical and clinical literature of SAMe's metabolism and alterations seen in disease states such as depressive disorders, pain disorders, fatigue, cognition, dementia, use in pregnancy and peripartum, children, adolescents, and adults, to the elderly with and without dementia, stroke, and neurodegeneration, in order to highlight its potential benefit in post-concussive sequelae after TBI.

MATERIALS AND METHODS

A MEDLINE/PubMed and Cochrane Database search was conducted between May 3, 2018 and July 30, 2019 by combining search terms for SAMe with terms for relevant disease states including depression, brain injury, dementia, Alzheimer's disease, Parkinson's disease, cognition, fatigue, and pain. This search retrieved a total of 676 references. 439 were excluded for being over a 10-year publication date, except where clinically relevant. After additional removal of repeated articles, the number of articles were totaled 197. An additional 59 articles were excluded: 10 not in English, 4 duplicates, 4 not original investigations, and 41 outside the scope of this article. The remaining 138 articles were used in this review and included 25 clinical studies, 46 preclinical studies, 63 reviews, and 4 case reports.

RESULTS

This narrative review examined the preclinical and clinical literature of SAMe's metabolism and alterations seen in MDD, pain disorders, fatigue, cognition and memory, dementia, and other disorders to highlight the potential benefit of SAMe in post-concussive sequelae in mTBI. The literature showed potential for improvement, safety, and tolerability in these symptom clusters commonly seen in military mild TBI (mTBI).

CONCLUSION

There is evidence of a potential benefit of SAMe as an intervention to help with symptoms across the range of post-concussive sequelae and syndromes commonly seen in military mTBI. Since the discovery of SAMe in 1952, this pleiotropic molecule has shown the significance of its involvement in several metabolic cascades in such disparate systems as epigenetics, bioenergetics, DNA methylation, neurotransmitter systems, and potential usefulness in military TBI. Significant limitations include disparate presentations seen in patients with mild TBI, those with post-concussive syndrome, as well as those with comorbid depression and posttraumatic stress disorder. Also, over-the-counter medications are not regulated and SAMe products may vary widely in price and quality. Given the potential for mania in patients with bipolar disorder, evaluation and recommendations should be made by a physician able to evaluate the underlying bipolar diathesis. Furthermore, this narrative review serves as the rationale for future open-label and double-blind placebo-controlled trials in military mTBI and SAMe.

Behavioral and Psychological Symptoms of Dementia (BPSD): Clinical Characterization and Genetic Correlates in an Italian Alzheimer's Disease Cohort

BACKGROUND

The occurrence of Behavioral and Psychological Symptoms of Dementia (BPSD) in Alzheimer's Disease (AD) patients hampers the clinical management and exacerbates the burden for caregivers. The definition of the clinical distribution of BPSD symptoms, and the extent to which symptoms are genetically determined, are still open to debate. Moreover, genetic factors that underline BPSD symptoms still need to be identified.

PURPOSE

To characterize our Italian AD cohort according to specific BPSD symptoms as well as to endophenotypes. To evaluate the associations between the considered BPSD traits and COMT, MTHFR, and APOE genetic variants.

METHODS

AD patients (n = 362) underwent neuropsychological examination and genotyping. BPSD were assessed with the Neuropsychiatric Inventory scale.

RESULTS

APOE and MTHFR variants were significantly associated with specific single BPSD symptoms. Furthermore, "Psychosis" and "Hyperactivity" resulted in the most severe endophenotypes, with APOE and MTHFR implicated as both single risk factors and "genexgene" interactions.

CONCLUSIONS

We strongly suggest the combined use of both BPSD single symptoms/endophenotypes and the "genexgene" interactions as valid strategies for expanding the knowledge about the BPSD aetiopathogenetic mechanisms.

