Metformin Inhibits Isoproterenol-induced Cardiac Hypertrophy in Mice

Geraniin attenuates isoproterenol-induced cardiac hypertrophy by inhibiting inflammation, oxidative stress and cellular apoptosis

Geraniin, a polyphenol derived from the fruit peel of Nephelium lappaceum L., has been shown to possess anti-inflammatory and antioxidant properties in the cardiovascular system. The present study explored whether geraniin could protect against an isoproterenol (ISO)-induced cardiac hypertrophy model. Mice in the ISO group received an intraperitoneal injection of ISO (5 mg/kg) once daily for 9 days, and the administration group were injected with ISO after 5 days of treatment with geraniin or spironolactone. Potential therapeutic effects and related mechanisms analysed by anatomical coefficients, histopathology, blood biochemical indices, reverse transcription-PCR and immunoblotting. Geraniin decreased the cardiac pathologic remodeling and myocardial fibrosis induced by ISO, as evidenced by the modifications to anatomical coefficients, as well as the reduction in collagen I/III á1mRNA and protein expression and cross-sectional area in hypertrophic cardiac tissue. In addition, geraniin treatment reduced ISO-induced increase in the mRNA and protein expression levels of interleukin (IL)-6, IL-1β and tumor necrosis factor-α, whereas ISO-induced IL-10 showed the opposite behaviour in hypertrophic cardiac tissue. Further analysis showed that geraniin partially reversed the ISO-induced increase in malondialdehyde and nitric oxide, and the ISO-induced decrease in glutathione, superoxide dismutase and glutathione. Furthermore, it suppressed the ISO-induced cellular apoptosis of hypertrophic cardiac tissue, as evidenced by the decrease in B-cell lymphoma-2 (Bcl-2)-associated X/caspase-3/caspase-9 expression, increase in Bcl-2 expression, and decrease in TdT-mediated dUTP nick-end labeling-positive cells. These findings suggest that geraniin can attenuate ISO-induced cardiac hypertrophy by inhibiting inflammation, oxidative stress and cellular apoptosis.

Exploring in vivo and in vitro models for heart failure with biomarker insights: a review

BACKGROUND

Heart failure (HF) is a condition characterized by the heart's inability to meet the body's demands, resulting in various complications. Two primary types of HF exist, namely HF with preserved left ventricular ejection fraction (LVEF) and HF reduced with LVEF. The progression of HF involves compensatory mechanisms such as cardiac hypertrophy, fibrosis, and alterations in gene expression. Pressure overload and volume overload are common etiologies of HF, with pressure overload often stemming from conditions like hypertension, leading to left ventricular hypertrophy and fibrosis. In contrast, volume overload can arise from chronic valvular regurgitant disease, also inducing left ventricular hypertrophy.

MAIN BODY

In vitro cell culture techniques serve as vital tools in studying HF pathophysiology, allowing researchers to investigate cellular responses and potential therapeutic targets. Additionally, biomarkers, measurable biological characteristics, play a crucial role in diagnosing and predicting HF. Some notable biomarkers include adrenomedullin, B-type natriuretic peptide, copeptin, galectin-3, interleukin-6, matrix metalloproteinases (MMPs), midregional pro-atrial natriuretic peptide, myostatin, procollagen type I C-terminal propeptide, procollagen type III N-terminal propeptide and tissue inhibitors of metalloproteinases (TIMPs). These biomarkers aid in HF diagnosis, assessing its severity, and monitoring treatment response, contributing to a deeper understanding of the disease and potentially leading to improved management strategies and outcomes.

CONCLUSIONS

This review provides comprehensive insights into various in vivo models of HF, commonly utilized cell lines in HF research, and pivotal biomarkers with diagnostic relevance for HF. By synthesizing this information, researchers gain valuable resources to further explore HF pathogenesis, identify novel therapeutic targets, and enhance diagnostic and prognostic approaches.

Metformin beyond an anti-diabetic agent: A comprehensive and mechanistic review on its effects against natural and chemical toxins

In addition to the anti-diabetic effect of metformin, a growing number of studies have shown that metformin has some exciting properties, such as anti-oxidative capabilities, anticancer, genomic stability, anti-inflammation, and anti-fibrosis, which have potent, that can treat other disorders other than diabetes mellitus. We aimed to describe and review the protective and antidotal efficacy of metformin against biologicals, chemicals, natural, medications, pesticides, and radiation-induced toxicities. A comprehensive search has been performed from Scopus, Web of Science, PubMed, and Google Scholar databases from inception to March 8, 2023. All in vitro, in vivo, and clinical studies were considered. Many studies suggest that metformin affects diseases other than diabetes. It is a radioprotective and chemoprotective drug that also affects viral and bacterial diseases. It can be used against inflammation-related and apoptosis-related abnormalities and against toxins to lower their effects. Besides lowering blood sugar, metformin can attenuate the effects of toxins on body weight, inflammation, apoptosis, necrosis, caspase-3 activation, cell viability and survival rate, reactive oxygen species (ROS), NF-κB, TNF-α, many interleukins, lipid profile, and many enzymes activity such as catalase and superoxide dismutase. It also can reduce the histopathological damages induced by many toxins on the kidneys, liver, and colon. However, clinical trials and human studies are needed before using metformin as a therapeutic agent against other diseases.

