Elevated plasma homocysteine elicits an increase in antioxidant enzyme activity

Associations of smoking status with carotid atherosclerosis: Mediated role of blood indexes and blood pressure

BACKGROUND AND AIMS

We aimed to assess the relationship between smoking status and carotid atherosclerosis (CA) with different manifestations and to explore the underlying mechanisms.

METHODS AND RESULTS

A total of 60,655 middle-aged and elderly participants were recruited. Logistic regression models were used to examine the association of smoking, various blood indexes [i.e., blood pressure, blood lipid, glycated hemoglobin (HbA1c) and homocysteine (Hcy)] with CA in different manifestations including carotid intima-media thickness (cIMT), plaques, and stenosis. Compared with nonsmokers, current smokers were associated with a higher prevalence of CA (OR = 3.48, 95%CI: 3.21-3.77) and its specific manifestations including cIMT (OR = 2.66, 95%CI: 2.42-2.93), plaques (OR = 3.67, 95%CI: 3.35-4.02) and stenosis (OR = 2.04, 95%CI: 1.64-2.54), after adjusting for potential confounders. Former smokers were also associated with an increased prevalence of CA (OR = 1.82, 95%CI: 1.54-2.14), cIMT (OR = 1.39, 95%CI: 1.14-1.69), plaques (OR = 2.04, 95%CI: 1.71-2.44) and stenosis (OR = 1.72, 95%CI: 1.18-2.51), but the associations were consistently weaker than that of the current smokers. The prevalence of CA, cIMT, plaques and stenosis among current smokers was positively associated with pack-years of cigarette smoking, partially mediated by SBP, HbA1c, TG, HDL-C and Hcy with a mediated proportion of 1.12%, 3.28%, 6.33%, 6.01% and 12.7%, respectively. Stratified analysis by sex showed a significantly higher CA among the current male smokers than females.

CONCLUSIONS

Current and former smoking was associated with increased carotid atherosclerosis, predominantly by current male smokers. A positive gradient between pack-years and carotid atherosclerosis among current smokers is partially mediated by SBP, HbA1c, TG, HDL-C and Hcy.

Evaluation of Effect of Garlic Aged Extracts and Vitamin B12 on Noise-Induced Hearing Loss

OBJECTIVE

This study investigated effects of S-allylmercaptocysteine (SAMC), diallyl disulfide (DADS), and vitamin B12 on inner ear functions and morphology after long-period high-level broadband noise exposure.

MATERIALS AND METHODS

Twenty-four healthy rats were randomly divided into four groups. First group was chosen as the control group. Vitamin B12, SAMC, and DADS were applied to other groups for 4 weeks. On the 14th day, each group was exposed to broadband noise. Auditory brainstem response test was performed before and immediately after noise exposure and repeated on the 2nd and 14th day.

RESULTS

Permanent threshold shifts were significantly lower in groups treated with vitamin B12, SAMC, and DADS. Histologically, cochleae of SAMC and DADS groups were found to be better preserved than the cochleae of vitamin B12 and control groups.

CONCLUSION

Physiologically and histologically, SAMC and DADS reduced the long-term effects of noise. However, physiological recovery was not consistent with the morphological findings in vitamin B12 group.

Review: Homocysteine, endothelial dysfunction and oxidative stress in type 1 diabetes mellitus

Type 1 diabetes is associated with an increased risk of cardiovascular disease, which cannot be fully explained by traditional risk factors. Elevated plasma homocysteine is an independent risk factor for macrovascular disease in the general population. This review examines the evidence for hyperhomocysteinaemia in patients with type 1 diabetes and describes the mechanisms that may lead to increased macrovascular susceptibility.

While reports of plasma homocysteine levels in type 1 diabetes are inconsistent, increased plasma homocysteine levels have been found in subgroups of patients with microalbuminuria, nephropathy and macrovascular disease. Although a direct causal relationship between plasma homocysteine and atherosclerosis remains to be proven, potential mechanisms of vascular damage by homocysteine include endothelial dysfunction linked to increased oxidative stress. This could contribute to the association between hyperhomocysteinaemia and macrovascular disease in type 1 diabetes.

Nutritional Epidemiology of Antenatal Smoking Cessation Among Japanese Women

This study compared the nutritional status before pregnancy, as well as dietary profiles and biomarkers during first trimester, between never-smokers and antenatal quitters among Japanese women. One hundred fifty pregnant women (79 never-smokers and 71 antenatal quitters) from two obstetrics and gynecology clinics were recruited in Japan. Subjects' prepregnancy nutritional status was indicated by their body mass index (BMI). In the first trimester, their dietary profiles were assessed by the Brief Diet-History Questionnaire (BDHQ) and pregnancy outcomes were screened by biomarker tests. Generalized linear regression was used to examine the differences of energy-adjusted dietary intakes and biomarker results between the two smoking groups, with adjustment of maternal age, BMI, gestation week, and parity. The results showed that antenatal quitters were more likely to have a prepregnancy underweight status than never-smokers. During the first trimester, antenatal quitters had significantly higher intakes of unsaturated fatty acids and antioxidants (vegetable lipids and isoflavone), and lower intakes of total cholesterol than never-smokers. Moreover, antenatal quitters had a significantly higher level of serum homocysteine (6.36 nmol/mL vs 4.88 nmol/mL) than never-smokers. In conclusion, antenatal quitters are more likely to have a poor nutritional status before pregnancy than never-smokers. Quitting smoking before pregnancy and having a good nutritional profile during the trimester may not sufficiently reverse the adverse effects of former smoking behaviors on pregnancy outcomes.

