Homocysteine impairs the nitric oxide synthase pathway: role of asymmetric dimethylarginine

Atherogenic Effect of Homocysteine, a Biomarker of Inflammation and Its Treatment

Hyperhomocysteinemia (HHcy) is an independent risk factor for atherosclerosis. Ischemic stroke and heart disease, coronary heart disease, and cardiovascular disease are events resulting from long-lasting and silent atherosclerosis. This paper deals with the synthesis of homocysteine (Hcy), causes of HHcy, mechanism of HHcy-induced atherosclerosis, and treatment of HHcy. Synthesis and metabolism of Hcy involves demethylation, transmethylation, and transsulfuration, and these processes require vitamin B 6 and vitamin B 12 folic acid (vitamin B 9 ). Causes of HHcy include deficiency of vitamins B 6 , B 9 , and B 12 , genetic defects, use of smokeless tobacco, cigarette smoking, alcohol consumption, diabetes, rheumatoid arthritis, low thyroid hormone, consumption of caffeine, folic acid antagonist, cholesterol-lowering drugs (niacin), folic acid antagonist (phenytoin), prolonged use of proton pump inhibitors, metformin, and hypertension. HHcy-induced atherosclerosis may be mediated through oxidative stress, decreased availability of nitric oxide (NO), increased expression of monocyte chemoattractant protein-1, smooth muscle cell proliferation, increased thrombogenicity, and induction of arterial connective tissue. HHcy increases the generation of atherogenic biomolecules such as nuclear factor-kappa B, proinflammatory cytokines (IL-1β, IL-6, and IL-8), cell adhesion molecules (intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and E-selection), growth factors (IGF-1 and TGF-β), and monocyte colony-stimulating factor which lead to the development of atherosclerosis. NO which is protective against the development of atherosclerosis is reduced by HHcy. Therapy with folic acid, vitamin B 6 , and vitamin B 12 lowers the levels of Hcy, with folic acid being the most effective. Dietary sources of folic acid, vitamin B 6 , vitamin B 12 , omega-3 fatty acid, and green coffee extract reduce Hcy. Abstaining from drinking coffee and alcohol, and smoking also reduces blood levels of Hcy. In conclusion, HHcy induces atherosclerosis by generating atherogenic biomolecules, and treatment of atherosclerosis-induced diseases may be by reducing the levels of Hcy.

Hyperhomocysteinemia and Disease-Is 10 μmol/L a Suitable New Threshold Limit?

Hyperhomocysteinemia (HHcy) is a medical condition characterized by an abnormally high level of homocysteine (Hcy) in the blood. Homocysteine is a toxic sulfur-containing amino acid that is produced during the metabolism of methionine. Under normal circumstances, Hcy is recycled back to methionine via the remethylation pathway, through the action of various enzymes and vitamins, particularly folic acid (vitamin B9) and B12 used when intracellular methionine levels are low, thus restoring the necessary levels to correctly maintain active protein synthesis. A second pathway, used in cases of intracellular methionine excess, (the trans-sulfuration pathway) is the one that recycles Hcy into cysteine (a precursor of glutathione), first passing through cystathionine (via the enzyme cystathionine beta-synthase), a reaction that requires vitamin B6 in its active form. HHcy has been identified as a risk factor for a variety of disorders, including cardiovascular diseases, multiple sclerosis, diabetes, Alzheimer's and Parkinson's diseases, osteoporosis and cancer. However, it remains unclear whether the slightly elevated concentration of Hcy (Hcy 7-10 μmol/L) is a causative factor or simply a marker of these pathologies. In human plasma, the concentration of Hcy ([Hcy]) is classified as mild (15 to 30 μmol/L), moderate (30 to 100 μmol/L), and severe (greater than 100 μmol/L). Interestingly, many laboratories continue to consider 25 μmol/L as normal. This review seeks to examine the controversial literature regarding the normal range of HHcy and emphasizes that even a [Hcy] level of 10 μmol/L may contribute to the development of several diseases, aiming to discuss whether it would be appropriate to lower the threshold of HHcy normal values.

The L-Arginine pathway may act as a mediator in the association between impaired one- carbon metabolism and hypertension

Elevated fasting plasma total homocysteine (tHcy) and the methylenetetrahydrofolate reductase C677T polymorphism (rs1801133) have been associated with hypertension. Whether the L-Arginine pathway is involved, is unclear. We aimed to investigate whether the association between tHcy, the rs1801133 polymorphism and hypertension involves the L-Arginine pathway. THcy, plasma folate and cobalamin, erythrocyte glutathionine reductase activation coefficient, rs1801133 genotype, plasma L-Arginine, asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) were determined in a cross-sectional study of 788 adults (aged 18 to 75), randomly selected from 2 town population registers. Participants participated in a medical checkup and provided a fasting blood sample. Associations between tHcy, rs1801133 genotype and L-Arginine pathway metabolites were assessed by multiple linear regression analysis and whether the tHcy and rs1801133 genotype are associated with hypertension via the L-Arginine pathway was investigated using mediation analysis. tHcy was positively associated with ADMA (B=0.003; SE=0.001; P<0.001) and SDMA (B=0.007; SE=0.002; P<0.001) and negatively associated with the L-Arginine/ADMA (B=-1.140; SE=0.451; P<0.05) and ADMA/SDMA (B=-0.006; SE=0.003; P<0.05) ratios. The MTHFR 677 CT vs CC genotype was negatively associated with ADMA (B=-0.013; SE=0.007; P<0.05) and with SDMA (B=-0.029; SE=0.013; P<0.05) in participants under 50 years. Each standard deviation increase (37.6) in the L-Arginine/ADMA ratio was associated with reduced hypertension risk (OR [95%CI], 0.6 [0.5, 0.8]). Mediation analysis showed that tHcy and ADMA were mediators in the association between the rs1801133 TT vs CC genotypes and hypertension. Our results support the L-Arginine pathway as a mediator in the association of impaired One-Carbon metabolism and hypertension.

Inverted U-shaped relationship between serum vitamin B12 and α-Klotho levels in US adults: a cross-sectional study

Background

Serum vitamin B12 and α-Klotho are important markers associated with aging. Limited studies have been conducted on the relationship between vitamin B12 and α-Klotho.

Objectives

This study investigated the relationship between circulating α-Klotho and vitamin B12.

Methods

A total of 4,502 American adults with circulating vitamin B12 levels and α-Klotho levels from the National Health and Nutrition Examination Survey (2011-2014) were included. A weighted multiple linear regression model was used to evaluate the correlation between vitamin B12 and α-Klotho levels. To clarify potential non-linearities, smoothed curve fitting and threshold effects analysis were employed.

Results

A statistically significant non-linear relationship was found between vitamin B12 levels and circulating α-Klotho levels after adjusting for potential confounders. We observed an inverted U-shaped relationship between serum vitamin B12 levels and circulating α-Klotho levels. Notably, serum vitamin B12 levels below the threshold (1,020 pg/mL) exhibited a positive correlation with circulating α-Klotho levels (β = 0.14, 95% confidence interval (CI): 0.09-0.18, p < 0.0001). Conversely, serum vitamin B12 levels above the threshold (1,020 pg/mL) exhibited a negative correlation with circulating α-Klotho levels (β = -0.12,95% CI: -0.17--0.06, p < 0.0001). Sensitivity analyses were performed and consistent results were obtained.

Conclusion

This study demonstrated an inverted U-shaped relationship between circulating vitamin B12 and α-Klotho in American adults. The optimal concentration of serum vitamin B12 in American adults was found.

Associations of total homocysteine and kidney function with all-cause and cause-specific mortality in hypertensive patients: a mediation and joint analysis

Plasma total homocysteine (tHcy) and kidney function are both associated with mortality risk, but the degree to which kidney function modifies the impact of tHcy on mortality remains unknown. This prospective cohort study included a total of 14,225 hypertensive adults. Cox proportional hazard regression was used to analyze the separate and combined association of tHcy and estimated glomerular filtration rate (eGFR) with all-cause and cause-specific mortality. Mediation analysis was conducted to explore the mediating effect of eGFR. During a median follow-up of 4.0 years, 805 deaths were identified, including 397 deaths from cardiovascular disease (CVD). There were significant, positive relationships of tHcy with all-cause mortality (per 5 μmol/L; HR: 1.09; 95% CI: 1.07, 1.11), CVD mortality (HR: 1.11; 95% CI: 1.08, 1.13), and non-CVD mortality (HR: 1.07; 95% CI: 1.04, 1.10). The proportions of eGFR mediating these relationships were 39.1%, 35.7%, and 49.7%, respectively. There were additive interactions between tHcy and eGFR. Compared with those with low tHcy (<15 μmol/L) and high eGFR (≥90 mL·min-1·1.73 m-2), participants with high tHcy (≥20 μmol/L) and low eGFR (<60 mL·min-1·1.73 m-2) had the highest risk of all-cause mortality (HR: 4.89; 95% CI: 3.81, 6.28), CVD mortality (HR: 5.80; 95% CI: 4.01, 8.40), and non-CVD mortality (HR: 4.25; 95% CI: 3.02, 5.97). In conclusion, among Chinese hypertensive adults, high tHcy and impaired kidney function were independently and jointly associated with higher risks of all-cause and cause-specific mortality. Importantly, kidney function explained most (nearly 40%) of the increased risk of mortality conferred by high tHcy.

