Plasma vitamin C modifies the association between hypertension and risk of stroke

Preoperative and postoperative administration of vitamin C in cardiac surgery patients - settings, dosages, duration, and clinical outcomes: a narrative review

Vitamin C or ascorbic acid is a water-soluble vitamin capable of directly donating electrons to reactive oxygen species, attenuating electrical remodeling, and cardiac dysfunction in patients undergoing cardiac surgery (CS), considered one of the most effective defenses against free radicals in the blood, thus being one of the first antioxidants consumed during oxidative stress. The aim of this review is to assess the effects of perioperative administration of vitamin C in CS patients. A comprehensive literature search was conducted in order to identify prospective cohort studies and/or randomized controlled trials reporting on the perioperative effects of vitamin C among adult patients undergoing CS. Studies published between January 1980 to December 2022 were included in our search, resulting in a total of 31 articles that met all our inclusion criteria. There seems to be a beneficial effect of vitamin C supplementation in arrhythmias such as in postoperative atrial fibrillation, reduction of ICU length of stay, and hospital length of stay, reduction in postoperative ventilation time, in inotropic demand, and in postoperative fatigue. Vitamin C can act as a scavenger of free radicals to decrease the peroxidation of the lipids present in the cell membrane, and to protect the myocardium postoperatively from ischemia/reperfusion injury, thus attenuating oxidative stress and inflammation. It represents a readily available and cost-effective strategy that could improve the outcome of patients undergoing CS, by reducing the risk of serious cardiovascular adverse events, both perioperatively and postoperatively.

From A to E: Uniting vitamins against stroke risk-A systematic review and network meta-analysis

BACKGROUND AND AIM

Stroke represents a significant public health challenge, necessitating the exploration of preventive measures. This network meta-analysis aimed to assess the efficacy of different vitamin treatments compared to a placebo in preventing stroke.

METHODS

A systematic electronic search in databases including PubMed, EmBASE, Web of Science, clinicaltrials.gov, and Google Scholar until 31 May 2023 was conducted, to identify published studies investigating the association between vitamin intake and the risk of stroke. Pooled risk ratio (RR) with 95% confidence intervals (CIs) was calculated using a frequentist network meta-analysis. Furthermore, we ranked vitamins based on p-scores, facilitating a comparative assessment of their effectiveness in preventing stroke.

RESULTS

A total of 56 studies, including 17 randomized controlled trials (RCTs) and 39 cohort studies were analyzed. Direct estimates obtained from network meta-analysis, we found that vitamin A (RR: .81 [.72-.91]), vitamin B-complex (RR: .85 [.74-.97]), vitamin B6 (RR: 79 [.68-.92]), folate (RR: .86 [.75-.97]), vitamin C (RR: .77 [.70-.85]) and vitamin D (RR: .73 [.64-.83]) were significantly associated with a decreased stroke risk. However, no significant association was observed for vitamin B2, vitamin B12, and vitamin E. Subsequent to network meta-analysis, vitamins were ranked in decreasing order of their efficacy in stroke prevention based on p-score, with vitamin D (p-score = .91), vitamin C (p-score = .79), vitamin B6 (p-score = .70), vitamin A (p-score = .65), vitamin B-complex (p-score = .53), folate (p-score = .49), vitamin B2 (p-score = .39), vitamin E (p-score = .28), vitamin B12 (.13) and placebo (.10).

CONCLUSION

Our study has established noteworthy connections between vitamin A, vitamin B-complex, vitamin B6, folate, vitamin C, and vitamin D in the realm of stroke prevention. These findings add substantial weight to the accumulating evidence supporting the potential advantages of vitamin interventions in mitigating the risk of stroke. However, to solidify and validate these observations, additional research is imperative. Well-designed clinical trials or cohort studies are needed to further explore these associations and formulate clear guidelines for incorporating vitamin supplementation into effective stroke prevention strategies.

Vitamin C Intake and Ischemic Stroke

Vitamin C is an essential micronutrient with important antioxidant properties. Ischemic stroke is a major public health problem worldwide. Extensive evidence demonstrates that vitamin C has protective effects against cardiovascular disease, and there is a close relationship between vitamin C intake and ischemic stroke risk. Based on the evidence, we conducted this umbrella review to clarify the relationship between vitamin C intake and ischemic stroke risk from four perspectives: cellular mechanisms, animal experiments, clinical trials, and cohort studies.

Research on Association between Levels of Serum Adiponectin, Hs-CRP, and sICAM-1 and Hypertensive Cerebrovascular Complications

The study is aimed at studying the association between the levels of serum adiponectin (ADPN), high-sensitivity C-reactive protein (hs-CRP), and soluble intercellular adhesion molecule-1 (sICAM-1) and hypertensive cerebrovascular complications. 50 patients with hypertensive cerebrovascular disease treated in Gansu Provincial Hospital from December 2016 to December 2018 were selected as the experimental group, and 50 normal people who underwent physical examination were selected as the control group. The blood pressure, heart rate, and the complications were recorded, and the serum blood lipid indexes were detected. Moreover, the content of serum ADPN, hs-CRP, and sICAM-1; the neurological indexes; brain-derived neurotrophic factor (BNDF); and neurone-specific enolase (NSE) were also determined using ELISA. The content of aspartate aminotransferase (AST), alanine aminotransferase (ALT), blood urea nitrogen (BUN), and serum creatinine (SCR) in the experimental group was significantly higher than that in control group (p < 0.05); the incidence of cerebrovascular complications, systolic blood pressure, diastolic blood pressure, and heart rate increased (p < 0.05); the content of total cholesterol (TC), triglyceride (TG), low-density lipoprotein (LDL), high-density lipoprotein (HDL), hs-CRP, and sICAM-1 obviously rose (p < 0.05); and the content of ADPN and HDL obviously declined (p < 0.05). Besides, the experimental group had evidently lower systolic blood flow velocity (Vs), diastolic blood flow velocity (Vd), and mean blood flow velocity (Vm) and evidently higher pulsatility index (PI) (p < 0.05). The levels of S100 and NSE in the experimental group increased significantly, and the level of BNDF decreased significantly (p < 0.05). In patients with hypertensive cerebrovascular disease, the level of ADPN declines; the levels of hs-CRP and sICAM-1 rise; the incidence rate of cerebrovascular complications is elevated; and there are changes in the blood lipid, cerebrovascular hemodynamic, and neurological indexes, thereby further promoting the occurrence and development of hypertensive cerebrovascular disease.

The relationship of lipid peroxidation and antioxidant status to selected modifiable risk factors in coronary artery disease patients

Background

Coronary artery disease (CAD) is found to be associated with a wide range of modifiable and non-modifiable risk factors.

Aim of the Study

To evaluate the relationship of lipid peroxidation and antioxidant status to selected modifiable risk factors in angiographically proven CAD patients.

Methods

150 angiographically proven CAD patients were categorized into three, based on selected risk factors. Data was collected using proforma and from hospital records. Peroxidation and antioxidant levels in blood samples were assessed using standard procedures.

Results

In category, I, significantly higher level of lipid peroxidation and the lower enzymatic antioxidant level were observed in patients with diabetes, hypertension, and with both diabetes and hypertension, when compared with patients without these clinical characteristics (p < 0.01). Similar results obtained for patients following a non-vegetarian diet when compared with patients following a vegetarian diet (category II). In BMI based group (category III), patients with BMI>25kg/m2 showed a significant increase in peroxidation and low enzymatic and non-enzymatic antioxidant levels than those with normal BMI.

Conclusion

The study confirmed a strong association between selected modifiable risk factors, higher lipid peroxidation, and lower antioxidant levels in angiographically proven CAD patients. This provides leads in the management of cardiovascular events in CAD patients.

