Effect of metformin on outcome after acute ischemic stroke in patients with type 2 diabetes mellitus

The possible therapeutic role of advanced glycation end-product inhibitors in ischemic stroke

The advanced glycation end-products (AGEs) are toxic molecules result from non-enzymatic interactions of sugar with lipids or proteins. AGEs promote the generation of reactive oxygen species that induce the release of pro-inflammatory cytokines, and alter the intracellular signaling leading to progressive biochemical and metabolic derangements. AGEs-induced cellular aging is implicated in the development and progression of different neurological disorders such as dementia, neuropsychiatric disorders, and cerebrovascular diseases. Particularly, AGEs-induced microangiopathy and macroangiopathy trigger the induction of prothrombotic/thrombotic cascades with subsequent increase risk of acute ischemic stroke (AIS). Many studies highlighted that AGEs serum levels are correlated with the incidence, pathogenicity, and severity of AIS. However, the relationship between AGEs and AIS is not elucidated completely. Therefore, this review aims to discuss how AGEs promote the development and progression of AIS, and how AGEs inhibitors could be effective in the management of AIS.

Repurposing metformin: A potential off-label indication for ischaemic stroke?

The term 'clinical cemetery' is frequently used to characterize ischaemic stroke, one of the leading causes of mortality and long-term morbidity globally. Over the past two decades, a number of novel therapies have been investigated for ischaemic stroke. However, aside from mechanical thrombectomy, the only FDA-approved prescription for treating ischaemic stroke is tissue plasminogen activator, which has a limited therapeutic period. Although post-stroke rehabilitation therapies are helpful in improving functional recovery, their benefits cannot be yielded promptly. Nowadays, drug repurposing might be an appealing approach to expanding therapeutic options for ischaemic stroke. During the last decade, metformin has been extensively researched as a potential repurposing medicine for ischaemic stroke, with a focus on both preventive and therapeutic approaches. With regard to the idea of repurposing metformin in ischaemic stroke, this review aims to compile the available data from pre-clinical and clinical trials, address and clarify any discrepancies, and offer solutions.

Impact of Prior Metformin Use on Stroke Outcomes: A Systematic Review and Updated Meta-Analysis

Background

Metformin is a commonly prescribed oral hypoglycemic agent for diabetic patients. Its effect in reducing the incidence of stroke has already been proven. We aimed to explore the impact of prior metformin use on stroke outcomes.

Methods

The Web of Science, PubMed, Embase, and Cochrane Library were searched to identify relevant studies involving stroke patients with a history of metformin use and comparing them to non-metformin users. We analyzed the following outcomes: modified Rankin Scale (mRS), National Institutes of Health Stroke Scale (NIHSS), mortality, or length of hospitalization.

Results

Eleven studies, with 13,825 participants, were included. The metformin group showed higher favorable mRS 0 - 2 than the non-metformin group (risk ratio (RR) = 1.14, 95% confidence interval (CI): 1.09 - 1.19, P value < 0.01). Also, significantly lower mortality rates were seen in the metformin group (RR = 0.54, 95% CI: 0.46 - 0.63, P value ≤ 0.01). NIHSS at discharge was lower in the metformin group than the non-metformin group (mean difference (MD) = -0.46, 95% CI: -0.82 - -0.11, P value < 0.01). The mRS 3 - 6 indicates less favorable outcomes were higher in the non-metformin group (RR = 0.85, 95% CI: 0.77 - 0.93). At the same time, NIHSS at admission showed no statistically significant difference between the two groups. These results indicate that metformin has a beneficial impact on the severity of stroke.

Conclusions

Pre-stroke metformin therapy is associated with better post-stroke clinical outcomes and lower mortality rates. These results highlight the potential neuroprotective role of metformin and emphasize its role as an adjunctive treatment in stroke management. Further research is required to understand its mechanism better.

Effect of metformin on the clinical outcomes of stroke in patients with diabetes: a systematic review and meta-analysis

OBJECTIVES

Stroke is a major cause of death and disability globally, especially among diabetic patients. In this study, we aim to scrutinise the effects of metformin on the clinical outcomes of stroke in diabetic patients.