DDAH1 promotes neurogenesis and neural repair in cerebral ischemia

Choline acetyltransferase (ChAT)-positive neurons in neural stem cell (NSC) niches can evoke adult neurogenesis (AN) and restore impaired brain function after injury, such as acute ischemic stroke (AIS). However, the relevant mechanism by which ChAT+ neurons develop in NSC niches is poorly understood. Our RNA-seq analysis revealed that dimethylarginine dimethylaminohydrolase 1 (DDAH1), a hydrolase for asymmetric NG,NG-dimethylarginine (ADMA), regulated genes responsible for the synthesis and transportation of acetylcholine (ACh) (Chat, Slc5a7 and Slc18a3) after stroke insult. The dual-luciferase reporter assay further suggested that DDAH1 controlled the activity of ChAT, possibly through hypoxia-inducible factor 1α (HIF-1α). KC7F2, an inhibitor of HIF-1α, abolished DDAH1-induced ChAT expression and suppressed neurogenesis. As expected, DDAH1 was clinically elevated in the blood of AIS patients and was positively correlated with AIS severity. By comparing the results among Ddah1 general knockout (KO) mice, transgenic (TG) mice and wild-type (WT) mice, we discovered that DDAH1 upregulated the proliferation and neural differentiation of NSCs in the subgranular zone (SGZ) under ischemic insult. As a result, DDAH1 may promote cognitive and motor function recovery against stroke impairment, while these neuroprotective effects are dramatically suppressed by NSC conditional knockout of Ddah1 in mice.

Transsulfuration and folate pathways in rheumatoid arthritis: A systematic review and meta-analysis

BACKGROUND

Metabolomic assessment of the transsulfuration and folic acid biochemical pathways could lead to the identification of promising biomarkers of nitric oxide dysregulation and oxidative stress in rheumatoid arthritis (RA).

METHODS

We conducted a systematic review and meta-analysis of transsulfuration (methionine, homocysteine, and cysteine) and folic acid (folic acid, vitamin B6 , and vitamin B12 ) metabolites in RA patients in remission and healthy controls. Electronic databases were searched from inception to 15 July 2023 for relevant articles. We assessed the risk of bias using the JBI checklist and the certainty of evidence using GRADE.

RESULTS

In 28 eligible studies, compared to controls, RA patients had significantly higher concentrations of homocysteine (standardized mean difference, SMD = 0.74, 95% CI 0.54-0.93, p < 0.001; low certainty of evidence) and methionine (SMD = 1.00, 95% CI 0.57-1.44, p < 0.001; low certainty) and lower concentrations of vitamin B6 (SMD = -6.62, 95% CI -9.65 to -3.60, p < 0.001; low certainty). By contrast, there were non-significant between-group differences in vitamin B12 and folic acid. In meta-regression and subgroup analysis, there were no associations between the effect size and several study and patient characteristics except for homocysteine (year of publication, C-reactive protein, triglycerides, and analytical method) and folic acid (biological matrix).

CONCLUSIONS

The results of our study suggest that homocysteine, methionine, and vitamin B6 are promising biomarkers to assess nitric oxide dysregulation and oxidative stress in RA. (PROSPERO registration number: CRD42023461081).

Early and late-onset preeclampsia: effects of DDAH2 polymorphisms on ADMA levels and association with DDAH2 haplotypes

Objective

To examine whether the DDAH2 promoter polymorphisms -1415G/A (rs2272592), -1151A/C (rs805304) and -449G/C (rs805305), and their haplotypes, are associated with PE compared with normotensive pregnant women, and whether they affect ADMA levels in these groups.

Methods

A total of 208 pregnant women were included in the study and classified as early-onset (N=57) or late-onset PE (N =49), and as normotensive pregnant women (N = 102).

Results

Pregnant with early-onset PE carrying the GC and GG genotypes for the DDAH2 -449G/C polymorphism had increased ADMA levels (P=0.01). No association of DDAH2 polymorphisms with PE in single-locus analysis was found. However, the G-C-G haplotype was associated with the risk for late-onset PE.

Conclusion

It is suggested that DDAH2 polymorphisms could affect ADMA levels in PE, and that DDAH2 haplotypes may affect the risk for PE.

Plasma trimethylamine N-oxide metabolites in the second trimester predict the risk of hypertensive disorders of pregnancy: a nested case-control study

The relationship between gut microbiota products trimethylamine oxide (TMAO) and related metabolites including betaine, choline and L-carnitine and hypertensive disorders of pregnancy (HDP) is unclear. In order to examine whether plasma TMAO and related metabolites predict the risk of HDP, a nested case-control study was conducted in Chinese women based on a prospective cohort including 9447 participants. 387 pairs of pregnant women (n = 774) were matched and their plasma TMAO, betaine, choline, and L-carnitine at 16-20 gestational weeks were measured by liquid chromatography-mass spectrometry. Odds ratio (OR) and the 95% confidence interval (95% CI) were calculated using the conditional logistic regression, to examine the association between TMAO metabolites and HDP. The findings showed that higher plasma betaine (≥24.94 μmol/L) was associated with a decreased risk of HDP and its subtype gestational hypertension (GH), with adjusted ORs of 0.404 (95% CI: 0.226-0.721) and 0.293 (95% CI: 0.134-0.642), respectively. Higher betaine/choline ratio (>2.64) was associated with a lower risk of HDP and its subtype preeclampsia or chronic hypertension with superimposed preeclampsia (PE/CH-PE), with adjusted ORs of 0.554 (95% CI: 0.354-0.866) and 0.226 (95% CI: 0.080-0.634). Moreover, compared with traditional factors (TFs) model, the TMAO metabolites+ TFs model had a higher predictive ability for PE/CH-PE (all indexes P values < 0.0001). Therefore, it suggests that the detection of plasma betaine and choline in the early second trimester of pregnancy can better assess the risk of HDP.

Factors associated with secondary coronary artery disease in rheumatoid arthritis patients: A systematic review and meta-analysis based on observational studies

OBJECTIVE

The main objective of this systematic review was to investigate the factors influencing the development of coronary artery disease (CAD) in patients with rheumatoid arthritis (RA).

METHODS

PubMed, Embase, Web of Science, Wan Fang Date, CBM, CNKI, and VIP databases were systematically searched to select the relevant literature. The quality of the incorporated studies was assessed with reference to the Newcastle-Ottawa Scale. Stata16 was adopted to summarise the odds ratios, risk ratios, hazard ratios, and 95% confidence intervals for meta-analysis.

RESULTS

A total of 29 studies were included in this analysis, wherein the average age of RA patients was 50.5-81 years and the proportion of women was 44.4%-92%. The present meta-analysis suggested that increased CAD risk in RA patients was associated with age, male gender, smoking, glucocorticoids, Health Assessment Questionnaire scores, hyperlipidaemia, hypertension, diabetes, and C-reactive protein concentration.

CONCLUSION

The present systematic review revealed the influencing factors of secondary CAD in RA patients, some of which could reduce the risk of secondary CAD through effective interventions, such as smoking cessation, exercise, and medications. However, the effects of age, RA severity, and different medication subgroups on CAD risk stratification warrant further investigation.

5-MTHF enhances the portal pressure reduction achieved with propranolol in patients with cirrhosis: A randomized placebo-controlled trial

BACKGROUND & AIMS

β-blockers reduce hepatic venous pressure gradient (HVPG) by decreasing portal inflow, with no reduction in intrahepatic vascular resistance. 5-Methyltetrahydrofolate (5-MTHF) can prevent oxidative loss of tetrahydrobiopterin (BH4), a cofactor for endothelial nitric oxide synthase coupling. It also converts homocysteine (tHcy) into methionine and enables the degradation of asymmetric dimethylarginine (ADMA), an inhibitor of endothelial nitric oxide synthase. The aim of this study was to evaluate the effects of 5-MTHF in combination with propranolol on HVPG and nitric oxide bioavailability markers in patients with cirrhosis and portal hypertension.

METHOD

Sixty patients with cirrhosis and HVPG ≥12 mmHg were randomized 1:1 to receive treatment with 5-MTHF+propranolol or placebo+propranolol for 90 days under double-blind conditions. HVPG and markers of nitric oxide bioavailability (BH4, ADMA and tHcy) were measured again at the end of treatment.