Vitamin C supplementation improves blood pressure and oxidative stress after acute exercise in patients with poorly controlled type 2 diabetes mellitus: A randomized, placebo-controlled, cross-over study

This study aimed to assess the effect of Vitamin C on blood pressure (BP), and subsequently on oxidative stress and nitric oxide (NO) release, following the low-intensity exercise in the patients. This study included 24 patients with type 2 diabetes mellitus (T2D) (age, 53 ± 7 years; hemoglobin A1c, 10.1% ± 0.9%) randomized into two 6-week daily arms based on the consumption of either placebo or 1000 mg Vitamin C. The crossover trial occurred after a 6-week washout. Before and after both supplementation arms, all patients performed cycling exercise at 33% of peak oxygen consumption for 20 min. BP was measured before, immediately, and 60 min after the exercise. Blood samples were drawn immediately before and after the exercise to determine plasma ascorbate, malondialdehyde (MDA), F₂-isoprostanes (F₂-IsoPs), and NO concentrations. Data showed significant lower BP in the Vitamin C arm when compared with the placebo arm (systolic BP [SBP] P < 0.001 at every time point, diastolic BP [DBP] P < 0.001 except at immediately after exercise, P < 0.05). Plasma ascorbate concentration (P < 0.05 at every time point) and plasma NO (at resting P < 0.001, immediately after exercise P < 0.05) were significantly increased in the Vitamin C arm than in the placebo arm. Plasma MDA (P < 0.05 at every time point) and F₂-IsoPs (P < 0.05 at every time point) concentrations were significantly lower in the Vitamin C arm than in the placebo arm. In addition, data showed significantly lower SBP (P < 0.001 at every time point), DBP (P < 0.001 except at immediately after exercise P < 0.05), plasma MDA (P < 0.001 at every time point), and F₂-IsoPs (P < 0.05 at every time point) at post-supplementation than at pre-supplementation. Besides, there were significantly higher plasma ascorbate (P < 0.05 at every time point) and NO (at rest P < 0.01, immediately after exercise P < 0.05) concentrations at post-supplementation than at pre-supplementation. This is in contrast to the placebo treatment arm which demonstrated no statistical difference in all outcomes throughout the experiment. This study suggests that 6-week Vitamin C supplementation decreased preexercise and postexercise BPs, possibly due to improved oxidative stress and NO release. However, exercise had no effect on any outcome measures.

Oxidative Stress Status in COVID-19 Patients Hospitalized in Intensive Care Unit for Severe Pneumonia. A Pilot Study

BACKGROUND

A key role of oxidative stress has been highlighted in the pathogenesis of COVID-19. However, little has been said about oxidative stress status (OSS) of COVID-19 patients hospitalized in intensive care unit (ICU).

MATERIAL AND METHODS

Biomarkers of the systemic OSS included antioxidants (9 assays), trace elements (3 assays), inflammation markers (4 assays) and oxidative damage to lipids (3 assays).

RESULTS

Blood samples were drawn after 9 (7-11) and 41 (39-43) days of ICU stay, respectively in 3 and 6 patients. Vitamin C, thiol proteins, reduced glutathione, γ-tocopherol, β-carotene and PAOT® score were significantly decreased compared to laboratory reference values. Selenium concentration was at the limit of the lower reference value. By contrast, the copper/zinc ratio (as a source of oxidative stress) was higher than reference values in 55% of patients while copper was significantly correlated with lipid peroxides (r = 0.95, p < 0.001). Inflammatory biomarkers (C-reactive protein and myeloperoxidase) were significantly increased when compared to normals.

CONCLUSIONS

The systemic OSS was strongly altered in critically ill COVID-19 patients as evidenced by increased lipid peroxidation but also by deficits in some antioxidants (vitamin C, glutathione, thiol proteins) and trace elements (selenium).

Positive Association of Dietary Inflammatory Index with Incidence of Cardiovascular Disease: Findings from a Korean Population-Based Prospective Study

Recently, diets with higher inflammatory potentials based on the dietary inflammatory index (DII^®) have been shown to be associated with increased cardiovascular disease (CVD) risk in the general population. We aimed to prospectively investigate the association between the DII and CVD risk in the large Korean Genome and Epidemiology Study_Health Examination (KoGES_HEXA) cohort comprised of 162,773 participants (men 55,070; women 107,703). A validated semi-quantitative food frequency questionnaire (SQ-FFQ) was used to calculate the DII score. Statistical analyses were performed by using a multivariable Cox proportional hazard model. During the mean follow-up of 7.4 years, 1111 cases of CVD were diagnosed. Higher DII score was associated with increased risk of CVD in men (hazard ratio [HR]_{Quintile 5 vs. 1} 1.43; 95% CI 1.04–1.96) and in women (HR_{Quintile 5 vs. 1} 1.19; 95% CI 0.85–1.67), although not significant for women. The risk of CVD was significantly higher in physically inactive men (HR_{Quintile 5 vs. 1} 1.80; 95% CI 1.03–3.12), obese men (HR_{Quintile 5 vs. 1} 1.77; 95% CI 1.13–2.76) and men who smoked (HR_{Quintile 5 vs. 1} 1.60; 95% CI 1.10–2.33), respectively. The risk of developing stroke was significantly higher for men (HR_{Quintile 5 vs. 1} 2.06; 95% CI 1.07–3.98; p = 0.003), but not for women. A pro-inflammatory diet, as indicated by higher DII scores, was associated with increased risk of CVD and stroke among men.

Dietary intake and blood concentrations of antioxidants and the risk of cardiovascular disease, total cancer, and all-cause mortality: a systematic review and dose-response meta-analysis of prospective studies

Background

High dietary intake or blood concentrations (as biomarkers of dietary intake) of vitamin C, carotenoids, and vitamin E have been associated with reduced risk of cardiovascular disease, cancer, and mortality, but these associations have not been systematically assessed.

Objective

We conducted a systematic review and meta-analysis of prospective studies of dietary intake and blood concentrations of vitamin C, carotenoids, and vitamin E in relation to these outcomes.

Design

We searched PubMed and Embase up to 14 February 2018. Summary RRs and 95% CIs were calculated with the use of random-effects models.

Results

Sixty-nine prospective studies (99 publications) were included. The summary RR per 100-mg/d increment of dietary vitamin C intake was 0.88 (95% CI: 0.79, 0.98, I2 = 65%, n = 11) for coronary heart disease, 0.92 (95% CI: 0.87, 0.98, I2 = 68%, n = 12) for stroke, 0.89 (95% CI: 0.85, 0.94, I2 = 27%, n = 10) for cardiovascular disease, 0.93 (95% CI: 0.87, 0.99, I2 = 46%, n = 8) for total cancer, and 0.89 (95% CI: 0.85, 0.94, I2 = 80%, n = 14) for all-cause mortality. Corresponding RRs per 50-μmol/L increase in blood concentrations of vitamin C were 0.74 (95% CI: 0.65, 0.83, I2 = 0%, n = 4), 0.70 (95% CI: 0.61, 0.81, I2 = 0%, n = 4), 0.76 (95% CI: 0.65, 0.87, I2 = 56%, n = 6), 0.74 (95% CI: 0.66, 0.82, I2 = 0%, n = 5), and 0.72 (95% CI: 0.66, 0.79, I2 = 0%, n = 8). Dietary intake and/or blood concentrations of carotenoids (total, β-carotene, α-carotene, β-cryptoxanthin, lycopene) and α-tocopherol, but not dietary vitamin E, were similarly inversely associated with coronary heart disease, stroke, cardiovascular disease, cancer, and/or all-cause mortality.

Conclusions

Higher dietary intake and/or blood concentrations of vitamin C, carotenoids, and α-tocopherol (as markers of fruit and vegetable intake) were associated with reduced risk of cardiovascular disease, total cancer, and all-cause mortality. These results support recommendations to increase fruit and vegetable intake, but not antioxidant supplement use, for chronic disease prevention.

Adipogenic and Lipolytic Effects of Ascorbic Acid in Ovariectomized Rats

PURPOSE

Ascorbic acid has been reported to have an adipogenic effect on 3T3-L1 preadipocytes, while evidence also suggests that ascorbic acid reduces body weight in humans. In this study, we tested the effects of ascorbic acid on adipogenesis and the balance of lipid accumulation in ovariectomized rats, in addition to long-term culture of differentiated 3T3-L1 adipocytes.

MATERIALS AND METHODS

Murine 3T3-L1 fibroblasts and ovariectomized rats were treated with ascorbic acid at various time points. In vitro adipogenesis was analyzed by Oil Red O staining, and in vivo body fat was measured by a body composition analyzer using nuclear magnetic resonance.

