Hyperhomocyst(e)inemia is a risk factor for arterial endothelial dysfunction in humans

Risk Factors for Premature Coronary Heart Disease in Women Compared to Men: Systematic Review and Meta-Analysis

Background: We aimed to systematically examine literature on the prevalence of known modifiable and nonmodifiable risk factors for premature coronary heart disease (PCHD) in women compared with men. Materials and Methods: PubMed, CINAHL, Embase, and Web of Science databases were searched. Review protocol is registered in PROSPERO (CRD42020173216). Quality was assessed using the National Heart, Lung, and Blood Institute tool. Review Manager 5.3 was used for meta-analysis. Effect sizes were expressed as odds ratio (OR) and mean differences/standardized mean differences (SMD) with 95% confidence intervals (CIs) for categorical and continuous variables. Results: In this PCHD cohort (age <65 years), the mean age of presentation in women was 3 years older than men. Women had higher total cholesterol (SMD 0.11; 95% CI 0.00 to 0.23) and higher high-density lipoprotein cholesterol (SMD 0.49; 95% CI 0.29 to 0.69). Women were more likely to have hypertension (OR 1.51, 95% CI 1.42 to 1.60), diabetes mellitus (OR 1.78, 95% CI 1.55 to 2.04), obesity (OR 1.33, 95% CI 1.24 to 1.42), metabolic syndrome (OR 3.73, 95% CI 1.60 to 8.69), stroke (OR 1.63, 95% CI 1.51 to 1.77), peripheral vascular disorder (OR 1.67, 95% CI 1.43 to 1.96), and depression (OR 2.29, 95% CI 1.96 to 2.67). Women were less likely to be smokers (OR 0.60, 95% CI 0.55 to 0.66), have reported alcohol intake (OR 0.36, 95% CI 0.33 to 0.40), and reported use of illicit drug (OR 0.32, 95% CI 0.16 to 0.62). Conclusions: Risk factor profile in PCHD has a clear sex difference that supports early, aggressive, holistic, but sex-specific, approach to prevention.

The interaction of hypertension and homocysteine increases the risk of mortality among middle-aged and older population in the United States

OBJECTIVES

To investigate the interaction of hypertension and total plasma homocysteine (tHcy) levels on risk of all-cause and cardiovascular disease (CVD) mortality among middle-aged and older population.

METHODS

This observational cohort study analyzed data from the National Health and Nutrition Examination Survey database (1999-2002 survey cycle). A generalized additive model (GAM) based on Cox proportional hazards models was applied to estimate the relationship of tHcy level with all-cause and CVD mortality. Stratification analyses by sex and renal function were performed.

RESULTS

Among 5724 individuals aged 40-85, 704 (12.3%) died, with 339 CVD deaths after a median follow-up period of 5.58 years. Mean age was 60.7 ± 13.4 years (49.6% men). In the fully adjusted model, we found that per 1 μmol/l increment of plasma tHcy was associated with 8% increased risk of all-cause mortality and 7% increased risk of CVD mortality in hypertensive participants. The adjusted hazard ratio (95% CIs) for all-cause and CVD mortality were 1.08 (1.06-1.10) and 1.07 (1.04-1.10), respectively. There were pronounced interactive effects between hypertension and tHcy levels on risk of all-cause mortality (P for interaction = 0.031).

CONCLUSION

Hypertension and tHcy levels can interactively affect the risk of all-cause mortality among middle-aged and older population. Conceivably, hypertension may further enhance the ability of elevated tHcy to provoke the risk of all-cause mortality.

Increased myoendothelial feedback is associated with increased connexin37 and IK1 channel expression in mesenteric arteries of diet-induced hyperhomocysteinemic mice

OBJECTIVE

Previously, we found that diet-induced HHcy in mice caused decreased eNOS expression and signaling in mesenteric arteries, but greatly enhanced non-NOS, non-prostacyclin-dependent vasodilation, which involves MEJ communication. To further assess whether HHcy enhances MEJ communication, this study examined endothelium-dependent attenuation of phenylephrine-induced vasoconstriction (myoendothelial feedback) and key molecules involved.

METHODS

Myoendothelial feedback was examined in isolated mouse mesenteric arteries, after 6-weeks diet-induced HHcy, using pressure myography. Gap junction (Cx37, Cx40, Cx43), NOS (eNOS, nNOS, iNOS), and potassium channel (IK1) protein expression were measured with immunoblots, and connexin mRNAs with real-time PCR. Contribution of nNOS + iNOS to vasomotor responses was assessed using the drug TRIM.

