Notable epigenetic role of hyperhomocysteinemia in atherogenesis

Association of Serum Homocysteine With Peripheral Arterial Disease in Patients Without Diabetes: A Study Based on National Health and Nutrition Examination Survey Database

This study aimed to investigate the association of serum homocysteine (Hcy) levels with peripheral arterial disease (PAD) in patients without diabetes on the basis of data from the National Health and Nutrition Examination Survey. The study used data from 3 survey cycles (1999 to 2004) in the National Health and Nutrition Examination Survey database as the research dataset. Serum Hcy levels were considered an independent variable, whereas PAD was a dependent variable. Weighted logistic regression and restricted cubic spline methods were used to explore the relation between Hcy level and PAD risk in patients without diabetes. A total of 4,819 samples were included. In the weighted logistics regression model, a significant positive association was observed between Hcy levels and the risk of PAD (odds ratio >1, p <0.05). Subgroup analysis results indicated a particularly significant association between Hcy levels and PAD risk in the older population (age ≥60 years), those with a history of smoking, and those without a history of myocardial infarction (all odds ratio >1, p <0.05) (p <0.05). Exploring the nonlinear association between Hcy levels and PAD risk through restricted cubic spline curves revealed an overall significant trend (p allover <0.05). In conclusion, elevated Hcy levels increased the risk of PAD, with a more pronounced effect observed in populations of patients without diabetes, especially in older patients (age ≥60 years), those with smoking history, and those without a history of myocardial infarction.

Advances in the role of epigenetics in homocysteine-related diseases

Homocysteine has a wide range of biological effects. However, the specific molecular mechanism of its pathogenicity is still unclear. The diseases induced by hyperhomocysteinemia (HHcy) are called homocysteine-related diseases. Clinical treatment of HHcy is mainly through folic acid and B-complex vitamins, which are not effective in reducing the associated end point events. Epigenetics is the alteration of heritable genes caused by DNA methylation, histone modification, noncoding RNAs and chromatin remodeling without altering the DNA sequence. In recent years the role of epigenetics in homocysteine-associated diseases has been gradually discovered. This article summarizes the latest evidence on the role of epigenetics in HHcy, providing new directions for its prevention and treatment.

Targeting Homocysteine and Hydrogen Sulfide Balance as Future Therapeutics in Cancer Treatment

A high level of homocysteine (Hcy) is associated with oxidative/ER stress, apoptosis, and impairment of angiogenesis, whereas hydrogen sulfide (H2S) has been found to reverse this condition. Recent studies have shown that cancer cells need to produce a high level of endogenous H2S to maintain cell proliferation, growth, viability, and migration. However, any novel mechanism that targets this balance of Hcy and H2S production has yet to be discovered or exploited. Cells require homocysteine metabolism via the methionine cycle for nucleotide synthesis, methylation, and reductive metabolism, and this pathway supports the high proliferative rate of cancer cells. Although the methionine cycle favors cancer cells for their survival and growth, this metabolism produces a massive amount of toxic Hcy that somehow cancer cells handle very well. Recently, research showed specific pathways important for balancing the antioxidative defense through H2S production in cancer cells. This review discusses the relationship between Hcy metabolism and the antiapoptotic, antioxidative, anti-inflammatory, and angiogenic effects of H2S in different cancer types. It also summarizes the historical understanding of targeting antioxidative defense systems, angiogenesis, and other protective mechanisms of cancer cells and the role of H2S production in the genesis, progression, and metastasis of cancer. This review defines a nexus of diet and precision medicine in targeting the delicate antioxidative system of cancer and explores possible future therapeutics that could exploit the Hcy and H2S balance.

Hyperhomocysteinemia in men and women of married couples with reproductive disorders. What is the difference?

Hyperhomocysteinemia (HHcy) is an autosomal recessive inherited metabolic disease caused by variations in folate metabolism genes, characterized by impaired methionine metabolism and accumulation of homocysteine (Hcy) in the blood serum. It was shown that men usually have higher plasma Hcy levels than women, but have not yet assessed the leading factors of these differences, which is important for the development of personalized protocols for the prevention of folate metabolism disorders in couples with reproductive disorders. This study aimed to analyze the effect of intergenic and gene-factor interactions on the risk of developing HHcy in men and women of married couples with reproductive disorders. In our study were involved 206 married Caucasian couples (206 males and 206 females) from central regions of Ukraine with early pregnancy losses in the anamnesis. We found that the incidence of HHcy in men was significantly higher than in women. Gender differences in folic acid and vitamin B12 levels were identified. The best predictors of HHcy in men (MTRR (A66G), MTHFR (C677T), MTR (A2756G), vitamin B12 level) and in women (MTHFR (C677T), MTR (A2756G), vitamin B12 level) were selected by binary logistic regression. There was no significant difference in the distribution of genotypes by the studied gene variants when comparing men and women with HHcy. Our findings demonstrate that there is a gender difference in the development of HHcy. This difference is caused by intergenic interaction and by environmental factors, in particular, nutrition and vitamins consumption.

