Methods for homocysteine analysis and biological relevance of the results

Hyperhomocysteinemia Increases Vascular Risk in Stroke Patients with Chronic Kidney Disease

AIMS

We aimed to assess the prognostic impact of hyperhomocysteinemia (HHcy) on the recurrent vascular event risk in stroke patients with or without chronic kidney disease (CKD).

METHODS

In this prospective observational study, 621 patients (mean age, 69.5 years; male, 62.2%) with ischemic stroke or transient ischemic attack were consecutively enrolled within 1 week of onset and followed-up for 1 year. HHcy was defined as elevated levels of fasting total homocysteine ＞15 µmol/L. CKD was defined as an estimated glomerular filtration rate of ＜60 mL/min/1.73 m2 or a history of renal replacement therapy. The primary outcome was a composite of major adverse cardiovascular events (MACEs), including nonfatal stroke, nonfatal acute coronary syndrome, major peripheral artery disease, and vascular death.

RESULTS

The prevalence of HHcy was 18.5%. Patients with HHcy were more likely to have intracranial (37.4% versus 24.8%; p=0.008) and extracranial (20.9% versus 13.0%; p=0.037) artery stenosis than were those without HHcy. At 1 year, patients with HHcy were at a greater risk of MACE than were those without HHcy (annual rate, 17.8% versus 10.4%; log-rank p=0.033). In the Cox proportional hazard regression models, HHcy was independently associated with an increased risk of MACE in patients with CKD (adjusted hazard ratio [HR], 2.06; 95% confidence interval [CI], 1.02-4.20), whereas HHcy was not predictive of MACE in those without CKD (adjusted HR, 1.00; 95% CI, 0.30-3.32).

CONCLUSIONS

Elevated levels of serum homocysteine can be an important modifiable risk factor in stroke patients with CKD, but not in those without CKD.

Effect of hyperhomocysteinemia on a murine model of smoke-induced pulmonary emphysema

Hyperhomocysteinemia was reported to enhance endoplasmic reticulum (ER) stress and subsequent apoptosis in several cells. However, the precise mechanisms of smoking susceptibility associated with hyperhomocysteinemia has not been fully elucidated. This study included 7- to 9-week-old C57BL6 male mice induced with hyperhomocysteinemia and were exposed to cigarette smoke (CS). A549 cells (human alveolar epithelial cell line) were cultured with homocysteine and were exposed to cigarette smoke extract (CSE) to observe cell viability and expression of proteins related to the ER stress. After 6 months of CS exposure, pulmonary emphysema was more severely induced in the group under the condition of hyperhomocysteinemia compared to that in the control group. The apoptotic A549 cells increased as homocysteine concentration increased and that was enhanced by CSE. Protein expression levels of ER stress markers were significantly increased after simultaneous stimulation. Notably, vitamin B12 and folate supplementation improved ER stress after simultaneous stimulation of A549 cells. In this study, we showed that hyperhomocysteinemia exacerbates CS exposure-induced emphysema in mice, suggesting that hyperhomocysteinemia and CS stimulation enhance ER stress and subsequent induced apoptosis in alveolar epithelial cells. It was suggested that there is a synergistic effect between homocysteine and CS.

Homocysteine Metabolism Pathway Is Involved in the Control of Glucose Homeostasis: A Cystathionine Beta Synthase Deficiency Study in Mouse

Cystathionine beta synthase (CBS) catalyzes the first step of the transsulfuration pathway from homocysteine to cystathionine, and its deficiency leads to hyperhomocysteinemia (HHcy) in humans and rodents. To date, scarce information is available about the HHcy effect on insulin secretion, and the link between CBS activity and the setting of type 2 diabetes is still unknown. We aimed to decipher the consequences of an inborn defect in CBS on glucose homeostasis in mice. We used a mouse model heterozygous for CBS (CBS+/−) that presented a mild HHcy. Other groups were supplemented with methionine in drinking water to increase the mild to intermediate HHcy, and were submitted to a high-fat diet (HFD). We measured the food intake, body weight gain, body composition, glucose homeostasis, plasma homocysteine level, and CBS activity. We evidenced a defect in the stimulated insulin secretion in CBS+/− mice with mild and intermediate HHcy, while mice with intermediate HHcy under HFD presented an improvement in insulin sensitivity that compensated for the decreased insulin secretion and permitted them to maintain a glucose tolerance similar to the CBS+/+ mice. Islets isolated from CBS+/− mice maintained their ability to respond to the elevated glucose levels, and we showed that a lower parasympathetic tone could, at least in part, be responsible for the insulin secretion defect. Our results emphasize the important role of Hcy metabolic enzymes in insulin secretion and overall glucose homeostasis.