DESIGN

This study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

DATA SOURCES

PubMed, Embase and Web of Science databases were searched between their inception and 5 December 2023.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Studies investigating the effect of metformin on the clinical outcomes of stroke in patients with diabetes were included.

DATA EXTRACTION AND SYNTHESIS

The effect of metformin on the clinical outcomes of stroke in patients with diabetes was identified using combined ORs and 95% CIs.

RESULTS

A total of 11 studies involving 18 525 participants were included in this review. Pooled analysis has demonstrated that prestroke metformin use could reduce the probability of poor course after stroke by 34% in diabetes mellitus (DM) patients (OR=0.66, 95% CI: 0.61 to 0.72) and reduce the probability of death by 43% (OR=0.57, 95% CI: 0.51 to 0.64).

CONCLUSIONS

Prestroke metformin use is beneficial for the improvement of clinical outcomes in patients who had a stroke with DM, although the potential bias should be carefully considered.

PROSPERO REGISTRATION NUMBER

CRD42024496056.

The mitochondria as a potential therapeutic target in cerebral I/R injury

Ischemic stroke is a major cause of mortality and disability worldwide. Among patients with ischemic stroke, the primary treatment goal is to reduce acute cerebral ischemic injury and limit the infarct size in a timely manner by ensuring effective cerebral reperfusion through the administration of either intravenous thrombolysis or endovascular therapy. However, reperfusion can induce neuronal death, known as cerebral reperfusion injury, for which effective therapies are lacking. Accumulating data supports a paradigm whereby cerebral ischemia/reperfusion (I/R) injury is coupled with impaired mitochondrial function, contributing to the pathogenesis of ischemic stroke. Herein, we review recent evidence demonstrating a heterogeneous mitochondrial response following cerebral I/R injury, placing a specific focus on mitochondrial protein modifications, reactive oxygen species, calcium (Ca2+), inflammation, and quality control under experimental conditions using animal models.

Evaluation of systemic and brain pharmacokinetic parameters for repurposing metformin using intravenous bolus administration

Metformin's potential in treating ischemic stroke and neurodegenerative conditions is of growing interest. Yet, the absence of established systemic and brain pharmacokinetic (PK) parameters at relevant preclinical doses presents a significant knowledge gap. This study highlights these PK parameters and the importance of using pharmacologically relevant preclinical doses to study pharmacodynamics in stroke and related neurodegenerative diseases. A liquid chromatography with tandem mass spectrometry method to measure metformin levels in plasma, brain, and cerebrospinal fluid was developed and validated. In vitro assays examined brain tissue binding and metabolic stability. Intravenous bolus administration of metformin to C57BL6 mice covered a low- to high-dose range maintaining pharmacological relevance. Quantification of metformin in the brain was used to assess brain PK parameters, such as unidirectional blood-to-brain constant (Kin) and unbound brain-to-plasma ratio (Kp, uu, brain). Metformin exhibited no binding in the mouse plasma and brain and remained metabolically stable. It rapidly entered the brain, reaching detectable levels in as little as 5 minutes. A Kin value of 1.87 ± 0.27 μL/g/min was obtained. As the dose increased, Kp, uu, brain showed decreased value, implying saturation, but this did not affect an increase in absolute brain concentrations. Metformin was quantifiable in the cerebrospinal fluid at 30 minutes but decreased over time, with concentrations lower than those in the brain across all doses. Our findings emphasize the importance of metformin dose selection based on PK parameters for preclinical pharmacological studies. We anticipate further investigations focusing on PKs and pharmacodynamics in disease conditions, such as stroke. SIGNIFICANCE STATEMENT: The study establishes crucial pharmacokinetic parameters of metformin for treating ischemic stroke and neurodegenerative diseases, addressing a significant knowledge gap. It further emphasizes the importance of selecting pharmacologically relevant preclinical doses. The findings highlight metformin's rapid brain entry, minimal binding, and metabolic stability. The necessity of considering pharmacokinetic parameters in preclinical studies provides a foundation for future investigations into metformin's efficacy for neurodegenerative disease(s).

