Long-term in vivo resistin overexpression induces myocardial dysfunction and remodeling in rats

The role of nonmyocardial cells in the development of diabetic cardiomyopathy and the protective effects of FGF21: a current understanding

Diabetic cardiomyopathy (DCM) represents a unique myocardial disease originating from diabetic metabolic disturbances that is characterized by myocardial fibrosis and diastolic dysfunction. While recent research regarding the pathogenesis and treatment of DCM has focused primarily on myocardial cells, nonmyocardial cells-including fibroblasts, vascular smooth muscle cells (VSMCs), endothelial cells (ECs), and immune cells-also contribute significantly to the pathogenesis of DCM. Among various therapeutic targets, fibroblast growth factor 21 (FGF21) has been identified as a promising agent because of its cardioprotective effects that extend to nonmyocardial cells. In this review, we aim to elucidate the role of nonmyocardial cells in DCM and underscore the potential of FGF21 as a therapeutic strategy for these cells.

Epigenetic Network in Immunometabolic Disease

Although a large amount of data consistently shows that genes affect immunometabolic characteristics and outcomes, epigenetic mechanisms are also heavily implicated. Epigenetic changes, including DNA methylation, histone modification, and noncoding RNA, determine gene activity by altering the accessibility of chromatin to transcription factors. Various factors influence these alterations, including genetics, lifestyle, and environmental cues. Moreover, acquired epigenetic signals can be transmitted across generations, thus contributing to early disease traits in the offspring. A closer investigation is critical in this aspect as it can help to understand the underlying molecular mechanisms further and gain insights into potential therapeutic targets for preventing and treating diseases arising from immuno-metabolic dysregulation. In this review, the role of chromatin alterations in the transcriptional modulation of genes involved in insulin resistance, systemic inflammation, macrophage polarization, endothelial dysfunction, metabolic cardiomyopathy, and nonalcoholic fatty liver disease (NAFLD), is discussed. An overview of emerging chromatin-modifying drugs and the importance of the individual epigenetic profile for personalized therapeutic approaches in patients with immuno-metabolic disorders is also presented.

Regulation of cardiovascular health and disease by visceral adipose tissue-derived metabolic hormones

Visceral adipose tissue (VAT) is a metabolic organ known to regulate fat mass, and glucose and nutrient homeostasis. VAT is an active endocrine gland that synthesizes and secretes numerous bioactive mediators called 'adipocytokines/adipokines' into systemic circulation. These adipocytokines act on organs of metabolic importance like the liver and skeletal muscle. Multiple preclinical and in vitro studies showed strong evidence of the roles of adipocytokines in the regulation of metabolic disorders like diabetes, obesity and insulin resistance. Adipocytokines, such as adiponectin and omentin, are anti-inflammatory and have been shown to prevent atherogenesis by increasing nitric oxide (NO) production by the endothelium, suppressing endothelium-derived inflammation and decreasing foam cell formation. By inhibiting differentiation of vascular smooth muscle cells (VSMC) into osteoblasts, adiponectin and omentin prevent vascular calcification. On the other hand, adipocytokines like leptin and resistin induce inflammation and endothelial dysfunction that leads to vasoconstriction. By promoting VSMC migration and proliferation, extracellular matrix degradation and inflammatory polarization of macrophages, leptin and resistin increase the risk of atherosclerotic plaque vulnerability and rupture. Additionally, the plasma concentrations of these adipocytokines alter in ageing, rendering older humans vulnerable to cardiovascular disease. The disturbances in the normal physiological concentrations of these adipocytokines secreted by VAT under pathological conditions impede the normal functions of various organs and affect cardiovascular health. These adipokines could be used for both diagnostic and therapeutic purposes in cardiovascular disease.

Adiposity-associated atrial fibrillation: molecular determinants, mechanisms, and clinical significance

Obesity is an important contributing factor to the pathophysiology of atrial fibrillation (AF) and its complications by causing systemic changes, such as altered haemodynamic, increased sympathetic tone, and low-grade chronic inflammatory state. In addition, adipose tissue is a metabolically active organ that comprises various types of fat deposits with discrete composition and localization that show distinct functions. Fatty tissue differentially affects the evolution of AF, with highly secretory active visceral fat surrounding the heart generally having a more potent influence than the rather inert subcutaneous fat. A variety of proinflammatory, profibrotic, and vasoconstrictive mediators are secreted by adipose tissue, particularly originating from cardiac fat, that promote atrial remodelling and increase the susceptibility to AF. In this review, we address the role of obesity-related factors and in particular specific adipose tissue depots in driving AF risk. We discuss the distinct effects of key secreted adipokines from different adipose tissue depots and their participation in cardiac remodelling. The possible mechanistic basis and molecular determinants of adiposity-related AF are discussed, and finally, we highlight important gaps in current knowledge, areas requiring future investigation, and implications for clinical management.

