Inflammation in the vascular bed: importance of vitamin C

Expression of Elastin, F-Box and WD-40 Domain-Containing Protein 2, Fibrillin-1, and Alpha-Smooth Muscle Actin in Utilized Blood Vessels for explant culture-A New 3D in Vitro Vascular Model from Bovine Legs

Elastic fibers of the internal and external elastic laminae maintain blood vessel shapes. Impairment of smooth muscle cell function leads to vascular disease development. F-box and WD-40 domain-containing protein 2 (FBXW2) is associated with elastic fibers and osteocalcin expression for bone regeneration in the periosteum. Here, it is hypothesized that FBXW2 has different roles in periosteum and blood vessels. Furthermore, if FBXW2 would be a component of elastic fiber of blood vessels, FBXW2 would be expressed where the well-known components elastin and fibrillin-1 are expressed. For this purpose, explant culture of blood vessels from bovine legs were performed for 5 weeks. It was found that elastin and FBXW2 were expressed within the elastic laminae, whereas fibrillin-1 was expressed around them. After explant culture, elastin and FBXW2 sustained the shape of the elastic fibers in the elastic lamina, whereas the fibrillin-1-rich layer became wide range and encompass toward intima and adventitia layers. Hematoxylin Eosin staining and immunohistochemistry of alpha-smooth muscle actin (α-SMA) revealed weakened media layer after 5 weeks culture. Although fibrillin-1 is a well-known component of elastic fibers and elastin, this study revealed that the location of fibrillin-1 is different from that of elastin, whereas FBXW2 is present in the same region as elastin from day 0 to week 5. In blood vessels, fibrillin-1 fibers around the elastic lamina may be oxytalan fibers. Thus, the proposed 3D in vitro model in this study is useful for identifying the mechanisms of vascular degradation.

Viral interactions with host factors (TIM-1, TAM -receptors, Glut-1) are related to the disruption of glucose and ascorbate transport and homeostasis, causing the haemorrhagic manifestations of viral haemorrhagic fevers

The haemorrhagic features of viral haemorrhagic fevers may be caused by common patterns of metabolic disturbances of the glucose and ascorbate homeostasis. Haemorrhages and vasculature disfunctions are a clinical feature not only of viral haemorrhagic fevers, but also in scurvy, diabetes and thrombotic microangiopathic haemolytic anaemia. Interestingly, the expression of glucose and ascorbate transporter Glut-1 on the erythrocyte membrane is associated with the inability to synthesize ascorbate and is restricted to that very species that are susceptible to filoviruses (primates, humans and fruit bats). Glut-1 may play a pivotal role in haemorrhagic fever pathogenesis. TIM-1 and TAM receptors have been recognized to enhance entry of Ebola, Lassa and Dengue viruses and viral interferences with TIM-1 could disturb its function, disturbing the expression of Glut-1. In those species not able to synthesize ascorbate and expressing Glut-1 on erythrocytes virus could interact with Glut-1 or other functionally related protein, and the influx of glucose into the cells would be severely impaired. As a consequence, transient hyperglycemia and a marked oxidative stress coupled with the high levels of glucose in plasma would be established, and then promote the activation of NF-κB transcription, exacerbating a pro-inflammatory response mediated by cytokines and chemokines: The inability to synthesize ascorbate is an Achilles Heel when trying to counteract the oxidative stress.

In Vitro Models of Cardiovascular Calcification

Cardiovascular calcification, characterized by hydroxyapatite deposition in the arterial wall and heart valves, is associated with high cardiovascular morbidity and mortality. Cardiovascular calcification is a hallmark of aging but is frequently seen in association with chronic diseases, such as chronic kidney disease (CKD), diabetes, dyslipidemia, and hypertension in the younger population as well. Currently, there is no therapeutic approach to prevent or cure cardiovascular calcification. The pathophysiology of cardiovascular calcification is highly complex and involves osteogenic differentiation of various cell types of the cardiovascular system, such as vascular smooth muscle cells and valve interstitial cells. In vitro cellular and ex vivo tissue culture models are simple and useful tools in cardiovascular calcification research. These models contributed largely to the discoveries of the numerous calcification inducers, inhibitors, and molecular mechanisms. In this review, we provide an overview of the in vitro cell culture and the ex vivo tissue culture models applied in the research of cardiovascular calcification.

Is vitamin C a booster of the effects of dietary nitrate on endothelial function? Physiologic rationale and implications for research

Endothelial dysfunction (ED) is an early marker of vascular damage linked to the loss of integrity of the endothelial lining and represents a key step in the pathogenesis of atherosclerosis and cardiovascular diseases (CVDs). ED may be reversible, hence the development and testing of effective early interventions could be beneficial for the prevention and treatment of CVDs. Recent studies have demonstrated that the consumption of dietary nitrate (NO₃^-), an inorganic anion that serves as a substrate for the gas transmitter nitric oxide (NO), can lower blood pressure, improve endothelial function and, in observational studies, reduce the risk for CVD. We hypothesize that the co-consumption of NO₃^- with vitamin C, which is a potent antioxidant, could enhance the "yield" of NO produced from a given NO₃^- dose byThis could translate into greater NO-dependent effects on endothelial function (EF) and overall vascular health (than may be experienced with NO₃^- supplementation alone). This review presents evidence to suggest that the combination of vitamin C and dietary nitrate could represent a promising and effective approach to improve EF and reduce CVD risk, and discuss opportunities for future research.

Vitamin C modulates adrenaline-augmented gastric injury via cardiac troponin/creatine kinase pathway in Wistar rats

Objectives

Vitamin C has anti-oxidant benefits in the gastrointestinal tract and heart. This study investigated the effect of vitamin C on some gastric parameters in myocardial injury in rats.

Materials and Methods

Thirty Wistar rats were divided into five groups (n = 6). Group 1 was the control and Group 2 (ADR) received 1 mg/kg of adrenaline subcutaneously on days 13 and 14. Group 3 received vitamin C (200 mg/kg) orally for 14 days. Group 4 received adrenaline (1 mg/kg) on days 1 and 2 and vitamin C from days 1 to 14. Group 5 received vitamin C till day 14 and adrenaline on days 13 and 14. All animals were sacrificed after 2 hr of pyloric ligation. Gastric secretion parameters were assessed while a blood sample was obtained for biochemical analysis.

Results

Gastric juice volume, total gastric acidity, pepsin activity, cardiac troponin 1, creatine kinase-MB, and lactate dehydrogenase levels increased (P<0.05) in ADR only group relative to the control. Pre- and post-vitamin C treatment reduced (P<0.05) these markers to near normal. However, treatment with vitamin C reduced (P<0.05) ulcer score, and increased (P<0.05) pepsin activity, mucus weight, and serum vitamin C levels when compared with the ADR-only group. Pre-treatment with vitamin C resulted in a marked decrease (P<0.05) in gastric juice volume, pepsin activity, and total gastric acidity compared with post-treatment in the adrenaline-induced injury group.

Conclusion

Vitamin C pretreatment reduces excessive gastric secretions, ulcer scores, and attenuates cardio-inflammatory responses in adrenaline-augmented myocardial injury in rats.

Oxidative stress in the pathophysiology of type 2 diabetes and related complications: Current therapeutics strategies and future perspectives

Type 2 diabetes (T2DM) is a persistent metabolic disorder rising rapidly worldwide. It is characterized by pancreatic insulin resistance and β-cell dysfunction. Hyperglycemia induced reactive oxygen species (ROS) production and oxidative stress are correlated with the pathogenesis and progression of this metabolic disease. To counteract the harmful effects of ROS, endogenous antioxidants of the body or exogenous antioxidants neutralise it and maintain bodily homeostasis. Under hyperglycemic conditions, the imbalance between the cellular antioxidant system and ROS production results in oxidative stress, which subsequently results in the development of diabetes. These ROS are produced in the endoplasmic reticulum, phagocytic cells and peroxisomes, with the mitochondrial electron transport chain (ETC) playing a pivotal role. The exacerbated ROS production can directly cause structural and functional modifications in proteins, lipids and nucleic acids. It also modulates several intracellular signaling pathways that lead to insulin resistance and impairment of β-cell function. In addition, the hyperglycemia-induced ROS production contributes to micro- and macro-vascular diabetic complications. Various in-vivo and in-vitro studies have demonstrated the anti-oxidative effects of natural products and their derived bioactive compounds. However, there is conflicting clinical evidence on the beneficial effects of these antioxidant therapies in diabetes prevention. This review article focused on the multifaceted role of oxidative stress caused by ROS overproduction in diabetes and related complications and possible antioxidative therapeutic strategies targeting ROS in this disease.

A First-in-Man Clinical Evaluation of Sirolimus and Ascorbic Acid-Eluting Stent Systems: a Multicenter, Subject-Blinded, Randomized Study

This prospective, multi-center, randomized, comparative, and pivotal clinical study in patients with coronary artery occlusive disease was conducted to evaluate the safety and efficacy of D+Storm™ drug-eluting stent (DES), a sirolimus-eluting stent coated with polylactic acid and ascorbic acid. Our results showed that in-segment late lumen loss of D+Storm™ DES group was non-inferior to BioMatrix Flex™ DES group and the total procedural success rate of D+Storm™ DES group was 100%. In addition, the safety of the D+Storm™ DES group at 36 weeks was also demonstrated in this study.

