Homocysteine and Folic Acid: Risk Factors for Alzheimer's Disease-An Updated Meta-Analysis

Elevated Homocysteine Level and Brain Atrophy Changes as Markers to Screen the Alzheimer Disease: Case Series

Alzheimer disease (AD) is the most common cause of dementia worldwide. Its clinical manifestations include a progressive loss of memory and other cognitive domains, as well as brain atrophy. An elevated homocysteine level (>15 µmol/L), known as hyperhomocysteinemia, is also an attributing risk factor for AD, vascular pathologies, and brain atrophy. Neuroimaging studies including T2-weighted magnetic resonance imaging scans revealed white matter hyperintensities in the periventricular and deep white matter, enlarged ventricles, widened sulci, and decreased white matter mass, which are features of aging, as well as cerebrovascular changes. This case series investigated changes in biochemical marker levels including serum homocysteine, folate, and vitamin B12, and the degree of atrophic variations in cortical-subcortical white matter in AD. The present study hypothesized that serum homocysteine levels might be used as a surrogate marker to screen for AD at an earlier stage.

Mendelian randomization to evaluate the effect of folic acid supplement on the risk of Alzheimer disease

We conducted a study to evaluate the impact of folic acid supplementation on the risk of Alzheimer disease (AD). A Mendelian randomization (MR) analysis model assessed the causal effects of folic acid supplementation on AD, utilizing data from recent genome-wide association studies. Effect estimates were scrutinized using various methods: inverse-variance weighted (IVW), simple mode, weighted mode, simple median, weighted median, penalized weighted median, and the MR-Egger method. The sensitivity analysis assessed heterogeneity and pleiotropy of individual single nucleotide polymorphisms (SNPs) using the IVW method with Cochran Q statistics and MR Egger intercept, respectively. Additionally, a leave-one-out sensitivity analysis determined potential SNP-driven associations. Both fixed-effect and random-effect IVW models in the MR analysis revealed a reduced risk of AD associated with folic acid supplementation (odds ratio, 0.930; 95% CI, 0.903-0.958, P < .001; odds ratio, 0.930; 95% CI, 0.910-0.950, P < .001) based on 7 SNPs as instrumental variables. The reverse MR analysis indicated no causal association between AD and folic acid supplementation. This study, utilizing genetic data, suggests that folic acid supplementation may potentially reduce the risk of AD and provides novel insights into its etiology and preventive measures.

Association between Alzheimer's disease, MAPT gene mutation and some biochemical biomarkers

Alzheimer's Disease (AD) is a multifactorial neurodegenerative disease and there is still no definitive treatment today. Early diagnosis of the disease is important, but there are almost no biomarkers that can be used in early diagnosis. The cerebrospinal fluid used in the diagnosis of the disease is not sufficient and is very difficult to obtain. Therefore, blood biomarkers that are less costly, less invasive, easily accessible, and can be used in long-term studies would be a better alternative. The aim of this study is to determine the relationship between Alzheimer's Disease and P301L MAPT gene mutation, homocysteine, folate and uric acid. 101 Alzheimer's patients and 101 healthy individuals were included in this study. Mutation analysis was performed using the Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) method with blood samples taken from the subjects. There was no significant difference between the patient and control groups in terms of homocysteine (p = 0.771), folate (p = 0.366) and uric acid (p = 0.860). When the genotypes were compared between the patient and control groups in terms of MAPT gene mutation (P301L), no statistically significant difference was detected (p = 0.081). There are very few studies in the literature investigating the relationship between Alzheimer's disease and P301L MAPT gene mutation. Additionally, there is no study investigating the relationship between Alzheimer's disease and homocysteine, folate, uric acid and P301L MAPT mutation in the Turkish population. We believe that this study has shed light on future studies.

Betaine alleviates cognitive impairment induced by homocysteine through attenuating NLRP3-mediated microglial pyroptosis in an m6A-YTHDF2-dependent manner

