Use of fasting urinary methylmalonic acid to screen for metabolic vitamin B12 deficiency in older persons

Cobalamin Deficiency in Children and Adolescents with Sickle Cell Disease

Background/Objective: Cobalamin (B12) deficiency is reported in 18% of adults with sickle cell disease (SCD) and only 10% without SCD; limited data are available on children. Diagnosing B12 deficiency is challenging given the lack of an established gold standard method of assessment and the unique renal features of SCD. B12 metabolism can be impacted by the clinical use of nitrous oxide gas (N2O), which is a standard therapy for SCD pain in some European countries. In response to emerging reports of neurologic sequalae in patients with SCD receiving N2O, we evaluated the prevalence of B12 deficiency in children with SCD pain. Methods: Secondary analysis of prospective blood and urine samples in children aged 3-21 hospitalized with SCD pain. B12 deficiency was defined as plasma methylmalonic acid (MMA) > 592 nmol/L or urine MMA/creatinine ≥ 2.2 mmol/mol. Results: Ninety-four children (13 ± 4 years, 54% female, 68% hemoglobin-SS, and 72% on hydroxyurea) were assessed. Further, 53% (50/94) had B12 deficiency diagnosed by either urine, plasma, or both; 27% (25/94) were deficient based on urine; 39% (37/94) were deficient by plasma; and 13% (12/94) were deficient by both plasma and urine. Plasma MMA and urine MMA/creatinine did not correlate with hemoglobin or mean corpuscular volume. Conclusions: B12 deficiency was common in children with SCD. The absence of a gold standard for diagnosing B12 deficiency compounded with the reliability issues of testing modalities make it impractical to determine whether this is an over- or under-estimation of the true prevalence. Future studies to better understand the dynamics of B12 metabolism during acute and steady states in SCD are warranted and could elucidate the influence of acute SCD pain on these biomarkers.

Effect of Vitamin B12 Replacement Intervals on Clinical Symptoms and Laboratory Findings in Gastric Cancer Patients after Total Gastrectomy

The management of patients with vitamin B12 deficiency after total gastrectomy (TG) remains controversial. We aimed to evaluate the effect of vitamin B12 replacement intervals on the clinical characteristics in these patients. The data from patients who received vitamin B12 supplementation after TG between 2007 and 2018 at the National Cancer Center, Korea, were retrospectively evaluated. Vitamin B12 deficiency was defined as a serum vitamin B12 level of <200 pg/mL or urine methylmalonic acid level > 3.8 mg/gCr. The patients were divided into a regular replacement group (patients received an intramuscular injection or oral medication regularly), and a lab-based replacement group (patients received vitamin B12 intermittently after checking the level). The symptoms and biochemical parameters were compared between these groups. The regular and lab-based replacement groups included 190 and 216 patients, respectively. The median vitamin B12 replacement intervals were 1 and 9 months, respectively (p < 0.001). After replacement, the regular replacement group had higher vitamin B12 levels than the lab-based replacement group (p < 0.001). However, the serum hemoglobin level showed no significant changes. After replacement, there was no significant difference in the proportion of the symptomatic patients between the groups. Replacing vitamin B12 with a lab-based protocol may be sufficient for TG patients.

Vitamin B-12 Intake from Dairy but Not Meat Is Associated with Decreased Risk of Low Vitamin B-12 Status and Deficiency in Older Adults from Quebec, Canada

BACKGROUND

Vitamin B-12 deficiency can result in irreversible neurologic damages. It is most prevalent among older adults (∼5%-15%), mainly due to impaired absorption. Vitamin B-12 bioavailability varies between food sources, so their importance in preventing deficiency may also vary.

OBJECTIVES

Using the NuAge Database and Biobank, we examined the associations between vitamin B-12 intake (total and by specific food groups) and low vitamin B-12 status and deficiency in older adults.

METHODS

NuAge-the Quebec Longitudinal Study on Nutrition and Successful Aging-included 1753 adults aged 67-84 y who were followed 4 y. Analytic samples comprised 1230-1463 individuals. Dietary vitamin B-12 intake was assessed annually using three 24-h dietary recalls. Vitamin B-12 status was assessed annually as low serum vitamin B-12 (<221 pmol/L), elevated urinary methylmalonic acid (MMA)/creatinine ratio (>2 μmol/mmol), and a combination of both (deficiency). Vitamin B-12 supplement users were excluded. Multilevel logistic regressions, adjusted for relevant confounders, were used.

