Oral folic acid improves endothelial dysfunction in cigarette smokers

Effects of folate supplementation on recurrence and metabolic status of cervical intraepithelial neoplasia grade 2/3 in overweight and obese women: a randomized double-blind placebo-controlled trial

BACKGROUND AND OBJECTIVE

Inconsistent evidence showed that folate supplementation may be associated with reduced risk of cancer due to improved metabolic profiles and reduced markers of oxidative stress and inflammation. The aim of this investigation was to quantify the effects of folate supplementation on the recurrence and other metabolic factors of women with cervical intraepithelial neoplasia grade 2/3 (CIN2/3).

METHODS

This randomized, double-blind, placebo-controlled clinical trial was performed among 60 overweight/obese women with CIN2/3. Definitive CIN2/3 confirmation was done via biopsy, pathological diagnosis, as well as colposcopy. Participants were randomly assigned to the intervention group to take 5 mg/day folate supplements or placebo group (n = 30 in each group) for 12 weeks.

RESULTS

The results of the current study showed a non-significant decrease in recurrence of CIN2/3 in the folate group in comparison with the placebo group (3.3% vs. 16.7%, P = 0.08). Compared with the placebo, folate supplementation significantly decreased plasma homocysteine (Hcy) levels (P < 0.001), serum insulin values (in the crude model) (P = 0.01), and homeostasis model assessment of insulin resistance (P = 0.01). Also, folate supplementation resulted in a significant improvement in the quantitative insulin sensitivity check index (P = 0.002) and total antioxidant capacity (P = 0.04) and a significant reduction in high-sensitivity C-reactive protein (P = 0.015) in comparison with the placebo group.

CONCLUSIONS

In conclusion, folate supplementation for 12 weeks among overweight/obese women with CIN2/3 showed a non-significant decrease in its recurrence and had beneficial effects on insulin sensitivity, inflammation, and oxidative stress markers.

Smokers making a quit attempt using e-cigarettes with or without nicotine or prescription nicotine replacement therapy: Impact on cardiovascular function (ISME-NRT) - a study protocol

Background

The estimated number of cigarette smokers in the world is 1.3 billion, expected to rise to 1.7 billion by 2025, with 10 million smokers living in the U.K. Smoking is the leading, preventable death-cause worldwide, being responsible for almost 650,000 deaths in the E.U. annually. A combination of pharmacological interventions, including nicotine replacement therapy, bupropion and varenicline, and behavioural support is the most effective approach to smoking cessation. However, even the best methods have high relapse rates of approximately 75% within 6 months. Electronic (or “e-“) cigarettes use battery power to disperse a solution that usually contains propylene glycol or glycerine, water, flavouring and nicotine. E-cigarettes have become the most popular smoking cessation aid in England, however, information on their effects on cardiovascular function is limited and contradictory. As e-cigarettes are not solely nicotine-based products, existing research exploring the effects of nicotine on the cardio-vasculature provides only limited information, while their extensive uptake urges the need of evidence to inform the general public, smokers and policy-makers.

Methods

This is a pragmatic, 3-group, randomised, assessor-blinded, single-centre trial exploring the cardiovascular physiological effects of the use of e-cigarettes (nicotine-free and nicotine-inclusive, assessed separately) combined with behavioural support as a smoking cessation method in comparison to the combination of NRT and behavioural support. The primary outcome will be macro-vascular function, determined by a Flow Mediated Dilatation ultrasound assessment, 6 months following participants’ “quit date”.

Discussion

Participants will be assessed at baseline, 3 days following their self-determined “quit date”, at intervention end (3 months) and 6 months following their “quite date”. Findings are expected to give an indication of the cardiovascular effects of e-cigarettes both in the short- and in the medium-term period, informing the general public, policy holders and researchers, helping to define the future role of e-cigarettes as a smoking cessation aid.

Trial registration

Clinicaltrials.gov NCT03061253. Registered 17th February 2017.

Effects of long-term folate supplementation on metabolic status and regression of cervical intraepithelial neoplasia: A randomized, double-blind, placebo-controlled trial

OBJECTIVE

This study was conducted to determine the effects of long-term folate supplementation on regression and metabolic status of patients with cervical intraepithelial neoplasia grade 1 (CIN1).

METHODS

This randomized, double-blind, placebo-controlled trial was performed among 58 women diagnosed with CIN1, ages 18 to 55 y old. Participants were randomly divided into two groups to receive 5 mg/d folate supplements (n = 29) or placebo (n = 29) for 6 mo. Fasting blood samples were taken at baseline and 6 mo after intervention to quantify related markers.

