Determinants of plasma methylmalonic acid in a large population: implications for assessment of vitamin B12 status

Low concentration of serum vitamin B12 may be a strong predictor of large-artery atherosclerosis stroke: A case-control study

INTRODUCTION

Identifying controllable risk factors for large-artery atherosclerosis (LAA) stroke is crucial due to its significant role as a leading cause of ischemic stroke. We aimed to validate the correlation of serum vitamin B12 with LAA stroke.

METHODS

Inpatients with LAA stroke and healthy controls were retrospectively collected for a case-control study from January 2020 to May 2022. Serum vitamin B12 concentration and other blood indicators, demographic, lifestyle factors and comorbidities were investigated. Logistic regression analysis was used to identify the correlation of serum vitamin B12 concentrations with LAA stroke, meanwhile adjusted for confounding factors.

RESULTS

Patients with LAA stroke had significantly lower serum vitamin B12 concentrations in comparison to those of controls. In the fully adjusted model, vitamin B12 (per 1 interquartile range increase, odds ratio [OR] = 0.84, 95 % confidence interval [CI]: 0.77-0.91), vitamin B12 < 200 pg/mL (OR=7.70, 95 %CI: 2.19-27.03) and vitamin B12 < 300 pg/mL (OR=4.19, 95 %CI: 1.82-9.66) were independently factors for LAA stroke. Furthermore, the optimal cut-off values for vitamin B12 to predict LAA stroke were 305.25 pg/mL (area under the curve [AUC] = 0.71) when unadjusted and 308.25 pg/mL when adjusted for age and sex (AUC=0.68). Lower vitamin B12 concentrations were significantly associated with male sex, smoking, older age, higher neutrophil count, higher creatinine, lower folate and higher total homocysteine.

CONCLUSION

Results indicate that low concentration of serum vitamin B12 may be a strong predictor for the risk of LAA stroke.

Vitamin B12 status and the risk of developing sepsis in patients with bacterial infection: a prospective observational cohort study

BACKGROUND

Data have shown that vitamin B12 has immunomodulatory effects via different pathways, which could influence the pathophysiology of sepsis. The objective of this study was to investigate whether vitamin B12 levels, assessed by the measurement of holotranscobalamin (HTC), total vitamin B12 (B12), and methylmalonic acid (MMA, which accumulates in case of B12 deficiency), are associated with the development of sepsis in patients with onset of bacterial infection.

METHODS

This was a single-center, prospective observational pilot study. Adult patients who presented to the emergency department with bacterial infection confirmed by a positive microbiological culture result were included in the study and followed up for 6 days to assess whether they developed sepsis or not. The primary objective was to compare HTC concentration in patients who developed sepsis to those who did not develop sepsis. Secondary objectives were the evaluation of B12 and MMA concentrations in those two groups. Multiple logistic regression models were used, with presence of sepsis as the outcome variable, and HTC, B12, and MMA concentrations as predictor variables, separately, and adjusted for potential confounders.

RESULTS

From 2019 to 2022, 2131 patients were assessed for eligibility, of whom 100 met the inclusion criteria. One patient was excluded from the analysis due to missing data. Of the 99 patients, 29 developed sepsis. There was no evidence for an association between HTC or B12 concentration and the development of sepsis (OR 0.65, 95% CI 0.31-1.29, p = 0.232, OR 0.84, 95% CI 0.44-1.54, p = 0.584, respectively). There was an association between MMA concentration and the development of sepsis, with a positive effect, i.e. with increasing MMA, the odds for sepsis increased (OR 2.36, 95% CI 1.21-4.87, p = 0.014). This association remained significant when adjusted for confounders (OR 2.72, 95% CI 1.23-6.60, p = 0.018).

CONCLUSIONS

Our study found an association between elevated MMA concentration and the development of sepsis. We did not find an association between HTC and B12 concentrations and the development of sepsis. Further, larger studies are warranted, as it could lead to interventional trials investigating whether B12 supplementation provides a clinical benefit to patients with infection or sepsis.

TRIAL REGISTRATION

The study was registered on ClinicalTrials.gov under the identifier NCT04008446 on June 17, 2019.

Serum methylmalonic acid concentrations at breast cancer diagnosis significantly correlate with clinical frailty

Methylmalonic acid (MMA), a by-product of propionate metabolism, is known to increase with age. This study investigates the potential of serum MMA concentrations as a biomarker for age-related clinical frailty in older patients with breast cancer. One hundred nineteen patients ≥ 70 years old with early-stage breast cancer were included (median age 76 years). G8 screening, full geriatric assessment, clinical parameters (i.e., estimated glomerular filtration rate (eGFR) and body mass index (BMI)), and serum sample collection were collected at breast cancer diagnosis before any therapy was administered. MMA concentrations were measured via liquid chromatography with tandem mass spectrometry. MMA concentrations significantly increased with age and eGFR (all P < 0.001) in this older population. The group with an abnormal G8 (≤ 14, 51% of patients) had significantly higher MMA levels than the group with normal G8 (> 14, 49%): 260 nmol/L vs. 188 nmol/L, respectively (P = 0.0004), even after correcting for age and eGFR (P = 0.001). Furthermore, in the detailed assessment, MMA concentrations correlated most with mobility (Eastern Cooperative Oncology Group (ECOG) Performance Status and Activities of Daily Living (ADL) tools, all P ≤ 0.02), comorbidity (Charlson Comorbidity Index (CCI) tool, P = 0.005), and polypharmacy (P < 0.001), whereas no significant associations were noted for instrumental ADL (IADL), Mini-Mental State Examination (MMSE), Geriatric Depression Scale-15 (GDS15), Mini Nutritional Assessment-Short Form (MNA-SF), and pain (all P > 0.1). In addition, our results showed that higher MMA levels correlate with poor overall survival in breast cancer patients (P = 0.003). Elevated serum MMA concentrations at initial diagnosis are significantly associated, not only with age but also independently with clinical frailty, suggesting a possible influence of MMA on clinical frailty in older patients with early-stage breast cancer.

Increased serum methylmalonic acid levels were associated with the presence of cognitive dysfunction in older chronic kidney disease patients with albuminuria

BACKGROUND

This study aimed to evaluate the correlation between serum methylmalonic acid (MMA) levels and cognition function in patients with chronic kidney disease (CKD).

METHODS

In this cross-sectional study, we included 537 CKD individuals aged ≥ 60-year-old with albuminuria from the National Health and Nutrition Examination Survey (NHANES) 2011-2014. Four cognitive tests including the Digit Symbol Substitution Test (DSST), the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) Delayed Recall and Word Learning tests, and the Animal Fluency test (AF) were performed. Associations between MMA and cognition scores were assessed with linear regression models.

RESULTS

MMA level was negatively associated with residual renal function and nutrition status. After multivariate adjustment, elevated serum MMA levels were independently correlated with decline of cognition in CKD patients with albuminuria.

CONCLUSION

Our study showed that higher serum MMA levels were independently associated with the presence of cognition dysfunction in CKD patients. The exact pathogenesis of MMA and cognition needs further research.

