Possible mechanisms of homocysteine toxicity

The association between frailty biomarkers and 20-year all-cause and cardiovascular mortality among community-dwelling older adults

OBJECTIVES

While several biomarkers were previously associated with frailty and mortality, data are still contradicting. We aimed to evaluate the association between novel biomarkers and frailty among community-dwelling older adults to enhance understanding of the pathophysiology of frailty.

METHODS

Nine hundred and sixty-three older adults were screened during the third phase (1999-2008) of the Israel study on Glucose Intolerance, Obesity, and Hypertension (GOH). Frailty was defined as sedentary individuals, past 10 years hospitalizations, or at least one of the following: body mass index (BMI) <21 kg/m2; albumin <3.2 g/dl; ≥2 major baseline diseases. Biomarkers were evaluated for their association with frailty, all-cause, and cardiovascular mortality.

RESULTS

Mean baseline age was 72 ± 7 years, 471 (49%) were women, and 195 (20%) were classified as frail. Median follow-up for cardiovascular and all-cause mortality was 11 and 13 years, with 179 (18.6%) and 466 (48.4%) deaths recorded, respectively. Multivariable logistic regression showed greater odds for frailty with lower quartile of alanine aminotransferase (ALT) (OR = 1.8, 95%CI: 1.2-2.8, p = 0.01), and for each 5 µmol/L increment in homocysteine levels (OR = 1.3, 95%CI: 1.1-1.5, p = 0.001). Multivariate Cox regression showed greater all-cause and cardiovascular mortality risk for individuals with low ALT (HR = 1.6, 95%CI: 1.3-2.0, p < 0.001 and HR = 1.5, 95% CI: 1.0-2.2, p = 0.03, respectively), and high homocysteine (HR = 1.1, 95%CI: 1.1-1.3, p = 0.003 and HR = 1.2, 95%CI: 1.0-1.3, p = 0.04, respectively). Homocysteine association with mortality was more pronounced in those with baseline ischemic heart disease (IHD) compared with subjects free of IHD (P for interaction = 0.01).

CONCLUSIONS

Lower ALT and higher homocysteine were associated with frailty, all-cause and cardiovascular mortality. These available and low-cost biomarkers underscore the nutritional and metabolic aspects of frailty when screening high-risk older adults, especially those with IHD, and may be considered as preferable screening biomarkers to be tested among these individuals for frailty and mortality risk.

Nicotinamide N-methyltransferase (NNMT): a novel therapeutic target for metabolic syndrome

Metabolic syndrome (MetS) represents a constellation of metabolic abnormalities, typified by obesity, hypertension, hyperglycemia, and hyperlipidemia. It stems from intricate dysregulations in metabolic pathways governing energy and substrate metabolism. While comprehending the precise etiological mechanisms of MetS remains challenging, evidence underscores the pivotal roles of aberrations in lipid metabolism and insulin resistance (IR) in its pathogenesis. Notably, nicotinamide N-methyltransferase (NNMT) has recently surfaced as a promising therapeutic target for addressing MetS. Single nucleotide variants in the NNMT gene are significantly correlated with disturbances in energy metabolism, obesity, type 2 diabetes (T2D), hyperlipidemia, and hypertension. Elevated NNMT gene expression is notably observed in the liver and white adipose tissue (WAT) of individuals with diabetic mice, obesity, and rats afflicted with MetS. Knockdown of NNMT elicits heightened energy expenditure in adipose and hepatic tissues, mitigates lipid accumulation, and enhances insulin sensitivity. NNMT catalyzes the methylation of nicotinamide (NAM) using S-adenosyl-methionine (SAM) as the donor methyl group, resulting in the formation of S-adenosyl-l-homocysteine (SAH) and methylnicotinamide (MNAM). This enzymatic process results in the depletion of NAM, a precursor of nicotinamide adenine dinucleotide (NAD+), and the generation of SAH, a precursor of homocysteine (Hcy). Consequently, this cascade leads to reduced NAD+ levels and elevated Hcy levels, implicating NNMT in the pathogenesis of MetS. Moreover, experimental studies employing RNA interference (RNAi) strategies and small molecule inhibitors targeting NNMT have underscored its potential as a therapeutic target for preventing or treating MetS-related diseases. Nonetheless, the precise mechanistic underpinnings remain elusive, and as of yet, clinical trials focusing on NNMT have not been documented. Therefore, further investigations are warranted to elucidate the intricate roles of NNMT in MetS and to develop targeted therapeutic interventions.

Role of folate receptor α in the partial rejuvenation of dentate gyrus cells: Improvement of cognitive function in 21-month-old aged mice

Neuronal aging may be, in part, related to a change in DNA methylation. Thus, methyl donors, like folate and methionine, may play a role in cognitive changes associated to neuronal aging. To test the role of these metabolites, we performed stereotaxic microinjection of these molecules into the dentate gyrus (DG) of aged mice (an average age of 21 month). Folate, but not S-Adenosyl-Methionine (SAM), enhances cognition in aged mice. In the presence of folate, we observed partial rejuvenation of DG cells, characterized by the expression of juvenile genes or reorganization of extracellular matrix. Here, we have also tried to identify the mechanism independent of DNA methylation, that involve folate effects on cognition. Our analyses indicated that folate binds to folate receptor α (FRα) and, upon folate binding, FRα is transported to cell nucleus, where it is acting as transcription factor for expressing genes like SOX2 or GluN2B. In this work, we report that a FRα binding peptide also replicates the folate effect on cognition, in aged mice. Our data suggest that such effect is not sex-dependent. Thus, we propose the use of this peptide to improve cognition since it lacks of folate-mediated side effects. The use of synthetic FRα binding peptides emerge as a future strategy for the study of brain rejuvenation.

Exploratory focused pharmacogenetic testing reveals novel markers associated with risperidone pharmacokinetics in Saudi children with autism

Background: Autism spectrum disorders (ASDs) encompass a broad range of phenotypes characterized by diverse neurological alterations. Genomic studies have revealed considerable overlap between the molecular mechanisms implicated in the etiology of ASD and genes involved in the pharmacokinetic (PK) and pharmacodynamic (PD) pathways of antipsychotic drugs employed in ASD management. Given the conflicting data originating from candidate PK or PD gene association studies in diverse ethnogeographic ASD populations, dosage individualization based on "actionable" pharmacogenetic (PGx) markers has limited application in clinical practice. Additionally, off-label use of different antipsychotics is an ongoing practice, which is justified given the shortage of approved cures, despite the lack of satisfactory evidence for its safety according to precision medicine. This exploratory study aimed to identify PGx markers predictive of risperidone (RIS) exposure in autistic Saudi children. Methods: This prospective cohort study enrolled 89 Saudi children with ASD treated with RIS-based antipsychotic therapy. Plasma levels of RIS and 9-OH-RIS were measured using a liquid chromatography-tandem mass spectrometry system. To enable focused exploratory testing, genotyping was performed with the Axiom PharmacoFocus Array, which included a collection of probe sets targeting PK/PD genes. A total of 720 PGx markers were included in the association analysis. Results: A total of 27 PGx variants were found to have a prominent impact on various RIS PK parameters; most were not located within the genes involved in the classical RIS PK pathway. Specifically, 8 markers in 7 genes were identified as the PGx markers with the strongest impact on RIS levels (p < 0.01). Four PGx variants in 3 genes were strongly associated with 9-OH-RIS levels, while 5 markers in 5 different genes explained the interindividual variability in the total active moiety. Notably, 6 CYP2D6 variants exhibited strong linkage disequilibrium; however, they significantly influenced only the metabolic ratio and had no considerable effects on the individual estimates of RIS, 9-OH-RIS, or the total active moiety. After correction for multiple testing, rs78998153 in UGT2B17 (which is highly expressed in the brain) remained the most significant PGx marker positively adjusting the metabolic ratio. For the first time, certain human leukocyte antigen (HLA) markers were found to enhance various RIS exposure parameters, which reinforces the gut-brain axis theory of ASD etiology and its suggested inflammatory impacts on drug bioavailability through modulation of the brain, gastrointestinal tract and/or hepatic expression of metabolizing enzymes and transporters. Conclusion: Our hypothesis-generating approach identified a broad spectrum of PGx markers that interactively influence RIS exposure in ASD children, which indicated the need for further validation in population PK modeling studies to define polygenic scores for antipsychotic efficacy and safety, which could facilitate personalized therapeutic decision-making in this complex neurodevelopmental condition.