From arylamine N-acetyltransferase to folate-dependent acetyl CoA hydrolase: impact of folic acid on the activity of (HUMAN)NAT1 and its homologue (MOUSE)NAT2

Acetyl Coenzyme A-dependent N-, O- and N,O-acetylation of aromatic amines and hydrazines by arylamine N-acetyltransferases is well characterised. Here, we describe experiments demonstrating that human arylamine N-acetyltransferase Type 1 and its murine homologue (Type 2) can also catalyse the direct hydrolysis of acetyl Coenzyme A in the presence of folate. This folate-dependent activity is exclusive to these two isoforms; no acetyl Coenzyme A hydrolysis was found when murine arylamine N-acetyltransferase Type 1 or recombinant bacterial arylamine N-acetyltransferases were incubated with folate. Proton nuclear magnetic resonance spectroscopy allowed chemical modifications occurring during the catalytic reaction to be analysed in real time, revealing that the disappearance of acetyl CH₃ from acetyl Coenzyme A occurred concomitantly with the appearance of a CH₃ peak corresponding to that of free acetate and suggesting that folate is not acetylated during the reaction. We propose that folate is a cofactor for this reaction and suggest it as an endogenous function of this widespread enzyme. Furthermore, in silico docking of folate within the active site of human arylamine N-acetyltransferase Type 1 suggests that folate may bind at the enzyme’s active site, and facilitate acetyl Coenzyme A hydrolysis. The evidence presented in this paper adds to our growing understanding of the endogenous roles of human arylamine N-acetyltransferase Type 1 and its mouse homologue and expands the catalytic repertoire of these enzymes, demonstrating that they are by no means just xenobiotic metabolising enzymes but probably also play an important role in cellular metabolism. These data, together with the characterisation of a naphthoquinone inhibitor of folate-dependent acetyl Coenzyme A hydrolysis by human arylamine N-acetyltransferase Type 1/murine arylamine N-acetyltransferase Type 2, open up a range of future avenues of exploration, both for elucidating the developmental role of these enzymes and for improving chemotherapeutic approaches to pathological conditions including estrogen receptor-positive breast cancer.

Homocysteine and carotid plaque stability: a cross-sectional study in Chinese adults

BACKGROUND AND PURPOSE

This study aimed to explore the possible association of plasma total homocysteine with carotid plaque stability.

METHODS

A cross-sectional study was conducted from 2010 to 2011. A stratified random sample of 2,919 Chinese participants aged 40 years or older was enrolled. Plasma total homocysteine levels were measured and carotid plaques were evaluated by ultrasonography. Logistic regression model was used to analyze the association of homocysteine levels to the progression of carotid plaque development, while adjusting for demographics and vascular risk factors.

RESULTS

The mean level of plasma homocysteine in the subjects was 14.9 µmol/l. Along with increase in homocysteine level, the risk of advanced carotid plaque elevated (odds ratio = 1.28; 95% confidence interval = 1.09-1.51) after adjusting for age, sex, and other potential confounders. Stratified by sex, higher homocysteine level was strongly associated with advanced carotid plaque in men (OR = 1.41; 95% confidence interval = 1.17-1.70), but not in women.

CONCLUSION

The findings suggest that plasma level of homocysteine may be associated with advanced carotid plaque, which constitutes high risks of stroke, in male Chinese adults.

Effects of dechlorane plus on the hepatic proteome of juvenile Chinese sturgeon (Acipenser sinensis)

Dechlorane Plus (DP), an alternative to decabromodiphenyl ether (BDE-209), is a widely used polychlorinated flame retardant that is frequently detected in aquatic ecosystems. While the mechanisms of toxicity of BDE-209 have been well documented, less is known about the toxicity of DP. In this study, juvenile Chinese sturgeon (Acipenser sinensis) were treated with DP at doses of 1, 10, and 100mg/kg wet weight for 14 days via a single intraperitoneal injection (i.p.). After 14 days, liver proteomes of juvenile Chinese sturgeon were analyzed using two-dimensional electrophoresis (2-DE) coupled matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometry (MALDI-TOF/TOF-MS). A total of 39 protein spots were significantly altered in abundance (>2-fold) and of these proteins, 27 were successfully identified. Proteins related to the stress response that included heat shock cognate protein 70 and T-complex protein 1 were significantly increased and decreased in abundance, respectively. Moreover, Ras-related protein Rab-6B and GDP dissociation inhibitor 2, proteins that are involved in small G-protein signal cascades, were decreased in abundance 2- to 5-fold. Annexin A4, which is associated with Ca(2+) signaling pathways, was also markedly decreased by 2-fold in the liver. Pathway analysis of differentially regulated proteins revealed that DP interfered with metabolism and was associated with proteins related to apoptosis and cell differentiation. Based upon protein responses, we suggest that DP has effects on the generalized stress response, small G-protein signal cascades, Ca(2+) signaling pathway, and metabolic process, and may induce apoptosis in the liver. This study offers novel mechanistic insight into the protein responses induced in the liver with DP, an increasingly used and understudied flame retardant.

