Cardiovascular Protective Effect of Metformin and Telmisartan: Reduction of PARP1 Activity via the AMPK-PARP1 Cascade

Revealing metabolic and biochemical variations via 1H NMR metabolomics in streptozotocin-nicotinamide-induced diabetic rats treated with metformin

The increasing prevalence of lean diabetes has prompted the generation of animal models that mimic metabolic disease in humans. This study aimed to determine the optimum streptozotocin-nicotinamide (STZ-NA) dosage ratio to elicit lean diabetic features in a rat model. It also used a proton nuclear magnetic resonance (1H NMR) urinary metabolomics approach to identify the metabolic effect of metformin treatment on this novel rat model. Three different STZ-NA dosage regimens (by body weight: Group A: 110 mg/kg NA and 45 mg/kg STZ; Group B: 180 mg/kg NA and 65 mg/kg STZ and Group C: 120 mg/kg NA and 60 mg/kg STZ) were administered to Sprague-Dawley rats along with oral metformin. Group A diabetic rats (A-DC) showed favorable serum biochemical analyses and a more positive response toward oral metformin administration relative to the other STZ-NA dosage ratio groups. Orthogonal partial least squares-discriminant analysis (OPLS-DA) revealed that glucose, citrate, pyruvate, hippurate, and methylnicotinamide differentiating the OPLS-DA of A-MTF rats (Group A diabetic rats treated with metformin) and A-DC model rats. Subsequent metabolic pathway analyses revealed that metformin treatment was associated with improvement in dysfunctions caused by STZ-NA induction, including carbohydrate metabolism, cofactor metabolism, and vitamin and amino acid metabolism. In conclusion, our results identify the best STZ-NA dosage ratio for a rat model to exhibit lean type 2 diabetic features with optimum sensitivity to metformin treatment. The data presented here could be informative to improve our understanding of non-obese diabetes in humans through the identification of possible activated metabolic pathways in the STZ-NA-induced diabetic rats model.

The Ser/Thr protein kinase FonKin4-poly(ADP-ribose) polymerase FonPARP1 phosphorylation cascade is required for the pathogenicity of watermelon fusarium wilt fungus Fusarium oxysporum f. sp. niveum

Poly(ADP-ribosyl)ation (PARylation), catalyzed by poly(ADP-ribose) polymerases (PARPs) and hydrolyzed by poly(ADP-ribose) glycohydrolase (PARG), is a kind of post-translational protein modification that is involved in various cellular processes in fungi, plants, and mammals. However, the function of PARPs in plant pathogenic fungi remains unknown. The present study investigated the roles and mechanisms of FonPARP1 in watermelon Fusarium wilt fungus Fusarium oxysporum f. sp. niveum (Fon). Fon has a single PARP FonPARP1 and one PARG FonPARG1. FonPARP1 is an active PARP and contributes to Fon pathogenicity through regulating its invasive growth within watermelon plants, while FonPARG1 is not required for Fon pathogenicity. A serine/threonine protein kinase, FonKin4, was identified as a FonPARP1-interacting partner by LC-MS/MS. FonKin4 is required for vegetative growth, conidiation, macroconidia morphology, abiotic stress response and pathogenicity of Fon. The S_TKc domain is sufficient for both enzyme activity and pathogenicity function of FonKin4 in Fon. FonKin4 phosphorylates FonPARP1 in vitro to enhance its poly(ADP-ribose) polymerase activity; however, FonPARP1 does not PARylate FonKin4. These results establish the FonKin4-FonPARP1 phosphorylation cascade that positively contributes to Fon pathogenicity. The present study highlights the importance of PARP-catalyzed protein PARylation in regulating the pathogenicity of Fon and other plant pathogenic fungi.

Administration of metformin rescues age-related vulnerability to ischemic insults through mitochondrial energy metabolism

Ischemic heart disease (IHD) is the leading cause of death on a global scale. Despite significant advances in the reperfusion treatment of acute myocardial infarction, there is still a significant early mortality rate among the elderly, as angioplasty-achieved reperfusion can exacerbate myocardial damage, leading to severe ischemia/reperfusion (I/R) injury and induce fatal arrhythmias. Mitochondria are a key mediator of ischemic insults; a transient blockade of the electron transport chain (ETC) at complex I during reperfusion can reduce myocardial infarct caused by ischemic insults. The reversible, transient modulation of complex I during early reperfusion is limited by the available of clinically tractable agents. We employed the novel use of acute, high dose metformin to modulate complex I activity during early reperfusion to decrease cardiac injury in the high-risk aged heart. Young (3-6 months) and aged (22-24 months) male and female C57BL/6 J mice were subjected to in vivo regional ischemia for 45 min, followed by metformin (2 mM, i. v.) injection 5 min prior to reperfusion for 24 h. The cardiac functions were measured with echocardiography. A Seahorse XF24 Analyzer was used to ascertain mitochondrial function. Cardiomyocyte sarcomere shortening and calcium transients were measured using the IonOptix Calcium and Contractility System. The results demonstrated that administration of acute, high dose metformin at the onset of reperfusion significantly limited cardiac damage and rescued cardiac dysfunction caused by I/R in both young and aged mice. Importantly, metformin treatment improves contractile functions of isolated cardiomyocytes and maintains mitochondrial integrity under I/R stress conditions. Thus, acute metformin administration at the onset of reperfusion has potential as a mitochondrial-based therapeutic to mitigate reperfusion injury and reduce infarct size in the elderly heart attack patient who remains at greater mortality risk despite reperfusion alone.

Metformin: Is it a drug for all reasons and diseases?

