Diabetes as a cause of clinically significant functional cobalamin deficiency

Prevalence of Functional Cobalamin Deficiency and Relevant Mortality Risk in the General Population: An Unheeded Phenotype Distinct from Cobalamin Deficiency

BACKGROUND

Current guidelines prioritize monitoring and managing cobalamin (Cbl) deficiency but insufficiently address the issue of functional Cbl deficiency (decreased Cbl sensitivity). This study aims to investigate the prevalence burden of functional Cbl deficiency and to examine its prospective association with mortality risk, compared to Cbl deficiency, among United States (US) adults.

METHOD

The cohort study included 22,513 US participants aged ≥20 years from 1999 to 2014 and was followed up through December 31, 2019. Cbl sensitivity was assessed using a combination of binary classifications for Cbl and methylmalonic acid (MMA) levels, with cutoff values set at 400 pg/mL for Cbl and 250 nmol/L for MMA. Functional Cbl deficiency was defined as elevated MMA and Cbl levels. Serum Cbl levels <148 pmol/L (200 pg/mL) were classified as Cbl deficiency.

RESULTS

In this study, approximately 2.1% of US adults had Cbl deficiency, while the age-adjusted prevalence of functional Cbl deficiency was 4.5%, corresponding to an estimated 10 million US adults. Over a median follow-up period of 10.7 years, there were 4636 recorded deaths. Compared to the MMAlowCbllow group (MMA ≤250 nmol/L, Cbl ≤400 pg/mL), the multivariable-adjusted hazard ratios for all-cause, cardiovascular, and cancer-related mortality in the MMAhighCblhigh group were 1.76 (95% confidence interval [CI]: 1.53-2.02, p < 0.001), 2.17 (95% CI: 1.78-2.67, p < 0.001), and 1.38 (95% CI: 0.95-2.00, p = 0.089). In contrast, the mortality risk associated with Cbl deficiency became insignificant after adjusting for similar confounders. While Cbl supplementation or dietary intake above recommended levels might alleviate Cbl deficiency, they do not appear to reduce the prevalence of functional Cbl deficiency or its associated mortality risk.

CONCLUSION

Compared with Cbl deficiency, functional Cbl deficiency is more frequent and is significantly associated with increased mortality risk in the general population.

The independent and joint associations of vitamin B12 and methylmalonic acid on the risk of mortality in individuals with metabolic dysfunction-associated steatotic liver disease

PURPOSE

To investigate the independent and joint associations of vitamin B12 and methylmalonic acid (MMA) with all-cause, cardiovascular disease (CVD), and cancer mortality in patients with metabolic dysfunction-associated steatotic liver disease (MASLD).

METHODS

We included 6797 individuals with MASLD from the U.S. National Health and Nutrition Examination Survey. Serum MMA was measured using gas/liquid chromatography-mass spectrometry. Serum vitamin B12 was measured using commercial kits. The separate and joint associations of dietary intake and serum vitamin B12 (cutoff: 400 pg/mL) and MMA (cutoff: 250 nmol/L) levels with mortality were assessed by Cox proportional hazards regression.

RESULTS

During a median follow-up of 9.3 years, 1604 deaths were documented, including 438 from CVD and 365 from cancer. In MASLD patients, dietary intake and serum vitamin B12 did not associate with mortality, while MMA was associated with a 1.35-fold increased risk of all-cause mortality (P-trend < 0.001). The adjusted hazard ratios for the joint association of vitamin B12 and MMA with all-cause and CVD mortality were 1 in the B12lowMMAlow group (reference), 1.02 (0.87-1.20) and 1.15 (0.90-1.47) in the B12highMMAlow group, 1.55 (1.29-1.86) and 1.84 (1.28-2.65) in the B12lowMMAhigh group, and 1.82 (1.49-2.21) and 2.28 (1.40-3.71) in the B12highMMAhigh group, respectively. The joint association was modified by serum folate (P-interaction = 0.001).

CONCLUSIONS

In MASLD patients, MMA rather than dietary and serum vitamin B12 was positively associated with all-cause mortality. The joint effect of high levels of MMA and vitamin B12 showed the strongest associations with all-cause and CVD mortality, with a significant interaction with serum folate.

Decreased cobalamin sensitivity and biological aging acceleration in the general population

BACKGROUND

The evidence on the association between cobalamin (Cbl) and aging or relevant outcomes is limited and controversial. We aimed to investigate the relationships between cobalamin intake- and function-related biomarkers and biological aging.

METHODS

The study encompassed 22,812 participants aged 20 years and older from the National Health and Nutrition Examination Survey. A panel of biomarkers or algorithms was used to assess biological aging, including Klemera-Doubal Age Acceleration (KDMAccel), Phenotypic age acceleration (PhenoAgeAccel), telomere length, α-Klotho, and PhenoAge advancement. Weighted generalized linear regression analysis was used to assess the associations between cobalamin-intake biomarkers (serum cobalamin, cobalamin intake from food, cobalamin supplement use, serum methylmalonic acid [MMA], and homocysteine [Hcy]) and function-related biomarkers (functional cobalamin deficiency and cobalamin insensitivity index).

RESULTS

Among the 22,812 individuals, the weighted mean (SE) age was 48.3 (0.2) years and 48.0% were males. Unexpectedly, serum and dietary cobalamin as well as serum MMA and Hcy levels were positively associated with most indicators of biological aging. Cobalamin sensitivity was assessed by the combination of binary Cbllow/high and MMAlow/high or Hcylow/high (cutoff values: 400 pg/mL for cobalamin, 250 nmol/L for MMA, and 12.1 μmol/l for Hcy) and a newly constructed cobalamin insensitivity index (based on the multiplicative term of serum cobalamin and serum MMA or Hcy). The multivariable-adjusted β (95%CIs) of KDMAccel in the MMAlowCbllow, MMAlowCblhigh, MMAhighCbllow, and MMAhighCblhigh groups were reference, 0.27 (0.03 to 0.51), 0.85 (0.41 to 1.29), and 7.97 years (5.77 to 10.17) respectively, which were consistent for the combination of serum Hcy and cobalamin. Both cobalamin insensitivity indices were robustly associated with biological aging acceleration in a dose-response pattern (each p < 0.001).

