Low availability of choline in utero disrupts development and function of the retina

Biallelic variation in the choline and ethanolamine transporter FLVCR1 underlies a severe developmental disorder spectrum

PURPOSE

FLVCR1 encodes a solute carrier protein implicated in heme, choline, and ethanolamine transport. Although Flvcr1-/- mice exhibit skeletal malformations and defective erythropoiesis reminiscent of Diamond-Blackfan anemia (DBA), biallelic FLVCR1 variants in humans have previously only been linked to childhood or adult-onset ataxia, sensory neuropathy, and retinitis pigmentosa.

METHODS

We identified individuals with undiagnosed neurodevelopmental disorders and biallelic FLVCR1 variants through international data sharing and characterized the functional consequences of their FLVCR1 variants.

RESULTS

We ascertained 30 patients from 23 unrelated families with biallelic FLVCR1 variants and characterized a novel FLVCR1-related phenotype: severe developmental disorders with profound developmental delay, microcephaly (z-score -2.5 to -10.5), brain malformations, epilepsy, spasticity, and premature death. Brain malformations ranged from mild brain volume reduction to hydranencephaly. Severely affected patients share traits, including macrocytic anemia and skeletal malformations, with Flvcr1-/- mice and DBA. FLVCR1 variants significantly reduce choline and ethanolamine transport and/or disrupt mRNA splicing.

CONCLUSION

These data demonstrate a broad FLVCR1-related phenotypic spectrum ranging from severe multiorgan developmental disorders resembling DBA to adult-onset neurodegeneration. Our study expands our understanding of Mendelian choline and ethanolamine disorders and illustrates the importance of anticipating a wide phenotypic spectrum for known disease genes and incorporating model organism data into genome analysis to maximize genetic testing yield.

Tracing the influence of prenatal risk factors on the offspring retina: Focus on development and putative long-term consequences

BACKGROUND

Pregnancy represents a window of vulnerability to fetal development. Disruptions in the prenatal environment during this crucial period can increase the risk of the offspring developing diseases over the course of their lifetime. The central nervous system (CNS) has been shown to be particularly susceptible to changes during crucial developmental windows. To date, research focused on disruptions in the development of the CNS has predominantly centred on the brain, revealing a correlation between exposure to prenatal risk factors and the onset of neuropsychiatric disorders. Nevertheless, some studies indicate that the retina, which is part of the CNS, is also vulnerable to in utero alterations during pregnancy. Such changes may affect neuronal, glial and vascular components of the retina, compromising retinal structure and function and possibly impairing visual function.

METHODS

A search in the PubMed database was performed, and any literature concerning prenatal risk factors (drugs, diabetes, unbalanced diet, infection, glucocorticoids) affecting the offspring retina were included.

RESULTS

This review collects evidence on the cellular, structural and functional changes occurring in the retina triggered by maternal risk factors during pregnancy. We highlight the adverse impact on retinal development and its long-lasting effects, providing a critical analysis of the current knowledge while underlining areas for future research.

CONCLUSIONS

Appropriate recognition of the prenatal risk factors that negatively impact the developing retina may provide critical clues for the design of preventive strategies and for early therapeutic intervention that could change retinal pathology in the progeny.

The Water Extract of Rhubarb Prevents Ischemic Stroke by Regulating Gut Bacteria and Metabolic Pathways

Rhubarb (RR), Chinese name Dahuang, is commonly used in the treatment of ischemic stroke (IS). However, its potential mechanism is not fully elucidated. This study intended to verify the effect of RR on IS and investigate the possible mechanism of RR in preventing IS. IS in male rats was induced by embolic middle cerebral artery occlusion (MCAO) surgery, and drug administration was applied half an hour before surgery. RR dramatically decreased the neurological deficit scores, the cerebral infarct volume, and the cerebral edema rate, and improved the regional cerebral blood flow (rCBF) and histopathological changes in the brain of MCAO rats. The 16S rRNA analysis showed the harmful microbes such as Fournierella and Bilophila were decreased, and the beneficial microbes such as Enterorhabdus, Defluviitaleaceae, Christensenellaceae, and Lachnospira were significantly increased, after RR pretreatment. 1H-nuclear magnetic resonance (1H-NMR) was used to detect serum metabolomics, and RR treatment significantly changed the levels of metabolites such as isoleucine, valine, N6-acetyllysine, methionine, 3-aminoisobutyric acid, N, N-dimethylglycine, propylene glycol, trimethylamine N-oxide, myo-inositol, choline, betaine, lactate, glucose, and lipid, and the enrichment analysis of differential metabolites showed that RR may participate in the regulation of amino acid metabolism and energy metabolism. RR exerts the role of anti-IS via regulating gut bacteria and metabolic pathways.