Zebrafish as a Model of Cardiac Pathology and Toxicity: Spotlight on Uremic Toxins

Chronic kidney disease (CKD) is an increasing health care problem. About 10% of the general population is affected by CKD, representing the sixth cause of death in the world. Cardiovascular events are the main mortality cause in CKD, with a cardiovascular risk 10 times higher in these patients than the rate observed in healthy subjects. The gradual decline of the kidney leads to the accumulation of uremic solutes with a negative effect on every organ, especially on the cardiovascular system. Mammalian models, sharing structural and functional similarities with humans, have been widely used to study cardiovascular disease mechanisms and test new therapies, but many of them are rather expensive and difficult to manipulate. Over the last few decades, zebrafish has become a powerful non-mammalian model to study alterations associated with human disease. The high conservation of gene function, low cost, small size, rapid growth, and easiness of genetic manipulation are just some of the features of this experimental model. More specifically, embryonic cardiac development and physiological responses to exposure to numerous toxin substances are similar to those observed in mammals, making zebrafish an ideal model to study cardiac development, toxicity, and cardiovascular disease.

Cross-sectional and prospective associations between homocysteine and a frailty index: A post-hoc analysis of the multidomain Alzheimer's prevention trial (MAPT)

BACKGROUND

Homocysteine (Hcy) has been associated with several health problems, including reduced physical capacity. No study appears to have looked at the role of Hcy values longitudinally on physical capacity deterioration in older adults. The objective is to examine cross-sectional and prospective associations between Hcy values and frailty in the elderly and investigate Hcy potential association with the onset of frailty.

METHODS

769 community-dwelling older adults from the MAPT study were recruited for this study. Total Hcy was measured at baseline. Frailty was evaluated at 5 different collection timepoints: baseline, 6-month, 1-, 2-, and 3-year using a frailty index (FI) composed of 19 items. Linear regressions adjusted for all the confounders (age, gender, educational level, MAPT group allocation and Omega-3) were performed to examine the cross-sectional associations of homocysteine values with the FI. A cox model was used to test the association of Hcy with the onset of frailty.

RESULTS

Mean Hcy values (15.9 ± 5.6 μmol\L) were obtained from 769 community-dwelling adults (75.7 ± 4.6 years old). After adjustments, a significant (β = 0.002, (00002-0.003)) and positive association between baseline Hcy values and FI was found (ß = 0.002). Additionally, higher values of Hcy were associated with a worsening of FI after 3 years (ß = 0.002, p = 0.003). A significant association between baseline Hcy values and the likelihood of developing frailty was discovered by incident event analysis (HR: 1.04 (1.01-1.06), p = 0.004).

CONCLUSION

High levels of Hcy are associated with the fragility process in community-dwelling older adults.

Maternal Hyperhomocysteinemia Disturbs the Mechanisms of Embryonic Brain Development and Its Maturation in Early Postnatal Ontogenesis

Maternal hyperhomocysteinemia causes the disruption of placental blood flow and can lead to serious disturbances in the formation of the offspring's brain. In the present study, the effects of prenatal hyperhomocysteinemia (PHHC) on the neuronal migration, neural tissue maturation, and the expression of signaling molecules in the rat fetal brain were described. Maternal hyperhomocysteinemia was induced in female rats by per os administration of 0.15% aqueous methionine solution in the period of days 4-21 of pregnancy. Behavioral tests revealed a delay in PHHC male pups maturing. Ultrastructure of both cortical and hippocampus tissue demonstrated the features of the developmental delay. PHHC was shown to disturb both generation and radial migration of neuroblasts into the cortical plate. Elevated Bdnf expression, together with changes in proBDNF/mBDNF balance, might affect neuronal cell viability, positioning, and maturation in PHHC pups. Reduced Kdr gene expression and the content of SEMA3E might lead to impaired brain development. In the brain tissue of E20 PHHC fetuses, the content of the procaspase-8 was decreased, and the activity level of the caspase-3 was increased; this may indicate the development of apoptosis. PHHC disturbs the mechanisms of early brain development leading to a delay in brain tissue maturation and formation of the motor reaction of pups.

Plant homocysteine, a methionine precursor and plant's hallmark of metabolic disorders

Homocysteine (Hcy) is a sulfur-containing non-proteinogenic amino acid, which arises from redox-sensitive methionine metabolism. In plants, Hcy synthesis involves both cystathionine β-lyase and S-adenosylhomocysteine hydrolase activities. Thus, Hcy itself is crucial for de novo methionine synthesis and S-adenosylmethionine recycling, influencing the formation of ethylene, polyamines, and nicotianamine. Research on mammalian cells has shown biotoxicity of this amino acid, as Hcy accumulation triggers oxidative stress and the associated lipid peroxidation process. In addition, the presence of highly reactive groups induces Hcy and Hcy derivatives to modify proteins by changing their structure and function. Currently, Hcy is recognized as a critical, independent hallmark of many degenerative metabolic diseases. Research results indicate that an enhanced Hcy level is also toxic to yeast and bacteria cells. In contrast, in the case of plants the metabolic status of Hcy remains poorly examined and understood. However, the presence of the toxic Hcy metabolites and Hcy over-accumulation during the development of an infectious disease seem to suggest harmful effects of this amino acid also in plant cells. The review highlights potential implications of Hcy metabolism in plant physiological disorders caused by environmental stresses. Moreover, recent research advances emphasize that recognizing the Hcy mode of action in various plant systems facilitates verification of the potential status of Hcy metabolites as bioindicators of metabolism disorders and thus may constitute an element of broadly understood biomonitoring.

Plasma metal concentrations and their interactions with genetic susceptibility on homocysteine levels

Limited studies have evaluated the associations of multiple metal exposures with homocysteine (Hcy) levels, which were independent risk factor for cardiovascular disease (CVD). Furthermore, the interactions between genetic variants and plasma metals in relation to Hcy levels were largely unknown. We aimed to explore the associations of multiple plasma metals (including metalloids arsenic [As] and selenium [Se]) with Hcy levels and whether their associations were modified by genetic susceptibility. We included 2989 participants from the baseline of the Dongfeng-Tongji cohort (DFTJ cohort) and conducted a cross-sectional study to explore the associations of 17 plasma metals with serum Hcy levels. Both multi-variable linear regression model (single-metal model) and LASSO penalized regression model (multiple-metal model) were used to identify the Hcy-associated metals. The weighted genetic risk score (GRS) was calculated based on 18 established Hcy-associated genetic variants. For metals that were associated with Hcy, we further assessed the gene-metal interactions on Hcy levels. Among 17 metals, plasma molybdenum (Mo), strontium (Sr), and Zinc (Zn) were positively associated with Hcy levels, whereas Se was inversely associated with Hcy levels in both single- and multiple-metal models. We also observed that the genetic predisposition to Hcy significantly modified the association between plasma Se and serum Hcy levels (P for interaction = 0.003), while no significant gene-metal interactions were found for Mo, Sr, and Zn (all P for interactions > 0.05). These findings provide novel insight into the associations of the plasma concentrations of Mo, Se, Sr and Zn with Hcy levels and address the importance of Se as a potential upstream modifiable factor for the personalized prevention of elevated Hcy levels and CVD.

The betaine-dependent remethylation pathway is a homocysteine metabolism pathway associated with the carnivorous feeding habits of spiders

Homocysteine (Hcy) is a sulfur-containing amino acid derived from the essential amino acid methionine (Met). Circulating levels of Hcy in animals can be increased by feeding on Met-enriched diets, which is generally considered harmful. Spiders are one of the largest groups of obligate carnivores and feed on animals high in protein and Met. We analyzed the Hcy metabolism pathways in 18 species of 3 taxa (Mammalia, Insecta, and Arachnida) and found that the betaine-dependent remethylation pathway (BRP) was present in all carnivorous arachnid species and mammals but absent in insects and red spider mites. We then studied the Hcy metabolism pathway in Pardosa pseudoannulata. In P. pseudoannulata, Hcy is metabolized through the transsulfuration pathway, BRP, and S-methylmethionine-dependent remethylation pathway. Because of a prior duplication event of the betaine homocysteine S-methyltransferase (BHMT) gene in the BRP, BHMTa and BHMTb are present in tandem in the genome of P. pseudoannulata. The high expression levels of BHMTa and its high abundance in detoxification tissues indicate that it plays an important role in the BRP; the ability of BHMTa and BHMTb to remethylate Hcy using betaine as substrate was similar. Compared with other Hcy metabolic enzyme genes, BHMT responded quickly to the application of Hcy or betaine. In sum, the BRP is important in Hcy metabolism in P. pseudoannulata and in other spider species.

