A Rich Man, Poor Man Story of S-Adenosylmethionine and Cobalamin Revisited.

S-adenosylmethionine (AdoMet) has been referred to as both "a poor man's adenosylcobalamin (AdoCbl)" and "a rich man's AdoCbl," but today, with the ever-increasing number of functions attributed to each cofactor, both appear equally rich and surprising. The recent characterization of an organometallic species in an AdoMet radical enzyme suggests that the line that differentiates them in nature will be constantly challenged. Here, we compare and contrast AdoMet and cobalamin (Cbl) and consider why Cbl-dependent AdoMet radical enzymes require two cofactors that are so similar in their reactivity. We further carry out structural comparisons employing the recently determined crystal structure of oxetanocin-A biosynthetic enzyme OxsB, the first three-dimensional structural data on a Cbl-dependent AdoMet radical enzyme. We find that the structural motifs responsible for housing the AdoMet radical machinery are largely conserved, whereas the motifs responsible for binding additional cofactors are much more varied.

Biochemistry of Catabolic Reductive Dehalogenation.

A wide range of phylogenetically diverse microorganisms couple the reductive dehalogenation of organohalides to energy conservation. Key enzymes of such anaerobic catabolic pathways are corrinoid and Fe-S cluster-containing, membrane-associated reductive dehalogenases. These enzymes catalyze the reductive elimination of a halide and constitute the terminal reductases of a short electron transfer chain. Enzymatic and physiological studies revealed the existence of quinone-dependent and quinone-independent reductive dehalogenases that are distinguishable at the amino acid sequence level, implying different modes of energy conservation in the respective microorganisms. In this review, we summarize current knowledge about catabolic reductive dehalogenases and the electron transfer chain they are part of. We review reaction mechanisms and the role of the corrinoid and Fe-S cluster cofactors and discuss physiological implications.

Bivalent molecular mimicry by ADP protects metal redox state and promotes coenzyme B12 repair.

Control over transition metal redox state is essential for metalloprotein function and can be achieved via coordination chemistry and/or sequestration from bulk solvent. Human methylmalonyl-Coenzyme A (CoA) mutase (MCM) catalyzes the isomerization of methylmalonyl-CoA to succinyl-CoA using 5'-deoxyadenosylcobalamin (AdoCbl) as a metallocofactor. During catalysis, the occasional escape of the 5'-deoxyadenosine (dAdo) moiety leaves the cob(II)alamin intermediate stranded and prone to hyperoxidation to hydroxocobalamin, which is recalcitrant to repair. In this study, we have identified the use of bivalent molecular mimicry by ADP, coopting the 5'-deoxyadenosine and diphosphate moieties in the cofactor and substrate, respectively, to protect against cob(II)alamin overoxidation on MCM. Crystallographic and electron paramagnetic resonance (EPR) data reveal that ADP exerts control over the metal oxidation state by inducing a conformational change that seals off solvent access, rather than by switching five-coordinate cob(II)alamin to the more air stable four-coordinate state. Subsequent binding of methylmalonyl-CoA (or CoA) promotes cob(II)alamin off-loading from MCM to adenosyltransferase for repair. This study identifies an unconventional strategy for controlling metal redox state by an abundant metabolite to plug active site access, which is key to preserving and recycling a rare, but essential, metal cofactor.

Structure of metallochaperone in complex with the cobalamin-binding domain of its target mutase provides insight into cofactor delivery.

