Treatment of coronary heart disease with folic acid: is there a future?

Modulation of the nitric oxide/cGMP pathway in cardiac contraction and relaxation: Potential role in heart failure treatment

Evidence exists that heart failure (HF) has an overall impact of 1-2 % in the global population being often associated with comorbidities that contribute to increased disease prevalence, hospitalization, and mortality. Recent advances in pharmacological approaches have significantly improved clinical outcomes for patients with vascular injury and HF. Nevertheless, there remains an unmet need to clarify the crucial role of nitric oxide/cyclic guanosine 3',5'-monophosphate (NO/cGMP) signalling in cardiac contraction and relaxation, to better identify the key mechanisms involved in the pathophysiology of myocardial dysfunction both with reduced (HFrEF) as well as preserved ejection fraction (HFpEF). Indeed, NO signalling plays a crucial role in cardiovascular homeostasis and its dysregulation induces a significant increase in oxidative and nitrosative stress, producing anatomical and physiological cardiac alterations that can lead to heart failure. The present review aims to examine the molecular mechanisms involved in the bioavailability of NO and its modulation of downstream pathways. In particular, we focus on the main therapeutic targets and emphasize the recent evidence of preclinical and clinical studies, describing the different emerging therapeutic strategies developed to counteract NO impaired signalling and cardiovascular disease (CVD) development.

Spaceflight-related ocular changes: the potential role of genetics, and the potential of B vitamins as a countermeasure

PURPOSE OF REVIEW

Within the last decade, it was realized that during and after long-duration spaceflight, some astronauts experience ophthalmic abnormalities including refractive changes, optic disc edema, globe flattening, choroidal folds, and cotton wool spots. Much research has been initiated and conducted, but little evidence is available to differentiate affected crewmembers.

RECENT FINDINGS

The first published data to distinguish between affected and nonaffected crewmembers identified biochemical differences in affected astronauts: one-carbon pathway metabolite concentrations were higher in these individuals than in nonaffected astronauts, even before flight. These data led to findings that genetics and B-vitamin status were predictors of the incidence of the ophthalmic abnormalities. A multihit hypothesis was developed, with genetics and B-vitamin status as two of several important elements that all contribute to endothelial dysfunction and ultimately to ophthalmic changes after flight. One of these contributing factors - response to carbon dioxide exposure - was recently documented to be affected by the same one-carbon pathway genetics.

SUMMARY

This line of research may help identify which astronauts are at risk of these ophthalmic changes, and allow targeted treatment. This research may have implications for clinical populations, including patients with polycystic ovary syndrome, that have similar biochemical, endocrine, and genetic characteristics, and it may shed light on why links between cardiovascular disease and the metabolites homocysteine and folate have been elusive and confounded.

Arsenic toxicity and epimutagenecity: the new LINEage

Global methylation pattern regulates the normal functioning of a cell. Research have shown arsenic alter these methylation landscapes within the genome leading to aberrant gene expression and inducts various pathophysiological outcomes. Long interspersed nuclear elements (LINE-1) normally remains inert due to heavy methylation of it's promoters, time and various environmental insults, they lose these methylation signatures and begin retro-transposition that has been associated with genomic instability and cancerous outcomes. Of the various high throughput technologies available to detect global methylation profile, development of LINE-1 methylation index shall provide a cost effect-screening tool to detect epimutagenic events in the wake of toxic exposure in a large number of individuals. In the present review, we tried to discuss the state of research and whether LINE-1 methylation can be considered as a potent epigenetic signature for arsenic toxicity.