Resistin Contribution to Cardiovascular Risk in Chronic Kidney Disease Male Patients

BACKGROUND

Resistin is a molecule that belongs to the Resistin-Like Molecules family (RELMs), the group of proteins taking part in inflammatory processes. Increased resistin concentrations are observed in cardiovascular complications. Resistin contributes to the onset of atherosclerosis and intensifies the atherosclerotic processes. The aim of this study was to investigate the relationship between resistin and cardiovascular (CV) risk in men with chronic kidney disease (CKD) not treated with dialysis.

MATERIALS AND METHODS

One hundred and forty-two men were included in the study: 99 men with eGFR lower than 60 mL/min/1.73 m² and 43 men with eGFR ≥ 60 mL/min/1.73 m². CV risk was assessed. Serum resistin, tumor necrosis factor-alpha (TNF-alpha) and plasminogen activator inhibitor-1 (PAI-1) were measured among other biochemical parameters.

RESULTS

We observed that resistin concentrations were significantly higher in patients with CKD compared to individuals with eGFR ≥ 60 mL/min/1.73 m² (p = 0.003). In CKD, after estimating the general linear model (GLM), we found that resistin is associated with CV risk (p = 0.026) and PAI-1 serum concentrations (0.012). The relationship of PAI-1 with resistin depends on the level of CV risk in CKD (p = 0.048).

CONCLUSIONS

Resistin concentrations rise with the increase of CV risk in CKD patients and thus resistin may contribute to the progression of cardiovascular risk in this group of patients. The relationship between resistin and CV risk is modified by PAI-1 concentrations.

Human Resistin Induces Cardiac Dysfunction in Pulmonary Hypertension

Background Cardiac failure is the primary cause of death in most patients with pulmonary arterial hypertension (PH). As pleiotropic cytokines, human resistin (Hresistin) and its rodent homolog, resistin-like molecule α, are mechanistically critical to pulmonary vascular remodeling in PH. However, it is still unclear whether activation of these resistin-like molecules can directly cause PH-associated cardiac dysfunction and remodeling. Methods and Results In this study, we detected Hresistin protein in right ventricular (RV) tissue of patients with PH and elevated resistin-like molecule expression in RV tissues of rodents with RV hypertrophy and failure. In a humanized mouse model, cardiac-specific Hresistin overexpression was sufficient to cause cardiac dysfunction and remodeling. Dilated hearts exhibited reduced force development and decreased intracellular Ca2+ transients. In the RV tissues overexpressing Hresistin, the impaired contractility was associated with the suppression of protein kinase A and AMP-activated protein kinase. Mechanistically, Hresistin activation triggered the inflammation mediated by signaling of the key damage-associated molecular pattern molecule high-mobility group box 1, and subsequently induced pro-proliferative Ki67 in RV tissues of the transgenic mice. Intriguingly, an anti-Hresistin human antibody that we generated protected the myocardium from hypertrophy and failure in the rodent PH models. Conclusions Our data indicate that Hresistin is expressed in heart tissues and plays a role in the development of RV dysfunction and maladaptive remodeling through its immunoregulatory activities. Targeting this signaling to modulate cardiac inflammation may offer a promising strategy to treat PH-associated RV hypertrophy and failure in humans.

Antiresistin Neutralizing Antibody Alleviates Doxorubicin-Induced Cardiac Injury in Mice

Background

Resistin is closely related to cardiovascular diseases, and this study is aimed at examining the role of resistin in doxorubicin- (DOX-) induced cardiac injury.

Methods

First, 48 mice were divided into 2 groups and treated with saline or DOX, and the expression of resistin at different time points was examined (N = 24). A total of 40 mice were pretreated with the antiresistin neutralizing antibody (nAb) or isotype IgG for 1 hour and further administered DOX or saline for 5 days. The mice were divided into 4 groups: saline-IgG, saline-nAb, DOX-IgG, and DOX-nAb (N = 10). Cardiac injury, cardiomyocyte apoptosis, inflammatory factors, and the biomarkers of M1 and M2 macrophages in each group were analyzed.