CONCLUSIONS

Decreased cobalamin sensitivity but not cobalamin insufficiency might be associated with biological aging acceleration. Further studies would improve understanding of the underlying mechanisms between decreased cobalamin sensitivity and biological aging acceleration.

The association between serum methylmalonic acid, cobalamin-related biomarkers, and long-term mortality risk in cancer survivors: a prospective cohort study

BACKGROUND

Elevated serum methylmalonic acid (MMA), a marker of cobalamin (vitamin B12) deficiency, has been linked to cancer progression. However, the impact of MMA or cobalamin on mortality risk in cancer survivors remains unknown.

OBJECTIVES

To explore the relationship between MMA, serum, dietary, and supplement of cobalamin, MMA metabolism-related genes, and poor prognosis in adult cancer survivors.

METHODS

We analyzed data from 1988 cancer survivors aged ≥20 y. Patients were selected from the National Health and Nutrition Examination Survey and followed up until December 31, 2019. Weighted Cox proportional hazard regression was used to estimate hazard ratios (HRs) and the corresponding 95% confidence intervals (CIs) for mortality risk assessment. Genomic analysis identified MMA metabolism-related genes linked to early death in a 33-cancer-type cohort from The Cancer Genome Atlas.

RESULTS

Among 1988 participants, 872 deaths occurred over a 10-year follow-up. Higher serum MMA levels were significantly linked to increased long-term mortality risk (tertile 3 compared with tertile 1: adjusted HR: 1.37; 95% CI: 1.11, 1.70; P-trend < 0.001). No associations were found between serum, dietary, and supplement of cobalamin and cancer survivor mortality (each P-trend > 0.143). However, MMA-associated mortality was notable in patients without deficiency. When combining cobalamin and MMA categories, multivariate-adjusted HR (95% CI) for all-cause mortality was 2.06 (95% CI: 1.60, 2.65) in participants with >250 nmol/L and cobalamin >295.1 pmol/L compared with those with MMA ≤250 nmol/L and cobalamin >295.1 pmol/L. Moreover, reduced transcriptional levels of MMA metabolism-related genes, indicating decreased mitochondrial MMA metabolism capability, are linked to an unfavorable prognosis in certain cancer types.

CONCLUSIONS

Serum MMA was associated with long-term mortality risk in adult cancer survivors, which was more significant among individuals with higher levels of serum cobalamin. These findings suggest that mortality related to MMA was attributed to the insufficient flux of MMA metabolism, not cobalamin deficiency.

Methylmalonic acid, vitamin B12, and mortality risk in patients with preexisting coronary heart disease: a prospective cohort study

BACKGROUND

The inconsistent relationship between Vitamin B12 (B12), methylmalonic acid (MMA, marker of B12 deficiency) and mortality was poorly understood, especially in patients with coronary heart disease (CHD). This study aims to investigate the association of serum MMA, and B12-related biomarkers (serum level, dietary intake, supplement use, and sensibility to B12) with all-cause and cardiovascular mortality in adults with CHD.

METHODS

The data of this study were from a subcohort within the US National Health and Nutrition Examination Survey (NHANES). We included adults with preexisting CHD with serum MMA and B12, and dietary B12 intake measurements at recruitment. All participants were followed up until 31 December 2019. Weighted Cox proportional hazard regression was used to estimate hazard ratios (HR) and 95% CI of mortality risk.

RESULTS

Overall, 1755 individuals (weighted mean [SE] age, 65.2 [0.5] years; 1047 men [weighted 58.5%]) with CHD were included, with geometric mean levels of serum MMA 182.4 nmol/L, serum B12 494.5 pg/ml, and dietary B12 intake 4.42 mg/day, and percentage of B12 supplements use 39.1%. During a median follow-up of 7.92 years, 980 patients died. Serum B12 concentration, dietary B12 intake and supplements use were not significantly associated with mortality risk (each p ≥ 0.388). In contrast, individuals in the top tertile of MMA had multivariable-adjusted HRs (95% CIs) of 1.70 (1.31-2.20) for all-cause mortality, and 2.00 (1.39-2.89) for cardiovascular mortality (both p trend < 0.001) compared to those in the bottom tertile of MMA. MMA-related mortality risk was particularly higher among participants with sufficient serum B12 (p < 0.001). CHD patients with increased levels of both MMA and B12 had a doubled mortality risk compared to those with lower MMA and B12 (p < 0.001).

CONCLUSION

MMA accumulation but not serum or dietary vitamin B12 was associated with increased cardiovascular mortality risk among patients with CHD. This paradox may be related to decreased response to vitamin B12.

Cobalamin Intake and Related Biomarkers: Examining Associations With Mortality Risk Among Adults With Type 2 Diabetes in NHANES

OBJECTIVE

Despite that periodical monitoring of cobalamin (vitamin B12) in metformin-treated patients with diabetes is recommended, cobalamin-associated mortality benefits or risks remain unclear. We investigated the association between cobalamin intake and related biomarkers and mortality risk in adults with diabetes using metformin or not.

RESEARCH DESIGN AND METHODS

This study included 3,277 adults with type 2 diabetes from the National Health and Nutrition Examination Survey (NHANES) and followed up until 31 December 2015. Weighted Cox proportional hazards regression was used to estimate hazard ratios (HRs) and 95% CIs for mortality risk.

RESULTS

Among 3,277 participants, 865 all-cause deaths occurred during a median follow-up of 7.02 years. There was no robust relationship between all-cause mortality and serum cobalamin or intake of foods or cobalamin supplements, regardless of metformin treatment (each P ≥ 0.120). The doubling of methylmalonic acid (MMA), a cobalamin-deficiency marker, was significantly associated with higher all-cause (HR 1.31 [95% CI 1.18-1.45], P < 0.001) and cardiac (HR 1.38 [95% CI 1.14-1.67], P = 0.001) mortality. Cobalamin sensitivity was assessed by the combination of binary B12low/high and MMAlow/high (cutoff values: cobalamin 400 pg/mL, MMA 250 nmol/L). Patients with decreased cobalamin sensitivity (MMAhighB12high) had the highest mortality risk. The multivariable-adjusted HRs (95% CIs) of all-cause mortality in MMAlowB12low, MMAlowB12high, MMAhighB12low, and MMAhighB12high groups were 1.00 (reference), 0.98 (0.75-1.28), 1.49 (1.16-1.92), and 1.96 (1.38-2.78), respectively. That association was especially significant in metformin nonusers.