Association between homocysteine status and the risk of nephropathy in type 2 diabetes mellitus

BACKGROUND

It is well documented that hyperhomocysteinemia induces renal injury. However, the association between homocysteine level and type 2 diabetic nephropathy (T2DN) remains elusive.

METHODS

We evaluated the alteration of plasma level of homocysteine in T2DN patients with macroalbuminuria or microalbuminuria compared with type 2 diabetes mellitus (T2DM) controls without albuminuria by performing a meta-analysis. We searched the PubMed, Embase and Cochrane databases from January 1990 to October 2013 to identify studies that met predefined criteria.

RESULTS

Seven studies were included in this investigation. T2DN patients with macroalbuminuria demonstrated a significantly higher level of plasma homocysteine than T2DM without albuminuria (4 studies, random effects SMD: 1.66, 95% CI: 0.46 to 2.87, P=0.007) and T2DN with microalbuminuria (3 studies, random effects SMD: 0.99, 95% CI: 0.62 to 1.36, P<0.001). T2DN patients with microalbuminuria demonstrated significantly higher level of plasma homocysteine than T2DM without albuminuria (6 studies, random effects SMD: 1.29, 95%. CI: 0.59 to 2, P<0.001). Exclusion of any single study had little impact on the pooled SMDs. No evidence of publication bias was observed.

CONCLUSIONS

Our findings indicate that the status of plasma homocysteine is associated with both the risk and severity of nephropathy in T2DM. Frequent monitoring and early intervention should be recommended.

Differential regulation of DNA methylation versus histone acetylation in cardiomyocytes during HHcy in vitro and in vivo: an epigenetic mechanism

The mechanisms of homocysteine-mediated cardiac threats are poorly understood. Homocysteine, being the precursor to S-adenosyl methionine (a methyl donor) through methionine, is indirectly involved in methylation phenomena for DNA, RNA, and protein. We reported previously that cardiac-specific deletion of N-methyl-d-aspartate receptor-1 (NMDAR1) ameliorates homocysteine-posed cardiac threats, and in this study, we aim to explore the role of NMDAR1 in epigenetic mechanisms of heart failure, using cardiomyocytes during hyperhomocysteinemia (HHcy). High homocysteine levels activate NMDAR1, which consequently leads to abnormal DNA methylation vs. histone acetylation through modulation of DNA methyltransferase 1 (DNMT1), HDAC1, miRNAs, and MMP9 in cardiomyocytes. HL-1 cardiomyocytes cultured in Claycomb media were treated with 100 μM homocysteine in a dose-dependent manner. NMDAR1 antagonist (MK801) was added in the absence and presence of homocysteine at 10 μM in a dose-dependent manner. The expression of DNMT1, histone deacetylase 1 (HDAC1), NMDAR1, microRNA (miR)-133a, and miR-499 was assessed by real-time PCR as well as Western blotting. Methylation and acetylation levels were determined by checking 5'-methylcytosine DNA methylation and chromatin immunoprecipitation. Hyperhomocysteinemic mouse models (CBS+/-) were used to confirm the results in vivo. In HHcy, the expression of NMDAR1, DNMT1, and matrix metalloproteinase 9 increased with increase in H3K9 acetylation, while HDAC1, miR-133a, and miR-499 decreased in cardiomyocytes. Similar results were obtained in heart tissue of CBS+/- mouse. High homocysteine levels instigate cardiovascular remodeling through NMDAR1, miR-133a, miR-499, and DNMT1. A decrease in HDAC1 and an increase in H3K9 acetylation and DNA methylation are suggestive of chromatin remodeling in HHcy.

Lack of association of homocysteine concentrations with oxidative stress, alterations in carotid intima media thickness and endothelial reactivity in prepubertal children

BACKGROUND AND AIMS

Our purpose was to assess the presence of risk factors for cardiovascular diseases (alterations in the lipid profile, fasting glycaemia, high arterial pressure values, oxidative stress, increased intima media thickness and impaired endothelium-dependent vasodilation) in prepubertal children with elevated homocysteine (Hcy) levels.

METHODS

In a cross-sectional study, 35 children with Hcy levels ≥7.3 μmol/l were matched by gender and age with 29 children with Hcy levels ≤4.1 μmol/l. Our collected data included weight, height, waist circumference, systemic arterial pressure, lipid profile, fasting glycaemia and oxidative stress markers. A Doppler ultrasound was performed to measure the carotid intima media thickness and the endothelium-dependent vasodilation of the brachial artery.

RESULTS

There were no statistically significant differences between the groups regarding the lipid profile and fasting glycaemia, blood pressure or oxidative stress. Overweight and obesity (body mass index z-score > +1) were more frequent in the group with Hcy ≥7.3 μmol/l when compared to the group with Hcy ≤4.1 μmol/l [13/35 (37.1%) vs. 4/29 (13.8%); p = 0.035]. After adjusting for nutritional status, there were no differences in the intima media thickness and endothelium-dependent vasodilation between children with high and low Hcy levels.

CONCLUSIONS

Among the cardiovascular risk factors investigated in the present study, which was based on prepubertal children, only overweight and obesity were associated with increased Hcy concentrations (≥7.3 μmol/l).