Association of serum VLDL level with hyperhomocysteinemia in hypertensive patients: A cross-sectional study

BACKGROUND

Increasing evidence suggests that hyperhomocysteinemia (HHcy) and hyperlipidemia have been recognized as two independent risks for cardiovascular disease. However, the association between hyperlipidemia and HHcy in hypertensive patients has not been systemically elucidated. The aim of this study was to investigate the relation between very low-density lipoprotein (VLDL) and HHcy in hypertensive patients.

METHODS

From July 2013 to March 2014, a large cross-sectional study was performed using 4012 participants from urban and rural communities in Hunan province, China. Participants underwent accurate assessment of lipid profiles, homocysteine (Hcy), anthropometric, blood pressure, and other biochemical indicators.

RESULTS

Among 1257 participants with hypertension, 626 (49.80%) were men and 631 (50.20%) were women. In total, 1081 (86.00%) of the participants were found to have HHcy, of which 559 (44.47%) were men and 522 (41.53%) were women. In the univariate analysis, the OR for patients with hypertension associated with hyperhomocysteinemia was significantly enhanced as the quartiles of the Log VLDL were increased. OR for quartile 4 was significantly higher than that for quartile 1 (OR = 3.7, 95% CI: 2.6-5.1; P< .001). Additional adjustment for the confounding variables did not reduce the ORs for the association between the Log VLDL and hypertension associated with hyperhomocysteinemia (OR = 3.8, 95% CI: 2.7-5.5; P< .001; OR = 4.3, 95% CI: 1.6-11.8; P= .004, respectively). We also conducted analyses with Log VLDL as a continuous variable. Each unit increase in the Log VLDL was associated with the 1.3-fold increased risk of hypertension associated with hyperhomocysteinemia (95% CI: 1.9-2.9; P< .001). Adjusting for Cr, TG, TC, and HDL did not affect the relationship.

CONCLUSIONS

Our data indicate that the Log VLDL concentrations appear to be an independent contributor to hypertension associated with hyperhomocysteinemia, even after adjusting for age and other covariables. The utility of the Log VLDL as a diagnostic, prognostic, and therapeutic indicator for the disease warrants further investigation.

ABBREVIATIONS

HHcy: hyperhomocysteinemia; Hcy: homocysteine; VLDL: very low-density lipoprotein; CVD: cardiovascular disease; SBP: systolic blood pressure; DBP: diastolic blood pressure; BMI: body mass index; ALT: alanine aminotransferase; Cr: creatinine; UA: uric acid; TG: triglycerides; TC: total cholesterol; HDL: high-density lipoprotein; LDL: low-density lipoprotein; FBG: fasting blood glucose; CRP: C-reactive protein; MTHFR: methylene tetrahydrofolate reductase; NO: nitric oxide; HDL-C: high-density lipoprotein cholesterol.

Altered circadian dynamics of Per2 after cystathionine-β-synthase and/or cystathionine-γ-lyase pharmacological inhibition in serum-shocked NIH-3T3 cells

Circadian clock genes are found in almost every cell that has a nucleus; they regulate the rhythmic nature of all processes that are cyclical. Among the genes controlled by the circadian clock, there are numerous factors that regulate key processes in the functioning of the cell. Disturbances in the functioning of the circadian clock are associated with numerous disorders. A recent study has shown the key role of H₂S in regulating circadian rhythm. In this study, we investigated the in vitro effect of pharmacological inhibition of cystathionine-β-synthase (CBS) and/or cystathionine-γ-lyase (CSE) on the circadian dynamics of Per2 expression in serum-shocked NIH-3T3 cells. Alternatively, Cbs and Cse were knocked down by transfection with siRNA. The 48-h treatment of serum-shocked NIH-3T3 cells with 1 mM dl-propargylglycine (PAG), a specific CSE inhibitor, significantly decreased the amplitude and baseline expression of Per2. During exposure to an effective CBS and CSE inhibitor (aminooxyacetic acid [AOAA]), the amplitude of oscillation and baseline expression of Per2 significantly increased. Incubation of NIH-3T3 cells with both inhibitors also significantly increased the amplitude and baseline expression of Per2 messenger RNA (mRNA). siCbs or siCse knockdowan significantly reduced the baseline and amplitude of oscillation of Per2. In conclusion, we showed that CBS/CSE/H₂S pathway participates in the regulation of the circadian clock system. PAG and AOAA, change the general expression and dynamics of Per2 genes, but the increase of amplitude and overall Per2 mRNA level due to exposure to AOAA is probably caused by factors other than CBS and CSE activity.

Activation of arginase II by asymmetric dimethylarginine and homocysteine in hypertensive rats induced by hypoxia: a new model of nitric oxide synthesis regulation in hypertensive processes?