Result

DOX administration increased the expression of resistin. DOX treatment exacerbated the loss of body and heart weight and cardiac vacuolation in mice. The antiresistin nAb reversed these conditions, downregulated the expression of myocardial injury markers, and decreased apoptosis. In addition, the antiresistin nAb decreased p65 pathway activation, decreased M1 macrophage differentiation and the expression of related inflammatory factors, and increased M2 macrophage differentiation and the expression of related inflammatory factors.

Conclusion

The antiresistin nAb protected against DOX-induced cardiac injury by reducing cardiac inflammation and may be a promising target to relieve DOX-related cardiac injury.

Cardiac ischemia modulates white adipose tissue in a depot-specific manner

The incidence of heart failure after myocardial infarction (MI) remains high and the underlying causes are incompletely understood. The crosstalk between heart and adipose tissue and stimulated lipolysis has been identified as potential driver of heart failure. Lipolysis is also activated acutely in response to MI. However, the role in the post-ischemic remodeling process and the contribution of different depots of adipose tissue is unclear. Here, we employ a mouse model of 60 min cardiac ischemia and reperfusion (I/R) to monitor morphology, cellular infiltrates and gene expression of visceral and subcutaneous white adipose tissue depots (VAT and SAT) for up to 28 days post ischemia. We found that in SAT but not VAT, adipocyte size gradually decreased over the course of reperfusion and that these changes were associated with upregulation of UCP1 protein, indicating white adipocyte conversion to the so-called ‘brown-in-white’ phenotype. While this phenomenon is generally associated with beneficial metabolic consequences, its role in the context of MI is unknown. We further measured decreased lipogenesis in SAT together with enhanced infiltration of MAC-2+ macrophages. Finally, quantitative PCR analysis revealed transient downregulation of the adipokines adiponectin, leptin and resistin in SAT. While adiponectin and leptin have been shown to be cardioprotective, the role of resistin after MI needs further investigation. Importantly, all significant changes were identified in SAT, while VAT was largely unaffected by MI. We conclude that targeted interference with lipolysis in SAT may be a promising approach to promote cardiac healing after ischemia.

Resistin and risks of incident heart failure subtypes and cardiac fibrosis: the Multi-Ethnic Study of Atherosclerosis

AIMS

Resistin is a circulating inflammatory biomarker that is associated with cardiovascular disease. We investigated the associations of resistin and incident heart failure (HF) and its subtypes, as well as specific measures of subclinical HF (myocardial fibrosis and relevant biomarkers).

METHODS

We analysed data from 1968 participants in the Multi-Ethnic Study of Atherosclerosis with measurements of plasma resistin levels at clinic visits from 2002 to 2005. Participants were subsequently followed for a median of 10.5 years for HF events. The associations between resistin levels and incident HF, HF with reduced ejection fraction (HFrEF), and HF with preserved ejection fraction (HFpEF) were examined using multivariable Cox proportional hazards models. Linear regression models assessed the associations between resistin levels and myocardial fibrosis from cardiac magnetic resonance imaging, as well as hs-cTnT and NT-proBNP.

RESULTS

The mean age of the cohort was 64.7 years, and 50.0% were female. Seventy-four participants (4%) developed incident HF during follow-up. In a Cox proportional hazards model adjusted for age, gender, education level, race/ethnicity, and traditional risk factors, higher resistin levels were significantly associated with incident HF (HR 1.44, CI 1.18-1.75, P = 0.001) and HFrEF (HR 1.47, CI 1.07-2.02, P = 0.016), but not with HFpEF (HR 1.25, CI 0.89-1.75, P = 0.195). Resistin levels showed no significant associations with myocardial fibrosis, NT-proBNP, or hs-cTnT levels.

CONCLUSIONS

In a multi-ethnic cohort free of cardiovascular disease at baseline, elevated resistin levels were associated with incident HF, more prominently with incident HFrEF than HFpEF, but not with subclinical myocardial fibrosis or biomarkers of HF.

Resistin deletion protects against heart failure injury by targeting DNA damage response

AIMS

Increased resistin (Retn) levels are associated with development of cardiovascular diseases. However, the role of Retn in heart failure (HF) is still unclear. Here we probed the functional and molecular mechanism underlying the beneficial effect of Retn deletion in HF.