RESULTS

When ascorbic acid was applied during an early time point in 3T3-L1 preadipocyte differentiation and after bilateral ovariectomy (OVX) in rats, adipogenesis and fat mass gain significantly increased, respectively. However, lipid accumulation in well-differentiated 3T3-L1 adipocytes showed a significant reduction when ascorbic acid was applied after differentiation (10 days after induction). Also, oral ascorbic acid administration 4 weeks after OVX in rats significantly reduced both body weight and subcutaneous fat layer. In comparison to the results of ascorbic acid, which is a well-known cofactor for an enzyme of collagen synthesis, and the antioxidant ramalin, a potent antioxidant but not a cofactor, showed only a lipolytic effect in well-differentiated 3T3-L1 adipocytes, not an adipogenic effect.

CONCLUSION

Taking these results into account, we concluded that ascorbic acid has both an adipogenic effect as a cofactor of an enzymatic process and a lipolytic effect as an antioxidant.

Associations of estimated Δ-5-desaturase and Δ-6-desaturase activities with stroke risk factors and risk of stroke: the Kuopio Ischaemic Heart Disease Risk Factor Study

Stroke is a leading cause of morbidity and mortality. The role of PUFA in reducing the risk of stroke is uncertain. The concentrations of PUFA in the human body are determined both by dietary intake and by activities of desaturase enzymes. Desaturase enzymes have been associated with chronic diseases, but little is known about their association with stroke risk. We investigated the associations of Δ-6-desaturase (D6D) and Δ-5-desaturase (D5D) activities with stroke risk factors and risk of stroke among 1842 men from the prospective, population-based Kuopio Ischaemic Heart Disease Risk Factor Study, aged 42-60 years and free of CVD at baseline in 1984-1989. ANCOVA and Cox regression models were used for the analyses. Whole serum desaturase activities were estimated as product:precursor ratios - γ-linolenic acid:linoleic acid for D6D and arachidonic acid:dihomo-γ-linolenic acid for D5D. Higher D6D activity was associated with higher systolic and diastolic blood pressure, BMI, serum insulin and TAG concentrations and worse homoeostatic model assessment (HOMA) indices. In contrast, higher D5D activity was associated with lower systolic and diastolic blood pressure, BMI, serum insulin, LDL-cholesterol, TAG and C-reactive protein concentrations, higher HDL-cholesterol concentration, and better HOMA indices. During the mean follow-up of 21·2 years, 202 stroke cases occurred. Neither D6D activity (multivariable-adjusted extreme-quartile hazard ratios (HR) 1·18; 95 % CI 0·80, 1·74) nor D5D activity (HR 1·06; 95 % CI 0·70, 1·60) were associated with stroke risk. In conclusion, higher D5D activity was favourably associated and higher D6D activity unfavourably associated with several stroke risk factors, but not with the risk of incident stroke.

Levels of vitamin C In the blood plasma patients treated with coronary artery bypass grafting increases significantly after surgery

One strong risk factor of coronary artery disease (CAD), which affects the levels of vitamin C in the blood is cigarette smoking. The supplementary effects of coronary artery bypass grafting (CABG) is smoking cessation by patients. Therefore, the aim of this study was to examine the level of vitamin C in the blood plasma one day before and one month after CABG. Human blood were collected from 20 patients (men); 1day before and 1 month after CABG. All patients were smoker and after CABG they declared their not smoking. The concentration of vitamin C in the blood plasma was assayed by FIA method with spectrophotometric detection. The mean value of the vitamin C concentration 1day before CABG was 12.36±2.84μmol/L (mean±SD), 1 month after CABG 40.07±10.95μmol/L (mean±SD). The average increase in the concentration of vitamin C was 3.27±0.73 times (mean±SD) and showed significant positive correlations (Pearson r=0.657, p=0.002). It should be consider incorporating the recommendations of preoperative smoking cessation for at least one month prior to CABG and/or additional supplementation. In addition it would be relevant to monitor the level of vitamin C in the patients' blood in the preoperative period.

The Comparison of Dietary Behaviors among Rural Controlled and Uncontrolled Hypertensive Patients

Nutrition is a dominant peripheral factor in increasing blood pressure; however, little information is available about the nutritional status of hypertensive patients in Iran. This study aimed to compare nutritional behaviors of the rural controlled and uncontrolled hypertensive patients and to determine the predictive power of nutritional behaviors from blood pressure. This cross-sectional study was conducted on 671 rural hypertensive patients, using multistage random sampling method in Ardabil city in 2013. Data were collected by a 3-day food record questionnaire. Nutritional data were extracted by Nutritionist 4 software and analyzed by the SPSS 18 software using Pearson correlation, multiple linear regression, ANOVA, and independent t-test. A significant difference was observed in the means of fat intake, cholesterol, saturated fat, sodium, energy, calcium, vitamin C, fiber, and nutritional knowledge between controlled and uncontrolled groups. In the controlled group, sodium, saturated fats, vitamin C, calcium, and energy intake explained 30.6% of the variations in blood pressure and, in the uncontrolled group, sodium, carbohydrate, fiber intake, and nutritional knowledge explained 83% of the variations in blood pressure. There was a significant difference in the nutritional behavior between the two groups and changes in blood pressure could be explained significantly by nutritional behaviors.

Levels of l-ascorbic acid and cadmium in the saphenous vein of patients with coronary artery disease are negatively correlated

BACKGROUND

The aim of this study was the simultaneous determination of levels of cadmium and l-ascorbic Acid (AA) in human saphenous vein (SV) used in coronary artery bypass grafting (CABG) and check whether there is a relationship between these levels.

METHODS

Human SV were collected from 40 patients (20 men and 20 women; age, 40-75 years) at the time of routine coronary artery surgical revascularization. The concentration of cadmium in the tissue was determined according to the GF AAS-atomic absorption method. The concentration of AA was assayed in supernatant by FIA method with spectrophotometric detection.

RESULTS

AA concentration (mean±SD); men: 98,7±13,18μg/g tissue, women: 96,06±11,98μg/g tissue. Cadmium concentration(mean±SD); men: 309±103,71ng/g tissue, women: 348,5±255,71ng/g tissue. Correlations among concentrations of AA and cadmium were insignificant negative in the group of men (Pearson r=-0,1504, p=0,5269) and in the group women (Pearson r=-0339, p=0144).

CONCLUSIONS

Negative correlations among concentrations of AA and cadmium in human SV obtained in our study may indicate a protective effect of this vitamin in relation to toxic cadmium.

Variation in the SLC23A1 gene does not influence cardiometabolic outcomes to the extent expected given its association with L-ascorbic acid

BACKGROUND

Observational studies showed that circulating L-ascorbic acid (vitamin C) is inversely associated with cardiometabolic traits. However, these studies were susceptible to confounding and reverse causation.

OBJECTIVES

We assessed the relation between L-ascorbic acid and 10 cardiometabolic traits by using a single nucleotide polymorphism in the solute carrier family 23 member 1 (SLC23A1) gene (rs33972313) associated with circulating L-ascorbic acid concentrations. The observed association between rs33972313 and cardiometabolic outcomes was compared with that expected given the rs33972313-L-ascorbic acid and L-ascorbic acid-outcome associations.

DESIGN

A meta-analysis was performed in the following 5 independent studies: the British Women's Heart and Health Study (n = 1833), the MIDSPAN study (n = 1138), the Ten Towns study (n = 1324), the British Regional Heart Study (n = 2521), and the European Prospective Investigation into Cancer (n = 3737).

RESULTS

With the use of a meta-analysis of observational estimates, inverse associations were shown between L-ascorbic acid and systolic blood pressure, triglycerides, and the waist-hip ratio [the strongest of which was the waist-hip ratio (-0.13-SD change; 95% CI: -0.20-, -0.07-SD change; P = 0.0001) per SD increase in L-ascorbic acid], and a positive association was shown with high-density lipoprotein (HDL) cholesterol. The variation at rs33972313 was associated with a 0.18-SD (95% CI: 0.10-, 0.25-SD; P = 3.34 × 10⁻⁶) increase in L-ascorbic acid per effect allele. There was no evidence of a relation between the variation at rs33972313 and any cardiometabolic outcome. Although observed estimates were not statistically different from expected associations between rs33972313 and cardiometabolic outcomes, estimates for low-density lipoprotein cholesterol, HDL cholesterol, triglycerides, glucose, and body mass index were in the opposite direction to those expected.