CONCLUSIONS

Serum and dietary cobalamin were not associated with reduced mortality. Decreased cobalamin sensitivity was significantly associated with all-cause and cardiac mortality, particularly among metformin nonusers.

Association between neuropathy and B-vitamins: A systematic review and meta-analysis

BACKGROUND

Peripheral neuropathy (PN) is common in patients with diseases that are in turn associated with deficiency of the B-vitamins, and vitamin treatment has shown mixed results.

METHODS

This systematic review and meta-analysis studied the association between PN/pain and B-vitamin biomarkers and investigated whether vitamin treatment can ameliorate the symptoms. PubMed and Web of Science were searched according to the study protocol.

RESULTS

A total of 46 observational and seven interventional studies were identified and included in the data synthesis. The presence of PN was associated with lowered B12 levels (pooled estimate [95% CIs] = 1.51 [1.23-1.84], n = 34, Cochran Q Test I²  = 43.3%, p = 0.003) and elevated methylmalonic acid (2.53 [1.39-4.60], n = 9, I²  = 63.8%, p = 0.005) and homocysteine (3.48 [2.01-6.04], n = 15, I²  = 70.6%, p < 0.001). B12 treatment (vs. the comparators) showed a non-significant association with symptom improvement (1.36 (0.66-2.79), n = 4, I²  = 28.9%). Treatment with B1 was associated with a significant improvement in symptoms (5.34 [1.87-15.19], n = 3, I²  = 64.6%, p = 0.059). Analysis of seven trials combined showed a non-significant higher odds ratio for improvement under treatment with the B-vitamins (2.58 [0.98-6.79], I²  = 80.0%, p < 0.001).

CONCLUSIONS

PN is associated with lowered plasma vitamin B12 and elevated methylmalonic acid and homocysteine. Overall, interventional studies have suggested that B-vitamins could improve symptoms of PN. Available trials have limitations and generally did not investigate vitamin status prior to treatment. Well-designed studies, especially in non-diabetes PN, are needed. This meta-analysis is registered at PROSPERO (ID: CRD42020144917).

Vitamin B12 Supplementation in Diabetic Neuropathy: A 1-Year, Randomized, Double-Blind, Placebo-Controlled Trial

AIM

To investigate the effect of normalizing vitamin B12 (B12) levels with oral B12 (methylcobalamin) 1000 μg/day for one year in patients with diabetic neuropathy (DN).

PATIENTS AND METHODS

In this prospective, double-blind, placebo-controlled trial, 90 patients with type 2 diabetes on metformin for at least four years and both peripheral and autonomic DN were randomized to an active treatment group (n = 44) receiving B12 and a control group (n = 46) receiving a placebo. All patients had B12 levels less than 400 pmol/L. Subjects underwent measurements of sural nerve conduction velocity (SNCV), sural nerve action potential (amplitude) (SNAP), and vibration perception threshold (VPT), and they performed cardiovascular autonomic reflex tests (CARTs: mean circular resultant (MCR), Valsalva test, postural index, and orthostatic hypotension). Sudomotor function was assessed with the SUDOSCAN that measures electrochemical skin conductance in hands and feet (ESCH and ESCF, respectively). We also used the Michigan Neuropathy Screening Instrument Questionnaire and Examination (MNSIQ and MNSIE, respectively) and questionnaires to evaluate quality of life (QoL) and level of pain (pain score).

RESULTS

B12 levels increased from 232.0 ± 71.8 at baseline to 776.7 ± 242.3 pmol/L at follow-up, p < 0.0001, in the active group but not in the control group. VPT, MNSIQ, QoL, pain score, SNCV, SNAP, and ESCF significantly improved in the active group (p < 0.001, p = 0.002, p < 0.0001, p < 0.000, p < 0.0001, p < 0.0001, and p = 0.014, respectively), whereas CARTS and MNSIE improved but not significantly. MCR, MNSIQ, SNCV, SNAP, and pain score significantly deteriorated in the control group (p = 0.025, p = 0.017, p = 0.045, p < 0.0001, and p < 0.0001, respectively).

CONCLUSIONS

The treatment of patients with DN with 1 mg of oral methylcobalamin for twelve months increased plasma B12 levels and improved all neurophysiological parameters, sudomotor function, pain score, and QoL, but it did not improve CARTS and MNSIE.

Efficacy and Safety of the Combination of Superoxide Dismutase, Alpha Lipoic Acid, Vitamin B12, and Carnitine for 12 Months in Patients with Diabetic Neuropathy

Aim: To investigate the efficacy of Superoxide Dismutase, Alpha Lipoic Acid, Acetyl L-Carnitine, and Vitamin B12 (B12) in one tablet in Diabetic Neuropathy (DN). Patients–methods: In this prospective, double-blind, placebo-controlled study, 85 patients with Diabetes Mellitus Type 2 (DMT2) were randomly assigned, either to receive the combination of four elements (active group, n = 43), or placebo (n = 42) for 12 months. We used the Michigan Neuropathy Screening Instrument Questionnaire and Examination (MNSIQ and MNSIE), measured the vibration perception threshold (BIO), and Cardiovascular Autonomic Reflex Tests (CARTs). Nerve function was assessed by DPN Check [sural nerve conduction velocity (SNCV) and amplitude (SNAP)]. Pain (PS) and quality of life (QL) questionnaires were administered. Results: At follow-up, BIO, MNSIQ, QL, PAIN, and SNCV, SNAP, and B12 levels had significantly improved inactive group (p < 0.001, p < 0.001, p < 0.001, p < 0.001, p = 0.027, p = 0.031, and p < 0.001 respectively), whereas the inplacebo group MCR (mean circular resultant) and PAIN deteriorated (p < 0.001, p < 0.001). The changes in MNSIQ, QL, SNCV, BIO, and PAIN differed significantly between groups (p < 0.001, p < 0.001, p = 0.031, p < 0.001, and p < 0.001 respectively). Conclusions: The combination of the four elements in one tablet for 12 months in patients with DMT2 improved all indices of peripheral neuropathy, including SNAP and SNCV, pain, and Quality of Life perception, except CARTs and MNSIE.