Elevated homocysteine and carotid plaque area and densitometry in the Northern Manhattan Study

BACKGROUND AND PURPOSE

Studies have linked elevated total homocysteine (tHcy) levels to atherosclerotic carotid plaque development, but data are limited to predominantly white populations. We examined the association between tHcy and carotid plaque burden and morphology in a multiethnic cohort.

METHODS

In the Northern Manhattan Study, we conducted a cross-sectional analysis among 1327 stroke-free subjects (mean age, 66 ± 9; 41% men; 19% black; 62% Hispanic; 17% white) with serum tHcy and ultrasonographic assessment of plaque morphology measured by gray-scale median (GSM) and total plaque area (TPA). GSM and TPA were examined in 4 categories. High and low GSM categories were considered echodense and echolucent plaque, respectively, and compared with no plaque. Logistic regression models were used to assess the associations of tHcy with GSM and TPA adjusting for demographics, vascular risk factors, renal insufficiency, and B(12) deficiency.

RESULTS

The mean tHcy was 9.4 ± 4.8 µmol/L (median=8.6). The prevalence of carotid plaque was 57% (52% among Hispanics, 58% black, and 70% white). Among those with plaque, the mean TPA was 20.3 ± 20.6 mm(2) (median=13.6) and mean GSM 90.9 ± 28.5 (median=93.0). The top 2 tHcy quartiles (versus quartile 1) had an elevated risk of having either echolucent plaque (tHcy Q3, odds ratio [OR]=1.8; [95% confidence interval {CI} 1.2-2.8]; tHcy Q4, OR=1.9 [95% CI 1.2-3.1]) or echodense plaque (tHcy Q3, OR=1.7 [95% CI, 1.1-2.7]; tHcy Q4, OR=1.9 [95% CI, 1.2-3.2]). The top 2 tHcy quartiles were also more likely to be in the highest TPA category (tHcy Q3, OR=1.8 [95% CI, 1.1-3.0]; tHcy Q4, OR=2.2 [95% CI, 1.3-3.7]).

CONCLUSIONS

In this population-based multiethnic cohort, elevated tHcy was independently associated with plaque morphology and increased plaque area, subclinical markers of stroke risk.

Methyl deficient diet aggravates experimental colitis in rats

Inflammatory bowel diseases (IBD) result from complex interactions between environmental and genetic factors. Low blood levels of vitamin B12 and folate and genetic variants of related target enzymes are associated with IBD risk, in population studies. To investigate the underlying mechanisms, we evaluated the effects of a methyl-deficient diet (MDD, folate, vitamin B12 and choline) in an experimental model of colitis induced by dextran sodium sulphate (DSS), in rat pups from dams subjected to the MDD during gestation and lactation. Four groups were considered (n= 12–16 per group): C DSS⁻ (control/DSS⁻), D DSS⁻ (deficient/DSS⁻), C DSS⁺ (control/DSS⁺) and D DSS⁺ (deficient/DSS⁺). Changes in apoptosis, oxidant stress and pro-inflammatory pathways were studied within colonic mucosa. In rat pups, the MDD produced a decreased plasma concentration of vitamin B12 and folate and an increased homocysteine (7.8 ± 0.9 versus 22.6 ± 1.2 μmol/l, P < 0.001). The DSS-induced colitis was dramatically more severe in the D DSS⁺ group compared with each other group, with no change in superoxide dismutase and glutathione peroxidase activity, but decreased expression of caspase-3 and Bax, and increased Bcl-2 levels. The mRNA levels of tumour necrosis factor (TNF)-α and protein levels of p38, cytosolic phospolipase A2 and cyclooxygenase 2 were significantly increased in the D DSS⁺ pups and were accompanied by a decrease in the protein level of tissue inhibitor of metalloproteinases (TIMP)3, a negative regulator of TNF-α. MDD may cause an overexpression of pro-inflammatory pathways, indicating an aggravating effect of folate and/or vitamin B12 deficiency in experimental IBD. These findings suggest paying attention to vitamin B12 and folate deficits, frequently reported in IBD patients.

Lipid metabolism and body composition in Gclm(-/-) mice

In humans and experimental animals, high fat diets (HFD) are associated with risk factors for metabolic diseases, such as excessive weight gain and adiposity, insulin resistance and fatty liver. Mice lacking the glutamate-cysteine ligase modifier subunit gene (Gclm(-/-)) and deficient in glutathione (GSH), are resistant to HFD-mediated weight gain. Herein, we evaluated Gclm-associated regulation of energy metabolism, oxidative stress, and glucose and lipid homeostasis. C57BL/6J Gclm(-/-) mice and littermate wild-type (WT) controls received a normal diet or an HFD for 11 weeks. HFD-fed Gclm(-/-) mice did not display a decreased respiratory quotient, suggesting that they are unable to process lipid for metabolism. Although dietary energy consumption and intestinal lipid absorption were unchanged in Gclm(-/-) mice, feeding these mice an HFD did not produce excess body weight nor fat storage. Gclm(-/-) mice displayed higher basal metabolic rates resulting from higher activities of liver mitochondrial NADH-CoQ oxidoreductase, thus elevating respiration. Although Gclm(-/-) mice exhibited strong systemic and hepatic oxidative stress responses, HFD did not promote glucose intolerance or insulin resistance. Furthermore, HFD-fed Gclm(-/-) mice did not develop fatty liver, likely resulting from very low expression levels of genes encoding lipid metabolizing enzymes. We conclude that Gclm is involved in the regulation of basal metabolic rate and the metabolism of dietary lipid. Although Gclm(-/-) mice display a strong oxidative stress response, they are protected from HFD-induced excessive weight gain and adipose deposition, insulin resistance and steatosis.