Dementia, with homocysteine (Hcy) as an important risk factor, is a severe public health problem in the aging society. Betaine serves as a methyl donor and plays an important role in reducing Hcy. However, the effects and mechanisms of betaine on Hcy-induced cognitive impairment remain unclear. Firstly, SD rats were injected with Hcy (400 μg/kg) through vena caudalis, and betaine (2.5 % w/v) was supplemented via drinking water for 14 days. Betaine supplementation could attenuate Hcy-induced cognitive impairment in the Y maze and novel object recognition tests by repairing brain injury. Meanwhile, microglial activation was observed to be inhibited by betaine supplementation using immunofluorescence and sholl analysis. Secondly, HMC3 cells were treated with betaine, which was found to decrease the ROS level, ameliorate cell membrane rupture, reduce the release of LDH, IL-18 and IL-1β, and attenuate the damage of microglia to neurons. Mechanistically, betaine alleviates cognitive impairment by inhibiting microglial pyroptosis via reducing the expressions of NLRP3, ASC, pro-caspase-1, cleaved-caspase-1, GSDMD, GSDMD-N, IL-18 and IL-1β. Betaine treatment can increase SAM/SAH ratio, confirming its enhancement on methylation capacity. Furthermore, betaine treatment was found to enhance N6-methyladenosine (m6A) modification of NLRP3 mRNA, and reduced the NLRP3 mRNA stability through increasing the expression of the m6A reader YTH N6-methyladenosine RNA binding protein 2 (YTHDF2). Finally, silencing YTHDF2 could reverse the inhibitory effect of betaine on pyroptosis. Our data demonstrated that betaine attenuated Hcy-induced cognitive impairment by suppressing microglia pyroptosis via inhibiting the NLRP3/caspase-1/GSDMD pathway in an m6A-YTHDF2-dependent manner.

Exploring the complexities of 1C metabolism: implications in aging and neurodegenerative diseases

The intricate interplay of one-carbon metabolism (OCM) with various cellular processes has garnered substantial attention due to its fundamental implications in several biological processes. OCM serves as a pivotal hub for methyl group donation in vital biochemical reactions, influencing DNA methylation, protein synthesis, and redox balance. In the context of aging, OCM dysregulation can contribute to epigenetic modifications and aberrant redox states, accentuating cellular senescence and age-associated pathologies. Furthermore, OCM's intricate involvement in cancer progression is evident through its capacity to provide essential one-carbon units crucial for nucleotide synthesis and DNA methylation, thereby fueling uncontrolled cell proliferation and tumor development. In neurodegenerative disorders like Alzheimer's and Parkinson's, perturbations in OCM pathways are implicated in the dysregulation of neurotransmitter synthesis and mitochondrial dysfunction, contributing to disease pathophysiology. This review underscores the profound impact of OCM in diverse disease contexts, reinforcing the need for a comprehensive understanding of its molecular complexities to pave the way for targeted therapeutic interventions across inflammation, aging and neurodegenerative disorders.

A Brief History of the Progress in Our Understanding of Genetics and Lifestyle, Especially Diet, in the Risk of Alzheimer's Disease

The two major determining factors for Alzheimer's disease (AD) are genetics and lifestyle. Alleles of the apolipoprotein E (APOE) gene play important roles in the development of late-onset AD, with APOEɛ4 increasing risk, APOEɛ3 being neutral, and APOEɛ2 reducing risk. Several modifiable lifestyle factors have been studied in terms of how they can modify the risk of AD. Among these factors are dietary pattern, nutritional supplements such as omega-3 fatty acids, and B vitamins, physical exercise, and obesity, and vitamin D. The Western diet increases risk of AD, while dietary patterns such as the Mediterranean and vegetarian/vegan diets reduce risk. Foods associated with reduced risk include coffee, fruits and vegetables, whole grains and legumes, and fish, while meat and ultraprocessed foods are associated with increased risk, especially when they lead to obesity. In multi-country ecological studies, the amount of meat in the national diet has the highest correlation with risk of AD. The history of research regarding dietary patterns on risk of AD is emphasized in this review. The risk of AD can be modified starting at least by mid-life. People with greater genetic risk for AD would benefit more by choosing lifestyle factors to reduce and/or delay incidence of AD.

Evaluation of white matter integrity by diffusion tensor imaging in the deficiencies of vitamin B12 and folate in older patients

OBJECTIVES

The aim of this study is to investigate whether white matter (WM) integrity is impaired in vitamin B12 and folate deficiency with Diffusion Tensor Imaging (DTI) in older patients.

METHODS

All the patients aged ≥65 years admitted to the geriatric clinic and performed DTI-MRI were included in the study. DTI parameters (fractional anisotropy, mean diffusivity, axial diffusivity, radial diffusivity) were calculated by ROI-based method in white matter tracts. Deficiency threshold for vitamin B12 were defined as <200 pg ml-1 and <400 pg ml-1 separately; and for folate as <3 ng ml-1 and <6 ng ml-1, separately.

RESULTS

DTI was performed to older patients having serum vitamin B12 level (n = 106, mean age = 80.7±7.7, 66% female) and folate level (n = 101, mean age = 80.7±7.5, 67.3% female). Significantly lower FA and higher MD and RD levels were observed in multiple WM areas including superior and middle cerebellar peduncles, cingulum and genu of corpus callosum in patients with vitamin B12 <400 pg ml-1 (p < 0.05). DTI indices also showed significant changes in the genu of corpus callosum, and right and left superior longitudinal fasciculus in patients with folate <6 ng ml-1 (p < 0.05).