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.

Vitamin B12 and Folate Concentrations in Recent-onset Type 2 Diabetes and the Effect of Metformin Treatment

CONTEXT

Vitamin B12 and folate deficiency are not only linked to hematological, neurological, and cardiovascular diseases, but are also associated with insulin resistance. Metformin can decrease vitamin B12 and folate concentrations.

OBJECTIVE

To examine (1) effects of short-term metformin treatment on serum holotranscobalamin (holoTC) and folate and (2) their association with insulin sensitivity in recent-onset type 2 diabetes.

DESIGN

This cross-sectional analysis comprised patients (known disease duration <12 months) on metformin monotherapy (MET, n = 123, 81 males, 53 ± 12 years) or nonpharmacological treatment (NPT, n = 126, 77 males, 54 ± 11 years) of the German Diabetes Study.

MAIN OUTCOME MEASURES

HoloTC (enzyme-linked immunosorbent assay), cobalamin, and folate (electrochemiluminescence); beta-cell function and whole-body insulin sensitivity, measured during fasting (HOMA-B, HOMA-IR) and intravenous glucose tolerance tests combined with hyperinsulinemic-euglycemic clamp tests.

RESULTS

HoloTC (105.4 [82.4, 128.3] vs 97 [79.7, 121.9] pmol/L) and folate concentrations (13.4 [9.3, 19.3] vs 12.7 [9.3, 22.0] nmol/L) were similar in both groups. Overall, holoTC was not associated with fasting or glucose-stimulated beta-cell function and insulin-stimulated glucose disposal. Cobalamin measurements yielded similar results in representative subgroups. In NPT but not MET, folate levels were inversely correlated with HOMA-IR (r = -0.239, P = .007). Folate levels did not relate to insulin sensitivity or insulin secretion in the whole cohort and in each group separately after adjustment for age, body mass index, and sex.

CONCLUSIONS

Metformin does not affect circulating holoTC and folate concentrations in recent-onset type 2 diabetes, rendering monitoring of vitamin B12 and folate dispensable, at least during the first 6 months after diagnosis or initiation of metformin.

The Role of Oxidative Stress in Peripheral Neuropathy

Peripheral neuropathy (PN) is a common disease affecting about 5% of the general population after the age of 50. Causes of PN are numerous and include genetic, diabetes, alcohol, vitamin deficiencies, and gluten sensitivity among others. This systematic review aimed to study the association between oxidative stress and PN in an attempt to better understand PN pathogenesis. A computer-based, systematic search was conducted on the PubMed database, and ensuing data from included articles was analyzed and discussed in this review. Sixty-nine papers were eligible and were used for this review. Peripheral neuropathy is associated with an increase of reactive oxygen species and a decrease in endogenous antioxidants. Genetic predisposition to oxidative damage may be a factor. Antioxidant treatment is promising regarding treatment. Though further research is necessary to better understand the underlying mechanism, it is evident that oxidative stress is implicated in the pathogenesis of - or is at least systematically present in - PN.

Metformin and Micronutrient Status in Type 2 Diabetes: Does Polypharmacy Involving Acid-Suppressing Medications Affect Vitamin B12 Levels?

Metformin is the first-choice drug in uncomplicated type 2 diabetes (T2DM) and is effective in improving glycaemic control. It is the most widely prescribed oral antidiabetic medicine and has a good safety profile. However, there is an abundance of evidence that metformin use is associated with decreased Vitamin B12 status, though the clinical implications of this in terms of increased risk of diabetic peripheral neuropathy are debated. There is growing evidence that other B vitamins, vitamin D and magnesium may also be impacted by metformin use in addition to alterations to the composition of the microbiome, depending on the dose and duration of therapy. Patients using metformin for prolonged periods may, therefore, need initial screening with intermittent follow-up, particularly since vitamin B₁₂ deficiency has similar symptoms to diabetic neuropathy which itself affects 40-50% of patients with T2DM at some stage. Among patients with T2DM, 40% are reported to experience symptomatic gastroesophageal reflux disease (GORD), of whom 70% use oral antidiabetic medications. The most common medications used to treat GORD are proton pump inhibitors (PPIs) and antagonists of histamine selective H₂ receptors (H₂RAs), both of which independently affect vitamin B₁₂ and magnesium status. Research indicates that co-prescribing metformin with either PPIs or H₂RAs can have further deleterious effects on vitamin B₁₂ status. Vitamin B12 deficiency related to metformin and polypharmacy is likely to contribute to the symptoms of diabetic neuropathy which may frequently be under-recognised. This review explores current knowledge surrounding these issues and suggests treatment strategies such as supplementation.

Blood concentrations of vitamins B1, B6, B12, C and D and folate in palliative care patients: Results of a cross-sectional study

Objective

The main purpose of palliative care is symptom relief. Frequently, the symptoms of patients requiring palliative care are the same as common symptoms of vitamin deficiency (e.g. pain, weakness, fatigue, depression). The study aim was to investigate whether patients in palliative care are vitamin deficient.

Method

This was a monocentre cross-sectional study. Patients attending the palliative care unit of a general hospital in Germany from October 2015 to April 2016 were examined for vitamin blood concentrations and symptoms. Data were analysed using univariate analysis and bivariate correlations.

Results

Data were available from 31 patients. Vitamin D3 deficiency (<62.5 nmol/L) affected 93.5% of patients, vitamin B6 deficiency (<4.1 ng/mL) 48.4%, vitamin C deficiency (<4.5 mg/L) 45.2%, vitamin B1 deficiency (<35 µg/L) 25.8% and vitamin B12 deficiency (<193 pg/mL) 12.9%. There was a significant negative correlation between vitamin B1 ranges and pain (r = −0.384) and depression (r = −0.439) symptoms.

Conclusion

All patients showed a deficiency in at least one of the measured vitamins; 68% had concurrent deficiencies in >1 vitamin. A follow-up study using validated questionnaires and a larger sample is needed to investigate the effects of targeted vitamin supplementation on quality of life and symptom burden.

