Study of Vitamin B12 deficiency and peripheral neuropathy in metformin-treated early Type 2 diabetes mellitus

Serum vitamin B12, distal symmetrical polyneuropathy and anaemia in type 2 diabetes: the Fremantle Diabetes Study Phase 2

BACKGROUND

There are limited data relating to the effects of metformin-associated vitamin B12 deficiency on the risk of distal symmetrical polyneuropathy (DSPN) and megaloblastic anaemia in well-characterised community-based cohorts.

AIMS

To assess inter-relationships between metformin therapy, vitamin B12 deficiency assessed using serum active B12 concentrations, and DSPN and anaemia in 1492 Fremantle Diabetes Study Phase 2 (FDS2) participants with type 2 diabetes.

METHODS

Prevalence rates of vitamin B12 deficiency (total <80 pmol/L, active <23 pmol/L) and borderline deficiency (total ≥80 and ≤200 pmol/L, active ≥23 and ≤35 pmol/L) were determined using baseline sera. The relationship between vitamin B12 status and both DSPN and anaemia was assessed using multivariable analyses.

RESULTS

Most FDS2 participants (94.4%) were vitamin B12 replete (total serum concentration >200 pmol/L, active >35 pmol/L), 2.0% were deficient (total <80 pmol/L, active <23 pmol/L) and the remainder (3.6%) borderline. Although metformin treatment increased the odds of deficiency (4.2%, 3.1% borderline) in a dose-dependent fashion (odds ratio (95% confidence interval) 39.4 (4.90-316) for >2000 mg daily compared with no treatment; P < 0.001), there was no significant association between vitamin B12 status and DSPN, anaemia (haemoglobin ≤130 g/L males, ≤120 g/L females), haemoglobin concentration or mean corpuscular volume (P ≥ 0.147). Metformin increased the likelihood of anaemia, especially at high doses, independent of vitamin B12 deficiency.

CONCLUSIONS

Since nutritional sources likely attenuate metformin-associated vitamin B12 malabsorption and its clinical sequelae in developed countries such as Australia, there is no need for routine/opportunistic serum vitamin B12 screening in metformin-treated patients.

Neuroprotective role of vitamin B12 in streptozotocin-induced type 1 diabetic rats

Chronic hyperglycemia-induced neuropathological changes include neuronal apoptosis, astrogliosis, decrease in neurotrophic support, impaired synaptic plasticity, and impaired protein quality control (PQC) system. Vitamin B12 is indispensable for neuronal development and brain function. Several studies reported the neuroprotective effect of B12 supplementation in diabetic patients. However, the underlying molecular basis for the neuroprotective effect of B12 supplementation in diabetes needs to be thoroughly investigated. Two-month-old Sprague-Dawley rats were randomly assigned into three groups: Control (CN), diabetes (D; induced with streptozotocin; STZ), and diabetic rats supplemented with vitamin B12 (DBS; vitamin B12; 50 μg/kg) for four months. At the end of 4 months of experimentation, the brain was dissected to collect the cerebral cortex (CC). The morphology of CC was investigated with H&E and Nissl body staining. Neuronal apoptosis was determined with TUNEL assay. The components of neurotrophic support, astrogliosis, synaptic plasticity, and PQC processes were investigated by immunoblotting and immunostaining methods. H& E, Nissl body, and TUNEL staining revealed that diabetes-induced neuronal apoptosis and degeneration. However, B12 supplementation ameliorated the diabetes-induced neuronal apoptosis. Further, B12 supplementation restored the markers of neurotrophic support (BDNF, NGF, and GDNF), and synaptic plasticity (SYP, and PSD-95) in diabetic rats. Interestingly, B12 supplementation also attenuated astrogliosis, ER stress, and ameliorated autophagy-related proteins in diabetic rats. Overall, these findings suggest that B12 acts as a neuroprotective agent by inhibiting the neuropathological changes in STZ-induced type 1 diabetes. Thus, B12 supplementation could produce beneficial outcomes including neuroprotective effects in diabetic patients.

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.

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.

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.

Association Between HbA1c Levels and Diabetic Peripheral Neuropathy: A Case-Control Study of Patients with Type 2 Diabetes Using Claims Data

BACKGROUND

Evidence on the efficacy of glycemic control for diabetic peripheral neuropathy (DPN) is limited in patients with type 2 diabetes mellitus. Despite the known relationship between hemoglobin A1c (HbA1c) and DPN, the parameters (e.g., mean values or variability) that play an important role have not been elucidated.

OBJECTIVE

The objective of this study was to explore factors associated with DPN, including long-term HbA1c parameters, among patients with type 2 diabetes, in a large-scale longitudinal study.

