Mechanisms of homocysteine neurotoxicity in neurodegenerative diseases with special reference to dementia

B Vitamins and Fatty Acids: What Do They Share with Small Vessel Disease-Related Dementia?

Many studies have been written on vitamin supplementation, fatty acid, and dementia, but results are still under debate, and no definite conclusion has yet been drawn. Nevertheless, a significant amount of lab evidence confirms that vitamins of the B group are tightly related to gene control for endothelium protection, act as antioxidants, play a co-enzymatic role in the most critical biochemical reactions inside the brain, and cooperate with many other elements, such as choline, for the synthesis of polyunsaturated phosphatidylcholine, through S-adenosyl-methionine (SAM) methyl donation. B-vitamins have anti-inflammatory properties and act in protective roles against neurodegenerative mechanisms, for example, through modulation of the glutamate currents and a reduction of the calcium currents. In addition, they also have extraordinary antioxidant properties. However, laboratory data are far from clinical practice. Many studies have tried to apply these results in everyday clinical activity, but results have been discouraging and far from a possible resolution of the associated mysteries, like those represented by Alzheimer's disease (AD) or small vessel disease dementia. Above all, two significant problems emerge from the research: No consensus exists on general diagnostic criteria-MCI or AD? Which diagnostic criteria should be applied for small vessel disease-related dementia? In addition, no general schema exists for determining a possible correct time of implementation to have effective results. Here we present an up-to-date review of the literature on such topics, shedding some light on the possible interaction of vitamins and phosphatidylcholine, and their role in brain metabolism and catabolism. Further studies should take into account all of these questions, with well-designed and world-homogeneous trials.

Dysregulation of 1-carbon metabolism and muscle atrophy: potential roles of forkhead box O proteins and PPARγ co-activator-1α

Homocysteine, a non-proteinogenic amino acid but an important metabolic intermediate is generated as an integral component for the “1-carbon metabolism” during normal physiology. It is catabolized to cysteine via the transulfuration pathway resulting in the generation of hydrogen sulfide, a naturally endogenous byproduct. Genetics or metabolic derangement can alter homocysteine concentration leading to hyperhomocysteinemia (HHcy), a physiologically unfavorable condition that causes serious medical conditions including muscle wasting. HHcy environment can derail physiological processes by targeting biomolecules such as Akt; however, not much is known regarding the effects of HHcy on regulation of transcription factors such as forkhead box O (FOXO) proteins. Recently, hydrogen sulfide has been shown to be highly effective in alleviating the effects of HHcy by serving as an antiapoptotic factor, but role of FOXO and its interaction with hydrogen sulfide are yet to be established. In this review, we discuss role(s) of HHcy in skeletal muscle atrophy and how HHcy interact with FOXO and peroxisome proliferator-activated receptor gamma coactivator 1-alpha expressions that are relevant in musculoskeletal atrophy. Further, therapeutic intervention with hydrogen sulfide for harnessing its beneficial effects might help mitigate the dysregulated 1-carbon metabolism that happens to be the hallmark of HHcy-induced pathologies such as muscle atrophy.

Homocysteine and Hyperhomocysteinaemia

Homocysteine (Hcy) is a thiol group containing the amino acid, which naturally occurs in all humans. Hcy is degraded in the body through two metabolic pathways, while a minor part is excreted through kidneys. The chemical reactions that are necessary for degradation of Hcy require the presence of folic acid, vitamins B6 and B12. Consequently, the level of the total Hcy in the serum is influenced by the presence or absence of these vitamins. An elevated level of the Hcy, hyperhomocysteinemia (HHcy) and homocystinuria is connected with occlusive artery disease, especially in the brain, the heart, and the kidney, in addition to venous thrombosis, chronic renal failure, megaloblastic anemia, osteoporosis, depression, Alzheimer's disease, pregnancy problems, and others. Elevated Hcy levels are connected with various pathologies both in adult and child population. Causes of HHcy include genetic mutations and enzyme deficiencies in 5, 10-methylenetetrahydrofolate reductase (MTHFR) methionine synthase (MS), and cystathionine β-synthase (CβS). HHcy can be caused by deficiencies in the folate, vitamin B12 and to a lesser extent, deficiency in B6 vitamin what influences methionine metabolism. Additionally, HHcy can be caused by the rich diet and renal impairment. This review presents literature data from recent research related to Hcy metabolism and the etiology of the Hcy blood level disorder. In addition, we also described various pathological mechanisms induced by hereditary disturbances or nutritional influences and their association with HHcy induced pathology in adults and children and treatment of these metabolic disorders.

Dietary intakes and biomarker patterns of folate, vitamin B6, and vitamin B12 can be associated with cognitive impairment by hypermethylation of redox-related genes NUDT15 and TXNRD1

BACKGROUND

B vitamins in the one-carbon metabolism pathway (folate, vitamin B₆, and vitamin B₁₂) have been implicated in DNA methylation, and their deficiency may contribute to cognitive decline through increased homocysteine (Hcy) levels and subsequent oxidative damage. The aim of this study was to investigate whether B vitamin deficiency and increased Hcy could interact with DNA methylation of oxidative-related genes and exacerbate cognitive impairment.

METHODS

Participants were selected from a large cohort study entitled the Effects and Mechanism Investigation of Cholesterol and Oxysterol on Alzheimer's disease (EMCOA) study. We included 2533 participants who completed a selection of comprehensive cognitive tests and a semiquantitative food frequency questionnaire (FFQ) and were followed for an average of 2.3 years. The longitudinal effects of B vitamin intake on cognitive decline were examined using linear mixed-effect models. Seven mild cognitive impairment (MCI) patients, in the predementia stage of Alzheimer's disease (AD), and fivev healthy controls were selected for the discovery of genome-wide differentially methylated CpG sites. Candidate oxidative stress-related genes significantly correlated with serum levels of B vitamins were selected for validation in 102 MCI patients and 68 controls. The correlations between DNA methylation levels and serum concentrations of B vitamins and oxidative biomarkers were analyzed with Spearman's correlation. The interactive effects of DNA methylation and B vitamins on cognitive performance were further evaluated by multiple linear regression.

RESULTS

In the prospective analysis, inadequate dietary intake of vitamin B₁₂ was significantly associated with accelerated cognitive decline, whereas adequate folate, vitamin B₆, and vitamin B₁₂ intakes were significantly associated with better cognitive reserve. In the case-control analysis, the DNA methylation levels of NUDT15 and TXNRD1 were examined, and significantly hypermethylated sites were identified in MCI patients. Significant correlations of hypermethylated sites with serum levels of folate, homocysteine (Hcy), and oxidative biomarkers were observed, and interactive effects of B vitamins and hypermethylated sites were significantly associated with cognitive performance.

CONCLUSION

Adequate dietary folate at baseline predicted a better cognitive reserve, while decreased serum levels of B vitamins may contribute to cognitive impairment by affecting methylation levels of specific redox-related genes.

TRIAL REGISTRATION

EMCOA, ChiCTR-OOC-17011882, Registered 5th, July 2017-Retrospectively registered, http://www.medresman.org/uc/project/projectedit.aspx?proj=2610.

Effect of Vitamin B Supplementation on Cognitive Function in the Elderly: A Systematic Review and Meta-Analysis

BACKGROUND

Vitamin B deficiency and elevated total plasma homocysteine have been associated with cognitive impairment and dementia in later life, although it is unknown if treatment with these vitamins improves cognitive outcomes.

OBJECTIVES

The objectives of this study were to examine the efficacy of treatment with vitamin B₁₂, vitamin B₆, or folic acid in slowing cognitive decline amongst older adults with and without cognitive impairment.

METHODS

We summarized findings from previous systematic reviews of clinical trials and performed a new systematic review and meta-analysis of 31 English-language, randomized placebo-controlled trials of B-vitamin supplementation of individuals with and without existing cognitive impairment.