CONCLUSIONS

Deficiencies of vitamin B12 and folate may be associated with impaired white matter integrity in elderly even at high laboratory levels, and DTI is a useful method to detect it.

ADVANCES IN KNOWLEDGE

Early detection of impaired WM integrity caused by micronutrient deficiencies poses a great significance in terms of prevention and intervention, and DTI is an effective non-invasive method to be used for this purpose.

Serum 5-Methyltetrahydrofolate Status Is Associated with One-Carbon Metabolism-Related Metabolite Concentrations and Enzyme Activity Indicators in Young Women

Maintaining optimal one-carbon metabolism (OCM) is essential for health and pregnancy. In this cross-sectional study, folate status was assessed based on 5-methyltetrahydrofolate (5-MTHF) levels, and the association between 5-MTHF and OCM-related metabolites was investigated in 227 female Japanese university students aged 18-25 years. The participants were divided into high and low 5-MTHF groups based on their folate status. Serum samples of the participants were collected while they were fasting, and 18 OCM-related metabolites were measured using stable-isotope dilution liquid chromatography-electrospray tandem mass spectrometry. The association between serum 5-MTHF and OCM-related metabolite concentrations was assessed using Spearman's rank correlation coefficient. Serum 5-MTHF concentrations were negatively correlated with total homocysteine (tHcy) concentrations and positively correlated with S-adenosylmethionine (SAM) and total cysteine (tCys) concentrations. Serum 5-MTHF concentrations demonstrated a stronger negative correlation with tHcy/tCys than with tHcy alone. The negative correlation between betaine and tHcy concentrations was stronger in the low 5-MTHF group than in the high 5-MTHF group. The 5-MTHF status could be linked to Hcy flux into the transsulfuration pathway via SAM. Therefore, the tHcy/tCys ratio may be a more sensitive indicator of the 5-MTHF status than tHcy alone. Furthermore, a low 5-MTHF status can enhance Hcy metabolism via betaine.

High homocysteine is associated with idiopathic normal pressure hydrocephalus in deep perforating arteriopathy: a cross-sectional study

BACKGROUND AND OBJECTIVE

The pathogenesis and pathophysiology of idiopathic normal pressure hydrocephalus (iNPH) remain unclear. Homocysteine may reduce the compliance of intracranial arteries and damage the endothelial function of the blood-brain barrier (BBB), which may be the underlying mechanism of iNPH. The overlap cases between deep perforating arteriopathy (DPA) and iNPH were not rare for the shared risk factors. We aimed to investigate the relationship between serum homocysteine and iNPH in DPA.

METHODS

A total of 41 DPA patients with iNPH and 49 DPA patients without iNPH were included. Demographic characteristics, vascular risk factors, laboratory results, and neuroimaging data were collected. Multivariable logistic regression analysis was performed to investigate the relationship between serum homocysteine and iNPH in DPA patients.

RESULTS

Patients with iNPH had significantly higher homocysteine levels than those without iNPH (median, 16.34 mmol/L versus 14.28 mmol/L; P = 0.002). There was no significant difference in CSVD burden scores between patients with iNPH and patients without iNPH. Univariate logistic regression analysis demonstrated that patients with homocysteine levels in the Tertile3 were more likely to have iNPH than those in the Tertile1 (OR, 4.929; 95% CI, 1.612-15.071; P = 0.005). The association remained significant after multivariable adjustment for potential confounders, including age, male, hypertension, diabetes mellitus, atherosclerotic cardiovascular disease (ASCVD) or hypercholesterolemia, and eGFR level.

CONCLUSION

Our study indicated that high serum homocysteine levels were independently associated with iNPH in DPA. However, further research is needed to determine the predictive value of homocysteine and to confirm the underlying mechanism between homocysteine and iNPH.

The Effects of Methylfolate on Cognitive Decline and Dementia: A Protocol for Systematic Review and Meta-Analysis

INTRODUCTION

Dementia and cognitive decline are highly prevalent in later life and are growing public health concerns worldwide due to the increasing aging population. Individuals diagnosed with dementia have reduced mental function, resulting in social and cognitive skill deficits, increased dependence, and reduced autonomy-all of which are conditions associated with higher mortality rates. This systematic review aims to assess the effectiveness of treating dementia and cognitive decline with methylfolate. The main outcomes analyzed will be dementia and changes in cognitive function measured by different instruments in older adults treated with methylfolate. Secondary outcomes, such as inflammatory markers, plasma folic-acid levels, and total homocysteine, will also be assessed.

METHODS AND ANALYSIS

This study will be carried out in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. This protocol is registered in the International Prospective Registry of Systematic Reviews, under the code CRD42021275755. We will include clinical trials conducted with older adults diagnosed with dementia or cognitive decline and treated with folic acid. The searches will be conducted on the PubMed, Scopus, and Embase databases, and the articles will be selected by reading their titles and abstracts first, followed by the full text. The quality of the selected studies will be assessed using GRADE and the risk of bias will be assessed using the Downs-and-Black method.