Metformin protects against pulmonary hypertension-induced right ventricular dysfunction in an age- and sex-specific manner independent of cardiac AMPK

Right ventricular (RV) function is the strongest predictor of survival in age-related heart failure as well as other clinical contexts in which aging populations suffer significant morbidity and mortality. However, despite the significance of maintaining RV function with age and disease, mechanisms of RV failure remain poorly understood and no RV-directed therapies exist. The antidiabetic drug and AMP-activated protein kinase (AMPK) activator metformin protects against left ventricular dysfunction, suggesting cardioprotective properties may translate to the RV. Here, we aimed to understand the impact of advanced age on pulmonary hypertension (PH)-induced right ventricular dysfunction. We further aimed to test whether metformin is cardioprotective in the RV and whether the protection afforded by metformin requires cardiac AMPK. We used a murine model of PH by exposing adult (4-6 mo) and aged (18 mo) male and female mice to hypobaric hypoxia (HH) for 4 wk. Cardiopulmonary remodeling was exacerbated in aged mice compared with adult mice as evidenced by elevated RV weight and impaired RV systolic function. Metformin attenuated HH-induced RV dysfunction but only in adult male mice. Metformin still protected the adult male RV even in the absence of cardiac AMPK. Together, we suggest that aging exacerbates PH-induced RV remodeling and that metformin may represent a therapeutic option for this disease in a sex- and age-dependent manner, but in an AMPK-independent manner. Ongoing efforts are aimed at elucidating the molecular basis for RV remodeling as well as delineating the mechanisms of cardioprotection provided by metformin in the absence of cardiac AMPK.NEW & NOTEWORTHY Right ventricular (RV) function predicts survival in age-related disease, yet mechanisms of RV failure are unclear. We show that aged mice undergo exacerbated RV remodeling compared with young. We tested the AMPK activator metformin to improve RV function and show that metformin attenuates RV remodeling only in adult male mice via a mechanism that does not require cardiac AMPK. Metformin is therapeutic for RV dysfunction in an age- and sex-specific manner independent of cardiac AMPK.

Improving mitochondrial function in preclinical models of heart failure: therapeutic targets for future clinical therapies?

INTRODUCTION

Heart failure is a complex clinical syndrome resulting from the unsuccessful compensation of symptoms of myocardial damage. Mitochondrial dysfunction is a process that occurs because of an attempt to adapt to the disruption of metabolic and energetic pathways occurring in the myocardium. This, in turn, leads to further dysfunction in cardiomyocyte processes. Currently, many therapeutic strategies have been implemented to improve mitochondrial function, but their effectiveness varies widely.

AREAS COVERED

This review focuses on new models of therapeutic strategies targeting mitochondrial function in the treatment of heart failure.

EXPERT OPINION

Therapeutic strategies targeting mitochondria appear to be a valuable option for treating heart failure. Currently, the greatest challenge is to develop new research models that could restore the disrupted metabolic processes in mitochondria as comprehensively as possible. Only the development of therapies that focus on improving as many dysregulated mitochondrial processes as possible in patients with heart failure will be able to bring the expected clinical improvement, along with inhibition of disease progression. Combined strategies involving the reduction of the effects of oxidative stress and mitochondrial dysfunction, appear to be a promising possibility for developing new therapies for a complex and multifactorial disease such as heart failure.

Metformin Prevents Low-dose Isoproterenol-induced Cardiac Dilatation and Systolic Dysfunction in Male Sprague-Dawley Rats

