Metformin: Therapeutic profile in the treatment of type 2 diabetes

Metformin (dimethyl-biguanide) can claim its origins in the use of Galega officinalis as a plant treatment for symptoms ascribed to diabetes. Since the first clinical use of metformin as a glucose-lowering agent in 1957, this medicine has emerged as a first-line pharmacological option to support lifestyle interventions in the management of type 2 diabetes (T2D). It acts through multiple cellular pathways, principally in the gut, liver and muscle, to counter insulin resistance and lower blood glucose without weight gain or risk of overt hypoglycaemia. Other effects include improvements in lipid metabolism, decreased inflammation and lower long-term cardiovascular risk. Metformin is conveniently combined with other diabetes medications, can be prescribed in prediabetes to reduce the risk of progression to T2D, and is used in some regions to assist glycaemic control in pregnancy. Consistent with its diversity of actions, established safety profile and cost-effectiveness, metformin is being assessed for further possible clinical applications. The use of metformin requires adequate renal function for drug elimination, and may cause initial gastrointestinal side effects, which can be moderated by taking with meals or using an extended-release formulation. Thus, metformin serves as a valuable therapeutic resource for use throughout the natural history of T2D.

Protection by metformin against severe Covid-19: an in-depth mechanistic analysis

Since the outbreak of Covid-19, several observational studies on diabetes and Covid-19 have reported a favourable association between metformin and Covid-19-related outcomes in patients with type 2 diabetes mellitus (T2DM). This is not surprising since metformin affects many of the pathophysiological mechanisms implicated in SARS-CoV-2 immune response, systemic spread and sequelae. A comparison of the multifactorial pathophysiological mechanisms of Covid-19 progression with metformin's well-known pleiotropic properties suggests that the treatment of patients with this drug might be particularly beneficial. Indeed, metformin could alleviate the cytokine storm, diminish virus entry into cells, protect against microvascular damage as well as prevent secondary fibrosis. Although our in-depth analysis covers many potential metformin mechanisms of action, we want to highlight more particularly its unique microcirculatory protective effects since worsening of Covid-19 disease clearly appears as largely due to severe defects in the structure and functioning of microvessels. Overall, these observations confirm that metformin is a unique, pleiotropic drug that targets many of Covid-19′s pathophysiology processes in a diabetes-independent manner.

Lemongrass essential oil and its major constituent citral isomers modulate adipogenic gene expression in 3T3-L1 cells

Obesity is a predisposing factor to diseases such as diabetes mellitus, hypertension, and coronary artery disease. Lemongrass essential oil (LEO), from Cymbopogon flexuosus, possesses numerous therapeutic properties including modulation of obesity in vivo. This experiment investigated the effect of LEO and its major components citral (3,7-dimethyl-2,6-octadienal), citral dimethyl acetal (1,1-dimethoxy-3,7-dimethylocta-2,6-diene), and citral diethyl acetal (1,1-diethoxy-3,7-dimethylocta-2,6-diene) in modulation of adipogenesis and genetic expression in adipocytes. Adipogenesis was induced from murine 3T3-L1 preadipocytes procured from ATCC and maintained in Dulbecco's modified Eagle's medium (DMEM) enriched with calf serum. Differentiation was conducted using DMEM enriched with 10% fetal bovine serum, Dexamethasone 0.25 µM, 3-isobutyl-methylxanthine 0.5 mM, and insulin 10 mg/ml for 2 days, followed by 5 days of insulin 10 mg/ml alone. Samples were subjected to experimental treatments at a concentration of 2.5 × 10^-3 . Intracellular triglycerides were quantified and photomicrographs were obtained following Oil red O (ORO) staining procedure. Total ribonucleic acid was extracted and expression of genes effecting in lipid metabolism were quantitated using real-time polymerase chain reaction. ORO staining procedure and spectrophotometric analysis demonstrated decreased lipid accumulation following treatments. LEO and its major constituents significantly inhibited expression of sterol response binding protein 2, cluster of differentiation 36, fatty acid binding protein 4, and peripilin. These results indicate modulation of lipid accumulation through decreased lipid uptake, increased lipolysis, decreased differentiation, and downregulated lipid biosynthesis. This investigation suggests that LEO and its constituents exert effects on adipocyte metabolism and are important for understanding metabolic disease. Further investigation is required to elucidate the degree that each mechanism implicated contributes to the observed effect.

