The Human Serum Metabolome of Vitamin B-12 Deficiency and Repletion, and Associations with Neurological Function in Elderly Adults

Impact of Alterations in Homocysteine, Asymmetric Dimethylarginine and Vitamins-Related Pathways in Some Neurodegenerative Diseases: A Narrative Review

Hyperhomocysteinemia (HHcy) influences the development and progression of neurodegenerative disorders in different ways. Homocysteine (Hcy) metabolism is related to that of asymmetric dimethylarginine (ADMA) and group B vitamins. The breakdown of the pathway involving nitric oxide (NO) and ADMA can be considered one of the causes of endothelial alteration that represents a crucial step in the development of several neurodegenerative disorders. Deficiencies of vitamins other than group B ones, such as D and A, have also been associated with central nervous system disorders. The aim of this narrative review is to describe the link between HHcy, ADMA, and vitamins in Parkinson's disease (PD), Alzheimer's disease (AD), and multiple sclerosis (MS) in terms of dysfunctional pathways and neuropathological processes, performing a literature search from 2015 to 2025 on PubMed. This review also provides an overview of the effects of vitamin supplementation on neurodegenerative diseases. The alteration of pathways involving NO production can lead to HHcy and elevated ADMA concentrations, causing neurodegeneration through various mechanisms, while vitamin supplementation has been shown to reduce Hcy levels, although with conflicting results about the improvement in clinical symptoms. Further studies are needed to develop optimal combined therapeutic strategies.

The combined indicator of vitamin B12 status calculated using 3-parameters (3cB12) is negatively associated with mortality among US adults: NHANES 1999 to 2004

The association between vitamin B12 status and the risk of mortality is controversial. The combined indicator calculated using 3 traditional parameters (3cB12) can be used to indicate vitamin B12 status. We hypothesize that vitamin B12 deficiency indicated by 3cB12 may be related to high mortality risks. To evaluate the association between 3cB12 and all-cause, cardiovascular disease (CVD) and cancer-related mortality, we used Cox proportional hazard models, cumulative Kaplan-Meier curves, and smooth curve fitting to assess data from NHANES 1999 to 2004. A total of 12,103 adults (20 years and older) were included in the analyses and 3595 participants were determined as deceased. The median follow-up duration was 202 months. In the fully adjusted model, all three mortality rates decreased along with the increase in 3cB12 scores, with hazard ratio (HR) [95% confidence interval (CI)]: 0.81 (0.75, 0.87) for all-cause mortality, HR (95% CI): 0.83 (0.72, 0.95) for CVD mortality, and HR (95% CI): 0.79 (0.66, 0.96) for cancer-related mortality. When 3cB12 was divided into two groups, individuals in the lower 3cB12 group (3cB12 < -0.5) showed increased risks of all-cause mortality [HR (95% CI): 1.73 (1.48, 2.02)] and CVD mortality [HR (95% CI): 1.84 (1.31, 2.59)], as compared to the higher 3cB12 group (3cB12 ≥ -0.5). The smooth fitting curves represented a negative linear relationship between 3cB12 and all three types of mortality (P for nonlinearity >.05). In conclusion, the extrapolation of 3cB12 from conventional metrics affords a novel perspective for evaluating B12 nutritional status and mortality risk.

Dissecting the role of vitamin B12 metabolism in craniofacial development through analysis of clinical phenotypes and model organism discoveries

Vitamin B12, otherwise known as cobalamin, is an essential water-soluble vitamin that is obtained from animal derived dietary sources. Mutations in the genes that encode proteins responsible for cobalamin uptake, transport, or processing cause inborn errors of cobalamin metabolism, a group of disorders characterized by accumulation of homocysteine and methylmalonic acid, neurodevelopmental defects, ocular dysfunction, anemia, and failure to thrive. Mild to moderate craniofacial phenotypes have been observed but these phenotypes are not completely penetrant and have not been consistently recognized in the literature. However, in the most recent decade, animal models of cblX and cblC, two cobalamin disorder complementation groups, have documented craniofacial phenotypes. These data indicate a function for cobalamin in facial development. In this review, we performed a literature review of all cobalamin complementation groups to identify which groups, and which human variants, are associated with dysmorphic features, microcephaly, or marfanoid phenotypes. We identified dysmorphic facial features in cblC, cblX, cblG, cblF, and cblJ, which are caused by mutations in MMACHC, HCFC1, MTR, LMBRD1, and ABCD4, respectively. Other complementation groups were associated primarily with microcephaly. Animal models (zebrafish and mouse) of cblC and cblX support these clinical phenotypes and have demonstrated neural crest cell deficits that include reduced expression of prdm1a, sox10, and sox9, key molecular markers of neural crest development. Characterization of a zebrafish mmachc germline mutant also suggests atypical chondrocyte development. Collectively, these data demonstrate an essential role for cobalamin in facial development and warrant future mechanistic inquiries that dissect the cellular and molecular mechanisms underlying human facial phenotypes in cobalamin disorders.

