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

Anemia in diabetes mellitus: Pathogenetic aspects and the value of early erythropoietin therapy

Anemia is a frequent, yet increasingly recognized, comorbidity in diabetes mellitus (DM), with prevalence often driven by multifactorial mechanisms. Hematinic deficiencies, common in this population, may arise from associated comorbidities or medications, such as metformin, as well as other drugs commonly employed for DM-related conditions. Among contributing factors, diabetic kidney disease (DKD) plays a pivotal role, with anemia developing more frequently and being more pronounced in earlier stages, than in CKD of other causes. This enhanced susceptibility stems primarily from the combined impact of impaired renal oxygen sensing and deficient erythropoietin (EPO) production linked to tubulointerstitial fibrosis. Additional mechanisms comprise glomerular dysfunction, shortened erythrocyte lifespan, uremia-induced bone marrow suppression, and increased bleeding risk. DM is also recognized as a chronic low-grade inflammatory condition, with its inflammatory burden driving iron maldistribution, suppression of erythropoiesis, and resistance to EPO. The diagnostic approach of anemia in DM mirrors that in the general population. Addressing modifiable causes such as hematinic deficiencies, and other chronic conditions, such as DKD and bone marrow disorders, is paramount. In total, the underlying pathophysiology of anemia in DM primarily reflects a state of absolute or relative EPO deficiency and/or diminished bone marrow responsiveness, effectively corresponding to 'anemia of chronic disease. Early initiation of EPO therapy, even in DM patients without overt DKD, may mitigate disease progression and improve outcomes. Future research should focus on diabetes-specific strategies integrating optimal EPO use, potentially implementing targeted management of renal and inflammatory contributors to anemia.

Diabetic Neuropathy: A Guide to Pain Management

PURPOSE OF REVIEW

Diabetic neuropathy is a common complication of diabetes mellitus (DM) and can affect up to 50% of DM patients during their lifetime. Patients typically present with numbness, tingling, pain, and loss of sensation in the extremities. Since there is no treatment targeting the underlying mechanism of neuropathy, strategies focus on preventative care and pain management.

RECENT FINDINGS

Up to 69% of patients with diabetic neuropathy receive pharmacological treatment for neuropathic pain. The United States Food and Drug Administration (FDA) confirmed four drugs for painful diabetic neuropathy (PDN): pregabalin, duloxetine, tapentadol, and the 8% capsaicin patch. Nonpharmacological treatments such as spinal cord stimulation (SCS) and transcutaneous electrical nerve stimulation (TENS) both show promise in reducing pain in DM patients. Despite the high burden associated with PDN, effective management remains challenging. This update covers the background and management of diabetic neuropathy, including its epidemiology, pathogenesis, preventative care, and current therapeutic strategies.

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.

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.

Severity of Neuropathy-Related Disability and Associated Factors of Diabetic Peripheral Neuropathy in a Tertiary Healthcare Center: A Comparative Cross-Sectional Study

BACKGROUND AND OBJECTIVES

The widespread presence of diabetic peripheral neuropathy (DN) and its related variables among diagnosed diabetes mellitus (DM) patients in Kerala lacks sufficient evidence. The objective of this study was to evaluate the frequency of DN and its related risk variables among those with DM who were receiving care at a tertiary health institution in Kerala.

MATERIALS AND METHODS

This study was conducted in a tertiary health center in Kerala using a cross-sectional design. The diagnosis of diabetes was established by assessing the glycated hemoglobin A1c (HbA1c) level and the fasting blood glucose (FBG) level. A validated survey questionnaire was employed to gather demographic data as well as the medical history of DM and associated ailments. A thorough physical examination, BMI, and blood pressure were recorded. Dermatological, musculoskeletal, neurological, and vascular assessments were conducted. The subjects were assessed for neuropathy using a neuropathy disability score (NDS). Consequently, those who met the criteria for DM were classified into two groups: those with neuropathy and those without neuropathy. All research participants underwent laboratory examinations such as blood lipid profiles, HbA1c, and vitamin B12 complex concentrations.