The association between methylmalonic acid, a biomarker of mitochondria dysfunction, and phenotypic age acceleration: A population-based study

Phenotypic age acceleration (PAA) is a sensitive marker of biological aging. Circulating methylmalonic acid (MMA) is a novel biomarker of mitochondrial dysfunction and has been associated with age-related disorders. Our study aimed to investigate to what extent circulating MMA was associated with PAA, and whether the association was independent of vitamin B12 status and renal function in the general population. We analyzed cross-sectional data from 13,023 participants across a wide age range (mean age: 38.9 years, range: 12 - 85 years, 51.1% women) from the US National Health and Nutrition Examination Survey (NHANES). PAA was calculated based on the published algorithm. Linear regression models were performed to assess the association between circulating MAA and PAA. Only 31% of the variation in MMA levels was explained by age, sex, race/ethnicity, social economic status, vitamin B12 status, and renal function. Per unit increase in circulating MAA (1.0 nmol/L) was associated with 1.59 years increase in PAA (β = 1.59, 95% CI: 1.17, 2.00, p < 0.001) after adjusting for multiple confounders. Importantly, PAA increased with circulating MMA levels independent of vitamin B12, creatine, and homocysteine levels. The association was more pronounced in subgroups of age ≥ 65 years, women, underweight, vitamin B12 < 400 μmol/L, and homocysteine ≥ 10 μmol/L. The association was much stronger among participants with cardiovascular diseases (CVDs) than without CVDs. In conclusion, our current population-based study showed that mitochondria-derived circulating MMA was associated with increased phenotypic age acceleration in the general population.

Vitamin B12 Status before and after Outpatient Treatment of Severe Acute Malnutrition in Children Aged 6-59 Months: A Sub-Study of a Randomized Controlled Trial in Burkina Faso

Severe acute malnutrition (SAM) is treated with ready-to-use therapeutic foods (RUTF) containing a vitamin-mineral premix. Yet little is known about micronutrient status in children with SAM before and after treatment. We aimed to investigate vitamin B12 status in children with uncomplicated SAM, aged 6-59 months in Burkina Faso, before and after treatment with a standard or a reduced dose of RUTF. Blood samples were collected at admission and discharge. Serum B12 was determined with microbiological assay and serum methylmalonic acid (MMA) and total homocysteine (tHcy) were analyzed with gas chromatography-tandem mass spectrometry. B12 status was classified using the combined indicator (3cB12). Among 374 children, the median [interquartile range] age was 11.0 [7.7-16.9] months, and 85.8% were breastfed. Marked or severe B12 deficiency, as judged by 3cB12, decreased from 32% to 9% between admission and discharge (p < 0.05). No differences in B12 status following treatment with either standard (n = 194) or reduced (n = 180) doses of RUTF were observed. Breastfed children showed a lower B12 status (3cB12) than non-breastfed ones (-1.10 vs -0.18, p < 0.001 at admission; -0.44 vs 0.19; p < 0.001 at discharge). In conclusion, treatment of SAM with RUTF improved children's B12 status but did not fully correct B12 deficiency.

Association of Serum Vitamin B12 and Circulating Methylmalonic Acid Levels with All-Cause and Cardiovascular Disease Mortality among Individuals with Chronic Kidney Disease

(1) Background: it is unclear whether serum vitamin B₁₂ and circulating methylmalonic acid (MMA) are related with a poor prognosis among individuals with chronic kidney disease (CKD); (2) Methods: this prospective cohort study included 2589 individuals with CKD who participated in the National Health and Nutrition Examination Survey (NHANES) from 1999 to 2004, and from 2011 to 2014, respectively. Hazard ratios (HRs) and 95% Cis for the associations of MMA and vitamin B₁₂ levels with the risk of all-cause and cardiovascular disease (CVD) mortality were calculated using multivariable Cox proportional hazards regression models. Restricted cubic spline analyses were used to examine the non-linear association of MMA levels with all-cause and CVD mortality. (3) Results: among the 2589 participants, we identified 1192 all-cause deaths and 446 CVD deaths, respectively, with a median follow-up of 7.7 years. Compared with participants with MMA < 123 nmol/L, those with MMA ≥ 240 nmol/L had an increased all-cause and CVD mortality in the multivariable-adjusted model [HR (95% CI), 2.01 (1.54-2.62) and 1.76 (1.18-2.63), respectively]; (4) Conclusions: higher circulating MMA levels were found to be strongly associated with an elevated all-cause and CVD mortality among individuals with CKD, while serum vitamin B₁₂ levels were not associated.

FUNCTIONAL VITAMIN B12 DEFICIENCY: IMPROVING METHYLMALONIC ACID REFERENCE INTERVALS IN URINE

BACKGROUND

AIM Most laboratory requests focus on the detection of possible vitamin B12 deficiency. In this context, methylmalonic acid (MMA) is reported as the best biomarker. The aim of our study was to establish the biological reference interval for MMA in urine, and assess the influence of age, sex, and vitamin B12 status on MMA concentrations.

METHODS

This is a prospective observational study considering individuals with normal results for blood count and liver and kidney function. Individuals who presented supplementation, any pathology or treatment that could cause cobalamin metabolism disorders, and pregnant women were excluded. Likewise, individuals whose vitamin B12 result presented antibody-mediated interference were excluded. Individuals were grouped by age-group and sex. Reference intervals were determined by non-parametric calculation (percentiles 1-99).

RESULTS

It was established a single reference interval [0.52 (CI_90%: 0.50-0.54) - 5.75 (CI_90%: 5.57-6.17) mmolMMA/mol creatinine], with 100% of individuals with MMA above the upper limit of reference presenting a total vitamin B12 concentration ≤238pmol/L.

CONCLUSION

The establishment of optimal reference intervals for methylmalonic acid excretion in urine is crucial in individuals with a suspicion of functional vitamin B12 deficiency. However, the possibility of establishing a cut-off value for total vitamin B12 suggesting subclinical deficiency remains a challenge for this magnitude.

Plasma methylmalonic acid predicts risk of acute myocardial infarction and mortality in patients with coronary heart disease: A prospective 2-cohort study

BACKGROUND

Elevated plasma methylmalonic acid (MMA) is reported in patients with established coronary heart disease (CHD) and is considered a marker of vitamin B12 deficiency. Moreover, MMA-dependent reactions have been linked to alterations in mitochondrial energy metabolism and oxidative stress, key features in the pathophysiology of cardiovascular diseases (CVDs).

OBJECTIVES

We examined whether plasma MMA prospectively predicted the long-term risk of acute myocardial infarction (AMI) and mortality.

METHODS AND RESULTS

Using Cox modeling, we estimated hazard ratios (HRs) for endpoints according to per 1-SD increment of log-transformed plasma MMA in two independent populations: the Western Norway Coronary Angiography Cohort (WECAC) (patients evaluated for CHD; n = 4137) and the Norwegian Vitamin Trial (NORVIT) (patients hospitalized with AMI; n = 3525). In WECAC and NORVIT, 12.8% and 18.0% experienced an AMI, whereas 21.8% and 19.9% died, of whom 45.5% and 60.3% from CVD-related causes during follow-up (range 3-11 years), respectively. In WECAC, age- and gender-adjusted HRs (95% confidence interval) were 1.18 (1.09-1.28), 1.25 (1.18-1.33), and 1.28 (1.17-1.40) for future AMI, total mortality, and CVD mortality, respectively. Corresponding risk estimates were 1.19 (1.10-1.28), 1.22 (1.14-1.31), and 1.30 (1.19-1.42) in NORVIT. These estimates were only slightly attenuated after multivariable adjustments. Across both cohorts, the MMA-risk association was stronger in older adults, women, and non-smokers.

CONCLUSIONS

Elevated MMA was associated with an increased risk of AMI and mortality in patients with suspected or verified CHD.

Correlations between circulating methylmalonic acid levels and all-cause and cause-specific mortality among patients with diabetes

Aims

Evidence regarding serum methylmalonic acid (MMA) levels and mortality in individuals with diabetes is limited. This study aimed to evaluate the correlation between MMA and all-cause and cause-specific deaths in patients with diabetes.