ETHICS AND DISSEMINATION

The results will be presented at scientific conferences and disseminated by publishing a scientific article in an international English-language journal. We hope to find robust and significant evidence regarding the effectiveness of methylfolate supplementation in improving dementia symptoms and cognitive decline among older adults. By systematizing this evidence and possibly performing a meta-analysis study, we expect to significantly contribute to the treatment of this health problem, reduce mortality, and improve the quality of life and health of this population, boosting the development of medical protocols capable of reducing the financial effects of public health.

Homocysteine-Potential Novel Diagnostic Indicator of Health and Disease in Horses

Homocysteine is an endogenous, non-protein sulfuric amino acid, an intermediate metabolite formed by the methionine transmethylation reaction. Its elevated serum concentration in humans, hyperhomocysteinemia, is a sensitive indicator and a risk factor for coagulation disorders, cardiovascular diseases and dementia. However, the role of homocysteine in veterinary species has not been unequivocally established. Although some research has been conducted in dogs, cats, cattle and pigs, relatively few studies on homocysteine have been conducted in horses. So far, it has been established in this species that homocysteine has an atherogenic effect, plays a role in early embryo mortality and is responsible for the induction of oxidative stress. These preliminary findings support establishing a reference range in a normal population of horses, including horses in training and merit further investigations into the role of this amino acid in health and disease in this species.

Selected Biomarkers of Oxidative Stress and Energy Metabolism Disorders in Neurological Diseases

Neurological diseases can be broadly divided according to causal factors into circulatory system disorders leading to ischemic stroke; degeneration of the nerve cells leading to neurodegenerative diseases, such as Alzheimer's (AD) and Parkinson's (PD) diseases, and immune system disorders; bioelectric activity (epileptic) problems; and genetically determined conditions as well as viral and bacterial infections developing inflammation. Regardless of the cause of neurological diseases, they are usually accompanied by disturbances of the central energy in a completely unexplained mechanism. The brain makes up only 2% of the human body's weight; however, while working, it uses as much as 20% of the energy obtained by the body. The energy requirements of the brain are very high, and regulatory mechanisms in the brain operate to ensure adequate neuronal activity. Therefore, an understanding of neuroenergetics is rapidly evolving from a "neurocentric" view to a more integrated picture involving cooperativity between structural and molecular factors in the central nervous system. This article reviewed selected molecular biomarkers of oxidative stress and energy metabolism disorders such as homocysteine, DNA damage such as 8-oxo2dG, genetic variants, and antioxidants such as glutathione in selected neurological diseases including ischemic stroke, AD, PD, and epilepsy. This review summarizes our and others' recent research on oxidative stress in neurological disorders. In the future, the diagnosis and treatment of neurological diseases may be substantially improved by identifying specific early markers of metabolic and energy disorders.

Nutritional metabolism and cerebral bioenergetics in Alzheimer's disease and related dementias

Disturbances in the brain's capacity to meet its energy demand increase the risk of synaptic loss, neurodegeneration, and cognitive decline. Nutritional and metabolic interventions that target metabolic pathways combined with diagnostics to identify deficits in cerebral bioenergetics may therefore offer novel therapeutic potential for Alzheimer's disease (AD) prevention and management. Many diet-derived natural bioactive components can govern cellular energy metabolism but their effects on brain aging are not clear. This review examines how nutritional metabolism can regulate brain bioenergetics and mitigate AD risk. We focus on leading mechanisms of cerebral bioenergetic breakdown in the aging brain at the cellular level, as well as the putative causes and consequences of disturbed bioenergetics, particularly at the blood-brain barrier with implications for nutrient brain delivery and nutritional interventions. Novel therapeutic nutrition approaches including diet patterns are provided, integrating studies of the gut microbiome, neuroimaging, and other biomarkers to guide future personalized nutritional interventions.

Hypertension and hyperhomocysteinemia as modifiable risk factors for Alzheimer's disease and dementia: New evidence, potential therapeutic strategies, and biomarkers

This review summarizes recent evidence on how mid-life hypertension, hyperhomocysteinemia (HHcy) and blood pressure variability, as well as late-life hypotension, exacerbate Alzheimer's disease (AD) and dementia risk. Intriguingly, HHcy also increases the risk for hypertension, revealing the importance of understanding the relationship between comorbid cardiovascular risk factors. Hypertension-induced dementia presents more evidently in women, highlighting the relevance of sex differences in the impact of cardiovascular risk. We summarize each major antihypertensive drug class's effects on cognitive impairment and AD pathology, revealing how carbonic anhydrase inhibitors, diuretics modulating cerebral blood flow, have recently gained preclinical evidence as promising treatment against AD. We also report novel vascular biomarkers for AD and dementia risk, highlighting those associated with hypertension and HHcy. Importantly, we propose that future studies should consider hypertension and HHcy as potential contributors to cognitive impairment, and that uncovering the underlying molecular mechanisms and biomarkers would aid in the identification of preventive strategies.

