Methionine diet-induced hyperhomocysteinemia accelerates cerebral aneurysm formation in rats

Animal Models of Intracranial Aneurysms: History, Advances, and Future Perspectives

Intracranial aneurysms (IA) are a disease process with potentially devastating outcomes, particularly when rupture occurs leading to subarachnoid hemorrhage. While some candidates exist, there is currently no established pharmacological prevention of growth and rupture. The development of prophylactic treatments is a critical area of research, and preclinical models using animals play a pivotal role. These models, which utilize various species and induction methods, each possess unique characteristics that can be leveraged depending on the specific aim of the study. A comprehensive understanding of these models, including their historical development, is crucial for appreciating the advantages and limitations of aneurysm research in animal models.We summarize the significant roles of animal models in IA research, with a particular focus on rats, mice, and large animals. We discuss the pros and cons of each model, providing insights into their unique characteristics and contributions to our understanding of IA. These models have been instrumental in elucidating the pathophysiology of IA and in the development of potential therapeutic strategies.A deep understanding of these models is essential for advancing research on preventive treatments for IA. By leveraging the unique strengths of each model and acknowledging their limitations, researchers can conduct more effective and targeted studies. This, in turn, can accelerate the development of novel therapeutic strategies, bringing us closer to the goal of establishing an effective prophylactic treatment for IA. This review aims to provide a comprehensive view of the current state of animal models in IA research.

Hyperhomocysteinemia increases the risk of vertebrobasilar dissecting aneurysm among the male Han Chinese population: a retrospective case-control study

OBJECT

Vertebrobasilar dissecting aneurysms (VBDAs) are known to have a poor natural history with high rates of re-bleeding and mortality. There is a strong relation between hyperhomocysteinemia (HHcy) and cerebrovascular disease; we perform a retrospective study within the male of Chinese Han population to explore the association between HHcy and VBDAs.

METHODS

Eighty-eight male patients with VBDA and Eighty-one male control subjects were evaluated for their serum total homocysteine levels. With multiple logistic regression analysis, the association between HHcy and the risk of VBDAs was estimated. Interaction and stratified analyses were conducted according to age, BMI, smoking status, drinking status, and chronic disease histories. The two-piecewise linear regression model examined the threshold effect.

RESULTS

The multivariate logistic regression analyses revealed a significant association between HHcy and VBDAs (odds ratio (OR) = 2.62; 95% confidence interval (CI), 1.02-6.71) after adjusting for classical vascular risk factors. The relationship was stable in all subgroup analysis. The interactive role was not found in the association between HHcy and VBDAs for the potential risk factor.

CONCLUSIONS

In summary, our study provides evidence that HHcy can increases the risk of VBDAs in the male Han Chinese population. Further researches with appropriate study designs including sex differences and aneurysm types are needed to verify this association.

Clinical relevance of critical plasma homocysteine levels in predicting rupture risk for small and medium-sized intracranial aneurysms

Plasma homocysteine (Hcy) has been globally recognized as an independent risk factor for various neurovascular diseases. In this study, the authors investigated the relationship between critical Hcy concentration and the risk of rupture in intracranial aneurysms (IAs). This study collected data from 423 patients with both ruptured and unruptured IAs. We compared demographic data, vascular rupture risk factors, and laboratory test results between the two groups. Multivariable logistic regression analysis was employed to determine the correlation between critical plasma Hcy levels and the risk of rupture in small to medium-sized IAs. A total of 330 cases of ruptured intracranial aneurysms (RIA) and 93 cases of unruptured intracranial aneurysms (UIA) were included. Univariate analysis revealed statistically significant differences between the ruptured and unruptured groups in terms of hypertension, hyperlipidemia, plasma Hcy levels, and IA morphology (all P < 0.05). Multivariable logistic regression analysis indicated that hypertension (odds ratio [OR] 0.504; 95% confidence interval [CI] 0.279-0.911; P = 0.023), hyperlipidemia (OR 1.924; 95% CI 1.079-3.429; P = 0.027), and plasma Hcy levels (OR 1.420; 95% CI 1.277-1.578; P < 0.001) were independently associated with the rupture of small to medium-sized IAs, all with statistical significance (P < 0.05). Our study suggests that critical plasma Hcy levels are an independent risk factor for increased rupture risk in small to medium-sized intracranial aneurysms. Therefore, reducing plasma Hcy levels may be considered a valuable strategy to mitigate the risk of intracranial vascular abnormalities rupture and improve patient prognosis.

Diet-induced hyperhomocysteinemia causes sex-dependent deficiencies in offspring musculature and brain function

Hyperhomocysteinemia (HHcy), characterized by elevated homocysteine (Hcy) levels, is a known risk factor for cardiovascular, renal, and neurological diseases, as well as pregnancy complications. Our study aimed to investigate whether HHcy induced by a high-methionine (high-Met) diet exacerbates cognitive and behavioral deficits in offspring and leads to other breeding problems. Dietary HHcy was induced four weeks before mating and continued throughout gestation and post-delivery. A battery of behavioral tests was conducted on offspring between postnatal days (PNDs) 5 and 30 to assess motor function/activity and cognition. The results were correlated with brain morphometric measurements and quantitative analysis of mammalian target of rapamycin (mTOR)/autophagy markers. The high-Met diet significantly increased parental and offspring urinary tHcy levels and influenced offspring behavior in a sex-dependent manner. Female offspring exhibited impaired cognition, potentially related to morphometric changes observed exclusively in HHcy females. Male HHcy pups demonstrated muscle weakness, evidenced by slower surface righting, reduced hind limb suspension (HLS) hanging time, weaker grip strength, and decreased activity in the beaker test. Western blot analyses indicated the downregulation of autophagy and the upregulation of mTOR activity in HHcy cortexes. HHcy also led to breeding impairments, including reduced breeding rate, in-utero fetal death, lower pups' body weight, and increased mortality, likely attributed to placental dysfunction associated with HHcy. In conclusion, a high-Met diet impairs memory and cognition in female juveniles and weakens muscle strength in male pups. These effects may stem from abnormal placental function affecting early neurogenesis, the dysregulation of autophagy-related pathways in the cortex, or epigenetic mechanisms of gene regulation triggered by HHcy during embryonic development.