Pinprick hypo- and hyperalgesia in diabetic rats: Can diet content affect experimental outcome?

Existing literature concerning the effect of experimentally-induced diabetes on pain thresholds in rodent models remains controversial. In this work, we describe a phenotypical switch from streptozotocin-induced pinprick hypoalgesia to hyperalgesia observed in the same laboratory, in the same strain of rats, obtained from the same vendor, and measured by the same technique carried out by the investigators. This switch was observed around January 2015, at the time when there was a change in the diet of rats at the Radley North Carolina Charles River facility. These data support the contention that diet may significantly modify disease progression, including progression of signs of diabetic neuropathy.

Long-term treatment with metformin in type 2 diabetes and methylmalonic acid: Post hoc analysis of a randomized controlled 4.3year trial

AIMS

Metformin treatment is associated with a decrease of serum vitamin B12, but whether this reflects tissue B12 deficiency is controversial. We studied the effects of metformin on serum levels of methylmalonic acid (MMA), a biomarker for tissue B12 deficiency, and on onset or progression of neuropathy.

METHODS

In the HOME trial, 390 insulin-treated patients with type 2 diabetes were treated with metformin or placebo for 52months. In a post hoc analysis, we analyzed the association between metformin, MMA and a validated Neuropathy Score (NPS).

RESULTS

Metformin vs placebo increased MMA at the end of the study (95%CI: 0.019 to 0.055, p=0.001). Mediation analysis showed that the effect of metformin on the NPS consisted of a beneficial effect through lowering HbA1c (-0.020 per gram year) and an adverse effect through increasing MMA (0.042 per gram year), resulting in a non-significant net effect (0.032 per gram year, 95% CI: -0.121 to 0.182, p=0.34).

CONCLUSION

Metformin not only reduces serum levels of B12, but also progressively increases serum MMA. The increase of MMA in metformin users was associated with significant worsening of the NPS. These results provide further support that metformin-related B12 deficiency is clinically relevant. Monitoring of B12 in users of metformin should be considered.

[Improvement of the efficacy and safety of the treatment of patients with low back pain]

Low back pain (LBP) is an extremely widespread syndrome in the population. Nonsteroidal Inflammatory drugs are most frequently used in treatment of patients with LBP. The use of these drugs causes adverse effects, the risk of which can be minimized. To decrease the risk, B-group vitamins are used in the complex treatment. The possibility of simultaneous using of artrozan (meloxicam) and cyanocobalamine (B-group vitamin complex) in the treatment of LBP is considered.

Methylmalonic Acid and Homocysteine as Indicators of Vitamin B-12 Deficiency in Cancer

Background/Aims

Normal or high serum vitamin B-12 levels can sometimes be seen in a B-12 deficient state, and can therefore be misleading. High levels of Methymalonic Acid (MMA) and Homocysteine (HC) have been identified as better indicators of B-12 deficiency than the actual serum B-12 level itself. We evaluated the prevalence of vitamin B-12 deficiency using appropriate cut-off levels of vitamin B-12, MMA and HC, and determined the relationship between serum levels of vitamin B-12, MMA and HC in cancer.

Methods

This is a cross-sectional study using a consecutive case series of 316 cancer patients first seen at Cancer Treatment Centers of America^® (CTCA) at Midwestern Regional Medical Center between April 2014 and June 2014. All patients were evaluated at baseline for vitamin B-12 (pg/mL), MMA (nmol/L) and HC (μmol/L) levels. In accordance with previously published research, the following cut-offs were used to define vitamin B-12 deficiency: <300 pg/mL for vitamin B-12, >260 nmol/L for MMA and >12 μmol/L for HC. The relationship between B-12, MMA and HC was evaluated using Spearman's rho correlation coefficient and cross-tabulation analysis. Receiver Operating Characteristic (ROC) curves were estimated using the non-parametric method to further evaluate the diagnostic accuracy of vitamin B-12 using Fedosov quotient as the "gold standard".

Results

Mean age at presentation was 52.5 years. 134 (42.4%) patients were males while 182 (57.6%) were females. Median vitamin B-12, MMA and HC levels were 582.5 pg/mL, 146.5 nmol/L and 8.4 μmol/L respectively. Of 316 patients, 28 (8.9%) were vitamin B-12 deficient based on vitamin B-12 (<300pg/mL), 34 (10.8%) were deficient based on MMA (>260 nmol/L) while 55 (17.4%) were deficient based on HC (>12 μmol/L). Correlation analysis revealed a significant weak negative correlation between vitamin B-12 and MMA (rho = -0.22) as well as B-12 and HC (rho = -0.35). ROC curves suggested MMA to have the best discriminatory power in predicting B-12 deficiency.

Conclusion

Vitamin B-12 is poorly correlated with MMA and HC in cancer. Using serum vitamin B-12 alone to evaluate B-12 status in cancer may fail to identify those with functional deficiency. A thorough clinical assessment is important to identify patients that may have risk factors and/or symptoms suggestive of deficiency. These patients should have additional testing of MMA and HC regardless of their B-12 levels.

Low Cobalamin Levels as Predictors of Cobalamin Deficiency: Importance of Comorbidities Associated with Increased Oxidative Stress

BACKGROUND

Cobalamin (B12) deficiency can lead to irreversible neurocognitive changes if unrecognized. Screening involves measurement of serum cobalamin levels, but the sensitive metabolic indicators of cobalamin deficiency, methylmalonic acid (MMA) and homocysteine (HCys), may be normal when cobalamin values are low and elevated when cobalamin values are normal. Because cobalamin is inactivated by oxidation, the relationship between these metabolites and comorbidities associated with increased oxidative stress (oxidant risks) in subjects with low and low-normal cobalamin levels was studied.

METHODS

A retrospective record-review was conducted of community-dwelling adults evaluated for cobalamin deficiency during a 12-year period with serum cobalamin values in the low (≤ 200 pg/mL; n = 49) or low-normal (201-300 pg/mL; n = 187) range and concurrent measurement of MMA.