G-protein metallochaperone MeaB in bacteria [methylmalonic aciduria type A (MMAA) in humans] is responsible for facilitating the delivery of adenosylcobalamin (AdoCbl) to methylmalonyl-CoA mutase (MCM), the only AdoCbl-dependent enzyme in humans. Genetic defects in the switch III region of MMAA lead to the genetic disorder methylmalonic aciduria in which the body is unable to process certain lipids. Here, we present a crystal structure of Methylobacterium extorquens MeaB bound to a nonhydrolyzable guanosine triphosphate (GTP) analog guanosine-5'-[(ß,γ)-methyleno]triphosphate (GMPPCP) with the Cbl-binding domain of its target mutase enzyme (MeMCMcbl). This structure provides an explanation for the stimulation of the GTP hydrolyase activity of MeaB afforded by target protein binding. We find that upon MCMcbl association, one protomer of the MeaB dimer rotates ~180°, such that the inactive state of MeaB is converted to an active state in which the nucleotide substrate is now surrounded by catalytic residues. Importantly, it is the switch III region that undergoes the largest change, rearranging to make direct contacts with the terminal phosphate of GMPPCP. These structural data additionally provide insights into the molecular basis by which this metallochaperone contributes to AdoCbl delivery without directly binding the cofactor. Our data suggest a model in which GTP-bound MeaB stabilizes a conformation of MCM that is open for AdoCbl insertion, and GTP hydrolysis, as signaled by switch III residues, allows MCM to close and trap its cofactor. Substitutions of switch III residues destabilize the active state of MeaB through loss of protein:nucleotide and protein:protein interactions at the dimer interface, thus uncoupling GTP hydrolysis from AdoCbl delivery.

The structure of the rat vitamin B12 transporter TC and its complex with glutathionylcobalamin.

Vitamin B12 (cobalamin or Cbl) functions as a cofactor in two important enzymatic processes in human cells, and life is not sustainable without it. B12 is obtained from food and travels from the stomach, through the intestine, and into the bloodstream by three B12-transporting proteins: salivary haptocorrin (HC), gastric intrinsic factor, and transcobalamin (TC), which all bind B12 with high affinity and require proteolytic degradation to liberate Cbl. After intracellular delivery of dietary B12, Cbl in the aquo/hydroxocobalamin form can coordinate various nucleophiles, for example, GSH, giving rise to glutathionylcobalamin (GSCbl), a naturally occurring form of vitamin B12. Currently, there is no data showing whether GSCbl is recognized and transported in the human body. Our crystallographic data shows for the first time the complex between a vitamin B12 transporter and GSCbl, which compared to aquo/hydroxocobalamin, binds TC equally well. Furthermore, sequence analysis and structural comparisons show that TC recognizes and transports GSCbl and that the residues involved are conserved among TCs from different organisms. Interestingly, haptocorrin and intrinsic factor are not structurally tailored to bind GSCbl. This study provides new insights into the interactions between TC and Cbl.

Differential utilization of vitamin B12-dependent and independent pathways for propionate metabolism across human cells.

Propionic acid links the oxidation of branched-chain amino acids and odd-chain fatty acids to the TCA cycle. Gut microbes ferment complex fiber remnants, generating high concentrations of short chain fatty acids, acetate, propionate and butyrate, which are shared with the host as fuel sources. Analysis of vitamin B12-dependent propionate utilization in skin biopsy samples has been used to characterize and diagnose underlying inborn errors of cobalamin (or B12) metabolism. In these cells, the B12-dependent enzyme, methylmalonyl-CoA mutase (MMUT), plays a central role in funneling propionate to the TCA cycle intermediate, succinate. Our understanding of the fate of propionate in other cell types, specifically, the involvement of the ß-oxidation-like and methylcitrate pathways, is limited. In this study, we have used [14C]-propionate tracing in combination with genetic ablation or inhibition of MMUT, to reveal the differential utilization of the B12-dependent and independent pathways for propionate metabolism in fibroblast versus colon cell lines. We demonstrate that itaconate can be used as a tool to investigate MMUT-dependent propionate metabolism in cultured cell lines. While MMUT gates the entry of propionate carbons into the TCA cycle in fibroblasts, colon-derived cell lines exhibit a quantitatively significant or exclusive reliance on the ß-oxidation-like pathway. Lipidomics and metabolomics analyses reveal that propionate elicits pleiotropic changes, including an increase in odd-chain glycerophospholipids, and perturbations in the purine nucleotide cycle and arginine/nitric oxide metabolism. The metabolic rationale and the regulatory mechanisms underlying the differential reliance on propionate utilization pathways at a cellular, and possibly tissue level, warrant further elucidation.

Causes and consequences of impaired methionine synthase activity in acquired and inherited disorders of vitamin B12 metabolism.

