The relationship between exacerbated diabetic peripheral neuropathy and metformin treatment in type 2 diabetes mellitus. Sci Rep. 2021;11:1940. [PMID: 33479439 PMCID: PMC7820469 DOI: 10.1038/s41598-021-81631-8]

Neuropathy of diabetes following initiation of a low-carbohydrate diet: Case report

Introduction

This case study portrays an unusual case of treatment-induced neuropathy of diabetes (TIND) in a patient with uncontrolled type 2 diabetes (T2D) who achieved rapid improvement in glucose control primarily with dietary intervention. Initial presentation was 50-year-old white male with a long-standing history of obesity and a family history of T2D with a screening glucose level >500mg/dL by glucometer, HbA1c of 14.9%, and initial weight 213 lbs.

Methods

The initial intervention included a low-carbohydrate diet, metformin, and a continuous glucose monitor (CGM). Semaglutide was added after seven days.

Results

His glycemia was within the target range within three weeks. Four weeks after initiation of therapy, he developed TIND symptoms consisting of burning, tightness, and numbness of bilateral feet along with 10/10 pain. At three months, his HbA1c dropped to 6.9% and his weight to 195 lbs. Treatment of his TIND reduced his pain from 10/10 to 2/10.

Conclusion

Whereas TIND is commonly associated with the use of insulin or sulfonylureas, this study adds evidence to the paucity of literature regarding TIND precipitated by dietary intervention.

Eleven neurology-related proteins measured in serum are positively correlated to the severity of diabetic neuropathy

About 20% of patients with diabetes suffer from chronic pain with neuropathic characteristics. We investigated the multivariate associations between 92 neurology-related proteins measured in serum from 190 patients with painful and painless diabetic neuropathy. Participants were recruited from the Pain in Neuropathy Study, an observational cross-sectional multicentre study in which participants underwent deep phenotyping. In the exploration cohort, two groups were defined by hierarchical cluster analyses of protein data. The proportion of painless vs painful neuropathy did not differ between the two groups, but one group had a significantly higher grade of neuropathy as measured by the Toronto Clinical Scoring System (TCSS). This finding was replicated in the replication cohort. Analyzing both groups together, we found that a group of 11 inter-correlated proteins (TNFRSF12A, SCARB2, N2DL-2, SKR3, EFNA4, LAYN, CLM-1, CD38, UNC5C, GFR-alpha-1, and JAM-B) were positively associated with TCSS values. Notably, EFNA4 and UNC5C are known to be part of axon guidance pathways. To conclude, although cluster analysis of 92 neurology-related proteins did not distinguish painful from painless diabetic neuropathy, we identified 11 proteins which positively correlated to neuropathy severity and warrant further investigation as potential biomarkers.

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

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

Correlation study of renal function indices with diabetic peripheral neuropathy and diabetic retinopathy in T2DM patients with normal renal function

Background

The anticipation of diabetes-related complications remains a challenge for numerous T2DM patients, as there is presently no effective method for early prediction of these complications. This study aims to investigate the association between renal function-related indicators and the occurrence of peripheral neuropathy and retinopathy in individuals diagnosed with type 2 diabetes mellitus (T2DM) who currently have normal renal function.

Methods

Patients with T2DM who met the criteria were selected from the MMC database and divided into diabetic peripheral neuropathy (DPN) and diabetic retinopathy (DR) groups, with a total of 859 and 487 patients included, respectively. Multivariate logistic regression was used to analyze the relationship between blood urea nitrogen (BUN), creatinine (Cr), uric acid (UA), urine albumin(ALB), albumin-to-creatinine ratio (ACR), estimated glomerular filtration rate (eGFR), and diabetic peripheral neuropathy and retinopathy. Spearman correlation analysis was used to determine the correlation between these indicators and peripheral neuropathy and retinopathy in diabetes.