RESULTS

A greater percentage of women in the folate group had regressed CIN1 (83.3 versus 52.0%, P = 0.019) than those in the placebo group. Long-term folate supplementation resulted in a significant decrease in serum insulin levels (-1.6 ± 6.2 versus +2.6 ± 6.9 μIU/mL, P = 0.018) and homeostatic model assessment-beta cell function (HOMA-B) (-13.0 ± 39.0 versus +11.2 ± 42.3, P = 0.028) compared with the placebo. Additionally, plasma glutathione (GSH) levels were significantly increased (+81.5 ± 264.1 versus -220.9 ± 342.5 μmol/L, P < 0.001) and malondialdehyde (MDA) levels were significantly reduced (-1.0 ± 1.1 versus +0.1 ± 1.6 μmol/L, P = 0.004) in the folate group compared to the placebo.

CONCLUSIONS

Taken together, folate supplementation (5 mg/d) for 6 mo among women with CIN1 resulted in its regression as well as led to decreased serum insulin, HOMA-B, plasma MDA and increased plasma GSH levels; however, it did not affect other metabolic profiles.

Mechanisms and potential therapeutic targets for folic acid in cardiovascular disease

Folic acid (FA) is a member of the B-vitamin family with cardiovascular roles in homocysteine regulation and endothelial nitric oxide synthase (eNOS) activity. Its interaction with eNOS is thought to be due to the enhancement of tetrahydrobiopterin bioavailability, helping maintain eNOS in its coupled state to favor the generation of nitric oxide rather than oxygen free radicals. FA also plays a role in the prevention of several cardiac and noncardiac malformations, has potent direct antioxidant and antithrombotic effects, and can interfere with the production of the endothelial-derived hyperpolarizing factor. These multiple mechanisms of action have led to studies regarding the therapeutic potential of FA in cardiovascular disease. To date, studies have demonstrated that FA ameliorates endothelial dysfunction and nitrate tolerance and can improve pathological features of atherosclerosis. These effects appear to be homocysteine independent but rather related to their role in eNOS function. Given the growing evidence that nitric oxide synthase uncoupling plays a major role in many cardiovascular disorders, the potential of exogenous FA as an inexpensive and safe oral therapy is intriguing and is stimulating ongoing investigations.

Dietary lipids and vascular function: UK Food Standards Agency workshop report

The UK Food Standards Agency convened a group of expert scientists to review current research investigating the effect of dietary lipids on vascular function. The workshop highlighted the need for intervention studies to be sufficiently powered for these measures and that they should be corroborated with other, more validated, risk factors for CVD. Work presented at the workshop suggested a beneficial effect of long-chain n-3 PUFA and a detrimental effect of trans fatty acids. The workshop also considered the importance of the choice of study population in dietary intervention studies and that ‘at risk’ subgroups within the general population may be more appropriate than subjects that are unrepresentatively healthy.

Two-week treatment with pravastatin improves ventriculo-vascular haemodynamic interactions in young men with type 1 diabetes

Young patients with diabetes but without established vascular disease have altered conduit and resistance artery reactivity. Early endothelial dysfunction is an initial step in atherogenesis: reductions in nitric oxide (NO) production in these vascular beds are implicated. The study aim was two-fold: first, to detect baseline abnormalities in cardiac function, conduit vessels and the microcirculation using applanation tonometry, brachial artery ultrasound and laser Doppler fluximetry, respectively; and second, to investigate any modification in these parameters with the use of pravastatin. Nine young men with diabetes and normoalbuminuria were randomised in a double-blind cross-over fashion to placebo or pravastatin (40 mg) treatment for two weeks. They underwent scans on three separate occasions. Control patients (n=12) underwent a baseline scan but were not given any drug treatment. It was found that patients with diabetes had significantly higher systolic and diastolic blood pressures, heart rate and Buckberg index (propensity to myocardial ischaemia). Brachial artery reactivity and microcirculatory dilation were both reduced. Levels of von Willebrand Factor, a marker of endothelial damage, were also elevated. Pravastatin treatment restored these sub-clinical abnormalities towards normal levels. In conclusion, pravastatin improves vascular abnormalities in young male patients with diabetes through alterations in microcirculation and conduit vessel function, with secondary myocardial effects. This may be of benefit in preventing end-organ injury.

