Measurement of Total Vitamin B12 and Holotranscobalamin, Singly and in Combination, in Screening for Metabolic Vitamin B12 Deficiency

Vitamin B12 Metabolism: A Network of Multi-Protein Mediated Processes

The water-soluble vitamin, vitamin B12, also known as cobalamin, plays a crucial role in cellular metabolism, particularly in DNA synthesis, methylation, and mitochondrial functionality. Its deficiency can lead to hematological and neurological disorders; however, the manifestation of these clinical outcomes is relatively late. It leads to difficulties in the early diagnosis of vitamin B12 deficiency. A prolonged lack of vitamin B12 may have severe consequences including increased morbidity to neurological and cardiovascular diseases. Beyond inadequate dietary intake, vitamin B12 deficiency might be caused by insufficient bioavailability, blood transport disruptions, or impaired cellular uptake and metabolism. Despite nearly 70 years of knowledge since the isolation and characterization of this vitamin, there are still gaps in understanding its metabolic pathways. Thus, this review aims to compile current knowledge about the crucial proteins necessary to efficiently accumulate and process vitamin B12 in humans, presenting these systems as a multi-protein network. The epidemiological consequences, diagnosis, and treatment of vitamin B12 deficiency are also highlighted. We also discuss clinical warnings of vitamin B12 deficiency based on the ongoing test of specific moonlighting proteins engaged in vitamin B12 metabolic pathways.

Oral vitamin B12 supplementation in pernicious anemia: a prospective cohort study

BACKGROUND

The absorption of vitamin B12 is hindered in pernicious anemia (PA) owing to intrinsic factor deficiency. Traditionally, intramuscular vitamin B12 injections were the standard treatment, bypassing the impaired absorption. Although there is potential for oral vitamin B12 supplementation through passive enteral absorption, it is not commonly prescribed in PA owing to limited studies assessing its efficacy.

OBJECTIVES

We aimed to assess the efficacy of oral vitamin B12 supplementation in PA.

METHODS

We enrolled participants diagnosed with incident vitamin B12 deficiency related to PA. The diagnosis of PA was based on the presence of classical immune gastritis and of anti-intrinsic factor and/or antiparietal cell antibodies. To evaluate the vitamin B12 status, we measured total plasma vitamin B12, plasma homocysteine, and plasma methylmalonic acid (pMMA) concentration and urinary methylmalonic acid-to-creatinine ratio. Participants were treated with oral cyanocobalamin at a dosage of 1000 μg/d throughout the study duration. Clinical and biological vitamin B12 deficiency related features were prospectively and systematically assessed over the 1-y study duration.

RESULTS

We included 26 patients with vitamin B12 deficiency revealing PA. Following 1 mo of oral vitamin B12 supplementation, 88.5% of patients were no longer deficient in vitamin B12, with significant improvement of plasma vitamin B12 [407 (297-485) compared with 148 (116-213) pmol/L; P < 0.0001], plasma homocysteine [13.5 (10.9-29.8) compared with 18.6 (13.7-46.8) μmol/L; P < 0.0001], and pMMA [0.24 (0.16-0.38) compared with 0.56 (0.28-1.09) pmol/L; P < 0.0001] concentrations than those at baseline. The enhancement of these biological parameters persisted throughout the 12-month follow-up, with no patients showing vitamin B12 deficiency by the end of the follow-up period. The median time to reverse initial vitamin B12 deficiency abnormalities ranged from 1 mo for hemolysis to 4 mo for mucosal symptoms.

CONCLUSIONS

Oral supplementation with 1000 μg/d of cyanocobalamin has been shown to improve vitamin B12 deficiency in PA.

Iron deficiency in pernicious anemia: Specific features of iron deficient patients and preliminary data on response to iron supplementation

BACKGROUND & AIMS

While vitamin B12 (B12) deficiency is considered as the hallmark of pernicious anemia (PA), iron deficiency (ID) is also prevalent. Indeed, this auto immune gastritis is responsible for parietal cell atrophy and increase in gastric pH, leading to impaired iron absorption. We compared PA patients' features according to their iron status at PA diagnosis, and we assessed the iron status recovery after oral or intravenous iron supplementation.

METHODS

We prospectively included patients presenting with a newly diagnosed PA in a tertiary referral hospital between November 2018 and October 2020. Iron status was assessed at PA diagnosis then regularly during a standardized follow-up. In case of ID, the decision of treatment with oral and/or intravenous iron supplementation was left to the clinician convenience.

RESULTS

We included 28 patients with newly diagnosed PA. ID was observed in 21/28 (75.0%) patients: from the PA diagnosis in 13 patients, or during the follow-up in 8 patients. Iron deficient PA patients had higher plasma B12 (p = 0.04) and lower homocysteine levels (p = 0.04). Also, ID was independently associated with the 'APCA (anti-parietal cell antibodies) alone' immunological status (absence of anti-intrinsic factor antibodies) after adjustment for age, gender and B12 level (aOR 12.1 [1.1-141.8], p = 0.04). High level of APCA was associated with lower ferritin level. After 3 months of supplementation, 3/11 PA patients normalized the iron status with oral iron supplementation, versus 7/8 with intravenous iron supplementation (p = 0.02).

CONCLUSION

The high frequency of iron deficiency in PA highlights the interest of regular assessment of iron status in this condition. ID was associated with a profile including APCA alone and less pronounced B12 deficiency. Intravenous iron supplementation seemed to be more efficient than an oral supplementation in these preliminary data.

Metformin-Induced Vitamin B12 Deficiency in Patients With Type-2 Diabetes Mellitus

Diabetes mellitus (DM) is the most common metabolic disease worldwide. Hence, the prevalence of the disease continues to increase across the globe. Metformin is used as a first-line oral hypoglycemic drug to keep control of type-2 DM (T2DM) in adults. Diabetic patients on metformin have been largely seen to be suffering from a deficiency of vitamin B12. It is a water-soluble vitamin mainly obtained from animal food like meat. At the basic cell level, it acts as a cofactor for enzymes essential for DNA synthesis and neuroprotection. As a result, vitamin B12 deficiency can show clinical effects such as progressive demyelination, peripheral neuropathy and haematological abnormalities (such as macrocytic anaemia and neutrophil hypersegmentation). Various studies also show a relation between vitamin B12 insufficiency and metformin-treated T2DM patients as decreased absorption of vitamin B12. There could be a severe complication of vitamin B12 deficiency in T2DM patients. The use of proton pump inhibitors, gastric bypass surgery, older patients and patients with a higher red blood cell turnover are factors that hasten the depletion of vitamin B12 reserves in the liver. Methylmalonic acid and homocysteine levels can be measured to identify vitamin B12 insufficiency at its early stage if blood vitamin B12 levels are borderline. The action of metformin on vitamin B12 absorption and its potential mechanisms of inhibition will be the main topics of discussion in this review. The review will also discuss how vitamin B12 deficiencies in T2DM patients using metformin affect their clinical results.

Cross-Sectional Study of the Prevalence of Cobalamin Deficiency and Vitamin B12 Supplementation Habits among Vegetarian and Vegan Children in the Czech Republic

Vegetarian (VG) and vegan (VN) diets in childhood are of growing interest due to their perceived health and environmental benefits. Concerns remain due to the possible disruption of healthy growth and development of children because of the scarcity of evidence-based studies. Among the nutrients of special concern is vitamin B12. Therefore, the Czech Vegan Children Study (CAROTS) decided to examine the relationship between B12 metabolism parameters and B12 intake through diet and supplementation. We analyzed laboratory parameters within n = 79 VG, n = 69 VN, and n = 52 omnivores (OM) children (0−18 years old). There were no significant differences in levels of holotranscobalamin (aB12), folate, homocysteine (hcys), or mean corpuscular volume. However, there was a significant difference in levels of cyanocobalamin (B12) (p = 0.018), even though we identified only n = 1 VG and n = 2 VN children as B12 deficient. On the other hand, we identified n = 35 VG, n = 28 VN, and n = 9 OM children with vitamin B12 hypervitaminosis (p = 0.004). This finding was related to a high prevalence of over-supplementation in the group (mean dose for VG 178.19 ± 238.5 µg per day; VN 278.35 ± 394.63 µg per day). Additionally, we found a significant (p < 0.05) difference between B12, aB12, and hcys levels of supplemented vs. non-supplemented VG/VN children. This can show that the intake of vitamin B12 via diet in the VG group might not be sufficient. Secondly, we analyzed a relation between supplement use in pregnancy and breastfeeding and its impact on vitamin B12 levels of children aged 0−3 years. Out of n = 46 mothers, only n = 3 (e.g., 6.5%) were not supplemented at all. We have not identified any clinical manifestation of B12 deficiency and only n = 1 child with low serum cobalamin, a child who did not receive vitamin B12 supplementation and whose mother took only low doses of vitamin B12 (25/µg/day).To conclude, we did not observe any life-threatening or severe consequences of laboratory-stated vitamin B12 deficiency; thus, our group was well supplemented. On the other hand, we have identified many subjects with vitamin B12 hypervitaminosis of unknown impact on their health. Further research and new guidelines for B12 supplementation among VG and VN children are needed.