Genetic regulatory element based whole-cell biosensors for the detection of metabolic disorders

Clinicians require simple, and cost-effective diagnostic tools for the quantitative determination of amino acids in physiological fluids for the detection of metabolic disorder diseases. Besides, amino acids also act as biological markers for different types of cancers and cardiovascular diseases. Herein, we applied an in-silico based approach to identify potential amino acid-responsive genetic regulatory elements for the detection of metabolic disorders in humans. Identified sequences were further transcriptionally fused with GFP, thus generating an optical readout in response to their cognate targets. Screening of genetic regulatory elements led us to discover two promoter elements (pmetE::GFP and ptrpL::GFP) that showed a significant change in the fluorescence response to homocysteine and tryptophan, respectively. The developed biosensors respond specifically and sensitively with a limit of detection of 3.8 μM and 3 μM for homocysteine and tryptophan, respectively. Furthermore, the clinical utility of this assay was demonstrated by employing it to identify homocystinuria and tryptophanuria diseases through the quantification of homocysteine and tryptophan in plasma and urine samples within 5 h. The precision and accuracy of the biosensors for disease diagnosis were well within an acceptable range. The general strategy used in this system can be expanded to screen different genetic regulatory elements present in other gram-negative and gram-positive bacteria for the detection of metabolic disorders.

Simultaneous determination of DL-cysteine, DL-homocysteine, and glutathione in saliva and urine by UHPLC-Q-Orbitrap HRMS: Application to studies of oxidative stress

A high-sensitivity and -selectivity mass spectrometry derivatization reagent, (R)-(5-(3-isothiocyanatopyrrolidin-1-yl)-5-oxopentyl) triphenylphosphonium (NCS-OTPP), was developed for the enantiomeric separation of chiral thiol compounds as prospectively important diagnostic markers for oxidative stress-related diseases. Complete separation of GSH, DL-Cys, and DL-Hcy was achieved. The parent ions of all derivatives had a fragment of m/z 473.18 and a structure of m/z 75.95 (R-S = C-S-R'), conducive to qualitative and quantitative analysis. Good linear relationships were obtained for all analytes (R²≥ 0.9995). The intra-day and inter-day precision were 0.82-5.16 % and 1.02-4.18 % in saliva, and 0.81-3.45 % and 0.99-6.47 % in urine, with mean recoveries of 83.31-105.66 % and 84.09-101.11 %, respectively. The limit of detection (S/N = 3) was 19.20-57.60 nM. Free and total GSH, DL-Cys, and DL-Hcy were detected simultaneously in saliva and urine from 10 volunteers in the normal, stressed, and stable states by UHPLC-Q-Orbitrap HRMS. The thiol compounds were quantitatively related to oxidative stress state changes.

Plasma homocysteine concentration in privately owned healthy adult cats: assessment of biological determinants and establishment of a reference interval

OBJECTIVES

The assessment of homocysteine status in diseased cats has indicated high plasma concentrations in chronic kidney disease and yielded conflicting results with respect to cardiovascular disorders. Previous investigations in small populations of normal cats revealed greater-than-expected variability in plasma homocysteine concentration. The purpose of this study was to determine biological determinants and the reference interval (RI) of plasma homocysteine concentration in the feline species, under strict pre-analytical conditions.

METHODS

In this prospective observational study, privately owned healthy adult cats underwent a complete physical examination, urinalysis and blood testing, in order to rule out any signs of disease. Plasma homocysteine concentration was measured using high-performance liquid chromatography-tandem mass spectrometry.

RESULTS

Of 151 cats recruited, 30 cats were not included owing to abnormal physical examination or fractious behaviour, and 30 cats were excluded based on abnormalities on blood work or urinalysis. Plasma homocysteine concentrations >28 µmol/l were associated with a dietary protein content >9.3 g/100 kcal metabolisable energy. The RI for plasma homocysteine concentration was determined to be 6.2-52.3 µmol/l.

CONCLUSIONS AND RELEVANCE

Normal values for plasma homocysteine concentration in cats have a wide RI, suggesting high inter-individual variability. Whether some healthy cats exhibit impaired homocysteine metabolism remains to be elucidated.

Analysis of Plasma Homocysteine Levels in Patients with Chronic Periodontitis Before and After Nonsurgical Periodontal Therapy Using High-Performance Liquid Chromatography

INTRODUCTION

Homocysteine (Hcy), an inflammatory biomarker, is a sulfur-containing amino acid. Elevated levels of plasma Hcy are evident in various inflammatory conditions and have been described as an independent risk factor for cardiovascular disease. The literature has also stated that a similar association could exist between the chronic periodontitis and plasma-Hcy levels, in otherwise systemically healthy individuals. However, studies on Hcy levels in periodontitis are scarce. Hence, this study aimed to assess the levels of plasma Hcy in patients with chronic periodontitis before and after nonsurgical periodontal therapy.

MATERIALS AND METHODS

This longitudinal, case-control clinical study included a total of 60 patients who were divided into two groups. Periodontal parameters including Plaque Index, Gingival Index, Sulcus Bleeding Index, probing depth, and clinical attachment level were recorded at baseline and 12 weeks after periodontal therapy. A high-performance liquid chromatography analysis was performed to measure the Hcy levels. The results were evaluated statistically for intergroup pair-wise comparisons by Mann-Whitney U-test and intragroup comparison by Wilcoxon-matched pairs test. Correlation between the plasma-Hcy levels with other clinical parameters in all groups was done by Spearman's rank correlation method.