Methyl-Cobalamin (Cbl) derives from dietary vitamin B12 and acts as a cofactor of methionine synthase (MS) in mammals. MS encoded by MTR catalyzes the remethylation of homocysteine to generate methionine and tetrahydrofolate, which fuel methionine and cytoplasmic folate cycles, respectively. Methionine is the precursor of S-adenosyl methionine (SAM), the universal methyl donor of transmethylation reactions. Impaired MS activity results from inadequate dietary intake or malabsorption of B12 and inborn errors of Cbl metabolism (IECM). The mechanisms at the origin of the high variability of clinical presentation of impaired MS activity are classically considered as the consequence of the disruption of the folate cycle and related synthesis of purines and pyrimidines and the decreased synthesis of endogenous methionine and SAM. For one decade, data on cellular and animal models of B12 deficiency and IECM have highlighted other key pathomechanisms, including altered interactome of MS with methionine synthase reductase, MMACHC, and MMADHC, endoplasmic reticulum stress, altered cell signaling, and genomic/epigenomic dysregulations. Decreased MS activity increases catalytic protein phosphatase 2A (PP2A) and produces imbalanced phosphorylation/methylation of nucleocytoplasmic RNA binding proteins, including ELAVL1/HuR protein, with subsequent nuclear sequestration of mRNAs and dramatic alteration of gene expression, including SIRT1. Decreased SAM and SIRT1 activity induce ER stress through impaired SIRT1-deacetylation of HSF1 and hypomethylation/hyperacetylation of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC1α), which deactivate nuclear receptors and lead to impaired energy metabolism and neuroplasticity. The reversibility of these pathomechanisms by SIRT1 agonists opens promising perspectives in the treatment of IECM outcomes resistant to conventional supplementation therapies.

Efficient NADPH-dependent dehalogenation afforded by a self-sufficient reductive dehalogenase.

Reductive dehalogenases are corrinoid and iron-sulfur cluster-containing enzymes that catalyze the reductive removal of a halogen atom. The oxygen-sensitive and membrane-associated nature of the respiratory reductive dehalogenases has hindered their detailed kinetic study. In contrast, the evolutionarily related catabolic reductive dehalogenases are oxygen tolerant, with those that are naturally fused to a reductase domain with similarity to phthalate dioxygenase presenting attractive targets for further study. We present efficient heterologous expression of a self-sufficient catabolic reductive dehalogenase from Jhaorihella thermophila in Escherichia coli. Combining the use of maltose-binding protein as a solubility-enhancing tag with the btuCEDFB cobalamin uptake system affords up to 40% cobalamin occupancy and a full complement of iron-sulfur clusters. The enzyme is able to efficiently perform NADPH-dependent dehalogenation of brominated and iodinated phenolic compounds, including the flame retardant tetrabromobisphenol, under both anaerobic and aerobic conditions. NADPH consumption is tightly coupled to product formation. Surprisingly, corresponding chlorinated compounds only act as competitive inhibitors. Electron paramagnetic resonance spectroscopy reveals loss of the Co(II) signal observed in the resting state of the enzyme under steady-state conditions, suggesting accumulation of Co(I)/(III) species prior to the rate-limiting step. In vivo reductive debromination activity is readily observed, and when the enzyme is expressed in E. coli strain W, supports growth on 3-bromo-4-hydroxyphenylacetic as a sole carbon source. This demonstrates the potential for catabolic reductive dehalogenases for future application in bioremediation.

Vitamin B12 deficiency misdiagnosed as TTP: What can we learn from it?

The case report by Dwyre et al. shows that vitamin B12 deficiency may be misdiagnosed as acute thrombotic thrombocytopenic purpura. Together with similar observations, this underlines that acquired vitamin B12 deficiency-besides the inherited disorder of intracellular cobalamin metabolism, cbl C disease-should be listed as a separate entity of the thrombotic microangiopathies. Commentary on: Dwyre et al. Microangiopathic thrombocytopenia caused by vitamin B12 deficiency responding to plasma exchange. Br J Haematol 2024 (Online ahead of print). doi: 10.1111/bjh.19625.

Crystal structure of methyltransferase CbiL from Akkermansia muciniphila.