How I investigate acquired megaloblastic anemia

In this review of megaloblastic anemia (MA), an overview of vitamin B₁₂ and folate body requirements, biochemical pathways, and laboratory testing strategies will be provided. However, the focus of this review is the classic and unique features of MA in blood and bone marrow. Acquired MA is a benign disorder for many, but can be detrimental for some. The clinical presentation can vary considerably, and the spectrum of symptoms and signs is diverse and quite broad. Prompt recognition and therapy are critical to prevent potential irreversible damage and clinical sequelae, especially in patients with vitamin B₁₂ deficiency. A delay in diagnosis of vitamin B₁₂ deficiency can result in significant neurologic sequelae that may not fully resolve with treatment, including in neonates and young infants. The blood and bone marrow features in MA can closely mimic thrombocytopenic purpura, myelodysplasia, and other myeloid neoplasms. Both pancytopenia and normal MCV at presentation are common in MA and raise unique challenges for the diagnostician. Partially treated MA is also a significant diagnostic "trap". MA is highly responsive to treatment, and patients tend to improve rapidly upon treatment initiation. However, the broad range of clinical and hematologic features makes the rapid, successful diagnosis of MA a unique challenge for the hematopathologist. Even in the era of state-of-the-art laboratory testing, a high suspicion is required.

Personalising laboratory medicine in the 'real world': Assessing clinical utility, by clinical indication, of serum total B12 and Active-B12® (holotranscobalamin) in the diagnosis of vitamin B12 deficiency

BACKGROUND

Assessing the pre- and post-test probability of disease in the context of routine health care is challenging. We wished to study how test performance parameters relating to clinical utility vary by clinical indication in a 'real-world' setting.

METHODS

The diagnostic accuracy of serum total B12 and Active-B12® (holotranscobalamin) was evaluated in a primary care population, using serum methylmalonic acid as the reference standard. We used electronic requesting to establish the clinical indication for each request. Routine requests from primary care for serum total B12 were included if creatinine was also measured and estimated glomerular filtration rate was at least 60 mL/min/1.73 m2.

RESULTS

Clinical indications included peripheral neuropathy (n = 168), anaemia (n = 168), cognitive decline (n = 125), suspected dietary deficiency (n = 76), other (n = 362). For peripheral neuropathy, the area under the receiver operator curve ± 95% confidence interval (AUC ± CI) was 0.63 (0.54-0.71) (P = 0.002) for total B12 and 0.68 (0.60-0.77) (P < 0.0001) for Active-B12®. For anaemia, AUC ± CI was 0.56 (0.47-0.66) (P = 0.10) for total B12 and 0.69 (0.59-0.78) (P < 0.0001) for Active-B12®. For cognitive decline, AUC ± CI was 0.54 (0.43-0.65) (P = 0.26) for total B12 and 0.69 (0.58-0.80) (P = 0.0002) for Active-B12®. The pre-post-test change in probability of disease varied by clinical indication.

CONCLUSION

Combining diagnostic accuracy studies and electronic testing in a 'real-world' setting allows clinical utility to be assessed by clinical indication. Wider application of this would permit more personalised laboratory medicine. In this study, diagnostic performance of total B12 and Active-B12® varied across all indications. Active-B12® provided better discrimination, but this may have reflected the cut-offs used.

Pernicious anemia: Pathophysiology and diagnostic difficulties

Pernicious anemia (PA) is the most common cause of vitamin B12 (cobalamin) deficiency anemia in the world. It is an autoimmune disease, comprising of salient features of autoimmune chronic atrophic gastritis (CAG) and cobalamin deficiency (CD). Although the anemia was first described as pernicious, it may well be controlled with vitamin B12 replacement. The onset and progression of PA is often insidious. Alternatively, patients may have no anemic symptoms since they become acclimatized to the subtle nature of the disease. Oftentimes, there is a possibility that the underlying disease may be missed unless a full blood count (FBC) is investigated, leading to hindrance in the treatment journey. Diagnostic challenges remain tangible for many practicing clinicians, since there is lack of reliable cobalamin assays to diagnose CD as well as clinical mimics, which simulate many other hematological conditions, such as myelodysplastic syndrome, acute leukemia, sideroblastic anemias, bone marrow failure states, thrombotic microangiopathy, and thromboembolism. Moreover, prompt recognition of the symptoms of CD is also vital, because some neurologic sequalae may become irreversible despite replenishing cobalamin. Herein, we discuss a literature review on the pathophysiology, challenging clinical presentations and diagnostic difficulties of PA. Since the cobalamin replacement therapy for PA is straightforward, it will not be discussed in this review.

The role of Vitamin B12 and genetic risk factors in the etiology of neural tube defects: A systematic review

Neural tube defects (NTDs) are birth defects that arise during embryogenesis when normal neural tube closure fails to occur. According to the World Health Organization, NTDs are detected annually in approximately 300,000 neonates worldwide. The exact etiology of NTDs remains complex and poorly understood. It is generally agreed that most NTD cases are of multifactorial origin, having a combination of multiple genes and a number of environmental risk factors. The role of folic acid, vitamin B12 deficiency, genetics and other risk factors, in the etiology of NTDs, has also been extensively studied. This knowledge synthesis brings together different types of evidence to update the role of vitamin B12 deficiency, genetics and other risk factors, in the etiology of NTDs. Following a PubMed search and screening for relevant articles, we included 40 studies in our review (30 case-control studies, 3 cross-sectional studies, 5 cohort studies, and 2 case reports). The available data showed that vitamin B12 levels were decreased in mothers and infants in NTD groups compared with control groups. Holo-transcobalamin, the active form of vitamin B12, was also found in lower levels in mothers with NTD-affected infants. Several studies reported elevated homocysteine levels in mothers and infants in NTD groups. Additionally, numerous studies reported links between genetic variants and increased NTD risk. These genes include GIF, LRP2, CUBN, TCb1R, MTHFR, and others. Several maternal factors have also been linked with significant NTD risk such as BMI, maternal diet, air pollutants, low maternal age, and many others. The majority of studies on NTDs have focused on the role of folic acid, hence there is a need for well-designed studies on the role of other risk factors like vitamin B12 deficiency in the etiology of NTDs.

Review of Vitamin B12 deficiency in pregnancy: a diagnosis not to miss as veganism and vegetarianism become more prevalent

Vegetarianism and veganism are increasingly popular. The Food Standards Agency, biennial Food and You Survey of adults aged 16 years and over living in the UK, found that between 2012 and 2018 the proportion of people who reported never consuming dairy products had increased from 2% to 5%. However, veganism risks development of vitamin B12 deficiency as it is not available from plant sources. Moreover, its impact may be slow to be detected because body stores of vitamin B12 can last years. There is currently no published guidance on antenatal diagnosis and management of vitamin B12 deficiency. This paper reviews the metabolism, diagnosis and treatment of vitamin B12 in pregnancy. It concludes that national screening policymakers should consider introducing screening for B12 deficiency into the Antenatal and Newborn Screening Programmes for mothers and their infants if at risk of vitamin B12 deficiency. In the interim, national policy should be developed for prophylactic vitamin B12 supplementation in high-risk groups around the time of pregnancy.