External Disruption of Ocular Development in Utero

The intricate steps of human ocular embryology are impacted by cellular and genetic signaling pathways and a myriad of external elements that can affect pregnancy, such as environmental, metabolic, hormonal factors, medications, and intrauterine infections. This review focuses on presenting some of these factors to recognize the multifactorial nature of ocular development and highlight their clinical significance. This review is based on English-language articles sourced from PubMed, Web of Science, and Google Scholar; keywords searched included "ocular development in pregnancy," "ocular embryology," "maternal nutrition," "ophthalmic change," and "visual system development." While some animal models show the disruption of ocular embryology from these external factors, there are limited post-birth assessments in human studies. Much remains unknown about the precise mechanisms of how these external factors can disrupt normal ocular development in utero, and more significant research is needed to understand the pathophysiology of these disruptive effects further. Findings in this review emphasize the importance of additional research in understanding the dynamic association between factors impacting gestation and neonatal ocular development, particularly in the setting of limited resources.

Oberg, Clark RD, Wenman C, Loughlin S, Saad R, Ashraf T, Male A, Tadros S, Boostani R, Abdel-Salam GM, Zaki M, Abdalla E, Manzini MC, Pehlivan D, Posey JE, Gibbs RA, Houlden H, Alkuraya FS, Bujakowska K, Maroofian R, Lupski JR, Nguyen LN. Biallelic variation in the choline and ethanolamine transporter FLVCR1 underlies a pleiotropic disease spectrum from adult neurodegeneration to severe developmental disorders

FLVCR1 encodes Feline leukemia virus subgroup C receptor 1 (FLVCR1), a solute carrier (SLC) transporter within the Major Facilitator Superfamily. FLVCR1 is a widely expressed transmembrane protein with plasma membrane and mitochondrial isoforms implicated in heme, choline, and ethanolamine transport. While Flvcr1 knockout mice die in utero with skeletal malformations and defective erythropoiesis reminiscent of Diamond-Blackfan anemia, rare biallelic pathogenic FLVCR1 variants are linked to childhood or adult-onset neurodegeneration of the retina, spinal cord, and peripheral nervous system. We ascertained from research and clinical exome sequencing 27 individuals from 20 unrelated families with biallelic ultra-rare missense and predicted loss-of-function (pLoF) FLVCR1 variant alleles. We characterize an expansive FLVCR1 phenotypic spectrum ranging from adult-onset retinitis pigmentosa to severe developmental disorders with microcephaly, reduced brain volume, epilepsy, spasticity, and premature death. The most severely affected individuals, including three individuals with homozygous pLoF variants, share traits with Flvcr1 knockout mice and Diamond-Blackfan anemia including macrocytic anemia and congenital skeletal malformations. Pathogenic FLVCR1 missense variants primarily lie within transmembrane domains and reduce choline and ethanolamine transport activity compared with wild-type FLVCR1 with minimal impact on FLVCR1 stability or subcellular localization. Several variants disrupt splicing in a mini-gene assay which may contribute to genotype-phenotype correlations. Taken together, these data support an allele-specific gene dosage model in which phenotypic severity reflects residual FLVCR1 activity. This study expands our understanding of Mendelian disorders of choline and ethanolamine transport and demonstrates the importance of choline and ethanolamine in neurodevelopment and neuronal homeostasis.

The Role of Choline in Neurodevelopmental Disorders-A Narrative Review Focusing on ASC, ADHD and Dyslexia

Neurodevelopmental disorders appear to be rising in prevalence, according to the recent Global Burden of Disease Study. This rise is likely to be multi-factorial, but the role of certain nutrients known to facilitate neurodevelopment should be considered. One possible contributing factor could be attributed to deficits in choline intake, particularly during key stages of neurodevelopment, which includes the first 1000 days of life and childhood. Choline, a key micronutrient, is crucial for optimal neurodevelopment and brain functioning of offspring. The present narrative review discusses the main research, describing the effect of choline in neurodevelopmental disorders, to better understand its role in the etiology and management of these disorders. In terms of findings, low choline intakes and reduced or altered choline status have been reported in relevant population subgroups: pregnancy (in utero), children with autism spectrum disorders, people with attention deficit hyperactivity disorder and those with dyslexia. In conclusion, an optimal choline provision may offer some neuronal protection in early life and help to mitigate some cognitive effects in later life attributed to neurodevelopmental conditions. Research indicates that choline may act as a modifiable risk factor for certain neurodevelopmental conditions. Ongoing research is needed to unravel the mechanisms and explanations.

