Relationship between metformin use, vitamin B12 deficiency, hyperhomocysteinemia and vascular complications in patients with type 2 diabetes

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.

The effects of daily dose and treatment duration of metformin on the prevalence of vitamin B12 deficiency and peripheral neuropathy in Chinese patients with type 2 diabetes mellitus: A multicenter cross-sectional study

AIMS

To evaluate the prevalence of vitamin B12 deficiency in Chinese patients with type 2 diabetes mellitus receiving metformin treatment and to investigate the effects of metformin daily dose and treatment duration on the prevalence of vitamin B12 deficiency and peripheral neuropathy (PN).

MATERIALS AND METHODS

In this multicenter cross-sectional study, 1027 Chinese patients who had been taking ≥1000 mg/day metformin for ≥1 year were enrolled using proportionate stratified random sampling based on daily dose and treatment duration. Primary measures included the prevalence of vitamin B12 deficiency (<148 pmol/L), borderline B12 deficiency (148 pmol/L-211 pmol/L), and PN.

RESULTS

The prevalence of vitamin B12 deficiency, borderline deficiency, and PN were 2.15%, 13.66%, and 11.59%, respectively. Patients receiving ≥1500 mg/day metformin had significantly higher prevalence of borderline vitamin B12 deficiency (16.76% vs. 9.91%, p = .0015) and serum B12 ≤221 pmol/L (19.25% vs. 11.64%, p < .001) than patients receiving <1500 mg/day metformin. No difference was found in prevalence of borderline vitamin B12 deficiency (12.58% vs. 15.49%, p = .1902) and serum B12 ≤221 pmol/L (14.91% vs. 17.32%, p = .3055) between patients receiving metformin for ≥3 and <3 years. Patients with vitamin B12 deficiency had numerically higher PN prevalence (18.18% vs. 11.27%, p = .3192) than patients without it. Multiple logistic analyses revealed that HbA1c and metformin daily dose were associated with the prevalence of borderline B12 deficiency and B12 ≤221 pmol/L.

CONCLUSIONS

High daily dosage (≥1500 mg/day) played an important role in metformin-associated vitamin B12 deficiency while not contributing to the risk of PN.

Association between Acid-Lowering Agents, Metformin, and Vitamin B12 among Boston-Area Puerto Ricans

BACKGROUND

Vitamin B12 involves several physiological functions, and malabsorption is reported with medication use.

OBJECTIVES

Studies have reported an inverse association between the use of metformin or acid-lowering agents (ALAs), such as proton pump inhibitors, histamine 2 receptor antagonists, and blood vitamin B12 concentration, because of malabsorption. The concomitant use of these medications is underreported. We sought to examine these associations in a cohort of Boston-area Puerto Rican adults.

METHODS

This analysis was conducted within the Boston Puerto Rican Health Study (BPRHS), an ongoing longitudinal cohort that enrolled 1499 Puerto Rican adults aged 45-75 y at baseline. Our study comprised 1428, 1155, and 782 participants at baseline, wave2 (2.2 y from baseline), and wave3 (6.2 y from baseline), respectively. Covariate-adjusted linear and logistic regression was used to examine the association between baseline medication use and vitamin B12 concentration or deficiency (vitamin B12 <148 pmol/L or methylmalonic acid >271 nmol/L), and long-term medication use (continuous use for ∼6.2 y) and wave3 vitamin B12 concentration and deficiency. Sensitivity analyses were done to examine these associations in vitamin B12 supplement users.

RESULTS

At baseline, we observed an association between metformin use (β = -0.069; P = 0.03) and concomitant ALA and metformin use (β = -0.112; P = 0.02) and vitamin B12 concentration, but not a deficiency. We did not observe associations between ALA, proton pump inhibitors, or histamine 2 receptor antagonists, individually, with vitamin B12 concentration or deficiency.

CONCLUSIONS

These results suggest an inverse relationship between metformin, concomitant ALA, metformin use, and serum vitamin B12 concentration.

Prevalence of Vitamin B12 Deficiency in Type 2 Diabetes Mellitus Patients on Metformin Therapy

