Association of metformin, elevated homocysteine, and methylmalonic acid levels and clinically worsened diabetic peripheral neuropathy

Vitamin B12 deficiency in diabetic patients treated with metformin: A narrative review

Metformin is the most prescribed oral hypoglycemic drug and is considered by many health practitioners as the first-line treatment for non-insulin-dependent diabetes mellitus (T2DM). It is used either as a monotherapy or adjuvant to other anti-hyperglycemic agents. Most of its side effects are usually mild and self-limiting. However, several studies have shown an association between the use of metformin and low vitamin B12 levels in diabetic patients. The current review aimed to provide a literature review of the current published reports on the association, the possible mechanisms, and the related individualized risk factors that might lead to this incidence. The most accepted mechanism of the effect of metformin on vitamin B12 level is related to the absorption process where metformin antagonism of the calcium cation and interference with the calcium-dependent IF-vitamin B12 complex binding to the ileal cubilin receptor. In addition, many risk factors have been associated with the impact of metformin on vitamin B12 levels in diabetic patients such as dose and duration where longer durations showed a greater prevalence of developing vitamin B12 deficiency. Male patients showed lower levels of vitamin B12 compared to females. Black race showed a lower prevalence of vitamin B12 deficiency in metformin-treated patients. Moreover, chronic diseases including T2DM, hyperlipidemia, coronary artery disease, polycystic ovary disease (PCOD), obesity, and metformin therapy were significantly associated with increased risk of vitamin B12 deficiency.

Metformin-Induced Vitamin B12 Deficiency in Patients with Type 2 Diabetes: A Narrative Review with a Practical Approach for Screening, Diagnosing, and Managing Vitamin B12 Deficiency

Metformin is the most widely used antihyperglycemic drug in patients with type 2 diabetes (T2D). Over the past 2 decades, several studies have highlighted a substantial increase in the risk of vitamin B12 deficiency in patients with T2D on metformin therapy. This can lead to several complications and induce or exacerbate peripheral neuropathy. Despite these data, there are no definite guidelines for screening, diagnosing, and treating vitamin B12 deficiency in patients with T2D on metformin therapy. Therefore, in this narrative review, we aimed to suggest a practical diagnostic and therapeutic strategy to address vitamin B12 deficiency in patients with T2D receiving metformin treatment. Clinical evidence supporting an increased risk of vitamin B12 deficiency in patients with T2D on metformin therapy and its risk factors and potential complications are also discussed.

Vitamin B12 deficiency in diabetic patients treated with metformin: A cross-sectional study

Metformin is a cornerstone medication in the management of type 2 diabetes. Metformin is safe, effective, and inexpensive; however, it is associated with vitamin B12 deficiency. This study set out to evaluate the rate of vitamin B12 deficiency in Vietnamese patients with type 2 diabetes who were treated with metformin and to investigate factors associated with vitamin B12 deficiency. This is a cross-sectional study that was conducted in Vinmec Central Park Hospital from February to June 2023. The clinical and paraclinical characteristics of the participants were recorded, and the levels of vitamin B12 and folate were measured. The rate of vitamin B12 deficiency in patients treated with metformin was found to be 18.6%. Further, the duration of diabetes, duration of metformin use, metformin dose, and hemoglobin levels were statistically associated with vitamin B12 deficiency with OR (95% CI) = 1.12 (1.03-1.19), 1.01 (1.00-1.02), 1.002 (1.001-1.002), 0.74 (0.55-0.99), respectively. After adjusting for covariates, a metformin dose greater than the median dose remained the only parameter associated with vitamin B12 deficiency, with OR (95% CI) = 4.10 (1.62-10.36). Moreover, when combining both long-term use of metformin and a metformin dose greater than the median dose, the OR increased to 5.25 (95% CI: 2.11-13.15). These results demonstrate that vitamin B12 deficiency in patients treated with metformin is quite prevalent in Vietnam and that those with long-term use of metformin (48 months or more) and high metformin dose (1000 mg/day or more) are at high risk of experiencing this adverse effect and so require screening.

View on Metformin: Antidiabetic and Pleiotropic Effects, Pharmacokinetics, Side Effects, and Sex-Related Differences

Metformin is a synthetic biguanide used as an antidiabetic drug in type 2 diabetes mellitus, achieved by studying the bioactive metabolites of Galega officinalis L. It is also used off-label for various other diseases, such as subclinical diabetes, obesity, polycystic ovary syndrome, etc. In addition, metformin is proposed as an add-on therapy for several conditions, including autoimmune diseases, neurodegenerative diseases, and cancer. Although metformin has been used for many decades, it is still the subject of many pharmacodynamic and pharmacokinetic studies in light of its extensive use. Metformin acts at the mitochondrial level by inhibiting the respiratory chain, thus increasing the AMP/ATP ratio and, subsequently, activating the AMP-activated protein kinase. However, several other mechanisms have been proposed, including binding to presenilin enhancer 2, increasing GLP1 release, and modification of microRNA expression. Regarding its pharmacokinetics, after oral administration, metformin is absorbed, distributed, and eliminated, mainly through the renal route, using transporters for cationic solutes, since it exists as an ionic molecule at physiological pH. In this review, particular consideration has been paid to literature data from the last 10 years, deepening the study of clinical trials inherent to new uses of metformin, the differences in effectiveness and safety observed between the sexes, and the unwanted side effects. For this last objective, metformin safety was also evaluated using both VigiBase and EudraVigilance, respectively, the WHO and European databases of the reported adverse drug reactions, to assess the extent of metformin side effects in real-life use.

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.

Prevalence of vitamin B12 deficiency in type 2 diabetic patients taking metformin, a cross-sectional study in primary healthcare

Background

Several studies documented that metformin use contributes to vitamin B12 deficiency in patients with type 2 diabetes mellitus (T2DM). However, there has been a lack of data assessing this issue in Jordan.

Aims

Assess the vitamin B12 serum levels, frequency of vitamin B12 deficiency, and related factors among Jordanian patients with T2DM patients treated with metformin.

Methods

a total of 447 subjects attending a primary health care center were included in this cross-sectional study consisting of T2DM patients who use metformin and a control group of non-diabetics. Serum B12 levels were evaluated and B12 deficiency was defined as serum B12 levels ≤ 200 pmol/L. Associations of B12 serum levels or B12 deficiency with other factors like gender, age, and duration of T2DM were analyzed.

Results

There was no significant difference in serum B12 levels nor the frequency of vitamin B12 deficiency between T2DM metformin-treated patients and control groups. Among metformin-treated patients there was no difference relating to age, type 2 diabetes mellitus duration, proton pump inhibitors use, and metformin use (duration, dose) between patients with or without B12 deficiency.

Conclusion

The prevalence of vitamin B12 deficiency among T2DM patients on metformin treatment in this study was high (48.9%). However, the treatment with metformin and the dose of metformin use was not associated with vitamin B12 deficiency.

Vitamin B12 levels in type 2 diabetic patients on Metformin compared to those never on Metformin: a cross sectional study in Tunisia

INTRODUCTION

Recent studies suggest that long-term use of metformin may decrease the plasma level of Vitamin B12.

AIM

To assess the Vitamin B12 status in Tunisian patients treated with metformin and to study its association with the dose, the duration of metformin use, and the clinical and biological parameters.

METHODS

It was a cross-sectional, comparative study on 200 type 2 diabetic (T2D) patients. A vitamin B12 assay was performed with a neurological examination and a Complete blood count.

RESULTS

The mean level of Vitamin B12 assayed in our population was 398.5±188.3 pg/ml. The serum Vitamin B12 levels were 356.9±153.5 pg/ml in the metformin group and 460.9±218.6 pg/ml in the no metformin group (p <0.01). Metformin intake was associated with an increased prevalence of Vitamin B12 deficiency and borderline level. The level of Vitamin B12 was correlated with the duration and the dose of metformin. Vitamin B12 deficiency was significantly associated with anemia, macrocytosis, and diabetic neuropathy. Multivariate analysis concluded that Vitamin B12 deficiency was significantly associated with the duration, cumulative metformin dose, clinical neuropathy, anemia, and macrocytosis.

CONCLUSION

Our study showed an association of Vitamin B12 deficiency with the dose and duration of metformin intake in Tunisian T2D patients, with hematological and neurological repercussions.