RESULTS

When "No" oxidant risk was present, elevated MMA (>250 nmol/L) and HCys (>12.1 μmol/L) values occurred in 50% and 30% of subjects, respectively (P <.01). In contrast, when "Three or More" oxidant risks were present, mean MMA and HCys values were significantly higher, and elevated MMA and HCys values occurred in 84% and 78% of these subjects, respectively (P ≤.012). Pharmacologic doses of cyanocobalamin significantly decreased metabolite values in ≥ 94% of treated subjects.

CONCLUSION

In subjects with low or low-normal cobalamin values, metabolic evidence of cobalamin deficiency is more frequent when 3 or more oxidant risks are present. Thus, defining a low serum cobalamin level to screen for cobalamin deficiency may be a "moving target" due to the variable presence and severity of often subtle, confounding clinical conditions in individual subjects.

Frequency of dementia syndromes with a potentially treatable cause in geriatric in-patients: analysis of a 1-year interval

In addition to neurodegenerative and vascular causes of dementia, in the differential diagnosis potentially reversible conditions of dementia also must be assessed. Routine laboratory parameters and neuroimaging, which are recommended for the differential diagnosis of suspected dementia by the German S3 Guideline "Dementia", were retrospectively studied in 166 geriatric patients with suspected dementia. Delirium was diagnosed in six patients (3.6%). These six patients were excluded from the study. Of the 160 remaining patients, there were 99 (59.6%) with an already known dementia. In this subgroup of patients, we found a potentially treatable cause of dementia in 18.2%. In the remaining 61 patients (36.8%), the newly diagnosed dementia syndrome was established according to ICD-10 criteria. Potentially reversible causes of the dementia syndrome were found in 19 of these patients (31.1%). The most common cause was depressive pseudodementia in eight patients followed by vitamin B12 deficiency in six patients. A significant amount of our patients showed laboratory or imaging changes suggestive of potentially reversible causes of the dementia syndrome upon admission. The results of our study indicate the importance of careful differential diagnosis of dementia based on the recommendations of guidelines. Although therapy of these potential causes is not always accompanied by a full recovery, the identification and therapy of treatable causes of cognitive deficits are possible even for general practitioners, who often are the primary contact persons of affected individuals.

Functional cobalamin (vitamin B12) deficiency: role of advanced age and disorders associated with increased oxidative stress

BACKGROUND/OBJECTIVE

Functional cobalamin (Cbl; vitamin B12) deficiency (that is, high levels of the Cbl-dependent metabolites, methylmalonic acid (MMA) and homocysteine (HCys), despite normal serum Cbl values) is common in the elderly and is associated with neurocognitive abnormalities, but its cause is unknown. As only reduced Cbls are metabolically active, the possibility that functional Cbl deficiency is associated with disorders having biomarkers indicative of increased oxidative stress (oxidant risks) was considered.

SUBJECTS/METHODS

A retrospective record review of community-dwelling adults evaluated over a 12-year period for Cbl deficiency in a primary care setting who had serum Cbl values ⩾400 pg/ml (n=170).

RESULTS

When no oxidant risks were present, older subjects (⩾70 years) had higher metabolite values than younger individuals (<70 years). MMA values were even higher in the elderly when one oxidant risk was present and in younger subjects when two or more oxidant risks were present. Even at Cbl levels ⩾800 pg/ml, MMA values were increased in 73% of elderly subjects with at least one oxidant risk. HCys values were also higher in both age groups when at least two oxidant risks were present. Cyanocobalamin therapy decreased MMA and HCys values in 86 and 76% of subjects, respectively, with nonresponders more likely to have two or more oxidant risks.

CONCLUSION

Functional Cbl deficiency is associated with disorders marked by increased oxidative stress particularly in the elderly; it occurs even when Cbl levels are high and is not consistently corrected with high-dose cyanocobalamin therapy. Thus, current approaches to recognizing and managing this disorder may be inadequate.

Metformin use in patients with type 2 diabetes mellitus is associated with reduced risk of deep vein thrombosis: a non-randomized, pair-matched cohort study

Background

Metformin, an insulin-sensitizer, may correct several physiologic abnormalities owing to insulin resistance in patients with type 2 diabetes mellitus (DM). The effects of metformin on venous thrombosis in patient with type 2 DM have not been reported. Our study strived to explore the relationship of metformin therapy and the subsequent development of deep vein thrombosis (DVT) using a nationwide, population-based database.

Methods

From 1997 to 2003, we identified a study cohort consisting of patients with type 2 DM using metformin 7154 cases in the National Health Insurance Research Database. A control cohort without metformin, matched for age, sex, comorbidities, and medications was selected for comparison.

Results

Of the 14945 patients (7167 patients with metformin vs. 7778 control), 60 (0.40%) patients developed DVT during a mean follow-up period of 3.74 years, including 16 (0.21%) from the cohort with metformin and 44 (0.56%) from the control group. Subjects with metformin experienced a 0.427 fold (95% confidence interval 0.240-0.758; P = 0.004) changes of risk reduction in development of DVT, which was independent of age, sex and co-morbidities. Kaplan-Meier analysis also revealed metformin therapy is associated with lower occurrence of DVT (log-rank test, P = 0.001).

Conclusions

Metformin may have protective effect in patients with type 2 DM for DVT.

Vitamin B12 deficiency is associated with adverse lipid profile in Europeans and Indians with type 2 diabetes

Background

Metformin, a standard therapy in type 2 diabetes, reduces vitamin B12 levels. Studies linking low vitamin B12 levels and cardiovascular disease are equivocal and suggest improving B12 levels may help in primary prevention. The role of vitamin B12 deficiency on cardiovascular risk factors, especially in type 2 diabetes has not been explored. The aim of this study is to investigate whether vitamin B12 deficiency in type 2 diabetes patients is associated with cardiovascular risk factors in two different ethnic groups in UK and India.

Methods

Type 2 diabetes patients from two secondary care diabetic centres (Europeans - UK and Indians - India) were studied. Serum vitamin B12, folate and biochemical parameters were measured.

Results

The prevalence rates of vitamin B12 deficiency (<191 ng/L) were 27% and 12% in Europeans and Indians, respectively and higher in metformin treated type 2 diabetes patients. In linear regression analysis, after adjusting for all likely confounding factors, vitamin B12 independently associated with triglycerides in both the populations and cholesterol/HDL ratio in Indians. Logistic regression showed type 2 diabetes patients with vitamin B12 deficiency were at significantly higher odds of having coexisting coronary artery disease (CAD) in Europeans with similar but non-significant trend in Indians, after adjusting for all likely confounding factors.