Choline Regulates SOX4 through miR-129-5p and Modifies H3K27me3 in the Developing Cortex

Choline availability regulates neural progenitor cell proliferation and differentiation in the developing cerebral cortex. Here, we investigated the molecular mechanism underlying this process and demonstrated that choline regulates the transcription factor SOX4 in neural progenitor cells. Specifically, we found that low choline intake during neurogenesis reduces SOX4 protein levels, causing the downregulation of EZH2, a histone methyltransferase. Importantly, we demonstrate that low choline is not involved in SOX4 protein degradation rate and established that protein reduction is caused by aberrant expression of a microRNA (miR-129-5p). To confirm the role of miR-129-5p, we conducted gain-of-function and loss-of-function assays in neural progenitor cells and demonstrated that directly altering miR-129-5p levels could affect SOX4 protein levels. We also observed that the reduction in SOX4 and EZH2 led to decreased global levels of H3K27me3 in the developing cortex, contributing to reduced proliferation and precocious differentiation. For the first time, to our knowledge, we demonstrate that a nutrient, choline, regulates a master transcription factor and its downstream targets, providing a novel insight into the role of choline in brain development.

Integrative genetic analysis identifies FLVCR1 as a plasma-membrane choline transporter in mammals

Genome-wide association studies (GWASs) of serum metabolites have the potential to uncover genes that influence human metabolism. Here, we combined an integrative genetic analysis that associates serum metabolites to membrane transporters with a coessentiality map of metabolic genes. This analysis revealed a connection between feline leukemia virus subgroup C cellular receptor 1 (FLVCR1) and phosphocholine, a downstream metabolite of choline metabolism. Loss of FLVCR1 in human cells strongly impairs choline metabolism due to the inhibition of choline import. Consistently, CRISPR-based genetic screens identified phospholipid synthesis and salvage machinery as synthetic lethal with FLVCR1 loss. Cells and mice lacking FLVCR1 exhibit structural defects in mitochondria and upregulate integrated stress response (ISR) through heme-regulated inhibitor (HRI) kinase. Finally, Flvcr1 knockout mice are embryonic lethal, which is partially rescued by choline supplementation. Altogether, our findings propose FLVCR1 as a major choline transporter in mammals and provide a platform to discover substrates for unknown metabolite transporters.

Determinants of approved acetylcholinesterase inhibitor response outcomes in Alzheimer's disease: relevance for precision medicine in neurodegenerative diseases

Acetylcholinesterase inhibitors (ChEI) are the global standard of care for the symptomatic treatment of Alzheimer's disease (AD) and show significant positive effects in neurodegenerative diseases with cognitive and behavioral symptoms. Although experimental and large-scale clinical evidence indicates the potential long-term efficacy of ChEI, primary outcomes are generally heterogeneous across outpatient clinics and regional healthcare systems. Sub-optimal dosing or slow tapering, heterogeneous guidelines about the timing for therapy initiation (prodromal versus dementia stages), healthcare providers' ambivalence to treatment, lack of disease awareness, delayed medical consultation, prescription of ChEI in non-AD cognitive disorders, contribute to the negative outcomes. We present an evidence-based overview of determinants, spanning genetic, molecular, and large-scale networks, involved in the response to ChEI in patients with AD and other neurodegenerative diseases. A comprehensive understanding of cerebral and retinal cholinergic system dysfunctions along with ChEI response predictors in AD is crucial since disease-modifying therapies will frequently be prescribed in combination with ChEI. Therapeutic algorithms tailored to genetic, biological, clinical (endo)phenotypes, and disease stages will help leverage inter-drug synergy and attain optimal combined response outcomes, in line with the precision medicine model.

An exploratory study on the effect of choline and folate deficiency on levels of vascularization proteins and transcription factors in first trimester trophoblast HTR-8/SVneo cells

AIMS

We studied the effect of choline and folate deficiencies on levels of predetermined placental proteins during early development.

METHODS

We incubated HTR-8/SVneo cells under choline and folate deficiency conditions and measured levels of some placental proteins using ELISA methods.

