The association between vitamin E intake and hypertension: results from the re-analysis of the National Health and Nutrition Survey

The Role of Oxidative Stress in Hypertension: The Insight into Antihypertensive Properties of Vitamins A, C and E

Hypertension stands as a pervasive global health challenge, contributing significantly to mortality rates worldwide. Various factors, including lifestyle choices and dietary habits, contribute to the development of hypertension. In recent years, oxidative stress has garnered significant attention as a factor influencing hypertension risk, prompting a shift in research focus towards exploring it as a potential target for prevention and treatment. Antioxidants found in our diet, such as vitamins C, E and carotenoids exhibit the ability to neutralize reactive oxygen species, thereby mitigating oxidative stress. In addition, Vitamin A has an antioxidant effect despite not being an antioxidant itself. Consequently, supplementation or increased intake of these antioxidants has been hypothesized to potentially lower blood pressure levels and aid in the management of hypertension, thereby potentially prolonging life expectancy. Research findings regarding this effect have been diverse. This paper examines the existing literature demonstrating favorable outcomes associated with antioxidant supplementation.

The effects of alpha lipoic acid (ALA) supplementation on blood pressure in adults: a GRADE-assessed systematic review and dose-response meta-analysis of randomized controlled trials

Introduction

There have been various clinical studies on the effect of Alpha lipoic acid (ALA) supplementation on blood pressure (BP), but the findings from these are contradictory. Therefore, we performed a systematic review and dose-response meta-analysis to summarize the relation of ALA supplementation and systolic blood pressure (SBP) and diastolic blood pressure (DBP) in adults.

Methods

A comprehensive search was conducted in Medline (PubMed), Embase, Scopus, and ProQuest up to July 2023. Randomized controlled trials (RCTs) evaluating the effect of ALA on SBP and DBP were included. The pooled weighted mean difference (WMD) of included trials was estimated using a random-effects model. The dose-dependent effect was also assessed.

Results and discussion

A total of 11 RCTs with the participation of 674 patients were included. The result of the meta-analysis indicated that using ALA supplementation significantly reduced the SBP (WMD = -5.46 mmHg; 95% CI: -9.27, -1.65; p < 0.001) and DBP (WMD = -3.36 mmHg, 95% CI: -4.99, -1.74; p < 0.001). The ALA administrations significantly reduced SBP and DBP at the dosages of <800 mg/day, when administered for ≤12 weeks. The present meta-analysis revealed that ALA supplementation could exert favorable effects on SBP and DBP. Further well-designed studies with larger samples are needed to ascertain the long-term effects of ALA on BP.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=447658, identifier PROSPERO: CRD42023447658.

Association of gamma-tocopherol serum concentrations and blood pressure among adults in the United States: a cross-sectional study

Background

hypertension is one of the major preventable risk factors for numerous diseases. The role of vitamin E in blood pressure (BP) has been controversial. We aimed to investigate the relationship between gamma-tocopherol serum concentration (GTSC) and BP.

Methods

Data from 15,687 US adults from the National Health and Nutrition Examination Survey (NHANES) were analyzed. The correlations of GTSC with systolic BP (SBP), diastolic BP (DBP), and prevalence of hypertension were investigated by multivariate logistic regression models, generalized summation models, and fitted smoothing curves. Subgroup analyses were performed to investigate possible effect modifiers between them.

Results

With each natural log increase in GTSC, SBP, and DBP increased by 1.28 mmHg (β 1.28, 95% CI 0.71-1.84) and 1.15 mmHg (β 1.15, 95% CI 0.72-1.57), respectively, both P for trend < 0.001; the prevalence of hypertension increased by 12% (OR 1.12, 95% CI 1.03-1.22), P for trend 0.008. In subgroup analysis, in drinkers, with each natural log increase in GTSC, SBP, and DBP increased by 1.77 mmHg (β 1.77,95% CI 1.13-2.41) and 1.37 mmHg (β 1.37,95% CI 0.9-1.85), respectively, whereas they were not correlated in non-drinkers.

Conclusion

GTSC was linearly and positively associated with SBP, DBP, and the prevalence of hypertension, and alcohol consumption may modify the relationship of GTSC with SBP and DBP.