La metformine est associée à une moindre mortalité chez les patients diabétiques hospitalisés pour la COVID-19

Les effets anti-inflammatoires et modulateurs de l’immunité de la metformine légitimaient la recherche d’un meilleur pronostic chez les diabétiques hospitalisés pour la maladie à coronavirus 2019 (COVID-19) traités par metformine, comparativement à ceux qui ne le sont pas. Une telle recherche a pu être menée à partir de la cohorte nationale CORONADO, qui a inclus les patients diabétiques de type 2 hospitalisés pour la COVID-19, entre le 10 mars et le 10 avril 2020 et avec une méthodologie robuste : un critère de jugement principal combinant à J7 l’intubation trachéale et le décès ; une courbe de survie Kaplan–Meier ; et, surtout, une analyse de régression logistique pondérée par un score de propension. Ce sont, au total, près de 2500 patients qui ont été étudiés, dont près des deux-tiers traités par metformine. Ces derniers avaient globalement moins de comorbidités, liées au diabète ou non, mais, en revanche, des signes de la COVID-19 plus francs. Parmi les résultats, le fait plus marquant a été une mortalité nettement moindre dans le groupe traité par metformine que dans le groupe non traité par metformine, et ce, dès J7 (8,2 % versus 16,1 %, respectivement). Ce différentiel persistait à J28 (16,0 % versus 28,6 %, respectivement). L’hypothèse d’un bénéfice lié à la metformine doit maintenant être confirmée par une étude d’intervention, dont dans la population générale.

Changing Fields-Diabetes Medications Invading the Cardiovascular Space

Cardiovascular disease (CVD) remains the leading cause of mortality in patients with type 2 diabetes, and treatment strategies that impact cardiovascular (CV) outcomes in this population is an area of growing interest. Pharmacologic agents that reduce CVD risk have been developed, and data supporting their use have grown extensively. Glucagon-like peptide 1 agonists and sodium-glucose cotransporter 2 inhibitors when added to metformin therapy provide the most CV benefit and should be considered in most patients. Data available suggest that sulfonylureas should be avoided in patients at risk for CVD and if a thiazolidinedione is utilized, pioglitazone may be preferred. When selecting an agent, the potential benefit, risk, and cost of each agent should be considered prior to initiation. The purpose of this review is to summarize the literature surrounding the CV effects of antidiabetic agents and to provide practical guidance on their use in patients with type 2 diabetes and CVD.

Effect of metformin combined with lifestyle modification versus lifestyle modification alone on proinflammatory-oxidative status in drug-naïve pre-diabetic and diabetic patients: A randomized controlled study

BACKGROUND

Targeting biomarkers of oxidative-proinflammatory stress may result in improvement of modifiable metabolic syndrome, pre-diabetes and diabetes risk factors and subsequent risk reduction.

METHODS

64 newly diagnosed antihyperglycemic treatment-naïve prediabetic and type 2 diabetes mellitus (T2DM) patients were randomly assigned using block design to either metformin combined with therapeutic lifestyle changes (TLC) or TLC alone. Body mass index (BMI), waist circumference, blood pressure, fasting plasma glucose (FPG), glycated hemoglobin (HbA1c), fasting lipid profile, plasma oxidative status and tumor necrosis factor (TNF)-α were measured at baseline, after 3 months and after 6 months from baseline.

