Homocysteinylation of neuronal proteins contributes to folate deficiency-associated alterations of differentiation, vesicular transport, and plasticity in hippocampal neuronal cells

A transgenic mice model of retinopathy of cblG-type inherited disorder of one-carbon metabolism highlights epigenome-wide alterations related to cone photoreceptor cells development and retinal metabolism

BACKGROUND

MTR gene encodes the cytoplasmic enzyme methionine synthase, which plays a pivotal role in the methionine cycle of one-carbon metabolism. This cycle holds a significant importance in generating S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH), the respective universal methyl donor and end-product of epigenetic transmethylation reactions. cblG type of inherited disorders of vitamin B12 metabolism due to mutations in MTR gene exhibits a wide spectrum of symptoms, including a retinopathy unresponsive to conventional therapies.

METHODS

To unveil the underlying epigenetic pathological mechanisms, we conducted a comprehensive study of epigenomic-wide alterations of DNA methylation by NGS of bisulfited retinal DNA in an original murine model with conditional Mtr deletion in retinal tissue. Our focus was on postnatal day 21, a critical developmental juncture for ocular structure refinement and functional maturation.

RESULTS

We observed delayed eye opening and impaired visual acuity and alterations in the one-carbon metabolomic profile, with a notable dramatic decline in SAM/SAH ratio predicted to impair DNA methylation. This metabolic disruption led to epigenome-wide changes in genes involved in eye development, synaptic plasticity, and retinoid metabolism, including promoter hypermethylation of Rarα, a regulator of Lrat expression. Consistently, we observed a decline in cone photoreceptor cells and reduced expression of Lrat, Rpe65, and Rdh5, three pivotal genes of eye retinoid metabolism.

CONCLUSION

We introduced an original in vivo model for studying cblG retinopathy, which highlighted the pivotal role of altered DNA methylation in eye development, cone differentiation, and retinoid metabolism. This model can be used for preclinical studies of novel therapeutic targets.

Parental Folate Deficiency Inhibits Proliferation and Increases Apoptosis of Neural Stem Cells in Rat Offspring: Aggravating Telomere Attrition as a Potential Mechanism

The effect of maternal folate status on the fetal central nervous system (CNS) is well recognized, while evidence is emerging that such an association also exists between fathers and offspring. The biological functions of telomeres and telomerase are also related to neural cell proliferation and apoptosis. The study aimed to investigate the effect of parental folate deficiency on the proliferation and apoptosis of neural stem cells (NSCs) in neonatal offspring and the role of telomeres in this effect. In this study, rats were divided into four groups: maternal folate-deficient and paternal folate-deficient diet (D-D) group; maternal folate-deficient and paternal folate-normal diet (D-N) group; maternal folate-normal and paternal folate-deficient diet (N-D) group; and the maternal folate-normal and paternal folate-normal diet (N-N) group. The offspring were sacrificed at postnatal day 0 (PND0), and NSCs were cultured from the hippocampus and striatum tissues of offspring for future assay. The results revealed that parental folate deficiency decreased folate levels, increased homocysteine (Hcy) levels of the offspring's brain tissue, inhibited proliferation, increased apoptosis, shortened telomere length, and aggravated telomere attrition of offspring NSCs in vivo and in vitro. In vitro experiments further showed that offspring NSCs telomerase activity was inhibited due to parental folate deficiency. In conclusion, parental folate deficiency inhibited the proliferation and increased apoptosis of offspring NSCs, maternal folate deficiency had more adverse effects than paternal, and the mechanisms may involve the telomere attrition of NSCs.

Epigenetic Mechanisms Involved in the Effects of Maternal Hyperhomocysteinemia on the Functional State of Placenta and Nervous System Plasticity in the Offspring

According to modern view, susceptibility to diseases, specifically to cognitive and neuropsychiatric disorders, can form during embryonic development. Adverse factors affecting mother during the pregnancy increase the risk of developing pathologies. Despite the association between elevated maternal blood homocysteine (Hcy) and fetal brain impairments, as well as cognitive deficits in the offspring, the role of brain plasticity in the development of these pathologies remains poorly studied. Here, we review the data on the negative impact of hyperhomocysteinemia (HHcy) on the neural plasticity, in particular, its possible influence on the offspring brain plasticity through epigenetic mechanisms, such as changes in intracellular methylation potential, activity of DNA methyltransferases, DNA methylation, histone modifications, and microRNA expression in brain cells. Since placenta plays a key role in the transport of nutrients and transmission of signals from mother to fetus, its dysfunction due to aberrant epigenetic regulation can affect the development of fetal CNS. The review also presents the data on the impact of maternal HHcy on the epigenetic regulation in the placenta. The data presented in the review are not only interesting from purely scientific point of view, but can help in understanding the role of HHcy and epigenetic mechanisms in the pathogenesis of diseases, such as pregnancy pathologies resulting in the delayed development of fetal brain, cognitive impairments in the offspring during childhood, and neuropsychiatric and neurodegenerative disorders later in life, as well as in the search for approaches for their prevention using neuroprotectors.

Association of Folic Acid Supplementation, Dietary Folate Intake and Serum Folate Levels with Risk of Gestational Diabetes Mellitus: A Matched Case-Control Study

Periconceptional folate supplementation is prevalent, raising concerns about possible side effects. The aim of this study was to investigate the associations of folic acid supplementation, dietary folate, serum folate with gestational diabetes mellitus (GDM) risk. In this matched case-control study, 81 pregnant women with GDM (cases) and 81 pregnant women with non-GDM (controls) were identified through age difference (≤3 y) and parity (Both primipara or multipara women) matching, and serum folate levels were measured during the GDM screening (24-28 gestational wk). Folic acid supplementation and dietary folate intake from three months prepregnancy through midpregnancy were assessed using a self-reported questionnaire and food frequency questionnaire. Multivariate binary logistic regression models were used to evaluate the association between folate and GDM. After adjusting for confounding factors, we observed that compared with folic acid supplementation dose ≤400 μg/d, pregnancies without folic acid supplementation and supplemental dose >800 μg/d were associated with GDM risk (adjusted odds ratio=7.25, 95% confidence interval: 1.34-39.36; adjusted odds ratio=4.20, 95% confidence interval: 1.03-17.22), while no significant association with a 400-800 μg/d dose of folic acid supplementation and GDM. Compared with folic acid supplementation dose ≤24 wk, pregnancies without folic acid supplementation were associated with GDM risk (adjusted odds ratio=6.70, 95% confidence interval: 1.22-36.77), while no significant association with folic acid supplementation dose >24 wk and GDM. No significant association of dietary folate and serum folate with GDM was found. No or a higher dose of folic acid supplementation would increase GDM risk and a dose of <800 μg/d is the safe dose.

Effect of in ovo feeding of folic acid on brain derived neurotrophic factor (BDNF) and gga-miR-190a-3p expression in the developing cerebral cortex of chickens

Folate plays important role in biosynthesis of purine and pyrimidine nucleotides and is therefore crucial for DNA synthesis and neurogenesis in fetal brains. Many genes comprising brain derived neurotrophic factor (BDNF) and miRNAs have been shown to play important role in brain development. Gga-miR-190a-3p targets many genes including BDNF. The aim of this project was to study the effects of in ovo administration of folic acid (FA) on BDNF and gga-miR-190a-3p expression in the cerebral cortex of chick embryo. A total number of 120 hatching eggs with the correct shape and weight were used in this experiment. Forty eggs was injected by FA into the yolk sac at a dose of 150-μg per egg, 40 eggs by PBS (SHAM) on embryonic day 11 and 40 eggs were left without injection as controls. Then the cerebral cortex was collected on E19 and BDNF and gga-miR-190a-3p expression was studied using Real time PCR. The results showed that BDNF expression in the cortex of FA treated, SHAM and controls were 2.06 ± 0.29, 1.12 ± 0.12 and 1.02 ± 0.21 fold changes, respectively and for gga-miR-190a-3p were 0.72 ± 0.08, 0.95 ± 0.09 and 1.007 ± 0.12 fold change, respectively. Statistical analysis showed that there is significant increase in BDNF expression and decreased gga-miR-190a-3p expression in FA injected cerebral cortex as compared either with SHAM or controls. Although, no significant change in BDNF and gga-miR-190a-3p expression were observed between SHAM and controls. It is concluded that in ovo administration of FA increases BDNF and decreases gga-miR-190a-3p expression in the developing chick cerebral cortex.