Relationship Between Vitamins and Diabetes

This review article aims to examine the relationship between specific vitamins and type 2 diabetes. Individuals with diabetes have been observed to have lower levels of specific antioxidant vitamins such as A, C, and E, possibly due to the need to manage oxidative stress caused by glucose metabolic abnormalities. Retinol-binding protein, which has adipocytokine activities, has a modulatory effect. Levels of thiamine, pyridoxine, and biotin are also lower in individuals with diabetes. While the reasons for this are unclear, some improvement in metabolic control has been observed with supplementation. Although metformin is the preferred treatment for type 2 diabetes, it has been found to limit the absorption of certain nutrients, including vitamin B9 and vitamin B12, necessitating regular supplementation of these nutrients for people with diabetes. Diabetes and its consequences, including cardiovascular disease, are more likely in those with low vitamin D levels. Although some research suggests that vitamin K intake may improve glucose metabolism, further evidence is required. Research on the effectiveness of multivitamins has produced inconsistent results, and there are no clear guidelines for vitamin supplementation in individuals with type 2 diabetes mellitus. However, people who use metformin for extended periods may benefit from additional folic acid and vitamin B12 supplements.

Morphological and Functional Remodeling of the Ischemic Heart Correlates with Homocysteine Levels

Background: Homocysteine (Hcy) is involved in various methylation processes, and its plasma level is increased in cardiac ischemia. Thus, we hypothesized that levels of homocysteine correlate with the morphological and functional remodeling of ischemic hearts. Thus, we aimed to measure the Hcy levels in the plasma and pericardial fluid (PF) and correlate them with morphological and functional changes in the ischemic hearts of humans. Methods: Concentration of total homocysteine (tHcy) and cardiac troponin-I (cTn-I) of plasma and PF were measured in patients undergoing coronary artery bypass graft (CABG) surgery (n = 14). Left-ventricular (LV) end-diastolic diameter (LVED), LV end-systolic diameter (LVES), right atrial, left atrial (LA) area, thickness of interventricular septum (IVS) and posterior wall, LV ejection fraction (LVEF), and right ventricular outflow tract end-diastolic area (RVOT EDA) of CABG and non-cardiac patients (NCP; n = 10) were determined by echocardiography, and LV mass was calculated (cLVM). Results: Positive correlations were found between Hcy levels of plasma and PF, tHcy levels and LVED, LVES and LA, and an inverse correlation was found between tHcy levels and LVEF. cLVM, IVS, and RVOT EDA were higher in CABG with elevated tHcy (>12 µM/L) compared to NCP. In addition, we found a higher cTn-I level in the PF compared to the plasma of CABG patients (0.08 ± 0.02 vs. 0.01 ± 0.003 ng/mL, p < 0.001), which was ~10 fold higher than the normal level. Conclusions: We propose that homocysteine is an important cardiac biomarker and may have an important role in the development of cardiac remodeling and dysfunction in chronic myocardial ischemia in humans.

[Cross-Sectional Study on Adverse Effects of Metformin Hydrochloride on 130 Patients Type 2 Diabetic Admitted to Medical Center and Diabetes Home of Sidi Bel-Abbès]

INTRODUCTION

MetforminHydrochloride is an antidiabetic used for many years, currently; it considered the first choice in treatment of type 2 diabetes (T2D). It decreases insulin resistance, does not induce hypoglycaemia, increases glucose utilization in the liver and skeletal muscle, and decreases hepatic glucose production. Its adverse effects (AE) are gastrointestinal, decrease in vitamin B12 absorption, abnormalities of hemogram and rarely skin reactions. The objective of this study was to report the type and frequency of AEs of MetforminHydrochloride used in the therapeutic management of T2D patients admitted to the medical center and the diabetes home of Sidi Bel-Abbès in Algeria.

MATERIALS AND METHODS

A cross-sectional descriptive study was carried out over a period of four months, from January 1st, 2017 to April 30th, 2017, involving 130 patients treated with MetforminHydrochloride consulting at Mimoun City Diabetes Home and Gambetta Diabetes Center in the town of Sidi Bel-Abbès. The primary outcome measure was the determination of the type and frequency of AEs related to normal dosages or overdose use of MetforminHydrochloride in T2D. Data were collected from patient records, using a questionnaire, and analyzed using Statistical Package for the Social Sciences, version 20 software.

RESULTS

130 patients were included, including 82 women, with a mean age of 51.08±8.85 years (30-66). One hundred and ninety-eight (198) AEs were reported, an average of 1.52 AEs per patient. Among them, 95 (47.98%) AEs are digestive disorders (30.77% of patients suffered from diarrhea, 10.77% had nausea and vomiting, 8.46% suffered from abdominal pain and bloating, 3.85% lost their taste, 7.69% complained of epigastric cramps and 11.54% of anorexia), 29 (14.65%) AEs are hypoglycaemia, 73 (36.87%) AEs are other symptoms and 1 (0.50%) EI is vitamin B12 deficiency and no cases of lactic acidosis or allergic reaction were reported. Five (3.85%) patients had a total and lasting intolerance to MetforminHydrochloride leading to its discontinuation following persistent diarrhoea.

CONCLUSION

AEs of MetforminHydrochloride used in the management of T2D patients consulting at the medical center and the Diabetes home of Sidi Bel-Abbès are frequent. Digestive disorders were the most frequent, diarrhea was very frequent and led to discontinuation of treatment in 3.85% of T2D patients, followed by nausea and vomiting, then abdominal pain, bloating and epigastric cramps, and rarely taste metallic. Hypoglycaemia was frequent following its association with insulin, the onset of headaches and fatigue were frequent, but no case of lactic acidosis or allergic reaction was reported. Due to a lack of means, the dosage of homocysteine and methylmalonic acid had not been carried out to confirm the vitamin B12 deficiency in the patient whose level was less than 200ng/mL. A precise assessment of the imputability of reported AEs is necessary.

Effect of Metformin on Vitamin B12 Deficiency in Patients With Type 2 Diabetes Mellitus and Factors Associated With It: A Meta-Analysis

The current meta-analysis aims to explore the effect of metformin use on vitamin B12 deficiency in patients with type 2 diabetes mellitus (T2DM) and the factors associated with it. This meta-analysis followed the Meta-analysis Of Observational Studies in Epidemiology (MOOSE) guidelines and the Preferred Reporting Items for Systematic reviews and Meta-Analysis (PRISMA) guidelines. We searched PubMed and EMBASE from January 1, 2010, to October 31, 2022, to collect the studies that reported the effect of metformin on the deficiency of vitamin B12 in patients with T2DM and the factors associated with it. A total of 17 studies were included in the current meta-analysis. Among all the included studies, 13 were cross-sectional studies, 3 were retrospective cohorts, and one was a case-control study. The pooled rate of deficiency of vitamin B12 in patients receiving metformin (23.16%) was significantly higher compared to patients who were not on metformin (17.4%) (OR: 2.95, 95% CI: 2.18-4.00, p-value: 0.001). Factors significantly associated with vitamin B12 deficiency in patients with T2DM and receiving metformin include the duration of metformin use and a greater dose of metformin. In conclusion, our meta-analysis found that the prevalence of vitamin B12 deficiency is greater in patients receiving metformin compared to patients who did not receive metformin. Given the importance of vitamin B12 in nutrition, metformin-induced B12 decrease may be harmful to patients with T2DM. Supplemental vitamin B12 may be advantageous for those on metformin.

The efficacy of vitamin B12 supplementation for treating vitamin B12 deficiency and peripheral neuropathy in metformin-treated type 2 diabetes mellitus patients: A systematic review

BACKGROUND AND AIMS

Metformin-treated type 2 diabetes mellitus (T2DM) patients are at higher risk of vitamin B₁₂ deficiency and more severe neuropathy symptoms. There is still no guideline suggesting vitamin B₁₂ supplementation for this population. This study aimed to analyze the efficacy of vitamin B₁₂ supplementation in this population.

METHOD

Studies reporting the efficacy of vitamin B₁₂ supplementation in metformin-treated T2DM patients were systematically searched in PubMed, Cochrane, EBSCOHost, and Scopus following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline. Additional relevant studies were searched manually through citations. Study quality and risk of bias were assessed using suitable tools.