CONCLUSIONS

The nature of the genetic association exploited in this study led to limited statistical application, but despite this, when all cardiometabolic traits were assessed, there was no evidence of any trend supporting a protective role of L-ascorbic acid. In the context of existing work, these results add to the suggestion that observational relations between L-ascorbic acid and cardiometabolic health may be attributable to confounding and reverse causation.

Lipophilization of ascorbic acid: a monolayer study and biological and antileishmanial activities

Ascorbyl lipophilic derivatives (Asc-C2 to Asc-C(18:1)) were synthesized in a good yield using lipase from Staphylococcus xylosus produced in our laboratory and immobilized onto silica aerogel. Results showed that esterification had little effect on radical-scavenging capacity of purified ascorbyl esters using DPPH assay in ethanol. However, long chain fatty acid esters displayed higher protection of target lipids from oxidation. Moreover, compared to ascorbic acid, synthesized derivatives exhibited an antibacterial effect. Furthermore, ascorbyl derivatives were evaluated, for the first time, for their antileishmanial effects against visceral (Leishmania infantum) and cutaneous parasites (Leishmania major). Among all the tested compounds, only Asc-C10, Asc-C12, and Asc-C(18:1) exhibited antileishmanial activities. The interaction of ascorbyl esters with a phospholipid monolayer showed that only medium and unsaturated long chain (Asc-C10 to Asc-C(18:1)) derivative esters were found to interact efficiently with mimetic membrane of leishmania. These properties would make ascorbyl derivatives good candidates to be used in cosmetic and pharmaceutical lipophilic formulations.

Vitamin C intake, circulating vitamin C and risk of stroke: a meta-analysis of prospective studies

Background

Though vitamin C supplementation has shown no observed effects on stroke prevention in several clinical trials, uncertainty remains as to whether long‐term, low‐dose intake influences the development of stroke among general populations. Furthermore, the association between circulating vitamin C and the risk of stroke is also unclear. For further clarification of these issues, we conducted a meta‐analysis of prospective studies.

Methods and Results

PubMed and EMBASE databases were searched, and the bibliographies of the retrieved articles were also reviewed to identify eligible studies. Summary relative risk (RRs) with corresponding 95% confidence intervals (CIs) were computed with a random‐effects model. The summary RR for the high‐versus‐low categories was 0.81 (95% CI: 0.74 to 0.90) for dietary vitamin C intake (11 studies), and 0.62 (95% CI: 0.49 to 0.79) for circulating vitamin C (6 studies). The summary RR for each 100 mg/day increment in dietary vitamin C was 0.83 (95% CI: 0.75 to 0.93) (10 studies), and for each 20 μmol/L increment in circulating vitamin C was 0.81 (95% CI: 0.75 to 0.88) (5 studies). Few studies reported results for vitamin C supplements (RR for high‐versus‐low intake=0.83, 95% CI: 0.62 to 1.10, 3 studies).

Conclusions

This meta‐analysis suggests significant inverse relationships between dietary vitamin C intake, circulating vitamin C, and risk of stroke.

Dietary fats and other nutrients on stroke

PURPOSE OF REVIEW

This review summarizes current epidemiologic evidence regarding the associations of dietary fat and other nutrients with risk of stroke.

RECENT FINDINGS

Recent epidemiologic studies show no association of total fat intake or absolute intakes of saturated, monounsaturated, or polyunsaturated fat with risk of stroke. Data on long-chain omega-3 polyunsaturated fatty acids in relation to stroke risk are inconclusive but may favor fewer strokes in women. Insufficient evidence exists for trans fatty acids, other fatty acids, and dietary cholesterol intake. Present evidence indicates that high dietary magnesium and potassium intakes may lower the risk of stroke, whereas a high sodium (salt) intake and a low dietary vitamin D intake likely increase stroke risk. Calcium does not prevent stroke in populations with moderate-to-high calcium intakes but might play a role in populations with low calcium intakes. Supplementation with single vitamins likely has no protective effect on stroke in well nourished populations.

SUMMARY

Available epidemiologic evidence indicates that diets high in magnesium and potassium may play a role in the prevention of stroke, whereas a high sodium intake is a risk factor. It remains unclear whether specific fatty acids, dietary cholesterol, and combinations of vitamins affect the risk of stroke.

Authors' perspective: What is the optimum intake of vitamin C in humans?

The recommended dietary allowance (RDA) of vitamin C has traditionally been based on the prevention of the vitamin C deficiency disease, scurvy. While higher intakes of vitamin C may exert additional health benefits, the limited Phase III randomized placebo-controlled trials (RCTs) of vitamin C supplementation have not found consistent benefit with respect to chronic disease prevention. To date, this has precluded upward adjustments of the current RDA. Here we argue that Phase III RCTs-designed principally to test the safety and efficacy of pharmaceutical drugs-are ill suited to assess the health benefits of essential nutrients; and the currently available scientific evidence is sufficient to determine the optimum intake of vitamin C in humans. This evidence establishes biological plausibility and mechanisms of action for vitamin C in the primary prevention of coronary heart disease, stroke, and cancer; and is buttressed by consistent data from prospective cohort studies based on blood analysis or dietary intake and well-designed Phase II RCTs. These RCTs show that vitamin C supplementation lowers hypertension, endothelial dysfunction, chronic inflammation, and Helicobacter pylori infection, which are independent risk factors of cardiovascular diseases and certain cancers. Furthermore, vitamin C acts as a biological antioxidant that can lower elevated levels of oxidative stress, which also may contribute to chronic disease prevention. Based on the combined evidence from human metabolic, pharmacokinetic, and observational studies and Phase II RCTs, we conclude that 200 mg per day is the optimum dietary intake of vitamin C for the majority of the adult population to maximize the vitamin's potential health benefits with the least risk of inadequacy or adverse health effects.

Oxidative stress, Noxs, and hypertension: experimental evidence and clinical controversies

Reactive oxygen species (ROS) are signaling molecules that influence many physiological processes. Increased ROS bioavailability and altered redox signaling (oxidative stress) have been implicated in chronic diseases including hypertension. Although oxidative stress may not be the sole cause of hypertension, it amplifies blood pressure elevation in the presence of other prohypertensive factors (salt, renin-angiotensin system, sympathetic hyperactivity). A major source for cardiovascular ROS is a family of non-phagocytic NADPH oxidases (Nox1, Nox2, Nox4, Nox5). Other sources of ROS involve mitochondrial electron transport enzymes, xanthine oxidase, and uncoupled nitric oxide synthase. Although evidence from experimental and animal studies supports a role for oxidative stress in the pathogenesis of hypertension, there is still no convincing proof that oxidative stress is a cause of human hypertension. However, what is clear is that oxidative stress is important in the molecular mechanisms associated with cardiovascular and renal injury in hypertension and that hypertension itself can contribute to oxidative stress. The present review addresses the putative function of ROS in the pathogenesis of hypertension and focuses on the role of Noxs in ROS generation in vessels and the kidney. Implications of oxidative stress in human hypertension are discussed, and clinical uncertainties are highlighted.

Traditional risk factor management for stroke: a never-ending challenge for health behaviors of diet and physical activity

PURPOSE OF REVIEW

Recently, many guidelines have given new evidence on the risk factors for stroke. In this review, I refer to the most important guidelines for primary prevention of stroke and hypertension, especially focused on diet and physical activity.

RECENT FINDINGS

The health behavior recommendations in recent guidelines for the primary prevention of stroke are virtually identical, and the same recommendations appear in the recent guidelines for the management of hypertension, especially with respect to diet and physical activity. The recommended health behaviors consist of weight reduction, reduction of salt intake, increase in fruit and vegetable intake, decrease in saturated and total fat intake (increase in fish intake), physical activity, and moderation of alcohol consumption. Fruits and vegetables have high levels of potassium, antioxidants, phytochemicals, and dietary fiber, and thus are also considered preventive of cardiovascular disease and its risk factors. It was found that individuals with many of these health behaviors have been shown to have a lowered risk of stroke.

