Effects of pravastatin on progression of glucose intolerance and cardiovascular remodeling in a type II diabetes model

Comparative effects of pravastatin and rosuvastatin on carbohydrate metabolism in an experimental diabetic rat model

Statin treatment may increase the risk of diabetes; there is insufficient data on how statins affect glucose regulation and glycemic control and the effects of statins on liver enzymes related to carbohydrate metabolism have not been fully studied. Therefore, we aimed to compare the effects of the statin derivatives, pravastatin, and rosuvastatin, on carbohydrate metabolism in an experimental diabetic rat model. Female Wistar albino rats were used and diabetes was induced by intraperitoneal injection of streptozotocin. Thereafter, 10 and 20 mg kg-1 day-1 doses of both pravastatin and rosuvastatin were administered by oral gavage to the diabetic rats for 8 weeks. At the end of the experiment, body masses, the levels of fasting blood glucose, serum insulin, insulin resistance (HOMA-IR), liver glycogen, and liver enzymes related to carbohydrate metabolism were measured. Both doses of pravastatin significantly in creased the body mass in diabetic rats, however, rosuvastatin, especially at the dose of 20 mg kg-1 day-1 reduced the body mass signi ficantly. Pravastatin, especially at a dose of 20 mg kg-1 day-1, caused significant increases in liver glycogen synthase and glucose 6-phosphate dehydrogenase levels but significant decreases in the levels of glycogen phosphorylase, lactate dehydrogenase, and glucose-6-phosphatase. Hence, pravastatin partially ameliorated the adverse changes in liver enzymes caused by diabetes and, especially at the dose of 20 mg kg-1 day-1, reduced the fasting blood glucose level and increased the liver glycogen content. However, rosuvastatin, especially at the dose of 20 mg kg-1 day-1, significantly reduced the liver glycogen synthase and pyruvate kinase levels, but increased the glycogen phosphorylase level in diabetic rats. Rosuvastatin, 20 mg kg-1 day-1 dose, caused significant decreases in the body mass and the liver glycogen content of diabetic rats. It can be concluded that pravastatin, especially at the dose of 20 mg kg-1 day-1 is more effective in ameliorating the negative effects of diabetes by modulating carbohydrate metabolism.

Pravastatin attenuates isoprenaline induced cardiac fibrosis in a mouse model

We investigated the effects of pravastatin (PRAVA) on isoprenaline (ISP) induced cardiac fibrosis using four groups of mice: untreated control, PRAVA, ISP, ISP + PRAVA groups. ISP, 20 mg/kg, was administered subcutaneously daily for 14 days. PRAVA, 20 mg/kg, was administered orally daily for 14 days. Mice were sacrificed on day15 and heart and blood samples were collected to investigate cardiac injury markers. The mean body weight for the ISP group on day 15 was decreased significantly compared to day 0; PRAVA increased the mean body weight slightly on day 15 of treatment compared to day 0. The heart:body weight ratio was increased in the ISP group compared to the control group, but the ratio was returned to near control ratio in the PRAVA + ISP group. The serum creatine kinase-myocardial band (CK-MB) level was reduced significantly in the PRAVA + ISP group compared to the ISP group. Serum triglyceride level was decreased significantly in ISP + PRAVA group compared to the ISP group. PRAVA administration significantly reduced tissue collagen I and III levels in the ISP + PRAVA group compared to the ISP group. Lipid oxidation was decreased and reduced glutathione activity was increased in the PRAVA + ISP group compared to the ISP group. IL-6, α-SMA, CTGF, TGF-β and SMAD-3 gene expressions were decreased in the PRAVA + ISP group compared to the ISP group. We found fewer inflammatory cells and less fibrosis in heart tissue in the PRAVA + ISP group compared to the ISP group. PRAVA decreased ISP induced cardiac fibrosis by reducing oxidative stress, collagen deposition and inflammation, as well as by decreasing expression of TGF-β, SMAD-3 and CTGF genes.

Animal models and animal-free innovations for cardiovascular research: current status and routes to be explored. Consensus document of the ESC Working Group on Myocardial Function and the ESC Working Group on Cellular Biology of the Heart

Cardiovascular diseases represent a major cause of morbidity and mortality, necessitating research to improve diagnostics, and to discover and test novel preventive and curative therapies, all of which warrant experimental models that recapitulate human disease. The translation of basic science results to clinical practice is a challenging task, in particular for complex conditions such as cardiovascular diseases, which often result from multiple risk factors and comorbidities. This difficulty might lead some individuals to question the value of animal research, citing the translational 'valley of death', which largely reflects the fact that studies in rodents are difficult to translate to humans. This is also influenced by the fact that new, human-derived in vitro models can recapitulate aspects of disease processes. However, it would be a mistake to think that animal models do not represent a vital step in the translational pathway as they do provide important pathophysiological insights into disease mechanisms particularly on an organ and systemic level. While stem cell-derived human models have the potential to become key in testing toxicity and effectiveness of new drugs, we need to be realistic, and carefully validate all new human-like disease models. In this position paper, we highlight recent advances in trying to reduce the number of animals for cardiovascular research ranging from stem cell-derived models to in situ modelling of heart properties, bioinformatic models based on large datasets, and state-of-the-art animal models, which show clinically relevant characteristics observed in patients with a cardiovascular disease. We aim to provide a guide to help researchers in their experimental design to translate bench findings to clinical routine taking the replacement, reduction, and refinement (3R) as a guiding concept.

Reciprocal organ interactions during heart failure: a position paper from the ESC Working Group on Myocardial Function

Heart failure-either with reduced or preserved ejection fraction (HFrEF/HFpEF)-is a clinical syndrome of multifactorial and gender-dependent aetiology, indicating the insufficiency of the heart to pump blood adequately to maintain blood flow to meet the body's needs. Typical symptoms commonly include shortness of breath, excessive fatigue with impaired exercise capacity, and peripheral oedema, thereby alluding to the fact that heart failure is a syndrome that affects multiple organ systems. Patients suffering from progressed heart failure have a very limited life expectancy, lower than that of numerous cancer types. In this position paper, we provide an overview regarding interactions between the heart and other organ systems, the clinical evidence, underlying mechanisms, potential available or yet-to-establish animal models to study such interactions and finally discuss potential new drug interventions to be developed in the future. Our working group suggests that more experimental research is required to understand the individual molecular mechanisms underlying heart failure and reinforces the urgency for tailored therapeutic interventions that target not only the heart but also other related affected organ systems to effectively treat heart failure as a clinical syndrome that affects and involves multiple organs.

Fibrosis of the diabetic heart: Clinical significance, molecular mechanisms, and therapeutic opportunities

In patients with diabetes, myocardial fibrosis may contribute to the pathogenesis of heart failure and arrhythmogenesis, increasing ventricular stiffness and delaying conduction. Diabetic myocardial fibrosis involves effects of hyperglycemia, lipotoxicity and insulin resistance on cardiac fibroblasts, directly resulting in increased matrix secretion, and activation of paracrine signaling in cardiomyocytes, immune and vascular cells, that release fibroblast-activating mediators. Neurohumoral pathways, cytokines, growth factors, oxidative stress, advanced glycation end-products (AGEs), and matricellular proteins have been implicated in diabetic fibrosis; however, the molecular links between the metabolic perturbations and activation of a fibrogenic program remain poorly understood. Although existing therapies using glucose- and lipid-lowering agents and neurohumoral inhibition may act in part by attenuating myocardial collagen deposition, specific therapies targeting the fibrotic response are lacking. This review manuscript discusses the clinical significance, molecular mechanisms and cell biology of diabetic cardiac fibrosis and proposes therapeutic targets that may attenuate the fibrotic response, preventing heart failure progression.