Molecular targets of TBBPA in zebrafish analysed through integration of genomic and proteomic approaches

Tetrabromobisphenol-A (TBBPA) is nowadays one of the most frequently used brominated flame retardants (BFRs) and can be considered as a high production volume chemical. Over the last decade, numerous reports of increasing concentrations of BFRs in the environment and humans have been published. However, the toxicological knowledge on TBBPA, and more specifically its molecular mode of action, is rather fragmentary. In this study two populations of adult zebrafish (Danio rerio) were exposed for 14 days to 0.75 microM and 1.5 microM TBBPA. Subsequently, we employed a combined transcriptomic and proteomic approach to evaluate the molecular effects of TBBPA in zebrafish liver. Oligonucleotide microarrays were used to study the effects on gene expression levels. These results were validated through real-time PCR. The proteome of the liver was analysed by means of differential in-gel electrophoresis (DiGE), an innovative application of traditional 2D-PAGE. Combination of the extracted datasets allowed reassembling of individual molecular responses into a comprehensive overview of affected molecular pathways. Interpretation of the results depicted an interference of thyroid and Vitamin A homeostasis in the exposed zebrafish, TBBPA also elicited responses indicating onset of oxidative stress and general stress responses. Additionally, numerous differentially expressed transcripts could be associated with defence mechanisms or corresponded to metabolizing enzymes. Furthermore, cellular metabolism was clearly affected, illustrated as disturbance of e.g. lipid, carbohydrate, and organic acid metabolic processes. Summarizing, these results enabled us to hypothesize several working mechanisms of TBBPA and demonstrated the potential of a combined genome and proteome approach to generate detailed mechanistic toxicological information.

Association of MTRR 66A>G polymorphism with superoxide dismutase and disease activity in patients with Crohn's disease

OBJECTIVES

The aim of this study was to evaluate the association of nutritional (folate, vitamin B12) and genetic (MTHFR, MTR, MTRR, TCN) determinants of homocysteine metabolism and of superoxide dismutase with Crohn's disease (CD).

METHODS

One hundred forty patients with CD were compared with 248 matched healthy controls.

RESULTS

Plasma homocysteine levels were higher in CD patients than controls (11.8 vs 10.4 micromol/L, P= 0.0004). Vitamin B12 and folate levels were lower in CD subjects compared to controls (207 vs 255 pmol/L, P= 0.0082, and 8.6 vs 11 nmol/L, P= 0036, respectively). Patients with a personal history of ileal resection, ileitis, or colectomy had significantly lower vitamin B12 levels. In multivariate analysis, vitamin B12 and MTHFR 677 TT carriers were the two significant independent factors of plasma homocysteine >15 micromol/L in CD patients (P= 0.0187 and 0.0048, respectively). The significant association between homocysteine and vitamin B12 levels remained significant only in patients with the highest superoxide dismutase values (P < 0.0001). The MTRR AA genotype was a significant independent predictor of CD risk (odds ratio 3.7, 95% CI 1.218-11.649, P= 0.0213). The level of superoxide dismutase was significantly higher (P= 0.0143) and was correlated with Crohn's Disease Activity Index (CDAI) scores (P for trend = 0.0276) in patients carrying MTRR AA genotype.

CONCLUSIONS

Vitamin B12 and MTHFR 677 TT genotype are the main determinants of hyperhomocysteinemia in CD patients. The association of MTRR 66A>G polymorphism with oxidant stress and disease activity provides rationale for screening vitamin deficiencies in these patients.

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.

Preferential response of glutathione-related enzymes to folate-dependent changes in the redox state of rat liver

BACKGROUND

Oxidative stress likely constitutes an important contributing factor in the onset of degenerative diseases associated with folate deficiency. Direct, as well as homocysteine-linked, antioxidant properties of folate could explain its preventive effect on these pathologies.

AIM OF THE STUDY

Our study aimed at determining the changes in the redox status of adult rats as a function of folate intake.

METHODS

Adult male rats were pair-fed for 4 weeks with a semi-synthetic diet containing 0, 0.5, 1.5, 8 or 20 mg of folic acid/kg. Folate and homocysteine concentrations, redox status markers and antioxidant enzyme activities were measured in the plasma and/or liver of the rats. A principal component analysis of the overall data was performed to draw a general scheme of the changes observed between the conditions.

RESULTS

Folate deficiency caused increased homocysteinemia and features of oxidative stress including reduced plasma antioxidant capacity together with increased lipid peroxidation in liver and heart. This was associated with an increase in the specific activity of several enzymes involved in liver glutathione metabolism (glutathione peroxidase, glutathione reductase and glutathione S-transferase), suggesting an adaptive tissue response to the oxidative stress induced by folate deficiency. In contrast, no such variation was observed for hepatic superoxide dismutase and catalase.