METHODS

We conducted a case-control study using a medical claims database. We extracted data of patients with type 2 diabetes and disease records of DPN (indicating that they received treatment for DPN) and those without DPN records (controls), and matched for age, sex, index year, and duration since the first type 2 diabetes record. A logistic regression analysis was performed to explore factors associated with DPN, and a receiver-operating characteristic analysis to estimate the optimal mean HbA1c target.

RESULTS

Of 1,792,037 patients with type 2 diabetes, data from 1632 patients (816 per group) were analyzed. The mean HbA1c levels in the 3-year observation period were 7.2 ± 1.0% in the DPN group and 6.9 ± 1.1% in the control group. Elevated 3-year mean HbA1c levels were significantly associated with DPN records (adjusted odds ratio: 1.23, 95% confidence interval 1.06-1.42), while HbA1c variability was not significantly associated. The mean HbA1c levels that discriminated between patients with and without DPN records were 6.5% (unadjusted) and 7.1% (adjusted).

CONCLUSIONS

The development or progression of DPN in patients with type 2 diabetes was associated with the 3-year mean HbA1c level in real-world data.

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.

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.

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.

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.

Changes of Peripheral Nerve Function and Vitamin B12 Level in People With Parkinson's Disease

Background and Purpose: Peripheral nerve function plays an important role in balance control. Impairment of peripheral sensory information appears in people with Parkinson's disease (PD). Furthermore, there is a link between peripheral nerve disorders and vitamin B₁₂ level. Here, we studied whether there were deficits of peripheral nerve function and vitamin B₁₂ level, which may lead to decreased postural stability in PD.

Methods: Fifty PD and 50 age-matched healthy subjects were enrolled in the study. This study evaluated folic acid and vitamin B₁₂ levels in serum. Postural balance was studied according to the clinical Tinetti scale. Some comprehensive physiological assessments of peripheral nerve functions, including peripheral sensation, the perception of temperature, pain, and touch sensations, were also undertaken in this study.

Results: Compared with the control group, vitamin B₁₂ and folic acid were decreased in PD (P < 0.05). Furthermore, the PD group exhibited declines in peripheral nerve functions, including touch, temperature, pain, and nerve conduction velocity (P < 0.05). Statistical tests identified a significant association between decreased peripheral nerve function and poor balance according to the Tinetti scale (P < 0.05). Low vitamin B₁₂ levels were also associated with deficits of peripheral nerve function, cumulative levodopa dose, and poor balance in PD (P < 0.05).

Conclusions: Data suggested that peripheral nerve function was impaired in people with PD. Deficits of sensory input and low vitamin B₁₂ level may contribute to balance deficits in PD.

Influence of the complex drug Cocarnit on the sciatic nerve in the development of diabetic polyneuropathy in rats

Ulcers and slow wound healing are common in diabetic polyneuropathy (DP), as well as shooting or burning pain, sensitivity to touch or lack of sensitivity, low oxygenation of nerve tissue, conductivity disorders and various vascular disorders. The mechanisms of DP development are complex and have not been completely studied. To take into account the role of B group vitamins, we investigated histological structure of nerve tissue, the level of different growth factors and the qualitative composition of active proteolytic enzymes in rats with DP and after the use of the metabolic drug Cocarnit for 9 days. This drug composition include nicotinamide, cocarboxylase, cyanocobalamin, adenosine triphosphate disodium trihydrate. We used an histological study of sciatic nerve; enzyme-linked immunosorbent assay and enzyme electrophoresis methods. In rats with DP, fragmentation of nerve tissue and their necrosis was established. Moreover, degraded forms of plasmin that has a fully functional serine proteinase domain are evident, and, therefore, it exhibits proteolytic properties. DP led to a decrease of neuron growth factor (NGF), vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF). After treatment, the histological structure of nerve tissue was significantly improved, and the expression of growth factors NGF and bFGF was increased. Our study demonstrated that administration of Corcarnit brought about the complete restoration of the activation potential of plasmin and the almost disappearance of all degraded forms which were evident in the group with DP.

Association of vitamin B12 deficiency in people with type 2 diabetes on metformin and without metformin: a multicenter study, Karachi, Pakistan

OBJECTIVE

To assess the prevalence of vitamin B₁₂ deficiency in people with type 2 diabetes mellitus (T2DM) on metformin and without metformin.

METHODOLOGY

Between May 2018 and January 2019, this prospective multicenter observational study recruited participants from seven centers in four provinces of Pakistan (Sindh, Punjab, Baluchistan and Khyber Pakhtunkhwa). Participants with T2DM treated with metformin for >2 years and those not on metformin underwent assessment of hemoglobin, vitamin B₁₂, homocysteine and diabetic neuropathy (vibration perception threshold (VPT) >15V) and painful diabetic neuropathy (Douleur Neuropathique 4 (DN4) ≥4) and Diabetic Neuropathy Symptom (DNS) score ≥1.

