Enhanced in vivo lipid peroxidation at elevated plasma total homocysteine levels

Homozygous MTHFR C667T carriers ≤45 years old develop central retinal vein occlusion five years earlier than wild type

PURPOSE

To assess age at 1st central retinal vein occlusion (CRVO) in carriers ≤ 45 years old of the methylenetetrahydrofolate reductase (MTHFR) C667T genotype compared to heterozygous and wild type, and to identify predictors of age at CRVO.

METHODS

Retrospective cohort study consisting of 18 MTHFR TT, 23 MTHFR TC and 28 MTHFR CC participants; information regarding age, sex, age at CRVO, history of dyslipidaemia, hypertension, smoking and plasma HC measured by immunoassay were collected.

RESULTS

Age at CRVO was lower in MTHFR TT than MTHFR TC and CC (32 ± 6 vs 38 ± 5 vs 37 ± 6 years, respectively, p = 0.005); plasma HC was higher in MTHFR TT than in the other genotypes [14.4 (10.8, 19.6) vs 10.4 ((8.6,12.5) vs 8.5 ((7.5,9.8) μmol/l, p = 0.0002). Smoking (cigarettes/day) independently predicted age at CRVO (p = 0.039) and plasma HC (p = 0.005); smoking status (yes/no) predicted ischemic CRVO (p = 0.01) that was more common in the MTHFR TT group (p = 0.006).

CONCLUSIONS

Carriers of the MTHFR TT genotype ≤ 45 years old develop their 1st CRVO on average 5 years earlier than the MTHFR CC genotype; smoking contributes to the prematurity and severity of CRVO in MTHFR TT carriers.

Homozygous MTHFR C677T carriers develop idiopathic portal vein thrombosis 20 years earlier than wild type

The aim of this study was to evaluate the impact of methylene tetrahydrofolate reductase (MTHFR) rs1801133 (C→T667 transition) on age at first idiopathic portal vein thrombosis (PVT) and to identify clinical and/or laboratory variables influencing age at first PVT, including plasma homocysteine and the prothrombin rs1799963 PT (G→A transition at position 20210) (PT) mutation. A retrospective cross-sectional cohort, including 15 MTHFR TT, 32 MTHFR TC and 22 MTHFR CC idiopathic PVT participants contributing demographics, age at PVT, plasma concentrations of homocysteine and of natural anticoagulants. MTHFR TT carriers presented with a lower age at PVT than heterozygous or wild-type genotypes (31 ± 8 vs. 48 ± 15 vs. 52 ± 13 years, P  = 0.001) and were more likely to have a plasma HC concentration above the cut-off (73.3 vs. 32 vs. 50%, P  = 0.04). MTHFR TT and protein C predicted age at PVT ( P  < 0.0001 and P  = 0.06); MTHFR TT predicted plasma homocysteine ( P  = 0.05). In the MTHFR TT group, plasma homocysteine inversely related to protein C ( P  = 0.03). Plasma homocysteine predicted the extent of PVT ( P  = 0.03). Compound MTHFR TT + PT GA did not lower age at first PVT compared to MTHFR TT alone (35 ± 9 vs. 30 ± 8 years). MTHFR TT is associated with a 20-year earlier PVT presentation than heterozygous and wild-type MTHFR genotypes. The inverse relation between plasma homocysteine and protein C contributes to the prematurity of PVT in the MTHFR TT group, whereas plasma homocysteine contributes to the extent of PVT. The recent exclusion of MTHFR genotyping from the thrombophilia screen needs revisiting in this setting.

Nitrous Oxide Abuse: Clinical Outcomes, Pharmacology, Pharmacokinetics, Toxicity and Impact on Metabolism

The recreational use of nitrous oxide (N2O), also called laughing gas, has increased significantly in recent years. In 2022, the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) recognized it as one of the most prevalent psychoactive substances used in Europe. Chronic nitrous oxide (N2O) exposure can lead to various clinical manifestations. The most frequent symptoms are neurological (sensitive or motor disorders), but there are also other manifestations like psychiatric manifestations or cardiovascular disorders (thrombosis events). N2O also affects various neurotransmitter systems, leading to its anesthetic, analgesic, anxiolytic and antidepressant properties. N2O is very challenging to measure in biological matrices. Thus, in cases of N2O intoxication, indirect biomarkers such as vitamin B12, plasma homocysteine and plasma MMA should be explored for diagnosis and assessment. Others markers, like oxidative stress markers, could be promising but need to be further investigated.

Interference of altered plasma trace elements profile with hyperhomocysteinemia and oxidative stress damage to insulin secretion dysfunction in Psammomys obesus: focus on the selenium

The objective of this study is to investigate the relationship between altered plasma trace elements, particularly selenium (Se), with Hyper-homocysteinemia (HhCys) as a predictive factor of insulin secretion dysfunction. The study is carried out on adult Psammomys obesus, divided in 4 experimental groups: (I) Normoglycemic/Normoinsulinemic; (II) Normoglycemic/Hyperinsulinemic; (III) Hyperglycaemic/Hyperinsulinemic and (IV) Hyperglycaemic/Insulin deficiency with ketoacidosis. The data showed that a drastic depletion of Se plasma levels is positively correlated with HhCys (>15 µmol/L; p < .001), concomitantly with decreased GPx activity, GSH levels, and GSH/GSSG ratio in group IV both in plasma and liver. In contrast, SOD activity is increased (p ≤ .001) in group IV both in plasma and liver. However, plasma Cu and Mn levels increased, while plasma Zn levels decreased in group IV (p < .001). Our study confirms the increase of plasma hCys levels seemed to be a major contributing factor to antioxidant capacities and alters the availability of selenium metabolism by interference with homocysteine synthesis in the insulin secretion deficiency stage.

Oxidative Stress and Cardiovascular Risk Factors: The Coronary Artery Risk Development in Young Adults (CARDIA) Study

Introduction—Oxidative stress is linked to cardiovascular diseases (CVD) and is suggested to vary by sex. However, few population-level studies have explored these associations and the majority comprise populations with advanced CVD. We assessed urinary isoprostane concentrations, a standard measure of oxidative stress, in a relatively young and healthy cohort, hypothesizing that higher oxidative stress is associated with an adverse cardiometabolic profile and female sex. Methods—Oxidative stress was measured in 475 women and 266 men, aged 48–55 years, from the Coronary Artery Risk Development in Young Adults (CARDIA) study using urinary 8-isoprostane (IsoP) and 2,3-dinor-8-isoprostane (IsoP-M). Multivariable-adjusted regression was used to evaluate cross-sectional associations. As secondary analysis, previously measured plasma F2-isoprostanes (plasma IsoP) from another CARDIA subset was similarly analyzed. Results—Mean (SD) ages for men and women were 52.1(2.3) and 52.2(2.2) years, respectively (p = 0.46), and 39% of the participants self-identified as Black (vs. White). Before adjustments, female sex was associated with higher median urinary IsoP (880 vs. 704 ng/g creatinine in men; p < 0.01) and IsoP m (1675 vs. 1284 ng/g creatinine in men; p < 0.01). Higher body mass index (BMI), high-density cholesterol (HDL-C), and triglycerides, current smoking, and less physical activity were associated with higher oxidative stress. Diabetes was not associated with urinary IsoP but was associated with lower IsoP m and plasma IsoP. Higher serum creatinine showed diverging associations with higher plasma and lower urinary isoprostane concentrations. Conclusions—Different isoprostane entities exhibit varying association patterns with CVD risk factors, and therefore are complementary, rather than interchangeable, in assessment of oxidative stress. Still, consistently higher isoprostanes among women, smokers, less active persons, and those with higher BMI and plasma triglycerides could reflect higher oxidative stress among these groups. While urinary isoprostanes are indexed to urinary creatinine due to variations in concentration, caution should be exercised when comparing groups with differing serum creatinine.