RESULTS

Myoendothelial feedback was significantly (P < .05) enhanced in HHcy arteries compared to control, coincident with significantly greater Cx37 and IK1 protein and Cx37 mRNA. Cx43 protein, but not mRNA, was significantly less in HHcy, and Cx40 was not different. eNOS protein was significantly less in HHcy. nNOS and iNOS were not different. TRIM had little effect on vasomotor function.

CONCLUSIONS

Diet-induced HHcy enhanced myoendothelial feedback, and increased Cx37 and IK1 expression may contribute. nNOS or iNOS did not upregulate to compensate for decreased eNOS, and they had little involvement in vasomotor function.

Serum levels of homocysteine, asymmetric dimethylarginine and nitric oxide in patients with Parkinson's disease

OBJECTIVES

Endothelial dysfunction has been implicated as a crucial event in the development of several neurodegenerative diseases. The aim of this study was to investigate the serum homocysteine, asymmetric dimethylarginine (ADMA) and nitric oxide (NO) levels in patients with Parkinson's disease (PD) and to compare the results with data from healthy controls.

METHODS

A total of 132 subjects, including 82 idiopathic PD patients who were newly diagnosed and untreated (47 males, 35 females, mean age of 60.8 ± 7.1 years) and 50 healthy controls (28 males, 22 females, mean age of 60.2 ± 6.7 years) were enrolled in this study. The serum ADMA and NO levels were determined using enzyme-linked immunosorbent assay (ELISA), while the homocysteine levels were determined by chemiluminescent microparticle immunoassay.

RESULTS

The ADMA and NO levels of the PD patients were significantly higher than those of the healthy controls. The serum ADMA levels were 0.70 ± 0.15 μmol/L in the PD patients and 0.50 ± 0.12 μmol/L in the healthy controls (p < 0.001). The serum NO levels were 78.7 ± 10.3 μmol/L in the PD patients and 59.9 ± 9.5 μmol/L in the healthy controls (p < 0.001). In addition, the ADMA and NO levels were significantly correlated with the serum homocysteine levels in patients with PD (r = 0.874, p < 0.001, r = 0.803, p = 0.005, respectively).

CONCLUSION

In our study, the high ADMA and NO levels of patients with PD indicate endothelial dysfunction, and this dysfunction may play a role in PD pathogenesis. Larger studies, including randomised clinical trials in humans and animal studies, are needed to validate our findings and help in developing a better understanding of the pathogenesis of PD.

Vascular endothelial dysfunction and pharmacological treatment

The endothelium exerts multiple actions involving regulation of vascular permeability and tone, coagulation and fibrinolysis, inflammatory and immunological reactions and cell growth. Alterations of one or more such actions may cause vascular endothelial dysfunction. Different risk factors such as hypercholesterolemia, homocystinemia, hyperglycemia, hypertension, smoking, inflammation, and aging contribute to the development of endothelial dysfunction. Mechanisms underlying endothelial dysfunction are multiple, including impaired endothelium-derived vasodilators, enhanced endothelium-derived vasoconstrictors, over production of reactive oxygen species and reactive nitrogen species, activation of inflammatory and immune reactions, and imbalance of coagulation and fibrinolysis. Endothelial dysfunction occurs in many cardiovascular diseases, which involves different mechanisms, depending on specific risk factors affecting the disease. Among these mechanisms, a reduction in nitric oxide (NO) bioavailability plays a central role in the development of endothelial dysfunction because NO exerts diverse physiological actions, including vasodilation, anti-inflammation, antiplatelet, antiproliferation and antimigration. Experimental and clinical studies have demonstrated that a variety of currently used or investigational drugs, such as angiotensin-converting enzyme inhibitors, angiotensin AT1 receptors blockers, angiotensin-(1-7), antioxidants, beta-blockers, calcium channel blockers, endothelial NO synthase enhancers, phosphodiesterase 5 inhibitors, sphingosine-1-phosphate and statins, exert endothelial protective effects. Due to the difference in mechanisms of action, these drugs need to be used according to specific mechanisms underlying endothelial dysfunction of the disease.

Early atherosclerosis in ulcerative colitis: cross-sectional case-control study

OBJECTIVE

To study the extent of early atherosclerosis in ulcerative colitis (UC) patients by measuring carotid intima-media thickness (CIMT) and the correlation between CIMT, serum homocysteine level and homeostasis model assessment-insulin resistance (HOMA-IR) in UC.

METHODS

We studied 60 UC patients and 60 healthy controls. Individuals with risk factors for atherosclerosis were excluded from the study. Fasting blood glucose, lipid profile, HOMA-IR, erythrocyte sedimentation rate (ESR), serum vitamin B12 and homocysteine levels were measured in all participants. CIMT was measured using a B-mode duplex imaging study.

