Reduction in plasma total homocysteine through increasing folate intake in healthy individuals is not associated with changes in measures of antioxidant activity or oxidant damage

Effects of Folic Acid Supplementation on Oxidative Stress Markers: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

(1) Background: This systematic review and meta-analysis aimed to assess the effects of folic acid supplementation on oxidative stress markers. (2) Methods: Online database including PubMed, Scopus, Web of Science, and Cochrane were searched up to January 2021, to retrieve randomized controlled trials (RCTs) which examined the effect of folic acid supplementation on markers of oxidative stress. Meta-analyses were carried out using a random-effects model. I² index was used to evaluate the heterogeneity of RCTs. (3) Results: Among the initial 2322 studies that were identified from electronic databases search, 13 studies involving 1013 participants were eligible. Pooled effect size from 13 studies indicated that folic acid supplementation elicits a significant rise in serum concentrations of glutathione (GSH) (WMD: 219.01 umol/L, 95% CI 59.30 to 378.71, p = 0.007) and total antioxidant capacity (TAC) (WMD: 91.70 umol/L, 95% CI 40.52 to 142.88, p < 0.001) but has no effect on serum concentrations of nitric oxide (NO) (WMD: 2.61 umol/L, 95% CI −3.48 to 8.72, p = 0.400). In addition, folic acid supplementation significantly reduced serum concentrations of malondialdehyde (MDA) (WMD: −0.13 umol/L, 95% CI −0.24 to −0.02, p = 0.020). (4) Conclusions: This meta-analysis study suggests that folic acid supplementation may significantly improve markers within the antioxidative defense system by increasing serum concentrations of GSH and TAC and decreasing serum concentrations of MDA.

Methyl-donor depletion of head and neck cancer cells in vitro establishes a less aggressive tumour cell phenotype

PURPOSE

DNA methylation plays a fundamental role in the epigenetic control of carcinogenesis and is, in part, influenced by the availability of methyl donors obtained from the diet. In this study, we developed an in-vitro model to investigate whether methyl donor depletion affects the phenotype and gene expression in head and neck squamous cell carcinoma (HNSCC) cells.

METHODS

HNSCC cell lines (UD-SCC2 and UPCI-SCC72) were cultured in medium deficient in methionine, folate, and choline or methyl donor complete medium. Cell doubling-time, proliferation, migration, and apoptosis were analysed. The effects of methyl donor depletion on enzymes controlling DNA methylation and the pro-apoptotic factors death-associated protein kinase-1 (DAPK1) and p53 upregulated modulator of apoptosis (PUMA) were examined by quantitative-PCR or immunoblotting.

RESULTS

HNSCC cells cultured in methyl donor deplete conditions showed significantly increased cell doubling times, reduced cell proliferation, impaired cell migration, and a dose-dependent increase in apoptosis when compared to cells cultured in complete medium. Methyl donor depletion significantly increased the gene expression of DNMT3a and TET-1, an effect that was reversed upon methyl donor repletion in UD-SCC2 cells. In addition, expression of DAPK1 and PUMA was increased in UD-SCC2 cells cultured in methyl donor deplete compared to complete medium, possibly explaining the observed increase in apoptosis in these cells.

CONCLUSION

Taken together, these data show that depleting HNSCC cells of methyl donors reduces the growth and mobility of HNSCC cells, while increasing rates of apoptosis, suggesting that a methyl donor depleted diet may significantly affect the growth of established HNSCC.

Serum Homocysteine and Total Antioxidant Status in Vitiligo: A Case Control Study in Indian Population

BACKGROUND

Oxidative stress is considered as an initial pathogenic event in melanocyte destruction. These free radicals are scavenged by antioxidants, whose sum of activity in serum is measured by total antioxidant status (TAS). In addition, homocysteine (Hcy) may mediate melanocyte destruction via increased oxidative damage. However, previous studies investigating these parameters in vitiligo provide equivocal results.

AIMS

To study and compare serum Hcy and TAS levels in vitiligo patients with controls and also to correlate these parameters with the various disease characteristics. The present study further looked into any correlation between serum Hcy and TAS in vitiligo.

MATERIALS AND METHODS

A case control study was conducted on 82 vitiligo patients and 83 controls aged 18-45 years after excluding factors which could potentially alter serum Hcy or TAS levels. Disease characteristics were studied and blood samples were obtained for measuring serum Hcy and TAS levels.

RESULTS

TAS levels were lower in vitiligo patients than controls (1.79 ± 0.51 vs. 2.16 ± 0.63 mmol/L; P < 0.001) and had a negative correlation with disease activity (r = -0.410, P < 0.001). However, serum Hcy levels were comparable between vitiligo patients (18.68 ± 9.90 μmol/L) and controls (20.21 ± 13.39 μmol/L) (P = 0.406). No significant correlation was found between serum Hcy and serum TAS levels.