RESULTS

Seven clinical trials with a total of 506 participants were included. Using the Cochrane's Risk of Bias 2 tools for clinical trials, 4 studies were assessed to have high risk of bias and 3 studies had low risk of bias. There were 5 studies that measured changes in serum vitamin B₁₂ level, all of which reported a statistically significant increase after supplementation. Significant reductions in homocysteine after supplementation were found in 2 studies. Its effect on neuropathy symptoms was still unclear, with 2 studies reporting a significant improvement and 1 study reporting no significant effect.

CONCLUSIONS

The results of this systematic review support the implementation of vitamin B₁₂ supplementation for metformin-treated T2DM to prevent or treat vitamin B₁₂ deficiency and neuropathy. More high-quality clinical studies are required to generate quantitative analysis and to encourage supplementation in available guidelines.

Is metformin a possible treatment for diabetic neuropathy?

Metformin is a hypoglycemic drug widely used in the treatment of type 2 diabetes. It has been proven to have analgesic and neuroprotective effects. Metformin can reverse pain in rodents, such as diabetic neuropathic pain, neuropathic pain caused by chemotherapy drugs, inflammatory pain and pain caused by surgical incision. In clinical use, however, metformin is associated with reduced plasma vitamin B12 levels, which can further neuropathy. In rodent diabetes models, metformin plays a neuroprotective and analgesic role by activating adenosine monophosphate-activated protein kinase, clearing methylgloxal, reducing insulin resistance, and neuroinflammation. This paper also summarized the neurological adverse reactions of metformin in diabetic patients. In addition, whether metformin has sexual dimorphism needs further study.

Metformin-induced vitamin B12 deficiency can cause or worsen distal symmetrical, autonomic and cardiac neuropathy in the patient with diabetes

Metformin blocks the absorption of vitamin B12 through a mechanism that has not been established but could be because of interference with the calcium-dependent binding of the intrinsic factor vitamin B12 complex to the cubam receptor in the terminal ileum. The subsequent deficiency of vitamin B12 may cause or accelerate distal symmetrical and autonomic neuropathy in the patient with diabetes. Several observational studies and meta-analyses have reported a significant association between metformin utilization and vitamin B12 deficiency. Prospective studies have shown that not only do metformin utilizers have lower vitamin B12 levels but they also have higher frequencies of distal symmetrical polyneuropathy and autonomic neuropathy (including cardiac denervation, which is associated with increased incidences of cardiac arrhythmias, cardiac events and mortality). Therefore, periodic monitoring of vitamin B12 is recommended in all patients who utilize metformin, particularly if metformin has been used for over 5 years at which stage hepatic stores of vitamin B12 would probably be depleted. Factors that accelerate the loss of hepatic vitamin B12 stores are proton pump inhibitors, bariatric surgery, being elderly and having an increased turnover of red blood cells. If serum vitamin B12 levels are borderline, measurement of methylmalonic acid and homocysteine levels can detect vitamin B12 deficiency at its earliest stage. Therapies include prophylactic calcium and vitamin B12 supplements, metformin withdrawal, replenishing vitamin B12 stores with intramuscular or oral vitamin B12 therapy and regular monitoring of vitamin B12 levels and vitamin B12 supplements if metformin continues to be utilized. With adequate vitamin B12 replacement, while symptoms of neuropathy may or may not improve, objective findings of neuropathy stabilize but do not improve.

The Regulation and Characterization of Mitochondrial-Derived Methylmalonic Acid in Mitochondrial Dysfunction and Oxidative Stress: From Basic Research to Clinical Practice

Methylmalonic acid (MMA) can act as a diagnosis of hereditary methylmalonic acidemia and assess the status of vitamin B12. Moreover, as a new potential biomarker, it has been widely reported to be associated with the progression and prognosis of chronic diseases such as cardiovascular events, renal insufficiency, cognitive impairment, and cancer. MMA accumulation may cause oxidative stress and impair mitochondrial function, disrupt cellular energy metabolism, and trigger cell death. This review primarily focuses on the mechanisms and epidemiology or progression in the clinical study on MMA.

Vitamin B12 Deficiency and Clinical Neuropathy with Metformin Use in Type 2 Diabetes

Introduction: Type 2 diabetes (T2DM), which is more prevalent (more than 90% of all diabetes cases) and the main driver of the diabetes epidemic, now affects 5.9% of the world’s adult population, with almost 80% of the total in developing countries. At present, 537 million adults (20−79 years) are living with diabetes—1 in 10. This number is predicted to rise to 643 million by 2030 and 783 million by 2045. In India, reports show that 69.2 million people are living with diabetes (8.7%) as per 2015 data. Long-term metformin treatment is a known pharmacological cause of vitamin B12 (Vit B12) deficiency, as was evident within the first 10−12 years after it started to be used. Methods: This was a cross-sectional study conducted in the Postgraduate Department of Medicine in one of the tertiary hospitals in Kashmir. A total of 1600 consecutive patients with T2DM were taken for the study. Out of which 700 patients met the inclusion criteria. These 700 patients were divided into two groups: those taking metformin, and those who were not on metformin. Cumulative metformin doses were recorded in patients taking metformin, using history of dose and duration of treatment. Serum Vit B12 levels were taken for all patients. Based on the results of Vit B12 levels, patients were classified into normal levels (20 pmol/L), possible B12 deficiency (150−220 pmol/l), and definite deficiency (<150 pmol/L). Results: Our results depicted that patients on prolonged metformin therapy showed an increase in Vit B12 deficiency by 11.16%. The prevalence of clinical neuropathy in the metformin-exposed group was 45%, whereas, a prevalence of 31.8% was found in the non-metformin group. The mean age of patients with neuropathy was higher than those without neuropathy (59.01 ± 7.14 vs. 49.95 ± 7.47) (p-value < 0.514, statistically insignificant). Conclusions: In our study, we found that metformin use is associated with Vit B12 deficiency, which is dependent upon the cumulative dose of metformin. Importantly, prolonged metformin use is also associated with an increase in the prevalence of clinical neuropathy.

Association between vitamin B12 level and clinical peripheral neuropathy in type 2 diabetic patients on metformin therapy

Background

Vitamin B12 malabsorption is one of the side effects of long-term metformin intake. Prolonged vitamin B12 deficiency can lead to irreversible nervous system damage. So, the current study aimed to determine the association between serum vitamin B12 level and clinical peripheral neuropathy among type 2 DM patients who are on metformin in comparison to those not taking it. It is a cross-sectional study that was conducted in Egypt and recruited 100 type 2 diabetic patients who were divided into 2 groups: metformin treated, and non-metformin treated (50 subjects per group). The collected data included personal history, medical history, dietetic history that included frequency of eating food rich in vitamin B12 and clinical peripheral neuropathy assessment by Toronto Clinical Scoring System (TCSS). Blood samples were collected for assessment of HbA1c and vitamin B12 level.

Results

Vitamin B12 deficiency was present in 4% of metformin group and 2% of non-metformin group. The mean value of vitamin B12 between metformin users (624.3 ± 364.1 pg/ml) and non-metformin users (991.0 ± 489.9 pg/ml) showed a high significant difference, p value < 0.001. There was a significant difference between study groups regarding HbA1c level (p value = 0.03). Peripheral neuropathy was significantly associated with HbA1c (p value = 0.04) and female gender (p value = 0.001).

Conclusions

Vitamin B12 level was lower in type 2 diabetic patients on metformin compared to those on other oral anti-diabetic drugs, but without significant deficiency. Peripheral neuropathy was significantly associated with poor glycemic control and female gender, but was not associated with vitamin B12 deficiency.

Frequency of Vitamin B12 Deficiency in Type 2 Diabetic Patients Taking Metformin

Introduction

Type 2 diabetes mellitus (DM) is a prevalent global health problem and is on a constant rise, especially in middle- and low-income countries. Vitamin B12 malabsorption is one of the reported side effects of metformin. Our study aims to assess the correlation of B12 deficiency in type 2 diabetics using metformin for their treatment.

Methods

This case-control study was conducted in a tertiary care hospital in Pakistan from February 2021 to December 2021. Patients (n=100) with a documented diagnosis of type 2 DM on metformin monotherapy for a minimum of six months were enrolled via consecutive convenient non-probability sampling. Another 100 patients without a history of diabetes were included in the study as a control group for comparison.