Folic acid promotes the myogenic differentiation of C2C12 murine myoblasts through the Akt signaling pathway

Folic acid is a water-soluble vitamin in the B-complex group, and an exogenous intake is required for health, growth and development. As a precursor to co-factors, folic acid is required for one-carbon donors in the synthesis of DNA bases and other essential biomolecules. A lack of dietary folic acid can lead to folic acid deficiency and can therefore result in several health problems, including macrocytic anemia, elevated plasma homocysteine levels, cardiovascular disease, birth defects, carcinogenesis, muscle weakness and difficulty in walking. Previous studies have indicated that folic acid exerts a positive effect on skeletal muscle functions. However, the precise role of folic acid in skeletal muscle cell differentiation remains poorly understood. Thus, in the present study, we examined the effects of folic acid on neo-myotube maturation and differentiation using C2C12 murine myoblasts. We found that folic acid promoted the formation of multinucleated myotubes, and increased the fusion index and creatine kinase (CK) activity in a concentration-dependent manner. In addition, western blot analysis revealed that the expression levels of the muscle-specific marker, myosin heavy chain (MyHC), as well as those of the myogenic regulatory factors (MRFs), MyoD and myogenin, were increased in the folic acid-treated myotubes during myogenic differentiation. Folic acid also promoted the activation of the Akt pathway, and this effect was inhibited by treatment of the C2C12 cells with LY294002 (Akt inhibitor). Blocking of the Akt pathway with a specific inhibitor revealed that it was necessary for mediating the stimulatory effects of folic acid on muscle cell differentiation and fusion. Taken together, our data suggest that folic acid promotes the differentiation of C2C12 cells through the activation of the Akt pathway.

Reduced-energy cranberry juice increases folic acid and adiponectin and reduces homocysteine and oxidative stress in patients with the metabolic syndrome

The metabolic syndrome (MetS) comprises pathological conditions that include insulin resistance, arterial hypertension, visceral adiposity and dyslipidaemia, which favour the development of CVD. Some reports have shown that cranberry ingestion reduces cardiovascular risk factors. However, few studies have evaluated the effect of this fruit in subjects with the MetS. The objective of the present study was to assess the effect of reduced-energy cranberry juice consumption on metabolic and inflammatory biomarkers in patients with the MetS, and to verify the effects of cranberry juice concomitantly on homocysteine and adiponectin levels in patients with the MetS. For this purpose, fifty-six individuals with the MetS were selected and divided into two groups: control group (n36) and cranberry-treated group (n20). After consuming reduced-energy cranberry juice (0·7 litres/d) containing 0·4 mg folic acid for 60 d, the cranberry-treated group showed an increase in adiponectin (P= 0·010) and folic acid (P= 0·033) and a decrease in homocysteine (P< 0·001) in relation to baseline values and also in comparison with the controls (P< 0·05). There was no significant change in the pro-inflammatory cytokines TNF-α, IL-1 and IL-6. In relation to oxidative stress measurements, decreased (P< 0·05) lipoperoxidation and protein oxidation levels assessed by advanced oxidation protein products were found in the cranberry-treated group when compared with the control group. In conclusion, the consumption of cranberry juice for 60 d was able to improve some cardiovascular risk factors. The present data reinforce the importance of the inverse association between homocysteine and adiponectin and the need for more specifically designed studies on MetS patients.

Folate and risk of coronary heart disease: a meta-analysis of prospective studies

BACKGROUND AND AIMS

Epidemiologic studies are inconsistent regarding the association between folate and coronary heart disease (CHD) risk. The aim was to perform a meta-analysis to determine whether an association exists between folate and total CHD endpoints in prospective studies.

METHODS AND RESULTS

We searched the PUBMED and EMBASE databases for studies conducted from 1966 through August 2010. Data were independently abstracted by 2 investigators using a standardized protocol. Study-specific risk estimates were combined by using a random effects model. A total of 14 studies were included in the meta-analysis: 7 studies on dietary folate intake and 8 studies on blood folate levels. For dietary intake, the summary relative risk (RR) indicated a significant association between the highest folate intake and reduced risk of CHD (summary RR: 0.69; 95% CI: 0.60, 0.80). Furthermore, an increase in folate intake of 200 ug/day was associated with a 12% decrease in the risk of developing CHD (summary RR: 0.88; 95% CI: 0.82, 0.94). For blood folate levels, we also found a borderline inverse association of highest blood folate levels on CHD risk (summary RR: 0.74; 95% CI: 0.53, 1.02); our dose-response analysis indicated that an increment in blood folate levels of 5 mmol/l was associated with an 8% decrease in the risk of developing CHD (summary RR: 0.92; 95% CI: 0.84, 1.00).