The SNHG12/microRNA-15b-5p/MYLK axis regulates vascular smooth muscle cell phenotype to affect intracranial aneurysm formation

OBJECTIVE

This research was dedicated to investigating the impact of the SNHG12/microRNA (miR)-15b-5p/MYLK axis on the modulation of vascular smooth muscle cell (VSMC) phenotype and the formation of intracranial aneurysm (IA).

METHODS

SNHG12, miR-15b-5p and MYLK expression in IA tissue samples from IA patients were tested by RT-qPCR and western blot. Human aortic vascular smooth muscle cells (VSMCs) were cultivated with H2O2 to mimic IA-like conditions in vitro, and the cell proliferation and apoptosis were measured by MTT assay and Annexin V/PI staining. IA mouse models were established by induction with systemic hypertension combined with elastase injection. The blood pressure in the tail artery of mice in each group was assessed and the pathological changes in arterial tissues were observed by HE staining and TUNEL staining. The expression of TNF-α and IL-1β, MCP-1, iNOS, caspase-3, and caspase-9 in the arterial tissues were tested by RT-qPCR and ELISA. The relationship among SNHG12, miR-15b-5p and MYLK was verified by bioinformatics, RIP, RNA pull-down, and luciferase reporter assays.

RESULTS

The expression levels of MYLK and SNHG12 were down-regulated and that of miR-15b-5p was up-regulated in IA tissues and H2O2-treated human aortic VSMCs. Overexpressed MYLK or SNHG12 mitigated the decrease in proliferation and increase in apoptosis of VSMCs caused by H2O2 induction, and overexpression of miR-15b-5p exacerbated the decrease in proliferation and increase in apoptosis of VSMCs caused by H2O2 induction. Overexpression of miR-15b-5p reversed the H2O2-treated VSMC phenotypic changes caused by SNHG12 up-regulation, and overexpression of MYLK reversed the H2O2-treated VSMC phenotypic changes caused by up-regulation of miR-15b-5p. Overexpression of SNHG12 reduced blood pressure and ameliorated arterial histopathological damage and VSMC apoptosis in IA mice. The mechanical analysis uncovered that SNHG12 acted as an endogenous RNA that competed with miR-15b-5p, thus modulating the suppression of its endogenous target, MYLK.

CONCLUSION

Decreased expression of SNHG12 in IA may contribute to the increasing VSMC apoptosis via increasing miR-15b-5p expression and subsequently decreasing MYLK expression. These findings provide potential new strategies for the clinical treatment of IA.

Homocysteine serum levels in patients with ruptured and unruptured intracranial aneurysms: a case-control study

BACKGROUND

There is very few data regarding homocysteine's influence on the formation and rupture of intracranial aneurysms.

OBJECTIVE

To compare homocysteine levels between patients with ruptured and unruptured intracranial aneurysms, and to evaluate possible influences of this molecule on vasospasm and functional outcomes.

METHODS

This is a retrospective, case-control study. We evaluated homocysteinemia differences between patients with ruptured and unruptured aneurysms; and the association of homocysteine levels with vasospasm and functional outcomes. Logistic regressions were performed.

RESULTS

A total of 348 participants were included: 114 (32.8%) with previous aneurysm rupture and 234 (67.2%) with unruptured aneurysms. Median homocysteine was 10.75µmol/L (IQR = 4.59) in patients with ruptured aneurysms and 11.5µmol/L (IQR = 5.84) in patients with unruptured aneurysms. No significant association was detected between homocysteine levels and rupture status (OR = 0.99, 95% CI = 0.96-1.04). Neither mild (>15µmol/L; OR = 1.25, 95% CI 0.32-4.12) nor moderate (>30µmol/L; OR = 1.0, 95% CI = 0.54-1.81) hyperhomocysteinemia demonstrated significant correlations with ruptured aneurysms. Neither univariate (OR = 0.86; 95% CI 0.71-1.0) nor multivariable age-adjusted (OR = 0.91; 95% CI = 0.75-1.05) models evidenced an association between homocysteine levels and vasospasm. Homocysteinemia did not influence excellent functional outcomes at 6 months (mRS≤1) (OR = 1.04; 95% CI = 0.94-1.16).

CONCLUSION

There were no differences regarding homocysteinemia between patients with ruptured and unruptured intracranial aneurysms. In patients with ruptured aneurysms, homocysteinemia was not associated with vasospasm or functional outcomes.

The Role of Methionine-Rich Diet in Unhealthy Cerebrovascular and Brain Aging: Mechanisms and Implications for Cognitive Impairment

As aging societies in the western world face a growing prevalence of vascular cognitive impairment and Alzheimer's disease (AD), understanding their underlying causes and associated risk factors becomes increasingly critical. A salient concern in the western dietary context is the high consumption of methionine-rich foods such as red meat. The present review delves into the impact of this methionine-heavy diet and the resultant hyperhomocysteinemia on accelerated cerebrovascular and brain aging, emphasizing their potential roles in cognitive impairment. Through a comprehensive exploration of existing evidence, a link between high methionine intake and hyperhomocysteinemia and oxidative stress, mitochondrial dysfunction, inflammation, and accelerated epigenetic aging is drawn. Moreover, the microvascular determinants of cognitive deterioration, including endothelial dysfunction, reduced cerebral blood flow, microvascular rarefaction, impaired neurovascular coupling, and blood-brain barrier (BBB) disruption, are explored. The mechanisms by which excessive methionine consumption and hyperhomocysteinemia might drive cerebromicrovascular and brain aging processes are elucidated. By presenting an intricate understanding of the relationships among methionine-rich diets, hyperhomocysteinemia, cerebrovascular and brain aging, and cognitive impairment, avenues for future research and potential therapeutic interventions are suggested.