RESULTS

The study included 200 DM patients; 120 men and 80 women. Study participants were 40-70 years old, with a median age of 53. The prevalence of DN significantly increased with age (p<0.001). The longer a patient had DM, the higher the prevalence of DN, and this variance in percentage was statistically significant (p<0.009) with an OR (odds ratio) of 9.246. A statistically significant 81 (40.5%) of participants graduated, compared to 119 (59.5%) with only higher secondary education or less (OR = 2.042; p = 0.014). Approximately 107 (53.5%) of individuals earned an income under two lakhs, and this disparity was deemed statistically significant (p = 0.003) with an OR of 2.357. In the group of individuals being studied, 53 (26.5%) of them experienced a decrease in pressure sensation, 47 (23.5%) had a decrease or absence of vibration perception, 48 (24%) had an absence or decreased pinprick response, and 46 (23%) had an absent ankle reflex. The study found that the most commonly reported symptoms were tingling (n = 44; 22%), numbness (n = 42; 21%), burning (n = 37; 18.5%), pricking (n = 29; 14.5%), and pain (n = 27; 13.5%). A strong association was found between DN and glycemic status, namely, FBG levels exceeding 140 mg/dL (OR = 4.511, p < 0.001) and HbA1c levels exceeding 6.5% (OR = 3.87, p < 0.001). The prevalence of abnormal vitamin B12 levels in individuals with DN was 63% (p = 0.19), indicating that the finding was not statistically significant. Within the group of individuals with DN being studied, 22% exhibited mild neuropathy, 34% displayed moderate neuropathy, and 44% had severe neuropathy. The DN individuals had significantly reduced ankle dorsiflexion in cases of severe NDS scores compared to those with mild to moderate NDS scores (p = 0.009). During the binary logistic regression analysis, it was shown that the duration of DM (OR = 1.73; p = 0.038) and FBG levels (OR = 2.87; p = 0.018) were determined as predictors for DN.

CONCLUSION

The findings of this study reveal that the duration of diabetes, age, literacy level, income, HbA1c, and FBG were substantially related to a higher likelihood of DN among diabetic patients.

Individuals Diagnosed With Type 2 Diabetes Mellitus and the Status of Vitamin B12 Deficiency: A Review

Type 2 diabetes mellitus (T2DM) is a complex metabolic disorder with a multifactorial etiology and a significant global burden. In recent years, emerging evidence has suggested a potential link between T2DM and vitamin B12 deficiency, raising concerns about its impact on disease progression, management, and associated complications. This comprehensive review critically examines the current understanding of the prevalence, risk factors, clinical implications, and management strategies related to vitamin B12 deficiency in individuals diagnosed with T2DM. The review begins by providing an overview of the epidemiology of T2DM and its associated complications, underscoring the need for comprehensive management approaches. Subsequently, it delves into the physiology of vitamin B12, including its sources, absorption mechanisms, and biological functions, laying the groundwork for understanding the potential implications of deficiency in T2DM. A thorough analysis of the literature is conducted to elucidate the prevalence and risk factors of vitamin B12 deficiency in individuals with T2DM, considering factors such as age, duration of diabetes, medication use (e.g., metformin), dietary patterns, and comorbidities. Special attention is given to the role of metformin, the first-line therapy for T2DM, in precipitating or exacerbating vitamin B12 deficiency through mechanisms involving alterations in the gut microbiota and intestinal absorption. The review further explores the clinical manifestations and diagnostic challenges associated with vitamin B12 deficiency in the context of T2DM, emphasizing the importance of recognizing subtle symptoms and implementing appropriate screening protocols. It discusses the potential implications of vitamin B12 deficiency on glycemic control, diabetic neuropathy, cognitive function, cardiovascular health, and overall quality of life in individuals with T2DM. In addressing the management of vitamin B12 deficiency in T2DM, the review examines various therapeutic strategies, including oral and parenteral supplementation, dietary modifications, and lifestyle interventions. It critically evaluates the evidence supporting routine screening for vitamin B12 deficiency in individuals with T2DM and discusses controversies surrounding optimal supplementation protocols, dosing regimens, and monitoring strategies. Furthermore, the review highlights gaps in current knowledge and identifies areas for future research, such as the long-term effects of vitamin B12 supplementation on clinical outcomes in T2DM, the impact of genetic factors on vitamin B12 metabolism, and the potential role of personalized interventions. Overall, this review consolidates existing evidence and provides insights into the complex relationship between T2DM and vitamin B12 deficiency, aiming to inform clinical practice, enhance patient care, and guide future research endeavors in this important area of metabolic medicine.