RESULTS

Previous reviews have generally reported no effect of B vitamins on cognitive function in older adults with or without cognitive impairment at study entry, although these vitamins effectively lowered total plasma homocysteine levels in participants. Ten randomized placebo-controlled trials of 1925 participants with pre-existing cognitive impairment and 21 trials of 15,104 participants without cognitive impairment have been completed to date but these generally confirmed findings from previous reviews with the exception of two trials that showed a modest but clinically uncertain benefit for vitamins in people with elevated plasma homocysteine. B-vitamin supplementation did not show an improvement in Mini-Mental State Examination scores for individuals with (mean difference 0.16, 95% confidence interval - 0.18 to 0.51) and without (mean difference 0.04, 95% confidence interval - 0.10 to 0.18) cognitive impairment compared to placebo.

CONCLUSIONS

Raised total plasma homocysteine is associated with an increased risk of cognitive impairment and dementia, although available evidence from randomized controlled trials shows no obvious cognitive benefit of lowering homocysteine using B vitamins. Existing trials vary greatly in the type of supplementation, population sampled, study quality, and duration of treatment, thereby making it difficult to draw firm conclusions from existing data. Findings should therefore be viewed in the context of the limitations of the available data and the lack of evidence of effect should not necessarily be interpreted as evidence of no effect.

Effects of altered maternal folate and vitamin B12 on neurobehavioral outcomes in F1 male mice

Maternal folate and vitamin B₁₂ status during pregnancy may influence development of central nervous system (CNS) in the offspring. Very little attention has been paid to understand the combined effects of both the vitamins during pregnancy. The present study was designed to evaluate the biochemical and behavioral outcomes following alterations in folate and vitamin B₁₂ levels in C57BL/6 mice. The female mice were fed with different combinations of folate and vitamin B₁₂ whereas; males were fed with normal diet for 4 weeks. The mice were mated and the pregnant mice received the same diets as before pregnancy. The F1 male mice were further continued on maternal diet for 6 weeks following neurobehavioral and biochemical assessment. The body weight of the F1 male mice was significantly decreased in the mice that received folate and vitamin B₁₂ deficient diet. Altered cognitive functions were observed in the folate and B₁₂ deficient F1 male mice as assessed by Morris water maze and novel object recognition tests. Spontaneous locomotor activity was decreased in F1 male mice fed with folate and B₁₂ deficient diets. Elevated homocysteine levels and decreased hydrogen sulfide levels were also observed in the brain of F1 male mice on folate and B₁₂ deficient diets. However, GSH and GSSG levels were increased in the brain of the animals supplemented with folate deficient diet with different combinations of B₁₂. The study suggests that exposure of female mice to folate and vitamin B₁₂ deficiency during pregnancy effects in-utero development of fetus, which further leads to behavioral anomalies in adult life and is sufficient to cause impaired cognitive behavior in the subsequent generation. Thus, elucidating the role and importance of maternal dietary folate and B₁₂ ratio during pregnancy.

Twelve weeks of resistance training does not influence peripheral levels of neurotrophic growth factors or homocysteine in healthy adults: a randomized-controlled trial

INTRODUCTION

There is growing evidence for a preventative effect of resistance training on cognitive decline through physiological mechanisms; yet, the effect of resistance training on resting growth factors and homocysteine levels is incompletely understood. This study aimed to investigate the effect of intense resistance training, for 12 weeks, on changes in peripheral growth factors and homocysteine in late middle-aged adults.

METHODS

45 healthy adults were enrolled into the single-site parallel groups' randomized-controlled trial conducted at the Department of Exercise Science, Strength and Conditioning Laboratory, Murdoch University. Participants were allocated to the following conditions: (1) high-load resistance training (n = 14), or (2) moderate-load resistance training (n = 15) twice per week for 12 weeks; or (3) non-exercising control group (n = 16). Data were collected from September 2016 to December 2017. Fasted blood samples were collected at baseline and within 7 days of trial completion for the analysis of resting serum brain-derived neurotrophic factor (BDNF), insulin-like growth factor 1, vascular endothelial growth factor, and plasma homocysteine levels.

RESULTS

No differences in baseline to post-intervention change in serum growth factors or plasma homocysteine levels were observed between groups. A medium effect was calculated for BDNF change within the high-load condition alone (+ 12.9%, g = 0.54).

CONCLUSIONS

High-load or moderate-load resistance training twice per week for 12 weeks has no effect on peripheral growth factors or homocysteine in healthy late middle-aged adults.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry: ACTRN12616000690459.

Functional and/or structural brain changes in response to resistance exercises and resistance training lead to cognitive improvements - a systematic review

BACKGROUND

During the aging process, physical capabilities (e.g., muscular strength) and cognitive functions (e.g., memory) gradually decrease. Regarding cognitive functions, substantial functional (e.g., compensatory brain activity) and structural changes (e.g., shrinking of the hippocampus) in the brain cause this decline. Notably, growing evidence points towards a relationship between cognition and measures of muscular strength and muscle mass. Based on this emerging evidence, resistance exercises and/or resistance training, which contributes to the preservation and augmentation of muscular strength and muscle mass, may trigger beneficial neurobiological processes and could be crucial for healthy aging that includes preservation of the brain and cognition. Compared with the multitude of studies that have investigated the influence of endurance exercises and/or endurance training on cognitive performance and brain structure, considerably less work has focused on the effects of resistance exercises and/or resistance training. While the available evidence regarding resistance exercise-induced changes in cognitive functions is pooled, the underlying neurobiological processes, such as functional and structural brain changes, have yet to be summarized. Hence, the purpose of this systematic review is to provide an overview of resistance exercise-induced functional and/or structural brain changes that are related to cognitive functions.

METHODS AND RESULTS

A systematic literature search was conducted by two independent researchers across six electronic databases; 5957 records were returned, of which 18 were considered relevant and were analyzed.

SHORT CONCLUSION

Based on our analyses, resistance exercises and resistance training evoked substantial functional brain changes, especially in the frontal lobe, which were accompanied by improvements in executive functions. Furthermore, resistance training led to lower white matter atrophy and smaller white matter lesion volumes. However, based on the relatively small number of studies available, the findings should be interpreted cautiously. Hence, future studies are required to investigate the underlying neurobiological mechanisms and to verify whether the positive findings can be confirmed and transferred to other needy cohorts, such as older adults with dementia, sarcopenia and/or dynapenia.

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.

Elevated Plasma Homocysteine Levels in Anti-N-methyl-D-aspartate Receptor Encephalitis

Objective: Homocysteine (Hcy) levels have been investigated in many diseases, such as neurodegenerative and autoimmune diseases. However, changes in Hcy levels in anti-N-Methyl-D-aspartate receptor (anti-NMDAR) encephalitis have not been investigated thus far.

Methods: Case data were collected from 45 patients with anti-NMDAR encephalitis and 179 age- and sex-matched healthy controls (HCs). Clinical characteristics, Hcy levels, C reactive protein (CRP) levels, and cerebrospinal fluid (CSF) parameters were determined. Association of Hcy and clinical parameters were evaluated in these patients. Among these 45 patients, 15 had a follow-up evaluation at 3 months after treatment.

Results: Hcy levels (p < 0.001) and CRP levels (p = 0.005) from the patients with anti-NMDAR encephalitis were significantly higher than those from HCs. Hcy levels from male patients were significantly lower than those from male HCs (p < 0.001). Comparing anti-NMDAR encephalitis patients after treatment with before treatment, the former has significantly higher Hcy levels (p = 0.004), CRP levels (p = 0.041) and mRS scores (p = 0.002). Furthermore, a significant negative correlation between the changes in Hcy levels and the changes in mRS scores (r = −0.534, p = 0.040) was observed.

Conclusion: Elevated plasma homocysteine occurs in anti-NMDAR encephalitis, and seems associated with male sex.