Results

Serum vitamin B-12 levels were higher in the non-diabetic participants as compared to the diabetic group (301.71 ± 72.12 vs. 189.25 ± 31.22; p-value: <0.0001). Hypovitaminosis was more significant in the diabetic group (p-value: 0.0000). Serum vitamin B12 levels were found to be declining with the increasing duration of metformin use (p-value: <0.0001).

Conclusion

Our study found a significant effect of vitamin B12 deficiency in metformin-treated patients. Therefore, it is prudent to recognize B12 deficiency as a potential side effect of long-term use of metformin. A periodic screening of B12 in such patients and subsequent supplementation of vitamin B12 is an effective and safe means of prevention of development or worsening of peripheral nerve damage and other clinical manifestations.

Does Metformin Treatment in Pediatric Population Cause Vitamin B12 Deficiency?

BACKGROUND/AIM

There have been no studies to date examining the effect of metformin treatment on vitamin B12 status in children and adolescents. In this prospective study, the effects of metformin on blood vitamin B12, serum methylmalonic acid (MMA), homocysteine and holo-transcobalamin-II (holo-TC-II) levels were assessed in pediatric age group.

MATERIALS AND METHODS

This prospective study was conducted at the Pediatric Endocrinology and Adolescent Department between January 2017 and March 2019. Metabolic syndrome and polycystic ovary syndrome diagnosed patients with insulin resistance and/or impaired glucose tolerance, patients with type 2 diabetes mellitus (DM) treated with metformin were enrolled in study. Blood vitamin B12, MMA, homocysteine, holo-TC-II levels and hemogram values were evaluated.

RESULTS

Twenty-four patients were enrolled in study. Among these, 15 (62.5%) were female. The mean age of patients was 13.7±2.3 (10-19) years. Sixteen patients were diagnosed with metabolic syndrome and 8 patients were type 2 DM. At 6-month follow-up of all patients, there was no statistically significant difference in terms of vitamin B12, homocysteine, MMA and holo-TC-II levels. A 0.6% decline in vitamin B12 levels were revealed. At 12-month follow-up of 11 patients (45.8%) (6 Type 2 DM, 5 metabolic syndrome), no statistically significant difference was determined in vitamin B12, homocysteine, MMA and holo-TC-II levels. There were 6% decline in vitamin B12 levels and 10.9% increase in homocysteine levels, 5.4% decrease was detected in holo-TC-II level.

CONCLUSION

Although no significant changes in the serum vitamin B12, homocysteine, MMA or holo-TC-II levels with metformin therapy were detected, long-term prospective studies with high-dose metformin treatment in pediatric population are needed to confirm our results.

Deficiency of folate and vitamin B12 increases oxidative stress in chronic pancreatitis patients

BACKGROUND

Folate and vitamin B₁₂ are involved in metabolic reactions for combating oxidative stress. We measured erythrocyte folate and plasma vitamin B₁₂ and compared these with blood antioxidants - erythrocyte glutathione (GSH), glutathione peroxidase (GPx), superoxide dismutase (SOD), and plasma vitamin C - and marker of lipid peroxidation, thiobarbituric acid reactive substance (TBARS), in chronic pancreatitis (CP) patients.

METHODS

One hundred and seventy-five CP patients (91 tropical, 84 alcoholic) and 113 healthy controls were recruited. Erythrocyte folate and plasma vitamin B₁₂ were measured using microbiological assay, and antioxidant levels and erythrocyte TBARS by spectrophotometry.

RESULTS

Erythrocyte folate and plasma vitamin B₁₂ were significantly lower in CP patients than controls (225.4 ± 9.13 vs. 380.38 ± 17.29 nmol/L, p < 0.001 and 233.23 ± 10.4 vs. 338.84 ± 19.01 pmol/L, p < 0.001), and in diabetic- vs. non-diabetic CP patients. Blood antioxidant levels were significantly lower and TBARS was higher in CP patients as compared to controls. Low folate level correlated with low GSH levels (r = 0.314, p < 0.001). CP patients with low folate and vitamin B₁₂ had low GSH and GPx levels as compared to patients with normal folate and vitamin B₁₂ levels. Low vitamin B₁₂ level was associated with 3.24 (95% CI 1.11-9.46, p < 0.05) fold increased risk of pancreatic insufficiency. Smoking was associated with 9.82 (95% confidence interval [CI] 3.3-29.22, p < 0.05) fold increased risk of having low folate levels.

CONCLUSION

Low folate and vitamin B₁₂ levels were associated with increased oxidative stress in CP patients.

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.

Diabetic Complications: An Update on Pathobiology and Therapeutic Strategies

Despite the advent of novel therapies which manage and control diabetes well, the increased risk of morbidity and mortality in diabetic subjects is associated with the devastating secondary complications it produces. Long-standing diabetes majorly drives cellular and molecular alterations, which eventually damage both small and large blood vessels. The complications are prevalent both in type I and type II diabetic subjects. The microvascular complications include diabetic neuropathy, diabetic nephropathy, diabetic retinopathy, while the macrovascular complications include diabetic heart disease and stroke. The current therapeutic strategy alleviates the complications to some extent but does not cure or prevent them. Also, the recent clinical trial outcomes in this field are disappointing. Success in the drug discovery of diabetic complications may be achieved by a better understanding of the underlying pathophysiology and by recognising the crucial factors contributing to the development and progression of the disease. In this review, we discuss the well-studied cellular mechanisms leading to the development and progression of diabetic complications. In addition, we also highlight the various therapeutic paradigms currently in clinical practice.

Effectiveness of Empagliflozin With Vitamin D Supplementation in Peripheral Neuropathy in Type 2 Diabetic Patients

Background: Neuropathy is the most prevalent broad-spectrum microvascular complication of diabetes. The present study aims to evaluate the effect of empagliflozin with vitamin D supplementation on diabetic peripheral neuropathy.

Methods: A prospective, randomized, controlled study was conducted for six months including 150 type 2 diabetic patients, divided into three groups (n=50/group): Group 1, patients on oral hypoglycemic agents; Group 2, patients on empagliflozin and Group 3, patients on empagliflozin with vitamin D. Biochemical parameters were estimated for outcome measurements and patients’ neuropathic pain was analysed using Douleur Neuropathique 4 Questions, Neuropathic Pain Symptom Inventory and Ipswich Touch the toes test questionnaire. Data were analysed using a one-way analysis of variance.

Results: Diabetic neuropathy in males was more prevalent (more than 50%) as compared to females in all three groups, with an average age of 50±6 years, along with a diabetic history of 15±4.5 years and a glycated hemoglobin A1C (HbA1C) level of >10%. The mean value of serum vitamin D level significantly increased by 64.7% (19±5 to 54±8 ng/mL; p<0.05). A remarkable decrease (by 17.4%) from baseline in the HbA1C level was observed after six months of treatment only in Group 3, whereas in other groups (1 and 2), there was a non-significant decrease in HbA1C levels when compared to baseline. Moreover, a significant improvement in neuropathic condition was seen only in Group 3.

Conclusion: The results indicated that empagliflozin with vitamin D supplementation significantly controlled or reduced HbA1C and improved diabetic neuropathic symptoms in patients. It is suggested that this combination can be considered as the primary therapeutic approach for neuropathic complications in diabetic patients.

Hyperhomocysteinemia: Metabolic Role and Animal Studies with a Focus on Cognitive Performance and Decline-A Review

Disturbances in the one-carbon metabolism are often indicated by altered levels of the endogenous amino acid homocysteine (HCys), which is additionally discussed to causally contribute to diverse pathologies. In the first part of the present review, we profoundly and critically discuss the metabolic role and pathomechanisms of HCys, as well as its potential impact on different human disorders. The use of adequate animal models can aid in unravelling the complex pathological processes underlying the role of hyperhomocysteinemia (HHCys). Therefore, in the second part, we systematically searched PubMed/Medline for animal studies regarding HHCys and focused on the potential impact on cognitive performance and decline. The majority of reviewed studies reported a significant effect of HHCys on the investigated behavioral outcomes. Despite of persistent controversial discussions about equivocal findings, especially in clinical studies, the present evaluation of preclinical evidence indicates a causal link between HHCys and cognition-related- especially dementia-like disorders, and points out the further urge for large-scale, well-designed clinical studies in order to elucidate the normalization of HCys levels as a potential preventative or therapeutic approach in human pathologies.