RESULTS

Across all study years, 21.8%-32.5% of participants had low serum vitamin B-12, 12.5%-17.0% had elevated urine MMA/creatinine, and 10.1%-12.7% had deficiency. Median (IQR) total vitamin B-12 intake was 3.19 μg/d (2.31-4.37). Main sources were "dairy" and "meat, poultry, and organ meats." The ORs (95% CIs) in the fifth quintile compared with the first of total vitamin B-12 intake were as follows: for low serum vitamin B-12, 0.52 (0.37, 0.75; P-trend < 0.0001); for elevated urine MMA/creatinine, 0.63 (0.37, 1.08; P-trend = 0.091); and for vitamin B-12 deficiency, 0.38 (0.18, 0.79; P-trend = 0.006). Similarly, ORs (95% CIs) in the fourth quartile compared with the first of dairy-derived vitamin B-12 intake were 0.46 (0.32, 0.66; P-trend < 0.0001), 0.51 (0.30, 0.87; P-trend = 0.006), and 0.35 (0.17, 0.73; P-trend = 0.003), respectively. No associations were observed with vitamin B-12 from "meat, poultry, and organ meats."

CONCLUSIONS

Higher dietary vitamin B-12 intake, especially from dairy, was associated with decreased risk of low vitamin B-12 status and deficiency in older adults. Food groups might contribute differently at reducing risk of deficiency in older populations.

Methylmalonic acid analysis using urine filter paper samples to screen for metabolic vitamin B12 deficiency in older adults

Aim: Methylmalonic acid (MMA) analysis in urine represents a noninvasive approach to screening for vitamin B₁₂ deficiency in older adults. A method allowing the analysis of MMA/creatinine in fasting urine collected on filter paper was developed/validated. Method: Dry urine specimens were eluted using a solution containing internal standards, filtrated and analyzed by ultra-performance LC-MS/MS. Results: The method allowed the chromatographic separation of MMA from succinic acid. Dried urine samples were stable for 86 days at room temperature. The MMA/creatinine ratios measured in urine collected on filter paper were highly correlated with values derived from the corresponding liquid specimens. Conclusion: This robust filter paper method might greatly improve the accessibility and cost-effectiveness of vitamin B₁₂ deficiency screening in older adults.

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.

Vitamin B12 among Vegetarians: Status, Assessment and Supplementation

Cobalamin is an essential molecule for humans. It acts as a cofactor in one-carbon transfers through methylation and molecular rearrangement. These functions take place in fatty acid, amino acid and nucleic acid metabolic pathways. The deficiency of vitamin B12 is clinically manifested in the blood and nervous system where the cobalamin plays a key role in cell replication and in fatty acid metabolism. Hypovitaminosis arises from inadequate absorption, from genetic defects that alter transport through the body, or from inadequate intake as a result of diet. With the growing adoption of vegetarian eating styles in Western countries, there is growing focus on whether diets that exclude animal foods are adequate. Since food availability in these countries is not a problem, and therefore plant foods are sufficiently adequate, the most delicate issue remains the contribution of cobalamin, which is poorly represented in plants. In this review, we will discuss the status of vitamin B12 among vegetarians, the diagnostic markers for the detection of cobalamin deficiency and appropriate sources for sufficient intake, through the description of the features and functions of vitamin B12 and its absorption mechanism.

A vitamin B-12 supplement of 500 μg/d for eight weeks does not normalize urinary methylmalonic acid or other biomarkers of vitamin B-12 status in elderly people with moderately poor vitamin B-12 status

Plasma vitamin B-12 is the most commonly used biomarker of vitamin B-12 status, but the predictive value for low vitamin B-12 status is poor. The urinary methylmalonic acid (uMMA) concentration has potential as a functional biomarker of vitamin B-12 status, but the response to supplemental vitamin B-12 is uncertain. A study was conducted to investigate the responsiveness of uMMA to supplemental vitamin B-12 in comparison with other biomarkers of vitamin B-12 status [plasma vitamin B-12, serum holotranscobalamin (holoTC), plasma MMA] in elderly people with moderately poor vitamin B-12 status. A double-blind, placebo-controlled, randomized 8-wk intervention study was carried out using vitamin B-12 supplements (500 μg/d, 100 μg/d, and 10 μg/d cyanocobalamin) in 100 elderly people with a combined plasma vitamin B-12 <250 pmol/L and uMMA ratio (μmol MMA/mmol creatinine) >1.5. All biomarkers had a dose response to supplemental vitamin B-12. Improvements in plasma vitamin B-12 and serum holoTC were achieved at cobalamin supplements of 10 μg/d, but even 500 μg/d for 8 wk did not normalize plasma vitamin B-12 in 8% and serum holoTC in 12% of people. The response in uMMA was comparable with plasma MMA; 15-25% of people still showed evidence of metabolic deficiency after 500 μg/d cobalamin for 8 wk. There was a differential response in urinary and plasma MMA according to smoking behavior; the response was enhanced in ex-smokers compared with never-smokers. uMMA offers an alternative marker of metabolic vitamin-B12 status, obviating the need for blood sampling.