Association of Primary Sjögren's Syndrome and Vitamin B12 Deficiency: A Cross-Sectional Case-Control Study

Descriptive and retrospective studies without control groups have suggested a possible association between primary Sjögren's syndrome (pSS) and vitamin B12 (B12) deficiency. This is of importance because several mucosal and neurological features are common to these two conditions and could be prevented or reversed in case of B12 deficiency. We aimed to evaluate the association between pSS and B12 deficiency. We prospectively assessed the B12 status of 490 patients hospitalized in an internal medicine department over a 15-week period. Patients with pernicious anemia were excluded. We extracted patients with pSS and paired them with controls according to age and sex, with a 1:5 ratio. Twenty-one pSS patients were paired with 105 control patients. The median age was 70 years old (51-75) and 95.2% of patients were women. The plasma B12 level was lower in pSS patients (329 (293-521) ng/L vs. 456 (341-587) ng/L, p < 0.0001). B12 deficiency was associated with pSS (42.9% among pSS patients vs. 11.4% among controls), even after adjustment for other causes of B12 deficiency (OR 6.45 (95%CI: 2.08-20.0)). In conclusion, pSS appeared to be associated with B12 deficiency, even after the exclusion of pernicious anemia. This justifies screening and treating B12 deficiency in pSS patients.

The relationship of severity of depression with homocysteine, folate, vitamin B12, and vitamin D levels in children and adolescents

BACKGROUND

Depression is a heterogeneous disorder and is thought to develop as a result of complex interactions between genetic and environmental factors. One-carbon metabolism that includes vitamin B12, folic acid, and homocysteine has been investigated in psychiatric disorders like depression. In recent years, vitamin D has also been considered to contribute to psychiatric disorders. In this study, serum levels of folate, vitamin B12, and homocysteine related to one-carbon metabolism and vitamin D were investigated in children and adolescents with depression and to assess possible roles in depression pathogenesis.

METHODS

The study included 89 children and adolescents with depression (69 female, 20 male; mean age ± SD = 15.08 ± 1.46) and 43 control subjects (31 female, 12 male; mean age ± SD = 14.41 ± 2.32) without any DSM-5 diagnosis. Each subject completed a sociodemographic form, Childhood Depression Inventory, State-Trait Anxiety Inventory 1-2 and measured serum folate, vitamin B12, homocysteine, and 25-OH vitamin D levels.

RESULTS

There was no significant difference between the groups in terms of folate levels (p = .052). In the patient group, the vitamin B12 and vitamin D levels were clearly low (p values for both levels were <.001), while homocysteine levels were found to be remarkably high (p < .001). In addition, there was a negative correlation between depression severity and vitamin B12 and vitamin D, while a positive correlation was found with homocysteine.

CONCLUSIONS

The results of the study show that vitamin B12 deficiency or insufficiency and elevated homocysteine may contribute to the etiopathogenesis of depression. Additionally, it was shown that lower vitamin D levels may be associated with depression.

KEY PRACTITIONER MESSAGE

Depression of children and adolescents is associated with the interaction of environmental and genetic factors. Homocysteine, vitamin B12, and folate related to one-carbon metabolism are associated with psychiatric disorders such as depression in adulthood. Vitamin D also contributes to psychiatric disorders pathogenesis. There are not enough studies in the literature about these parameters in children with depression. Low vitamin B12 and vitamin D levels and increased homocysteine levels may play a role in the pathogenesis of depression in children and adolescents. Investigation of vitamin B12, folate, homocysteine, and vitamin D levels are recommended in children and adolescents with depression.

Diagnostic Performances of Urinary Methylmalonic Acid/Creatinine Ratio in Vitamin B12 Deficiency

Sole measurement of plasma vitamin B12 is no longer enough to identify vitamin B12 (B12) deficiency. When plasma vitamin B12 is in the low-normal range, especially between 201 and 350 ng/L, B12 deficiency should be assessed by measurements of plasma homocysteine and/or plasma methylmalonic acid (MMA). However, these biomarkers also accumulate during renal impairment, leading to a decreased specificity for B12 deficiency. In such cases, urinary methylmalonic acid/creatinine ratio (uMMA/C) could be of interest, due to the stable urinary excretion of MMA. The objectives were to evaluate the influence of renal impairment on uMMA/C compared to plasma homocysteine and plasma methylmalonic acid, and to determine the diagnostic performances of uMMA/C in the diagnosis of B12 deficiency. We prospectively studied 127 patients with a plasma B12 between 201 and 350 ng/L. We noticed that uMMA/C was not dependent on renal function (p = 0.34), contrary to plasma homocysteine and plasma methylmalonic acid. uMMA/C showed a perspective diagnostic performance (AUC 0.71 [95% CI: 0.62–0.80]) and the threshold of 1.45 umol/mmol presented a high degree of specificity (87.9% [95% CI: 72.0–98.9]). In conclusion, uMMA/C is a promising biomarker to assess vitamin B12 status in doubtful cases, notably during renal impairment.

Less is more: Two automated interventions to increase vitamin B12 measurement when long-term proton pump inhibitor and decrease redundant testing

INTRODUCTION

To test the efficacy of two interventions to promote the measurement of serum vitamin B₁₂ (s- vitamin B₁₂) in patients with long-term proton pump inhibitor (PPI) use and to decrease inadequate s-vitamin B₁₂ measurement by implementing a minimum retest interval.

MATERIAL AND METHODS

The Laboratory Information System (LIS) automatically registered s-vitamin B₁₂ when not ordered by General Practitioners to all requests patients with long term (>3years) PPI treatment, and with no s-vitamin B₁₂ testing in the previous year. Through the second intervention, the LIS reported the previous s-vitamin B₁₂ result through an explanatory comment in the report, when the test had been requested in the previous three months. We calculated the new diagnoses of vitamin deficiency (s-vitamin B₁₂ < 200 pg/mL), examined the number of tests needed to detect a new case and investigated the economic cost of each one identified by the intervention. Additionally, we counted the s-vitamin B₁₂ that were requested but not measured, and calculated the savings in reagent.

RESULTS

The strategy added 548 s-vitamin B₁₂ and identified 47 new cases of vitamin B₁₂ deficit. The number of added s-vitamin B₁₂ needed to identify a new case by means of the intervention was 12. The total intervention reagent cost was 1446€, with a cost of 30.7€ per new case. The second intervention avoided unnecessary measurement of 611 tests, with 1613€ savings.

CONCLUSIONS

Through the two automated interventions we improved the diagnosis of vitamin B₁₂ deficiency, and decreased inadequate redundant s-vitamin B₁₂ measurement, cutting unnecessary laboratory costs.

Associations of Circulating Methylmalonic Acid and Vitamin B-12 Biomarkers Are Modified by Vegan Dietary Pattern in Adult and Elderly Participants of the Adventist Health Study 2 Calibration Study

BACKGROUND

Elevated plasma methylmalonic acid (MMA) is a functional biomarker of vitamin B-12 status but limited information is available on its prevalence in US vegetarians.

OBJECTIVES

The study examines the prevalence of plasma MMA ≥0.27 µmol/L in those consuming vegetarian diets, its associations with vitamin B-12 intake and biomarkers, and the modifying effect of vegetarian patterns on these associations.

METHODS

In this cross-sectional study (n = 785), concentrations of MMA, vitamin B-12, holotranscobalamin (holoTC), and homocysteine (Hcy) were determined in participants of the calibration substudy of the Adventist Health Study 2 (AHS-2). Vitamin B-12 intake from food, fortified food, and supplements was assessed by six 24-h recalls. Regression models were used to estimate ORs of having high MMA as related to vitamin B-12 status biomarkers, vitamin B-12 intake, and dietary pattern.

RESULTS

The prevalence of low vitamin B-12 status defined by serum vitamin B-12 <148 pmol/L, holoTC <35 pmol/L, MMA ≥0.27 and ≥0.37 μmol/L, or Hcy ≥15 μmol/L, and the OR of having high MMA did not differ by dietary pattern, possibly due to intake from fortified food and supplements. Total daily vitamin B-12 intake in the second tertile range of 4.4-14.5 μg/d reduced the likelihood of elevated MMA by 69%; and a doubling of vitamin B-12 intake was associated with a 4.3% decrease in plasma MMA. The association between log plasma MMA and biomarkers was modified by diet, with the vegan pattern showing an ∼3-fold stronger association with log serum vitamin B-12 and Hcy than did the nonvegetarian pattern.

CONCLUSIONS

The prevalence of vitamin B-12 intake <2.0 μg/d was 15.2% in vegans, 10.6% in lacto-ovo-vegetarians, and 6.5% in nonvegetarians. Given the irreversible neurological consequences of vitamin B-12 inadequacy, the importance of regular supplemental vitamin B-12 intake in adult and elderly individuals is stressed.