Conclusions

The prevalence of vitamin B12 deficiency is common in type 2 diabetes patients and is associated with adverse lipid parameters. Type 2 diabetes management guidelines should include the recommendation for regular testing for B12 levels, especially for those on metformin.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-014-0129-4) contains supplementary material, which is available to authorized users.

Guidelines for the diagnosis and treatment of cobalamin and folate disorders

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

The relationship of serum cobalamin to methylmalonic acid concentrations and clinical variables in cats

BACKGROUND

Serum cobalamin concentration [CBL] suggests CBL deficiency in cats but serum methylmalonic acid concentration [MMA] more accurately indicates CBL deficiency.

OBJECTIVE

To examine the ability of [CBL] to predict CBL deficiency defined by increased [MMA], and relationships of [CBL] and [MMA] with select clinical and clinicopathological variables.

ANIMALS

One hundred sixty-three client-owned cats with [CBL] measurements, 114 cats with simultaneous [MMA] measurements; 88 cats with medical information.

METHODS

Prospectively collected [CBL] and [MMA] were compared using scatter plots, receiver operating characteristic and correlative analyses with historical [CBL] thresholds and those identified in the study. [CBL] and [MMA] were compared retrospectively to specific clinical and clinicopathological variables.

RESULTS

[CBL] correlated negatively with [MMA] (τ = -0.334, P < .0001). [MMA] ≥ 1,343 nmol/L identified CBL deficiency. [CBL] = 209 pg/mL optimized sensitivity (0.51), specificity (0.96), PPV (0.89), and NPV (0.74) for detecting [MMA] ≥ 1,343 nmol/L. Prevalence of CBL deficiency was 42% (48/114) when defined by [MMA] ≥ 1,343 nmol/L versus 23% (27/114) by [CBL] ≤ 209 pg/mL. Unexpectedly, 23 and 45% of 48 cats with [MMA] ≥ 1,343 nmol/L had [CBL] > 900 pg/mL and 290 pg/mL (historical thresholds). [CBL] correlated with mean corpuscular volume (τ = -0.199, P = .013) and [MMA] with hematocrit (τ = -0.28, P = .006).

CONCLUSIONS AND CLINICAL IMPORTANCE

Cobalamin deficiency ([MMA] ≥ 1,343 nmol/L) occurred in 42% of cats and is predicted with high specificity by [CBL] ≤ 209 pg/mL. CBL status correlates with microcytosis and anemia. Discordance between [CBL] and [MMA] cautions against relying on any single marker for determining CBL status.

The pathophysiology of elevated vitamin B12 in clinical practice

Hypercobalaminemia (high serum vitamin B12 levels) is a frequent and underestimated anomaly. Clinically, it can be paradoxically accompanied by signs of deficiency, reflecting a functional deficiency linked to qualitative abnormalities, which are related to defects in tissue uptake and action of vitamin B12. The aetiological profile of high serum cobalamin predominantly encompasses severe disease entities for which early diagnosis is critical for prognosis. These entities are essentially comprised of solid neoplasms, haematological malignancies and liver and kidney diseases. This review reflects the potential importance of the vitamin B12 assay as an early diagnostic marker of these diseases. A codified approach is needed to determine the potential indications of a search for high serum cobalamin and the practical clinical strategy to adopt upon discovery of elevated cobalamin levels. While low serum cobalamin levels do not necessarily imply deficiency, an abnormally high serum cobalamin level forms a warning sign requiring exclusion of a number of serious underlying pathologies. Functional cobalamin deficiency can thus occur at any serum level.

Advanced age as a risk factor for folate-associated functional cobalamin deficiency

OBJECTIVES

To determine whether high serum folate levels contribute to metabolite changes in elderly subjects with normal cobalamin levels.

DESIGN

Case series.

SETTING

Outpatient clinic at a university-based staff model health maintenance organization.

PARTICIPANTS

Two hundred thirty-three ambulatory individuals without diabetes mellitus with normal renal function and normal cobalamin levels evaluated for cobalamin deficiency.

MEASUREMENTS

Cobalamin, serum folate, methylmalonic acid (MMA), and homocysteine.

RESULTS

Older individuals (≥60) with low-normal cobalamin levels (201-300 pg/mL) had higher MMA and lower homocysteine levels when serum folate levels were high (>20 ng/mL) than when serum folate levels were normal (P < .02), but serum folate levels within the normal range were not a determinant of either metabolite. In younger subjects with low-normal cobalamin levels, high serum folate levels were not associated with significant differences in either metabolite. At mid-normal cobalamin levels (301-600 pg/mL), high serum folate levels were associated with lower homocysteine levels in older adults (P < .001) but not with differences in MMA in either age group. Cobalamin therapy decreased or normalized MMA and homocysteine in 89% or more of participants even at pretherapy cobalamin levels greater than 600 pg/mL.

CONCLUSION

High serum folate levels are associated with higher MMA levels when cobalamin levels are low-normal, and this effect is age dependent, not progressive within the normal serum folate range (suggesting a threshold effect), and reversed by cobalamin therapy. Because MMA may be neurotoxic, these findings suggest caution in the use of folic acid supplements in elderly adults.

Metanx in type 2 diabetes with peripheral neuropathy: a randomized trial

PURPOSE

To determine whether a combination of L-methylfolate, methylcobalamin, and pyridoxal-5'-phosphate (LMF-MC-PLP [Metanx; Pamlab LLC, Covington, La]) improves sensory neuropathy.

RESEARCH DESIGN AND METHODS

This multicenter, randomized, double-blind, placebo-controlled trial involved 214 patients with type 2 diabetes and neuropathy (baseline vibration perception threshold [VPT]: 25-45 volts), who were randomly assigned to 24 weeks of treatment with either L-methylfolate calcium 3 mg, methylcobalamin 2 mg, and pyridoxal-5'-phosphate 35 mg or placebo. The primary end point was effect on VPT. Secondary end points included Neuropathy Total Symptom Score (NTSS-6) and Short Form 36 (SF-36), as well as plasma levels of folate, vitamins B(6) and B(12), methylmalonic acid (MMA), and homocysteine.