Materials and methods

This is a population-based cohort study based on data from both the National Health and Nutrition Examination Survey (NHANES) and National Death Index from 1999 to 2014. We assessed the association of serum MMA concentrations with mortality using Cox proportional hazard models after adjusting for lifestyle, demographic factors, and comorbidities.

Results

Among the 3,097 participants, 843 mortalities occurred during a median follow-up of 4.42 years. There were 242 deaths due to cardiovascular disease (CVD) and 131 cancer-associated deaths. After multivariate adjustment, elevated serum MMA levels were markedly correlated with a high risk of all-cause, CVD-, and cancer-related deaths. Each one-unit increase in the natural log-transformed MMA level correlated with increased risk of all-cause mortality (2.652 times), CVD mortality risk (3.153 times), and cancer-related mortality risk (4.514). Hazard ratios (95% confidence intervals [CIs]) after comparing participants with MMA &lt; 120 and ≥250 nmol/L were 2.177 (1.421–3.336) for all-cause mortality, 3.560 (1.809–7.004) for CVD mortality, and 4.244 (1.537–11.721) for cancer mortality.

Conclusion

Higher serum MMA levels were significantly associated with higher all-cause, CVD, and cancer mortality. These findings suggest that maintaining lower MMA status may lower mortality risk in individuals with diabetes.

Vitamin B12 deficiency: correction of P-methylmalonic acid for estimated glomerular filtration rate to improve diagnostic value - a confirmatory study

Objectives: For diagnosis of vitamin B12 deficiency, plasma methylmalonic acid (P-MMA) is considered superior to plasma vitamin B12 (P-B12). Reduced kidney function elevates P-MMA, hence, hampering P-MMA as a biomarker. We assessed whether correcting P-MMA for estimated glomerular filtration rate (eGFR) can affect the estimated prevalence of B12 deficiency. Methods: We included 115,245 patients with concomitant measurements of P-MMA, P-B12 and P-Creatinine. B12 deficiency was classified using P-MMA decision limits at >0.75 and >0.43 µmol/L. The non-linear relation between eGFR and P-MMA was estimated using spline regression. We calculated the percentage-wise reclassification of B12 deficiency by using an eGFR corrected P-MMA formula with eGFR reference points of 90 and 60 mL/min. Results: 6% with B12 deficiency were reclassified as non-deficient after adjusting for eGFR (reference point eGFR 90 mL/min) with both P-MMA decision limits. Overall B12 deficiency prevalence was reduced from 9.6% to 9.0% (P-MMA decision limit 0.43 µmol/L). With P-MMA decision limits at 0.75 and 0.43 µmol/L, 33.6% and 44.8% of B12 deficient patients with an eGFR <60 mL/min were reclassified as non-deficient. Conclusions: We have demonstrated that correcting P-MMA for eGFR can reclassify P-MMA levels across decision limits for diagnosing B12 deficiency, in particular for patients with reduced kidney function. This may have clinical implications for avoiding overdiagnosis of this chronic disease.

Pernicious Anemia: The Hematological Presentation of a Multifaceted Disorder Caused by Cobalamin Deficiency

Pernicious anemia is still a neglected disorder in many medical contexts and is underdiagnosed in many patients. Pernicious anemia is linked to but different from autoimmune gastritis. Pernicious anemia occurs in a later stage of autoimmune atrophic gastritis when gastric intrinsic factor deficiency and consequent vitamin B₁₂ deficiency may occur. The multifaceted nature of pernicious anemia is related to the important role of cobalamin, which, when deficient, may lead to several dysfunctions, and thus, the proteiform clinical presentations of pernicious anemia. Indeed, pernicious anemia may lead to potentially serious long-term complications related to micronutrient deficiencies and their consequences and the development of gastric cancer and type 1 gastric neuroendocrine tumors. When not recognized in a timely manner or when pernicious anemia is diagnosed with delay, these complications may be potentially life-threatening and sometimes irreversible. The current review aimed to focus on epidemiology, pathogenesis, and clinical presentations of pernicious anemia in an attempt to look beyond borders of medical specialties. It aimed to focus on micronutrient deficiencies besides the well-known vitamin B₁₂ deficiency, the diagnostic approach for pernicious anemia, its long-term complications and optimal clinical management, and endoscopic surveillance of patients with pernicious anemia.

Reference intervals for plasma vitamin B12 and plasma/serum methylmalonic acid in Danish children, adults and elderly

BACKGROUND

Plasma/serum vitamin B12 (B12) is often used to screen for B12 deficiency complemented with analysis of methylmalonic acid (MMA) in case of low B12. The concentration of both analytes likely depends on age, and we, therefore, aimed at establishing 95% age-adjusted reference intervals (RIs) for plasma B12 and serum/plasma MMA in the Danish population.

METHODS

We collected and analysed blood samples from healthy children, adults, and elderly individuals and extracted routine clinical B12 and MMA results to establish RIs. We also evaluated the association between matching B12 and MMA results.

RESULTS

We suggest the following RIs for plasma B12 and plasma/serum MMA, respectively. 0-<1 year: 180-1400 pmol/L, 0.10-1.25 µmol/L; 1-<11 years: 260-1200 pmol/L, 0.10-0.30 µmol/L; 12-<18 years: 200-800 pmol/L, 0.10-0.35 µmol/L; 18-<65 years: 200-600 pmol/L, 0.10-0.40 µmol/L; 65 + years: 200-600 pmol/L, 0.12-0.46 µmol/L. Finally, the proportion of patients with elevated MMA differed between age groups independently of B12 and was highest in children.

CONCLUSION

We propose new age-adjusted RIs for B12 and MMA and suggest that age-dependent cut-off values should be implemented if plasma B12 is used to screen for B12 deficiency.

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.

Methylmalonic acid, vitamin B12, renal function, and risk of all-cause mortality in the general population: results from the prospective Lifelines-MINUTHE study

BACKGROUND

Methylmalonic acid (MMA) is best known for its use as a functional marker of vitamin B12 deficiency. However, MMA concentrations not only depend on adequate vitamin B12 status, but also relate to renal function and endogenous production of propionic acid. Hence, we aimed to investigate to what extent variation in MMA levels is explained by vitamin B12 and eGFR and whether MMA levels are associated with mortality if vitamin B12 and eGFR are taken into account.

METHODS

A total of 1533 individuals (aged 60-75 years, 50% male) were included from the Lifelines Cohort and Biobank Study. Individuals were included between 2006 and 2013, and the total follow-up time was 8.5 years.

RESULTS

Median [IQR] age of the study population was 65 [62-69] years, 50% was male. At baseline, median MMA concentration was 170 [138-216] nmol/L, vitamin B12 290 [224-362] pmol/L, and eGFR 84 [74-91] mL/min/1.73 m2. Log₂ vitamin B12, log₂ eGFR, age, and sex were significantly associated with log₂ MMA in multivariable linear regression analyses (model R² = 0.22). After a total follow-up time of 8.5 years, 72 individuals had died. Log₂ MMA levels were significantly associated with mortality (hazard ratio [HR] 1.67 [95% CI 1.25-2.22], P < 0.001). Moreover, we found a significant interaction between MMA and eGFR with respect to mortality (P_interaction < 0.001).

CONCLUSIONS

Only 22% of variation in MMA levels was explained by vitamin B12, eGFR, age, and sex, indicating that a large part of variation in MMA levels is attributable to other factors (e.g., catabolism, dietary components, or gut microbial production). Higher MMA levels are associated with an increased risk for mortality, independent of vitamin B12, eGFR, and sex. This association was more pronounced in individuals with impaired renal function.