Metformin was first used to treat type 2 diabetes in the late 1950s and in 2022 remains the first-choice drug used daily by approximately 150 million people. An accumulation of positive pre-clinical and clinical data has stimulated interest in re-purposing metformin to treat a variety of diseases including COVID-19. In polycystic ovary syndrome metformin improves insulin sensitivity. In type 1 diabetes metformin may help reduce the insulin dose. Meta-analysis and data from pre-clinical and clinical studies link metformin to a reduction in the incidence of cancer. Clinical trials, including MILES (Metformin In Longevity Study), and TAME (Targeting Aging with Metformin), have been designed to determine if metformin can offset aging and extend lifespan. Pre-clinical and clinical data suggest that metformin, via suppression of pro-inflammatory pathways, protection of mitochondria and vascular function, and direct actions on neuronal stem cells, may protect against neurodegenerative diseases. Metformin has also been studied for its anti-bacterial, -viral, -malaria efficacy. Collectively, these data raise the question: Is metformin a drug for all diseases? It remains unclear as to whether all of these putative beneficial effects are secondary to its actions as an anti-hyperglycemic and insulin-sensitizing drug, or result from other cellular actions, including inhibition of mTOR (mammalian target for rapamycin), or direct anti-viral actions. Clarification is also sought as to whether data from ex vivo studies based on the use of high concentrations of metformin can be translated into clinical benefits, or whether they reflect a 'Paracelsus' effect. The environmental impact of metformin, a drug with no known metabolites, is another emerging issue that has been linked to endocrine disruption in fish, and extensive use in T2D has also raised concerns over effects on human reproduction. The objectives for this review are to: 1) evaluate the putative mechanism(s) of action of metformin; 2) analyze the controversial evidence for metformin's effectiveness in the treatment of diseases other than type 2 diabetes; 3) assess the reproducibility of the data, and finally 4) reach an informed conclusion as to whether metformin is a drug for all diseases and reasons. We conclude that the primary clinical benefits of metformin result from its insulin-sensitizing and antihyperglycaemic effects that secondarily contribute to a reduced risk of a number of diseases and thereby enhancing healthspan. However, benefits like improving vascular endothelial function that are independent of effects on glucose homeostasis add to metformin's therapeutic actions.

Effects of Metformin in Heart Failure: From Pathophysiological Rationale to Clinical Evidence

Type 2 diabetes mellitus (T2DM) is a worldwide major health burden and heart failure (HF) is the most common cardiovascular (CV) complication in affected patients. Therefore, identifying the best pharmacological approach for glycemic control, which is also useful to prevent and ameliorate the prognosis of HF, represents a crucial issue. Currently, the choice is between the new drugs sodium/glucose co-transporter 2 inhibitors that have consistently shown in large CV outcome trials (CVOTs) to reduce the risk of HF-related outcomes in T2DM, and metformin, an old medicament that might end up relegated to the background while exerting interesting protective effects on multiple organs among which include heart failure. When compared with other antihyperglycemic medications, metformin has been demonstrated to be safe and to lower morbidity and mortality for HF, even if these results are difficult to interpret as they emerged mainly from observational studies. Meta-analyses of randomized controlled clinical trials have not produced positive results on the risk or clinical course of HF and sadly, large CV outcome trials are lacking. The point of force of metformin with respect to new diabetic drugs is the amount of data from experimental investigations that, for more than twenty years, still continues to provide mechanistic explanations of the several favorable actions in heart failure such as, the improvement of the myocardial energy metabolic status by modulation of glucose and lipid metabolism, the attenuation of oxidative stress and inflammation, and the inhibition of myocardial cell apoptosis, leading to reduced cardiac remodeling and preserved left ventricular function. In the hope that specific large-scale trials will be carried out to definitively establish the metformin benefit in terms of HF failure outcomes, we reviewed the literature in this field, summarizing the available evidence from experimental and clinical studies reporting on effects in heart metabolism, function, and structure, and the prominent pathophysiological mechanisms involved.

Metformin in cardiovascular diabetology: a focused review of its impact on endothelial function

As a first-line treatment for diabetes, the insulin-sensitizing biguanide, metformin, regulates glucose levels and positively affects cardiovascular function in patients with diabetes and cardiovascular complications. Endothelial dysfunction (ED) represents the primary pathological change of multiple vascular diseases, because it causes decreased arterial plasticity, increased vascular resistance, reduced tissue perfusion and atherosclerosis. Caused by “biochemical injury”, ED is also an independent predictor of cardiovascular events. Accumulating evidence shows that metformin improves ED through liver kinase B1 (LKB1)/5'-adenosine monophosphat-activated protein kinase (AMPK) and AMPK-independent targets, including nuclear factor-kappa B (NF-κB), phosphatidylinositol 3 kinase-protein kinase B (PI3K-Akt), endothelial nitric oxide synthase (eNOS), sirtuin 1 (SIRT1), forkhead box O1 (FOXO1), krüppel-like factor 4 (KLF4) and krüppel-like factor 2 (KLF2). Evaluating the effects of metformin on endothelial cell functions would facilitate our understanding of the therapeutic potential of metformin in cardiovascular diabetology (including diabetes and its cardiovascular complications). This article reviews the physiological and pathological functions of endothelial cells and the intact endothelium, reviews the latest research of metformin in the treatment of diabetes and related cardiovascular complications, and focuses on the mechanism of action of metformin in regulating endothelial cell functions.

Halofuginone, a promising drug for treatment of pulmonary hypertension

BACKGROUND AND PURPOSE

Halofuginone is a febrifugine derivative originally isolated from Chinese traditional herb Chang Shan that exhibits anti-hypertrophic, anti-fibrotic and anti-proliferative effects. We sought to investigate whether halofuginone induced pulmonary vasodilation and attenuates chronic hypoxia-induced pulmonary hypertension (HPH).

EXPERIMENTAL APPROACH

Patch-clamp experiments were conducted to examine the activity of voltage-dependent Ca²⁺ channels (VDCCs) in pulmonary artery smooth muscle cells (PASMCs). Digital fluorescence microscopy was used to measure intracellular Ca²⁺ concentration in PASMCs. Isolated perfused and ventilated mouse lungs were used to measure pulmonary artery pressure (PAP). Mice exposed to hypoxia (10% O₂ ) for 4 weeks were used as model of HPH for in vivo experiments.

KEY RESULTS

Halofuginone increased voltage-gated K⁺ (K_v ) currents in PASMCs and K⁺ currents through KCNA5 channels in HEK cells transfected with KCNA5 gene. HF (0.03-1 μM) inhibited receptor-operated Ca²⁺ entry in HEK cells transfected with calcium-sensing receptor gene and attenuated store-operated Ca²⁺ entry in PASMCs. Acute (3-5 min) intrapulmonary application of halofuginone significantly and reversibly inhibited alveolar hypoxia-induced pulmonary vasoconstriction dose-dependently (0.1-10 μM). Intraperitoneal administration of halofuginone (0.3 mg·kg^-1 , for 2 weeks) partly reversed established PH in mice.