RESULTS

The Hcy was detectable in all the samples. At baseline, the mean levels of plasma Hcy were found to be low in the control group, whereas in the test group, it is found to be higher. These plasma-Hcy levels and all periodontal parameters were reduced significantly after nonsurgical periodontal therapy.

CONCLUSION

The results demonstrated that plasma-Hcy levels are reduced after nonsurgical periodontal therapy but not to the levels comparable with those found in healthy individuals. Therefore, nonsurgical periodontal therapy may be used as an adjunctive Hcy-lowering therapy, contributing toward primary prevention against cardiovascular diseases.

Molecular Rescue of Dyrk1A Overexpression Alterations in Mice with Fontup® Dietary Supplement: Role of Green Tea Catechins

Epigallocatechin gallate (EGCG) is an inhibitor of DYRK1A, a serine/threonine kinase considered to be a major contributor of cognitive dysfunctions in Down syndrome (DS). Two clinical trials in adult patients with DS have shown the safety and efficacy to improve cognitive phenotypes using commercial green tea extract containing EGCG (45% content). In the present study, we performed a preclinical study using FontUp®, a new nutritional supplement with a chocolate taste specifically formulated for the nutritional needs of patients with DS and enriched with a standardized amount of EGCG in young mice overexpressing Dyrk1A (TgBACDyrk1A). This preparation is differential with previous one used, because its green tea extract has been purified to up 94% EGCG of total catechins. We analyzed the in vitro effect of green tea catechins not only for EGCG, but for others residually contained in FontUp®, on DYRK1A kinase activity. Like EGCG, epicatechin gallate was a noncompetitive inhibitor against ATP, molecular docking computations confirming these results. Oral FontUp® normalized brain and plasma biomarkers deregulated in TgBACDyrk1A, without negative effect on liver and cardiac functions. We compared the bioavailability of EGCG in plasma and brain of mice and have demonstrated that EGCG had well crossed the blood-brain barrier.

LPS-Induced Inflammation Abolishes the Effect of DYRK1A on IkB Stability in the Brain of Mice

Down syndrome is characterized by premature aging and dementia with neurological features that mimic those found in Alzheimer's disease. This pathology in Down syndrome could be related to inflammation, which plays a role in other neurodegenerative diseases. We previously found a link between the NFkB pathway, long considered a prototypical proinflammatory signaling pathway, and the dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A). DYRK1A is associated with early onset of Alzheimer's disease in Down syndrome patients. Here, we sought to determine the role of DYRK1A on regulation of the NFkB pathway in the mouse brain. We found that over-expression of Dyrk1A (on a C57BL/6J background) stabilizes IκBα protein levels by inhibition of calpain activity and increases cytoplasmic p65 sequestration in the mouse brain. In contrast, Dyrk1A-deficient mice (on a CD1 background) have decreased IκBα protein levels with an increased calpain activity and decreased cytoplasmic p65 sequestration in the brain. Taken together, our results demonstrate a role of DYRK1A in regulation of the NFkB pathway. However, decreased IκBα and DYRK1A protein levels associated with an increased calpain activity were found in the brains of mice over-expressing Dyrk1A after lipopolysaccharide treatment. Although inflammation induced by lipopolysaccharide treatment has a positive effect on calpastatin and a negative effect on DYRK1A protein level, a positive effect on microglial activation is maintained in the brains of mice over-expressing Dyrk1A.

Homocysteine-lowering gene therapy rescues signaling pathways in brain of mice with intermediate hyperhomocysteinemia

Hyperhomocysteinemia due to cystathionine beta synthase (CBS) deficiency is associated with diverse cognitive dysfunction. Considering the role of the serine/threonine kinase DYRK1A, not only in developmental defects with life-long structural and functional consequences, but also in multiple neurodegenerative diseases, its protein expression and kinase activity has been analyzed in brain of heterozygous CBS deficient mice and found to be increased. We previously demonstrated that specific liver treatment with an adenovirus expressing Dyrk1A normalizes hepatic DYRK1A level and decreases hyperhomocysteinemia in mice with moderate to intermediate hyperhomocysteinemia. We here use a hepatocyte-specific recombinant adeno-associated viral (AAV) serotype 8-mediated DYRK1A gene therapy (AAV2/8-DYRK1A) to analyze the effect of hepatic Dyrk1A gene transfer on some altered molecular mechanisms in brain of mice with intermediate hyperhomocysteinemia. Our selective hepatic treatment alleviates altered DYRK1A protein level and signaling pathways in brain of mice, the MAPK/ERK and PI3K/Akt pathways initiated by receptor tyrosine kinase, the BDNF dependent TrkB pathway, and NFkB pathway. These results demonstrate the positive effect of AAV2/8-DYRK1A gene transfer on neuropathological and inflammatory processes in brain of mice with intermediate hyperhomocysteinemia.