METHODS AND RESULTS

Wild-type (WT) and adipose tissue-specific Retn-knockout (RKO) mice were subjected to transverse aortic constriction (TAC)-induced HF. Cardiac function and haemodynamic changes were measured by echocardiography and left ventricular catheterization. Adipose tissue Retn deletion attenuated while Retn cardiac-selective overexpression, via a recombinant adeno-associated virus-9 vector, exacerbated TAC-induced hypertrophy, cardiac dysfunction, and myocardial fibrosis in WT and RKO mice. Mechanistically, we showed that Gadd45α was significantly increased in RKO HF mice while cardiac overexpression of Retn led to its downregulation. miR148b-3p directly targets Gadd45α and inhibits its expression. Retn overexpression upregulated miR148b-3p expression and triggered DNA damage response (DDR) in RKO-HF mice. Inhibition of miR148b-3p in vivo normalized Gadd45α expression, decreased DDR, and reversed cardiac dysfunction and fibrosis. In vitro Retn overexpression in adult mouse cardiomyocytes activated miR148b-3p and reduced Gadd45α expression. Gadd45α overexpression in H9C2-cardiomyoblasts protected against hydrogen peroxide- and Retn-induced DDR.

CONCLUSION

These findings reveal that diminution in circulating Retn reduced myocardial fibrosis and apoptosis, and improved heart function in a mouse model of HF, at least in part, through attenuation of miR148b-3p and DDR. The results of this study indicate that controlling Retn levels may provide a potential therapeutic approach for treating pressure overload-induced HF.

Mechanisms and clinical implications of endothelium-dependent vasomotor dysfunction in coronary microvasculature

Coronary microvascular disease (CMD), which affects the arterioles and capillary endothelium that regulate myocardial perfusion, is an increasingly recognized source of morbidity and mortality, particularly in the setting of metabolic syndrome. The coronary endothelium plays a pivotal role in maintaining homeostasis, though factors such as diabetes, hypertension, hyperlipidemia, and obesity can contribute to endothelial injury and consequently arteriolar vasomotor dysfunction. These disturbances in the coronary microvasculature clinically manifest as diminished coronary flow reserve, which is a known independent risk factor for cardiac death, even in the absence of macrovascular atherosclerotic disease. Therefore, a growing body of literature has examined the molecular mechanisms by which coronary microvascular injury occurs at the level of the endothelium and the consequences on arteriolar vasomotor responses. This review will begin with an overview of normal coronary microvascular physiology, modalities of measuring coronary microvascular function, and clinical implications of CMD. These introductory topics will be followed by a discussion of recent advances in the understanding of the mechanisms by which inflammation, oxidative stress, insulin resistance, hyperlipidemia, hypertension, shear stress, endothelial cell senescence, and tissue ischemia dysregulate coronary endothelial homeostasis and arteriolar vasomotor function.

Short-term Obesity Worsens Heart Inflammation and Disrupts Mitochondrial Biogenesis and Function in an Experimental Model of Endotoxemia

Cardiomyopathy is a well-known complication of sepsis that may deteriorate when accompanied by obesity. To test this hypothesis we fed C57black/6 male mice for 6 week with a high fat diet (60% energy) and submitted them to endotoxemic shock using E. coli LPS (10 mg/kg). Inflammatory markers (cytokines and adhesion molecules) were determined in plasma and heart tissue, as well as heart mitochondrial biogenesis and function. Obesity markedly shortened the survival rate of mouse after LPS injection and induced a persistent systemic inflammation since TNFα, IL-1β, IL-6 and resistin plasma levels were higher 24 h after LPS injection. Heart tissue inflammation was significantly higher in obese mice, as detected by elevated mRNA expression of pro-inflammatory cytokines (IL-1β, IL-6 and TNFα). Obese animals presented reduced maximum respiratory rate after LPS injection, however fatty acid oxidation increased in both groups. LPS decreased mitochondrial DNA content and mitochondria biogenesis factors, such as PGC1α and PGC1β, in both groups, while NRF1 expression was significantly stimulated in obese mice hearts. Mitochondrial fusion/fission balance was only altered by obesity, with no influence of endotoxemia. Obesity accelerated endotoxemia death rate due to higher systemic inflammation and decreased heart mitochondrial respiratory capacity.