How prevalent is vitamin B(12) deficiency among vegetarians?

Vegetarians are at risk for vitamin B(12) (B12) deficiency due to suboptimal intake. The goal of the present literature review was to assess the rate of B12 depletion and deficiency among vegetarians and vegans. Using a PubMed search to identify relevant publications, 18 articles were found that reported B12 deficiency rates from studies that identified deficiency by measuring methylmalonic acid, holo-transcobalamin II, or both. The deficiency rates reported for specific populations were as follows: 62% among pregnant women, between 25% and almost 86% among children, 21-41% among adolescents, and 11-90% among the elderly. Higher rates of deficiency were reported among vegans compared with vegetarians and among individuals who had adhered to a vegetarian diet since birth compared with those who had adopted such a diet later in life. The main finding of this review is that vegetarians develop B12 depletion or deficiency regardless of demographic characteristics, place of residency, age, or type of vegetarian diet. Vegetarians should thus take preventive measures to ensure adequate intake of this vitamin, including regular consumption of supplements containing B12.

Understanding Vitamin B12

Vitamin B12 (B12) is essential in activating folate needed in DNA synthesis. Inadequate intake results in the impairment of nerve transmission and inadequate synthesis of erythrocytes and other hematological cells. Two separate mechanisms of B12 absorption exist, a receptor-mediated endocytosis that occurs in the distal ileum and the mass-action pharmacologic mechanism. The recommended dietary allowance for B12 for adults issued by the Institute of Medicine is 2.4 µg/d. B12 is only found in meats and other foods of animal origin. B12 deficiency is widespread. Two main causes of deficiency include inadequate absorption and intake. Elderly and vegetarians are at highest risk for deficiency. Prevalence of deficiency ranges from 7% of the US population 3 years and older to 90% among vegans. The best way to assess deficiency is by using methylmalonic acid. Populations at risk could benefit from using B12 supplements and from fortification of flour.

Determinants of urinary methylmalonic acid concentration in an elderly population in the United Kingdom

BACKGROUND

An age-related deterioration of vitamin B-12 status has been well documented. The early detection of deficiency may prevent the development of serious clinical symptoms, but plasma vitamin B-12 concentration is known to be an imperfect measure of vitamin B-12 status. Urinary methylmalonic acid (MMA) may be a more informative biomarker of vitamin B-12 status; however, biochemical, dietary, and other lifestyle determinants are not known.

OBJECTIVE

We identified determinants of urinary MMA concentrations in free-living men and women aged ≥65 y in the United Kingdom.

DESIGN

A cross-sectional study in 591 men and women aged 65-85 y, with no clinical evidence of vitamin B-12 deficiency, was conducted to determine the demographic, clinical, and lifestyle determinants of urinary MMA concentration expressed as the ratio of micromoles of MMA to millimoles of creatinine (uMMA ratio).

RESULTS

Twenty percent of subjects had plasma vitamin B-12 concentrations <200 pmol/L. Seventeen percent of the variation in the uMMA ratio could be explained by plasma holotranscobalamin and sex; total vitamin B-12 intake and measures of renal function and gastric function made only a small contribution to the model. The uMMA ratio was lower in people with moderately impaired renal function.

CONCLUSIONS

Plasma holotranscobalamin and sex were the most important determinants of uMMA ratio in elderly people with no clinical diagnosis of renal impairment. This biomarker might underestimate vitamin B-12 deficiency in a population in which renal impairment is prevalent. This trial was registered at www.controlled-trials.com as ISRCJN83921062.

Serum vitamin B12 concentrations within reference values do not exclude functional vitamin B12 deficiency in PKU patients of various ages

Homocysteine (Hcy) and in particular methylmalonic acid (MMA) are considered reliable parameters for vitamin B(12) status in healthy individuals. Phenylketonuria (PKU) patients are at risk for functional vitamin B(12) deficiency based on their diet.

OBJECTIVE

The aim of this study was to investigate the prevalence of functional vitamin B(12) deficiency in continuously treated PKU patients and the association of parameters of vitamin B(12) and metabolic control.

METHODS

In 75 continuously treated PKU patients of 1-37 years of age, serum vitamin B(12) concentrations, plasma Hcy, MMA, and phenylalanine concentrations were studied.

RESULTS

Eight patients had vitamin B(12) concentrations below normal. Out of these eight patients, two had elevated MMA and/or Hcy concentrations. Ten other patients with normal vitamin B(12) concentrations had elevated concentrations of MMA and/or Hcy.

CONCLUSIONS

A vitamin B(12) concentration within the reference range does not automatically imply a sufficient vitamin B(12) status. We recommend measuring serum MMA, or alternatively plasma Hcy, yearly in all PKU patients to diagnose functional vitamin B(12) deficiency.