Long-term metformin therapy and vitamin B12 deficiency: An association to bear in mind

To date, metformin remains the first-line oral glucose-lowering drug used for the treatment of type 2 diabetes thanks to its well-established long-term safety and efficacy profile. Indeed, metformin is the most widely used oral insulin-sensitizing agent, being prescribed to more than 100 million people worldwide, including patients with prediabetes, insulin resistance, and polycystic ovary syndrome. However, over the last decades several observational studies and meta-analyses have reported a significant association between long-term metformin therapy and an increased prevalence of vitamin B12 deficiency. Of note, evidence suggests that long-term and high-dose metformin therapy impairs vitamin B12 status. Vitamin B12 (also referred to as cobalamin) is a water-soluble vitamin that is mainly obtained from animal-sourced foods. At the cellular level, vitamin B12 acts as a cofactor for enzymes that play a critical role in DNA synthesis and neuroprotection. Thus, vitamin B12 deficiency can lead to a number of clinical consequences that include hematologic abnormalities (e.g., megaloblastic anemia and formation of hypersegmented neutrophils), progressive axonal demyelination and peripheral neuropathy. Nevertheless, no definite guidelines are currently available for vitamin B12 deficiency screening in patients on metformin therapy, and vitamin B12 deficiency remains frequently unrecognized in such individuals. Therefore, in this "field of vision" article we propose a list of criteria for a cost-effective vitamin B12 deficiency screening in metformin-treated patients, which could serve as a practical guide for identifying individuals at high risk for this condition. Moreover, we discuss additional relevant topics related to this field, including: (1) The lack of consensus about the exact definition of vitamin B12 deficiency; (2) The definition of reliable biomarkers of vitamin B12 status; (3) Causes of vitamin B12 deficiency other than metformin therapy that should be identified promptly in metformin-treated patients for a proper differential diagnosis; and (4) Potential pathophysiological mechanisms underlying metformin-induced vitamin B12 deficiency. Finally, we briefly review basic concepts related to vitamin B12 supplementation for the treatment of vitamin B12 deficiency, particularly when this condition is induced by metformin.

Serum vitamin B12 status of patients with type 2 diabetes mellitus on metformin: A single-center cross-sectional study from Bangladesh

Background:

Metformin use is a known cause of B12 deficiency in patients with type 2 DM (T2DM). Diabetic peripheral neuropathy (DPN) often has clinically indistinguishable clinical features of B12 deficiency-induced peripheral neuropathy (PN).

Objective:

The present study aims to assess serum vitamin B12 levels in patients with T2DM on metformin.

Subjects and Methods:

This cross-sectional study was conducted at a specialized endocrine outpatient clinic in Cumilla, Bangladesh, over six months from January 2020 to June 2020. Non-pregnant adults (≥18 years age) receiving metformin for T2DM for at least six months were evaluated for PN and assessed for serum B12 levels.

Results:

Among 90 subjects evaluated, 28 (31.1%) had B12 deficiency and 6 (6.7%) had borderline B12 deficiency; 56 (62.2%) had normal B12 levels. Study subjects with subnormal B12 used metformin for a longer duration [8.5 (7.0-14.0) vs. 5.0 (2.25-10.0) years, median (IQR), P = 0.006], gram-years of metformin use was higher in them [12.0 (7.9-14.0) vs. 5.75 (2.0-13.6) years, median (IQR), P = 0.005] and they had a higher mean corpuscular volume [85.9±7.2 vs. 82.4±6.4 fL, mean±SD, P = 0.020] compared to those having normal B12 levels. Serum B12 levels had a strong negative correlation with duration of metformin use and gram-years of metformin use. B12 status did not influence the presence and severity of PN.

Conclusions:

A considerable number of patients with T2DM have subnormal B12 levels. Periodic screening for serum vitamin B12 level may be of clinical benefit in such patients.

Adverse Effects of Medications on Micronutrient Status: From Evidence to Guidelines

Recent dietary reference intake workshops focusing on nutrient requirements in chronic disease populations have called attention to the potential adverse effects of chronic medication use on micronutrient status. Although this topic is mostly ill defined in the literature, several noteworthy drug-nutrient interactions (DNIs) are of clinical and public health significance. The purpose of this narrative review is to showcase classic examples of DNIs and their impact on micronutrient status, including those related to antidiabetic, anticoagulant, antihypertensive, antirheumatic, and gastric acid-suppressing medications. Purported DNIs related to other drug families, while relevant and worthy of discussion, are not included. Unlike previous publications, this review is primarily focused on DNIs that have sufficient evidence supporting their inclusion in US Food and Drug Administration labeling materials and/or professional guidelines. While the evidence is compelling, more high-quality research is needed to establish clear and quantitative relationships between chronic medication use and micronutrient status. Expected final online publication date for the Annual Review of Nutrition, Volume 41 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Stellenwert klinischer, funktioneller und bildgebender Diagnostik zur Früherkennung, Differenzialdiagnose und Verlaufskontrolle diabetischer Neuropathien

Von weltweit mehr als 400 Mio. Menschen mit Diabetes mellitus entwickeln bis zu 50% im Laufe ihrer Erkrankung eine Neuropathie. Trotz oder gerade wegen dieser Häufigkeit darf jedoch nicht jede Neuropathie, die in Koinzidenz mit einem Diabetes mellitus auftritt, unkritisch als diabetische Neuropathie diagnostiziert werden. Eine präzise Ausschluss- und Ausmaßdiagnostik ist entscheidend, um andere behandelbare Erkrankungen wie z. B. die Chronisch Inflammatorische Demyelinisierende Polyradikuloneuropathie oder die hereditäre Transthyretin-Amyloidose nicht zu übersehen. Einfache, nicht-invasive, preiswerte und allzeit verfügbare Screeningmethoden stellen Anamnese und klinische Untersuchung dar. Ergänzend ist in frühen Erkrankungsstadien die Quantitativ Sensorische Testung hilfreich zur Eingrenzung einer Small Fiber-Dysfunktion. Sind, typischerweise im Verlauf, große Nervenfasern geschädigt, so ist das charakteristische elektrophysiologische Bild das einer längenabhängigen, axonalen, sensibel betonten oder sensomotorischen Neuropathie. Die Nervensonografie kann zur Unterscheidung von autoimmun-demyelinisierenden Neuropathien hilfreich sein. Moderne Untersuchungsverfahren wie die MR-Neurografie können auch proximale Nervenabschnitte bis auf Faszikelebene darstellen, sind allerdings nur an wenigen Zentren verfügbar. Haut- und Nervenbiopsien sind v. a. bei untypischen Verläufen zur Abgrenzung von Differenzialdiagnosen hilfreich. Diabetische Neuropathien können zu einer erheblichen Reduktion von Lebensqualität und Lebensdauer führen. Zur frühest- und bestmöglichen ursächlichen und symptomatischen Therapieeinleitung ist eine präzise Diagnostik essentiell.

Vitamin B12 status in health and disease: a critical review. Diagnosis of deficiency and insufficiency - clinical and laboratory pitfalls

Vitamin B₁₂ (cobalamin) is an essential cofactor for two metabolic pathways. It is obtained principally from food of animal origin. Cobalamin becomes bioavailable through a series of steps pertaining to its release from dietary protein, intrinsic factor-mediated absorption, haptocorrin or transcobalamin-mediated transport, cellular uptake, and two enzymatic conversions (via methionine synthase and methylmalonyl-CoA-mutase) into cofactor forms: methylcobalamin and adenosylcobalamin. Vitamin B₁₂ deficiency can masquerade as a multitude of illnesses, presenting different perspectives from the point of view of the hematologist, neurologist, gastroenterologist, general physician, or dietician. Increased physician vigilance and heightened patient awareness often account for its early presentation, and testing sometimes occurs during a phase of vitamin B₁₂ insufficiency before the main onset of the disease. The chosen test often depends on its availability rather than on the diagnostic performance and sensitivity to irrelevant factors interfering with vitamin B₁₂ markers. Although serum B₁₂ is still the most commonly used and widely available test, diagnostics by holotranscobalamin, serum methylmalonic acid, and plasma homocysteine measurements have grown in the last several years in routine practice. The lack of a robust absorption test, coupled with compromised sensitivity and specificity of other tests (intrinsic factor and gastric parietal cell antibodies), hinders determination of the cause for depleted B₁₂ status. This can lead to incorrect supplementation regimes and uncertainty regarding later treatment. This review discusses currently available knowledge on vitamin B₁₂, informs the reader about the pitfalls of tests for assessing its deficiency, reviews B₁₂ status in various populations at different disease stages, and provides recommendations for interpretation, treatment, and associated risks. Future directions for diagnostics of B₁₂ status and health interventions are also discussed.