RESULTS

Except for HbA1c, baseline values did not differ significantly between the two groups. The post 3-months relative reductions in BMI (P=0.014) and HbA1c (P=0.037) in metformin combined with TLC intervention were significantly greater than those in TLC alone group. TNFα plasma levels were decreased significantly vs. baseline by metformin combined with TLC intervention (-22.90±46.76%, P=0.01). Conversely, TLC alone basically worsened proinflammatory status (42.40±40.82 %), P<0.001. Metformin with TLC treatment effected a therapeutic decrement of the oxidative stress (-15.44±35.32%, P=0.029 vs. baseline) unlike TLC alone (61.49±122.66%, P=0.01 vs. baseline). Both interventions' effects were sustained in the 6-month follow up periods.

CONCLUSION

In both intervention groups, the relative changes in plasma TNFα were significantly correlated (P<0.01) with systolic blood pressure and the relative changes in oxidative stress were markedly correlated (P<0.05) with total cholesterol.

Metformin: historical overview

Metformin (dimethylbiguanide) has become the preferred first-line oral blood glucose-lowering agent to manage type 2 diabetes. Its history is linked to Galega officinalis (also known as goat's rue), a traditional herbal medicine in Europe, found to be rich in guanidine, which, in 1918, was shown to lower blood glucose. Guanidine derivatives, including metformin, were synthesised and some (not metformin) were used to treat diabetes in the 1920s and 1930s but were discontinued due to toxicity and the increased availability of insulin. Metformin was rediscovered in the search for antimalarial agents in the 1940s and, during clinical tests, proved useful to treat influenza when it sometimes lowered blood glucose. This property was pursued by the French physician Jean Sterne, who first reported the use of metformin to treat diabetes in 1957. However, metformin received limited attention as it was less potent than other glucose-lowering biguanides (phenformin and buformin), which were generally discontinued in the late 1970s due to high risk of lactic acidosis. Metformin's future was precarious, its reputation tarnished by association with other biguanides despite evident differences. The ability of metformin to counter insulin resistance and address adult-onset hyperglycaemia without weight gain or increased risk of hypoglycaemia gradually gathered credence in Europe, and after intensive scrutiny metformin was introduced into the USA in 1995. Long-term cardiovascular benefits of metformin were identified by the UK Prospective Diabetes Study (UKPDS) in 1998, providing a new rationale to adopt metformin as initial therapy to manage hyperglycaemia in type 2 diabetes. Sixty years after its introduction in diabetes treatment, metformin has become the most prescribed glucose-lowering medicine worldwide with the potential for further therapeutic applications.

Effects of two weeks of metformin treatment on whole-body glycocalyx barrier properties in db/db mice

Background

The anti-diabetic drug metformin has been demonstrated to exert a protective effect against vascular complications in diabetes independent of its glucose lowering action. Since the endothelial glycocalyx has been indicated to have important vasculoprotective properties and to be vulnerable to degradation by hyperglycemic conditions, we evaluated in the current study the effect of short-term metformin treatment on whole-body glycocalyx barrier properties in a mouse model of non-insulin dependent diabetes mellitus (db/db mouse).

Methods

Glycocalyx barrier properties were measured in an acute experiment in three groups of mice: 1) db/db mice without treatment serving as controls, 2) db/db mice which received metformin for two weeks in the drinking water serving as experimental group, and 3) C57Bl/6 mice serving as reference group. Animals were put under anesthesia (ketamine, medetomidine, and atropine) and carotid artery blood pressure was continuously monitored. To probe the glycocalyx a mixture of the tracers FITC-labeled 70 kDa dextrans (Dex70) or fluorescein-labeled red blood cells (RBCs) versus Texas Red-labeled 40 kDa dextrans (Dex40) was infused and blood samples subsequently collected for 30 min to determine the initial vascular distribution volume and clearance of these tracers. Urine was collected and dry-to-wet weight of heart and kidney were determined after the experiment. Group differences were tested using unpaired t-tests.