A robust and versatile mass spectrometry platform for comprehensive assessment of the thiol redox metabolome

Several diseases are associated with perturbations in redox signaling and aberrant hydrogen sulfide metabolism, and numerous analytical methods exist for the measurement of the sulfur-containing species affected. However, uncertainty remains about their concentrations and speciation in cells/biofluids, perhaps in part due to differences in sample processing and detection principles. Using ultrahigh-performance liquid chromatography in combination with electrospray-ionization tandem mass spectrometry we here outline a specific and sensitive platform for the simultaneous measurement of 12 analytes, including total and free thiols, their disulfides and sulfide in complex biological matrices such as blood, saliva and urine. Total assay run time is < 10 min, enabling high-throughput analysis. Enhanced sensitivity and avoidance of artifactual thiol oxidation is achieved by taking advantage of the rapid reaction of sulfhydryl groups with N-ethylmaleimide. We optimized the analytical procedure for detection and separation conditions, linearity and precision including three stable isotope labelled standards. Its versatility for future more comprehensive coverage of the thiol redox metabolome was demonstrated by implementing additional analytes such as methanethiol, N-acetylcysteine, and coenzyme A. Apparent plasma sulfide concentrations were found to vary substantially with sample pretreatment and nature of the alkylating agent. In addition to protein binding in the form of mixed disulfides (S-thiolation) a significant fraction of aminothiols and sulfide appears to be also non-covalently associated with proteins. Methodological accuracy was tested by comparing the plasma redox status of 10 healthy human volunteers to a well-established protocol optimized for reduced/oxidized glutathione. In a proof-of-principle study a deeper analysis of the thiol redox metabolome including free reduced/oxidized as well as bound thiols and sulfide was performed. Additional determination of acid-labile sulfide/thiols was demonstrated in human blood cells, urine and saliva. Using this simplified mass spectrometry-based workflow the thiol redox metabolome can be determined in samples from clinical and translational studies, providing a novel prognostic/diagnostic platform for patient stratification, drug monitoring, and identification of new therapeutic approaches in redox diseases.

Maternal serum homocysteine and uterine artery Doppler as predictors of preeclampsia and poor placentation

PURPOSE

The aim of this study was to evaluate the role of maternal serum total Homocysteine (tHcy) and uterine artery (Ut-A) Doppler as predictors of preeclampsia (PE), intrauterine growth restriction (IUGR), and other complications related to poor placentation.

PATIENTS AND METHODS

A prospective cohort study was conducted on 500 women with spontaneous pregnancies. tHcy was measured at 15-19 weeks, and then, Ut-A Doppler was performed at 18-22 weeks of pregnancy.

RESULTS

453 pregnant women completed the follow-up of the study. The tHcy and Ut-A resistance index were significantly higher in women who developed PE, IUGR, and other complications when compared to controls (tHcy: 7.033 ± 2.744, 6.321 ± 3.645, and 6.602 ± 2.469 vs 4.701 ± 2.082 μmol/L, respectively, p value <0.001 and Ut-A resistance index: 0.587 ± 0.072, 0.587 ± 0.053, and 0.597 ± 0.069 vs 0.524 ± 0.025, respectively, p value <0.001). The use of both tHcy assessment and Ut-A Doppler improved the sensitivity of prediction of PE relative to the use of each one alone (85.2 relative to 73.33 and 60%, respectively).

CONCLUSION

The use of elevated homocysteine and uterine artery Doppler screening are valuable in prediction of preeclampsia, IUGR, and poor placentation disorders. CLINCALTRIAL.

GOV ID

NCT02854501.

Combined assessment of DYRK1A, BDNF and homocysteine levels as diagnostic marker for Alzheimer's disease

Early identification of Alzheimer's disease (AD) risk factors would aid development of interventions to delay the onset of dementia, but current biomarkers are invasive and/or costly to assess. Validated plasma biomarkers would circumvent these challenges. We previously identified the kinase DYRK1A in plasma. To validate DYRK1A as a biomarker for AD diagnosis, we assessed the levels of DYRK1A and the related markers brain-derived neurotrophic factor (BDNF) and homocysteine in two unrelated AD patient cohorts with age-matched controls. Receiver-operating characteristic curves and logistic regression analyses showed that combined assessment of DYRK1A, BDNF and homocysteine has a sensitivity of 0.952, a specificity of 0.889 and an accuracy of 0.933 in testing for AD. The blood levels of these markers provide a diagnosis assessment profile. Combined assessment of these three markers outperforms most of the previous markers and could become a useful substitute to the current panel of AD biomarkers. These results associate a decreased level of DYRK1A with AD and challenge the use of DYRK1A inhibitors in peripheral tissues as treatment. These measures will be useful for diagnosis purposes.