Complementary and Alternative Medicine Approaches in Alzheimer Disease and Other Neurocognitive Disorders

As our population ages, there is interest in delaying or intervening in cognitive decline. While newer agents are under development, agents in mainstream use do not impact the course of diseases that cause cognitive decline. This increases interest in alternative strategies. Even as we welcome possible new disease-modifying agents, they are likely to remain costly. Herein, we review the evidence behind other complementary and alternative strategies for cognitive enhancement and prevention of cognitive decline.

Diet's Role in Modifying Risk of Alzheimer's Disease: History and Present Understanding

Diet is an important nonpharmacological risk-modifying factor for Alzheimer's disease (AD). The approaches used here to assess diet's role in the risk of AD include multi-country ecological studies, prospective and cross-sectional observational studies, and laboratory studies. Ecological studies have identified fat, meat, and obesity from high-energy diets as important risk factors for AD and reported that AD rates peak about 15-20 years after national dietary changes. Observational studies have compared the Western dietary pattern with those of the Dietary Approaches to Stop Hypertension (DASH), Mediterranean (MedDi), and Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diets. Those studies identified AD risk factors including higher consumption of saturated and total fats, meat, and ultraprocessed foods and a lower risk of AD with higher consumption of fruits, legumes, nuts, omega-3 fatty acids, vegetables, and whole grains. Diet-induced factors associated with a significant risk of AD include inflammation, insulin resistance, oxidative stress, elevated homocysteine, dietary advanced glycation end products, and trimethylamine N-oxide. The molecular mechanisms by which dietary bioactive components and specific foods affect risk of AD are discussed. Given most countries' entrenched food supply systems, the upward trends of AD rates would be hard to reverse. However, for people willing and able, a low-animal product diet with plenty of anti-inflammatory, low-glycemic load foods may be helpful.

5-Methyltetrahydrofolate Alleviates Memory Impairment in a Rat Model of Alzheimer's Disease Induced by D-Galactose and Aluminum Chloride

The effects of 5-methyltetrahydrofolate (5-MTHF) on a rat model of Alzheimer's disease (AD) induced by D-galactose (D-gal) and aluminum chloride (AlCl₃) were investigated. Wistar rats were given an i.p. injection of 60 mg/kg D-gal and 10 mg/kg AlCl₃ to induce AD and three doses of 1 mg/kg, 5 mg/kg or 10 mg/kg 5-MTHF by oral gavage. A positive control group was treated with 1 mg/kg donepezil by gavage. Morris water maze performance showed that 5 and 10 mg/kg 5-MTHF significantly decreased escape latency and increased the number of platform crossings and time spent in the target quadrant for AD rats. The administration of 10 mg/kg 5-MTHF decreased the brain content of amyloid β-protein 1-42 (Aβ_1-42) and phosphorylated Tau protein (p-Tau) and decreased acetylcholinesterase and nitric oxide synthase activities. Superoxide dismutase activity, vascular endothelial growth factor level and glutamate concentration were increased, and malondialdehyde, endothelin-1, interleukin-6, tumor necrosis factor-alpha and nitric oxide decreased. The administration of 10 mg/kg 5-MTHF also increased the expression of disintegrin and metallopeptidase domain 10 mRNA and decreased the expression of β-site amyloid precursor protein cleavage enzyme 1 mRNA. In summary, 5-MTHF alleviates memory impairment in a D-gal- and AlCl₃-exposed rat model of AD. The inhibition of Aβ_1-42 and p-Tau release, reduced oxidative stress, the regulation of amyloid precursor protein processing and the release of excitatory amino acids and cytokines may be responsible.

Effect of a Vegan Diet on Alzheimer's Disease

There is evidence indicating that a vegan diet could be beneficial in the prevention of neurodegenerative disorders, including Alzheimer's disease (AD). The purpose of this review is to summarize the current knowledge on the positive and negative aspects of a vegan diet regarding the risk of AD. Regarding AD prevention, a vegan diet includes low levels of saturated fats and cholesterol, contributing to a healthy blood lipid profile. Furthermore, it is rich in phytonutrients, such as vitamins, antioxidants, and dietary fiber, that may help prevent cognitive decline. Moreover, a vegan diet contributes to the assumption of quercetin, a natural inhibitor of monoamine oxidase (MAO), which can contribute to maintaining mental health and reducing AD risk. Nonetheless, the data available do not allow an assessment of whether strict veganism is beneficial for AD prevention compared with vegetarianism or other diets. A vegan diet lacks specific vitamins and micronutrients and may result in nutritional deficiencies. Vegans not supplementing micronutrients are more prone to vitamin B12, vitamin D, and DHA deficiencies, which have been linked to AD. Thus, an evaluation of the net effect of a vegan diet on AD prevention and/or progression should be ascertained by taking into account all the positive and negative effects described here.