SARS-CoV-2 Infection: What Is Currently Known about Homocysteine Involvement?

Since December 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread rapidly throughout the world causing health, social and economic instability. The severity and prognosis of patients with SARS-CoV-2 infection are associated with the presence of comorbidities such as cardiovascular disease, hypertension, chronic lung disease, cerebrovascular disease, diabetes, chronic kidney disease, and malignancy. Thrombosis is one of the most serious complications that can occur in patients with COVID-19. Homocysteine is a non-proteinogenic α-amino acid considered a potential marker of thrombotic diseases. Our review aims to provide an updated analysis of the data on the involvement of homocysteine in COVID-19 to highlight the correlation of this amino acid with disease severity and the possible mechanisms by which it intervenes.

Exploration for biomarkers of postpartum depression based on metabolomics: A systematic review

BACKGROUND

Postpartum depression (PPD) is the most frequent psychiatric complication during the postnatal period and its mechanisms are not fully understood. Metabolomics, can quantitatively measure metabolites in a high-throughput method, and thus uncover the underlying pathophysiology of disease.

OBJECTIVES

In this study, we reviewed metabolomics studies conducted on PPD, aiming to understand the changes of metabolites in PPD patients and analyze the potential application of metabolomics in PPD prediction and diagnosis.

METHODS

Relevant articles were searched in PubMed, Google scholar, and Web of Science databases from January 2011 to July 2022. The metabolites involved were systematically examined and compared. MetaboAnalyst online software was applied to analyze metabolic pathways.

RESULTS

A total of 14 papers were included in this study. There were several highly reported metabolites, such as kynurenine, kynurenic acid, and eicosapentaenoic acid. Dysregulation of metabolic pathways involved amino acids metabolism, fatty acids metabolism, and steroids metabolism.

LIMITATIONS

The included studies are relatively inadequate, and further work is needed.

CONCLUSIONS

This study summarized significant metabolic alterations that provided clues for the prediction, diagnosis, and pathogenesis of PPD.

Liver Cirrhosis Patients Homozygous for MTHFR C677T Develop Portal Vein Thrombosis 8 Years Earlier Than Wild Type

BACKGROUND AND AIM

Age at portal vein thrombosis (PVT) in liver cirrhosis (LC) carriers of the methylene tetrahydrofolate reductase (MTHFR) rs1801133 (C → T667 transition) polymorphism has never been addressed; we compared age at PVT in LC patients genotyped for the MTHFR and explored the interrelated clinical and laboratory factors predicting age at PVT.

APPROACH AND RESULTS

Retrospective cross-sectional cohort study. PVT participants: MTHFR CC n = 36, MTHFR CT n = 53, MTHFR TT n = 19; age, sex, age at PVT, Child-Pugh score, rs1799963 PT polymorphisms (G → A 20,210 transition), plasma HC and natural anticoagulants available for all participants. Age at PVT was lower in MTHFR TT than CT and CC (56 ± 13 vs. 57 ± 13 vs. 64 ± 9 years, p = 0.001); median (IQR) plasma HC was higher in MTHFR TT than in the other groups [(17 (9.4, 23.3) vs 13 (8,14.7) vs 11 (8.9, 12.7) μmol/l, p = 0.03)]. MTHFR TT, male gender and protein C predicted age at PVT (p = 0.02, p = 0.04 and p = 0.08); MTHFR TT and Child-Pugh score predicted plasma HC (p = 0.005 and p = 0.01) as well as low plasma protein C (p < 0.0001 and p = 0.0002). Plasma HC inversely related to protein C in the MTHFR TT group (p < 0.0001). Compound MTHFR TT with PT GA had lower age at PVT compared to MTHFR TT alone (49 ± 18 vs 58 ± 12 years).

CONCLUSIONS

MTHFR TT anticipates PVT associated with LC by an average of 8 years; MTHFR TT associates with severity of liver disease and to high plasma HC; the latter may contribute to the prematurity of PVT by interfering with the anticoagulant activity of protein C.

Juvenile patients with the homozygous MTHFR C677T genotype develop ischemic stroke 5 years earlier than wild type

To compare age at 1st ischaemic stroke (IS) in a cohort of juvenile (< 46 years of age) IS patients evaluated for the rs1801133 polymorphism (C → T677) of the methylene tetrahydrofolate reductase (MTHFR) gene; to identify predictors of age at IS and of type of cerebral vessel involvement, small vessel disease (SVD) vs large vessel disease (LVD) responsible for the IS; to evaluate possible associations between other clinical and laboratory variables. Retrospective cohort study on 82 MTHFR TT, 54 MTHFR TC and 34 MTHFR CC participants; data regarding age, sex, age at IS, history of dyslipidaemia, hypertension, smoking, migraine and homocysteine (HC) as well as neuroimaging were collected. Age at IS was lower in MTHFR TT than MTHFR TC and CC (35 ± 4 vs 38 ± 0 vs 40 ± 3 years, respectively, p = 0.002); plasma HC (median, interquartile range) was higher in MTHFR TT than in the other groups [16.7 (11.8, 28.6) vs 11.4 (8.2, 16.1) vs 9.8 (7.9, 1.3) respectively, p < 0.0001)] and was higher in SVD than LVD [17.4 (12.4, 32.5) vs  11.4 (8.8, 16.4) p < 0.0001]. MTHFR TT independently predicted age at IS (p = 0.0008) alongside smoking both as a categorical (p = 0.003) or continuous variable (p = 0.02), whereas HC independently predicted SVD as categorical (p = 0.01) and continuous variable (p < 0.0001). Smoking positively predicted plasma HC (p = 0.005) and negatively the activated partial thromboplastin ratio (aPTTr) (p = 0.02). Juvenile IS carriers of the MTHFR TT genotype develop their 1st occlusion on average 5 years earlier compared to the CC genotype; smoking contributes to this prematurity adversely affecting plasma HC and coagulation whereas plasma HC predicts IS secondary to SVD. Public health campaigns against smoking should highlight the prematurity of IS in the juvenile population.

Endothelium-derived Microparticles Are Increased in Teenagers With Cobalamin Deficiency

INTRODUCTION

Vitamin B 12 (cobalamin) deficiency may be a significant cause of hyperhomocysteinemia, and high homocysteine (Hcy) levels are associated with an increased risk of cardiovascular disease. Endothelium-derived microparticles (EMPs) are a new marker in endothelial dysfunction and atherosclerosis, which play a role in cardiovascular diseases' pathogenesis. This study aimed to evaluate the EMPs, the markers of endothelial dysfunction and atherosclerosis, and lipid profile in teenagers with cobalamin deficiency.

