Metformin, arterial function, intima-media thickness and nitroxidation in metabolic syndrome: the mefisto study

Predictive role of triglyceride-glucose index and HOMA index on development of arterial stiffening in non-diabetic men

BACKGROUND AND AIMS

Insulin resistance (IR) is a major risk factor for cardiovascular disease. Recently, a novel index (triglyceride-glucose index-TyG) has been proposed as a surrogate marker of IR and a better expression of IR than the Homeostatic Model Assessment of IR (HOMA-IR) index. Few and heterogeneous data are so far available on the relationship between vascular damage and this novel index. Therefore, we aimed to estimate the predictive role of TyG, in comparison with the HOMA-IR, on the development of arterial stiffening (AS), defined as a pulse pressure>60 mmHg, in an 8-year follow-up observation of a sample of non-diabetic adult men (the Olivetti Heart Study).

METHODS AND RESULTS

The analysis included 527 non-diabetic men, with normal arterial elasticity at baseline and not on antihypertensive or hypolipidemic treatment. TyG was significantly greater in those who developed AS than those who did not (p = 0.006). On the contrary, the HOMA-IR index was not different between the two groups (p = 0.24). Similar trends were shown by logistic regression analysis adjusting for main confounders. After the stratification by the optimal cut-off point, values of TyG >4.70 were significantly associated with the development of AS, also after adjustment for main confounders. On the contrary, the HOMA-IR index >1.90 was not associated with the risk of AS development in multivariate models.

CONCLUSION

The results of this study indicate a predictive role of TyG on AS, independently of the main potential confounders. Moreover, the predictive power of TyG seems to be greater than that of the HOMA-IR index.

Long-term effects of different hypoglycemic drugs on carotid intima-media thickness progression: a systematic review and network meta-analysis

Objective

The progression of carotid intima-media thickness (cIMT) can partially predict the occurrence of future cardiovascular events. This network meta-analysis compared the effects of 14 antidiabetic drugs (acarbose, alogliptin, exenatide, glibenclamide, glimepiride, ipragliflozin, metformin, nateglinide, pioglitazone, rosiglitazone, sitagliptin, tofoglifozin, troglitazone, voglibose) on the progression of cIMT.

Method

PubMed, EMBASE, Cochrane Library, and Web of Science were searched to screen all clinical trials of treatment of cIMT with hypoglycemic agents before March 1, 2024. The differences in the changes in cIMT between the treatment group and control group were evaluated.

Result

After screening 8395 citations, 25 studies (6675 patients) were included. The results indicated that exenatide had the best efficacy in slowing down cIMT progress, and exenatide [MD=-0.13,95%CI (-0.25, -0.01)], alogliptin [MD=-0.08,95%CI (-0.13, -0.02)] and metformin [MD=-0.05, 95%CI (-0.09, -0.02)] are more effective than placebo.

Conclusion

Long-term treatment of exenatide, alogliptin, and metformin may be more effective than other hypoglycemic drugs in slowing the progression of cIMT.

Systematic Review Registration

https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42024519474.

Causal association of metformin treatment with diverse cardiovascular diseases: a Mendelian randomization analysis

BACKGROUND

The cardiovascular effects of metformin continue to be a subject of debate within the medical community.

METHODS

The Mendelian randomization (MR) study used data from genome-wide association studies (GWAS) to explore the causal association with six diseases that are associated with bimatoprost treatment and myocardial infarction, chronic heart failure, atrial fibrillation, hypertrophic and dilated cardiomyopathy, and valvular disease. Genome-wide significant single nucleotide polymorphisms (SNPs), that are associated with metformin use were selected as the instrumental variables. To determine the causal relationship between metformin use and various cardiovascular diseases, MR analysis was conducted, employing methods such as Instrumental Variable Weighting (IVW).

RESULTS

The IVW analysis demonstrated a positive association between metformin treatment and the risk of myocardial infarction (OR = 22.67, 95% CI 3.22-34.01; P = 0.002). Conversely, metformin treatment exhibited a negative association with the risk of developing valvular disease (OR = 0.98, 95% CI 0.95-1.00; P = 0.046) and hypertrophic cardiomyopathy (OR = 0.01, 95% CI 0.00-0.22; P = 0.016). Multiple test correction found that metformin treatment was causally associated with the risk of both hypertrophic cardiomyopathy (PFDR = 0.048) and myocardial infarction (PFDR = 0.012). The analysis revealed limited heterogeneity in the individual results, absence of pleiotropy evidence, and indications of stability in the findings.

CONCLUSION

The MR study discovered from a genetic standpoint that metformin may lower the risk of hypertrophic cardiomyopathy and valvular heart disease, yet it could elevate the risk of myocardial infarction.

Effect of Metformin on Oxidative Stress and Left Ventricular Geometry in Nondiabetic Heart Failure Patients: A Randomized Controlled Trial

Introduction: There is an increasing interest in using metformin in cardiovascular diseases and its potential new roles. Only two randomized controlled trials investigated the effect of metformin in nondiabetic heart failure (HF) patients. However, none of these studies assess the role of metformin in reducing oxidative stress. We hypothesized that metformin might improve oxidative stress and left ventricular remodeling in nondiabetic HF patients with reduced ejection fraction (HFrEF). Methods and Methods: Seventy HFrEF patients (EF 37% ± 8%; median age 66 years) were randomized to metformin (n = 35) or standard of care (SOC) for HF (n = 35) for 6 months in addition to standard therapy. Outcomes included the difference in the change (Δ) in total antioxidant capacity (TAC) and malondialdehyde (MDA), both assessed colorimetrically and left ventricular mass index (LVMI) assessed through transthoracic echocardiography. Results: Compared with the SOC, metformin treatment increased TAC [Δ = 0.12 mmol/L, confidence intervals (95% CIs): 0.03-0.21; P = 0.007]. TAC increased significantly only in the metformin group (0.90 ± 0.08 mmol/L at baseline vs. 1.04 ± 0.99 mmol/L at 6 months, P < 0.05). Metformin therapy preserved LVMI (Δ = -23 g/m2, 95% CI: -42.91 to -4.92; P = 0.014) and reduced fasting plasma glucose (Δ = -6.16, 95% CI: -12.31 to -0.02, P = 0.047) compared with the SOC. Results did not change after adjusting for baseline values. Changes in MDA left ventricular ejection fraction (LVEF) and blood pressure were not significantly different between groups. Conclusion: Metformin treatment in HF patients with reduced LVEF improved TAC and prevented the increase in LVMI compared with the SOC. These effects of metformin warrant further research in HF patients without diabetes to explore the potential benefits of metformin. Trial Registration Number: This protocol was registered in ClinicalTrials.gov under the number NCT05177588.

Micro- and Macrovascular Effects of Inflammation in Peripheral Artery Disease-Pathophysiology and Translational Therapeutic Approaches

Inflammation has a critical role in the development and progression of atherosclerosis. On the molecular level, inflammatory pathways negatively impact endothelial barrier properties and thus, tissue homeostasis. Conformational changes and destruction of the glycocalyx further promote pro-inflammatory pathways also contributing to pro-coagulability and a prothrombotic state. In addition, changes in the extracellular matrix composition lead to (peri-)vascular remodelling and alterations of the vessel wall, e.g., aneurysm formation. Moreover, progressive fibrosis leads to reduced tissue perfusion due to loss of functional capillaries. The present review aims at discussing the molecular and clinical effects of inflammatory processes on the micro- and macrovasculature with a focus on peripheral artery disease.