Neuropathic Pain in Aged People: An Unresolved Issue Open to Novel Drug Approaches, Focusing on Painful Diabetic Neuropathy

A majority of older patients suffer from neuropathic pain (NP) that significantly alters their daily activities and imposes a significant burden on health care. Multiple comorbidities and the risk of polypharmacy in the elderly make it challenging to determine the appropriate drug, dosage, and maintenance of therapy. Age-dependent processes play a contributing role in neuropathy given that diabetic neuropathy (DN) is the most common form of neuropathy. This narrative review is mainly focused on the drug treatment approach for neuropathy-associated pain in aged people including both drugs and dietary supplements, considering the latter as add-on mechanism-based treatments to increase the effectiveness of usual treatments by implementing their activity or activating other analgesic pathways. On one hand, the limited clinical studies assessing the effectiveness and the adverse effects of existing pain management options in this age segment of the population (> 65), on the other hand, the expanding global demographics of the elderly contribute to building up an unresolved pain management problem that needs the attention of healthcare providers, researchers, and health authorities as well as the expansion of the current therapeutic options.

Bidirectional association between diabetic peripheral neuropathy and vitamin B12 deficiency: Two longitudinal 9-year follow-up studies using a national sample cohort

AIM

This study aims to investigate the association among metformin use, vit B12 deficiency, and DPN occurrence in diabetes.

METHODS

This retrospective, propensity-matched cohort study was performed using National Health Insurance Service database - National Sample Cohort in South Korea. Study 1 analyzed DPN incidence according to vit B12 deficiency and study 2 analyzed vit B12 deficiency incidence according to the presence/absence of DPN. Moreover, we compared the results with respect to metformin use.

RESULTS

In study 1, DPN incidence per 10000 person-year (PY) was 179.7 and 76.6 in the vit B12 and non-vit B12 deficiency groups, respectively. The adjusted HR was 1.32 (95% CI; 1.21-1.44, P < 0.05) and metformin use elicited a more significant effect of DPN occurrence in patient with vit B12 deficiency (HR: 5.76 (95% CI; 5.28-6.29). In study 2, vit B12 deficiency incidence per 10000 PY was 250.6 and 129.4 in the DPN and non-DPN groups, respectively. The adjusted HR was 2.44 (95% CI; 2.24-2.66, P < 0.05), however, metformin prescription was associated with the reduced incidence of vit B12 deficiency in DPN patients (HR 0.68 (95% CI; 0.62-0.74, P < 0.05).

CONCLUSION

DPN occurrence increased in diabetes with vit B12 deficiency and the incidence of vit B12 deficiency was also high in DPN patients. However, metformin showed opposite effects in both cohorts. Further studies clarifying the causal relationship among DPN occurrence, vit B12 deficiency, and metformin use are warranted.

Painful Diabetic Peripheral Neuropathy: Practical Guidance and Challenges for Clinical Management

Painful diabetic peripheral neuropathy (PDPN) is present in nearly a quarter of people with diabetes. It is estimated to affect over 100 million people worldwide. PDPN is associated with impaired daily functioning, depression, sleep disturbance, financial instability, and a decreased quality of life. Despite its high prevalence and significant health burden, it remains an underdiagnosed and undertreated condition. PDPN is a complex pain phenomenon with the experience of pain associated with and exacerbated by poor sleep and low mood. A holistic approach to patient-centred care alongside the pharmacological therapy is required to maximise benefit. A key treatment challenge is managing patient expectation, as a good outcome from treatment is defined as a reduction in pain of 30-50%, with a complete pain-free outcome being rare. The future for the treatment of PDPN holds promise, despite a 20-year void in the licensing of new analgesic agents for neuropathic pain. There are over 50 new molecular entities reaching clinical development and several demonstrating benefit in early-stage clinical trials. We review the current approaches to its diagnosis, the tools, and questionnaires available to clinicians, international guidance on PDPN management, and existing pharmacological and non-pharmacological treatment options. We synthesise evidence and the guidance from the American Association of Clinical Endocrinology, American Academy of Neurology, American Diabetes Association, Diabetes Canada, German Diabetes Association, and the International Diabetes Federation into a practical guide to the treatment of PDPN and highlight the need for future research into mechanistic-based treatments in order to prioritise the development of personalised medicine.