The sulfite molecule enhances homocysteine toxicity in SH-SY5Y cells

Homocysteine (hcy) is an amino acid that contains sulfur species. In healthy individuals, plasma hcy levels are low. The aim of this study was to investigate the potential neurotoxic effects of hcy and sulfite (sft) molecules alone and in their combination, and also to identify the relationship of these substances on oxidative stress. SH-SY5Y cells were used as an invitro neurodegenerative disease model. The SH-SY5Y cells were treated with various concentrations of hcy alone, sft alone (final concentrations in the well were 10-250 µM and 0.1-5 mM, respectively) and a combination of both (hcy + sft). Their cytotoxicity and genotoxic effects were investigated using the XTT test and Comet assay and, their impact on oxidative stress was examined using total antioxidant-oxidant status (TAS-TOS) kits. The highest toxic doses of hcy and sft were found to be 250 μM and 5 mM, respectively, but the maximum toxic effect was observed for hcy + sft (p < 0.001). In addition, an increase in DNA damage was evident in all groups, but maximal damage was inflicted using in hcy + sft (p < 0.001). The oxidative stress index was significantly increased in hcy + sft (p < 0.05). Determining the increase in sft and hcy levels may contribute to delaying the occurrence of diseases before symptoms of neurodegenerative disease appear.

Chronic mild Hyperhomocysteinemia impairs energy metabolism, promotes DNA damage and induces a Nrf2 response to oxidative stress in rats brain

Homocysteine (HCY) has been linked to oxidative stress and varied metabolic changes that are dependent on its concentration and affected tissues. In the present study we evaluate parameters of energy metabolism [succinate dehydrogenase (SDH), complex II and IV (cytochrome c oxidase), and ATP levels] and oxidative stress [DCFH oxidation, nitrite levels, antioxidant enzymes and lipid, protein and DNA damages, as well as nuclear factor erythroid 2-related (Nrf2) protein abundance] in amygdala and prefrontal cortex of HCY-treated rats. Wistar male rats were treated with a subcutaneous injection of HCY (0.03 µmol/g of body weight) from the 30th to 60th post-natal day, twice a day, to induce mild hyperhomocysteinemia (HHCY). The rats were euthanatized without anesthesia at 12 h after the last injection, and amygdala and prefrontal cortex were dissected for biochemical analyses. In the amygdala, mild HHCY increased activities of SDH and complex II and decreased complex IV and ATP level, as well as increased antioxidant enzymes activities (glutathione peroxidase and superoxide dismutase), nitrite levels, DNA damage, and Nrf 2 protein abundance. In the prefrontal cortex, mild HHCY did not alter energy metabolism, but increased glutathione peroxidase, catalase and DNA damage. Other analyzed parameters were not altered by HCY-treatment. Our findings suggested that chronic mild HHCY changes each brain structure, particularly and specifically. These changes may be associated with the mechanisms by which chronic mild HHCY has been linked to the risk factor of fear, mood disorders and depression, as well as in neurodegenerative diseases.

Folate/Vitamin B Alleviates Hyperhomocysteinemia-Induced Alzheimer-Like Pathologies in Rat Retina

Hyperhomocysteinemia (Hhcy) is an independent risk factor for Alzheimer's disease (AD). Visual dysfunction is commonly found and is positively correlated with the severity of cognitive defects in AD patients. Our previous study demonstrated that Hhcy induces memory deficits with AD-like tau and amyloid-β (Aβ) pathologies in the hippocampus, and supplementation with folate and vitamin B12 (FB) prevents the Hhcy-induced AD-like pathologies in the hippocampus. Here, we investigated whether Hhcy also induces AD-like pathologies in the retina and the effects of FB. An Hhcy rat model was produced by vena caudalis injection of homocysteine for 14 days, and the effects of FB were assessed by simultaneous supplementation with FB in drinking water. We found that Hhcy induced vessel damage with Aβ and tau pathologies in the retina, while simultaneous supplementation with FB remarkably attenuated the Hhcy-induced tau hyperphosphorylation at multiple AD-related sites and Aβ accumulation in the retina. The mechanisms involved downregulation of amyloid precursor protein (APP), presenilin-1, beta-site APP-cleaving enzyme 1, and protein phosphatase-2A. Our data suggest that the retina may serve as a window for evaluating the effects of FB on hyperhomocysteinemia-induced Alzheimer-like pathologies.

Hyperhomocysteinemia leads to exacerbation of ischemic brain damage: Role of GluN2A NMDA receptors

Hyperhomocysteinemia has been implicated in several neurodegenerative disorders including ischemic stroke. However, the pathological consequences of ischemic insult in individuals predisposed to hyperhomocysteinemia and the associated etiology are unknown. In this study, we evaluated the outcome of transient ischemic stroke in a rodent model of hyperhomocysteinemia, developed by subcutaneous implantation of osmotic pumps containing L-homocysteine into male Wistar rats. Our findings show a 42.3% mortality rate in hyperhomocysteinemic rats as compared to 7.7% in control rats. Magnetic resonance imaging of the brain in the surviving rats shows that mild hyperhomocysteinemia leads to exacerbation of ischemic injury within 24 h, which remains elevated over time. Behavioral studies further demonstrate significant deficit in sensorimotor functions in hyperhomocysteinemic rats compared to control rats. Using pharmacological inhibitors targeting the NMDAR subtypes, the study further demonstrates that inhibition of GluN2A-containing NMDARs significantly reduces ischemic brain damage in hyperhomocysteinemic rats but not in control rats, indicating that hyperhomocysteinemia-mediated exacerbation of ischemic brain injury involves GluN2A-NMDAR signaling. Complementary studies in GluN2A-knockout mice show that in the absence of GluN2A-NMDARs, hyperhomocysteinemia-associated exacerbation of ischemic brain injury is blocked, confirming that GluN2A-NMDAR activation is a critical determinant of the severity of ischemic damage under hyperhomocysteinemic conditions. Furthermore, at the molecular level we observe GluN2A-NMDAR dependent sustained increase in ERK MAPK phosphorylation under hyperhomocysteinemic condition that has been shown to be involved in homocysteine-induced neurotoxicity. Taken together, the findings show that hyperhomocysteinemia triggers a unique signaling pathway that in conjunction with ischemia-induced pathways enhance the pathology of stroke under hyperhomocysteinemic conditions.

Disturbed homocysteine metabolism is associated with cancer

Hyperhomocysteinemia/Homocysteinuria is characterized by an increased level of toxic homocysteine in the plasma. The plasma concentration of homocysteine is 5–15 μmol/L in healthy individuals, while in hyperhomocysteinemic patients, it can be as high as 500 μmol/L. While increased homocysteine levels can cause symptoms such as osteoporosis and eye lens dislocation, high homocysteine levels are most closely associated with cardiovascular complications. Recent advances have shown that increased plasma Hcy is also a fundamental cause of neurodegenerative diseases (including Alzheimer’s disease, Parkinson’s disease, and dementia), diabetes, Down syndrome, and megaloblastic anemia, among others. In recent years, increased plasma homocysteine has also been shown to be closely related to cancer. In this review, we discuss the relation between elevated plasma Hcy levels and cancer, and we conclude that disturbed homocysteine metabolism is associated with cancer. Future clinical perspectives are also discussed.

Cancer can be added to the wide range of diseases known to be associated with elevated blood levels of the small amino acid homocysteine. Abnormally high levels of this compound are already known to contribute to conditions including cardiovascular problems, neurodegenerative diseases, neural tube defects, Down’s syndrome, diabetes and megaloblastic anemia. This review, by Laishram R. Singh and colleagues at the University of Delhi, India, concludes that disturbed homocysteine metabolism is associated with many forms of human cancer. The authors discuss a range of genetic, epigenetic and environmental factors that may be involved in the cause and effect relationships between homocysteine metabolism and cancer. It is particularly interesting that low folate (vitamin B9) levels result in high homocysteine levels, and vice versa. Further research may yield insights leading to new forms of cancer treatment and diagnosis.