Metformin protects against vascular calcification through the selective degradation of Runx2 by the p62 autophagy receptor

Vascular calcification is associated with aging, type 2 diabetes, and atherosclerosis, and increases the risk of cardiovascular morbidity and mortality. It is an active, highly regulated process that resembles physiological bone formation. It has previously been established that pharmacological doses of metformin alleviate arterial calcification through adenosine monophosphate-activated protein kinase (AMPK)-activated autophagy, however the specific pathway remains elusive. In the present study we hypothesized that metformin protects against arterial calcification through the direct autophagic degradation of runt-related transcription factor 2 (Runx2). Calcification was blunted in vascular smooth muscle cells (VSMCs) by metformin in a dose-dependent manner (0.5-1.5 mM) compared to control cells (p < 0.01). VSMCs cultured under high-phosphate (Pi) conditions in the presence of metformin (1 mM) showed a significant increase in LC3 puncta following bafilomycin-A1 (Baf-A; 5 nM) treatment compared to control cells (p < 0.001). Furthermore, reduced expression of Runx2 was observed in the nuclei of metformin-treated calcifying VSMCs (p < 0.0001). Evaluation of the functional role of autophagy through Atg3 knockdown in VSMCs showed aggravated Pi-induced calcification (p < 0.0001), failure to induce autophagy (punctate LC3) (p < 0.001) and increased nuclear Runx2 expression (p < 0.0001) in VSMCs cultured under high Pi conditions in the presence of metformin (1 mM). Mechanistic studies employing three-way coimmunoprecipitation with Runx2, p62, and LC3 revealed that p62 binds to both LC3 and Runx2 upon metformin treatment in VSMCs. Furthermore, immunoblotting with LC3 revealed that Runx2 specifically binds with p62 and LC3-II in metformin-treated calcified VSMCs. Lastly, we investigated the importance of the autophagy pathway in vascular calcification in a clinical setting. Ex vivo clinical analyses of calcified diabetic lower limb artery tissues highlighted a negative association between Runx2 and LC3 in the vascular calcification process. These studies suggest that exploitation of metformin and its analogues may represent a novel therapeutic strategy for clinical intervention through the induction of AMPK/Autophagy Related 3 (Atg3)-dependent autophagy and the subsequent p62-mediated autophagic degradation of Runx2.

Metformin's Impact on the Microvascular Response to Insulin

Metformin improves insulin's action on whole-body glucose metabolism in various insulin-resistant populations. The detailed cellular mechanism(s) for its metabolic actions are multiple and still incompletely understood. Beyond metabolic actions, metformin also impacts microvascular function. However, the effects of metformin on microvascular function and microvascular insulin action specifically are poorly defined. In this mini-review, we summarize what is currently known about metformin's beneficial impact on both microvascular function and the microvascular response to insulin while highlighting methodologic issues in the literature that limit straightforward mechanistic understanding of these effects. We examine potential mechanisms for these effects based on pharmacologically dosed studies and propose that metformin may improve human microvascular insulin resistance by attenuating oxidative stress, inflammation, and endothelial dysfunction. Finally, we explore several important evidence gaps and discuss avenues for future investigation that may clarify whether metformin's ability to improve microvascular insulin sensitivity is linked to its positive impact on vascular outcomes.

Protective effects of metformin in various cardiovascular diseases: Clinical evidence and AMPK-dependent mechanisms

Metformin, a well-known AMPK agonist, has been widely used as the first-line drug for treating type 2 diabetes. There had been a significant concern regarding the use of metformin in people with cardiovascular diseases (CVDs) due to its potential lactic acidosis side effect. Currently growing clinical and preclinical evidence indicates that metformin can lower the incidence of cardiovascular events in diabetic patients or even non-diabetic patients beyond its hypoglycaemic effects. The underlying mechanisms of cardiovascular benefits of metformin largely involve the cellular energy sensor, AMPK, of which activation corrects endothelial dysfunction, reduces oxidative stress and improves inflammatory response. In this minireview, we summarized the clinical evidence of metformin benefits in several widely studied cardiovascular diseases, such as atherosclerosis, ischaemic/reperfusion injury and arrhythmia, both in patients with or without diabetes. Meanwhile, we highlighted the potential AMPK-dependent mechanisms in in vitro and/or in vivo models.

Metformin Reverses the Effects of Angiotensin 2 in Human Mammary Arteries by Modulating the Expression of Nitric Oxide Synthases

Angiotensin 2 impairs vascular function by activation of reactive oxygen species (ROS) production and development of endothelial dysfunction. Metformin, the first-line therapeutic agent for type 2 diabetes mellitus, has vascular protective properties, beyond its glucose lowering effects. The aim of the present study was to in-vestigate the interaction between metformin and angiotensin 2 in human internal mammary arteries harvested from patients with coronary heart disease undergoing revascularization procedure, by evaluation of vascular function, reactive oxygen species (ROS) production and the gene expression of nitric oxide (NO) synthases (endothelial – eNOS, neuronal – nNOS and inducible – iNOS). To this aim, vascular samples were incubated with angiotensin 2 (Ang2, 12 h) with/without metformin (Metf, 10 μM) and used for ROS measurement (FOX assay), vascular reactivity in organ bath (contractility to phenylephrine, relaxation to acetylcholine, con-tractility to NG-nitro-L-arginine methyl ester/L-NAME) and RT-PCT studies. Acute incubation of the vascular rings with Ang2 im-paired vascular reactivity (increase contractility, decrease relax-ation), increased ROS production, supressed eNOS/nNOS and in-creased iNOS mRNA expression. Ex vivo incubation with metfor-min at a clinically relevant concentration reversed all these ef-fects. These data suggest that Metformin might be useful in allevi-ating endothelial dysfunction by improving the endothelial-de-pendent relaxation and mitigating oxidative stress in clinical set-ting associated with cardiovascular disease regardless the pres-ence of impaired glucose metabolism.

Cardiovascular Effects of Metformin

Type 2 diabetes mellitus is one of the most important independent risk factors for the development, progression and mortality from cardiovascular diseases (CVD). The world communities are faced with the question of developing the optimal management tactics for such comorbidity patients. Thus, the prescribed drug should not only have an adequate hypoglycemic effect, but also have a number of cardioprotective properties, be safe in patients with CVD, and possibly even improve the prognosis and reduce mortality rates. This review is devoted to a representative of the biguanide class - metformin, which is one of the earliest and most effective antihyperglycemic drugs, both as monotherapy and in combination with other antihyperglycemic drugs and insulin; while the evidence base for its cardiovascular profile is only gaining momentum. Thus, the purpose of this review is to highlight the cardiovascular effects of metformin in the context of recent research.

Looking for Crumbs in the Obesity Forest: Anti-obesity Interventions and Obesity-Associated Cardiometabolic Traits in the Mexican Population. History and Systematic Review With Meta-Analyses

Mexicans and Mexican Americans share culture, genetic background, and predisposition for chronic complications associated with obesity and diabetes making imperative efficacious treatments and prevention. Obesity has been treated for centuries focused-on weight loss while other treatments on associated conditions like gout, diabetes (T2D), and hypertriglyceridemia. To date, there is no systematic review that synthesizes the origin of obesity clinics in Mexico and the efforts to investigate treatments for obesity tested by randomized clinical trials (RCT). We conducted systematic searches in Pubmed, Scopus, and Web of Science to retrieve anti-obesity RCT through 2019 and without an inferior temporal limit. The systematic review included RCT of anti-obesity treatments in the Mexican adult population, covering alternative medicine, pharmacological, nutritional, behavioral, and surgical interventions reporting metabolism-associated traits such as BMI, weight, waist circumference, triglycerides, glucose, among others. Only the studies with at least 3 months of treatment were included in the meta-analyses in order to reduce placebo effects. We found 634 entries, after removal of duplicates and screening the studies based on eligibility criteria, we analyzed 43 national, and 2 multinational-collaborative studies. Most of the national studies had small sample sizes, and the implemented strategies do not have replications in the population. The nutrition/behavioral interventions were difficult to blind, and most studies have medium-to-high risk of bias. Nutritional/behavioral interventions and medications showed effects on BMI, waist circumference, and blood pressure. Simple measures like pure water instead of sweet beverages decrease triglycerides and systolic blood pressure. Dark chocolate showed the highest effect for BMI and high blood pressure, and treatment with insulin increased weight in those with T2D. The study of obesity in Mexico has been on-going for more than four decades, the interest on RCT just increased until this millennium, but with small sample sizes and lack of replication. The interventions affect different cardiometabolic associated traits, which should be analyzed in detail in the population living near the Mexico-U.S. border; therefore, bi-national collaboration is desirable to disentangle the cultural effects on this population's treatment response.