Results

In a total of 221 patients diagnosed with DPN, we found positive correlation between the prevalence of DPN and eGFR (18.2, 23.3, 35.7%, p < 0.05). Specifically, as BUN (T1: references; T2:OR:0.598, 95%CI: 0.403, 0.886; T3:OR:1.017, 95%CI: 0.702, 1.473; p < 0.05) and eGFR (T1: references; T2:OR:1.294, 95%CI: 0.857, 1.953; T3:OR:2.142, 95%CI: 1.425, 3.222; p < 0.05) increased, the odds ratio of DPN also increased. Conversely, with an increase in Cr(T1: references; T2:OR:0.86, 95%CI: 0.56, 1.33; T3:OR:0.57, 95%CI: 0.36, 0.91; p < 0.05), the odds ratio of DPN decreased. Furthermore, when considering sensitivity and specificity, eGFR exhibited a sensitivity of 65.2% and specificity of 54.4%, with a 95% confidence interval of 0.568-0.656.

Conclusion

In this experimental sample, we found a clear positive correlation between eGFR and DPN prevalence.

Lower serum branched-chain amino acid catabolic intermediates are predictive signatures specific to patients with diabetic foot

Diabetic foot (DF) is one of the serious chronic complications of diabetes. Accurate prediction of the risk of DF may take timely intervention measures to prevent its occurrence. The understanding of metabolomic changes in the progression of diabetes to DF may reveal new targets for interventions. We hypothesized that changes in metabolic pathways during DF would lead to changes in the metabolic profile, which could be predictive signature specific to it. In the present study, 43 participants with type 2 diabetes mellitus (T2DM), 32 T2DM participants with DF (T2DM-F), and 36 healthy subjects were enrolled and their serum samples were used for targeted and nonpolar metabolic analysis with liquid chromatography-tandem mass spectrometry. Differential metabolites related to T2DM-F were discovered in metabolomic analysis. Lasso machine learning regression model, random forest algorithm, causal mediation analysis, disease risk assessment, and clinical decision model were carried out. T2DM and T2DM-F groups could be distinguished with the healthy control group. The differential metabolites were all enriched in alpha-linolenic acid and linoleic acid metabolic pathways including arachidonic acid, docosapentaenoic-acid 22N-6, and docosahexaenoic-acid, which were significantly lower in the T2DM and T2DM-F groups compared with the healthy control group. The differential metabolites in T2DM-F vs T2DM groups were enriched to branched-chain amino acid (BCAA) catabolic pathways involving in methylmalonic acid, succinic acid, 3-methyl-2-oxovaleric acid, and ketoleucine, which were the BCAA catabolic intermediates and significantly lower in the T2DM-F compared with the T2DM group except for succinic acid. We reveal a new set of predictive signatures and associate the lower BCAA catabolic intermediates with the progression from T2DM to T2DM-F.

How vitamins act as novel agents for ameliorating diabetic peripheral neuropathy: A comprehensive overview

Diabetic peripheral neuropathy (DPN) is a pervasive and incapacitating sequela of diabetes, affecting a significant proportion of those diagnosed with the disease, yet an effective treatment remains elusive. Vitamins have been extensively studied, emerging as a promising target for diagnosing and treating various systemic diseases, but their role in DPN is not known. This review collates and synthesizes knowledge regarding the interplay between vitamins and DPN, drawing on bibliographies from prior studies and relevant articles, and stratifying the therapeutic strategies from prophylactic to interventional. In addition, the clinical evidence supporting the use of vitamins to ameliorate DPN is also evaluated, underscoring the potential of vitamins as putative therapeutic agents. We anticipate that this review will offer novel insights for developing and applying vitamin-based therapies for DPN.

Metformin-Induced Vitamin B12 Deficiency in Patients With Type-2 Diabetes Mellitus

Diabetes mellitus (DM) is the most common metabolic disease worldwide. Hence, the prevalence of the disease continues to increase across the globe. Metformin is used as a first-line oral hypoglycemic drug to keep control of type-2 DM (T2DM) in adults. Diabetic patients on metformin have been largely seen to be suffering from a deficiency of vitamin B12. It is a water-soluble vitamin mainly obtained from animal food like meat. At the basic cell level, it acts as a cofactor for enzymes essential for DNA synthesis and neuroprotection. As a result, vitamin B12 deficiency can show clinical effects such as progressive demyelination, peripheral neuropathy and haematological abnormalities (such as macrocytic anaemia and neutrophil hypersegmentation). Various studies also show a relation between vitamin B12 insufficiency and metformin-treated T2DM patients as decreased absorption of vitamin B12. There could be a severe complication of vitamin B12 deficiency in T2DM patients. The use of proton pump inhibitors, gastric bypass surgery, older patients and patients with a higher red blood cell turnover are factors that hasten the depletion of vitamin B12 reserves in the liver. Methylmalonic acid and homocysteine levels can be measured to identify vitamin B12 insufficiency at its early stage if blood vitamin B12 levels are borderline. The action of metformin on vitamin B12 absorption and its potential mechanisms of inhibition will be the main topics of discussion in this review. The review will also discuss how vitamin B12 deficiencies in T2DM patients using metformin affect their clinical results.