Alzheimer's Disease-like Pathological Features in the Dorsal Hippocampus of Wild-Type Rats Subjected to Methionine-Diet-Evoked Mild Hyperhomocysteinaemia

Multifactorial interactions, including nutritional state, likely participate in neurodegeneration's pathogenesis and evolution. Dysregulation in methionine (Met) metabolism could lead to the development of hyperhomocysteinaemia (hHcy), playing an important role in neuronal dysfunction, which could potentially lead to the development of Alzheimer's disease (AD)-like pathological features. This study combines proton magnetic resonance spectroscopy (1H MRS) with immunohistochemical analysis to examine changes in the metabolic ratio and histomorphological alterations in the dorsal rat hippocampus (dentate gyrus-DG) subjected to a high Met diet. Male Wistar rats (420-480 g) underwent hHcy evoked by a Met-enriched diet (2 g/kg of weight/day) lasting four weeks. Changes in the metabolic ratio profile and significant histomorphological alterations have been found in the DG of hHcy rats. We have detected increased morphologically changed neurons and glial cells with increased neurogenic markers and apolipoprotein E positivity parallel with a diminished immunosignal for the N-Methyl-D-Aspartate receptor 1 in hHcy animals. A Met diet induced hHcy, likely via direct Hcy neurotoxicity, an interference with one carbon unit metabolism, and/or epigenetic regulation. These conditions lead to the progression of neurodegeneration and the promotion of AD-like pathological features in the less vulnerable hippocampal DG, which presents a plausible therapeutic target.

Hyperhomocysteinemia and intracranial aneurysm: A mendelian randomization study

Objective

To investigate the link between genetic variants associated with plasma homocysteine levels and risk of intracranial aneurysm (IA) using two-sample Mendelian randomization.

Methods

We used single-nucleotide polymorphisms associated with human plasma homocysteine levels as instrumental variables for the primary analysis in a genome-wide association study of 44,147 subjects of European ancestry. Summary-level statistics were obtained for 79,429 individuals, including 7,495 IA cases and 71,934 controls. To enhance validity, five different Mendelian randomization methods (MR-Egger, weighted median, inverse variance weighted, simple mode, and weighted mode) were used for the analyses.

Results

The inverse variance weighted analysis method produced P-values of 0.398 for aneurysmal subarachnoid hemorrhage [odds ratio (OR): 1.104; 95% confidence interval (CI): 0.878–1.387], 0.246 for IA (OR: 1.124; 95% CI: 0.923–1.368), and 0.644 for unruptured IA (OR: 1.126; 95% CI: 0.682–1.858). The MR-Egger analysis showed no association between IAs and homocysteine, with all P > 0.05.

Conclusion

Using gene-related instrumental variables, the Mendelian randomization analyses demonstrated a lack of an association between plasma homocysteine levels and IAs or aneurysmal subarachnoid hemorrhage.

Homocysteine Levels Are Associated With the Rupture of Intracranial Aneurysms

Background

Homocysteine (Hcy) levels may be associated with the development of intracranial aneurysms (IAs). However, whether it increases the risk of rupture of IAs is unknown. This study aimed to determine the association between homocysteine levels and IA rupture.

Methods

We retrospectively reviewed patients with IAs and subarachnoid hemorrhage (SAH) at our hospital between January 2019 and May 2021. Clinical data, including Hcy levels and IA images, were assessed. The association between Hcy level and IA rupture was investigated using multivariate logistic regression analyses in patients with IAs and SAH.

Results

A total of 589 patients were included. 546 patients with IAs, including 331 UIA (Unruptured IA) and 215 RIA (Ruptured IA). The average age was 57.43 ± 10.86 years old, and 67.03% were women. Among them, all 215 RIAs lead to SAH. In addition, we also enrolled 43 non-aneurysmal subarachnoid hemorrhage (Na-SAH) patients. The average age was 54.12 ± 10.55 years old, and 53.48% were female. After adjusting for confounders in the multivariate model, Hcy levels were correlated with the rupture of IA (odds ratio [OR] 1.069; 95% confidence interval [CI] 1.025–1.114, p = 0.002) and a-SAH (OR 1.083; 95% CI 1.002–1.170, p = 0.046).

Conclusion

Hcy levels were associated with IA rupture. These findings provide novel insights into IAs rupture, and future studies are needed to confirm this relationship.

Fetal hyperhomocysteinemia is associated with placental inflammation and early breakdown of maternal-fetal tolerance in Pre-term birth

PROBLEM

Hyperhomocysteinemia (hypHcy) due to impaired folate metabolism is shown to be a risk factor for preterm birth (PTB) and low birth weight (LBW) in mothers. However, the relationship of fetal hypHcy with adverse pregnancy outcomes is under-represented. The present study aims to investigate the association of fetal hypHcy with oxidative stress and placental inflammation that can contribute to an early breakdown of maternal-fetal tolerance in pre-term birth (PTB).