The protective mechanism of folic acid on hyperhomocysteinemia-related arterial injury in spontaneously hypertensive rats: Folic acid against arterial inflammation

BACKGROUND

Hypertension associated with hyperhomocysteinemia (HHcy) is correlated with a high risk of vascular diseases. Studies found that folic acid (FA) supplementation can reduce the risk of cardiovascular and cerebrovascular events. The aim of the present study was to explore the potential mechanisms of FA attenuating HHcy-related arterial injury in spontaneously hypertensive rats (SHRs).

METHODS

24 SHRs were randomized into the control group, the HHcy group, and the HHcy + FA group (8 per group). The SHRs in the HHcy group and the HHcy + FA group were given DL-Hcy intraperitoneally to mimic hypertension associated with HHcy. The SHRs in the HHcy + FA group were given FA by gavage to mimic an FA-fortified diet. The histopathology and immunohistochemistry of rat aorta and carotid artery were analyzed, and the relative expression levels of immune/inflammation and oxidative stress molecules in arterial tissue were detected by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot.

RESULTS

FA significantly reduced the expression levels of nuclear factor-κ-gene binding (NF-κB) p65/Rela and interleukin-6 (IL-6) in rat arterial tissues, as well as the levels of plasma HHcy and serum malondialdehyde (MDA) in hypertension associated with HHcy rats (p < 0.05). At the same time, FA significantly increased the serum superoxide dismutase (SOD) level in hypertension associated with HHcy rats, and even the SOD level of the HHcy + FA group was higher than that of the control group (p < 0.05). However, HHcy induced the opposite results of the above indicators in SHRs compared with the control group (p < 0.05).

CONCLUSIONS

The arterial protection mechanisms of FA are related to reducing the concentration of HHcy to eliminate the tissue toxicity of HHcy, inhibiting NF-κBp65/Rela/IL-6 pathway molecules to regulate inflammatory response, and promoting the potential anti-oxidative stress pathway molecules to reduce oxidative stress level.

Folic acid intervention during pregnancy alters DNA methylation, affecting neural target genes through two distinct mechanisms

Background

We previously showed that continued folic acid (FA) supplementation beyond the first trimester of pregnancy appears to have beneficial effects on neurocognitive performance in children followed for up to 11 years, but the biological mechanism for this effect has remained unclear. Using samples from our randomized controlled trial of folic acid supplementation in second and third trimester (FASSTT), where significant improvements in cognitive and psychosocial performance were demonstrated in children from mothers supplemented in pregnancy with 400 µg/day FA compared with placebo, we examined methylation patterns from cord blood (CB) using the EPIC array which covers approximately 850,000 cytosine–guanine (CG) sites across the genome. Genes showing significant differences were verified using pyrosequencing and mechanistic approaches used in vitro to determine effects on transcription.

Results

FA supplementation resulted in significant differences in methylation, particularly at brain-related genes. Further analysis showed these genes split into two groups. In one group, which included the CES1 gene, methylation changes at the promoters were important for regulating transcription. We also identified a second group which had a characteristic bimodal profile, with low promoter and high gene body (GB) methylation. In the latter, loss of methylation in the GB is linked to decreases in transcription: this group included the PRKAR1B/HEATR2 genes and the dopamine receptor regulator PDE4C. Overall, methylation in CB also showed good correlation with methylation profiles seen in a published data set of late gestation foetal brain samples.

Conclusion

We show here clear alterations in DNA methylation at specific classes of neurodevelopmental genes in the same cohort of children, born to FA-supplemented mothers, who previously showed improved cognitive and psychosocial performance. Our results show measurable differences at neural genes which are important for transcriptional regulation and add to the supporting evidence for continued FA supplementation throughout later gestation. This trial was registered on 15 May 2013 at www.isrctn.com as ISRCTN19917787.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13148-022-01282-y.

Organometallic Folate Gold Nanoparticles Ameliorate Lipopolysaccharide-Induced Oxidative Damage and Inflammation in Zebrafish Brain

Synthesized organometallic gold-based folate nanoparticles (FAuNPs) were characterized, and its defense against lipopolysaccharide (LPS)-induced brain inflammation in Zebra fish was proven. Vitamin entrapment efficiency of these particles was found to be nearly 70%. The in vitro pH-dependent drug release dialysis study of FAuNPs confirmed a slow, sustained, and gradual release of folate for a period of 24 h. Both AuNPs and FAuNPs did not cause any marked changes in food intake, body weight, color, behavioral pattern, blood parameters, and hepatotoxicity. Histology of liver showed no changes between treated and control groups of fishes. The ex vivo study showed significant uptake of FAuNPs to free folate in folate receptor negative Hek293 cells, confirming a strategy to overcome folate deficiency in the brain. Antioxidant status and activities of few crucial brain enzymes were also measured to assess the brain function and found to be returned to the basal level, following FAuNP treatment. The transcription factor NRF2-Keap 1 expression pattern was also noted, and a prominent modulation was observed in the LPS-treated and FAuNP-administered group. Decisive brain enzymes like AChE and Na⁺K⁺ATPase were decreased significantly after LPS treatment, which is restored with FAuNP treatment. Caspases increased sharply after LPS treatment and diminished following FAuNP treatment. We conclude that FAuNP due to its high physical stability and uptake could be utilized against severe brain inflammation, leading to brain injury and neurodegeneration.

Moderate Folic Acid Supplementation in Pregnant Mice Results in Altered Sex-Specific Gene Expression in Brain of Young Mice and Embryos

Food fortification and increased vitamin intake have led to higher folic acid (FA) consumption by many pregnant women. We showed that FA-supplemented diet in pregnant mice (fivefold higher FA than the recommended level (5xFASD)) led to hyperactivity-like behavior and memory impairment in pups. Disturbed choline/methyl metabolism and altered placental gene expression were identified. The aim of this study was to examine the impact of 5xFASD on the brain at two developmental stages, postnatal day (P) 30 and embryonic day (E) 17.5. Female C57BL/6 mice were fed a control diet or 5xFASD for 1 month before mating. Diets were maintained throughout the pregnancy and lactation until P30 or during pregnancy until E17.5. The 5xFASD led to sex-specific transcription changes in P30 cerebral cortex and E17.5 cerebrum, with microarrays showing a total of 1003 and 623 changes, respectively. Enhanced mRNA degradation was observed in E17.5 cerebrum. Expression changes of genes involved in neurotransmission, neuronal growth and development, and angiogenesis were verified by qRT-PCR; 12 and 15 genes were verified at P30 and E17.5, respectively. Hippocampal collagen staining suggested decreased vessel density in FASD male embryos. This study provides insight into the mechanisms of neurobehavioral alterations and highlights potential deleterious consequences of moderate folate oversupplementation during pregnancy.

Low folate induces abnormal neuronal maturation and DNA hypomethylation of neuronal differentiation-related genes in cultured mouse neural stem and progenitor cells

Folate deficiency in a fetus is well known to cause neurodevelopment defects and development disorders. A low level of folate is also thought to be a risk for depression in adults. We have previously shown that post-weaning low folate induces neuronal immaturity in the dentate gyrus in mice, which suggests that low folate causes neuropsychological disorders via inhibition of neuronal maturation. In this study, we examined the effects of low folate on expression and epigenetic modification of genes involved in neuronal differentiation and maturation in primary mouse neural stem/progenitor cells (NSPCs) in vitro. An increase in Nestin (NSPC marker)-positive cells was observed in cells differentiated in a low folate medium for 3 days. An increase in βIII-tubulin (Tuj1: immature neuron marker)-positive cells and a decrease in microtubule-associated protein 2 (MAP2: mature neuron marker)-positive cells were observed in cells differentiated in a low folate medium for 7 days. In these cells, mRNA levels for genes involved in neuronal differentiation and maturation were altered. Hypomethylation of DNA, but not of histone proteins, was also observed at some promoters of these neuronal genes. The level of S-adenosylmethionine (SAM), a methyl donor, was decreased in these cells. The abnormalities in neural maturation and changes in gene expression in culture under low folate conditions were partially normalized by addition of SAM (5 μM). Based on these results, decreased SAM may induce DNA hypomethylation at genes involved in neuronal differentiation and maturation under low folate conditions, and this hypomethylation may be associated with low folate-induced neuronal immaturity.