Background Long-term metformin treatment in individuals with type 2 diabetes mellitus causes vitamin B12 insufficiency, which is typically neglected, undetected, and under-treated. A severe deficit may cause life-threatening neurological problems. This study assessed the prevalence of vitamin B12 deficiencies among T2DM patients and its factors at a tertiary hospital in the Tamil Nadu district of Salem. Materials and Methods This is an analytical cross-sectional study conducted in a tertiary care hospital in the Salem district, Tamil Nadu, India. Patients with type 2 diabetes mellitus who were prescribed metformin at the outpatient department of general medicine took part in the trial. Our research instrument was a structured questionnaire. We used a questionnaire containing information on sociodemographic characteristics, metformin use among diabetic mellitus patients, diabetes mellitus history, lifestyle behaviors, anthropometric measurement, examination findings, and biochemical markers. Prior to administering the interview schedule, each participant's parents provided written informed consent. A thorough medical history, physical exam, and anthropometric examination were performed. Data were entered in Microsoft Excel (Microsoft Corporation, Redmond, WA) and analyzed using SPSS version 23 (IBM Corp., Armonk, NY). Results Among the study participants, we diagnosed nearly 43% of diabetes cases in participants between the ages of 40-50 years, while we diagnosed 39% aged under 40 years. Nearly 51% had diabetes for 5-10 years, while only 14% had diabetes for over 10 years. In addition, 25% of the study sample had a positive family history of type 2 diabetes. Nearly 48% and 13% of the study group had been on metformin for 5-10 years and >10 years, respectively. The majority, 45%, were found to take 1000 mg of metformin per day, whereas just 15% take 2 g per day. In our study, the prevalence of vitamin B12 insufficiency was 27%, and nearly 18% had borderline levels. The duration of diabetes mellitus, the duration of metformin intake, and the dose of metformin were statistically significant (p-value = 0.05) among the variables associated with diabetes mellitus and vitamin B12 deficiency. Conclusion The results of the study show that a deficiency in vitamin B12 increases the likelihood that diabetic neuropathy would worsen. Therefore, individuals with diabetes who take larger dosages of metformin (more than 1000mg) for an extended period must have their vitamin B12 levels monitored often. Preventative or therapeutic vitamin B12 supplementation can mitigate this issue.

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.

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.

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.

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.

Metformin Improves Learning and Memory in the SAMP8 Mouse Model of Alzheimer's Disease

Metformin is used for the treatment of insulin resistant diabetes. Diabetics are at an increased risk of developing dementia. Recent epidemiological studies suggest that metformin treatment prevents cognitive decline in diabetics. A pilot clinical study found cognitive improvement with metformin in patients with mild cognitive impairment (MCI). Preclinical studies suggest metformin reduces Alzheimer-like pathology in mouse models of Alzheimer's disease (AD). In the current study, we used 11-month-old SAMP8 mice. Mice were given daily injections of metformin at 20 mg/kg/sc or 200 mg/kg/sc for eight weeks. After four weeks, mice were tested in T-maze footshock avoidance, object recognition, and Barnes maze. At the end of the study, brain tissue was collected for analysis of PKC (PKCζ, PKCι, PKCα, PKCγ, PKCɛ), GSK-3β, pGSK-3βser9, pGSK-3βtyr216, pTau404, and APP. Metformin improved both acquisition and retention in SAMP8 mice in T-maze footshock avoidance, retention in novel object recognition, and acquisition in the Barnes maze. Biochemical analysis indicated that metformin increased both atypical and conventional forms of PKC; PKCζ, and PKCα at 20 mg/kg. Metformin significantly increased pGSK-3βser9 at 200 mg/kg, and decreased Aβ at 20 mg/kg and pTau404 and APPc99 at both 20 mg/kg and 200 mg/kg. There were no differences in blood glucose levels between the aged vehicle and metformin treated mice. Metformin improved learning and memory in the SAMP8 mouse model of spontaneous onset AD. Biochemical analysis indicates that metformin improved memory by decreasing APPc99 and pTau. The current study lends support to the therapeutic potential of metformin for AD.

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.

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.

Association between metformin dose and vitamin B12 deficiency in patients with type 2 diabetes

BACKGROUND

Metformin can cause serum vitamin B12 deficiency, but studies on the influence of its duration and dose are lacking. We investigated vitamin B12 deficiency in patients with type 2 diabetes using metformin, in conjunction with other related factors.

METHOD

This cross-sectional study included 1111 patients with type 2 diabetes who took metformin for at least 6 months. Serum vitamin B12 levels were quantified using a competitive-binding immunoenzymatic assay, and vitamin B12 deficiency was defined as serum B12 <300 pg/mL. Information on metformin use and confounding variables were collected from records or questionnaires and interviews.

RESULT

Serum vitamin B12 deficiency occurred in 22.2% of patients (n = 247). After adjusting for confounders, a 1 mg increase in daily metformin dose was associated with a 0.142 pg/mL decrease in vitamin B12 (P < .001). Compared with a daily dose of <1000 mg, the adjusted odds ratios for 1000 to 1500, 1500 to 2000, and ≥2000 mg metformin were 1.72 (P = .080), 3.34 (P < .001), and 8.67 (P < .001), respectively. Vitamin B12 deficiency occurred less often in patients taking multivitamins (odds ratio 0.23; P < .001). After adjusting for confounding factors, there was no correlation between B12 deficiency and duration of metformin use. Serum homocysteine levels showed significant negative correlation with vitamin B12.