Systematic Review Registration:https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42020221436, identifier: CRD42020221436.

Metabolic syndrome and its components predict the development of arterial stiffening in a sample of adult men

BACKGROUND AND OBJECTIVE

Metabolic syndrome (MS) and its components are associated with greater cardiovascular risk. A number of studies found a positive association between MS and vascular damage, but few observational studies evaluated the predictive role of MS on arterial stiffening (AS). Therefore, the aim of this study was to estimate the ability of MS and its components to predict the risk of AS in an 8-year follow-up of a sample of adult men (Olivetti Heart Study).

METHODS

The analysis included 778 men without AS (pulse pressure >60 mmHg) at baseline. A positive diagnosis of MS was made by recognized criteria, if at least three components were present.

RESULTS

At the end of the follow-up period, there was an incidence of 11% in AS. The percentage of participants that developed AS was greater in the MS group than those without MS, also after adjustment for main confounders (odds ratio: 2.5, 95% confidence interval: 1.3-4.9). The risk of AS also increased with increase in the numbers of MS elements (p for trend <.01). In addition, the analysis of the predictive role of the single MS component showed that high blood pressure (HBP) was the strongest predictor.

CONCLUSIONS

The results of this prospective study indicate a predictive role of MS on AS, independently of main confounders. In addition, HBP seems the strongest predictor of AS among MS components.

Endothelial function in cardiovascular medicine: a consensus paper of the European Society of Cardiology Working Groups on Atherosclerosis and Vascular Biology, Aorta and Peripheral Vascular Diseases, Coronary Pathophysiology and Microcirculation, and Thrombosis

Endothelial cells (ECs) are sentinels of cardiovascular health. Their function is reduced by the presence of cardiovascular risk factors, and is regained once pathological stimuli are removed. In this European Society for Cardiology Position Paper, we describe endothelial dysfunction as a spectrum of phenotypic states and advocate further studies to determine the role of EC subtypes in cardiovascular disease. We conclude that there is no single ideal method for measurement of endothelial function. Techniques to measure coronary epicardial and micro-vascular function are well established but they are invasive, time-consuming, and expensive. Flow-mediated dilatation (FMD) of the brachial arteries provides a non-invasive alternative but is technically challenging and requires extensive training and standardization. We, therefore, propose that a consensus methodology for FMD is universally adopted to minimize technical variation between studies, and that reference FMD values are established for different populations of healthy individuals and patient groups. Newer techniques to measure endothelial function that are relatively easy to perform, such as finger plethysmography and the retinal flicker test, have the potential for increased clinical use provided a consensus is achieved on the measurement protocol used. We recommend further clinical studies to establish reference values for these techniques and to assess their ability to improve cardiovascular risk stratification. We advocate future studies to determine whether integration of endothelial function measurements with patient-specific epigenetic data and other biomarkers can enhance the stratification of patients for differential diagnosis, disease progression, and responses to therapy.

The effect of metformin on carotid intima-media thickness (CIMT): A systematic review and meta-analysis of randomized clinical trials

Metformin administration has been reported to influence the carotid intima-media thickness (CIMT) in humans. However, since previously conducted studies have yielded inconsistent results, the exact effect of metformin on CIMT remains unclear. Causes that could lead to inconsistency in reported research could be the duration and dose of the intervention, as well as the sample size. To address this inconsistency, we conducted a systematic review and meta-analysis to evaluate the influence of metformin on CIMT in human subjects. We identified eligible studies by searching several electronic databases (EMBASE, PubMed-MEDLINE, Web of Science and Google Scholar) up to December 12, 2019. Data were pooled using the random-effects model. Combining data from 1087 participants (9 studies), our meta-analysis revealed that the administration of metformin resulted in a significant reduction in CIMT (WMD = -0.049 mm; 95% CI: -0.095, -0.004). Stratified analyses showed that an intervention lasting ≥12 months (WMD: -0.084 mm, 95% CI: -0.145, -0.024) and an intake of metformin ≤1500 mg/day (WMD: -0.081 mm, 95% CI: -0.132, -0.029) resulted in a significantly greater reduction in CIMT. However, an intervention duration of less than 12 months and an intake of metformin ˃1500 mg/day yielded no significant effects on CIMT. The results of the current study confirm that metformin administration is associated with a significant reduction in CIMT. Taking into account that CIMT reflects the burden of atherosclerosis, the clinical utility of metformin might also be related to its anti-atherogenic effects.

Repurposing Antidiabetic Drugs for Cardiovascular Disease

Metabolic diseases and diabetes represent an increasing global challenge for human health care. As associated with a strongly elevated risk of developing atherosclerosis, kidney failure and death from myocardial infarction or stroke, the treatment of diabetes requires a more effective approach than lowering blood glucose levels. This review summarizes the evidence for the cardioprotective benefits induced by antidiabetic agents, including sodium-glucose cotransporter 2 inhibitor (SGLT2i) and glucagon-like peptide-1 receptor agonist (GLP1-RA), along with sometimes conversely discussed effects of dipeptidyl peptidase-4 inhibitor (DPP4i) and metformin in patients with high cardiovascular risk with or without type 2 diabetes. Moreover, the proposed mechanisms of the different drugs are described based on the results of preclinical studies. Recent cardiovascular outcome trials unexpectedly confirmed a beneficial effect of GLP-1RA and SGLT2i in type 2 diabetes patients with high cardiovascular risk and with standard care, which was independent of glycaemic control. These results triggered a plethora of studies to clarify the underlying mechanisms and the relevance of these effects. Taken together, the available data strongly highlight the potential of repurposing the original antidiabetics GLP1-RA and SGLT2i to improve cardiovascular outcome even in non-diabetic patients with cardiovascular diseases.

Metformin protects against diabetes-induced heart injury and dunning prostate cancer model

In this study, both diabetes and Dunning prostate cancer were induced for the first time in Copenhagen rats in vivo. Thus, the effects of metformin against heart tissue damage of these rats were investigated by biochemical methods. Dunning prostate cancer was induced in Copenhagen rats using high metastatic MAT-LyLu cells. The rats were divided as follows: Control group: only injected with 0.9% NaCl for 14 days; Diabetic group: only injected single dose of streptozotocin (STZ) (65 mg/kg); Cancer group: subcutaneously (s.c) inoculated with 2 x 10⁴ MAT-LyLu cells only; Diabetic + cancer (DC) group: inoculated with 2 x 10⁴ MAT-LyLu cells and STZ injection, Cancer + metformin (CM) group: injected with metformin for 14 days after Mat-LyLu cells application; Diabetic + cancer + metformin (DCM) group: metformin administered for 14 days together with STZ and Mat-LyLu cells. At the end of the experimental period, heart tissues were taken. Reduced glutathione and total antioxidant status levels in heart tissues were decreased, whereas lipid peroxidation, advanced oxidized protein products, nitric oxide, homocysteine, and reactive oxygen species levels, total oxidant status and catalase, superoxide dismutase, glutathione peroxidase, glutathione reductase, glutathione-S-transferase, alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase and xanthine oxidase activities increased in the diabetic, cancer and DC groups. Treatment with metformin reversed these effects. In conclusion, the present study shows that metformin has a protective effect against heart tissue damage in STZ-induced diabetic rats with Dunning prostate cancer.