SUMMARY

The health behaviors, especially those related to diet and physical activity, appearing in recent guidelines for the management of hypertension are also important for the primary prevention of stroke, and appear in recent stroke guidelines.

Fat intake leads to differential response of rat adipocytes to glucose, insulin and ascorbic acid

Antioxidant-based treatments have emerged as novel and interesting approaches to counteract fat accumulation in obesity and associated metabolic disturbances. Adipocytes from rats that were fed on chow or high-fat diet (HFD) for 50 d were isolated (primary adipocytes) and incubated (72 h) on low (LG; 5.6 mmol/L) or high (HG; 25 mmol/L) glucose levels, in the presence or absence of 1.6 nmol/L insulin and 200 μmol/L vitamin C (VC). Adipocytes from HFD-fed animals presented lower insulin-induced glucose uptake, lower lactate and glycerol release, and lower insulin-induced secretion of some adipokines as compared with controls. HG treatment restored the blunted response to insulin regarding apelin secretion in adipocytes from HFD-fed rats. VC treatment inhibited the levels of nearly all variables, irrespective of the adipocytes’ dietary origin. The HG treatment reduced adipocyte viability, and VC protected from this toxic effect, although more drastically in control adipocytes. Summing up, in vivo chow or HFD intake determines a differential response to insulin and glucose treatments that appears to be dependent on the insulin-resistance status of the adipocytes, while VC modifies some responses from adipocytes independently of the previous dietary intake of the animals.

Induction of NAD(P)H-quinone oxidoreductase 1 by antioxidants in female ACI rats is associated with decrease in oxidative DNA damage and inhibition of estrogen-induced breast cancer

Exact mechanisms underlying the initiation and progression of estrogen-related cancers are not clear. Literature, evidence and our studies strongly support the role of estrogen metabolism-mediated oxidative stress in estrogen-induced breast carcinogenesis. We have recently demonstrated that antioxidants vitamin C and butylated hydroxyanisole (BHA) or estrogen metabolism inhibitor α-naphthoflavone (ANF) inhibit 17β-estradiol (E2)-induced mammary tumorigenesis in female ACI rats. The objective of the current study was to identify the mechanism of antioxidant-mediated protection against E2-induced DNA damage and mammary tumorigenesis. Female ACI rats were treated with E2 in the presence or absence of vitamin C or BHA or ANF for up to 240 days. Nuclear factor erythroid 2-related factor 2 (NRF2) and NAD(P)H-quinone oxidoreductase 1 (NQO1) were suppressed in E2-exposed mammary tissue and in mammary tumors after treatment of rats with E2 for 240 days. This suppression was overcome by co-treatment of rats with E2 and vitamin C or BHA. Time course studies indicate that NQO1 levels tend to increase after 4 months of E2 treatment but decrease on chronic exposure to E2 for 8 months. Vitamin C and BHA significantly increased NQO1 levels after 120 days. 8-Hydroxydeoxyguanosine (8-OHdG) levels were higher in E2-exposed mammary tissue and in mammary tumors compared with age-matched controls. Vitamin C or BHA treatment significantly decreased E2-mediated increase in 8-OHdG levels in the mammary tissue. In vitro studies using silencer RNA confirmed the role of NQO1 in prevention of oxidative DNA damage. Our studies further demonstrate that NQO1 upregulation by antioxidants is mediated through NRF2.

Bioavailability of vitamin C from mashed potatoes and potato chips after oral administration in healthy Japanese men

Potato (Solanum tuberosum) tubers contain vitamin C (VC) and commercial potato chips have more VC content per wet weight by dehydration during frying. However, intestinal absorption of VC from orally ingested potatoes and its transfer to the blood remains questionable. The present study was designed to determine whether the dietary consumption of potatoes affects VC concentration in plasma and urinary excretion of VC in human subjects. After overnight fasting, five healthy Japanese men between 22 and 27 years of age consumed 87 g mashed potatoes and 282 g potato chips. Each portion contained 50 mg of VC, 50 mg VC in mineral water and mineral water. Before and after a single episode of ingestion, blood and urine samples were collected every 30 min or 1 h for 8 h. When measured by subtraction of the initial baseline value before administration of potatoes from the values measured throughout the 8 h test period, plasma VC concentrations increased almost linearly up to 3 h. Subsequently, the values of potato-fed subjects were higher than those of water, but did not differ significantly from those of VC in water (P = 0·14 andP = 0·5). Less VC tended to be excreted in urine during the 8 h test than VC in water alone (17·0 (sem7·5) and 25·9 (sem8·8)v.47·9 (sem17·9) μmol/mmol creatinine). Upon human consumption, mashed potatoes and potato chips provide VC content that is effectively absorbed in the intestine and transferred to the blood. Clearly, potatoes are a readily available source of dietary VC.

Total antioxidant capacity of the diet is associated with lower risk of ischemic stroke in a large Italian cohort

Experimental studies suggest that oxidative stress and systemic inflammation are involved in the pathogenesis of ischemic stroke. Consuming a diet with a high total antioxidant capacity (TAC) has been related to reduced inflammation and increased circulating antioxidants in cross-sectional and randomized intervention studies. This study investigates the relation between dietary TAC and risk of ischemic and hemorrhagic stroke in 41,620 men and women not previously diagnosed with stroke or myocardial infarction, representing the Italian segment of the European Prospective Investigation into Cancer and Nutrition. Controlling for potential confounders, a diet rich in TAC was associated with a reduction in HR for all types of stroke, but this association was only marginally significant (P-trend = 0.054). When only ischemic stroke cases were considered, data suggest a stronger inverse association with dietary TAC, with HR = 0.41 (95% CI = 0.23-0.74). Regarding single antioxidants, data from subanalyses on stroke types suggest that vitamin C is significantly associated with a decreased risk of ischemic stroke [HR = 0.58 (95% CI = 0.34-0.99)], whereas vitamin E was associated with increased HR of hemorrhagic stroke in the highest tertile of intake [HR = 2.94 (95% CI = 1.13-7.62)]. In conclusion, our findings suggest that antioxidants may play a role in reducing the risk of cerebral infarction but not hemorrhagic stroke. However, a high intake of vitamin E could be positively associated to the risk of brain hemorrhagic events; therefore, more focused investigations about this observation are needed.

Handling Practices to Control Ascorbic Acid and β-Carotene Lossess in Collards (Brassica oleracea)

Knowledge of the alterations in the nutrient content of vegetables after harvest and during preparation is still limited although studies have been reported. The objective of this study was to select handling practices to control losses of vitamin C (ascorbic acid (AA) and dehydroascorbic acid) and β-carotene in collards during storage, sanitization, slicing, and time after preparation. Determination of carotenoids was carried out by HPLC. β-carotene retention was greater at 10°C than 23°C after 24-h storage. Sanitization for a period longer than 15 min negatively affected AA retention in the sample stored under refrigeration. Increased waiting time between frying and consumption of stir-fried collards increased AA losses both in sliced and torn collards. Storage under refrigeration, sanitization time control, and reduced time between preparation and consumption are therefore recommended.