METHODS

Cord blood and placenta tissue were collected from PTB and term infant group. Levels of homocysteine, folic acid, vitamin B12 and oxidative stress markers (MDA, T-AOC, 8-OHdG) were measured in cord blood serum using ELISA and respective standard assay kits. Relative expression of candidate genes (TNF-α, IL-6, IL1-β, VEGF-A, MMP2 and MMP9) was also checked using RT-PCR and immunoblotting/immunohistochemistry.

RESULTS

PTB infants showed significantly higher levels of homocysteine (p = 0.02) and lower levels of vitamin B12 (p = 0.005) as compared to term infants. We also found that PTB infants with hypHcy had lower T-AOC (p = 0.003) and higher MDA (p = 0.04) levels as compared to term infants with normal homocysteine levels. The mRNA and protein levels of TNF-α, VEGF-A, MMP2 and MMP9 were significantly higher in hypHcy PTB infants.

CONCLUSION

Our results show that fetal hypHcy is associated with oxidative stress and an increase in inflammatory markers in the placenta. Thus, in conclusion, our study demonstrates that fetal hypHcy during pregnancy is a potential risk factor that may initiate an early breakdown of uterine quiescence due to activation of inflammatory processes leading to PTB. This article is protected by copyright. All rights reserved.

Vitamin B12 as a Cholinergic System Modulator and Blood Brain Barrier Integrity Restorer in Alzheimer's Disease

So far, the cholinergic hypothesis of Alzheimer's disease (AD) remains the fundamental explanation for the complex etiopathology of AD. However, therapeutics raising synaptic acetylcholine (Ach) or having cholinergic receptors agonistic activity had shown limited clinical efficacy, possibly, due to lacking capability to aggregate cholinergic receptors within the degenerated cholinergic neurons. Vitamin-B12 (B12) is an epigenetic modifier. It has a specific CNS transport system via the cubam receptors. The later enclose a cholinergic aggregator; agrin protein, suggesting that B12 administration may cause cholinergic receptors aggregation. Further, B12 involvement in homocysteine (Hcy) metabolism may restore blood brain barrier (BBB) integrity disrupted by elevated Hcy levels in AD. Here in, using a pharmacological model of cholinergic amnesia, three different B12 doses were compared to the standard of care; donepezil (DON) regarding cholinergic system modulation, and Hcy metabolic pathways. Further, AD-associated cerebro-vascular pathology was assessed by morphometric analyses of cerebro-vasculature morphology and ultrastructure using scanning and transmission electron-microscopes, respectively. Consequent effect on key AD-hallmarks and behavioral cognitive tests was also examined. The highest B12-tested dose (B12-HD) showed the greatest hippocampal cholinergic modulation with dose-dependent preferential upregulation of one cholinergic receptor over the other. Altered Hcy metabolism was proved to be a consequence of cholinergic disruption that was variably reversed by different B12 doses. In spite of equipotent effect of DON and B12-HD therapies in decreasing β-amyloid synthesis, B12-HD-treated group revealed the greatest restoration of BBB integrity indicating superior capability of β-amyloid clearance. Therefore, B12-HD therapy may represent a promising AD-modifying agent with extra-ability over conventional cholinergic modulators to aggregate cholinergic receptors.

РОЗРОБЛЕННЯ ЗАСОБУ ДЛЯ ПОКРАЩЕННЯ КОГНІТИВНИХ ФУНКЦІЙ ТА ЗНИЖЕННЯ РІВНЯ ГОМОЦИСТЕЇНУ

Вступ. Гіпергомоцистеїнемія є небезпечним метаболічним порушенням, що призводить до виникнення низки захворювань.Проблематика. Нагальним завданням є розроблення препаратів, які здатні знижувати рівень гомоцистеїну, не спричиняючи побічних ефектів.Мета. Розробити дієтичну добавку, що при мінімальному вмісті компонентів, які здатні викликати побічні реакції, знижує рівень гомоцистеїну; а також дослідити, чи впливає розроблена добавка на когнітивні здібності тварин, та впровадити її у виробництво.Матеріали й методи. До складу розробленої дієтичної добавки «Альфакогнітин» включено вітаміни В6, В9, В12, С і холін. Моделювання експериментальної гіпергомоцистенемії у щурів проводили шляхом утримання тварин наL-метіоніновій дієті. Вміст гомоцистеїну у крові визначали за допомогою іонообмінної рідинно-колонної хроматографії з використанням автоматичного аналізатору амінокислот. Поведінкові реакції та когнітивні здібності щурів досліджували за допомогою поведінкових тестів «Відкрите поле», «Електрична стимуляція кінцівки» і «Соціальнавзаємодія». Роботи щодо впровадження у виробництво виконано за участі компанії ТОВ «Нутрімед» (Київ).Результати. Показано, що у тварин із гіпергомоцистеїнемією «Альфакогнітин» знижував рівень гомоцистеїну, підвищував когнітивні здібності, ефективність соціальної взаємодії та комунікабельність, а також нормалізував функціональні порушення пам’яті та здатності до навчання. Затверджено технічні умови виробництва дієтичної добавки,відпрацьовано пілотну технологію отримання її капсульованої форми та виготовлено дослідну партію.Висновки. «Альфакогнітин» може знижувати рівень гомоцистеїну, що дозволяє використовувати його з метою нормалізації функціонального стану серцево-судинної та нервової систем за гіпергомоцистеїнемії, а також для покращення когнітивних функцій, зокрема після захворювання на COVID-19.

Simvastatin increases circulating endothelial progenitor cells and inhibits the formation of intracranial aneurysms in rats with diet-induced hyperhomocysteinemia

BACKGROUND AND PURPOSE

Endothelial dysfunction triggers early pathological changes in artery, leading to the formation of intracranial aneurysm (ICA). Increase in plasma homocysteine (Hcy) impairs endothelium and endothelial progenitor cells (EPCs) are critical in repairing damaged endothelium. The aim of this study was to assess the impact of simvastatin on ICA formation in rats with hyperhomocysteinemia (HHcy).