Behaviour of carbonyl groups in several clinical conditions: Analysis of our survey

Protein carbonylation is a marker of oxidative protein damage, that is likely involved in the pathogenesis of several diseases. The aim of this study was to evaluate the protein carbonyl (PC) groups in different clinical conditions. It included different groups of subjects: 81 trained subjects; 23 subjects with mild essential hypertension; 31 middle-aged subjects with metabolic syndrome (MS); 106 subjects with MS not selected for age (subdivided into two subgroups, with and without diabetes mellitus); 91 obese adults subdivided in two subgroups (BMI 30-35 Kg/m2 and BMI > 35 kg/m2); 48 subjects with obstructive sleep apnea syndrome (OSAS) subdivided in accordance with the apnea/hypopnea index (AHI); 27 subjects with chronic kidney disease (CKD) on conservative therapy; 31 subjects with CKD on haemodialysis treatment; and 50 subjects with juvenile myocardial infarction. PC groups were reduced in trained subjects in comparison with sedentary controls, while no variation was observed in mild essential hypertension. PC groups were increased in MS subjects and in adult obese subjects. In MS subjects the PC groups were not influenced by the presence of diabetes mellitus and in adult obese subjects were not influenced by the obesity degree. In OSAS subjects only those with AHI > 30 showed an increase of PC groups. PC groups increased in CKD subjects undergoing conservative treatment and haemodialysis therapy. In dialyzed subjects, after a standard dialysis session, there was a marked increase in PC groups. In juvenile myocardial infarction PC groups were higher than in controls; there was no difference between STEMI and NSTEMI and their concentration was unaffected by the number of cardiovascular risk factors or stenosed coronary vessels.

S. Ferreira KC, Neto JCR. Pharmacological Strategies for Insulin Sensitivity in Obesity and Cancer: Thiazolidinediones and Metformin

Background:

Chronic diseases, such as obesity and cancer, have high prevalence rates. Both diseases have hyperinsulinemia, hyperglycemia, high levels of IGF-1 and inflammatory cytokines in common. Therefore, these can be considered triggers for cancer development and growth. In addition, low-grade inflammation that modulates the activation of immune cells, cellular metabolism, and production of cytokines and chemokines are common in obesity, cancer, and insulin resistance. Pharmacological strategies are necessary when a change in lifestyle does not improve glycemic homeostasis. In this regard, thiazolidinediones (TZD) possess multiple molecular targets and regulate PPARγ in obesity and cancer related to insulin resistance, while metformin acts through the AMPK pathway.

Objective:

The aim of this study was to review TZD and metformin as pharmacological treatments for insulin resistance associated with obesity and cancer.

Conclusions:

Thiazolidinediones restored adiponectin secretion and leptin sensitivity, reduced lipid droplets in hepatocytes and orexigen peptides in the hypothalamus. In cancer cells, TZD reduced proliferation, production of reactive oxygen species, and inflammation by acting through the mTOR and NFκB pathways. Metformin has similar effects, though these are AMPK-dependent. In addition, both drugs can be efficient against certain side effects caused by chemotherapy.

Metformin to reduce metabolic complications and inflammation in patients on systemic glucocorticoid therapy: a randomised, double-blind, placebo-controlled, proof-of-concept, phase 2 trial

BACKGROUND

An urgent need to reduce the metabolic side-effects of glucocorticoid overexposure has been recognised, as glucocorticoid excess can lead to Cushing's syndrome, which is associated with high morbidity. We aimed to evaluate the potential of metformin to reverse such effects while sparing the anti-inflammatory benefits of glucocorticoids.

METHODS

We did a randomised, double-blind, placebo-controlled, proof-of-concept, phase 2 trial involving four hospitals in the UK. Patients without diabetes were eligible if they were between the ages of 18 and 75 years with an inflammatory disease treated with continuous prednisolone (≥20 mg/day for ≥4 weeks and remaining on ≥10 mg/day for the subsequent 12 weeks, or its cumulative dose-equivalent). Eligible patients were randomly allocated (1:1) to either the metformin or placebo groups, using a computer-generated randomisation table stratified according to age and BMI. Metformin and placebo were administered orally for 12 weeks in escalating doses: 850 mg/day for the first 5 days, 850 mg twice a day for the next 5 days, and 850 mg three times a day subsequently. The primary outcome was the between-group difference in visceral-to-subcutaneous fat area ratio over 12 weeks, assessed by CT. Secondary outcomes included changes in metabolic, bone, cardiovascular, and inflammatory parameters over 12 weeks. Our analysis followed a modified intention-to-treat principle for the primary outcome. This study is registered with ClinicalTrials.gov, NCT01319994.

FINDINGS

Between July 17, 2012, and Jan 14, 2014, 849 patients were assessed for study eligibility, of which 53 were randomly assigned to receive either metformin (n=26) or placebo (n=27) for 12 weeks. 19 patients in the metformin group and 21 in the placebo group were eligible for the primary outcome analysis. Both groups received an equivalent cumulative dose of glucocorticoids (1860 mg prednisolone-equivalent [IQR 1060-2810] in the metformin group vs 1770 mg [1020-2356] in the placebo group); p=0·76). No change in the visceral-to-subcutaneous fat area ratio between the treatment groups was observed (0·11, 95% CI -0·02 to 0·24; p=0·09), but patients in the metformin group lost truncal subcutaneous fat compared with the placebo group (-3835 mm², 95% CI -6781 to -888; p=0·01). Improvements in markers of carbohydrate, lipid, liver, and bone metabolism were observed in the metformin group compared with the placebo group. Additionally, those in the metformin group had improved fibrinolysis, carotid intima-media thickness, inflammatory parameters, and clinical markers of disease activity. The frequency of pneumonia (one event in the metformin group vs seven in the placebo group; p=0·01), overall rate of moderate-to-severe infections (two vs 11; p=0·001), and all-cause hospital admissions due to adverse events (one vs nine; p=0·001) were lower in the metformin group than in the placebo group. Patients in the metformin group had more events of diarrhoea than the placebo group (18 events vs eight; p=0·01).

INTERPRETATION

No significant changes in the visceral-to-subcutaneous fat area ratio between the treatment groups were observed; however, metformin administration did improve some of the metabolic profile and clinical outcomes for glucocorticoid-treated patients with inflammatory disease, which warrants further investigation.

FUNDING

Barts Charity and Merck Serono.

Inhibition of neointima hyperplasia by the combined therapy of linagliptin and metformin via AMPK/Nox4 signaling in diabetic rats

BACKGROUND

Neointima hyperplasia is the pathological basis of atherosclerosis and restenosis which have been associated with diabetes mellitus (DM). It is controversial for linagliptin and metformin to protect against vascular neointimal hyperplasia caused by DM. Given the combined therapy of linagliptin and metformin in clinical practice, we investigated whether the combination therapy inhibited neointimal hyperplasia in the carotid artery in diabetic rats.

METHODS AND RESULTS

Neointima hyperplasia in the carotid artery was induced by balloon-injury in the rats fed with high fat diet (HFD) combined with low dose streptozotocin (STZ) administration. In vitro, vascular smooth muscle cells (VSMCs) were incubated with high glucose (HG, 30 mM) and the proliferation, migration, apoptosis and collagen deposition were analyzed in VSMCs. We found that the combined therapy, not the monotherapy of linagliptin and metformin significantly inhibited the neointima hyperplasia and improved the endothelium-independent contraction in the balloon-injured cardia artery of diabetic rats, which was associated with the inhibition of superoxide (O₂^-.) production in the cardia artery. In vitro, HG-induced VSMC remodeling was shown as the remarkable upregulation of PCNA, collagan1, MMP-9, Bcl-2 and migration rate as well as the decreased apoptosis rate. Such abnormal changes were dramatically reversed by the combined use of linagliptin and metformin. Moreover, the AMP-activated protein kinase (AMPK)/Nox4 signal pathway was found to mediate VSMC remodeling responding to HG. Linagliptin and metformin were synergistical to target AMPK/Nox4 signal pathway in VSMCs incubated with HG and in the cardia artery of diabetic rats, which was superior to the monotherapy.