MTHFR: Genetic variants, expression analysis and COMT interaction in major depressive disorder

BACKGROUND

Methylenetetrahydrofolate reductase (MTHFR) genetic variations have been widely studied in major depressive disorder (MDD) and antidepressants outcome. An interaction with catechol-O-methyltransferase (COMT) has also been proved affecting depression. The aim of this study was to clarify the role of the most commonly studied single nucleotide polymorphisms (SNPs) of MTHFR gene in MDD and in treatment response mechanisms, along with the impact of the interaction with COMT.

METHODS

A total of 613 MDD patients, of whom 389 were classified as having treatment resistant depression (TRD), and 463 controls were enrolled. The A1298C, C677T and COMT Val158Met were genotyped. Genetic data were integrated with a transcriptional level analysis in peripheral blood cells (PBCs) and fibroblasts.

RESULTS

The A1298C CC homozygotes were more frequent in MDD patients compared to controls in women, increasing twice the genetic risk to develop depression. Moreover this genotype resulted in epistasis with COMT Met carriers in association with MDD. No significant effects were obtained concerning response to treatment. Transcriptional analyses highlighted a strong correlation between the mRNA levels of MTHFR in fibroblasts and COMT genotypes whereas no significant association with MDD was found. PBCs results revealed relevant influences of environmental factors.

LIMITATION

We did not measure folate and homocisteine levels.

CONCLUSION

This study showed the involvement of A1298C, Val158Met and their interaction in MDD. The transcriptional analyses supported the participation of COMT in the folate pathway, which partakes in the complex network of gene×gene and gene×environment interactions of MDD etiopathogenesis.

Methylation potential associated with diet, genotype, protein, and metabolite levels in the Delta Obesity Vitamin Study

Micronutrient research typically focuses on analyzing the effects of single or a few nutrients on health by analyzing a limited number of biomarkers. The observational study described here analyzed micronutrients, plasma proteins, dietary intakes, and genotype using a systems approach. Participants attended a community-based summer day program for 6-14 year old in 2 years. Genetic makeup, blood metabolite and protein levels, and dietary differences were measured in each individual. Twenty-four-hour dietary intakes, eight micronutrients (vitamins A, D, E, thiamin, folic acid, riboflavin, pyridoxal, and pyridoxine) and 3 one-carbon metabolites [homocysteine (Hcy), S-adenosylmethionine (SAM), and S-adenosylhomocysteine (SAH)], and 1,129 plasma proteins were analyzed as a function of diet at metabolite level, plasma protein level, age, and sex. Cluster analysis identified two groups differing in SAM/SAH and differing in dietary intake patterns indicating that SAM/SAH was a potential marker of nutritional status. The approach used to analyze genetic association with the SAM/SAH metabolites is called middle-out: SNPs in 275 genes involved in the one-carbon pathway (folate, pyridoxal/pyridoxine, thiamin) or were correlated with SAM/SAH (vitamin A, E, Hcy) were analyzed instead of the entire 1M SNP data set. This procedure identified 46 SNPs in 25 genes associated with SAM/SAH demonstrating a genetic contribution to the methylation potential. Individual plasma metabolites correlated with 99 plasma proteins. Fourteen proteins correlated with body mass index, 49 with group age, and 30 with sex. The analytical strategy described here identified subgroups for targeted nutritional interventions.

Peripheral neuropathy in Parkinson's disease: levodopa exposure and implications for duodenal delivery

In advanced Parkinson's disease (PD) patients, continuous intra-duodenal infusion of levodopa/carbidopa intestinal gel (LCIG) is an established approach in the management of motor complications that cannot be further improved by conventional oral therapy. In general, tolerability of LCIG has resembled that of oral dopaminergic therapy; however, cases of symptomatic peripheral neuropathy (PN), sometimes severe, have been reported in patients receiving LCIG. Cases are generally a sensorimotor polyneuropathy with both subacute and chronic onsets, often associated with vitamin B12 and/or B6 deficiency. Rare cases clinically resemble Guillain-Barré syndrome. In the absence of prospectively collected data on possible associations between LCIG and PN, it is prudent to explore potential mechanisms that may explain a possible relationship. The PN may be linked to use of high-dose levodopa, promoting high levels of homocysteine and methylmalonic acid or reduced absorption of vitamins essential for homocysteine metabolism. Cases of LCIG-associated PN often have responded to vitamin supplementation without need for LCIG cessation, although LCIG cessation is sometimes necessary. It may be advisable to monitor vitamin B12/B6 status before and after patients start LCIG and be vigilant for signs of PN. Prospective, large-scale, long-term studies are needed to clarify whether vitamin supplementation and routine use of a catechol-O-methyltransferase inhibitor may help prevent PN in LCIG recipients and whether these measures should be routine practice in patients with PD on high-dose oral levodopa.