Toxic Metabolites and Inborn Errors of Amino Acid Metabolism: What One Informs about the Other

In inborn errors of metabolism, such as amino acid breakdown disorders, loss of function mutations in metabolic enzymes within the catabolism pathway lead to an accumulation of the catabolic intermediate that is the substrate of the mutated enzyme. In patients of such disorders, dietarily restricting the amino acid(s) to prevent the formation of these catabolic intermediates has a therapeutic or even entirely preventative effect. This demonstrates that the pathology is due to a toxic accumulation of enzyme substrates rather than the loss of downstream products. Here, we provide an overview of amino acid metabolic disorders from the perspective of the ‘toxic metabolites’ themselves, including their mechanism of toxicity and whether they are involved in the pathology of other disease contexts as well. In the research literature, there is often evidence that such metabolites play a contributing role in multiple other nonhereditary (and more common) disease conditions, and these studies can provide important mechanistic insights into understanding the metabolite-induced pathology of the inborn disorder. Furthermore, therapeutic strategies developed for the inborn disorder may be applicable to these nonhereditary disease conditions, as they involve the same toxic metabolite. We provide an in-depth illustration of this cross-informing concept in two metabolic disorders, methylmalonic acidemia and hyperammonemia, where the pathological metabolites methylmalonic acid and ammonia are implicated in other disease contexts, such as aging, neurodegeneration, and cancer, and thus there are opportunities to apply mechanistic or therapeutic insights from one disease context towards the other. Additionally, we expand our scope to other metabolic disorders, such as homocystinuria and nonketotic hyperglycinemia, to propose how these concepts can be applied broadly across different inborn errors of metabolism and various nonhereditary disease conditions.

Antihypertensive effect and underlying mechanism of tripeptide NCW on spontaneously hypertensive rats using metabolomics analysis

Tripeptide NCW identified in our previous study displayed a strong ACE inhibitory activity, but whether it has any antihypertensive effect in vivo remains unknown. Thus, in this study, we aimed to investigate the protective effects of tripeptide NCW in spontaneously hypertensive rats (SHRs) and to further figure out the serum metabolic profiling variations due to its oral administration via UPLC-Q-TOF-MS/MS-based metabolomics analysis to clarify the underlying hypotensive mechanism. After three weeks of oral administration, the tripeptide NCW-treated group (NCW/SHR group, 80 mg per kg BW per d) showed significantly reduced systolic and diastolic blood pressure by 48.08 ± 3.84 mmHg and 48.92 ± 5.77 mmHg, respectively. Additionally, a total of 25 blood pressure-related metabolites were identified as being significantly changed in SHRs given tripeptide NCW after three weeks. These 25 metabolites might be biomarkers that indicated that the tripeptide NCW exhibits antihypertensive activity via regulating bile acid metabolism, lipid metabolism, amino acid metabolism, purinergic signaling, pantothenate and CoA biosynthesis, and the citrate cycle. Collectively, tripeptide NCW has a protective effect on SHRs associated with serum metabolite abnormalities.

Folic Acid Homeostasis and Its Pathways Related to Hepatic Oxidation in Adolescent Rats Exposed to Binge Drinking

Chronic ethanol consumption and liver disease are intimately related to folic acid (FA) homeostasis. Despite the fact that FA decreases lipid oxidation, its mechanisms are not yet well elucidated. Lately, adolescents have been practising binge drinking (BD), consisting of the intake of a high amount of alcohol in a short time; this is a particularly pro-oxidant form of consumption. The aim of this study is to examine, for the first time, FA homeostasis in BD adolescent rats and its antioxidant properties in the liver. We used adolescent rats, including control rats and rats exposed to an intermittent intraperitoneal BD model, supplemented with or without FA. Renal FA reabsorption and renal FA deposits were increased in BD rats; hepatic deposits were decreased, and heart and serum levels remained unaffected. This depletion in the liver was accompanied by higher transaminase levels; an imbalance in the antioxidant endogenous enzymatic system; lipid and protein oxidation; a decrease in glutathione (GSH) levels; hyper-homocysteinemia (HHcy); an increase in NADPH oxidase (NOX) 1 and NOX4 enzymes; an increase in caspase 9 and 3; and a decrease in the anti-apoptotic metallopeptidase inhibitor 1. Furthermore, BD exposure increased the expression of uncoupled endothelial nitric oxide synthase (eNOS) by increasing reactive nitrogen species generation and the nitration of tyrosine proteins. When FA was administered, hepatic FA levels returned to normal levels; transaminase and lipid and protein oxidation also decreased. Its antioxidant activity was due, in part, to the modulation of superoxide dismutase activity, GSH synthesis and NOX1, NOX4 and caspase expression. FA reduced HHcy and increased the expression of coupled eNOS by increasing tetrahydrobiopterin expression, avoiding nitrosative stress. In conclusion, FA homeostasis and its antioxidant properties are affected in BD adolescent rats, making it clear that this vitamin plays an important role in the oxidative, nitrosative and apoptotic hepatic damage generated by acute ethanol exposure. For this, FA supplementation becomes a potential BD therapy for adolescents, preventing future acute alcohol-related harms.

RESEARCH OF INDICATORS OF OXIDATIVE STRESS IN THE KIDNEYS OF IMMATURE RATS WITH HYPERHOMOCYSTEINEMIA

Purpose: Hyperhomocysteinemia in children can develop as a result of genetic defects, endocrine abnormalities or under the influence of dietary factors. An elevated level of homocysteine is considered a risk factor for the progression of chronic kidney disease. The aim of the work was to investigate the indicators of oxidative stress in the homogenate of the kidneys of immature rats in control and with hyperhomocysteinemia. Methods: The concentration of reduced and oxidized glutathione, the activity of superoxide dismutase, catalase and nitric oxide synthase were determined. The model of hyperhomocysteinemia was reproduced on one-month-old male rats, which were kept on a standard vivarium diet. The experimental group was intragastrically administered by D,L-thiolactone homocysteine hydrochloride in a 1% starch solution at a dose of 200 mg/kg of body weight 1 per day for 8 weeks. The corresponding volume of 1% starch solution was injected into the control group of animals. The activity of superoxide dismutase, catalase and nitric oxide synthase were determined spectrophotometrically. Concentration of reduced and oxidized glutathione by fluorometric method. Results: It was established that upon hyperhomocysteinemia the concentration of reduced glutathione, the activity of superoxide dismutase, catalase, and nitric oxide synthase was decreased against the background of an increase in the concentration of oxidized glutathione in the homogenate of the kidneys of immature rats. Conclusions: The obtained results indicate that in the kidneys of immature rats, the development of oxidative stress occurs in the direction characteristic of adult animals. The obtained results indicate that in the kidneys of immature rats the development of oxidative stress resembles the adult animals. The obtained results showed a decrease in the concentration of reduced glutathione and the activity of antioxidant defense enzymes which may indicate the development of pathological processes in the kidneys

The synthesis of fibroblast growth factor 23 is upregulated by homocysteine in UMR106 osteoblast-like cells

OBJECTIVES

Fibroblast growth factor 23 (FGF23) controls the production and degradation of biologically active vitamin D, 1,25(OH)₂D₃, and phosphate reabsorption in the kidney as a hormone synthesized by bone cells. Additional paracrine effects in other organs exist as well. As a biomarker, the FGF23 plasma concentration increases in renal and cardiovascular diseases, and is correlated with outcome. The regulation of FGF23 is incompletely understood and dependent on several factors, including oxidative stress. L-homocysteine is an amino acid produced in methionine metabolism, and can be converted into further metabolites depending on the availability of vitamin B. Hyperhomocysteinemia is a potential cardiovascular risk factor. Our study aimed to explore whether homocysteine impacts FGF23 synthesis.

METHODS

Experiments were performed in UMR106 osteoblast-like cells. Fgf23 gene expression and FGF23 protein concentration were measured by quantitative real-time polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. Oxidative stress was determined by 2',7'-dichlorofluorescein diacetate fluorescence.

RESULTS

Homocysteine dose-dependently upregulated Fgf23 gene expression and protein synthesis. Moreover, homocysteine imposed oxidative stress on UMR106 cells. The effect of homocysteine on Fgf23 was abrogated by antioxidant ascorbic acid.

CONCLUSIONS

Homocysteine is a potent stimulator of FGF23 production, an effect at least in part mediated by oxidative stress. The homocysteine-dependent upregulation of FGF23 presumably contributes to its role as a cardiovascular risk factor.

Effects of low-crude protein diets supplemented with arginine, glutamine, threonine, and methionine on regulating nutrient absorption, intestinal health, and growth performance of Eimeria-infected chickens

The study was conducted to evaluate the effects of low crude protein diets supplemented with arginine, glutamine, methionine, and/or threonine on apparent ileal digestibility of amino acids, intestinal morphology, intestinal permeability, gene expression of nutrient transporters, and tight junction proteins of broiler chickens challenged with mixed Eimeria spp. A total of five hundred seventy-six, 12-day-old male broiler chickens were allocated into 8 treatments, and 6 replicate cages of 12 chickens per cage. This experiment included a nonchallenged control (NC) fed regular corn-soybean meal-based diet (Regular diet, 19% crude protein), an Eimeria-challenged control (CC) fed Regular diet, an Eimeria challenge group fed low-crude protein diet (LCP, 16% crude protein), 4 Eimeria challenge groups fed low-crude protein diet supplemented with 0.75% arginine, glutamine, methionine, and threonine, respectively (ARG, GLN, MET, and THR), and an Eimeria challenge group fed low-crude protein diet with 0.75% supplemented arginine, glutamine, methionine, and threonine collectively as a combination group (COMB). On d 14, birds in the challenge groups were gavaged with a mixed Eimeria spp. solution containing 12,500 oocysts of E. maxima, 12,500 oocysts of E. tenella, and 62,500 oocysts of E. acervulina. The results showed that the Eimeria challenge reduced overall growth performance, but the LCP had no adverse impacts on intestinal health and growth of Eimeria-infected birds compared to the CC. Additionally, supplementation of crystalline arginine, glutamine, methionine, and threonine improved the apparent ileal digestibility of these specific amino acids on 6 dpi. Moreover, the THR treatment increased villus height in the duodenum. The ARG treatment decreased intestinal permeability and gene expression of amino acid transporters, whereas the GLN and THR treatments both reversed adverse effects of coccidiosis on gene expression of tight junction protein (claudin 1). However, the MET and COMB treatments exacerbated infection severity of coccidiosis. In summary, adding 0.75% of arginine, glutamine, or threonine in a low crude protein diet can improve the intestinal health of birds challenged with a mild coccidia infection.