Serum folate levels and cognitive performance in the ELSA-Brasil baseline assessment

BACKGROUND

Most studies that analyze the association between serum folate levels and cognitive function either restrict their assessments to specific clinical scenarios or do not include middle-aged individuals, to whom strategies for preventing cognitive impairment may be more feasible.

OBJECTIVE

To examine the association between serum folate levels and cognitive function in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) baseline assessment.

METHODS

Data from 4,571 ELSA-Brasil participants who live in the state of São Paulo, aged 35-74 years, were analyzed. The word list learning, delayed recall, word recognition, verbal fluency, and Trail Making Test Part B consisted in the cognitive tests. For each test, age, sex, and education-specific standardized scores and a global cognitive score were calculated. Crude and adjusted linear regression models were used to examine the associations of serum folate levels with cognitive test scores.

RESULTS

In multivariable-adjusted models, serum folate was not associated with global cognitive score (β=-0.043; 95% confidence interval [95%CI] -0.135 to 0.050 for lowest vs. highest quintile group), nor with any cognitive test performance. We did not find associations between serum folate and global cognitive scores in subgroups stratified by age, sex, or use of vitamin supplements either.

CONCLUSIONS

We did not find significant associations between serum folate and cognitive performance in this large sample, which is characterized by a context of food fortification policies and a consequent low frequency of folate deficiency. Positive results from previous studies may not apply to the increasingly common contexts in which food fortification is implemented, or to younger individuals.

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.

Influences of Folate Supplementation on Homocysteine and Cognition in Patients with Folate Deficiency and Cognitive Impairment

Although folate deficiency was reported to be associated with hyperhomocysteinemia, influence of folate supplementation on cognition remains controversial. Therefore, we explored the effects of folate supplementation on the cognition and Homocysteine (Hcy) level in relatively short periods in patients with folate deficiency and cognitive impairment. Enrolled 45 patients (mean age of 79.7 ± 7.9 years old) with folate deficiency (<3.6 ng/mL) with cognitive impairment underwent Mini-Mental State Examination (MMSE), and laboratory examinations, including folate, vitamin B₁₂, and Hcy. The degree of hippocampal atrophy in MRI was estimated using a voxel-based specific regional analysis system for Alzheimer’s disease (VSRAD). Patients were administrated folate (5 mg/day), then Hcy, and MMSE score were re-examined after 28 to 63 days. Mean Hcy significantly decreased from 25.0 ± 18.0 to 11.0 ± 4.3 nmol/mL (p < 0.001). Average MMSE scores also significantly changed from 20.1 ± 4.7 to 22.2 ± 4.3 (p < 0.001). The degree of change in the MMSE score and basic Hcy or Hcy change was significantly positively correlated, while degree of hippocampal atrophy in MRI did not. Although several factors should be taken into account, folate supplementation ameliorated cognitive impairment, at least for a short period, in patients with folate deficiency.

Homocysteine aggravates DNA damage by impairing the FA/Brca1 Pathway in NE4C murine neural stem cells

There is existing evidence that elevated homocysteine (Hcy) levels are risk factors for some neurodegenerative disorders. The pathogenesis of neurological diseases could be contributed to excessive cell dysfunction and death caused by defective DNA damage response (DDR) and accumulated DNA damage. Hcy is a neurotoxic amino acid and acts as a DNA damage inducer. However, it is not clear whether Hcy participates in the DDR. To investigate the effects of Hcy on DNA damage and the DDR, we employed mitomycin C (MMC) to cause DNA damage in NE4C murine neural stem cells (NSCs). Compared to treatment with MMC alone, we found that co-treatment with MMC and Hcy worsened DNA damage and increased death in NE4C cells. Intriguingly, in this DNA damage model mimicked by MMC, immunoblotting results showed that the monoubiquitination levels of Fanconi anemia complementation group I (Fanci) and Fanconi anemia complementation group D2 (Fancd2) were decreased to about 60.3% and 55.7% by supplementing cell culture medium with Hcy, indicating Hcy inactivates the function of Fanci and Fancd2 in DNA damage conditions. Given Breast Cancer 1 (BRCA1) is an important downstream of FANCD2, we next detected the interaction between Fancd2 and Brca1 in NE4C cells. Compared to treatment with MMC alone, the Fancd2-Brca1 interaction and the amount of Brca1 on chromatin were decreased when cells were co-exposed to MMC and Hcy, suggesting Hcy could impair the Fanconi anemia (FA)/Brca1 pathway. Taken together, our study demonstrates that Hcy may enhance cell death, which contributes to the accumulation of DNA damage and promotion of hypersensitivity to cytotoxicity by impairing the FA/Brca1 pathway in murine NSCs in the presence of DNA damage.

Alzheimer's Amyloidopathy: An Alternative Aspect

The ‘amyloid hypothesis’ dominates Alzheimer’s disease (AD) research but has failed to deliver effective therapies. Amyloid precursor protein (APP) and presenilin-1 (PSEN1) genetic mutations are undoubtedly pathogenic, albeit by unclear mechanisms. Conversely, high dose B-vitamins convincingly slow brain atrophy in a pre-stage state of sporadic AD. Here we suggest a link between sporadic and genetic AD: 1) Increased serum homocysteine, a marker of B-vitamin deficiencies, is a significant risk factor for sporadic AD. It also correlates with elevated levels of antichymotrypsin, a serine protease inhibitor. 2) Family members with codon 717 APP mutations and dementia have low serum vitamin B₁₂ values. Overexpression of the APP domain coding for a Kunitz type serine protease inhibitor might explain this. 3) PSEN1 mutations disrupt lysosomal function due to reduced proteolytic activity. They also trap cobalamin (B₁₂) within lysosomes, leading to intracellular deficiency of the vitamin. In summary, APP and PSEN1 mutations both confer a risk for reduced protease activity and B₁₂ bio-availability. Comparably, sporadic AD features a constellation of increased protease inhibition and B-vitamin deficiencies, the central part of which is believed to be B₁₂. These concordant observations in three disparate AD etiologies suggest a common neuropathogenic pathway. This hypothesis is evaluable in laboratory and clinical trials.

Role of environmental factors and epigenetics in autism spectrum disorders

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder thought to be caused by predisposing high-risk genes that may be altered during the early development by environmental factors. The impact of maternal challenges during pregnancy on the prevalence of ASD has been widely studied in clinical and animal studies. Here, we review some clinical and pre-clinical evidence that links environmental factors (i.e., infection, air pollution, pesticides, valproic acid and folic acid) and the risk of ASD. Additionally, certain prenatal environmental challenges such as the valproate and folate prenatal exposures allow us to study mechanisms possibly linked to the etiology of ASD, for instance the epigenetic processes. These mechanistic pathways are also presented and discussed in this chapter.

Facts and hypotheses about the programming of neuroplastic deficits by prenatal malnutrition

Studies in rats have shown that a decrease in either protein content or total dietary calories results in molecular, structural, and functional changes in the cerebral cortex and hippocampus, among other brain regions, which lead to behavioral disturbances, including learning and memory deficits. The neurobiological bases underlying those effects depend at least in part on fetal programming of the developing brain, which in turn relies on epigenetic regulation of specific genes via stable and heritable modifications of chromatin. Prenatal malnutrition also leads to epigenetic programming of obesity, and obesity on its own can lead to poor cognitive performance in humans and experimental animals, complicating understanding of the factors involved in the fetal programming of neuroplasticity deficits. This review focuses on the role of epigenetic mechanisms involved in prenatal malnutrition-induced brain disturbances, which are apparent at a later postnatal age, through either a direct effect of fetal programming on brain plasticity or an indirect effect on the brain mediated by the postnatal development of obesity.