Drug therapy in patients with Parkinson's disease

Parkinson`s disease (PD) is a progressive, disabling neurodegenerative disorder with onset of motor and non-motor features. Both reduce quality of life of PD patients and cause caregiver burden. This review aims to provide a survey of possible therapeutic options for treatment of motor and non motor symptoms of PD and to discuss their relation to each other. MAO-B-Inhibitors, NMDA antagonists, dopamine agonists and levodopa with its various application modes mainly improve the dopamine associated motor symptoms in PD. This armentarium of PD drugs only partially influences the onset and occurrence of non motor symptoms. These PD features predominantly result from non dopaminergic neurodegeneration. Autonomic features, such as seborrhea, hyperhidrosis, orthostatic syndrome, salivation, bladder dysfunction, gastrointestinal disturbances, and neuropsychiatric symptoms, such as depression, sleep disorders, psychosis, cognitive dysfunction with impaired execution and impulse control may appear. Drug therapy of these non motor symptoms complicates long-term PD drug therapy due to possible occurrence of drug interactions, - side effects, and altered pharmacokinetic behaviour of applied compounds. Dopamine substituting compounds themselves may contribute to onset of these non motor symptoms. This complicates the differentiation from the disease process itself and influences therapeutic options, which are often limited because of additional morbidity with necessary concomitant drug therapy.

L-tyrosine and L-dihydroxyphenylalanine as hormone-like regulators of melanocyte functions

There is evidence that L-tyrosine and L-dihydroxyphenylalanine (L-DOPA), besides serving as substrates and intermediates of melanogenesis, are also bioregulatory agents acting not only as inducers and positive regulators of melanogenesis but also as regulators of other cellular functions. These can be mediated through action on specific receptors or through non-receptor-mediated mechanisms. The substrate induced (L-tyrosine and/or L-DOPA) melanogenic pathway would autoregulate itself as well as regulate the melanocyte functions through the activity of its structural or regulatory proteins and through intermediates of melanogenesis and melanin itself. Dissection of regulatory and autoregulatory elements of this process may elucidate how substrate-induced autoregulatory pathways have evolved from prokaryotic or simple eukaryotic organisms to complex systems in vertebrates. This could substantiate an older theory proposing that receptors for amino acid-derived hormones arose from the receptors for those amino acids, and that nuclear receptors evolved from primitive intracellular receptors binding nutritional factors or metabolic intermediates.

Motor complications, levodopa metabolism and progression of Parkinson's disease

INTRODUCTION

Oxidative stress is an essential component of neuronal death in Parkinson's disease (PD). Clinically, progression of PD is also characterised by onset of motor complications (MC). MC results from the peripheral and central degree of fluctuations of levodopa (LD) and of dopamine.

AREAS COVERED

This review highlights aspects of LD and dopamine metabolism in chronic neurodegeneration in PD. A Medline search (terms: homocysteine, LD, PD, progression [from 2000 onwards]) was performed and considered preclinical and clinical investigations. The author discusses pharmacokinetic and metabolic aspects of chronic LD administration in PD patients and provides a therapeutic concept to reduce probable PD accelerating consequences of chronic LD application.

EXPERT OPINION

The author suggests that the future 'ideal' oral LD therapy should be homocysteine-reducing, methyl-group-donating, oxidative-stress-decreasing and antiglutamatergic while also allowing continuous delivery to the brain. This may slow the progression of PD and delay the onset of MC, both of which represent unmet needs in the treatment of PD patients.