Results

Metformin treatment did not affect body weight, fasting blood glucose and arterial blood pressure. Compared to C57Bl/6 mice, db/db mice showed a diminished initial exclusion and increased vascular clearance of Dex70 versus Dex40 (P < 0.05), and both were improved by the metformin treatment (P < 0.05). While urine production was higher in the db/db mice compared to C57Bl/6 (P < 0.05), heart and kidney of the metformin treated animals showed comparable dry-to-wet weights compared to the C57Bl/6 mice.

Conclusions

Two weeks of metformin in the drinking water is associated with an improvement in glycocalyx barrier properties in db/db mice, as evidence by an enhanced exclusion and retention of 70 kDa dextrans in the vasculature. In addition, metformin improved hydration of heart and kidney. Previous reported cardiovascular benefits of metformin may well involve an improvement of the endothelial glycocalyx.

The effect of metformin on the myocardial tolerance to ischemia-reperfusion injury in the rat model of diabetes mellitus type II

In recent years, evidence has been accumulated that metformin, an antidiabetic drug in the biguanide class, in addition to its well-recognized glucose-lowering effect, can also reduce cardiovascular mortality in the patients with type 2 diabetes mellitus (T2DM). Besides, there are a few experimental studies on the possibility of the direct anti-ischemic effect of the drug in both type 1 diabetes mellitus and T2DM. In our study, myocardial tolerance to ischemia in rats with neonatal streptozotocin T2DM was investigated using the model of global ischemia-reperfusion of the isolated perfused heart. Metformin was administered i.p. at a dose of 200 mg/kg/day for 3 days prior to isolated heart perfusion. The results showed that both the infarct size and postischemic recovery of left ventricular function were not different between controls and metformin-treated animals. At the same time, the infarct size in the T2DM animals was significantly lower than that in the controls (24.4 ± 7.6% versus 45.0 ± 10.4%, resp., P < .01), indicative of the metabolic preconditioning in T2DM. It follows that the protocol of metformin administration used in this study had not elicited cardioprotective effect in animals with T2DM so that the different mechanism(s) may underlie the beneficial effect of metformin on cardiovascular complications in patients with T2DM which, however, would need further investigation.

Lactic acidosis induced by metformin: incidence, management and prevention

Lactic acidosis associated with metformin treatment is a rare but important adverse event, and unravelling the problem is critical. First, this potential event still influences treatment strategies in type 2 diabetes mellitus, particularly in the many patients at risk of kidney failure, in those presenting contraindications to metformin and in the elderly. Second, the relationship between metformin and lactic acidosis is complex, since use of the drug may be causal, co-responsible or coincidental. The present review is divided into three parts, dealing with the incidence, management and prevention of lactic acidosis occurring during metformin treatment. In terms of incidence, the objective of this article is to counter the conventional view of the link between metformin and lactic acidosis, according to which metformin-associated lactic acidosis is rare but is still associated with a high rate of mortality. In fact, the direct metformin-related mortality is close to zero and metformin may even be protective in cases of very severe lactic acidosis unrelated to the drug. Metformin has also inherited a negative class effect, since the early biguanide, phenformin, was associated with more frequent and sometimes fatal lactic acidosis. In the second part of this review, the objective is to identify the most efficient patient management methods based on our knowledge of how metformin acts on glucose/lactate metabolism and how lactic acidosis may occur (at the organ and cellular levels) during metformin treatment. The liver appears to be a key organ for both the antidiabetic effect of metformin and the development of lactic acidosis; the latter is attributed to mitochondrial impairment and subsequent adenosine triphosphate depletion, acceleration of the glycolytic flux, increased glucose uptake and the generation of lactate, which effluxes into the circulation rather than being oxidized further. Haemodialysis should systematically be performed in severe forms of lactic acidosis, since it provides both symptomatic and aetiological treatment (by eliminating lactate and metformin). In the third part of the review (prevention), the objective is to examine the list of contraindications to metformin (primarily related to renal and cardiovascular function). Diabetes is above all a vascular disease and metformin is a vascular drug with antidiabetic properties. Given the importance of the liver in lactate clearance, we suggest focusing on the severity of and prognosis for liver disease; renal dysfunction is only a prerequisite for metformin accumulation, which may only be dangerous per se when associated with liver failure. Lastly, in view of metformin's impressive overall effectiveness profile, it would be paradoxical to deny the majority of patients with long-established diabetes access to metformin because of the high prevalence of contraindications. The implications of these contraindications are discussed.