CONCLUSION

Despite no changes in hepatic levels of total glutathione, our findings indicate that glutathione-dependent antioxidant pathways could be particularly involved in the compensatory mechanism committed by liver to counteract the oxidative stress induced by folate deficiency. They also suggest that folate supplementation may not be associated with a better antioxidant protection of rats.

Hyperhomocysteinaemia induced by dietary folate restriction causes kidney oxidative stress in rats

Diet is the most common cause of mild hyperhomocysteinaemia (HHcy), which occurs in approximately 5–7 % of the general population. Since HHcy causes endothelial damage by oxidative stress in different organs, the present study was designed to examine whether HHcy might be involved in renal oxidative stress. Twenty-five male Wistar rats were randomly divided into two groups: one (n13) was fedad libituma folate-free diet (FF) and the other (n12) was fed the same diet supplemented with folic acid (control, CO). After 8 weeks the animals were killed and kidneys removed. Malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities were measured in plasma and kidney homogenates. Renal tissue sections were analysed by indirect immunostaining with the primary antibody against oxidatively modified LDL receptor (LOX-1). A marked HHcy was confirmed in the FF group. As compared with CO animals, MDA levels in plasma and kidney homogenate were significantly higher in FF rats (P<0·05). Similarly, renal GPx and SOD activities were significantly higher in the FF group (P<0·001). No differences were found in LOX-1 immunohistochemical expression, which in the two groups was displayed in tubular cells. The present study provides evidence that HHcy does produce renal oxidative stress mediated by lipid peroxidation, and that the increased kidney MDA displayed by FF animals may enhance kidney antioxidant activity and thereby attenuate both kidney damage and expression of LOX-1.

Plasma homocysteine, oxidative stress and endothelial function in patients with Type 1 diabetes mellitus and microalbuminuria

AIMS

The purpose of this study was to examine the associations between endothelial function, plasma homocysteine and oxidative stress in patients with Type 1 diabetes mellitus (DM) and microalbuminuria compared with DM patients with normoalbuminuria and non-diabetic control subjects. We wished to test the hypothesis that increased cardiovascular risk in patients with Type 1 diabetes and microalbuminuria may be in part as a result of hyperhomocysteinaemia-mediated oxidative stress leading to impaired endothelial function.

METHODS

We measured forearm blood flow, total plasma homocysteine, total antioxidant status (TAOS) and whole blood glutathione in 31 DM patients, 16 with microalbuminuria and 15 with normoalbuminuria, and 15 non-diabetic control subjects.

RESULTS

Plasma homocysteine levels were significantly higher in the microalbuminuric diabetic patients compared with the normoalbuminuric patients and the control subjects. TAOS was significantly lower in the micoalbuminuric and normoalbuminuric diabetic patients compared with the control subjects, although TAOS levels were similar in both groups of diabetic patients. There was no difference in forearm blood flow between the groups and no association between measured endothelial function and antioxidant defence/oxidative stress and homocysteine in each group. There was no association between plasma total homocysteine and TAOS or whole blood glutathione within the groups.

CONCLUSIONS

We have found mild hyperhomocysteinaemia in microalbuminuric DM patients compared with normoalbuminuric DM patients and non-diabetic subjects and some evidence for reduced antioxidant defence in DM patients. These findings add to our understanding of the increased risk of vascular disease in patients with Type 1 diabetes.

Proteomic analysis reveals changes in the liver protein pattern of rats exposed to dietary folate deficiency

Epidemiologic and experimental studies showed that folate deficiency is associated with increased risk of degenerative diseases by enhancing abnormal one-carbon metabolism. We studied the changes in the proteome of liver, the main tissue of folate storage and metabolism, in a rat model of dietary folate depletion. Four-month-old rats were fed for 4 wk an amino acid-defined diet without folate and compared with pair-fed rats given the same diet adequately supplemented with folic acid. Folate deprivation decreased plasma and hepatic folate concentrations dramatically, while increasing homocysteinemia significantly. Using 2-dimensional electrophoresis and matrix-assisted laser desorption/ionization time-of-flight MS, we identified 9 spots corresponding to differentially expressed proteins in the liver of folate-deficient rats compared with controls. Among those spots, 4 had a significantly increased volume, whereas the volume of the 5 other spots was decreased. Upregulated proteins included glutathione peroxidase (GPx) 1 and peroxiredoxin 6, 2 enzymes involved in the response to oxidative stress, and MAWD binding protein (MAWDBP), which has been associated with cancer. MAWDBP was simultaneously identified as a second spot with a lower isoelectric point (pI) that vanished almost completely after folate deficiency. Decreased abundance was also observed for cofilin 1, a protein linked to tumorigenesis, and for the GRP 75 precursor and preproalbumin, both of which are responsive to oxidative stress and/or inflammation. Moreover, an enzyme activity assay and/or Western blot analysis of GPx-1 and MAWDBP confirmed the proteomic findings. Our results show that folate deficiency modifies the abundance of several liver proteins consistently with adaptive tissue responses to oxidative and degenerative processes.

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.

Comparative analysis of serum homocysteine, folic acid and Vitamin B12 levels in patients with noise-induced hearing loss

OBJECTIVE

The aim of the present study was to determine the levels of homocysteine, folic acid, and Vitamin B12 in subjects with noise-induced hearing loss. Furthermore, possible links between these parameters and noise-induced hearing loss were aimed to be evaluated.