CONCLUSION AND IMPLICATIONS

Halofuginone is a potent pulmonary vasodilator by activating K_v channels and blocking VDCC and receptor-operated and store-operated Ca²⁺ channels in PASMCs. The therapeutic effect of halofuginone on experimental PH is probably due to combination of its vasodilator effects, via inhibition of excitation-contraction coupling and anti-proliferative effects, via inhibition of the PI3K/Akt/mTOR signalling pathway.

Telmisartan detection by UV spectrophotometry in mice drinking water

Animal models are often used to test the safety and efficacy of drugs in cell culture and body systems. Several researchers deliver drugs to rodents in drinking water, although it has some limitations. For instance, drug stability, water consumption, and body mass fluctuation may change drug dose. Thus, we investigated telmisartan (TEL) stability in mice drinking water by UV spectrophotometry, and if water intake and body mass were fluctuated then it changes the predicted drug dose. The results showed that UV spectrophotometry could detect TEL at the wavelength of 300 nm, and the concentration curve was set between 1.25 and 60 µg/mL. Also, it remained stable in mice drinking water for 7 days at the predicted concentration. Mice gained weight after 8 weeks on a high-fat high-sucrose diet, and it was reduced by TEL 5 mg/kg/day after 3 weeks. Although water intake remained stable, not adjusting the TEL concentration weekly by body mass would lead to higher consumption of TEL by mice. In conclusion, we demonstrated that body mass and water intake fluctuations significantly change the amount of drug that the animal receives, which would add bias to the experiment. TEL remains stable for at least 7 days in wrapped mice water bottles in the animal care facility, and UV spectrophotometry proved to be a simple and low-cost method to detect TEL in mice drinking water.

Telmisartan alleviates alcohol-induced liver injury by activation of PPAR-γ/ Nrf-2 crosstalk in mice

Excessive consumption of alcohol may induce severe liver damage, in part via oxidative stress and inflammatory responses, which implicates these processes as potential therapeutic approaches. Prior literature has shown that Telmisartan (TEL) may provide protective effects, presumably mediated by its anti-oxidant and anti-inflammatory activities. The purpose of this study was to determine TEL's hepatoprotective effects and to identify its possible curative mechanisms in alcoholic liver disease. A mouse chronic alcohol plus binge feedings model was used in the current study for induction of alcoholic liver disease (ALD). Our results showed that TEL (10 mg/kg/day) has the ability to reduce serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP). TEL also increased the activity of superoxide dismutase (SOD) and glutathione (GSH) with concomitant reduction of nitric oxide (NO) malonaldehyde (MDA) in the liver homogenate. Moreover, TEL downregulated nuclear factor kappa B (NF-κB) expression and decreased liver content of interleukin-6 (IL-6), interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α). These anti-inflammatory and anti-oxidant activities were associated with a significant increase in the expression of nuclear factor erythroid 2-related factor 2 (Nrf-2), peroxisome proliferator-activated receptors -γ (PPAR-γ), and heme oxygenase-1 (Hmox-1). In conclusion, TEL's hepatoprotective effects against ALD may be attributable to its anti-inflammatory and anti-oxidant activities which may be in part via the modulation of PPAR-γ/ Nrf-2/ NF-κB crosstalk.

GLP-1-Induced AMPK Activation Inhibits PARP-1 and Promotes LXR-Mediated ABCA1 Expression to Protect Pancreatic β-Cells Against Cholesterol-Induced Toxicity Through Cholesterol Efflux

T2DM (Type 2 diabetes) is a complex, chronic disease characterized as insulin resistance and islet β-cell dysfunction. Bariatric surgeries such as Roux-en-Y gastric bypass (RYGB) surgery and laparoscopic sleeve gastrectomy (LSG) have become part of a critical treatment regimen in the treatment of obesity and T2DM. Moreover, GLP-1 increase following bariatric surgery has been regarded as a significant event in bariatric surgery-induced remission of T2DM. In this study, a high concentration cholesterol-induced lipotoxicity was observed in INS-1 cells, including inhibited cell viability and insulin secretion. Enhanced cell apoptosis and inhibited cholesterol efflux from INS-1 cells; meanwhile, ABCA1 protein level was decreased by cholesterol stimulation. Cholesterol-induced toxicity and ABCA1 downregulation were attenuated by GLP-1 agonist EX-4. GLP-1 induced AMPK phosphorylation during the protection against cholesterol-induced toxicity. Under cholesterol stimulation, GLP-1-induced AMPK activation inhibited PARP-1 activity, therefore attenuating cholesterol-induced toxicity in INS-1 cells. In INS-1 cells, PARP-1 directly interacted with LXR, leading to the poly(ADP-ribosyl)ation of LXRα and downregulation of LXR-mediated ABCA1 expression. In the STZ-induced T2DM model in rats, RYGB surgery or EX-4 treatment improved the glucose metabolism and lipid metabolism in rats through GLP-1 inhibition of PARP-1 activity. In conclusion, GLP-1 inhibits PARP-1 to protect islet β cell function against cholesterol-induced toxicity in vitro and in vivo through enhancing cholesterol efflux. GLP-1-induced AMPK and LXR-mediated ABCA1 expression are involved in GLP-1 protective effects.

Synergistic effect of micronutrients and metformin in alleviating diabetic nephropathy and cardiovascular Dysfunctioning in diabetic rat

Purpose

Diabetic nephropathy (DN) and Cardiovascular Dysfunctioning (CVD) are interlinked with each other and one of the leading causes of irreversible renal damage and cardiovascular disease. Micronutrients play an effective role in type-2 diabetes (T2D) and its related complications. Our work aimed to elucidate the effect of micronutrients alone and in combination with standard anti-diabetic drug metformin on DN and CVD using streptozotocin induced diabetes in rats.