ABSTRACT

Myocardial metabolic abnormalities are well recognized alterations in chronic heart failure, effects that may contribute to progressive cardiac dysfunction. However, whether metabolic alterations in-part mediate their deleterious effects by modifying the chronic impact of excess low dose sympathetic stimulation on cardiac chamber dilatation, is uncertain. We therefore aimed to determine the effect of metformin administration on cardiac function and mitochondrial architectural changes in a rat model of chronic sympathetic-induced left ventricular (LV) remodeling and systolic dysfunction (daily subcutaneous isoproterenol [ISO] injection at a low-dose of 0.02 mg/kg for 7 months). Echocardiography was used to assess in vivo LV dimensions and function, and mitochondrial and myofibril arrangement was assessed using transmission electron microscopy. 7 months of low-dose ISO administration increased left ventricular diastolic diameter (in mm) (CONT: 7.29±0.19 vs. ISO: 8.76±0.21; p=0.001), an effect that was attenuated by metformin (ISO+MET: 7.63±0.29 vs ISO: p=0.001) administration. Similarly, ISO increased LV end systolic diameter (CONT: 4.43±0.16 vs ISO: 5.49±0.16: p<0.0001) an effect prevented by metformin (ISO+MET: 4.04±0.25 vs. ISO: p<0.0001). Moreover, chronic ISO administration reduced LV endocardial fractional shortening (p=0.0001), midwall fractional shortening (p=0.0001) and ejection fraction (p=0.0001), effects similarly prevented by metformin administration. Furthermore, changes in mitochondrial arrangement and relative mitochondrial area (CONT: 37.7±2.2 vs. ISO: 28.1±2.9; p=0.05) were produced by ISO administration, effects prevented by metformin. In conclusion, metformin offers cardiac protection against chronic sympathetic-induced LV dilatation and systolic dysfunction. These data support a role for myocardial metabolic changes in mediating LV dilatation and LV dysfunction produced by chronic neurohumoral activation in cardiac disease.

AMP-activated protein kinase: A remarkable contributor to preserve a healthy heart against ROS injury

Heart failure is one of the leading causes of death and disability worldwide. Left ventricle remodeling, fibrosis, and ischemia/reperfusion injury all contribute to the deterioration of cardiac function and predispose to the onset of heart failure. Adenosine monophosphate-activated protein kinase (AMPK) is the universally recognized energy sensor which responds to low ATP levels and restores cellular metabolism. AMPK activation controls numerous cellular processes and, in the heart, it plays a pivotal role in preventing onset and progression of disease. Excessive reactive oxygen species (ROS) generation, known as oxidative stress, can activate AMPK, conferring an additional role of AMPK as a redox-sensor. In this review, we discuss recent insights into the crosstalk between ROS and AMPK. We describe the molecular mechanisms by which ROS activate AMPK and how AMPK signaling can further prevent heart failure progression. Ultimately, we review the potential therapeutic approaches to target AMPK for the treatment of cardiovascular disease and prevention of heart failure.

Cardioprotective effect of garlic extract in isoproterenol-induced myocardial infarction in a rat model: assessment of pro-apoptotic caspase-3 gene expression

Background

Myocardial Infarction (MI), also known as heart attack, is one of the most common cardiovascular diseases. Although certain drugs or mechanical means are used, day by day natural products such as herbs and spices based MI treatment is getting much popularity over the drugs or mechanical means for their pharmacological effects and have low or no side effects. This study was designed to assess the cardio-protective effect of methanolic extract of Bangladeshi multi clove garlic (Allium sativum) cultivar, a highly believed spice having cardioprotective activity, against isoproterenol (ISO) induced MI through cardiac histopathology as well as cardiac apoptotic caspase-3 gene expression study in female Wistar albino rats. Four groups containing 35 rats treated with respective agents like distill water / garlic extract (200 mg/kg-body-weight/day) up to 28 days and normal saline / ISO (100 mg/kg-body-weight/day) on 29th and 30th day were sacrificed (two rats/group/sacrifice) on the day 31, 46 and 61 and collecting the heart, cardiac histology and gene expression analysis were performed.

Results

ISO induced MI rats pretreated with garlic extract revealed up regulated expression of the cardiac apoptotic caspase-3 gene at the initial stage but finally the expressions gradually getting down regulated along with gradual improving the cardiac damage caused by apoptosis. Furthermore, only garlic extract pretreated rats were found undamaged cardioarchitecture and normal expressions of this gene.

Conclusions

These findings suggested that garlic extract confers having significant cardioprotective effect and consuming this spice with regular diet may reduce the risk of MI.

Metformin attenuates cardiac remodeling in mice through the Nrf2/Keap1 signaling pathway

Obesity results in a variety of metabolic alterations that may contribute to abnormalities in cardiac structure and function. Although metformin (Met) has been previously reported to exhibit beneficial effects against cardiomyopathy associated obesity, the mechanism underlying this observation remains unclear. The aim of the present study was to investigate the status of the nuclear factor (erythroid-derived 2)-like 2 (Nrf2)/kelch-like ECH-associated protein 1 (Keap1) system underlying the protective effects of Met against cardiac remodeling. High-fat diet-induced obesity mouse models were first generated, which were subsequently treated with Met. Metabolic parameters, heart weight index and degree of cardiac fibrosis were examined. The expression levels of genes and proteins associated with the Nrf2/Keap1 signaling pathway were assessed using reverse transcription-quantitative PCR and western blotting. In obese mice, Met treatment significantly ameliorated the obesity phenotype, improved metabolic disorders, reduced the heart weight index and attenuated cardiac fibrosis. The cardioprotective effects of Met may be mediated through the promotion of Keap1 degradation whilst increasing the expression of Nrf2 and associated downstream antioxidant factors.