MATERIALS AND METHODS

This prospective study included 143 teenagers, 75 vitamin B 12 deficient patients and 68 healthy controls between 11 and 18 years of age. Routine laboratory tests, hemogram, vitamin B 12 , folic acid, ferritin, Hcy, lipid profile and EMPs were examined and compared. EMP subgroups were analyzed by flow cytometry method according to the expression of membrane-specific antigens. The microparticles released from the endothelium studied were VE-cadherin (CD144), S-endo1 (CD146), and Endoglin (CD105).

RESULTS

The present study demonstrates that circulating CD105+ EMP, CD144+ EMP, CD146+ EMPs, and Hcy were increased, and high-density lipoprotein (HDL) cholesterol was reduced in teenagers with cobalamin deficiency. Vitamin B 12 showed a negative correlation with EMPs and Hcy, positive correlation with folate and HDL. All EMPs showed a significant positive correlation with triglyceride, vitamin B 12 , and HDL.

CONCLUSION

Vitamin B 12 deficiency may predispose to endothelial damage and atherosclerosis by increasing EMPs and harms lipid metabolism in the long term.

Biochemical basis and metabolic interplay of redox regulation

Accumulated evidence strongly indicates that oxidative stress, characterized by an imbalance between reactive oxygen species (ROS) production and antioxidants in favor of oxidants, plays an important role in disease pathogenesis. However, ROS can act as signaling molecules and fulfill essential physiological functions at basal levels. Each ROS would be different in the extent to stimulate and contribute to different pathophysiological effects. Importantly, multiple ROS generators can be activated either concomitantly or sequentially by relevant signaling molecules for redox biological functions. Here, we summarized the current knowledge related to chemical and biochemical features of primary ROS species and corresponding antioxidants. Metabolic pathways of five major ROS generators and five ROS clearance systems were described, including their ROS products, specific ROS enriched tissue, cell and organelle, and relevant functional implications. We provided an overview of ROS generation and induction at different levels of metabolism. We classified 11 ROS species into three types based on their reactivity and target selectivity and presented ROS homeostasis and functional implications in pathological and physiological status. This article intensively reviewed and refined biochemical basis, metabolic signaling and regulation, functional insights, and provided guidance for the identification of novel therapeutic targets.

Association between homocysteine level and blood pressure traits among Tibetans: A cross-sectional study in China

Studies on hypertension (HTN) in Tibetans who live in high altitude areas are less and whether total homocysteine level (tHcy) is associated with blood pressure (BP) levels or HTN status in Tibetans is unknown.A total of 1486 Tibetans with complete information from a cross-sectional survey conducted in Lhasa Chengguan County of Tibet were included in this study. Demographic data, self-reported history of disease, and life styles were collected using a questionnaire. Blood tHcy, creatinine, fasting plasma-glucose, total cholesterol, triglycerides, and BP were measured with equipment.The median tHcy level of the whole population was 14.60 (13.17-16.50) μmol/L, and the prevalence of HTN was 26.99%. Regression models, adjusted for possible covariates, showed that an average increase of 1 lnHcy (log transformation of tHcy level) was associated with an increase of 3.78 mmHg of systolic BP (SBP, P = .011) and 3.02 mmHg of diastolic BP (DBP, P = .003). The prevalence of HTN, levels of SBP and DBP in the third (OR for HTN: 1.60, P = .026; β for SBP: 3.41, P = .004; β for DBP: 2.57, P = .002) and fourth (OR for HTN: 2.19, P < .001; β for SBP: 5.08, P < .001; β for DBP: 3.09, P < .001) quartile of tHcy level were higher than those in the first quartile.THcy is associated with BP levels and HTN status among Tibetans. Both HTN management and tHcy level should be paid more attention in Tibetans.

Predictive Value of Oxidized Low-Density Lipoprotein/β2-Glycoprotein-I Complexes (oxLDL/β2GPI) in Nonautoimmune Atherothrombosis

INTRODUCTION

Lipid oxidation is a definite feature of atherosclerosis, and oxidized low-density lipoprotein (oxLDL) is not only highly immunogenic but toxic to several cell types. Beta-2-glycoprotein-I (β₂GPI) dampens oxLDL toxicity by forming binary oxLDL/β₂GPI complexes. We evaluated whether circulating oxLDL/β₂GPI complexes are associated to atherosclerosis-related events (ARE) and to venous thromboembolism (VTE).

METHODS

In a cross-sectional case-control study, cases were (a) 57 consecutive patients (male/female [M/F] 33/24, mean age 57 [10] years) attending a thrombosis unit for ARE (myocardial infarction [MI] n = 20, peripheral vascular disease n = 7, and ischemic strokes n = 30); (b) 52 consecutive patients (M/F 22/30, mean age 55 [17] years) attending the same unit for unprovoked (VTE); (c) normal controls comprised 90 participants (M/F 35/55, mean age 41 [15] years); and (d) oxLDL/β₂GPI complexes were measured by immunoassay and resulting levels divided into quartiles.

RESULTS

The odds ratio (OR) of ARE was greater in the fourth and second quartiles than in the first quartile (8.5 and 6.0, respectively); the OR of developing MI was greatest in the fourth quartile (17.8). By multivariable analysis with age, sex, smoking, lipid status, statin, and ARE phenotypes as independent variables and oxLDL/β₂GPI as the dependent variable, only MI predicted oxLDL/β₂GPI ( P < .0001).

CONCLUSIONS

OxLDL/β₂GPI may be regarded as a marker of ARE, in particular of MI.

Oxidative stress and platelet activation in subjects with moderate hyperhomocysteinaemia due to MTHFR 677 C→T polymorphism

The methylenetetrahydrofolate reductase (MTHFR) 677 C→T polymorphism may be associated with elevated total homocysteine (tHcy) levels, an independent risk factor for cardiovascular disease. It was the study objective to evaluate in vivo lipid peroxidation and platelet activation in carriers of the MTHFR 677 C→T polymorphism and in non-carriers, in relation to tHcy and folate levels. A cross-sectional comparison of urinary 8-iso-prostaglandin (PG)F2α and 11-dehydro-thromboxane (TX)B2 (markers of in vivo lipid peroxidation and platelet activation, respectively) was performed in 100 carriers and 100 non-carriers of the polymorphism. A methionine-loading test and folic acid supplementation were performed to investigate the causal relationship of the observed associations. Urinary 8-iso-PGF2α and 11-dehydro-TXB2 were higher in carriers with hyperhomocysteinaemia than in those without hyperhomocysteinaemia (p<0.0001). Hyperhomocysteinaemic carriers had lower folate levels (p=0.0006), higher urinary 8-iso-PGF2α (p<0.0001) and 11-dehydro-TXB2 (p<0.0001) than hyperhomocysteinaemic non-carriers. On multiple regression analysis, high tHcy (p<0.0001), low folate (p<0.04) and MTHFR 677 C→T polymorphism (p<0.001) independently predicted high rates of 8-iso-PGF2α excretion. Methionine loading increased plasma tHcy (p=0.002), and both urinary prostanoid metabolites (p=0.002). Folic acid supplementation was associated with decreased urinary 8-iso-PGF2α and 11-dehydro-TXB2 excretion (p<0.0003) in the hyperhomocysteinaemic group, but not in the control group, with substantial inter-individual variability related to baseline tHcy level and the extent of its reduction. In conclusion, hyperhomocysteinaemia due to the MTHFR 677 C→T polymorphism is associated with enhanced in vivo lipid peroxidation and platelet activation that are reversible, at least in part, following folic acid supplementation. An integrated biomarker approach may help identifying appropriate candidates for effective folate supplementation.