RESULTS

Groups were similar in terms of baseline clinical and hemodynamic data and nitric oxide bioavailability markers. HVPG decreased in both groups, but the magnitude of the change was significantly greater in the group treated with 5-MTHF+propranolol compared to placebo+propranolol (percentage decrease, 20 [29-9] vs. 12.5 [22-0], p = 0.028), without differences in hepatic blood flow. At the end of treatment, 5-MTHF+propranolol (vs. placebo+propranolol) was associated with higher BH4 (1,101.4 ± 1,413.3 vs. 517.1 ± 242.8 pg/ml, p <0.001), lower ADMA (109.3 ± 52.7 vs. 139.9 ± 46.7 μmol/L, p = 0.027) and lower tHcy (μmol/L, 11.0 ± 4.6 vs. 15.4 ± 7.2 μmol/L, p = 0.010) plasma levels.

CONCLUSION

In patients with cirrhosis and portal hypertension, 5-MTHF administration significantly enhanced the HVPG reduction achieved with propranolol. This effect appears to be mediated by improved nitric oxide bioavailability in the hepatic microcirculation.

CLINICAL TRIAL EUDRACT NUMBER

2014-002018-21.

IMPACT AND IMPLICATIONS

Currently, the pharmacological prevention of cirrhosis complications due to portal hypertension, such as esophageal varices rupture, is based on the use of β-blockers, but some patients still present with acute variceal bleeding, mainly due to an insufficient reduction of portal pressure. In this study, we sought to demonstrate that the addition of folic acid to β-blockers is more effective in reducing portal pressure than β-blockers alone. This finding could represent the basis for validation studies in larger cohorts, which could impact the future prophylactic management of variceal bleeding in cirrhosis. Enhancing the benefit of β-blockers with a safe, accessible, cost-effective drug could improve clinical outcomes in cirrhosis, which in turn could translate into a reduction in the rates and costs of hospitalization, and ultimately into improved survival.

Arginine, Transsulfuration, and Folic Acid Pathway Metabolomics in Chronic Obstructive Pulmonary Disease: A Systematic Review and Meta-Analysis

There is an increasing interest in biomarkers of nitric oxide dysregulation and oxidative stress to guide management and identify new therapeutic targets in patients with chronic obstructive pulmonary disease (COPD). We conducted a systematic review and meta-analysis of the association between circulating metabolites within the arginine (arginine, citrulline, ornithine, asymmetric, ADMA, and symmetric, SDMA dimethylarginine), transsulfuration (methionine, homocysteine, and cysteine) and folic acid (folic acid, vitamin B6, and vitamin B12) metabolic pathways and COPD. We searched electronic databases from inception to 30 June 2023 and assessed the risk of bias and the certainty of evidence. In 21 eligible studies, compared to healthy controls, patients with stable COPD had significantly lower methionine (standardized mean difference, SMD = -0.50, 95% CI -0.95 to -0.05, p = 0.029) and folic acid (SMD = -0.37, 95% CI -0.65 to -0.09, p = 0.009), and higher homocysteine (SMD = 0.78, 95% CI 0.48 to 1.07, p < 0.001) and cysteine concentrations (SMD = 0.34, 95% CI 0.02 to 0.66, p = 0.038). Additionally, COPD was associated with significantly higher ADMA (SMD = 1.27, 95% CI 0.08 to 2.46, p = 0.037), SDMA (SMD = 3.94, 95% CI 0.79 to 7.08, p = 0.014), and ornithine concentrations (SMD = 0.67, 95% CI 0.13 to 1.22, p = 0.015). In subgroup analysis, the SMD of homocysteine was significantly associated with the biological matrix assessed and the forced expiratory volume in the first second to forced vital capacity ratio, but not with age, study location, or analytical method used. Our study suggests that the presence of significant alterations in metabolites within the arginine, transsulfuration, and folic acid pathways can be useful for assessing nitric oxide dysregulation and oxidative stress and identifying novel treatment targets in COPD. (PROSPERO registration number: CRD42023448036.).

Hyperhomocysteinemia and Accelerated Aging: The Pathogenic Role of Increased Homocysteine in Atherosclerosis, Osteoporosis, and Neurodegeneration

Cardiovascular diseases and osteoporosis, seemingly unrelated disorders that occur with advanced age, share major pathogenetic mechanisms contributing to accelerated atherosclerosis and bone loss. Hyperhomocysteinemia (hHcy) is among these mechanisms that can cause both vascular and bone disease. In its more severe form, hHcy can present early in life as homocystinuria, an inborn error of metabolic pathways of the sulfur-containing amino acid methionine. In its milder forms, hHcy may go undiagnosed and untreated into adulthood. As such, hHcy may serve as a potential therapeutic target for cardiovascular disease, osteoporosis, thrombophilia, and neurodegeneration, collectively representing accelerated aging. Multiple trials to lower cardiovascular risk and improve bone density with homocysteine-lowering agents, yet none has proven to be clinically meaningful. To understand this unmet clinical need, this review will provide mechanistic insight into the pathogenesis of vascular and bone disease in hHcy, using homocystinuria as a model for accelerated atherosclerosis and bone density loss, a model for accelerated aging.

The effect of exenatide (a GLP-1 analogue) and sitagliptin (a DPP-4 inhibitor) on asymmetric dimethylarginine (ADMA) metabolism and selected biomarkers of cardiac fibrosis in rats with fructose-induced metabolic syndrome

Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide (NO) synthesis, is a risk factor for endothelial dysfunction, a common pathophysiological denominator for both atherogenesis and cardiac fibrosis. We aimed to investigate whether the cardioprotective and antifibrotic effects of incretin drugs, exenatide and sitagliptin, may be associated with their ability to affect circulating and cardiac ADMA metabolism. Normal and fructose-fed rats were treated with sitagliptin (5.0/10 mg/kg) or exenatide (5/10 µg/kg) for 4 weeks. The following methods were used: LC-MS/MS, ELISA, Real-Time-PCR, colorimetry, IHC and H&E staining, PCA and OPLS-DA projections. Eight-week fructose feeding resulted in an increase in plasma ADMA and a decrease in NO concentration. Exenatide administration into fructose-fed rats reduced the plasma ADMA level and increased NO level. In the heart of these animals exenatide administration increased NO and PRMT1 level, reduced TGF-ß1, α-SMA levels and COL1A1 expression. In the exenatide treated rats renal DDAH activity positively correlated with plasma NO level and negatively with plasma ADMA level and cardiac α-SMA concentration. Sitagliptin treatment of fructose-fed rats increased plasma NO concentration, reduced circulating SDMA level, increased renal DDAH activity and reduced myocardial DDAH activity. Both drugs attenuated the myocardial immunoexpression of Smad2/3/P and perivascular fibrosis. In the metabolic syndrome condition both sitagliptin and exenatide positively modulated cardiac fibrotic remodeling and circulating level of endogenous NOS inhibitors but had no effects on ADMA levels in the myocardium.

Stroke in Parkinson's disease: a review of epidemiological studies and potential pathophysiological mechanisms

Parkinson's disease (PD) is the fastest growing neurological disorder and one of the leading neurological causes of disability worldwide following stroke. An overall aging global population, as well as general changes in lifestyle associated with mass industrialization in the last century, may be linked to both increased incidence rates of PD and an increase in cumulative cardiovascular risk. Recent epidemiological studies show an increased risk of stroke, post-stroke complications, and subclinical ischemic insults in PD. PD patients have a host of characteristics that might contribute to increasing the risk of developing ischemic stroke including motor impairment, dysautonomia, and sleep disorders. This increases the urgency to study the interplay between PD and other neurological disorders, and their combined effect on mortality, morbidity, and quality of life. In this review, we provide a comprehensive overview of the studied etiological factors and pathological processes involved in PD, specifically with regard to their relationship to stroke. We hope that this review offers an insight into the relationship between PD and ischemic stroke and motivates further studies in this regard.