RESULTS

Concentrations of LRP2 protein in cell lysates were higher in cells incubated in choline and folate deficient media compared to the control media (mean [SD] = 2.95 [1.30] vs. 1.65 [0.27] ng/mg protein, p = 0.004). The levels of LRP2 protein in lysates of cells incubated in choline and folate deficient media were significantly higher than the concentrations in lysates of cells incubated in choline deficient but folate sufficient media (1.96 [0.28] ng/mg protein) or those incubated in choline sufficient but folate deficient media (1.77 [0.24] ng/mg protein) (p < 0.05 for both). The cellular levels of CDX2 protein were significantly higher in cells incubated in choline and folate deficient media compared to the control media (1.78 [0.60] vs. 0.99 [0.42] pg/mg protein, p = 0.002); and compared to CDX2 levels in cells incubated in choline deficient but folate sufficient media (0.87 [0.13] pg/mg protein, p < 0.001) or in choline sufficient but folate deficient media (0.96 [0.16] pg/mg protein, p < 0.001). The levels of sFLT-1 and IGF1 in culture media and that of EOMES in HTR-8/SVneo cell lysates remained unchanged under all deficiency conditions.

DISCUSSION

LRP2 and CDX2 are likely to be molecular targets for early choline and folate deficiencies in human trophoblast cells. The results should be confirmed in animal models and in other models of placental cells.

SAMe, Choline, and Valproic Acid as Possible Epigenetic Drugs: Their Effects in Pregnancy with a Special Emphasis on Animal Studies

In this review, we discuss the functions and main effects on pregnancy outcomes of three agents that have the ability to induce epigenetic modifications: valproic acid (VPA), a well-known teratogen that is a histone deacetylase inhibitor; S-adenosylmethionine (SAMe), the most effective methyl donor; and choline, an important micronutrient involved in the one methyl group cycle and in the synthesis of SAMe. Our aim was to describe the possible effects of these compounds when administered during pregnancy on the developing embryo and fetus or, if administered postnatally, their effects on the developing child. These substances are able to modify gene expression and possibly alleviate neurobehavioral changes in disturbances that have epigenetic origins, such as autism spectrum disorder (ASD), depression, Rett syndrome, and fetal alcohol spectrum disorder (FASD). Valproic acid and SAMe are antagonistic epigenetic modulators whether administered in utero or postnatally. However, VPA is a major human teratogen and, whenever possible, should not be used by pregnant women. Most currently relevant data come from experimental animal studies that aimed to explore the possibility of using these substances as epigenetic modifiers and possible therapeutic agents. In experimental animals, each of these substances was able to alleviate the severity of several well-known diseases by inducing changes in the expression of affected genes or by other yet unknown mechanisms. We believe that additional studies are needed to further explore the possibility of using these substances, and similar compounds, for the treatment of "epigenetic human diseases".

Two methods for assessment of choline status in a randomized crossover study with varying dietary choline intake in people: isotope dilution MS of plasma and in vivo single-voxel magnetic resonance spectroscopy of liver

BACKGROUND

Choline deficiency has numerous negative health consequences; although the preponderance of the US population consumes less than the recommended Adequate Intake (AI), clinical assessment of choline status is difficult. Further, several pathways involved in primary metabolism of choline are estrogen-sensitive and the AI for premenopausal women is lower than that for men.

OBJECTIVES

We sought to determine whether in vivo magnetic resonance spectroscopy (MRS) of liver and/or isotope-dilution MS of plasma could identify biomarkers reflective of choline intake (preregistered primary outcomes 1 and 2, secondary outcome 1). Determination of whether biomarker concentrations showed sex dependence was a post hoc outcome. This substudy is a component of a larger project to identify a clinically useful biomarker panel for assessment of choline status.

METHODS

In a double-blind, randomized, crossover trial, people consumed 3 diets, representative of ∼100%, ∼50%, and ∼25% of the choline AI, for 2-wk periods. We measured the concentrations of choline and several metabolites using 1H single-voxel MRS of liver in vivo and using 2H-labeled isotope dilution MS of several choline metabolites in extracted plasma.

RESULTS

Plasma concentrations of 2H9-choline, unlabeled betaine, and 2H9-betaine, and the isotopic enrichment ratio (IER) of betaine showed highly significant between-diet effects (q < 0.0001), with unlabeled betaine concentration decreasing 32% from highest to lowest choline intake. Phosphatidylcholine IER was marginally significant (q = 0.03). Unlabeled phosphatidylcholine plasma concentrations did not show between-diet effects (q = 0.34). 2H9 (trimethyl)-phosphatidylcholine plasma concentrations (q = 0.07) and MRS-measured total soluble choline species liver concentrations (q = 0.07) showed evidence of between-diet effects but this was not statistically significant.