CONCLUSION

Metformin at ≥1500 mg/d could be a major factor related to vitamin B12 deficiency, whereas concurrent supplementation of multivitamins may potentially protect against the deficiency. Serum homocysteine levels were negatively correlated with vitamin B12 levels, suggesting that B12 deficiency due to metformin use may occur at the tissue level. However, this hypothesis will require further study.

Associations between metformin use and vitamin B12 levels, anemia, and neuropathy in patients with diabetes: a meta-analysis

BACKGROUND

Metformin is first-line therapy for patients with diabetes. However, it may lower vitamin B₁₂ concentrations, which could have hematological or neurological implications. This meta-analyses reviewed all available studies on associations between metformin use and vitamin B₁₂ levels, anemia, and neuropathy in diabetic patients.

METHODS

PubMed, Web of Knowledge, Cochrane Library, and Embase were searched to identify all relevant studies published in English prior to March 2018. Pooled risk ratios (RRs) and 95% confidence intervals (CIs) were calculated for dichotomous outcomes and pooled mean differences (MDs) and 95% CIs were calculated for continuous outcomes.

RESULTS

Thirty-one studies were included in the meta-analyses. Compared with diabetic patients not taking metformin, patients taking metformin had a significantly higher risk of vitamin B₁₂ deficiency (RR 2.09; 95% CI 1.49, 2.93; P < 0.0001; I²  = 64%) and significantly lower serum vitamin B₁₂ concentrations (MD -63.70; 95% CI -74.35, -53.05] pM; P < 0.00001; I²  = 87%), which depended on dose and duration of treatment. Metformin use was also associated with significantly greater percentage decrease in serum vitamin B₁₂ concentrations from baseline in diabetic patients (MD -14.68%; 95% CI -17.98%, -11.39%; P < 0.00001; I²  = 33%). Analyses revealed no significant association between metformin use and the prevalence of anemia or neuropathy.

CONCLUSIONS

Metformin use led to significantly lowered vitamin B₁₂ concentrations and significantly higher risk of vitamin B₁₂ deficiency in diabetic patients. More quality studies are needed to explore the associations between metformin use and anemia and neuropathy in these patients. Annual vitamin B₁₂ assessment in diabetic patients taking metformin is recommended.

Efficacy Study of Folic Acid Supplementation on Homocysteine Levels in Adolescent Epileptics Taking Antiepileptic Drugs: A Single Blind Randomized Controlled Clinical Trial

BACKGROUND

Epilepsy is a chronic medical condition that requires long-term therapy with antiepileptic drugs (AEDs). However, long-term employment of AEDs may lead to the onset of hyperhomocysteinemia, which has been found to modulate imperative metabolic mechanisms and induce cardiovascular disorders (CVDs). Therefore, adolescent population that have been diagnosed with epilepsy and utilize AEDs are among the most vulnerable, exhibiting higher risks of developing CVDs.

PURPOSE

The present study was designed to explore the effects of folic acid (FA) supplementation on AED-induced hyperhomocysteinemia and CVD risk factors in adolescent epileptics.

METHODS

The randomized clinical trial included adolescent epileptics (i.e., 10-19 years of age) of either sex, on antiepileptic therapy for > 6 months with high homocysteine levels (i.e., >10.9 µmol/L). At the time of enrolment, their baseline BP, lipid and homocysteine levels were recorded. Participants were randomly assigned to either treatment or placebo groups and received the respective treatments. At the end of the first month, BP, lipid and homocysteine levels were recorded and compared to determine the effect of FA on these parameters.

RESULTS AND CONCLUSION

A significant fall in homocysteine levels was observed with FA supplementation (P < 0.05). However, this fall was significantly high in valproic acid treated epileptic patients. In addition, we observed an improvement in high-density lipoprotein levels, a risk factor for CVDs, but the change was statistically insignificant (P > 0.05). The study results suggest that FA supplementation in epileptic patients receiving AED therapy may minimize AED-induced hyperhomocysteinemia and other CVD risk factors.

Important drug-micronutrient interactions: A selection for clinical practice

Interactions between drugs and micronutrients have received only little or no attention in the medical and pharmaceutical world in the past. Since more and more pharmaceutics are used for the treatment of patients, this topic is increasingly relevant. As such interactions - depending on the duration of treatment and the status of micronutrients - impact the health of the patient and the action of the drugs, physicians and pharmacists should pay more attention to such interactions in the future. This review aims to sensitize physicians and pharmacists on drug micronutrient interactions with selected examples of widely pescribed drugs that can precipitate micronutrient deficiencies. In this context, the pharmacist, as a drug expert, assumes a particular role. Like no other professional in the health care sector, he is particularly predestined and called up to respond to this task. The following article intends to point out the relevance of mutual interactions between micronutrients and various examples of widely used drugs, without claiming to be exhaustive.