Unexplored Roles of Erythrocytes in Atherothrombotic Stroke

Stroke constitutes the second highest cause of morbidity and mortality worldwide while also impacting the world economy, triggering substantial financial burden in national health systems. High levels of blood glucose, homocysteine, and cholesterol are causative factors for atherothrombosis. These molecules induce erythrocyte dysfunction, which can culminate in atherosclerosis, thrombosis, thrombus stabilization, and post-stroke hypoxia. Glucose, toxic lipids, and homocysteine result in erythrocyte oxidative stress. This leads to phosphatidylserine exposure, promoting phagocytosis. Phagocytosis by endothelial cells, intraplaque macrophages, and vascular smooth muscle cells contribute to the expansion of the atherosclerotic plaque. In addition, oxidative stress-induced erythrocytes and endothelial cell arginase upregulation limit the pool for nitric oxide synthesis, leading to endothelial activation. Increased arginase activity may also lead to the formation of polyamines, which limit the deformability of red blood cells, hence facilitating erythrophagocytosis. Erythrocytes can also participate in the activation of platelets through the release of ADP and ATP and the activation of death receptors and pro-thrombin. Damaged erythrocytes can also associate with neutrophil extracellular traps and subsequently activate T lymphocytes. In addition, reduced levels of CD47 protein in the surface of red blood cells can also lead to erythrophagocytosis and a reduced association with fibrinogen. In the ischemic tissue, impaired erythrocyte 2,3 biphosphoglycerate, because of obesity or aging, can also favor hypoxic brain inflammation, while the release of damage molecules can lead to further erythrocyte dysfunction and death.

Endothelial dysfunction: developmental mechanisms and therapeutic strategies

Introduction: Every year the importance of the normal functioning of the endothelial layer of the vascular wall in maintaining the health of the body becomes more and more obvious.

The physiological role of the endothelium: The endothelium is a metabolically active organ actively involved in the regulation of hemostasis, modulation of inflammation, maintenance of hemovascular homeostasis, regulation of angiogenesis, vascular tone, and permeability.

Risk factors for the development of endothelial dysfunction: Currently, insufficient bioavailability of nitric oxide is considered the most significant risk factor for endothelial dysfunction.

Mechanisms of development of endothelial dysfunction: The genesis of endothelial dysfunction is a multifactorial process. Among various complex mechanisms, this review examines oxidative stress, inflammation, hyperglycemia, vitamin D deficiency, dyslipidemia, excess visceral fat, hyperhomocysteinemia, hyperuricemia, as well as primary genetic defect of endotheliocytes, as the most common causes in the population underlying the development of endothelial dysfunction.

Markers of endothelial dysfunction in various diseases: This article discusses the main biomarkers of endothelial dysfunction currently used, as well as promising biomarkers in the future for laboratory diagnosis of this pathology.

Therapeutic strategies: Therapeutic approaches to the endothelium in order to prevent or reduce a degree of damage to the vascular wall are briefly described.

Conclusion: Endothelial dysfunction is a typical pathological process involved in the pathogenesis of many diseases. Thus, pharmacological agents with endothelioprotective properties can provide more therapeutic benefits than a drug without such an effect.

Identifying a metabolomics profile associated with masked hypertension in two independent cohorts: Data from the African-PREDICT and SABPA studies

Individuals with masked hypertension (MHT) have a greater risk of adverse cardiovascular outcomes than normotensive (NT) individuals. Exploring metabolomic differences between NT and MHT individuals may help provide a better understanding of the etiology of MHT. We analyzed data from 910 young participants (83% NT and 17% MHT) (mean age 24 ± 3 years) from the African-PREDICT and 210 older participants (63% NT and 37% MHT) from the SABPA (mean age 42 ± 9.6 years) studies. Clinic and ambulatory blood pressures (BPs) were used to define BP phenotypes. Urinary amino acids and acylcarnitines were measured using liquid chromatography time-of-flight mass spectrometry in SABPA and liquid chromatography tandem mass spectrometry in the African-PREDICT studies. In the SABPA study, amino acids (leucine/isoleucine, valine, methionine, phenylalanine), free carnitine (C0-carnitine), and acylcarnitines C3 (propionyl)-, C4 (butyryl)-carnitine and total acylcarnitine) were higher in MHT than NT adults. In the African-PREDICT study, C0- and C5-carnitines were higher in MHT individuals. With unadjusted analyses in NT adults from the SABPA study, ambulatory SBP correlated positively with only C3-carnitine. In MHT individuals, positive correlations of ambulatory SBP with leucine/isoleucine, valine, methionine, phenylalanine, C0-carnitine and C3-carnitine were evident (all p < 0.05). In the African-PREDICT study, ambulatory SBP correlated positively with C0-carnitine (r = 0.101; p = 0.006) and C5-carnitine (r = 0.195; p < 0.001) in NT adults and C5-carnitine in MHT individuals (r = 0.169; p = 0.034). We demonstrated differences between the metabolomic profiles of NT and MHT adults, which may reflect different stages in the alteration of branched-chain amino acid metabolism early on and later in life.

An Overview of Circulating Pulmonary Arterial Hypertension Biomarkers

Pulmonary arterial hypertension (PAH), also known as Group 1 Pulmonary Hypertension (PH), is a PH subset characterized by pulmonary vascular remodeling and pulmonary arterial obstruction. PAH has an estimated incidence of 15-50 people per million in the United States and Europe, and is associated with high mortality and morbidity, with patients' survival time after diagnosis being only 2.8 years. According to current guidelines, right heart catheterization is the gold standard for diagnostic and prognostic evaluation of PAH patients. However, this technique is highly invasive, so it is not used in routine clinical practice or patient follow-up. Thereby, it is essential to find new non-invasive strategies for evaluating disease progression. Biomarkers can be an effective solution for determining PAH patient prognosis and response to therapy, and aiding in diagnostic efforts, so long as their detection is non-invasive, easy, and objective. This review aims to clarify and describe some of the potential new candidates as circulating biomarkers of PAH.

Elevated Homocysteine Levels Predict Hospital-Acquired Pneumonia and Poor Functional Outcomes in Primary Intracerebral Hemorrhage

Background

Homocysteine (Hcy) has been extensively acknowledged to be correlated with inflammation. In this study, the relationship between Hcy and hospital-acquired pneumonia (HAP) in primary intracerebral hemorrhage (pICH) was explored.

Methods

We conducted a hospital-based study on screened eligible patients with primary intracerebral hemorrhage admitted within 24 h after symptom onset from January 2019 to June 2021. The associations between Hcy and HAP and poor outcomes in pICH were investigated using univariate and multivariate logistic regression analyses. The predictive accuracy of Hcy was assessed by the receiver operating characteristic curve and the optimal cutoff value of Hcy was determined by Youden Index. The patterns and magnitudes of associations between Hcy and HAP and poor outcomes were evaluated using a restricted cubic spline (RCS).

Results

A total of 579 patients with pICH were included in the study. Hcy level was significantly higher in patients with HAP and poor outcomes (p &lt; 0.001). The univariate and multivariate logistic regression analyses demonstrated that elevated Hcy was independently associated with both HAP and poor outcomes (p &lt; 0.001). Furthermore, receiver operating characteristic analysis indicated that Hcy exhibited a moderate predictive accuracy for both HAP and poor outcomes after pICH. The RCS model showed that there were linear relationships between Hcy and HAP and poor outcomes.

Conclusions

Higher Hcy level was independently associated with HAP and poor outcomes in patients with pICH.

Benchmark Examination of Blood Amino Acids Patterns in Phenylketonuria Neonates and Young Children on Phenylalanine-Restricted Dietary Treatment

Background: Phenylalanine-restricted diets have been the basis of therapy for phenylketonuria; however, little is known how this treatment effects homeostasis of other amino acids. This study aimed to assess blood amino acid alterations in phenylketonuric neonates before and after treatment to identify any residual amino acid alterations with phenylalanine restriction in these treated children. Methods: Concentrations of 11 amino acids were measured using liquid chromatography-tandem mass spectrometry performed on dried blood spots. Results: Elevated blood phenylalanine, arginine, citrulline, valine, methionine concentrations and decreased tyrosine, proline concentrations were observed in phenylketonuria neonates relative to controls, of which phenylalanine, arginine, methionine, tyrosine, and proline levels could be either partially or completely restored with dietary intervention, whereas citrulline and valine were not restored and remained higher. Conclusions: Blood amino acid homeostasis is disrupted in phenylketonuria. Although dietary intervention adjusts amino acid homeostasis in the direction of a healthy equilibrium, complete restoration is not achieved.

Oxidative Stress-Induced Male Infertility: Role of Antioxidants in Cellular Defense Mechanisms

Male infertility is linked to several environmental and mutagenic factors. Most of these factors, i.e., lifestyle, radiations, and chemical contaminations, work on the fundamental principles of physics, chemistry, and biology. Principally, it may induce oxidative stress (OS) and produce free radicals within the cells. The negative effect of OS may enhance the reactive oxygen species (ROS) levels in male reproductive organs and impair basic functions in a couple's fertility. Evidence suggests that infertile men have significantly increased ROS levels and a reduced antioxidant capacity compared with fertile men. Although, basic spermatic function and fertilizing capacity depend on a delicate balance between physiological activity of ROS and antioxidants to protect from cellular oxidative injury in sperm, that is essential to achieve pregnancy. The ideal oxidation-reduction (REDOX) equilibrium requires a maintenance of a range of ROS concentrations and modulation of antioxidants. For this reason, the chapter focuses on the effects of ROS in sperm functions and the current concepts regarding the benefits of medical management in men with diminished fertility and amelioration of the effect to improve sperm function. Also, this evidence-based study suggests an increasing rate of infertility that poses a global challenge for human health, urging the need of health care professionals to offer a correct diagnosis, comprehension of the process, and an individualized management of the patients.