METHODS

In the present study, blood samples were obtained from all subjects after overnight fasting for biochemical analysis. We examined the levels of homocysteine, Vitamin B12 and folic acid levels in subjects with noise-induced hearing loss. Twenty-eight male patients with noise-induced hearing loss (mean age 37 +/- 5 year) were included in the study group whereas the control group was composed of 32 healthy male volunteers (mean age 36 +/- 4 year).

RESULTS

It was found that homocysteine levels of subjects with noise-induced hearing loss as significantly high compared to healthy controls (P < 0.05). On the other hand, Vitamin B12 and folic acid levels of patients with noise-induced hearing loss were determined to be significantly low compared to the controls (P < 0.05 and < 0.01, respectively).

CONCLUSION

Our findings indicate that there might be a link between increased homocysteine levels and noise-induced hearing loss. Since increased homocysteine levels cause elevated levels of free radicals in addition to its atherogenic and thrombogenic effects. Further experimental studies are needed to decipher how this relationship is linked.

Homocysteine and cardiovascular disease in renal disease. Review Article

Elevated homocysteine (hyperhomocysteinaemia) in renal patients is a major concern for physicians. Although cause and effect between homocysteine and cardiovascular disease (CVD) has not been established in either the general population or renal patients, there is much evidence that this relationship does exist. Purported mechanisms that may explain this effect include increases in endothelial injury, smooth muscle cell proliferation, low-density lipoprotein oxidation and changes in haemostatic balance. Renal patients have a much greater incidence of hyperhomocysteinaemia and this may be explained by decreases in either the renal or extrarenal metabolism of the compound. We conclude that data from long-term placebo-controlled trials are urgently required to determine whether hyperhomocysteinaemia in renal patients is a cause of CVD events and requires therapeutic targeting.

Effects of prostaglandin E1, melatonin, and oxytetracycline on lipid peroxidation, antioxidant defense system, paraoxonase (PON1) activities, and homocysteine levels in an animal model of spinal cord injury

STUDY DESIGN

Investigation of the effects of prostaglandin E1, melatonin, and oxytetracycline on lipid peroxidation, antioxidant and paraoxonase activities, and homocysteine levels in an experimental model of spinal cord injury.

OBJECTIVES

To determine the antioxidant efficacy of prostaglandin E1, melatonin, and oxytetracycline and whether paraoxonase and homocysteine can be used as monitoring parameters in the acute oxidative stress of spinal cord injury.

SUMMARY OF BACKGROUND DATA

Melatonin has been found useful in spinal cord injury in previous studies. No study exists investigating the effects of melatonin, prostaglandin E1, and oxytetracycline as well as the response type of paraoxonase enzyme and homocysteine levels in the acute oxidative stress of spinal cord injury.

METHODS

Sixty-three male albino Wistar rats were anesthetized with 400 mg/kg chloral hydrate and divided into 5 groups. The G1 (n = 7) control group provided the baseline levels. G2-G5 underwent T3-T6 total laminectomies and spinal cord injuries by clip compression at the T4-T5 levels. Medications were applied to G3-G5 right after clip compression. Hence, G2 constituted laminectomy + injury, G3 laminectomy + injury + prostaglandin E1; G4 laminectomy + injury + melatonin, and G5 laminectomy + injury + oxytetracycline groups. Animals were decapitated either the first or fourth hour after injury. Spinal cord tissue and blood malonyldialdehyde and plasma homocysteine levels, plasma glutathione peroxidase, superoxide dismutase, paraoxonase activities were assayed. The SPSS 9.0 program was used for statistical analysis and graphics. Intergroup comparisons were made by Bonferroni corrected Mann Whitney U test (P < 0.025) and intragroups comparisons by Wilcoxon Rank test (P < 0.03).

RESULTS

In injury groups, plasma homocysteine levels decreased and paraoxonase activities increased as erythrocyte superoxide dismutase levels and plasma glutathione peroxidase activities decreased in parallel to increases of tissue and blood malonyldialdehyde levels. These alterations were relatively suppressed by prostaglandin E1, melatonin, and oxytetracycline administrations in varying degrees. Melatonin was the most powerful agent, particularly at the fourth hour. Oxytetracycline was also effective, both at the first and fourth hour. Prostaglandin E1 was effective in comparison to injury group, but not as much as melatonin and oxytetracycline.

CONCLUSIONS

Melatonin and oxytetracycline are effective in preventing lipid peroxidation in spinal cord injury. Paraoxonase and homocysteine can be used in monitoring the antioxidant defense system as well as superoxide dismutase and plasma glutathione peroxidase, both in injury and medicated groups.

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

BACKGROUND

Various mechanisms have been proposed to explain the association between plasma total homocysteine (tHcy) and risk of cardiovascular disease, including oxidative activity of homocysteine.

OBJECTIVE

To explore the putative role of reactive oxygen species in the association between plasma tHcy and risk of cardiovascular disease in healthy individuals.

DESIGN

A double-blind, placebo-controlled crossover intervention to increase folate intake through diet (increased consumption of folate-rich foods) and supplement (400 micro g folic acid) was carried out in 126 healthy men and women. Measurements were made of antioxidant activity in red blood cells and plasma, and products of oxidant damage in plasma.