Plasma 3-hydroxyisobutyrate (3-HIB) and methylmalonic acid (MMA) are markers of hepatic mitochondrial fatty acid oxidation in male Wistar rats

OBJECTIVE

Discovery of specific markers that reflect altered hepatic fatty acid oxidation could help to detect an individual's risk of fatty liver, type 2 diabetes and cardiovascular disease at an early stage. Lipid and protein metabolism are intimately linked, but our understanding of this crosstalk remains limited.

METHODS

In male Wistar rats, we used synthetic fatty acid analogues (3-thia fatty acids) as a tool to induce hepatic fatty acid oxidation and mitochondrial biogenesis, to gain new insight into the link between fatty acid oxidation, amino acid metabolism and TCA cycle-related intermediate metabolites in liver and plasma.

RESULTS

Rats treated with 3-thia fatty acids had 3-fold higher hepatic, but not adipose and skeletal muscle, expression of the thioesterase 3-hydroxyisobutyryl-CoA hydrolase (Hibch), which controls the formation of 3-hydroxyisobutyrate (3-HIB) in the valine degradation pathway. Consequently, 3-thia fatty acid-stimulated hepatic fatty acid oxidation and ketogenesis was accompanied by decreased plasma 3-HIB and increased methylmalonic acid (MMA) concentrations further downstream in BCAA catabolism. The higher plasma MMA corresponded to higher MMA-CoA hydrolase activity and hepatic expression of GTP-specific succinyl-CoA synthase (Suclg2) and succinate dehydrogenase (Sdhb), and lower MMA-CoA mutase activity. Plasma 3-HIB correlated positively to plasma and hepatic concentrations of TAG, plasma total fatty acids, plasma NEFA and insulin/glucose ratio, while the reverse correlations were seen for MMA.

CONCLUSION

Our study provides new insight into TCA cycle-related metabolic changes associated with altered hepatic fatty acid flux, and identifies 3-HIB and MMA as novel circulating markers reflective of mitochondrial β-oxidation in male Wistar rats.

Profiling immuno-metabolic mediators of vitamin B12 deficiency among metformin-treated type 2 diabetic patients in Ghana

BACKGROUND

The association between prolong metformin usage and B12 deficiency has been documented. However, the prevalence estimates of metformin-induced vitamin B12 deficiency showed substantial disparity among studies due to varied study definitions of vitamin B12 deficiency. Metformin blocks the calcium dependent absorption of the vitamin B12-Intrinsic Factor complex at the terminal ileum. Lack of intrinsic factor due to the presence of auto-antibodies to parietal cells (IFA) could lead to vitamin B12 deficiency and subsequently cause peripheral neuropathy. We investigated the prevalence of vitamin B12 deficiency using more sensitive, combined markers of vitamin B12 status (4cB12) and the immuno-biochemical mediators of vitamin B12 deficiency.

METHODS

In this observational study, 200 consecutive consenting metformin-treated T2DM patients, aged 35 and above, attending the diabetic clinic at KATH were recruited. Vitamin B12 deficiency was classified based on the Fedosov age-normalized wellness quotient. Anthropometric measurement was taken as well as blood samples for immunological and biochemical mediators. Peripheral neuropathy was assessed using the Michigan Neuropathy Screening Instrument (MNSI). Statistical analysis was performed using the R Language for Statistical Computing.

RESULTS

Using the combined indicator (4cB12), the prevalence of metformin induced vitamin B12 deficiency was 40.5% whilst the prevalence of MNSI-Q and MNSI-PE diabetic neuropathy was 32.5% and 6.5% respectively. Participants with vitamin B12 deficiency had significantly higher levels of IFA, GPA, TNF-α, TC, LDL and albumin compared to those with normal vitamin B12 levels (p < 0.05). Correlation analysis revealed a statistically significant negative association between 4cB12 and the immunological markers [IFA (rs = -0.301, p<0.0001), GPA (rs = -0.244, p = 0.001), TNF-α (rs = -0.242, p = 0.001) and IL-6 (rs = -0.145, p = 0.041)]. Likewise, 4cB12 was negatively associated with TC (rs = -0.203, p = 0.004) and LDL (rs = -0.222, p = 0.002) but positively correlated with HDL (rs = 0.196, p = 0.005).

CONCLUSION

Vitamin B12 deficiency and diabetic neuropathy are very high among metformin-treated T2DM patients and it is associated with increased GPA, IFA, TNF-α and cardiometabolic risk factors (higher LDL and TC and lower HDL). Upon verification of these findings in a prospective case-control study, it may be beneficial to include periodic measurement of Vitamin B12 using the more sensitive combined indicators (4cB 12) in the management of patients with T2DM treated with metformin in Ghana.

Age-induced metabolic reprogramming underlies cancer progression

Aging is a main risk factor for cancer. Using human serum we demonstrated that tumor progression and metastases occur, at least in part, as a manifestation of global metabolic deregulation of the aged host. This shows that the role of aging in cancer goes far beyond increased exposure time to mutagens; the aging process coordinates various aspects required for malignancy.

The relationship between exacerbated diabetic peripheral neuropathy and metformin treatment in type 2 diabetes mellitus

Metformin-treated diabetics (MTD) showed a decrease in cobalamin, a rise in homocysteine, and methylmalonic acid, leading to accentuated diabetic peripheral neuropathy (DPN). This study aimed to determine whether or not metformin is a risk factor for DPN. We compared MTD to non-metformin-treated diabetics (NMTD) clinically using the Toronto Clinical Scoring System (TCSS), laboratory (methylmalonic acid, cobalamin, and homocysteine), and electrophysiological studies. Median homocysteine and methylmalonic acid levels in MTD vs. NMTD were 15.3 vs. 9.6 µmol/l; P < 0.001 and 0.25 vs. 0.13 µmol/l; P = 0.02, respectively with high statistical significance in MTD. There was a significantly lower plasma level of cobalamin in MTD than NMTD. Spearman’s correlation showed a significant negative correlation between cobalamin and increased dose of metformin and a significant positive correlation between TCSS and increased dose of metformin. Logistic regression analysis showed that MTD had significantly longer metformin use duration, higher metformin dose > 2 g, higher TCSS, lower plasma cobalamin, and significant higher homocysteine. Diabetics treated with metformin for prolonged duration and higher doses were associated with lower cobalamin and more severe DPN.

Assessment of Serum Vitamin B12 and Folate Levels and Macrocytosis in Patients with Type 2 Diabetes Mellitus on Metformin Attending Tikur Anbessa Specialized Hospital, Addis Ababa, Ethiopia: A Cross-Sectional Study

BACKGROUND

Metformin is the first-line drug in the treatment of type 2 diabetes mellitus. Monitoring vitamin B₁₂ deficiency associated with long-term and high-dose therapy is not a common practice in many clinical settings in Ethiopia.

OBJECTIVE

The study aimed to measure levels of serum vitamin B₁₂ and folate and to assess the macrocytic status of type 2 diabetes mellitus patients on metformin.

METHODS

A cross-sectional study was conducted on 80 type 2 diabetes mellitus patients who had been on metformin for 5 months or more at the diabetic clinic of Tikur Anbessa Specialized Teaching Hospital. Serum vitamin B₁₂ and folate levels were quantified by chemiluminescent immunoassays. Mean corpuscular volume was determined by complete blood count. Differences in vitamin B₁₂ and folate levels and mean corpuscular volume between different groups were assessed using Kruskal-Wallis H and Mann-Whitney U tests.