In recent years, the increase in blood pressure at high altitudes has become an interesting topic among high-altitude researchers. In our animal studies using Wistar rats, we observed the existence of two rat populations that exhibit differential physiological responses during hypoxic exposure. These rats were classified as hypoxia-induced hypertensive rats and nonhypertensive rats. A decrease in nitric oxide levels was reported in different hypertension models associated with increased concentrations of asymmetric dimethylarginine (ADMA) and homocysteine, and we recently described an increase in arginase type II expression under hypoxia. ADMA and homocysteine decrease nitric oxide (NO) bioavailability; however, whether ADMA and homocysteine have a regulatory effect on arginase activity and therefore regulate another NO synthesis pathway is unknown. Therefore, the aim of this study was to measure basal ADMA and homocysteine levels in hypoxia-induced hypertensive rats and evaluate their effect on arginase II activity. Our results indicate that hypoxia-induced hypertensive rats presented lower nitric oxide concentrations than nonhypertensive rats, associated with higher concentrations of homocysteine and ADMA. Hypoxia-induced hypertensive rats also presented lower dimethylarginine dimethylaminohydrolase-2 and cystathionine β-synthase levels, which could explain the high ADMA and homocysteine levels. In addition, we observed that both homocysteine and ADMA had a significant effect on arginase II activation in the hypertensive rats. Therefore, we suggest that ADMA and homocysteine have dual regulatory effects on NO synthesis. The former has an inhibitory effect on eNOS, and the latter has a secondary activating effect on arginase II. We propose that arginase II is activated by AMDA and homocysteine in hypoxia-induced hypertensive rats.

Hydrogen Sulfide Alleviates Anxiety, Motor, and Cognitive Dysfunctions in Rats with Maternal Hyperhomocysteinemia via Mitigation of Oxidative Stress

Hydrogen sulfide (H₂S) is endogenously produced from sulfur containing amino acids, including homocysteine and exerts neuroprotective effects. An increase of homocysteine during pregnancy impairs fetal growth and development of the offspring due to severe oxidative stress. We analyzed the effects of the H₂S donor—sodium hydrosulfide (NaHS) administered to female rats with hyperhomocysteinemia (hHcy) on behavioral impairments and levels of oxidative stress of their offspring. Rats born from females fed with control or high methionine diet, with or without H₂S donor injections were investigated. Rats with maternal hHcy exhibit increased levels of total locomotor activity and anxiety, decreased muscle endurance and motor coordination, abnormalities of fine motor control, as well as reduced spatial memory and learning. Oxidative stress in brain tissues measured by activity of glutathione peroxidases and the level of malondialdehyde was higher in rats with maternal hHcy. Concentrations of H₂S and the activity and expression of the H₂S generating enzyme—cystathionine-beta synthase—were lower compared to the control group. Administration of the H₂S donor to females with hHcy during pregnancy prevented behavioral alterations and oxidative stress of their offspring. The acquisition of behavioral together with biochemical studies will add to our knowledge about homocysteine neurotoxicity and proposes H₂S as a potential agent for therapy of hHcy associated disorders.

Administration of metformin alleviates atherosclerosis by promoting H2S production via regulating CSE expression

The therapeutic effect of metformin (Met) on atherosclerosis was studied here. Effects of methionine and Met on the induction of inflammatory response and H₂ S expression in peritoneal macrophages were evaluated. Enzyme-linked immunosorbent assay, immunohistochemistry assay, western blot, and quantitative reverse transcription polymerase chain reaction were conducted to observe the levels of cystathionine γ-lyase (CSE), DNA methyltransferases 1 (DNMT1), DNMT3a, DNMT3b, tumor necrosis factor (TNF- α), interleukin 1b (IL-1β), and hydrogen sulfide (H ₂ S). Luciferase and bisulfite sequencing assays were also utilized to evaluate the CSE promoter activity as well as the methylation status of CSE in transfected cells. Methionine significantly elevated Hcy, TNF-a, H ₂ S, and IL-1β expression while decreasing the level of CSE in C57BL/6 mice. In contrary, co-treatment with Methionine and Met reduced the detrimental effect of Methionine. Homocysteine (Hcy) decreased H ₂ S expression while promoting the synthesis of IL-1β and TNF-α in THP-1 and raw264.7 cells. Treatment of THP-1 and raw264.7 cells with methionine and Met reduced the activity of methionine in dose dependently. Moreover, Hcy increased the expression of DNMT and elevated the level of methylation in the CSE promoter, whereas the co-treatment with methionine and Met attenuated the effects of Hcy. Methionine significantly decreased plasma level of CSE while increasing the severity of inflammatory responses and plasma level of Hcy, which in turn suppressed H ₂ S synthesis and enhanced DNA hypermethylation of CSE promoter to promote the pathogenesis of atherosclerosis. In contrary, co-treatment with methionine and Met reduced the detrimental effect of methionine.