CONCLUSIONS

Serum TAS may be further investigated to establish its role as biomarker for vitiligo since its levels also correlate with disease activity. However, serum Hcy may not be a reliable marker in Indian population probably because of differences in dietary habits.

Methoxistasis: integrating the roles of homocysteine and folic acid in cardiovascular pathobiology

Over the last four decades, abnormalities in the methionine-homocysteine cycle and associated folate metabolism have garnered great interest due to the reported link between hyperhomocysteinemia and human pathology, especially atherothrombotic cardiovascular disease. However, clinical trials of B-vitamin supplementation including high doses of folic acid have not demonstrated any benefit in preventing or treating cardiovascular disease. In addition to the fact that these clinical trials may have been shorter in duration than appropriate for modulating chronic disease states, it is likely that reduction of the blood homocysteine level may be an oversimplified approach to a complex biologic perturbation. The methionine-homocysteine cycle and folate metabolism regulate redox and methylation reactions and are, in turn, regulated by redox and methylation status. Under normal conditions, a normal redox-methylation balance, or “methoxistasis”, exists, coordinated by the methionine-homocysteine cycle. An abnormal homocysteine level seen in pathologic states may reflect a disturbance of methoxistasis. We propose that future research should be targeted at estimating the deviation from methoxistasis and how best to restore it. This approach could lead to significant advances in preventing and treating cardiovascular diseases, including heart failure.

Fecal lactic acid bacteria increased in adolescents randomized to whole-grain but not refined-grain foods, whereas inflammatory cytokine production decreased equally with both interventions

The intake of whole-grain (WG) foods by adolescents is reported to be approximately one-third the recommended intake of 48 g/d. This 6-wk randomized interventional study determined the effect of replacing grains within the diet with refined-grain (RG; n = 42) or WG (n = 41) foods/d on gastrointestinal and immune health in adolescents (aged 12.7 ± 0.1 y). A variety of grain-based foods were delivered weekly to participants and their families. Participants were encouraged to eat 3 different kinds of study foods (e.g., bread, cereals, snacks)/d with goals of 0 g/d (RG) and 80 g/d (WG). Stool samples were obtained during the prebaseline and final weeks to measure bifidobacteria and lactic acid bacteria (LAB) using qPCR. Stool frequency was recorded daily. Blood was drawn at baseline and at final visits for immune markers. Across groups, total-grain intake increased by one serving. The intake of WG was similar at baseline (18 ± 3 g) between groups but increased to 60 ± 5 g in the WG group and decreased to 4 ± 1 g in the RG group. Fecal bifidobacteria increased from baseline with both interventions, but LAB increased (P < 0.05) from baseline [2.4 ± 0.2 log(10) genome equivalents (eq)] to wk 6 (3.0 ± 0.2 log(10) genome eq) in the WG group but not in the RG group (baseline: 2.9 ± 0.2 log(10) genome eq; wk 6: 3.0 ± 0.1 log(10) genome eq). There was no difference in stool frequency, serum antioxidant potential, or in vitro LPS-stimulated mononuclear cell production of inflammatory cytokines between groups. However, across both groups the number of daily stools tended to increase (P = 0.08) by 0.0034 stools/g WG or by 0.2 stools with 60 g WG, mean antioxidant potential increased by 58%, and mean production of TNF-α, IL-1β, and IL-6 decreased by 24, 22, and 42%, respectively, between baseline and wk 6. Overall, incorporating either WG or RG foods increased serum antioxidant concentrations and decreased inflammatory cytokine production; however, WG study foods had more of an effect on aspects of gastrointestinal health.

New hypotheses for the health-protective mechanisms of whole-grain cereals: what is beyond fibre?

Epidemiological studies have clearly shown that whole-grain cereals can protect against obesity, diabetes, CVD and cancers. The specific effects of food structure (increased satiety, reduced transit time and glycaemic response), fibre (improved faecal bulking and satiety, viscosity and SCFA production, and/or reduced glycaemic response) and Mg (better glycaemic homeostasis through increased insulin secretion), together with the antioxidant and anti-carcinogenic properties of numerous bioactive compounds, especially those in the bran and germ (minerals, trace elements, vitamins, carotenoids, polyphenols and alkylresorcinols), are today well-recognised mechanisms in this protection. Recent findings, the exhaustive listing of bioactive compounds found in whole-grain wheat, their content in whole-grain, bran and germ fractions and their estimated bioavailability, have led to new hypotheses. The involvement of polyphenols in cell signalling and gene regulation, and of sulfur compounds, lignin and phytic acid should be considered in antioxidant protection. Whole-grain wheat is also a rich source of methyl donors and lipotropes (methionine, betaine, choline, inositol and folates) that may be involved in cardiovascular and/or hepatic protection, lipid metabolism and DNA methylation. Potential protective effects of bound phenolic acids within the colon, of the B-complex vitamins on the nervous system and mental health, of oligosaccharides as prebiotics, of compounds associated with skeleton health, and of other compounds such as alpha-linolenic acid, policosanol, melatonin, phytosterols and para-aminobenzoic acid also deserve to be studied in more depth. Finally, benefits of nutrigenomics to study complex physiological effects of the 'whole-grain package', and the most promising ways for improving the nutritional quality of cereal products are discussed.