Homocysteine as a Pathological Biomarker for Bone Disease

In the last few decades, perturbation in methyl-group and homocysteine (Hcy) balance have emerged as independent risk factors in a number of pathological conditions including neurodegenerative disease, cardiovascular dysfunction, cancer development, autoimmune disease, and kidney disease. Recent studies report Hcy to be a newly recognized risk factor for osteoporosis. Elevated Hcy levels are known to modulate osteoclastgenesis by causing detrimental effects on bone via oxidative stress induced metalloproteinase-mediated extracellular matrix degradation and decrease in bone blood flow. Evidence from previous studies also suggests that the decreased chondrocytes mediated bone mineralization in chick limb-bud mesenchymal cells and during the gestational period of ossification in rat model. However, Hcy imbalance and its role in bone loss, regression in vascular invasion, and osteoporosis, are not clearly understood. More investigations are required to explore the complex interplay between Hcy imbalance and onset of bone disease progression. This article reviews the current body of knowledge on regulation of Hcy mediated oxidative stress and its role in bone remodeling, vascular blood flow and progression of bone disease. J. Cell. Physiol. 232: 2704-2709, 2017. © 2016 Wiley Periodicals, Inc.

Plasma and Aorta Biochemistry and MMPs Activities in Female Rabbit Fed Methionine Enriched Diet and Their Offspring

This study investigated whether a high Met diet influences biochemical parameters, MMPs activities in plasma, and biochemical and histological remodeling in aorta, in both pregnant female rabbits and their offspring. Four female rabbit groups are constituted (each n = 8), nonpregnant control (NPC), pregnant control (PC) that received normal commercial chow, nonpregnant Met (NPMet), and pregnant Met (PMet) that received the same diet supplemented with 0,35% L-methionine (w/w) for 3 months (500 mg/d). All pregnant females realize 3 successive pregnancies. Plasma results showed that Met excess increased Hcy, raised CRP in NPMet and decreased it in PMet, enhanced significantly proMMP-2 and proMMP-9 activities in NPMet, and reduced them in PMet. Aorta showed a rise in collagen level, essentially in PMet, a reduction of elastin content in both PMet and NPMet, and a significant decrease in lipid content in PMet, with histological changes that are more pronounced in NPMet than PMet. Met excess enhanced proMMP-9 activities in NPMet while it decreased them in PMet. PMet newborn presented increase in uremia and CRP and significant rise of active MMP-2 and MMP-9 forms. In aorta, media and adventitia thickness increased, total lipids content decreased, proMMP-9 activity decreased, and proMMP-2 activity increased.

Assessment of Isoprostanes in Human Plasma: Technical Considerations and the Use of Mass Spectrometry

Oxygenated lipid mediators released from non-enzymatic peroxidation of polyunsaturated fatty acids (PUFA) are known to have functional roles in humans. Notably, among these lipid mediators, isoprostanes molecules are robust biomarkers of oxidative stress but those from n-3 PUFA are also bioactive molecules. In order to identify and assess the isoprostanes, the use of mass spectrometry (MS) for analysis is preferable and has been used for over two decades. Gas chromatography (GC) is commonly coupled to the MS to separate the derivatized isoprostanes of interest in biological samples. In order to increase the accuracy of the analytical performance, GC-MS/MS was also applied. Lately, MS or MS/MS has been coupled with high-performance liquid chromatography to assess multiple isoprostane molecules in a single biological sample without derivatization process. However, there are limitations for the use of LC-MS/MS in the measurement of plasma isoprostanes, which will be discussed in this review.

Plasma Homocysteine, Vitamin B12 and Folate Levels in Multiple System Atrophy: A Case-Control Study

Background

Multiple system atrophy (MSA) is a neurodegenerative disease, and its pathological hallmark is the accumulation of α-synuclein proteins. Homocysteine (Hcy) is an intermediate amino acid generated during the metabolism of methionine. Hcy may contribute to the pathogenesis of neurodegenerative disorders. Vitamin B12 and folate are cofactors necessary for the methylation of homocysteine.

Methods

This study compared the levels of serum Hcy, vitamin B12 and folate in patients with MSA with those in healthy people to reveal the possible association between MSA and plasma levels of Hcy, vitamin B12 and folate. We enrolled 161 patients with MSA and 161 healthy people in this study. The association between MSA and the levels of Hcy, vitamin B12 and folate were analyzed using binary logistic regression.

Results

The mean level of Hcy in patients with MSA was significantly higher than that in healthy controls (16.23 ± 8.09 umol/l vs 14.04 ± 4.25 umol/l, p < 0.05). After adjusting for age, sex and medical history, the odds ratio for Hcy was 1.07 (95% CI = 1.01–1.13, p < 0.05) for patients with MSA. Vitamin B12 and folate levels were not significantly different between patients with MSA and controls.

Conclusion

Our data suggest that higher levels of Hcy may be associated with an increased risk for MSA.

Activation of AMP-activated protein kinase protects against homocysteine-induced apoptosis of osteocytic MLO-Y4 cells by regulating the expressions of NADPH oxidase 1 (Nox1) and Nox2

BACKGROUND

Elevated plasma homocysteine (Hcy) level is associated with the risk of osteoporotic fracture. While Hcy increases oxidative stress, AMP-activated protein kinase (AMPK) activation ameliorates it. This study aimed to investigate whether Hcy induces apoptosis of osteocytic MLO-Y4 cells through regulating expressions of oxidant and anti-oxidant enzymes and determine the effects of AMPK activation by 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR) and metformin on the Hcy-induced apoptosis of the cells.

RESULTS

DNA fragment ELISA and TUNEL staining assays showed that Hcy treatments (0.1-5.0 mM) induced apoptosis of MLO-Y4 cells in a dose-dependent manner. The detrimental effect of Hcy was partly but significantly reversed by an antioxidant (N-acetylcysteine) and NADPH oxidase (Nox) inhibitors (apocynin and diphenyleneiodonium). In addition, treatment with AICAR (0.05-0.1 mM) and metformin (10-100 μM) ameliorated Hcy-induced apoptosis of the cells. The favorable effect of metformin on Hcy-induced apoptosis was completely canceled by an AMPK inhibitor Ara-A. Hcy increased the expression levels of Nox1 and Nox2, while it had no effects on the expressions of Nox4 or the anti-oxidant enzymes, superoxide dismutase 1 and 2. Hcy-induced increases in the expressions of Nox1 and Nox2 decreased significantly by treatments with AICAR.