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.

l-Methylfolate in Diabetic Peripheral Neuropathy: A Narrative Review

OBJECTIVE

One of the most frequently occurring complications of diabetes mellitus is peripheral neuropathy. Despite the painful symptoms associated with diabetic peripheral neuropathy (DPN), the current treatment landscape focuses on managing symptoms without addressing the underlying causes of DPN. This narrative review describes the mechanistic effects and clinical trial data supporting the use of l-methylfolate calcium (LMF), the bioactive form of folate, which is available in the United States as a prescription medical food that also contains other B vitamins for the dietary management of DPN.

METHODS

Preclinical and clinical trial data evaluating the impact of LMF on DPN was identified using PubMed searches for articles published between 2010 and 2023. Search terms included: folate, l-methylfolate, diabetes, neuropathy, and neuropathic pain. Additionally, a literature search was conducted to identify studies related to LMF, genetic polymorphisms, and DPN pathophysiology.

RESULTS

Several studies show that the C677T variant of the methylenetetrahydrofolate reductase (MTHFR) gene is linked to greater risk of DPN than other MTHFR variants due to its inhibitory effects on several folic acid metabolic pathways. One double-blind, randomized controlled trial, five open-label studies, and one retrospective study found that LMF has a significant beneficial effect on DPN that extends beyond symptomatic relief to include modulating the underlying pathophysiology that leads to the progression and symptoms of DPN. LMF also significantly improves patient quality of life, with minimal adverse effects.

CONCLUSION

Preclinical and clinical studies have found that LMF can be used to treat the underlying causes of DPN and provide long-lasting symptomatic relief.

Inflammatory Processes in Alzheimer's Disease-Pathomechanism, Diagnosis and Treatment: A Review

Alzheimer's disease is one of the most commonly diagnosed cases of senile dementia in the world. It is an incurable process, most often leading to death. This disease is multifactorial, and one factor of this is inflammation. Numerous mediators secreted by inflammatory cells can cause neuronal degeneration. Neuritis may coexist with other mechanisms of Alzheimer's disease, contributing to disease progression, and may also directly underlie AD. Although much has been established about the inflammatory processes in the pathogenesis of AD, many aspects remain unexplained. The work is devoted in particular to the pathomechanism of inflammation and its role in diagnosis and treatment. An in-depth and detailed understanding of the pathomechanism of neuroinflammation in Alzheimer's disease may help in the development of diagnostic methods for early diagnosis and may contribute to the development of new therapeutic strategies for the disease.

Metformin treatment and risk of diabetic peripheral neuropathy in patients with type 2 diabetes mellitus in Beijing, China

BACKGROUND

Metformin treatment is associated with vitamin B12 deficiency, which is a risk factor for neuropathy. However, few studies have examined the relationship between metformin treatment and diabetic peripheral neuropathy (DPN), and the available findings are contradictory. We aimed to assess whether metformin treatment is associated with DPN in patients with type 2 diabetes mellitus (T2DM) in Beijing, China.

METHODS

All patients with newly diagnosed T2DM between January 2010 and September 2012 in the Medical Claim Data for Employees database were included. Metformin treatment was defined as any record of metformin prescription. The average daily dose of metformin during follow-up was calculated. DPN was defined as DPN admissions occurring after a diagnosis of T2DM in the database. Hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated using Cox proportional hazards models.