Research Progress on Epigenetics of Diabetic Cardiomyopathy in Type 2 Diabetes

Diabetic cardiomyopathy (DCM) is characterized by diastolic relaxation abnormalities in its initial stages and by clinical heart failure (HF) without dyslipidemia, hypertension, and coronary artery disease in its last stages. DCM contributes to the high mortality and morbidity rates observed in diabetic populations. Diabetes is a polygenic, heritable, and complex condition that is exacerbated by environmental factors. Recent studies have demonstrated that epigenetics directly or indirectly contribute to pathogenesis. While epigenetic mechanisms such as DNA methylation, histone modifications, and non-coding RNAs, have been recognized as key players in the pathogenesis of DCM, some of their impacts remain not well understood. Furthering our understanding of the roles played by epigenetics in DCM will provide novel avenues for DCM therapeutics and prevention strategies.

Resistin induces cardiac fibroblast-myofibroblast differentiation through JAK/STAT3 and JNK/c-Jun signaling

Cardiac fibrosis is characterized by excessive deposition of extracellular matrix proteins and myofibroblast differentiation. Our previous findings have implicated resistin in cardiac fibrosis; however, the molecular mechanisms underlying this process are still unclear. Here we investigated the role of resistin in fibroblast-to-myofibroblast differentiation and elucidated the pathways involved in this process. Fibroblast-to-myofibroblast transdifferentiation was induced with resistin or TGFβ1 in NIH-3T3 and adult cardiac fibroblasts. mRNA and protein expression of fibrotic markers were analyzed by qPCR and immunoblotting. Resistin-knockout mice, challenged with a high-fat diet (HFD) for 20 weeks to stimulate cardiac impairment, were analyzed for cardiac function and fibrosis using histologic and molecular methods. Cardiac fibroblasts stimulated with resistin displayed increased fibroblast-to-myofibroblast conversion, with increased levels of αSma, col1a1, Fn, Ccn2 and Mmp9, with remarkable differences in the actin network appearance. Mechanistically, resistin promotes fibroblast-to-myofibroblast transdifferentiation and fibrogenesis via JAK2/STAT3 and JNK/c-Jun signaling pathways, independent of TGFβ1. Resistin-null mice challenged with HFD showed an improvement in cardiac function and a decrease in tissue fibrosis and reduced mRNA levels of fibrogenic markers. These findings are the first to delineate the role of resistin in the process of cardiac fibroblast-to-myofibroblast differentiation via JAK/STAT3 and JNK/c-Jun pathways, potentially leading to stimulation of cardiac fibrosis.

Association of Plasma C1q/TNF-Related Protein 3 (CTRP3) in Patients with Atrial Fibrillation

Atrial fibrillation (AF) is a highly prevalent cardiac arrhythmia characterized by atrial remodeling. Complement C1q tumor necrosis factor-related protein 3 (CTRP3) is one of the adipokines associated with obesity, diabetes, and coronary heart disease. The association between plasma CTRP3 levels and AF is uncertain. The aim of this study was to investigate whether plasma CTRP3 concentrations were correlated with AF. Our study included 75 AF patients who underwent catheter ablation at our hospital and 47 sinus rhythm patients to determine the difference in plasma CTRP3 concentrations. Blood samples before the ablation were collected, and ELISA was used to measure the concentrations of CTRP3. Plasma CTRP3 concentrations were significantly lower in AF patients compared with control group (366.9 ± 105.2 ng/ml vs. 429.1 ± 100.1 ng/ml, p = 0.002). In subgroup studies, patients with persistent AF had lower plasma CTRP3 concentrations than those with paroxysmal AF (328.3 ± 83.3 ng/ml vs. 380.0 ± 109.2 ng/ml, p = 0.037). The concentrations of plasma CTRP3 in the recurrence group after radiofrequency catheter ablation of AF were lower than those in the nonrecurrence group (337.9 ± 77.3 ng/ml vs. 386.6 ± 108.1 ng/ml, p = 0.045). Multivariate regression analysis revealed the independent correlation between plasma CTRP3 level and AF. Plasma CTRP3 concentrations were correlated with the presence of AF and AF recurrence.