Dysregulation of Epigenetic Mechanisms of Gene Expression in the Pathologies of Hyperhomocysteinemia

Hyperhomocysteinemia (HHcy) exerts a wide range of biological effects and is associated with a number of diseases, including cardiovascular disease, dementia, neural tube defects, and cancer. Although mechanisms of HHcy toxicity are not fully uncovered, there has been a significant progress in their understanding. The picture emerging from the studies of homocysteine (Hcy) metabolism and pathophysiology is a complex one, as Hcy and its metabolites affect biomolecules and processes in a tissue- and sex-specific manner. Because of their connection to one carbon metabolism and editing mechanisms in protein biosynthesis, Hcy and its metabolites impair epigenetic control of gene expression mediated by DNA methylation, histone modifications, and non-coding RNA, which underlies the pathology of human disease. In this review we summarize the recent evidence showing that epigenetic dysregulation of gene expression, mediated by changes in DNA methylation and histone N-homocysteinylation, is a pathogenic consequence of HHcy in many human diseases. These findings provide new insights into the mechanisms of human disease induced by Hcy and its metabolites, and suggest therapeutic targets for the prevention and/or treatment.

Targeting epigenetics and non-coding RNAs in atherosclerosis: from mechanisms to therapeutics

Atherosclerosis, the principal cause of cardiovascular death worldwide, is a pathological disease characterized by fibro-proliferation, chronic inflammation, lipid accumulation, and immune disorder in the vessel wall. As the atheromatous plaques develop into advanced stage, the vulnerable plaques are prone to rupture, which causes acute cardiovascular events, including ischemic stroke and myocardial infarction. Emerging evidence has suggested that atherosclerosis is also an epigenetic disease with the interplay of multiple epigenetic mechanisms. The epigenetic basis of atherosclerosis has transformed our knowledge of epigenetics from an important biological phenomenon to a burgeoning field in cardiovascular research. Here, we provide a systematic and up-to-date overview of the current knowledge of three distinct but interrelated epigenetic processes (including DNA methylation, histone methylation/acetylation, and non-coding RNAs), in atherosclerotic plaque development and instability. Mechanistic and conceptual advances in understanding the biological roles of various epigenetic modifiers in regulating gene expression and functions of endothelial cells (vascular homeostasis, leukocyte adhesion, endothelial-mesenchymal transition, angiogenesis, and mechanotransduction), smooth muscle cells (proliferation, migration, inflammation, hypertrophy, and phenotypic switch), and macrophages (differentiation, inflammation, foam cell formation, and polarization) are discussed. The inherently dynamic nature and reversibility of epigenetic regulation, enables the possibility of epigenetic therapy by targeting epigenetic "writers", "readers", and "erasers". Several Food Drug Administration-approved small-molecule epigenetic drugs show promise in pre-clinical studies for the treatment of atherosclerosis. Finally, we discuss potential therapeutic implications and challenges for future research involving cardiovascular epigenetics, with an aim to provide a translational perspective for identifying novel biomarkers of atherosclerosis, and transforming precision cardiovascular research and disease therapy in modern era of epigenetics.

Association of homocysteine with body mass index, blood pressure, HbA1c and duration of diabetes in type 2 diabetics

Objective

To determine the Homocysteine levels in type 2 diabetics and correlate homocysteine with HbA1c levels, BMI, blood pressure and duration of diabetes.

Methods

This cross-sectional study was conducted in Endocrinology Unit of Hayatabad Medical Complex (HMC) Peshawar and Rehman Medical Institute (RMI) Peshawar over a period of six months from July 2015 to December 2015. Data was recorded and analyzed in SPSS v 20. P value of less than 0.05 was taken as significant. Bivariate Pearson's correlation test was used to see the relationship between homocysteine and BMI, systolic BP and duration of diabetes.

Results

One hundred twenty five patients were included in our study in which female were 68% and 32% were male with mean age of 51.45 ±8.37 years. Mean BMI expressed in kg/m² was 28.71±4.76, mean systolic blood pressure was 130±20.98 mmHg, mean diastolic blood pressure was 83.36±11.28 mmHg and mean duration of diabetes was 7.018± 6.18 years. Significant correlation was found between systolic blood pressure (r: 0.239, p: 0.007) and duration of diabetes with homocysteine (r: 0.302, p: 0.001). The correlation of homocysteine with HbA1c and BMI was not significant.

Conclusion

Systolic blood pressure and duration of diabetes showed a significant positive correlation with homocysteine. The correlation of homocysteine with HbA1c was not certain from researcher's point of view and further studies of larger sample size and longer duration must be conducted to ascertain the association between the two variables.

Maternal One-Carbon Metabolism and Infant DNA Methylation between Contrasting Seasonal Environments: A Case Study from The Gambia

Background

The periconceptional period is a time in which environmentally induced changes to the epigenome could have significant consequences for offspring health. Metastable epialleles (MEs) are genomic loci demonstrating interindividual variation in DNA methylation with intraindividual crosstissue correlation, suggesting that methylation states are established in the very early embryo before gastrulation. In our previous Gambian studies, we have shown that ME methylation states in the offspring are predicted by maternal concentrations of certain nutritional biomarkers around the time of conception.

Objective

We aimed to assess whether the profile of maternal biomarker predictors of offspring methylation differs between rainy and dry seasons in a population of rural Gambians, using a larger set of 50 recently identified MEs.