Ocular manifestations in patients with inborn errors of intracellular cobalamin metabolism: a systematic review

Inherited disorders of cobalamin (cbl) metabolism (cblA-J) result in accumulation of methylmalonic acid (MMA) and/or homocystinuria (HCU). Clinical presentation includes ophthalmological manifestations related to retina, optic nerve and posterior visual alterations, mainly reported in cblC and sporadically in other cbl inborn errors.We searched MEDLINE EMBASE and Cochrane Library, and analyzed articles reporting ocular manifestations in cbl inborn errors. Out of 166 studies a total of 52 studies reporting 163 cbl and 24 mut cases were included. Ocular manifestations were found in all cbl defects except for cblB and cblD-MMA; cblC was the most frequent disorder affecting 137 (84.0%) patients. The c.271dupA was the most common pathogenic variant, accounting for 70/105 (66.7%) cases. One hundred and thirty-seven out of 154 (88.9%) patients presented with early-onset disease (0-12 months). Nystagmus and strabismus were observed in all groups with the exception of MMA patients while maculopathy and peripheral retinal degeneration were almost exclusively found in MMA-HCU patients. Optic nerve damage ranging from mild temporal disc pallor to complete atrophy was prevalent in MMA-HCU.and MMA groups. Nystagmus was frequent in early-onset patients. Retinal and macular degeneration worsened despite early treatment and stabilized systemic function in these patients. The functional prognosis remains poor with final visual acuity < 20/200 in 55.6% (25/45) of cases. In conclusion, the spectrum of eye disease in Cbl patients depends on metabolic severity and age of onset. The development of visual manifestations over time despite early metabolic treatment point out the need for specific innovative therapies.

Sulfur Amino Acids: From Prebiotic Chemistry to Biology and Vice Versa

Two sulfur-containing amino acids are included in the list of the 20 classical protein amino acids. A methionine residue is introduced at the start of the synthesis of all current proteins. Cysteine, thanks to its thiol function, plays an essential role in a very large number of catalytic sites. Here we present what is known about the prebiotic synthesis of these two amino acids and homocysteine, and we discuss their introduction into primitive peptides and more elaborate proteins.

1 Introduction

2 Sulfur Sources

3 Prebiotic Synthesis of Cysteine

4 Prebiotic Synthesis of Methionine

5 Homocysteine and Its Thiolactone

6 Methionine and Cystine in Proteins

7 Prebiotic Scenarios Using Sulfur Amino Acids

8 Introduction of Cys and Met in the Genetic Code

9 Conclusion

Melatonin as a Reducer of Neuro- and Vasculotoxic Oxidative Stress Induced by Homocysteine

The antioxidant properties of melatonin can be successfully used to reduce the effects of oxidative stress caused by homocysteine. The beneficial actions of melatonin are mainly due to its ability to inhibit the generation of the hydroxyl radical during the oxidation of homocysteine. Melatonin protects endothelial cells, neurons, and glia against the action of oxygen radicals generated by homocysteine and prevents the structural changes in cells that lead to impaired contractility of blood vessels and neuronal degeneration. It can be, therefore, assumed that the results obtained in experiments performed mainly in the in vitro models and occasionally in animal models may clear the way to clinical applications of melatonin in patients with hyperhomocysteinemia, who exhibit a higher risk of developing neurodegenerative diseases (e.g., Parkinson’s disease or Alzheimer’s disease) and cardiovascular diseases of atherothrombotic etiology. However, the results that have been obtained so far are scarce and have seldom been performed on advanced in vivo models. All findings predominately originate from the use of in vitro models and the scarcity of clinical evidence is huge. Thus, this mini-review should be considered as a summary of the outcomes of the initial research in the field concerning the use of melatonin as a possibly efficient attenuator of oxidative stress induced by homocysteine.

Association of High Serum Homocysteine Levels and Severe Chronic Venous Disease

BACKGROUND

Homocysteine (Hcy) is considered as a modifiable risk factor for vascular disease. This study was aimed to explore the association between serum concentration and the severity of primary chronic venous disease (CVD).

METHODS

Clinical data of 582 patients diagnosed with primary CVD were collected and analyzed retrospectively. The Clinical Etiology Anatomy Pathophysiology classification system was used to grade the severity of chronic venous disease. Patients were divided into 2 groups (group A: C1-C3; group B: C4-C6). The association between serum homocysteine levels and the severity of primary chronic venous disease was investigated using rank sum test and logistic regression.

RESULTS

The difference between the level of homocysteine in each grade has statistical significance. Group A has higher median Hcy concentrations than Group B (15.40 μmol/L vs. 14.05 μmol/L, P< 0.01). Further binary logistic regression showed no statistical significance among the level of Hcy (11.00-14.75 μmol/L [OR 0.66, 95% CI 0.40-1.11, P= 0.12], 14.75-20.38μmol/L [OR 0.97, 95% CI 0.59-1.69, P = 0.89], ≥20.38 μmol/L [OR 0.67, 95% CI 0.41-1.10, P = 0.11]), but age (OR 1.03, 95% CI 1.01-1.04, P< 0.01) and female (OR 0.41, 95% CI 0.28-0.59, P< 0.01) are associated with more severe stages of CVD.

CONCLUSIONS

Higher level of Hcy is associated with more severe stages of CVD, but it not an independent risk factor. However, Advanced age and female are risk factors for CVD development based on logistic regression analysis.

Involvements of Hyperhomocysteinemia in Neurological Disorders

Homocysteine (HCY), a physiological amino acid formed when proteins break down, leads to a pathological condition called hyperhomocysteinemia (HHCY), when it is over a definite limit. It is well known that an increase in HCY levels in blood, can contribute to arterial damage and several cardiovascular disease, but the knowledge about the relationship between HCY and brain disorders is very poor. Recent studies demonstrated that an alteration in HCY metabolism or a deficiency in folate or vitamin B12 can cause altered methylation and/or redox potentials, that leads to a modification on calcium influx in cells, or into an accumulation in amyloid and/or tau protein involving a cascade of events that culminate in apoptosis, and, in the worst conditions, neuronal death. The present review will thus summarize how much is known about the possible role of HHCY in neurodegenerative disease.

Homocysteine and Mitochondria in Cardiovascular and Cerebrovascular Systems

Elevated concentration of homocysteine (Hcy) in the blood plasma, hyperhomocysteinemia (HHcy), has been implicated in various disorders, including cardiovascular and neurodegenerative diseases. Accumulating evidence indicates that pathophysiology of these diseases is linked with mitochondrial dysfunction. In this review, we discuss the current knowledge concerning the effects of HHcy on mitochondrial homeostasis, including energy metabolism, mitochondrial apoptotic pathway, and mitochondrial dynamics. The recent studies suggest that the interaction between Hcy and mitochondria is complex, and reactive oxygen species (ROS) are possible mediators of Hcy effects. We focus on mechanisms contributing to HHcy-associated oxidative stress, such as sources of ROS generation and alterations in antioxidant defense resulting from altered gene expression and post-translational modifications of proteins. Moreover, we discuss some recent findings suggesting that HHcy may have beneficial effects on mitochondrial ROS homeostasis and antioxidant defense. A better understanding of complex mechanisms through which Hcy affects mitochondrial functions could contribute to the development of more specific therapeutic strategies targeted at HHcy-associated disorders.

Targeting Methionine Synthase in a Fungal Pathogen Causes a Metabolic Imbalance That Impacts Cell Energetics, Growth, and Virulence

Fungal pathogens are responsible for millions of life-threatening infections on an annual basis worldwide. The current repertoire of antifungal drugs is very limited and, worryingly, resistance has emerged and already become a serious threat to our capacity to treat fungal diseases. The first step to develop new drugs is often to identify molecular targets in the pathogen whose inhibition during infection can prevent its growth. However, the current models are not suitable to validate targets in established infections. Here, we have characterized the promising antifungal target methionine synthase in great detail, using the prominent fungal pathogen Aspergillus fumigatus as a model. We have uncovered the underlying reason for its essentiality and confirmed its druggability. Furthermore, we have optimized the use of a genetic system to show a beneficial effect of targeting methionine synthase in established infections. Therefore, we believe that antifungal drugs to target methionine synthase should be pursued and additionally, we provide a model that permits gaining information about the validity of antifungal targets in established infections.