Mechanisms of mitophagy and oxidative stress in cerebral ischemia-reperfusion, vascular dementia, and Alzheimer's disease

Neurological diseases have consistently represented a significant challenge in both clinical treatment and scientific research. As research has progressed, the significance of mitochondria in the pathogenesis and progression of neurological diseases has become increasingly prominent. Mitochondria serve not only as a source of energy, but also as regulators of cellular growth and death. Both oxidative stress and mitophagy are intimately associated with mitochondria, and there is mounting evidence that mitophagy and oxidative stress exert a pivotal regulatory influence on the pathogenesis of neurological diseases. In recent years, there has been a notable rise in the prevalence of cerebral ischemia/reperfusion injury (CI/RI), vascular dementia (VaD), and Alzheimer's disease (AD), which collectively represent a significant public health concern. Reduced levels of mitophagy have been observed in CI/RI, VaD and AD. The improvement of associated pathology has been demonstrated through the increase of mitophagy levels. CI/RI results in cerebral tissue ischemia and hypoxia, which causes oxidative stress, disruption of the blood-brain barrier (BBB) and damage to the cerebral vasculature. The BBB disruption and cerebral vascular injury may induce or exacerbate VaD to some extent. In addition, inadequate cerebral perfusion due to vascular injury or altered function may exacerbate the accumulation of amyloid β (Aβ) thereby contributing to or exacerbating AD pathology. Intravenous tissue plasminogen activator (tPA; alteplase) and endovascular thrombectomy are effective treatments for stroke. However, there is a narrow window of opportunity for the administration of tPA and thrombectomy, which results in a markedly elevated incidence of disability among patients with CI/RI. It is regrettable that there are currently no there are still no specific drugs for VaD and AD. Despite the availability of the U.S. Food and Drug Administration (FDA)-approved clinical first-line drugs for AD, including memantine, donepezil hydrochloride, and galantamine, these agents do not fundamentally block the pathological process of AD. In this paper, we undertake a review of the mechanisms of mitophagy and oxidative stress in neurological disorders, a summary of the clinical trials conducted in recent years, and a proposal for a new strategy for targeted treatment of neurological disorders based on both mitophagy and oxidative stress.

Promising use of metformin in treating neurological disorders: biomarker-guided therapies

Neurological disorders are a diverse group of conditions that affect the nervous system and include neurodegenerative diseases (Alzheimer's disease, multiple sclerosis, Parkinson's disease, Huntington's disease), cerebrovascular conditions (stroke), and neurodevelopmental disorders (autism spectrum disorder). Although they affect millions of individuals around the world, only a limited number of effective treatment options are available today. Since most neurological disorders express mitochondria-related metabolic perturbations, metformin, a biguanide type II antidiabetic drug, has attracted a lot of attention to be repurposed to treat neurological disorders by correcting their perturbed energy metabolism. However, controversial research emerges regarding the beneficial/detrimental effects of metformin on these neurological disorders. Given that most neurological disorders have complex etiology in their pathophysiology and are influenced by various risk factors such as aging, lifestyle, genetics, and environment, it is important to identify perturbed molecular functions that can be targeted by metformin in these neurological disorders. These molecules can then be used as biomarkers to stratify subpopulations of patients who show distinct molecular/pathological properties and can respond to metformin treatment, ultimately developing targeted therapy. In this review, we will discuss mitochondria-related metabolic perturbations and impaired molecular pathways in these neurological disorders and how these can be used as biomarkers to guide metformin-responsive treatment for the targeted therapy to treat neurological disorders.

Effects of Prior Metformin Use on Stroke Outcomes in Diabetes Patients with Acute Ischemic Stroke Receiving Endovascular Treatment