Safety, Tolerability, Pharmacokinetics and Initial Pharmacodynamics of a Subcommissural Organ-Spondin-Derived Peptide: A Randomized, Placebo-Controlled, Double-Blind, Single Ascending Dose First-in-Human Study

INTRODUCTION

This randomized, double-blind, placebo-controlled study in healthy volunteers assessed the safety, tolerability, and pharmacokinetics of single ascending doses of intravenously administered NX210-a linear peptide derived from subcommissural organ-spondin-and explored the effects on blood/urine biomarkers and cerebral activity.

METHODS

Participants in five cohorts (n = 8 each) were randomized to receive a single intravenous dose of NX210 (n = 6 each) (0.4, 1.25, 2.5, 5, and 10 mg/kg) or placebo (n = 2 each); in total, 10 and 29 participants received placebo and NX210, respectively. Blood samples were collected for pharmacokinetics within 180 min post dosing. Plasma and urine were collected from participants (cohorts: 2.5, 5, and 10 mg/kg) for biomarker analysis and electroencephalography (EEG) recordings within 48 h post dosing. Safety/tolerability and pharmacokinetic data were assessed before ascending to the next dose.

RESULTS

The study included 39 participants. All dosages were safe and well tolerated. All treatment-emergent adverse events (n = 17) were of mild severity and resolved spontaneously (except one with unknown outcome). Twelve treatment-emergent adverse events (70.6%) were deemed drug related; seven of those (58.3%) concerned nervous system disorders (dizziness, headache, and somnolence). The pharmacokinetic analysis indicated a short half-life in plasma (6-20 min), high apparent volume of distribution (1870-4120 L), and rapid clearance (7440-16,400 L/h). In plasma, tryptophan and homocysteine showed dose-related increase and decrease, respectively. No drug dose effect was found for the glutamate or glutamine plasma biomarkers. Nevertheless, decreased blood glutamate and increased glutamine were observed in participants treated with NX210 versus placebo. EEG showed a statistically significant decrease in beta and gamma bands and a dose-dependent increasing trend in alpha bands. Pharmacodynamics effects were sustained for several hours (plasma) or 48 h (urine and EEG).

CONCLUSION

NX210 is safe and well tolerated and may exert beneficial effects on the central nervous system, particularly in terms of cognitive processing.

Medicine-food herb: Angelica sinensis, a potential therapeutic hope for Alzheimer's disease and related complications

Alzheimer's disease (AD) is a progressive neurodegenerative disease, which has brought a huge burden to the world. The current therapeutic approach of one-molecule-one-target strategy fails to address the issues of AD because of multiple pathological features of AD. Traditionally, the herb of Angelica sinensis (AS) comes from the root of an umbrella plant Angelica sinensis (Oliv.) Diels. As a typical medicine-food herb, studies have shown that AS can alleviate AD and AD-complications by multiple targets through the various foundations of pharmaceutical material and dietary supply basis. Therefore, this review summarizes the pharmacological effects of AS for the treatment of AD and AD-complications for the first time. AS contains many effective components, such as ligustilide, z-ligustilide, n-butylidenephthalide, α-pinene, p-cymene, myrcene, ferulic acid, vanillic acid and coniferyl ferulate. It is found that AS, AS-active compounds and AS-compound recipes mainly treat AD through neuroprotective, anti-inflammation, and anti-oxidant effects, improving mitochondrial dysfunction, anti-neuronal apoptosis, regulating autophagy, regulating intestinal flora and enhancing the central cholinergic system, which shows the multi-component and multi-target effect of AS. The role of dietary supplement components in AS for AD intervention is summarized, including vitamin B₁₂, folic acid, arginine, and oleic acid, which can improve the symptoms of AD. Besides, this review focuses on the safety and toxicity evaluation of AS, which provides a basis for its application. This review will provide further support for the research on AD and the application of medicine-food herb AS in a healthy lifestyle in the future.

Blood levels of circulating methionine components in Alzheimer’s disease and mild cognitive impairment: A systematic review and meta-analysis

Background

Circulating methionine components have been reported to be associated with Alzheimer’s disease (AD) and mild cognitive impairment (MCI), although outcomes are not always consistent.