There is an urgent need to develop novel antifungals to tackle the threat fungal pathogens pose to human health. Here, we have performed a comprehensive characterization and validation of the promising target methionine synthase (MetH). We show that in Aspergillus fumigatus the absence of this enzymatic activity triggers a metabolic imbalance that causes a reduction in intracellular ATP, which prevents fungal growth even in the presence of methionine. Interestingly, growth can be recovered in the presence of certain metabolites, which shows that metH is a conditionally essential gene and consequently should be targeted in established infections for a more comprehensive validation. Accordingly, we have validated the use of the tetOFF genetic model in fungal research and improved its performance in vivo to achieve initial validation of targets in models of established infection. We show that repression of metH in growing hyphae halts growth in vitro, which translates into a beneficial effect when targeting established infections using this model in vivo. Finally, a structure-based virtual screening of methionine synthases reveals key differences between the human and fungal structures and unravels features in the fungal enzyme that can guide the design of novel specific inhibitors. Therefore, methionine synthase is a valuable target for the development of new antifungals.

Impact of a nutritional supplement (Impryl) on male fertility: study protocol of a multicentre, randomised, double-blind, placebo-controlled clinical trial (SUppleMent Male fERtility, SUMMER trial)

INTRODUCTION

Infertility is a worldwide problem and about 10%-15% of all couples will be affected by the inability to have children. In approximately 50% of infertile couples, a male factor is involved. Most of the male infertile cases are characterised as 'idiopathic', except for a small percentage of cases which are causative by a genetic aetiology. In the past decade, the role of oxidative stress related to sperm quality has been researched thoroughly and estimated to be the problem in 25%-87% of male infertility cases. Impryl is a nutritional supplement which works on the metabolic system and the regulation of oxidative stress by activating the 1-carbon cycle and therefore recycling of homocysteine. We hypothesise that the nutritional supplement Impryl in men of infertile couples might improve the ongoing pregnancy rate.

METHODS AND ANALYSIS

We designed a multicentre, randomised, double-blind, placebo-controlled clinical trial. We aimed to include 1200 male adults aged 18-50 years, part of a couple that is diagnosed with infertility. The couple will either start or has already been started with fertility treatment, that is, expectative management (duration of 6 months), intrauterine insemination (IUI) with or without mild ovarian stimulation or ovulation induction, either in vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI) treatment. Male participants will be randomised in either the Impryl or the placebo group, with identical appearance of the tablets to be distributed (doses: one tablet each day), for a total duration of maximal 6 months. Patients can start directly with fertility treatment and/or natural conception. The primary outcome is the number of ongoing pregnancies confirmed by ultrasound at ≥10 to 12 weeks, and conceived in the time window between randomisation up to and including month 6 of intervention use. Secondary outcomes are change in semen parameters between baseline and after 3 months of intervention in the IUI/IVF/ICSI group, based on (prewash) total motile sperm count. Furthermore the number of pregnancies conceived in the optimal intervention time window (after full spermatogenesis of 72 days), overall number of pregnancies, time to pregnancy, embryo fertilisation rate in IVF/ICSI, embryo-utilisation rate in IVF/ICSI, number of miscarriages, live birth rate and adverse events are documented within the study period of 15 months.

ETHICS AND DISSEMINATION

The protocol is approved by the local medical ethical review committee at the Radboud University Medical Centre and by the national Central Committee on Research Involving Human Subjects. Findings will be shared with the academic and medical community, funding and patient organisations in order to contribute to optimisation of medical care and quality of life for patients with infertility.

TRIAL REGISTRATION NUMBERS

NCT03337360 and NTR6551.

Exposure to Toxic Heavy Metals Can Influence Homocysteine Metabolism?

BACKGROUND

Homocysteine is a sulfur amino acid whose metabolism is activated in two pathways: remethylation to methionine, which requires folate and vitamin B₁₂, and transsulfuration to cystathionine, which needs pyridoxal-5'-phosphate. High homocysteine level increases the risk of developing heart disease, stroke, peripheral vascular diseases, and cognitive impairment. Some evidence showed that exposure to these metals increased plasma homocysteine levels.

METHODS

A systematic review was carried out to clarify the relationship between homocysteine blood levels and exposure to toxic heavy metals (Lead, Cadmium, Mercury, and Chromium).

RESULTS

The results of this systematic review indicate that exposure to Pb, Cr, Cd, and Hg is connected with nonphysiological homocysteine levels or vitamin B₁₂ and folate serum concentrations.

CONCLUSIONS

These findings reinforce the importance of involvement in exposure to heavy metals in homocysteine metabolism. This supports the role of blood metals as potential upstream modifiable risk factors to prevent the development of other established risk factors as hyperhomocysteinemia.

Vitamin B12 Deficiency Induces Imbalance in Melanocytes Homeostasis-A Cellular Basis of Hypocobalaminemia Pigmentary Manifestations

Vitamin B₁₂ deficiency causes significant changes in cellular metabolism leading to various clinical symptoms, such as hematological, psychiatric, and neurological disorders. We hypothesize that skin pigmentation disorders may be a diagnostically important manifestation of vitamin B₁₂ deficiency, however the cellular and molecular mechanisms underlying these effects remain unknown. The aim of this study was to examine the effect of vitamin B₁₂ deficiency on melanocytes homeostasis. Hypocobalaminemia in vitro model was developed by treating epidermal melanocytes with synthesized vitamin B₁₂ antagonist—hydroxycobalamin(c-lactam). The cells were examined using immunoenzymatic, spectrophotometric, and fluorimetric assays as well as image cytometry. Significant melanogenesis stimulation—the increase of relative melanin content and tyrosinase activity up to 131% and 135%, respectively—has been indicated. Cobalamin-deficient cells displayed the elevation (by 120%) in reactive oxygen species level. Moreover, the redox status imbalance was stated. The study provided a scientific evidence for melanocytes homeostasis disturbance under hypocobalaminemia, thus indicating a significant element of the hyperpigmentation mechanism due to vitamin B₁₂ deficiency. Furthermore, the implication between pigmentary and hematological and/or neuropsychiatric symptoms in cobalamin-deficient patients may be an important issue.

Modification of erythropoietin structure by N-homocysteinylation affects its antiapoptotic and proliferative functions

Many patients under therapy with recombinant human erythropoietin (rhuEPO) show resistance to the treatment, an effect likely associated with the accumulation of tissue factors, especially in renal and cardiovascular diseases. Hyperhomocysteinemia due to high serum levels of homocysteine has been suggested among the risk factors in those pathologies. Its main effect is the N-homocysteinylation of proteins due to the interaction between the highly reactive homocysteine thiolactone (HTL) and lysine residues. The aim of this study was to evaluate the effect of N-homocysteinylation on the erythropoietic and antiapoptotic abilities of EPO, which can be a consequence of structural changes in the modified protein. We found that both cellular functions were altered in the presence of HTL-EPO. A decreased net positive charge of HTL-EPO was detected by capillary zone electrophoresis, while analysis of polyacrylamide gel electropherograms suggested formation of aggregates. Far-UV spectra, obtained by Circular Dichroism Spectroscopy, indicated a switch of the protein's secondary structure from α-helix to β-sheet structures. Results of Congo red and Thioflavin T assays confirm the formation of repetitive β-sheet structures, which may account for aggregates. Accordingly, Dynamic Light Scattering analysis showed a markedly larger radius of the HTL-EPO structures, supporting the formation of soluble oligomers. These structural changes might interfere with the conformational adaptations necessary for efficient ligand-receptor interaction, thus affecting the proliferative and antiapoptotic functions of EPO. The present findings may contribute to explain the resistance exhibited by patients with cardio-renal syndrome to treatment with rhuEPO, as a consequence of structural modifications due to protein N-homocysteinylation.

Ideal cardiovascular health and the subclinical impairments of cardiovascular diseases: a cross-sectional study in central south China

Background

Ideal cardiovascular health (CVH) is related to a low cardiovascular disease risk profile. This study aimed to investigate CVH metrics with both the biomarkers and markers of subclinical impairments of cardiovascular diseases (CVDs) in subjects from central south China.

Methods

The ideal CVH score (non-smoking status; ideal body mass index; regular physical activity; healthy diet; and an optimal serum cholesterol, blood pressure, and glucose profile; 1 point for each; total score: 0–7) was collected from 3009 participants without a history of CVDs. Subclinical biomarkers were assessed using C-reactive protein, homocysteine, and microalbuminuria. The presence of subclinical disease markers was defined as having at least one of the following: increased carotid intima-media thickness, carotid plaque, left ventricular hypertrophy, left ventricular systolic dysfunction, or a reduced ankle-brachial index. The association of biomarkers and markers with the CVH score was evaluated using multivariate logistic regression and linear regression analyses.