Nutritional neuropathies

Neuropathies associated with nutritional deficiencies are routinely encountered by the practicing neurologist. Although these neuropathies assume different patterns, most are length-dependent, sensory axonopathies. Cobalamin deficiency neuropathy is the exception, often presenting with a non-length-dependent sensory neuropathy. Patients with cobalamin and copper deficiency neuropathy characteristically have concomitant myelopathy, whereas vitamin E deficiency is uniquely associated with a spinocerebellar syndrome. In contrast to those nutrients for which deficiencies produce neuropathies, pyridoxine toxicity results in a non-length-dependent sensory neuronopathy. Deficiencies occur in the context of malnutrition, malabsorption, increased nutrient loss (such as with dialysis), autoimmune conditions such as pernicious anemia, and with certain drugs that inhibit nutrient absorption. When promptly identified, therapeutic nutrient supplementation may result in stabilization or improvement of these neuropathies.

Vitamin B12 Deficiency and Foot Ulcers in Type 2 Diabetes Mellitus: A Case-Control Study

OBJECTIVE

To assess the association between vitamin B12 deficiency and the development of diabetic foot ulcers (DFU) in type 2 diabetes mellitus (T2DM).

METHODS

This is a case-control study that enrolled 323 Saudi adults with T2DM randomly selected from the Jazan Diabetes & Endocrine Center, Saudi Arabia from January 1, 2019, to July 31, 2019. The sample included 108 newly diagnosed cases with DFU and 215 control participants with T2DM unaffected by and free of foot ulcers (1:2 ratio). Logistic regression analysis was performed to determine the DFU predictors and to examine the association of DFU and vitamin B12 deficiency.

RESULTS

The highest DFU rates were found among the male participants and the participants older than 45 years. Neuropathy, vasculopathy, vitamin B12 deficiency, poor glycemic control, poor feet self-care, Charcot foot, physical inactivity, and spending long time standing at work were significantly associated with DFU, and all except physical inactivity and spending long time standing at work were independent predictors of DFU. After adjustment for the covariates, vitamin B12 deficiency was significantly associated with DFU (odds ratio 3.1), indicating that the patients with T2DM and vitamin B12 deficiency had a three times higher risk of developing DFU than those with normal vitamin B12 levels.

CONCLUSION

Vitamin B12 deficiency had a significant association with DFU among the Saudi participants with T2DM. Establishing the causality and clarifying the biological role of vitamin B12 deficiency in DFU is important aims for future studies.

What is the cobalamin status among vegetarians and vegans in Australia?

Water-soluble vitamin B12 (cobalamin) plays a vital role in normal blood function and neurological functioning. Clinical and subclinical B12 deficiency has been notably reported in vegans, vegetarians, the elderly and metformin-treated diabetics. Currently, the prevalence of cobalamin deficiency among vegans and vegetarians in Australia is lacking; data on dietary intake including supplements and nutritional status are also limited. The increasing multiculturalism of Australia has seen an influx of imported foods, of which some may contain considerable vitamin B12. However, values for such foods are not included in the food composition databases. This review highlights the need to update the food composition database with culturally diverse foods containing vitamin B12. Moreover, the need for assessing dietary intakes and status using the most current best evidence and best practice on nutritional indicators (biochemical and functional biomarkers) to estimate the risk of deficiency and/or depletion is discussed.

Vitamin B12 Intake From Animal Foods, Biomarkers, and Health Aspects

The EAT-Lancet commission recently suggested that transformation to healthy diets by 2050 will require a reduction of at least 50% in consumption of foods such as red meat and sugar, and a doubling in the global consumption of fruits, vegetables, nuts, and legumes. A diet rich in plant-based foods and with fewer animal source foods confers both improved health and environmental benefits. Notably, the risk of vitamin B12 deficiency increases when consuming a diet low in animal products. Humans are dependent on animal foods such as dairy products, meat, fish and eggs. Vitamin B12 deficiency is common worldwide, especially in populations with low consumption of animal foods because of low socioeconomic status, ethical reasons, or because of their lifestyle (i.e., vegans). According to the European Food Safety Authoroty, the recommended adequate intake of vitamin B12 is 4.0 μg/d for adults, and vitamin B12 requirements are higher during pregnancy and lactation. Infants and children from deficient mothers and elderly people are at risk for vitamin B12 deficiency. Diagnosis of vitamin B12 deficiency is hampered by low specificity of available biomarkers, and there is no consensus yet regarding the optimal definition of low vitamin B12 status. In general, a combination of at least two biomarkers is recommended. Therefore, this review presents an overview of vitamin B12 biochemistry and its biomarkers. We further summarize current recommendations of vitamin B12 intake, and evidence on the associations of vitamin B12 intake from different nutrient-dense animal foods with vitamin B12 status markers. Finally, potential consequences of low vitamin B12 status on different health outcomes for pregnant women, infants and elderly are presented.

Multicentre evaluation of the Roche Elecsys® Active B12 (holotranscobalamin) electro-chemiluminescence immunoassay

Background

Vitamin B₁₂ deficiency is a common disorder. In circulation, vitamin B₁₂ is bound to transcobalamin (holotranscobalamin), which is considered the active form of cobalamin. The objective of this study was to evaluate the analytical performance of the Roche Elecsys Active B₁₂ immunoassay.

Methods

Limit of quantification and linearity were assessed according to CLSI EP17-A2 and EP-6A guidelines. Precision and bias of Roche Active B₁₂ test against Architect ci8200 (Abbott) were performed according to CLSI EP-5 A3 guideline at three European laboratories. Precision requirements were set at <4% for within-run precision and <15% for intermediate precision. Requirements for method comparison were set at a slope of 1.00 ± 20%. In addition, 95% reference interval was conducted in European adults according to CLSI-EP28 guideline.

Results

The assay was shown to be linear and precise and met the requirements. Lot-to-lot variation and lab-to-lab variation both were ≤4%. Method comparison with Abbott Architect showed a significant bias of 9 pmol/L, which increases to up to 23 pmol/L around the current medical decision point. The 95% reference interval of the Roche Elecsys Active B₁₂ test was determined at 37–188 pmol/L.

Conclusion

Although Roche Elecsys Active B₁₂ immunoassay met the requirements, this test has a positive bias of 9 pmol/L, which led to an increase in lower limit of reference interval compared with Abbott test. This test first needs to be clinically validated before it can be applied as a first-line screening test in the diagnosis of vitamin B₁₂ deficiency.

Methylmalonic Acid and Homocysteine as Indicators of Vitamin B12 Deficiency in Patients with Gastric Cancer after Gastrectomy

Vitamin B12 deficiency is a common complication in patients after gastrectomy. Elevated methylmalonic acid (MMA) and homocysteine are better indications of vitamin B12 deficiency than vitamin B12 serum level. We compared MMA and homocysteine levels of patients with gastric cancer after gastrectomy (n = 151) with controls (n = 142) and evaluated the prevalence of vitamin B12 deficiency using MMA and homocysteine in patients. MMA and homocysteine levels were significantly higher (p < 0.05) in patients with gastric cancer after gastrectomy. Of the 151 patients assessed after gastrectomy, 32 patients (21.2%) were vitamin B12 deficient as defined by serum MMA levels > 350 nmol/L, and 8 patients (5.3%) were vitamin B12 deficient as defined by serum homocysteine levels > 15 μmol/L. Both MMA and homocysteine levels were elevated in 7 patients. Among 33 patients with elevated MMA or homocysteine levels, 8 patients (24.2%) were vitamin B12 deficient based on a serum vitamin B12 level < 200 pg/mL. Additionally, levels of MMA and homocysteine were compared pre- and post-gastrectomy in 27 patients. The median MMA level was higher in patients with post-gastrectomy compared to pre-gastrectomy, while the median serum homocysteine level was not significantly different. These results indicate that using serum vitamin B12 levels alone may fail to detect vitamin B12 deficiency. Additional assessments of MMA and homocysteine levels are useful to evaluate possible vitamin B12 deficiency in patients who underwent a gastrectomy, and MMA is a better indicator than homocysteine to detect early changes in vitamin B12 levels.