Methods

T2D was induced with a single intraperitoneal (i.p.) injection of freshly prepared streptozotocin (55 mg/kg), 15 min after intraperitoneal injection of nicotinamide (230 mg/kg). Commercially available kits were used to measure kidney parameters and cardiac marker level. Creatinine clearance was calculated by using formula and heart rate was recorded using powerlab software.

Results

Significant decrease in blood glucose levels were observed 14 days after initial administration in metformin treated, micronutrients treated and metformin with micronutrients treated groups compared with diabetic group. After 6 weeks of metformin and micronutrients treatment, serum creatinine, blood urea nitrogen (BUN) and lactate dehydrogenase (LDH) levels were significantly decreased as compared to diabetic group. Moreover, urine creatinine level, creatinine clearance and heart rate (HR) was increased significantly in metformin and micronutrients treated group compared with a diabetic group. Micronutrients therapy also normalised the general symptoms of diabetes.

Conclusion

The results obtained from this study indicate the synergistic effect of metformin and micronutrients against diabetic heart and kidney. Therefore, micronutrients may be used as an effective add-on therapy for DN and CVD.

Can Metformin Exert as an Active Drug on Endothelial Dysfunction in Diabetic Subjects?

Cardiovascular mortality is a major cause of death among in type 2 diabetes (T2DM). Endothelial dysfunction (ED) is a well-known important risk factor for the development of diabetes cardiovascular complications. Therefore, the prevention of diabetic macroangiopathies by preserving endothelial function represents a major therapeutic concern for all National Health Systems. Several complex mechanisms support ED in diabetic patients, frequently cross-talking each other: uncoupling of eNOS with impaired endothelium-dependent vascular response, increased ROS production, mitochondrial dysfunction, activation of polyol pathway, generation of advanced glycation end-products (AGEs), activation of protein kinase C (PKC), endothelial inflammation, endothelial apoptosis and senescence, and dysregulation of microRNAs (miRNAs). Metformin is a milestone in T2DM treatment. To date, according to most recent EASD/ADA guidelines, it still represents the first-choice drug in these patients. Intriguingly, several extraglycemic effects of metformin have been recently observed, among which large preclinical and clinical evidence support metformin’s efficacy against ED in T2DM. Metformin seems effective thanks to its favorable action on all the aforementioned pathophysiological ED mechanisms. AMPK pharmacological activation plays a key role, with metformin inhibiting inflammation and improving ED. Therefore, aim of this review is to assess metformin’s beneficial effects on endothelial dysfunction in T2DM, which could preempt development of atherosclerosis.

BETs inhibition attenuates oxidative stress and preserves muscle integrity in Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) affects 1 in 3500 live male births. To date, there is no effective cure for DMD, and the identification of novel molecular targets involved in disease progression is important to design more effective treatments and therapies to alleviate DMD symptoms. Here, we show that protein levels of the Bromodomain and extra-terminal domain (BET) protein BRD4 are significantly increased in the muscle of the mouse model of DMD, the mdx mouse, and that pharmacological inhibition of the BET proteins has a beneficial outcome, tempering oxidative stress and muscle damage. Alterations in reactive oxygen species (ROS) metabolism are an early event in DMD onset and they are tightly linked to inflammation, fibrosis, and necrosis in skeletal muscle. By restoring ROS metabolism, BET inhibition ameliorates these hallmarks of the dystrophic muscle, translating to a beneficial effect on muscle function. BRD4 direct association to chromatin regulatory regions of the NADPH oxidase subunits increases in the mdx muscle and JQ1 administration reduces BRD4 and BRD2 recruitment at these regions. JQ1 treatment reduces NADPH subunit transcript levels in mdx muscles, isolated myofibers and DMD immortalized myoblasts. Our data highlight novel functions of the BET proteins in dystrophic skeletal muscle and suggest that BET inhibitors may ameliorate the pathophysiology of DMD.

E3 Ubiquitin ligase NEDD4 family‑regulatory network in cardiovascular disease

Protein ubiquitination represents a critical modification occurring after translation. E3 ligase catalyzes the covalent binding of ubiquitin to the protein substrate, which could be degraded. Ubiquitination as an important protein post-translational modification is closely related to cardiovascular disease. The NEDD4 family, belonging to HECT class of E3 ubiquitin ligases can recognize different substrate proteins, including PTEN, ENaC, Nav1.5, SMAD2, PARP1, Septin4, ALK1, SERCA2a, TGFβR3 and so on, via the WW domain to catalyze ubiquitination, thus participating in multiple cardiovascular-related disease such as hypertension, arrhythmia, myocardial infarction, heart failure, cardiotoxicity, cardiac hypertrophy, myocardial fibrosis, cardiac remodeling, atherosclerosis, pulmonary hypertension and heart valve disease. However, there is currently no review comprehensively clarifying the important role of NEDD4 family proteins in the cardiovascular system. Therefore, the present review summarized recent studies about NEDD4 family members in cardiovascular disease, providing novel insights into the prevention and treatment of cardiovascular disease. In addition, assessing transgenic animals and performing gene silencing would further identify the ubiquitination targets of NEDD4. NEDD4 quantification in clinical samples would also constitute an important method for determining NEDD4 significance in cardiovascular disease.

ACE2, Metformin, and COVID-19

COVID-19 is becoming a leading cause of mortality throughout the world, and few effective therapies are currently available. Angiotensin converting enzyme 2 (ACE2) is essential to COVID-19 pathogenesis, as the binding of SARS-CoV-2 spike protein (S protein) is required for viral entry and development of COVID-19. ACE2 regulates the protective arm of the renin-angiotensin-aldosterone system (RAAS) that endows anti-hypertensive and anti-inflammatory effects in the cardiovascular and pulmonary systems. Preclinical data suggest ACE2 might be downregulated after SARS-CoV-2 binding, and treatments that increase ACE2 may prevent cardiopulmonary injury. Development, testing, and mass production of novel ACE2 therapies may take years, whereas more effective treatments for COVID-19 are needed urgently. Metformin is a widely available anti-diabetic agent that has an excellent safety profile, and clinical and preclinical data suggest metformin may offer cardiopulmonary protection in COVID-19 via enhanced ACE2 expression.