Diabetic fibrosis

Diabetes-associated morbidity and mortality is predominantly due to complications of the disease that may cause debilitating conditions, such as heart and renal failure, hepatic insufficiency, retinopathy or peripheral neuropathy. Fibrosis, the excessive and inappropriate deposition of extracellular matrix in various tissues, is commonly found in patients with advanced type 1 or type 2 diabetes, and may contribute to organ dysfunction. Hyperglycemia, lipotoxic injury and insulin resistance activate a fibrotic response, not only through direct stimulation of matrix synthesis by fibroblasts, but also by promoting a fibrogenic phenotype in immune and vascular cells, and possibly also by triggering epithelial and endothelial cell conversion to a fibroblast-like phenotype. High glucose stimulates several fibrogenic pathways, triggering reactive oxygen species generation, stimulating neurohumoral responses, activating growth factor cascades (such as TGF-β/Smad3 and PDGFs), inducing pro-inflammatory cytokines and chemokines, generating advanced glycation end-products (AGEs) and stimulating the AGE-RAGE axis, and upregulating fibrogenic matricellular proteins. Although diabetes-activated fibrogenic signaling has common characteristics in various tissues, some organs, such as the heart, kidney and liver develop more pronounced and clinically significant fibrosis. This review manuscript summarizes current knowledge on the cellular and molecular pathways involved in diabetic fibrosis, discussing the fundamental links between metabolic perturbations and fibrogenic activation, the basis for organ-specific differences, and the promises and challenges of anti-fibrotic therapies for diabetic patients.

Possible mechanisms involved in the effect of the subchronic administration of rosuvastatin on endothelial function in rats with metabolic syndrome

Metabolic syndrome is a multifaceted condition associated with a greater risk of various disorders (e.g., diabetes and heart disease). In a rat model of metabolic syndrome, an acute in vitro application of rosuvastatin causes relaxation of aortic rings. Since the outcome of a subchronic rosuvastatin treatment is unknown, the present study explored its effect on acetylcholine-induced vasorelaxation of aortic rings from rats with metabolic syndrome. Animals were submitted to a 16-week treatment, including a standard diet, a cafeteria-style diet (CAF-diet), or a CAF-diet with daily rosuvastatin treatment (10 mg/kg). After confirming the development of metabolic syndrome in rats, aortic segments were extracted from these animals (those treated with rosuvastatin and untreated) and the acetylcholine-induced relaxant effect on the corresponding rings was evaluated. Concentration-response curves were constructed for this effect in the presence/absence of L-NAME, ODQ, KT 5823, 4-aminopyridine (4-AP), tetraethylammonium (TEA), apamin plus charybdotoxin, glibenclamide, indomethacin, clotrimazole, and cycloheximide pretreatment. Compared to rings from control rats, acetylcholine-induced vasorelaxation decreased in rings from animals with metabolic syndrome, and was maintained at a normal level in animals with metabolic syndrome plus rosuvastatin treatment. The effect of rosuvastatin was inhibited by L-NAME, ODQ, KT 5823, TEA, apamin plus charybdotoxin, but unaffected by 4-AP, glibenclamide, indomethacin, clotrimazole, or cycloheximide. In conclusion, the subchronic administration of rosuvastatin to rats with metabolic syndrome improved the acetylcholine-induced relaxant response, involving stimulation of the NO/cGMP/PKG/Ca2+-activated K+ channel pathway.

The statins effects on HbA1c control among diabetic patients: An umbrella review of systematic reviews and meta-analyses of observational studies and clinical trials

Statins have impacts on the metabolism of glucose that might influence the progress of diabetes in non-diabetics or affect glycemic control in patients with existing diabetes. Experimental proof has been contradictory about whether some statins display beneficial properties while others indicate harmful impressions. Some systematic reviews of statins had stated conflicting findings on the concern of glucose metabolism. The current study investigates the published systematic reviews and meta-analyses to combine their results and give a clear situation regarding the influence of statins therapy on glycated hemoglobin (HbA1c). This study has valuable strength points; long follow-up period and big sample size.

Latest Updates on Lipid Management

Atherosclerotic cardiovascular disease (ASCVD) is the leading cause of death worldwide. Despite the clinical long-term and near-term benefits of lowering cholesterol in, respectively, primary and secondary prevention of ASCVD, cholesterol levels remain under-treated, with many patients not achieving their recommended targets. The present article will review the latest updates on lipid management with emphases on the different classes of cholesterol-lowering agents and their clinical uses.

Risk and Benefits of Statins in Glucose Control Management of Type II Diabetes

Worldwide statins are considered to be the first-line pharmacological treatment for dyslipidemia and reducing the risk of coronary heart disease. However, recently various studies have shown its adverse effect on glucose control among diabetic patients and the U.S. Food and Drug Administration have revised statin drug labels to include information that increases in fasting serum glucose and glycated hemoglobin levels have been reported. This systematic review objective is to evaluate the risks and benefits of statins in glucose control management of type 2 diabetes patients based on the 44 published journal articles included and obtained through MEDLINE full text, PubMed, Science Direct, Pro Quest, SAGE, Taylor and Francis Online, Google Scholar, High Wire, and Elsevier Clinical Key. Statins were found to affect glucose control through several ways, namely, by affecting insulin production and secretion by β-pancreatic cells, insulin resistance, insulin uptake by the muscles and adipocytes and production of adipokines. Current evidence available shows that most of the statins give unfavorable side effects with regards to glucose control among diabetic patients. A dose-dependent and time-dependent effect was also observed in some statins which may be present among other statins as well.

Effects of Pravastatin on Type 1 Diabetic Rat Heart with or without Blood Glycemic Control

Although statins have been suggested to attenuate the progression of diabetic cardiomyopathy, its effect without glycemic control remains unclear. Therefore, we evaluated the effect of pravastatin on diabetic rat hearts according to glycemic control. Rats were randomly divided into five groups: control (C), diabetes (D), diabetes with insulin (I), diabetes with pravastatin (P), and diabetes with insulin and pravastatin (IP). Eight weeks after allocated treatments, the heart was extracted and analyzed following echocardiography. Cardiac fibrosis was measured using Masson's trichrome stain. Cardiac expression of collagen I/III, matrix metalloproteinase (MMP)-2, MMP-9, and angiotensin-converting enzyme (ACE)/ACE2 was evaluated by immunohistochemistry and/or Western blot. Enzyme-linked immunosorbent assay was used for measuring reactive oxygen species (ROS). Diabetic groups without glycemic control (D and P) showed significantly impaired diastolic function and increased levels of cardiac fibrosis, collagen I/III, MMP-2, MMP-9, and ROS production. However, there were little significant differences in the outcomes among the control and two glucose-controlled diabetic groups (I and IP). Groups C and IP showed more preserved ACE2 and lower ACE expressions than the other groups did (D, I, and P). Our study suggested glycemic control would be more important to attenuate the progression of diabetic cardiomyopathy than pravastatin medication.

Medical management of aortic disease in Marfan syndrome

Marfan syndrome (MFS) is a hereditary disorder with numerous pathophysiological effects, some specifically creating elastic dysfunction in cardiovascular organs. Aortic dilatation, dissection and rupture are major concerns in the management of MFS patients. Predilection to form aneurysms is an indication for prophylactic medical management of thoracic aortic aneurysm disease in these patients. The current guidelines describe β-blockers as the standard of care with angiotensin receptor blockers (ARBs) emerging as an equal, if not better alternative. We elaborate current evidence for and against different medical regimens used for the medical management of MFS patients.

Atorvastatin reduces β-Adrenergic dysfunction in rats with diabetic cardiomyopathy

Background

In the diabetic heart the β-adrenergic response is altered partly by down-regulation of the β1-adrenoceptor, reducing its positive inotropic effect and up-regulation of the β3-adrenoceptor, increasing its negative inotropic effect. Statins have clinical benefits on morbidity and mortality in diabetic patients which are attributed to their “pleiotropic” effects. The objective of our study was to investigate the role of statin treatment on β-adrenergic dysfunction in diabetic rat cardiomyocytes.

Methods

β-adrenergic responses were investigated in vivo (echocardiography) and ex vivo (left ventricular papillary muscles) in healthy and streptozotocin-induced diabetic rats, who were pre-treated or not by oral atorvastatin over 15 days (50 mg.kg^-1.day^-1). Micro-array analysis and immunoblotting were performed in left ventricular homogenates. Data are presented as mean percentage of baseline ± SD.

Results

Atorvastatin restored the impaired positive inotropic effect of β-adrenergic stimulation in diabetic hearts compared with healthy hearts both in vivo and ex vivo but did not suppress the diastolic dysfunction of diabetes. Atorvastatin changed the RNA expression of 9 genes in the β-adrenergic pathway and corrected the protein expression of β1-adrenoceptor and β1/β3-adrenoceptor ratio, and multidrug resistance protein 4 (MRP4). Nitric oxide synthase (NOS) inhibition abolished the beneficial effects of atorvastatin on the β-adrenoceptor response.