Effect of folic acid on endothelial function following acute myocardial infarction

The aim of this study was to test the influence of high-dose folic acid (10 mg/d) on endothelial function in patients referred for coronary intervention after an acute myocardial infarction (AMI) and determine its relation to homocysteine levels. Flow-mediated dilation (FMD) of the brachial artery was performed in 40 patients after AMI (16 with normal homocysteine levels and 24 patients with elevated levels [>11 micromol/L]). Subjects were randomized to receive first folic acid (10 mg/day; group A) or placebo (group B) for 6 weeks in a double-blind crossover trial with a 2-week washout. Plasma folate, total homocysteine and its subtypes (oxidized, reduced, and protein-bound), FMD, and nitroglycerin-mediated dilation were assessed at baseline and at 6 and 14 weeks. In group A, folic acid improved FMD from 3.98 +/- 0.35% to 6.44 +/- 0.56% (p <0.001). This effect persisted after the crossover with placebo (5.42 +/- 0.59, p = 0.13). In group B, placebo did not increase FMD (4.01 +/- 0.34% vs 4.46 +/- 0.38, p = 0.38); however, a significant increase was observed in the second active treatment period (6.49 +/- 0.56%, p = 0.005). In both groups, improved FMD neither correlated with basal levels of homocysteine and its subtypes nor with changes induced during the folate treatment. Nitroglycerin-mediated dilation did not change significantly in either group. Folic acid increased FMD in both normo- and hyperhomocysteinanemic groups (p = 0.006 and p <0.001). In conclusion, 6-week treatment with high-dose folic acid improves endothelial function in post-AMI patients, independent from homocysteine status. Folic acid can be recommended to improve postinfarction endothelial dysfunction in patients with normo- and hyperhomocysteinemia.

Folate and vitamin B6 rapidly normalize endothelial dysfunction in children with type 1 diabetes mellitus

BACKGROUND

Endothelial dysfunction, a precursor of vascular disease, begins early in type 1 diabetes mellitus and is associated with folate status.

METHODS

A randomized, double-blind, placebo-controlled study of folate (5 mg daily) and vitamin B6 (100 mg daily) in 124 children with type 1 diabetes determined the immediate and 8-week effects of these vitamins, alone and in combination, on endothelial function. Endothelial function, assessed as flow-mediated dilation and glyceryltrinitrate-induced dilation with high-resolution ultrasound of the brachial artery, was measured at baseline, at 2 and 4 hours after the first dose (n = 35), and at 4 and 8 weeks of treatment (n = 122).

RESULTS

Flow-mediated dilation normalized in all treatment groups. From baseline to 8 weeks, flow-mediated dilation improved with folate from 2.6% +/- 4.3% (mean +/- SD) to 9.7% +/- 6.0%, with vitamin B6 from 3.5% +/- 4.0% to 8.3% +/- 4.2%, and with folate/vitamin B6 from 2.8% +/- 3.5% to 10.5% +/- 4.4%. This improvement in flow-mediated dilation occurred within 2 hours and was maintained at 8 weeks for each treatment. Flow-mediated dilation in the placebo group, and glyceryltrinitrate-induced dilation in all groups, did not change. Increases in serum folate, red cell folate, and serum vitamin B6 levels related to increases in flow-mediated dilation. Improvement in flow-mediated dilation was independent of changes in total plasma homocyst(e)ine, glucose, hemoglobin A1c, and high-sensitivity C-reactive protein levels. Baseline red cell folate levels and baseline diastolic blood pressure were related inversely to improvement in flow-mediated dilation. Serum triglyceride and low-density lipoprotein cholesterol inversely related to baseline flow-mediated dilation.

CONCLUSIONS

High-dose folate and vitamin B6 normalized endothelial dysfunction in children with type 1 diabetes. This effect was maintained over 8 weeks, with no additional benefit from combination treatment.

Vascular dysfunction produced by hyperhomocysteinemia is more severe in the presence of low folate