Materials and methods

Database searching was conducted using PubMed, Embase, Cochrane Library, and Web of Science from inception to 26 December 2021. In this study, two reviewers independently identified eligible articles and extracted the data. We used Joanna Briggs Institute (JBI) Critical Appraisal tools to assess the overall quality of the included studies. STATA software was employed to perform meta-analysis evaluating the standardized mean difference (SMD) with its 95% confidence intervals (CIs) using random-effects models. Evidence quality was assessed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) criteria.

Results

Totally, 30 observational studies were eligible for inclusion. Compared with cognitively normal controls, patients with AD had increased homocysteine (Hcy) levels in the blood [standardized mean difference (SMD) = 0.59, 95% confidence interval [CI]: 0.36–0.82, P = 0.000], plasma (SMD = 0.39, 95% CI: 0.23–0.55, P = 0.000), and serum (SMD = 1.56, 95% CI: 0.59–2.95, P = 0.002). Patients with MCI were not significantly different from controls (SMD = 0.26, 95% CI: –0.07–0.58, P = 0.127). Patients with AD or MCI did not significantly differ from controls of blood vitamin B12 levels, AD (SMD = –0.05, 95% CI: –0.19–0.08, P = 0.440), or MCI (SMD = 0.01, 95% CI: –0.16–0.17, P = 0.94). Some cohort studies have suggested that higher Hcy, methionine, and S-adenosylmethionine levels may accelerate cognitive decline in patients with MCI or AD, and vitamin B12 deficiency is a risk factor for the disease; however, the results of other studies were inconsistent. According to the GRADE system, all these outcomes scored very low to low quality, and no high-quality evidence was found.

Conclusion

Only Hcy levels in the plasma and serum were found to be inversely related to the risk of AD. However, due to the low quality of supporting these results, high-quality studies are needed to verify these findings.

Systematic Review Registration

http://www.crd.york.ac.uk/PROSPERO/, identifier CRD42022308961.

Chronic Kidney Disease and Cognitive Impairment: The Kidney-Brain Axis

Background

Cognitive impairment, increasingly recognized as a major social burden, is commonly found in chronic kidney disease (CKD) patients.

Summary

Vascular damage, uremic toxicity, oxidative stress, and peripheral/central inflammation induced by CKD might be involved in brain lesions and ultimately result in cognitive decline. Uncovering the pathophysiology of CKD-associated cognitive impairment is important for early diagnosis and prevention, which undoubtedly prompts innovative pharmacological treatments.

Key Messages

Here, we sequentially review the current understanding and advances in the epidemiology, risk factors, and pathological mechanisms of cognitive impairment in CKD. Furthermore, we summarize the currently available therapeutic strategies for cognitive impairment in CKD.

Circulating folate concentrations and the risk of mild cognitive impairment: a prospective study on the older Chinese population without folic acid fortification

BACKGROUND

The longitudinal association between serum folate concentrations and the risk of cognitive impairment remains unclear in populations with low folate levels. We examined the association between serum folate concentrations and mild cognitive impairment (MCI) in older adults in China, where mandatory fortification of foods with folic acid was not implemented. We further explored if homocysteine (Hcy) and leukocyte telomere length (LTL) mediate the association between serum folate and MCI.

METHODS

We performed a longitudinal analysis of 3974 participants aged ≥ 60 years from the Tianjin Elderly Nutrition and Cognition (TENC) cohort study. The associations between serum folate level and the risk of cognitive impairment overall and stratified by apolipoprotein E (APOE) ε4 genotypes were evaluated using multivariable Cox proportional hazards models. The mediating effects of Hcy and LTL on the folate-MCI association were explored via a path analysis approach.

RESULTS

Within a 3-year follow-up, we documented 560 incident MCI cases. After multivariable adjustment, higher serum folate concentrations were associated with lower incidence of MCI, with hazard ratios (95% confidence interval) across quartiles of folate (from lowest to highest concentrations) of 1.00 (reference), 0.66 (0.52, 0.83), 0.57 (0.45, 0.73), 0.66 (0.52, 0.84), respectively (P for trend < 0.001). In mediation analyses, the status of serum folate deficiency and MCI were correlated via two intermediary pathways, Hcy and Hcy-telomere (P < 0.05).

CONCLUSIONS

Lower folate concentrations, independently of APOE genotype, were associated with increased risk of MCI among elderly Chinese people, a population with relatively low folate intake. Our data were compatible with the mediation hypothesis that the association between folate status and MCI was mediated by Hcy and LTL.