Antioxidant therapy reverses sympathetic dysfunction, oxidative stress, and hypertension in male hyperadipose rats

AIMS

The rostral ventrolateral medulla (RVLM) is the main sympathetic output of the central nervous system to control blood pressure. Reportedly, reactive oxygen species (ROS) can increase arterial pressure, leading to hypertension. As ROS increase the sympathetic tone in RVLM and obese animals present grater oxidative stress, it would be important to note this relationship.

MAIN METHODS

Therefore, we evaluated the systemic and central effects (in the RVLM) of vitamin C (vit C, an antioxidant) on the redox balance and cardiovascular and autonomic profiles in hyperadipose male rats. We also evaluated the neurotransmission by L-glutamate (L-glu) and vit C in the RVLM of awake hyperadipose rats.

KEY FINDINGS

Our study confirmed that hyperadipose rats were hypertensive and tachycardic, presented increased sympathetic and decreased parasympathetic modulation of the heart, and had increased plasma lipoperoxidation compared with the control rats (CTR). Oral vitamin C treatment reverted cardiovascular, autonomic, and plasma redox dysfunction. Hyperadipose rats presented a higher blood pressure increase after L-glu microinjection and a lower response to vit C in the RVLM compared with the CTR group. Biochemical analysis of redox balance in RVLM punches showed that hyperadipose rats have increased NBT and T-BARS, and after treatment with vit C, the oxidative profile decreased. The antioxidative activity of vit C reduced the amount of ROS in the RVLM area that might have resulted in lowered blood pressure and sympathetic modulation.

SIGNIFICANCE

Our data suggest central and peripheral benefits of vit C treatment on cardiovascular, autonomic, and oxidative dysfunctions in hyperadipose animals.

Impact of oats in the prevention/management of hypertension

Oats are a rich source of a soluble fibre, beta-glucan, phenolic compounds, as well as functional lipid and protein components that could potentially aid in preventing and managing hypertension. Processing techniques commonly used to manufacture oat based foods have been shown to improve its physiological efficacy. Hypertension is a common condition that is a risk factor for cardiovascular disease, a primary cause of mortality worldwide. Though exercise and pharmacological interventions are often used in the management of hypertension, diet is an incredibly important factor. One preclinical study and a handful of clinical studies have shown that oat components/products are effective in lowering blood pressure. However, research in this area is limited and more studies are needed to elucidate the anti-hypertensive potential of oats.

Associations of Dietary and Circulating Vitamin E Level With Metabolic Syndrome. A Meta-Analysis of Observational Studies

Objective: The associations of dietary and circulating vitamin E level with metabolic syndrome (MetS) remains conflicting. This meta-analysis of observational study was therefore employed to investigate the issue above.

Methods: The PubMed, Web of Science and Embase database were searched up to April 2021. The observational studies on the associations of dietary and circulating vitamin E level with MetS were specified. The pooled relative risk (RR) of MetS for the highest vs. lowest dietary and circulating vitamin E level, and the standard mean difference (SMD) of dietary and circulating vitamin E level for MetS vs. control subjects, were calculated.

Results: A total of 25 observational studies with 51,276 participants, were included in this meta-analysis. The overall multi-variable adjusted RR demonstrated that the dietary vitamin E level was inversely associated with MetS (RR = 0.92, 95%CI: 0.85–1.00; P = 0.044). In addition, the dietary vitamin E level in MetS was also lower than that in control subjects according to the overall combined SMD (SMD = −0.08, 95%CI: −0.14 to −0.02; P = 0.024). On the other hand, the overall multi-variable adjusted RR showed no significant relationship between the circulating vitamin E level and MetS (RR = 1.46, 95%CI: 0.85–2.48; P = 0.17). However, the circulating vitamin E level in MetS was lower than that in control subjects according to the overall combined SMD (SMD = −0.58, 95%CI: −1.04 to −0.13; P = 0.013).

Conclusions: The results of this meta-analysis suggest that the dietary vitamin E level is inversely associated with MetS. On the other hand, current evidence is still insufficient to conclude a relationship between the circulating vitamin E level and MetS. More well-designed prospective cohort studies are needed to address the issues further.