Methods

We measured 1-carbon biomarkers in maternal plasma back-extrapolated to conception, and cytosine-phosphate-guanine (CpG) methylation at 50 ME loci in their infants’ blood at a mean age of 3.3 mo (n = 120 mother-child pairs). We tested for interactions between seasonality and effects of biomarker concentrations on mean ME methylation z score. We used backward stepwise linear regression to select the profile of nutritional predictors of methylation in each season and repeated this analysis with biomarker principal components (PCs) to capture biomarker covariation.

Results

We found preliminary evidence of seasonal differences in biomarker-methylation associations for folate, choline, and homocysteine (interaction P values ≤0.03). Furthermore, in stratified analyses, biomarker predictors of methylation changed between seasons. In the dry season, vitamin B-2 and methionine were positive predictors. In the rainy season, however, choline and vitamin B-6 were positive predictors, and folate and vitamin B-12 were negative predictors. PC1 captured covariation in the folate metabolism cycle and predicted methylation in dry season conceptions. PC2 represented the betaine remethylation pathway and predicted rainy season methylation.

Conclusions

Underlying nutritional status may modify the association between nutritional biomarkers and methylation, and should be considered in future studies.

Cystathionine β-Synthase in Physiology and Cancer

Cystathionine β-synthase (CBS) regulates homocysteine metabolism and contributes to hydrogen sulfide (H₂S) biosynthesis through which it plays multifunctional roles in the regulation of cellular energetics, redox status, DNA methylation, and protein modification. Inactivating mutations in CBS contribute to the pathogenesis of the autosomal recessive disease CBS-deficient homocystinuria. Recent studies demonstrating that CBS promotes colon and ovarian cancer growth in preclinical models highlight a newly identified oncogenic role for CBS. On the contrary, tumor-suppressive effects of CBS have been reported in other cancer types, suggesting context-dependent roles of CBS in tumor growth and progression. Here, we review the physiological functions of CBS, summarize the complexities regarding CBS research in oncology, and discuss the potential of CBS and its key metabolites, including homocysteine and H₂S, as potential biomarkers for cancer diagnosis or therapeutic targets for cancer treatment.

Epigenetic modifications in hyperhomocysteinemia: potential role in diabetic retinopathy and age-related macular degeneration

To study Hyperhomocysteinemia (HHcy)-induced epigenetic modifications as potential mechanisms of blood retinal barrier (BRB) dysfunction, retinas isolated from three- week-old mice with elevated level of Homocysteine (Hcy) due to lack of the enzyme cystathionine β-synthase (cbs^-/- , cbs^+/- and cbs^+/+ ), human retinal endothelial cells (HRECs), and human retinal pigmented epithelial cells (ARPE-19) treated with or without Hcy were evaluated for (1) histone deacetylases (HDAC), (2) DNA methylation (DNMT), and (3) miRNA analysis. Differentially expressed miRNAs in mice with HHcy were further compared with miRNA analysis of diabetic mice retinas (STZ) and miRNAs within the exosomes released from Hcy-treated RPEs. Differentially expressed miRNAs were further evaluated for predicted target genes and associated pathways using Ingenuity Pathway Analysis. HHcy significantly increased HDAC and DNMT activity in HRECs, ARPE-19, and cbs mice retinas, whereas inhibition of HDAC and DNMT decreased Hcy-induced BRB dysfunction. MiRNA profiling detected 127 miRNAs in cbs^+/- and 39 miRNAs in cbs^-/- mice retinas, which were significantly differentially expressed compared to cbs^+/+ . MiRNA pathway analysis showed their involvement in HDAC and DNMT activation, endoplasmic reticulum (ER), and oxidative stresses, inflammation, hypoxia, and angiogenesis pathways. Hcy-induced epigenetic modifications may be involved in retinopathies associated with HHcy, such as age-related macular degeneration and diabetic retinopathy.

Endothelial Cell Metabolism

Endothelial cells (ECs) are more than inert blood vessel lining material. Instead, they are active players in the formation of new blood vessels (angiogenesis) both in health and (life-threatening) diseases. Recently, a new concept arose by which EC metabolism drives angiogenesis in parallel to well-established angiogenic growth factors (e.g., vascular endothelial growth factor). 6-Phosphofructo-2-kinase/fructose-2,6-bisphosphatase-3-driven glycolysis generates energy to sustain competitive behavior of the ECs at the tip of a growing vessel sprout, whereas carnitine palmitoyltransferase 1a-controlled fatty acid oxidation regulates nucleotide synthesis and proliferation of ECs in the stalk of the sprout. To maintain vascular homeostasis, ECs rely on an intricate metabolic wiring characterized by intracellular compartmentalization, use metabolites for epigenetic regulation of EC subtype differentiation, crosstalk through metabolite release with other cell types, and exhibit EC subtype-specific metabolic traits. Importantly, maladaptation of EC metabolism contributes to vascular disorders, through EC dysfunction or excess angiogenesis, and presents new opportunities for anti-angiogenic strategies. Here we provide a comprehensive overview of established as well as newly uncovered aspects of EC metabolism.