Homocysteine and Dementia: An International Consensus Statement

Identification of modifiable risk factors provides a crucial approach to the prevention of dementia. Nutritional or nutrient-dependent risk factors are especially important because dietary modifications or use of dietary supplements may lower the risk factor level. One such risk factor is a raised concentration of the biomarker plasma total homocysteine, which reflects the functional status of three B vitamins (folate, vitamins B12, B6). A group of experts reviewed literature evidence from the last 20 years. We here present a Consensus Statement, based on the Bradford Hill criteria, and conclude that elevated plasma total homocysteine is a modifiable risk factor for development of cognitive decline, dementia, and Alzheimer’s disease in older persons. In a variety of clinical studies, the relative risk of dementia in elderly people for moderately raised homocysteine (within the normal range) ranges from 1.15 to 2.5, and the Population Attributable risk ranges from 4.3 to 31%. Intervention trials in elderly with cognitive impairment show that homocysteine-lowering treatment with B vitamins markedly slows the rate of whole and regional brain atrophy and also slows cognitive decline. The findings are consistent with moderately raised plasma total homocysteine (>11 μmol/L), which is common in the elderly, being one of the causes of age-related cognitive decline and dementia. Thus, the public health significance of raised tHcy in the elderly should not be underestimated, since it is easy, inexpensive, and safe to treat with B vitamins. Further trials are needed to see whether B vitamin treatment will slow, or prevent, conversion to dementia in people at risk of cognitive decline or dementia.

An appraisal of folates as key factors in cognition and ageing-related diseases

Folic acid (FA) is often consumed as a food supplement and can be found in fortified staple foods in various western countries. Even though FA supplementation during pregnancy is known to prevent severe congenital anomalies in the developing child (e.g., neural tube defects), much less is known about its influence on cognition and neurological functioning. In this review, we address the advances in this field and situate how folate intake during pregnancy, postnatal life, adulthood and in the elderly affects cognition. In addition, an association between folate status and ageing, dementia and other neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis is discussed. While its role in the incidence and severity of these diseases is becoming apparent, the underlying action of folates and related metabolites remains elusive. Finally, the potential of FA as a nutraceutical has been proposed, although the efficacy will highly depend on the interplay with other micronutrients, the disease stage and the duration of supplementation. Hence, the lack of consistent data urges for more animal studies and (pre)clinical trials in humans to ascertain a potential beneficial role for folates in the treatment or amelioration of cognitive decline and ageing-related disorders.

The impact of homocysteine, B12, and D vitamins levels on functional neurocognitive performance in HIV-positive subjects

Background

The correlation among high levels of total homocysteine, low levels of B₁₂vitamin, and neurocognitive impairment in HIV negative patients has been the main research topic in some of the latest reviews. The aim of this study was to examine if the alteration of homocysteine, B₁₂ vitamin, and D vitamins plasma levels was present in HIV-positive, and their relationship with cognitive function.

Methods

57 HIV infected were enrolled and underwent the serum measurement of homocysteine, B₁₂, and D vitamins. The neurocognitive evaluation investigated 5 cognitive domains, through a neuropsychological battery test

Results

Homocysteine was found to be elevated in 70.2% of cases, B₁₂ vitamin mean levels were low in 8 participants (14.0%), and 8 patients had D hypovitaminosis (14.0%). Abnormal homocysteine levels were associated with worse performance of verbal fluency (p = 0.003) and worse executive function (Stroop E test p = 0.040). The 25-OH D hypovitaminosis was associated with worse performances in executive functions in three different tests: Stroop E (p = 0.049), Trail B (p = 0.035), and Wais Digit Span (p = 0.042). Pathological levels of B₁₂ Vitamin were also associated to worse performances in executive functions (Trail B Test and Wais Digit Span respectively p = 0.002 and 0.029) and with a lower speed in psychomotor processing (Peg Board Test on dominant hand, p = 0.014).

Conclusions

In this study serum homocysteine, B₁₂, and D vitamin levels are associated with neurocognitive performances; in fact low performance neurocognitive was correlated with hyperhomocysteine and low B₁₂vitamin, and D vitamin levels. Evidence of the alteration of these parameters could facilitate the early identification of a neurocognitive impairment.

Repeat-associated non-AUG translation in C9orf72-ALS/FTD is driven by neuronal excitation and stress

Nucleotide repeat expansions (NREs) are prevalent mutations in a multitude of neurodegenerative diseases. Repeat-associated non-AUG (RAN) translation of these repeat regions produces mono or dipeptides that contribute to the pathogenesis of these diseases. However, the mechanisms and drivers of RAN translation are not well understood. Here we analyzed whether different cellular stressors promote RAN translation of dipeptide repeats (DPRs) associated with the G4C2 hexanucleotide expansions in C9orf72, the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). We found that activating glutamate receptors or optogenetically increasing neuronal activity by repetitive trains of depolarization induced DPR formation in primary cortical neurons and patient derived spinal motor neurons. Increases in the integrated stress response (ISR) were concomitant with increased RAN translation of DPRs, both in neurons and different cell lines. Targeting phosphorylated-PERK and the phosphorylated-eif2α complex reduces DPR levels revealing a potential therapeutic strategy to attenuate DPR-dependent disease pathogenesis in NRE-linked diseases.

Nutrients in Alzheimer’s Disease: The Interaction of Diet, Drugs and Disease

In recent decades, clinical trials in Alzheimer’s disease (AD) have failed at an unprecedented rate. The etiology of AD has since come under renewed scrutiny, both to elucidate the underlying pathologies and to identify novel therapeutic strategies. Here, diet has emerged as a potential causative/protective agent. A variety of nutrients, including lipids, minerals, vitamins, antioxidants and sugars as well as broader dietary patterns and microbiotal interactions have demonstrated associations with AD. Although clinical trials have yet to definitively implicate any singular dietary element as therapeutic or causative, it is apparent that dietary preferences, likely in complex synergies, may influence the risk, onset and course of AD. This review catalogs the impact of major dietary elements on AD. It further examines an unexplored reciprocal association where AD may modulate diet, as well as how potential therapeutics may complicate these interactions. In doing so, we observe diet may have profound effects on the outcome of a clinical trial, either as a confounder of a drug/disease interaction or as a generally disruptive covariate. We therefore conclude that future clinical trials in AD should endeavor to control for diet, either in study design or subsequent analyses.

The Controversial Role of Homocysteine in Neurology: From Labs to Clinical Practice

Homocysteine (Hcy) is a sulfur-containing amino acid that is generated during methionine metabolism. Physiologic Hcy levels are determined primarily by dietary intake and vitamin status. Elevated plasma levels of Hcy can be caused by deficiency of either vitamin B12 or folate. Hyperhomocysteinemia (HHcy) can be responsible of different systemic and neurological disease. Actually, HHcy has been considered as a risk factor for systemic atherosclerosis and cardiovascular disease (CVD) and HHcy has been reported in many neurologic disorders including cognitive impairment and stroke, independent of long-recognized factors such as hyperlipidemia, hypertension, diabetes mellitus, and smoking. HHcy is typically defined as levels >15 micromol/L. Treatment of hyperhomocysteinemia with folic acid and B vitamins seems to be effective in the prevention of the development of atherosclerosis, CVD, and strokes. However, data from literature show controversial results regarding the significance of homocysteine as a risk factor for CVD and stroke and whether patients should be routinely screened for homocysteine. HHcy-induced oxidative stress, endothelial dysfunction, inflammation, smooth muscle cell proliferation, and endoplasmic reticulum (ER) stress have been considered to play an important role in the pathogenesis of several diseases including atherosclerosis and stroke. The aim of our research is to review the possible role of HHcy in neurodegenerative disease and stroke and to understand its pathogenesis.