Conclusions

Atorvastatin restored the positive inotropic effect of the β-adrenoceptor stimulation in diabetic cardiomyopathy. This effect is mediated by multiple modifications in expression of proteins in the β-adrenergic signaling pathway, particularly through the NOS pathway.

Attenuation of carotid neointimal formation after direct delivery of a recombinant adenovirus expressing glucagon-like peptide-1 in diabetic rats

AIMS

Enhancement of glucagon-like peptide-1 (GLP-1) reduces glucose levels and preserves pancreatic β-cell function, but its effect against restenosis is unknown.

METHODS AND RESULTS

We investigated the effect of subcutaneous injection of exenatide or local delivery of a recombinant adenovirus expressing GLP-1 (rAd-GLP-1) into carotid artery, in reducing the occurrence of restenosis following balloon injury. As a control, we inserted β-galactosidase cDNA in the same vector (rAd-βGAL). Otsuka Long-Evans Tokushima rats were assigned to three groups (n = 12 each): (1) normal saline plus rAd-βGAL delivery (NS + rAd-βGAL), (2) exenatide plus rAd-βGAL delivery (Exenatide + rAd-βGAL), and (3) normal saline plus rAd-GLP-1 delivery (NS + rAd-GLP-1). Normal saline or exenatide were administered subcutaneously from 1 week before to 2 weeks after carotid injury. After 3 weeks, the NS + rAd-βGAL group showed the highest intima-media ratio (IMR; 3.73 ± 0.90), the exenatide + rAd-βGAL treatment was the next highest (2.80 ± 0.51), and NS + rAd-GLP-1 treatment showed the lowest IMR (1.58 ± 0.48, P < 0.05 vs. others). The proliferation and migration of vascular smooth muscle cells and monocyte adhesion were decreased significantly after rAd-GLP-1 treatment, showing the same overall patterns as the IMR. In injured vessels, the apoptosis was greater and MMP2 expression was less in the NS + rAd-GLP-1 than in the exenatide or rAd-βGAL groups. In vitro expressions of matrix metalloproteinases-2 and monocyte chemoattractant protein-1 and nuclear factor-kappa-B-p65 translocation were decreased more in the NS + rAd-GLP-1 group than in the other two groups (all P < 0.05).

CONCLUSION

Direct GLP-1 overexpression showed better protection against restenosis after balloon injury via suppression of vascular smooth muscle cell migration, increased apoptosis, and decreased inflammatory processes than systemic exenatide treatment. This has potential therapeutic implications for treating macrovascular complications in diabetes.

Animal models of heart failure with preserved ejection fraction

Heart failure with preserved ejection fraction (HFpEF) constitutes a clinical syndrome in which the diagnostic criteria of heart failure are not accompanied by gross disturbances of systolic function, as assessed by ejection fraction. In turn, under most circumstances, diastolic function is impaired. Although it now represents over 50 % of all patients with heart failure, the mechanisms of HFpEF remain understood, precluding effective therapy. Understanding the pathophysiology of HFpEF has been restricted by both limited access to human myocardial biopsies and by the lack of animal models that fully mimic human pathology. Animal models are valuable research tools to clarify subcellular and molecular mechanisms under conditions where the comorbidities and other confounding factors can be precisely controlled. Although most of the heart failure animal models currently available represent heart failure with reduced ejection fraction, several HFpEF animal models have been proposed. However, few of these fulfil all the features present in human disease. In this review we will provide an overview of the currently available models to study HFpEF from rodents to large animals as well as present advantages and disadvantages of these models.

Treatment with atorvastatin attenuates progression of insulin resistance and pancreatic fibrosis in the Otsuka Long-Evans Tokushima fatty rats

PURPOSE

The effects of statins on insulin resistance (IR) and type 2 diabetes mellitus (T2DM) are still controversial and its effects on pancreatic fibrosis are poorly defined. The purpose of this study is to examine the effects of atorvastatin on these issues using the Otsuka Long-Evans Tokushima Fatty (OLETF) rat, an animal model of IR, T2DM and pancreatic fibrosis.

METHODS

Male OLETF rats were divided into 2 groups at 6weeks of age. The first group received a standard diet until the end of experimental period at age 28weeks. The second group was given a diet containing 0.05% atorvastatin from 6weeks of age, before the onset of IR and pancreatic fibrosis. The age-matched Long-Evans Tokushima Otsuka rats without presence of IR, T2DM and pancreatic fibrosis, received a standard diet and were used as a normal control.

RESULTS

Atorvastatin slightly decreased serum fasting glucose and insulin levels, but significantly improved index of IR compared with the untreated OLETF rats. In addition, atorvastatin markedly decreased transforming growth factor-β1 mRNA expression, myeloperoxidase activity and proportion of fibrotic area, and elevated superoxide dismutase activity in the pancreas compared with the untreated OLETF rats.

CONCLUSIONS

These findings suggest that atorvastatin exerts favorable influence on progression of IR and pancreatic inflammation and fibrosis via pleiotropic effect such as anti-oxidative property.

Biochemistry of Statins

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality worldwide. Elevated blood lipids may be a major risk factor for CVD. Due to consistent and robust association of higher low-density lipoprotein (LDL)-cholesterol levels with CVD across experimental and epidemiologic studies, therapeutic strategies to decrease risk have focused on LDL-cholesterol reduction as the primary goal. Current medication options for lipid-lowering therapy include statins, bile acid sequestrants, a cholesterol-absorption inhibitor, fibrates, nicotinic acid, and omega-3 fatty acids, which all have various mechanisms of action and pharmacokinetic properties. The most widely prescribed lipid-lowering agents are the HMG-CoA reductase inhibitors, or statins. Since their introduction in the 1980s, statins have emerged as the one of the best-selling medication classes to date, with numerous trials demonstrating powerful efficacy in preventing cardiovascular outcomes (Kapur and Musunuru, 2008 [1]). The statins are commonly used in the treatment of hypercholesterolemia and mixed hyperlipidemia. This chapter focuses on the biochemistry of statins including their structures, pharmacokinetics, and mechanism of actions as well as the potential adverse reactions linked to their clinical uses.

Diabetes-associated cardiac fibrosis: Cellular effectors, molecular mechanisms and therapeutic opportunities

Both type 1 and type 2 diabetes are associated with cardiac fibrosis that may reduce myocardial compliance, contribute to the pathogenesis of heart failure, and trigger arrhythmic events. Diabetes-associated fibrosis is mediated by activated cardiac fibroblasts, but may also involve fibrogenic actions of macrophages, cardiomyocytes and vascular cells. The molecular basis responsible for cardiac fibrosis in diabetes remains poorly understood. Hyperglycemia directly activates a fibrogenic program, leading to accumulation of advanced glycation end-products (AGEs) that crosslink extracellular matrix proteins, and transduce fibrogenic signals through reactive oxygen species generation, or through activation of Receptor for AGEs (RAGE)-mediated pathways. Pro-inflammatory cytokines and chemokines may recruit fibrogenic leukocyte subsets in the cardiac interstitium. Activation of transforming growth factor-β/Smad signaling may activate fibroblasts inducing deposition of structural extracellular matrix proteins and matricellular macromolecules. Adipokines, endothelin-1 and the renin-angiotensin-aldosterone system have also been implicated in the diabetic myocardium. This manuscript reviews our current understanding of the cellular effectors and molecular pathways that mediate fibrosis in diabetes. Based on the pathophysiologic mechanism, we propose therapeutic interventions that may attenuate the diabetes-associated fibrotic response and discuss the challenges that may hamper clinical translation.