Role of hyperhomocysteinemia in proliferative diabetic retinopathy: A case-control study

Purpose:

Hyperhomocysteinemia has been postulated as a potential risk factor for the development and progression of diabetic retinopathy. The aim of this study was to determine the association of hyperhomocysteinemia with proliferative diabetic retinopathy (PDR).

Methods:

This was a hospital-based, case–control study, conducted at a tertiary care ophthalmic center in South India. Thirty-nine patients with proliferative diabetic retinopathy were enrolled as cases, and 39 age- and gender-matched patients with no diabetic retinopathy (No DR) were enrolled as controls. Fasting serum homocysteine estimation, as well as baseline investigations, were done in all participants. Data regarding demographic profile and risk factors were documented. Data were analyzed using Chi-square test and independent t-test, as appropriate.

Results:

The prevalence of hyperhomocysteinemia was higher in PDR (59%) compared to “No DR” (48.7%); however, this difference was not statistically significant (P = 0.36). Similarly, the mean serum homocysteine level in cases was higher than in controls, but this was not statistically significant (17.98 + 6.26 μmol/L vs. 17.71 + 8.17 μmol/L; P = 0.87). Longer duration of diabetes, hypertension, anemia, and renal dysfunction were found to be significantly associated with PDR.

Conclusion:

The prevalence of hyperhomocysteinemia as well as the mean serum levels of homocysteine were found to be higher in the cases with PDR, compared to the controls with No DR, although the difference was not statistically significant. Longer duration of diabetes, hypertension, anemia, and renal dysfunction were significantly associated with PDR.

Review of Biguanide (Metformin) Toxicity

In the 1920s, guanidine, the active component of Galega officinalis, was shown to lower glucose levels and used to synthesize several antidiabetic compounds. Metformin (1,1 dimethylbiguanide) is the most well-known and currently the only marketed biguanide in the United States, United Kingdom, Canada, and Australia for the treatment of non-insulin-dependent diabetes mellitus. Although phenformin was removed from the US market in the 1970s, it is still available around the world and can be found in unregulated herbal supplements. Adverse events associated with therapeutic use of biguanides include gastrointestinal upset, vitamin B₁₂ deficiency, and hemolytic anemia. Although the incidence is low, metformin toxicity can lead to hyperlactatemia and metabolic acidosis. Since metformin is predominantly eliminated from the body by the kidneys, toxicity can occur when metformin accumulates due to poor clearance from renal insufficiency or in the overdose setting. The dominant source of metabolic acidosis associated with hyperlactatemia in metformin toxicity is the rapid cytosolic adenosine triphosphate (ATP) turnover when complex I is inhibited and oxidative phosphorylation cannot adequately recycle the vast quantity of H+ from ATP hydrolysis. Although metabolic acidosis and hyperlactatemia are markers of metformin toxicity, the degree of hyperlactatemia and severity of acidemia have not been shown to be of prognostic value. Regardless of the etiology of toxicity, treatment should include supportive care and consideration for adjunct therapies such as gastrointestinal decontamination, glucose and insulin, alkalinization, extracorporeal techniques to reduce metformin body burden, and metabolic rescue.

Epigenetic modifications in hyperhomocysteinemia: potential role in diabetic retinopathy and age-related macular degeneration

To study Hyperhomocysteinemia (HHcy)-induced epigenetic modifications as potential mechanisms of blood retinal barrier (BRB) dysfunction, retinas isolated from three- week-old mice with elevated level of Homocysteine (Hcy) due to lack of the enzyme cystathionine β-synthase (cbs^-/- , cbs^+/- and cbs^+/+ ), human retinal endothelial cells (HRECs), and human retinal pigmented epithelial cells (ARPE-19) treated with or without Hcy were evaluated for (1) histone deacetylases (HDAC), (2) DNA methylation (DNMT), and (3) miRNA analysis. Differentially expressed miRNAs in mice with HHcy were further compared with miRNA analysis of diabetic mice retinas (STZ) and miRNAs within the exosomes released from Hcy-treated RPEs. Differentially expressed miRNAs were further evaluated for predicted target genes and associated pathways using Ingenuity Pathway Analysis. HHcy significantly increased HDAC and DNMT activity in HRECs, ARPE-19, and cbs mice retinas, whereas inhibition of HDAC and DNMT decreased Hcy-induced BRB dysfunction. MiRNA profiling detected 127 miRNAs in cbs^+/- and 39 miRNAs in cbs^-/- mice retinas, which were significantly differentially expressed compared to cbs^+/+ . MiRNA pathway analysis showed their involvement in HDAC and DNMT activation, endoplasmic reticulum (ER), and oxidative stresses, inflammation, hypoxia, and angiogenesis pathways. Hcy-induced epigenetic modifications may be involved in retinopathies associated with HHcy, such as age-related macular degeneration and diabetic retinopathy.