A review on the cardioprotective mechanisms of metformin against doxorubicin

Doxorubicin (DOX) is an antineoplastic agent obtained from Streptomyces peucetius. It is utilized in treating different kinds of cancers, such as leukemia, lymphoma, and lung, and breast cancers. The main side effect of DOX is cardiotoxicity. Metformin (MET) is an antihyperglycemic drug used for type 2 diabetes treatment. It is proposed that MET has a protective effect against DOX cardiotoxicity. Our review demonstrated that MET has several possible mechanisms of action, which can prevent or at least reduce DOX cardiotoxicity including a decrease of free radical generation and oxidative stress, 5' adenosine monophosphate-activated protein kinase activation, and ferritin heavy chain expression in cardiomyocytes cells. The combination of MET and DOX has been shown to enhance the anticancer activity of DOX by a number of authors. The literature reviewed in the present report supports the hypothesis that MET can reduce the cardiotoxicity that often occurs with DOX treatment.

Metformin as a protective agent against natural or chemical toxicities: a comprehensive review on drug repositioning

BACKGROUND

Metformin is the first prescribed drug for hyperglycemia in type 2 diabetes mellitus. Mainly by activating AMPK pathway, this drug exerts various functions that among them protective effects are of the interest.

PURPOSE

Herein, we aimed to gather data about the protective impacts of metformin against various natural or chemical toxicities.

RESULTS

An extensive search among PubMed, Scopus, and Google Scholar was conducted by keywords related to protection, toxicity, natural and chemical toxins and, metformin. Our literature review showed metformin alongside its anti-hyperglycemic effect has a wide range of anti-toxic effects against anti-tumour and routine drugs, natural and chemical toxins, herbicides and, heavy metals.

CONCLUSION

It is evident that metformin is a potent drug against the toxicity of a broad spectrum of natural, chemical toxic agents which is proved by a vast number of studies. Metformin mainly through AMPK axis can protect different organs against toxicities. Moreover, metformin preserves DNA integrity and can be an option for adjuvant therapy to ameliorate side effect of other therapeutics.

Isosteviol prevents the development of isoprenaline‑induced myocardial hypertrophy

Isosteviol sodium (STVNa), which is a derivate of the natural sweet-tasting glycoside stevioside, has recently been developed and it has been determined that this compound exhibits neuro- and cardio-protective properties. In the current study, whether STVNa interferes with the development of cardiac hypertrophy, which is induced by isoprenaline (Iso), was investigated in an experimental rat model. Rats were treated with a vehicle (0.9% NaCl; control), isoprenaline (Iso; 5 mg/kg) or Iso (5 mg/kg) with STVNa (4 mg/kg; Iso + STVNa). Cardiomyocytes were isolated using enzymatic dissociation and were treated with 5 µM Iso for 24 h and co-treated with 5 µM STVNa. Brain natriuretic peptide (BNP) mRNA expression was determined using PCR analysis. Cell surface area, intracellular reactive oxygen species (ROS), mitochondrial transmembrane potential (ΔΨm), cytoplasmic Ca²⁺ and Ca²⁺ and contractile function were examined using a laser scanning confocal microscope. The current study demonstrated that STVNa inhibited Iso-induced cardiac hypertrophy by inhibiting cardiomyocyte size. STVNa significantly reduced cell surface area and decreased BNP mRNA expression in ventricular cardiomyocyte Iso-induced hypertrophy. STVNa was also revealed to restore ΔΨm and reduce ROS generation and intracellular Ca²⁺ concentration when compared with the Iso-treated group. Additionally, STVNa preserved Ca²⁺ transients in hypertrophic cardiomyocytes. In conclusion, the present study demonstrated that STVNa protects against Iso-induced myocardial hypertrophy by reducing oxidative stress, restoring ΔΨm and maintaining Ca²⁺ homeostasis.