Background and Objectives

This clinical trial was conducted to evaluate the safety and efficacy of D+Storm™ drug-eluting stent (DES) and BioMatrix Flex™ DES.

Methods

This study was a multicenter, subject-single-blind, randomized, and confirmed comparative clinical trial. According to the inclusion criteria, those diagnosed with stable angina, unstable angina, silent ischemia, or non-ST-segment myocardial infarction were selected among patients with coronary artery stenosis as subjects. Among the subjects with 50% stenosis on coronary angiography, the experiment was performed on those who had a lesion with reference vessel 2.5–4.0 mm in diameter and ≤40 mm in length. The primary endpoint was an in-segment late loss and the secondary endpoints were in-stent late lumen loss, stent malapposition, the incidence of mortality, myocardial infarction, reoperation, and stent thrombosis at 36 weeks.

Results

57 patients in the D+Storm™ DES group and 55 patients in the BioMatrix Flex™ DES group were enrolled in the study. Fifty-seven patients in the D+Storm™ DES group and Fifty-five patients in the BioMatrix Flex™ DES group were enrolled in the study. An average of in-segment late lumen loss was 0.08±0.13 mm in the D+Storm™ DES group and 0.14±0.32 mm in the BioMatrix Flex™ DES group with no significant difference between the 2 groups (p=0.879). In addition, there was no significant difference in adverse events between D+Storm™ DES and BioMatrix Flex™ DES.

Conclusions

This study demonstrated the clinical effectiveness and safety of D+Storm™ DES implantation in patients with coronary artery disease over a 36-week follow-up period.

Coating small-diameter ePTFE vascular grafts with tunable poly(diol-co-citrate-co-ascorbate) elastomers to reduce neointimal hyperplasia

Lack of long-term patency has hindered the clinical use of small-diameter prosthetic vascular grafts with the majority of these failures due to the development of neointimal hyperplasia. Previous studies by our laboratory revealed that small-diameter expanded polytetrafluoroethylene (ePTFE) grafts coated with antioxidant elastomers are a promising localized therapy to inhibit neointimal hyperplasia. This work is focused on the development of poly(diol-co-citrate-co-ascorbate) (POCA) elastomers with tunable properties for coating ePTFE vascular grafts. A bioactive POCA elastomer (@20 : 20 : 8, [citrate] : [diol] : [ascorbate]) coating was applied on a 1.5 mm diameter ePTFE vascular graft as the most promising therapeutic candidate for reducing neointimal hyperplasia. Surface ascorbate density on the POCA elastomer was increased to 67.5 ± 7.3 ng mg-1 cm-2. The mechanical, antioxidant, biodegradable, and biocompatible properties of POCA demonstrated desirable performance for in vivo use, inhibiting human aortic smooth muscle cell proliferation, while supporting human aortic endothelial cells. POCA elastomer coating number was adjusted by a modified spin-coating method to prepare small-diameter ePTFE vascular grafts similar to natural vessels. A significant reduction in neointimal hyperplasia was observed after implanting POCA-coated ePTFE vascular grafts in a guinea pig aortic interposition bypass graft model. POCA elastomer thus offers a new avenue that shows promise for use in vascular engineering to improve long-term patency rates by coating small-diameter ePTFE vascular grafts.

Effect of Dietary or Supplemental Vitamin C Intake on Vitamin C Levels in Patients with and without Cardiovascular Disease: A Systematic Review

Atherosclerosis is a pro-oxidative and pro-inflammatory disease state, which is the underlying cause of most cardiovascular events, estimated to affect 5.2% of the Australian population. Diet, and specifically vitamin C, through its antioxidant properties can play a role in impeding the development and progression of atherosclerosis. This systematic review conducted comprehensive searches in Medline, Emcare, Scopus, PubMed, and Cochrane using key search terms for vitamin C, plasma vitamin C, supplementation, and cardiovascular disease (CVD). The results demonstrated that vitamin C supplementation resulted in a significant increase in vitamin C levels in populations with or without CVD, except for one study on the CVD population. It was also seen that the healthy population baseline and post-intervention vitamin C levels were high compared to the CVD population. However, further research is indicated for CVD population groups with varying baseline vitamin C levels, such as low baseline vitamin C, within a more representative elderly cohort in order to formulate and update vitamin C repletion guidelines.

Mesotherapy using Vitamin C as an anti-inflammatory agent in persistent gingival inflammation: A case series

Background:

Mesotherapy is a minimally invasive procedure which involves local intradermal therapy (LIT) with biologically active substances given in minor quantities to the area of pathology. Vitamin C is an important antioxidant agent which can modulate the attenuation of inflammatory process and enhance tissue repair.

Aim:

The aim of this study was to investigate the efficacy of local injections of Vitamin C for treating persisting inflammation of the gingiva.

Materials and Methods:

After phase I therapy was completed, five patients with persisting chronic inflammation of the gingiva were injected with the same dosages of Vitamin C into the gingival tissues. Patients were evaluated each week for resolution of gingival inflammation.

Results:

Clinical observation showed a significant improvement in inflammation of the injected sites during recall appointments.

Conclusions:

LIT with Vitamin C has a synergistic interaction along with scaling and root planing in the treatment of persistent gingival inflammation.

Development of Poly(1,8-octanediol-co-citrate-co-ascorbate) Elastomers with Enhanced Ascorbate Performance for Use as a Graft Coating to Prevent Neointimal Hyperplasia

Small-diameter expanded polytetrafluoroethylene (ePTFE) graft surfaces have poor long-term patency due to limited endothelial cell (EC) coverage and anastomotic intimal hyperplasia. Multifunctional elastomers that coat the ePTFE graft surface to promote EC adhesion while simultaneously inhibiting intimal hyperplasia are highly desirable. Poly(diol-co-citrate) (PDC), a thermoset elastomer, is biodegradable, biocompatible, and mimics vascular mechanical properties. Engineering antioxidant components into PDC polymeric structures improves biocompatibility by attenuating oxidative stress yet is limited by bioavailability. Herein, we develop a new ascorbate protection and deprotection strategy (APDS) for loading bioactive ascorbic acid into the structure of PDC elastomers to improve poly(1,8-octanediol-co-citrate-co-ascorbate) (POCA) prepolymer ascorbate activity. Elastomers cured from APDS POCA prepolymers provide twice the active ascorbate sites on the elastomer surface (35.19 ± 1.64 ng mg-1 cm-2) versus unprotected POCA (Un.POCA, 18.31 ± 0.97 ng mg-1 cm-2). APDS POCA elastomers displayed suitable mechanical properties for vascular graft coating [Young's modulus (2.15-2.61 MPa), elongation (189.5-214.6%) and ultimate tensile strength (2.73-3.61 MPa)], and superior surface antioxidant performance through 1,1-diphenyl-2-picrylhydrazyl free radical scavenging and lipid peroxidation inhibition as compared to poly(1,8-octanediol-co-citrate) (POC) and Un.POCA. Hydrolytic degradation of APDS POCA occurred within 12 weeks under physiological conditions with a mass loss of 25.8 ± 3.4% and the degradation product retaining ascorbate activity. APDS POCA elastomer surfaces supported human aortic endothelial cell proliferation while inhibiting human aortic smooth muscle cell proliferation in vitro. APDS POCA elastomer surfaces displayed superior decomposition of S-nitrosothiols compared to POC and Un.POCA. Taken together, these findings indicate the potential of APDS POCA elastomers to serve as bioactive, therapeutic coatings that enhance the long-term patency of small diameter ePTFE grafts.

Ascorbic acid inhibits vascular remodeling induced by mental stress in overweight/obese men

BACKGROUND

Mental stress (MS) is related to endothelial dysfunction in overweight/obese men. It is believed that the pro-oxidant profile, associated with an imbalance in the vascular remodeling process, may contribute to deleterious effects of MS on endothelial function. However, it is unknown whether administration of ascorbic acid (AA), a potent antioxidant, can prevent oxidative and remodeling dysfunction during MS in these subjects.

METHODS

Fourteen overweight/obese grade I men (27 ± 7 years; 29.7 ± 2.6 kg·m^-2) underwent the Stroop Color Word Test for 5 min to induce MS after AA (3 g) or placebo (PL, 0.9% NaCl) intravenous infusions. Venous blood samples were collected at baseline and the last minute of MS to measure nitrite concentration (chemiluminescence), protein carbonylation, thiobarbituric acid reactive substances (TBARS) and catalase activity (colorimetric assays), superoxide dismutase (SOD; immunoenzymatic assay), activities of active/inactive (pro) forms of metalloproteinases-9 and -2 (MMP; zymography) and its respective tissue inhibitors concentration (TIMP-1 and TIMP-2; immunoenzymatic assays).