An Overview of Thrombophilia and Associated Laboratory Testing

Venous thromboembolism, usually entailing deep vein thrombosis, pulmonary embolism, or both, is a complex and multifactorial disorder, in which a number of putative conditions interplay and finally contribute to propel the individual risk over a certain degree, so ultimately culminating in the development of venous occlusive disorders. Thrombophilia is commonly defined as a propensity to develop venous thromboembolism on the basis of an underlying hypercoagulable state attributable to inherited or acquired disorders of blood coagulation or fibrinolysis. The thrombophilic conditions are conventionally classified as inherited (or genetically determined) and acquired. The former include deficiencies of natural anticoagulants such as antithrombin, protein C, protein S, increased values of clotting factors (especially factor VIII), as well as prothrombotic polymorphisms in genes encoding for factor V (i.e., factor V Leiden) and prothrombin. The latter conditions mainly entail antiphospholipid antibody syndrome, malignancy, acquired elevations of coagulation factors or acquired reduction of natural inhibitors, or hyperhomocysteinemia. Deepened knowledge of all potential risk factors, as well as the clear understanding of their role in the pathophysiology of venous thrombosis, are both essential to help achieve a faster and more efficient diagnosis of this condition as well as a more effective prophylaxis of patients at higher risk and treatment of those with manifest disease.

Impact of Dyrk1A level on alcohol metabolism

Alcoholic liver diseases arise from complex phenotypes involving many genetic factors. It is quite common to find hyperhomocysteinemia in chronic alcoholic liver diseases, mainly due to deregulation of hepatic homocysteine metabolism. Dyrk1A, involved in homocysteine metabolism at different crossroads, is decreased in liver of hyperhomocysteinemic mice. Here, we hypothesized that Dyrk1A contributes to alcohol-induced hepatic impairment in mice. Control, hyperhomocysteinemic and mice overexpressing Dyrk1A were fed using a Lieber-DeCarli liquid diet with or without ethanol (5% v/v ethanol) for one month, and liver histological examination and liver biochemical function tests were performed. Plasma alanine aminotransferase and homocysteine levels were significantly decreased in mice overexpressing Dyrk1A compared to control mice with or without alcohol administration. On the contrary, the mean plasma alanine aminotransferase and homocysteine levels were significantly higher in hyperhomocysteinemic mice than that of control mice after alcohol administration. Paraoxonase 1 and CYP2E1, two phase I xenobiotic metabolizing enzymes, were found increased in the three groups of mice after alcohol administration. However, NQO1, a phase II enzyme, was only found increased in hyperhomocysteinemic mice after alcohol exposure, suggesting a greater effect of alcohol in liver of hyperhomocysteinemic mice. We observed positive correlations between hepatic alcohol dehydrogenase activity, Dyrk1A and ADH4 protein levels. Importantly, a deleterious effect of alcohol consumption on hepatic Dyrk1A protein level was found. Our study reveals on the one hand a role of Dyrk1A in ethanol metabolism and on the other hand a deleterious effect of alcohol administration on hepatic Dyrk1A level.

Search for Correlations Between Genotypes and Electrophysiological Patterns in Migraine: The MTHFR C677T Polymorphism and Visual Evoked Potentials

Interictally, migraineurs have on average a reduction in habituation of pattern-reversal visual evoked potentials (PR-VEP) and in mitochondrial energy reserve. 5,10-Methylenetetrahydrofolate reductase (MTHFR) is involved in folate metabolism and its C677T polymorphism may be more prevalent in migraine. The aim of this study was to search in migraineurs for a correlation between the MTHFR C677T polymorphism and the PR-VEP profile. PR-VEP were recorded in 52 genotyped migraine patients: 40 female, 24 without (MoA), 28 with aura (MA). Among them 21 had a normal genotype (CC), 18 were heterozygous (CT) and 13 homozygous (TT) for the MTHFR C677T polymorphism. Mean PR-VEP N1-P1 amplitude was significantly lower in CT compared with CC, and tended to be lower in TT with increasing age. The habituation deficit was significantly greater in CC compared with TT subjects. The correlation between the cortical preactivation level, as reflected by the VEP amplitude in the first block of averages, and habituation was stronger in CC than in CT or TT.

The MTHFR C677T polymorphism could thus have an ambiguous role in migraine. On one hand, the better VEP habituation which is associated with its homozygosity, and possibly mediated by homocysteine derivatives increasing serotoninergic transmission, may protect the brain against overstimulation. On the other hand, MTHFR C677T homozygosity is linked to a reduction of grand average VEP amplitude with illness duration, which has been attributed to brain damage.

Effect of cadmium administration in hyperhomocysteinemic mice due to cystathionine beta synthase deficiency

Homocysteine, a sulfur-containing amino acid formed during the metabolism of methionine, is commonly slightly elevated in the plasma of the general population. Additionally, we previously found that cystathionine beta synthase-deficient mice, a murine model of hyperhomocysteinemia, exhibit altered activities of xenobiotic metabolizing enzymes (XME), which dispose of foreign chemicals, in the liver. Thus, hyperhomocysteinemia may result in susceptibility to xenobiotics like cadmium, a heavy-metal toxicant found in drinking water, atmospheric air, and food. Consequently, we exposed hyperhomocysteinemic mice to cadmium via their drinking water for one month to analyze the combined effects of hyperhomocysteinemia and cadmium exposure in liver. No difference in plasma homocysteine level was found after cadmium administration in control and hyperhomocysteinemic mice, but the glutathione level was significantly lower in exposed hyperhomocysteinemic mice compared to control mice, reflecting oxidative stress. We therefore analyzed the effect of Cd administration on hepatic XMEs known to be dysregulated in hyperhomocysteinemic mice: paraoxonase 1, a phase I XME, and