Age-associated B vitamin deficiency as a determinant of chronic diseases

The number of elderly individuals is growing rapidly worldwide and degenerative diseases constitute an increasing problem in terms of both public health and cost. Nutrition plays a role in the ageing process and there has been intensive research during the last decade on B vitamin-related risk factors in vascular and neurological diseases and cancers. Data from epidemiological studies indicate that subclinical deficiency in most water-soluble B vitamins may occur gradually during ageing, possibly due to environmental, metabolic, genetic, nutritional and pathological determinants, as well as to lifestyle, gender and drug consumption. Older adults have distinct absorption, cell transport and metabolism characteristics that may alter B vitamin bioavailability. Case–control and longitudinal studies have shown that, concurrent with an insufficient status of certain B vitamins, hyperhomocysteinaemia and impaired methylation reactions may be some of the mechanisms involved before a degenerative pathology becomes evident. The question that arises is whether B vitamin inadequacies contribute to the development of degenerative diseases or result from ageing and disease. The present paper aims to give an overview of these issues at the epidemiological, clinical and molecular levels and to discuss possible strategies to prevent B vitamin deficiency during ageing.

Augmentation index and carotid intima-media thickness are differently related to age, C-reactive protein and oxidized low-density lipoprotein

OBJECTIVE

Ageing, plasma circulating C-reactive protein (CRP), oxidized low-density lipoprotein (OxLDL) and homocysteine (Hcy) are associated with atherosclerosis. The aim of this study was to evaluate the relationship between age, inflammatory and oxidative stress-related markers with functional and structural changes of the arteries in asymptomatic persons.

METHODS

CRP, OxLDL and Hcy were measured in 175 clinically healthy subjects, aged 40-70 years. Ultrasonography and pulse wave analysis were used to measure carotid intima-media thickness (IMT) and augmentation index (AIx).

RESULTS

OxLDL was correlated with IMT (r = 0.24, P = 0.003), whereas CRP was correlated with AIx (r = 0.21, P = 0.005). No correlation was detected between Hcy and AIx or age-adjusted IMT. There was a significant association between AIx and age <or=50 years (r = 0.33; P = 0.001) and between IMT and age > 50 years (r = 0.40; P = 0.001). In stepwise regression analysis age, weight, white blood cell count, OxLDL, heart rate and timing of the reflected waveform adjusted for height were significantly and independently associated with IMT (R = 0.41; P < 0.001). At the same time, AIx as the dependent variable correlated positively with age, gender, CRP and mean arterial pressure, and negatively with heart rate, weight and height, in stepwise regression analysis (R = 0.63; P < 0.001).

CONCLUSION

The results of the present study showed that CRP, OxLDL, Hcy and age are not similarly related to AIx and IMT in asymptomatic persons. The results suggest that CRP and younger age are related to arterial stiffness, whereas OxLDL and older age become more important determinants of structural changes of the arteries in asymptomatic persons.

Association between homocysteine, vitamin B6 concentrations and inflammation

During the last years, a growing body of evidence has been accumulated on the role of hyperhomocysteinemia in the occurrence of coronary artery disease and other arterial occlusive diseases. The mechanism by which high circulating homocysteine concentrations are a risk factor for atherothrombosis is incompletely understood. The present review is aimed to evaluate the role of inflammation in influencing homocysteine (Hcy) and vitamin B

Clin Chem Lab Med 2007;45:1728–36.

Oxidative stress decreases extracellular homocysteine concentration in human hepatoma (HepG2) cell cultures

BACKGROUND

Mild hyperhomocysteinemia is associated with premature vascular disease. The mechanism behind the vascular injuries is, however, still unknown. Homocysteine may be catabolized in the trans-sulfuration pathway to cysteine. Cystathionine beta-synthase, which catalyses the first step in the trans-sulfuration pathway is redox-sensitive. We have therefore investigated total extracellular homocysteine turnover in the presence of oxidative stress in human cell lines.

METHODS

The turnover of total extracellular homocysteine in HeLa and hepatoma cell cultures has been investigated in the presence of hydrogen peroxide. Furthermore, the effect of hydrogen peroxide on the removal of high amounts of exogenously added homocysteine was also studied.