RESULTS

At baseline, MMP-9 activity (p < 0.01), the MMP-9/proMMP-9 ratio (p = 0.02) and TIMP-1 concentration (p = 0.05) were reduced, whereas proMPP-9 activity was increased (p = 0.02) after AA compared to PL infusion. After PL infusion, MS increased protein carbonylation (p < 0.01), catalase (p < 0.01), and the MMP-9/proMMP-9 ratio (p = 0.04) when compared to baseline. AA infusion reduced protein carbonylation (p = 0.02), MMP-9 activity (p < 0.01), and MMP-9/pro-MMP-9 ratio (p < 0.01), while SOD (p = 0.04 vs baseline), proMPP-9 (p < 0.01 vs PL), MMP-2 (p < 0.01 vs PL) and TIMP-2 (p = 0.02 vs baseline) remained elevated during MS.

CONCLUSIONS

AA appears to minimize the oxidative imbalance and vascular remodeling induced by MS.

Effects of inorganic nitrate and vitamin C co-supplementation on blood pressure and vascular function in younger and older healthy adults: A randomised double-blind crossover trial

BACKGROUND

Vitamin C and inorganic nitrate have been linked to enhanced nitric oxide (NO) production and reduced oxidative stress. Vitamin C may also enhance the conversion of nitrite into NO.

AIMS

We investigated the potential acute effects of vitamin C and inorganic nitrate co-supplementation on blood pressure (BP) and peripheral vascular function. The secondary aim was to investigate whether age modified the effects of vitamin C and inorganic nitrate on these vascular outcomes.

METHODS

Ten younger (age 18-40 y) and ten older (age 55-70 y) healthy participants were enrolled in a randomised double-blind crossover clinical trial. Participants ingested a solution of potassium nitrate (7 mg/kg body weight) and/or vitamin C (20 mg/kg body weight) or their placebos. Acute changes in resting BP and vascular function (post-occlusion reactive hyperemia [PORH], peripheral pulse wave velocity [PWV]) were monitored over a 3-h period.

RESULTS

Vitamin C supplementation reduced PWV significantly (vitamin C: -0.70 ± 0.31 m/s; vitamin C placebo: +0.43 ± 0.30 m/s; P = 0.007). There were significant interactions between age and vitamin C for systolic, diastolic, and mean arterial BP (P = 0.02, P = 0.03, P = 0.02, respectively), with systolic, diastolic and mean BP decreasing in older participants and diastolic BP increasing in younger participants following vitamin C administration. Nitrate supplementation did not influence BP (systolic: P = 0.81; diastolic: P = 0.24; mean BP: P = 0.87) or vascular function (PORH: P = 0.05; PWV: P = 0.44) significantly in both younger and older participants. However, combined supplementation with nitrate and vitamin C reduced mean arterial BP (-2.6 mmHg, P = 0.03) and decreased PWV in older participants (PWV: -2.0 m/s, P = 0.02).

CONCLUSIONS

The co-administration of a single dose of inorganic nitrate and vitamin C lowered diastolic BP and improved PVW in older participants. Vitamin C supplementation improved PWV in both age groups but decreased systolic and mean BP in older participants only.

CLINICAL TRIAL REGISTRATION

Current Controlled Trials (ISRCTN98942199).

Atopic Dermatitis in Older Adults: A Review of Treatment Options

Atopic dermatitis (AD) in older adults (elderly AD) has recently emerged as a newly defined subgroup of AD. When selecting treatment options, clinical characteristics of elderly AD and age-specific factors of older patients must be considered. As in other age groups, regular application of moisturizers in combination with topical corticosteroids and calcineurin inhibitors, adjunctive administration of oral antihistamines/anti-allergic drugs, and avoidance of exacerbating factors comprise basic treatments for elderly AD. For moderate-to-severe cases and/or in those with a decreased ability to use topical treatments, powerful anti-inflammatory treatments may become necessary as additional treatment options. While low-dose oral corticosteroids may be useful for cases of elderly AD, careful attention should be paid to adverse effects. Oral cyclosporine (ciclosporin) is less commonly used due to the increased risk of malignancy and organ toxicity in older patients with AD. Narrow-band ultraviolet B phototherapy may also be useful for older patients, although the necessity of frequent hospital visits for irradiation therapy may become a burden of disease for such patients. As a biologic, dupilumab therapy markedly improves skin lesions and itch in older patients with AD, with a rapid response and non-serious adverse effects. Nevertheless, injection pain, expensive medical care, and regular follow-up every 2 weeks are disadvantages of dupilumab therapy. Therefore, clinicians must prioritize individualized treatment options that will reduce the burden of disease for cases of elderly AD.

Resveratrol potentiates intracellular ascorbic acid enrichment through dehydroascorbic acid transport and/or its intracellular reduction in HaCaT cells

L-Ascorbic acid (AsA), a reduced vitamin C (VC), is an important antioxidant, and the internal accumulation and maintenance of AsA are thought to play a significant role in various physiological activities in humans. We focused on resveratrol (RSV), a natural polyphenolic compound, as a candidate for an AsA transport modulator and investigated whether RSV can affect the intracellular VC accumulation after either AsA or dehydroascorbic acid (DHA) addition in HaCaT keratinocytes. Our results demonstrate that RSV treatment could significantly enhance intracellular VC levels after either AsA or DHA supplementation, and intracellular VC accumulated mainly as AsA. Our results also indicate that most of the intracellular transported DHA was reduced to AsA and accumulated after uptake into cells. In addition, RSV could induce several AsA or DHA transport-related and intracellular DHA reduction-related genes including SVCT2, GLUT3, TXNRD2, and TXNRD3, necessary for AsA transport, DHA transport, and DHA reduction/regeneration, respectively. On the other hand, the both protein expression levels and the localizations of sodium-dependent vitamin C transporters 2 (SVCT2) and glucose transporter 3(GLUT3) were scarcely affected by RSV treatment. Furthermore, RSV-induced enrichment of intracellular AsA levels was completely suppressed by a GLUT inhibitor cytochalasin B. These results suggest that RSV can potentiate intracellular AsA accumulation via activation of the DHA transport and subsequent intracellular reduction from DHA to AsA. Thus, RSV might be useful for maintaining substantial AsA accumulation in the skin keratinocytes.

Therapeutic Options Targeting Oxidative Stress, Mitochondrial Dysfunction and Inflammation to Hinder the Progression of Vascular Complications of Diabetes

Type 2 diabetes mellitus is a leading cause of morbidity and mortality worldwide, given its serious associated complications. Despite constant efforts and intensive research, an effective, ubiquitous treatment still eludes the scientific community. As such, the identification of novel avenues of research is key to the potential discovery of this evasive "silver bullet." We focus on this review on the matter of diabetic injury to endothelial tissue and some of the pivotal underlying mechanisms, including hyperglycemia and hyperlipidemia evoked oxidative stress and inflammation. In this sense, we revisited the most promising therapeutic interventions (both non-pharmacological and antidiabetic drugs) targeting oxidative stress and inflammation to hinder progression of vascular complications of diabetes. This review article gives particular attention to the relevance of mitochondrial function, an often ignored and understudied organelle in the vascular endothelium. We highlight the importance of mitochondrial function and number homeostasis in diabetic conditions and discuss the work conducted to address the aforementioned issue by the use of various therapeutic strategies. We explore here the functional, biochemical and bioenergetic alterations provoked by hyperglycemia in the endothelium, from elevated oxidative stress to inflammation and cell death, as well as loss of tissue function. Furthermore, we synthetize the literature regarding the current and promising approaches into dealing with these alterations. We discuss how known agents and therapeutic behaviors (as, for example, metformin, dietary restriction or antioxidants) can restore normality to mitochondrial and endothelial function, preserving the tissue's function and averting the aforementioned complications.

Limited evidence for a beneficial effect of vitamin C supplementation on biomarkers of cardiovascular diseases: an umbrella review of systematic reviews and meta-analyses

Vitamin C is an essential nutrient with important antioxidant properties. Higher vitamin C intake appears to be associated with positive effects on cardiovascular risk factors in cohort studies, whereas large randomized controlled clinical trials did not confirm the benefits of supplemental vitamin C on cardiovascular disease (CVD) outcomes. In this overview of systematic reviews and meta-analyses, an "umbrella review," we investigated the effects of vitamin C supplementation on biomarkers of cardiovascular risk, that is, arterial stiffness, blood pressure, endothelial function, glycemic control, and lipid profile. In addition, we assessed the strength of the evidence and the methodological qualities of available studies. Two independent investigators searched 4 databases (Medline, Embase, Scopus, and The Cochrane Library databases) from inception until February 2018. After full text examination, 10 systematic reviews and meta-analyses were included in the umbrella review which included 6409 participants. Three systematic reviews investigated the effects of vitamin C on endothelial function with contrasting results (2 reviews reported a significant effect, and all 3 showed a high heterogeneity [I2> 50%]); 1 systematic review reported significant improvement for each of the following risk factors: blood pressure, and blood concentrations of glucose, low-density lipoprotein cholesterol, and triglycerides. There were no overall effects of vitamin C on arterial stiffness and blood concentration of insulin, total cholesterol, and high-density lipoprotein cholesterol, but subgroup analyses revealed some evidence for significant improvements in subpopulations with higher body mass index, higher plasma concentrations of glucose or cholesterol, and low plasma concentration of vitamin C. Results from this umbrella review emphasize the weakness of the current evidence base about effects of vitamin C supplementation on markers of CVD risk. There is limited evidence that some population subgroups (older people, the obese, those with lower vitamin C status at baseline, and those at higher CVD risk) may be more responsive to vitamin C supplementation and offer opportunities for tailored nutritional interventions to improve cardiometabolic health. Future studies should implement a selective recruitment strategy that is informed by evidence-based literature synthesis.