Association Between Cognitive Impairment and Vitamin B12, Folate, and Homocysteine Status in Elderly Adults: A Retrospective Study

BACKGROUND

Cognitive disorders in old age have a serious impact on the health and social aspects of patients and their families.

OBJECTIVE

The scope of this paper is to explore the role of cobalamin and folate that has been linked to cognitive decline, not only as a deficiency state depending on malnutrition, but also a determinant in cognitive impairment.

METHODS

A 6-year observational, retrospective study was conducted by collecting the routine blood analyses and cognitive screening scores of patients aged 60 years or older, followed at our Centre for the Diagnosis and Treatment of Cognitive Disorders.

RESULTS

In a linear regression with a multi-vitamin model, higher folate concentrations were correlated with better cognitive performances through MMSE score, even after correction for sex, age, and years of education (beta = 0.144, p = 0.001). Estimated MMSE marginal means for folate versus homocysteine showed that folate deficiency was associated with worse cognitive performances, with a more severe cognitive impairment when hyperhomocysteinemia was present.

CONCLUSION

The assessment of B-vitamin status among elderly adults can contribute to an economic and practical approach to the prevention and management of cognitive decline. Future studies focused to define optimal vitamin status are warranted.

Mitochondria-derived methylmalonic acid, a surrogate biomarker of mitochondrial dysfunction and oxidative stress, predicts all-cause and cardiovascular mortality in the general population

BACKGROUND

Inherited methylmalonic acidemia is characterized by mitochondrial dysfunction, oxidative stress, and damage of mitochondria-rich organs in children. It is unclear whether methylmalonic acid (MMA) is related to poor prognosis in adults. The study aims to investigate the associations of MMA with all-cause and cause-specific mortality in the general population.

METHODS

Overall, 23,437 adults from the US National Health and Nutrition Examination Survey (NHANES) were enrolled. NHANES 1999-2004 and 2011-2014 were separately used as primary and validation subsets (median follow-up 13.5 and 2.8 years, respectively). Circulating MMA was measured with gas chromatography/mass spectrophotometry. Hazard ratios (HR) were estimated using weighted Cox regression models.

RESULTS

During 163,632 person-years of follow-up in NHANES 1999-2004, 3019 deaths occurred. Compared with participants with MMA <120 nmol/L, those with MMA≥250 nmol/L had increased all-cause and cardiovascular mortality in the multivariable-adjusted model [HR(95%CI), 1.62 (1.43-1.84) and 1.66 (1.22-2.27), respectively]. The association was especially significant among participants with normal cobalamin. MMA remained an independent predictor of all-cause mortality occurring whether within 5-year, 5-10 years, or beyond 10-year of follow-up (each p for trend≤0.007). That association was repeatable in NHANES 2011-2014. Moreover, baseline MMA improved reclassification for 10-year mortality in patients with cardiovascular disease (net reclassification index 0.239, integrated discrimination improvement 0.022), overmatched established cardiovascular biomarkers C-reactive protein or homocysteine.

CONCLUSIONS

Circulating level of mitochondrial-derived MMA is strongly associated with elevated all-cause and cardiovascular mortality. Our results support MMA as a surrogate biomarker of mitochondrial dysfunction to predict poor prognosis in adults. The biological mechanisms under cardiovascular disease warrant further investigation.

Reference intervals for serum total vitamin B12 and holotranscobalamin concentrations and their change points with methylmalonic acid concentration to assess vitamin B12 status during early and mid-pregnancy

Background Maternal vitamin B12 (B-12) adequacy is important for maternal health and optimal fetal growth. However, pregnancy-specific cut-offs for B-12 biomarkers are lacking. Methods Reference intervals for serum total B-12, holotranscobalamin (holoTC) and methylmalonic acid (MMA) concentrations were calculated following CLSI EP28-A3c guidelines in 723 pregnant women of European (50%) and South Asian (50%) ethnicity, residing in British Columbia, Canada, at median (range) 11.4 (8.3-13.9) and 16.1 (14.9-20.9) weeks of gestation. Change point analyses described relationships between log serum MMA concentration with serum total B-12 and holoTC concentrations, assuming linear-linear relationships. Results The central 95% reference interval limits indicated that serum total B-12 <89.9 and <84.0 pmol/L, holoTC <29.5 and <26.0 pmol/L and MMA >371 and >374 nmol/L, in the first and second trimesters, respectively, may indicate B-12 deficiency in pregnant women. The lower limits of total B-12 and holoTC and the upper limits of MMA significantly differed by ethnicity in both trimesters. According to the change point analysis, total B-12 <186 and <180 pmol/L and holoTC <62.2 and <67.5 pmol/L in the first and second trimesters, respectively, suggested an increased probability of impaired intracellular B-12 status, with no difference between ethnicities. Conclusions We present novel reference limits and change points for B-12 biomarkers, which may be employed to identify possible B-12 deficiency in women during early and mid-pregnancy. Future research is needed to validate these cut-offs and determine the predictors and functional outcomes associated with impaired B-12 status in ethnically diverse populations.

Older adults with obesity have higher risks of some micronutrient inadequacies and lower overall dietary quality compared to peers with a healthy weight, National Health and Nutrition Examination Surveys (NHANES), 2011-2014

OBJECTIVE

To evaluate total usual intakes and biomarkers of micronutrients, overall dietary quality and related health characteristics of US older adults who were overweight or obese compared with a healthy weight.

DESIGN

Cross-sectional study.

SETTING

Two 24-h dietary recalls, nutritional biomarkers and objective and subjective health characteristic data were analysed from the National Health and Nutrition Examination Survey 2011-2014. We used the National Cancer Institute method to estimate distributions of total usual intakes from foods and dietary supplements for eleven micronutrients of potential concern and the Healthy Eating Index (HEI)-2015 score.

PARTICIPANTS

Older adults aged ≥60 years (n 2969) were categorised by sex and body weight status, using standard BMI categories. Underweight individuals (n 47) were excluded due to small sample size.

RESULTS

A greater percentage of obese older adults compared with their healthy-weight counterparts was at risk of inadequate Mg (both sexes), Ca, vitamin B6 and vitamin D (women only) intakes. The proportion of those with serum 25-hydroxyvitamin D < 40 nmol/l was higher in obese (12 %) than in healthy-weight older women (6 %). Mean overall HEI-2015 scores were 8·6 (men) and 7·1 (women) points lower in obese than in healthy-weight older adults. In addition, compared with healthy-weight counterparts, obese older adults were more likely to self-report fair/poor health, use ≥ 5 medications and have limitations in activities of daily living and cardio-metabolic risk factors; and obese older women were more likely to be food-insecure and have depression.

CONCLUSIONS

Our findings suggest that obesity may coexist with micronutrient inadequacy in older adults, especially among women.

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.

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.

Age-specific reference ranges are needed to interpret serum methylmalonic acid concentrations in the US population

BACKGROUND

Serum vitamin B-12 is measured to evaluate vitamin B-12 status. Serum methylmalonic acid (MMA) is a specific functional indicator of vitamin B-12 status; however, concentrations increase with impaired renal function.

OBJECTIVE

The aim of this study was to describe the distribution of serum vitamin B-12 and MMA in US adults, and estimate age-specific reference intervals for serum MMA in a healthy subpopulation with replete vitamin B-12 status and normal renal function.

METHODS

We examined cross-sectional data for serum vitamin B-12 and MMA in adults participating in the NHANES from 2011 to 2014. Vitamin B-12 was measured by electrochemiluminescence assay and MMA by isotope-dilution liquid chromatography-tandem mass spectrometry.