Taurine/chenodeoxycholic acid ratio as a potential serum biomarker for low vitamin B12 levels in humans

Deficiency of vitamin B12 (B12 or cobalamin), an essential water-soluble vitamin, leads to neurological damage, which can be irreversible and anaemia, and is sometimes associated with chronic disorders such as osteoporosis and cardiovascular diseases. Clinical tests to detect B12 deficiency lack specificity and sensitivity. Delays in detecting B12 deficiency pose a major threat because the progressive decline in organ functions may go unnoticed until the damage is advanced or irreversible. Here, using targeted unbiased metabolomic profiling in the sera of subjects with low B12 levels v control individuals, we set out to identify biomarker(s) of B12 insufficiency. Metabolomic profiling identified seventy-seven metabolites, and partial least squares discriminant analysis and hierarchical clustering analysis showed a differential abundance of taurine, xanthine, hypoxanthine, chenodeoxycholic acid, neopterin and glycocholic acid in subjects with low B12 levels. Random forest multivariate analysis identified a taurine/chenodeoxycholic acid ratio, with an AUC score of 1, to be the best biomarker to predict low B12 levels. Mechanistic studies using a mouse model of B12 deficiency showed that B12 deficiency reshaped the transcriptomic and metabolomic landscape of the cell, identifying a downregulation of methionine, taurine, urea cycle and nucleotide metabolism and an upregulation of Krebs cycle. Thus, we propose taurine/chenodeoxycholic acid ratio in serum as a potential biomarker of low B12 levels in humans and elucidate using a mouse model of cellular metabolic pathways regulated by B12 deficiency.

Multiomics: Functional Molecular Biomarkers of Micronutrients for Public Health Application

Adequate micronutrient intake and status are global public health goals. Vitamin and mineral deficiencies are widespread and known to impair health and survival across the life stages. However, knowledge of molecular effects, metabolic pathways, biological responses to variation in micronutrient nutriture, and abilities to assess populations for micronutrient deficiencies and their pathology remain lacking. Rapidly evolving methodological capabilities in genomics, epigenomics, proteomics, and metabolomics offer unparalleled opportunities for the nutrition research community to link micronutrient exposure to cellular health; discover new, arguably essential micronutrients of microbial origin; and integrate methods of molecular biology, epidemiology, and intervention trials to develop novel approaches to assess and prevent micronutrient deficiencies in populations. In this review article, we offer new terminology to specify nutritional application of multiomic approaches and encourage collaboration across the basic to public health sciences to advance micronutrient deficiency prevention.

Vitamin B12 Ameliorates Pesticide-Induced Sociability Impairment in Zebrafish (Danio rerio): A Prospective Controlled Intervention Study

Constant exposure to a variety of environmental factors has become increasingly problematic. A variety of illnesses are initiated or aided by the presence of certain perturbing factors. In the case of autism spectrum disorder, the environmental component plays an important part in determining the overall picture. Moreover, the lack of therapies to relieve existing symptoms complicates the fight against this condition. As a result, animal models have been used to make biomedical research easier and more suited for disease investigations. The current study used zebrafish as an animal model to mimic a real-life scenario: acute exposure to an increased dose of pesticides, followed by prospective intervention-based therapy with vitamin B12 (vit. B12). It is known that vit. B12 is involved in brain function nerve tissue, and red blood cell formation. Aside from this, the role of vit. B12 in the redox processes is recognized for its help against free radicals. To investigate the effect of vit. B12, fish were divided into four different groups and exposed to a pesticide mixture (600 μg L-1 fipronil + 600 μg L-1 pyriproxyfen) and 0.24 μg L-1 vit. B12 for 14 days. The impact of the compounds was assessed daily with EthoVision XT 11.5 software for behavioral observations, especially for sociability, quantified by the social interaction test. In addition, at the end of the study, the activities of superoxide dismutase (SOD), glutathione peroxidase (GPx), and malondialdehyde (MDA) were measured. The results showed significant improvements in locomotor activity parameters and a positive influence of the vitamin on sociability. Regarding the state of oxidative stress, high activity was found for SOD and GPx in the case of vit. B12, while fish exposed to the mixture of pesticides and vit. B12 had a lower level of MDA. In conclusion, the study provides new data about the effect of vit. B12 in zebrafish, highlighting the potential use of vitamin supplementation to maintain and support the function of the organism.