CONCLUSIONS

We demonstrated that the potential protection of the combined use of linagliptin and metformin on VSMC remodeling through AMPK/Nox4 signal pathway, resulting in the improvement of neointima hyperplasia in diabetic rats. This study provided new therapeutic strategies for vascular stenosis associated with diabetes.

Metformin in patients with and without diabetes: a paradigm shift in cardiovascular disease management

With an increasing global burden of coronary artery disease (CAD), early detection and timely management of risk factors are crucial to reduce morbidity and mortality in such patients. Diabetes mellitus (DM) is considered an independent risk factor for the development of CAD. Metformin, an anti-diabetic drug, has been shown in pre-clinical and clinical studies, to lower the cardiovascular events in the DM patients. Growing evidence suggests that metformin has a protective effect on coronary artery beyond its hypoglycemic effects. Given its global availability, route of administration and cost, metformin provides an alternate/additional therapeutic option for primary and secondary prevention of CAD in DM and non-diabetics alike. Future prospective cohort-based studies and randomized clinical trials are needed to identify 'at-risk' population who may potentially benefit from metformin.

The effects of metformin on simple obesity: a meta-analysis

OBJECTIVE

To evaluate the efficacy of metformin versus a placebo in the treatment of patients with simple obesity without obesity related diseases.

METHODS

A search was done on Pub-Med, EMBASE, Cochrane, and Science Citation Index Expanded databases. The main inclusion criteria included the following:(1) randomized controlled trials. (2) patients diagnosed as being overweight or obese. (3) patients were randomly assigned to receive metformin or control. Exclusion criteria included the following: patients diagnosed with an obesity related disease, such as diabetes mellitus (DM) or polycystic ovary syndrome (PCOS).

RESULTS

Compared with the placebo, weighted mean difference (WMD) was 2.33 (95% CI 0.31, 4.35) kg higher with metformin (p = 0.02). Compared with the placebo, WMD was 0.57 (95% CI 0.35, 0.79) kg/m² higher with metformin(p < 0.00001). There was no significant difference in the reduction of waist circumference between the metformin group and the control group (p = 0.05). The fasting blood glucose levels were significantly lower in the metformin group than in the control group (p < 0.00001). However, no hypoglycemia was noted in the metformin group or the control group.

CONCLUSION

Metformin is effective in reducing body weight of simple obesity patients, and metformin does not induce hypoglycemia as a side effect.

Metformin added to bosentan therapy in patients with pulmonary arterial hypertension associated with congenital heart defects: a pilot study

Pulmonary arterial hypertension (PAH) is a common complication of a congenital heart defect (CHD). Recent studies suggest metformin may be a potential drug to improve cardiac function in PAH. A pilot study was conducted to investigate the efficacy of short-term treatment with a combination regimen consisting of bosentan and metformin in PAH-CHD patients as compared with bosentan monotherapy in a prospective, randomised study.

Patients with PAH-CHD were randomised to receive bosentan (initially at 62.5 mg twice daily for 4 weeks and then 125 mg twice daily) for 3 months with or without the combination treatment of metformin (500 mg twice daily).

93 patients were enrolled to bosentan monotherapy (n=48) or bosentan/metformin combination treatment (n=45). After 3 months, both treatments significantly improved World Health Organization functional class, 6-min walking distance (6MWD), N-terminal pro-brain natriuretic peptide and right heart haemodynamic parameters. The improvements in 6MWD and pulmonary vascular resistance index were significantly greater in patients treated with combination therapy than in those who received monotherapy (mean±sd 95±136 versus 48±119 m (p=0.017) and −1.8±1.2 versus −1.2±1.3 Wood units per m² (p<0.001), respectively). Pulmonary endothelin (EDN)1 was significantly decreased after combination therapy (p=0.006). However, plasma EDN1 levels were not affected.

Combination therapy with bosentan and metformin in PAH-CHD patients provides improvements in important outcomes such as exercise capacity and pulmonary haemodynamics, compared with bosentan alone.

This study investigated, for the first time, the efficacy of a combination regimen consisting of bosentan and metformin in patients with pulmonary arterial hypertension associated with congenital heart defect as compared with bosentan monotherapyhttp://ow.ly/n4nJ30kT98d

A new perspective on metformin therapy in type 1 diabetes

Metformin is quite frequently used off-label in type 1 diabetes to limit insulin dose requirement. Guidelines recommend that it can improve glucose control in those who are overweight and obese but evidence in support of this is limited. Recently-published findings from the REducing with MetfOrmin Vascular Adverse Lesions (REMOVAL) trial suggest that metformin therapy in type 1 diabetes can reduce atherosclerosis progression, weight and LDL-cholesterol levels. This provides a new perspective on metformin therapy in type 1 diabetes and suggests a potential role for reducing the long-term risk of cardiovascular disease.

Klein B, Klein R, Ooi TC, Rossing P, Sattar N, Stehouwer CDA, Colhoun HM. Metformin in adults with type 1 diabetes: Design and methods of REducing with MetfOrmin Vascular Adverse Lesions (REMOVAL): An international multicentre trial

AIMS

Cardiovascular (CV) disease is a major cause of reduced life expectancy in type 1 diabetes (T1D). Intensive insulin therapy prevents CV complications but is constrained by hypoglycaemia and weight gain. Adjunct metformin reduces insulin dose requirement and stabilizes weight but there are no data on its cardiovascular effects. We have therefore initiated an international double-blind, randomized, placebo-controlled trial (REMOVAL: REducing with MetfOrmin Vascular Adverse Lesions in type 1 diabetes) to examine whether metformin reduces progression of atherosclerosis in adults with T1D. Individuals ≥40 years of age with T1D for ≥5 years are eligible if they have ≥3 of 10 specified CV risk factors. The enrolment target is 500 participants in 17 international centres.

MATERIALS AND METHODS

After 12 weeks of single-blind placebo-controlled run-in, participants with ≥ 70% adherence are randomized to metformin or matching placebo for 3 years with insulin titrated towards HbA1c 7.0% (53 mmol/mol). The primary endpoint is progression of averaged mean far wall common carotid intima-media thickness (cIMT) measured by ultrasonography at baseline, 12, 24 and 36 months. This design provides 90% power to detect a mean difference of 0.0167 mm in cIMT progression between treatment arms (α = 0.05), assuming that up to 20% withdraw or discontinue treatment. Other endpoints include HbA1c, weight, LDL cholesterol, insulin requirement, progression of retinopathy, endothelial function and frequency of hypoglycaemia.

CONCLUSION

REMOVAL is the largest clinical trial of adjunct metformin therapy in T1D to date and will provide clinically meaningful information on its potential to impact CV disease and other complications.