RESULTS

In both bivariate and multivariate analyses, age, race/Hispanic origin, and vitamin B-12 supplement use were generally significantly associated with serum vitamin B-12 and MMA concentrations. Serum MMA concentrations increased with age, particularly in persons aged ≥70 y. Non-Hispanic white persons had lower vitamin B-12 and higher MMA concentrations than non-Hispanic black persons. Shorter fasting times and impaired renal function were significantly associated with higher serum MMA concentrations, but not with serum vitamin B-12 concentrations after controlling for covariates. The central 95% reference intervals for serum vitamin B-12 and MMA concentrations were widest for persons aged ≥70 y compared with younger age groups. Compared with the overall population, the central 95% reference intervals for serum MMA concentrations were considerably narrower for a vitamin B-12-replete subpopulation with normal renal function, but still age-dependent. Serum vitamin B-12 showed little, whereas serum MMA showed notable, increases with impaired renal function.

CONCLUSIONS

The higher serum MMA concentrations throughout the entire distribution in older persons (especially persons aged ≥70 y) who are vitamin B-12-replete and have normal renal function indicate the need for age-specific MMA reference intervals to better interpret vitamin B-12 status in epidemiologic research.

Monitoring Vitamin B12 in Women Treated with Metformin for Primary Prevention of Breast Cancer and Age-Related Chronic Diseases

Metformin (MET) is currently being used in several trials for cancer prevention or treatment in non-diabetics. However, long-term MET use in diabetics is associated with lower serum levels of total vitamin B₁₂. In a pilot randomized controlled trial of the Mediterranean diet (MedDiet) and MET, whose participants were characterized by different components of metabolic syndrome, we tested the effect of MET on serum levels of B₁₂, holo transcobalamin II (holo-TC-II), and methylmalonic acid (MMA). The study was conducted on 165 women receiving MET or placebo for three years. Results of the study indicate a significant overall reduction in both serum total B₁₂ and holo-TC-II levels according with MET-treatment. In particular, in the MET group 26 of 81 patients and 10 of the 84 placebo-treated subjects had B₁₂ below the normal threshold (<221 pmol/L) at the end of the study. Considering jointly all B₁₂, Holo-TC-II, and MMA, 13 of the 165 subjects (10 MET and 3 placebo-treated) had at least two deficits in the biochemical parameters at the end of the study, without reporting clinical signs. Although our results do not affect whether women remain in the trial, B₁₂ monitoring for MET-treated individuals should be implemented.

Homocysteine Metabolism in Children and Adolescents: Influence of Age on Plasma Biomarkers and Correspondent Genotype Interactions

Background: Imbalance of homocysteine (Hcy) metabolism links with several pathologies; nevertheless, it is poorly characterized in pediatric populations. This study investigated the impact of age on plasma concentrations of Hcy and relevant biomarkers along with correspondent genotype interactions. Methods: A healthy pediatric cohort aged 9 (n = 195) and 17 (n = 128) years old (yo) was studied. Immunoassays and GC-MS-SIM-mode quantified plasma levels of Hcy and biomarkers. PCR-RFLP or quantitative-PCR assays assessed common variations in related genes. Results: Age impacted on levels of Hcy and metabolic markers: older children presented with the lowest folates and total-cobalamin (tCbl), while with the highest Hcy concentrations, whereas methylmalonic acid (MMA) and holotranscobalamin (Holo-TC) levels remained similar in 9-yo and 17-yo children. The relationships between B-vitamins and metabolic markers were also dependent on age. Only in the older children, MMA correlated with tCbl and Holo-TC, and MMA levels were markedly higher in the 17-yo subjects presenting with the lowest quartiles of Holo-TC concentrations. Lastly, age also impacted on the correlations between genotype and biomarkers. In the 17-yo group, however not in the 9-yo children, tHcy differed between MTHFR 677 genotypes, with subjects who had the MTHFR 677TT genotype displaying the highest tHcy concentrations. Conclusions: Age impacts on the Hcy metabolism dynamics in a pediatric population.

Vitamin B 12 deficiency and hyperhomocysteinaemia in outpatients with stroke or transient ischaemic attack: a cohort study at an academic medical centre

OBJECTIVE

We sought to assess the current magnitude of the opportunity for secondary stroke prevention with B vitamins.

DESIGN

A cohort study.

SETTING

The Urgent TIA (Transient Ischaemic Attack) Clinic at an academic medical centre.

MAIN OUTCOME MEASURES

We assessed the prevalence of biochemical vitamin B12 deficiency (B12Def, serum B12 <156 pmol/L), hyperhomocysteinaemia (HHcy; plasma total homocysteine [tHcy] >14 µmol/L) and metabolic B12 deficiency (MetB12Def, serum B12 <258 pmol/L and HHcy) between 2002 and 2017, by age group and by stroke subtype.

RESULTS

Data were available in 4055 patients. B12Def was present in 8.2% of patients overall; it declined from 10.9% of patients referred before 2009 to 5.4% thereafter (p=0.0001). MetB12Def was present in 10.6% of patients, and HHcy was present in 19.1% of patients. Among the patients aged ≥80 years, MetB12Def was present in 18.1% and HHcy in 35%. Among the 3410 patients whose stroke subtype was determined, HHcy was present in 18.4% of patients: 23.3% of large artery atherosclerosis, 18.1% of cardioembolic, 16.3% of small vessel disease, 10.8% of other unusual aetiologies and 13.6% of undetermined subtypes (p=0.0001).

CONCLUSIONS

Despite a decline in our referral area since 2009, B12Def, MetB12Def and HHcy remain common in patients with stroke/TIA. Because these conditions are easily treated and have serious consequences, all patients with stroke/TIA should have their serum B12 and tHcy measured.

Intakes of Vitamin B-12 from Dairy Food, Meat, and Fish and Shellfish Are Independently and Positively Associated with Vitamin B-12 Biomarker Status in Pregnant Dutch Women

Background

The effect of vitamin B-12 from different animal foods on vitamin B-12 biomarker status has not previously been evaluated in pregnant women.

Objective

We examined the association of vitamin B-12 intake from dairy, meat, fish (including shellfish), and eggs with circulating concentrations of vitamin B-12 biomarkers and with the presence of vitamin B-12 deficiency in 1266 pregnant women participating in the KOALA Birth Cohort Study.

Methods

Blood samples were collected in weeks 34-36 of pregnancy, and vitamin B-12 intake from foods and supplements was estimated with a semiquantitative food-frequency questionnaire (FFQ). Total vitamin B-12, holotranscobalamin (holoTC), and methylmalonic acid (MMA) were determined in plasma. Vitamin B-12 deficiency was defined as holoTC <35 pmol/L and MMA >0.45 μmol/L. Associations were evaluated with linear and logistic regression analyses, adjusting for potential confounders.

Results

Significant dose-response relations were observed between vitamin B-12 intake from dairy, meat, and fish and plasma vitamin B-12, holoTC, and MMA [P-trend for (shell)fish with MMA = 0.002; P-trend for dairy, meat, and fish with all other markers < 0.001]. The OR (95% CI) of vitamin B-12 deficiency in the third compared with the first tertile of dairy-derived vitamin B-12 was 0.13 (0.04, 0.49), and the ORs for vitamin B-12 from meat and fish were 0.33 (0.11, 0.97) and 0.25 (0.08, 0.82), respectively. Egg-derived vitamin B-12 was only associated with holoTC. Additional analyses showed that self-defined vegetarians and FFQ-defined lacto-ovo-vegetarians had lower median total dietary vitamin B-12 intake and considerably worse vitamin B-12 biomarker status than omnivores and pescatarians.