Analysis of fibroblasts from patients with cblC and cblG genetic defects of cobalamin metabolism reveals global dysregulation of alternative splicing

Vitamin B12 or cobalamin (Cbl) metabolism can be affected by genetic defects leading to defective activity of either methylmalonyl-CoA mutase or methionine synthase or both enzymes. Patients usually present with a wide spectrum of pathologies suggesting that various cellular processes could be affected by modifications in gene expression. We have previously demonstrated that these genetic defects are associated with subcellular mislocalization of RNA-binding proteins (RBP) and subsequent altered nucleo-cytoplasmic shuttling of mRNAs. In order to characterize the possible changes of gene expression in these diseases, we have investigated global gene expression in fibroblasts from patients with cblC and cblG inherited disorders by RNA-seq. The most differentially expressed genes are strongly associated with developmental processes, neurological, ophthalmologic and cardiovascular diseases. These associations are consistent with the clinical presentation of cblC and cblG disorders. Multivariate analysis of transcript processing revaled splicing alterations that led to dramatic changes in cytoskeleton organization, response to stress, methylation of macromolecules and RNA binding. The RNA motifs associated with this differential splicing reflected a potential role of RBP such as HuR and HNRNPL. Proteomic analysis confirmed that mRNA processing was significantly disturbed. This study reports a dramatic alteration of gene expression in fibroblasts of patients with cblC and cblG disorders, which resulted partly from disturbed function of RBP. These data suggest to evaluate the rescue of the mislocalization of RBP as a potential strategy in the treatment of severe cases who are resistant to classical treatments with co-enzyme supplements.

Methyl Donor Deficiency during Gestation and Lactation in the Rat Affects the Expression of Neuropeptides and Related Receptors in the Hypothalamus

The micronutrients vitamins B9 and B12 act as methyl donors in the one-carbon metabolism involved in transmethylation reactions which critically influence epigenetic mechanisms and gene expression. Both vitamins are essential for proper development, and their deficiency during pregnancy has been associated with a wide range of disorders, including persisting growth retardation. Energy homeostasis and feeding are centrally regulated by the hypothalamus which integrates peripheral signals and acts through several orexigenic and anorexigenic mediators. We studied this regulating system in a rat model of methyl donor deficiency during gestation and lactation. At weaning, a predominance of the anorexigenic pathway was observed in deficient pups, with increased plasma peptide YY and increased hypothalamic pro-opiomelanocortin (POMC) mRNA, in line with abnormal leptin, ghrelin, and insulin secretion and/or signaling during critical periods of fetal and/or postnatal development of the hypothalamus. These results suggest that early methyl donor deficiency can affect the development and function of energy balance circuits, resulting in growth and weight deficits. Maternal administration of folic acid (3 mg/kg/day) during the perinatal period tended to rectify peripheral metabolic signaling and central neuropeptide and receptor expression, leading to reduced growth retardation.

Implication of homocysteine in protein quality control processes

Homocysteine (Hcy) is a key metabolite generated during methionine metabolism. The elevated levels of Hcy in the blood are reffered to as hyperhomocystenimeia (HHcy). The HHcy is caused by impaired metabolism/deficiency of either folate or B12 or defects in Hcy metabolism. Accumulating evidence suggests that HHcy is associated with cardiovascular and brain diseases including atherosclerosis, endothelial injury, and stroke etc. Vitamin B12 (cobalamin; B12) is a water-soluble vitamin essential for two metabolic reactions. It acts as a co-factor for methionine synthase and L-methylmalonyl-CoA mutase. Besides, it is also vital for DNA synthesis and maturation of RBC. Deficiency of B12 is associated with haematological and neurological disorders. Hyperhomocysteinemia (HHcy)-induced toxicity is thought to be mediated by the accumulation of Hcy and its metabolites, homocysteinylated proteins. Cellular protein quality control (PQC) is essential for the maintenance of proteome integrity, and cell viability and its failure contributes to the development of multiple diseases. Chaperones, unfolded protein response (UPR), ubiquitin-proteasome system (UPS), and autophagy are analogous strategies of PQC that maintain cellular proteome integrity. Recently, multiple studies reported that HHcy responsible for perturbation of PQC by reducing chaperone levels, activating UPR, and impairing autophagy. Besides, HHcy also induce cytotoxicity, inflammation, protein aggregation and apoptosis. It has been shown that some of the factors including altered SIRT1-HSF1 axis and irreversible homocysteinylation of proteins are responsible for folate and/or B12 deficiency or HHcy-induced impairment of PQC. Therefore, this review highlights the current understanding of HHcy in the context of cellular PQC and their pathophysiological and clinical consequences, epigenomic changes, therapeutic implications of B12, and chemical chaperones based on cell culture and experimental animal models.

Improving Outcome in Infantile Autism with Folate Receptor Autoimmunity and Nutritional Derangements: A Self-Controlled Trial

Background

In contrast to multiple rare monogenetic abnormalities, a common biomarker among children with infantile autism and their parents is the discovery of serum autoantibodies directed to the folate receptor alpha (FRα) localized at blood-brain and placental barriers, impairing physiologic folate transfer to the brain and fetus. Since outcome after behavioral intervention remains poor, a trial was designed to treat folate receptor alpha (FRα) autoimmunity combined with correction of deficient nutrients due to abnormal feeding habits.

Methods

All participants with nonsyndromic infantile autism underwent a routine protocol measuring CBC, iron, vitamins, coenzyme Q10, metals, and trace elements. Serum FRα autoantibodies were assessed in patients, their parents, and healthy controls. A self-controlled therapeutic trial treated nutritional derangements with addition of high-dose folinic acid if FRα autoantibodies tested positive. The Childhood Autism Rating Scale (CARS) monitored at baseline and following 2 years of treatment was compared to the CARS of untreated autistic children serving as a reference.

Results

In this self-controlled trial (82 children; mean age ± SD: 4.4 ± 2.3 years; male:female ratio: 4.8:1), FRα autoantibodies were found in 75.6 % of the children, 34.1 % of mothers, and 29.4 % of fathers versus 3.3 % in healthy controls. Compared to untreated patients with autism (n=84) whose CARS score remained unchanged, a 2-year treatment decreased the initial CARS score from severe (mean ± SD: 41.34 ± 6.47) to moderate or mild autism (mean ± SD: 34.35 ± 6.25; paired t-test p<0.0001), achieving complete recovery in 17/82 children (20.7 %). Prognosis became less favorable with the finding of higher FRα autoantibody titers, positive maternal FRα autoantibodies, or FRα antibodies in both parents.

Conclusions

Correction of nutritional deficiencies combined with high-dose folinic acid improved outcome for autism, although the trend of a poor prognosis due to maternal FRα antibodies or FRα antibodies in both parents may warrant folinic acid intervention before conception and during pregnancy.

Sex affects N-homocysteinylation at lysine residue 212 of albumin in mice

The modification of protein lysine residues by the thioester homocysteine (Hcy)-thiolactone has been implicated in cardiovascular and neurodegenerative diseases. However, only a handful of proteins carrying Hcy on specific lysine residues have been identified and quantified in humans or animals. In the present work, we developed a liquid chromatography/mass spectrometry targeted assay, based on multiple reaction monitoring, for quantification of N-Hcy-Lys212 (K212Hcy) and N-Hcy-Lys525 (K525Hcy) sites in serum albumin in mice. Using this assay, we found that female (n = 20) and male (n = 13) Cbs^−/− mice had significantly elevated levels of K212Hcy and K525Hcy modifications in serum albumin relative to their female (n = 19) and male (n = 17) Cbs^+/− littermates. There was significantly more K212Hcy modification in Cbs^−/− males than in Cbs^−/− females (5.78 ± 4.21 vs. 3.15 ± 1.38 units, P = 0.023). Higher K212Hcy levels in males than in females were observed also in Cbs^+/− mice (2.72 ± 0.81 vs. 1.89 ± 1.07 units, P = 0.008). In contrast, levels of the K525Hcy albumin modification were similar between males and females, both in Cbs^−/− and Cbs^+/− mice. These findings suggest that the sex-specific K212Hcy modification in albumin might have an important biological function in mice that is not affected by the Cbs genotype.