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

Diabetes mellitus (DM) is still one of the most common diseases worldwide, and its prevalence is still increasing globally. According to the American and European recommendations, metformin is considered a first-line oral hypo-glycemic drug for controlling type 2 DM (T2DM) patients. Metformin is the ninth most often prescribed drug in the world, and at least 120 million diabetic people are estimated to receive the drug. In the last 20 years, there has been increasing evidence of vitamin B12 deficiency among metformin-treated diabetic patients. Many studies have reported that vitamin B12 deficiency is related to the ma-labsorption of vitamin B12 among metformin-treated T2DM patients. Vitamin B12 deficiency may have a very bad complication for the T2DM patient. In this review, we will focus on the effect of metformin on the absorption of vitamin B12 and on its proposed mechanisms in hindering vitamin B12 absorption. In addition, the review will describe the clinical outcomes of vitamin B12 deficiency in metformin-treated T2DM.

A Double-Blind, Randomized, Placebo-Controlled Study to Assess the Efficacy of a Nerve Support Formula on Neuropathic Pain in Individuals Suffering from Type II Diabetes Mellitus

Background

The primary objective of the present study was to evaluate the effects of a Nerve Support Formula NeuropAWAY® on diabetic neuropathic pain.

Methods

This double-blind, placebo-controlled, randomized trial was conducted between August 2020 and February 2021. Patients aged ≥40 and ≤65 years with a history of type 2 diabetes (T2D) with a confirmed diagnosis of diabetic neuropathic pain were included in the study. The primary efficacy endpoint was to assess the effect of the 42 days administration of the Nerve Support Formula on the neuropathic pain as assessed by the 11 point Pain Intensity Numeric Rating Scale (PI-NRS). The secondary objectives were to assess the effect on plasma vitamin B12 levels, nerve conduction velocity, blood flow velocity, Brief Pain Inventory, Neuropathy Total Symptom Score, and Insomnia Severity Index.

Results

The enrolled study population (n=59) was randomized in two study groups; the Investigational Product (IP) group - Nerve Support Formula (n=27) and placebo group (n=32). The mean age of these participants was 52.63 and 53.72 for IP and placebo group, respectively. The mean (SD) HbA1c levels for IP and placebo group were 8.37 (0.85) and 8.16 (0.86), respectively. By the end of the study (Day 42) the decrease in PI-NRS scores for the IP group was maximal (↓61.32%) and highly significant (p<0.001) in comparison to the placebo group (↑2.47%). Significant improvements (p<0.05) were also noted in the secondary efficacy variables after 42 days of IP intake.

Conclusion

The formula was found to be significantly effective as compared to placebo in reducing pain and other sensory symptoms related to the diabetic peripheral neuropathy.

Metformin: Sex/Gender Differences in Its Uses and Effects—Narrative Review

Metformin (MTF) occupies a major and fundamental position in the therapeutic management of type 2 diabetes mellitus (T2DM). Gender differences in some effects and actions of MTF have been reported. Women are usually prescribed lower MTF doses compared to men and report more gastrointestinal side effects. The incidence of cardiovascular events in women on MTF has been found to be lower to that of men on MTF. Despite some promising results with MTF regarding pregnancy rates in women with PCOS, the management of gestational diabetes, cancer prevention or adjunctive cancer treatment and COVID-19, most robust meta-analyses have yet to confirm such beneficial effects.

Vitamin B12 Supplementation and Vitamin B12 Blood Serum Levels: Evaluation of Effect Modification by Gender and Smoking Status