Identification of differentially methylated BRCA1 and CRISP2 DNA regions as blood surrogate markers for cardiovascular disease

Genome-wide Illumina InfiniumMethylation 450 K DNA methylation analysis was performed on blood samples from clinical atherosclerosis patients (n = 8) and healthy donors (n = 8) in the LVAD study (NCT02174133, NCT01799005). Multiple differentially methylated regions (DMR) could be identified in atherosclerosis patients, related to epigenetic control of cell adhesion, chemotaxis, cytoskeletal reorganisations, cell proliferation, cell death, estrogen receptor pathways and phagocytic immune responses. Furthermore, a subset of 34 DMRs related to impaired oxidative stress, DNA repair, and inflammatory pathways could be replicated in an independent cohort study of donor-matched healthy and atherosclerotic human aorta tissue (n = 15) and human carotid plaque samples (n = 19). Upon integrated network analysis, BRCA1 and CRISP2 DMRs were identified as most central disease-associated DNA methylation biomarkers. Differentially methylated BRCA1 and CRISP2 regions were verified by MassARRAY Epityper and pyrosequencing assays and could be further replicated in blood, aorta tissue and carotid plaque material of atherosclerosis patients. Moreover, methylation changes at BRCA1 and CRISP2 specific CpG sites were consistently associated with subclinical atherosclerosis measures (coronary calcium score and carotid intima media thickness) in an independent sample cohort of middle-aged men with subclinical cardiovascular disease in the Aragon Workers’ Health Study (n = 24). Altogether, BRCA1 and CRISP2 DMRs hold promise as novel blood surrogate markers for early risk stratification and CVD prevention.

Vitamin D, Homocysteine, and Folate in Subcortical Vascular Dementia and Alzheimer Dementia

Dementia is a worldwide health problem which affects millions of patients; Alzheimer's disease (AD) and subcortical vascular dementia (sVAD) are the two most frequent forms of its presentation. As no definite therapeutic options have been discovered, different risk factors for cognitive impairment have been searched for potential therapies. This report focuses on the possible evidence that vitamin D deficiency and hyper-homocysteinemia can be considered as two important factors for the development or the progression of neurodegenerative or vascular pathologies. To this end, we assessed: the difference in vascular risk factors and vitamin D-OH25 levels among groups of sVAD, AD, and healthy age-matched controls; the association of folate, B12, homocysteine, and vitamin D with sVAD/AD and whether a deficiency of vitamin D and an increment in homocysteine levels may be related to neurodegenerative or vessel damages. The commonly-considered vascular risk factors were collected in 543 patients and compared with those obtained from a healthy old volunteer population. ANOVA group comparison showed that vitamin D deficiency was present in demented cases, as well as low levels of folate and high levels of homocysteine, more pronounced in sVAD cases. The statistical models we employed, with regression models built, and adjustments for biochemical, demographic and neuropsychiatric scores, confirmed the association between the three measures (folate decrease, hyperhomocysteinemia and vitamin D decrease) and dementia, more pronounced in sVAD than in AD.

Hypermethylation: Causes and Consequences in Skeletal Muscle Myopathy

A detrimental consequence of hypermethylation is hyperhomocysteinemia (HHcy), that causes oxidative stress, inflammation, and matrix degradation, which leads to multi-pathology in different organs. Although, it is well known that hypermethylation leads to overall gene silencing and hypomethylation leads to overall gene activation, the role of such process in skeletal muscle dysfunction during HHcy condition is unclear. In this study, we emphasized the multiple mechanisms including epigenetic alteration by which HHcy causes skeletal muscle myopathy. This review also highlights possible role of methylation, histone modification, and RNA interference in skeletal muscle dysfunction during HHcy condition and potential therapeutic molecules, putative challenges, and methodologies to deal with HHcy mediated skeletal muscle dysfunction. We also highlighted that B vitamins (mainly B12 and B6), with folic acid supplementation, could be useful as an adjuvant therapy to reverse these consequences associated with this HHcy conditions in skeletal muscle. However, we would recommend to further study involving long-term trials could help to assess efficacy of the use of these therapeutic agents. J. Cell. Biochem. 118: 2108-2117, 2017. © 2017 Wiley Periodicals, Inc.