A Systematic Review of Effects of Vitamin E on the Cardiovascular System

Vitamin E is a fat-soluble vitamin and an antioxidant that prevents the peroxidation of lipid in vitro. The antioxidant role of vitamin E in preventing adverse cardiovascular outcomes is controversial as some studies support it, while others reject it. Therefore, this review aims to determine whether there is an association between vitamin E and cardiovascular diseases (CVDs). An electronic search was done to find out relevant articles. Papers were shortlisted after the initial title and abstract screen. A full-text study was done, and inclusion and exclusion criteria were applied before the quality assessment of each paper was done. Only high-quality papers were selected for analysis. Full-text articles of the last ten years were included, while non-English articles, gray literature, and animal studies were excluded. The majority of the papers, including 75% of the total population in this review, suggested no role of vitamin E in preventing CVD and CVD mortality. Some studies also suggested that a high level of vitamin E can be associated with adverse cardiovascular outcomes. Thus, one should be prudent about taking vitamin E supplementation for cardiovascular risk prevention.

Novel Combined Antioxidant Strategy against Hypertension, Acute Myocardial Infarction and Postoperative Atrial Fibrillation

Reactive oxygen species (ROS) play a physiological role in the modulation of several functions of the vascular wall; however, increased ROS have detrimental effects. Hence, oxidative stress has pathophysiological impacts on the control of the vascular tone and cardiac functions. Recent experimental studies reported the involvement of increased ROS in the mechanism of hypertension, as this disorder associates with increased production of pro-oxidants and decreased bioavailability of antioxidants. In addition, increased ROS exposure is found in ischemia-reperfusion, occurring in acute myocardial infarction and cardiac surgery with extracorporeal circulation, among other settings. Although these effects cause major heart damage, at present, there is no available treatment. Therefore, it should be expected that antioxidants counteract the oxidative processes, thereby being suitable against cardiovascular disease. Nevertheless, although numerous experimental studies agree with this notion, interventional trials have provided mixed results. A better knowledge of ROS modulation and their specific interaction with the molecular targets should contribute to the development of novel multitarget antioxidant effective therapeutic strategies. The complex multifactorial nature of hypertension, acute myocardial infarction, and postoperative atrial fibrillation needs a multitarget antioxidant strategy, which may give rise to additive or synergic protective effects to achieve optimal cardioprotection.

Pharmacology of apocynin: a natural acetophenone

Apocynin is a naturally occurring acetophenone, found in the roots of Apocynum cannabinum and Picrorhiza kurroa. Various chemical and pharmaceutical modifications have been carried out to enhance the absorption and duration of action of apocynin, like, formulation of chitosan-based apocynin-loaded solid lipid nanoparticles, chitosan-oligosaccharide based nanoparticles, and biodegradable polyanhydride nanoparticles. Apocynin has been subjected to a wide range of experimental screening and has proved to be useful for amelioration of a variety of disorders, like diabetic complications, neurodegeneration, cardiovascular disorders, lung cancer, hepatocellular cancer, pancreatic cancer, and pheochromocytoma. Apocynin has been primarily reported as an NADPH oxidase (NOX) inhibitor and prevents translocation of its p47^phox subunit to the plasma membrane, observed in neurodegeneration and hypertension. However, recent studies highlight its off-target effects that it is able to function as a scavenger of non-radical oxidant species, which is relevant for its activity against NOX 4 mediated production of hydrogen peroxide. Additionally, apocynin has shown inhibition of eNOS-dependent superoxide production in diabetic cardiomyopathy, reduction of NLRP3 activation and TGFβ/Smad signaling in diabetic nephropathy, diminished VEGF expression and decreased retinal NF-κB activation in diabetic retinopathy, inhibition of P38/MAPK/Caspase3 pathway in pheochromocytoma, inhibition of AKT-GSK3β and ERK1/2 pathways in pancreatic cancer, and decreased FAK/PI3K/Akt signaling in hepatocellular cancer. This review aims to discuss the pharmacokinetics and mechanisms of the pharmacological actions of apocynin.

Cardiovascular and Metabolic Protection by Vitamin E: A Matter of Treatment Strategy?