RESULTS

UC patients had significantly higher CIMT than controls (P < 0.05). ESR, fasting insulin, HOMA-IR and serum homocysteine levels were also significantly higher in UC patients (P < 0.05). Pearson's correlation coefficient showed significant correlations between: (i) CIMT and patients' age, duration of UC, HOMA-IR, and homocysteine level (P < 0.05); (ii) serum homocysteine and duration of UC, fasting insulin level, HOMA-IR and CIMT (P < 0.01); (iii) HOMA-IR and age, duration of UC, serum homocysteine and CIMT (P < 0.01). Multi-regression models showed that serum homocysteine affects CIMT and duration of UC independently, whereas participants' age and duration of UC affects HOMA-IR independently.

CONCLUSIONS

Higher CIMT might indicate subclinical atherosclerosis in UC patients. Patients' age, duration of UC, HOMA-IR and homocysteine levels are important factors associated with increased CIMT.

Predictors of survival in children with methymalonic acidemia with homocystinuria in Beijing, China: a prospective cohort study

OBJECTIVE

(i) To determine whether clinical features and biochemical parameters help to predict survival of methylmalonic acidemia with homocystinuria; (ii) To find the cutoff values of biochemical parameters for predicting survival of methylmalonic acidemia with homocystinuria.

DESIGN

A prospective cohort study.

SETTING

A pediatric tertiary hospital in Beijing; all patients were followed until death or June 2013.

SUBJECTS

45 pediatric patients diagnosed with methylmalonic acidemia with homocystinuria between 2006 and 2012.

OUTCOME MEASURES

The data of clinical characteristics and pretreatment biochemical parameters were collected. The Cox regression analysis was performed to identify independent risk factors for survival of patients with methylmalonic acidemia and homocystinuria. The best cutoff values for these independent factors were determined by the receiver characteristic curve.

RESULTS

Newborn onset (OR=6.856, 95%CI=2.241-20.976, P=0.001), high level of methylmalonic acid in urine (OR=1.022, 95%CI=1.011-1.033, P<0.001), and high level of urea in serum (OR=1.083, 95%CI=1.027-1.141, P=0.003) were independent negative risk factors for survival of patients with methylmalonic acidemia and homocystinuria. The cutoff values of maximum predictive accuracy of methylmalonic acid in urine and urea in serum were respectively 5.41 mmol/mmol creatinine and 7.80 mmol/L by receiver operating characteristic curve analysis.

CONCLUSIONS

The patients of methylmalonic acidemia with homocystinuria tend to have an adverse outcome if they have newborn onsets. Elevated urea and urinary methylmalonic acid are predictors of adverse outcomes for the patients. They show similar effect for predicting severe adverse prognosis. The combination of methylmalonic acid in urine concentration and urea in serum concentration provided the most accurate predictive tool.

Hyperhomocysteinemia-Induced Monocyte Chemoattractant Protein-1 Promoter DNA Methylation by Nuclear Factor-κB/DNA Methyltransferase 1 in Apolipoprotein E-Deficient Mice

Hyperhomocysteinemia is considered to be a significant risk factor in atherosclerosis and plays an important role in it. The purpose of this study was to determine the molecular mechanism of blood monocyte chemoattractant protein-1 (MCP-1) promoter DNA hypomethylation in the formation of atherosclerosis induced by hyperhomocysteinemia, and to explore the effect of nuclear factor-κB (NF-κB)/DNA methyltransferase 1 (DNMT1) in this mechanism. The atherosclerotic effect of MCP-1 in apolipoprotein E–deficient (ApoE^−/−) and wild-type C57BL/6J mice was evaluated using atherosclerotic lesion area; serum NF-κB, MCP-1, and DNMT1 levels; and MCP-1 promoter DNA methylation expression. In vitro, the mechanism responsible for the effect of NF-κB/DNMT1 on foam cells was investigated by measuring NF-κB and DNMT1 levels to determine whether NF-κB/DNMT1 had an effect on gene expression. Compared with the control group, atherosclerotic lesions in ApoE^−/− mice fed a high methionine diet significantly increased, as did the expression of MCP-1. In vitro study showed that pyrrolidine dithiocarbamate treatment down-regulated levels of NF-κB and raised DNMT1 concentrations, confirming the effect of NF-κB/DNMT1 in the MCP-1 promoter DNA methylation process. In conclusion, our results suggest that through NF-κB/DNMT1, MCP-1 promoter DNA hypomethylation may play a key role in formation of atherosclerosis under hyperhomocysteinemia.