Conclusions

In pregnant Dutch women, higher intakes of vitamin B-12 from dairy, meat, and fish were positively associated with vitamin B-12 status, suggesting that dairy, meat, and fish are good sources of bioactive vitamin B-12 in pregnancy. Nevertheless, for (lacto-)vegetarians, vitamin B-12 supplementation is recommended.

Intakes, Adequacy, and Biomarker Status of Iron, Folate, and Vitamin B12 in Māori and Non-Māori Octogenarians: Life and Living in Advanced Age: A Cohort Study in New Zealand (LiLACS NZ)

Advanced-age adults may be at risk of iron, folate, and vitamin B₁₂ deficiency due to low food intake and poor absorption. This study aimed to investigate the intake and adequacy of iron, folate, and vitamin B₁₂ and their relationship with respective biomarker status. Face-to-face interviews with 216 Māori and 362 non-Māori included a detailed dietary assessment using 2 × 24-h multiple pass recalls. Serum ferritin, serum iron, total iron binding capacity, transferrin saturation, red blood cell folate, serum folate, serum vitamin B₁₂ and hemoglobin were available at baseline. Regression techniques were used to estimate the association between dietary intake and biomarkers. The Estimated Average Requirement (EAR) was met by most participants (>88%) for dietary iron and vitamin B₁₂ (>74%) but less than half (>42%) for folate. Increased dietary folate intake was associated with increased red blood cell (RBC) folate for Māori (p = 0.001), non-Māori (p = 0.014) and serum folate for Māori (p < 0.001). Folate intake >215 µg/day was associated with reduced risk of deficiency in RBC folate for Māori (p = 0.001). Strategies are needed to optimize the intake and bioavailability of foods rich in folate. There were no significant associations between dietary iron and vitamin B₁₂ intake and their respective biomarkers, serum iron and serum vitamin B₁₂.

Improved testing for vitamin B12 deficiency: correcting MMA for eGFR reduces the number of patients classified as vitamin B12 deficient

Background Methylmalonic acid (MMA) can detect functional vitamin B₁₂ deficiencies as it accumulates early when intracellular deficits arise. However, impaired clearance of MMA from blood due to decreased glomerular filtration rate (eGFR) also results in elevated plasma MMA concentrations. Alternative to clinical trials, a data mining approach was chosen to quantify and compensate for the effect of decreased eGFR on MMA concentration. Methods Comprehensive data on patient's vitamin B₁₂, eGFR and MMA concentrations were collected ( n = 2906). The relationship between vitamin B₁₂, renal function (eGFR) and MMA was modelled using weighted multiple linear regression. The obtained model was used to estimate the influence of decreased eGFR on MMA. Clinical impact was examined by comparing the number of patients labelled vitamin B₁₂ deficient with and without adjustment in MMA. Results Adjusting measured MMA concentrations for eGFR in the group of patients with low-normal vitamin B₁₂ concentrations (90-300 pmol/L) showed that the use of unadjusted MMA concentrations overestimates vitamin B₁₂ deficiency by 40%. Conclusions Through a data mining approach, the influence of eGFR on the relation between MMA and vitamin B₁₂ can be quantified and used to correct the measured MMA concentration for decreased eGFR. Especially in the elderly, eGFR-based correction of MMA may prevent over-diagnosis of vitamin B₁₂ deficiency and corresponding treatment.

Cardioembolic stroke: everything has changed

Historically, because of the difficulty of using warfarin safely and effectively, many patients with cardioembolic stroke who should have been anticoagulated were instead given ineffective antiplatelet therapy (or no antithrombotic therapy). With the arrival of new oral anticoagulants that are not significantly more likely than aspirin to cause severe haemorrhage, everything has changed. Because antiplatelet agents are much less effective in preventing cardioembolic stroke, it is now more prudent to anticoagulate patients in whom cardioembolic stroke is strongly suspected. Recent advances include the recognition that intermittent atrial fibrillation is better detected with more prolonged monitoring of the cardiac rhythm, and that percutaneous closure of patent foramen ovale (PFO) may reduce the risk of stroke. However, because in most patients with stroke and PFO the PFO is incidental, this should be reserved for patients in whom paradoxical embolism is likely. A high shunt grade on transcranial Doppler saline studies, and clinical clues to paradoxical embolism, can help in appropriate selection of patients for percutaneous closure. For patients with atrial fibrillation who cannot be anticoagulated, ablation of the left atrial appendage is an emerging option. It is also increasingly recognised that high levels of homocysteine, often due to undiagnosed metabolic deficiency of vitamin B12, markedly increase the risk of stroke in atrial fibrillation, and that B vitamins (folic acid and B12) do prevent stroke by lowering homocysteine. However, with regard to B12, methylcobalamin should probably be used instead of cyanocobalamin. Many important considerations for judicious application of therapies to prevent cardioembolic stroke are discussed.

Vitamin B12

The biosynthesis of B₁₂, involving up to 30 different enzyme-mediated steps, only occurs in bacteria. Thus, most eukaryotes require an external source of B₁₂, and yet the vitamin appears to have only two functions in eukaryotes: as a cofactor for the enzymes methionine synthase and methylmalonylCoA mutase. These two functions are crucial for normal health in humans, and in particular, the formation of methionine is essential for providing methyl groups for over 100 methylation processes. Interference with the methionine synthase reaction not only depletes the body of methyl groups but also leads to the accumulation of homocysteine, a risk factor for many diseases. The syndrome pernicious anemia, characterized by lack of intrinsic factor, leads to a severe, sometimes fatal form of B₁₂ deficiency. However, there is no sharp cutoff for B₁₂ deficiency; rather, there is a continuous inverse relationship between serum B₁₂ and a variety of undesirable outcomes, including neural tube defects, stroke, and dementia. The brain is particularly vulnerable; in children, inadequate B₁₂ stunts brain and intellectual development. Suboptimal B₁₂ status (serum B₁₂<300pmol/L) is very common, occurring in 30%-60% of the population, in particular in pregnant women and in less-developed countries. Thus, many tens of millions of people in the world may suffer harm from having a poor B₁₂ status. Public health steps are urgently needed to correct this inadequacy.

Vitamin B12 deficiency and impaired expression of amnionless during aging

BACKGROUND

Physical frailty and loss of mobility in elderly individuals lead to reduced independence, quality of life, and increased mortality. Vitamin B12 deficiency has been linked to several age-related chronic diseases, including in the musculo-skeletal system, where vitamin B12 deficiency is generally believed to be linked to poor nutritional intake. In the present study, we asked whether aging and frailty associate with altered vitamin B12 homeostasis in humans and investigated the underlying molecular mechanisms using preclinical models.

METHODS

We analysed a subset of the Singapore Longitudinal Aging Study and stratified 238 participants based on age and Fried frailty criteria. Levels of methyl-malonic acid (MMA), a marker for vitamin B12 deficiency, and amnionless, the vitamin B12 co-receptor that anchors the vitamin B12 transport complex to the membrane of epithelial cells, were measured in plasma. In addition, vitamin B12 levels and the molecular mechanisms of vitamin B12 uptake and excretion were analysed in ileum, kidney, liver, and blood using a rat model of natural aging where nutritional intake is fully controlled.

RESULTS

We demonstrate that aging and frailty are associated with a higher prevalence of functional vitamin B12 deficiency that can be detected by increased levels of MMA in blood (ρ = 0.25; P = 0.00013). The decline in circulating vitamin B12 levels is recapitulated in a rat model of natural aging where food composition and intake are stable. At the molecular level, these perturbations involve altered expression of amnionless in the ileum and kidney. Interestingly, we demonstrate that amnionless can be detected in serum where its levels increase during aging in both rodents and human (P = 3.3e-07 and 9.2e-07, respectively). Blood amnionless levels negatively correlate with vitamin B12 in rats (r²  = 0.305; P = 0.0042) and positively correlate with the vitamin B12 deficiency marker MMA in humans (ρ = 0.22; P = 0.00068).