CONCLUSIONS

Although MRS is a more direct measure of choline status, variable spectral quality limited interpretation. MS analysis of plasma showed clear correlation of plasma betaine concentration, but not plasma phosphatidylcholine concentration, with dietary choline intake. Plasma betaine concentrations also correlate with sex status (premenopausal women, postmenopausal women, men).This trial was registered at clinicaltrials.gov as NCT03726671.

Role of Choline in Ocular Diseases

Choline is essential for maintaining the structure and function of cells in humans. Choline plays an important role in eye health and disease. It is a precursor of acetylcholine, a neurotransmitter of the parasympathetic nervous system, and it is involved in the production and secretion of tears by the lacrimal glands. It also contributes to the stability of the cells and tears on the ocular surface and is involved in retinal development and differentiation. Choline deficiency is associated with retinal hemorrhage, glaucoma, and dry eye syndrome. Choline supplementation may be effective for treating these diseases.

The effect of choline availability from gestation to early development on brain and retina functions and phospholipid composition in a male mouse model

OBJECTIVES

Although choline is essential for brain development and neural function, the effect of choline on retina function is not well understood. This study examined the effects of choline on neural tissues of brain and retina, and membrane phospholipid (PL) composition during fetal development.

METHODS

Pregnant C57BL/6 mice were fed one of 4 choline modified diets: i) control (Cont, 2.5g/kg), ii) choline deficient (Def, 0g/kg), iii) supplemented with choline chloride (Cho, 10g/kg) and iv) supplemented with egg phosphatidylcholine (PC, 10g/kg). At postnatal day (PD) 21, pups were weaned onto their mothers' respective diets until PD 45. Spatial memory was measured using the Morris Water Maze; retina function by electroretinogram (ERG); and PL composition with nuclear magnetic resonance spectroscopy.

RESULTS

Cho and PC supplementation enhanced cued learning and spatial memory abilities, respectively (p Def > PC > Cho, with no statistically significant alterations in cone-driven responses. There were no differences in the composition of major PLs in the brain and retina. In the brain, subclasses of ether PL, alkyl acyl- phosphatidylethanolamine (PEaa) and phosphatidylcholine (PCaa) were significantly greater among the PC supplemented group in comparison to the Def group.

DISCUSSION

These results indicate that while choline supplementation during gestation to an early developmental period is beneficial for spatial memory, contributions to retina function are minor. Assessment with a larger sample size of retinas could warrant the essentiality of choline for retina development.

Insufficient dietary choline aggravates disease severity in a mouse model of Citrobacter rodentium-induced colitis

Dietary choline, which is converted to phosphatidylcholine (PC) in intestinal enterocytes, may benefit inflammatory bowel disease patients who typically have reduced intestinal choline and PC. The present study investigated the effect of dietary choline supplementation on colitis severity and intestinal mucosal homoeostasis using a Citrobacter rodentium-induced colitis model. C57BL/6J mice were fed three isoenergetic diets differing in choline level: choline-deficient (CD), choline-sufficient (CS) and choline-excess (CE) for 3 weeks prior to infection with C. rodentium. The effect of dietary choline levels on the gut microbiota was also characterised in the absence of infection using 16S rRNA gene amplicon sequencing. At 7 d following infection, the levels of C. rodentium in CD mice were significantly greater than that in CS or CE groups (P < 0·05). CD mice exhibited greater damage to the surface epithelium and goblet cell loss than the CS or CE mice, which was consistent with elevated pro-inflammatory cytokine and chemokine levels in the colon. In addition, CD group exhibited decreased concentrations of PC in the colon after C. rodentium infection, although the decrease was not observed in the absence of challenge. Select genera, including Allobaculum and Turicibacter, were enriched in response to dietary choline deficiency; however, there was minimal impact on the total bacterial abundance or the overall structure of the gut microbiota. Our results suggest that insufficient dietary choline intake aggravates the severity of colitis and demonstrates an essential role of choline in maintaining intestinal homoeostasis.

Choline: Exploring the Growing Science on Its Benefits for Moms and Babies

The importance of ensuring adequate choline intakes during pregnancy is increasingly recognized. Choline is critical for a number of physiological processes during the prenatal period with roles in membrane biosynthesis and tissue expansion, neurotransmission and brain development, and methyl group donation and gene expression. Studies in animals and humans have shown that supplementing the maternal diet with additional choline improves several pregnancy outcomes and protects against certain neural and metabolic insults. Most pregnant women in the U.S. are not achieving choline intake recommendations of 450 mg/day and would likely benefit from boosting their choline intakes through dietary and/or supplemental approaches.