Homocysteine is a determinant of ApoA-I and both are associated with ankle brachial index, in an ambulatory elderly population

OBJECTIVE

The ankle brachial index (ABI) is an indicator of lower extremity peripheral arterial disease (PAD) and a predictor of atherothrombosis. ApoA-I and HDL are associated with PAD, in humans. Homocysteine influences the liver expression of ApoA-I and decreases its blood level and HDL in genetic mice models. We aimed therefore to evaluate whether homocysteine and its nutritional determinants, folate and vitamin B12 are associated with ABI by influencing HDL metabolism, in an ambulatory elderly population.

METHODS

667 elderly volunteers from rural Sicily were assessed for ABI, homocysteine and its determinants, lipid markers and other predictors of PAD. HDL size was assessed in 15 sera in upper and lower quartiles of Hcy distribution.

RESULTS

In multivariate analysis, ApoA-I and homocysteine were two predictors of ABI (β-coefficient = 2.86, P<0.004 and β-coefficient = -3.41, P<0.001, respectively). Homocysteine correlated negatively with ApoA-I (R = -0.147, P<0.001) and with HDL-Cholesterol (R = -0.113, P = 0.003). The associations of homocysteine, vitamin B12 and methylmalonic acid with ApoA-I and HDL2a particles and that of homocysteine with increased small size HDL3c suggested mechanisms related with impaired synthesis of ApoA-I and HDL and abnormal maturation of HDL particles.

CONCLUSION

The influence of homocysteine on ApoA-I and HDL metabolism provides new insights on its role on vascular diseases, at a cross-point between atherosclerosis and atherothrombosis.

Homocysteine-induced extracellular superoxide dismutase and its epigenetic mechanisms in monocytes

Although a modest homocysteine (Hcy) elevation is associated with an increased cardiovascular risk, the underlying mechanisms whereby Hcy triggers the accumulation of cholesterol and the roles of the extracellular superoxide dismutase (EC-SOD) in the development of foam cells have not yet been elucidated. In this study, we found both increased numbers of foam cells and an accumulation of cholesterol, and the H(2)O(2) and oxidized low-density lipoprotein content also increased. Levels of EC-SOD were significantly suppressed by Hcy, however, while 5-azacytidine (AZC), a potent DNA methyltransferase (DNMT) inhibitor, increased the expression of EC-SOD. A quantitative real-time PCR of EC-SOD revealed that Hcy (100 micromol l(-1)) accelerates DNA methylation of EC-SOD, but selectively increases the activity of DNA methyl transferase 1 (DNMT1). It showed that Hcy can reduce binding of methyl CpG and binding protein 2 (MeCP2) but has no effect on the activity of DNMT3. Moreover, chromatin immunoprecipitation assays demonstrated that Hcy increased the binding of acetylated histone H3 and H4 in monocytes. Based on the fact that the binding of MeCP2 with the EC-SOD was completely suppressed by AZC and trichostatin A [TSA, a histone deacetylase (HDAC) inhibitor], it is indicated that DNA methylation and HDAC mediate the binding of MeCP2 with EC-SOD gene. In conclusion, the study found that Hcy accelerates the development of foam cells by repressing EC-SOD transcription, and that Hcy exerts this function by upregulating DNA methylation via suppression of HDAC activity and increased DNMT1 activity.

Genetically based hypertension generated through interaction of mild hypoalphalipoproteinemia and mild hyperhomocysteinemia

BACKGROUND

Hyperhomocysteinemia and hypoalphalipoproteinemia are two well-reported risk factors for cardiovascular disease. The effects of the synergistic combination of these two factors on vascular function need to be investigated.

METHODS AND RESULTS

Four groups of male mice were used: a control wild-type group; a group of mice heterozygous for cystathionine beta-synthase deficiency; a group of mice heterozygous for apolipoprotein A-I deficiency; and, finally, a group of double heterozygous mice, with both cystathionine beta-synthase and apolipoprotein A-I deficiency. To characterize the resulting phenotype, several parameters including plasma apolipoproteins, lipid profiles, homocysteine, blood pressure and aortic protein were analyzed. As expected, our results indicate that double heterozygous mice are a model of mild hypoalphalipoproteinemia and hyperhomocysteinemia. Further, the additive combination of both risk factors resulted in a significant increase in blood pressure compared with control animals (136 +/- 8.0 versus 126 +/- 7.5 mm Hg, P < 0.01) that was not present in single heterozygous mice. The increase in blood pressure was associated with decreased plasma nitric oxide levels, left ventricle hypertrophy and was independent of low-density lipoprotein (LDL) cholesterol, para-oxonase activity and kidney histological changes. Concomitant decreases in levels of apolipoprotein A-IV (APOA-IV) and caveolin-1 content were also found in the double heterozygous group.