Results

Only 0.2% of the study participants met all 7 ideal CVH metrics (CVH score = 7). Compared to the female participants, the male participants had poorer CVH profiles and a higher incidence of subclinical lesions (P < 0.05). In the fully adjusted models, per 1-unit increase in the CVH score was inversely associated with the biomarker levels (β = -0.092 – -0.224, P < 0.05 for all) and the odds of the presence of markers (odds ratio, 0.808; 95% confidence interval, 0.755–0.865). Similar relationships were observed in the gender subgroups and were stronger in the females.

Conclusion

A clear inverse association was observed between the biomarkers or markers of subclinical impairments and the CVH score in a central south Chinese population, implying the importance of ideal CVH for the primordial prevention of CVDs.

Electronic supplementary material

The online version of this article (10.1186/s12872-017-0697-9) contains supplementary material, which is available to authorized users.

Blood lead, cadmium and mercury in relation to homocysteine and C-reactive protein in women of reproductive age: a panel study

BACKGROUND

To examine the relationship between cadmium, lead, and mercury concentrations with high-sensitivity C-reactive protein (hs-CRP) and homocysteine in women.

METHODS

Metals were measured at enrollment in whole blood. Homocysteine and hs-CRP were measured in one (N = 9) or two (N = 250) menstrual cycles up to 3 and 8 times per cycle, respectively. Linear mixed models with inverse probability of exposure weights to account for time varying confounding were used and models were stratified by dietary and serum vitamin status (dietary: vitamin B₆, B₁₂, folate; serum: folate).

RESULTS

Geometric mean (95% confidence interval (CI)) concentrations for cadmium, lead, and mercury were 0.29 (0.26-0.31) μg/L, 0.91 (0.86-0.96) μg/dL, and 1.05 (0.93-1.18) μg/L, respectively. Lead was associated with increased homocysteine (0.08; 95% CI: 0.01, 0.15) and this persisted among those in the lower three quartiles of consumption of vitamin B₆, B₁₂, folate, and serum folate but was not significant among those in the upper quartile. No associations were observed between metals and hs-CRP.

CONCLUSIONS

Blood lead was associated with increased homocysteine in a cohort of healthy, premenopausal women but these associations did not persist among those consuming ≥75th percentile of essential micronutrients. Cadmium, lead, and mercury were not associated with hs-CRP concentrations.

Comparison of Protein N-Homocysteinylation in Rat Plasma under Elevated Homocysteine Using a Specific Chemical Labeling Method

Elevated blood concentrations of homocysteine have been well established as a risk factor for cardiovascular diseases and neuropsychiatric diseases, yet the etiologic relationship of homocysteine to these disorders remains poorly understood. Protein N-homocysteinylation has been hypothesized as a contributing factor; however, it has not been examined globally owing to the lack of suitable detection methods. We recently developed a selective chemical method to label N-homocysteinylated proteins with a biotin-aldehyde tag followed by Western blotting analysis, which was further optimized in this study. We then investigated the variation of protein N-homocysteinylation in plasma from rats on a vitamin B₁₂ deficient diet. Elevated “total homocysteine” concentrations were determined in rats with a vitamin B₁₂ deficient diet. Correspondingly, overall levels of plasma protein N-homocysteinylation displayed an increased trend, and furthermore, more pronounced and statistically significant changes (e.g., 1.8-fold, p-value: 0.03) were observed for some individual protein bands. Our results suggest that, as expected, a general metabolic correlation exists between “total homocysteine” and N-homocysteinylation, although other factors are involved in homocysteine/homocysteine thiolactone metabolism, such as the transsulfuration of homocysteine by cystathionine β-synthase or the hydrolysis of homocysteine thiolactone by paraoxonase 1 (PON1), may play more significant or direct roles in determining the level of N-homocysteinylation.

Improvement of gamete quality by stimulating and feeding the endogenous antioxidant system: mechanisms, clinical results, insights on gene-environment interactions and the role of diet

Oxidative damage triggers extensive repair in gametes and thereafter in the zygote but it results in clinically relevant damage when affecting the maturation of the gametes chromatin, i.e. padlocking and epigenetic marking. It associates with defective DNA methylation and/or with oxidation of the methyl marks leading to derangement of gamete epigenetics, defects of chromatin condensation and aneuploidy. A proper feed to the one carbon cycle has the potential to stimulate the endogenous antioxidant defences, i.e. gluthatione synthesis, and to activate compensative homeostatic mechanisms restoring both the oxy-redox balance and DNA methylation, which are indeed strictly cross-regulated. This has been shown to produce measurable clinical improvements of male reproductive potential in pilot studies herein summarised. However, the effects of dietary habits and of supplementations are variable according to the individual genetic substrate, as genetic variants of several of the concerned enzymes occur with high frequency. Individual risk assessments and personalised interventions are still difficult to implement, in the meantime, a very varied diet may facilitate metabolic compensation in the majority of the cases. This review aims to report on the mechanisms of damage, on the opportunities to modulate the physiologic oxy-redox homeostasis by means of a varied diet or dietary supplements and on the open issues related to the genetic variability of the population.

Homocysteine induces PUMA-mediated mitochondrial apoptosis in SH-SY5Y cells

Previous studies have reported that homocysteine induced endoplasmic reticulum (ER) stress in neuronal cells, proposing the underlying mechanism by which it could induce neurotoxicity. Induction of pro-apoptotic transcription factor C/EBP homologous protein (CHOP) and activation of caspase-4 by calpain have been suggested to be an important route in inducing apoptosis in response to ER stress. In this study, we investigated the molecular pathway of homocysteine-induced apoptosis in caspase-4 deficient SH-SY5Y human neuroblastoma cells. Homocysteine significantly increased mRNA levels of CHOP and p53, resulting in the upregulation of their downstream target gene, p53 up-regulated modulator of apoptosis (PUMA). In cells treated with homocysteine, Bcl-2-associated X protein (BAX) protein levels, cytochrome c release from the mitochondria, and caspase-9 activation were significantly increased. Consistently, a caspase-9 inhibitor significantly alleviated homocysteine-induced cytotoxicity. Significantly lower BAX mRNA levels and caspase-9 activation were observed in cells transfected with siRNA for PUMA. Taken together, our findings suggest that PUMA would be involved in the possible crosstalk between the ER and the mitochondria in the homocysteine-induced apoptosis of caspase-4 deficient SH-SY5Y cells.

Ophthalmic Manifestations and Long-Term Visual Outcomes in Patients with Cobalamin C Deficiency

PURPOSE

To explore the ocular manifestations of cobalamin C (cblC) deficiency, an inborn error of intracellular vitamin B12 metabolism.

DESIGN

Retrospective, observational case series.

PARTICIPANTS

Twenty-five cblC patients underwent clinical and ophthalmic examination at the National Institutes of Health between August 2004 and September 2012. Patient ages ranged from 2 to 27 years at last ophthalmic visit, and follow-up ranged from 0 to 83 months (median, 37 months; range, 13-83 months) over a total of 69 visits.

METHODS

Best-corrected visual acuity, slit-lamp biomicroscopy, dilated fundus examination, wide-field photography, fundus autofluorescence imaging, sedated electroretinography, optical coherence tomography, genetics and metabolite assessment.

MAIN OUTCOME MEASURES

Visual acuity and presence and degree of retinal degeneration and optic nerve pallor.

RESULTS

Nystagmus (64%), strabismus (52%), macular degeneration (72%), optic nerve pallor (68%), and vascular changes (64%) were present. c.271dupA (p.R91KfsX14) homozygous patients (n = 14) showed early and extensive macular degeneration. Electroretinography showed that scotopic and photopic responses were reduced and delayed, but were preserved remarkably in some patients despite severe degeneration. Optical coherence tomography images through the central macular lesion of a patient with severe retinal degeneration showed extreme thinning, some preservation of retinal lamination, and nearly complete loss of the outer nuclear layer. Despite hyperhomocysteinemia, no patients exhibited lens dislocation.

CONCLUSIONS

This longitudinal study reports ocular outcomes in the largest group of patients with cblC deficiency systematically examined at a single center over an extended period. Differences in progression and severity of macular degeneration, optic nerve pallor, and vascular attenuation between homozygous c.271dupA (p.R91KfsX14) patients and compound heterozygotes were noted. The pace and chronicity of ophthalmic manifestations lacked strict correlation to metabolic status as measured during visits. Prenatal or early treatment, or both, may have mitigated ocular disease, leading to better functional acuity, but patients still progressed to severe macular degeneration. The effects of prenatal or early treatment, or both, in siblings; the manifestation of severe disease in infancy; the presence of comorbid developmental abnormalities; and the possible laminar structural defect noted in many patients are findings showing that cblC deficiency displays a developmental as well as a degenerative ocular phenotype.