CONCLUSIONS

Our results demonstrate that aging and frailty cause intrinsic vitamin B12 deficiencies, which can occur independently of nutritional intake. Mechanistically, vitamin B12 deficiency involves the physio-pathological decline of both the intestinal uptake and the renal reabsorption system for vitamin B12. Finally, amnionless is a novel biomarker which can detect perturbed vitamin B12 bioavailability during aging and physical frailty.

The FUT2 secretor variant p.Trp154Ter influences serum vitamin B12 concentration via holo-haptocorrin, but not holo-transcobalamin, and is associated with haptocorrin glycosylation

Vitamin B12 deficiency is common in older individuals. Circulating vitamin B12 concentration can be used to diagnose deficiency, but this test has substantial false positive and false negative rates. We conducted genome-wide association studies (GWAS) in which we resolved total serum vitamin B12 into the fractions bound to transcobalamin and haptocorrin: two carrier proteins with very different biological properties. We replicated reported associations between total circulating vitamin B12 concentrations and a common null variant in FUT2. This allele determines the secretor phenotype in which blood group antigens are found in non-blood body fluids. Vitamin B12 bound to haptocorrin (holoHC) remained highly associated with FUT2 rs601338 (p.Trp154Ter). Transcobalamin bound vitamin B12 (holoTC) was not influenced by this variant. HoloTC is the bioactive the form of the vitamin and is taken up by all tissues. In contrast, holoHC is only taken up by the liver. Using holoHC from individuals with known FUT2 genotypes, we demonstrated that FUT2 rs601338 genotype influences the glycosylation of haptocorrin. We then developed an experimental model demonstrating that holoHC is transported into cultured hepatic cells (HepG2) via the asialoglycoprotein receptor (ASGR). Our data challenge current published hypotheses on the influence of genetic variation on this clinically important measure and are consistent with a model in which FUT2 rs601338 influences holoHC by altering haptocorrin glycosylation, whereas B12 bound to non-glycosylated transcobalamin (i.e. holoTC) is not affected. Our findings explain some of the observed disparity between use of total B12 or holoTC as first-line clinical tests of vitamin B12 status.

Recent advances in preventing stroke recurrence

Recent advances in secondary stroke prevention include new evidence in hypertension, nutrition, anticoagulation, antiplatelet therapy, intracranial stenosis, percutaneous closure of patent foramen ovale, and lipid-lowering therapy. Individualized therapy for hypertension based on phenotyping with plasma renin and aldosterone markedly improves blood pressure control in patients with resistant hypertension. A Mediterranean diet can reduce the risk of stroke by nearly half. The diagnosis and treatment of metabolic vitamin B12 deficiency, and B vitamins to lower homocysteine, can reduce the risk of stroke by approximately 30%. There are problems with clopidogrel that can be overcome by using ticagrelor, and new anticoagulant drugs markedly improve anticoagulation for stroke prevention, particularly in atrial fibrillation. There are pharmacokinetic problems with dabigatran that deserve attention. Intensive medical therapy is better than stenting for intracranial stenosis, and new therapies directed at proprotein convertase subtilisin–kexin type 9 (PCSK9) will revolutionize lipid-lowering therapy. In the past, it was estimated that rational therapy could reduce recurrent stroke by about 80%. With recent advances, we should be able to do even better.

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.

South Asian Ethnicity Is Related to the Highest Risk of Vitamin B12 Deficiency in Pregnant Canadian Women

Vitamin B12 (B12) adequacy during pregnancy is crucial for maternal health and optimal fetal development; however, suboptimal B12 status has been reported in pregnant Canadian women. Methylmalonic acid (MMA) is a sensitive indicator of B12 status. Since few studies have measured MMA during pregnancy in Canadian women, the objective of this study was to evaluate B12 status in pregnant women living in Metro Vancouver, using both plasma total B12 and MMA. We recruited a convenience sample of 320 pregnant women between 20 and 35 gestational weeks from local healthcare facilities. Plasma total B12 concentrations indicative of deficiency (<148 pmol/L) and suboptimal B12 status (148–220 pmol/L) were found in 18% and 33% of the women, respectively. Normal plasma MMA concentration (<210 nmol/L) was observed in 82% of all women. Gestational age was a strong predictor of plasma total B12 and MMA concentration, and South Asian ethnicity of B-12 deficiency and MMA concentrations. Overall, there was a high discrepancy between the prevalence of B12 inadequacy depending on the biomarker used. Independently, however, South Asian women were at particular risk for B12 deficiency, likely due to lower animal source food intake. Further study of this vulnerable group and performance testing of B12 biomarkers is warranted.

Sensory Neuronopathy Revealing Severe Vitamin B12 Deficiency in a Patient with Anorexia Nervosa: An Often-Forgotten Reversible Cause

Vitamin B12 (B12) deficiency is known to be associated with various neurological manifestations. Although central manifestations such as dementia or subacute combined degeneration are the most classic, neurological manifestations also include sensory neuropathies. However, B12 deficiency is still rarely integrated as a potential cause of sensory neuronopathy. Moreover, as many medical conditions can falsely normalize serum B12 levels even in the context of a real B12 deficiency, some cases may easily remain underdiagnosed. We report the illustrating case of an anorexic patient with sensory neuronopathy and consistently normal serum B12 levels. After all classical causes of sensory neuronopathy were ruled out, her clinical and electrophysiological conditions first worsened after folate administration, but finally improved dramatically after B12 administration. B12 deficiency should be systematically part of the etiologic workup of sensory neuronopathy, especially in a high risk context such as anorexia nervosa.

Vitamin B12 Intake and Related Biomarkers: Associations in a Dutch Elderly Population

BACKGROUND

Vitamin B12 status is measured by four plasma/ serum biomarkers: total vitamin B12 (total B12), holotranscobalamin (holoTC), methylmalonic acid (MMA) and homocysteine (tHcy). Associations of B12 intake with holoTC and tHcy and associations between all four biomarkers have not been extensively studied. A better insight in these associations may contribute to an improved differentiation between vitamin B12 deficiency and a normal vitamin B12 status.

OBJECTIVE

This study investigates associations between vitamin B12 intake and biomarkers and associations between biomarkers.

DESIGN

In this cross-sectional observational study, levels of total B12, HoloTC, MMA and tHcy were determined in participants of the B-PROOF study: 2919 elderly people (≥65 years, with a mean age of 74.1 years, a mean BMI of 27.1 and 50% women) with elevated tHcy levels (≥12 µmol/L). B12 intake was assessed in a subsample. We assessed the association between intake and status with multivariate regression analysis. We explored the dose-response association between B12 intake and biomarkers and the association of total B12 and holoTC with tHcy and MMA with restricted cubic spline plots.

RESULTS

A doubling of B12 intake was associated with 9% higher total B12, 15% higher HoloTC, 9% lower MMA and 2% lower tHcy. Saturation of biomarkers occurs with dietary intakes of >5 μg B12. Spline regression showed that levels of MMA and tHcy started to rise when vitamin B12 levels fall below 330 pmol/L and with HoloTC levels below 100 pmol/L, with a sharp increase with levels of B12 and HoloTC below 220 and 50 pmol/L respectively.