Resistin: Potential biomarker and therapeutic target in atherosclerosis

Resistin, a cysteine-rich secretory protein, has a pleiotropic role in humans. Resistin usually presents as trimer or hexamer in plasma, and targets specific receptors Toll Like Receptor 4 (TLR4) or Adenylyl Cyclase-Associated Protein 1 (CAP1). Upon binding to TLR4 and CAP1, resistin can trigger various intracellular signal transduction pathways to induce vascular inflammation, lipid accumulation, and plaque vulnerability. These pro-atherosclerotic effects of resistin appear in various cell types, including endothelial cells, vessel smooth muscle cells and macrophages, which cause diverse damages to cardiovascular system from dyslipidemia, atherosclerosis rupture and ventricular remodeling. In this review, we gather recent evidence about the pro- atherosclerotic effects of resistin and highlight it as a candidate therapeutic or diagnostic target for cardiovascular disease.

Boron improves cardiac contractility and fibrotic remodeling following myocardial infarction injury

Myocardial fibrosis is a major determinant of clinical outcomes in heart failure (HF) patients. It is characterized by the emergence of myofibroblasts and early activation of pro-fibrotic signaling pathways before adverse ventricular remodeling and progression of HF. Boron has been reported in recent years to augment the innate immune system and cell proliferation, which play an important role in the repair and regeneration of the injured tissue. Currently, the effect of boron on cardiac contractility and remodeling is unknown. In this study, we investigated, for the first time, the effect of boron supplementation on cardiac function, myocardial fibrosis, apoptosis and regeneration in a rat model myocardial infarction (MI)-induced HF. MI was induced in animals and borax, a sodium salt of boron, was administered for 7 days, p.o., 21 days post-injury at a dose level of 4 mg/kg body weight. Transthoracic echocardiographic analysis showed a significant improvement in systolic and diastolic functions with boron treatment compared to saline control. In addition, boron administration showed a marked reduction in myocardial fibrosis and apoptosis in the injured hearts, highlighting a protective effect of boron in the ischemic heart. Interestingly, we observed a tenfold increase of nuclei in thin myocardial sections stained positive for the cell cycle marker Ki67 in the MI boron-treated rats compared to saline, indicative of increased cardiomyocyte cell cycle activity in MI hearts, highlighting its potential role in regeneration post-injury. We similarly observed increased Ki67 and BrdU staining in cultured fresh neonatal rat ventricular cardiomyocytes. Collectively, the results show that boron positively impacted MI-induced HF and attenuated cardiac fibrosis and apoptosis, two prominent features of HF. Importantly, boron has the potential to induce cardiomyocyte cell cycle entry and potentially cardiac tissue regeneration after injury. Boron might be beneficial as a supplement in MI and may be a good candidate substance for anti-fibrosis approach.

Inotropic and lusitropic, but not arrhythmogenic, effects of adipocytokine resistin on human atrial myocardium

The adipocytokine resistin is released from epicardial adipose tissue (EAT). Plasma resistin and EAT deposition are independently associated with atrial fibrillation. The EAT secretome enhances arrhythmia susceptibility and inotropy of human myocardium. Therefore, we aimed to determine the effect of resistin on the function of human myocardium and how resistin contributes to the proarrhythmic effect of EAT. EAT biopsies were obtained from 25 cardiac surgery patients. Resistin levels were measured by ELISA in 24-h EAT culture media (n = 8). The secretome resistin concentrations increased over the culture period to a maximal level of 5.9 ± 1.2 ng/mL. Coculture with β-adrenergic agonists isoproterenol (n = 4) and BRL37344 (n = 13) had no effect on EAT resistin release. Addition of resistin (7, 12, 20 ng/mL) did not significantly increase the spontaneous contraction propensity of human atrial trabeculae (n = 10) when given alone or in combination with isoproterenol. Resistin dose-dependently increased trabecula-developed force (maximal 2.9-fold increase, P < 0.0001), as well as the maximal rates of contraction (2.6-fold increase, P = 0.002) and relaxation (1.8-fold increase, P = 0.007). Additionally, the postrest potentiation capacity of human trabeculae was reduced at all resistin doses, suggesting that the inotropic effect induced by resistin might be due to altered sarcoplasmic reticulum Ca²⁺ handling. EAT resistin release is not modulated by common arrhythmia triggers. Furthermore, exogenous resistin does not promote arrhythmic behavior in human atrial trabeculae. Resistin does, however, induce an acute dose-dependent positive inotropic and lusitropic effect.