Physical therapy in the 21st century (Part I): toward practice informed by epidemiology and the crisis of lifestyle conditions

Part I of this two-part introduction to this Special Issue on the practice of physical therapy in the 21st century outlines the epidemiological basis and rationale for evidence-informed physical therapy practice for addressing contemporary health priorities. This evidence emanates from the definition of health by the World Health Organization (WHO) and the International Classification of Functioning (ICF), and WHO and other international databases on the prevalence of lifestyle conditions. Lifestyle conditions include ischemic heart disease, smoking-related conditions, hypertension and stroke, obesity, diabetes, and cancer. Epidemiological data combined with evidence supporting the effectiveness of noninvasive interventions related to physical therapy to address these priorities (e.g., health education and exercise) are highly consistent with the promotion of health and wellness and the ICF. Given their commitment to exploiting effective noninvasive interventions, physical therapists are in a preeminent position to focus on prevention of these disabling and lethal conditions in every client or patient, their cure in some cases, as well as their management. Thus, a compelling argument can be made that clinical competencies in 21st century physical therapy need to include assessment of smoking and smoking cessation (or at least its initiation), basic nutritional assessment and counseling, recommendations for physical activity and exercise, stress assessment and basic stress reduction recommendations, and sleep assessment and basic sleep hygiene recommendations. The physical therapist can then make an informed clinical judgment regarding whether a client or patient needs to be referred to another professional related to one or more of these specialty areas. The prominence of physical therapy as an established health care profession and its unique pattern of practice (prolonged visits over prolonged periods of time) attest further to the fact that physical therapists are uniquely qualified to lead in the assault on lifestyle conditions. Evidence-based physical therapy practiced within the context of epidemiological indicators (i.e., evidence-informed practice) maximally empowers clinicians to promote lifelong health in every person and in turn, the health of communities. This vision of physical therapy's leading role in health promotion and health care in the 21st century holds the promise of reducing the need for invasive health interventions (drugs and surgery). Part II of this introduction describes evidence-based physical therapy practice within this context of evidence-informed practice.

Plant foods and the risk of cerebrovascular diseases: a potential protection of fruit consumption

Studies on the association between plant foods and cerebrovascular diseases have given contradictory results suggesting the existence of some effect-modifying factors. The present study determines whether the consumption of plant foods (i.e. fruits and berries, vegetables, and cereals) predicts a decreased cerebrovascular disease incidence in a population with low fruit and vegetable and high wholegrain intake. This cohort study on 3932 men and women was based on data from the Finnish Mobile Clinic Health Examination Survey, conducted in 1968-72. The participants were 40-74 years of age and free of cardiovascular diseases at baseline. Data on the plant food consumption were derived from a 1-year dietary history interview. During a 24-year follow-up 625 cases of cerebrovascular diseases occurred, leading to either hospitalisation or death. An inverse association was found between fruit consumption and the incidence of cerebrovascular diseases, ischaemic stroke and intracerebral haemorrhage. The adjusted relative risks (RR) between the highest and lowest quartiles of intake of any cerebrovascular disease, ischaemic stroke and intracerebral haemorrhage were 0.75 (95 % CI 0.59, 0.94), 0.73 (95 % CI 0.54, 1.00) and 0.47 (95 % CI 0.24, 0.92), respectively. These associations were primarily due to the consumption of citrus fruits and occurred only in men. Total consumption of vegetables or cereals was not associated with the cerebrovascular disease incidence. The consumption of cruciferous vegetables, however, predicted a reduced risk of cerebrovascular diseases (RR 0.79; 95 % CI 0.63, 0.99), ischaemic stroke (RR 0.67; 95 % CI 0.49, 0.92) and intracerebral haemorrhage (RR 0.49; 95 % CI 0.25, 0.98). In conclusion, the consumption of fruits, especially citrus, and cruciferous vegetables may protect against cerebrovascular diseases.

Stroke: roles of B vitamins, homocysteine and antioxidants

In the present review concerning stroke, we evaluate the roles of B vitamins, homocysteine and antioxidant vitamins. Stroke is a leading cause of death in developed countries. However, current therapeutic strategies for stroke have been largely unsuccessful. Several studies have reported important benefits on reducing the risk of stroke and improving the post-stroke-associated functional declines in patients who ate foods rich in micronutrients, including B vitamins and antioxidant vitamins E and C. Folic acid, vitamin B6and vitamin B12are all cofactors in homocysteine metabolism. Growing interest has been paid to hyperhomocysteinaemia as a risk factor for CVD. Hyperhomocysteinaemia has been linked to inadequate intake of vitamins, particularly to B-group vitamins and therefore may be amenable to nutritional intervention. Hence, poor dietary intake of folate, vitamin B6and vitamin B12are associated with increased risk of stroke. Elevated consumption of fruits and vegetables appears to protect against stroke. Antioxidant nutrients have important roles in cell function and have been implicated in processes associated with ageing, including vascular, inflammatory and neurological damage. Plasma vitamin E and C concentrations may serve as a biological marker of lifestyle or other factors associated with reduced stroke risk and may be useful in identifying those at high risk of stroke. After reviewing the observational and intervention studies, there is an incomplete understanding of mechanisms and some conflicting findings; therefore the available evidence is insufficient to recommend the routine use of B vitamins, vitamin E and vitamin C for the prevention of stroke. A better understanding of mechanisms, along with well-designed controlled clinical trials will allow further progress in this area.

Total and cancer mortality after supplementation with vitamins and minerals: follow-up of the Linxian General Population Nutrition Intervention Trial

BACKGROUND

The General Population Nutrition Intervention Trial was a randomized primary esophageal and gastric cancer prevention trial conducted from 1985 to 1991, in which 29,584 adult participants in Linxian, China, were given daily vitamin and mineral supplements. Treatment with "factor D," a combination of 50 microg selenium, 30 mg vitamin E, and 15 mg beta-carotene, led to decreased mortality from all causes, cancer overall, and gastric cancer. Here, we present 10-year follow-up after the end of active intervention.

METHODS

Participants were assessed by periodic data collection, monthly visits by village health workers, and quarterly review of the Linxian Cancer Registry. Hazard ratios (HRs) and 95% confidence intervals (CIs) for the cumulative effects of four vitamin and mineral supplementation regimens were calculated using adjusted proportional hazards models.

RESULTS

Through May 31, 2001, 276 participants were lost to follow-up; 9727 died, including 3242 from cancer (1515 from esophageal cancer and 1199 from gastric cancer). Participants who received factor D had lower overall mortality (HR = 0.95, 95% CI = 0.91 to 0.99; P = .009; reduction in cumulative mortality from 33.62% to 32.19%) and gastric cancer mortality (HR = 0.89, 95% CI = 0.79 to 1.00; P = .043; reduction in cumulative gastric cancer mortality from 4.28% to 3.84%) than subjects who did not receive factor D. Reductions were mostly attributable to benefits to subjects younger than 55 years. Esophageal cancer deaths between those who did and did not receive factor D were not different overall; however, decreased 17% among participants younger than 55 (HR = 0.83, 95% CI = 0.71 to 0.98; P = .025) but increased 14% among those aged 55 years or older (HR = 1.14, 95% CI = 1.00 to 1.30; P = .047) [corrected]. Vitamin A and zinc supplementation was associated with increased total and stroke mortality; vitamin C and molybdenum supplementation, with decreased stroke mortality.

CONCLUSION

The beneficial effects of selenium, vitamin E, and beta-carotene on mortality were still evident up to 10 years after the cessation of supplementation and were consistently greater in younger participants. Late effects of other supplementation regimens were also observed.

Is the anti-hypertensive effect of dietary supplements via aldehydes reduction evidence based? A systematic review

Growing evidence indicates that insulin resistance and oxidative stress are involved in the pathogenesis of essential hypertension. In insulin-resistant states, like obesity and type 2 diabetes, altered glucose metabolism may lead to increased formation of methylglyoxal and other ketoaldehydes. Animal studies have shown that increased levels of endogenous aldehydes may lead to hypertension and oxidative stress. In animal models, the administration of vitamin C, vitamin B6 or alpha-lipoic acid reduced tissue levels of aldehydes, prevented oxidative stress, and lowered blood pressure. The purpose of this review article is to critically evaluate the available evidence for the role of dietary supplements in hypertension treatment.