The Old and the New in the Treatment of Type 2 Diabetes: Focus on the Combination Therapy with Dipeptidyl Peptidase-4 Inhibitors and Metformin

Type 2 diabetes mellitus (T2DM) is a complex multifactorial disease which affects the length and quality of life by severe chronic complications. Chronic hyperglycemia, which is the main alteration in T2DM, is strictly related to microvascular complications (such as retinopathy and nephropathy) and neuropathy, whereas large vessel atherosclerosis is also dependent on lipid and hemostasis abnormalities, arterial hypertension and other known cardiovascular risk factors. An early intervention to control hyperglycemia and to prevent deterioration of β-cell function is considered mandatory in patients with T2DM to minimize the risk of chronic complications. Recently, the availability of new pharmacological agents with different targets, including the activation of the incretin system has allowed the proposal of more effective strategies for early treatment of metabolic alterations in patients with T2DM. This commentary will focus on the role of new oral agents influencing the incretin system and the putative advantages of their co-administration with metformin, an old, effective anti-hyperglycemic agent also able to exert beneficial actions on arterial vessels, reducing the risk of macrovascular-related events. The vasoprotective role of metformin is largely independent of its hypoglycemic action, and has been ascribed to pleiotropic effects.

Metformin prevents experimental gentamicin-induced nephropathy by a mitochondria-dependent pathway

The antidiabetic drug metformin can diminish apoptosis induced by oxidative stress in endothelial cells and prevent vascular dysfunction even in nondiabetic patients. Here we tested whether it has a beneficial effect in a rat model of gentamicin toxicity. Mitochondrial analysis, respiration intensity, levels of reactive oxygen species, permeability transition, and cytochrome c release were assessed 3 and 6 days after gentamicin administration. Metformin treatment fully blocked gentamicin-mediated acute renal failure. This was accompanied by a lower activity of N-acetyl-beta-D-glucosaminidase, together with a decrease of lipid peroxidation and increase of antioxidant systems. Metformin also protected the kidney from histological damage 6 days after gentamicin administration. These in vivo markers of kidney dysfunction and their correction by metformin were complemented by in vitro studies of mitochondrial function. We found that gentamicin treatment depleted respiratory components (cytochrome c, NADH), probably due to the opening of mitochondrial transition pores. These injuries, partly mediated by a rise in reactive oxygen species from the electron transfer chain, were significantly decreased by metformin. Thus, our study suggests that pleiotropic effects of metformin can lessen gentamicin nephrotoxicity and improve mitochondrial homeostasis.

Metformin: effects on micro and macrovascular complications in type 2 diabetes

INTRODUCTION

The antihyperglycaemic agent metformin is widely used in the treatment of type 2 diabetes. Data from the UK Prospective Diabetes Study and retrospective analyses of large healthcare databases concur that metformin reduces the incidence of myocardial infarction and increases survival in these patients. This apparently vasoprotective effect appears to be independent of the blood glucose-lowering efficacy.

EFFECTS OF METFORMIN

Metformin has long been known to reduce the development of atherosclerotic lesions in animal models, and clinical studies have shown the drug to reduce surrogate measures such as carotid intima-media thickness. The anti-atherogenic effects of metformin include reductions in insulin resistance, hyperinsulinaemia and obesity. There may be modest favourable effects against dyslipidaemia, reductions in pro-inflammatory cytokines and monocyte adhesion molecules, and improved glycation status, benefiting endothelial function in the macro- and micro-vasculature. Additionally metformin exerts anti-thrombotic effects, contributing to overall reductions in athero-thrombotic risk in type 2 diabetic patients.