Insights into prevention mechanisms of bioactive components from healthy diets against Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease in which senile plaques, neurofibrillary tangles, insulin resistance, oxidative stress, chronic neuroinflammation, and abnormal neurotransmission are the potential mechanisms involved in its onset and development. Although it is still an intractable disorder, diet intervention has been developed as an innovative strategy for AD prevention. Some bioactive compounds and micronutrients from food, including soy isoflavones, rutin, vitamin B1, etc., have exhibited numerous neuronal health-promoting effects in both in vivo and in vitro studies. It is well known that their antiapoptotic, antioxidative, and anti-inflammatory properties prevent the neuronal or glial cells from injury or death, minimize oxidative damage, inhibit the production of proinflammatory cytokines by modulating typical signaling pathways of MAPK, NF-kβ, and TLR, and further reduce Aβ genesis and tau hyperphosphorylation. However, parts of the dietary components trigger AD-related proteins productions and inflammasome as well as inflammatory gene upregulation. This review summarized the neuroprotective or nerve damage-promoting role and underlying molecular mechanisms of flavonoids, vitamins, and fatty acids via the data from library databases, PubMed, and journal websites, which provides a comprehensive analysis of the prevention potential of these dietary components against AD.

Quantification of 10 B vitamins in mouse colon by LC-MS/MS: Application on breast cancer mice treated with doxorubicin

B vitamins play important roles in various physiological processes, including cell metabolism and DNA synthesis. The intestine is critical for the absorption and utilization of B vitamins, but few analytical methods for detecting intestinal B vitamins are currently available. In this study, we developed a novel liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the simultaneous quantification of 10 B vitamins in mouse colon tissue, including thiamin (B1), riboflavin (B2), nicotinic acid (B3), niacinamide (B3-AM), pantothenic acid (B5), pyridoxine (B6), pyridoxal 5'-phosphate (B6-5P), biotin (B7), folic acid (B9), and cyanocobalamin (B12). The method was thoroughly validated following the U.S. Food and Drug Administration (FDA) guidelines and yielded good results in terms of linearity (r² > 0.9928), lower limit of quantification (40-600 ng/g), accuracy (88.9-119.80 %) and precision (relative standard deviation ≤ 19.71 %), recovery (87.95-113.79 %), matrix effect (91.26-113.78 %), and stability (85.65-114.05 %). Furthermore, we applied our method to profile B vitamins in the colons of mice with breast cancer after doxorubicin chemotherapy treatment, which revealed that the doxorubicin treatment led to significant colon damage and accumulation of several B vitamins including B1, B2 and B5. We also confirmed the capability of this method for quantifying B vitamins in other intestinal tissues like the ileum, jejunum, and duodenum. The newly developed method is simple, specific, and useful for targeted profiling of B vitamins in mouse colon, with a potential for future studies on the role of these micronutrients in healthy and diseased states.

Vitamin B12 Attenuates Changes in Phospholipid Levels Related to Oxidative Stress in SH-SY5Y Cells