Exercise Mediated Nrf2 Signaling Protects the Myocardium From Isoproterenol-Induced Pathological Remodeling

Although exercise derived activation of Nrf2 signaling augments myocardial antioxidant signaling, the molecular mechanisms underlying the benefits of moderate exercise training (MET) in the heart remain elusive. Here we hypothesized that exercise training stabilizes Nrf2-dependent antioxidant signaling, which then protects the myocardium from isoproterenol-induced damage. The present study assessed the effects of 6 weeks of MET on the Nrf2/antioxidant function, glutathione redox state, and injury in the myocardium of C57/BL6J mice that received isoproterenol (ISO; 50 mg/kg/day for 7 days). ISO administration significantly reduced the Nrf2 promoter activity (p < 0.05) and downregulated the expression of cardiac antioxidant genes (Gclc, Nqo1, Cat, Gsr, and Gst-μ) in the untrained (UNT) mice. Furthermore, increased oxidative stress with severe myocardial injury was evident in UNT+ISO when compared to UNT mice receiving PBS under basal condition. Of note, MET stabilized the Nrf2-promoter activity and upheld the expression of Nrf2-dependent antioxidant genes in animals receiving ISO, and attenuated the oxidative stress-induced myocardial damage. Echocardiography analysis revealed impaired diastolic ventricular function in UNT+ISO mice, but this was partially normalized in the MET animals. Interestingly, while there was a marginal reduction in ubiquitinated proteins in MET mice that received ISO, the pathological signs were attenuated along with near normal cardiac function in response to exercise training. Thus, moderate intensity exercise training conferred protection against ISO-induced myocardial injury by augmentation of Nrf2-antioxidant signaling and attenuation of isoproterenol-induced oxidative stress.

Cardiac fibroblast-specific p38α MAP kinase promotes cardiac hypertrophy via a putative paracrine interleukin-6 signaling mechanism

Recent studies suggest that cardiac fibroblast-specific p38α MAPK contributes to the development of cardiac hypertrophy, but the underlying mechanism is unknown. Our study used a novel fibroblast-specific, tamoxifen-inducible p38α knockout (KO) mouse line to characterize the role of fibroblast p38α in modulating cardiac hypertrophy, and we elucidated the mechanism. Myocardial injury was induced in tamoxifen-treated Cre-positive p38α KO mice or control littermates via chronic infusion of the β-adrenergic receptor agonist isoproterenol. Cardiac function was assessed by pressure-volume conductance catheter analysis and was evaluated for cardiac hypertrophy at tissue, cellular, and molecular levels. Isoproterenol infusion in control mice promoted overt cardiac hypertrophy and dysfunction (reduced ejection fraction, increased end systolic volume, increased cardiac weight index, increased cardiomyocyte area, increased fibrosis, and up-regulation of myocyte fetal genes and hypertrophy-associated microRNAs). Fibroblast-specific p38α KO mice exhibited marked protection against myocardial injury, with isoproterenol-induced alterations in cardiac function, histology, and molecular markers all being attenuated. In vitro mechanistic studies determined that cardiac fibroblasts responded to damaged myocardium by secreting several paracrine factors known to induce cardiomyocyte hypertrophy, including IL-6, whose secretion was dependent upon p38α activity. In conclusion, cardiac fibroblast p38α contributes to cardiomyocyte hypertrophy and cardiac dysfunction, potentially via a mechanism involving paracrine fibroblast-to-myocyte IL-6 signaling.-Bageghni, S. A., Hemmings, K. E., Zava, N., Denton, C. P., Porter, K. E., Ainscough, J. F. X., Drinkhill, M. J., Turner, N. A. Cardiac fibroblast-specific p38α MAP kinase promotes cardiac hypertrophy via a putative paracrine interleukin-6 signaling mechanism.

AMPK activation counteracts cardiac hypertrophy by reducing O-GlcNAcylation

AMP-activated protein kinase (AMPK) has been shown to inhibit cardiac hypertrophy. Here, we show that submaximal AMPK activation blocks cardiomyocyte hypertrophy without affecting downstream targets previously suggested to be involved, such as p70 ribosomal S6 protein kinase, calcineurin/nuclear factor of activated T cells (NFAT) and extracellular signal-regulated kinases. Instead, cardiomyocyte hypertrophy is accompanied by increased protein O-GlcNAcylation, which is reversed by AMPK activation. Decreasing O-GlcNAcylation by inhibitors of the glutamine:fructose-6-phosphate aminotransferase (GFAT), blocks cardiomyocyte hypertrophy, mimicking AMPK activation. Conversely, O-GlcNAcylation-inducing agents counteract the anti-hypertrophic effect of AMPK. In vivo, AMPK activation prevents myocardial hypertrophy and the concomitant rise of O-GlcNAcylation in wild-type but not in AMPKα2-deficient mice. Treatment of wild-type mice with O-GlcNAcylation-inducing agents reverses AMPK action. Finally, we demonstrate that AMPK inhibits O-GlcNAcylation by mainly controlling GFAT phosphorylation, thereby reducing O-GlcNAcylation of proteins such as troponin T. We conclude that AMPK activation prevents cardiac hypertrophy predominantly by inhibiting O-GlcNAcylation.