CGRP Receptor Signalling Pathways

Calcitonin gene-related peptide (CGRP) is a promiscuous peptide, similar to many other members of the calcitonin family of peptides. The potential of CGRP to act on many different receptors with differing affinities and efficacies makes deciphering the signalling from the CGRP receptor a challenging task for researchers.Although it is not a typical G protein-coupled receptor (GPCR), in that it is composed not just of a GPCR, the CGRP receptor activates many of the same signalling pathways common for other GPCRs. This includes the family of G proteins and a variety of protein kinases and transcription factors. It is now also clear that in addition to the initiation of cell-surface signalling, GPCRs, including the CGRP receptor, also activate distinct signalling pathways as the receptor is trafficking along the endocytic conduit.Given CGRP's characteristic of activating multiple GPCRs, we will first consider the complex of calcitonin receptor-like receptor (CLR) and receptor activity-modifying protein 1 (RAMP1) as the CGRP receptor. We will discuss the discovery of the CGRP receptor components, the molecular mechanisms controlling its internalization and post-endocytic trafficking (recycling and degradation) and the diverse signalling cascades that are elicited by this receptor in model cell lines. We will then discuss CGRP-mediated signalling pathways in primary cells pertinent to migraine including neurons, glial cells and vascular smooth muscle cells.Investigation of all the CGRP- and CGRP receptor-mediated signalling cascades is vital if we are to fully understand CGRP's role in migraine and will no doubt unearth new targets for the treatment of migraine and other CGRP-driven diseases.

High methionine, low folate and low vitamin B6/B12 (HM-LF-LV) diet causes neurodegeneration and subsequent short-term memory loss

Methionine is an essential amino acid found in rich quantities in average American diet such as meats, fish and eggs. Excessive consumption of such food often exceeds the normal requirement of the methionine in our body; which found to be related to the development of neurodegenerative disorders. However, the mechanistic pathways of methionine's influence on the brain are unclear. The present study is focus on the effects of high methionine, low folate and low vitamin B6/B12 (HM-LF-LV) diet on the dysfunction of neuronal and vascular specific markers in the brain. C57BL6/J male mice (8-10 week old) were fed with HM-LF-LV diet for a 6 week period. Cognitive function of mice was determine by measuring short-term memory using a Novel Object Recognition test (NORT). Neuronal dysfunction were evaluate by measuring the levels of Neuronal nuclear antigen (NeuN), Neuron-specific-enolase (NSE) and Fluoro-jade C(FJC) fluorescence; while cerebrovascular disruption were evaluate by assessing levels of endothelial junction proteins Vascular Endothelial-Cadherin (VE-Cadherin) and Claudin-5 in harvested brain tissue. Cerebrovascular permeability was assess by evaluating microvascular leakage of fluorescently labeled albumin in vivo. Endothelial and Neuronal Nitric Oxide Synthase (eNOS, nNOS) regulation and vascular inflammation (ICAM: intercellular adhesion molecules) were also evaluate in brain tissue. All assessments were conduct at weekly intervals throughout the study duration. NORT showed a significant temporal decrease in short-term memory of mice fed on HM-LF-LV diet for 6 weeks compared to the wild-type control group. Our experimental data showed that neuronal dysfunction (decreased NeuN levels and increased FJC positive neurons in brain) was more prominent in HM-LF-LV diet fed mice compared to normal diet fed control mice. In experimental mice, cerebrovascular disruption was found to be elevated as evident from increased pial venular permeability (microvascular leakage) and decreased in VE-Cadherin expression compared to control. Slight decrease in nNOS and increase in eNOS in experimental mice suggest a trend towards the decrease in potential for neuronal development due to the long-term HM-LF-LV diet fed. Collectively, our results suggest that a diet containing high methionine, low folate and low vitamin B6/B12 results in increased neuronal degeneration and vascular dysfunction, leading to short-term memory loss. Interestingly, significant neuronal damage precedes vascular dysfunction.

Elevated plasma homocysteine levels are associated with disability progression in patients with multiple sclerosis

The aims of this study were to verify whether hyperhomocysteinemia is associated with disability progression in Multiple Sclerosis (MS) patients and whether TNF pathways and cellular adhesion molecules (CAM) are involved in this process. This study included 180 MS patients, who were divided according to their levels of homocysteine (Hyperhomocysteinemia ≥11.35 μmol/L) and 204 healthy individuals (control group). MS patients showed higher levels of homocysteine (p < 0.001), tumor necrosis factor alpha (TNF-α, p < 0.001), TNF receptor 1 (TNFR1, p = 0.038), TNF receptor 2 (TNFR2, p < 0.001), and lower levels of PECAM (p = 0.001), ICAM (p < 0.001) and VCAM (p = 0.005) than controls. The multivariate binary logistic regression analysis showed that plasma levels of homocysteine, TNFR1, TNFR2 and PECAM were associated with the presence of disease. MS patients with hyperhomocysteinemia showed higher disease progression evaluated by the Multiple Sclerosis Severity Score (MSSS, p < 0.001), disability evaluated by Expanded Disability Status Score EDSS (p < 0.001), TNFR1 (p = 0.039) and ICAM (p = 0.034) than MS patients with lower levels of homocysteine. Hyperhomocysteinemia was independently associated with MSSS in MS patients, but were not associated with TNF-α, TNFR, and CAM. Homocysteine levels was higher in progressive forms than relapsing-remitting MS (p < 0.001), independently of sex and age. In conclusion, this is the first study in which homocysteinemia was associated with progression of the disease (MSSS), although this finding was not directly related to TNF-α and TNFR pathways or to CAM.

The anxiolytic effects of atorvastatin and simvastatin on dietary-induced increase in homocysteine levels in rats

The aim of this study was to evaluate the effects of atorvastatin and simvastatin on behavioral manifestations that followed hyperhomocysteinemia induced by special dietary protocols enriched in methionine and deficient in B vitamins (B6, B9, B12) by means of alterations in anxiety levels in rats. Simultaneously, we investigated the alterations of oxidative stress markers in rat hippocampus induced by applied dietary protocols. Furthermore, considering the well-known antioxidant properties of statins, we attempted to assess their impact on major markers of oxidative stress and their possible beneficial role on anxiety-like behavior effect in rats. The 4-week-old male Wistar albino rats were divided (eight per group) according to basic dietary protocols: standard chow, methionine-enriched, and methionine-enriched vitamins B (B6, B9, B12) deficient. Each dietary protocol (30 days) included groups with atorvastatin (3 mg/kg/day i.p.) and simvastatin (5 mg/kg/day i.p.). The behavioral testing was performed in the open field and elevated plus maze tests. Parameters of oxidative stress (index of lipid peroxidation, superoxide dismutase, catalase activity, glutathione) were determined in hippocampal tissue samples following decapitation after anesthesia. Methionine-load dietary protocols induced increased oxidative stress in rat hippocampus, which was accompanied by anxiogenic behavioral manifestations. The methionine-enriched diet with restricted vitamins B intake induced more pronounced anxiogenic effect, as well as increased oxidative stress compared to the methionine-load diet with normal vitamins B content. Simultaneous administration of statins showed beneficial effects by means of both decreased parameters of oxidative stress and attenuation of anxiety. The results obtained with simvastatin were more convincible compared to atorvastatin.

Hydrogen sulfide attenuates homocysteine-induced neurotoxicity by preventing mitochondrial dysfunctions and oxidative damage: In vitro and in vivo studies

Elevated homocysteine (Hcy) levels have been implicated in neurodevelopmental and neurodegenerative disorders. Induction of oxidative stress and apoptosis has been reported as major mechanism in Hcy-induced neurotoxicity. Hydrogen sulfide (H₂S), as an antioxidant molecule has been reported to exhibit novel protective effect against Hcy-induced cell damage. However, the mechanisms involved in protective effect of H₂S against Hcy-induced toxicity in neurons have not been fully elucidated. Herein, effect of sodium hydrogen sulfide (NaHS, a source of H₂S) on Hcy-induced neurotoxicity was studied on Neuro-2a (N2a) cells in vitro and in animals subjected to hyperhomocysteinemia. DCFH-DA staining revealed that NaHS effectively attenuated Hcy-induced oxidative damage by reducing intracellular reactive oxygen species (ROS) generation. JC-1 staining and western blot results showed that NaHS pre-treatment prevented Hcy-induced mitochondrial dysfunctions and mitochondria-mediated apoptosis. MTT assay, cell cycle analysis, ethidium bromide/acridine orange (EB/AO) and Hoechst staining results demonstrated that NaHS significantly alleviated Hcy-induced cytotoxicity in N2a cells by preventing oxidative damage. Importantly, the results from agarose gel electrophoresis, comet and TUNEL assay indicated that NaHS also prevented neurodegeneration by reducing DNA damage and apoptotic cell death in animals with hyperhomocysteinemia. Taken together, the results demonstrate that the protective potential of H₂S against Hcy-induced neurotoxicity is mediated by preventing oxidative DNA damage and mitochondrial dysfunctions. The findings validate that H₂S is a promising therapeutic molecule in neurodegenerative conditions associated with hyperhomocysteinemia.