Ascorbic acid 6-palmitate suppresses gap-junctional intercellular communication through phosphorylation of connexin 43 via activation of the MEK-ERK pathway

Although the health benefits of dietary antioxidants have been extensively studied, their potential negative effects remain unclear. L-Ascorbic acid 6-palmitate (AAP), a synthetic derivative of ascorbic acid (AA), is widely used as an antioxidant and preservative in foods, vitamins, drugs, and cosmetics. Previously, we found that AA exerted an antitumor effect by protecting inhibition of gap-junctional intercellular communication (GJIC), which is closely associated with tumor progression. In this study, we examined whether AAP, an amphipathic derivative of AA, has chemopreventive effects using a GJIC model. AAP and AA exhibited dose-dependent free radical-scavenging activities and inhibited hydrogen peroxide (H(2)O(2))-induced intracellular reactive oxygen species (ROS) production in normal rat liver epithelial cells. Unexpectedly, however, AAP did not protect against the inhibition of GJIC induced by H(2)O(2); instead, it inhibited GJIC synergistically with H(2)O(2). AAP inhibited GJIC in a dose-dependent and reversible manner. This inhibitory effect was not due to the conjugated lipid structure of AAP, as treatment with palmitic acid alone failed to inhibit GJIC under the same conditions. The inhibition of GJIC by AAP was restored in the presence of mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) kinase (MEK) inhibitor U0126, but not in the presence of other signal inhibitors and antioxidant (PKC inhibitors, EGFR inhibitor, NADPH oxidase inhibitor, catalase, vitamin E, or AA), indicating the critical involvement of MEK signaling in the GJIC inhibitory activity of AAP. Phosphorylation of ERK and connexin 43 (Cx43) was observed following AAP treatment, and this was reversed by U0126. These results suggest that the AAP-induced inhibition of GJIC is mediated by the phosphorylation of Cx43 via activation of the MEK-ERK pathway. Taken together, our results indicate that AAP has a potent carcinogenic effect, and that the influence of dietary antioxidants on carcinogenesis may be paradoxical.

Oxidative stress and inflammation in atrial fibrillation: role in pathogenesis and potential as a therapeutic target

Atrial fibrillation (AF) is one of the most prevalent and vexing cardiovascular conditions. Available treatments for AF based on ion channel blockade are only poorly effective. The fundamental mechanisms that underlie AF are still not clearly understood, and likely vary depending on the etiology of AF. In older individuals with senile AF, likely mechanisms include abnormal calcium cycling, oxidant stress, and deleterious inflammatory responses. Clinical and experimental evidence is provided to support the role of oxidant and inflammatory mechanisms in AF. On the basis of these studies, the prospects of manipulating oxidant and inflammatory pathways as targets for therapeutic intervention are discussed.

Lack of effect of acute oral ingestion of vitamin C on oxidative stress, arterial stiffness or blood pressure in healthy subjects

Vitamin C is a potent antioxidant in vitro and has been reported to act as a vasodilator, possibly by increasing nitric oxide bioavailability. This study examined the antioxidant and vascular effects of a single large oral dose of vitamin C in 26 healthy human volunteers. Haemodynamic and oxidative DNA and lipid damage markers were measured for 8 h following an oral dose of 2 g vitamin C or placebo. Vitamin C had no effect on vasodilation (measured by augmentation index (mean change=0.04%, 90% CI=- 2.20% to 2.28%) or forearm blood flow (-0.19%/min (-0.68, 0.30)), in comparison to placebo) or on several markers of oxidative stress including DNA base oxidation products in blood cells, 8-hydroxy-2'-deoxyguanosine (8O HdG) in urine (0.068 (-0.009, 0.144)) or urinary or plasma total F(2)-isoprostanes (-0.005 ng/ml (-0.021, 0.010), -0.153 ng/mg (-0.319, 0.014), respectively).

Targeting reactive oxygen species in hypertension

Oxidative stress plays an important role in the pathogenesis of hypertension. A number of sources of reactive oxygen species have been identified including NADPH oxidase, endothelial NO synthase, and xanthine oxidase. Inhibitors of these systems reduce blood pressure in experimental models. Targeted overexpression of antioxidant systems and interference with expression of oxidant systems has also been successfully used in animal models of hypertension. It is expected that these strategies will eventually be translated to human disease, but currently, the specificity and toxicity of such measures are not yet fulfilling quality criteria for treatment of humans. In the meantime, presumably nontoxic measures, such as administration of antioxidant vitamins, are the only available treatments for oxidative stress in humans. In this review, we discuss strategies to target oxidative stress both in experimental models and in humans. We also discuss how patients could be selected who particularly benefit from antioxidant treatment. In clinical practice, diagnostic procedures beyond measurement of blood pressure will be necessary to predict the response to antioxidants; these procedures will include measurement of antioxidant status and detailed assessment of vascular structure and function.

The planetary biology of ascorbate and uric acid and their relationship with the epidemic of obesity and cardiovascular disease

Humans have relatively low plasma ascorbate levels and high serum uric acid levels compared to most mammals due to the presence of genetic mutations in l-gulonolactone oxidase and uricase, respectively. We review the major hypotheses for why these mutations may have occurred. In particular, we suggest that both mutations may have provided a survival advantage to early primates by helping maintain blood pressure during periods of dietary change and environmental stress. We further propose that these mutations have the inadvertent disadvantage of increasing our risk for hypertension and cardiovascular disease in today's society characterized by Western diet and increasing physical inactivity. Finally, we suggest that a "planetary biology" approach in which genetic changes are analyzed in relation to their biological action and historical context may provide the ideal approach towards understanding the biology of the past, present and future.

Vitamin C promotes human endothelial cell growth via the ERK-signaling pathway

BACKGROUND

Epidemiological, secondary prevention and small interventional trials suggest a preventive role of vitamin C for cardiovascular diseases (CAD), especially through improving endothelial dysfunction. Large primary prevention trials failed to confirm this. Mechanistic studies may contribute to resolve this discrepancy.

AIM OF THE STUDY

We examined whether vitamin C activates mitogen-activated protein kinases (MAPK) in human umbilical cord venous endothelial cells (HUVECs) and whether reactive oxygen species (ROS) play a role in this process.

METHODS

Subconfluent quiescent HUVECs were incubated with vitamin C alone or in combination with catalase (CAT) and/or hydrogenperoxide (H2O2). Intracellular MAPK were determined by Western blot, proliferation by cell count and DNA-synthesis by [3H]-thymidine-uptake.

RESULTS

HUVECs were incubated with vitamin C (60 microM) for 5-60 min or for 20 min (30-90 microM). A dose-dependent phosphorylation of extracellular signal-regulated-kinases (ERKs)-1 and -2 with a maximum of phosphorylation at 15-20 min was observed and inhibitable by MEK1/2-inhibitor U0126 (5-10 microM). Vitamin C (60 microM) stimulated phosphorylation of ERK5, but not of p38 and c-Jun, demonstrating a different MAPK-activation pattern compared to H2O2. Vitamin C (60 microM) induced proliferation and a dose-dependent [3H]-thymidine-uptake (30-120 microM) within 20 h. CAT (0.3 U/ml) did neither suppress the vitamin C induced [3H]-thymidine-uptake nor ERK1/2-phosphorylation. CAT (0.3 U/ml), but not vitamin C (60 microM) abrogated the inhibitory effects of H2O2 (100 microM) on [3H]-thymidine-uptake.

CONCLUSION

Physiological vitamin C-concentrations promote proliferation of subconfluent ECs by activating an ERK1/2 controlled pathway. Targeting MAPK by vitamin C may improve, besides antioxidant mechanisms, endothelial dysfunction by promoting a fast regeneration of the endothelium after tissue injury, particularly required during secondary prevention and early development.

Mortality in the Sami population of North Norway, 1970-98

AIMS

The pattern of mortality among many groups of indigenous people has been shown to be disadvantageous in comparison with the general population. Knowledge regarding causes of death among the Sami population in the northern part of Norway is limited. The Sami constitute an ethnic minority whose lifestyle diverges from that of the rest of the population.

METHODS

A cohort of 19,801 persons of Sami origin was followed up to evaluate specific causes of mortality during the period 1970-98. Standardized mortality rates (SMR) were calculated using the rural population of the three Norwegian counties included in the study as a reference population.