NAD(P)H

quinone oxidoreductase, a phase II XME. Cadmium exposure negatively affected activity of paraoxonase 1, a calcium-dependent enzyme. Thus, we analyzed another calcium-dependent enzyme known to be dysregulated in liver of hyperhomocysteinemic mice, calpain, which was also significantly lower after cadmium administration. A comparison of the calculated affinities of cadmium docking versus calcium redocking suggested that cadmium ions may inhibit enzymatic activities by preventing the binding of calcium ions. Moreover, the increased

NAD(P)H

quinone oxidoreductase activity observed after cadmium administration could indicate the presence of protective mechanisms in liver of mice. In conclusion, although cadmium administration had no effect on plasma homocysteine level, its effects on plasma glutathionine level suggest a susceptibility to cadmium in the condition of hyperhomocysteinemia, which could be countered by an increased

NAD(P)H

quinone oxidoreductase activity.

Biomarkers of Nutrition for Development-Folate Review

The Biomarkers of Nutrition for Development (BOND) project is designed to provide evidence-based advice to anyone with an interest in the role of nutrition in health. Specifically, the BOND program provides state-of-the-art information and service with regard to selection, use, and interpretation of biomarkers of nutrient exposure, status, function, and effect. To accomplish this objective, expert panels are recruited to evaluate the literature and to draft comprehensive reports on the current state of the art with regard to specific nutrient biology and available biomarkers for assessing nutrients in body tissues at the individual and population level. Phase I of the BOND project includes the evaluation of biomarkers for 6 nutrients: iodine, iron, zinc, folate, vitamin A, and vitamin B-12. This review represents the second in the series of reviews and covers all relevant aspects of folate biology and biomarkers. The article is organized to provide the reader with a full appreciation of folate's history as a public health issue, its biology, and an overview of available biomarkers (serum folate, RBC folate, and plasma homocysteine concentrations) and their interpretation across a range of clinical and population-based uses. The article also includes a list of priority research needs for advancing the area of folate biomarkers related to nutritional health status and development.

One-carbon cycle alterations induced by Dyrk1a dosage

Hyperhomocysteinemia due to cystathionine beta synthase deficiency confers diverse clinical manifestations. It is characterized by elevated plasma homocysteine levels, a common amino acid metabolized by remethylation to methionine or transsulfuration to cysteine. We recently found a relationship between hepatic Dyrk1A protein expression, a serine/threonine kinase involved in signal transduction in biological processes, hepatic S-adenosylhomocysteine activity, and plasma homocysteine levels. We aimed to study whether there is also a relationship between Dyrk1a and cystathionine beta synthase activity. We used different murine models carrying altered gene coy numbers for Dyrk1a, and found a decreased cystathionine beta synthase activity in the liver of mice under-expressing Dyrk1a, and an increased in liver of mice over-expressing Dyrk1a. For each model, a positive correlation was found between cystathionine beta synthase activity and Dyrk1a protein expression in the liver of mice, which was confirmed in a non-modified genetic context. The positive correlation found between liver Dyrk1a protein expression and CBS activity in modified and non-modified genetic context strengthens the role of this kinase in one carbon metabolism.

The association between plasma homocysteine and coronary heart disease is modified by the MTHFR 677C>T polymorphism

OBJECTIVE

An elevated level of total plasma homocysteine (tHcy) has been associated with risk of coronary heart disease (CHD). The level of tHcy is affected by lifestyle, in addition to genetic predisposition. The methylene tetrahydrofolate reductase (MTHFR) 677C>T polymorphism (rs1801133) is among the strongest genetic predictors of tHcy. We examined whether the association between tHcy and CHD is modified by the MTHFR 677C>T polymorphism.

DESIGN AND SETTING

Data from two case-control studies of first-time myocardial infarction (MI), Stockholm Heart Epidemiology Programme (SHEEP), and for MI and unstable angina, INTERGENE, were analysed in parallel.

PATIENTS

THcy was determined in a total of 1150 cases and 1753 controls.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

The outcome comprised first-time MI and unstable angina, subsumed as CHD. Logistic regression was used to investigate the association between tHcy and CHD, and its modification by genotype.

RESULTS

High tHcy was confirmed to be a risk factor for CHD in both studies. In SHEEP, the association between tHcy and MI was observed in MTHFR 677 C-homozygotes (OR=1.4, 95% CI 1.2 to 1.6, for a difference by 1 SD of log tHcy) and in heterozygotes (OR=1.3, 95% CI 1.1 to 1.6) but not in T-homozygotes, independent of smoking, physical activity and obesity. An effect modification of similar magnitude was observed but not statistically significant in the smaller INTERGENE study, and confirmed in a meta-analysis of both studies.