Targeting mTORs by omega-3 fatty acids: A possible novel therapeutic strategy for neurodegeneration?

Neurodegenerative diseases (NDs) such as Parkinson's (PD), Alzheimer's (AD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS) cause significant world-wide morbidity and mortality. To date, there is no drug of cure for these, mostly age-related diseases, although approaches in delaying the pathology and/or giving patients some symptomatic relief have been adopted for the last few decades. Various studies in recent years have shown the beneficial effects of omega-3 poly unsaturated fatty acids (PUFAs) through diverse mechanisms including anti-inflammatory effects. This review now assesses the potential of this class of compounds in NDs therapy through specific action against the mammalian target of rapamycin (mTOR) signaling pathway. The role of mTOR in neurodegenerative diseases and targeted therapies by PUFAs are discussed.

Identification of homocysteine-suppressive mitochondrial ETC complex genes and tissue expression profile - Novel hypothesis establishment

Hyperhomocysteinemia (HHcy) is an independent risk factor for cardiovascular disease (CVD) which has been implicated in matochondrial (Mt) function impairment. In this study, we characterized Hcy metabolism in mouse tissues by using LC-ESI-MS/MS analysis, established tissue expression profiles for 84 nuclear-encoded Mt electron transport chain complex (nMt-ETC-Com) genes in 20 human and 19 mouse tissues by database mining, and modeled the effect of HHcy on Mt-ETC function. Hcy levels were high in mouse kidney/lung/spleen/liver (24-14 nmol/g tissue) but low in brain/heart (~5 nmol/g). S-adenosylhomocysteine (SAH) levels were high in the liver/kidney (59-33 nmol/g), moderate in lung/heart/brain (7-4 nmol/g) and low in spleen (1 nmol/g). S-adenosylmethionine (SAM) was comparable in all tissues (42-18 nmol/g). SAM/SAH ratio was as high as 25.6 in the spleen but much lower in the heart/lung/brain/kidney/liver (7-0.6). The nMt-ETC-Com genes were highly expressed in muscle/pituitary gland/heart/BM in humans and in lymph node/heart/pancreas/brain in mice. We identified 15 Hcy-suppressive nMt-ETC-Com genes whose mRNA levels were negatively correlated with tissue Hcy levels, including 11 complex-I, one complex-IV and two complex-V genes. Among the 11 Hcy-suppressive complex-I genes, 4 are complex-I core subunits. Based on the pattern of tissue expression of these genes, we classified tissues into three tiers (high/mid/low-Hcy responsive), and defined heart/eye/pancreas/brain/kidney/liver/testis/embryonic tissues as tier 1 (high-Hcy responsive) tissues in both human and mice. Furthermore, through extensive literature mining, we found that most of the Hcy-suppressive nMt-ETC-Com genes were suppressed in HHcy conditions and related with Mt complex assembly/activity impairment in human disease and experimental models. We hypothesize that HHcy inhibits Mt complex I gene expression leading to Mt dysfunction.

Trillium tschonoskii maxim extract attenuates abnormal Tau phosphorylation

Large-scale epidemiological studies have found that hyperhomocysteinemia is a powerful, independent risk factor for Alzheimer’s disease. Trillium tschonoskii maxim is a traditional Chinese medicine that is used to promote memory. However, scientific understanding of its mechanism of action is limited. This report studied the potential neuroprotective effects of Trillium tschonoskii maxim extract against homocysteine-induced cognitive deficits. Rats were intravenously injected with homocysteine (400 μg/kg) for 14 days to induce a model of Alzheimer’s disease. These rats were then intragastrically treated with Trillium tschonoskii maxim extract (0.125 or 0.25 g/kg) for 7 consecutive days. Open field test and Morris water maze test were conducted to measure spontaneous activity and learning and memory abilities. Western blot assay was used to detect the levels of Tau protein and other factors involved in Tau phosphorylation in the hippocampus. Immunohistochemical staining was used to examine Tau protein in the hippocampus. Golgi staining was applied to measure hippocampal dendritic spines. Our results demonstrated that homocysteine produced learning and memory deficits and increased levels of Tau phosphorylation, and diminished the activity of catalytic protein phosphatase 2A. The total number of hippocampal dendritic spines was also decreased. Trillium tschonoskii maxim extract treatment reversed the homocysteine-induced changes. The above results suggest that Trillium tschonoskii maxim extract can lessen homocysteine-induced abnormal Tau phosphorylation and improve cognitive deterioration such as that present in Alzheimer’s disease.

Effects of exercise training on stroke risk factors, homocysteine concentration, and cognitive function according the APOE genotype in stroke patients

The apolipoprotein E (APOE) gene has been suggested to be associated with stroke and dementia. However, the effects of exercise training on dementia according to the APOE genotype are not consistent to those reported by previous studies. Therefore, we examined the effects of exercise training on stroke risk factors including blood pressure, lipid profiles, homocysteine (Hcy) concentrations, and cognitive function according to the APOE genotype in stroke patients. We examined the stroke risk factors, Hcy, and cognitive function in 28 ischemic stroke patients before and after 6 months of exercise training. After exercise training, body weight, body mass index (BMI), and percent body fat decreased significantly in both APOE groups. According to the APOE genotype, the changes in BMI in the APOE ɛ4 group higher than those in APOE ɛ3 group significantly. Total cholesterol (TC), low-density lipoprotein (LDL)-C, triglyceride (TG), and Hcy decreased and high-density lipoprotein (HDL)-C increased significantly in the both groups. According to the APOE genotype, systolic blood pressure in the APOE ɛ4 group decreased, but in the APOE ɛ3 group increased after exercise training. TC, LDL-C, and TG in the APOE ɛ4 group decreased more extensively than those in the APOE ɛ3 group after exercise training. VO_2max (maximal oxygen consumption) and cognition increased significantly in both groups. Folate acid intake also increased significantly in both groups. The APOE genotype affects variations in the risk factors of stroke after exercise training. However, the Hcy and cognitive function did not differ based on the APOE genotype.

Excess homocysteine upregulates the NRF2-antioxidant pathway in retinal Müller glial cells

This study evaluated the effects of elevated homocysteine (Hcy) on the oxidative stress response in retinal Müller glial cells. Elevated Hcy has been implicated in retinal diseases including glaucoma and optic neuropathy, which are characterized by retinal ganglion cell (RGC) loss. To understand the mechanisms of Hcy-induced RGC loss, in vitro and in vivo models have been utilized. In vitro isolated RGCs are quite sensitive to elevated Hcy levels, while in vivo murine models of hyperhomocysteinemia (HHcy) demonstrate a more modest RGC loss (∼20%) over a period of many months. This differential response to Hcy between isolated cells and the intact retina suggests that the retinal milieu invokes mechanisms that buffer excess Hcy. Oxidative stress has been implicated as a mechanism of Hcy-induced neuron loss and NRF2 is a transcription factor that plays a major role in regulating cytoprotective responses to oxidative stress. In the present study we investigated whether HHcy upregulates NRF2-mediated stress responses in Müller cells, the chief retinal glial cell responsible for providing trophic support to retinal neurons. Primary Müller cells were exposed to L-Hcy-thiolactone [50μM-10mM] and assessed for viability, reactive oxygen species (ROS), and glutathione (GSH) levels. Gene/protein levels of Nrf2 and levels of NRF2-regulated antioxidants (NQO1, CAT, SOD2, HMOX1, GPX1) were assessed in Hcy-exposed Müller cells. Unlike isolated RGCs, isolated Müller cells are viable over a wide range of Hcy concentrations [50 μM - 1 mM]. Moreover, when exposed to elevated Hcy, Müller cells demonstrate decreased oxidative stress and decreased ROS levels. GSH levels increased by ∼20% within 24 h exposure to Hcy. Molecular analyses revealed 2-fold increase in Nrf2 expression. Expression of antioxidant genes Nqo1, Cat, Sod2, Hmox1, Gpx1 increased significantly. The consequences of Hcy exposure were evaluated also in Müller cells harvested from Nrf2^-/- mice. In contrast to WT Müller cells, in which oxidative stress decreased upon exposure to Hcy, the Nrf2^-/- Müller cells showed a significant increase in oxidative stress. Our data suggest that at least during early stages of Hhcy, a cytoprotective response may be in place, mediated in part by NRF2 in Müller cells.