Plasma homocysteine and B vitamins levels in Nigerian children with nephrotic syndrome

INTRODUCTION

Available data on plasma homocysteine level in patients with nephrotic syndrome (NS) are controversial with increased, decreased and unchanged values reported. Therefore, plasma homocysteine and serum B vitamins in Nigerian children with NS were assessed in this study.

METHODS

Fasting blood samples were analysed for plasma homocysteine, serum folate and B vitamins in 42 children with NS and 42 age and sex-matched healthy controls in this case control study. Data were compared between NS and control using t test and Chi square. Relationships were tested with regression analysis with p set at 0.05.

RESULTS

Prevalence of hyperhomocysteinaemia, low folate and cyanocobalamin in NS was 57.1%, 14.3% and 9.5% respectively. The mean homocysteine level was significantly higher in NS than control (11.3±2.6 µmol/L versus 5.5±2.3 µmol/L). Also, NS had lower folate and cyanocobalamin than control: 9.1±3.9 ng/mL versus 11.2±3.1 ng/dL and 268.5±95.7 pg/mL versus 316±117.2 pg/mL respectively. Weak but significant correlation between homocysteine and serum albumin (r = 0.347), folate (r = -0.607) and vitamin B12 (r = -0.185) were found in the NS group. Significant relationship was also found between homocysteine and vitamin B12 (ß = -0.64, 95% CI = -1.20, -0.08) after controlling for folate and vitamin B6 levels.

CONCLUSION

Clinically important hyperhomocysteinaemia and low B vitamins occur in Nigerian children with nephrotic syndrome. This data suggest that potential usefulness of folate and vitamin B supplementation for reducing high homocysteine levels in nephrotic syndrome need to be further investigated.

Effect of choline on antioxidant defenses and gene expressions of Nrf2 signaling molecule in the spleen and head kidney of juvenile Jian carp (Cyprinus carpio var. Jian)

The present work evaluates the effects of various levels of dietary choline on antioxidant defenses and gene expressions of Nrf2 signaling molecule in spleen and head kidney of juvenile Jian carp (Cyprinus carpio var. Jian). Fish were fed with six different experimental diets containing graded levels of choline at 165 (choline-deficient control), 310, 607, 896, 1167 and 1820 mg kg(-1) diet for 65 days. At the end of the feeding trail, fish were challenged with Aeromonas hydrophila and mortalities were recorded over 17 days. Dietary choline significantly decreased malondialdehyde and protein carbonyl contents in spleen and head kidney. However, anti-superoxide anion and anti-hydroxyl radical activities in spleen and head kidney also decreased. Interestingly, activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione-S-transferase (GST) and glutathione reductase (GR) in spleen, GPx activity in head kidney, and glutathione contents in spleen and head kidney were decreased with increase of dietary choline levels up to a certain point, whereas, activities of SOD, GST and GR in head kidney showed no significantly differences among groups. Similarly, expression levels of CuZnSOD, MnSOD, CAT, GPx1a, GPx1b and GR gene in spleen and head kidney were significantly lower in group with choline level of 607 mg kg(-1) diet than those in the choline-deficient group. The relative gene expressions of Nrf2 in head kidney and Keap1a in spleen and head kidney were decreased with increasing of dietary choline up to a certain point. However, the relative gene expression of Nrf2 in spleen were not significantly affected by dietary choline. In conclusion, dietary choline decreased the oxidant damage and regulated the antioxidant system in immune organs of juvenile Jian carp.

The potential role of homocysteine mediated DNA methylation and associated epigenetic changes in abdominal aortic aneurysm formation

Previous studies have suggested that homocysteine (Hcy) has wide-ranging biological effects, including accelerating atherosclerosis, impairing post injury endothelial repair and function, deregulating lipid metabolism and inducing thrombosis. However, the biochemical basis by which hyperhomocysteinemia (HHcy) contributes to cardiovascular diseases (CVDs) remains largely unknown. Several case-control studies have reported an association between HHcy and the presence of abdominal aortic aneurysms (AAA) and there are supportive data from animal models. Genotypic data concerning the association between variants of genes involved in the methionine cycle and AAA are conflicting probably due to problems such as reverse causality and confounding. The multifactorial nature of AAA suggests the involvement of additional epigenetic factors in disease formation. Elevated Hcy levels have been previously linked to altered DNA methylation levels in various diseases. Folate or vitamin B12 based methods of lowering Hcy have had disappointingly limited effects in reducing CVD events. One possible reason for the limited efficacy of such therapy is that they have failed to reverse epigenetic changes induced by HHcy. It is possible that individuals with HHcy have an "Hcy memory effect" due to epigenetic alterations which continue to promote progression of cardiovascular complications even after Hcy levels are lowered. It is possible that deleterious effect of prior, extended exposure to elevated Hcy concentrations have long-lasting effects on target organs and genes, hence underestimating the benefit of Hcy lowering therapies in CVD patients. Therapies targeting the epigenetic machinery as well as lowering circulating Hcy concentrations may have a more efficacious effect in reducing the incidence of cardiovascular complications.

Therapy of hyperhomocysteinemia in hemodialysis patients: effects of folates and N-acetylcysteine

OBJECTIVE

Uremia represents a state where hyperhomocysteinemia is resistant to folate therapy, thus undermining intervention trials' efficacy. N-acetylcysteine (NAC), an antioxidant, in addition to folates (5-methyltetrahydrofolate, MTHF), was tested in a population of hemodialysis patients.

DESIGN

The study is an open, parallel, intervention study.

SETTING

Ambulatory chronic hemodialysis patients.

SUBJECTS

Clinically stable chronic hemodialysis patients, on hemodialysis since more than 3 months, undergoing a folate washout. Control group on standard therapy (n = 50).

INTERVENTION

One group was treated with intravenous MTHF (MTHF group, n = 48). A second group was represented by patients treated with MTHF, and, during the course of 10 hemodialysis sessions, NAC was administered intravenous (MTHF + NAC group, n = 47).

MAIN OUTCOME MEASURE

Plasma homocysteine measured before and after dialysis at the first and the last treatment.

RESULTS

At the end of the study, there was a significant decrease in predialysis plasma homocysteine levels in the MTHF group and MTHF + NAC group, compared with the control group, but no significant difference between the MTHF group and MTHF + NAC group. A significant decrease in postdialysis plasma homocysteine levels in MTHF + NAC group (10.27 ± 0.94 μmol/L, 95% confidence interval: 8.37-12.17) compared with the MTHF group (16.23 ± 0.83, 95% confidence interval: 14.55-17.90) was present. In the MTHF + NAC group, 64% of patients reached a postdialysis homocysteine level <12 μmol/L, compared with 19% in the MTHF group and 16% in the control group.

CONCLUSIONS

NAC therapy induces a significant additional decrease in homocysteine removal during dialysis. The advantage is limited to the time of administration.

Comparative in vivo antioxidant capacity of DL-2-hydroxy-4-methylthiobutanoic acid (HMTBA) and DL-methionine in male mice fed a high-fat diet

BACKGROUND

In animal diets, methionine (Met) is considered to be the first limiting amino acid, and the activity of synthetic Met is typically added either as DL-methionine (DLM) or as DL-2-hydroxy-4-methylthiobutanoic acid (HMTBA). It has been demonstrated that HMTBA exhibits a higher antioxidant capability in vitro as compared to DLM. However, the difference in antioxidant capability between DLM and HMTBA in vivo is unknown.

METHODS

In the present study, 60 male C57BL/6 mice were randomly divided into six groups and fed either a normal diet (NFD, 5.37% fat) or a high-fat diet (HFD, 19.7% fat) in conjunction with 0.2% DLM, 0.2% HMTBA or 0.1% DLM and 0.1% HMTBA for 4 weeks.

RESULTS

HFD supplemented with 2% DLM and NFD with 2% HMTBA both induced adverse affects in relation to serum lipid parameters and depressed antioxidant defense systems in the digestive system. However, these changes were restored in the 0.2% HMTBA-treated HFD group. Furthermore, no significant differences were found in the lipid parameters and antioxidant status in the NFD and HFD group supplemented with 0.1% DLM and 0.1% HMTBA.

CONCLUSION

HMTBA restored oxidative redox status under OS conditions and its antioxidant properties were positively correlated with the dosage included in diet.

Contribution of dietary intakes of antioxidants to homocysteine-induced low density lipoprotein (LDL) oxidation in atherosclerotic patients

PURPOSE

Elevated circulating oxidized low density lipoprotein (Ox-LDL) levels are associated with increased risk of atherosclerosis, which may be due to high plasma homocysteine (Hcy) and low intakes of antioxidants. We investigated the contribution of dietary intakes of antioxidants to Hcy-induced LDL oxidation in atherosclerotic patients (AP) and controls.