Mechanisms of action of metformin in type 2 diabetes: Effects on mitochondria and leukocyte-endothelium interactions

Type 2 diabetes (T2D) is a very prevalent, multisystemic, chronic metabolic disorder closely related to atherosclerosis and cardiovascular diseases. It is characterised by mitochondrial dysfunction and the presence of oxidative stress. Metformin is one of the safest and most effective anti-hyperglycaemic agents currently employed as first-line oral therapy for T2D. It has demonstrated additional beneficial effects, unrelated to its hypoglycaemic action, on weight loss and several diseases, such as cancer, cardiovascular disorders and metabolic diseases, including thyroid diseases. Despite the vast clinical experience gained over several decades of use, the mechanism of action of metformin is still not fully understood. This review provides an overview of the existing literature concerning the beneficial mitochondrial and vascular effects of metformin, which it exerts by diminishing oxidative stress and reducing leukocyte-endothelium interactions. Specifically, we describe the molecular mechanisms involved in metformin's effect on gluconeogenesis, its capacity to interfere with major metabolic pathways (AMPK and mTORC1), its action on mitochondria and its antioxidant effects. We also discuss potential targets for therapeutic intervention based on these molecular actions.

Abdominal aortic aneurysm: a review on the role of oral antidiabetic drugs

INTRODUCTION

A paradoxical negative association between diabetes mellitus and abdominal aortic aneurysm (AAA) prevalence and growth is established. However, so far is not possible to determine whether this protection comes from the disease itself or the medication for Diabetes. The aim of this manuscript is to review the association between oral antidiabetic drugs and AAA incidence and growth.

EVIDENCE ACQUISITION

A search was conducted on PubMed and Scopus databases until December 2019 to identify publications reporting on the association between oral antidiabetic drugs (biguanides/metformin, sulfonylureas(SU), thiazolidinediones(TZD), dipeptidyl-peptidase 4(DPP-4) inhibitors, glucagon-like peptide 1(GLP-1) agonists, sodium-glucose transporter protein-2(SGLT2) inhibitors) and the outcomes AAA incidence and growth. Only data from human studies were considered, with a minimum of 3 months follow-up.

EVIDENCE SYNTHESIS

Six studies enrolling 25,810 patients were included: one reporting on the AAA risk and five reporting on AAA growth. Metformin prescription was associated with a 28% reduction in AAA occurrence, while SU and TZD were associated with a 18% decrease in AAA risk. Regarding AAA enlargement, results were concordant for a slower expansion rate associated with metformin, with a decrease ranging from -0.30 mm/y to -1.30 mm/y, but not consistent for other antidiabetic drugs.

CONCLUSIONS

Metformin seems to be associated with a decrease in AAA risk and enlargement rate. Evidence for the other classes is lacking. Studies evaluating the association between oral antidiabetic drugs and AAA progression, independently of the diabetic status, are needed.

The Multifactorial Role of PARP-1 in Tumor Microenvironment

Poly(ADP-ribose) polymerases (PARPs), represent a family of 17 proteins implicated in a variety of cell functions; some of them possess the enzymatic ability to synthesize and attach poly (ADP-ribose) (also known as PAR) to different protein substrates by a post-translational modification; PARPs are key components in the cellular response to stress with consequences for different physiological and pathological events, especially during neoplasia. In recent years, using PARP inhibitors as antitumor agents has raised new challenges in understanding their role in tumor biology. Notably, the function of PARPs and PAR in the dynamic of tumor microenvironment is only starting to be understood. In this review, we summarized the conclusions arising from recent studies on the interaction between PARPs, PAR and key features of tumor microenvironment such as hypoxia, autophagy, tumor initiating cells, angiogenesis and cancer-associated immune response.

The E3 ubiquitin ligase Smurf2 regulates PARP1 stability to alleviate oxidative stress-induced injury in human umbilical vein endothelial cells

Oxidative stress injury is involved in many cardiovascular diseases, like hypertension and myocardial infarction. Ubiquitination is a ubiquitous protein post-translational modification that controls a wide range of biological functions and plays a crucial role in maintaining the homeostasis of cells in physiology and disease. Many studies have shown that oxidative stress damage is inextricably linked to ubiquitination. We demonstrate that Smurf2, an E3 ubiquitinated ligase, is involved in HUVEC apoptosis induced by oxidative stress to alleviate H₂ O₂ -induced reactive oxygen species (ROS) production and the apoptosis of human umbilical vein endothelial cells (HUVECs). At the same time, we found that Smurf2 can bind the poly(ADP-ribose) polymerase-1(PARP1), and the interaction is enhanced under the stimulation of oxidative stress. We further study and prove that Smurf2 can promote PARP1 ubiquitination and degradation. Collectively, we demonstrate Smurf2 degradation of overactivated PARP1 by ubiquitin-proteasome pathway to protect HUVEC and alleviate oxidative stress injury.

Endothelial mechanobiology

Lining the luminal surface of the vasculature, endothelial cells (ECs) are in direct contact with and differentially respond to hemodynamic forces depending on their anatomic location. Pulsatile shear stress (PS) is defined by laminar flow and is predominantly located in straight vascular regions, while disturbed or oscillatory shear stress (OS) is localized to branch points and bifurcations. Such flow patterns have become a central focus of vascular diseases, such as atherosclerosis, because the focal distribution of endothelial dysfunction corresponds to regions exposed to OS, whereas endothelial homeostasis is maintained in regions defined by PS. Deciphering the mechanotransduction events that occur in ECs in response to differential flow patterns has required the innovation of multidisciplinary approaches in both in vitro and in vivo systems. The results from these studies have identified a multitude of shear stress-regulated molecular networks in the endothelium that are implicated in health and disease. This review outlines the significance of scientific findings generated in collaboration with Dr. Shu Chien.

Anti-inflammatory Property of AMP-activated Protein Kinase

BACKGROUND

One of the many debated topics in inflammation research is whether this scenario is really an accelerated form of human wound healing and immunityboosting or a push towards autoimmune diseases. The answer requires a better understanding of the normal inflammatory process, including the molecular pathology underlying the possible outcomes. Exciting recent investigations regarding severe human inflammatory disorders and autoimmune conditions have implicated molecular changes that are also linked to normal immunity, such as triggering factors, switching on and off, the influence of other diseases and faulty stem cell homeostasis, in disease progression and development.