Metformin inhibits proliferation and migration of glioblastoma cells independently of TGF-β2

To this day, glioblastoma (GBM) remains an incurable brain tumor. Previous research has shown that metformin, an oral anti-diabetic drug, may decrease GBM cell proliferation and migration especially in brain tumor initiating cells (BTICs). As transforming growth factor β 2 (TGF-β2) has been reported to promote high-grade glioma and is inhibited by metformin in other tumors, we explored whether metformin directly interferes with TGF-β2-signaling. Functional investigation of proliferation and migration of primary BTICs after treatment with metformin+/-TGF-β2 revealed that metformin doses as low as 0.01 mM metformin thrice a day were able to inhibit proliferation of susceptible cell lines, whereas migration was impacted only at higher doses. Known cellular mechanisms of metformin, such as increased lactate secretion, reduced oxygen consumption and activated AMPK-signaling, could be confirmed. However, TGF-β2 and metformin did not act as functional antagonists, but both rather inhibited proliferation and/or migration, if significant effects were present. We did not observe a relevant influence of metformin on TGF-β2 mRNA expression (qRT-PCR), TGF-β2 protein expression (ELISA) or SMAD-signaling (Western blot). Therefore, it seems that metformin does not exert its inhibitory effects on GBM BTIC proliferation and migration by altering TGF-β2-signaling. Nonetheless, as low doses of metformin are able to reduce proliferation of certain GBM cells, further exploration of predictors of BTICs' susceptibility to metformin appears justified.

Metformin and its effects on myocardial dimension and left ventricular hypertrophy in normotensive patients with coronary heart disease (the MET-REMODEL study): rationale and design of the MET-REMODEL study

Left ventricular hypertrophy (LVH) is a common and independent risk factor for cardiovascular events in patients with coronary artery disease (CAD). Controlling blood pressure is the standard approach to the management of LVH, but this is only partially effective as LVH also persists in normotensive patients. Apart from blood pressure (BP), other main risk factors associated with LVH are insulin resistance (IR) and central obesity. The diabetic medication, Metformin, reduces IR and aids weight loss and may therefore regress LVH. The MET REMODEL study will investigate the ability of Metformin to regress LVH in 64 patients with CAD. The MET-REMODEL trial is a single-center, phase IV, double blind, randomized, placebo-controlled trial to investigate the efficacy of Metformin in regression of the independent cardiac risk factor of LVH in patients with CAD who are insulin resistant. A minimum of 64 adults with a history of CAD with LVH and IR will be randomized into two groups to receive, either Metformin XL or placebo. The primary endpoint of this trial is to investigate any change in left ventricular mass index. Secondary endpoints include changes to insulin resistance measured using fasting insulin resistance index (FIRI), obesity, LV size, and function and improvement in endothelial function. A positive result will assist clinicians to identify a new mechanism for LVH regression by administering Metformin XL. This may also lead to investigating the mortality benefit of Metformin in patients with CAD and LVH.

Simvastatin prevents isoproterenol-induced cardiac hypertrophy through modulation of the JAK/STAT pathway

Simvastatin (SIM) is a lipid-soluble inhibitor of hydroxy-3-methylglutaryl coenzyme A reductase with multiple reported therapeutic benefits. The present study was designed to investigate the effect of pretreatment with SIM on isoproterenol (ISO)-induced cardiac hypertrophy in rats. Twenty-four male albino Wistar rats weighing 180–200 g were divided into four groups. Groups I and III received normal saline while groups II and IV received SIM (10 mg/kg body weight) for 30 days per gavage. In the last 7 days, rats of groups III and IV were administered ISO (5 mg/kg) intraperitoneally to induce cardiac hypertrophy. Administration of ISO induced an increase in heart-to-body weight (HW/BW) ratio, an increase in serum interleukin-6, and elevated systolic and diastolic blood pressure. Serum levels of lipids, cardiovascular risk indices, and cardiac troponin I and creatine phosphokinase-MB showed significant increase in ISO-induced hypertrophic rats. Histopathological examination of heart tissue revealed focal areas of subendocardium degeneration, mononuclear cellular infiltrations, fibrous tissue deposition, and increased thickness of the myocardium of left ventricle. In addition, ISO-administered rats exhibited significant upregulation of cardiac Janus kinase, phosphorylated signal transducer and activator of transcription, and nuclear factor-kappa B. Pretreatment with SIM significantly prevented ISO-induced cardiac hypertrophy, alleviated the altered biochemical parameters, and improved the heart architecture. In conclusion, our study provides evidence that SIM prevented the development of cardiac hypertrophy via modulation of the Janus kinase/signal transducer and activator of transcription-signaling pathway in the heart of ISO-administered animals.