Developmental Impairments in a Rat Model of Methyl Donor Deficiency: Effects of a Late Maternal Supplementation with Folic Acid

Vitamins B9 (folate) and B12 act as methyl donors in the one-carbon metabolism which influences epigenetic mechanisms. We previously showed that an embryofetal deficiency of vitamins B9 and B12 in the rat increased brain expression of let-7a and miR-34a microRNAs involved in the developmental control of gene expression. This was reversed by the maternal supply with folic acid (3 mg/kg/day) during the last third of gestation, resulting in a significant reduction of associated birth defects. Since the postnatal brain is subject to intensive developmental processes, we tested whether further folate supplementation during lactation could bring additional benefits. Vitamin deficiency resulted in weaned pups (21 days) in growth retardation, delayed ossification, brain atrophy and cognitive deficits, along with unchanged brain level of let-7a and decreased expression of miR-34a and miR-23a. Whereas maternal folic acid supplementation helped restore the levels of affected microRNAs, it led to a reduction of structural and functional defects taking place during the perinatal/postnatal periods, such as learning/memory capacities. Our data suggest that a gestational B-vitamin deficiency could affect the temporal control of the microRNA regulation required for normal development. Moreover, they also point out that the continuation of folate supplementation after birth may help to ameliorate neurological symptoms commonly associated with developmental deficiencies in folate and B12.

An appraisal of folates as key factors in cognition and ageing-related diseases

Folic acid (FA) is often consumed as a food supplement and can be found in fortified staple foods in various western countries. Even though FA supplementation during pregnancy is known to prevent severe congenital anomalies in the developing child (e.g., neural tube defects), much less is known about its influence on cognition and neurological functioning. In this review, we address the advances in this field and situate how folate intake during pregnancy, postnatal life, adulthood and in the elderly affects cognition. In addition, an association between folate status and ageing, dementia and other neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis is discussed. While its role in the incidence and severity of these diseases is becoming apparent, the underlying action of folates and related metabolites remains elusive. Finally, the potential of FA as a nutraceutical has been proposed, although the efficacy will highly depend on the interplay with other micronutrients, the disease stage and the duration of supplementation. Hence, the lack of consistent data urges for more animal studies and (pre)clinical trials in humans to ascertain a potential beneficial role for folates in the treatment or amelioration of cognitive decline and ageing-related disorders.

Homocysteine Modification in Protein Structure/Function and Human Disease

Epidemiological studies established that elevated homocysteine, an important intermediate in folate, vitamin B₁₂, and one carbon metabolism, is associated with poor health, including heart and brain diseases. Earlier studies show that patients with severe hyperhomocysteinemia, first identified in the 1960s, exhibit neurological and cardiovascular abnormalities and premature death due to vascular complications. Although homocysteine is considered to be a nonprotein amino acid, studies over the past 2 decades have led to discoveries of protein-related homocysteine metabolism and mechanisms by which homocysteine can become a component of proteins. Homocysteine-containing proteins lose their biological function and acquire cytotoxic, proinflammatory, proatherothrombotic, and proneuropathic properties, which can account for the various disease phenotypes associated with hyperhomocysteinemia. This review describes mechanisms by which hyperhomocysteinemia affects cellular proteostasis, provides a comprehensive account of the biological chemistry of homocysteine-containing proteins, and discusses pathophysiological consequences and clinical implications of their formation.

Early Manifestations of Brain Aging in Mice Due to Low Dietary Folate and Mild MTHFR Deficiency

Folate is an important B vitamin required for methylation reactions, nucleotide and neurotransmitter synthesis, and maintenance of homocysteine at nontoxic levels. Its metabolism is tightly linked to that of choline, a precursor to acetylcholine and membrane phospholipids. Low folate intake and genetic variants in folate metabolism, such as the methylenetetrahydrofolate reductase (MTHFR) 677 C>T polymorphism, have been suggested to impact brain function and increase the risk for cognitive decline and late-onset Alzheimer's disease. Our study aimed to assess the impact of genetic and nutritional disturbances in folate metabolism, and their potential interaction, on features of cognitive decline and brain biochemistry in a mouse model. Wild-type and Mthfr^+/- mice, a model for the MTHFR 677 C>T polymorphism, were fed control or folate-deficient diets from weaning until 8 and 10 months of age. We observed short-term memory impairment measured by the novel object paradigm, altered transcriptional levels of synaptic markers and epigenetic enzymes, as well as impaired choline metabolism due to the Mthfr^+/- genotype in cortex or hippocampus. We also detected changes in mRNA levels of Presenillin-1, neurotrophic factors, one-carbon metabolic and epigenetic enzymes, as well as reduced levels of S-adenosylmethionine and acetylcholine, due to the folate-deficient diet. These findings shed further insights into the mechanisms by which genetic and dietary folate metabolic disturbances increase the risk for cognitive decline and suggest that these mechanisms are distinct.

Mutations in Homocysteine Metabolism Genes Increase Keratin N-Homocysteinylation and Damage in Mice

Genetic or nutritional deficiencies in homocysteine (Hcy) metabolism increase Hcy-thiolactone, which causes protein damage by forming isopetide bonds with lysine residues, generating N-Hcy-protein. In the present work, we studied the prevalence and genetic determinants of keratin damage caused by homocysteinylation. We found that in mammals and birds, 35 to 98% of Hcy was bound to hair keratin via amide or isopeptide bond (Hcy-keratin), while 2 to 65% was S-Hcy-keratin. A major fraction of hair Hcy-keratin (56% to 93%), significantly higher in birds than in mammals, was sodium dodecyl sulfate-insoluble. Genetic hyperhomocysteinemia significantly increased N-Hcy-keratin levels in the mouse pelage. N-Hcy-keratin was elevated 3.5-, 6.3-, and 11.7-fold in hair from Mthfr -/-, Cse -/-, or Cbs -/- mice, respectively. The accumulation of N-Hcy in hair keratin led to a progressive reduction of N-Hcy-keratin solubility in sodium dodecyl sulfate, from 0.39 ± 0.04 in wild-type mice to 0.19 ± 0.03, 0.14 ± 0.01, and 0.07 ± 0.03 in Mthfr -/-, Cse -/-, or Cbs -/-animals, respectively. N-Hcy-keratin accelerated aggregation of unmodified keratin in Cbs -/- mouse hair. Keratin methionine, copper, and iron levels in mouse hair were not affected by hyperhomocysteinemia. These findings provide evidence that pelage keratin is N-homocysteinylated in vivo in mammals and birds, and that this process causes keratin damage, manifested by a reduced solubility.

Chronic folate deficiency induces glucose and lipid metabolism disorders and subsequent cognitive dysfunction in mice

Previous studies have shown that folate levels were decreased in patients with type 2 diabetes (T2D) and further lowered in T2D patients with cognitive impairment. However, whether folate deficiency could cause T2D and subsequent cognitive dysfunction is still unknown. The present study aimed to explore the effects of chronic folate deficiency (CFD) on glucose and lipid metabolism and cognitive function in mice. Seven-week-old mice were fed with either a CFD or control diet for 25 weeks. Serum folate was significantly reduced, whereas serum total homocysteine was significantly increased in the CFD group. Moreover, CFD induced obesity after a 6-week diet treatment, glucose intolerance and insulin resistance after a 16-week-diet treatment. In addition, CFD reduced the hepatic p-Akt/Akt ratio in response to acute insulin administration. Moreover, CFD increased serum triglyceride levels, upregulated hepatic Acc1 and Fasn mRNA expression, and downregulated hepatic Cd36 and ApoB mRNA expression. After a 24-week diet treatment, CFD induced anxiety-related activities and impairment of spatial learning and memory performance. This study demonstrates that folate deficiency could induce obesity, glucose and lipid metabolism disorders and subsequent cognitive dysfunction.