Antioxidant and antimicrobial potential of selected varieties of Piper betle L. (Betel leaf)

Piper betle L., is an evergreen perennial creeper belonging to family Piperaceae and is known to possess numerous medicinal properties. Current study focuses on evaluating antioxidant and antimicrobial potential of betel leaf. For the present study, distilled water, hexane, acetone and ethanolic extracts of two varieties of betel leaves: Meetha paan and Banarasi paan were used. Biochemical tests such as proximate analysis (moisture, ash, protein, lipids, minerals viz., sodium and potassium), antioxidant activity tests (DPPH radical scavenging activity, total phenolics, ascorbic acid, reducing power) and antimicrobial test (antibacterial and antifungal susceptibility test) against four pathogens viz., B. subtilis, E. coli, A. niger and S. cerevisiae were determined. Ethanolic extract had the highest antioxidant activity (89.46% inhibition), while the aqueous extract exhibited lowest antioxidant activity (62.03% inhibition). With increasing concentration (5, 10, 25 and 50 µg/mL), the reducing power of leaf extracts also increased. The ascorbic acid was not significant in Banarasi paan (5.21mg/100 g) and Meetha paan (5.20mg/100 g). The highest antibacterial activity of ethanolic extract (Banarasi paan) may be attributed to the presence of phytosterols in the leaf varieties. Antioxidant and antimicrobial potential study will help to build a database and promote the utilization of betel leaf as a medicinal herb.

U-Shaped Association Between Serum Uric Acid Levels With Cardiovascular and All-Cause Mortality in the Elderly: The Role of Malnourishment

BACKGROUND

The link between elevated serum uric acid (SUA) levels and cardiovascular disease (CVD)-related mortality in the elderly population remains inconclusive. Nutritional status influences both SUA and CVD outcomes. Therefore, we investigated whether SUA-predicted mortality and the effect-modifying roles of malnourishment in older people.

METHODS AND RESULTS

A longitudinal Taiwanese cohort including 127 771 adults 65 years and older participating in the Taipei City Elderly Health Examination Program from 2001 to 2010 were stratified by 1-mg/dL increment of SUA. Low SUA (<4 mg/dL) strata was categorized by malnourishment status defined as Geriatric Nutritional Risk Index <98, serum albumin <38 g/L, or body mass index <22 kg/m2. Study outcomes were all-cause and CVD-related mortality. Cox models were used to estimate hazard ratios (HRs) of mortality, after adjusting for 20 demographic and comorbid covariates. Over a median follow-up of 5.8 years, there were 16 439 all-cause and 3877 CVD-related deaths. Compared with the reference SUA strata of 4 to <5 mg/dL, all-cause mortality was significantly higher at SUA <4 mg/dL (HR, 1.16; 95% confidence interval, 1.07-1.25) and ≥8 mg/dL (HR, 1.13; confidence interval, 1.06-1.21), with progressively elevated risks at both extremes. Similarly, increasingly higher CVD-related mortality was found at the SUA level <4 mg/dL (HR, 1.19; confidence interval, 1.00-1.40) and ≥7 mg/dL (HR, 1.17; confidence interval, 1.04-1.32). Remarkably, among the low SUA (<4 mg/dL) strata, only malnourished participants had greater all-cause and CVD-related mortality. This modifying effect of malnourishment remained consistent across subgroups.

CONCLUSIONS

SUA ≥8 or <4 mg/dL independently predicts higher all-cause and CVD-related mortality in the elderly, particularly in those with malnourishment.

Evaluation of the Anti-Inflammatory Effect of Locally Delivered Vitamin C in the Treatment of Persistent Gingival Inflammation: Clinical and Histopathological Study

Objective. The purpose of this study is to investigate the role and efficiency of the locally injected vitamin C in the treatment of persistent gingival inflammation. Design. Twenty adult patients with persistent chronic gingival inflammation were included in this study. The same dose of sterile vitamin C was injected in gingival tissues after the completion of phase I therapy. Gingival biopsies were taken after total resolution of inflammation. The specimens were examined histologically, using H&E stain. Results. Clinical evaluation revealed great improvement of the injected sites with recall visits. Histopathological results revealed marked decrease in inflammatory cells and epithelial thickness and a higher number of newly formed subbasal capillaries. Conclusions. Vitamin C is an effective adjunctive treatment in reducing various degrees of chronic gingival inflammation.

Effects of vitamin C treatment on collar-induced intimal thickening

Vitamin C has efficient antioxidant properties and is involved in important physiological processes such as collagen synthesis. As such, vitamin C deficiency leads to serious complications, including vascular diseases. The aim of this study was to investigate the effects of vitamin C treatment on collar-induced intimal thickening. Rabbits were fed a normocholesterolemic diet and a non-occlusive silicon collar was placed around the left carotid artery for 3, 7, and 14 days. The rabbits were treated with or without vitamin C (150 mg/kg/day). Collar-induced intimal thickening became apparent at day 7. The effect of the collar on intimal thickening was more prominent at day 14. Vitamin C treatment significantly inhibited collar-induced intimal thickening at day 14. The placement of the collar around the carotid artery decreased maximum contractile responses against contractile agents (KCl, phenylephrine, 5-hydroxytryptamine). The effect of the collar on contractile responses was enhanced as days elapsed. Decreased contractile responses of collared carotid arteries normalized at day 14 in the vitamin C treatment group. Vitamin C treatment also restored sensitivity to phenylephrine. The collar also significantly decreased acetylcholine-induced relaxations at day 3 and day 7. Acetylcholine-induced relaxations normalized in collared-arteries in the placebo group at day 14. Vitamin C treatment significantly increased acetylcholine-induced relaxations of both normal and collared carotid arteries at day 14. MMP-9 expression increased in collared arteries at day 3 and day 7 but did not change at day 14. MMP-2 expression increased in collared arteries at day 14. However, vitamin C treatment reduced collar-stimulated expression of MMP-2 at day 14. These findings indicate that vitamin C may have potentially beneficial effects on the early stages of atherosclerosis. Furthermore these results, for the first time, may indicate that vitamin C can also normalize decreased contractile response through perivascular collar placement.

Effect of vitamin C on endothelial function of children with chronic renal failure: An experimental study

Background:

It is well established that improvement of endothelial dysfunction (ED) could prevent or delay the occurrence of cardiovascular disease (CVD) and its related morbidity and mortality in patients with chronic kidney disease (CKD). In this study we investigated whether administration of vitamin C could be effective by improving brachial artery flow-mediated dilation (FMD) and intima media thickness (IMT), two surrogate markers of ED, in children with CKD or chronic renal failure (CRF).

Materials and Methods:

In this analytic-experimental study children aged 3-18 years with a diagnosis of CRF and a group of healthy children were enrolled. Vitamin C (250 mg/day) administrated for the two studied groups for 1 month. Endothelial function was evaluated by FMD and IMT measurement using vascular Doppler ultrasonography, before and after trial.

Results:

In this study 18 patients with CRF and 19 normal children as the control group were studied. At baseline mean of IMT and FMD was not different in the two studied groups (P > 0.05). After vitamin C administration IMT decreased significantly in the two studied groups (P < 0.05). FMD increased in the two studied groups but the difference was significant in the control group (P < 0.05).

Conclusion:

The findings of this interventional trial have demonstrated that vitamin C could have protective effect on ED of patients with CRF possibly in those with severe form of the disease but for obtaining more conclusive results larger sample size is needed.

The active role of vitamin C in mammalian iron metabolism: much more than just enhanced iron absorption!

Ascorbate is a cofactor in numerous metabolic reactions. Humans cannot synthesize ascorbate owing to inactivation of the gene encoding the enzyme l-gulono-γ-lactone oxidase, which is essential for ascorbate synthesis. Accumulating evidence strongly suggests that in addition to the known ability of dietary ascorbate to enhance nonheme iron absorption in the gut, ascorbate within mammalian systems can regulate cellular iron uptake and metabolism. Ascorbate modulates iron metabolism by stimulating ferritin synthesis, inhibiting lysosomal ferritin degradation, and decreasing cellular iron efflux. Furthermore, ascorbate cycling across the plasma membrane is responsible for ascorbate-stimulated iron uptake from low-molecular-weight iron-citrate complexes, which are prominent in the plasma of individuals with iron-overload disorders. Importantly, this iron-uptake pathway is of particular relevance to astrocyte brain iron metabolism and tissue iron loading in disorders such as hereditary hemochromatosis and β-thalassemia. Recent evidence also indicates that ascorbate is a novel modulator of the classical transferrin-iron uptake pathway, which provides almost all iron for cellular demands and erythropoiesis under physiological conditions. Ascorbate acts to stimulate transferrin-dependent iron uptake by an intracellular reductive mechanism, strongly suggesting that it may act to stimulate iron mobilization from the endosome. The ability of ascorbate to regulate transferrin iron uptake could help explain the metabolic defect that contributes to ascorbate-deficiency-induced anemia.