The Effect of Whey and Soy Protein Isolates on Cognitive Function in Older Australians with Low Vitamin B12: A Randomised Controlled Crossover Trial

Whey protein isolate (WPI) is high in vitamin B₁₂ and folate. These and other related markers (holotranscobalamin, methylmalonic acid and homocysteine) have been linked with cognitive health. This study explored the efficacy of WPI for improving cognitive function via delivery of vitamin B₁₂. Moderately vitamin B₁₂-deficient participants aged between 45 and 75 years (n = 56) were recruited into this randomised controlled crossover trial. Participants (55% female) consumed 50 g whey (WPI; active) or soy protein isolate (SPI; control) for eight weeks. Following a 16-week washout phase, they consumed the alternative supplement. Consumption of WPI significantly improved active B₁₂ and folate status but did not result in direct improvements in cognitive function. However, there was evidence of improvement in reaction time (p = 0.02) and reasoning speed (p = 0.04) in the SPI condition for females. Additional analyses showed that changes in active B₁₂, HcY and folate measures during WPI treatment correlated with improvements in cognitive function (all p < 0.05). Results indicate that WPI itself did not result in improved cognitive function but some evidence of benefit of SPI for females was found. However, consistent with previous research, we present further evidence of a role for active B₁₂, HcY and folate in supporting cognitive improvement in adults with low B vitamin status.

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.

Proton Pump Inhibitors, H2-Receptor Antagonists, Metformin, and Vitamin B-12 Deficiency: Clinical Implications

There is clear evidence that proton-pump inhibitors (PPIs), H2-receptor antagonists (H2RAs), and metformin can reduce serum vitamin B-12 concentrations by inhibiting the absorption of the vitamin. However, it is unclear if the effects of these drugs on serum vitamin B-12 are associated with increased risk of biochemical or functional deficiency (as is indicated by elevated blood concentrations of homocysteine and methylmalonic acid) or clinical deficiency (including megaloblastic anemia and neurologic disorders such as peripheral neuropathy and cognitive dysfunction). This review provides an overview of vitamin B-12 absorption and biochemistry and the mechanisms by which PPIs, H2RAs, and metformin affect these functions. It also summarizes the literature relating the use of these drugs to the risk of vitamin B-12 deficiency. Also discussed is that strategies for assessing vitamin B-12 status and diagnosing vitamin B-12 deficiency have evolved in recent years beyond solely measuring serum total vitamin B-12. Multiple analyte testing, a strategy in which ≥2 of 4 biomarkers of vitamin B-12 status-serum total vitamin B-12, holotranscobalamin, homocysteine, and methylmalonic acid-are measured, increases sensitivity and specificity for diagnosing vitamin B-12 deficiency. It is concluded that randomized controlled trials are now needed that use the strategy of multiple analyte testing to determine if PPIs, H2RAs, and metformin do indeed increase the risk of vitamin B-12 deficiency. Until these studies are conducted, a reasonable recommendation for physicians and their patients who are taking these drugs is to monitor vitamin B-12 status and to provide vitamin B-12 supplements if altered blood biomarkers or clinical signs consistent with low or deficient vitamin B-12 status develop.

Identification of vitamin B12 deficiency in vegetarian Indians

The prevalence of a sub-clinical vitamin B12 deficiency in the vegetarians is high. Total serum vitamin B12 concentration alone does not reliably reflect vitamin B12 status. Holotranscobalamin (holo-TC) II is a bioactive B12 fraction promoting specific uptake of B12 by cells and the circulating concentration reflects the intake of B12, whereas total homocysteine (tHcy) indicates the metabolic ability. In this study, we investigated the diagnostic value of circulating holo-TC, B12, folate and homocysteine in vegetarians who were at risk of B12 deficiency. B12-related biomarkers were measured in 119 young, healthy graduate vegetarians. None was folate deficient. As per reported definition, half were B12 deficient; 70 % of males and 50 % of females had low plasma holo-TC concentrations; and 92 % of males and half of females had hyperhomocysteinaemia. None had any clinical signs of B12 deficiency. Receiver operating characteristic curve analysis demonstrated similar AUC at the B12 concentration of 100 and 150 pmol/l when holo-TC (0·777 and 0·784) and homocysteine (0·924 and 0·928) were used as variables. Cut-off value of 100 pmol/l resulted in the highest sensitivity of 77·78 % and specificity of 71·05 % with a predictive value of 19·6 pmol/l for holo-TC and a sensitivity of 82·72 % and specificity of 89·7 % with a predictive value of 21·7 µmol/l for homocysteine. The combination of B12, holo-TC and tHcy improves the diagnostic accuracy at these cut-offs, and we suggest that for the young Indian vegetarians the cut-off for plasma B12 and holotrancobalamin is 100 pmol/l and 19·6 pmol/l, respectively, and for homocysteine it is 17·6 (females) and 27 µmol/l (males) for identifying B12 deficiency.

The distribution of total vitamin B12, holotranscobalamin, and the active vitamin B12 fraction in the first 5 weeks postpartum

INTRODUCTION

Total vitamin B12 levels decrease significantly during pregnancy and recover to normal values within 8-week postpartum. Holotranscobalamin (holoTC) reflects the active part of vitamin B12 and has been shown to remain constant during pregnancy and postpartum. A mechanism of redistribution of vitamin B12 is suggested, with a shift toward holoTC if there is insufficient total vitamin B12 available. Our objective was to examine vitamin B12 deficiency and the active vitamin B12 fraction in postpartum women.

METHODS

Total vitamin B12 and holoTC were measured in 171 women within 48 hours (T0) and at 5 weeks (T5) postpartum. Vitamin B12 deficiency was defined as total vitamin B12 < 180 pmol/L or holoTC <32 pmol/L. The active vitamin B12 fraction was defined as holoTC/total vitamin B12.

RESULTS

Without intervention, vitamin B12 deficiency based on both serum total vitamin B12 and holoTC changed from 75% and 60%, to respectively 10% and 6% at T5. The fraction of active vitamin B12 was significant higher in vitamin B12 deficient women at both time points and across time (P < .0001 and P = .002). A high fraction of active vitamin B12 was only present in women with total vitamin B12 deficiency at T0. At T5, no high vitamin B12 fraction was found.

CONCLUSION

The changes in total vitamin B12 levels seem to be based on a physiological changes rather than vitamin B12 deficiency. The results of this study confirm the hypothesis that a shift toward the metabolic active vitamin B12 (holoTC) occurs in women with insufficient available total vitamin B12.

Vitamin B12 deficiency

Vitamin B₁₂ (B12; also known as cobalamin) is a B vitamin that has an important role in cellular metabolism, especially in DNA synthesis, methylation and mitochondrial metabolism. Clinical B12 deficiency with classic haematological and neurological manifestations is relatively uncommon. However, subclinical deficiency affects between 2.5% and 26% of the general population depending on the definition used, although the clinical relevance is unclear. B12 deficiency can affect individuals at all ages, but most particularly elderly individuals. Infants, children, adolescents and women of reproductive age are also at high risk of deficiency in populations where dietary intake of B12-containing animal-derived foods is restricted. Deficiency is caused by either inadequate intake, inadequate bioavailability or malabsorption. Disruption of B12 transport in the blood, or impaired cellular uptake or metabolism causes an intracellular deficiency. Diagnostic biomarkers for B12 status include decreased levels of circulating total B12 and transcobalamin-bound B12, and abnormally increased levels of homocysteine and methylmalonic acid. However, the exact cut-offs to classify clinical and subclinical deficiency remain debated. Management depends on B12 supplementation, either via high-dose oral routes or via parenteral administration. This Primer describes the current knowledge surrounding B12 deficiency, and highlights improvements in diagnostic methods as well as shifting concepts about the prevalence, causes and manifestations of B12 deficiency.

Vitamin B12 deficiency from the perspective of a practicing hematologist

B₁₂ deficiency is the leading cause of megaloblastic anemia, and although more common in the elderly, can occur at any age. Clinical disease caused by B₁₂ deficiency usually connotes severe deficiency, resulting from a failure of the gastric or ileal phase of physiological B₁₂ absorption, best exemplified by the autoimmune disease pernicious anemia. There are many other causes of B₁₂ deficiency, which range from severe to mild. Mild deficiency usually results from failure to render food B₁₂ bioavailable or from dietary inadequacy. Although rarely resulting in megaloblastic anemia, mild deficiency may be associated with neurocognitive and other consequences. B₁₂ deficiency is best diagnosed using a combination of tests because none alone is completely reliable. The features of B₁₂ deficiency are variable and may be atypical. Timely diagnosis is important, and treatment is gratifying. Failure to diagnose B₁₂ deficiency can have dire consequences, usually neurological. This review is written from the perspective of a practicing hematologist.