Cardiovascular diseases (CVD) cause about 1/3 of global deaths. Therefore, new strategies for the prevention and treatment of cardiovascular events are highly sought-after. Vitamin E is known for significant antioxidative and anti-inflammatory properties, and has been studied in the prevention of CVD, supported by findings that vitamin E deficiency is associated with increased risk of cardiovascular events. However, randomized controlled trials in humans reveal conflicting and ultimately disappointing results regarding the reduction of cardiovascular events with vitamin E supplementation. As we discuss in detail, this outcome is strongly affected by study design, cohort selection, co-morbidities, genetic variations, age, and gender. For effective chronic primary and secondary prevention by vitamin E, oxidative and inflammatory status might not have been sufficiently antagonized. In contrast, acute administration of vitamin E may be more translatable into positive clinical outcomes. In patients with myocardial infarction (MI), which is associated with severe oxidative and inflammatory reactions, decreased plasma levels of vitamin E have been found. The offsetting of this acute vitamin E deficiency via short-term treatment in MI has shown promising results, and, thus, acute medication, rather than chronic supplementation, with vitamin E might revitalize vitamin E therapy and even provide positive clinical outcomes.

Association between dietary carotenoid intakes and hypertension in adults: National Health and Nutrition Examination Survey 2007-2014

OBJECTIVE

Few epidemiological studies concentrated on dietary carotenoids and hypertension since new hypertension guideline released in 2017. Thus, this study was aimed to evaluate their association.

METHODS

Data from National Health and Nutrition Examination Survey (NHANES) 2007-2014 were used in this cross-sectional study. Dietary carotenoids data were obtained from 24-h dietary recall interviews. Hypertension was defined as SBP at least 130 mmHg or DBP at least 80 mmHg, taking antihypertensive medicine or self-report. Logistic regression models and restricted cubic spline models were applied to explore the associations between α-carotene, β-carotene, β-cryptoxanthin, lycopene, lutein with zeaxanthin, and total carotenoids from diet and supplements and hypertension. Total carotenoids showed significant reductive risk of hypertension at 100 μg/kg per day and over.

RESULTS

A total of 17 398 adults aged 20 years and over were identified. High dose of β-carotene, lycopene, lutein with zeaxanthin, and total carotenoids were significantly associated with decreased risk of hypertension in crude results. After multivariate-adjustment in model 2, the odds ratios (OR) with 95% confidence intervals (CI) of β-cryptoxanthin, lycopene, lutein with zeaxanthin and total carotenoids for hypertension were 0.79 (0.67-0.93), 0.85 (0.73-0.98), 0.69 (0.58-0.83), 0.73 (0.62-0.86) for the highest versus lowest quartile intakes, respectively. Dose-response analyses showed that all of the carotenoids were inversely associated with hypertension in a linear manner. Total carotenoids showed significant effect of lower risk of hypertension at 100 μg/kg per day.

CONCLUSION

Intakes of α-carotene, β-carotene, β-cryptoxanthin, lycopene, lutein with zeaxanthin, and total carotenoids were inversely associated with hypertension in US adults. The intake of total carotenoids was suggested at least 100 μg/kg per day for general adult population.

Renal Hydrogen Peroxide Production Prevents Salt-Sensitive Hypertension

Background The regulation of sodium excretion is important in the pathogenesis of hypertension and salt sensitivity is predictive of cardiovascular events and mortality. C57Bl/6 and BALB/c mice have different blood pressure sensitivities to salt intake. High salt intake increases blood pressure in some C57Bl/6J mouse strains but not in any BALB/c mouse strain. Methods and Results We determined the cause of the difference in salt sensitivity between C57Bl/6 and BALB/c mice. Basal levels of superoxide and H2O2 were higher in renal proximal tubule cells (RPTCs) from BALB/c than C57Bl/6J mice. High salt diet increased H2O2 production in kidneys from BALB/c but C57Bl/6J mice. High sodium concentration (170 mmol/L) in the incubation medium increased H2O2 levels in BALB/c-RPTCs but not in C57Bl/6J-RPTCs. H2O2 (10 μmol/L) treatment decreased sodium transport in RPTCs from BALB/c but not C57Bl/6J mice. Overexpression of catalase in the mouse kidney predisposed BALB/c mice to salt-sensitive hypertension. Conclusions Our data show that the level of salt-induced H2O2 production negatively regulates RPTC sodium transport and determines the state of salt sensitivity in 2 strains of mice. High concentrations of antioxidants could prevent H2O2 production in renal proximal tubules, which would result in sodium retention and increased blood pressure.