RESULTS

Among 49,705 T2DM patients, 1,933 DPN events were recorded during a median follow-up of 6.36 years. The crude incidence rates were 7.12 and 3.91 per 1000 person-years for patients treated with metformin (N=37,052) versus those not treated (N=12,653). Patients treated with metformin had an 84% increased risk of DPN compared with patients not using metformin (HR, 1.84; 95% CI, 1.62, 2.10). The daily dose was positively associated with DPN risk (HR, 1.48; 95% CI, 1.46, 1.51; P for trend <0.001). The risk of DPN was 1.53-fold (1.30, 1.81) and 4.31-fold (3.76, 4.94) higher in patients with daily doses of 1.0-2.0 g and >2.0 g, respectively, than in patients who did not receive treatment. Patients aged less than 60 years had a higher risk of DPN (P<0.05 for interaction test). Among patients taking vitamin B12 at baseline, there was no increased risk of DPN in the metformin group (1.92: 0.79, 4.69).

CONCLUSIONS

In Chinese patients with T2DM, metformin treatment was associated with an increased risk of DPN admission and this risk responds positively to the daily dose of metformin. In particular, metformin use was a major risk factor for DPN in younger patients. Concomitant use of vitamin B12 may avoid the increased risk of DPN associated with metformin use.

Magnolol effectively ameliorates diabetic peripheral neuropathy in mice

BACKGROUND

Diabetic peripheral neuropathy (DPN) is a common complication of diabetes lacking efficient treatment. Magnolol (MG), a peroxisome proliferator-activated receptor γ (PPARγ) agonist, is a natural product derived from Magnolia officinalis and widely used to treat a variety of diseases as a traditional Chinese medicine and Japanese Kampo medicine.

PURPOSE

Here, we aimed to investigate the potential of MG in ameliorating DPN-like pathology in mice and decipher the mechanism of MG in treating DPN.

MATERIALS AND METHODS

12-week-old male streptozotocin (STZ)-induced type 1 diabetic (T1DM) mice and 15-week-old male BKS Cg-m^+/+Lepr db/J (db/db) type 2 diabetic mice (T2DM) were used as DPN mice. MG was administrated (i.p) daily for 4 weeks. Peripheral nerve functions of mice were evaluated by measuring mechanical response latency, thermal response latency and motor nerve conduction velocity (MNCV). The mechanisms underlying the amelioration of MG on DPN-like pathology were examined by qRT-PCR, western blot and immunohistochemistry assays, and verified in the DPN mice with PPARγ-specific knockdown in dorsal root ganglia (DRG) neuron and sciatic nerve tissues by injecting adeno-associated virus (AAV)8-PPARγ-RNAi.

RESULTS

MG promoted DRG neuronal neurite outgrowth and effectively ameliorated neurological dysfunctions in both T1DM and T2DM diabetic mice, including improvement of paw withdrawal threshold, thermal response latency and MNCV. Additionally, MG promoted neurite outgrowth of DRG neurons, protected sciatic nerve myelin sheath structure, and ameliorated foot skin intraepidermal nerve fiber (IENF) density in DPN mice by targeting PPARγ. Mechanism research results indicated that MG improved mitochondrial dysfunction involving PPARγ/MKP-7/JNK/SIRT1/LKB1/AMPK/PGC-1α pathway in DRG neurons, repressed inflammation via PPARγ/NF-κB signaling and inhibited apoptosis through regulation of PPARγ-mediated Bcl-2 family proteins in DRG neurons and sciatic nerves.

CONCLUSIONS

Our work has detailed the mechanism underlying the amelioration of PPARγ agonist on DPN-like pathology in mice with MG as a probe, and highlighted the potential of MG in the treatment of DPN.

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.

Dry eye disease in patients with type II diabetes mellitus: A retrospective, population-based cohort study in Taiwan

Purpose

To investigate the risk and protective factors of dry eye disease (DED) in patients with type II diabetes mellitus (DM).

Design

A retrospective cohort study using Chang- Gung research database collecting data from 2005 to 2020.

Methods

Patients with type II DM were included, and those with previous ocular diseases were excluded. Ten thousand twenty nine developed DED (DED group), and 142,491 didn't (non-DED group). The possible risk and protective factors were compared and analyzed using the logistic regression model.