Research suggests that high intake of supplemental vitamin B₁₂ may be associated with increased risk of cancer, with some evidence that this association may vary by gender and smoking status. This investigation evaluates if similar patterns in association are observed for data for 11,757 adults from the National Health and Nutrition Examination Survey (1999-2006). Survey-weighted multivariable-adjusted linear regression was used to evaluate the association between regular B₁₂ supplement use and log-transformed serum B₁₂ levels. Persons taking vitamin B₁₂ through a multivitamin/multimineral (MVMM) had a median supplemental intake of 12 mcg/day (Q1: 6, Q3: 25), compared to 100 mcg/day (Q1: 22, Q3: 500) for persons reporting supplemental B₁₂ intake through a MVMM-exclusive source. MVMM users had a geometric mean serum B12 26% (95% CI: 23%-30%) higher than nonusers, whereas MVMM-exclusive users' geometric mean was 61% (95% CI: 53%-70%) higher than nonusers (p-trend < 0.001). Although a positive trend (p-trend < 0.001) was observed for both men and women, the association was stronger among women (p-interaction < 0.001). No interaction was observed for smoking status (p-interaction = 0.45). B₁₂ supplementation is associated with higher levels of serum B₁₂, with significant interaction by gender but not smoking. Further work is needed to better understand the interplay of B₁₂ and gender.

Physicians' Perception About Use of Vitamin B12 in the Treatment or Prevention of Diabetic Neuropathy: A Cross-sectional Survey in Saudi Arabia

BACKGROUND

Diabetic neuropathy is a condition that is prevalent among type 2 diabetic patients. Some physicians prescribe vitamin B12 or vitamin B complex supplements to improve symptoms, but studies have shown that there is little to no evidence of vitamin B12 being an effective treatment for diabetic neuropathy. Thus, this study aims to investigate local physicians' knowledge and tendency to prescribe vitamin B12 or vitamin B complex for the treatment or prevention of diabetic peripheral neuropathy.

METHODS

It was a cross-sectional study, conducted between May and November of 2019, in several primary healthcare centers in different cities of Saudi Arabia. A total of 412 physicians with a minimum of three years of experience answered a three-part questionnaire on their demographic information, prescribing behavior, and knowledge of the relationship between vitamin B12 or vitamin B complex and diabetic neuropathy.

RESULTS

The study found that only 42% of the physicians believed that vitamin B12 supplementation did not prevent diabetic neuropathy, while only 52.7% found it to be an ineffective treatment for this condition. Moreover, 58.7% stated that they had certainly prescribed vitamin B12 or multivitamins as a form of treatment or prevention of diabetic neuropathy. 47.8% of the patients requested a vitamin B12 prescription 1-6 times from their physicians, while 31.6% of them requested it ≥ 7 times, with 42.5% of physicians agreeing that their prescriptions of vitamin B12 had been a result of patient demand more than clinical justification. Likewise, 43% of respondents were aware that vitamin B12 levels should be tested annually. Furthermore, a higher proportion of consultants chose not to prescribe vitamin B12 to prevent or treat diabetic neuropathy than any other rank.

CONCLUSION

The findings of this study indicate a tendency of unnecessarily prescribing vitamin B12 supplementation for the prevention or treatment of diabetic neuropathy as well as a lack of knowledge on the matter among doctors in primary care hospitals in Saudi Arabia. The study has also shown that there are patients who often request this prescription, adding pressure on their physicians to comply. Future studies should investigate most of the hospitals in Saudi cities and include less experienced residents and medical students.

Impacts of statin and metformin on neuropathy in patients with type 2 diabetes mellitus: Korean Health Insurance data

BACKGROUND

Neuropathy is a common chronic complication in type 2 diabetes mellitus (T2DM). Statin and metformin are commonly used medications in T2DM patients, and some studies showed statin- or metformin-induced neuropathy.

AIM

To evaluate the incidence of neuropathy among patients with T2DM associated with statin and metformin therapies.

METHODS

Korean Health Insurance Review and Assessment national patient sample data from 2016 and 2017 were used. Patients with T2DM and no complications were divided into statin/metformin/statin + metformin users and non-users. Neuropathy incidence was defined by International Statistical Classification of Diseases and Related Health Problems, 10^th revision codes and concomitant prescriptions for anticonvulsants or antidepressants. Logistic regression analyses were conducted to examine the associations between statin/metformin/statin + metformin therapies and the incidence of neuropathy. Propensity score (PS) matching was performed on the basis of age, sex and comorbidities.