Association between homocysteine level and the risk of diabetic retinopathy: a systematic review and meta-analysis

BACKGROUND

Previous studies have demonstrated that elevated homocysteine (Hcy) level represents an independent risk factor for macrovascular disease. However, the relationship between hyperhomocysteinemia and the progression of diabetic retinopathy in patients remains controversial. Hence, the purpose of this systematic review and meta-analysis was to explore any potential association between Hcy and the risk of diabetic retinopathy.

METHODS

PubMed, Embase, and the Cochrane Library databases were searched to screen studies that fulfilled the inclusion criteria from date of database inception to November 2017. The summary odds ratio (OR) with 95% confidence intervals (CIs) was used to calculate the pooled effect estimate for the relationship between Hcy and diabetic retinopathy risk. Sensitivity, subgroup analyses, and publication bias were also assessed.

RESULTS

Eleven studies involving a total of 2184 diabetic patients were included in the meta-analysis. The summary OR suggested that increased Hcy level in diabetic patients was associated with an increased risk of diabetic retinopathy (OR 1.62; 95% CI 1.29-2.03; p < 0.001). Although significant heterogeneity was detected among the included studies, the findings of sensitivity analysis remained statistically significant. Subgroup analyses found a significant association between Hcy and diabetic retinopathy in most subsets, but no significant association was found if the sample size was < 100, participants had type 1 diabetes mellitus, and the study quality was low.

CONCLUSIONS

The findings of this study suggested that elevated Hcy level was associated with an increased risk of diabetic retinopathy, especially in type 2 diabetic patients. This finding may help diabetic patients to achieve effective management strategy to prevent the progression of diabetic retinopathy.

Perspectives on Peripheral Neuropathy as a Consequence of Metformin-Induced Vitamin B12 Deficiency in T2DM

Peripheral neuropathy (PN) is a primary complication of type 2 diabetes mellitus (T2DM) and a direct manifestation of vitamin B12 deficiency. Examining the effects of metformin use on PN status became imperative following clinical studies that showed the vitamin B12-lowering effect of the medication. The complexity of the topic and the inconsistency of the results warrant consideration of topic-specific perspectives for better understanding of the available evidence and more appropriate design of future studies.

Metformin Treatment and Homocysteine: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

The aim of this systematic review is to assess whether metformin could change the concentration of serum homocysteine (Hcy) with and without simultaneous supplementation of B-group vitamins or folic acid. A literature search was conducted in PubMed, EmBase, and Cochrane Central Register of Controlled Trials (CENTRAL) to identify randomized controlled trials (RCTs) reporting the concentration of serum Hcy in metformin-treated adults. Meta-analysis was applied to assess the association between metformin and the changes of Hcy concentration. Twelve publications were included in this study. In the overall analysis, metformin administration was not statistically associated with the change of Hcy when compared with the control treatment (mean difference (MD), 0.40 μmol/L; 95% confidence interval (CI), -0.07~0.87 μmol/L, p = 0.10). In the subgroup analysis, metformin was significantly associated with an increased concentration of Hcy in the absence of exogenous supplementation of folic acid or B-group vitamins (MD, 2.02 μmol/L; 95% CI, 1.37~2.67 μmol/L, p < 0.00001), but with a decreased concentration of serum Hcy in the presence of these exogenous supplementations (MD, -0.74 μmol/L; 95% CI, -1.19~-0.30 μmol/L, p = 0.001). Therefore, although the overall effect of metformin on the concentration of serum Hcy was neutral, our results suggested that metformin could increase the concentration of Hcy when exogenous B-group vitamins or folic acid supplementation was not given.

Diagnosis of Lingual Atrophic Conditions: Associations with Local and Systemic Factors. A Descriptive Review

Atrophic glossitis is a condition characterised by absence of filiform or fungiform papillae on the dorsal surface of the tongue. Consequently, the ordinary texture and appearance of the dorsal tongue, determined by papillary protrusion, turns into a soft and smooth aspect.

Throughout the years, many factors, both local and systemic, have been associated with atrophic glossitis as the tongue is currently considered to be a mirror of general health. Moreover, various tongue conditions were wrongly diagnosed as atrophic glossitis. Oral involvement can conceal underlying systemic conditions and, in this perspective, the role of clinicians is fundamental.

Early recognition of oral signs and symptoms, through a careful examination of oral anatomical structures, plays a crucial role in providing patients with a better prognosis.

Association Between Serum B12 and Serum Homocysteine Levels in Diabetic Patients on Metformin

INTRODUCTION

Type-2 Diabetes Mellitus (T2DM) and metformin both can lower serum B12 (s.B12). Raised serum Homocysteine (s.Hcy) is considered as an early marker of B12 deficiency.

AIM

The study aimed to check whether homocysteine levels are more sensitive indicator of s. B12 deficiency or not among diabetics using metformin.

MATERIALS AND METHODS

Mean s.B12 and s.Hcy levels of 30 cases (diabetics on metformin <5years) were compared with 30 diabetic controls not on metformin and 31 nondiabetic controls and statistically analysed by ANOVA and post-hoc tests.