RESULTS

Total extracellular homocysteine concentration in hepatoma cell cultures decreased in the presence of hydrogen peroxide, whereas the extracellular homocysteine concentration in HeLa cell cultures was not influenced. There was no significant change of intracellular homocysteine in any type of cell cultures. Furthermore, the presence of hydrogen peroxide did not increase the removal of exogenously added homocysteine.

CONCLUSION

The presence of hydrogen peroxide probably increases the activity of the trans-sulfuration pathway in hepatoma cell cultures, which increases the intracellular use of homocysteine and lowers its extracellular release. Consequently this mechanism might tend to lower total plasma homocysteine concentration in oxidative stress.

No evidence for oxidative stress as a mechanism of action of hyperhomocysteinemia in humans

Oxidative stress has been suggested as one of the physiopathologic conditions underlying the association of total plasma homocysteine (p-tHcy) with cardiovascular disease (CVD), but this hypothesis has not been validated in human epidemiological studies. We measured plasma and erythrocyte antioxidant enzymes glutathione peroxidase (GPx) and superoxide dismutase (SOD), along with serum lipid-soluble antioxidants alpha-tocopherol, beta-carotene, lycopene and retinol, in a sample of 123 healthy elderly subjects (54 men, 69 women). Plasma malondialdehyde (p-MDA) was determined as a marker of lipid peroxidation, and p-tHcy was quantified by HPLC. No significant differences were found for p-MDA, GPx or SOD activities or serum antioxidant concentrations, in subjects with elevated p-tHcy (> or =15 micromol/l) as compared to those with lower plasma homocysteine. Hyperhomocysteinemia did not lead to increased risk of having the highest p-MDA values, in either sex. We found no evidence that p-tHcy was associated with lipid peroxidation in this elderly human sample. Our results do not support the view that hyperhomocysteinemia would induce an adaptive response of antioxidant systems, either. More epidemiologic and clinical research is needed to clarify whether homocysteine promotes atherosclerosis by means of an oxidative stress mechanism.

Folate supplementation reduces serum hsp70 levels in patients with type 2 diabetes

Type 2 diabetes patients are subject to oxidative stress as a result of hyperglycemia. The aim of this study was to determine whether administration of the antioxidant folic acid, previously shown to reduce homocysteine levels, would reduce circulating levels of Hsp70 while improving the condition of type 2 diabetes patients with microalbuminuria. Plasma homocysteine fell from pretreatment values of 12.9 to 10.3 microM (P < 0.0001). The urine albumin-creatinine ratio fell from 12.4 to 10.4 mg/mM (P = 0.38). Pretreatment Hsp70 levels were higher in patients not taking insulin (5.32 ng/mL) compared with those on insulin (2.44 ng/mL) (P = 0.012). Folic acid supplementation resulted in a significant fall in Hsp70 (5.32 to 2.05 ng/mL) (P = 0.004). There was no change in Hsp70 in those receiving insulin. Folic acid supplementation in non-insulin-treated type 2 diabetes patients, therefore, resulted in a fall in Hsp70, reflecting an improvement in oxidative stress. The data shows that improvement in homocysteine status can lead to a reduction in Hsp70, indicating the possibility of its use as a marker for severity of disease.

Effect of Folic Acid Supplementation on the Folate Status of Buccal Mucosa and Lymphocytes

Folate deficiency may be associated with an increased risk of cancer at certain sites. There is a need to measure folate status and putative biomarkers of cancer risk in the same target tissue, or in surrogate tissues. A study was carried out to develop a method for the rapid measurement of folate in human buccal mucosa and lymphocytes and to evaluate the responsiveness of this measurement in both tissues to folic acid supplementation in healthy subjects, relative to conventional markers of folate status. Three hundred and twenty-three adults, ages between 20 and 60 years, were screened for RBC folate concentrations. Sixty-five subjects with red cell folate between 200 and 650 nmol/L participated in a randomized, double blind, placebo-controlled, folic acid (1.2 mg) intervention trial, lasting 12 weeks. As anticipated, a significant baseline correlation (r = 0.36, P &lt; 0.01) was observed between red cell folate and plasma 5-methyltetrahydrofolate (5-MeTHF). Lymphocyte total folate was significantly associated with plasma 5-MeTHF (r = 0.28, P &lt; 0.05) and plasma total homocysteine concentration (r = −0.34, P &lt; 0.05). Buccal mucosa total folate showed no correlation with either red cell folate or 5-MeTHF, but was significantly associated with lymphocyte total folate (r = 0.35, P &lt; 0.01). Supplementation elicited a significant increase in lymphocyte total folate (P &lt; 0.01), and this was strongly associated with the increase in RBC total folate (P &lt; 0.01) and plasma 5-MeTHF (P &lt; 0.01). Buccal mucosa total folate was not influenced by folate supplementation. Methods have been developed for the rapid measurement of lymphocyte and buccal mucosal total folate. Lymphocyte folate is sensitive to folate intake and is reflected by plasma 5-MeTHF.