CONCLUSIONS

Our findings suggest an additive adverse effect of hypoalphalipoproteinemia and hyperhomocysteinemia on endothelial function to generate clinical hypertension and cardiac muscle hypertrophy mediated by dysregulation in nitric oxide metabolism.

Anti-heparan sulphate antibodies and homocysteine in dementia: markers of vascular pathology?

Increasing evidence supports a pathogenic role of heparan sulphate (HS) in the development of dementia. Since HS proteoglycans are present in the endothelial cells and perivascular basement membrane, we wanted to assess blood titres of HS antibodies (Abs) in patients with vascular dementia (VD) and in patients with Alzheimer's disease (AD) with cerebrovascular disease (CVD) [mixed dementia (MixD)]. Moreover, plasma levels of homocysteine, an independent risk factor for the development of dementia as well as for CVD, were also determined. High HS Abs titres were present in one patient with VD and in two patients with mixed dementia, as well as in two neurological control patients (stroke and epilepsy). Increased homocysteine levels were found in 62.5% of patients with mixed dementia, in 22.2% of the VD subjects, in 54.2% of patients with CVD, and in 41.2% of patients with other neurological diseases. The present findings suggest that neither elevated HS Abs titres nor increased homocysteinemia may represent a useful biochemical marker for the diagnosis of VD.

Homocysteine and cardiovascular disease

Research over the past decade has shown that elevated levels of homocysteine have a strong association with all forms of atherothrombotic disease and venous thromboembolism. This association is particularly strong for coronary disease and newer data indicate that screening for homocysteine levels may be warranted in those with unexplained thrombotic tendencies and in young patients who develop coronary events or disease without the usual predisposing factors such as hypertension, smoking, hypercholesterolemia, or diabetes. Although the link between hyperhomocysteinemia and cardiac disease has not been conclusively shown to be causal as yet, data are emerging that lowering homocysteine levels may be beneficial in patients at high risk. Such lowering can be done safely and inexpensively with increased intake of fruits and vegetables and in those patients who are particularly at high risk using supplementation with folic acid and the B vitamins. Preliminary studies have shown that lowering homocysteine levels in this manner may slow the progression of atherosclerosis in coronary and carotid vessels. No mortality data exist yet showing that reducing homocysteine reduces cardiac or total mortality, although it is likely that ongoing and planned trials that are underway will shed light on these important questions soon.

Folic acid improves arterial endothelial function in adults with hyperhomocystinemia

OBJECTIVES

To evaluate whether oral folic acid supplementation might improve endothelial function in the arteries of asymptomatic adults with hyperhomocystinemia.

BACKGROUND

Hyperhomocystinemia is an independent risk factor for endothelial dysfunction and occlusive vascular disease. Folic acid supplementation can lower homocystine levels in subjects with hyperhomocystinemia; however, the effect of this on arterial physiology is not known.

METHODS

Adults subjects were recruited from a community-based atherosclerosis study on healthy volunteers aged 40 to 70 years who had no history of hypertension, diabetes mellitus, hyperlipidemia, ischemic heart disease or family history of premature atherosclerosis (n = 89). Seventeen subjects (aged 54 +/- 10 years, 15 male) with fasting total homocystine levels above 75th percentile (mean, 9.8 +/- 2.8 micromol/liter) consented to participate in a double-blind, randomized, placebo-controlled and crossover trial; each subject received oral folic acid (10 mg/day) and placebo for 8 weeks, each separated by a washout period of four weeks. Flow-mediated endothelium-dependent dilation (percent increase in diameter) of the brachial artery was assessed by high resolution ultrasound, before and after folic acid or placebo supplementation.

RESULTS

Compared with placebo, folic acid supplementation resulted in higher serum folate levels (66.2 +/- 7.0 vs. 29.7 +/- 14.8 nmol/liter; p < 0.001), lower total plasma homocystine levels (8.1 +/- 3.1 vs. 9.5 +/- 2.5 micromol/liter, p = 0.03) and significant improvement in endothelium-dependent dilation (8.2 +/- 1.6% vs. 6 +/- 1.3%, p < 0.001). Endothelium-independent responses to nitroglycerin were unchanged. No adverse events were observed.

CONCLUSION

Folic acid supplementation improves arterial endothelial function in adults with relative hyperhomocystinemia, with potentially beneficial effects on the atherosclerotic process.