RESULTS

No significant differences in either s.B12 mean or s.Hcy mean were found between cases and diabetic controls. s.B12 mean did not differ significantly but s.Hcy mean was significantly higher among nondiabetics as compared to diabetic control. s. B12 level of Nondiabetic group was in borderline category while mean s. B12 levels of cases and diabetic control groups was in normal category but nearer to the lower cut off. Mean s.Hcy values in all the groups were high. Pearson correlation showed strong association between s.B12 and s.Hcy in all the groups. Additionally equation based on linear regression was derived to calculate either of the s.B12 or s.Hcy. On Receiver Operative Characteristic (ROC) curve, area under curve value was 0.842 for the value of s.Hcy.

CONCLUSION

In this study neither metformin nor T2DM could be identified as a cause for s.B12 lowering and raised s.Hcy in the scenario of low normal levels of s.B12 (<300pmol/L). If B12 deficiency recognized early using s. Hcy, consequences due to B12 deficiency can be prevented or delayed among nondiabetics as well as among diabetics and metformin users.

Long-term Metformin Use and Vitamin B12 Deficiency in the Diabetes Prevention Program Outcomes Study

CONTEXT

Vitamin B12 deficiency may occur with metformin treatment, but few studies have assessed risk with long-term use.

OBJECTIVE

To assess the risk of B12 deficiency with metformin use in the Diabetes Prevention Program (DPP)/DPP Outcomes Study (DPPOS).

DESIGN

Secondary analysis from the DPP/DPPOS. Participants were assigned to the placebo group (PLA) (n = 1082) or the metformin group (MET) (n = 1073) for 3.2 years; subjects in the metformin group received open-label metformin for an additional 9 years.

SETTING

Twenty-seven study centers in the United States.

PATIENTS

DPP eligibility criteria were: elevated fasting glucose, impaired glucose tolerance, and overweight/obesity. The analytic population comprised participants with available stored samples. B12 levels were assessed at 5 years (n = 857, n = 858) and 13 years (n = 756, n = 764) in PLA and MET, respectively.

INTERVENTION

Metformin 850 mg twice daily vs placebo (DPP), and open-label metformin in the metformin group (DPPOS).

MAIN OUTCOME MEASURES

B12 deficiency, anemia, and peripheral neuropathy.

RESULTS

Low B12 (≤ 203 pg/mL) occurred more often in MET than PLA at 5 years (4.3 vs 2.3%; P = .02) but not at 13 years (7.4 vs 5.4%; P = .12). Combined low and borderline-low B12 (≤ 298 pg/mL) was more common in MET at 5 years (19.1 vs 9.5%; P < .01) and 13 years (20.3 vs 15.6%; P = .02). Years of metformin use were associated with increased risk of B12 deficiency (odds ratio, B12 deficiency/year metformin use, 1.13; 95% confidence interval, 1.06–1.20). Anemia prevalence was higher in MET, but did not differ by B12 status. Neuropathy prevalence was higher in MET with low B12 levels.

CONCLUSIONS

Long-term use of metformin in DPPOS was associated with biochemical B12 deficiency and anemia. Routine testing of vitamin B12 levels in metformin-treated patients should be considered.

Diabetic neuropathy is not associated with homocysteine, folate, vitamin B12 levels, and MTHFR C677T mutation in type 2 diabetic outpatients taking metformin

BACKGROUND

Hyperhomocysteinemia and vitamin B12 deficiency may be involved in the development of diabetic peripheral neuropathy (DPN). Metformin therapy may reduce vitamin B12 plasma levels, thus contributing to DPN.

AIM AND METHODS

The purposes of this cross-sectional study were to assess (1) the potential associations of DPN with serum levels of homocysteine (tHcy), B-vitamins, and/or the common methylenetetrahydrofolate reductase (MTHFR) C677T mutation; (2) the influence of chronic treatment with metformin on tHcy and B-vitamins concentrations and, finally, (3) to evaluate whether, by this influence, metformin is a risk factor for DPN in a group of type 2 diabetic outpatients.

RESULTS

Our data showed that fasting tHcy, folate, and vitamin B12 levels and the MTHFR C677T genotype distribution were comparable between subjects with (n = 79, 30 %) and without DPN (n = 184, 70 %). Metformin-treated subjects (n = 124, 47 %) showed significantly lower levels of vitamin B12 (P < 0.001), but the prevalence of DPN was not different when compared to those not treated with this drug (33 vs. 27 %, P = NS). At univariate regression analysis, DPN was associated with age, duration of diabetes, HbA1c, creatinine levels, and the presence of coronary heart disease (CHD), and negatively with HDL-C concentrations (P < 0.05 all), but at multivariate regression analysis, high creatinine levels (P = 0.06), low HDL-C levels (P = 0.013), and a higher prevalence of CHD (P = 0.001) were the only variables independently associated with DPN in this population.