Oxidative stress is closely linked to Alzheimer’s disease (AD), and is detected peripherally as well as in AD-vulnerable brain regions. Oxidative stress results from an imbalance between the generation and degradation of reactive oxidative species (ROS), leading to the oxidation of proteins, nucleic acids, and lipids. Extensive lipid changes have been found in post mortem AD brain tissue; these changes include the levels of total phospholipids, sphingomyelin, and ceramide, as well as plasmalogens, which are highly susceptible to oxidation because of their vinyl ether bond at the sn-1 position of the glycerol-backbone. Several lines of evidence indicate that a deficiency in the neurotropic vitamin B12 is linked with AD. In the present study, treatment of the neuroblastoma cell line SH-SY5Y with vitamin B12 resulted in elevated levels of phosphatidylcholine, phosphatidylethanolamine, sphingomyelin, and plasmalogens. Vitamin B12 also protected plasmalogens from hydrogen peroxide (H₂O₂)-induced oxidative stress due to an elevated expression of the ROS-degrading enzymes superoxide-dismutase (SOD) and catalase (CAT). Furthermore, vitamin B12 elevates plasmalogen synthesis by increasing the expression of alkylglycerone phosphate synthase (AGPS) and choline phosphotransferase 1 (CHPT1) in SH-SY5Y cells exposed to H₂O₂-induced oxidative stress.

Fewer US adults had low or transitional vitamin B12 status based on the novel combined indicator of vitamin B12 status compared with individual, conventional markers, NHANES 1999-2004

BACKGROUND

Elevated plasma methylmalonic acid (MMA) and/or total homocysteine (tHcy), as well as low serum vitamin B12 and/or holotranscobalamin (holoTC) are indicative of vitamin B12 deficiency. Combined indicators (cB12), which pool some or all 4 markers into an index, may be a more reliable diagnostic tool to overcome inconclusive diagnoses with individual markers.

OBJECTIVES

We aimed to describe different cB12 score combinations and estimate the prevalence of low or transitional vitamin B12 status compared with individual markers.

DESIGN

Using cross-sectional data for B12, MMA, and tHcy in persons ≥20 y participating in NHANES 1999-2004 (n = 12,335), we examined raw and covariate-adjusted regression models to assess determinants of 3cB12 (all 3 markers) and combinations of 2cB12 (2 markers).

RESULTS

3cB12 was significantly associated with B12 (Spearman r = 0.75), MMA (r = -0.70), and tHcy (r = -0.59). The 3cB12 reference interval (2.5th to 97.5th percentile) was -0.538 to 1.60. In covariate-adjusted models, we found no association of 3cB12 with age; adult females and users of B12 supplements had higher, while adults with advanced chronic kidney disease had lower 3cB12 levels regardless of race-Hispanic origin group (self-reported). Only 2.7% of adults had low or transitional vitamin B12 status using the proposed cB12 cutoff of ≤-0.5, while the prevalence of low (or low-normal) status depended on the selected individual marker and its cutoff: 2.2% and 13% for B12 < 148 and 148-222 pmol/L, respectively; 6.0% for MMA exceeding an age-specific cutoff (250-320 nmol/L); and 8.4% for tHcy > 13 µmol/L. The reference intervals for B12, MMA, and tHcy overlapped from the low (<-2.5) to the transitional (-2.5 to -0.5) and to the adequate (>-0.5) cB12 categories.

CONCLUSIONS

Vitamin B12 deficiency may be overestimated among US adults when individual, conventional markers are used. When only 2 markers are available, the combination of B12 and MMA provides results comparable to 3cB12.

The snapshot of metabolic health in evaluating micronutrient status, the risk of infection and clinical outcome of COVID-19

COVID-19 has re-established the significance of analyzing the organism through a metabolic perspective to uncover the dynamic interconnections within the biological systems. The role of micronutrient status and metabolic health emerge as pivotal in COVID-19 pathogenesis and the immune system's response. Metabolic disruption, proceeding from modifiable factors, has been proposed as a significant risk factor accounting for infection susceptibility, disease severity and risk for post-COVID complications. Metabolomics, the comprehensive study and quantification of intermediates and products of metabolism, is a rapidly evolving field and a novel tool in biomarker discovery. In this article, we propose that leveraging insulin resistance biomarkers along with biomarkers of micronutrient deficiencies, will allow for a diagnostic window and provide functional therapeutic targets. Specifically, metabolomics can be applied as: a. At-home test to assess the risk of infection and propose nutritional support, b. A screening tool for high-risk COVID-19 patients to develop serious illness during hospital admission and prioritize medical support, c(i). A tool to match nutritional support with specific nutrient requirements for mildly ill patients to reduce the risk for hospitalization, and c(ii). for critically ill patients to reduce recovery time and risk of post-COVID complications, d. At-home test to monitor metabolic health and reduce post-COVID symptomatology. Metabolic rewiring offers potential virtues towards disease prevention, dissection of high-risk patients, taking actionable therapeutic measures, as well as shielding against post-COVID syndrome.