Megaloblastic Anemias: Nutritional and Other Causes

Vitamin B₁₂ and folate deficiencies are major causes of megaloblastic anemia. Causes of B₁₂ deficiency include pernicious anemia, gastric surgery, intestinal disorders, dietary deficiency, and inherited disorders of B₁₂ transport or absorption. The prevalence of folate deficiency has decreased because of folate fortification, but deficiency still occurs from malabsorption and increased demand. Other causes include drugs and inborn metabolic errors. Clinical features of megaloblastic anemia include anemia, cytopenias, jaundice, and megaloblastic marrow morphology. Neurologic symptoms occur in B₁₂ deficiency, but not in folate deficiency. Management includes identifying any deficiency, establishing its cause, and replenishing B₁₂ or folate parenterally or orally.

False low holotranscobalamin levels in a patient with a novel TCN2 mutation

BACKGROUND

Measurement of holotranscobalamin (holoTC) is increasingly used as a screening test for cobalamin (Cbl) deficiency. A level well below the reference interval strongly supports a deficient state. We examined a 21-year-old woman diagnosed as Cbl deficient because of an extremely low holoTC level as measured by the Abbott Architect Assay.

METHODS

The patient was evaluated for Cbl deficiency employing an in-house holoTC method as well as other routine markers of Cbl status. Further analyses included exploration of the Cbl binding proteins employing gel filtration of a serum sample saturated with 57 Co-labeled Cbl and Sanger sequencing of exons 1-9 and the intron-exon boundaries of the TCN2 gene, the gene coding for transcobalamin (TC).

RESULTS

The patient had normal hematological variables throughout. Despite initial treatment with Cbl, holoTC as measured by the Abbott assay remained low, while holoTC measured with the in-house assay was normal, and behaved as TC upon gel-filtration. By Sanger sequencing, we detected a homozygous single point mutation c.855T>A in exon 6 of TCN2, corresponding to a asparagine (Asn) to lysine (Lys) substitution in position 267 of the mature protein.

CONCLUSIONS

We describe a novel point mutation of the TCN2 gene. The mutation does not seem to interfere with the function of TC, but the mutation may well explain the low level of holoTC detected by the Abbott assay. Our results underscores that mutations of TCN2 have to be considered when implausible holoTC results are obtained.

A Prospective Study on Serum Methylmalonic Acid and Homocysteine in Pregnant Women

This study aimed to investigate serum methylmalonic acid (MMA) and homocysteine levels and to assess their effects on pregnancy and neonatal outcomes. Serum MMA and homocysteine levels in 278 pregnant Korean women, determined by liquid chromatography–tandem mass spectrometry in each trimester, were compared with those of previous studies in other ethnic groups. We investigated the association between MMA and homocysteine status with pregnancy and neonatal events: gestational diabetes, preeclampsia, gestational age at delivery, preterm birth, small for gestational age, neonatal birth weight, and congenital abnormalities. The median (range) MMA level was 0.142 (0.063–0.446) µmol/L and homocysteine level was 10.6 (4.4–38.0) µmol/L in pregnant women. MMA levels were significantly higher in the third trimester than during other trimesters (p < 0.05), while homocysteine levels were not. No significant association was observed between MMA or homocysteine levels and any of the maternal or neonatal outcomes examined. Future studies are needed to assess the associations among maternal serum concentrations of MMA and homocysteine, and maternal and neonatal outcomes.

Holotranscobalamin (HoloTC, Active-B12) and Herbert's model for the development of vitamin B12 deficiency: a review and alternative hypothesis

The concentration of total vitamin B12 in serum is not a sufficiently sensitive or specific indicator for the reliable diagnosis of vitamin B12 deficiency. Victor Herbert proposed a model for the staged development of vitamin B12 deficiency, in which holotranscobalamin (HoloTC) is the first indicator of deficiency. Based on this model, a commercial immunoassay has been controversially promoted as a replacement for the total vitamin B12 test. HoloTC is cobalamin (vitamin B12) attached to the transport protein transcobalamin, in the serum, for delivery to cells for metabolism. Although there have been many published reports supporting the claims for HoloTC, the results of some studies were inconsistent with the claim of HoloTC as the most sensitive marker of vitamin B12 deficiency. This review examines the evidence for and against the use of HoloTC, and concludes that the HoloTC immunoassay cannot be used to measure vitamin B12 status any more reliably than total vitamin B12, or to predict the onset of a metabolic deficiency, because it is based on an erroneous hypothesis and a flawed model for the staged development of vitamin B12 deficiency. The author proposes an alternative model for the development of vitamin B12 deficiency.

Laboratory assessment of vitamin B12 status

The detection and correction of vitamin B₁₂ (B₁₂) deficiency prevents megaloblastic anaemia and potentially irreversible neuropathy and neuropsychiatric changes. B₁₂ status is commonly estimated using the abundance of the vitamin in serum, with ∼148 pmol/L (200 ng/L) typically set as the threshold for diagnosing deficiency. Serum B₁₂ assays measure the sum of haptocorrin-bound and transcobalamin-bound (known as holotranscobalamin) B₁₂ It is only holotranscobalamin that is taken up by cells to meet metabolic demand. Although receiver operator characteristic curves show holotranscobalamin measurement to be a moderately more reliable marker of B₁₂ status than serum B₁₂, both assays have an indeterminate range. Biochemical evidence of metabolic abnormalities consistent with B₁₂ insufficiency is frequently detected despite an apparently sufficient abundance of the vitamin. Laboratory B₁₂ status markers that reflect cellular utilisation rather than abundance are available. Two forms of B₁₂ act as coenzymes for two different reactions. Methionine synthase requires methylcobalamin for the remethylation of methionine from homocysteine. A homocysteine concentration >20 µmol/L may suggest B₁₂ deficiency in folate-replete patients. In the second B₁₂-dependent reaction, methylmalonyl-CoA mutase uses adenosylcobalamin to convert methylmalonyl-CoA to succinyl-CoA. In B₁₂ deficiency excess methylmalonyl-CoA is hydrolysed to methylmalonic acid. A serum concentration >280 nmol/L may suggest suboptimal status in young patients with normal renal function. No single laboratory marker is suitable for the assessment of B₁₂ status in all patients. Sequential assay selection algorithms or the combination of multiple markers into a single diagnostic indicator are both approaches that can be used to mitigate inherent limitations of each marker when used independently.

A review of the cut-off points for the diagnosis of vitamin B12 deficiency in the general population

Vitamin B12 deficit is one of the most common vitamin deficiencies. However, there is no consensus on the cut-off points for vitamin B12 and its co-markers, such as folate, holotranscobalamin, methylmalonic acid and homocysteine. In order to establish the state of the art about cut-off points used to determine vitamin B12 deficiency in the last decades, the database MEDLINE was used for searching studies published in adults between December 1992 and May 2014 (69 articles), using search terms like 'vitamin B12', 'cobalamin', 'cut-off', 'deficiency' alone or in combinations. Broad ranges of cut-off points for vitamin B12 and its biomarkers were identified: vitamin B12 ranged between 100 pmol/L and 350 pmol/L, holotranscobalamin 20-50 pmol/L, methylmalonic acid 0.210-0.470 μmol/L, homocysteine 10-21.6 μmol/L, serum folate 3.7-15.9 nmol/L and red blood cell 124-397 nmol/L. For the majority of studies, the potential influence of age, analytical methods, gender and fortified food consumption was not taken in account when choosing cut-off values. This could explain the discrepancies between studies on vitamin B12 and folate deficiency prevalences. We conclude that there is inconsistency in the literature regarding vitamin B12 cut-offs. It would be necessary to establish different reference cut-offs according to age, considering the analytical methods used.