CONCLUSION

These findings suggest that Hcy induces apoptosis of osteocytes by increasing the expressions of Nox1 and Nox2, and AMPK activation by AICAR and metformin effectively prevents the detrimental reactions. Thus, AMPK activation may be a potent therapeutic candidate for preventing Hcy-induced osteocyte apoptosis and the resulting bone fragility.

Oxidative stress, insulin resistance, dyslipidemia and type 2 diabetes mellitus

Oxidative stress is increased in metabolic syndrome and type 2 diabetes mellitus (T2DM) and this appears to underlie the development of cardiovascular disease, T2DM and diabetic complications. Increased oxidative stress appears to be a deleterious factor leading to insulin resistance, dyslipidemia, β-cell dysfunction, impaired glucose tolerance and ultimately leading to T2DM. Chronic oxidative stress, hyperglycemia and dyslipidemia are particularly dangerous for β-cells from lowest levels of antioxidant, have high oxidative energy requirements, decrease the gene expression of key β-cell genes and induce cell death. If β-cell functioning is impaired, it results in an under production of insulin, impairs glucose stimulated insulin secretion, fasting hyperglycemia and eventually the development of T2DM.

High‑dose folic acid improves endothelial function by increasing tetrahydrobiopterin and decreasing homocysteine levels

The aim of this study was to investigate the effect of folic acid (FA) on tetrahydrobiopterin (BH4), neopterin, nitric oxide (NO) and homocysteine (Hcy) levels in endothelial cells. Human umbilical vein endothelial cells (HUVECs) were cultured in vitro in the presence or absence of Hcy. The effect of various doses of FA on Hcy, BH4, neopterin and NO concentrations in HUVECs was then assessed. In the 5 and 10 nmol/l FA treatment groups, FA was found to significantly increase the levels of BH4 (10.56±3.86 and 11.23±2.1919 pmol/g vs 6.32+2.87 nmol/g; P<0.05 vs. control) and NO production (37.86±12.34 nmol/l, 38.45±11.23 nmol/l vs 26.21±9.24 nmol/l; P<0.001 vs. paired Hcy group), but reduce the levels of Hcy (132.87±29.67 and 140.87±26.76 nmol/l vs. 165.23±30.56 nmol/l; P<0.05 vs. Hcy group). No significant differences were observed in neopterin levels among the different groups of HUVECs. In conclusion, high doses of FA may be capable of protecting endothelial cells through reducing levels of Hcy and increasing BH4 and NO production.

Differential expression of lipid peroxidation and total antioxidant status in Indian patients with cardiovascular and cerebrovascular disease

Data from studies examining lipid peroxidation as a mechanism involved with hyperhomocysteinemia (HHcy)-induced vascular remodeling in patients with occlusive vascular disease have been contradictory. It has not yet been studied in Indians within the context of atherogenesis. Therefore, we measured the levels of homocysteine (Hcy), malondialdehyde (MDA) as a measure of lipid peroxides (LPOs), and total antioxidant status (TAS) in the serum of 167 patients with occlusive vascular disease [coronary artery disease (CAD) = 43; cerebrovascular disease (CVD) = 82; peripheral vascular disease (PVD) = 42]. Each of these groups was further divided into groups of individuals with or without HHcy. In the case of CAD and CVD, patients with HHcy had significantly higher LPOs than those without HHcy (p = 0.009, 0.001, respectively). TAS was significantly lower in CVD patients with HHcy than in those without (p = 0.014). In patients with CAD or CVD, Hcy directly correlated with LPOs (p = 0.002, 0.001, respectively). Lipid peroxidation is a significant mechanism in HHcy-induced vascular remodeling in CAD and CVD, but not in PVD, probably because it is not relevant in thrombosis (38 of 42 patients of PVD had deep-vein thrombosis). To explain the significantly lower TAS in CVD, we hypothesized that CVD patients present very early with grave symptoms, whereas CAD and PVD occur over a longer period of time. Therefore, when CVD presents, TAS is still overwhelmed by HHcy-induced oxidative stress. Hence, adjuvant therapy with antioxidants would benefit patients with CVD.

F2-isoprostanes as markers of oxidant stress: an overview

The isoprostanes are a unique series of prostaglandin-like compounds formed in vivo via a non-enzymatic mechanism involving the free radical-initiated peroxidation of arachidonic acid. This unit summarizes selected aspects regarding current knowledge of these compounds and their value as markers of oxidative injury. Novel aspects related to the biochemistry of isoprostane formation are discussed and methods by which these compounds can be analyzed and quantified are summarized. A considerable portion of this unit examines the utility of F(2)-isoprostanes as markers of oxidant injury in vitro and in vivo. Numerous studies carried out over the past decade have shown that these compounds are extremely accurate measures of lipid peroxidation in animals and humans and have illuminated the role of oxidant injury in a number of human diseases.

Seminal plasma levels of 15-F2α-isoprostane, malondialdehyde and total homocysteine in normozoospermic and asthenozoospermic males

It has been proposed that oxidative stress plays an important role in male infertility. The aims of this study were to compare seminal plasma levels of 15-F2t-isoprostane (8-iso-PGF2α), malondialdehyde (MDA), and total (sum of free and bound) homocysteine (tHcy) from normozoospermic vs. asthenozoospermic men, and to examine the relationships between tHcy and lipid peroxidation products. The study was a case-control study with a simple random sampling. The case group was consisted of 15 asthenozoospermic males. This group was compared with 15 normozoospermic men. Seminal plasma levels of 15-F2α-isoprostane and tHcy were measured using commercially available enzyme immunoassay (EIA) kits. MDA levels were determined by the thiobarbituric acid (TBA) assay. The Mann-Whitney U test was used to compare two groups. Coefficients of correlation were calculated using Spearman's correlation analysis. All hypothesis tests were two-tailed with statistical significance assessed at the p value <0.05 level. MDA levels were higher in asthenozoospermic subjects than in control subjects (0.72±0.06 μM vs. 0.40±0.06 μM; p<0.05). No differences were seen in 15-F2α-isoprostane levels in asthenozoospermic subjects and controls (65.00±3.20 pg/ml vs. 58.17±4.12 pg/ml; p>0.05). Interestingly, tHcy levels were to be slightly higher in asthenozoospermic subjects than in controls (6.18±1.17 μM vs. 4.8±0.52 μM). Sperm motility was inversely correlated with seminal plasma 15-F2α-isoprostane and MDA levels, respectively (p<0.05). In summary, seminal plasma levels of 15-F2α-isoprostane and tHcy showed no significant difference between normozoospermic and asthenozoospermic men. Sperm motility was not correlated with seminal plasma levels of tHcy. No relationship was found between tHcy and lipid peroxidation.