Vitamin-C delivery from CoCr alloy surfaces using polymer-free and polymer-based platforms for cardiovascular stent applications

Antiproliferative drugs such as paclitaxel and sirolimus are delivered from stents to inhibit the growth of smooth muscle cells (SMCs) for preventing neointimal hyperplasia. However, these drugs delay the growth of endothelial cells (ECs) as well and cause late stent thrombosis. We recently demonstrated the use of Vitamin-C (l-ascorbic acid, l-AA) over paclitaxel and sirolimus for inhibiting SMCs growth and promoting EC growth simultaneously. In this study, we have investigated the delivery of l-AA from CoCr alloy surfaces for potential use in stents. A polymer-free phosphoric acid (PA) platform and a polymer-based poly(lactic-co-glycolic acid) (PLGA) platform were used for coating l-AA onto CoCr surfaces. For the PA platform, FTIR confirmed that the PA was coated on CoCr, while the AFM showed that the PA coating on the CoCr surface was homogeneous. The successful deposition of l-AA on PA-coated CoCr was also confirmed by FTIR. The uniform distribution of l-AA crystals on PA-coated CoCr was shown by SEM, optical profilometer, and AFM. The drug release studies showed that l-AA (276 μg/cm(2)) was burst released from the PA platform by 1 h. For the PLGA platform, SEM showed that the l-AA incorporated polymer films were smoothly and uniformly coated on CoCr. FTIR showed that l-AA was incorporated into the bulk of the PLGA film. DSC showed that the l-AA was present in an amorphous form and formed an intermolecular bonding interaction with PLGA. The drug release studies showed that l-AA was sustained released from the PLGA coated CoCr for up to 24 h. The SEM, FTIR, and DSC characterizations of samples collected post drug release shed light on the mechanism of l-AA release from PLGA coated CoCr. Thus, this study demonstrated the delivery of l-AA from biomaterial surfaces for potential applications in stents and other implantable medical devices.

A rapid and specific microplate assay for the determination of intra- and extracellular ascorbate in cultured cells

Vitamin C (ascorbate) plays numerous important roles in cellular metabolism, many of which have only come to light in recent years. For instance, within the brain, ascorbate acts in a neuroprotective and neuromodulatory manner that involves ascorbate cycling between neurons and vicinal astrocytes--a relationship that appears to be crucial for brain ascorbate homeostasis. Additionally, emerging evidence strongly suggests that ascorbate has a greatly expanded role in regulating cellular and systemic iron metabolism than is classically recognized. The increasing recognition of the integral role of ascorbate in normal and deregulated cellular and organismal physiology demands a range of medium-throughput and high-sensitivity analytic techniques that can be executed without the need for highly expensive specialist equipment. Here we provide explicit instructions for a medium-throughput, specific and relatively inexpensive microplate assay for the determination of both intra- and extracellular ascorbate in cell culture.

Does vitamin C deficiency increase lifestyle-associated vascular disease progression? Evidence based on experimental and clinical studies

SIGNIFICANCE

Despite continuous advances in the prevention of cardiovascular disease (CVD), critical issues associated with an unhealthy lifestyle remain an increasing cause of morbidity and mortality in industrialized countries.

RECENT ADVANCES

A growing body of literature supports a specific role for vitamin C in a number of reactions that are associated with vascular function and control including, for example, nitric oxide bioavailability, lipid metabolism, and vascular integrity.

CRITICAL ISSUES

A large body of epidemiological evidence supports a relationship between poor vitamin C status and increased risk of developing CVD, and the prevalence of deficiency continues to be around 10%-20% of the general Western population although this problem could easily and cheaply be solved by supplementation. However, large intervention studies using vitamin C have not found a beneficial effect of supplementation. This review outlines the proposed mechanism by which vitamin C deficiency worsens CVD progression. In addition, it discusses problems with the currently available literature, including the discrepancies between the large intervention studies and the experimental and epidemiological literature.

FUTURE DIRECTIONS

Increased insights into vitamin C deficiency-mediated CVD progression will enable the design of future randomized controlled trials that are better suited to test the efficacy of vitamin C in disease prevention as well as the identification of high-risk individuals which could possibly benefit from supplementation.

Role of vitamin C in the function of the vascular endothelium

SIGNIFICANCE

Vitamin C, or ascorbic acid, has long been known to participate in several important functions in the vascular bed in support of endothelial cells. These functions include increasing the synthesis and deposition of type IV collagen in the basement membrane, stimulating endothelial proliferation, inhibiting apoptosis, scavenging radical species, and sparing endothelial cell-derived nitric oxide to help modulate blood flow. Although ascorbate may not be able to reverse inflammatory vascular diseases such as atherosclerosis, it may well play a role in preventing the endothelial dysfunction that is the earliest sign of many such diseases.

RECENT ADVANCES

Beyond simply preventing scurvy, evidence is mounting that ascorbate is required for optimal function of many dioxygenase enzymes in addition to those involved in collagen synthesis. Several of these enzymes regulate the transcription of proteins involved in endothelial function, proliferation, and survival, including hypoxia-inducible factor-1α and histone and DNA demethylases. More recently, ascorbate has been found to acutely tighten the endothelial permeability barrier and, thus, may modulate access of ascorbate and other molecules into tissues and organs.

CRITICAL ISSUES

The issue of the optimal cellular content of ascorbate remains unresolved, but it appears that low millimolar ascorbate concentrations are normal in most animal tissues, in human leukocytes, and probably in the endothelium. Although there may be little benefit of increasing near maximal cellular ascorbate concentrations in normal people, many diseases and conditions have either systemic or localized cellular ascorbate deficiency as a cause for endothelial dysfunction, including early atherosclerosis, sepsis, smoking, and diabetes.

FUTURE DIRECTIONS

A key focus for future studies of ascorbate and the vascular endothelium will likely be to determine the mechanisms and clinical relevance of ascorbate effects on endothelial function, permeability, and survival in diseases that cause endothelial dysfunction.

A review of the mechanisms and effectiveness of dietary polyphenols in reducing oxidative stress and thrombotic risk

Dietary sources of polyphenols, which are derivatives and/or isomers of flavones, isoflavones, flavonols, catechins and phenolic acids, possess antioxidant properties and therefore might be important in preventing oxidative-stress-induced platelet activation and attenuating adverse haemostatic function. Free radicals, including reactive oxygen and nitrogen species, promote oxidative stress, leading to platelet hyperactivation and the risk of thrombosis. The consumption of antioxidant/polyphenol rich foods might therefore impart anti-thrombotic and cardiovascular protective effects via their inhibition of platelet hyperactivation or aggregation. Most commonly-used anti-platelet drugs such as aspirin block the cyclooxygenase (COX)-1 pathway of platelet activation, similar to the action of antioxidants with respect to neutralising hydrogen peroxide (H2 O2 ), with a similar effect on thromboxane production via the COX-1 pathway. Polyphenols also target various additional platelet activation pathways (e.g. by blocking platelet-ADP, collagen receptors); thus alleviating fibrinogen binding to platelet surface (GPIIb-IIIa) receptors, reducing further platelet recruitment for aggregation and inhibiting platelet degranulation. As a result of the ability of polyphenols to target additional pathways of platelet activation, they may have the potential to substitute or complement currently used anti-platelet drugs in sedentary, obese, pre-diabetic or diabetic populations who can be resistant or sensitive to pharmacological anti-platelet therapy.

A comparative study of the effects of vitamin C, sirolimus, and paclitaxel on the growth of endothelial and smooth muscle cells for cardiovascular medical device applications

Antiproliferative drugs such as sirolimus (SIR) and paclitaxel (PAT) are currently released from stents and vascular grafts to inhibit the growth of smooth muscle cells (SMCs), thereby preventing neointimal hyperplasia. However, these drugs delay or impair the growth of endothelial cells (ECs) on implant surfaces causing late thrombosis. Hence, there is a need to use alternative drugs in these implants to encourage the growth of ECs and to inhibit the growth of SMCs. Vitamin C (L-ascorbic acid [L-AA]) is one such drug which has been shown to encourage EC growth and inhibit SMC growth when orally administered or added directly to the cell cultures. In this research, four sets of in vitro cell culture experiments were carried out to compare the effects of L-AA, SIR, and PAT on the growth of ECs and SMCs under similar conditions, and to compare the effects of different doses of L-AA to determine the optimal dose for promoting maximum EC growth and inhibiting SMC growth. The ECs and SMCs treated with different drugs were characterized for their viability and proliferation, and morphology using the quantitative resazurin assay (as well as qualitative fluorescence microscopy characterization) and phase contrast microscopy, respectively, for up to 7 days. Also, the phenotype of ECs was characterized using immunofluorescence microscopy. Both SIR and PAT significantly inhibited the EC growth while L-AA significantly encouraged EC growth even more than that of the controls with no drugs. Also, L-AA significantly inhibited SMC growth although the inhibitory effect was inferior to that of SIR and PAT. The L-AA dosage study demonstrated that 100 μg and 300 μg of L-AA showed maximum EC growth after 7 days when compared to other dosages (1 μg, 500 μg, and 1000 μg) of L-AA and controls investigated in this study. Also, the 100 μg and 300 μg L-AA doses significantly inhibited the SMC growth. Thus, this study demonstrates that L-AA is a promising drug for potential use in stents and vascular grafts, to promote their endothelialization and inhibit neointimal hyperplasia.