RESULTS

Vitamin B₁₂ and folate deficiency were documented in 5% and 23.8% of participants, respectively, and 6.2% of patients were macrocytic. Levels of vitamin B₁₂ and folate in patients who had been on metformin >1,500 mg/day ≥4 years were significantly lower those who had been on metformin 1,000-1,500 mg/day and <1,000 mg/day <4 years, respectively.

CONCLUSION

Low serum vitamin B₁₂ and folate levels and macrocytosis were found to be associated with prolonged metformin treatment.

Metformin as a potential therapeutic for neurological disease: mobilizing AMPK to repair the nervous system

Introduction:

Metformin is currently first line therapy for type 2 diabetes (T2D). The mechanism of action of metformin involves activation of AMP-activated protein kinase (AMPK) to enhance mitochondrial function (for example, biogenesis, refurbishment and dynamics) and autophagy. Many neurodegenerative diseases of the central and peripheral nervous systems arise from metabolic failure and toxic protein aggregation where activated AMPK could prove protective.

Areas covered:

The authors review literature on metformin treatment in Parkinson’s disease, Huntington’s disease and other neurological diseases of the CNS along with neuroprotective effects of AMPK activation and suppression of the mammalian target of rapamycin (mTOR) pathway on peripheral neuropathy and neuropathic pain. The authors compare the efficacy of metformin with the actions of resveratrol.

Expert opinion:

Metformin, through activation of AMPK and autophagy, can enhance neuronal bioenergetics, promote nerve repair and reduce toxic protein aggregates in neurological diseases. A long history of safe use in humans should encourage development of metformin and other AMPK activators in preclinical and clinical research. Future studies in animal models of neurological disease should strive to further dissect in a mechanistic manner the pathways downstream from metformin-dependent AMPK activation, and to further investigate mTOR dependent and independent signaling pathways driving neuroprotection.

Peripheral Neuropathy in de novo Patients with Parkinson's Disease

PURPOSE

This study aimed to investigate the prevalence of peripheral neuropathy (PNP) and its related serum metabolites in de novo patients with Parkinson's disease (PD). PNP is a type of frequent comorbidity in PD. Although the administration of levodopa has been described as a presumptive risk factor in its development, few studies have explored its effect on unmedicated PD patients.

MATERIALS AND METHODS

This study included 105 drug-naïve de novo PD patients. A standardized nerve conduction study (NCS) technique was used to evaluate motor or sensory neuropathy. We analyzed serologic tests including metabolic markers of vitamin B12, homocysteine (Hcy), and uric acid (UA).

RESULTS

We found abnormal nerve conduction velocity findings in 24 out of 105 total patients. Among them, 20 patients showed a type of combined motor-sensory, while three were a type of pure sensory and one was a pure motor. Nine patients had carpal tunnel syndrome. PD with PNP group demonstrated higher serum levels of Hcy and UA compared to PD without PNP group.

CONCLUSION

Our data demonstrated a potential role of Hcy and UA on PNP in de novo patients with PD. These results suggest the contribution of the inherent metabolic pathway in deterioration of the peripheral nervous system in PD.

Long-term metformin treatment and risk of peripheral neuropathy in older Veterans

AIM

Our objective was to assess whether increased duration of metformin therapy is associated with incident peripheral neuropathy (PN) in older Veterans with diabetes.

METHODS

Using national Veterans Affairs registry data from 2002 to 2015, we examined Veterans (50 + years) with diabetes. Long-term metformin therapy was defined as prescription ≥ 500 mg/day, filled for ≥ 6 consecutive months. Metformin therapy duration was examined both as continuous and categorical measures. Incident PN was defined by medical chart review. We estimated unadjusted and adjusted (variables selecteda priori)odds ratios (OR) and 95% confidence intervals (CI) using logistic regression.

RESULTS

The study included n = 210,004 individuals (mean ± SD: age: 66.2 ± 8.4 yrs, 96% male) prescribed metformin for 47.0 ± 34.0 months. Nineteen percent developed PN during follow-up. After adjusting for age, body mass index, duration of time receiving health care within the VA, smoking status, alcohol abuse, and vitamin B12 testing and treatment, the number of months of metformin treatment was associated with elevated odds for incident PN (aOR (metformin treatment - continuous) = 1.009 (95% CI = 1.009, 1.010); aOR (metformin treatment - categorical (ref: 6-<18 months): 18-<44.1 months = 1.57 (1.51-1.63), 44.1-<61 months = 2.05 (1.97-2.14), 61 + months = 2.69 (2.58-2.79), all p-values < 0.0001).

CONCLUSION

Our study suggests that Veterans treated for at least 18 months with metformin are approximately 2-3 times more likely to develop PN than those treated at least six, but<18 months. Future studies are needed to determine whether the association we found may be due to a decline in vitamin B12 status following metformin initiation.

Emerging Concepts in Nutrient Needs

Dietary reference intakes (DRIs) are quantitative, nutrient intake-based standards used for assessing the diets and specific nutrient intakes of healthy individuals and populations and for informing national nutrition policy and nutrition programs. Because nutrition needs vary by age, sex, and physiological state, DRIs are often specified for healthy subgroups within a population. Diet is known to be the leading modifiable risk factor for chronic disease, and the prevalence of chronic disease is growing in all populations globally and across all subgroups, but especially in older adults. It is known that nutrient needs can change in some chronic disease and other clinical states. Disease states and/or disease treatment can cause whole-body or tissue-specific nutrient depletion or excess, resulting in the need for altered nutrient intakes. In other cases, disease-related biochemical dysfunction can result in a requirement for a nonessential nutrient, rendering it as conditionally essential, or result in toxicity for a food component at levels usually tolerated by healthy people, as seen in inborn errors of metabolism. Here we summarize examples from a growing body of literature of disease-altering nutrient requirements, supporting the need to give more consideration to special nutrient requirements in disease states.

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.

Metformin Usage Index and assessment of vitamin B12 deficiency among metformin and non-metformin users with type 2 diabetes mellitus

AIM

The present study aimed to evaluate the combined effect of both dose and duration of metformin therapy on vitamin B12 levels in patients with type 2 diabetes mellitus (T2D).

METHODS

We recruited 2887 patients with T2D between January 2018 and November 2019 and categorized them into two groups (metformin and non-metformin users) matched for age, mean duration of diabetes, and BMI. We calculated the "Metformin Usage Index" (MUI) which was defined as the product of the dose of metformin (mg) used and its duration divided by 1000. Vitamin B12 levels were compared between the two groups, and its association with MUI was assessed using correlation and multistep logistic regression analyses.

RESULTS

Vitamin B12 levels < 200 pg/ml and between 200 and 300 pg/ml were noted among 24.5% and 34.5% metformin users, respectively; this was significantly higher than among non-metformin users (17.3% and 22.6%, respectively) [P < 0.001]. Overall, a vitamin B12 level < 300 pg/ml was found in 52.2% of the subjects. There was a significant association between an MUI > 5 and a high risk of vitamin B12 deficiency [P < 0.01]. The highest risk was observed among patients with an MUI > 15 [odds ratio (OR) 6.74, 95% CI 4.39-10.4] followed by patients with an MUI > 10 (OR 5.12, 95% CI 3.12-8.38).

CONCLUSIONS

The MUI can be employed as a risk assessment tool for evaluation of vitamin B12 deficiency in patients with T2D. Further prospective studies are required to determine the MUI thresholds in populations with good nutritional statuses and low prevalence of vitamin B12 deficiency.

[Causes, spectrum, and treatment of the diabetic neuropathy]

BACKGROUND

Half of all diabetics are affected by a diabetic neuropathy. Microangiopathy, dysfunctional Schwann cell interactions, accumulation of toxic metabolites, and inflammatory processes all contribute to nerve damage.

OBJECTIVE

Overview and perspectives of the pathophysiology as well as the current and future treatment implications.

METHODS

Literature search (1990-2020).