Untargeted metabolomics revealed therapeutic mechanisms of icariin on low bone mineral density in older caged laying hens

Osteoporosis is a common chronic disease in the elderly population and in some domestic animals. Caged layer osteoporosis (CLO) is a common bone metabolism disease that was recently recommended as an ideal animal model for osteoporosis. This study aimed to investigate the therapeutic effect and mechanism of dietary icariin (ICA), the main bioactive component of the Chinese herb Epimedium, on low bone mineral density (BMD) in older caged laying hens. A total of 216, 54-week-old Lohmann pink-shell laying hens were allocated to three groups, comprising one control group and two treatment groups that were additionally supplied with 0.5 or 2.0 g kg-1 ICA. The results showed that dietary ICA significantly increased the femur BMD by 49.3% and the tibia BMD by 38.9%, improved the microstructure of bone tissue, decreased levels of the bone metabolism index, enhanced serum antioxidant capacity and regulated messenger RNA expression of bone-related genes. ICA-induced differential metabolites were clarified by using untargeted metabolomics assays. Furthermore, correlation analysis between differential metabolites and BMD indicated that eight differential metabolites correlated highly with both femur and tibia BMD, including uridine, taurine, palmitic acid, adrenic acid, fexofenadine, lysoPC(18 : 1), lysoPE(20 : 3/0 : 0) and 3-acetyl-11-keto-beta-boswellic acid. ICA mainly perturbed pyrimidine metabolism, taurine metabolism and lipid metabolism, which led to increased BMD in older caged laying hens. These findings revealed underlying therapeutic mechanisms of dietary ICA on low BMD, and provided reference metabolites for the early diagnosis of osteoporosis.

Plasma phosphatidylcholines and vitamin B12/folate levels are possible prognostic biomarkers for progression of Alzheimer's disease

OBJECTIVES

In clinical practice it is important to identify patients suffering from mild cognitive impairment (MCI) who will progress to Alzheimer's disease (AD). The purpose of this study is to investigate whether lipid metabolites and vitamin B12 and folate levels are effective biomarker for an accurate prediction of MCI-to-AD conversion.

METHODS

During the standard diagnostic assessment at our memory clinic 48 cognitively healthy subjects and MCI patients were recruited. These participants were followed up after 7-9 years. Blood was collected, various biochemical markers (including vitamin B12 and folate) analysed and plasma lipids were measured using the AbsoluteIDQ p150 Kit.

RESULTS

There was no significant change in lipid levels in controls converting to MCI. However, we found significant changes in five lipids in converters from controls to AD. Interestingly, also two lipids were altered when MCI re-converted to controls. Vitamin B12 levels were not affected by conversion but folate levels significantly decreased in MCI-AD conversion.

CONCLUSIONS

Taken together, our study provides evidence that some plasma lipids are significantly altered in subjects converting to AD. Future studies will investigate whether the peripheral lipid changes correspond with changes in the brain during the course of the disease. Although this is a small study, there are indications that lipids may be suitable as prognostic markers.

Intraoperative anti-inflammatory drugs combined with no drainage after MIS-TLIF in the treatment of recurrent lumbar disc herniation: an RCT

Background

Minimally invasive-transforaminal lumbar interbody fusions (MIS-TLIF), in which the nerve root pain is caused by early postoperative edema reaction, is a common clinical complication. However, there is no effective method to solve this problem. We aimed to use gelatin sponge impregnated with mixed anti-inflammatory drugs combined with no drainage after MIS-TLIF to optimize postoperative effect in the treatment of recurrent lumbar disc herniation (LDH).

Methods

From June 2018, the middle-aged patients (45–60 years old) with recurrent LDH were recruited. Included patients were treated with MIS-TLIF surgery, and no drainage tube was placed after surgery. All patients were randomly divided into intervention group (gelatin sponge impregnated with mixed anti-inflammatory drugs) and control group (saline was immersed in gelatin sponge as a control).

Results

The intervention group included 63 cases, and the control group included 65 cases. The length of hospital stays and bedridden period in the intervention group were significantly lower than those in the control group (P < 0.05). The VAS score of low back pain in the intervention group was significantly lower than that of the control group at postoperative days 1–6 (P < 0.05, for all). The VAS scores of leg pain in the intervention group at postoperative days 1–9 were statistically lower than the control group (P < 0.05, for all).