Liver metabolic/oxidative stress induces hepatic and extrahepatic changes in the expression of the vitamin C transporters SVCT1 and SVCT2

PURPOSE

Owing to its ability to inactivate harmful radicals, vitamin C plays a key role in antioxidant defense. The bioavailability of this vitamin depends upon the nutritional intake and its uptake by cells, mainly through the sodium-dependent transporters SVCT1/Svct1 and SVCT2/Svct2 (human/rat). Here, we investigated the effect of liver metabolic/oxidative stress on the expression of these transporters in extrahepatic tissues.

METHODS AND RESULTS

In Zucker rats, used here as a model of liver steatosis, Svct1-2 mRNA levels were similar in obese and lean animals, except for lung tissue, where Svct2 was up-regulated. Diabetes mellitus, developed by streptozotocin administration, was accompanied by a down-regulation of Svct1 in liver and kidney, together with a down-regulation of Svct2 in kidney and brain. Complete obstructive cholestasis due to bile duct ligation for 1 week induced a significant down-regulation of both Svct1 and Svct2 in ileum, whereas Svct2 was up-regulated in liver, and no significant changes in the expression of either transporter were found in kidney, brain or lung. In rat hepatoma Can-10 cells, bile acids, but not the FXR agonist GW4064, induced an up-regulation of Svct1 and Svct2. In human hepatoma Alexander cells transfected with FXR/RXRα/OATP1B1, neither GW4064 nor unconjugated or glycine-/taurine-conjugated major bile acids were able to up-regulate either SVCT1 or SVCT2.

CONCLUSIONS

Pathological circumstances characterized by the presence of metabolic/oxidative stress in the liver induce different responses in the expression of ascorbic acid transporters in intrahepatic and extrahepatic tissues, which may affect the overall bioavailability and cellular uptake of this vitamin.

Senescence-induced increases in intracellular oxidative stress and enhancement of the need for ascorbic acid in human fibroblasts

Many studies have suggested that there is a close correlation among declines in internal ascorbic acid (AsA) levels, various disorders, and senescence. To clarify the relationships between age-associated changes in intracellular AsA levels and the effects of AsA administration on intracellular reactive oxygen species (ROS) levels, we investigated aging-related changes in AsA uptake, ROS levels, and the effects of AsA administration on intracellular ROS levels in young and old (senescent) human fibroblasts. Our results demonstrated that AsA uptake was increased in old cells compared with young cells, although mRNA and protein expression of sodium-dependent vitamin C transporter 2 was barely altered between the young and old cells. We also demonstrated that the intracellular superoxide anion level was higher in young cells, whereas the level of intracellular peroxides was significantly increased in old cells under both normal and oxidative stress conditions. Moreover, AsA administration markedly decreased the augmentation of intracellular peroxides in old cells, whereas there was no effect of AsA treatment in young cells under both normal and oxidative stress conditions. Therefore, our results also indicate that AsA could play an important role in regulating the intracellular ROS levels in senescent cells and that the need for AsA is enhanced by cellular senescence.

Efficacy of vitamin and antioxidant supplements in prevention of cardiovascular disease: systematic review and meta-analysis of randomised controlled trials

OBJECTIVE

To assess the efficacy of vitamin and antioxidant supplements in the prevention of cardiovascular diseases.

DESIGN

Meta-analysis of randomised controlled trials.

DATA SOURCES AND STUDY SELECTION

PubMed, EMBASE, the Cochrane Library, Scopus, CINAHL, and ClinicalTrials.gov searched in June and November 2012. Two authors independently reviewed and selected eligible randomised controlled trials, based on predetermined selection criteria.

RESULTS

Out of 2240 articles retrieved from databases and relevant bibliographies, 50 randomised controlled trials with 294,478 participants (156,663 in intervention groups and 137,815 in control groups) were included in the final analyses. In a fixed effect meta-analysis of the 50 trials, supplementation with vitamins and antioxidants was not associated with reductions in the risk of major cardiovascular events (relative risk 1.00, 95% confidence interval 0.98 to 1.02; I(2)=42%). Overall, there was no beneficial effect of these supplements in the subgroup meta-analyses by type of prevention, type of vitamins and antioxidants, type of cardiovascular outcomes, study design, methodological quality, duration of treatment, funding source, provider of supplements, type of control, number of participants in each trial, and supplements given singly or in combination with other supplements. Among the subgroup meta-analyses by type of cardiovascular outcomes, vitamin and antioxidant supplementation was associated with a marginally increased risk of angina pectoris, while low dose vitamin B(6) supplementation was associated with a slightly decreased risk of major cardiovascular events. Those beneficial or harmful effects disappeared in subgroup meta-analysis of high quality randomised controlled trials within each category. Also, even though supplementation with vitamin B(6) was associated with a decreased risk of cardiovascular death in high quality trials, and vitamin E supplementation with a decreased risk of myocardial infarction, those beneficial effects were seen only in randomised controlled trials in which the supplements were supplied by the pharmaceutical industry.

CONCLUSION

There is no evidence to support the use of vitamin and antioxidant supplements for prevention of cardiovascular diseases.

Ascorbic acid levels in various tissues, plasma and urine of mice during aging

Here we quantified ascorbic acid (AA) levels in 14 tissues, plasma and urine of C57BL/6 male mice to track its turnover during 3 to 30 mo of aging. The AA content of adrenal glands and testes decreased somewhat with age, and eventually rose, but increased in the spleen, lungs, eyes and heart. AA levels rose in the liver, skin and skeletal muscles from 6 to 12 mo of age, but declined from 12 to 24 mo. In the cerebellum, cerebrum, small intestine, kidney and plasma, amounts of AA remained almost constant as the animals aged. Most notably, urinary AA decreased markedly until becoming almost undetectable at 24 and 30 mo of age. Collectively, these results, which compare changes in AA levels in specific physiologic targets throughout the aging process, strongly suggest that the AA synthesizing capacity declines over time to become a major factor in senescence-related diseases.

Role of the immune system in hypertension: modulation by dietary antioxidants

Hypertension is a major health problem worldwide. Individuals with hypertension are at an increased risk for stroke, heart disease, and kidney failure. Although the etiology of essential hypertension has a genetic component, lifestyle factors such as diet play an important role. Insulin resistance is a common feature of hypertension in both humans and animal models affecting glucose and lipid metabolism producing excess aldehydes including methylglyoxal. These aldehydes react with proteins to form conjugates called advanced glycation end products (AGEs). This alters protein structure and function and can affect vascular and immune cells leading to their activation and secretion of inflammatory cytokines. AGEs also act via receptors for advanced glycation end products on these cells altering the function of antioxidant and metabolic enzymes, and ion channels. This results in an increase in cytosolic free calcium, decrease in nitric oxide, endothelial dysfunction, oxidative stress, peripheral vascular resistance, and infiltration of vascular and kidney tissue with inflammatory cells leading to hypertension. Supplementation with dietary antioxidants including vitamins C, E, or B(6), thiols such as cysteine and lipoic acid, have been shown to lower blood pressure and plasma inflammatory cytokines in animal models and humans with essential hypertension. A well-balanced diet rich in antioxidants that includes vegetables, fruits, low fat dairy products, low salt, and includes whole grains, poultry, fish and nuts, lowers blood pressure and vascular inflammation. These antioxidants may achieve their antihypertensive and anti-inflammatory/immunomodulatory effects by reducing AGEs and improving insulin resistance and associated alterations. Dietary supplementation with antioxidants may be a beneficial, inexpensive, front-line alterative treatment modality for hypertension.

Association between circulating ascorbic acid, α-tocopherol, 25-hydroxyvitamin D, and plasma cytokine concentrations in young adults: a cross-sectional study

BACKGROUND

Inflammation and oxidative stress are associated with the development of numerous chronic diseases. Circulating ascorbic acid, α-tocopherol, and 25-hydroxyvitamin D (25(OH)D) may help reduce concentrations of pro-inflammatory cytokines through their antioxidant and anti-inflammatory properties. These micronutrients may act synergistically, and they may have different anti-inflammatory effects, but previous studies have assessed the link between each of these micronutrients and inflammation in isolation without controlling for the other micronutrients. Our objective was to examine the association between circulating concentrations of ascorbic acid, α-tocopherol, and 25(OH) D and a panel of pro-inflammatory cytokines in an ethnically diverse population of young adults.