The Roles of Long-Term Hyperhomocysteinemia and Micronutrient Supplementation in the AppNL–G–F Model of Alzheimer’s Disease

A causal contribution of hyperhomocysteinemia to cognitive decline and Alzheimer’s disease (AD), as well as potential prevention or mitigation of the pathology by dietary intervention, have frequently been subjects of controversy. In the present in vivo study, we attempted to further elucidate the impact of elevated homocysteine (HCys) and homocysteic acid (HCA) levels, induced by dietary B-vitamin deficiency, and micronutrient supplementation on AD-like pathology, which was simulated using the amyloid-based App^NL–G–F knock-in mouse model. For this purpose, cognitive assessment was complemented by analyses of ex vivo parameters in whole blood, serum, CSF, and brain tissues from the mice. Furthermore, neurotoxicity of HCys and HCA was assessed in a separate in vitro assay. In confirmation of our previous study, older App^NL–G–F mice also exhibited subtle phenotypic impairment and extensive cerebral amyloidosis, whereas dietary manipulations did not result in significant effects. As revealed by proximity extension assay-based proteome analysis, the App^NL–G–F genotype led to an upregulation of AD-characteristic neuronal markers. Hyperhomocysteinemia, in contrast, indicated mainly vascular effects. Overall, since there was an absence of a distinct phenotype despite both a significant amyloid-β burden and serum HCys elevation, the results in this study did not corroborate the pathological role of amyloid-β according to the “amyloid hypothesis,” nor of hyperhomocysteinemia on cognitive performance. Nevertheless, this study aided in further characterizing the App^NL–G–F model and in elucidating the role of HCys in diverse biological processes. The idea of AD prevention with the investigated micronutrients, however, was not supported, at least in this mouse model of the disease.

Blood and CSF Homocysteine Levels in Alzheimer's Disease: A Meta-Analysis and Meta-Regression of Case-Control Studies

OBJECTIVE

Hyperhomocysteinemia (HHcy), as an important risk factor for Alzheimer's disease (AD), would aggravate cognitive dysfunction. This study aimed to investigate whether and to what degree the homocysteine (Hcy) levels in blood and cerebrospinal fluid (CSF) were elevated in AD patients compared with healthy controls and to explore the factors related to the elevated Hcy levels in AD patients.

METHODS

PubMed and Embase databases were searched to identify eligible studies, and study quality was evaluated using the Newcastle-Ottawa Quality Assessment Scale. Ratio of mean (RoM) Hcy concentrations was used as a measure of fold-change between AD patients and healthy control subjects.

RESULTS

We identified 35 eligible studies, consisting a total of 2172 patients with AD and 2289 healthy controls. The pooled results showed that patients with AD had a significantly higher blood level of Hcy (RoM, 1.32; 95% CI, 1.25-1.40; p<0.001) than controls did, with large heterogeneity across studies (I²=81.4%, p<0.001). Hcy level in CSF did not differ significantly between patients with AD than controls (RoM, 1.12; 95% CI, 0.90-1.39, p=0.293; I²=69.4%, p=0.02). A random effects meta-regression analysis revealed that there was an inverse correlation between the blood levels of Hcy and folate (p=0.006). There was no link found between the blood levels of vitamin B_12, or the Mini-Mental Status Examination scores reflecting the degree of cognitive impairment, and blood levels of Hcy.

CONCLUSION

Regardless of dementia severity, there is an approximate one-third increase in blood Hcy in AD patients, which is robustly associated with a decreased level of blood folate in AD, but not with that of blood vitamin B₁₂ nor the degree of dementia. Future investigation on the cause-and-effect link between Hcy and folate is warranted to clarify this issue.

Association Between Serum Vitamins and the Risk of Alzheimer's Disease in Chinese Population

BACKGROUND

Alzheimer's disease (AD) is a chronic and fatal neurodegenerative disease; accumulating evidence suggests that vitamin deficiency is associated with the risk of AD. However, studies attempting to elucidate the relationship between vitamins and AD varied widely.

OBJECTIVE

This study aimed to investigate the relationship between serum vitamin levels and AD in a cohort of the Chinese population.

METHODS

A total of 368 AD patients and 574 healthy controls were recruited in this study; serum vitamin A, B1, B6, B9, B12, C, D, and E were measured in all participants.

RESULTS

Compared with the controls, vitamin B2, B9, B12, D, and E were significantly reduced in AD patients. Lower levels of vitamin B2, B9, B12, D, and E were associated with the risk of AD. After adjusting for age and gender, low levels of vitamin B2, B9, and B12 were still related to the risk of AD. In addition, a negative correlation was determined between vitamin E concentration and Activity of Daily Living Scale score while no significant association was found between serum vitamins and age at onset, disease duration, Mini-Mental State Examination, and Neuropsychiatric Inventory Questionnaire score.

CONCLUSION

We conclude that lower vitamin B2, B9, B12, D, and E might be associated with the risk of AD, especially vitamin B2, B9, and B12. And lower vitamin E might be related to severe ability impairment of daily activities.