Variable Methylation Potential in Preterm Placenta: Implication for Epigenetic Programming of the Offspring

Children born preterm are reported to be at increased risk of developing noncommunicable diseases in later life. Altered placental DNA methylation patterns are implicated in fetal programming of adult diseases. Our earlier animal studies focus on micronutrients (folic acid, vitamin B₁₂) and long-chain polyunsaturated fatty acids (LCPUFAs) that interact in the 1 carbon cycle, thereby influencing methylation reactions. Our previous studies in women delivering preterm show altered plasma levels of micronutrients and lower plasma LCPUFA levels. We postulate that alterations in the micronutrient metabolism may affect the regulation of enzymes, methionine adenosyltransferase ( MAT2A), and SAH-hydrolase ( AHCY), involved in the production of methyl donor S-adenosylmethionine (SAM), thereby influencing the methylation potential (MP) in the placenta of women delivering preterm. The present study, therefore, examines the mRNA, protein levels of enzymes ( MAT2A and AHCY), SAM, S-adenosylhomocysteine (SAH) levels, and global DNA methylation levels from preterm (n = 73) and term (n = 73) placentae. The enzyme messenger RNA (mRNA) levels were analyzed by real-time quantitative polymerase chain reaction, protein levels by enzyme-linked immunosorbent assay, and SAM-SAH levels by high-performance liquid chromatography. The mRNA levels for MAT2A and AHCY are higher ( P < .05 for both) in the preterm group as compared to the term group. S-Adenosylmethionine and SAH levels were similar in both groups, although SAM:SAH ratio was lower ( P < .05) in the preterm group as compared to the term group. The global DNA methylation levels were higher ( P < .05) in women delivering small for gestation age infants as compared to women delivering appropriate for gestation age infants at term. Our data showing lower MP in the preterm placenta may have implications for the epigenetic programming of the developing fetus.

Association of High Homocysteine Levels With the Risk Stratification in Hypertensive Patients at Risk of Stroke

PURPOSE

We aimed to investigate the association between stroke morbidity and different stratifications of classic risk factors, such as increasing age, body mass index (BMI), blood lipids, and blood glucose, in hypertensive patients with high homocysteine levels.

METHODS

A cross-sectional study of 2258 patients with primary hypertension were enrolled in this study, including 871 stroke cases (62.89%) in 1385 hypertensive patients without hyperhomocysteinemia (HHcy) and 647 (74.11%) stroke cases in 873 hypertensive patients with HHcy. Basic information of patients were collected, including age, sex, height, weight, smoking, alcohol consumption, and disease history. Blood chemical assays were performed to determine the levels of glucose, triglycerides, high-density lipoprotein cholesterol (HDL-C), total cholesterol, and homocysteine. Subsequently, comparison of stroke morbidity between the 2 groups was performed after the stratification of risk factors. Moreover, the correlation between the stroke morbidity and the risk factors was analyzed using a trend test in patients with H-type hypertension. Univariate and multivariate logistic regression analyses were used to evaluate the association between baseline factors and prevalence of stroke in H-type hypertensive patients.

FINDINGS

After the stratification of risk factors, a statistical difference was noted in age (range, 45-74 yrs), glucose ranges (<6.1 and ≥7.0 mmol/L), BMI, systolic blood pressure (SBP), diastolic blood pressure (DBP), non-HDL-C, and triglyceride level of <200 mg/dL (P<0.05) in the H-type hypertension group compared with those in non-H-type hypertension group. Gradual elevation of stroke morbidity was identified with the increase of fasting glucose, SBP, and DBP. In multivariate logistic regression analysis, only higher SBP, DBP, fasting glucose level, homocysteine, and history of diabetes mellitus were the independent predictors for the stroke morbidity.

IMPLICATIONS

Comprehensive evaluation and strict management of multiple risk factors have become increasingly important in the alleviation of stroke morbidity for H-type hypertensive patients because these patients were more sensitive to the classic risk factors.

Activation of the methylation cycle in cells reprogrammed into a stem cell-like state

Generation of induced pluripotent stem (iPS) cells and cancer biogenesis share similar metabolic switches. Most studies have focused on how the establishment of a cancer-like glycolytic phenotype is necessary for the optimal routing of somatic cells for achieving stemness. However, relatively little effort has been dedicated towards elucidating how one-carbon (1C) metabolism is retuned during acquisition of stem cell identity. Here we used ultra-high pressure liquid chromatography coupled to an electrospray ionization source and a triple-quadrupole mass spectrometer [UHPLC-ESI-QqQ-MS/MS] to quantitatively examine the methionine/folate bi-cyclic 1C metabolome during nuclear reprogramming of somatic cells into iPS cells. iPS cells optimize the synthesis of the universal methyl donor S-adenosylmethionine (SAM), apparently augment the ability of the redox balance regulator NADPH in SAM biosynthesis, and greatly increase their methylation potential by triggering a high SAM:S-adenosylhomocysteine (SAH) ratio. Activation of the methylation cycle in iPS cells efficiently prevents the elevation of homocysteine (Hcy), which could alter global DNA methylation and induce mitochondrial toxicity, oxidative stress and inflammation. In this regard, the methyl donor choline is also strikingly accumulated in iPS cells, suggesting perhaps an overactive intersection of the de novo synthesis of choline with the methionine-Hcy cycle. Activation of methylogenesis and maintenance of an optimal SAM:Hcy ratio might represent an essential function of 1C metabolism to provide a labile pool of methyl groups and NADPH-dependent redox products required for successfully establishing and maintaining an embryonic-like DNA methylation imprint in stem cell states.