RESULTS

Of 932 subjects, 645 (69.2%) were treated with metformin, while 287 (30.8%) were not on metformin. Overall, B₁₂ deficiency (<200 pg/mL) was significantly higher in metformin users of 25 (3.9%), compared with non-metformin users of 6 (2.1%), while B₁₂ insufficiency (200-300 pg/mL) was significantly lower in metformin users of 117 (18.4%) compared with non-metformin users of 80 (27.9%). Subjects with B₁₂ deficiency and insufficiency with hyperhomocysteinemia (≥15) were found in 19 (76%) µmol/L and 69 (60.5%) µmol/L in metformin users compared with 6 (100%) µmol/L and 57 (73.1%) μmol/L in non-metformin users, respectively. VPT>25 and DN4 score ≥4 were significantly higher in B₁₂-deficient metformin users compared with non-metformin users. Similarly, DNS score ≥1 was non-significantly higher in B₁₂-deficient metformin users compared with non-metformin users.

CONCLUSION

This study shows that vitamin B₁₂ insufficiency was frequently found in our population and may progress into B₁₂ deficiency. It is also associated with neuropathy in subjects on metformin. Further interventional studies to assess the benefit of B₁₂ treatment on painful neuropathy in patients on metformin may be warranted. B₁₂ levels may be checked in people with T2DM using metformin for >2 years.

Discovering metformin-induced vitamin B12 deficiency in patients with type 2 diabetes in primary care

BACKGROUND

Although metformin is the preferred initial pharmacological choice in type 2 diabetes, there is evidence that reveals a link between metformin use and vitamin B12 deficiency. The American Diabetes Association (ADA) has recently recommended periodic measurement of B12 levels for all patients on metformin.

LOCAL PROBLEM

Medical record data collected for the preintervention period showed that only 5% (n = 23) of patients diagnosed with diabetes and on metformin had B12 levels checked at an internal medicine primary care practice.

METHODS

This was a quasi-experimental project of preintervention and postintervention design using a checklist containing important measures of diabetes control. The project sample population consisted of data of adults with type 2 diabetes aged 18 years and older who were prescribed metformin in the previous year at the primary care practice.

INTERVENTIONS

The intervention focused on revising an existing diabetes measures checklist to include a prompt for an annual measurement of B12 levels.

RESULTS

There was significant improvement in monitoring vitamin B12 levels and discovery of low vitamin B12 levels. These data show that the number of B12 levels checked increased from 23 during the preintervention to 155 during the intervention (p ≤ 0.0000).

CONCLUSIONS

This project supports a conclusion that including a prompt to check B12 levels to an existing checklist increases B12 monitoring in this patient population. Results may encourage other providers to follow the ADA guidelines for monitoring vitamin B12 levels for patients taking metformin.

Vitamin B12 deficiency and diabetic neuropathy in patients taking metformin: a cross-sectional study

OBJECTIVE

Vitamin B12 deficiency resulting from metformin use has been demonstrated in multiple studies. In this study, we aimed to evaluate the prevalence of vitamin B12 deficiency in patients with chronic metformin use and the relationship between vitamin B12 deficiency and diabetic neuropathy.

METHODS

A cross-sectional study was conducted with 162 patients. Vitamin B12 levels were measured by chemiluminescence immunoassay. Diabetic neuropathy was evaluated by patient record, nerve conduction and Michigan test for the diagnosis of diabetic neuropathy. Additional data, including demographic characteristics were collected. A linear regression model was used to evaluate variables that correlated with vitamin B12 levels and diabetic neuropathy.

RESULTS

Low vitamin B12 levels were found in 7.3% (95% CI: 4.0-12%) of patients. In those with diabetic neuropathy, altered (low and borderline) vitamin B12 level was 64% (95% CI: 47-78%) compared to 17% (95% CI: 10-26%) in patients without diabetic neuropathy (coefficient: -110.8; CI 95%: -165.8, -59.7). Those taking a higher metformin dose had lower levels of vitamin B12 (coefficient: -0.061; CI 95%: -0.09, -0.024). In addition, female patients had higher levels of vitamin B12 compared to men (coefficient: 49.1; CI 95%: 2.3-95).

CONCLUSIONS

Vitamin B12 deficiency is highly prevalent, especially in patients with diabetic neuropathy. In this study an inverse correlation was found between diabetic neuropathy and the plasma level of vitamin B12. Higher doses of metformin and male sex were factors related to lower levels of vitamin B12.