Cardiac NO signalling in the metabolic syndrome

It is well documented that metabolic syndrome (i.e. a group of risk factors, such as abdominal obesity, elevated blood pressure, elevated fasting plasma glucose, high serum triglycerides and low cholesterol level in high-density lipoprotein), which raises the risk for heart disease and diabetes, is associated with increased reactive oxygen and nitrogen species (ROS/RNS) generation. ROS/RNS can modulate cardiac NO signalling and trigger various adaptive changes in NOS and antioxidant enzyme expressions/activities. While initially these changes may represent protective mechanisms in metabolic syndrome, later with more prolonged oxidative, nitrosative and nitrative stress, these are often exhausted, eventually favouring myocardial RNS generation and decreased NO bioavailability. The increased oxidative and nitrative stress also impairs the NO-soluble guanylate cyclase (sGC) signalling pathway, limiting the ability of NO to exert its fundamental signalling roles in the heart. Enhanced ROS/RNS generation in the presence of risk factors also facilitates activation of redox-dependent transcriptional factors such as NF-κB, promoting myocardial expression of various pro-inflammatory mediators, and eventually the development of cardiac dysfunction and remodelling. While the dysregulation of NO signalling may interfere with the therapeutic efficacy of conventional drugs used in the management of metabolic syndrome, the modulation of NO signalling may also be responsible for the therapeutic benefits of already proven or recently developed treatment approaches, such as ACE inhibitors, certain β-blockers, and sGC activators. Better understanding of the above-mentioned pathological processes may ultimately lead to more successful therapeutic approaches to overcome metabolic syndrome and its pathological consequences in cardiac NO signalling.

Murine models of diastolic dysfunction and heart failure with preserved ejection fraction

Left ventricular diastolic dysfunction leads to heart failure with preserved ejection fraction, an increasingly prevalent condition largely driven by modern day lifestyle risk factors. As heart failure with preserved ejection fraction accounts for almost one-half of all patients with heart failure, appropriate nonhuman animal models are required to improve our understanding of the pathophysiology of this syndrome and to provide a platform for preclinical investigation of potential therapies. Hypertension, obesity, and diabetes are major risk factors for diastolic dysfunction and heart failure with preserved ejection fraction. This review focuses on murine models reflecting this disease continuum driven by the aforementioned common risk factors. We describe various models of diastolic dysfunction and highlight models of heart failure with preserved ejection fraction reported in the literature. Strengths and weaknesses of the different models are discussed to provide an aid to translational scientists when selecting an appropriate model. We also bring attention to the fact that heart failure with preserved ejection fraction is difficult to diagnose in animal models and that, therefore, there is a paucity of well described animal models of this increasingly important condition.

The potential role of leptin in the vascular remodeling associated with obesity

BACKGROUND/OBJECTIVES

Extracellular matrix (ECM) participates in the vascular remodeling associated with obesity. We investigated the effects of leptin on the production of ECM components in primary cultured vascular smooth muscle cells (VSMCs) and whether leptin could be a mediator of obesity-induced vascular remodeling.

METHODS

T he effects of leptin (100 ng ml(-1)) on ECM components and superoxide anion production (O(2)(.-)) were evaluated in presence or absence of the antioxidant melatonin (10(-)(3) mmol l(-1)) or the inhibitor of phosphatidylinositol 3'-kinase (PI3K), LY294002 (2 × 10(-)(4) mmol l(-1)) in VSMCs from adult rats in order to explore the role of both oxidative stress and the participation of PI3K/Akt pathway in the effects of leptin. ECM components and O(2)(.-) were quantified in the aortic media of male Wistar rats fed a high-fat diet (HFD; 33.5% fat), or a standard diet (CT; 3.5% fat) for 6 weeks.

RESULTS

In VSMCs, leptin enhanced gene and protein levels of collagen I, fibronectin, transforming growth factor (TGF)-β and connective tissue growth factor (CTGF) but did not change those of collagen III and galectin-3. Leptin also increased O(2)(.-) and Akt phosphorylation in VSMCs. These effects were prevented by the presence of either melatonin or LY294002, except O(2)(.-) production in the case of PI3K inhibition. The increase in body weight in HFD rats was accompanied by aorta thickening due to an increase in media area. The aortic fibrosis observed in HFD rats was associated with high levels of leptin, collagen type I, fibronectin, TGF-β, CTGF, phosphorylated Akt and O(2)(.-). Aortic leptin levels were positively correlated with total collagen, collagen I, TGF-β and CTGF levels. No differences were observed in the levels of collagen III, elastin or galectin-3 between both the groups.

CONCLUSIONS

Leptin could participate in the vascular remodeling and stiffness associated with obesity by ECM production in VSMCs through the activation of oxidative stress-PI3K/Akt pathway and the production of the profibrotic factors TGF-β and CTGF.

Combination pravastatin and valsartan treatment has additive beneficial effects to simultaneously improve both metabolic and cardiovascular phenotypes beyond that of monotherapy with either drug in patients with primary hypercholesterolemia

Statin and angiotensin II type 1 receptor blocker therapy improves endothelial dysfunction using distinct mechanisms. We evaluated simultaneous vascular and metabolic responses to pravastatin and valsartan therapy, alone or in combination, in hypercholesterolemic patients. Forty-eight hypercholesterolemic patients (23 had metabolic syndrome) were given pravastatin 40 mg and placebo, pravastatin 40 mg and valsartan 160 mg, or valsartan 160 mg and placebo daily during each 2-month treatment period in a randomized, single-blind, placebo-controlled, crossover trial with three treatment arms and two washout periods (each 2 months). Brachial artery flow-mediated dilation and C-reactive protein improved to a greater extent with combined therapy compared with either monotherapy. Importantly, we also observed simultaneous improvement in metabolic phenotypes, with all three treatments causing increased plasma adiponectin levels, reduced fasting insulin levels, and increased insulin sensitivity relative to baseline measurements. For the first time in a statin combination trial, pravastatin combined with valsartan therapy increased plasma adiponectin, lowered fasting insulin levels, and improved insulin sensitivity in an additive manner when compared with monotherapy alone. In contrast to other statins, hydrophilic pavastatin may be combined with other drugs to safely reach lipid target levels while simultaneously improving the metabolic and cardiovascular phenotype of patients at high risk.

Murine models for pharmacological studies of the metabolic syndrome

Metabolic syndrome has been described as the association of insulin resistance, hypertension, hyperlipidemia and obesity. Its prevalence increased dramatically, mainly in developed countries. Animal models are essential to understand the pathophysiology of this syndrome. This review presents the murine models of metabolic syndrome the most often used in pharmacological studies. The most common metabolic syndrome models exhibit a non-functional leptin pathway, or metabolic disorders induced by high fat diets. In a first part, and after a short introduction on leptin, its receptor and mechanism of action, we provide a detailed description of each model: SHROB, SHHF, JCR:LA-cp, Zucker, ZDF, Wistar Ottawa Karlsburg W, and Otsuka Long-Evans Tokushima Fatty rats, ob/ob, db/db, agouti yellow and Mc4R KO mice. The second part of this review is dedicated to metabolic syndrome models obtained by high fat feeding.

Monocyte Chemoattractant Protein 1 (MCP-1) in obesity and diabetes

Monocyte Chemoattractant Protein-1 (MCP-1) is the first discovered and most extensively studied CC chemokine, and the amount of studies on its role in the etiologies of obesity- and diabetes-related diseases have increased exponentially during the past two decades. This review attempted to provide a panoramic perspective of the history, regulatory mechanisms, functions, and therapeutic strategies of this chemokine. The highlights of this review include the roles of MCP-1 in the development of obesity, diabetes, cardiovascular diseases, insulitis, diabetic nephropathy, and diabetic retinopathy. Therapies that specifically or non-specifically inhibit MCP-1 overproduction have been summarized.

Pravastatin normalizes endothelium-derived contracting factor-mediated response via suppression of Rho-kinase signalling in mesenteric artery from aged type 2 diabetic rat

AIM

Although pravastatin has known pleiotropic effects against adverse cardiovascular conditions, little is known about its effects on endothelium-derived contracting factor (EDCF)-mediated signalling. We aimed to determine the effects of pravastatin on the production of and responses to EDCF in superior mesenteric arteries isolated from rats at the chronic stage of type 2 diabetes.

METHODS

Contractions to acetylcholine (ACh) were examined in superior mesenteric artery rings from aged type 2 diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats (56-60 weeks old), from control age-matched non-diabetic Long-Evans Tokushima Otsuka (LETO) rats and from pravastatin-treated (10 mg kg(-1) , p.o., daily for 4 weeks) OLETF rats. Mesenteric artery expressions of cyclo-oxygenases (COXs), microsomal-PGE synthases (mPGESs), RhoA and Rho-kinase proteins, and also the level of phosphorylated ezrin, radixin and moesin (PERM), a substrate for Rho-kinase, were detected by Western blotting.