Conclusions

Application of gelatin sponge impregnated with mixed anti-inflammatory drugs combined with no drainage after MIS-TLIF can significantly further optimize the surgical effect of recurrent LDH and shorten the bedridden period and hospital stays, to achieve the purpose of early rehabilitation.

Trial registration

China Clinical Trial Registration Center, ChiCTR1800016236. Registered on May 21, 2018, http://www.chictr.org.cn/listbycreater.aspx

Metabolomics Reveals Altered Hepatic Bile Acids, Gut Microbiome Metabolites, and Cell Membrane Lipids Associated with Marginal Vitamin A Deficiency in a Mongolian Gerbil Model

SCOPE

This study is designed to provide a broad evaluation of the impacts of vitamin A (VA) deficiency on hepatic metabolism in a gerbil model.

METHODS AND RESULTS

After 28 days of VA depletion, male Mongolian gerbils (Meriones unguiculatus) are randomly assigned to experimental diets for 28 days. Groups are fed a white-maize-based diet with ≈50 µL cottonseed oil vehicle either alone (VA-, n = 10) or containing 40 µg retinyl acetate (VA+, n = 10) for 28 days. Liver retinol is measured by high-performance liquid chromatography. Primary metabolomics, aminomics, lipidomics, bile acids, oxylipins, ceramides, and endocannabinoids are analyzed in post-mortem liver samples by liquid chromatography-mass spectrometry.

RESULTS

Liver retinol is lower (p < 0.001) in the VA- versus VA+ group, with concentrations indicating marginal VA deficiency. A total of 300 metabolites are identified. Marginal VA deficiency is associated with lower bile acids, trimethylamine N-oxide, and a variety of acylcarnitines, phospholipids and sphingomyelins (p < 0.05). Components of DNA, including deoxyguanosine, cytidine, and N-carbomoyl-beta-alanine (p < 0.05), are differentially altered.

CONCLUSIONS

Hepatic metabolomics in a marginally VA-deficient gerbil model revealed alterations in markers of the gut microbiome, fatty acid and nucleotide metabolism, and cellular structure and signaling.

Mini Nutritional Assessment May Identify a Dual Pattern of Perturbed Plasma Amino Acids in Patients with Alzheimer's Disease: A Window to Metabolic and Physical Rehabilitation?

Conflicting results about alterations of plasma amino acid (AA) levels are reported in subjects with Alzheimer’s disease (AD). The current study aimed to provide more homogeneous AA profiles and correlations between AAs and cognitive tests. Venous plasma AAs were measured in 54 fasting patients with AD (37 males, 17 females; 74.63 ± 8.03 yrs; 3.2 ± 1.9 yrs from symptom onset). Seventeen matched subjects without neurodegenerative symptoms (NNDS) served as a control group (C-NNDS). Patients were tested for short-term verbal memory and attention capacity and stratified for nutritional state (Mini Nutritional Assessment, MNA). Compared to C-NNDS, patients exhibited lower plasma levels of aspartic acid and taurine (p < 0.0001) and higher 3-methylhistidine (p < 0.0001), which were independent of patients’ MNA. In comparison to normonourished AD, the patients at risk of and with malnutrition showed a tendency towards lower ratios of Essential AAs/Total AAs, Branched-chain AAs/Total AAs, and Branched-chain AAs/Essential AAs. Serine and histidine were positively correlated with verbal memory and attention capacity deficits, respectively. Total AAs negatively correlated with attention capacity deficits. Stratifying patients with AD for MNA may identify a dual pattern of altered AAs, one due to AD per se and the other linked to nutritional state. Significant correlations were observed between several AAs and cognitive tests.