Sex, Oxidative Stress, and Hypertension: Insights From Animal Models

One of the mechanisms responsible for blood pressure (BP) regulation is thought to be oxidative stress. In this review, we highlight preclinical studies that strongly support a role for oxidative stress in development and maintenance of hypertension in male animals, based on depressor responses to antioxidants, particularly tempol and apocynin. In females, oxidative stress seems to be important in the initial development of hypertension. However, whether maintenance of hypertension in females is mediated by oxidative stress is not clear. In clinical studies, pharmacological intervention to reduce BP with antioxidants has conflicting results, mostly negative. This review will discuss the uncertainties regarding blood pressure control and oxidative stress and potential reasons for these outcomes.

Metabolic syndrome, Mediterranean diet, and polyphenols: Evidence and perspectives

Metabolic syndrome (MetS) is defined as the co-occurrence of metabolic risk factors that includes insulin resistance, hyperinsulinemia, impaired glucose tolerance, type 2 diabetes mellitus, dyslipidemia, and visceral obesity. The clinical significance of MetS consists of identifying a subgroup of patients sharing a common physiopathological state predisposing to chronic diseases. Clinical and scientific studies pinpoint lifestyle modification as an effective strategy aiming to reduce several features accountable for the risk of MetS onset. Among the healthy dietary patterns, the Mediterranean diet (MedDiet) emerges in terms of beneficial properties associated with longevity. Current evidence highlights the protective effect exerted by MedDiet on the different components of MetS. Interestingly, the effect exerted by polyphenols contained within the representative MedDiet components (i.e., olive oil, red wine, and nuts) seems to be accountable for the beneficial properties associated to this dietary pattern. In this review, we aim to summarize the principal evidence regarding the effectiveness of MedDiet-polyphenols in preventing or delaying the physiopathological components accountable for MetS onset. These findings may provide useful insights concerning the health properties of MedDiet-polyphenols as well as the novel targets destined to a tailored approach to MetS.

Does Alpha-lipoic Acid Supplement Regulate Blood Pressure? A Systematic Review of Randomized, Double-blind Placebo-controlled Clinical Trials

Although several animal and human studies have investigated the effect of alpha-lipoic acid (ALA) on blood pressure (BP), these findings are inconsistent. This systematic review of randomized clinical trials was conducted to summarize the evidence on the effect of ALA on BP. PubMed, SCOPUS, and Google Scholar databases were searched based on MESH term (“Thioctic acid” in combination with “Hypertension” and “Blood pressure”) to identify related papers published up to December 2015. We summarized the results of the relevant studies in this review. In total, nine studies included in this review, seven parallel-designed trials and two crossover-designed trials. The results of parallel-designed studies are inconsistent. Five studies indicate no significant effects for ALA supplementation on BP, but two trials show effects on BP. Unlike parallel-designed trials, two crossover-designed trials have shown similar results and both report no effect for ALA on BP. Several studies investigated the effect of ALA on BP. Most of the papers show no significant effect for supplementation and the studies have shown that associations are limited. However, these findings are limited and there is a need for further and more accurate researches to be clarified.

Focus on Pivotal Role of Dietary Intake (Diet and Supplement) and Blood Levels of Tocopherols and Tocotrienols in Obtaining Successful Aging

Numerous specific age-related morbidities have been correlated with low intake and serum levels of tocopherols and tocotrienols. We performed a review in order to evaluate the extant evidence regarding: (1) the association between intake and serum levels of tocopherols and tocotrienols and age-related pathologies (osteoporosis, sarcopenia and cognitive impairment); and (2) the optimum diet therapy or supplementation with tocopherols and tocotrienols for the treatment of these abnormalities. This review included 51 eligible studies. The recent literature underlines that, given the detrimental effect of low intake and serum levels of tocopherols and tocotrienols on bone, muscle mass, and cognitive function, a change in the lifestyle must be the cornerstone in the prevention of these specific age-related pathologies related to vitamin E-deficient status. The optimum diet therapy in the elderly for avoiding vitamin E deficiency and its negative correlates, such as high inflammation and oxidation, must aim at achieving specific nutritional goals. These goals must be reached through: accession of the elderly subjects to specific personalized dietary programs aimed at achieving and/or maintaining body weight (avoid malnutrition); increase their intake of food rich in vitamin E, such as derivatives of oily seeds (in particular wheat germ oil), olive oil, hazelnuts, walnuts, almonds, and cereals rich in vitamin E (such as specific rice cultivar rich in tocotrienols) or take vitamin E supplements. In this case, vitamin E can be correctly used in a personalized way either for the outcome from the pathology or to achieve healthy aging and longevity without any adverse effects.