Trefoil Factor 3, Cholinesterase and Homocysteine: Potential Predictors for Parkinson's Disease Dementia and Vascular Parkinsonism Dementia in Advanced Stage

Trefoil factor 3 (TFF3), cholinesterase activity (ChE activity) and homocysteine (Hcy) play critical roles in modulating recognition, learning and memory in neurodegenerative diseases, such as Parkinson's disease dementia (PDD) and vascular parkinsonism with dementia (VPD). However, whether they can be used as reliable predictors to evaluate the severity and progression of PDD and VPD remains largely unknown.

METHODS

We performed a cross-sectional study that included 92 patients with PDD, 82 patients with VPD and 80 healthy controls. Serum levels of TFF3, ChE activity and Hcy were measured. Several scales were used to rate the severity of PDD and VPD. Receivers operating characteristic (ROC) curves were applied to map the diagnostic accuracy of PDD and VPD patients compared to healthy subjects.

RESULTS

Compared with healthy subjects, the serum levels of TFF3 and ChE activity were lower, while Hcy was higher in the PDD and VPD patients. These findings were especially prominent in male patients. The three biomarkers displayed differences between PDD and VPD sub-groups based on genders and UPDRS (III) scores' distribution. Interestingly, these increased serum Hcy levels were significantly and inversely correlated with decreased TFF3/ChE activity levels. There were significant correlations between TFF3/ChE activity/Hcy levels and PDD/VPD severities, including motor dysfunction, declining cognition and mood/gastrointestinal symptoms. Additionally, ROC curves for the combination of TFF3, ChE activity and Hcy showed potential diagnostic value in discriminating PDD and VPD patients from healthy controls.

CONCLUSIONS

Our findings suggest that serum TFF3, ChE activity and Hcy levels may underlie the pathophysiological mechanisms of PDD and VPD. As the race to find biomarkers or predictors for these diseases intensifies, a better understanding of the roles of TFF3, ChE activity and Hcy may yield insights into the pathogenesis of PDD and VPD.

Glial scars are permeable to the neurotoxic environment of chronic stroke infarcts

Following stroke, the damaged tissue undergoes liquefactive necrosis, a stage of infarct resolution that lasts for months although the exact length of time is currently unknown. One method of repair involves reactive astrocytes and microglia forming a glial scar to compartmentalize the area of liquefactive necrosis from the rest of the brain. The formation of the glial scar is a critical component of the healing response to stroke, as well as other central nervous system (CNS) injuries. The goal of this study was to evaluate the toxicity of the extracellular fluid present in areas of liquefactive necrosis and determine how effectively it is segregated from the remainder of the brain. To accomplish this goal, we used a mouse model of stroke in conjunction with an extracellular fluid toxicity assay, fluorescent and electron microscopy, immunostaining, tracer injections into the infarct, and multiplex immunoassays. We confirmed that the extracellular fluid present in areas of liquefactive necrosis following stroke is toxic to primary cortical and hippocampal neurons for at least 7 weeks following stroke, and discovered that although glial scars are robust physical and endocytic barriers, they are nevertheless permeable. We found that molecules present in the area of liquefactive necrosis can leak across the glial scar and are removed by a combination of paravascular clearance and microglial endocytosis in the adjacent tissue. Despite these mechanisms, there is delayed atrophy, cytotoxic edema, and neuron loss in regions adjacent to the infarct for weeks following stroke. These findings suggest that one mechanism of neurodegeneration following stroke is the failure of glial scars to impermeably segregate areas of liquefactive necrosis from surviving brain tissue.

Elevated circulating homocysteine and high-sensitivity C-reactive protein jointly predicts post-stroke depression among Chinese patients with acute ischemic stroke

BACKGROUND

Homocysteine (HCY) and high sensitivity C reactive protein (hs-CRP) were suggested to be involved in post-stroke depression (PSD), which is a frequent mood disorder after stroke. However, the combined effect of HCY and hs-CRP on PSD remains unclear.

METHODS

A total of 598 acute ischemic stroke patients from 7 of 26 centers participating in the China Antihypertensive Trial in Acute Ischemic Stroke with HCY or hs-CRP measurements were included in this analysis. PSD status was evaluated by 24-item Hamilton Depression Rating Scale at 3 months after stroke.

RESULTS

Two hundred and forty-one (40.30%) participants were considered as PSD. HCY and hs-CRP levels were not significantly different between PSD and non-PSD patients. Interesting, in a maximally adjusted model, the odds ratio (95% confidence interval) of PSD was 1.90 (1.18-3.06) for coexistence of HCY ≥ 14.65 μmol/l and hs-CRP ≥ 1.90 mg/l compared with the other levels (HCY < 14.65 μmol/l and/or hs-CRP < 1.90 mg/l). Adding combination of HCY and hs-CRP to a model containing conventional risk factors could significantly improve risk reclassification for PSD.

CONCLUSIONS

Coexistence of both higher HCY and higher hs-CRP in the acute phase of ischemic stroke were associated with subsequent PSD, independently of established conventional risk factors.

Dietary sources and intakes of folates and vitamin B12 in the Spanish population: Findings from the ANIBES study

Background

Folates and vitamin B₁₂ are key nutrients in one-carbon metabolism and related diseases. Updated and plausible information on population intakes and their major dietary sources is scarce and urgently needed in Spain in order to increase the knowledge that can lead as previous step to prevention by fortification and supplementation policies.

Aims

The present study aims to evaluate main dietary folate and vitamin B₁₂ sources and intakes in the Spanish population.

Materials and methods

Results were derived from the ANIBES cross-sectional study using a nationally representative sample of the Spanish population (9–75 years, n = 2,009).

Results

Food groups with the highest mean proportional contribution to total folate intakes in both males and females were vegetables (21.7–24.9%) and cereals (10.7–11.2%), while meat and meat products (26.4%) and milk and dairy products (27.3%) were for B₁₂. Total median folate and B₁₂ intakes amongst women were 156.3 μg/d and 4.0 μg/d while for men were 163.6 μg/d and 4.5 μg/d, respectively. In all age groups, vitamin intakes were significantly higher in plausible than in non-plausible energy reporters.

Conclusion

A limited number of participants had adequate folate intakes, whereas vitamin B₁₂ intakes were adequate for practically the entire population. There is a clear need for improving folates intake in the Spanish population.

Chronic Mild Hyperhomocysteinemia Alters Inflammatory and Oxidative/Nitrative Status and Causes Protein/DNA Damage, as well as Ultrastructural Changes in Cerebral Cortex: Is Acetylsalicylic Acid Neuroprotective?