Therapeutic potential of folic acid supplementation for cardiovascular disease prevention through homocysteine lowering and blockade in rheumatoid arthritis patients

Rheumatoid arthritis (RA) is a chronic inflammatory disease that preferentially affects joints, and characterized by an approximately two-fold increased risk of cardiovascular diseases compared with the general population. Beyond classical cardiovascular risk factors, systemic inflammatory markers are primarily involved. Hence, anti-inflammatory strategies such as homocysteine-lowering interventions are warranted. Indeed, hyperhomocysteinemia is commonly found in RA patients as a result of both genetic and non-genetic factors including older age, male gender, disease-specific features and disease-modifying antirheumatic drugs. Most importantly in the pathophysiology of hyperhomocysteinemia and its related cardiovascular diseases in RA, there is a bi-directional link between immuno-inflammatory activation and hyperhomocysteinemia. As such, chronic immune activation causes B vitamins (including folic acid) depletion and subsequent hyperhomocysteinemia. In turn, hyperhomocysteinemia may perpetrate immuno-inflammatory stimulation via nuclear factor ƙappa B enhancement. This chronic immune activation is a key determinant of hyperhomocysteinemia-related cardiovascular diseases in RA patients. Folate, a homocysteine-lowering therapy could prove valuable for cardiovascular disease prevention in RA patients in the near future with respect to homocysteine reduction along with blockade of subsequent oxidative stress, lipid peroxidation, and endothelial dysfunction. Thus, large scale and long term homocysteine-lowering clinical trials would be helpful to clarify the association between hyperhomocysteinemia and cardiovascular diseases in RA patients and to definitely state conditions surrounding folic acid supplementation. This article reviews direct and indirect evidence for cardiovascular disease prevention with folic acid supplementation in RA patients.

DNA hypermethylation in hyperhomocysteinemia contributes to abnormal extracellular matrix metabolism in the kidney

Hyperhomocysteinemia (HHcy) is prevalent in patients with chronic kidney disease (CKD) and end-stage renal disease (ESRD). Emerging studies suggest that epigenetic mechanisms contribute to the development and progression of fibrosis in CKD. HHcy and its intermediates are known to alter the DNA methylation pattern, which is a critical regulator of epigenetic information. In this study, we hypothesized that HHcy causes renovascular remodeling by DNA hypermethylation, leading to glomerulosclerosis. We also evaluated whether the DNA methylation inhibitor, 5-aza-2'-deoxycytidine (5-Aza) could modulate extracellular matrix (ECM) metabolism and reduce renovascular fibrosis. C57BL/6J (wild-type) and cystathionine-β-synthase (CBS(+/-)) mice, treated without or with 5-Aza (0.5 mg/kg body weight, i.p.), were used. CBS(+/-) mice showed high plasma Hcy levels, hypertension, and significant glomerular and arteriolar injury. 5-Aza treatment normalized blood pressure and reversed renal injury. CBS(+/-) mice showed global hypermethylation and up-regulation of DNA methyltransferase-1 and -3a. Methylation-specific PCR showed an imbalance between matrix metalloproteinase (MMP)-9 and tissue inhibitor of metalloproteinase (TIMP)-1 and -2 and also increased collagen and galectin-3 expression. 5-Aza reduced abnormal DNA methylation and restored the MMP-9/TIMP-1, -2 balance. In conclusion, our data suggest that during HHcy, abnormal DNA methylation and an imbalance between MMP-9 and TIMP-1 and -2 lead to ECM remodeling and renal fibrosis.

Homocysteine Triggers Inflammatory Responses in Macrophages through Inhibiting CSE-H2S Signaling via DNA Hypermethylation of CSE Promoter

Hyperhomocysteinemia (HHcy) is an independent risk factor of atherosclerosis and other cardiovascular diseases. Unfortunately, Hcy-lowering strategies were found to have limited effects in reducing cardiovascular events. The underlying mechanisms remain unclear. Increasing evidence reveals a role of inflammation in the pathogenesis of HHcy. Homocysteine (Hcy) is a precursor of hydrogen sulfide (H₂S), which is formed via the transsulfuration pathway catalyzed by cystathionine β-synthase and cystathionine γ-lyase (CSE) and serves as a novel modulator of inflammation. In the present study, we showed that methionine supplementation induced mild HHcy in mice, associated with the elevations of TNF-α and IL-1β in the plasma and reductions of plasma H₂S level and CSE expression in the peritoneal macrophages. H₂S-releasing compound GYY4137 attenuated the increases of TNF-α and IL-1β in the plasma of HHcy mice and Hcy-treated raw264.7 cells while CSE inhibitor PAG exacerbated it. Moreover, the in vitro study showed that Hcy inhibited CSE expression and H₂S production in macrophages, accompanied by the increases of DNA methyltransferase (DNMT) expression and DNA hypermethylation in cse promoter region. DNMT inhibition or knockdown reversed the decrease of CSE transcription induced by Hcy in macrophages. In sum, our findings demonstrate that Hcy may trigger inflammation through inhibiting CSE-H₂S signaling, associated with increased promoter DNA methylation and transcriptional repression of cse in macrophages.