RESULTS

Diet and supplement-based interventions led to an increase in measures of folate status and a reduction in plasma tHcy. This was not associated with any significant change in measures of antioxidant activity (plasma and red blood cell glutathione peroxidase activity and red blood cell superoxide dismutase activity) or oxidant damage (plasma malondialdehyde), although an improvement in plasma total antioxidant capacity just failed to reach significance.

CONCLUSIONS

In healthy individuals lowering plasma tHcy does not have any functional implications regarding oxidative damage.

Vitamin C therapy ameliorates vascular endothelial dysfunction in treated patients with homocystinuria

OBJECTIVES

We sought to investigate the effects of short- and long-term vitamin C therapy on endothelial dysfunction in patients with homocystinuria.

BACKGROUND

Untreated homocystinuria due to cystathionine beta-synthase deficiency is associated with premature atherothrombotic disease; 25% of untreated patients suffer a vascular event by the age of 16 years and 50% by 29 years. Treatment directed at reducing homocysteine accumulation significantly reduces this risk. However, despite 'optimal' treatment and compliance, hyperhomocysteinaemia usually persists and individuals exhibit endothelial dysfunction indicative of an adverse cardiovascular prognosis. Additional intervention is therefore required to further reduce cardiovascular risk.

METHODS

We investigated the endothelial effects of acute (2 g single dose) and chronic (1 g/day for 6 months) administration of oral vitamin C in 5 patients with homocystinuria (mean age 26 years, 1 male) and 5 age- and sex-matched controls. Brachial artery endothelium-dependent flow-mediated dilatation (FMD) and endothelium-independent responses to nitroglycerin (NTG) were measured using high-resolution ultrasonic vessel wall-tracking.

RESULTS

Baseline: Plasma total homocysteine was 100.8 +/- 61.6 and 9.2 +/- 1.9 micromol/L in the patient and control groups, respectively (p < 0.001). FMD responses were impaired in the patient group (20 +/- 40 microm) compared with the controls (116 +/- 30 microm) (p < 0.001). Vitamin C administration: FMD responses in the patient group improved both acutely, 160 +/- 65 microm at 4 h (p < 0.001), and chronically, 170 +/- 70 microm at 2 weeks (p < 0.001) and 170 +/- 40 microm at 6 months (p < 0.001). FMD responses in the control group were unaltered (p = 0.526). Within both groups, neither the vascular response to NTG nor plasma homocysteine was altered (p > 0.4).

CONCLUSIONS

Vitamin C ameliorates endothelial dysfunction in patients with homocystinuria, independent of changes in homocysteine concentration and should therefore be considered as an additional adjunct to therapy to reduce the potential long-term risk of atherothrombotic disease.

Correlates of plasma homocysteine, cysteine and cysteinyl-glycine in respondents in the British National Diet and Nutrition Survey of young people aged 4-18 years, and a comparison with the survey of people aged 65 years and over

Plasma total homocysteine (tHcy), cysteine and cysteinyl-glycine were measured in a representative sample of 922 young people aged 4-18 years, participating in the National Diet and Nutrition Survey in mainland Britain in 1997. Both tHcy and cysteine increased markedly with age; cysteinyl-glycine less so. Neither tHcy nor cysteine differed between genders; cysteinyl-glycine was higher in males. tHcy concentrations were lowest in the winter; cysteine and cysteinyl-glycine varied only slightly with season. In respondents aged >15 years, tHcy was higher in smokers, but in respondents aged 7-11 years, tHcy was higher in those whose mothers smoked. tHcy was inversely correlated with serum folate, serum vitamin B12 and vitamin B6 status, but neither cysteine nor cysteinyl-glycine shared these relationships. The relationships between tHcy and B-vitamin status indices ran parallel with those of the 65 years and over survey, but at much lower tHcy concentrations for any given B-vitamin concentration. Age-adjusted tHcy was not correlated with anthropometric indices, blood pressure, haematology, plasma creatinine, urea or cholesterol, but was directly correlated with fasting triacylglycerol. We conclude that disease-risk indices, like tHcy and perhaps cysteine, if established during early life, may be modulated by diet and lifestyle, thereby providing an opportunity for public health intervention.

Evidence against oxidative stress as mechanism of endothelial dysfunction in methionine loading model

Endothelial dysfunction reflects reduced nitric oxide (NO) bioavailability due to either reduced production, inactivation of NO, or reduced smooth muscle responsiveness. Oral methionine loading causes acute endothelial dysfunction in healthy subjects and provides a model in which to study mechanisms. Endothelial function was assessed using flow-mediated dilatation (FMD) of the brachial artery in humans. Three markers of oxidative stress were measured ex vivo in venous blood. NO responsiveness was assessed in vascular smooth muscle and platelets. Oral methionine loading induced endothelial dysfunction (FMD decreased from 2.8 +/- 0.8 to 0.3 +/- 0.3% with methionine and from 2.8 +/- 0.8 to 1.3 +/- 0.3% with placebo; P < 0.05). No significant changes in measures of plasma oxidative stress or in vascular or platelet sensitivity to submaximal doses of NO donors were detected. These data suggest that oxidative stress is not the mechanism of endothelial dysfunction after oral methionine loading. Furthermore, the preservation of vascular and platelet NO sensitivity makes a signal transduction abnormality unlikely.