Demethylation of methionine and keratin damage in human hair

Growing human head hair contains a history of keratin and provides a unique model for studies of protein damage. Here, we examined mechanism of homocysteine (Hcy) accumulation and keratin damage in human hair. We found that the content of Hcy-keratin increased along the hair fiber, with levels 5-10-fold higher levels in older sections at the hair's tip than in younger sections at hair's base. The accumulation of Hcy led to a complete loss of keratin solubility in sodium dodecyl sulfate. The increase in Hcy-keratin was accompanied by a decrease in methionine-keratin. Levels of Hcy-keratin were correlated with hair copper and iron in older hair. These relationships were recapitulated in model experiments in vitro, in which Hcy generation from Met exhibited a similar dependence on copper or iron. Taken together, these findings suggest that Hcy-keratin accumulation is due to copper/iron-catalyzed demethylation of methionine residues and contributes to keratin damage in human hair.

Folate action in nervous system development and disease

The vitamin folic acid has been recognized as a crucial environmental factor for nervous system development. From the early fetal stages of the formation of the presumptive spinal cord and brain to the maturation and maintenance of the nervous system during infancy and childhood, folate levels and its supplementation have been considered influential in the clinical outcome of infants and children affected by neurological diseases. Despite the vast epidemiological information recorded on folate function and neural tube defects, neural development and neurodegenerative diseases, the mechanisms of folate action in the developing neural tissue have remained elusive. Here we compiled studies that argue for a unique role for folate in nervous system development and function and its consequences to neural disease and repair. © 2018 Wiley Periodicals, Inc. Develop Neurobiol 78: 391-402, 2018.

Impact of diet-derived signaling molecules on human cognition: exploring the food-brain axis

The processes that define mammalian physiology evolved millions of years ago in response to ancient signaling molecules, most of which were acquired by ingestion and digestion. In this way, evolution inextricably linked diet to all major physiological systems including the nervous system. The importance of diet in neurological development is well documented, although the mechanisms by which diet-derived signaling molecules (DSMs) affect cognition are poorly understood. Studies on the positive impact of nutritive and non-nutritive bioactive molecules on brain function are encouraging but lack the statistical power needed to demonstrate strong positive associations. Establishing associations between DSMs and cognitive functions like mood, memory and learning are made even more difficult by the lack of robust phenotypic markers that can be used to accurately and reproducibly measure the effects of DSMs. Lastly, it is now apparent that processes like neurogenesis and neuroplasticity are embedded within layers of interlocked signaling pathways and gene regulatory networks. Within these interdependent pathways and networks, the various transducers of DSMs are used combinatorially to produce those emergent adaptive gene expression responses needed for stimulus-induced neurogenesis and neuroplasticity. Taken together, it appears that cognition is encoded genomically and modified by epigenetics and epitranscriptomics to produce complex transcriptional programs that are exquisitely sensitive to signaling molecules from the environment. Models for how DSMs mediate the interplay between the environment and various neuronal processes are discussed in the context of the food–brain axis.

Low and high dietary folic acid levels perturb postnatal cerebellar morphology in growing rats

The brain is particularly sensitive to folate metabolic disturbances, because methyl groups are critical for brain functions. This study aimed to investigate the effects of different dietary levels of folic acid (FA) on postnatal cerebellar morphology, including the architecture and organisation of the various layers. A total of forty male OFA rats (a Sprague-Dawley strain), 5 weeks old, were classified into the following four dietary groups: FA deficient (0 mg/kg FA); FA supplemented (8 mg/kg FA); FA supra-supplemented (40 mg/kg FA); and control (2 mg/kg FA) (all n 10 per group). Rats were fed ad libitum for 30 d. The cerebellum was quickly removed and processed for histological and immunohistochemical analysis. Slides were immunostained for glial fibrillary acidic protein (to label Bergmann glia), calbindin (to label Purkinje cells) and NeuN (to label post-mitotic neurons). Microscopic analysis revealed two types of defect: partial disappearance of fissures and/or neuronal ectopia, primarily in supra-supplemented animals (incidence of 80 %, P≤0·01), but also in deficient and supplemented groups (incidence of 40 %, P≤0·05), compared with control animals. The primary fissure was predominantly affected, sometimes accompanied by defects in the secondary fissure. Our findings show that growing rats fed an FA-modified diet, including both deficient and supplemented diets, have an increased risk of disturbances in cerebellar corticogenesis. Defects caused by these diets may have functional consequences in later life. The present study is the first to demonstrate that cerebellar morphological defects can arise from deficient, as well as high, FA levels in the diet.

The Evaluation of Folic Acid-Deficient or Folic Acid-Supplemented Diet in the Gestational Phase of Female Rats and in Their Adult Offspring Subjected to an Animal Model of Schizophrenia

Although folic acid (FA) supplementation is known to influence numerous physiological functions, especially during pregnancy, little is known about its direct effects on the mothers' health. However, this vitamin is essential for the health of the mother and for the normal growth and development of the fetus. Thus, the aim of this study was (1) to evaluate the cognitive effects and biochemical markers produced by the AIN-93 diet (control), the AIN-93 diet supplemented with different doses of FA (5, 10, and 50 mg/kg), and a FA-deficient diet during pregnancy and lactation in female mother rats (dams) and (2) to evaluate the effect of maternal diets on inflammatory parameters in the adult offspring which were subjected to an animal model of schizophrenia (SZ) induced by ketamine (Ket). Our study demonstrated through the Y-maze test that rats subjected to the FA-deficient diet showed significant deficits in spatial memory, while animals supplemented with FA (5 and 10 mg/kg) showed no deficit in spatial memory. Our results also suggest that the rats subjected to the FA-deficient diet had increased levels of carbonylated proteins in the frontal cortex and hippocampus and also increased plasma levels of homocysteine (Hcy). Folate was able to prevent cognitive impairments in the rats supplemented with FA (5 and 10 mg/kg), data which may be attributed to the antioxidant effect of the vitamin. Moreover, FA prevented protein damage and elevations in Hcy levels in the rats subjected to different doses of this vitamin (5, 10, and 50 mg/kg). We verified a significant increase of the anti-inflammatory cytokine (interleukin-4 (IL-4)) and a reduction in the plasma levels of proinflammatory cytokines (interleukin-6 (IL-6)) and TNF-α) in the dams that were subjected to the diets supplemented with FA (5, 10, and 50 mg/kg), showing the possible anti-inflammatory effects of FA during pregnancy and lactation. In general, we also found that in the adult offspring that were subjected to an animal model of SZ, FA had a protective effect in relation to the levels of IL-4, IL-6, and TNF-α, which indicates that the action of FA persisted in the adult offspring, since FA showed a lasting effect on the inflammatory response, which was similar in both the dams and their offspring. In conclusion, the importance of supplementation with FA during pregnancy and lactation should be emphasized, not only for the benefit of the offspring but also for the health of the mother. All this is due to the considerable protective effect of this vitamin against oxidative damage, cognitive impairment, hyperhomocysteinemia, immune function, and also its ability in preventing common processes in post-pregnancy stages, as well as in reducing the risks of neurodevelopmental disorders and enhancing fetal immune development.