Homocysteine is a sulfur-containing amino acid derived from methionine metabolism. When plasma homocysteine levels exceed 10-15 μM, there is a condition known as hyperhomocysteinemia, which occur as a result of an inborn error of methionine metabolism or by non-genetic causes. Mild hyperhomocysteinemia is considered a risk factor for development of neurodegenerative diseases. The objective of the present study was to evaluate whether acetylsalicylic acid has neuroprotective role on the effect of homocysteine on inflammatory, oxidative/nitrative stress, and morphological parameters in cerebral cortex of rats subjected to chronic mild hyperhomocysteinemia. Wistar male rats received homocysteine (0.03 μmol/g of body weight) by subcutaneous injections twice a day and acetylsalicylic acid (25 mg/Kg of body weight) by intraperitoneal injections once a day from the 30th to the 60th postpartum day. Control rats received vehicle solution in the same volume. Results showed that rats subjected to chronic mild hyperhomocysteinemia significantly increased IL-1β, IL-6, and acetylcholinesterase activity and reduced nitrite levels. Homocysteine decreased catalase activity and immunocontent and superoxide dismutase activity, caused protein and DNA damage, and altered neurons ultrastructure. Acetylsalicylic acid totally prevented the effect of homocysteine on acetylcholinesterase activity and catalase activity and immunocontent, as well as the ultrastructural changes, and partially prevented alterations on IL-1β levels, superoxide dismutase activity, sulfhydryl content, and comet assay. Acetylsalicylic acid per se increased DNA damage index. In summary, our findings showed that chronic chemically induced model of mild hyperhomocysteinemia altered some parameters and acetylsalicylic acid administration seemed to be neuroprotective, at least in part, on neurotoxicity of homocysteine.

Hesperidin, a citrus flavonoid, protects against l-methionine-induced hyperhomocysteinemia by abrogation of oxidative stress, endothelial dysfunction and neurotoxicity in Wistar rats

CONTEXT

Hesperidin (HSP), a flavanoglycone found in citrus fruits, has antioxidant, anti-inflammatory and neuroprotective properties.

OBJECTIVE

This study evaluates the protective effect of HSP on l-methionine-induced hyperhomocysteinemia (HHcy) in rats.

MATERIALS AND METHODS

Male Wistar rats were randomly divided into seven groups as DMSO, l-methionine, HSP (25, 50 and 100 mg/kg), HSP-per se (100 mg/kg) and donepezil (0.1 mg/kg). HHcy was induced by oral administration of l-methionine (1.7 g/kg) for 32 days. From the 14^th day of study HSP (25, 50 and 100 mg/kg) and donepezil was administered orally to l-methionine-treated rats. Cognitive impairment induced by HHcy was determined using the Morris water maze (MWM) and Y-maze on video tracking system (28^th-32^nd day). Different biomarkers of HHcy in serum and brain and vascular reactivity were evaluated and histopathology (thoracic aorta and brain) was done.

RESULTS

HSP (100 mg/kg) treatment in l-methionine-treated rats exhibited significant (p < 0.001) dose-dependent activity and reduced behavioural deficits, brain acetylcholinesterase (25.99 ± 2.36 versus 10.73 ± 1.26 μmoles/mg), brain lipid peroxidation (15.25 ± 1.65 versus 6.18 ± 0.74 nM/mg), serum homocysteine (Hcy) (22.37 ± 0.30 versus 11.01 ± 1.01 μg/mL) and serum cholesterol (182.7 ± 2.15 versus 101.5 ± 2.76 mg/dL) and increased brain antioxidant levels. HSP significantly (p < 0.001) reduced endothelial dysfunction (ED) by abolishing the effect of l-methionine on acetylcholine-induced endothelial-dependent relaxation and increased serum nitrite and vascular nitric oxide bioavailability along with the restoration of histological aberrations.

CONCLUSION

HSP exerts a protective effect on HHcy by abrogating oxidative stress, ED and neurotoxicity.

Homocysteine exaggerates microglia activation and neuroinflammation through microglia localized STAT3 overactivation following ischemic stroke

Background

Elevated plasma homocysteine (Hcy) levels have been indicated as a strong and modifiable risk factor of ischemic stroke; the previous studies have shown that exposure to Hcy activates cultured microglia. However, whether neurotoxicity of Hcy involves microglia activation following brain ischemia and the underlying mechanisms remains incompletely understood.

Methods

The cerebral damage was evaluated by staining with 2,3,5-triphenyltetrazolium chloride, hematoxylin-eosin, and Fluoro Jade B. The activation state of microglia was assessed via immunoreaction using the microglial markers Iba1 and OX-42. Then, the inflammatory factors such as tumor necrosis factor α (TNF-α), interleukin 6 (IL-6), and phosphorylated signal transducer and activator of transcription 3 (pSTAT3) were examined by Western blot analysis and fluorescence immunohistochemistry.

Results

Elevated Hcy level augmented brain damage and neural cell toxicity in the brain cortex and the dentate gyrus region of the hippocampus after cerebral ischemia/reperfusion. Meanwhile, Hcy activated microglia and induced the expression of the inflammatory factors such as TNF-α and IL-6. Moreover, Hcy caused an increase in pSTAT3 expression which occurs in microglial cells. AG490, a JAK2-STAT3 inhibitor, effectively inhibited the phosphorylation of STAT3, microglial cell activation and the secretion of IL-6, TNF-α raised by Hcy treatment.

Conclusions

STAT3 signaling pathway located in microglia plays a critical role in mediating Hcy-induced activation of microglia and neuroinflammation in rat MCAO model. This suggests the feasibility of targeting the JAK2/STAT3 pathway as an effective therapeutic strategy to alleviate the progression of Hcy-associated ischemia stroke.

Electronic supplementary material

The online version of this article (10.1186/s12974-017-0963-x) contains supplementary material, which is available to authorized users.

Sleep mediates the association between homocysteine and oxidative status in mild cognitive impairment

Tremendous progress has been made over the last few years in understanding how sleep and amyloid-β (Aβ) cooperate to speed up the progression of Alzheimer's disease (AD). However, it remains unknown whether sleep deficits also interact with other risk factors that exacerbate the pathological cascade of AD. Based on evidence showing that higher levels of homocysteine (HCY) and sleep loss increase oxidative damage, we here investigate whether the relationship between HCY and total antioxidant capacity (TAC) is mediated by changes in objective sleep in healthy older (HO, N = 21) and mild cognitive impairment (MCI, N = 21) subjects. Results revealed that reduced TAC levels in MCI was significantly correlated with increased HCY, shorter sleep duration, lower sleep efficiency, and reduced volume of temporal regions. However, only the HCY-TAC association showed diagnostic value, and this relationship was mediated by poorer sleep quality in MCI patients. We further showed that HCY-related cerebral volume loss in MCI depended on the serial relationship between poorer sleep quality and lower TAC levels. These findings provide novel insights into how impaired sleep may contribute to maintain the relationship between HCY and oxidative stress in prodromal AD, and offer empirical foundations to design therapeutic interventions aimed to weaken this link.

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.

Morphine pre- and post-conditioning exacerbates apoptosis in rat hippocampus cells in a model of homocysteine-induced oxidative stress

Recent investigations indicated that morphine has protective effects in different ischemia/reperfusion models and may protect against neuronal cell death, while other evidence showed that morphine induces apoptosis in neurons. Therefore, the current study was conducted to investigate pre- and post-conditioning effects of morphine on hippocampal cell apoptosis in a rat model of homocysteine (Hcy)-induced oxidative stress. In the present study, 0.5 µmol/µl Hcy was injected into bilateral intrahipocampal in the rat brain and morphine at a therapeutic dose of 10 mg/kg was injected intraperitoneally 5 days before and after Hcy injection in rats. The left and right rat hippocampus were removed for biochemical and histopathological analysis. In addition, hippocampal cell apoptosis was assayed by the TUNEL kit. Our results indicated that malondialdehyde (MDA) and superoxide anion (SOA) levels in the Hcy group were increased significantly compared to the control group (P<0.001). In addition, morphine pre- and post-treatment increased the MDA and SOA levels significantly in rat hippocampus compared with other groups (P<0.001). It was found that Hcy alone induced apoptosis in hippocampus cells and significantly increased the number of TUNEL-positive cells in rat hippocampus compared to the other group (P<0.001). Notably, our results indicated that pre- and post-treatment by morphine increased apoptosis in hippocampus cells compared with the other group (P<0.001). In conclusion, morphine neuroprotection and neurotoxicity needs to be further investigated to determine morphine side-effects in medical applications and to identify new targets for potential therapies.