Results

A majority of the DED group were female with significantly higher initial and average glycated hemoglobin levels, and higher incidence of diabetic neuropathy and retinopathy. In conditional logistic regression model, advanced age was a risk factor. After adjusting for sex, age, and DM duration; average glycated hemoglobin level, diabetic neuropathy, retinopathy, and nephropathy with eGFR 30 ~ 59 and intravitreal injection, vitrectomy, pan-retinal photocoagulation, and cataract surgery were contributing factors of DED. Considering antihyperglycemic agents, DPP4 inhibitor, SGLT2 inhibitor, GLP-1 agonist, and insulin monotherapy and dual medications combining any two of the aforementioned agents were protective factors against DED compared with metformin alone. In the monotherapy group, SLGT2 inhibitor had the lowest odds ratio, followed by GLP1 agonist, DPP4 inhibitor, and insulin.

Conclusions

DED in patients with DM is associated with female sex, advanced age, poor diabetic control, microvascular complications and receiving ocular procedures. GLP-1 agonist, SGLT-2 inhibitor, DPP4 inhibitor, and insulin are superior to metformin alone in preventing DM-related DED. A prospective randomized control trial is warranted to clarify our results.

The role of MicroRNA networks in tissue-specific direct and indirect effects of metformin and its application

Metformin is a first-line oral antidiabetic agent that results in clear benefits in relation to glucose metabolism and diabetes-related complications. The specific regulatory details and mechanisms underlying these benefits are still unclear and require further investigation. There is recent mounting evidence that metformin has pleiotropic effects on the target tissue development in metabolic organs, including adipose tissue, the gastrointestinal tract and the liver. The mechanism of actions of metformin are divided into direct effects on target tissues and indirect effects via non-targeted tissues. MicroRNAs (miRNAs) are a class of endogenous, noncoding, negative gene regulators that have emerged as important regulators of a number of diseases, including type 2 diabetes mellitus (T2DM). Metformin is involved in many aspects of miRNA regulation, and metformin treatment in T2DM should be associated with other miRNA targets. A large number of miRNAs regulation by metformin in target tissues with either direct or indirect effects has gradually been revealed in the context of numerous diseases and has gradually received increasing attention. This paper thoroughly reviews the current knowledge about the role of miRNA networks in the tissue-specific direct and indirect effects of metformin. Furthermore, this knowledge provides a novel theoretical basis and suggests therapeutic targets for the clinical treatment of metformin and miRNA regulators in the prevention and treatment of cancer, cardiovascular disorders, diabetes and its complications.

Dose-Response Association of Metformin with Parkinson's Disease Odds in Type 2 Diabetes Mellitus

Background. Studies have demonstrated that patients with diabetes mellitus who receive metformin have a lower risk of developing Parkinson’s disease (PD). However, studies have also suggested that metformin may increase the risk of PD. In this study, we investigated whether metformin use was associated with the risk of PD in type 2 diabetes mellitus (T2DM). Methods. In this population-based cross-sectional study, patients with T2DM diagnosed between 2001 and 2018 were enrolled. We categorized these patients as metformin users or nonusers. Participants below 50 years old were excluded. Two models were employed to evaluate the associations of metformin exposure and use intensity with PD after 3 and 5 years of follow-up. Results. Patients with T2DM who received <300 cumulative defined daily doses (cDDD) of metformin and those with metformin use intensity of <10 DDD/month had respective odds ratios (ORs) for PD of 0.88 (95% confidence interval [CI] = 0.83−0.94) and 0.87 (95% CI = 0.81−0.93) in a 3-year follow-up. In a 5-year follow-up, such patients had respective ORs for PD of 0.94 (95% CI = 0.90−0.98) and 0.93 (95% CI = 0.89−0.98). Patients with T2DM who received ≥300 cDDD of metformin or used metformin with intensity of ≥10 DDD/month experienced no neuroprotective effects after 3 or 5 years. Conclusions. Metformin was associated with PD odds in T2DM in a dose−response association manner. Patients who received low dosage and intensity of metformin use were associated with lower odds of PD, while higher dosage and intensity of metformin use had no neuroprotective effect.

Metformin for Cardiovascular Protection, Inflammatory Bowel Disease, Osteoporosis, Periodontitis, Polycystic Ovarian Syndrome, Neurodegeneration, Cancer, Inflammation and Senescence: What Is Next?