CONCLUSIONS

Two Swedish case-control studies showed that the association between elevated tHcy and CHD was confined to carriers of the MTHFR 677 C-allele, which could have implications for the efficiency of tHcy-lowering treatment.

Dyrk1A, a serine/threonine kinase, is involved in ERK and Akt activation in the brain of hyperhomocysteinemic mice

Hyperhomocysteinemia due to cystathionine beta synthase (CBS) deficiency is associated with diverse brain disease. Whereas the biological actions linking hyperhomocysteinemia to the cognitive dysfunction are not well understood, we tried to establish relationships between hyperhomocysteinemia and alterations of signaling pathways. In the brain of CBS-deficient mice, a murine model of hyperhomocysteinemia, we previously found an activation of extracellular signal-regulated kinase (ERK) pathway and an increase of Dyrk1A, a serine/threonine kinase involved in diverse functions ranging from development and growth to apoptosis. We then investigated the relationship between Dyrk1A and the signaling pathways initiated by receptor tyrosine kinases (RTK), the ERK and PI3K/Akt pathways. We found a significant increase of phospho-ERK, phospho-MEK, and phospho-Akt in the brain of CBS-deficient and Dyrk1a-overexpressing mice. This increase was abolished when CBS-deficient and Dyrk1A-transgenic mice were treated with harmine, an inhibitor of Dyrk1A kinase activity, which emphasizes the role of Dyrk1A activity on ERK and Akt activation. Sprouty 2 protein level, a negative feedback loop modulator that limits the intensity and duration of RTK activation, is decreased in the brain of CBS-deficient mice, but not in the brain of Dyrk1A transgenic mice. Furthermore, a reduced Dyrk1A and Grb2 binding on sprouty 2 and an increased interaction of Dyrk1A with Grb2 were found in the brain of Dyrk1A transgenic mice. The consequence of Dyrk1A overexpression on RTK activation seems to be a decreased interaction of sprouty 2/Grb2. These observations demonstrate ERK and Akt activation induced by Dyrk1A in the brain of hyperhomocysteinemic mice and open new perspectives to understand the basis of the cognitive defects in hyperhomocysteinemia.

Hyperhomocysteinemia and thrombophilia

It is now widely accepted that hyperhomocysteinemia (HHC) is a risk factor for thrombophilia. HHC is the result of either impaired enzyme function or a deficiency of vitamin B (folate, B₆, B₁₂), or both, and can be treated with vitamin supplements. Measuring plasma total homocysteine (tHcy) is included in the routine thrombophilia panel in many laboratories, despite having a limited value to the clinician. Many methods are available for tHcy measurements. High-pressure liquid chromatography (HPLC) with fluorescence detection is a widely used method, but is being replaced by more convenient immuno- or enzyme assays. In this paper a general overview on homocysteine is given, with an emphasis on laboratory methods.

An improved method for simultaneous analysis of aminothiols in human plasma by high-performance liquid chromatography with fluorescence detection

Altered levels of aminothiols in biological fluids are thought to be an important risk indicator for several diseases, and reliable methods for the accurate determination of aminothiols concentrations in plasma are thus required. In this paper ammonium 5-bromo-7-fluorobenzo-2-oxa-1,3-diazole-4-sulphonate (SBD-BF) is proposed as a convenient fluorogenic derivatizating reagent for the determination of aminothiols (cysteine, cysteinylglycine, homocysteine and glutathione) by HPLC with fluorescence detection. The reactions of SBD-BF with aminothiols at room temperature are about three-times faster than those of ammonium 7-fluorobenzo-2-oxa-1,3-diazole-4-sulphonate (the most frequently employed reagent) at 60 degrees C. The derivatives of SBD-BF with cysteine, cysteinylglycine, homocysteine and glutathione are easily separated by HPLC and their calibration curves show excellent linearity over the range 0.05-20 micromol/L with excellent r(2) values for all analytes. SBD-BF reacts with thiols under mild conditions, i.e. at 25 degrees C over about 30 min, and is proposed as a suitable fluorogenic reagent for thiol derivatization to be introduced in analytical clinical chemistry. The detection limits of Cys, Cys-Gly, Hcy and GSH at a signal-to-noise ratio of 5 were 0.1 microM for Cys, 0.01 microM for Cys-Gly and Hcy, and 0.02 microM for GSH. Furthermore, validation parameters of the proposed method are quite satisfactory. As an application of this method the determination of thiol derivatives in human plasma was carried out on a number of samples.

DYRK1A, a novel determinant of the methionine-homocysteine cycle in different mouse models overexpressing this Down-syndrome-associated kinase

BACKGROUND

Hyperhomocysteinemia, characterized by increased plasma homocysteine level, is associated with an increased risk of atherosclerosis. On the contrary, patients with Down syndrome appear to be protected from the development of atherosclerosis. We previously found a deleterious effect of hyperhomocysteinemia on expression of DYRK1A, a Down-syndrome-associated kinase. As increased expression of DYRK1A and low plasma homocysteine level have been associated with Down syndrome, we aimed to analyze the effect of its over-expression on homocysteine metabolism in mice.