Metabolic Therapy of Heart Failure: Is There a Future for B Vitamins?

Heart failure (HF) is a plague of the aging population in industrialized countries that continues to cause many deaths despite intensive research into more effective treatments. Although the therapeutic arsenal to face heart failure has been expanding, the relatively short life expectancy of HF patients is pushing towards novel therapeutic strategies. Heart failure is associated with drastic metabolic disorders, including severe myocardial mitochondrial dysfunction and systemic nutrient deprivation secondary to severe cardiac dysfunction. To date, no effective therapy has been developed to restore the cardiac energy metabolism of the failing myocardium, mainly due to the metabolic complexity and intertwining of the involved processes. Recent years have witnessed a growing scientific interest in natural molecules that play a pivotal role in energy metabolism with promising therapeutic effects against heart failure. Among these molecules, B vitamins are a class of water soluble vitamins that are directly involved in energy metabolism and are of particular interest since they are intimately linked to energy metabolism and HF patients are often B vitamin deficient. This review aims at assessing the value of B vitamin supplementation in the treatment of heart failure.

Homocysteine metabolism as the target for predictive medical approach, disease prevention, prognosis, and treatments tailored to the person

Homocysteine (Hcy) metabolism is crucial for regulating methionine availability, protein homeostasis, and DNA-methylation presenting, therefore, key pathways in post-genomic and epigenetic regulation mechanisms. Consequently, impaired Hcy metabolism leading to elevated concentrations of Hcy in the blood plasma (hyperhomocysteinemia) is linked to the overproduction of free radicals, induced oxidative stress, mitochondrial impairments, systemic inflammation and increased risks of eye disorders, coronary artery diseases, atherosclerosis, myocardial infarction, ischemic stroke, thrombotic events, cancer development and progression, osteoporosis, neurodegenerative disorders, pregnancy complications, delayed healing processes, and poor COVID-19 outcomes, among others. This review focuses on the homocysteine metabolism impairments relevant for various pathological conditions. Innovative strategies in the framework of 3P medicine consider Hcy metabolic pathways as the specific target for in vitro diagnostics, predictive medical approaches, cost-effective preventive measures, and optimized treatments tailored to the individualized patient profiles in primary, secondary, and tertiary care.

Naringenin ameliorates homocysteine induced endothelial damage via the AMPKα/Sirt1 pathway

Introduction

Endothelial damage (ED) has been implicated in accelerating the development of atherosclerosis. The latter condition is a risk factor for developing several cardiovascular diseases (CVDs) associated with high morbidity and mortality rates worldwide.

Objectives

In our previous studies, we found naringenin (Nar), a bioactive flavanone compound, to protect against mitochondrial damage and oxidative stress. Though the pleiotropic effects of Nar have been well described, precise cytoprotective mechanisms of Nar against homocysteine (Hcy) induced ED remains elusive. Understanding these events may give an insight in to prevention and treatment of CVDs.

Methods

After ruling out the NMDA-R1 mediated pathway, RNA-Seq, a novel transcriptomic technique uncovered AMPK signaling pathway was identified as the mechanism with which Nar corrects ED. Further in vivo and in vitro tests validated the role of Nar against ED.

Results

In particular, Nar activates AMPKα/Sirt1 signaling pathway, which restores mitochondrial Ca2+ balance and ultimately lowered production of reactive oxygen species (ROS). Activated AMPKα/Sirt1 signaling pathway also up-regulates endothelial nitric oxide synthase (eNOS) activity, and then increasing the production of nitric oxide (NO), ultimately ameliorating ED.

Conclusion

Nar could increase the ROS elimination and decrease eNOS uncoupling, subsequently upregulate the NO bioavailability and endothelial function by activating AMPKα/Sirt1 signaling pathway.

Association of Inflammatory Markers/Cytokines with Cardiovascular Risk Manifestation in Patients with Endometriosis

This study is aimed at determining the association of inflammatory markers and proinflammatory cytokines with cardiovascular risk manifestation in women with endometriosis as compared to healthy controls. A total of 181 females of reproductive age with the absence of other inflammatory or autoimmune disorders and a lack of hormonal therapy for at least 6 months voluntarily participated in this investigation. Patients were 81 females, laparoscopically diagnosed with endometriosis, while the control group comprised 80 healthy females without any pelvic pathology. All subjects were 20-40 years of age. Exclusion criteria were diabetes, obesity, hypertension, metabolic diseases, cardiovascular, and renal disorders. C-reactive protein, fibrinogen, homocysteine, interleukin-17, and interleukin-33 were analyzed using commercially available ELISA kits. For statistical interpretation, the unpaired Student “t” test was used. All inflammatory markers and cytokines demonstrated elevated levels (P < 0.001) in endometriosis patients as compared to healthy controls. The results of the study revealed that the patients with endometriosis demonstrate a hypercoagulable status due to inflammation, which initiates atherosclerosis and associated complications. Hence, endometriosis can cause a risk of cardiovascular disorders in these patients.

Asymmetric Dimethylarginine: a Key Player in the Pathophysiology of Endothelial Dysfunction, Vascular Inflammation and Atherosclerosis in Rheumatoid Arthritis?

Patients with rheumatoid arthritis (RA), a chronic and disabling autoimmune condition that is characterized by articular and extra-articular manifestations and a pro-inflammatory and pro-oxidant state, suffer from premature atherosclerosis and excessive cardiovascular disease burden. A key step in the pathogenesis of atherosclerosis is impaired synthesis of the endogenous messenger nitric oxide (NO) by endothelial cells which, in turn, alters local homeostatic mechanisms and favors vascular damage and plaque deposition. While the exact mechanisms of endothelial dysfunction in RA remain to be established, there is good evidence that RA patients have relatively high circulating concentrations of the methylated arginine asymmetric dimethylarginine (ADMA), a potent endogenous inhibitor of endothelial NO synthase (eNOS). This review discusses the biological and pathophysiological role of ADMA, the interplay between ADMA, inflammation and oxidative stress, and the available evidence on the adverse impact of ADMA on endothelial function and atherosclerosis and potential ADMA-lowering therapies in RA patients.

Vascular and immunopathological role of Asymmetric Dimethylarginine (ADMA) in Experimental Autoimmune Encephalomyelitis

Asymmetric dimethylarginine (ADMA) is an endogenous nitric oxide synthase (NOS) inhibitor/uncoupler inducing vascular pathology. Vascular pathology is an important factor for the development and progression of CNS pathology of MS, yet the role of ADMA in MS remains elusive. Patients with multiple sclerosis (MS) are reported to have elevated blood levels of ADMA, and mice with experimental autoimmune encephalomyelitis (EAE, an animal model of MS) generated by auto-immunization of myelin oligodendrocyte glycoprotein (MOG) and blood-brain barrier (BBB) disruption by pertussis toxin also had increased blood ADMA levels in parallel with induction of clinical disease. To explore the role of ADMA in EAE pathogenesis, EAE mice were treated with a daily dose of ADMA. It is of special interest that ADMA treatment enhanced the BBB disruption in EAE mice and exacerbated the clinical and CNS disease of EAE. ADMA treatment also induced the BBB disruption and EAE disease in MOG-immunized mice even without pertussis toxin treatment, suggesting the role of ADMA in BBB dysfunction in EAE. T-cell polarization studies also documented that ADMA treatment promotes T_H 1- and T_H 17-mediated immune responses but without affecting Treg-mediated immune response in EAE mice as well as in in vitro T-cell culture. Taken together, these data, for the first time, document the vascular and immunopathogenic roles of ADMA in EAE, thus pointing to the potential of ADMA-mediated mechanism as a new target of potential therapy for MS.

Functional inhibition of redox regulated heme proteins: A novel mechanism towards oxidative stress induced by homocysteine

Homocysteine (Hcy) is a sulfur containing non-protein toxic amino acid synthesized from methionine. Elevated level of Hcy is associated with cardiovascular complications and neurodegeneration. Hcy is believed to induce organ damage and apoptosis via oxidative stress. The pro-oxidant nature of Hcy is considered to originate from the metal-induced oxidation of thiol group-containing molecules forming disulfides (Hcy-Hcy, Hcy-cysteine, Hcy-glutathione, etc) or with free cysteine residues of proteins (a process called protein S-homocysteinylation). Formation of such disulfides indeed results in the generation of reactive oxygen species (ROS) which eventually leads to loss of cellular integrity. In the present manuscript, we performed systematic investigation of the effect of Hcy on iron containing proteins. We discover a novel mechanism of Hcy toxicity wherein Hcy oxidation is linked with the functional loss of the protein with iron as cofactors. Our results indicate that redox regulated heme proteins might be primarily involved in the Hcy toxicity and associated oxidative stress.