Diabetes is accompanied by several complications. Higher prevalence of cancers, cardiovascular diseases, chronic kidney disease (CKD), obesity, osteoporosis, and neurodegenerative diseases has been reported among patients with diabetes. Metformin is the oldest oral antidiabetic drug and can improve coexisting complications of diabetes. Clinical trials and observational studies uncovered that metformin can remarkably prevent or alleviate cardiovascular diseases, obesity, polycystic ovarian syndrome (PCOS), osteoporosis, cancer, periodontitis, neuronal damage and neurodegenerative diseases, inflammation, inflammatory bowel disease (IBD), tuberculosis, and COVID-19. In addition, metformin has been proposed as an antiaging agent. Numerous mechanisms were shown to be involved in the protective effects of metformin. Metformin activates the LKB1/AMPK pathway to interact with several intracellular signaling pathways and molecular mechanisms. The drug modifies the biologic function of NF-κB, PI3K/AKT/mTOR, SIRT1/PGC-1α, NLRP3, ERK, P38 MAPK, Wnt/β-catenin, Nrf2, JNK, and other major molecules in the intracellular signaling network. It also regulates the expression of noncoding RNAs. Thereby, metformin can regulate metabolism, growth, proliferation, inflammation, tumorigenesis, and senescence. Additionally, metformin modulates immune response, autophagy, mitophagy, endoplasmic reticulum (ER) stress, and apoptosis and exerts epigenetic effects. Furthermore, metformin protects against oxidative stress and genomic instability, preserves telomere length, and prevents stem cell exhaustion. In this review, the protective effects of metformin on each disease will be discussed using the results of recent meta-analyses, clinical trials, and observational studies. Thereafter, it will be meticulously explained how metformin reprograms intracellular signaling pathways and alters molecular and cellular interactions to modify the clinical presentations of several diseases.

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

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

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

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

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

Association of vitamin B12 deficiency with metformin use in patients with type 2 diabetes treated in the largest tertiary care hospital in Qatar

BACKGROUND

Data on the effect of metformin on serum vitamin B12 (VitB12) level in patients with type 2 diabetes mellitus (T2DM) in Qatar are limited; therefore, we aimed to assess the prevalence of VitB12 deficiency and its related factors among patients with tbl2DM treated with metformin at Hamad General Hospital in Doha, Qatar, from January 1, 2017, to December 31, 2017.

METHODS

This cross-sectional analytical study involved patients with tbl2DM aged ≥ 18 years who used metformin for at least 3 months. The serum VitB12 was quantified on a chemiluminescent enzyme immunoassay analyzer using Cobas e 801 module, Roche, and VitB12 deficiency was defined as serum VitB12 level of ≤ 145 pmol/L. All data were obtained from the patients' electronic medical records.

RESULTS

The study recruited 3124 eligible patients with tbl2DM. The overall prevalence of metformin-associated VitB12 deficiency was 30.7% [95% confidence of interval, 0.290-0.323]. A significant difference exists in the median VitB12 levels between the VitB12-normal and VitB12-deficient groups [129 vs. 286; p < 0.001]. Compared with the VitB12-normal group, the VitB12-deficient group had higher mean body mass index (BMI) (p < 0.001) and consumed higher doses of metformin (p = 0.001). They also more often used sulfonylurea (p = 0.004), dipeptidyl peptidase-4 inhibitor (p < 0.001), thiazolidinediones (p < 0.001), glucagon-like peptide 1 [GLP-1] receptor agonists (p < 0.001), alpha-glucosidase inhibitor (p < 0.001), and H2 blocker/proton pump inhibitors [PPI] (p < 0.001) than the VitB12-normal group. Moreover, the VitB12-normal group consumed more calcium supplements (p < 0.001) than the VitB12-deficient group. In the multivariate analysis, independent risk factors for metformin-associated VitB12 deficiency in patients with tbl2DM include high daily dose of metformin >2000 mg, male gender, high BMI, smoking, sulfonylurea, dipeptidyl peptidase-4 inhibitor, H2 blockers/PPI, low fasting blood glucose, and low hemoglobin.

CONCLUSION

This study showed a high prevalence of VitB12 deficiency in patients with tbl2DM taking metformin and a significant negative correlation between the daily dose of metformin and serum VitB12 level. Therefore, regular screening for serum VitB12 is necessary in patients with tbl2DM on metformin treatment, especially those who have the abovementioned risk factors.

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

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