METHODS

Participants (n = 1,007) from the Toronto Nutrigenomics and Health study provided fasting blood samples for biomarker measurements and were subsequently categorized into tertiles for each micronutrient based on their circulating concentrations. We conducted Pearson's correlation analyses across all micronutrients and cytokines. The associations between individual micronutrients and cytokines were examined using analysis of covariance with age, sex, waist circumference, ethnicity, physical activity, season of blood collection, total cholesterol, hormonal contraceptive use among women, and the other two micronutrients as covariates.

RESULTS

We observed weak micronutrient-cytokine correlations, moderate correlations between certain cytokines, and strong correlations between specific cytokines, particularly interleukin 1- receptor antagonist (IL-1RA), interferon-γ (IFN-γ), and platelet-derived growth factor BB (PDGF-bb). After full covariate adjustment, circulating α-tocopherol was inversely associated with IFN-γ and regulated upon activation normal T-cell expressed and secreted (RANTES). We observed an unexpected positive association between ascorbic acid and IFN-γ. 25(OH)D was not associated with altered concentrations of any inflammatory biomarkers.

CONCLUSIONS

These findings suggest that α-tocopherol, but not ascorbic acid or 25(OH)D, is inversely associated with inflammation in healthy young adults.

Tetrahydrobiopterin, L-arginine and vitamin C act synergistically to decrease oxidant stress and increase nitric oxide that increases blood flow recovery after hindlimb ischemia in the rat

Nitric oxide (NO) derived from endothelial nitric oxide synthase (eNOS) is a potent vasodilator and signaling molecule that plays essential roles in neovascularization. During limb ischemia, decreased NO bioavailability occurs secondary to increased oxidant stress, decreased L-arginine and tetrahydrobiopterin. This study tested the hypothesis that dietary cosupplementation with tetrahydrobiopterin (BH4), L-arginine and vitamin C acts synergistically to decrease oxidant stress, increase NO and thereby increase blood flow recovery after hindlimb ischemia. Rats were fed normal chow, chow supplemented with BH4 or L-arginine (alone or in combination) or chow supplemented with BH4 + L-arginine + vitamin C for 1 wk before induction of hindlimb ischemia. In the is-chemic hindlimb, cosupplementation with BH4 + L-arginine resulted in greater eNOS and phospho-eNOS (P-eNOS) expression, Ca(2+)-dependent NOS activity and NO concentration in the ischemic calf region (gastrocnemius), as well as greater NO concentration in the region of collateral arteries (gracilis). Rats receiving cosupplementation of BH4 + L-arginine led to greater recovery of foot perfusion and greater collateral enlargement than did rats receiving either agent separately. The addition of vitamin C to the BH4 + L-arginine regimen further increased these dependent variables. In addition, rats given all three supplements showed significantly less Ca(2+)-independent activity, less nitrotyrosine accumulation, greater glutathione (GSH)-to-glutathione disulfide (GSSG) ratio and less gastrocnemius muscle necrosis, on both macroscopic and microscopic levels. In conclusion, co-supplementation with BH4 + L-arginine + vitamin C significantly increased blood flow recovery after hindlimb ischemia by reducing oxidant stress, increasing NO bioavailability, enlarging collateral arteries and reducing muscle necrosis. Oral cosupplementation of BH4, L-arginine and vitamin C holds promise as a biological therapy to induce collateral artery enlargement.

Differing Relations to Early Atherosclerosis between Vitamin C from Supplements vs. Food in the Los Angeles Atherosclerosis Study: A Prospective Cohort Study

OBJECTIVE

To determine the relationship of vitamin c intake from supplements vs food on early atherosclerosis detected by carotid intima media thickness (IMT).

BACKGROUND

Oxidative stress and endothelial dysfunction play a critical role in the pathogenesis of atherosclerosis. Dietary vitamin C appears to have anti-oxidant properties and beneficial relations to endothelial function, yet vitamin C taken as a vitamin supplement does not appear to protect from cardiovascular events. The impact of vitamin c intake from supplements vs food on progression of atherosclerosis is unknown.

METHODS

We examined 3-year progression of carotid IMT in a randomly sampled cohort of 573 healthy women and men aged 40-60 years. Progression of carotid IMT was determined bilaterally with B-mode ultrasound at 3 examinations (1.5-year intervals). Intake of dietary vitamin C was measured by six, 24-hour recall interviews. Intake of vitamin C from vitamin supplements was measured by questionnaire in quartiles of supplement intake and no supplement. Vitamin C wasmeasured in plasma as ascorbic acid.

RESULTS

Carotid IMT progressed 10.0±16.5 μm/year (mean±SD) among all those with follow-up (n=500; 87%). For those who took vitamin C supplements, carotid IMT progression increased with dose (p-trend=0.0009). Among persons in the highest quartile (857-5000 mg/day) of vitamin C supplement intake compared to those not consuming any vitamin C supplements, carotid IMT progression increased three-fold (20.3±2.6 versus 7.6±1.8 μm/year (mean±SD); p<0.001). The adverse association of vitamin C supplement intake with carotid IMT was two-fold greater in the upper tertile of serum cholesterol compared to the lower two tertiles (p=0.01). In contrast to the adverse association of vitamin C supplements, vitamin C intake from food had a weak protective relationship on carotid IMT progression (reduced progression -5.0±1.9 μm/year; p=0.008).

CONCLUSIONS

Vitamin C supplementation is associated with accelerated early atherosclerosis measured by carotid IMT compared to a protective association with vitamin C from food. Theadverse association of vitamin C supplementation may be greater in patients with higher serum cholesterol levels. The current results provide a potential mechanistic understanding for the observed differences between Vitamin C in supplements vs food in prior studies. Given these observations,vitamin C supplementation does not appear to be currently advisable for prevention or treatment of atherosclerosis.

Does pharmacodynamic interaction of nonenzymatic antioxidants modify response to antioxidant therapy in the process of atherosclerosis?

A discrepancy exists between clinical trials and epidemiological studies on the effect of antioxidants on cardiovascular disease. This discrepancy could be attributed to the lack of knowledge on the effect of interaction of exogenous antioxidant supplementation with one another or on the effect of interaction of exogenously administered antioxidant vitamins with endogenous ones. This study attempts a systematic review of available data on possible synergistic, additive, or antagonistic action of nonenzymatic antioxidants in atherosclerosis. Electronic databases were searched with the available search terms up to and including February 2010. Eligibility criteria were full publications, clinical trials, epidemiological studies, or in vitro or in vivo studies that investigated the effect of pharmacodynamic interaction of 2 or more antioxidants in the process of atherosclerosis and /or the mechanism of interaction. Eligible clinical trials should have at least 4 arms, 1 arm for the study of each antioxidant alone, 1 for the effect of both antioxidants, and 1 arm for the effect of placebo. In vitro data as well as the limited number of identified randomized clinical trials suggested that coadministration of antioxidants results in synergistic or additive interaction in the process of atherosclerosis. No study demonstrated antagonistic interaction between antioxidants.

Tetrahydrobiopterin, L-arginine and vitamin C actsynergistically to decrease oxidative stress, increase nitricoxide and improve blood flow after induction of hindlimbischemia in the rat

Nitric oxide (NO) derived from endothelial nitric oxide synthase (eNOS) is a potent vasodilator and signaling molecule that plays an essential role in vascular remodeling of collateral arteries and perfusion recovery in response to hindlimb ischemia. In ischemic conditions, decreased NO bioavailability was observed because of increased oxidative stress, decreased L-arginine and tetrahydrobiopterin. This study tested the hypothesis that dietary cosupplementation with tetrahydrobiopterin (BH4), L-arginine, and vitamin C acts synergistically to decrease oxidative stress, increase nitric oxide and improve blood flow in response to acute hindlimb ischemia. Rats were fed normal chow, chow supplemented with BH4 or L-arginine (alone or in combination) or chow supplemented with BH4 + L-arginine + vitamin C for 1 wk before induction of unilateral hindlimb ischemia. Cosupplementation with BH4 + L-arginine resulted in greater eNOS expression, Ca²⁺-dependent NOS activity and NO concentration in gastrocnemius from the ischemic hindlimb, as well as greater recovery of foot perfusion and more collateral artery enlargement than did rats receiving either agent separately. The addition of vitamin C to the BH4 + L-arginine regimen did further increase these dependent variables, although only the increase in eNOS expression reached statistical significances. In addition, rats given all three supplements demonstrated significantly less Ca²⁺-independent activity, less nitrotyrosine accumulation, greater glutathione:glutathione disulfide (GSH:GSSG) ratio and less gastrocnemius muscle necrosis, on both macroscopic and microscopic levels. In conclusion, cosupplementation with BH4 + L-arginine + vitamin C significantly increased vascular perfusion after hindlimb ischemia by increasing eNOS activity and reducing oxidative stress and tissue necrosis. Oral cosupplementation of L-arginine, BH4 and vitamin C holds promise as a biological therapy to induce collateral artery enlargement.