EGCG Blocked Phenylephrin-Induced Hypertrophy in H9C2 Cardiomyocytes, by Activating AMPK-Dependent Pathway

AMP-activated protein kinase (AMPK) is a key regulator of energy metabolism. Previous studies have shown that activation of AMPK results in suppression of cardiac myocyte hypertrophy via inhibition of the p70S6 kinase (p70S6K) and eukaryotic elongation factor-2 (eEF2) signaling pathways. Epigallocatechin-3-gallate (EGCG), the major polyphenol found in green tea, possesses multiple protective effects on the cardiovascular system including cardiac hypertrophy. However, the molecular mechanisms has not been well investigated. In this study, we found that EGCG could significantly reduce natriuretic peptides type A (Nppa), brain natriuretic polypeptide (BNP) mRNA expression and decrease cell surface area in H9C2 cardiomyocytes stimulated with phenylephrine (PE). Moreover, we showed that AMPK is activated in H9C2 cardiomyocytes by EGCG, and AMPK-dependent pathway participates in the inhibitory effects of EGCG on cardiac hypertrophy. Taken together, our findings provide the first evidence that the effect of EGCG against cardiac hypertrophy may be attributed to its activation on AMPK-dependent signaling pathway, suggesting the therapeutic potential of EGCG on the prevention of cardiac remodeling in patients with pressure overload hypertrophy.

Searching for biomarkers of comorbidities in sera of treated HIV-infected patients by isoelectric focusing

Based on their characteristics, we hypothesized that the following parameters, namely collagen IV, glutathione S-transferase, secretory component (SC), and AMP-activated protein kinase α1α2 may be useful serum markers in the detection of comorbidities in treated HIV-infected patients. These parameters were determined in 204 HIV-infected patients and 35 controls by using IEF and densitometry. Collagen IV was undetectable in controls and the majority of HIV-infected patients. Twenty-two HIV-infected patients presented significantly elevated levels of collagen IV, most of them were coinfected with hepatitis C virus and/or hepatitis B virus. SC was undetectable in controls. SC was significantly increased in 81 HIV-infected patients and significantly correlated with aspartate aminotransferase (r = 0.267, p = 0.0049), alkaline phosphatase (r = 0.309, p = 0.0011), and γ-glutamyl-transferase (r = 0.264, p = 0.0054). Glutathione S-transferase levels of HIV-infected patients were significantly higher than the controls (3779 ± 5860 vs. 785 ± 71 DU, p = 0.0007) and significantly correlated with serum urea (r = 0.204, p = 0.0038), triglycerides (r = 0.209, p = 0.0033), and lipase (r = 0.219, p = 0.0025). AMP-activated protein kinase α1α2 levels of HIV-infected patients were significantly higher than the controls (5676 ± 6248 vs. 1189 ± 6248 DU, p = 0.0009). Further studies are needed to demonstrate the relevance of these results to diagnose non-AIDS-related illnesses in HIV-infected patients.

Metformin attenuates myocardial remodeling and neutrophil recruitment after myocardial infarction in rat

Introduction: Acute treatment with metformin has a cardio-protective effects by suppression of inflammatory responses during myocardial infarction (MI) through activation of AMP-activated protein kinase (AMPK). Neutrophils have a pivotal role during MI-induced inflammatory responses. Some anti-inflammatory treatments have decreased cardiac injury and infarct size in MI. Here we evaluated the effects of chronic pre-treatment with metformin on myocardial remodeling and neutrophil recruitment after isoproterenol-induced MI.

Methods: Male wistar rats were randomly assigned into 6 groups (n=6) of untreated control, sham, isoproterenol (Iso), and pre-treated orally with 25, 50, and 100 mg/kg of metformin, twice daily, for 14 days. Isoproterenol was injected subcutaneously (sc) at 13th and 14th days for induction of acute MI. Histopathological examinations were done on the harvested hearts. Number of neutrophils in peripheral blood and their infiltration to myocardium were evaluated by Gimsa staining and myeloperoxidase (MPO) assay, respectively.

Results: Histopathological analysis showed a significant attenuation of isoproterenol-induced cardiomyocyte necrosis and fibrosis by all three doses of metformin. The heart to body weight ratio was also decreased with all doses of metformin. Pre-treatment with metformin in comparison to Iso (MI) group reduced peripheral neutrophils (p<0.05, p<0.01, and p<0.001 at 25, 50, and 100 mg/kg; respectively) as well as MPO activity (p<0.05 and p<0.01 at 50 and 100 mg/ kg, respectively).

Conclusion: Pre-treatment with metformin decreased post-MI myocardial injuries by reducing cardiac remodeling and myocardial neutrophil activity. The results could be explained as a new mechanism for cardio-protective effect of metformin.