Akkermansia muciniphila is a mucin-degrading probiotic that colonizes the gastrointestinal tract. Genomic analysis identified a set of genes involved in the biosynthesis of corrin ring, including the cobalt factor II methyltransferase CbiL, in some phylogroups of A. muciniphila, implying a potential capacity for de novo synthesis of cobalamin. In this work, we determined the crystal structure of CbiL from A. muciniphila at 2.3 Å resolution. AmCbiL exists as a dimer both in solution and in crystal, and each protomer consists of two α/ß domains, the N-terminal domain and the C-terminal domain, consistent with the folding of typical class III MTases. The two domains create an open trough, potentially available to bind the substrates SAM and cobalt factor II. Sequence and structural comparisons with other CbiLs, assisted by computer modeling, suggest that AmCbiL should have cobalt factor II C-20 methyltransferase activity. Our results support that certain strains of A. muciniphila may be capable of synthesizing cobalamin de novo.

Vitamin B12 inhibits peptidylarginine deiminases and ameliorates rheumatoid arthritis in CAIA mice.

Rheumatoid arthritis is an autoimmune disease whose early onset correlates with dysregulated citrullination, a process catalyzed by peptidylarginine deiminase isoform 4 (PADI-4). Here, we report that PADI-4 is a novel target of vitamin B12, a water-soluble vitamin that serves as a cofactor in DNA synthesis and the metabolism of fatty and amino acids. Vitamin B12 preferentially inhibited PADI-4 over PADI-2 with comparable inhibitory activity to the reference compound Cl-amidine in enzymatic inhibition assays, and reduced total cellular citrullination levels including that of histone H3 citrullination mediated by PADI-4. We also demonstrated that hydroxocobalamin, a manufactured form of vitamin B12, significantly ameliorated the severity of collagen type II antibody induced arthritis (CAIA) in mice and diminished gene expression of the rheumatoid inflammatory factors and cytokines IL17A, TNFα, IL-6, COX-II and ANXA2, as well PADI-4. Therefore, the use of vitamin B12 to treat rheumatoid arthritis merits further study.

Promoting salt tolerance, growth, and phytochemical responses in coriander (Coriandrum sativum L. cv. Balady) via eco-friendly Bacillus subtilis and cobalt.

In plant production, evaluation of salt stress protectants concerning their potential to improve growth and productivity under saline stress is critical. Bacillus subtilis (Bs) and cobalt (Co) have been proposed to optimize salt stress tolerance in coriander (Coriandrum sativum L. cv. Balady) plants by influencing some physiological activities. The main aim of this work is to investigate the response of (Bs) and (Co) as eco-safe salt stress protectants to resist the effect of salinity, on growth, seed, and essential oil yield, and the most important biochemical constituents of coriander produced under salt stress condition. Therefore, in a split-plot factorial experiment design in the RCBD (randomized complete block design), four levels of salinity of NaCl irrigation water (SA) were assigned to the main plots; (0.5, 1.5, 4, and 6 dS m-1); and six salt stress protectants (SP) were randomly assigned to the subplots: distilled water; 15 ppm (Co1); 30 ppm (Co2); (Bs); (Co1 + Bs); (Co2 + Bs). The study concluded that increasing SA significantly reduced coriander growth and yield by 42.6%, which could be attributed to ion toxicity, oxidative stress, or decreased vital element content. From the results, we recommend that applying Bs with Co (30 ppm) was critical for significantly improving overall growth parameters. This was determined by the significant reduction in the activity of reactive oxygen species scavenging enzymes: superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA) and non-enzyme: proline by 5, 11.3, 14.7, and 13.8% respectively, while increasing ascorbic acid by 8% and preserving vital nutrient levels and enhancing plant osmotic potential to buffer salt stress, seed yield per plant, and essential oil yield increased by 12.6 and 18.8% respectively. The quality of essential oil was indicated by highly significant quantities of vital biological phytochemicals such as linalool, camphor, and protein which increased by 10.3, 3.6, and 9.39% respectively. Additional research is suggested to determine the precise mechanism of action of Bs and Co's dual impact on medicinal and aromatic plant salt stress tolerance.

MTHFR polymorphisms and vitamin B12 deficiency: correlation between mthfr polymorphisms and clinical and laboratory findings.