Metformin Use Is Not Associated With B12 Deficiency or Neuropathy in Patients With Type 2 Diabetes Mellitus in Qatar

BACKGROUND

Metformin may lead to B₁₂ deficiency and neuropathy. There are no published data on the prevalence of Metformin-related B₁₂ deficiency and neuropathy in the Arabian Gulf.

AIMS

Determine whether Metformin intake is associated with B₁₂ deficiency and whether B₁₂ deficiency is associated with diabetic peripheral neuropathy (DPN) and painful diabetic neuropathy.

METHODS

Patients with type 2 diabetes mellitus (T2DM) (n = 362) attending outpatient clinics at HMC underwent assessment of B₁₂ levels, the DN4 questionnaire, and vibration perception threshold (VPT).

RESULTS

Comparing Metformin to non-Metformin users there were no differences in B₁₂ levels, VPT, or DN4. The prevalence of B₁₂ deficiency (B₁₂ <133 pmol/l) was lower (P < 0.01) in Metformin (8%) compared to non-Metformin (19%) users. Patients with B₁₂ deficiency had a comparable prevalence and severity of sensory neuropathy and painful neuropathy to patients without B₁₂ deficiency.

CONCLUSION

Serum B₁₂ levels were comparable between Metformin and non-Metformin users with T2DM in Qatar. T2DM patients on Metformin had a lower prevalence of B₁₂ deficiency. Furthermore, the prevalence and severity of neuropathy and painful diabetic neuropathy were comparable between patients with and without B₁₂ deficiency.

Investigation of the vitamin B12 deficiency with peripheral neuropathy in patients with type 2 diabetes mellitus treated using metformin

OBJECTIVE:

The relationship between vitamin B12 deficiency and peripheral neuropathy has been shown in a number of previous studies. Metformin is the indispensable first-line treatment for type 2 diabetes mellitus (DM) worldwide. One of the adverse effects of the use of metformin is vitamin B12 deficiency. In the present study, we investigated the relationship between vitamin B12 deficiency and peripheral neuropathy due to the use of metformin.

METHODS:

Patient’s laboratory and electromyography (EMG) data were retrospectively reviewed. Patients with no EMG report and other necessary information were excluded from the study.

RESULTS:

Eighty-six patients with type 2 DM using metformin were included in the study. Of these patients, 26 were males and 60 were females. The mean age of the patients was 55.1±7.7 years. The mean body mass index of the patients was 29.1±9.01 kg/m². The mean HbA1c level of the patients was 8.6%±2.1%. The mean duration of diabetes was 8.02±5.4 years. The incidence of vitamin B12 deficiency was 38.4%. Peripheral neuropathy was detected in 33.7% patients. There was no statistically significant difference in vitamin B12 levels between patients with peripheral neuropathy and those without peripheral neuropathy (p=0.64).

CONCLUSION:

Therefore, it can be concluded that the lack of vitamin B12 secondary to the use of metformin did not significantly increase the frequency of peripheral neuropathy.

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.

Erratum: Study of Vitamin B12 deficiency and peripheral neuropathy in metformin-treated early Type 2 diabetes mellitus

[This corrects the article on p. 631 in vol. 20, PMID: 27730072.].

Diabetic Polyneuropathy in Type 2 Diabetes Mellitus: Inflammation, Oxidative Stress, and Mitochondrial Function

Diabetic polyneuropathy (DPN) is defined as peripheral nerve dysfunction. There are three main alterations involved in the pathologic changes of DPN: inflammation, oxidative stress, and mitochondrial dysfunction. Inflammation induces activation of nuclear factor kappa B, activator protein 1, and mitogen-activated protein kinases. Oxidative stress induced by hyperglycemia is mediated by several identified pathways: polyol, hexosamine, protein kinase C, advanced glycosylation end-products, and glycolysis. In addition, mitochondrial dysfunction accounts for most of the production of reactive oxygen and nitrosative species. These free radicals cause lipid peroxidation, protein modification, and nucleic acid damage, to finally induce axonal degeneration and segmental demyelination. The prevalence of DPN ranges from 2.4% to 78.8% worldwide, depending on the diagnostic method and the population assessed (hospital-based or outpatients). Risk factors include age, male gender, duration of diabetes, uncontrolled glycaemia, height, overweight and obesity, and insulin treatment. Several diagnostic methods have been developed, and composite scores combined with nerve conduction studies are the most reliable to identify early DPN. Treatment should be directed to improve etiologic factors besides reducing symptoms; several approaches have been evaluated to reduce neuropathic impairments and improve nerve conduction, such as oral antidiabetics, statins, and antioxidants (alpha-lipoic acid, ubiquinone, and flavonoids).