Whole-Body Cryotherapy Increases the Activity of Nitric Oxide Synthase in Older Men

Aging causes oxidative stress, endothelial dysfunction and a reduction in the bioavailability of nitric oxide. The study aim was to determine whether, as a result of repeated whole-body exposure to cryogenic temperature (3 min −130 °C), there is an increase of inducible nitric oxide synthase (iNOS) concentration in senior subjects (59 ± 6 years), and if this effect is stronger in athletes. In 10 long-distance runners (RUN) and 10 untraining (UTR) men, 24 whole-body cryotherapy (WBC) procedures were performed. Prior to WBC, after 12th and 24th treatments and 7 days later, the concentration of iNOS, asymmetric dimethylarginine (ADMA), 3-nitrotyrosine (3-NTR), homocysteine (HCY), C-reactive protein (CRP) and interleukins such as: IL-6, IL-1β, IL-10 were measured. In the RUN and UTR groups, after 24 WBC, iNOS concentration was found to be comparable and significantly higher (F = 5.95, p < 0.01) (large clinical effect size) compared to before 1st WBC and after 12th WBC sessions. There were no changes in the concentration of the remaining markers as a result of WBC (p > 0.05). As a result of applying 24 WBC treatments, using the every-other-day model, iNOS concentration increased in the group of older men, regardless of their physical activity level. Along with this increase, there were no changes in nitro-oxidative stress or inflammation marker levels.

A systematic survey of PRMT interactomes reveals the key roles of arginine methylation in the global control of RNA splicing and translation

Thousands of proteins undergo arginine methylation, a widespread post-translational modification catalyzed by several protein arginine methyltransferases (PRMTs). However, global understanding of their biological functions is limited due to the lack of a complete picture of the catalytic network for each PRMT. Here, we systematically identified interacting proteins for all human PRMTs and demonstrated their functional importance in mRNA splicing and translation. We demonstrated significant overlapping of interactomes of human PRMTs with the known methylarginine-containing proteins. Different PRMTs are functionally redundant with a high degree of overlap in their substrates and high similarities between their putative methylation motifs. Importantly, RNA-binding proteins involved in regulating RNA splicing and translation contain highly enriched arginine methylation regions. Moreover, inhibition of PRMTs globally alternates alternative splicing (AS) and suppresses translation. In particular, ribosomal proteins are extensively modified with methylarginine, and mutations in their methylation sites suppress ribosome assembly, translation, and eventually cell growth. Collectively, our study provides a global view of different PRMT networks and uncovers critical functions of arginine methylation in regulating mRNA splicing and translation.

PM2.5 induces intestinal damage by affecting gut microbiota and metabolites of rats fed a high-carbohydrate diet

PM_2.5 has a major impact on the gastrointestinal system, but the specific mechanism behind this action is not fully understood. Current studies have focused on the relationship between PM_2.5 and intestinal flora disorder, while ignoring the important influence of diet on gut microbes. In this study, SD rats were fed either a normal, high-fat, or high-carbohydrate diet for two months and exposed to PM_2.5 (7 mg/kg b.w.) by intratracheal instillation. The results showed that the body and kidney weights of the rats in the high-fat diet group were significantly increased relative to those with a normal diet, and changes in the intestinal microbes and metabolites induced by PM_2.5 were observed. Rats in the high-carbohydrate diet group had a significant response, and the diversity and richness indices of the flora were reduced (p < 0.05); additionally, intestinal Biffidobacterium and Lactobacillus were enriched, while many endogenous metabolites were found. Some amino acids derivatives and long-chain fatty acids were increased (p < 0.05). Both diet structure and PM_2.5 exposure can affect the composition of gut microbiota, and intestinal metabolites may be associated with cell membrane damage when a high-carbohydrate diet interacts with PM_2.5. This study considers multiple dietary factors to further supplement the evidence of intestinal damage via PM_2.5.

Periodontal Inflamed Surface Area Mediates the Link between Homocysteine and Blood Pressure

Here, we assess the association between homocysteine (Hcy) serum levels and periodontal status in a large representative sample of the National Health and Nutrition Examination Survey (NHANES). Using the 2001–2002 and 2003–2004 NHANES databases, participants with a periodontal examination, medical self-reported data, blood pressure (BP) and blood samples to determine complete blood count, C-reactive protein (CRP) and Hcy levels. We then calculated the periodontal inflamed surface area (PISA) and the periodontal epithelial surface area (PESA). Multivariable regression analysis explored the association between Hcy, periodontal measures and BP. Mediation analysis was performed to understand the effect of PISA and PESA in the link between Hcy and BP. 4021 participants fulfilled the inclusion criteria. Hcy levels showed significant correlations with systolic BP, diastolic BP, PISA, PESA and age. PESA showed to be significantly associated with Hcy both for the crude and adjusted models (p < 0.01), but not PISA (p > 0.05). In the association of Hcy with systolic BP, PISA significantly mediated 17.4% and PESA 0.9%. In the association of Hcy with diastolic BP, PISA significantly mediated 16.3% and PESA 47.2%. In conclusion, Hcy and periodontitis are associated. Further, both PISA and PESA significantly mediated the association of Hcy with systolic BP and diastolic BP. Future studies shall deepen the mechanisms by which Hcy levels increase in a clinical situation of periodontitis.

Interplay Between Reactive Oxygen/Reactive Nitrogen Species and Metabolism in Vascular Biology and Disease

Reactive oxygen species (ROS; e.g., superoxide [O₂^•-] and hydrogen peroxide [H₂O₂]) and reactive nitrogen species (RNS; e.g., nitric oxide [NO^•]) at the physiological level function as signaling molecules that mediate many biological responses, including cell proliferation, migration, differentiation, and gene expression. By contrast, excess ROS/RNS, a consequence of dysregulated redox homeostasis, is a hallmark of cardiovascular disease. Accumulating evidence suggests that both ROS and RNS regulate various metabolic pathways and enzymes. Recent studies indicate that cells have mechanisms that fine-tune ROS/RNS levels by tight regulation of metabolic pathways, such as glycolysis and oxidative phosphorylation. The ROS/RNS-mediated inhibition of glycolytic pathways promotes metabolic reprogramming away from glycolytic flux toward the oxidative pentose phosphate pathway to generate nicotinamide adenine dinucleotide phosphate (NADPH) for antioxidant defense. This review summarizes our current knowledge of the mechanisms by which ROS/RNS regulate metabolic enzymes and cellular metabolism and how cellular metabolism influences redox homeostasis and the pathogenesis of disease. A full understanding of these mechanisms will be important for the development of new therapeutic strategies to treat diseases associated with dysregulated redox homeostasis and metabolism. Antioxid. Redox Signal. 34, 1319-1354.

Management of Cirrhotic Ascites under the Add-on Administration of Tolvaptan

Tolvaptan is a recently available diuretic that blocks arginine vasopressin receptor 2 in the renal collecting duct. Its diuretic mechanism involves selective water reabsorption by affecting the water reabsorption receptor aquaporin 2. Given that liver cirrhosis patients exhibit hyponatremia due to their pseudo-aldosteronism and usage of natriuretic agents, a sodium maintaining agent, such as tolvaptan, is physiologically preferable. However, large scale studies indicating the patients for whom this would be effective and describing management under its use have been insufficient. The appropriate management of cirrhosis patients treated with tolvaptan should be investigated. In the present review, we collected articles investigating the effectiveness of tolvaptan and factors associated with survival and summarized their management reports. Earlier administration of tolvaptan before increasing the doses of natriuretic agents is recommended because this may preserve effective arterial blood volume.

Asymmetric dimethylarginine: Is it a risk facgtor in the repair of aortic coarctation?

BACKGROUND

Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase, causes endothelial dysfunction which is an important risk factor for mortality in adult cardiovascular diseases. We aimed to investigate whether there was a relationship between the aortic cross-clamping (ACC) time and serum ADMA level in aortic coarctation surgery and importance of the serum ADMA level as a marker of mortality and morbidity.

METHOD

Twenty-two patients undergoing surgery for aortic coarctation in the neonatal and early infant period were included in the study, and the patients were divided into two groups according to the aortic cross-clamping time (Group I: <20-min, Group II: >20-min).

RESULTS

In Group I, preoperative and postoperative mean ADMA values of the patients were 0.57 ± 0.78 and 0.54 ± 0.83 µmol/L, respectively. In Group II, preoperative and postoperative mean ADMA values of the patients were 0.69 ± 0.93 and 1.10 ± 0.30 µmol/L, respectively. Preoperative-postoperative change of ADMA correlates with ACC time (r = .802, p < .005) and duration of postoperative inotropic support (r = .719, p < .05). Also a high correlation has been found between the ACC time and duration of inotropic support in both groups (r = .689, p < .05).