RESULTS

Arteries from OLETF rats exhibited (vs. LETO rats) (1) enhanced ACh-induced EDCF-mediated contractions, which were inhibited by the Rho-kinase inhibitor Y27632, (2) reductions in the ACh-stimulated release of both PGE(2) and superoxide and (3) increased COX-1 and PERM protein expressions. Mesenteric arteries from OLETF rats treated with pravastatin exhibited (vs. untreated OLETF) (1) reduced ACh-induced contraction, (2) suppressed ACh-induced PGE(2) production and superoxide generation and (3) reduced ACh-induced PERM protein expression.

CONCLUSIONS

These results suggest that pravastatin exerts beneficial effects against abnormal EDCF signalling by suppressing Rho-kinase and promoting antioxidant activity in the mesenteric arteries of rats at the chronic stage of type 2 diabetes.

Effect of a dipeptidyl peptidase-IV inhibitor, des-fluoro-sitagliptin, on neointimal formation after balloon injury in rats

BACKGROUND

Recently, it has been suggested that enhancement of incretin effect improves cardiac function. We investigated the effect of a DPP-IV inhibitor, des-fluoro-sitagliptin, in reducing occurrence of restenosis in carotid artery in response to balloon injury and the related mechanisms.

METHODS AND FINDINGS

Otsuka Long-Evans Tokushima Fatty rats were grouped into four: control (normal saline) and sitagliptin 100, 250 and 500 mg/kg per day (n = 10 per group). Sitagliptin or normal saline were given orally from 1 week before to 2 weeks after carotid injury. After 3 weeks of treatment, sitagliptin treatment caused a significant and dose-dependent reduction in intima-media ratio (IMR) in obese diabetic rats. This effect was accompanied by improved glucose homeostasis, decreased circulating levels of high-sensitivity C-reactive protein (hsCRP) and increased adiponectin level. Moreover, decreased IMR was correlated significantly with reduced hsCRP, tumor necrosis factor-α and monocyte chemoattractant protein-1 levels and plasminogen activator inhibitor-1 activity. In vitro evidence with vascular smooth muscle cells (VSMCs) demonstrated that proliferation and migration were decreased significantly after sitagliptin treatment. In addition, sitagliptin increased caspase-3 activity and decreased monocyte adhesion and NFκB activation in VSMCs.

CONCLUSIONS

Sitagliptin has protective properties against restenosis after carotid injury and therapeutic implications for treating macrovascular complications of diabetes.

Current and future pharmacological treatment strategies with regard to aortic disease in Marfan syndrome

INTRODUCTION

Marfan syndrome is a multisystemic connective tissue disorder caused mainly by mutations in the fibrillin-1 gene. The entire cardiovascular system is affected in patients with Marfan syndrome. Aortic root dilatation, aortic valve regurgitation or - the most feared and life-threatening symptom - aortic root dissection are the most common manifestations. Therapeutic strategies, such as prophylactic aortic root surgery and pharmacological therapy, focus on the prevention of aortic dissection. Currently, the standard medicinal treatments targeting aortic dilatation and dissection consist of agents generally used to lower blood pressure and/or the inotropic state of the heart. By these means, the cyclic repetitive forces exerted on the aortic wall are diminished and thus the onset of aortic dilatation is potentially prevented. Although these pharmacological agents may offer some benefit in reduction of aortic aneurysm expansion rate, they do not target the underlying cause of the progressive aortic degradation.

AREAS COVERED

This review discusses the effectiveness of frequently prescribed medications used to prevent and delay aortic complications in Marfan syndrome. New insights on the biochemical pathways leading to aortic disease are also discussed to highlight new targets for pharmacological therapy.

EXPERT OPINION

Recent insights in the transforming growth factor beta signaling pathway and inflammatory mechanisms in a well-established mouse model of Marfan syndrome, have led to studies exploring new pharmacological treatment strategies with doxycycline, statins and angiotensin II receptor blockers. Pharmacological therapy is focused more on prevention than on delay of aortic wall pathology in Marfan syndrome. Of the new pharmacological treatment strategies targeting aortic pathology in Marfan syndrome, angiotensin receptor type 1 blockers are promising candidates, with several clinical trials currently ongoing.

Pravastatin reduces Marfan aortic dilation

BACKGROUND

The sequelae of aortic root dilation are the lethal consequences of Marfan syndrome. The root dilation is attributable to an imbalance between deposition of matrix elements and metalloproteinases in the aortic medial layer as a result of excessive transforming growth factor-beta signaling. This study examined the efficacy and mechanism of statins in attenuating aortic root dilation in Marfan syndrome and compared effects to the other main proposed preventative agent, losartan.

METHODS AND RESULTS

Marfan mice heterozygous for a mutant allele encoding a cysteine substitution in fibrillin-1 (C1039G) were treated daily from 6 weeks old with pravastatin 0.5 g/L or losartan 0.6 g/L. The end points of aortic root diameter (n=25), aortic thickness, and architecture (n=10), elastin volume (n=5), dp/dtmax (maximal rate of change of pressure) (cardiac catheter; n=20), and ultrastructural analysis with stereology (electron microscopy; n=5) were examined. The aortic root diameters of untreated Marfan mice were significantly increased in comparison to normal mice (0.161 ± 0.001 cm vs 0.252 ± 0.004 cm; P<0.01). Pravastatin (0.22 ± 0.003 cm; P<0.01) and losartan (0.221 ± 0.004 cm; P<0.01) produced a significant reduction in aortic root dilation. Both drugs also preserved elastin volume within the medial layer (pravastatin 0.23 ± 0.02 and losartan 0.29 ± 0.03 vs untreated Marfan 0.19 ± 0.02; P=0.01; normal mice 0.27 ± 0.02). Ultrastructural analysis showed a reduction of rough endoplasmic reticulum in smooth muscle cells with pravastatin (0.022 ± 0.004) and losartan (0.013 ± 0.001) compared to untreated Marfan mice (0.035 ± 0.004; P<0.01).

CONCLUSIONS

Statins are similar to losartan in attenuating aortic root dilation in a mouse model of Marfan syndrome. They appear to act through reducing the excessive protein manufacture by vascular smooth muscle cells, which occurs in the Marfan aorta. As a drug that is relatively well-tolerated for long-term use, it may be useful clinically.

Impairment of long-term potentiation in the hippocampus of alcohol-treated OLETF rats

Type 2 diabetes and chronic heavy alcohol consumption each have been known to be associated with the impairment of hippocampus-dependent cognitive functions. Although both conditions often coexist clinically and there is accumulated evidence of a relationship between the two, the combined effect on hippocampal long-term potentiation (LTP) has not yet been investigated. We compared the effect of type 2 diabetes itself with that of type 2 diabetes with chronic heavy alcohol consumption on the hippocampal LTP using Otsuka Long-Evans Tokushima Fatty (OLETF) rat model, which resembles the characteristics of human type 2 diabetes. Ten of 16-week-old male OLETF rats were randomized into two treatment groups according to weight: the OLETF-Alcohol (O-A, n=5) and the OLETF-Control (O-C, n=5). The rats in the O-A group were fed Lieber-DeCarli Regular EtOH over a 10-week period and the amount of alcohol consumption was 8.42±2.52g/kg/day. To ensure the effect of poor glycemic control on LTP, intraperitoneal glucose tolerance test was performed after a 10-week treatment. The hippocampal LTP was measured by extracellular field excitatory post-synaptic potentials at Shaffer collateral (SC) synapses in the CA1 region. Although the O-A group showed significantly lower fasting and postprandial glucose (P<0.01 and P=0.02, respectively), the hippocampal LTP was more significantly attenuated in the O-A group than the O-C group (P=0.032). The results of this study suggested that chronic heavy alcohol consumption could potentiate the impairment of hippocampal LTP in individuals with impaired glucose tolerance or early type 2 diabetes, even though it did not aggravate, but did improve glycemic control. Clinical attention to chronic heavy drinking will be required in preventing cognitive impairment in individuals with type 2 diabetes.