METHODS

ICAs were induced in Male Sprague-Dawley rats after surgical induction in the presence of HHcy induced by a high L-methionine diet with or without oral simvastatin treatment. The size and media thickness of ICAs were evaluated 2 months after aneurysm induction. EPCs and serum vascular endothelial grow factor (VEGF) were measured be flow cytometry and ELISA respectively. Plasma Hcy levels and expression of VEGF, endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS), matrix metalloproteinase-2 (MMP-2), and MMP-9 in aneurysmal walls were examined and correlated with ICA formation.

RESULTS

HHcy accelerates ICA formation and rats treated with simvastatin exhibited a significant increase in media thickness and a reduction in aneurysmal size. Simvastatin increased levels of circulating EPCs and decreased iNOS, MMP-2, MMP-9 and VEGF mRNA levels, while increased eNOS mRNA in aneurysmal tissue.

CONCLUSION

In a rat model, HHcy reduces circulating EPCs and accelerates ICA formation. Simvastatin treatment increases circulating EPCs and inhabits the formation of ICA. We have shown a close association among circulating EPCs, biochemical markers related to vascular remodeling and the formation of ICA.

Methionine Diet Evoked Hyperhomocysteinemia Causes Hippocampal Alterations, Metabolomics Plasma Changes and Behavioral Pattern in Wild Type Rats

L-methionine, an essential amino acid, plays a critical role in cell physiology. High intake and/or dysregulation in methionine (Met) metabolism results in accumulation of its intermediate(s) or breakdown products in plasma, including homocysteine (Hcy). High level of Hcy in plasma, hyperhomocysteinemia (hHcy), is considered to be an independent risk factor for cerebrovascular diseases, stroke and dementias. To evoke a mild hHcy in adult male Wistar rats we used an enriched Met diet at a dose of 2 g/kg of animal weight/day in duration of 4 weeks. The study contributes to the exploration of the impact of Met enriched diet inducing mild hHcy on nervous tissue by detecting the histo-morphological, metabolomic and behavioural alterations. We found an altered plasma metabolomic profile, modified spatial and learning memory acquisition as well as remarkable histo-morphological changes such as a decrease in neurons' vitality, alterations in the morphology of neurons in the selective vulnerable hippocampal CA 1 area of animals treated with Met enriched diet. Results of these approaches suggest that the mild hHcy alters plasma metabolome and behavioural and histo-morphological patterns in rats, likely due to the potential Met induced changes in "methylation index" of hippocampal brain area, which eventually aggravates the noxious effect of high methionine intake.

Homocysteine Level and Risk of Hemorrhage in Brain Arteriovenous Malformations

Objective

We aimed to investigate the risk factors associated with hemorrhage and clarify the relation of homocysteine (Hcy) with brain arteriovenous malformations (bAVMs).

Method

We retrospectively reviewed bAVM patients from Beijing Tiantan Hospital between January 2019 and December 2019. Clinical and laboratory variables were analyzed in enrolled patients with bAVMs. Potential predictors associated with hemorrhage were evaluated by logistic regression analysis.

Results

A total of 143 bAVM patients were identified in the study, including 69 unruptured and 74 ruptured cases. Patients with hemorrhage were less likely to have hyperhomocysteinemia (P = 0.023). Logistic regression analysis showed that increased maximum diameter of bAVM lesions (odds ratio (OR) 0.634, 95% confidence intervals (CI) 0.479-0.839; P = 0.001) and serum Hcy level (OR 0.956, 95% CI 0.920-0.993; P = 0.021) were associated with lower risk of hemorrhage in bAVMs.

Conclusion

The present study provided evidence regarding the association between serum Hcy and hemorrhage in patients with bAVMs. Higher Hcy level was correlated with a lower risk of rupture. Detection of factors for subsequent hemorrhage is necessary to develop therapeutic strategies for bAVMs preferably.

Endogenous animal models of intracranial aneurysm development: a review

The pathogenesis and natural history of intracranial aneurysm (IA) remains poorly understood. To this end, animal models with induced cerebral vessel lesions mimicking human aneurysms have provided the ability to greatly expand our understanding. In this review, we comprehensively searched the published literature to identify studies that endogenously induced IA formation in animals. Studies that constructed aneurysms (i.e., by surgically creating a sac) were excluded. From the eligible studies, we reported information including the animal species, method for aneurysm induction, aneurysm definitions, evaluation methods, aneurysm characteristics, formation rate, rupture rate, and time course. Between 1960 and 2019, 174 articles reported endogenous animal models of IA. The majority used flow modification, hypertension, and vessel wall weakening (i.e., elastase treatment) to induce IAs, primarily in rats and mice. Most studies utilized subjective or qualitative descriptions to define experimental aneurysms and histology to study them. In general, experimental IAs resembled the pathobiology of the human disease in terms of internal elastic lamina loss, medial layer degradation, and inflammatory cell infiltration. After the early 2000s, many endogenous animal models of IA began to incorporate state-of-the-art technology, such as gene expression profiling and 9.4-T magnetic resonance imaging (MRI) in vivo imaging, to quantitatively analyze the biological mechanisms of IA. Future studies aimed at longitudinally assessing IA pathobiology in models that incorporate aneurysm growth will likely have the largest impact on our understanding of the disease. We believe this will be aided by high-resolution, small animal, survival imaging, in situ live-cell imaging, and next-generation omics technology.