Diabetes mellitus (DM) predisposes individuals to vascular injury, leading to poor outcomes after ischemic stroke and symptomatic hemorrhagic transformation (SHT) after thrombolytic and endovascular treatment (EVT). Metformin (MET), an oral antidiabetic drug, has shown potential neuroprotective effects, but its impact on stroke prognosis in DM patients undergoing EVT remains unclear. In a multicenter study, 231 patients with DM undergoing EVT for acute ischemic stroke were enrolled. Prior MET use was identified, and patients were stratified into MET+ and MET- groups. Demographics, clinical data, and outcomes were compared between groups. Multivariate analysis was used to assess the effect of MET on stroke prognosis. Of the enrolled patients, 59.3% were previously on MET. MET+ patients had lower initial infarct volumes and NIHSS scores compared to MET-taking patients. Multivariate analysis showed that MET+ was associated with a lower risk of stroke progression and SHT (with stroke progression as follows: odd ratio [OR] 0.24, 95% confidence interval [CI] [0.12-0.48], p < 0.001; SHT: OR 0.33, 95% CI [0.14-0.75], p = 0.01) and was also associated with better 3-month functional outcomes (mRS 0-2) after EVT. Prestroke MET use in DM patients undergoing EVT is associated with improved stroke prognosis, including reduced risk of stroke progression and SHT and better functional outcomes. These findings suggest the potential neuroprotective role of MET in this population and highlight its clinical utility as an adjunctive therapy in the management of ischemic stroke. Further research is warranted to elucidate the underlying mechanisms and to optimize MET therapy in this setting.

Metformin alleviates cerebral ischemia/reperfusion injury aggravated by hyperglycemia via regulating AMPK/ULK1/PINK1/Parkin pathway-mediated mitophagy and apoptosis

Stroke remains the main leading cause of death and disabilities worldwide, with diabetes mellitus being a significant independent risk factor for it. Metformin, as an efficient hypoglycemic drug in treating type 2 diabetes, has been reported to alleviate the risk of diabetes-related stroke. However, its underlying mechanisms remain unclear. This study aimed to investigate the role of mitophagy and its regulatory pathway in the neuroprotective mechanism of metformin against cerebral ischemia/reperfusion (I/R) injury aggravated by hyperglycemia. A hyperglycemic cerebral I/R animal model and a high glucose cultured oxygen-glucose deprivation/reperfusion (OGD/R) cell model were used in the experiment. The indexes of brain injury, cell activity, mitochondrial morphology and function, mitophagy, mitochondrial pathway apoptosis and the AMPK pathway were observed. In diabetic rats, metformin treatment decreased cerebral infarction volume and neuronal apoptosis, and improved neurological symptoms following I/R injury. Additionally, metformin induced activation of the AMPK/ULK1/PINK1/Parkin mitophagy pathway to have neuroprotective effects. In vitro, high glucose culture and OGD/R treatment impaired mitochondrial morphology and function, mitochondrial membrane potential, and induced apoptosis. However, metformin activated AMPK/ULK1/PINK1/Parkin mitophagy pathway, normalized mitochondrial injury. This protection was reversed by autophagy inhibitor 3-methyladenine (3MA) and AMPK inhibitor compound C. In conclusion, our present study validates the potential mechanism of metformin in alleviating hyperglycemia aggravated cerebral I/R injury by the activation of AMPK/ULK1/PINK1/Parkin mitophagy pathway.

Metformin: evidence from preclinical and clinical studies for potential novel applications in cardiovascular disease

INTRODUCTION

For a long time, metformin has been the first-line treatment for glycaemic control in type 2 diabetes, however, the results of recent cardiovascular outcome trials of sodium-glucose co-transporter 2 inhibitors and glucagon-like peptide 1 receptor agonists have caused many to question metformin's position in the guidelines. Although there are several plausible mechanisms by which metformin might have beneficial cardiovascular effects, for example its anti-inflammatory effects and metabolic properties, and numerous observational data suggesting improved cardiovascular outcomes with metformin use, the main randomised clinical trial data for metformin was published over 20 years ago. Nevertheless, the overwhelming majority of participants in contemporary type 2 diabetes trials were prescribed metformin.

AREAS COVERED

In this review we will summarise the potential mechanisms of cardiovascular benefit with metformin, before discussing clinical data in individuals with or without diabetes.

EXPERT OPINION

Metformin may have some cardiovascular benefit in patients with and without diabetes, however the majority of clinical trials were small and are before the use SGLT2 inhibitors and GLP1-RAs. Larger contemporary randomised trials with metformin evaluating its cardiovascular benefit are warranted.