Experimental vitamin B12 deficiency in a human subject: a longitudinal investigation of the performance of the holotranscobalamin (HoloTC, Active-B12) immunoassay

Based on Victor Herbert’s model for sequential stages in the development of vitamin B₁₂ deficiency, the holotranscobalamin (HoloTC) immunoassay has controversially been promoted as a more specific and sensitive replacement for the total vitamin B₁₂ test, for the diagnosis of deficiency. There have been no longitudinal studies, by means of experimental cobalamin deficiency, because ethical considerations prevent such risky studies on patients or healthy human volunteers. The objective was to provide a detailed record of the response of HoloTC, compared to total vitamin B₁₂ and metabolites, to the development of experimental vitamin B₁₂ deficiency in an initially replete human subject. This 54 year old male, with a vitamin B₁₂ deficiency possibly caused by a defect in the intracellular cobalamin metabolism, ensured an initially replete condition by means of oral doses of cyanocobalamin supplements at 1000 μg/day for 12 weeks. The subject then depleted himself of vitamin B₁₂, by withholding treatment and using a low-cobalamin diet, until significant metabolic disturbances were observed. The responses of serum total vitamin B₁₂ and HoloTC and the two metabolites, plasma methylmalonic acid and homocysteine, were monitored by weekly blood tests. HoloTC was not significantly more sensitive than either total serum vitamin B₁₂ or total homocysteine, and was much less sensitive than methylmalonic acid. HoloTC decreased from an initial concentration of >128 pmol/L to a minimum of 33 pmol/L on day 742, the only day on which it fell below the lower limit of the reference interval. Total vitamin B₁₂ decreased from an initial concentration of 606 pmol/L to a minimum of 171 pmol/L on day 728. Total homocysteine increased from an initial concentration of 8.4 μmol/L to a maximum of 14.2 μmol/L on day 609. Methylmalonic acid unexpectedly contained four distinct peaks; initially at 0.17 μmol/L, it first exceeded the upper limit of the reference interval on day 386, finally reaching a maximum peak of 0.90 μmol/L on day 658. The results of this experiment are inconsistent with Herbert’s hypothesis that HoloTC is the earliest marker of vitamin B₁₂ deficiency, and therefore do not support his model for the staged development of vitamin B₁₂ deficiency.

Prevalence and Risk Factors for Functional Vitamin B12 Deficiency in Patients with Crohn's Disease

BACKGROUND

Crohn's disease (CD) is a risk factor for vitamin B12 deficiency due to frequent involvement of the terminal ileum. Conventional screening for B12 deficiency with serum B12 is relatively insensitive and measures total B12 concentration, of which a minority is present in a biologically active form. Holotranscobalamin (holoTC) combined with methylmalonic acid (MMA) is believed to be more accurate in identifying impaired B12 status. We evaluated the prevalence and risk factors for B12 deficiency using holoTC supported by MMA among patients with CD.

METHODS

We performed a single-center service evaluation of 381 patients with CD who underwent B12 assessment (holoTC/MMA) and compared them with 141 patients with ulcerative colitis. Eighty-nine patients with CD underwent paired serum B12 and holoTC. Among patients with CD, risk factors including terminal ileal resection length, ileal inflammation on endoscopy, and disease characteristics on magnetic resonance imaging were recorded.

RESULTS

Prevalence of B12 deficiency among patients with CD was 33% compared with 16% in ulcerative colitis (P < 0.0001). In 89 patients who underwent paired tests, conventional testing identified B12 deficiency in 5% of patients with CD, which increased to 32% using holoTC/MMA. Independent risk factors for B12 deficiency were ileal resection length ≤20 cm (odds ratio: 3.0, 95% confidence interval, 1.5-6.0, P = 0.002) and >20 cm (odds ratio: 6.7, 95% confidence interval, 3.0-14.7, P < 0.0001) and ileal inflammation (odds ratio: 3.9, 95% confidence interval, 2.2-6.9, P < 0.0001). On magnetic resonance imaging, active terminal ileal inflammation (P = 0.02) and an increased disease burden (≥1 skip lesion, P = 0.01 and prestenotic dilatation >3 cm, P = 0.01) were associated with B12 deficiency.

CONCLUSIONS

Vitamin B12 deficiency is common in patients with CD. holoTC supported by MMA identifies patients with B12 deficiency considered replete on conventional testing.

Long-term treatment for hyperphenylalaninemia and phenylketonuria: a risk for nutritional vitamin B12 deficiency?

PURPOSE

The objective of the study was to determine the incidence of vitamin B12 deficiency in patients under long-term treatment for phenylketonuria (PKU) and hyperphenylalaninemia (HPA), as well as its associations with B12 vitamin parameters (holotranscobalamin - active vitamin B12, serum folate, total plasma homocysteine, and plasma methylmalonic acid concentration).

PATIENTS AND METHODS

The group consisted of 51 PKU (n=29) and HPA (n=22) patients aged 3-48 years (28 children, 23 adults).

RESULTS

A significant difference in serum folate levels was discovered between adult HPA patients and PKU patients (p=0.004, Mann-Whitney U-test). A significant difference in plasma homocysteine concentrations within the normal levels (p=0.032, χ2-test) was detected between adult HPA and PKU patients. In the group of adults, we also found significant differences in serum holotranscobalamin concentrations regarding both concentration levels and the proportion of patients with concentrations within the normal levels (p=0.031, Mann-Whitney U-test; p=0.006, χ2-test).

CONCLUSION

We have proven that adult patients with PKU and HPA are at risk of vitamin B12 nutritional deficiency. The most effective parameter for these adults is the monitoring of holotranscobalamin in the serum.

Combined indicator of vitamin B12 status: modification for missing biomarkers and folate status and recommendations for revised cut-points

A novel approach to determine vitamin B

We used a database with all four markers (n=5211) plus folate measurements (n=972). A biomarker

The predictive functions

We provide equations that combine two, three or four biomarkers into one diagnostic indicator, thereby rescaling unmatched data into the same coordinate system. Adjustment of this indicator is required if serum folate is <10 nmol/L and tHcy is measured. Revised cut-points and guidelines for using this approach are provided.

Physiological and molecular aspects of cobalamin transport

Minute doses of a complex cofactor cobalamin (Cbl, vitamin B12) are essential for metabolism. The nutritional chain for humans includes: (1) production of Cbl by bacteria in the intestinal tract of herbivores; (2) accumulation of the absorbed Cbl in animal tissues; (3) consumption of food of animal origin. Most biological sources contain both Cbl and its analogues, i.e. Cbl-resembling compounds physiologically inactive in animal cells. Selective assimilation of the true vitamin requires an interplay between three transporting proteins - haptocorrin (HC), intrinsic factor (IF), transcobalamin (TC) - and several receptors. HC is present in many biological fluids, including gastric juice, where it assists in disposal of analogues. Gastric IF selectively binds dietary Cbl and enters the intestinal cells via receptor-mediated endocytosis. Absorbed Cbl is transmitted to TC and delivered to the tissues with blood flow. The complex transport system guarantees a very efficient uptake of the vitamin, but failure at any link causes Cbl-deficiency. Early detection of a negative B12 balance is highly desirable to prevent irreversible neurological damages, anaemia and death in aggravated cases. The review focuses on the molecular mechanisms of cobalamin transport with emphasis on interaction of corrinoids with the specific proteins and protein-receptor recognition. The last section briefly describes practical aspects of recent basic research concerning early detection of B12-related disorders, medical application of Cbl-conjugates, and purification of corrinoids from biological samples.

Guidelines for the diagnosis and treatment of cobalamin and folate disorders

The clinical picture is the most important factor in assessing the significance of test results assessing cobalamin status because there is no 'gold standard' test to define deficiency. Serum cobalamin currently remains the first-line test, with additional second-line plasma methylmalonic acid to help clarify uncertainties of underlying biochemical/functional deficiencies. Serum holotranscobalamin has the potential as a first-line test, but an indeterminate 'grey area' may still exist. Plasma homocysteine may be helpful as a second-line test, but is less specific than methylmalonic acid. The availability of these second-line tests is currently limited. Definitive cut-off points to define clinical and subclinical deficiency states are not possible, given the variety of methodologies used and technical issues, and local reference ranges should be established. In the presence of discordance between the test result and strong clinical features of deficiency, treatment should not be delayed to avoid neurological impairment. Treatment of cobalamin deficiency is recommended in line with the British National Formulary. Oral therapy may be suitable and acceptable provided appropriate doses are taken and compliance is not an issue. Serum folate offers equivalent diagnostic capability to red cell folate and is the first-line test of choice to assess folate status.

Neurodegeneration in multiple sclerosis involves multiple pathogenic mechanisms

Multiple sclerosis (MS) is a complex autoimmune disease that impairs the central nervous system (CNS). The neurological disability and clinical course of the disease is highly variable and unpredictable from one patient to another. The cause of MS is still unknown, but it is thought to occur in genetically susceptible individuals who develop disease due to a nongenetic trigger, such as altered metabolism, a virus, or other environmental factors. MS patients develop progressive, irreversible, neurological disability associated with neuronal and axonal damage, collectively known as neurodegeneration. Neurodegeneration was traditionally considered as a secondary phenomenon to inflammation and demyelination. However, recent data indicate that neurodegeneration develops along with inflammation and demyelination. Thus, MS is increasingly recognized as a neurodegenerative disease triggered by an inflammatory attack of the CNS. While both inflammation and demyelination are well described and understood cellular processes, neurodegeneration might be defined by a diverse pool of any of the following: neuronal cell death, apoptosis, necrosis, and virtual hypoxia. In this review, we present multiple theories and supporting evidence that identify common biological processes that contribute to neurodegeneration in MS.