Metabolic signs of vitamin B(12) deficiency in humans: computational model and its implications for diagnostics

Early diagnostics of cobalamin (Cbl, vitamin B(12)) deficiency is primarily based on measurements of the relevant metabolic markers in blood plasma--total B(12), specific Cbl-saturated transporter holo-transcobalamin (holoTC), and substrates of Cbl-dependent enzymatic reactions methylmalonic acid (MMA) and homocysteine (Hcy). Concentrations of B(12) and holoTC decrease whereas MMA and Hcy increase under deficiency. Yet, the results of individual tests are often contradictory and do not guarantee unambiguous diagnosis. The current work describes the metabolic manifestation of vitamin B(12) deficiency in terms of flux equations fitted to data sets from literature. The model mathematically connects all the markers and presents 4 independent measurements as a single point (x, y) in the combined coordinates x = (holoTC x B(12))((1/2)) and y = (1/2)log(10)(MMA x Hcy). Pairwise averaging compensates for the individual fluctuations of the markers caused by (1) irregular spikes of holoTC, (2) delayed change of the total plasma B(12) buffered by an internal Cbl depot, and (3) variations in the production/excretion velocities of MMA and Hcy. Bivariate distribution of the marker combinations (x, y) reveals several peaks of frequency in the analyzed mixed population. The peaks seem to represent the reference subgroups with different B(12) physiology and characteristic values of "wellness parameter": w = log(10)(holoTC(n)) + log(10)(B(12n)) - log(10)(MMA(n)) - log(10)(Hcy(n)), where concentrations are normalized (eg, MMA(n) = MMA/MMA(normal)). Dynamic response of the organism to B(12) intake is quantified and described as an additional analytical tool when classifying uncertain cases. The discussed mathematical approaches are of general applicability in diagnostics.

Urinary methylmalonic acid levels in patients with acute ischemic stroke

OBJECTIVES

Vitamin B-12 and folate deficiency are common, especially in people aged 55 or over, and accompanied by elevated methylmalonic acid (MMA) and homocysteine concentrations. The aims of the study were to investigate the relationship between serum vitamin B-12, homocysteine, folate, erythrocyte folate and urinary MMA in patients with ischemic stroke, and to develop a simple screening HPLC method for the measurement of urinary MMA.

DESIGN AND METHODS

Twenty-eight patients aged 55 years and over with ischemic stroke and 23 age- and sex- matched healthy controls were included in the study. Serum vitamin B-12 and folate were measured by immunoassay; serum total homocysteine and urinary MMA concentrations by HPLC.

RESULTS

There was no significant difference in vitamin B-12, folate and homocysteine concentrations between the patient and control groups. Urinary MMA concentrations and erythrocyte folate levels were significantly higher in patients than controls. There was a significantly negative correlation between vitamin B-12 and MMA.

CONCLUSIONS

Increased urinary MMA excretion is associated with ischemic stroke and it may more robustly reflect vitamin B-12 deficiency in patients with ischemic stroke. The method used in this study is eligible for routine urinary MMA measurements.

[Neurological manifestations of vitamin B12 deficiency: a retrospective study of 26 cases]

PURPOSE

Neurological symptoms of B12 vitamin deficiency are polymorph. Causes are dominated by Biermer's disease and B12 vitamin non dissociation that is frequent in the elderly.

METHODS

We realized a retrospective study during 11 years. Patients with neurological symptoms associated to megaloblastosis were included. Treatment with B12 vitamin lead to haematological manifestation regression.

RESULTS

26 cases were analyzed. Mean age was 50+/-14.5 years and there were 11 women and 15 men. Neurological signs included combined medullar sclerosis (N = 10), peripheral neuropathy (N = 10), isolated paresthesia (N = 5) and inferior limb pyramidal syndrome (N = 1). Neurological signs revealed vitamin B12 deficiency in 4 cases. Mean haemoglobin rate was 6.2+/-2.6 g/dl, mean MCV was 109+/-56 fl. Eight patients had macrocytic anaemia, nine bi-cytopenia and eight deep pancytopenia. Electromyography (N = 8) confirmed neuropathy and medullar MRI (N = 2) showed antero-posterior cordonal demyelinisation of cervico-dorsal medulla. Causes of B12 vitamin deficiency were Biermer's disease (N = 11), non dissociation of B12 vitamin's syndrome (N = 8) and partial gastrectomy (N = 1). In 6 patients, no aetiology was found. Treatment with parenteral vitamin B12 induced neurological symptoms regression in 14 cases. Patient with neurological disorder had significantly higher platelet count and haemoglobin level as compared with patients without neurological disorder. Reticulocyte crisis was more precocious in patients with neurological disorders.

CONCLUSION

Neurological symptoms in vitamin B12 deficiency are frequent. We insist on isolated forms, inaugural forms and on the interest of medullar MRI for early diagnosis.