Vitamin B12 deficiency is a common condition that causes a variety of disorders ranging from the development of megaloblastic anemia to the building up of neurological damage. Historically one of the leading causes of B12 deficiency appears to be secondary to malabsorption in part caused by the development of atrophic gastritis in pernicious anemia. More recently B12 deficiency could also depend on dietary restrictions. Cobalamin deficiency also appears to be closely related to folate metabolism, causing a reduction in methionine synthase activity. This results in the accumulation of 5-methyltetrahydrofolate (5-MTHF) and defective DNA synthesis. It has been hypothesized that reduced activity of the enzyme methylene-tetrahydrofolate reductase (MTHFR) could reduce the production of 5-MTHF, thereby shifting folate metabolism to thymidylate synthesis and promoting proper DNA synthesis. Our aim was to investigate the role of the C677T and A1298C MTHFR gene polymorphisms, which are associated with reduced enzyme activity, in predisposing to the development of anemia, neurological symptoms, and atrophic gastritis in a population of 105 consecutive Italian patients with cobalamin deficiency. We found statistically significant correlations between the degree of anemia and thrombocytopenia and the C677T MTHFR polymorphism, while hemoglobin levels alone significantly correlated with A1298C polymorphism, contradicting the potential protective role of these polymorphisms. Furthermore, in patients with atrophic gastritis, we found an association between the absence of parietal cell antibodies and the presence of the C677T polymorphism in homozygosity. Our results suggest a role for MTHFR enzyme activity in the severity of hematologic manifestations of vitamin B12 deficiency and as an independent mechanism of predisposition to the development of atrophic gastritis.

Radiation-Activated Cobalamin-Kinase Inhibitors for Treatment of Pancreatic Ductal Adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) remains one of the most dismal diagnoses that a patient can receive. PDAC is extremely difficult to treat, as drug delivery is challenging in part due to the lack of vascularization, high stromal content, and high collagen content of these tumors. We have previously demonstrated that attaching drugs to the cobalamin scaffold provides selectivity for tumors over benign cells due to a high vitamin demand in these rapidly growing cells and an overexpression of transcobalamin receptors in a variety of cancer types. Importantly, we have shown the ability to deliver cobalamin derivatives to orthotopic pancreas tumors. Tyrosine kinase inhibitors have shown promise in treating PDAC as well as other cancer types. However, some of these inhibitors suffer from drug resistance, and as such, their success has been diminished. With this in mind, we synthesized the tyrosine kinase inhibitors erlotinib (EGFR) and dasatinib (Src) that are attached to this cobalamin platform. Both of these cobalamin-drug conjugates cause visible light-induced apoptosis, and the cobalamin-erlotinib conjugate (2) causes X-ray-induced apoptosis in MIA PaCa-2 cells. Both visible light and X-rays provide spatial control of drug release; however, utilizing X-ray irradiation offers the advantage of deeper tissue penetration. Therefore, we explored the utilization of 2 as a synergistic therapy with radiation in athymic nude mice implanted with MIA PaCa-2 tumors. We discovered that the addition of 2 caused an enhanced reduction in tumor margins in comparison with radiation therapy alone. In addition, treatment with 2 in the absence of radiation caused no significant reduction in tumor size in comparison with the controls. The cobalamin technology presented here allows for the spatial release of drugs in conjunction with external beam radiation therapy, potentially allowing for more effective treatment of deep-seated tumors with less systemic side effects.

Transmembrane helix 6 of ABCD4 is indispensable for cobalamin transport.

ABCD4, which belongs to the ABC protein subfamily D, plays a role in the transport of cobalamin from lysosomes to the cytosol by cooperating with ATP-binding and ATP-hydrolysis. Pathogenic variants in the ABCD4 gene lead to an inherited metabolic disorder characterized by cobalamin deficiency. However, the structural requirements for cobalamin transport in ABCD4 remain unclear. In this study, six proteoliposomes were prepared, each containing a different chimeric ABCD4 protein, wherein each of the six transmembrane (TM) helices was replaced with the corresponding ABCD1. We analyzed the cobalamin transport activities of the ABCD mutants. In the proteoliposome with chimeric ABCD4 replacing TM helix 6, the cobalamin transport activity disappeared without a reduction in ATPase activity, indicating that TM helix 6 contributes to substrate recognition. Furthermore, the substitution of aspartic acid at position 329 or threonine at position 332 in TM helix 6 with the basic amino acid lysine led to a decrease in cobalamin-transport activity without causing a reduction in ATPase activity. The amino acids in TM helix 6 may be critically involved in substrate recognition; the charged state in the C-terminal half of TM helix 6 of ABCD4 is responsible for cobalamin transport activity.