Synergistic effect of aluminum and ionizing radiation upon ultrastructure, oxidative stress and apoptotic alterations in Paneth cells of rat intestine

Environmental and occupational exposure to aluminum along with ionizing radiation results in serious health problems. This study was planned to investigate the impact of oxidative stress provoked by exposure to ionizing radiation with aluminum administration upon cellular ultra structure and apoptotic changes in Paneth cells of rat small intestine . Animals received daily aluminum chloride by gastric gavage at a dose 0.5 mg/Kg BW for 4 weeks. Whole body gamma irradiation was applied at a dose 2 Gy/week up to 8 Gy. Ileum malondialdehyde, advanced oxidative protein products, protein carbonyl and tumor necrosis factor-alpha were assessed as biomarkers of lipid peroxidation, protein oxidation and inflammation respectively along with superoxide dismutase, catalase, and glutathione peroxidase activities as enzymatic antioxidants. Moreover, analyses of cell cycle division and apoptotic changes were evaluated by flow cytometry. Intestinal cellular ultra structure was investigated using transmission electron microscope.Oxidative and inflammatory stresses assessment in the ileum of rats revealed that aluminum and ionizing radiation exposures exhibited a significant effect upon the increase in oxidative stress biomarkers along with the inflammatory marker tumor necrosis factor-α accompanied by a significant decreases in the antioxidant enzyme activities. Flow cytometric analyses showed significant alterations in the percentage of cells during cell cycle division phases along with significant increase in apoptotic cells. Ultra structurally, intestinal cellular alterations with marked injury in Paneth cells at the sites of bacterial translocation in the crypt of lumens were recorded. The results of this study have clearly showed that aluminum and ionizing radiation exposures induced apoptosis with oxidative and inflammatory disturbance in the Paneth cells of rat intestine, which appeared to play a major role in the pathogenesis of cellular damage. Furthermore, the interaction of these two intestinal toxic routes was found to be synergistic.

High-dose metformin (420mg/kg daily p.o.) increases insulin sensitivity but does not affect neointimal thickness in the rat carotid balloon injury model of restenosis

OBJECTIVE

Our laboratory has shown that insulin's effect to decrease neointimal thickness after arterial injury is greatly diminished in insulin resistant conditions. Thus, in these conditions, a better alternative to insulin could be to use an insulin sensitizing agent. Metformin, the most commonly prescribed insulin sensitizer, has a cardiovascular protective role. Therefore, the objective of this study was to investigate the potential benefit of metformin on neointimal area after arterial injury in a rat model of restenosis.

METHODS

Rats fed with either normal or high fat diet and treated with or without oral metformin (420mg/kg daily) underwent carotid balloon injury. Effects of metformin on clamp-determined insulin sensitivity, vessel AMPK (AMP-activated protein kinase) phosphorylation (activation marker) and neointimal area were evaluated.

RESULTS

Metformin increased insulin sensitivity, but did not affect neointimal thickness in either the normal fat or high fat diet-fed rats. Furthermore, metformin activated AMPK in uninjured but not in injured vessels. Similarly, 10mmol/L metformin inhibited proliferation and activated AMPK in smooth muscle cells of uninjured but not injured vessels, whereas 2mmol/L metformin did not have any effect.

CONCLUSION

In rats, metformin does not decrease neointimal growth after arterial injury, despite increasing whole body insulin sensitivity.

Cardiovascular function in male and female JCR:LA-cp rats: effect of high-fat/high-sucrose diet

Thirty percent of the world population is diagnosed with metabolic syndrome. High-fat/high-sucrose (HF/HS) diet (Western diet) correlates with metabolic syndrome prevalence. We characterized effects of the HF/HS diet on vascular (arterial stiffness, vasoreactivity, and coronary collateral development) and cardiac (echocardiography) function, oxidative stress, and inflammation in a rat model of metabolic syndrome (JCR rats). Furthermore, we determined whether male versus female animals were affected differentially by the Western diet. Cardiovascular function in JCR male rats was impaired versus normal Sprague-Dawley (SD) rats. HF/HS diet compromised cardiovascular (dys)function in JCR but not SD male rats. In contrast, cardiovascular function was minimally impaired in JCR female rats on normal chow. However, cardiovascular function in JCR female rats on the HF/HS diet deteriorated to levels comparable to JCR male rats on the HF/HS diet. Similarly, oxidative stress was markedly increased in male but not female JCR rats on normal chow but was equally exacerbated by the HF/HS diet in male and female JCR rats. These results indicate that the Western diet enhances oxidative stress and cardiovascular dysfunction in metabolic syndrome and eliminates the protective effect of female sex on cardiovascular function, implying that both males and females with metabolic syndrome are at equal risk for cardiovascular disease.NEW & NOTEWORTHY Western diet abolished protective effect of sex against cardiovascular disease (CVD) development in premenopausal animals with metabolic syndrome. Western diet accelerates progression of CVD in male and female animals with preexisting metabolic syndrome but not normal animals. Exacerbation of baseline oxidative stress correlates with accelerated progression of CVD in metabolic syndrome animals on Western diet.

Metformin attenuates fluctuating glucose-induced endothelial dysfunction through enhancing GTPCH1-mediated eNOS recoupling and inhibiting NADPH oxidase

AIMS

The aim of this study was to investigate whether and how metformin ameliorated endothelial dysfunction induced by fluctuating glucose (FG) in human umbilical vein endothelial cells (HUVECs).

METHODS

HUVECs, which were exposed to FG to induce endothelial dysfunction, were incubated with nitric oxide synthase (NOS) inhibitor N-nitro-l-arginine-methyl ester (l-NAME), nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor apocynin, metformin and/or adenosine monophosphate-activated protein kinase (AMPK) inhibitor compound C. The oxidative stress and endothelial NOS (eNOS) coupling were evaluated.

RESULTS

FG induced endothelial dysfunction as indicated by increased reactive oxygen species (ROS) generation and decreased nitric oxide (NO) production. Although FG increased eNOS phosphorylation, uncoupled eNOS was evidenced by downregulated guanosine 5'-triphosphate cyclohydrolase 1 (GTPCH1) and tetrahydrobiopterin (BH4) levels. FG also upregulated the level of p47-phox, a subunit of NADPH oxidase. Similar to l-NAME and apocynin, metformin ameliorated the FG-induced endothelial dysfunction by decreasing ROS generation. Furthermore, metformin recoupled eNOS through upregulating GTPCH1 and BH4 levels, and attenuated the upregulation of p47-phox in FG-treated HUVECs. Addition of compound C abolished the above effects of metformin.

CONCLUSION

Metformin improves the FG-induced endothelial dysfunction in HUVECs. The protective effect of metformin may be mediated through activation of GTPCH1-mediated eNOS recoupling and inhibition of NADPH oxidase via an AMPK-dependent pathway.

The Effect of Metformin Use on Left Ventricular Ejection Fraction and Mortality Post-Myocardial Infarction

BACKGROUND

Animal studies showed that the use of metformin after myocardial infarction (MI) resulted in a protective effect on cardiac myocytes. In this study, we examined the effect of metformin in patients with diabetes mellitus (DM) on left ventricular ejection fraction (LVEF) and post-MI mortality.

METHODS

We reviewed charts of patients with MI admitted to the UAMS medical center. Baseline characteristics and 12-month follow up data were collected. Patients were classified into three groups: Control group- no DM (n = 464), Metformin group- DM + MI (n = 88) and No-Metformin group- DM + MI (n = 168). First, we compared Metformin and No-Metformin groups to the Control group. Second, we performed propensity-score matching in patients with DM, and compared Metformin to No-Metformin groups.

RESULTS

All-cause 30-day and 12-month mortality was significantly higher in the No-Metformin group compared to controls (13.5 vs 9.3% p = 0.03 at 30 days, 23.7 vs 15.9 % p = 0.03 at 12 months). However, all-cause 30-day and 12-month mortality were similar in the Controls and Metformin group (9.3 vs 6.8 % p = 0.93 at 30 days, 15.9 vs 11.4 % p = 0.97 at 12 months). Mean LVEF on presentation (45 % in the three groups) and at follow up (47.84, 46.38 and 43.62 % in Control, Metformin, and No-Metformin groups, respectively) were not statistically different. There were no significant differences in regard to re-hospitalization, re-intervention, new stroke, CHF development, new MI, or identifiable arrhythmias. Metformin was an independent predictor of lower 30-day and 12-month all-cause mortality in patients with DM (HR 0.25, p = 0.02 and HR 0.32, p = 0.01, respectively). In the matched analysis, 30-day all-cause mortality was significantly higher in the No-Metformin compared to the Metformin group (21.1 vs 8.8 %, p = 0.05). However the difference in 12-month all-cause mortality did not reach statistical significance (24.6 vs 15.8 %, p = 0.15).