The amino acid metabolite homocysteine activates mTORC1 to inhibit autophagy and form abnormal proteins in human neurons and mice

The molecular mechanisms leading to and responsible for age-related, sporadic Alzheimer's disease (AD) remain largely unknown. It is well documented that aging patients with elevated levels of the amino acid metabolite homocysteine (Hcy) are at high risk of developing AD. We investigated the impact of Hcy on molecular clearance pathways in mammalian cells, including in vitro cultured induced pluripotent stem cell-derived forebrain neurons and in vivo neurons in mouse brains. Exposure to Hcy resulted in up-regulation of the mechanistic target of rapamycin complex 1 (mTORC1) activity, one of the major kinases in cells that is tightly linked to anabolic and catabolic pathways. Hcy is sensed by a constitutive protein complex composed of leucyl-tRNA-synthetase and folliculin, which regulates mTOR tethering to lysosomal membranes. In hyperhomocysteinemic human cells and cystathionine β-synthase-deficient mouse brains, we find an acute and chronic inhibition of the molecular clearance of protein products resulting in a buildup of abnormal proteins, including β-amyloid and phospho-Tau. Formation of these protein aggregates leads to AD-like neurodegeneration. This pathology can be prevented by inhibition of mTORC1 or by induction of autophagy. We conclude that an increase of intracellular Hcy levels predisposes neurons to develop abnormal protein aggregates, which are hallmarks of AD and its associated onset and pathophysiology with age.-Khayati, K., Antikainen, H., Bonder, E. M., Weber, G. F., Kruger, W. D., Jakubowski, H., Dobrowolski, R. The amino acid metabolite homocysteine activates mTORC1 to inhibit autophagy and form abnormal proteins in human neurons and mice.

Late Maternal Folate Supplementation Rescues from Methyl Donor Deficiency-Associated Brain Defects by Restoring Let-7 and miR-34 Pathways

The micronutrients folate and vitamin B12 are essential for the proper development of the central nervous system, and their deficiency during pregnancy has been associated with a wide range of disorders. They act as methyl donors in the one-carbon metabolism which critically influences epigenetic mechanisms. In order to depict further underlying mechanisms, we investigated the role of let-7 and miR-34, two microRNAs regulated by methylation, on a rat model of maternal deficiency. In several countries, public health policies recommend periconceptional supplementation with folic acid. However, the question about the duration and periodicity of supplementation remains. We therefore tested maternal supply (3 mg/kg/day) during the last third of gestation from embryonic days (E) 13 to 20. Methyl donor deficiency-related developmental disorders at E20, including cerebellar and interhemispheric suture defects and atrophy of selective cerebral layers, were associated with increased brain expression (by 2.5-fold) of let-7a and miR-34a, with subsequent downregulation of their regulatory targets such as Trim71 and Notch signaling partners, respectively. These processes could be reversed by siRNA strategy in differentiating neuroprogenitors lacking folate, with improvement of their morphological characteristics. While folic acid supplementation helped restoring the levels of let-7a and miR-34a and their downstream targets, it led to a reduction of structural and functional defects taking place during the perinatal period. Our data outline the potential role of let-7 and miR-34 and their related signaling pathways in the developmental defects following gestational methyl donor deficiency and support the likely usefulness of late folate supplementation in at risk women.

Cerebral hypoperfusion and glucose hypometabolism: Key pathophysiological modulators promote neurodegeneration, cognitive impairment, and Alzheimer's disease

Aging, hypertension, diabetes, hypoxia/obstructive sleep apnea (OSA), obesity, vitamin B12/folate deficiency, depression, and traumatic brain injury synergistically promote diverse pathological mechanisms including cerebral hypoperfusion and glucose hypometabolism. These risk factors trigger neuroinflammation and oxidative-nitrosative stress that in turn decrease nitric oxide and enhance endothelin, Amyloid-β deposition, cerebral amyloid angiopathy, and blood-brain barrier disruption. Proinflammatory cytokines, endothelin-1, and oxidative-nitrosative stress trigger several pathological feedforward and feedback loops. These upstream factors persist in the brain for decades, upregulating amyloid and tau, before the cognitive decline. These cascades lead to neuronal Ca²⁺ increase, neurodegeneration, cognitive/memory decline, and Alzheimer's disease (AD). However, strategies are available to attenuate cerebral hypoperfusion and glucose hypometabolism and ameliorate cognitive decline. AD is the leading cause of dementia among the elderly. There is significant evidence that pathways involving inflammation and oxidative-nitrosative stress (ONS) play a key pathophysiological role in promoting cognitive dysfunction. Aging and several comorbid conditions mentioned above promote diverse pathologies. These include inflammation, ONS, hypoperfusion, and hypometabolism in the brain. In AD, chronic cerebral hypoperfusion and glucose hypometabolism precede decades before the cognitive decline. These comorbid disease conditions may share and synergistically activate these pathophysiological pathways. Inflammation upregulates cerebrovascular pathology through proinflammatory cytokines, endothelin-1, and nitric oxide (NO). Inflammation-triggered ONS promotes long-term damage involving fatty acids, proteins, DNA, and mitochondria; these amplify and perpetuate several feedforward and feedback pathological loops. The latter includes dysfunctional energy metabolism (compromised mitochondrial ATP production), amyloid-β generation, endothelial dysfunction, and blood-brain-barrier disruption. These lead to decreased cerebral blood flow and chronic cerebral hypoperfusion- that would modulate metabolic dysfunction and neurodegeneration. In essence, hypoperfusion deprives the brain from its two paramount trophic substances, viz., oxygen and nutrients. Consequently, the brain suffers from synaptic dysfunction and neuronal degeneration/loss, leading to both gray and white matter atrophy, cognitive dysfunction, and AD. This Review underscores the importance of treating the above-mentioned comorbid disease conditions to attenuate inflammation and ONS and ameliorate decreased cerebral blood flow and hypometabolism. Additionally, several strategies are described here to control chronic hypoperfusion of the brain and enhance cognition. © 2016 Wiley Periodicals, Inc.

The interplay between DNA methylation, folate and neurocognitive development

DNA methylation provides an attractive possible means for propagating the effects of environmental inputs during fetal life and impacting subsequent adult mental health, which is leading to increasing collaboration between molecular biologists, nutritionists and psychiatrists. An area of interest is the potential role of folate, not just in neural tube closure in early pregnancy, but in later major neurodevelopmental events, with consequences for later sociocognitive maturation. Here, we set the scene for recent discoveries by reviewing the major events of neural development during fetal life, with an emphasis on tissues and structures where dynamic methylation changes are known to occur. Following this, we give an indication of some of the major classes of genes targeted by methylation and important for neurological and behavioral development. Finally, we highlight some cognitive disorders where methylation changes are implicated as playing an important role.

Ethnopharmacology, phytochemistry, and biological activities of Cymbopogon citratus (DC.) Stapf extracts

Cymbopogon citratus is a widely distributed perennial herb belonging to the Poaceae family and has been extensively consumed for its medicinal, cosmetic, and nutritional effects for centuries. A large number of reports have been published describing the pharmacological, biological, and therapeutic actions of this herb. In this review, we summarized the literatures on related studies (up to January, 2014) that highlighted the pharmacologic and biological effects of the major phytochemicals isolated from C. citratus extracts and its essential oil. The components of the essential oils found in C. citratus have a similar pharmacokinetic properties, including absorption, distribution, metabolism, and excretion. They are quickly absorbed following oral, pulmonary, and dermal administration. Based on the published reports, it can also be inferred that, after absorption from the small intestine, some phytochemicals in C. citratus can undergo oxidation, glucuronidation, sulfation, and/or O-methylation. Excretion is through urine, feces and/or expired volatiles. The biotransformation reactions of C. citratus bioactive constituents are essential for its relatively safe consumption and therapeutic applications. The data available so far warrant further studies evaluating C. citratus pharmacokinetics. Reliable pharmacokinetic data in humans would be critical for a better understanding of the the systemic handling of C. citratus.