MicroRNA-1 in Cardiac Diseases and Cancers

MicroRNAs (miRs) are endogenous ≈22-nt non-coding RNAs that participate in the regulation of gene expression at post-transcriptional level. MiR-1 is one of the muscle-specific miRs, aberrant expression of miR-1 plays important roles in many physiological and pathological processes. In this review, we focus on the recent studies about miR-1 in cardiac diseases and cancers. The findings indicate that miR-1 may be a novel, important biomarker, and a potential therapeutic target in cardiac diseases and cancers.

Perivascular fat, AMP-activated protein kinase and vascular diseases

Perivascular adipose tissue (PVAT) is an active endocrine and paracrine organ that modulates vascular function, with implications for the pathophysiology of cardiovascular disease (CVD). Adipocytes and stromal cells contained within PVAT produce mediators (adipokines, cytokines, reactive oxygen species and gaseous compounds) with a range of paracrine effects modulating vascular smooth muscle cell contraction, proliferation and migration. However, the modulatory effect of PVAT on the vascular system in diseases, such as obesity, hypertension and atherosclerosis, remains poorly characterized. AMP-activated protein kinase (AMPK) regulates adipocyte metabolism, adipose biology and vascular function, and hence may be a potential therapeutic target for metabolic disorders such as type 2 diabetes mellitus (T2DM) and the vascular complications associated with obesity and T2DM. The role of AMPK in PVAT or the actions of PVAT have yet to be established, however. Activation of AMPK by pharmacological agents, such as metformin and thiazolidinediones, may modulate the activity of PVAT surrounding blood vessels and thereby contribute to their beneficial effect in cardiometabolic diseases. This review will provide a current perspective on how PVAT may influence vascular function via AMPK. We will also attempt to demonstrate how modulating AMPK activity using pharmacological agents could be exploited therapeutically to treat cardiometabolic diseases.

The Signaling Mechanism of TGF-β1 Induced Bovine Mammary Epithelial Cell Apoptosis

The present study showed that Transforming growth factor beta 1 (TGF-β₁) can induce apoptosis of bovine mammary epithelial cells. This apoptosis was also observed with phosphorylation of Smad2/3 within 0.5–2 h. Afterwards the signal transferred into the nucleus. Moreover, intracellular free Ca²⁺ concentration was significantly elevated as well as Caspase-3 activated and DNA lysised, thereby inducing the programmed cell death. This signaling pathway of TGF-β₁ was blocked by SB-431542 (10⁻² μM) via inhibiting ALK-5 kinase activity, which thus reversed the anti-proliferation and apoptosis effect of TGF-β₁ in mammary epithelial cells. These results indicated that TGF-β₁ induced apoptosis of bovine mammary epithelial cells through the ALK-5-Smad2/3 pathway, which plays an important role in inhibiting survival of mammary epithelial cells. Moreover, intracellular Ca²⁺ also played a critical role in TGF-β₁-induced cell apoptosis.

Metformin attenuates streptozotocin-induced diabetic nephropathy in rats through modulation of oxidative stress genes expression

Diabetes mellitus is a group of metabolic diseases characterized by hyperglycemia resulting from defects in insulin secretion and/or action. One of the most important complications of this metabolic disease is diabetic nephropathy. Hyperglycemia promotes oxidative stress and hence generation of reactive oxygen species (ROS), which is known to play a crucial role in the pathogenesis of diabetic nephropathy. Recent studies have established that metformin, an oral hypoglycemic drug, possesses antioxidant effects. However, whether metformin can protect against diabetic nephropathy has not been reported before. The overall objectives of the present study are to elucidate the potential nephroprotective effect of metformin in a rat diabetic nephropathy model and explore the exact underlying mechanism(s) involved. The effect of metformin on the biochemical changes associated with hyperglycemia induced by streptozotocin was investigated in rat kidney tissues. In addition, energy nucleotides (AMP and ATP), and Acetyl-CoA in the kidney homogenates and mitochondria, and the mRNA expression of oxidative stress and pro-inflammatory mediators were assessed. Our results showed that treatment of normoglycemic rats with metformin caused significant increase in ATP, Acetyl-CoA, and CoA-SH contents in kidney homogenates and mitochondria along with profound decrease in AMP level. On the other hand, treatment of diabetic nephropathy rats with metformin normalized all biochemical changes and the energy status in kidney tissues. At the transcriptional levels, metformin treatment caused significant restoration in diabetic nephropathy-induced oxidative stress mRNA levels, particularly GSTα, NQO1, and CAT genes, whereas inhibited TNF-α and IL-6 pro-inflammatory genes. Our data lend further credence for the contribution of metformin in the nephroprotective effect in addition to its well known hypoglycemic action.