CONCLUSIONS

In conclusion, in these type 2 diabetic outpatients circulating levels of tHcy, folate, and the MTHFR C677T mutation are not associated with DPN, which was predicted by creatinine levels, CHD, and dyslipidemia. Metformin therapy is associated with a mild vitamin B12 level reduction, but not with DPN.

The effect of testosterone on cardiovascular risk factors in men with type 2 diabetes and late-onset hypogonadism treated with metformin or glimepiride

BACKGROUND

Men with type 2 diabetes are often characterized by abnormal plasma testosterone levels. This study was aimed at investigating whether testosterone treatment has an impact on cardiovascular risk factors in patients with type 2 diabetes and late-onset hypogonadism (LOH), chronically treated with hypoglycemic agents.

METHODS

This study included 51 men with type 2 diabetes, 26 of whom had already been treated with metformin and 25 with glimepiride for at least 6 months. On the basis of patient preference, 15 men receiving metformin and 12 receiving glimepiride were treated with intramuscular testosterone enanthate (100mg weekly) for 12 weeks. Plasma lipids, glucose homeostasis markers, as well as plasma levels of androgens, uric acid, high-sensitivity C-reactive protein (hsCRP), homocysteine and fibrinogen were determined before and at the end of the study.

RESULTS

With the exception of insulin sensitivity, plasma hsCRP and homocysteine, there were no differences between patients treated with metformin and glimepiride. Testosterone enanthate administered to both groups of patients increased plasma testosterone, reduced plasma hsCRP and improved insulin sensitivity. Testosterone-metformin combination therapy reduced also circulating levels of uric acid, homocysteine and fibrinogen. These effects, stronger in patients treated with metformin than glimepiride, correlated with the impact of testosterone on insulin sensitivity.

CONCLUSIONS

Our results suggest that testosterone may bring more clinical benefits to metformin- than sulfonylurea-treated men with diabetes and LOH.

Identifying Common Genetic Risk Factors of Diabetic Neuropathies

Type 2 diabetes mellitus (T2DM) is a global public health problem of epidemic proportions, with 60-70% of affected individuals suffering from associated neurovascular complications that act on multiple organ systems. The most common and clinically significant neuropathies of T2DM include uremic neuropathy, peripheral neuropathy, and cardiac autonomic neuropathy. These conditions seriously impact an individual's quality of life and significantly increase the risk of morbidity and mortality. Although advances in gene sequencing technologies have identified several genetic variants that may regulate the development and progression of T2DM, little is known about whether or not the variants are involved in disease progression and how these genetic variants are associated with diabetic neuropathy specifically. Significant missing heritability data and complex disease etiologies remain to be explained. This article is the first to provide a review of the genetic risk variants implicated in the diabetic neuropathies and to highlight potential commonalities. We thereby aim to contribute to the creation of a genetic-metabolic model that will help to elucidate the cause of diabetic neuropathies, evaluate a patient's risk profile, and ultimately facilitate preventative and targeted treatment for the individual.

Sulfur as a signaling nutrient through hydrogen sulfide

Hydrogen sulfide (H₂S) has emerged as an important signaling molecule with beneficial effects on various cellular processes affecting, for example, cardiovascular and neurological functions. The physiological importance of H₂S is motivating efforts to develop strategies for modulating its levels. However, advancement in the field of H₂S-based therapeutics is hampered by fundamental gaps in our knowledge of how H₂S is regulated, its mechanism of action, and its molecular targets. This review provides an overview of sulfur metabolism; describes recent progress that has shed light on the mechanism of H₂S as a signaling molecule; and examines nutritional regulation of sulfur metabolism, which pertains to health and disease.

The role of metformin on vitamin B12 deficiency: a meta-analysis review

Metformin is the only biguanide oral hypoglycemic drug, that is used to treat patients with type-2 diabetes mellitus. There are some reports of metformin being associated with decreased serum levels of vitamin B12 (VB12). The objective of this study is to systematically analyze the impact of metformin on the frequency of VB12 deficiency and serum levels of VB12. A search of various databases provided 18 retrospective cohort studies and 11 randomized controlled trials. Pooled estimates of odds ratio with 95% confidence interval using random effect model were conducted. Studies were examined for heterogeneity, publication bias and sensitivity analysis. Separate analysis of randomized control trials (RCTs) including both low-risk and high-risk bias was also conducted. 29 studies were selected with a total of 8,089 patients. 19 studies were rated intermediate or high quality. Primary outcome suggested increased incidence of VB12 deficiency in metformin group (OR = 2.45, 95% CI 1.74-3.44, P < 0.0001.) Heterogeneity was relatively high (I(2) = 53%), with minor publication bias. Secondary outcome suggested lower serum VB12 concentrations in metformin group (Mean difference = -65.8, 95% CI -78.1 to -53.6 pmol/L, P < 0.00001) with high heterogeneity (I(2) = 98%,) and low publication bias. RCTs analysis of low-and high-risk group revealed similar trends. We conclude that metformin treatment is significantly associated with an increase in incidence of VB12 deficiency and reduced serum VB12 levels.