Improved biochemical and neurodevelopmental profiles with high-dose hydroxocobalamin therapy in cobalamin C defect.

Cobalamin C (Cbl-C) defect causes methylmalonic acidemia, homocystinuria, intellectual disability and visual impairment, despite treatment adherence. While international guidelines recommend parenteral hydroxocobalamin (OH-Cbl) as effective treatment, dose adjustments remain unclear. We assessed OH-Cbl therapy impact on biochemical, neurocognitive and visual outcomes in early-onset Cbl-C patients treated with different OH-Cbl doses over 3 years. Group A (n = 5), diagnosed via newborn screening (NBS), received high-dose OH-Cbl (median 0.55 mg/kg/day); Group B1 (n = 3), NBS-diagnosed, received low-dose OH-Cbl (median 0.09 mg/kg/day); Group B2 (n = 12), diagnosed on clinical bases, received low-dose OH-Cbl (median 0.06 mg/kg/day). Biochemical analyses revealed better values of homocysteine, methionine and methylmalonic acid in Group A compared to Group B1 (p < 0.01, p < 0.05 and p < 0.01, respectively) and B2 (p < 0.001, p < 0.01 and p < 0.001, respectively). Neurodevelopmental assessment showed better outcome in Group A compared to low-dose treated Groups B1 and B2, especially in Developmental Quotient, Hearing and Speech and Performance subscales without significant differences between Group B2 and Group B1. Maculopathy was detected in 100%, 66% and 83% of patients in the three groups, respectively. This study showed that "high-dose" OH-Cbl treatment in NBS-diagnosed children with severe early-onset Cbl-C defect led to a significant improvement in the metabolic profile and in neurocognitive outcome, compared to age-matched patients treated with a "low-dose" regimen. Effects on maculopathy seem unaffected by OH-Cbl dosage. Our findings, although observed in a limited number of patients, may contribute to improve the long-term outcome of Cbl-C patients.

Intranasal vitamin B12 administration in elderly patients: A randomized controlled comparison of two dosage regimens.

AIM: Vitamin B12 deficiency is common in the elderly population. Standard treatment via intramuscular injections, however, has several disadvantages. Safer and more convenient dosage forms such as intranasal are therefore being explored. This study compares the effects of two intranasal vitamin B12 dosage regimens in elderly vitamin B12-deficient patients. METHODS: Sixty patients ≥65 years were randomly assigned to either a loading dose (daily administration for 14 days followed by weekly administration) or a no loading dose (administration every 3 days) regimen for 90 days. Each dose contained 1000 µg cobalamin. Total vitamin B12, holotranscoblamin (holoTC), methylmalonic acid (MMA) and total homocysteine (tHcy) levels in serum were measured on days 0, 7, 14, 30, 60 and 90. RESULTS: Both dosage regimens resulted in a rapid increase of vitamin B12 and holoTC concentrations and normalization of initial high, MMA and tHcy concentrations. The loading dose regimen resulted in the fastest and greatest increase to a median vitamin B12 of 1090 pmol/L (reference 350-650 pmol/L) concentration after 14 days. Following weekly administration, B12 rapidly decreased to a median concentration of 530 pmol/L after 90 days. The no loading dose regimen resulted in a steady increase to a median vitamin B12 of 717 pmol/L after 90 days. CONCLUSIONS: Intranasal vitamin B12 administration is an effective and suitable way to replenish and sustain vitamin B12 levels in elderly patients.

Vitamin B12 Supplementation in Psychiatric Practice.