Prevalence of vitamin B(12) depletion and deficiency in Liechtenstein

OBJECTIVE

Data about vitamin B(12) (B(12)) deficiency in the general population are scarce. The present study was performed to determine the prevalence of B(12) deficiency in the general population of the Principality of Liechtenstein, as well as to identify sub-populations potentially at high risk.

DESIGN

Retrospective study.

SETTING

Ambulatory setting, population of the Principality of Liechtenstein.

SUBJECTS

Seven thousand four hundred and twenty-four patients seeking medical attention whose serum samples were referred for routine work-up in an ambulatory setting were consecutively enrolled. Serum total B(12) was determined in all patients in this cohort. In addition, for a subgroup of 1328 patients, serum holotranscobalamin was also measured. Prevalence of B(12) deficiency was calculated. Further, multivariate logistical regression models were applied to identify covariates independently associated with B(12) deficiency and depletion.

RESULTS

Nearly 8% of the general population was suffering from either B(12) depletion or deficiency. The ratio between B(12) depletion and deficiency was 2:1 for all age ranges. Pathological changes were detected predominantly in older people. Female gender was a significant predictor of B(12) depletion. In the cohort, nearly 40% exhibited either depletion or deficiency of B(12).

CONCLUSIONS

B(12) depletion and deficiency are common in Liechtenstein, a Central European country. The measurement of biochemical markers represents a cost-efficient and valid assessment of the B(12) state. When a deficiency of B(12) is diagnosed at an early stage, many cases can be treated or prevented, with beneficial effects on individual outcomes and subsequent potential reductions in health-care costs.

Neurologic aspects of cobalamin (B12) deficiency

Optimal functioning of the central and peripheral nervous system is dependent on a constant supply of appropriate nutrients. Particularly important for optimal functioning of the nervous system is cobalamin (vitamin B12). Cobalamin deficiency is particularly common in the elderly and after gastric surgery. Many patients with clinically expressed cobalamin deficiency have intrinsic factor-related malabsorption such as that seen in pernicious anemia. The commonly recognized neurological manifestations of cobalamin deficiency include a myelopathy with or without an associated neuropathy. This review deals with neurological aspects of vitamin B12 deficiency and attempts to highlight recent developments.

Interactions between plasma concentrations of folate and markers of vitamin B(12) status with cognitive performance in elderly people not exposed to folic acid fortification: the Hordaland Health Study

A combination of high folate with low vitamin B12 plasma status has been associated with cognitive impairment in a population exposed to mandatory folic acid fortification. The objective of the present study was to examine the interactions between plasma concentrations of folate and vitamin B12 markers in relation to cognitive performance in Norwegian elderly who were unexposed to mandatory or voluntary folic acid fortification. Cognitive performance was assessed by six cognitive tests in 2203 individuals aged 72-74 years. A combined score was calculated using principal component analysis. The associations of folate concentrations, vitamin B12 markers (total vitamin B12, holotranscobalamin (holoTC) and methylmalonic acid (MMA)) and their interactions in relation to cognitive performance were evaluated by quantile regression and least-squares regression, adjusted for sex, education, apo-ɛ4 genotype, history of CVD/hypertension and creatinine. Cross-sectional analyses revealed an interaction (P= 0·009) between plasma concentrations of folate and vitamin B12 in relation to cognitive performance. Plasma vitamin B12 concentrations in the lowest quartile ( < 274 pmol/l) combined with plasma folate concentrations in the highest quartile (>18·5 nmol/l) were associated with a reduced risk of cognitive impairment compared with plasma concentrations in the middle quartiles of both vitamins (OR 0·22, 95 % CI 0·05, 0·92). The interaction between folate and holoTC or MMA in relation to cognitive performance was not significant. In conclusion, this large study population unexposed to mandatory folic acid fortification showed that plasma folate, but not plasma vitamin B12, was associated with cognitive performance. Among the elderly participants with vitamin B12 concentrations in the lower range, the association between plasma folate and cognitive performance was strongest.

Low plasma vitamin B-12 is associated with a lower pregnancy-associated rise in plasma free choline in Canadian pregnant women and lower postnatal growth rates in their male infants

BACKGROUND

Choline needs are increased in pregnancy. Choline can be used as a source of methyl for homocysteine remethylation to methionine, but choline synthesis requires methyls from methionine. Vitamin B-12 deficiency increases choline use for homocysteine methylation.

OBJECTIVES

We investigated whether poor vitamin B-12 status occurs and contributes to low plasma choline and altered biomarkers of choline synthesis in pregnant women. With the use of a post hoc analysis, we addressed the association of maternal plasma vitamin B-12 status with postnatal growth rates in term infants.

DESIGN

Blood was analyzed for a prospective study of 264 and 220 pregnant women at 16 and 36 wk of gestation, respectively, and 88 nonpregnant women as a reference.

RESULTS

The proportion of women with a plasma total vitamin B-12 concentration <148 pmol/L (deficient) or 148-220 pmol/L (marginal) increased with pregnancy and pregnancy duration, which affected 3% and 9% of nonpregnant women, 10% and 21% of women at 16 wk of gestation, and 23% and 35% of women at 36 wk of gestation, respectively. Plasma free choline, betaine, and dimethylglycine were lower in women at 36 wk of gestation with a deficient or marginal compared with sufficient plasma total vitamin B-12 concentration (>220 pmol/L). Plasma total vitamin B-12 was positively associated with the increase in plasma free choline from midgestation to late gestation (P < 0.001). The postnatal growth rate to 9 mo was lower in infant boys of women classified as total vitamin B-12 deficient compared with sufficient.

CONCLUSION

This study shows that maternal vitamin B-12 status is related to choline status in late gestation in a folate-replete population and may be a determinant of infant growth even in the absence of undernutrition.

Daily milk intake improves vitamin B-12 status in young vegetarian Indians: an intervention trial

Background

Asymptomatic Indian lacto vegetarians, who make up more than half of the Indian population in different geographic regions, have distinctly low vitamin B-12 concentrations than non- vegetarians. Vegetarians consume milk but it seems that the amount is not enough to improve vitamin B-12 status or vitamin B-12 concentration in milk itself may be low. The aim of this study was to determine if daily milk consumption can improve vitamin B-12 status.

Methods

Fifteen male and 36 female, young healthy post-graduate volunteers participated. Blood from ten participants (4 males and 6 females) was collected (day-1). They continued their regular diet for next fourteen days and on day-15, blood of all 51 participants was collected, plasma vitamin B-12 concentration was measured and were divided into two groups; Normal (vitamin B-12 >148 pmol/L, n = 22) and Vitamin B-12 deficient (<148 pmol/L, n = 29), the remaining plasma was stored. All participants consumed 600 ml. of non-enriched buffalo milk (200 × 3) during the day along with their usual diet. Next day blood was collected for plasma holotranscobalamin II measurement. Subjects from deficient group continued to drink 400 ml of milk daily for next 14 days and blood was collected on day-30. Plasma holotranscoabalamin II (day-1, 15, 16, 30), vitamin B-12, folate, total homocysteine, creatinine and hematoloical parameters (day-1, 15, 30), and milk vitamin B-12 concentrations (day-15, 16, 30) were measured.

Results

Fifty seven per cent of the participants were vitamin B-12 deficient and 65% were hyperhomocysteinemic. No significant difference in biomarkers was observed when there was no intervention. Plasma holotranscobalamin II concentration increased from 19.6 to 22.27 pmol/L (p < 0.0001) 24 hrs after milk load in the whole group. Plasma vitamin B-12 increased from 92.5 to 122 pmol/L and tHcy concentrations decreased from 31.9 to 24.9 μ mol/L (p < 0.0001 for both) 14 days after regular milk intake in vitamin B-12 deficient subjects.

Conclusions

Regular intake of milk improved vitamin B-12 status of vitamin B-12 deficient vegetarians indicating a potential dietary strategy to improve the vitamin status.