Evaluation of oxidative stress markers and cardiovascular risk factors in Fabry Disease patients

Fabry Disease, an X-linked inborn error of metabolism, is characterized by progressive renal insufficiency, with cardio and cerebrovascular involvement. Homocysteine (Hcy) is considered a risk factor for vascular diseases, but the mechanisms by which it produces cardiovascular damage are still poorly understood. Regarding the vascular involvement in FD patients, the analysis of factors related to thromboembolic events could be useful to improving our understanding of the disease. The aim of this study was to evaluate plasma Hcy and other parameters involved in the methionine cycle, as well as oxidative stress markers. The sample consisted of a group of 10 male FD patients and a control group of 8 healthy individuals, paired by age. Venous blood was collected for Hcy determination, molecular analysis, identification of thiobarbituric acid reactive substances, total glutathione and antioxidant enzymes activity, as well as vitamins quantification. Comparative analysis of FD patients versus the control group indicated hyperhomocysteinemia in 8 of the 10 FD patients, as well as a significant increase in overall glutathione levels and catalase activity. It is inferred that FD patients, apart from activation of the antioxidant system, present increased levels of plasma Hcy, although this is probably unrelated to common alterations in the methionine cycle.

Enzymatic and non-enzymatic antioxidative effects of folic acid and its reduced derivates

A great part of the population appears to have insufficient folate intake, especially subgroups with higher demand, as determined through more sensitive methods and parameters currently in use. As the role of folate deficiency in congenital defects, e.g. in cardiovascular and neurodegenerative diseases, and in carcinogenesis has become better understood, folate has been recognized as having great potential to prevent these many disorders through folate supplementation or fortification for the general population. Folates are essential cofactors in the transfer and utilization of one-carbon groups in the process of DNA-biosynthesis with implications for genomic repair and stability. Folate acts indirectly to lower homocysteine levels and insures optimal functioning of the methylation cycle. Homocysteine was shown to be an independent risk factor for neurodegenerative and cardiovascular disease, which includes peripheral vascular disease, coronary artery disease, cerebrovascular disease and venous thrombosis. In fact, it was long believed that the beneficial effects of folate on vascular function and disease are related directly to the mechanism of homocysteine-diminution. Recent investigations have, however, demonstrated beneficial effects of folates unrelated to homocysteine-diminution, suggesting independent properties. One such mechanism could be free radical scavenging and antioxidant activity, as it is now recognized that free radicals play an important role in the oxidative stress leading to many diseases. It was found that folic acid and, in particular, its reduced derivates act both directly and indirectly to produce antioxidant effects. Folates interact with the endothelial enzyme NO synthase (eNOS) and, exert effects on the cofactor bioavailability of NO and thus, on peroxynitrite formation. Folate metabolism provides an interesting example of gene-environmental interaction.

F2-isoprostanes as an indicator and risk factor for coronary heart disease

Coronary heart disease (CHD) is the leading single cause of death in the United States and most Western countries, killing more than 400,000 Americans per year. Although CHD often manifests suddenly as a fatal myocardial infarction, the atherosclerosis that gives rise to the infarction develops gradually and can be markedly slowed or even reversed through pharmacological and lifestyle interventions. These same atherosclerotic processes also drive related vascular diseases such as stroke and peripheral artery disease, and individuals surviving occlusive events often develop additional complications including ischemic cardiomyopathy and heart failure. Therefore, better detection of subclinical atherosclerosis, along with more effective treatments, could significantly reduce the rate of death from CHD and related vascular diseases in the United States. In recent years, oxidation of polyunsaturated fatty acids (PUFAs) in plasma lipoproteins has been postulated to be a critical step in the development of atherosclerosis. If so, then monitoring lipid peroxidation should be a useful indicator of disease risk and progression. This review focuses on the evidence that specific PUFA peroxidation products, the F(2)-isoprostanes, are useful biomarkers that could potentially be utilized as indicators of CHD.

Novel risk factors in long-term hypertension incidence in type 1 diabetes mellitus

BACKGROUND

Data from longitudinal studies suggest that biomarkers of inflammation and endothelial dysfunction are associated with development of hypertension. None of these studies have examined the association of these markers with hypertension risk in persons with diabetes. We examined the associations of inflammatory and endothelial dysfunction markers with long-term hypertension incidence in persons with type 1 diabetes mellitus.

METHODS

The 15-year cumulative incidence of hypertension was measured in Wisconsin Epidemiologic Study of Diabetic Retinopathy participants (n = 795). Hypertension was defined as a systolic blood pressure > or =140 mm Hg and/or a diastolic blood pressure > or =90 mm Hg and/or history of current antihypertensive treatment. We measured serum high-sensitivity C-reactive protein, interleukin-6, tumor necrosis factor-alpha, soluble vascular cell adhesion molecule-1 (sVCAM-1), soluble intercellular adhesion molecule-1, and serum total homocysteine as "novel" markers of hypertension development. The relation of risk factors to hypertension incidence was determined using a proportional hazards approach with discrete linear logistic regression modeling.

RESULTS

After controlling for age, gender, diabetes duration, body mass index, glycosylated hemoglobin, baseline systolic and diastolic blood pressure, proteinuria, and chronic kidney disease status, sVCAM-1 was significantly related to higher odds of developing incident hypertension (odds ratio per log sVCAM-1 1.95, 95% CI 1.01-3.74). None of the other markers of inflammation and endothelial dysfunction were related to incident hypertension in the cohort.

CONCLUSIONS

Our data showed that sVCAM-1 as a marker of endothelial dysfunction was the strongest predictor of hypertension risk in individuals with type 1 diabetes. This association was independent of the presence of diabetic nephropathy.

Oxidant stress in HIV-infected women from the Women's Interagency HIV Study

BACKGROUND

Oxidant stress contributes to the pathogenesis of multiple conditions and can be assessed by measuring plasma F(2)-isoprostane concentrations. We hypothesized that oxidant stress is associated with plasma homocysteine concentration and risk factors for atherosclerosis in HIV-infected women.

METHODS

We measured plasma F(2)-isoprostane concentrations in a cross-sectional study of 249 HIV-infected women attending the Bronx (NY, USA) site of the Women's Interagency HIV Study and assessed associations with plasma homocysteine concentration and other metabolic parameters by linear regression.

RESULTS

In multivariate analysis, hepatitis C virus (HCV) viraemia, waist circumference, homocysteine concentration and serum aspartate aminotransferase level were positively associated with log F(2)-isoprostane concentration (all P<0.005). There was a trend for an inverse association between log F(2)-isoprostane and CD4(+) T-cell percentage (P=0.06). Among women with HCV infection, the FIB-4 index, an indirect marker of liver fibrosis derived from routine laboratory tests, was positively associated with log F(2)-isoprostane concentration.

CONCLUSIONS

In this cross-sectional study of HIV-infected women, plasma F(2)-isoprostane concentration was positively associated with homocysteine concentration, as well as HCV infection, abdominal obesity and aspartate aminotransferase level.

Dietary intake and urinary excretion of lignans in Finnish men

Intake of lignans has been assessed in different study populations, but so far none of the studies has compared the daily intake of lignans and the urinary excretion of plant and enterolignans. We assessed the intake of lariciresinol, pinoresinol, secoisolariciresinol and matairesinol in 100 Finnish men consuming their habitual omnivorous diet, and measured the 24 h urinary excretion of plant and enterolignans to compare the intake and metabolism. Dietary determinants of lignan intake and their urinary excretion were also determined. The mean intake of lignans was 1224 (sd 539) mug/d, of which lariciresinol and pinoresinol covered 78 %. Almost half (47 %) of the intake of lignans was explained by the intake of rye products, berries, coffee, tea and roots. The urinary excretion of plant lignans corresponded to 17 % and enterolignans to 92 % of the intake of lignans. The urinary excretion of plant lignans was explained 14 % by the intake of rye products and intake of coffee, and consequently 3-7 % by the intake of water-insoluble fibre. The urinary excretion of enterolactone was explained 11 % by the intake of vegetables and rye products, 14 % by the intake of water-soluble fibre and only 4 % by the intake of lariciresinol. Although the assessed intake of lignans corresponded well with the urinary excretion of lignans, the enterolactone production in the human body depended more on the dietary sources of lignans than the absolute intake of lignans.