PURPOSE OF REVIEW: Vitamin B12 (B12, cobalamin) deficiency has been associated with neuropsychiatric symptoms, suggesting a role for B12 supplementation both as a treatment for psychiatric symptoms due to B12 deficiency and as an augmentation strategy for pharmacological treatments of psychiatric disorders. This critical review discusses the major causes of B12 deficiency, the range of psychiatric and non-psychiatric manifestations of B12 deficiency, the indications for testing B12 levels, and the evidence for B12 supplementation for major psychiatric disorders. RECENT FINDINGS: We find that high-quality evidence shows no benefit to routine B12 supplementation for mild depressive symptoms or to prevent depression. There is very limited evidence on the role of B12 supplementation to augment antidepressants. No high-quality evidence to date suggests a role for routine B12 supplementation in any other major psychiatric disorder. No formal guidelines indicate when clinicians should test B12 levels for common psychiatric symptoms, in the absence of major risk factors for deficiency or cardinal symptoms of deficiency. No robust evidence currently supports routine B12 supplementation for major psychiatric disorders. However, psychiatrists should be aware of the important risk factors for B12 deficiency and should be able to identify symptoms of B12 deficiency, which requires prompt testing, medical workup, and treatment. Testing for B12 deficiency should be considered for atypical or severe psychiatric presentations.

Effect of roasted purple laver (nori) on vitamin B12 nutritional status of vegetarians: a dose-response trial.

PURPOSE: To investigate the bioavailability of vitamin B12 from nori and to evaluate the required dosage for improving vitamin B12 nutritional status in vegetarians not using supplements. METHODS: The study design is an open-label, parallel, dose-response randomized controlled trial. Thirty vegetarians were assigned to control (no nori), low-dose (5 g nori, aiming to provide 2.4 µg vitamin B12 per day), or high-dose (8 g nori, aiming to provide 4 µg vitamin B12 per day) groups. The primary outcome was changes in vitamin B12 status as measured by serum vitamin B12, holotranscobalamin (holoTC), homocysteine (Hcy), and methylmalonic acid (MMA), and a combined score of these four markers (4cB12 score) during the four-week intervention. Dietary vitamin B12 intakes were assessed at baseline and end of the trial with a 17-item food frequency questionnaire designed for vitamin B12 assessment. General linear model was used to compare least square means of changes in each biomarker of vitamin B12 status, among the three groups, while adjusting for respective baseline biomarker. RESULTS: After adjusting for baseline status, nori consumption led to significant improvement in serum vitamin B12 (among-group P-value = 0.0029), holoTC (P = 0.0127), Hcy (P = 0.0225), and 4cB12 (P = 0.0094). Changes in MMA did not differ significantly across groups, but showed within-group pre-post improvement in the low-dose group (median [p25, p75] = -339 [-461, -198] nmol/L). Vitamin B12 status appeared to plateau at low dose (5 g of nori), which compared with control group, improved serum vitamin B12 (lease square mean [95% CI] = + 59 [25, 93] pmol/L, P = 0.0014); holoTC (+ 28.2 [10.1, 46.3] pmol/L, P = 0.0035); Hcy (-3.7 [-6.8, -0.6] µmol/L, p = 0.0226); and 4cB12 score (+ 0.67 [0.24, 1.09], p = 0.0036). High-dose resulted in similar improvements. There was no significant difference between low-dose and high-dose groups in all biomarkers of vitamin B12. CONCLUSIONS: Consuming 5 g of nori per day for 4 weeks significantly improved vitamin B12 status in vegetarians. A higher dose (8 g) may not confer additional benefits. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT05614960. Date of registration: November 14th 2022.

Pediatric reference intervals for serum folate and cobalamin based on a European population without exposure to folic acid fortification.

The aim of the present study was to define pediatric reference intervals for serum cobalamin and folate utilizing data generated from a population not exposed to food fortified with folic acid. Folate and cobalamin results analyzed by electrochemiluminescence immunoassay (Roche Cobas) were obtained from 2375 children (2 months to 17.99 years of age). The serum samples were collected between 2011 and 2015 as part of the LIFE (Leipzig Research Centre for Civilization Diseases) Child cohort study in Germany, where folic acid fortification of food is not mandated. These results were used to generate age- and gender-specific reference intervals presented as non-parametric 2.5 and 97.5 percentiles. Because of a subsequent restandardisation of the Roche folate assay in 2016, folate values were recalculated accordingly for adaptation to results obtained using the present calibration. In both genders, folate concentrations decreased continuously with age, whereas cobalamin concentrations peaked at five years of age and then declined. Teenage females had higher concentrations of cobalamin in the age group 12-17.99 years.