CONCLUSION

This meta-analysis suggests that dietary folate intake and blood folate level are inversely associated with CHD risk.

Mechanism of dihydrofolate reductase downregulation in melanoma by 3-O-(3,4,5-trimethoxybenzoyl)-(-)-epicatechin

In our search to improve the stability and cellular absorption of tea polyphenols, we synthesized 3-O-(3,4,5-trimethoxybenzoyl)-(-)-epicatechin (TMECG), which showed high antiproliferative activity against melanoma. TMECG downregulates dihydrofolate reductase (DHFR) expression in melanoma cells and we detail the sequential mechanisms that result from this even. TMECG is specifically activated in melanoma cells to form a stable quinone methide (TMECG-QM). TMECG-QM has a dual action on these cells. First, it acts as a potent antifolate compound, disrupting folate metabolism and increasing intracellular oxidized folate coenzymes, such as dihydrofolate, which is a non-competitive inhibitor of dihydropterine reductase, an enzyme essential for tetrahydrobiopterin (H(4)B) recycling. Such inhibition results in H(4)B deficiency, endothelial nitric oxide synthase (eNOS) uncoupling and superoxide production. Second, TMECG-QM acts as an efficient superoxide scavenger and promotes intra-cellular H(2)O(2) accumulation. Here, we present evidence that TMECG markedly reduces melanoma H(4)B and NO bioavailability and that TMECG action is abolished by the eNOS inhibitor N(omega)-nitro-L-arginine methyl ester or the H(2)O(2) scavenger catalase, which strongly suggests H(2)O(2)-dependent DHFR downregulation. In addition, the data presented here indicate that the simultaneous targeting of important pathways for melanoma survival, such as the folate cycle, H(4)B recycling, and the eNOS reaction, could represent an attractive strategy for fighting this malignant skin pathology.

Plasma total homocysteine: instigator or indicator of cardiovascular disease?

Cardiovascular disease (CVD) is a major cause of morbidity and mortality in developed countries. However, traditional risk factors cannot fully account for this. In the last 20 years, there has been an explosion of interest in plasma total homocysteine (tHcy) as a potential modifiable risk factor for CVD. Recent meta-analyses of epidemiological studies support the concept that increased tHcy concentrations are associated with CVD. This has led to the ‘homocysteine hypothesis’, which states that lowering plasma tHcy using folic acid and other B-vitamins will reduce the risk of CVD. In experimental studies, homocysteine has been shown to cause oxidative stress, endothelial cell dysfunction and promote thrombogenesis. However, data from recent large randomized controlled trials have shown that there is no clinical benefit to lowering plasma tHcy concentrations with folic acid and other B-vitamins. This lack of effect of tHcy lowering strongly suggests that homocysteine is not an instigator but merely an indicator of CVD.

Folate augmentation of treatment - evaluation for depression (FolATED): protocol of a randomised controlled trial

BACKGROUND

Clinical depression is common, debilitating and treatable; one in four people experience it during their lives. The majority of sufferers are treated in primary care and only half respond well to active treatment. Evidence suggests that folate may be a useful adjunct to antidepressant treatment: 1) patients with depression often have a functional folate deficiency; 2) the severity of such deficiency, indicated by elevated homocysteine, correlates with depression severity, 3) low folate is associated with poor antidepressant response, and 4) folate is required for the synthesis of neurotransmitters implicated in the pathogenesis and treatment of depression.