CONCLUSIONS

In this study we observed a significant association between vitamin B12 intake and vitamin B12 biomarkers and between the biomarkers. The observed inflections for total B12 and holoTC with MMA and tHcy could indicate cut-off levels for further testing for B12 deficiency and determining subclinical B12 deficiency.

Intakes of Folate and Vitamin B12 and Biomarkers of Status in the Very Old: The Newcastle 85+ Study

Very old adults are at increased risk of folate and vitamin B12 deficiencies due to reduced food intake and gastrointestinal absorption. The main aim was to determine the association between folate and vitamin B12 intake from total diets and food groups, and status. Folate or vitamin B12 intakes (2 × 24 h multiple pass recalls) and red blood cell (RBC) folate or plasma vitamin B12 (chemiluminescence immunoassays) concentrations were available at baseline for 731 participants aged 85 from the Newcastle 85+ Study (North-East England). Generalized additive and binary logistic models estimated the associations between folate and vitamin B12 intakes from total diets and food groups, and RBC folate and plasma B12. Folate intake from total diets and cereal and cereal products was strongly associated with RBC folate (p < 0.001). Total vitamin B12 intake was weakly associated with plasma vitamin B12 (p = 0.054) but those with higher intakes from total diets or meat and meat products were less likely to have deficient status. Women homozygous for the FUT2 G allele had higher concentrations of plasma vitamin B12. Cereals and cereal products are a very important source of folate in the very old. Higher intakes of folate and vitamin B12 lower the risk of "inadequate" status.

Effect of multi-nutrient insufficiency on markers of one carbon metabolism in young women: response to a methionine load

BACKGROUND/OBJECTIVES

Multi-nutrient insufficiencies as a consequence of nutritional and economic factors are common in India and other developing countries. We have examined the impact of multi-nutrient insufficiency on markers of one carbon (1C) metabolism in the blood, and response to a methionine load in clinically healthy young women.

SUBJECTS/METHODS

Young women from Pune, India (n=10) and Cleveland, USA (n=13) were studied. Blood samples were obtained in the basal state and following an oral methionine load (50 mg/kg of body weight in orange juice). Plasma concentrations of vitamin B12, folate and B6 were measured in the basal state. The effect of methionine load on the levels of methionine, total homocysteine, cysteine, glutathione and amino acids was examined.

RESULTS

Indian women were significantly shorter and lighter compared with the American women and had lower plasma concentration of vitamins B12, folate and B6, essential amino acids and glutathione, but higher concentration of total homocysteine. The homocysteine response to methionine load was higher in Indian women. The plasma concentrations of glycine and serine increased in the Indian women after methionine (in juice) load. A significant negative correlation between plasma B6 and homocysteine (r= -0.70), and plasma folate and glycine and serine levels were observed in the Indian group (P<0.05) but not in the American group.

CONCLUSIONS

Multi-nutrient insufficiency in the Indian women caused unique changes in markers of whole body protein and 1C metabolism. These data would be useful in developing nutrient intervention strategies.

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 Common Polymorphism in HIBCH Influences Methylmalonic Acid Concentrations in Blood Independently of Cobalamin

Methylmalonic acid (MMA) is a by-product of propionic acid metabolism through the vitamin B12 (cobalamin)-dependent enzyme methylmalonyl CoA mutase. Elevated MMA concentrations are a hallmark of several inborn errors of metabolism and indicators of cobalamin deficiency in older persons. In a genome-wide analysis of 2,210 healthy young Irish adults (median age 22 years) we identified a strong association of plasma MMA with SNPs in 3-hydroxyisobutyryl-CoA hydrolase (HIBCH, p = 8.42 × 10(-89)) and acyl-CoA synthetase family member 3 (ACSF3, p = 3.48 × 10(-19)). These loci accounted for 12% of the variance in MMA concentration. The most strongly associated SNP (HIBCH rs291466; c:2T>C) causes a missense change of the initiator methionine codon (minor-allele frequency = 0.43) to threonine. Surprisingly, the resulting variant, p.Met1?, is associated with increased expression of HIBCH mRNA and encoded protein. These homozygotes had, on average, 46% higher MMA concentrations than methionine-encoding homozygotes in young adults with generally low MMA concentrations (0.17 [0.14-0.21] μmol/L; median [25(th)-75(th) quartile]). The association between MMA levels and HIBCH rs291466 was highly significant in a replication cohort of 1,481 older individuals (median age 79 years) with elevated plasma MMA concentrations (0.34 [0.24-0.51] μmol/L; p = 4.0 × 10(-26)). In a longitudinal study of 185 pregnant women and their newborns, the association of this SNP remained significant across the gestational trimesters and in newborns. HIBCH is unique to valine catabolism. Studies evaluating flux through the valine catabolic pathway in humans should account for these variants. Furthermore, this SNP could help resolve equivocal clinical tests where plasma MMA values have been used to diagnose cobalamin deficiency.

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.

Advances in clinical determinants and neurological manifestations of B vitamin deficiency in adults

B vitamin deficiency is a leading cause of neurological impairment and disability throughout the world. Multiple B vitamin deficiencies often coexist, and thus an understanding of the complex relationships between the different biochemical pathways regulated in the brain by these vitamins may facilitate prompter diagnosis and improved treatment. Particular populations at risk for multiple B vitamin deficiencies include the elderly, people with alcoholism, patients with heart failure, patients with recent obesity surgery, and vegetarians/vegans. Recently, new clinical settings that predispose individuals to B vitamin deficiency have been highlighted. Moreover, other data indicate a possible pathogenetic role of subclinical chronic B vitamin deficiency in neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. In light of these findings, this review examines the clinical manifestations of B vitamin deficiency and the effect of B vitamin deficiency on the adult nervous system. The interrelationships of multiple B vitamin deficiencies are emphasized, along with the clinical phenotypes related to B vitamin deficiencies. Recent advances in the clinical determinants and diagnostic clues of B vitamin deficiency, as well as the suggested therapies for B vitamin disorders, are described.

Vitamin B12 concentrations in pregnant Colombian women: analysis of nationwide data 2010

Background

Vitamin B12 deficiency is associated with many adverse health outcomes and is highly prevalent worldwide. The present study assesses the prevalence and socio-demographic factors associated with vitamin B12 deficiency in a representative sample of pregnant women in Colombia.

Method

We used data from the cross-sectional, nationally representative survey (ENSIN, 2010). A total of 1.781, (13–49 years old) pregnant women were enrolled. Serum Vitamin B12 a concentration was determined by chemiluminescence and sociodemographic date was assessed by computer-assisted personal interview technology. Multivariate analyses using unordered multinomial logistic regression models were conducted in the main analysis.

Results

Vitamin B12 concentrations ranged from 45 to 1000 pg/mL (mean 299.2 pg/mL, 95 % CI 290.6 to 303.7 pg/mL). A total of 18.6 % of pregnant women had vitamin B12 concentrations below 200 pg/mL and 41.3 % had concentrations between 200 and 300 pg/mL. Being of indigenous ethnicity, living in the east and living in a rural area showed the lowest mean values (273.2 pg/mL, 270.8 pg/mL and 290.1 pg/mL, respectively). The multivariate logistic regression shows that pregnant women belonging to the indigenous ethnic group OR 2.2, (95 % CI 1.1 to 4.3), living in the pacific region (west) OR 4.4, (95 % CI 2.8 to 6.9), or national territories (south) OR 2.3, (95 % CI 1.4 to 3.7) were associated with a higher probability of serum vitamin B12 deficiency.

Conclusion

The prevalence of vitamin B12 deficiency in Colombian pregnant women is substantial. Factors associated with depletion among pregnant women should be considered for future interventions in countries experiencing nutritional transition.