Earlier we reported that dietary folate depletion causes hyperhomocysteinemia (HHcy) and arterial dysfunction in rats (Symons JD, Mullick AE, Ensunsa JL, Ma AA, and Rutledge JC. Arterioscler Thromb Vasc Biol 22: 772-780, 2002). Both HHcy and low folate (LF) are risk factors for cardiovascular disease. Therefore, the dysfunction we observed could have resulted from HHcy, LF, and/or their combination (HHcy + LF). We tested the hypothesis that HHcy-induced vascular dysfunction is more severe in the presence of LF. Four groups of rats consumed diets for approximately 10 wk that produced plasma homocysteine (microM) and liver folate (microg folate/g liver) concentrations, respectively, of 7 +/- 1 and 15 +/- 1 (Control; Con; n = 16), 17 +/- 2 and 15 +/- 2 (HHcy; n = 17), 10 +/- 1 and 8 +/- 1 (LF; n = 14), and 21 +/- 2 and 8 +/- 1 (HHcy + LF; n = 18). We observed that maximal ACh-evoked vasorelaxation was greatest in aortas and mesenteric arteries from Con rats vs. all groups. While the extent of dysfunction was similar between LF and HHcy animals, it was less severe compared with arteries from HHcy + LF rats. Maximal ACh-evoked vasorelaxation in coronary arteries was not different between Con and LF rats, but both were greater than HHcy + LF animals. In segments of aortas, 1) ACh-evoked vasorelaxation was similar among groups after incubation with the nonenzymatic intracellular O2(-) scavenger Tiron, 2) vascular O2(-) estimated using dihydroethidium staining was greatest in HHcy + LF vs. all groups, and 3) tension development in response to nitric oxide (NO) synthase inhibition was greatest in Con vs. all other groups. We conclude that HHcy + LF evokes greater dysfunction than either HHcy alone (aortas, mesentery) or LF alone (aortas, mesentery, coronary), likely by producing more O2(-) within the vasculature and thereby reducing NO bioavailability.

Smoking and Passive Smoking as Conditioners of Folate Status in Young Women

OBJECTIVE

For women of fertile age, an adequate supply of folate is important for preventing a range of health problems, especially congenital malformations in their offspring. Since congenital deformities are more common in children of mothers who smoke, the objective was to analyse the folate status of smokers, passive smokers and non-smokers.

METHODS

Folate intake was monitored in 319 women aged 18-35 (112 smokers, 100 passive smokers and 107 non-smokers) using a three day food record. Serum and erythrocyte folate concentrations were measured by radioimmunoassay. Exposure to tobacco smoke was established by a questionnaire on present and past tobacco consumption, the number of hours in contact with smokers, and by assessing urine cotinine concentrations.

RESULTS

The folate intake of smokers (S) (159.1 +/- 65.7 microg/day) and passive smokers (PS) (165.2 +/- 66.6 microg/day) was lower than that of non-smokers (N) (181.7 +/- 72.4 microg/day) (p < 0.05 between S and N). No subject fully met the recommended intake of the vitamin, but S and PS subjects both took less than N subjects (39.8 +/- 16.4% and 41.3 +/- 16.6% compared to 45.4 +/- 18.1% respectively). Serum folate concentrations were also lower in S and PS subjects grouped together (16.6 +/- 5.9 nmol/L) compared to N subjects (18.4 +/- 6.7 nmol/L) (p < 0.05).

CONCLUSIONS

None of the studied women took the 400 microg/day of folate recommended. 6.7% had serum folate concentrations of < 9.2 nmol/L. The situation was worse in S and PS subjects, which might contribute to an increased risk of developing certain diseases and to giving birth to children with congenital deformations.

Hyperhomocysteinemia in healthy young men and elderly men with normal serum folate concentration is not associated with poor vascular reactivity or oxidative stress

The mechanism by which homocysteine (Hcy) causes endothelial dysfunction is probably mediated by oxidative stress. The aim of this study was to evaluate the effect of oxidative stress on endothelial function in young and elderly hyperhomocysteinemic (HHcy) men. A total of 35 HHcy (Hcy > 15 micro mol/L), young (n = 15; 20-40 y) and elderly men (n = 20; > 65 y) and 33 normohomocysteinemic (NHcy; controls) young (n = 14) and elderly (n = 19) men (Hcy < 13 micro mol/L), without classic cardiovascular risk factors were recruited. Serum Hcy, folate, and vitamin B-12, whole-blood glutathione, plasma total antioxidants status, TBARS, and 8-F(2alpha) isoprostanes were determined. Noninvasive ultrasound measurements of endothelium-dependent (EDVR) and -independent dilatation (EIVR) were performed. EDVR, EIVR, and markers of oxidative stress did not differ among the groups. Folate concentrations were higher in elderly than in young men (P < 0.001), independent of Hcy concentrations. Vitamin B-12 concentrations were lower in HHcy than in NHcy elderly men (P < 0.045). EDVR was correlated with folate concentrations in young men (r = 0.40, P = 0.04) and negatively with BMI in elderly men (r = -0.52, P = 0.002). In the present study, HHcy with normal serum folate concentrations was not associated with poor EDVR or oxidative stress in healthy young and elderly men.