RESULTS

Overall, 34964 and 35887 patients with T2DM and no complications were included in the Korean Health Insurance Review and Assessment national patient sample datasets from 2016 and 2017, respectively. Statin therapy was associated with increased risks of neuropathy in 2016 and 2017 [PS-matched odds ratio (OR) = 1.22, 95% confidence interval (CI): 1.08-1.38; PS-matched OR = 1.17, 95%CI: 1.03-1.33, respectively]. Metformin therapy was associated with reduced risks of neuropathy in 2016 and 2017 (PS-matched OR = 0.30, 95%CI: 0.21-0.42; PS-matched OR = 0.44, 95%CI: 0.32-0.60, respectively). Combined statin + metformin therapy was not significantly associated with neuropathy in 2016 or 2017 (PS-matched OR = 0.85, 95%CI: 0.61-1.19; PS-matched OR = 0.95, 95%CI: 0.66-1.38, respectively).

CONCLUSION

Statin therapy was associated with enhanced risk of new-onset neuropathy in patients with T2DM, but metformin therapy showed the opposite association.

Metformin for diabetes prevention: update of the evidence base

We have conducted a narrative review based on a structured search strategy, focusing on the effects of metformin on the progression of non-diabetic hyperglycemia to clinical type 2 diabetes mellitus. The principal trials that demonstrated a significantly lower incidence of diabetes in at-risk populations randomized to metformin (mostly with impaired glucose tolerance [IGT]) were published mainly from 1999 to 2012. Metformin reduced the 3-year risk of diabetes by -31% in the randomized phase of the Diabetes Prevention Program (DPP), vs. -58% for intensive lifestyle intervention (ILI). Metformin was most effective in younger, heavier subjects. Diminishing but still significant reductions in diabetes risk for subjects originally randomized to these groups were present in the trial's epidemiological follow-up, the DPP Outcomes Study (DPPOS) at 10 years (-18 and -34%, respectively), 15 years (-18 and -27%), and 22 years (-18 and -25%). Long-term weight loss was also seen in both groups, with better maintenance under metformin. Subgroup analyses from the DPP/DPPOS have shed important light on the actions of metformin, including a greater effect in women with prior gestational diabetes, and a reduction in coronary artery calcium in men that might suggest a cardioprotective effect. Improvements in long-term clinical outcomes with metformin in people with non-diabetic hyperglycemia ("prediabetes") have yet to be demonstrated, but cardiovascular and microvascular benefits were seen for those in the DPPOS who did not vs. did develop diabetes. Multiple health economic analyses suggest that either metformin or ILI is cost-effective in a community setting. Long-term diabetes prevention with metformin is feasible and is supported in influential guidelines for selected groups of subjects. Future research will demonstrate whether intervention with metformin in people with non-diabetic hyperglycemia will improve long-term clinical outcomes.

Molecular Aspects in the Potential of Vitamins and Supplements for Treating Diabetic Neuropathy

PURPOSE OF REVIEW

To discuss and provide evidence-based data on dietary supplements as part of treating diabetic neuropathy RECENT FINDINGS: Few randomized controlled trials are available, but some have shown beneficial efficacy of various dietary supplements on objective primary endpoints including nerve conduction velocities and axon potentials as well as subjective patient-reported outcomes. No medical cure for diabetic neuropathy exists, and prevention is therefore crucial. Tight glucose control slows the progression of nerve damage in diabetes, but an unmet clinical need for effective interventions is warranted. Consequently, a growing number of patients turn to dietary supplements proposed to possess neuroprotective properties. However, the postulated effects are often not evidence-based as they have not been tested scientifically. Taken together, this review will focus on dietary supplements investigated in clinical trials for their potential capabilities in targeting the molecular mechanisms involved in the underlying pathogenesis of diabetic neuropathy.

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.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Diabetic Neuropathy: a Critical, Narrative Review of Published Data from 2019

PURPOSE OF REVIEW

This manuscript is a systematic, narrative review that compiles and describes all data available from 2019 related to epidemiologic, diagnostic, and therapeutic advances in diabetic neuropathy (DN).