CONCLUSION

Perioperative serum ADMA levels could be used as a prognostic bio-marker in the patients undergoing aortic coarctation repair. Treatments to reduce serum ADMA levels can be valuable for preventing mortality and morbidity which develop after surgeries in a transient ischemia setting by clamping the aorta.

Methylation as a key regulator of Tau aggregation and neuronal health in Alzheimer's disease

Neurodegenerative diseases like Alzheimer's, Parkinson's and Huntington's disease involves abnormal aggregation and accumulation of toxic proteins aggregates. Post-translational modifications (PTMs) of the causative proteins play an important role in the etiology of disease as they could either slow down or accelerate the disease progression. Alzheimer disease is associated with the aggregation and accumulation of two major protein aggregates-intracellular neurofibrillary tangles made up of microtubule-associated protein Tau and extracellular Amyloid-β plaques. Post-translational modifications are important for the regulation of Tau`s function but an imbalance in PTMs may lead to abnormal Tau function and aggregation. Tau methylation is one of the important PTM of Tau in its physiological state. However, the methylation signature on Tau lysine changes once it acquires pathological aggregated form. Tau methylation can compete with other PTMs such as acetylation and ubiquitination. The state of PTM at these sites determines the fate of Tau protein in terms of its function and stability. The global methylation in neurons, microglia and astrocytes are involved in multiple cellular functions involving their role in epigenetic regulation of gene expression via DNA methylation. Here, we have discussed the effect of methylation on Tau function in a site-specific manner and their cross-talk with other lysine modifications. We have also elaborated the role of methylation in epigenetic aspects and neurodegenerative conditions associated with the imbalance in methylation metabolism affecting global methylation state of cells. Video abstract.

The role of B vitamins in stroke prevention

Elevated plasma levels of homocysteine (Hcy) are a recognized risk factor for stroke. This relationship represents one aspect of the debated `Hcy hypothesis'. Elevated Hcy may be an independent and treatable cause of atherosclerosis and thrombotic vascular diseases. Further observations indicate that proper dietary supplementation with B-vitamins decreases total plasma Hcy concentrations and may be an effective intervention for stroke prevention. Metabolic vitamin B₁₂ deficiency is a nutritional determinant of total Hcy and stroke risk. Genetic factors may link B vitamins with stroke severity due to the impact on Hcy metabolism of polymorphism in the genes coding for methylenetetrahydrofolate reductase, methionine-synthase, methionine synthase reductase, and cystathionine β-synthase. Several meta-analyses of large randomized controlled trials exist. However, they are not completely in agreement about B vitamins' role, particularly folic acid levels, vitamin B₁₂, and B₆, in lowering the homocysteine concentrations in people at high stroke risk. A very complex relationship exists between Hcy and B vitamins, and several factors appear to modify the preventive effects of B vitamins in stroke. This review highlights the regulating factors of the active role of B vitamins active in stroke prevention. Also, inputs for further large, well-designed studies, for specific, particularly sensitive subgroups are given.

Estimation of folic acid/micro nutrients levels; Does it reflect sperm parameters

OBJECTIVE

To study the impact of vitamin B12, folic acid (FA) and methylmalonic acid (MMA) on sperm parameters; count, motility and morphology leading to male fertility.

METHODS

The cross-sectional study comprised of one hundred and eighty-six subjects with normal sperm parameters (fertile) and 88 subjects with abnormal sperm parameters labelled as "infertile" from a sample population of Karachi, Pakistan. Vitamin B12, FA and MMA levels in serum were analysed by enzyme linked immune sorbent assay. Unadjusted and adjusted prevalence ratio with their 95% CI were reported by using cox regression algorithm to assess the association of Vitamin B12, FA and MMA and other factors with male Infertility. Unadjusted and adjusted beta coefficients with 95% CI were reported by using linear regression analysis for assessing relationship of Vitamin B12, FA and MMA and other factors with semen parameters (count, motility and morphology); P value of <.05 was considered significant.

RESULTS

It was declared that with every 1 unit increase in vitamin B12, FA and MMA the prevalence of infertility was decreased by 1%, 17% and 74%, respectively. Multivariate analysis revealed that vitamin B12, FA and MMA had a significant association with total sperm count, motility and morphology. The sperm parameters were also affected by increase in; LH, BMI and body fat %. There was a significant positive correlation of; LH with Vitamin B12 and FA (0.423 < 0.001, 0.338 < 0.001) and testosterone with vitamin B12 and FA (0.326 < 0.001, 0.291 < 0.001), respectively.

CONCLUSION

All the studied micronutrients; Vitamin B12, FA and MMA had a positive effect on sperm parameters; count, motility and morphology and the associated reproductive hormones which explains their role on reproductive functions required to acquire fertility.

Homocysteine in Neurology: A Possible Contributing Factor to Small Vessel Disease

Homocysteine (Hcy) is a sulfur-containing amino acid generated during methionine metabolism, accumulation of which may be caused by genetic defects or the deficit of vitamin B12 and folate. A serum level greater than 15 micro-mols/L is defined as hyperhomocysteinemia (HHcy). Hcy has many roles, the most important being the active participation in the transmethylation reactions, fundamental for the brain. Many studies focused on the role of homocysteine accumulation in vascular or degenerative neurological diseases, but the results are still undefined. More is known in cardiovascular disease. HHcy is a determinant for the development and progression of inflammation, atherosclerotic plaque formation, endothelium, arteriolar damage, smooth muscle cell proliferation, and altered-oxidative stress response. Conversely, few studies focused on the relationship between HHcy and small vessel disease (SVD), despite the evidence that mice with HHcy showed a significant end-feet disruption of astrocytes with a diffuse SVD. A severe reduction of vascular aquaporin-4-water channels, lower levels of high-functioning potassium channels, and higher metalloproteinases are also observed. HHcy modulates the N-homocysteinylation process, promoting a pro-coagulative state and damage of the cellular protein integrity. This altered process could be directly involved in the altered endothelium activation, typical of SVD and protein quality, inhibiting the ubiquitin-proteasome system control. HHcy also promotes a constant enhancement of microglia activation, inducing the sustained pro-inflammatory status observed in SVD. This review article addresses the possible role of HHcy in small-vessel disease and understands its pathogenic impact.

Hyperhomocysteinemia and Cardiovascular Disease: Is the Adenosinergic System the Missing Link?

The influence of hyperhomocysteinemia (HHCy) on cardiovascular disease (CVD) remains unclear. HHCy is associated with inflammation and atherosclerosis, and it is an independent risk factor for CVD, stroke and myocardial infarction. However, homocysteine (HCy)-lowering therapy does not affect the inflammatory state of CVD patients, and it has little influence on cardiovascular risk. The HCy degradation product hydrogen sulfide (H2S) is a cardioprotector. Previous research proposed a positive role of H2S in the cardiovascular system, and we discuss some recent data suggesting that HHCy worsens CVD by increasing the production of H2S, which decreases the expression of adenosine A2A receptors on the surface of immune and cardiovascular cells to cause inflammation and ischemia, respectively.

Multi-omic signatures of atherogenic dyslipidaemia: pre-clinical target identification and validation in humans

BACKGROUND

Dyslipidaemia is a major risk factor for atherosclerosis and cardiovascular diseases. The molecular mechanisms that translate dyslipidaemia into atherogenesis and reliable markers of its progression are yet to be fully elucidated. To address this issue, we conducted a comprehensive metabolomic and proteomic analysis in an experimental model of dyslipidaemia and in patients with familial hypercholesterolemia (FH).

METHODS

Liquid chromatography/mass spectrometry (LC/MS) and immunoassays were used to find out blood alterations at metabolite and protein levels in dyslipidaemic ApoE^-/-/LDLR^-/- mice and in FH patients to evaluate their human relevance.

RESULTS

We identified 15 metabolites (inhibitors and substrates of nitric oxide synthase (NOS), low-molecular-weight antioxidants (glutamine, taurine), homocysteine, methionine, 1-methylnicotinamide, alanine and hydroxyproline) and 9 proteins (C-reactive protein, proprotein convertase subtilisin/kexin type 9, apolipoprotein C-III, soluble intercellular adhesion molecule-1, angiotensinogen, paraoxonase-1, fetuin-B, vitamin K-dependent protein S and biglycan) that differentiated FH patients from healthy controls. Most of these changes were consistently found in dyslipidaemic mice and were further amplified if mice were fed an atherogenic (Western or low-carbohydrate, high-protein) diet.