Moderately elevated maternal homocysteine at preconception is inversely associated with cognitive performance in children 4 months and 6 years after birth

Prenatal methyl donor deficiency leads to homocysteine accumulation in the brain and impaired neurodevelopment in rats. We investigated the effect of moderately elevated preconception fasting total plasma homocysteine (tHcy) on child neurodevelopment in a prospective study of 67 and 76 mother-child pairs at 4 months and 6 years of age, respectively. Fasting blood samples at 2-10 weeks preconception, from the cord (nonfasting) and the mother and child 6 years after birth, were collected. Psychomotor and mental development were assessed at 4 months using the Bayley Scale of Infant Development (BSID) and cognitive development at 6 years using the Wechsler Preschool and Primary Scale of Intelligence (WPPSI). Highest tertile preconception tHcy (≥9.04 µmol/L) was categorized as moderately elevated and low-mid tertile tHcy as normal. Children, born to mothers with moderately elevated compared to normal preconception tHcy, scored lower [mean (95% CI)] in the BSID psychomotor [115 (105, 124) vs. 126 (121, 130), p = 0.03] and mental [101 (93, 109) vs. 113 (107, 119), p = 0.03] development tests. Multiple logistic regression analysis showed that moderately elevated compared to normal preconception tHcy was associated with greater probability, OR (95%CI), of scoring in the lowest tertile for BSID psychomotor development (≤120): 4.0 (1.1, 14.3) and lowest tertiles for WPPSI full (≤111), verbal (≤104) and performance (≤111), intellectual quotient: 6.0 (1.5, 23.7), 3.5 (1.1, 11.2) and 4.1 (1.1, 15.7), respectively. We conclude that moderately elevated preconception tHcy is inversely associated with psychomotor and cognitive development scores in infants and children.

Homocysteine in Chronic Kidney Disease

Hyperhomocysteinemia occurs in chronic- and end-stage kidney disease at the time when dialysis or transplant becomes indispensable for survival. Excessive accumulation of homocysteine (Hcy) aggravates conditions associated with imbalanced homeostasis and cellular redox thereby resulting in severe oxidative stress leading to oxidation of reduced free and protein-bound thiols. Thiol modifications such as N-homocysteinylation, sulfination, cysteinylation, glutathionylation, and sulfhydration control cellular responses that direct complex metabolic pathways. Although cysteinyl modifications are kept low, under Hcy-induced stress, thiol modifications persist thus surpassing cellular proteostasis. Here, we review mechanisms of redox regulation and show how cysteinyl modifications triggered by excess Hcy contribute development and progression of chronic kidney disease. We discuss different signaling events resulting from aberrant cysteinyl modification with a focus on transsulfuration.

Folate- and vitamin B12-deficient diet during gestation and lactation alters cerebellar synapsin expression via impaired influence of estrogen nuclear receptor α

Deficiency in the methyl donors vitamin B12 and folate during pregnancy and postnatal life impairs proper brain development. We studied the consequences of this combined deficiency on cerebellum plasticity in offspring from rat mothers subjected to deficient diet during gestation and lactation and in rat neuroprogenitor cells expressing cerebellum markers. The major proteomic change in cerebellum of 21-d-old deprived females was a 2.2-fold lower expression of synapsins, which was confirmed in neuroprogenitors cultivated in the deficient condition. A pathway analysis suggested that these proteomic changes were related to estrogen receptor α (ER-α)/Src tyrosine kinase. The influence of impaired ER-α pathway was confirmed by abnormal negative geotaxis test at d 19-20 and decreased phsophorylation of synapsins in deprived females treated by ER-α antagonist 1,3-bis(4-hydroxyphenyl)-4-methyl-5-[4-(2-piperidinylethoxy)phenol]-1H-pyrazole dihydrochloride (MPP). This effect was consistent with 2-fold decreased expression and methylation of ER-α and subsequent decreased ER-α/PPAR-γ coactivator 1 α (PGC-1α) interaction in deficiency condition. The impaired ER-α pathway led to decreased expression of synapsins through 2-fold decreased EGR-1/Zif-268 transcription factor and to 1.7-fold reduced Src-dependent phosphorylation of synapsins. The treatment of neuroprogenitors with either MPP or PP1 (4-(4'-phenoxyanilino)-6,7-dimethoxyquinazoline, 6,7-dimethoxy-N-(4-phenoxyphenyl)-4-quinazolinamine, SKI-1, Src-l1) Src inhibitor produced similar effects. In conclusion, the deficiency during pregnancy and lactation impairs the expression of synapsins through a deregulation of ER-α pathway.

HDAC4 as a potential therapeutic target in neurodegenerative diseases: a summary of recent achievements

For the past decade protein acetylation has been shown to be a crucial post-transcriptional modification involved in the regulation of protein functions. Histone acetyltransferases (HATs) mediate acetylation of histones which results in the nucleosomal relaxation associated with gene expression. The reverse reaction, histone deacetylation, is mediated by histone deacetylases (HDACs) leading to chromatin condensation followed by transcriptional repression. HDACs are divided into distinct classes: I, IIa, IIb, III, and IV, on the basis of size and sequence homology, as well as formation of distinct repressor complexes. Implications of HDACs in many diseases, such as cancer, heart failure, and neurodegeneration, have identified these molecules as unique and attractive therapeutic targets. The emergence of HDAC4 among the members of class IIa family as a major player in synaptic plasticity raises important questions about its functions in the brain. The characterization of HDAC4 specific substrates and molecular partners in the brain will not only provide a better understanding of HDAC4 biological functions but also might help to develop new therapeutic strategies to target numerous malignancies. In this review we highlight and summarize recent achievements in understanding the biological role of HDAC4 in neurodegenerative processes.

Crosstalk of homocysteinylation, methylation and acetylation on histone H3

Homocysteinylation on histone H3 was first identified by LC-MS/MS, which affects methylation and acetylation levels of histone H3.

Folate deficiency in rat pups during weaning causes learning and memory deficits

Folate is essential for fetal development, and its deficiency during gestation causes behavioural deficits in the offspring. The present study investigated its influence during weaning on brain function in the pups of rats that were put on a folate-deficient (FD) diet on postnatal day (PND) 1. Systemic folate deficiency in pups on the FD diet (n 15) was evident from the dramatically lower hepatic folate concentrations (median 23·7, range 8·1–48·4 ng/mg protein) and higher homocysteine concentrations (median 27·7, range 14·7–45·5 pmol/mg protein), respectively, compared with those of pups on the normal diet (ND; n 9) (median 114·5, range 64·5–158·5 ng/mg protein and median 15·5, range 11·6–18·9 pmol/mg protein) on PND 23. Brain folate concentrations although low were similar in pups on the FD diet (median 10·5, range 5·5–24·5 ng/mg protein) and ND (median 11·1, range 7·1–24·2 ng/mg protein). There was a high accumulation of homocysteine in the brain of FD pups, mostly in the hippocampus (median 58·1, range 40·8–99·7 pmol/mg protein) and cerebellum (median 69·1, range 50·8–126·6 pmol/mg protein), indicating metabolic folate deficiency despite normal brain folate concentrations. Developmental deficits or autistic traits were more frequent in the FD group than in the ND group and repetitive self-grooming occurred, on average, three times (range 1–8) v. once (range 0–3) during 5 min, respectively. Long-term memory or spatial learning and set-shifting deficits affected 12 to 62 % of rats in the FD group compared with none in the ND group. Post-weaning folic acid supplementation did not correct these deficits. These observations indicate that folate deficiency during weaning affects postnatal development even when gestational folate supply is normal.

Environmental alterations of epigenetics prior to the birth

The etiology of many brain diseases remains allusive to date after intensive investigation of genomic background and symptomatology from the day of birth. Emerging evidences indicate that a third factor, epigenetics prior to the birth, can exert profound influence on the development and functioning of the brain and over many neurodevelopmental syndromes. This chapter reviews how aversive environmental exposure to parents might predispose or increase vulnerability of offspring to neurodevelopmental deficit through alteration of epigenetics. These epigenetic altering environmental factors will be discussed in the category of addictive agents, nutrition or diet, prescriptive medicine, environmental pollutant, and stress. Epigenetic alterations induced by these aversive environmental factors cover all aspects of epigenetics including DNA methylation, histone modification, noncoding RNA, and chromatin modification. Next, the mechanisms how these environmental inputs influence epigenetics will be discussed. Finally, how environmentally altered epigenetic marks affect neurodevelopment is exemplified by the alcohol-induced fetal alcohol syndrome. It is hoped that a thorough understanding of the nature of prenatal epigenetic inputs will enable researchers with a clear vision to better unravel neurodevelopmental deficit, late-onset neuropsychiatric diseases, or idiosyncratic mental disorders.