RECENT FINDINGS

Epidemiology of DN is discussed. Diagnostic modalities include predictive models, electrodiagnostics, imaging, and biomarkers. A majority of studies on the treatment of diabetic peripheral neuropathy (DPN) involve pharmacotherapy, but complementary and alternative medicine, exercise, modalities, psychological, interventional, and surgical options are also explored. DN is a highly prevalent and debilitating consequence of diabetes that can present challenges to the clinician as the assessment is largely subjective with different phenotypic presentations among patients. Treatment of DN is largely symptomatic as the pathogenesis of DN is not fully understood and is likely multifactorial. It is evident from the broad range of treatments that too often provide unsatisfactory relief that there is no consensus about a single most effective treatment for DN, and monotherapy rarely proves to be successful.

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

AIM

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

PATIENTS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

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

Introduction:

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

Areas covered:

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

Expert opinion:

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

Management of Neuropathic Pain in Polyneuropathy

PURPOSE OF REVIEW

Many polyneuropathies cause significant neuropathic pain, resulting in substantial morbidity and reduced quality of life. Appropriate management is crucial for maintaining quality of life for patients with painful polyneuropathies. The US Food and Drug Administration (FDA) has only approved one new drug for painful diabetic neuropathy in the past decade, a topical capsaicin patch that was initially approved for the treatment of postherpetic neuralgia in 2009. Gabapentinoids and serotonin norepinephrine reuptake inhibitors (SNRIs) continue to have an advantage in safety profiles and efficacy. Other antiepileptic medications remain second-line agents because of fewer studies documenting efficacy.

RECENT FINDINGS

This article reviews recent literature on complementary and pharmacologic therapies for the management of painful polyneuropathies. Exercise has emerged as an important therapeutic tool and may also improve the underlying polyneuropathy in the setting of obesity, metabolic syndrome, and diabetes.

SUMMARY

The approach to management of painful polyneuropathies is multifactorial, using both pharmacologic and nonpharmacologic measures to improve pain severity and patient quality of life.

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.

Current Concepts in Pharmacometabolomics, Biomarker Discovery, and Precision Medicine

Pharmacometabolomics (PMx) studies use information contained in metabolic profiles (or metabolome) to inform about how a subject will respond to drug treatment. Genome, gut microbiome, sex, nutrition, age, stress, health status, and other factors can impact the metabolic profile of an individual. Some of these factors are known to influence the individual response to pharmaceutical compounds. An individual’s metabolic profile has been referred to as his or her “metabotype.” As such, metabolomic profiles obtained prior to, during, or after drug treatment could provide insights about drug mechanism of action and variation of response to treatment. Furthermore, there are several types of PMx studies that are used to discover and inform patterns associated with varied drug responses (i.e., responders vs. non-responders; slow or fast metabolizers). The PMx efforts could simultaneously provide information related to an individual’s pharmacokinetic response during clinical trials and be used to predict patient response to drugs making pharmacometabolomic clinical research valuable for precision medicine. PMx biomarkers can also be discovered and validated during FDA clinical trials. Using biomarkers during medical development is described in US Law under the 21st Century Cures Act. Information on how to submit biomarkers to the FDA and their context of use is defined herein.

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.

A review of therapeutic options for managing the metabolic aspects of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a common endocrine disorder in women of reproductive age. Metabolic sequelae associated with PCOS range from insulin resistance to type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD). Insulin resistance plays a significant role in the pathophysiology of PCOS and it is a reliable marker for cardiometabolic risk. Although insulin sensitising agents such as metformin have been traditionally used for managing metabolic aspects of PCOS, their efficacy is low in terms of weight reduction and cardiovascular risk reduction compared with newer agents such as incretin mimetics and SGLT2 inhibitors. With current pharmaceutical advances, potential therapeutic options have increased, giving patients and clinicians more choices. Incretin mimetics are a promising therapy with a unique metabolic target that could be used widely in the management of PCOS. Likewise, bariatric procedures have become less invasive and result in effective weight loss and the reversal of metabolic morbidities in some patients. Therefore, surgical treatment targeting weight loss becomes increasingly common in the management of obese women with PCOS. Newer emerging therapies, including twincretins, triple GLP-1 agonists, glucagon receptor antagonists and imeglemin, are promising therapeutic options for treating T2DM. Given the similarity of metabolic and pathological features between PCOS and T2DM and the variety of therapeutic options, there is the potential to widen our strategy for treating metabolic disorders in PCOS in parallel with current therapeutic advances. The review was conducted in line with the recommendations from the international evidence-based guideline for the assessment and management of polycystic ovary syndrome 2018.