Effect of Methionine Diet on Time-Related Metabolic and Histopathological Changes of Rat Hippocampus in the Model of Global Brain Ischemia

Hyperhomocysteinemia (hHcy) represents a strong risk factor for atherosclerosis-associated diseases, like stroke, dementia or Alzheimer's disease. A methionine (Met)-rich diet leads to an elevated level of homocysteine in plasma and might cause pathological alterations across the brain. The hippocampus is being constantly studied for its selective vulnerability linked with neurodegeneration. This study explores metabolic and histo-morphological changes in the rat hippocampus after global ischemia in the hHcy conditions using a combination of proton magnetic resonance spectroscopy and magnetic resonance-volumetry as well as immunohistochemical analysis. After 4 weeks of a Met-enriched diet at a dose of 2 g/kg of animal weight/day, adult male Wistar rats underwent 4-vessel occlusion lasting for 15 min, followed by a reperfusion period varying from 3 to 7 days. Histo-morphological analyses showed that the subsequent ischemia-reperfusion insult (IRI) aggravates the extent of the sole hHcy-induced degeneration of the hippocampal neurons. Decreased volume in the grey matter, extensive changes in the metabolic ratio, deeper alterations in the number and morphology of neurons, astrocytes and their processes were demonstrated in the hippocampus 7 days post-ischemia in the hHcy animals. Our results suggest that the combination of the two risk factors (hHcy and IRI) endorses and exacerbates the rat hippocampal neurodegenerative processes.

Preclinical Intracranial Aneurysm Models: A Systematic Review

Intracranial aneurysms (IA) are characterized by weakened cerebral vessel walls that may lead to rupture and subarachnoid hemorrhage. The mechanisms behind their formation and progression are yet unclear and warrant preclinical studies. This systematic review aims to provide a comprehensive, systematic overview of available animal models for the study of IA pathobiology. We conducted a systematic literature search using the PubMed database to identify preclinical studies employing IA animal models. Suitable articles were selected based on predefined eligibility criteria following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Included studies were reviewed and categorized according to the experimental animal and aneurysm model. Of 4266 returned results, 3930 articles were excluded based on the title and/or abstract and further articles after screening the full text, leaving 123 studies for detailed analysis. A total of 20 different models were found in rats (nine), mice (five), rabbits (four), and dogs (two). Rat models constituted the most frequently employed intracranial experimental aneurysm model (79 studies), followed by mice (31 studies), rabbits (12 studies), and two studies in dogs. The most common techniques to induce cerebral aneurysms were surgical ligation of the common carotid artery with subsequent induction of hypertension by ligation of the renal arteries, followed by elastase-induced creation of IAs in combination with corticosterone- or angiotensin-induced hypertension. This review provides a comprehensive summary of the multitude of available IA models to study various aspects of aneurysm formation, growth, and rupture. It will serve as a useful reference for researchers by facilitating the selection of the most appropriate model and technique to answer their scientific question.

Effect of Methionine Diet on Metabolic and Histopathological Changes of Rat Hippocampus

Hyperhomocysteinemia (hHcy) is regarded as an independent and strong risk factor for cerebrovascular diseases, stroke, and dementias. The hippocampus has a crucial role in spatial navigation and memory processes and is being constantly studied for neurodegenerative disorders. We used a moderate methionine (Met) diet at a dose of 2 g/kg of animal weight/day in duration of four weeks to induce mild hHcy in adult male Wistar rats. A novel approach has been used to explore the hippocampal metabolic changes using proton magnetic resonance spectroscopy (1H MRS), involving a 7T MR scanner in combination with histochemical and immunofluorescence analysis. We found alterations in the metabolic profile, as well as remarkable histo-morphological changes such as an increase of hippocampal volume, alterations in number and morphology of astrocytes, neurons, and their processes in the selective vulnerable brain area of animals treated with a Met-enriched diet. Results of both methodologies suggest that the mild hHcy induced by Met-enriched diet alters volume, histo-morphological pattern, and metabolic profile of hippocampal brain area, which might eventually endorse the neurodegenerative processes.

Hyperhomocysteinemia and myocardial remodeling in the sand rat, Psammomys obesus

OBJECTIVE

Numerous studies have shown that a methionine-rich diet induces hyperhomocysteinemia (Hhcy), a risk factor for cardiovascular diseases. The objective of the present study was to determine the involvement of Hhcy in cardiac remodeling in the sand rat Psammomys obesus.

MATERIALS AND METHODS

An experimental Hhcy was induced, in the sand rat Psammomys obesus, by intraperitoneal injection of 300 mg/kg of body weight/day of methionine for 1 month. The impact of Hhcy on the cellular and matricial structures of the myocardium was analyzed with histological techniques (Masson trichrome and Sirius red staining). Immunohistochemistry allowed us to analyze several factors involved in myocardial remodeling, such as fibrillar collagen I and III, metalloproteases (MMP-2 and -9) and their inhibitors (TIMP-1 and -2), TGF-β1 and activated caspase 3.

RESULTS

Our results show that Hhcy induced by an excess of methionine causes, in the myocardium of Psammomys obesus, a significant accumulation of fibrillar collagens I and III at the interstitial and perivascular scales, indicating the appearance of fibrosis, which is associated with an immuno-expression increase of TGF-β1, MMP-9 and TIMP-2 and an immuno-expression decrease of MMP-2 and TIMP-1. Also, Hhcy induces apoptosis of some cardiomyocytes and cardiac fibroblasts by increasing of activated caspase 3 expression. These results highlight a remodeling of cardiac tissue in hyperhomocysteinemic Psammomys obesus.