Peripheral neuropathy in Parkinson's disease

Peripheral neuropathy (PN) is a common neurological problem defined as a dysfunction of sensory, motor, and autonomic nerves. The presence of peripheral neuropathy has recently been noticed in Parkinson's disease (PD) This comorbidity is concerning as it increases the burden on patients whose motor functions are previously compromised. A comprehensive computer-based literature review utilizing multiple peer-reviewed databases (e.g., Embase, PsycINFO, CINAHL, etc.) was conducted. There is evidence for the utility of robust diagnostic criteria to distinguish between large fiber neuropathy (LFN) and small fiber neuropathy (SFN). Some studies have established links between prolonged L-DOPA exposure and prevalence with increased levels of homocysteine (HCY) and methylmalonic acid (MMA) as pathological underlying mechanisms. PN in PD patients with relatively truncated exposure to L-DOPA therapy may have underlying mutations in the Parkin and MHTFR gene or separate mitochondrial disorders. Vitamin B12 and cobalamin deficiencies have also been implicated as drivers of PN. Accumulation of phosphorylated α-synuclein is another central feature in PN and deems urgent exploration via large cohort studies. Importantly, these underlying mechanisms have been linked to peripheral denervation. This review delves into the potential treatments for PN targeting B12 deficiencies and the use of COMT inhibitors along with other novel approaches. Avenues of research with powerful randomized controlled and long-term cohort studies exploring genetic mechanisms and novel treatment pathways is urgently required to alleviate the burden of disease exerted by PN on PD.

The Many Faces of Cobalamin (Vitamin B12) Deficiency

Although cobalamin (vitamin B12) deficiency was described over a century ago, it is still difficult to establish the correct diagnosis and prescribe the right treatment. Symptoms related to vitamin B12 deficiency may be diverse and vary from neurologic to psychiatric. A number of individuals with vitamin B12 deficiency may present with the classic megaloblastic anemia. In clinical practice, many cases of vitamin B12 deficiency are overlooked or sometimes even misdiagnosed. In this review, we describe the heterogeneous disease spectrum of patients with vitamin B12 deficiency in whom the diagnosis was either based on low serum B12 levels, elevated biomarkers like methylmalonic acid and/or homocysteine, or the improvement of clinical symptoms after the institution of parenteral vitamin B12 therapy. We discuss the possible clinical signs and symptoms of patients with B12 deficiency and the various pitfalls of diagnosis and treatment.

Vitamin B12 in Relation to Oxidative Stress: A Systematic Review

The triage theory posits that modest micronutrient deficiencies may induce reallocation of nutrients to processes necessary for immediate survival at the expense of long-term health. Neglected processes could in time contribute to the onset of age-related diseases, in which oxidative stress is believed to be a major factor. Vitamin B12 (B12) appears to possess antioxidant properties. This review aims to summarise the potential antioxidant mechanisms of B12 and investigate B12 status in relation to oxidative stress markers. A systematic query-based search of PubMed was performed to identify eligible publications. The potential antioxidant properties of B12 include: (1) direct scavenging of reactive oxygen species (ROS), particularly superoxide; (2) indirect stimulation of ROS scavenging by preservation of glutathione; (3) modulation of cytokine and growth factor production to offer protection from immune response-induced oxidative stress; (4) reduction of homocysteine-induced oxidative stress; and (5) reduction of oxidative stress caused by advanced glycation end products. Some evidence appears to suggest that lower B12 status is related to increased pro-oxidant and decreased antioxidant status, both overall and for subclinically deficient individuals compared to those with normal B12 status. However, there is a lack of randomised controlled trials and prospective studies focusing specifically on the relation between B12 and oxidative stress in humans, resulting in a low strength of evidence. Further work is warranted.

Biomarkers of Nutrition for Development (BOND): Vitamin B-12 Review

This report on vitamin B-12 (B12) is part of the Biomarkers of Nutrition for Development (BOND) Project, which provides state-of-the art information and advice on the selection, use, and interpretation of biomarkers of nutrient exposure, status, and function. As with the other 5 reports in this series, which focused on iodine, folate, zinc, iron, and vitamin A, this B12 report was developed with the assistance of an expert panel (BOND B12 EP) and other experts who provided information during a consultation. The experts reviewed the existing literature in depth in order to consolidate existing relevant information on the biology of B12, including known and possible effects of insufficiency, and available and potential biomarkers of status. Unlike the situation for the other 5 nutrients reviewed during the BOND project, there has been relatively little previous attention paid to B12 status and its biomarkers, so this report is a landmark in terms of the consolidation and interpretation of the available information on B12 nutrition. Historically, most focus has been on diagnosis and treatment of clinical symptoms of B12 deficiency, which result primarily from pernicious anemia or strict vegetarianism. More recently, we have become aware of the high prevalence of B12 insufficiency in populations consuming low amounts of animal-source foods, which can be detected with ≥1 serum biomarker but presents the new challenge of identifying functional consequences that may require public health interventions.