Treatment with pravastatin attenuates progression of chronic pancreatitis in rat

As appropriate therapies for pancreatic fibrosis and inflammation are limited, prognosis of chronic pancreatitis has not improved to date. Recent studies have shown that statins improve inflammation and fibrosis in several organs. We therefore examined the therapeutic effect of pravastatin on progression of chronic pancreatitis by starting this treatment after induction of pancreatic fibrosis in rats. Chronic pancreatitis was induced by continuous pancreatic ductal hypertension (PDH) for 14 days according to our previous study. Pravastatin at a dose of 10 mg/kg/day was administrated directly into the duodenum via cannula from 2 days after induction of PDH. Progression of pancreatic fibrosis and expression levels of transforming growth factor-β1 and tumor necrosis factor-α mRNA were markedly attenuated after commencement of pravastatin compared with untreated group with PDH. In addition, pravastatin treatment markedly improved pancreatic exocrine function and significantly elevated expression level of interleukin (IL)-10 and superoxide dismutase activity in the pancreas compared with the untreated group with PDH. These results revealed that pravastatin substantially attenuates the progression of pancreatic inflammation, fibrosis and exocrine dysfunction probably by its anti-oxidative property and overproduction of IL-10 in animal model of chronic pancreatitis. These results provide an experimental evidence that pravastatin exerts beneficial effect for progression of chronic pancreatitis.

Resistant hypertension in the high-risk metabolic patient

The metabolic syndrome is a constellation of metabolic and vascular abnormalities that include insulin resistance with compensatory hyperinsulinemia, central or visceral obesity, hypertension, dyslipidemia, microalbuminuria, and oxidative stress as well as prothrombotic and inflammatory abnormalities that contribute to a hypercoagulable state and systemic endothelial dysfunction. Visceral adipose tissue is now known to secrete into the circulation a number of protein and nonprotein factors that regulate glucose metabolism in traditional insulin-sensitive tissue as well as nontraditional insulin-sensitive tissue including cardiovascular tissue. Collectively, this constellation of factors that lead to metabolic dysregulation contributes to a substantial risk for adverse cardiovascular and renal outcomes. The development of a particularly resistant form of hypertension in these individuals can be attributed to a number of factors including vasoconstriction from increased sympathetic activation, proinflammatory cytokines, and inappropriate activation of the renin-angiotensin-aldosterone system. The management of hypertension in such patients can be challenging and generally requires nonpharmacologic as well as pharmacologic interventions.

Effects of fluvastatin on insulin resistance and cardiac morphology in hypertensive patients

Among hypertensive patients, cardiovascular disease morbidity is common, even in those who are adequately treated. New pharmacological strategies to mitigate the burden of arterial hypertension are needed. This 12-month, randomized, double-blind placebo-controlled study investigated the effect of statin (fluvastatin) treatment on ambulatory blood pressure (ABP), exercise blood pressure (EBP), myocardial structure, endothelial function and insulin resistance in 50 hypertensive patients. At baseline, the groups were comparable in terms of demographic characteristics, ABP, EBP, endothelial function and homeostasis model assessment of insulin resistance (HOMA-IR). At the end of the study, there was no difference between groups in terms of resting systolic blood pressure. However, maximum systolic EBP was lower in the treatment group than in the placebo group (175 ± 18 vs 192 ± 23 mm Hg, P<0.05), as was left ventricular mass index (LVMI; 82 ± 15 vs 100 ± 23, P<0.05), and HOMA-IR index was lower after fluvastatin treatment (2.77 ± 1.46 vs 3.33 ± 1.73, P<0.05). Changes in lipid profile were not correlated with blood pressure, endothelial function, LVMI or HOMA-IR data. In hypertensive patients, fluvastatin can improve maximum systolic EBP, myocardial remodelling and insulin resistance, independently of lipid profile variations and endothelial function.

Beneficial direct adipotropic actions of pitavastatin in vitro and their manifestations in obese mice

OBJECTIVE

Prevention of cardiovascular complications in obese patients frequently includes statin administration for coexisting dyslipidemia. Herein, we investigated the impacts of pitavastatin at clinically relevant doses on adipose dysfunction and insulin resistance.

METHODS

We treated 3T3-L1 preadipocytes with 10-100 ng/ml pitavastatin from initiation of differentiation (Day 0) to Day 8 (differentiation/maturation phase) or from Day 8 to Day 16 (post-maturation phase). Subsequently, we administered pitavastatin (6.2mg/day/kg) to 7-week-old female KKAy mice for 6 weeks; untreated KKAy mice served as obese controls.

RESULTS

Pitavastatin impaired neither lipogenesis nor adiponectin expression during the differentiation/maturation phase. During the post-maturation phase, pitavastatin prevented excessive triglyceride accumulation, which was associated with attenuated glucose transporter-4 expression, and dose-dependently upregulated hormone-sensitive lipase expression. Decrements in the adiponectin/plasminogen activator-1 ratio were also dose-dependently inhibited. In KKAy mice, Coulter counter analyses revealed that pitavastatin treatment significantly decreased (by 16.8%) the frequency of hypertrophic adipocytes (>150 microm in diameter) in parametrial adipose pads, of which total weight remained unaltered. Correspondingly, plasma adiponectin was significantly higher in pitavastatin-treated KKAy mice than in the untreated KKAy mice (12.5+/-3.8 microg/ml vs. 8.3+/-1.5 microg/ml, p<0.05). Moreover, the area under the time-glucose curve after intraperitoneal insulin was decreased by 16% in pitavastatin-treated KKAy mice (p<0.05 vs. untreated controls).

CONCLUSIONS

Pitavastatin did not impair differentiation/maturation of preadipocytes and prevented their deterioration with hypertrophy after maturation at clinical concentrations in vitro. These effects likely contributed to improved insulin sensitivity, in an obese model, via prevention of adipocyte hypertrophy and adipocytokine dysregulation.

Effect of long- and short-term treatments with pravastatin on diabetes mellitus and pancreatic fibrosis in the Otsuka-Long-Evans-Tokushima fatty rat

BACKGROUND AND PURPOSE

The effects of statins on diabetes mellitus (DM) are controversial, and their effects on pancreatic fibrosis are poorly defined. We investigated the effect of long- and short-term treatments with pravastatin on the development of DM and pancreatic fibrosis in DM-prone Otsuka-Long-Evans-Tokushima Fatty (OLETF) rats.

EXPERIMENTAL APPROACH

Male OLETF rats were divided into four groups at 12 weeks of age. The first group received a standard rat diet until the end of the experimental period at age 80 weeks. The second group was given a diet containing 0.05% pravastatin from 12 weeks of age, before the onset of DM and pancreatic fibrosis, and the third group was given the same pravastatin diet from 28 weeks of age, after the onset of DM and pancreatic fibrosis, until age 80 weeks. The fourth group received the same pravastatin diet only for 16 weeks, from 12 to 28 weeks of age, and switched to a standard diet. Progressions of DM and pancreatic fibrosis were evaluated.

KEY RESULTS

Long-term treatments with pravastatin, either from 12 or 28 weeks of age, decreased serum glucose concentration and fibrotic area, elevated superoxide dismutase activity and down-regulated transforming growth factor-beta1 mRNA in the pancreas. In contrast, after a short-term treatment with pravastatin, these parameters markedly deteriorated after its cessation.

CONCLUSIONS AND IMPLICATIONS

The results suggest that long-term treatment with pravastatin improves DM and pancreatic fibrosis via anti-oxidative and anti-fibrotic properties, whereas cessation of pravastatin abolishes these beneficial effects, and accelerates DM and pancreatic fibrosis.

Characteristic changes in coronary artery at the early hyperglycaemic stage in a rat type 2 diabetes model and the effects of pravastatin

BACKGROUND AND PURPOSE

Diabetes is a risk factor for the development of coronary artery disease but it is not known whether the functions of endothelium-derived nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF) in coronary arteries are altered in the early stage of diabetes. Such alterations and the effects of pravastatin were examined in left anterior descending coronary arteries (LAD) from Otsuka Long-Evans Tokushima Fatty (OLETF) rats (type 2 diabetes model) at the early hyperglycaemic stage [vs. non-diabetic Long-Evans Tokushima Otsuka (LETO) rats].

EXPERIMENTAL APPROACH

Isometric tension, membrane potential and superoxide production were measured, as were protein expression of NAD(P)H oxidase components and endothelial NO synthase (eNOS).