Influence of duration and dose of metformin on cobalamin deficiency in type 2 diabetes patients using metformin

Metformin use is associated with cobalamin (vitamin B12) deficiency. However, the influence of both duration and dose of metformin is unclear. Studies using holotranscobalamin, a marker for cellular cobalamin deficiency, are scarce. We therefore investigated the prevalence of cobalamin deficiency in type 2 diabetes patients using both markers, and its relation with duration and dose of metformin use. This cross-sectional study among 550 type 2 diabetes patients using metformin (mean daily dose 1,306 mg; mean duration 64 months) was conducted in four primary care centers in Utrecht, the Netherlands. Cobalamin and holotranscobalamin concentrations were measured at the annual diabetes check. Detailed information on metformin use and confounding variables was collected from medical records. The prevalence of a cobalamin deficiency was 28.1 %, while a holotranscobalamin deficiency occurred in 3.9 % of the patients. Adjusting for multiple confounders, a 1 mg/day increase in daily metformin dose was associated (p < 0.001) with 0.042 (95 % CI -0.060, -0.023) decrease in cobalamin concentrations. Similarly, a 10 g increase of cumulative metformin dose was associated (p = 0.006) with -0.070 (-0.12, -0.021) lower cobalamin concentrations after adjustment for confounders. Duration of metformin use was not associated with cobalamin concentrations after multivariable adjustment. Similar results were observed for holotranscobalamin. Cobalamin deficiency occurs frequently among diabetes patients using metformin. A higher daily and cumulative doses of metformin were strongly associated with lower cobalamin and holotranscobalamin concentrations, while duration was not. It is thus important to account for metformin dose in recommendations for screening for cobalamin deficiency.

Vitamins and type 2 diabetes mellitus

The present review evaluates the relationship between type 2 diabetes mellitus and individual or combined vitamins. Antioxidant vitamins A, C and E are found decreased in diabetic subjects, possibly due to an increased need to control the excessive oxidative stress produced by abnormalities in glucose metabolism. On the other hand, retinol binding protein exerts a modulating effect, as it has adipokine functions. With respect to the B group vitamins, thiamin, pyridoxine and biotin have been found decreased but the mechanisms are not clear, however supplementation has shown some improvement of the metabolic control in diabetic patients. The absorption of folic acid and vitamin B12 is importantly decreased by the prolongued use of metformin, which is the first choice drug in uncomplicated diabetes, thus these two nutrients have been found deficient in the disease and most probably need to be supplemented regularly. On the other hand, vitamin D is considered a risk factor for the development of diabetes as well as its complications, particularly cardiovascular ones. Although some studies have found an association of vitamin K intake with glucose metabolism further research is needed. Studies on the use of multivitamin supplements have shown unconclusive results. After reviewing the evidence, no real recommendation on the use of vitamin supplements in type 2 diabetes mellitus can be issued, however patients using metformin during prolongued periods may need folic acid and vitamin B12.

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 status in metformin treated patients: systematic review

Objective

Randomized controlled trials and observational studies have yielded inconsistent results on the effects of metformin on vitamin B₁₂ reduction. We therefore performed a systematic review to analyze the effects of metformin on vitamin B₁₂ concentration.

Methods

PubMed, Medline, Embase, and the Cochrane central registry of controlled trials were searched to identify randomized controlled trials and observational studies exploring the association between metformin and vitamin B₁₂ concentration in patients with type 2 diabetes mellitus or polycystic ovary syndrome. The main outcome measure was changes in serum vitamin B₁₂ concentration after 6–208 weeks of treatment with metformin, as compared with placebo or other anti-hyperglycemic therapy.

Results

Six randomized controlled trials met the inclusion criteria. Serum vitamin B₁₂ concentrations were significantly lower in patients treated with metformin than in those who received placebo or rosiglitazone (mean difference [MD], −53.93 pmol/L; 95% confidence interval [CI], −81.44 to −26.42 pmol/L, P = 0.0001). Subgroup analysis identified four trials in which patients received a lower dose of metformin (<2000 mg/d) and two in which they received a higher dose (≥2000 mg/d), with MDs in vitamin B₁₂ concentration after metformin treatment of −37.99 pmol/L (95% CI, −57.44 to −18.54 pmol/L, P = 0.0001) and −78.62 pmol/L (95% CI, −106.37 to −50.86 pmol/L, P<0.00001), respectively.

Conclusions

The reduction of vitamin B₁₂ may be induced by metformin in a dose dependent manner.