F(2)-isoprostanes as novel biomarkers for type 2 diabetes: a review

Oxidative stress (OS) has been implicated as one of the major underlying mechanisms behind many acute and chronic diseases. However, the measurement of free radicals or their end products is complicated. Isoprostanes, derived from the non-enzymatic peroxidation of arachidonic acid are now considered to be reliable biomarkers of oxidant stress in the human body. Isoprostanes are involved in many of the human diseases such as type 2 diabetes. In type 2 diabetes elevated levels of F₂-Isoprostanes (F₂-IsoPs) have been observed. The measurement of bioactive F₂-IsoPs levels offers a unique noninvasive analytical tool to study the role of free radicals in physiology, oxidative stress-related diseases, and acute or chronic inflammatory conditions. Measurement of oxidative stress by various other methods lacks specificity and sensitivity. This review aims to shed light on the implemention of F₂-IsoPs measurement as a gold-standard biomarker of oxidative stress in type 2 diabetics.

Genetic and environmental influences on total plasma homocysteine and coronary artery disease (CAD) risk among South Indians

BACKGROUND

Hyperhomocysteinemia, a documented risk factor for CAD is highly prevalent in Indians. The rationale behind the current study is to explore the genetic and environmental causes for such high prevalence as there are limited studies in this context.

METHODS

A total of 108 CAD cases and 108 controls were analyzed for tHcy and 4 folate pathway genetic polymorphisms [methylene tetrahydrofolate reductase (MTHFR) C677T, 5-methyltetrahydrofolate homocysteine methyl transferase (MTR) A2756G, methionine synthase reductase (MTRR) A66G and glutamate carboxypeptidase II (GCPII) C1561T] using reverse phase HPLC and PCR-RFLP methods respectively.

RESULTS

MTHFR 677T, MTRR 66A, GCPII 1561T, male gender, alcohol intake, smoking, diabetes, creatinine and hypertension were found to influence tHcy. After controlling for confounding factors, Hyperhomocysteinemia and two of its genetic determinants i.e. MTHFR C677T [OR: 1.96, 95% CI: 1.06-3.61] and GCP II C1561T [OR: 2.09, 95% CI: 1.09-3.97] were found to be associated with risk for CAD. Significant epistatic interactions were observed between MTHFR 677T/MTR 2756G and GCP II 1561T/MTRR 66G. Alcohol intake in subjects with MTR 2756G allele was found to inflate the risk for CAD [OR: 4.15, 95% CI: 1.35-12.69].

CONCLUSION

Hyperhomocysteinemia, C677T MTHFR and C1561T GCPII are risk factors for CAD. Potential gene--gene and gene--environment interactions indicate the need for multi-variate analyses for risk prediction.

Serum total homocysteine, folate, 5,10-methylenetetrahydrofolate reductase (MTHFR) 677C-->T genotype and subclinical atherosclerosis

OBJECTIVE

To determine the relationship of serum total homocysteine (tHcy), serum folate and 5,10-methylenetetrahydrofolate reductase (MTHFR) 677C-->T genotype with ultrasonic arterial wall measurements associated with subclinical atherosclerosis.

STUDY DESIGN

Cross-sectional analysis of 767 participants in an ongoing prospective study. Intima-media thickness (IMT) of the common carotid (IMTcc), IMT of the internal carotid including plaque when present (IMT(max)) and the sum of the thickest plaques present in both carotid and both common femoral bifurcations (total plaque thickness (TPT)) were measured using ultrasound.

RESULTS

People in the upper homocysteine quartile were more likely to have clinical cardiovascular disease (CVD) than those in the lowest three quartiles. They were also more likely to have plaques. The MTHFR 677C-->T genotype was not associated with any of the measures of subclinical atherosclerosis in either men or women but was the most important determinant of total homocysteine levels in men under 60 years of age.

CONCLUSIONS

Increased homocysteine levels but not MTHFR 677C-->T genotype, are associated with subclinical atherosclerosis and the presence of plaques. Our results indicate that measurements of blood levels of homocysteine and folate in people at intermediate risk for atherosclerotic CVD before symptoms occur, might improve risk stratification and facilitate the decision to provide folate/B vitamin intervention in primary prevention.

Beyond prostaglandins--chemistry and biology of cyclic oxygenated metabolites formed by free-radical pathways from polyunsaturated fatty acids

Polyunsaturated fatty acids (PUFAs) are important constituents in all organisms. They fulfil many functions, ranging from modulating the structure of membranes to acting as precursors of physiologically important molecules, such as the prostaglandins, which for a long time were the most prominent cyclic PUFA metabolites. However, since the beginning of the 1990s a large variety of cyclic metabolites have been discovered that form under autoxidative conditions in vivo to a much larger extent than do prostaglandins. These compounds--isoprostanes, neuroprostanes, phytoprostanes, and isofurans--proved subsequently to be ubiquitous in nature. They display a wide range of biological activities, and isoprostanes have become the currently most reliable indicators of oxidative stress in humans. In a relatively short time, the structural variety, properties, and applications of the autoxidatively formed cyclic PUFA derivatives have been uncovered.

Traffic-related particles are associated with elevated homocysteine: the VA normative aging study

RATIONALE

Recent epidemiologic studies have shown that homocysteine, a sulfur-containing amino acid formed during the metabolism of methionine, is a risk factor for atherosclerosis, myocardial infarction, stroke, and thrombosis. Particulate air pollution has been related to cardiovascular death and hospital admission, but the underlying mechanisms are not fully elucidated.

OBJECTIVES

We examined the associations between ambient particulate air pollution and plasma concentrations of homocysteine among 960 community-residing older men (mean age, 73.6 +/- 6.9 yr).

METHODS

Total homocysteine in plasma, measured using high-performance liquid chromatography with fluorescence detection, was regressed on each ambient particulate pollutant (black carbon, organic carbon, sulfate or PM(2.5)), and effect modification by plasma and dietary B vitamins (folate, B6, and B12) was examined.

MEASUREMENTS AND MAIN RESULTS

The median concentration of total homocysteine was 10.6 micromol/L. Statistically significant positive associations of total homocysteine were observed with traffic-related particles (black carbon and organic carbon). No association was observed with sulfate, an indicator of coal combustion particles, or PM(2.5) (particulate matter < or = 2.5 microm in aerodynamic diameter). The effects of black carbon and organic carbon were more pronounced in persons with low concentrations of plasma folate and vitamin B12.

CONCLUSIONS

Exposures to ambient particles, particularly from traffic, are associated with elevated plasma total homocysteine. Homocysteine may be a component or biological marker of the oxidation pathways underlying the effect of ambient particles on the cardiovascular system.