RESULTS

Clinically predominant are sensory and autonomic symptoms; however, muscle weakness can occur as well. Complications such as unrecognized myocardial infarctions and the diabetic foot syndrome are potentially life-threatening and can cause major disability. The pathophysiology of neuropathies in type 1 and type 2 diabetes mellitus differs due to additional risk factors of the metabolic syndrome. To reduce the risk of neuropathy, an intensive insulin therapy is superior compared to the conventional insulin therapy. Oral antidiabetic drugs should be chosen based on individual risk profiles. Metformin can cause an iatrogenic vitamin B12 deficiency. In the treatment of neuropathic pain, the calcium channel blocker pregabalin has the highest recommendation level. The tricyclic antidepressant amitriptyline is considered to be equally effective, but it is contraindicated in autonomic dysregulation and cognitive impairment. Alternatively, the serotonin-norepinephrine reuptake inhibitor duloxetine is approved for the symptomatic treatment of diabetic neuropathies. Controversially discussed medications include alpha-lipoic acid, epalrestat, and L‑serine.

CONCLUSION

The diabetic neuropathy is frequent and causes severe complications. A good understanding of the underlying pathophysiology can contribute to the development of novel treatment strategies in the future.

Relationship between metformin use and vitamin B12 status in patients with type 2 diabetes in Japan

AIMS/INTRODUCTION

Metformin therapy has been associated with vitamin B12 (VB12) deficiency, but information regarding this adverse effect in Asian populations is limited. We have now examined the relationship between metformin use and VB12 status in individuals with type 2 diabetes mellitus in Japan.

MATERIALS AND METHODS

This cross-sectional study was carried out with type 2 diabetes mellitus patients treated (Met group, n = 122) or not treated (control group, n = 63) with metformin. The primary end-point was the difference in the serum concentration of homocysteine, a marker of VB12 activity, between the two groups. The serum concentrations of VB12, blood hemoglobin level and mean corpuscular volume were also compared between the groups. Subset analysis was carried out with individuals aged ≥70 years. The potential correlation between the daily dose or duration of metformin treatment and the other measured parameters was also examined.

RESULTS

The level of homocysteine, as well as the VB12 level, hemoglobin concentration and mean corpuscular volume, did not differ significantly between the control and treated with metformin groups. The level of homocysteine was positively and that of VB12 negatively correlated with the daily dose of metformin. Among elderly individuals, the hemoglobin level was significantly lower in the treated with metformin group than in the control group, although the mean corpuscular volume was similar in the two groups.

CONCLUSIONS

The risk of VB12 deficiency during metformin treatment appears to be low in Japanese type 2 diabetes mellitus patients. However, high doses of metformin might result in a moderate decrease in the circulating VB12 level, as well as in anemia in elderly individuals.

Evaluating the correlation between serum vitamin B12 levels and various haematologic indices among metformin-treated type 2 diabetic patients: A prospective analytical study

Background:

Metformin-induced vitamin B12 deficiency state or metformin-induced hypocobalaminemia is gradually becoming an epidemic among diabetic patients on moderate-to-high doses of metformin or those diabetic patients on metformin for a long period of time. The potential effect of chronic metformin pharmacotherapy to cause vitamin B12 deficiency with abnormalities in haematologic indices and central/peripheral neuropathy has been widely reported. Long-term usage of metformin has been reported to be associated with intestinal malabsorption of vitamin B12 culminating in vitamin B12 deficiency with likely associated haematologic abnormalities (including macro-ovalocytic anaemia and immune dysfunctioning due to hypersegmentation of polymorphonuclear leukocytes), central/peripheral neuropathy and manifestation of biochemical derangements such as elevated homocysteine and methyl malonate levels.

Aim:

This study aimed to determine the correlation between serum vitamin B12 levels and various haematologic indices among metformin-treated type 2 diabetic patients in a clinical practice setting with the rational purpose of alleviating/preventing the associated derangements.

Materials and Methods:

This was a case-control, prospective, analytical, observational study of 200 adult participants (100 per group) attending the Endocrinology Out-patients Clinic of Irrua Specialist Teaching Hospital, Irrua, Edo State, Nigeria. For each participant, serum vitamin B12 level was determined using a vitamin B12 immunoassay technique, while the corresponding complete blood count was done using PCE-210N autohaematology analyser. Data were presented using tables and figures. Chi-square test was used to compare categorical variables, Student t-test was used in comparing means of continuous variables, while Pearson’s correlation study was done to determine the existence of any statistically significant correlation(s) between the serum vitamin B12 levels and various haematologic indices among the participants.

Results:

Approximately 41% versus 20% of the metformin-treated and metformin-naive diabetic patients, respectively, had frank vitamin B12 deficiency. There was a statistical difference between the total serum vitamin B12 levels in male and female diabetic patients with p = 0.048. Also, statistically significant differences existed with respect to mean corpuscular volume (MCV), mean corpuscular haemoglobin and total white blood cells count among the metformin-treated and metformin-naive diabetic patients. Furthermore, a statistically significant weak positive correlation existed between pack cell volume (PCV) and serum vitamin B12 level ( r = +0.148, p = 0.037), but a statistically significant weak negative correlation existed between MCV and serum vitamin B12 level ( r = −0.245, p = 0.0001). In addition, the test for associations between the serum vitamin B12 categorization status or metformin exposure status and the peripheral neuropathy components assessment revealed that there were statistically significant associations between the serum vitamin B12 categorization status or metformin exposure status versus pain sense ( p < 0.0001 or <0.001), vibration sense ( p < 0.0001 or <0.001) and light touch sense ( p < 0.0001 or <0.001) among the participants.

Conclusion:

In this study, statistically significant weak positive and weak negative correlations existed between serum vitamin B12 level versus PCV, and serum vitamin B12 level versus MCV, respectively. The peripheral neuropathy components assessment revealed that there were statistically significant associations between the serum vitamin B12 categorization status or metformin exposure status versus pain sense, vibration sense and light touch sense among the participants.

Evaluation of Vitamin B12 Monitoring in Veterans With Type 2 Diabetes on Metformin Therapy

BACKGROUND

Studies have shown an association between metformin use and vitamin B₁₂ deficiency. Since 2017, the American Diabetes Association (ADA) Standards of Medical Care in Diabetes Guideline has included a recommendation for periodic vitamin B₁₂ measurements in metformin-treated patients, especially those with anemia or peripheral neuropathy.

OBJECTIVE

To determine the overall incidence and impact of the ADA Guideline on vitamin B₁₂ monitoring in a veteran population on long-term metformin therapy.

METHODS

Retrospective chart review was performed for patients on metformin who started therapy prior to 2005 at the VA North Texas Health Care System (VANTXHCS). The primary outcome was the proportion of patients with at least 1 vitamin B₁₂ level drawn during 2016 versus 2018. Metformin dose and duration, vitamin B₁₂ supplementation, and incident neuropathy prescriptions or diagnosis were also analyzed.

RESULTS

Of 394 patients included for the primary outcome, 136 (34.5%) had at least 1 vitamin B₁₂ level in 2016 versus 198 (50.3%) patients in 2018 (odds ratio: 1.94, P < .001). Of the 394 patients, 157 were diagnosed with neuropathy or prescribed a medication for neuropathy without a vitamin B₁₂ level in the previous year or with a low level that was not supplemented.

CONCLUSION

Vitamin B₁₂ monitoring significantly increased between 2016 and 2018, aligning with the release of the 2017 ADA guidelines. However, a large proportion of patients were identified who were diagnosed with or treated for neuropathy without adequate vitamin B₁₂ monitoring.

Water Soluble Vitamins and their Role in Diabetes and its Complications

BACKGROUND

Diabetes is a metabolic disorder associated with abnormally high levels of glucose in the blood due to inadequate production of insulin or inadequate sensitivity of cells to the action of insulin. Diabetes has become an increasing challenge in the world. The predicted diabetic population according to the World Health Organization is 8.7% between the age group 20-70 years. There are many complications linked to prolonged high blood glucose levels, such as microvascular complications and macrovascular complications. Vitamins play an important role in glucose metabolism and the potential utility of supplementation is relevant for the prevention and/or management of diabetes mellitus and its complications.

METHODS

Literature search was performed using various dataset like PUBMED, EBSCO, ProQuest, Scopus and selected websites like the National Institute of Health and the World Health Organization.

RESULT

Water-soluble vitamins have been thoroughly studied for their activity in diabetes and diabetic complications.

CONCLUSION

Water-soluble vitamins like B1, B3, B6, B7, B9 and B12 have notable effects in diabetes mellitus and its related complications like nephropathy, neuropathy, retinopathy and cardiomyopathy.

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.