CONCLUSION

This proof-of-concept study shows that use of metformin in patients with DM is associated with lower 30-day all-cause mortality and tendency for a lower 12-month all-cause mortality following MI without discernible improvement in LVEF.

Erratum to "Does Metformin Increase Paraoxonase Activity in Patients with the Metabolic Syndrome? Additional Data from the MEFISTO Study"

[This corrects the article DOI: 10.1111/j.1752-8062.2012.00391.x.].

Effect of metformin treatment on circulating osteoprotegerin in patients with nonalcoholic fatty liver disease

PURPOSE/INTRODUCTION

Growing evidence suggests complex interplay between nonalcoholic fatty liver disease (NAFLD) and bone health. The present study's aim was to examine the impact of metformin treatment on circulating osteoprotegerin (OPG) in patients with NAFLD, a population in which this relationship has not yet been studied.

METHODS

In a randomized, placebo-controlled study, 63 patients with NAFLD were assigned to one of two groups: Group 1 received daily metformin; Group 2 received a placebo. Metabolic parameters, insulin resistance markers and OPG levels were examined at baseline and at the end of the study.

RESULTS

In the placebo group, liver function and OPG levels did not change during the study. Among metformin-treated patients, significant declines in OPG and alkaline phosphatase were observed. CRP and ALT decreased marginally during the 4-month treatment period. While at baseline circulating OPG levels did not differ significantly between the groups, by the end of the study OPG was significantly lower in patients treated with metformin than in the placebo group (p < 0.0001). Delta OPG was significantly greater in the metformin group than the placebo group (p = 0.001). In the general linear model, metformin treatment was the only significant independent predictor of endpoint and delta OPG.

CONCLUSIONS

Metformin treatment was associated with a significant decrease in OPG levels in patients with NAFLD. The effect on OPG was associated with exposure to metformin per se.

CLINICAL TRIAL REGISTRATION NUMBER

NCT01084486.

Impact of glucose-lowering drugs on cardiovascular disease in type 2 diabetes

Type 2 diabetes mellitus (T2DM) is characterized by multiple pathophysiologic abnormalities. With time, multiple glucose-lowering medications are commonly required to reduce and maintain plasma glucose concentrations within the normal range. Type 2 diabetes mellitus individuals also are at a very high risk for microvascular complications and the incidence of heart attack and stroke is increased two- to three-fold compared with non-diabetic individuals. Therefore, when selecting medications to normalize glucose levels in T2DM patients, it is important that the agent not aggravate, and ideally even improve, cardiovascular risk factors (CVRFs) and reduce cardiovascular morbidity and mortality. In this review, we examine the effect of oral (metformin, sulfonylureas, meglitinides, thiazolidinediones, DPP4 inhibitors, SGLT2 inhibitors, and α-glucosidase inhibitors) and injectable (glucagon-like peptide-1 receptor agonists and insulin) glucose-lowering drugs on established CVRFs and long-term studies of cardiovascular outcomes. Firm evidence that in T2DM cardiovascular disease can be reversed or prevented by improving glycaemic control is still incomplete and must await large, long-term clinical trials in patients at low risk using modern treatment strategies, i.e., drug combinations designed to maximize HbA1c reduction while minimizing hypoglycaemia and excessive weight gain.

Effect of metformin on insulin-resistant endothelial cell function

The aim of the present study was to investigate the effect of metformin on the function of insulin-resistant (IR) endothelial cells. A model of IR endothelial cells was established by incubating cells with 30 mM glucose, 1 μM dexamethasone and various concentrations of insulin. The nitric oxide (NO) content of the endothelial cells was determined by measuring the rate of nitroreductase production; the endothelin (ET) concentration was examined by enzyme-linked immunosorbent assay; and the expression levels of endothelial nitric oxide synthase (eNOS) were detected using western blotting. The optimal conditions for inducing insulin resistance in endothelial cells were a combination treatment of 10⁻⁴ mmol/l insulin, 30 mM glucose and 1 μM dexamethasone for 48 h. Notably, metformin administration significantly increased the NO content and reduced the ET-1 concentration in the IR cells compared with the non-treated control cells (P<0.05); furthermore, metformin significantly increased the intracellular eNOS protein expression in IR endothelial cells compared with the non-treated control cells (P<0.05), with an optimal metformin concentration of 10⁻³ mmol/l. Thus, the present study identified that metformin improves the function of IR endothelial cells, possibly through promoting eNOS protein expression and increasing the NO content.

The cardiovascular effects of metformin: lost in translation?

PURPOSE OF REVIEW

In overweight patients with diabetes, treatment with metformin improves cardiovascular outcomes. This observation has fuelled the hypothesis that metformin has direct cardiovascular protective properties over and above glucose lowering. Here, we discuss the various cardiovascular effects of metformin observed in preclinical studies and recent clinical trials in patients, which fail to reproduce these findings.

RECENT FINDINGS

Laboratory studies suggest that metformin limits atherosclerosis. Also, metformin consistently limits myocardial infarct size and reduces postinfarction remodeling in rodents.Confirmation of these effects in patients, however, appears difficult. In nondiabetic patients, metformin does not reduce carotid intima media thickness. In myocardial infarction patients, the effects of metformin on infarct size are inconclusive, but these studies suffer from methodological shortcomings. Finally, chronic administration of metformin does not affect postinfarction cardiac remodeling in nondiabetic patients.

SUMMARY

Although recent trials in nondiabetic patients could not confirm direct effects of metformin on atherosclerosis and cardiac remodeling, an acute cardioprotective effect of metformin cannot be excluded yet. We might have to consider, though, that the beneficial effect of metformin on cardiovascular prognosis in patients with diabetes is due to its effects on glucose metabolism and body weight rather than due to pleiotropic direct cardiovascular effects.

Fish oil omega-3 fatty acids reduce the severity of radiation-induced oxidative stress in the rat brain

PURPOSE

To evaluate the modulator role of fish oil (FO) on some biochemical changes in the brain of gamma-irradiated rats (RAD).

MATERIAL AND METHODS

Male albino rats Sprague Dawley were divided into four groups (n = 10). (i)

CONTROL

received vehicle via gavages during 28 days; (ii) FO: received fish oil (400 mg/kg/day) via gavages during 28 days; (iii) RAD: received vehicle for 7 days before whole body gamma-irradiation with 8 Gy given in four fractions each 7 days apart and continued during the irradiation period; and (iv) FO+ RAD: received FO for 7 days before exposure to the first dose of irradiation and FO treatment was continued during the irradiation period. Animals were sacrificed 24 hours post the last irradiation dose.

RESULTS

A significant increase of malondialdehyde (MDA) and protein carbonyl (CO) content associated with a significant decrease of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) activities and glutathione (GSH) content were recorded in the brain of irradiated rats. Oxidative stress was accompanied by a significant decrease of eicosapentaenoic (EPA) and docosahexaenoic (DHA) levels. Aspartic (Asp) and glutamic (Glu) acid levels were increased. Serotonin level showed a decrease associated with enhanced monoamine oxidase (MAO) activity and increased 5-hydroxyindolacetic acid (5-HIAA) level. FO treatment reduced the severity of radiation-induced oxidative stress, alteration of Asp and Glu levels and serotonin metabolism concomitant with increased EPA and DHA levels.

CONCLUSION

FO attenuates the severity of radiation-induced biochemical disorders in the brain by counteracting the radiation-induced decrease of EPA and DHA. Further studies are needed concerning the long-term implications of our findings.

Metformin for non-diabetic patients with coronary heart disease (the CAMERA study): a randomised controlled trial

BACKGROUND

Metformin reduces cardiovascular risk in patients with type 2 diabetes seemingly independent of lowering blood glucose concentration. We assessed the cardiovascular effects of metformin in individuals without type 2 diabetes.