METHODS/DESIGN

The primary objective of this trial is to estimate the effect of folate augmentation in new or continuing treatment of depressive disorder in primary and secondary care. Secondary objectives are to evaluate the cost-effectiveness of folate augmentation of antidepressant treatment, investigate how the response to antidepressant treatment depends on genetic polymorphisms relevant to folate metabolism and antidepressant response, and explore whether baseline folate status can predict response to antidepressant treatment. Seven hundred and thirty patients will be recruited from North East Wales, North West Wales and Swansea. Patients with moderate to severe depression will be referred to the trial by their GP or Psychiatrist. If patients consent they will be assessed for eligibility and baseline measures will be undertaken. Blood samples will be taken to exclude patients with folate and B12 deficiency. Some of the blood taken will be used to measure homocysteine levels and for genetic analysis (with additional consent). Eligible participants will be randomised to receive 5 mg of folic acid or placebo. Patients with B12 deficiency or folate deficiency will be given appropriate treatment and will be monitored in the 'comprehensive cohort study'. Assessments will be at screening, randomisation and 3 subsequent follow-ups.

DISCUSSION

If folic acid is shown to improve the efficacy of antidepressants, then it will provide a safe, simple and cheap way of improving the treatment of depression in primary and secondary care.

TRIAL REGISTRATION

Current controlled trials ISRCTN37558856.

B-vitamins, genotype and disease causality

Despite a great deal of research effort there is still considerable uncertainty surrounding the importance of the B-vitamins in health and disease. This continuing uncertainty is partly a result of the difficulty of measuring intake, confounding in observational studies and the very large numbers required to evaluate primary prevention in randomised controlled trials. Consequently, genetic data are increasingly being used to infer nutritional effects on health and even in the formulation of nutrition policy using the approach of ‘mendelian randomisation’. Genetic information has already contributed greatly to the understanding of B-vitamin metabolism and the heterogeneity of responses to intake. It has the potential to provide further nutritional insights and to assist in the elucidation of causal mechanisms, but it is important that genetic data is not viewed as an alternative to nutritional information, both are necessary when addressing nutritional problems. Similarly, the interpretation of nutrient and biomarker status in some experimental designs may require knowledge of genotype. Formal tests of gene–gene and gene–nutrient interaction are of limited value in nutritional studies and the formulation of policy. Graphical representation of diet–genotype–health data greatly assists in the elucidation of the nature of genetic effects, their interaction with nutrition and the implications for nutrition policy.

The effects of folic acid and nitric oxide synthase inhibition on coronary flow and oxidative stress markers in isolated rat heart

The aim of this study was to assess the effects of folic acid on coronary flow and oxidative stress markers with or without non-specific inhibition of nitric oxide synthase by L-NAME in isolated rat hearts. The hearts of male Wistar albino rats (n = 12, age 8 weeks, body mass 180-200 g) were retrograde perfused according to the Langendorff technique at gradually increased constant perfusion pressure (40-120 cmH2O). Coronary flow and markers of oxidative stress: nitrite outflow, superoxide anion production, and index of lipid peroxidation (by measuring thiobarbituric acid reactive substances) in coronary effluent were calculated. The experiments were performed during control conditions and in presence of folic acid (100 microM) alone or folic acid (100 microM) plus L-NAME (30 microM). Control values of coronary flow varied in range from 4.37 +/- 0.10 ml/min/g wt at 40 cmH2O to 12.05 +/- 0.42 ml/min/g wt at 120 cmH2O. Nitrite outflow varied from 1.68 +/- 0.17 nmol/min/g wt at 40 cmH2O to 3.56 +/- 0.17 nmol/min/g wt at 120 cmH2O and was parallel with coronary perfusion pressure-coronary flow curve. Folic acid significantly increased coronary flow (40-120 cmH2O, 5.63 +/- 0.10 ml/min/g wt and 15.2 +/- 0.42 ml/min/g wt, respectively) and was accompanied by significant increase in nitrite outflow (2.28 +/- 0.29 nmol/min/g wt at 40 cmH2O to 6.66 +/- 0.50 nmol/min/g wt at 120 cmH2O). In addition, folic acid significantly decreased superoxide anion production especially at upper coronary perfusion pressure values (60% at 120 cmH2O) and increased index of lipid peroxidation (37.16% at 120 cmH2O), respectively. Folic acid plus L-NAME did not change control values of coronary flow significantly. However, folic acid plus L-NAME increased nitrite outflow especially at upper coronary perfusion pressure values (43.05% at 120 cmH2O) and did not change significantly superoxide anion production or index of lipid peroxidation versus control values, respectively. The results clearly showed that on isolated rat hearts at gradually increased constant perfusion pressure, folic acid increased coronary flow, increased nitrite outflow, decreased superoxide anion production, and increased index of lipid peroxidation. These effects were reversed or blocked by L-NAME thus demonstrating mediation or at least participation of NO in the mechanism of the folic acid-induced effects.