METHODS

We gathered around and collected recent online researches on immunity, inflammation, inflammatory disorders and AMPK. We basically searched PubMed, Scopus and Google Scholar to assemble the studies which were published since 2010.

RESULTS

Our findings suggested that inflammation and related disorders are on the verge and interfere in the treatment of other diseases. AMPK serves as a key component that prevents various kinds of inflammatory signaling. In addition, our table and hypothetical figures may open a new door in inflammation research, which could be a greater therapeutic target for controlling diabetes, obesity, insulin resistance and preventing autoimmune diseases.

CONCLUSION

The relationship between immunity and inflammation becomes easily apparent. Yet, the essence of inflammation turns out to be so startling that the theory may not be instantly established and many possible arguments are raised for its clearance. However, this study might be able to reveal some possible approaches where AMPK can reduce or prevent inflammatory disorders.

c-Abl-Mediated Tyrosine Phosphorylation of PARP1 Is Crucial for Expression of Proinflammatory Genes

Poly(ADP-ribosyl)ation is a rapid and transient posttranslational protein modification mostly catalyzed by poly(ADP-ribose) polymerase-1 (PARP1). Fundamental roles of activated PARP1 in DNA damage repair and cellular response pathways are well established; however, the precise mechanisms by which PARP1 is activated independent of DNA damage, and thereby playing a role in expression of inflammatory genes, remain poorly understood. In this study, we show that, in response to LPS or TNF-α exposure, the nonreceptor tyrosine kinase c-Abl undergoes nuclear translocation and interacts with and phosphorylates PARP1 at the conserved Y829 site. Tyrosine-phosphorylated PARP1 is required for protein poly(ADP-ribosyl)ation of RelA/p65 and NF-κB-dependent expression of proinflammatory genes in murine RAW 264.7 macrophages, human monocytic THP1 cells, or mouse lungs. Furthermore, LPS-induced airway lung inflammation was reduced by inhibition of c-Abl activity. The present study elucidated a novel signaling pathway to activate PARP1 and regulate gene expression, suggesting that blocking the interaction of c-Abl with PARP1 or pharmaceutical inhibition of c-Abl may improve the outcomes of PARP1 activation-mediated inflammatory diseases.

Angiotensin II Receptor Type 1 Antagonists Modulate Vascular Smooth Muscle Cell Proliferation and Migration via AMPK/mTOR

The aberrant proliferation and migration of vascular smooth muscle cells (VSMCs) in the vascular wall are crucial pathological events involved in cardiovascular impairments including hypertension, heart failure, and atherosclerosis. At the molecular level, the mammalian target of rapamycin (mTOR)-ribosomal protein S6 kinase beta-1 (p70S6K) signaling pathway is essential to potentiate VSMC proliferation and migration. Although angiotensin II receptor type 1 -(AT1-R) antagonists such as valsartan and telmisartan have a significant cardiovascular protective effect, the molecular basis of this class of drugs in VSMC proliferation and migration remains elusive. By using cultured VSMCs, adenosine monophosphate-activated protein kinase (AMPK) α2 knockout mice, and hypertensive rat models, this study investigated whether AT1-R antagonists can inhibit the mTOR-p70S6K signaling pathway in VSMCs and the vascular wall. Valsartan activated AMPK, which in turn suppressed reactive oxygen species production and consequently attenuated VSMC proliferation and migration. In vivo, a clinical dose of telmisartan significantly inhibited the mTOR-p70S6K signaling pathway in the vascular wall of wild-type but not AMPKα2-/- mice. Furthermore, spontaneously hypertensive rats had significantly elevated phosphorylation of mTOR and p70S6K in the aorta compared to Wistar-Kyoto rats, which were reduced by telmisartan administration. These data suggest that AT1-R antagonists inhibit VSMC proliferation and migration via their regulation of AMPK, mTOR, and p70S6K, which contribute to the cardioprotective effects of these drugs.

CHK2-mediated regulation of PARP1 in oxidative DNA damage response

Poly(ADP-ribose) polymerase 1 (PARP1) is a DNA damage sensor, which upon activation, recruits downstream proteins by poly(ADP-ribosyl)ation (PARylation). However, it remains largely unclear how PARP1 activity is regulated. Interestingly, the data obtained through this study revealed that PARP1 was co-immunoprecipitated with checkpoint kinase 2 (CHK2), and the interaction was increased after oxidative DNA damage. Moreover, CHK2 depletion resulted in a reduction in overall PARylation. To further explore the functional relationship between PARP1 and CHK2, this study employed H₂O₂ to induce an oxidative DNA damage response in cells. Here, we showed that CHK2 and PARP1 interact in vitro and in vivo through the CHK2 SCD domain and the PARP1 BRCT domain. Furthermore, CHK2 stimulates the PARylation activity of PARP1 through CHK2-dependent phosphorylation. Consequently, the impaired repair associated with PARP1 depletion could be rescued by re-expression of wild-type PARP1 and the phospho-mimic but not the phospho-deficient mutant. Mechanistically, we showed that CHK2-dependent phosphorylation of PARP1 not only regulates its cellular localization but also promotes its catalytic activity and its interaction with XRCC1. These findings indicate that CHK2 exerts a multifaceted impact on PARP1 in response to oxidative stress to facilitate DNA repair and to maintain cell survival.

Metformin regulates metabolic and nonmetabolic pathways in skeletal muscle and subcutaneous adipose tissues of older adults

Administration of metformin increases healthspan and lifespan in model systems, and evidence from clinical trials and observational studies suggests that metformin delays a variety of age-related morbidities. Although metformin has been shown to modulate multiple biological pathways at the cellular level, these pleiotropic effects of metformin on the biology of human aging have not been studied. We studied ~70-year-old participants (n = 14) in a randomized, double-blind, placebo-controlled, crossover trial in which they were treated with 6 weeks each of metformin and placebo. Following each treatment period, skeletal muscle and subcutaneous adipose tissue biopsies were obtained, and a mixed-meal challenge test was performed. As expected, metformin therapy lowered 2-hour glucose, insulin AUC, and insulin secretion compared to placebo. Using FDR<0.05, 647 genes were differentially expressed in muscle and 146 genes were differentially expressed in adipose tissue. Both metabolic and nonmetabolic pathways were significantly influenced, including pyruvate metabolism and DNA repair in muscle and PPAR and SREBP signaling, mitochondrial fatty acid oxidation, and collagen trimerization in adipose. While each tissue had a signature reflecting its own function, we identified a cascade of predictive upstream transcriptional regulators, including mTORC1, MYC, TNF, TGFß1, and miRNA-29b that may explain tissue-specific transcriptomic changes in response to metformin treatment. This study provides the first evidence that, in older adults, metformin has metabolic and nonmetabolic effects linked to aging. These data can inform the development of biomarkers for the effects of metformin, and potentially other drugs, on key aging pathways.