METHODS

We did a single-centre, double-blind, placebo-controlled trial at the Glasgow Clinical Research Facility (Glasgow, UK). We enrolled patients taking statins who did not have type 2 diabetes but who did have coronary heart disease and large waist circumferences. Participants were randomly assigned (1:1) by computer to either metformin (850 mg twice daily) or matching placebo in block sizes of four. Patients, investigators, trial staff, and statisticians were masked to treatment allocation. The primary endpoint was progression of mean distal carotid intima-media thickness (cIMT) over 18 months in the modified intention-to-treat population. Secondary endpoints were changes in carotid plaque score (in six regions), measures of glycaemia (HbA1c, fasting glucose, and insulin concentrations, and Homeostasis Model Assessment of Insulin Resistance [HOMA-IR]), and concentrations of lipids, high sensitivity C-reactive protein, and tissue plasminogen activator. The trial was registered at ClinicalTrials.gov, number NCT00723307.

FINDINGS

We screened 356 patients, of whom we enrolled 173 (86 in the metformin group, 87 in the placebo group). Average age was 63 years. At baseline, mean cIMT was 0·717 mm (SD 0·129) and mean carotid plaque score was 2·43 (SD 1·55). cIMT progression did not differ significantly between groups (slope difference 0·007 mm per year, 95% CI -0·006 to 0·020; p=0·29). Change of carotid plaque score did not differ significantly between groups (0·01 per year, 95% CI -0·23 to 0·26; p=0·92). Patients taking metformin had lower HbA1c, insulin, HOMA-IR, and tissue plasminogen activator compared with those taking placebo, but there were no significant differences for total cholesterol, HDL-cholesterol, non-HDL-cholesterol, triglycerides, high sensitivity C-reactive protein, or fasting glucose. 138 adverse events occurred in 64 patients in the metformin group versus 120 in 60 patients in the placebo group. Diarrhoea and nausea or vomiting were more common in the metformin group than in the placebo group (28 vs 5).

INTERPRETATION

Metformin had no effect on cIMT and little or no effect on several surrogate markers of cardiovascular disease in non-diabetic patients with high cardiovascular risk, taking statins. Further evidence is needed before metformin can be recommended for cardiovascular benefit in this population.

FUNDING

Chief Scientist Office (Scotland).

(-)-Epicatechin rich cocoa mediated modulation of oxidative stress regulators in skeletal muscle of heart failure and type 2 diabetes patients

BACKGROUND

Type 2 diabetes (T2D) and heart failure (HF) are associated with high levels of skeletal muscle (SkM) oxidative stress (OS). Health benefits attributed to flavonoids have been ascribed to antioxidation. However, for flavonoids with similar antioxidant potential, end-biological effects vary widely suggesting other mechanistic venues for reducing OS. Decreases in OS may follow the modulation of key regulatory pathways including antioxidant levels (e.g. glutathione) and enzymes such as mitochondrial superoxide dismutase (SOD2) and catalase.

METHODS

We examined OS-related alterations in SkM in T2D/HF patients (as compared vs. healthy controls) and evaluated the effects of three-month treatment with (-)-epicatechin (Epi) rich cocoa (ERC). To evidence Epi as the mediator of the improved OS profile we examined the effects of pure Epi (vs. water) on SkM OS regulatory systems in a mouse model of insulin resistance and contrasted results vs. normal mice.

RESULTS

There were severe alterations in OS regulatory systems in T2D/HF SkM as compared with healthy controls. Treatment with ERC induced recovery in glutathione levels and decreases in the nitrotyrosilation and carbonylation of proteins. With treatment, key transcriptional factors translocate into the nucleus leading to increases in SOD2 and catalase protein expression and activity levels. In insulin resistant mice, there were alterations in muscle OS and pure Epi replicated the beneficial effects of ERC found in humans.

CONCLUSIONS

Major perturbations in SkM OS can be reversed with ERC in T2D/HF patients. Epi likely mediates such effects and may provide an effective means to treat conditions associated with tissue OS.

The association of oxidative stress markers with conventional risk factors in the metabolic syndrome

BACKGROUND AND AIMS

The metabolic syndrome (MetS) is a common and complex disorder that consists of various abnormalities, including dyslipidemia, obesity, hypertension and hyperglycemia. We investigated the relationships between the levels of advanced protein oxidation products (AOPPs), the total antioxidant capacity (TAC) and the pro-oxidant-antioxidant balance (PAB) in MetS patients.

METHODS

A total of 55 patients (37 women, 18 men) with MetS and 20 healthy controls (14 women, 6 men) with a body mass index (BMI) less than 25 kg/m(2) were enrolled in the study. Colorimetric methods were used to determine the levels of AOPPs, the TAC, and the PAB.

RESULTS

AOPP, TAC, and PAB values were significantly higher in patients with MetS than in control subjects (p<0.001, p=0.050, and p<0.001, respectively). A positive correlation was observed between the AOPP levels and the glucose, triglyceride, insulin and HOMA-IR levels. PAB values also exhibited significant positive correlations with diastolic blood pressure and fibrinogen levels. Logistic regression analysis revealed that higher serum PAB values were positively and independently associated with the MetS (odds ratio: 1.110; 95% confidence interval: 1.006-1.224; P<0.37).

CONCLUSIONS

Increased AOPP levels and higher PAB values are likely to be a result of oxidative stress, a condition in which an imbalance occurs between the production and inactivation of reactive oxygen species. In addition, it appears that serum PAB values may accurately reflect the levels of oxidative stress in MetS patients.

Protein oxidation in a group of subjects with metabolic syndrome

AIMS

To examine the protein oxidation, marker of the oxidative stress, in metabolic syndrome (MS).

METHODS

We enrolled 106 subjects (45 women and 61 men) with MS of which 43 (14 women and 27 men) were with diabetes mellitus and 63 (31 women and 32 men) were without diabetes mellitus, and 54 subjects (19 women and 35 men) as control group. The protein oxidation, expressed as carbonyl groups, was measured by an enzyme-like immunosorbent assay (ELISA) kit (BioCell PC test kit, Enzo Life Sciences AG, Switzerland).

RESULTS

In the whole group of MS subjects, in comparison with control group, a significant increase in carbonyl groups was present. The same datum was also evident between control group and diabetic subjects with MS and between control group and nondiabetic subjects with MS. No difference was observed between the two subgroups (diabetic and nondiabetic subjects with MS) about NOx. Few information were obtained examining the linear regression among carbonyl groups, age, BMI, waist circumference, blood pressure values and metabolic pattern of MS subjects.

CONCLUSIONS

In MS subject we observed an increase of protein oxidation not influenced by diabetes mellitus. Several strategies may be employed to reduce this parameter.

Does metformin increase paraoxonase activity in patients with the metabolic syndrome? Additional data from the MEFISTO study

In a subanalysis on the metformin, arterial function, intima-media thickness, and nitroxidation in the metabolic syndrome (MEFISTO)(8) (an open-label fashion, with 1 year of 850 mg daily of metformin) subjects' samples, we measured the paraoxonase 1 (PON1) activity in 39 patients that finished the study and relate values with high density lipoprotein (HDL). The comparative PON1 activities at the beginning and at the end of the study were 5.528 ± 0.588 and 4.743 ± 0.619 nmol/mg protein/min (NS) for control group and 3.229 ± 0.403 and 5.135 ± 0.585 nmol/mg protein/min (p < 0.02) for the metformin group. Our data showed an enhance of PON1 activity in patients with metabolic syndrome treated with metformin, although in them, the raise of HDL concentration was less than control patients, suggesting that the increase in quality (measured here as PON1 activity) could be at least as important as an increase in its concentration. Our results point out that there is a relationship among PON1 activity and the reduction of carotideal intima-media thickness.