F2-isoprostanes are not just markers of oxidative stress

F(2)-isoprostanes are not just markers of oxidative stress. The discovery of F(2)-isoprostanes (F(2)-IsoPs) as specific and reliable markers of oxidative stress in vivo is briefly summarized here. F(2)-IsoPs are also agonists of important biological effects, such as the vasoconstriction of renal glomerular arterioles, the retinal vessel, and the brain microcirculature. In addition to the F(2)-IsoPs, E(2)- and D(2)-IsoPs can be formed by rearrangement of H(2)-IsoP endoperoxides and can give rise to cyclopentenone IsoPs, which are very reactive alpha,beta-unsaturated aldehydes. The same type of reactivity is also shown by acyclic gamma-ketoaldehydes formed as products of the IsoP pathway. Because previous studies suggested a relation between oxidative stress and collagen hyperproduction, it was investigated whether collagen synthesis is induced by F(2)-IsoPs, the most proximal products of lipid peroxidation. In contrast to aldehydes, F(2)-IsoPs act through receptors able to elicit definite signal transduction pathways. In a rat model of carbon tetrachloride-induced hepatic fibrosis, plasma F(2)-IsoPs were markedly elevated for the entire experimental period; hepatic collagen content was also increased. When hepatic stellate cells from normal liver were cultured up to activation (expression of smooth muscle alpha-actin) and then treated with F(2)-IsoPs in the concentration range found in the in vivo studies (10(-9) to 10(-8) M), a striking increase in DNA synthesis, cell proliferation, and collagen synthesis was observed. Total collagen content was similarly increased. All these stimulatory effects were reversed by the specific antagonist of the thromboxane A(2) receptor, SQ 29 548, whereas the receptor agonist, I-BOP, also had a stimulatory effect. Therefore F(2)-IsoPs generated by lipid peroxidation in hepatocytes may mediate hepatic stellate cell proliferation and collagen hyperproduction seen in hepatic fibrosis.

New techniques to detect oxidative stress markers: mass spectrometry-based methods to detect isoprostanes as the gold standard for oxidative stress in vivo

Free radical-induced lipid oxidation under oxidative stress has been implicated in a number of human diseases. Isoprostanes (IsoPs), isomers of prostaglandins, are one of the major classes of oxidation products derived from this oxidation process. Measurement of the levels of IsoPs by Mass Spectrometry-based methods has become the "gold standard" biomarker of oxidative stress in vivo. Significant advances have been made in understanding this important pathway of lipid peroxidation since the discovery of IsoP formation in vivo 18 years ago. Studies from our laboratory and others are discussed that have provided insights into the mechanism of formation. Furthermore, new independent studies have demonstrated that IsoPs are the most reliable available marker of lipid peroxidation in vivo, and recent work examining IsoP formation has provided valuable information about the pathogenesis of numerous human diseases. Thus, the complexity of the IsoP pathway has expanded, providing novel insights into mechanisms of lipid peroxidation in vivo and allowing investigators to explore the role of oxidative stress in human disease.

Serum gamma-glutamyl transferase is associated with plasma total homocysteine in Japanese patients with type 2 diabetes

Serum gamma-glutamyl transferase (gamma-GT), a marker of oxidative stress, predicts morbidity and mortality from cardiovascular disease. Plasma total homocysteine (tHcy), a pro-oxidant and also an independent risk factor for cardiovascular disease, correlates with gamma-GT among some populations. It is not known whether tHcy correlates with gamma-GT among type 2 diabetic patients in whom oxidative stress is increased and implicated for the development of diabetic complications. In the present study, we analyzed the association between gamma-GT, tHcy and related vitamins cross-sectionally among patients with type 2 diabetes without overt nephropathy (age range 17-76 years; n = 110). In a univariate regression analysis model, gamma-GT (logarithm) was positively associated with tHcy (beta = 0.288, P = 0.002) but not with folate or vitamin B(12). The association between tHcy and gamma-GT (logarithm) remained significant in a multivariate analysis model including age, lifestyle factors, folate, vitamin B(12), creatinine, HbA(1c) and medical history (beta = 0.219, P = 0.027). These results suggest that tHcy generates oxidative stress among type 2 diabetic patients and may partly explain the reported association between gamma-GT and cardiovascular disease.

Evidence for oxidative stress at elevated plasma thiol levels in chronic exposure to carbon disulfide (CS2) and coronary heart disease

OBJECTIVES

Oxidative stress in plasma may be promoted by plasma thiols such as homocysteine. However, other thiols such as glutathione may also exert antioxidant effects in vitro and in vivo. To further investigate whether plasma thiols act as prooxidants or antioxidants, we compared plasma oxidative status in patients with coronary heart disease (CHD) and in subjects occupationally exposed to carbon disulfide (CS(2)).

METHODS

Fifty-five subjects chronically exposed to CS(2), 53 CHD patients, and 52 healthy controls were examined. To assess plasma oxidative status, concentrations of thiobarbituric reactive substances (TBARS) and total antioxidative capacity (TAC), as well as ferritin and ceruloplasmin were determined. Antioxidative reserve was assessed by the determination of vitamine E, uric acid, superoxide dismutase, catalase, and glutathion peroxidase. In addition, protein and non-protein plasma thiol levels were measured.

RESULTS

Patients in both groups had increased levels of plasma thiols as compared to controls: CS(2)-exposed subjects presented with increased levels of thiols associated with plasma proteins, whereas CHD patients presented with elevated total homocysteine and cysteine levels. TBARS were significantly increased and TAC was significantly decreased both in CS(2)-exposed subjects and in CHD patients. In addition decreased activity of glutathione peroxidase, an antioxidative enzyme inhibited by thiol-containing compounds, was noted in both groups.

CONCLUSION

These results demonstrate that regardless of their metabolic origin increased thiols are associated with increased oxidative stress in plasma.

Hyperhomocysteinemia and elevated ox-LDL in Tunisian type 2 diabetic patients: Role of genetic and dietary factors

INTRODUCTION

Total plasma homocysteine (tHcy) is an emerging risk factor for the development of atherosclerosis. However, its relationship with diabetes is still unclear.

OBJECTIVES

We evaluated the association between tHcy levels and methylenetetrahydrofolate reductase (MTHFR) 677C-->T genotype in a type 2 diabetes mellitus (DM) population and their relationship with oxidized LDL (ox-LDL) according to dietary habits and vascular complications.

DESIGN AND METHODS

Eighty-six DM patients were compared to 120 healthy volunteers.

RESULTS

Associated higher tHcy levels and significantly higher ox-LDL levels (p<0.001) were found in DM patients compared to healthy subjects. Homozygosity for the T allele of MTHFR was more frequent in diabetics than in healthy subjects (12.8% vs. 7.2%) and it was associated with higher tHcy levels. Moreover, this elevated level was associated with significantly higher ox-LDL levels in DM patients with hypertension (p<0.05). Improving folate and vitamin C intakes could have beneficial effects on lowering the tHcy and ox-LDL levels.

CONCLUSIONS

The interplay of genetic and dietary factors modulates the effect of homocysteine on cardiovascular risk factors.