Combined Antihypertensive Effect of Paeoniflorin Enriched Extract and Metoprolol in Spontaneously Hypertensive Rats

Background:

Hypertension is a great global health challenge and it mostly requires drug combination therapy with the various advantages. Metoprolol (MP) and paeoniflorin are both commonly used for the treatment of hypertension. However, whether they exert synergistic effects on antihypertension or not remains unclear, especially on vascular endothelial function.

Objective:

The purpose of the study is to investigate the advantages of the combined antihypertensive effects of paeoniflorin enriched extract from Radix Paeoniae Alba (RE) and MP in spontaneously hypertensive rats (SHR).

Materials and Methods:

SHR divided into six groups (n = 8 each group), animals in each group were administrated orally with distilled water, MP (6 and 20 mg/kg), RE (30 and 90 mg/kg), and MP (6 mg/kg) combined with RE (30 mg/kg) (MP + RE), respectively, daily for 6 weeks. Blood pressure (BP) and microcirculation were assessed. The organ bath experiment and hematoxylin and eosin staining were, respectively, performed for the functional and pathological vascular function analysis. Immunohistochemistry was applied to detect endothelial nitric oxide synthase (eNOS) expression in aorta, heart, and kidney. Further, high-performance liquid chromatography was employed to quantitatively determine paeoniflorin in RE and MP + RE sample solvent, as well as in plasma of Sprague-Dawley rats (SD) after single-dose administration of them.

Results:

The results showed that MP + RE significantly reduced BP, increased microcirculation, improved vascular function and pathological changes, and upregulated eNOS expression. MP was also found to increase the blood concentration of paeoniflorin in SD.

Conclusion:

The combination of RE and MP could be used for the treatment of hypertension and could improve microcirculation, upregulate eNOS expression, and mitigate endothelial dysfunction in SHR.

SUMMARY

Paeoniflorin enriched extract from Radix Paeoniae Alba and metoprolol exert synergistic antihypertensive effects.

Abbreviations used: RE: Paeoniflorin enriched extract from Radix Paeoniae Alba, MP: Metoprolol, MP + RE: MP combined with RE, NC: Normal control, MC: Model control, SHR: Spontaneously hypertensive rats, SD: Sprague-Dawley rats, H and E: Hematoxylin and eosin, BP: Blood pressure, SBP: Systolic blood pressure, DBP: Diastolic blood pressure, MBP: Mean arterial blood pressure, NA: Norepinephrine, ACh: Acetylcholine, SNP: Nitroprusside, NO: Nitric oxide, eNOS: Endothelial nitric oxide synthase, RPA: Radices Paeoniae Alba, IHC: Immunohistochemistry, C_max: Peak concentration, T_max: The time to reach C_max, t_½: Half-life, AUC_0-t: Area under the curve of 0-t time; MRT_0-t: Mean residence of 0-t time; CL: Clearance rate.

Does Metformin Protect Diabetic Patients from Oxidative Stress and Leukocyte-Endothelium Interactions?

Since metformin can exert beneficial vascular effects, we aimed at studying its effect on reactive oxygen species (ROS) production, antioxidant enzyme expression, levels of adhesion molecules, and leukocyte-endothelium interactions in the leukocytes from type 2 diabetic (T2D) patients. The study was carried out in 72 T2D patients (41 of whom were treated with metformin for at least 12 months at a dose of 1700 mg per day), and in 40 sex- and age-matched control subjects. Leukocytes from T2D patients exhibited enhanced levels of mitochondrial ROS and decreased mRNA levels of glutathione peroxidase 1 (gpx1) and sirtuin 3 (sirt3) with respect to controls, whereas metformin was shown to revert these effects. No changes were observed on total ROS production and the expression levels of superoxide dismutase 1 and catalase. Furthermore, increases in leukocyte-endothelial interactions and intercellular adhesion molecule-1 and P-selectin levels were found in T2D and were also restored in metformin-treated patients. Our findings raise the question of whether metformin could modulate the appearance of atherosclerosis in T2D patients and reduce vascular events by decreasing leukocyte oxidative stress through an increase in gpx1 and sirt3 expression, and undermining adhesion molecule levels and leukocyte-endothelium interactions. Antioxid. Redox Signal. 27, 1439-1445.

Polycystic ovarian syndrome-associated cardiovascular complications: An overview of the association between the biochemical markers and potential strategies for their prevention and elimination

Polycystic ovarian syndrome (PCOS) is associated with multiple cardiovascular risk factors (CVRF) including endothelial dysfunction (ED) and presence of metabolic syndrome (MS). The probable reason suggested for elevated CVRF in PCOS is oxidative stress (OS), which is an integral factor in cardiometabolic complications (CMC) seen in PCOS women. The interrelated mechanisms by which CVRF instigate clinical manifestation plays a crucial role in identification of a strategy to treat different comorbidities in PCOS. The existing treatment for PCOS mostly focuses on management of individual disorders, however, therapeutic strategies or novel targets to address cardiovascular complications in PCOS deserve extensive analysis.

MTLD, a Database of Multiple Target Ligands, the Updated Version

Polypharmacology plays an important role in drug discovery and polypharmacology drug strategies provide a novel path in drug design. However, to develop a polypharmacology drug with the desired profile remains a challenge. Previously, we developed a free web-accessible database called Multiple Target Ligand Database (MTLD, www.mtdcadd.com). Herein, the MTLD database has been updated, containing 2444 Multiple Target Ligands (MTLs) that bind with 21,424 binding sites from 18,231 crystal structures. Of the MTLs, 304 entries are approved drugs, and 1911 entries are drug-like compounds. Also, we added new functions such as multiple conditional search and linkage visualization. Through querying the updated database, extremely useful information for the development of polypharmacology drugs may be provided.