RESULTS

There was no significant effect on VPT. However, patients receiving LMF-MC-PLP consistently reported symptomatic relief, with clinically significant improvement in NTSS-6 scores at week 16 (P=.013 vs placebo) and week 24 (P=.033). Improvement in NTSS scores was related to baseline MMA and inversely related to baseline PLP and metformin use. Quality-of-life measures also improved. Homocysteine decreased by 2.7±3.0 μmol/L with LMF-MC-PLP versus an increase of 0.5±2.4 μmol/L with placebo (P=.0001). Adverse events were infrequent, with no single event occurring in ≥2% of subjects.

CONCLUSIONS

LMF-MC-PLP appears to be a safe and effective therapy for alleviation of peripheral neuropathy symptoms, at least in the short term. Additional long-term studies should be conducted, as the trial duration may have been too short to show an effect on VPT. In addition, further research on the effects in patients with cobalamin deficiency would be useful.

Vitamin B(12) in type 2 diabetic patients treated with metformin

OBJECTIVE

To test vitamin B12 plasma levels in type 2 diabetic patients treated with metformin in our area.

METHODS

A cross-sectional, observational study of consecutive type 2 diabetic patients on drug treatment attending an internal medicine outpatient clinic.

RESULTS

One hundred and nine patients (81 treated with metformin) were enrolled into the study. Mean time on metformin treatment was 43.5 months and mean drug dose was 1,779 mg/day. Patients treated with metformin had significantly lower vitamin B(12) plasma levels (393.5 vs. 509 pg/mL, P = .0008). Seven (8.6%) of 81 patients treated with metformin and none of the 28 patients not treated with the drug had vitamin B(12) plasma levels lower than 197 pg/mL. No correlation was found between vitamin B12 plasma levles and metformin treatment time or dosage.

CONCLUSIONS

In type 2 diabetic patients, treatment with metformin is associated to lower vitamin B12 plasma levels. Vitamin B12 deficiency associated with metformin is relatively common in our area.

Disturbance of B-vitamin status in people with type 2 diabetes in Indonesia--link to renal status, glycemic control and vascular inflammation

BACKGROUND

Diabetes is associated with mishandling of thiamine in the kidney and development of diabetic nephropathy. The aim of this study is to assess the disturbance of thiamine and other B-vitamin status of patients with type 2 diabetes in Indonesia.

METHODS

One hundred and fifteen patients with type 2 diabetes with and without microalbuminuria or albuminuria and 39 healthy people were recruited. After a 2-month washout period for B-vitamin supplementation, markers of vitamins B(1), B(6), B(9) and B(12), were determined.

RESULTS

Fractional excretion of thiamine (22.8 versus 33.5%; P<0.05) and urinary excretion of the vitamin B(6) degradation product 4-pyridoxic acid (0.081 versus 0.133 μmol/g creatinine, P<0.001) was increased in patients with type 2 diabetes with respect to healthy controls. There was also increased total plasma cobalamin (398 versus 547 pmol/l, P<0.001) and holotranscobalamin (74 versus 97 pmol/l, P<0.001) in patients with type 2 diabetes. In multiple regression analysis these were linked to HbA1c, duration of diabetes and systolic blood pressure, and fasting plasma glucose, folate and C-reactive protein, respectively.

CONCLUSIONS

There was renal mishandling of thiamine, increased degradation of vitamin B(6) and cytosolic metabolic resistance to vitamin B(12) in patients with type 2 diabetes in Indonesia.

Association of biochemical B₁₂ deficiency with metformin therapy and vitamin B₁₂ supplements: the National Health and Nutrition Examination Survey, 1999-2006

OBJECTIVE

To describe the prevalence of biochemical B(12) deficiency in adults with type 2 diabetes taking metformin compared with those not taking metformin and those without diabetes, and explore whether this relationship is modified by vitamin B(12) supplements.

RESEARCH DESIGN AND METHODS

Analysis of data on U.S. adults ≥50 years of age with (n = 1,621) or without type 2 diabetes (n = 6,867) from the National Health and Nutrition Examination Survey (NHANES), 1999-2006. Type 2 diabetes was defined as clinical diagnosis after age 30 without initiation of insulin therapy within 1 year. Those with diabetes were classified according to their current metformin use. Biochemical B(12) deficiency was defined as serum B(12) concentrations ≤148 pmol/L and borderline deficiency was defined as >148 to ≤221 pmol/L.

RESULTS

Biochemical B(12) deficiency was present in 5.8% of those with diabetes using metformin compared with 2.4% of those not using metformin (P = 0.0026) and 3.3% of those without diabetes (P = 0.0002). Among those with diabetes, metformin use was associated with biochemical B(12) deficiency (adjusted odds ratio 2.92; 95% CI 1.26-6.78). Consumption of any supplement containing B(12) was not associated with a reduction in the prevalence of biochemical B(12) deficiency among those with diabetes, whereas consumption of any supplement containing B(12) was associated with a two-thirds reduction among those without diabetes.

CONCLUSIONS

Metformin therapy is associated with a higher prevalence of biochemical B(12) deficiency. The amount of B(12) recommended by the Institute of Medicine (IOM) (2.4 μg/day) and the amount available in general multivitamins (6 μg) may not be enough to correct this deficiency among those with diabetes.

Advanced glycation end products overload might explain intracellular cobalamin deficiency in renal dysfunction, diabetes and aging

Advanced glycation end products (AGEs) contribute to aging. Cobalamin (Cbl) is required for cell growth and functions, and its deficiency causes serious complications. Diabetics and renal patients show high concentrations of Cbl, but metabolic evidence of Cbl deficiency that is reversible after Cbl treatment. Cbl might be sequestered in blood and cannot be delivered to the cell. Megalin mediates the uptake of transcobalamin-Cbl complex into the proximal tubule cells. Megalin is involved in the uptake and degradation of AGEs. In aging, diabetes or renal dysfunction, AGEs might overload megalin thus lowering Cbl uptake. Transcobalamin-Cbl might retain in blood. Shedding of megalin and transcobalamin receptor under glycation conditions is also a possible mechanism of this phenomenon.