Premorbid Use of Beta-Blockers or Angiotensin-Converting Enzyme Inhibitors/Angiotensin Receptor Blockers in Patients with Acute Ischemic Stroke

This study was designed to investigate the impact of the preexisting use of beta-blockers, angiotensin-converting enzyme inhibitors (ACEIs), or angiotensin receptor blockers (ARBs) on the cellular immune response in peripheral blood and the clinical outcomes of patients with acute ischemic stroke. We retrospectively collected clinical data from a cohort of 69 patients with premorbid beta-blockers and 56 patients with premorbid ACEIs/ARBs. Additionally, we selected a cohort of 107 patients with acute ischemic stroke to be the control of the same age and sex. We analyzed cellular immune parameters in peripheral blood 1 day after the appearance of symptoms, including the frequencies of circulating white blood cell subpopulations, the neutrophil-to-lymphocyte ratio (NLR), and the lymphocyte-to-monocyte ratio (LMR). We found that the count of lymphocytes and the lymphocyte-to-monocyte ratio were significantly higher in the peripheral blood of patients treated with beta-blockers before stroke than in matched controls. However, the premorbid use of ACEIs/ARBs did not considerably impact the circulating immune parameters listed above in patients with acute ischemic stroke. Furthermore, we found that premorbid use of beta-blockers or ACEIs/ARBs did not significantly change functional outcomes in patients 3 months after the onset of stroke. These results suggest that premorbid use of beta-blockers, but not ACEIs/ARBs, reversed lymphopenia associated with acute ischemic stroke. As cellular immune changes in peripheral blood could be an independent predictor of stroke prognosis, more large-scale studies are warranted to further verify the impact of premorbid use of beta-blockers or ACEIs/ARBs on the prognosis of patients with ischemic stroke. Our research is beneficial to understanding the mechanism of the systemic immune response induced by stroke and has the potential for a therapeutic strategy in stroke interventions and treatment.

Neuropharmacological efficacy of metformin for stroke in rodents: A meta-analysis of preclinical trials

Background: Stroke, including ischemic stroke, intracerebral hemorrhage, and subarachnoid hemorrhage (SAH), remains a leading cause of mortality globally. Different stroke subtypes have similar detrimental effects in multiple fields of health. Previous research has shown that metformin plays a neuroprotective role in experimental animal models of stroke; however, a preclinical quantitative analysis on the ability of metformin to treat stroke is still lacking. This meta-analysis evaluates the efficacy of metformin in improving stroke prognosis in rodent models of stroke. Methods: Relevant preclinical trials were retrieved from PubMed, EMBASE, and the Web of Science. The neurological score (NS), brain water content (BWC), infarct size, rotarod test, TUNEL, neuron quantity, microglia quantity, and p-AMPK levels were compared between a control group and a metformin group using the standardized mean difference (SMD) and corresponding confidence interval (CI). Quality was assessed with SYRCLE's risk of bias tool. Results: Fifteen articles published from 2010 to 2022 were included in the meta-analysis. The metformin group had statistically significant differences compared to the control group in the following aspects: NS (SMD -1.45; 95% CI -2.32, -0.58; p = 0.001), BWC (SMD -3.22; 95% CI -4.69, -1.76; p < 0.0001), infarct size (SMD -2.90; 95% CI -3.95, -1.85; p < 0.00001), rotarod test (SMD 2.55; 95% CI 1.87, 3.23; p < 0.00001), TUNEL (SMD -3.63; 95% CI -5.77, -1.48; p = 0.0009), neuron quantity (SMD 3.42; 95% CI 2.51, 4.34; p < 0.00001), microglia quantity (SMD -3.06; 95% CI -4.69, -1.44; p = 0.0002), and p-AMPK levels (SMD 2.92; 95% CI 2.02, 3.82; p < 0.00001). Furthermore, sensitivity analysis and stratified analysis were conducted for heterogeneous outcome indicators. Conclusion: Overall, metformin treatment improves severe outcomes triggered by stroke. Despite the limitations intrinsic to animal studies, this systematic review may provide a vital reference for future high-quality preclinical trials and clinical use.