Effects of dietary folic acid supplementation on cerebrovascular endothelial dysfunction in rats with induced hyperhomocysteinemia

This study shows, for the first time, that hyperhomocysteinemia induces endothelial dysfunction in a rat brain, and that this can be alleviated by dietary folic acid supplementation. Our experiments examined the effects of folic acid supplementation on the endothelial nitric oxide synthase (eNOS) expression in the hyperhomocysteinemic rat brain, and related the observed changes in eNOS expression to the expression of the cell adhesion molecule and the glucose transporter protein. The animals were raised on an experimental diet containing 0.3% homocystine for 2 weeks and then they were placed either on a 0.3% homocystine, 0.3% homocystine with 8 mg/kg folic acid, or folic acid (8 mg/kg) diet for 2 weeks. The cerebrovascular eNOS activity was examined immunohistochemically. Cerebral levels of eNOS, glucose transporter-1 (GLUT-1), and the vascular cell adhesion molecule-1 (VCAM-1) proteins were evaluated by Western blot analysis. At 4 weeks, the homocystine diet induced a fourfold increase in plasma homocysteine (control: 6.5+/-0.4 micromol/l, homocystine: 26.2+/-2.5 micromol/l), and a reduction in the cerebral eNOS and GLUT-1 expression levels with a concomitant increase in the level of VCAM-1 expression. Dietary folic acid supplementation caused a significant decrease in the plasma homocysteine levels, a concomitant increase in the hyperhomocysteinemia-induced reduction in the cerebral eNOS and GLUT-1 expression levels, and a decrease in the hyperhomocysteinemia-induced VCAM-1 expression levels.

Influence of smoking on predictors of vascular disease

Beyond the already well-established strong causative relationship with cancer, smoking increases the risk for vascular disease. Smoking may act directly or adversely influence risk factors contributing to the development of vascular disease. Smoking causes endothelial dysfunction, dyslipidemia (decreased high-density lipoprotein cholesterol levels, hypertriglyceridemia and increased oxidation of low-density lipoprotein cholesterol) and platelet activation leading to a prothrombotic state. Smoking increases emerging risk factors (eg, fibrinogen, homocysteine, and high-sensitivity C-reactive protein) and increases insulin resistance and the risk of developing type 2 diabetes mellitus. The beneficial effects of statins and antioxidants (eg, vitamins C and E, beta-carotene) are counteracted by smoking. Smoking-induced alterations in growth factors, adhesion molecules, and even in genes can accelerate the progression of atherosclerosis. The aim of this review is to consider the adverse consequences of smoking on the factors predisposing to vascular disease and to emphasize the beneficial effects of smoking cessation.

Relationship of systolic blood pressure with plasma homocysteine: importance of smoking status

BACKGROUND

Elevated plasma homocysteine is a risk factor for cardiovascular disease. Elevations in plasma homocysteine occur in both smokers and hypertensives, but the combined effect of smoking and hypertension on homocysteine is unknown.

METHODS

Resting plasma homocysteine levels and blood pressure were determined in 56 normotensives (12 smokers) and 20 essential hypertensives (10 smokers).

RESULTS

Plasma homocysteine was significantly higher in all smokers versus all non-smokers (9.46 +/- 0.5 versus 7.9 +/- 0.5 micromol/l, P = 0.041) by two-way ANOVA, and was also significantly higher in all hypertensives versus all normotensives (9.8 +/- 0.6 versus 7.6 +/- 0.4 micromol/l, P = 0.004). There was no interaction between the effects of hypertension and smoking on plasma homocysteine. Hypertensive smokers had significantly higher plasma homocysteine than either normotensive non-smokers (10.65 +/- 0.84 versus 7.05 +/- 0.26 micromol/l), hypertensive non-smokers (7.88 +/- 0.64 micromol/l) or normotensive smokers (8.36 +/- 0.5 micromol/l). In subjects overall, homocysteine levels were correlated (r = 0.306, P = 0.015) with systolic blood pressure but not with diastolic (r = 0.186). This relationship was also significant in smokers, but not non-smokers. Furthermore, subjects in the highest quintile for plasma homocysteine had significantly higher systolic BP than those in the lowest quintile. This effect was not observed when smokers were removed from the analysis.

CONCLUSION

Smoking compounds the modest effect of hypertension on plasma homocysteine. The strong relationship between systolic blood pressure and homocysteine that exists only in smokers suggests that smoking-induced homocysteine elevations may raise systolic blood pressure. We speculate that smoking compounds the risk of cardiovascular disease in hypertensives, in part, by elevating homocysteine.