KEY RESULTS

Superoxide production and the protein expressions of both the nicotinamide adenine dinucleotide (phosphate) [NAD(P)H] oxidase components and eNOS were increased in OLETF rats. These changes were normalized by pravastatin administration. Not only acetylcholine (ACh)-induced endothelial NO production but also functions of endothelium-derived NO [from (i) the absolute tension induced by epithio-thromboxane A(2) (STA(2)) or high K(+); (ii) enhancement of the STA(2)-contraction by a nitric oxide synthase (NOS) inhibitor; and (iii) the ACh-induced endothelium-dependent relaxation of high K(+)-induced contraction] or EDHF [from (iv) ACh-induced endothelium-dependent smooth muscle cell hyperpolarization and relaxation in the presence of a NOS inhibitor] were similar between LETO and OLETF rats [whether or not the latter were pravastatin-treated or -untreated].

CONCLUSIONS AND IMPLICATIONS

Under conditions of increased vascular superoxide production, endothelial function is retained in LAD in OLETF rats at the early hyperglycaemic stage, partly due to enhanced endothelial NOS protein expression. Inhibition of superoxide production may contribute to the beneficial vascular effects of pravastatin.

Improvement of glucose intolerance by combination of pravastatin and olmesartan in type II diabetic KK-A(y) mice

The effects of the coadministration of pravastatin and an angiotensin type 1 (AT(1)) receptor blocker, olmesartan, on glucose intolerance were examined using type II diabetic mice. Male KK-A(y) mice (8 weeks of age) were treated with pravastatin and/or olmesartan for 2 weeks. An oral glucose tolerance test (OGTT) was performed with an administration of 2 g kg(-1) glucose. Tissue glucose uptake was determined using 2-[(3)H]deoxyglucose. The treatment of mice with pravastatin attenuated the increase in the plasma glucose level during OGTT in a dose-dependent manner, without affecting the plasma insulin level. Pravastatin increased glucose uptake in insulin-sensitive tissue such as the skeletal muscle and adipose tissue after treatment at 5-20 mg kg(-1) day(-1) for 2 weeks, but not at 1 mg kg(-1) day(-1). The combination of a noneffective dose of pravastatin (1 mg kg(-1) day(-1)) and a noneffective dose of olmesartan (0.5 mg kg(-1) day(-1)) synergistically improved OGTT without affecting the plasma insulin level. This combination also increased 2-[(3)H]deoxyglucose uptake in the skeletal muscle and adipose tissue. The effects of pravastatin or olmesartan on OGTT and tissue 2-[(3)H]deoxyglucose uptake were significantly enhanced by an antioxidant, tempol, whereas the effects of a pravastatin-olmesartan combination were not further enhanced by tempol. These results indicate that the combination of pravastatin and olmesartan synergistically improves glucose intolerance through an increase in tissue glucose uptake. The effects seem to be mediated by an increase in insulin sensitivity through the inhibition of oxidative stress.

Effects of combined olmesartan and pravastatin on glucose intolerance and cardiovascular remodeling in a metabolic-syndrome model

Hypertension and dyslipidemia frequently coexist in patients with progressive insulin resistance and thus constitute metabolic syndrome. We sought to determine the merits of combining an angiotensin II receptor blocker and a 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitor in treating this pathological condition. Five-week-old Otsuka Long-Evans Tokushima Fatty rats, a model of metabolic syndrome, were untreated or treated with olmesartan 3 mg kg(-1) per day, pravastatin 30 mg kg(-1) per day or their combination for 25 weeks. Long-Evans Tokushima Otsuka rats served as normal controls. The antihypertensive effect of olmesartan and the lipid-lowering properties of pravastatin were both augmented by the combination. The oral glucose tolerance test revealed that only the combined treatment significantly reduced the area under the time-glucose curve, which was accompanied by augmented adiponectin messenger RNA expression in epididymal adipose tissue. Although the total cardiac endothelial nitric oxide synthetase (eNOS) content did not significantly differ among the groups, the combined treatment significantly increased the content of dihydrofolate reductase, a key eNOS coupler. Dihydroethidium staining of the aorta showed that the combination most significantly attenuated superoxide production. Moreover, Azan-Mallory staining revealed that the combination most significantly limited the perivascular fibrosis and wall thickening of intramyocardial coronary arteries. In conclusion, the combination of olmesartan and pravastatin augmented adiponectin expression in white adipose tissue and improved glucose tolerance in a rat model of metabolic syndrome, which was associated with more significant ameliorations of cardiovascular redox state and remodeling than those by treatments with either agent alone.

Therapeutic interventions and oxidative stress in diabetes

Many therapeutic agents that are used in patients with diabetes mitigate oxidative stress. These agents are of particular interest because oxidative stress is elevated in diabetes and is thought to contribute to vascular dysfunction. Agents that merely quench already formed reactive oxygen species have demonstrated limited success in improving cardiovascular outcomes. Thus, although vitamin E, C, and alpha lipoic acid appeared promising in animal models and initial human studies, subsequent larger trials have failed to demonstrate improvement in cardiovascular outcomes. Drugs that limit the production of oxidative stress are more successful in improving vascular outcomes in patients with diabetes. Thus, although statins, ACE inhibitors, ARBs and thiazolinediones are used for varied clinical purposes, their increased efficacy in improving cardiovascular outcomes is likely related to their success in reducing the production of reactive oxygen species at an earlier part of the cascade, thereby more effectively decreasing the oxidative stress burden. In particular, statins and ACE inhibitors/ ARBs appear the most successful at reducing oxidative stress and vascular disease and have potential for synergistic effects.

Progenitor cell therapy in a porcine acute myocardial infarction model induces cardiac hypertrophy, mediated by paracrine secretion of cardiotrophic factors including TGFbeta1

Administration of endothelial progenitor cells (EPC) is a promising therapy for post-infarction cardiac repair. However, the mechanisms that underlie apparent beneficial effects on myocardial remodeling are unclear. In a porcine model of acute myocardial infarction, we investigated the therapeutic effects of a mixed population of culture modified peripheral blood mononuclear cells (termed hereafter porcine EPC). Porcine EPC were isolated using methods identical to those previously adopted for harvest of EPC in human cell therapy studies. In addition the therapeutic effects of paracrine factors secreted by these cells was evaluated in vitro and in vivo. Intracoronary injection of autologous porcine EPC was associated with increased infarct territory mass and improved regional ventricular systolic function at 2 months compared to control. Treatment with conditioned media derived from autologous EPC was associated with similar improved effects on infarct territory mass and function. Histologic analysis of the infarct territory revealed significantly increased cardiomyocyte size in EPC and conditioned media treated groups, when compared to controls. A paracrine EPC effect was also verified in a pure myocardial preparation in which cardiomyocytes devoid of fibroblast, neuronal and vascular elements directly responded by increasing cell mass when exposed to the same conditioned media. Analysis of conditioned media revealed elevated levels of TGFbeta1 (human 267.3+/-11.8 pg/ml, porcine 57.1+/-6.1 pg/ml), a recognized mediator of hypertrophic signaling in the heart. Neutralizing antibodies to TGFbeta1 attenuated the pro-hypertrophic effect of conditioned media, and use of recombinant TGFbeta1 added to fresh media replicated the pro-hypertrophic effects of conditioned media in vitro. These data demonstrate the potential of paracrine factors secreted from endothelial progenitor cells to induce cardiomyocyte hypertrophy contributing to increased infarct territory LV mass, with favorable medium term effects on regional function following myocardial infarction.

Effects of pravastatin on obesity, diabetes, and adiponectin in diet-induced obese mice

OBJECTIVE

The aim of this study was to investigate the in vivo effects of pravastatin on the development of obesity and diabetes in diet-induced obese (DIO) mice.

METHODS AND PROCEDURES

We examined food intake, body-weight changes, visceral white adipose tissue (WAT) adiponectin and resistin levels, and energy metabolism.

RESULTS

Treatment with 100 mg/kg/day pravastatin for 28 days decreased diet-induced weight gain and visceral adiposity. In addition, the weight of the WAT, the triglyceride (TG) contents of the liver and muscles, and the levels of serum insulin improved in the pravastatin-treated DIO mice. Furthermore, pravastatin treatment changed the WAT adiponectin and resistin mRNA expression and serum levels compared with the controls. Finally, pravastatin treatment increased oxygen consumption and decreased the respiratory quotient (RQ).

DISCUSSION

Pravastatin treatment prevents the development of obesity and diabetes in DIO mice. The prevention of obesity may be mediated by increased oxygen consumption and a decrease in the RQ. These results provide novel insights into the use of pravastatin as a therapeutic tool for metabolic syndromes.