MATERIALS AND METHODS

Male AP (n = 101) who were confirmed by coronary angiography and 91 controls were evaluated by blood biochemistry and dietary intakes. To determine whether homocysteine is an independent risk factor for atherosclerosis, subjects were divided into three groups; low- (<or= 6.9 uM/L), normal- (7 uM-12 uM/L) and high- (>or= 12.1 uM/L) Hcy.

RESULTS

Plasma levels of homocysteine and LDL were higher, but plasma apo A-I in HDL and folate were lower in the AP group. The odds ratio (OR) for the risk of atherosclerosis was 3.002 [95% confidence interval (CI), 1.27-7.09] for patients in the highest tertile with homocysteine >or= 12.1 uM/L. AP having high homocysteine levels had low intakes of vitamin A, beta-carotene and vitamin C. By logistic regression analysis, age, body mass index (BMI), plasma LDL, plasma folate, and low intakes of vitamin A and beta-carotene were found to be risk factors for atherosclerosis in patients with high-Hcy, but dietary B vitamins including folate were not.

CONCLUSION

A high-Hcy level was a risk factor for atherosclerosis in patients with high Ox-LDL levels. High intakes of antioxidants appeared to be a protective factor for atherosclerosis, perhaps exerting a pro-oxidative effect on LDL when combined with high levels of Hcy and LDL. However, more evidence for the benefits of B vitamins as a homocysteine-lowering therapy is needed.

Assessment of serum homocysteine, endothelin-1, and nitric oxide levels in behçet's disease

BACKGROUND

Some prominent features of Behçet's disease (BD) are arterial and venous thromboses as a result of endothelial dysfunction. Hyperhomocysteinemia is responsible for vascular endothelial injury due to an increased frequency of thrombogenesis. Endothelin-1 (ET-1) is a vasoconstrictor whereas nitric oxide (NO) is an endothelial vasorelaxing peptide that is responsible for the inhibition of platelet adhesion.

AIM

To evaluate serum levels of homocysteine (Hcy) and determine whether hyperhomocysteinemia is considered as a contributing risk factor for venous and arterial thromboses of BD, and to correlate serum levels of ET-1 and NO with disease activity.

MATERIALS AND METHODS

We measured serum levels of Hcy, ET-1, and nitrite (NO(2) (-)) in 25 patients who fulfilled the criteria of the International Study Group for BD, and compared them to those of 15 healthy control subjects. Levels of Hcy and ET-1 were measured by using enzyme-linked immunosorbent assay (ELISA), whereas serum nitrite (NO(2) (-)) levels were measured by using Griess reaction as an indicator for NO production. All the patients were screened for a history of venous thrombosis and subdivided into thrombotic and nonthrombotic subgroups according to their thrombotic history. Patients with BD were divided into two subgroups, active and inactive, according to their clinical and laboratory findings.

RESULTS

There were significant increases in serum levels of Hcy, ET-1, and nitrite in BD patients compared to those in controls. There was a significant increase in serum Hcy levels in thrombotic compared to nonthrombotic subgroups. Positive correlations were detected between the serum ET-1 and nitrite levels with disease activity in BD patients.

CONCLUSION

Hyperhomocysteinemia may play some role in the development of venous and arterial thromboses in BD. Increased NO production might ave critical biological activities that are relevant to pathological events in the active period of the disease.

Relationship of impairment induced by intracellular S-adenosylhomocysteine accumulation with DNA methylation in human umbilical vein endothelial cells treated with 3-deazaadenosine

The aim of this study was to estimate the relationship of endothelial dysfunction induced by intracellular S-adenosylhomocysteine (SAH) accumulation and DNA methylation in human umbilical vein endothelial cells (HUVEC). The isolated HUVEC were incubated with 3-deazaadenosine (DZA) to induce experimental intracellular SAH accumulation. The impairment of HUVEC function was assessed by changes in morphology and proliferative ability. The expression of DNA methyltransferase-1 (DNMT1) and the atherosclerosis related genes [oestrogen receptor-alpha (ER-alpha), extracellular superoxide dismutase (EC-SOD) and monocyte chemoattractant protein-1 (MCP-1)] were analysed using quantitative real-time PCR. Global DNA methylated status was measured using the cytosine extension assay. The methylated patterns of ER-alpha, EC-SOD and MCP-1 genes were determined with methylation-specific PCR. We found that DZA administration increased intracellular SAH levels progressively and simultaneously decreased Hcy content in medium. Moreover, the supplementation induced HUVEC apoptosis, inhibited proliferation ability and DNMT1 mRNA expression (P < 0.05) and furthermore reduced global DNA methylation status (P < 0.05). Correlation analysis showed the presence of a negative correlation between intracellular SAH concentration, proliferative ability, and expression of ER-alpha, EC-SOD, and DNMT1 (r = -0.89, -0.86, -0.92 and -0.88 respectively, P < 0.001); and a positive correlation with MCP-1 expression and DNA [(3)H]-dCTP incorporation (r = 0.89 and 0.93 respectively, P < 0.001). Our results showed that endothelial dysfunction induced by intracellular SAH accumulation is mediated by regulating the expression of atherosclerosis related genes in HUVEC, which is not related with gene promoter methylated patterns, but may be associated with altered global DNA hypomethylated status. These findings suggest that SAH can act as the potential molecular biological marker in the promotion of atherogenesis.

Body mass index is an important determinant of methylation biomarkers in women of reproductive ages

B vitamin deficiencies lead to moderate hyperhomocysteinemia, which has been associated with health and disease. However, concomitant derangements in cellular methylation, reflected by altered plasma S-adenosylmethionine (SAM) or S-adenosylhomocysteine (SAH) concentrations, may be the primary cause. Therefore, we identified determinants of homocysteine, SAM, and SAH concentrations in 336 women, aged 20-48 y, as part of a large study focusing on risk factors for reproductive disorders. Blood was obtained to determine plasma SAM, SAH, and total homocysteine (tHcy), serum vitamin B-12 and folate, RBC folate concentrations, and the related single nucleotide polymorphisms 5,10-methylenetetrahydrofolate reductase (MTHFR) 677C > T and 1298A > C, methionine synthase reductase (MTRR) 66A > G, and nicotinamide N-methyltransferase IVS1-151G > A. Questionnaires provided information on demographics, lifestyles, and nutrient intakes. Correlation coefficients were calculated and multivariable associations were assessed with a general linear model. Serum folate was positively correlated with SAM concentrations (r = 0.159; P = 0.004). Folate and vitamin B-12 were not correlated with SAH concentrations or the SAM:SAH ratio but were inversely correlated with tHcy concentrations (serum folate r = -0.324; RBC folate r = -0.294; vitamin B-12 r = -0.307; P < 0.01). From the multivariable analysis, BMI was the strongest determinant of SAM (standardized beta = 19.145; P < 0.001) and SAH concentrations (standardized beta = 3.241; P = 0.010). MTHFR 677TT (standardized beta = 0.195; P = 0.001), B vitamin supplement use (standardized beta = -0.156; P < 0.001) and dietary protein intake (standardized beta = -0.011; P < 0.001) were the strongest determinants of tHcy concentrations. Thus, the determinants of SAM and SAH differ from those of tHcy concentrations. Given that BMI was a strong determinant of SAM concentrations, it should be included in future studies on cellular methylation.

Intravenous N-acetylcysteine with saline hydration improves renal function and ameliorates plasma total homocysteine in patients undergoing cardiac angiography

Proinflammatory cytokines and hyperhomocysteinemia are associated with clinically relevant restenosis in coronary artery disease. N-acetylcysteine (NAC) can decrease proinflammatory cytokines and plasma homocystine as well as reduce contrast-induced nephropathy. The aim of this study, therefore, was to compare normal saline hydration with and without intravenous NAC in terms of changes in renal function, proinflammatory cytokines, inflammatory markers, and plasma total homocysteine during coronary angiography. Forty-six patients who underwent coronary angiography and/or stent implantation for unstable angina were enrolled and assigned to NAC or NS treatment groups based on normal saline hydration with or without intravenous NAC, respectively. The NS group had lower serum creatinine (Cre: p = 0.02) and plasma total homocysteine (tHcy; p < 0.001) and increased glomerular filtration rate (GFR; p = 0.003) after angiography. In the NAC group, the serum blood urea nitrogen (BUN; p = 0.001), Cre (p < 0.001), and plasma tHcy (p < 0.001) were lower, and the GFR (P = 0.013) was increased after angiography. There were no statistically significant differences in serum high-sensitivity C reactive protein (hs-CRP), tumor necrosis factor-alpha (TNF-alpha), or interleukin-10 (IL-10) before and after angiography in the NS and NAC groups. Intergroup comparison revealed that plasma tHcy level was lower for the NAC-treated patients (p = 0.002), with lower plasma tHcy level before and after treatment in this group (p < 0.001). Normal saline hydration can improve renal function and decrease plasma tHcy after coronary angiography with or without NAC; however, the combination of the two decreases plasma tHcy more than normal saline hydration alone.