Metformin effects on the heart and the cardiovascular system: A review of experimental and clinical data

BACKGROUND

Metformin, the eldest and most widely used glucose lowering drug, is likely to be effective also on cardiac and vascular disease prevention. Nonetheless, uncertainty still exists with regard to its effects on the cardiovascular system as a whole and specifically on the myocardium, both at the organ and cellular levels.

METHODS

We reviewed the available data on the cardiac and vascular effects of metformin, encompassing both in vitro, either tissue or isolated organ, and in vivo studies in experimental animals and humans, as well as the evidence generated by major clinical trials.

RESULTS

At the cellular level metformin's produces both AMP-activated kinase (AMPK) dependent and independent effects. At the systemic level, possibly also through other pathways, this drug improves endothelial function, protects from oxidative stress and inflammation, and from the negative effects of angiotensin II. On the myocardium it attenuates ischemia-reperfusion injury and prevents adverse remodeling induced by humoral and hemodynamic factors. The effects on myocardial cell metabolism and contractile function being not evident at rest or in more advanced stages of cardiac dysfunction, could be relevant during transient ischemia, during an acute increase in workload and in the early stages of diabetic/hypertensive cardiomyopathy as confirmed by few small clinical trials and some observational studies. The overall evidence emerging from both clinical trials and real world registry is in favor of a protective effect of metformin with respect to both coronary events and progression to heart failure.

CONCLUSIONS

Given this potential, its efficacy and its safety (and also its low cost) metformin remains the central pillar of the therapy of diabetes.

MicroRNAs Modulate Oxidative Stress in Hypertension through PARP-1 Regulation

Oxidative stress is thought to contribute to aging and age-related diseases, such as cardiovascular and neurodegenerative diseases, and is a risk factor for systemic arterial hypertension. Previously, we reported differential mRNA and microRNA (miRNA) expression between African American (AA) and white women with hypertension. Here, we found that the poly-(ADP-ribose) polymerase 1 (PARP-1), a DNA damage sensor protein involved in DNA repair and other cellular processes, is upregulated in AA women with hypertension. To explore this mechanism, we identified two miRNAs, miR-103a-2-5p and miR-585-5p, that are differentially expressed with hypertension and were predicted to target PARP1. Through overexpression of each miRNA-downregulated PARP-1 mRNA and protein levels and using heterologous luciferase reporter assays, we demonstrate that miR-103a-2-5p and miR-585-5p regulate PARP1 through binding within the coding region. Given the important role of PARP-1 in DNA repair, we assessed whether overexpression of miR-103a-2-5p or miR-585-5p affected DNA damage and cell survival. Overexpression of these miRNAs enhanced DNA damage and decreased both cell survival and colony formation. These findings highlight the role for PARP-1 in regulating oxidative DNA damage in hypertension and identify important new miRNA regulators of PARP-1 expression. These insights may provide additional avenues to understand hypertension health disparities.

Therapeutic Targeting of Cellular Stress to Prevent Cardiovascular Disease: A Review of the Evidence

The availability of effective drugs targeting the major risk factors of cardiovascular disease (CVD) has reduced morbidity and mortality. Cumulative relative risk of CVD events can be reduced by 75 % with a combination of aspirin, a β-adrenoceptor antagonist (β-blocker), an HMG-CoA reductase inhibitor (statin), and an angiotensin-converting enzyme inhibitor. The principal pharmacodynamics of these drugs cannot explain the entirety of their cardioprotective action, as other drugs with similar pharmacologic targets have not been associated with favorable clinical effects. This raises the possibility that the cardioprotective drugs have a unique pleiotropic activity that contributes to their clinical efficacy. Recent data suggest that reducing cellular stress such as oxidative, inflammatory, and endoplasmic reticulum stress, might be a common denominator of the drugs with proven efficacy in reducing CVD risk. In this communication, the evidence in favor of this hypothesis is discussed, and ongoing trials with therapeutic agents targeting cellular stresses are reviewed.

Metformin improves cardiac function in mice with heart failure after myocardial infarction by regulating mitochondrial energy metabolism

To investigate whether metformin can improve the cardiac function through improving the mitochondrial function in model of heart failure after myocardial infarction. Male C57/BL6 mice aged about 8 weeks were selected and the anterior descending branch was ligatured to establish the heart failure model after myocardial infarction. The cardiac function was evaluated via ultrasound after 3 days to determine the modeling was successful, and the mice were randomly divided into two groups. Saline group (Saline) received the intragastric administration of normal saline for 4 weeks, and metformin group (Met) received the intragastric administration of metformin for 4 weeks. At the same time, Shame group (Sham) was set up. Changes in cardiac function in mice were detected at 4 weeks after operation. Hearts were taken from mice after 4 weeks, and cell apoptosis in myocardial tissue was detected using TUNEL method; fresh mitochondria were taken and changes in oxygen consumption rate (OCR) and respiratory control rate (RCR) of mitochondria in each group were detected using bio-energy metabolism tester, and change in mitochondrial membrane potential (MMP) of myocardial tissue was detected via JC-1 staining; the expressions and changes in Bcl-2, Bax, Sirt3, PGC-1α and acetylated PGC-1α in myocardial tissue were detected by Western blot. RT-PCR was used to detect mRNA levels in Sirt3 in myocardial tissues. Metformin improved the systolic function of heart failure model rats after myocardial infarction and reduced the apoptosis of myocardial cells after myocardial infarction. Myocardial mitochondrial respiratory function and membrane potential were decreased after myocardial infarction, and metformin treatment significantly improved the mitochondrial respiratory function and mitochondrial membrane potential; Metformin up-regulated the expression of Sirt3 and the activity of PGC-1α in myocardial tissue of heart failure after myocardial infarction. Metformin decreases the acetylation level of PGC-1α through up-regulating Sirt3, mitigates the damage to mitochondrial membrane potential of model of heart failure after myocardial infarction and improves the respiratory function of mitochondria, thus improving the cardiac function of mice.