Effects of atorvastatin and pravastatin on glucose tolerance, adipokine levels and inflammatory markers in hypercholesterolaemic patients

Several randomized clinical trials have suggested that atorvastatin and pravastatin may differ in terms of their pleiotropic effects. To verify this, we compared the effects of both statins on glucose tolerance, adipokine concentrations and inflammatory markers. A total of 36 hypercholesterolaemic patients without known coronary heart disease (CHD) were enrolled in an open-label, randomized, crossover study. The patients received pravastatin or atorvastatin (10 mg/day) for 4 months and then switched to the other statin for an additional 4 months. At the end of both treatment periods, atorvastatin significantly reduced the concentration of serum lipids (total and low-density lipoprotein-cholesterol and triglycerides) and inflammatory markers (high-sensitivity C-reactive protein and tumour necrosis factor-a) and increased serum adiponectin levels compared with pravastatin treatment. Although these effects would be expected to improve insulin sensitivity, atorvastatin did not affect glucose tolerance, which was assessed by fasting glucose and insulin concentrations, the homeostasis model assessment index and glycosylated haemoglobin (HbA(1c)) levels. Only obese patients showed increased HbA(1c) levels after atorvastatin treatment. Our results suggest that atorvastatin has both advantages and disadvantages compared with pravastatin treatment. Further studies are required to compare the relative clinical value of atorvastatin and pravastatin, especially in obese patients without CHD.

Fluvastatin decreases cardiac fibrosis possibly through regulation of TGF-beta(1)/Smad 7 expression in the spontaneously hypertensive rats

Statins ameliorate myocardial fibrosis after myocardial infarction. We designed this study to determine whether fluvastatin reduced hypertension-induced myocardial hypertrophy and fibrosis and whether these fluvastatin effects involved transforming growth factor beta1 (TGF-beta1) and Smad 7, factors known to play a role in the myocardial hypertrophy and fibrosis. We randomized 14 week old spontaneously hypertensive rats (SHRs) to receiving vehicle or 5-20 mg/kg/day fluvastatin for 8 weeks. Wistar Kyoto (WKY) rats receiving vehicle or 10 mg/kg/day fluvastatin were also studied. SHRs had an increased blood pressure, left ventricular hypertrophy and fibrosis compared with WKY rats. SHRs also had an elevated TGF-beta1 expression and a decreased Smad 7 expression. These changes in SHRs were dose-dependently attenuated by fluvastatin. For example, the hydroxyproline content was 3.2+/-0.1, 4.0+/-0.1 and 3.5+/-0.1 microg/mg heart and the Smad 7 protein expression was 5.1+/-0.6, 1.0+/-0.1 and 4.1+/-0.7 arbitrary units for WKY rats, SHRs and SHRs receiving 20 mg/kg/day fluvastatin, respectively. The hydroxyproline content in the SHRs treated with or without fluvastatin was positively correlated with the left ventricular mass index, systolic blood pressure and the amount of TGF-beta1 proteins and negatively correlated with the Smad 7 expression level. The left ventricular mass index was positively correlated with the systolic blood pressure. Fluvastatin did not alter the blood pressure, left ventricular mass index and collagen content of WKY rats. These results suggest that fluvastatin reduces hypertension-induced myocardial hypertrophy and fibrosis. These effects may involve an increased expression of Smad 7 and a decreased expression of TFG-beta1. Our results call for clinical studies to evaluate these fluvastatin effects in hypertensive patients.

Exogenous ghrelin attenuates the progression of chronic hypoxia-induced pulmonary hypertension in conscious rats

Chronic exposure to hypoxia, a common adverse consequence of most pulmonary disorders, can lead to a sustained increase in pulmonary arterial pressure (PAP), right ventricular hypertrophy, and is, therefore, closely associated with heart failure and increased mortality. Ghrelin, originally identified as an endogenous GH secretagogue, has recently been shown to possess potent vasodilator properties, likely involving modulation of the vascular endothelium and its associated vasoactive peptides. In this study we hypothesized that ghrelin would impede the pathogenesis of pulmonary arterial hypertension during chronic hypoxia (CH). PAP was continuously measured using radiotelemetry, in conscious male Sprague Dawley rats, in normoxia and during 2-wk CH (10% O(2)). During this hypoxic period, rats received a daily sc injection of either saline or ghrelin (150 microg/kg). Subsequently, heart and lung samples were collected for morphological, histological, and molecular analyses. CH significantly elevated PAP in saline-treated rats, increased wall thickness of peripheral pulmonary arteries, and, consequently, induced right ventricular hypertrophy. In these rats, CH also led to the overexpression of endothelial nitric oxide synthase mRNA and protein, as well as endothelin-1 mRNA within the lung. Exogenous ghrelin administration attenuated the CH-induced overexpression of endothelial nitric oxide synthase mRNA and protein, as well as endothelin-1 mRNA. Consequently, ghrelin significantly attenuated the development of pulmonary arterial hypertension, pulmonary vascular remodeling, and right ventricular hypertrophy. These results demonstrate the therapeutic benefits of ghrelin for impeding the pathogenesis of pulmonary hypertension and right ventricular hypertrophy, particularly in subjects prone to CH (e.g. pulmonary disorders).

Differential impact of atorvastatin vs pravastatin on progressive insulin resistance and left ventricular diastolic dysfunction in a rat model of type II diabetes

BACKGROUND

Controversy exists regarding the effects of statin therapy on progressive insulin resistance (IR) and its consequences, in the present study a rat model of spontaneously developing type II diabetes mellitus (DM) was used to examine the impact of atorvastatin (AS) vs pravastatin (PS).

METHODS AND RESULTS

The Otsuka Long-Evans Tokushima Fatty rats were either untreated or treated with 100 mg/kg per day of AS or PS from 6 weeks of age for 24 weeks. AS achieved much greater lipid lowering than PS. Serial oral glucose tolerance tests revealed new-onset diabetes was delayed by PS only. The untreated rats exhibited a progressive decrease in plasma adiponectin, increases in plasma leptin and tumor necrosis factor-alpha, and reduction of plasma nitric oxide (NO), which were limited more by PS than AS. PS, but not AS, enhanced adiponectin mRNA expression in white adipose tissue at 30 weeks. Cardiac endothelial NO synthase expression was upregulated, and overexpression of both transforming growth factor-beta1 and monocyte chemoattractant protein-1 mRNA was limited more by PS than AS. Coronary perivascular fibrosis at 30 weeks was suppressed only by PS, which was accompanied by preserved left ventricular diastolic function assessed with Doppler echocardiography.

CONCLUSIONS

The moderate lipid lowering by PS, but not the intensive lipid lowering by AS, prevented new-onset DM and diastolic dysfunction in a rat model of IR, and this was associated with preferable adipocytokine profiles and cardiac redox states.

Role of AT1 receptor in isoproterenol-induced cardiac hypertrophy and oxidative stress in mice

Elevated activities of the sympathetic nerve and renin-angiotensin systems are common features of heart failure. This study was designed to investigate the roles of the AT1 receptor in cardiac hypertrophy and oxidative stress during excessive beta-adrenoceptor stimulation using an AT1 receptor antagonist (ARB) and AT1a receptor-deficient (AT1aR(-/-)) mice. Isoproterenol (ISO) was given to C57BL mice with or without ARB (olmesartan) treatment and to AT1aR(-/-) mice by a subcutaneously implanted osmotic mini-pump for 11 days at a rate of 15 mg/kg/day. Chronic ISO infusion to C57BL mice caused concentric cardiac hypertrophy (sham; 4.1+/-0.1, ISO; 5.2+/-0.2 mg/g heart to body weight ratio), accompanied by enhancement of cardiac collagen accumulation, lipid peroxidation, superoxide generation and NADPH oxidase activity. The AT1a and beta-1,2 receptor mRNA expressions were down-regulated in the heart of ISO-infused mice. Olmesartan markedly suppressed cardiac mass enlargement as well as increases of oxidative indicators without any effects on heart rate. Olmesartan did not affect the cardiac angiotensin and beta-adrenergic receptor mRNA expression patterns. The AT1a receptor contribution to ISO-induced cardiac hypertrophy was reproduced in AT1aR(-/-) mice. These data suggest that the AT1 receptor plays a crucial role in the development of cardiac hypertrophy and oxidative stress under excessive beta-adrenergic stimulation, and that ARB treatment is beneficial for sympatho-excitatory cardiac hypertrophy and failure in mice.