CONCLUSIONS

The alterations highlighted the involvement of an immune-inflammatory response system, oxidative stress, hyper-coagulation and impairment in the vascular function/regenerative capacity in response to dyslipidaemia that may also be directly engaged in development of atherosclerosis. Our study further identified potential biomarkers for an increased risk of atherosclerosis that may aid in clinical diagnosis or in the personalized treatment.

Exhaustive Exercise and Post-exercise Protein Plus Carbohydrate Supplementation Affect Plasma and Urine Concentrations of Sulfur Amino Acids, the Ratio of Methionine to Homocysteine and Glutathione in Elite Male Cyclists

Plasma and tissue sulfur amino acid (SAA) availability are crucial for intracellular methylation reactions and cellular antioxidant defense, which are important processes during exercise and in recovery. In this randomized, controlled crossover trial among eight elite male cyclists, we explored the effect of exhaustive exercise and post-exercise supplementation with carbohydrates and protein (CHO+PROT) vs. carbohydrates (CHO) on plasma and urine SAAs, a potential new marker of methylation capacity (methionine/total homocysteine ratio [Met/tHcy]) and related metabolites. The purpose of the study was to further explore the role of SAAs in exercise and recovery. Athletes cycled to exhaustion and consumed supplements immediately after and in 30 min intervals for 120 min post-exercise. After ~18 h recovery, performance was tested in a time trial in which the CHO+PROT group cycled 8.5% faster compared to the CHO group (41:53 ± 1:51 vs. 45:26 ± 1:32 min, p < 0.05). Plasma methionine decreased by ~23% during exhaustive exercise. Two h post-exercise, further decline in methionine had occured by ~55% in the CHO group vs. ~33% in the CHO+PROT group (p_group × _time < 0.001). The Met/tHcy ratio decreased by ~33% during exhaustive exercise, and by ~54% in the CHO group vs. ~27% in the CHO+PROT group (p_group × _time < 0.001) post-exercise. Plasma cystathionine increased by ~72% in the CHO group and ~282% in the CHO+PROT group post-exercise (p_group × _time < 0.001). Plasma total cysteine, taurine and total glutathione increased by 12% (p = 0.03), 85% (p < 0.001) and 17% (p = 0.02), respectively during exhaustive exercise. Using publicly available transcriptomic data, we report upregulated transcript levels of skeletal muscle SLC7A5 (log₂ fold-change: 0.45, FDR:1.8^e−07) and MAT2A (log₂ fold-change: 0.38, FDR: 3.4^e−0.7) after acute exercise. Our results show that exercise acutely lowers plasma methionine and the Met/tHcy ratio. This response was attenuated in the CHO+PROT compared to the CHO group in the early recovery phase potentially affecting methylation capacity and contributing to improved recovery.

The Link between Exercise and Homocysteine in the Alzheimer's Disease: A Bioinformatic Network Model

Elevated peripheral expression of homocysteine (Hcy) is associated with an increased risk of coronary heart disease and stroke, diabetes, and cancer. It is also associated with cognitive impairment as it has been reported that high levels of Hcy cause cognitive dysfunction and memory deficit. Among several etiological factors that contribute to the pathogenesis of neurodegenerative diseases, including Alzheimer's disease (AD), Hcy seems to directly contribute to the generation of neurotoxicity factors. This study aims to hypothesize the molecular mechanism by which exercise can reduce the risk of neurological complications promoted by hyperhomocysteinemia (HHcy), and discuss how exercise could reduce the risk of developing AD by using bioinformatics network models. According to the genes network, there are connections between proteins and amino acids associated with Hcy, exercise, and AD. Studies have evidenced that exercise may be one of several processes by which acid nitric availability can be maximized in the human body, which is particularly important in reducing cell loss and tau pathology and, thereby, leading to a reduced risk of complications associated with HHcy and AD.

Cystathionine γ-lyase promotes estrogen-stimulated uterine artery blood flow via glutathione homeostasis

During pregnancy, estrogen (E₂) stimulates uterine artery blood flow (UBF) by enhancing nitric oxide (NO)-dependent vasodilation. Cystathionine γ-lyase (CSE) promotes vascular NO signaling by producing hydrogen sulfide (H₂S) and by maintaining the ratio of reduced-to-oxidized intracellular glutathione (GSH/GSSG) through l-cysteine production. Because redox homeostasis can influence NO signaling, we hypothesized that CSE mediates E₂ stimulation of UBF by modulating local intracellular cysteine metabolism and GSH/GSSG levels to promote redox homeostasis. Using non-pregnant ovariectomized WT and CSE-null (CSE KO) mice, we performed micro-ultrasound of mouse uterine and renal arteries to assess changes in blood flow upon exogenous E₂ stimulation. We quantified serum and uterine artery NO metabolites (NO_x), serum amino acids, and uterine and renal artery GSH/GSSG. WT and CSE KO mice exhibited similar baseline uterine and renal blood flow. Unlike WT, CSE KO mice did not exhibit expected E₂ stimulation of UBF. Renal blood flow was E₂-insensitive for both genotypes. While serum and uterine artery NO_x were similar between genotypes at baseline, E₂ decreased NO_x in CSE KO serum. Cysteine was also lower in CSE KO serum, while citrulline and homocysteine levels were elevated. E₂ and CSE deletion additively decreased GSH/GSSG in uterine arteries. In contrast, renal artery GSH/GSSG was insensitive to E₂ or CSE deletion. Together, these findings suggest that CSE maintenance of uterine artery GSH/GSSG facilitates nitrergic signaling in uterine arteries and is required for normal E₂ stimulation of UBF. These data have implications for pregnancy pathophysiology and the selective hormone responses of specific vascular beds.

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CSE-null mice exhibit abnormal estrogen augmentation of uterine artery blood flow.

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Estrogen lowers uterine artery nitric oxide metabolites in CSE null mice.

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CSE loss and estrogen additively impair uterine artery glutathione homeostasis.

•

Neither CSE loss nor estrogen influences renal artery blood flow or glutathione.

High expression of a vascular stricture-related marker is predictive of an early response to tolvaptan, and a low fractional excretion of sodium is predictive of a poor long-term survival after tolvaptan administration for liver cirrhosis

AIM

Tolvaptan is a newly available diuretic that has a specific function in water reabsorption inhibition. Given that spironolactone or furosemide induces the aggravation of cirrhotic hyponatremia and dehydration, tolvaptan affects the management strategy of liver cirrhosis. Representative predictive markers of its response include renal function-related markers such as urea nitrogen or creatinine. However, vascular function-related markers have not been well investigated. We investigated the effect of the vascular function-related marker asymmetric dimethylarginine (ADMA) and the effective arterial blood volume (EABV) marker, fractional excretion of sodium (FENa), on the early tolvaptan response and survival in liver cirrhosis.

METHODS

We prospectively recruited 49 patients who required add-on tolvaptan for refractory ascites or edema. Laboratory data were obtained immediately before and 1 day after tolvaptan administration. Patients exhibiting >1.5 kg weight loss after 1 week were categorized as early responders to tolvaptan. Patients were followed for a median of 200 days and were assessed for survival.

RESULTS

Early responders showed lower creatinine levels (<1.0 mg/dL), and higher ADMA levels (≥0.61 nmol/mL) than others in a multivariate analysis. Patients with a shorter survival were positive for hepatocellular carcinoma and had a low FENa (<0.35%).

CONCLUSION

Early responders showed higher ADMA levels reflecting vascular stricture, suggesting that higher vascular tonus is required for a tolvaptan early response. Patients with a shorter survival showed a lower FENa, reflecting a lower EABV and suggesting that adequate EABV is required for the prolonged survival after tolvaptan administration.

The Antioxidant Role of One-Carbon Metabolism on Stroke

One-carbon (1C) metabolism is a metabolic network that is centered on folate, a B vitamin; it integrates nutritional signals with biosynthesis, redox homeostasis, and epigenetics. This metabolic pathway also reduces levels of homocysteine, a non-protein amino acid. High levels of homocysteine are linked to increased risk of hypoxic events, such as stroke. Several preclinical studies have suggested that 1C metabolism can impact stroke outcome, but the clinical data are unclear. The objective of this paper was to review preclinical and clinical research to determine whether 1C metabolism has an antioxidant role on stroke. To accomplish the objective, we searched for publications using the following medical subject headings (MeSH) keywords: antioxidants, hypoxia, stroke, homocysteine, one-carbon metabolism, folate, methionine, and dietary supplementation of one-carbon metabolism. Both pre-clinical and clinical studies were retrieved and reviewed. Our review of the literature suggests that deficiencies in 1C play an important role in the onset and outcome of stroke. Dietary supplementation of 1C provides beneficial effects on stroke outcome. For stroke-affected patients or individuals at high risk for stroke, the data suggest that nutritional modifications in addition to other therapies could be incorporated into a treatment plan.