Hyperhomocysteinemia as a Risk Factor for Saccular Intracranial Aneurysm: A Cohort Study in a Chinese Han Population

BACKGROUND

We evaluated the possible relationships between serum total homocysteine and folate and Vitamin B₁₂ in patients with intracranial aneurysm.

METHODS

We enrolled consecutive patients with intracranial aneurysm from the Han population who were admitted to the hospital, as well as control subjects who received medical examination on an outpatient basis. The serum total homocysteine, folate, and Vitamin B₁₂ levels were measured in patients with intracranial aneurysm and the control group, and the associations between those factors were analyzed using multivariate logistic analysis.

RESULTS

A total of 140 patients with intracranial aneurysm and 140 control subjects were enrolled from July 2014 to December 2015. The mean serum total homocysteine level in the patient group (19.98 ± 10.84 µmol/L) was significantly higher than that in the control group (15.13 ± 5.55 µmol/L, P < .001). The serum total homocysteine level was negatively correlated with folate and Vitamin B₁₂ levels (r = -.349, P < .001; r = -.531, P < .001, respectively) in the patient group. Homocysteine had an adjusted odds ratio of 2.196 (95% confidence interval: 1.188-4.057, P = .012) for the development of intracranial aneurysm.

CONCLUSIONS

The present study provides evidence regarding the association between serum total homocysteine and folate and Vitamin B₁₂ in patients with intracranial aneurysm. Hyperhomocysteinemia is an independent risk factor for intracranial aneurysm, and folate and Vitamin B₁₂ are protective against intracranial aneurysm due to their roles in regulating the metabolism of homocysteine.

Neuroprotective effects of pretreatment with quercetin as assessed by acetylcholinesterase assay and behavioral testing in poloxamer-407 induced hyperlipidemic rats

Hyperlipidemia is a group of disorders characterized by excessive lipids in the bloodstream. It is associated with the incidence of cardiovascular diseases and recognized as the most important factor underlying the occurrence of atherosclerosis. This study was conducted to investigate whether pretreatment with quercetin can protect against possible memory impairment and deterioration of the cholinergic system in hyperlipidemic rats. Animals were divided into ten groups (n=7): saline/control, saline/quercetin 5mg/kg, saline/quercetin 25mg/kg, saline/quercetin 50mg/kg, saline/simvastatin (0.04mg/kg), hyperlipidemia, hyperlipidemia/quercetin 5mg/kg, hyperlipidemia/quercetin 25mg/kg, hyperlipidemia/quercetin 50mg/kg and hyperlipidemia/simvastatin. The animals were pretreated with quercetin by oral gavage for a period of 30days and hyperlipidemia was subsequently induced by intraperitoneal administration of a single dose of 500mg/kg of poloxamer-407. Simvastatin was administered after the induction of hyperlipidemia. The results demonstrated that hyperlipidemic rats had memory impairment compared with the saline control group (P<0.001). However, pretreatment with quercetin and simvastatin treatment attenuated the damage caused by hyperlipidemia compared with the hyperlipidemic group (P<0.05). Acetylcholinesterase (AChE) activity in the cerebral hippocampus was significantly (P<0.001) reduced in the hyperlipidemic group compared with the control saline group. Pretreatment with quercetin and simvastatin treatment in the hyperlipidemic groups significantly (P<0.05) increased AChE activity compared with the hyperlipidemic group. Our results thus suggest that quercetin may prevent memory impairment, alter lipid metabolism, and modulate AChE activity in an experimental model of hyperlipidemia.

Hyperhomocysteinemia induced by excessive methionine intake promotes rupture of cerebral aneurysms in ovariectomized rats

Background

Hyperhomocysteinemia (HHcy) is associated with inflammation and a rise in the expression of matrix metalloproteinase-9 (MMP-9) in the vascular wall. However, the role of HHcy in the growth and rupture of cerebral aneurysms remains unclear.

Methods

Thirteen-week-old female Sprague-Dawley rats were subject to bilateral ovariectomy and ligation of the right common carotid artery and fed an 8 % high-salt diet to induce cerebral aneurysms. Two weeks later, they underwent ligation of the bilateral posterior renal arteries. They were divided into two groups and methionine (MET) was or was not added to their drinking water. In another set of experiments, the role of folic acid (FA) against cerebral aneurysms was assessed.

Results

During a 12-week observation period, subarachnoid hemorrhage due to aneurysm rupture was observed at the anterior communicating artery (AcomA) or the posterior half of the circle of Willis. HHcy induced by excessive MET intake significantly increased the incidence of ruptured aneurysms at 6–8 weeks. At the AcomA of rats treated with MET, we observed the promotion of aneurysmal growth and infiltration by M1 macrophages. Furthermore, the mRNA level of MMP-9, the ratio of MMP-9 to the tissue inhibitor of metalloproteinase-2, and the level of interleukin-6 were higher in these rats. Treatment with FA abolished the effect of MET, suggesting that the inflammatory response and vascular degradation at the AcomA is attributable to HHcy due to excessive MET intake.

Conclusions

We first demonstrate that in hypertensive ovariectomized rats, HHcy induced by excessive MET intake may be associated with the propensity of the aneurysm wall to rupture.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0634-3) contains supplementary material, which is available to authorized users.

Treatment of unruptured intracranial aneurysms: a review

INTRODUCTION

Unruptured brain aneurysms (UIAs) present a challenge due to the lack of definitive understanding of their natural history and treatment outcomes. As the treatment of UIAs is aimed at preventing the possibility of rupture, the immediate risk of treatment must be weighed against the risk of rupture in the future. As such, treatment for a large proportion of UIAs is currently individualized.