RESULTS

Among Sami, 5,955 total deaths were observed, as opposed to 5,537 expected (SMR = 1.08). For both Sami women and men a significantly higher SMR for cerebrovascular diseases was found, which was more pronounced for women. For Sami men, an excess SMR for violent death was observed (SMR 1.32, 95% confidence interval (CI) 1.20-1.46); this was highest among Sami men living in a reindeer-breeding family. For both genders, mortality from all malignant neoplasms combined was lower than in the reference population. SMRs were 0.86 (95% CI 0.79-0.94) and 0.89 (95% CI 0.80-0.99) for men and women, respectively. Low SMRs were also observed for chronic liver diseases, 0.18 (95% CI 0.02-0.63) and 0.12 (95% CI 0.00-0.68) for Sami men and women, respectively. To be a member of a reindeer breeding household appeared to offer protection from mortality caused by circulatory system diseases in men, especially mortality from ischaemic heart disease.

CONCLUSIONS

The total mortality in the North Norway Sami population, an ethnic minority in Norway, was slightly higher when compared with a regional reference population. The differences observed when evaluating mortality by diagnosis might be due to lifestyle, diet, psychosocial, and/or genetic factors.

Treatment of essential hypertension and non-insulin dependent diabetes mellitus with vitamin C

Inappropriate response of the carotid body region to encroachment of its perfusion results in essential hypertension (EH) and/or non-insulin dependent diabetes mellitus (NIDDM). This encroachment is caused by atherosclerosis. The carotid body perceives the encroachment on the lumen as a reduction in the availability of oxygen and glucose for the brain. Raising the perfusion pressure (thus, resulting in EH) and/ or inducing insulin resistance (causing NIDDM) are seen as compensatory mechanisms in response to the primary pathology, ie the encroachment of the lumen by atherosclerosis. Therefore, the reduction or reversal of the atherosclerosis process will help improve perfusion to the carotid bodies, which will in turn reduce or reverse the pathophysiological compensatory adjustments described above. A supplemental therapy, in addition to the standard treatment, with vitamin C is suggested here. The argument in favour of this suggestion is the basis of this paper. Vitamin C is a very important antioxidant. It is suggested to be used without any interference with the usual therapy prescribed for these two chronic diseases. It is recommended to be administered in small, frequent doses of 100mg every 2h, except during sleep. There is no need for compensation for the occasional missed dose. The safety of larger doses of vitamin C than the current recommendations, represents the beauty and is reassuring in recommending this approach.

A Cerebroprotective Dose of Intravenous Citrate/Sorbitol-stabilized Dehydroascorbic Acid is Correlated with Increased Cerebral Ascorbic Acid and Inhibited Lipid Peroxidation after Murine Reperfused Stroke

OBJECTIVE

Oxidative damage has been implicated in the pathogenesis of cerebral ischemia. We previously demonstrated that exogenously supplied dehydroascorbic acid (DHA), an oxidized, blood-brain barrier transportable form of the antioxidant ascorbic acid (AA), improves outcome after experimental stroke.

METHODS

To investigate the neuroprotective effect of DHA therapy, we measured cerebral AA levels using a novel assay, quantified markers of lipid peroxidation, and evaluated infarct volume after reperfused stroke in a murine model. All experiments were performed using a new citrate/sorbitol-stabilized DHA formulation to improve the stability of the compound.

RESULTS

Intraparenchymal AA levels declined after cerebral ischemia/reperfusion and were repleted in a dose-dependent fashion by postischemic administration of intravenous DHA (P < 0.01). Repletion of these levels was associated with reductions in cerebral malondialdehyde levels (P < 0.05), which were also elevated after reperfused stroke. DHA repletion of interstitial AA levels and reduction in cerebral lipid peroxidation was associated with dose-dependent reductions in infarct volume (P < 0.05).

CONCLUSION

Together, these results indicate that an intravenous cerebroprotective dose of citrate/sorbitol-stabilized DHA is correlated with increased brain ascorbate levels and a suppression of excessive oxidative metabolism.

Biphasic effects of dietary antioxidants on oxidative stress-mediated carcinogenesis

There is now strong evidence implicating the generation of reactive oxygen species (ROS) and the corresponding response to oxidative stress as key factors in the pathogenesis of several human diseases including cancer, atherosclerosis, and neurodegenerative disorders, and in ageing. The carcinogenicity of oxidative stress is primarily attributable to the genotoxicity of ROS, but ROS can promote cancer through diverse cellular processes. Therefore, dietary or pharmaceutical augmentation of the endogenous antioxidant defense capacity has been considered a plausible way to prevent ROS-mediated carcinogenicity, but actual antioxidant therapies have been equivocal at best. In fact, most free-radical scavengers act in reversible oxidation-reduction reactions, and some antioxidants can act both as antioxidants and prooxidants, depending on their structures and the conditions. This article summarizes the possible cancer-preventive and -enhancing mechanisms of dietary antioxidants, with an emphasis on epigenetic mechanisms.

Metabolic Syndrome and the Risk of Stroke in Middle-Aged Men

BACKGROUND AND PURPOSE

The metabolic syndrome, a clustering of disturbed glucose and insulin metabolism, obesity and abdominal fat distribution, dyslipidemia, and hypertension is associated with cardiovascular diseases. The aim of this study was to examine the relationship of metabolic syndrome, as defined by National Cholesterol Education Program (NCEP) and World Health Organization (WHO) criteria, with the risk for stroke.

METHODS

Population-based cohort study with an average follow-up of 14.3 years from eastern Finland. A total of 1131 men with no history of cardiovascular disease and diabetes at baseline participated. Sixty-five strokes occurred, of which 47 were ischemic strokes.

RESULTS

Men with the metabolic syndrome as defined by the NCEP criteria had a 2.05-fold (95% CI, 1.03 to 4.11; P=0.042) risk for all strokes and 2.41-fold (95% CI, 1.12 to 5.32; P=0.025) risk for ischemic stroke, after adjusting for socioeconomic status, smoking, alcohol, and family history of coronary heart disease. Additional adjustment for ischemic changes during exercise test, serum low-density lipoprotein cholesterol, plasma fibrinogen, energy intake for saturated fats, energy expenditure of leisure time physical activity, and white blood cell count, the results remained significant. The risk ratios among men with metabolic syndrome as defined by the WHO criteria were 1.82 (95% CI, 1.01 to 3.26; P=0.046) for all strokes and 2.16 (95% CI, 1.11 to 4.19; P=0.022) for ischemic stroke. After further adjustment, the respective risks were 2.08 (95% CI, 1.12 to 3.87; P=0.020) and 2.47 (95% CI, 1.21 to 5.07; P=0.013).

CONCLUSIONS

The risk of any stroke is increased in men with metabolic syndrome, in the absence of stroke, diabetes and cardiovascular disease at baseline. Prevention of the metabolic syndrome presents a great challenge for clinicians with respect to stroke.

Place of drug therapy in the treatment of carotid stenosis

Carotid stenosis is an important cause of transient ischaemic attacks and stroke. The cause of carotid stenosis is most often atherosclerosis; contributing to the pathogenesis of the lesion are endothelial injury, inflammation, lipid deposition, plaque formation, fibrin, platelets and thrombin. Carotid stenosis accounts for 10-20% of cases of brain infarction, depending on the population studied. Despite successful treatment of selected patients who have had an acute ischaemic stroke with tissue plasminogen activator and the promise of other experimental therapies, prevention remains the best approach to reducing the impact of ischaemic stroke. High-risk or stroke-prone patients can be identified and targeted for specific interventions. At this juncture, treatment of carotid stenosis is a well established therapeutic target and a pillar of stroke prevention. There are two main strategies for the treatment of carotid stenosis. The first approach is to stabilise or halt the progression of the carotid plaque through risk factor modification and medication. Hypertension, diabetes mellitus, smoking, obesity and high cholesterol levels are closely associated with carotid stenosis and stroke; control of these factors may decrease the risk of plaque formation and progression. The second approach is to eliminate or reduce carotid stenosis through carotid endarterectomy or carotid angioplasty and stenting. Carotid endarterectomy, which is the mainstay of therapy for severe carotid stenosis, is beyond the scope of this review. Anticoagulants seem to play little role (if any) in the medical (i.e. non-surgical) treatment of carotid stenosis. Adoption of a healthy lifestyle combined with the reduction of risk factors has been shown to lead to a reduction in the extent of carotid stenosis. The medical treatment of carotid stenosis should be based on the triad of the reduction of risk factors, patient education, and use of antiplatelet agents.