Folic acid reverses endothelial dysfunction induced by inhibition of tetrahydrobiopterin biosynthesis

While folic acid has been shown to reverse endothelial dysfunction, the exact underlying mechanism remains elusive. Here, folic acid reversed both the endothelial dysfunction and increased production of superoxide following depletion of rabbit aortic ring tetrahydrobiopterin (BH4) levels with 2,4-diamino-6-hydroxy-pyrimidine (DAHP) and N-acetyl-5-hydroxy-tryptamine (NAS). Incubation with l-nitroarginine methyl ester also attenuated the production of superoxide. DAHP and NAS reduced BH4 concentrations in both aorta and cultured porcine aortic endothelial cells. Folic acid had no effect on BH4 concentrations in either preparation. The superoxide anion scavenger Tiron but not folic acid reversed the endothelial dysfunction produced in aortic rings by inhibition of copper-zinc superoxide dismutase with diethyldithiocarbamic acid. Neither folic acid nor its metabolite 5-methyltetrahydrofolate prevented the in vitro oxidation of BH4. This study demonstrates that folic acid reverses the endothelial dysfunction induced by BH4 depletion independently of either the regeneration or stabilization of BH4 or an antioxidant effect.

Endothelial cell dysfunction: can't live with it, how to live without it

Endothelial cell dysfunction is emerging as an ultimate culprit for diverse cardiovascular diseases and cardiovascular complications of chronic renal diseases, yet the definition of this new syndrome, its pathophysiology, and therapy remain poorly defined. Here, I summarize some molecular mechanisms leading from hyperhomocystinemia, elevated asymmetric dimethylarginine, and advanced glycolation end product-modified protein level to the proatherogenic, prothrombogenic, and proinflammatory endothelial phenotype and offer a model of endothelial dysfunction based on the interconnectedness of diverse functions. Finally, several therapeutic strategies to prevent and correct endothelial dysfunction are discussed in the light of uncertainty of their action modulated by the endothelial dysfunction per se.

Folic acid supplementation to prevent adverse events in individuals with chronic kidney disease and end stage renal disease

PURPOSE OF REVIEW

This review summarizes our current understanding of the role of folate in the treatment of hyperhomocysteindemia and the prevention of cardiovascular disease in patients with chronic kidney disease and end stage renal disease. Relevant papers published between 2003 and 2004 are referenced.

RECENT FINDINGS

With the exception of one paper, recent therapeutic studies supported previous findings that folate therapy achieves only a modest reduction in plasma homocysteine and seldom normalizes homocysteine. Large prospective studies are under way to evaluate the causal relationship between homocysteine and cardiovascular risk. Recent work supports earlier data that suggested that homocysteine inflicts its damage by oxidative stress. A newly described consequence of hyperhomocysteindemia is DNA hypomethylation and alteration of gene expression. A recent study in the general population suggested that while folate may lower homocysteine it does not improve endothelial function in individuals without cardiovascular disease.

SUMMARY

The causes of hyperhomocysteindemia in renal failure remain obscure. The possibilities include impairment of both renal and extrarenal metabolic pathways by uraemia. Hyperhomocysteindemia is associated in some but not all studies with an increased risk for cardiovascular disease. A low homocysteine may reflect malnutrition and predict a poor outcome. Folate achieves modest reductions of homocysteine in some but not all studies. There are no data to support therapy with very high-dose folic acid. Hyperhomocysteindemia impairs endothelial function which is not adequately reversed by folate.