AREAS COVERED

In this article, we discuss the important natural history studies of UIAs and discuss the existing scientific evidence and recent advances that help identify the rupture risk guide management of UIAs. We also address the recent advances in pharmacological therapy of UIAs. Expert commentary: In the recent years, there have been great advances in understanding the pathophysiology of UIAs and determining the rupture risk going beyond the traditional parameter of aneurysm size. Aneurysm morphology and hemodynamics play a pivotal role in growth and rupture. A true randomized trial for the management of UIAs is the need of the hour.

High Methionine Diet Poses Cardiac Threat: A Molecular Insight

High methionine diet (HMD) for example red meat which includes lamb, beef, pork can pose cardiac threat and vascular dysfunction but the mechanisms are unclear. We hypothesize that a diet rich in methionine can malfunction the cardiovascular system in three ways: (1) by augmenting oxidative stress; (2) by inflammatory manifestations; and (3) by matrix/vascular remodeling. To test this hypothesis we used four groups of mice: (1) WT; (2) WT + methionine; (3) CBS(+/-) ; (4) CBS(+/-) +methionine. We observed high oxidative stress in mice fed with methionine which was even higher in CBS(+/-) and CBS(+/-) +methionine. Higher oxidative stress was indicated by high levels of SOD-1 in methionine fed mouse hearts whereas IL-1β, IL-6, TNFα, and TLR4 showed high inflammatory manifestations. The upregulated levels of eNOS/iNOS and upregulated levels of MMP2/MMP9 along with high collagen deposition indicated vascular and matrix remodeling in methionine fed mouse. We evaluated the cardiac function which was dysregulated in the mice fed with HMD. These mice had decreased ejection fraction and left ventricular dysfunction which subsequently leads to adverse cardiac remodeling. In conclusion, our study clearly shows that HMD poses a cardiac threat by increasing oxidative stress, inflammatory manifestations, matrix/vascular remodeling, and decreased cardiac function.

Brachial artery aneurysm accompanying a homozygous methylenetetrahydrofolate reductase mutation

Elevated plasma homocysteine (Hcy) is one of the suggested risk factors for endothelial dysfunction. There is evidence of association between raised plasma Hcy and an increased risk of developing peripheral arterial disease. A causal relationship, however, has not been established. In this report, a 37-year old male patient with the complaints of intermittent hand pain is presented. Brachial artery aneurysm accompanying a homozygous methylenetetrahydrofolate reductase mutation was detected.

The potential role of homocysteine mediated DNA methylation and associated epigenetic changes in abdominal aortic aneurysm formation

Previous studies have suggested that homocysteine (Hcy) has wide-ranging biological effects, including accelerating atherosclerosis, impairing post injury endothelial repair and function, deregulating lipid metabolism and inducing thrombosis. However, the biochemical basis by which hyperhomocysteinemia (HHcy) contributes to cardiovascular diseases (CVDs) remains largely unknown. Several case-control studies have reported an association between HHcy and the presence of abdominal aortic aneurysms (AAA) and there are supportive data from animal models. Genotypic data concerning the association between variants of genes involved in the methionine cycle and AAA are conflicting probably due to problems such as reverse causality and confounding. The multifactorial nature of AAA suggests the involvement of additional epigenetic factors in disease formation. Elevated Hcy levels have been previously linked to altered DNA methylation levels in various diseases. Folate or vitamin B12 based methods of lowering Hcy have had disappointingly limited effects in reducing CVD events. One possible reason for the limited efficacy of such therapy is that they have failed to reverse epigenetic changes induced by HHcy. It is possible that individuals with HHcy have an "Hcy memory effect" due to epigenetic alterations which continue to promote progression of cardiovascular complications even after Hcy levels are lowered. It is possible that deleterious effect of prior, extended exposure to elevated Hcy concentrations have long-lasting effects on target organs and genes, hence underestimating the benefit of Hcy lowering therapies in CVD patients. Therapies targeting the epigenetic machinery as well as lowering circulating Hcy concentrations may have a more efficacious effect in reducing the incidence of cardiovascular complications.

Salutary effect of NFκB inhibitor and folacin in hyperhomocysteinemia-hyperlipidemia induced vascular dementia

Dementia of vascular origin or vascular dementia (VaD) is considered as the second commonest form of dementia after Alzheimer's disease (AD). In the last ten years various researchers have reported a strong association of hyperhomocysteinemia (HHcy), hyperlipidemia (HL) and dementia. This study investigates the salutary effect of natrium diethyl dithio carbamate trihydrate (NDDCT), a nuclear factor-kappaB (NF-κB) inhibitor as well as folacin (Vitamin-B(9)) in HHcy-HL induced VaD. l-methionone was used to induce HHcy-HL and associated VaD. Morris water-maze (MWM) was used for testing learning and memory. Vascular system assessment was done by testing endothelial function. Biochemical estimations were performed to assess HHcy (serum homocysteine), HL (serum cholesterol), oxidative stress (aortic superoxide anion, serum and brain thiobarbituric acid reactive species and brain glutathione), nitric oxide levels (serum nitrite/nitrate) and cholinergic activity (brain acetyl cholinesterase activity). L-methionine treated animals have shown HHcy-HL, endothelial dysfunction, impairment of learning, memory, reduction in serum nitrite/nitrate levels and brain glutathione (GSH) along with increase in serum and brain thiobarbituric acid reactive species (TBARS), and brain acetylcholinesterase activity. NDDCT, folacin and donepezil (positive control) significantly improved HHcy-HL induced impairment of learning, memory, endothelial dysfunction, and changes in various biochemical parameters. l-methionine induced HHcy-HL has caused VaD development in rats. NFκ-B inhibitors and folacin may be considered as potential agents for the management of HHcy-HL induced VaD.