Functional foods and nutraceuticals in the primary prevention of cardiovascular diseases

Cardiovascular disease (CVD) is now the leading cause of death globally and is a growing health concern. Dietary factors are important in the pathogenesis of CVD and may to a large degree determine CVD risk, but have been less extensively investigated. Functional foods are those that are thought to have physiological benefits and/or reduce the risk of chronic disease beyond their basic nutritional functions. The food industry has started to market products labelled as “functional foods.” Although many review articles have focused on individual dietary variables as determinants of CVD that can be modified to reduce the risk of CVD, the aim of this current paper was to examine the impact of functional foods in relation to the development and progression of CVD. Epidemiologic studies have demonstrated the association between certain dietary patterns and cardiovascular health. Research into the cardio-protective potential of their dietary components might support the development of functional foods and nutraceuticals. This paper will also compare the effect of individual bioactive dietary compounds with the effect of some dietary patterns in terms of their cardiovascular protection.

Post-exposure antioxidant treatment in rats decreases airway hyperplasia and hyperreactivity due to chlorine inhalation

We assessed the safety and efficacy of combined intravenous and aerosolized antioxidant administration to attenuate chlorine gas-induced airway alterations when administered after exposure. Adult male Sprague-Dawley rats were exposed to air or 400 parts per million (ppm) chlorine (a concentration likely to be encountered in the vicinity of industrial accidents) in environmental chambers for 30 minutes, and returned to room air, and they then received a single intravenous injection of ascorbic acid and deferoxamine or saline. At 1 hour and 15 hours after chlorine exposure, the rats were treated with aerosolized ascorbate and deferoxamine or vehicle. Lung antioxidant profiles, plasma ascorbate concentrations, airway morphology, and airway reactivity were evaluated at 24 hours and 7 days after chlorine exposure. At 24 hours after exposure, chlorine-exposed rats had significantly lower pulmonary ascorbate and reduced glutathione concentrations. Treatment with antioxidants restored depleted ascorbate in lungs and plasma. At 7 days after exposure, in chlorine-exposed, vehicle-treated rats, the thickness of the proximal airways was 60% greater than in control rats, with twice the amount of mucosubstances. Airway resistance in response to methacholine challenge was also significantly elevated. Combined treatment with intravenous and aerosolized antioxidants restored airway morphology, the amount of airway mucosubstances, and airway reactivity to control levels by 7 days after chlorine exposure. Our results demonstrate for the first time, to the best of our knowledge, that severe injury to major airways in rats exposed to chlorine, as characterized by epithelial hyperplasia, mucus accumulation, and airway hyperreactivity, can be reversed in a safe and efficacious manner by the post-exposure administration of ascorbate and deferoxamine.

Vitamins C and E: beneficial effects from a mechanistic perspective

The mechanistic properties of two dietary antioxidants that are required by humans, vitamins C and E, are discussed relative to their biological effects. Vitamin C (ascorbic acid) is an essential cofactor for α-ketoglutarate-dependent dioxygenases. Examples are prolyl hydroxylases, which play a role in the biosynthesis of collagen and in down-regulation of hypoxia-inducible factor (HIF)-1, a transcription factor that regulates many genes responsible for tumor growth, energy metabolism, and neutrophil function and apoptosis. Vitamin C-dependent inhibition of the HIF pathway may provide alternative or additional approaches for controlling tumor progression, infections, and inflammation. Vitamin E (α-tocopherol) functions as an essential lipid-soluble antioxidant, scavenging hydroperoxyl radicals in a lipid milieu. Human symptoms of vitamin E deficiency suggest that its antioxidant properties play a major role in protecting erythrocyte membranes and nervous tissues. As an antioxidant, vitamin C provides protection against oxidative stress-induced cellular damage by scavenging of reactive oxygen species, by vitamin E-dependent neutralization of lipid hydroperoxyl radicals, and by protecting proteins from alkylation by electrophilic lipid peroxidation products. These bioactivities bear relevance to inflammatory disorders. Vitamin C also plays a role in the function of endothelial nitric oxide synthase (eNOS) by recycling the eNOS cofactor, tetrahydrobiopterin, which is relevant to arterial elasticity and blood pressure regulation. Evidence from plants supports a role for vitamin C in the formation of covalent adducts with electrophilic secondary metabolites. Mechanism-based effects of vitamin C and E supplementation on biomarkers and on clinical outcomes from randomized, placebo-controlled trials are emphasized in this review.

Hepatic expression of sodium-dependent vitamin C transporters: ontogeny, subtissular distribution and effect of chronic liver diseases

Ascorbic acid uptake is a key step in determining the overall bioactivity of this vitamin. Expression of Na-dependent vitamin C transporters (SVCT; SLC23A1 and SLC23A2) during long-term oxidative stress occurring in several chronic liver diseases may determine the antioxidant defence in this organ. In patients with hepatocellular cholestasis, primary biliary cirrhosis, haemochromatosis and non-alcoholic steatohepatitis, using real-time RT-PCR, an enhanced hepatic expression of both SLC23A1 and SLC23A2, but not other organic anions transporters, such as OATP1A2, OATP1B1 and OATP1B3, was found. To further investigate these findings, we used secondary biliary cirrhosis induced in rats by long-term biliary obstruction as a model of chronic liver disease accompanied by oxidative stress because of bile acid accumulation. In control rat liver, expression of Slc23a1 was low at birth, increased progressively up to adulthood and decreased in senescence, whereas expression of Slc23a2 did not change significantly after birth. In 8-week-old rats, immunohistochemistry and confocal microscopy studies revealed the expression in hepatocytes and bile duct cells of mainly Slc23a1, whereas both Slc23a1 and Slc23a2 were expressed in endothelial, stellate and Kupffer cells. In adult rats, when obstructive cholestasis was maintained for 8 weeks, a significant up-regulation of Slc23a2 accompanied by a down-regulation of Slc23a1 was found. In sum, there is a selective cell-type distribution of SVCT in the liver tissue, which, in addition to differential control in the expression of both isoforms, may play a role in the ability of different liver cell types to take up vitamin C under physiological and pathological conditions.

Ascorbic acid increases the activity and synthesis of tyrosinase in B16F10 cells through activation of p38 mitogen-activated protein kinase

Ascorbic acid, a potential antioxidant, is known to inhibit melanogenesis. However, there are conflicting findings that ascorbic acid has very low stability and acts as a pro-oxidant, eventually increasing proliferation and melanin content in melanoma cells. In the present study, we explored the effects of ascorbic acid on the activity and expression of tyrosinase and melanin pigmentation in the presence and absence of α-melanocyte-stimulating hormone (α-MSH) using B16F10 melanoma cells. The mechanism by which ascorbic acid stimulated the expression of tyrosinase was also investigated. No inhibitory effect on melanin content was observed in ascorbic acid-treated cells, regardless of the presence of α-MSH. Ascorbic acid stimulated the activity and expression of tyrosinase and increased the expression of melanogenic regulatory factors, such as tyrosinase-related protein-1 (TRP-1), dihydroxyphenylalaminechrome tautomerase (TRP-2), and microphthalmia-associated transcription factor (MITF). Ascorbic acid also induced phosphorylation of p38 mitogen-activated protein kinase (MAPK). The inhibition of p38 MAPK pathway by SB203580 led to the suppression of tyrosinase, TRP-1, and TRP-2 expression in cells treated with ascorbic acid. Combined treatment with N-acetyl-L: -cysteine and/or desferrioxamine mesylate attenuated the stimulating effect of ascorbic acid on tyrosinase activation in the cells. Collectively, ascorbic acid stimulates tyrosinase activity and expression in B16F10 cells via activation of p38 MAPK signaling and subsequent up-regulation of MITF, tyrosinase, and TRP expression.

Vitamins D, C, and E in the prevention of type 2 diabetes mellitus: modulation of inflammation and oxidative stress

The incidence of type 2 diabetes mellitus (T2DM) is increasing worldwide, and certain population subgroups are especially vulnerable to the disease. To reduce T2DM risk and progression at the population level, preventative strategies are needed that can be implemented on a population-wide scale with minimal cost and effort. Chronic low-grade inflammation resulting from oxidative stress and imbalances in the innate immune system has been associated with obesity, metabolic syndrome, and insulin resistance – critical stages in the development and progression of T2DM. Therefore, inflammation may play a causal role in the pathogenesis of T2DM, and reducing it via modulation of oxidative stress and the innate immune response could lead to a status of improved insulin sensitivity and delayed disease onset. Dietary supplementation with anti-inflammatory and antioxidant nutritional factors, such as micronutrients, might present a novel strategy toward the prevention and control of T2DM at the population level. This review examines current knowledge linking oxidation, inflammatory signaling pathways, and vitamin supplementation or intake to the risk of T2DM. The concept that micronutrients, via attenuation of inflammation, could be employed as a novel preventive measure for T2DM is evaluated in the context of its relevance to public health.