METHODOLOGY/PRINCIPAL FINDINGS

Effects of DYRK1A over-expression were examined by biochemical analysis of methionine metabolites, real-time quantitative reverse-transcription polymerase chain reaction, and enzyme activities. We found that over-expression of Dyrk1a increased the hepatic NAD(P)H:quinone oxidoreductase and S-adenosylhomocysteine hydrolase activities, concomitant with decreased level of plasma homocysteine in three mice models overexpressing Dyrk1a. Moreover, these effects were abolished by treatment with harmine, the most potent and specific inhibitor of Dyrk1a. The increased NAD(P)H:quinone oxidoreductase and S-adenosylhomocysteine hydrolase activities were also found in lymphoblastoid cell lines from patients with Down syndrome.

CONCLUSIONS/SIGNIFICANCE

Our results might give clues to understand the protective effect of Down syndrome against vascular defect through a decrease of homocysteine level by DYRK1A over-expression. They reveal a link between the Dyrk1a signaling pathway and the homocysteine cycle.

Grape products and cardiovascular disease risk factors

Many in vivo trials have evaluated the effects of grape products on different CVD risk factors. Most published studies have dealt with some specific aspects of mechanisms of grape flavonoid action or have focused only on one product, such as wine. The aim of the present paper is to review trials dealing with grape products and CVD published during the last 13 years (seventy-five trials). Polyphenols, alcohol and dietary fibre are the main constituents of the tested products. In animal and human studies, grape products have been shown to produce hypotensive, hypolipidaemic and anti-atherosclerotic effects, and also to improve antioxidant status as measured in terms of plasma antioxidant capacity, oxidation biomarkers, antioxidant compounds or antioxidant enzymes. Differences in the design of the studies and in the composition of the tested products (not always provided) could explain the different results of these studies.

Cysteinylation and homocysteinylation of plasma protein thiols during ageing of healthy human beings

The purpose of the present study was to determine the relative amount of S-thiolated proteins (i.e. S-homocysteinylated, S-cysteinylglycinylated, S-glutathionylated and S-cysteinylated proteins) to the total protein thiols (i.e. the sum of reduced protein sulphydryl groups (PSHs) and protein mixed disulphides with homocysteine [HcySH], cysteinylglycine, cysteine [CysSH] and glutathione) in the plasma of healthy individuals aged 20 to 93. After plasma separation, total protein thiols, S-thiolated proteins, as well as CysSH, cystine, HcySH and homocystine were measured by high-performance liquid chromatography (HPLC) with fluorescence determination of the thiol-monobromobimane conjugate. Determination of plasma levels of protein thiols was performed by spectrophotometry with 5,5′-dithiobis(2-nitrobenzoic acid) as a titrating agent. The present study demonstrates an age-dependent reduction in the amount of PSHs, and an age-dependent increase in cysteinylated and homocysteinylated plasma proteins in healthy human beings. This indicates that the efficiency of the reduced protein thiol pool as an antioxidant defence system decreases with age, possibly causing an increased risk of irreversible oxidation (i.e. further oxidation to sulphinic and sulphonic acids, which are usually not reducible by thiol reducing agents) of sulphydryl groups of plasma proteins. The drop in the plasma level of protein sulphydryl groups suggests depletion and/or impairment of the antioxidant capacity of plasma, likely related to an alteration of the delicate balance between the different redox forms of thiols.

Commutability of NIST SRM 1955 Homocysteine and Folate in Frozen Human Serum with selected total homocysteine immunoassays and enzymatic assays

BACKGROUND

The National Institute of Standards and Technology (NIST) has recently developed Standard Reference Material (SRM) 1955 Homocysteine and Folate in Frozen Human Serum with certified values for total homocysteine (tHcy) and 5-methyl-tetrahydrofolic acid. NIST has performed an international, interlaboratory assessment of SRM 1955 commutability; results are reported for tHcy only.

METHODS

Total Hcy was measured in 20 patient sera and in 3 levels of SRM 1955 using 14 immunoassays and/or enzymatic assays. Liquid chromatography/tandem mass spectrometry was utilized as the reference assay. An "errors-in-variables" statistical model was utilized to assess the commutability of SRM 1955.

RESULTS

Normalized residuals ranged from -2.65 to 2.19 for SRM 1955. The median interlaboratory/interassay imprecision (CV) was approximately 4% for patient specimens and ranged from approximately 3% to approximately 7% for SRM 1955. The median intra-assay imprecision ranged from approximately 1% to approximately 13%. Orthogonal residuals, as a descriptor of assay accuracy, ranged from 0.29 to 7.71 and from 0.20 to 2.22 for patient specimens and SRM 1955 samples, respectively.

CONCLUSION

The current study suggests that SRM 1955 is commutable with the investigated tHcy assays; however, a broader specimen set needs to be evaluated to completely substantiate this conclusion.