Mechanisms linking adipose tissue inflammation to cardiac hypertrophy and fibrosis

Adipose tissue is classically recognized as the primary site of lipid storage, but in recent years has garnered appreciation for its broad role as an endocrine organ comprising multiple cell types whose collective secretome, termed as adipokines, is highly interdependent on metabolic homeostasis and inflammatory state. Anatomical location (e.g. visceral, subcutaneous, epicardial etc) and cellular composition of adipose tissue (e.g. white, beige, and brown adipocytes, macrophages etc.) also plays a critical role in determining its response to metabolic state, the resulting secretome, and its potential impact on remote tissues. Compared with other tissues, the heart has an extremely high and constant demand for energy generation, of which most is derived from oxidation of fatty acids. Availability of this fatty acid fuel source is dependent on adipose tissue, but evidence is mounting that adipose tissue plays a much broader role in cardiovascular physiology. In this review, we discuss the impact of the brown, subcutaneous, and visceral white, perivascular (PVAT), and epicardial adipose tissue (EAT) secretome on the development and progression of cardiovascular disease (CVD), with a particular focus on cardiac hypertrophy and fibrosis.

GIP as a Potential Therapeutic Target for Atherosclerotic Cardiovascular Disease-A Systematic Review

Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are gut hormones that are secreted from enteroendocrine L cells and K cells in response to digested nutrients, respectively. They are also referred to incretin for their ability to stimulate insulin secretion from pancreatic beta cells in a glucose-dependent manner. Furthermore, GLP-1 exerts anorexic effects via its actions in the central nervous system. Since native incretin is rapidly inactivated by dipeptidyl peptidase-4 (DPP-4), DPP-resistant GLP-1 receptor agonists (GLP-1RAs), and DPP-4 inhibitors are currently used for the treatment of type 2 diabetes as incretin-based therapy. These new-class agents have superiority to classical oral hypoglycemic agents such as sulfonylureas because of their low risks for hypoglycemia and body weight gain. In addition, a number of preclinical studies have shown the cardioprotective properties of incretin-based therapy, whose findings are further supported by several randomized clinical trials. Indeed, GLP-1RA has been significantly shown to reduce the risk of cardiovascular and renal events in patients with type 2 diabetes. However, the role of GIP in cardiovascular disease remains to be elucidated. Recently, pharmacological doses of GIP receptor agonists (GIPRAs) have been found to exert anti-obesity effects in animal models. These observations suggest that combination therapy of GLP-1R and GIPR may induce superior metabolic and anti-diabetic effects compared with each agonist individually. Clinical trials with GLP-1R/GIPR dual agonists are ongoing in diabetic patients. Therefore, in this review, we summarize the cardiovascular effects of GIP and GIPRAs in cell culture systems, animal models, and humans.

Associations between circulating resistin concentrations and left ventricular mass are not accounted for by effects on aortic stiffness or renal dysfunction

Background

Although, in-part through an impact on left ventricular mass (LVM), resistin (an adipokine) may contribute to heart failure, whether this is explained by the adverse effects of resistin on aortic stiffness and renal function is unknown.

Methods

Relationships between circulating resistin concentrations and LVM index (LVMI), and LVM beyond that predicted by stroke work (inappropriate LVM [LVM_inappr]) (echocardiography) were determined in 647 randomly selected community participants, and in regression analysis, the extent to which these relations could be explained by aortic pulse wave velocity (PWV) or estimated glomerular filtration rate (eGFR) was evaluated.

Results

Independent of confounders, resistin concentrations were independently associated with LVMI, LVM_inappr, LV hypertrophy (LVH), PWV and eGFR. Furthermore, independent of confounders, LVMI, LVM_inappr and LVH were independently associated with PWV and eGFR. However, adjustments for either PWV or eGFR failed to modify the relationships between resistin concentrations and LVMI, LVM_inappr or LVH. Moreover, in multivariate regression analysis neither PWV nor eGFR significantly modified the contribution of resistin to LVM_inappr or LVMI.

Conclusions

Independent relationships between circulating concentrations of the adipocytokine resistin and LVM are not explained by the impact of resistin on ventricular-vascular coupling or renal dysfunction. Resistin’s effects on LVM are therefore likely to be through direct actions on the myocardium.

Review on Chamber-Specific Differences in Right and Left Heart Reactive Oxygen Species Handling

Reactive oxygen species (ROS) exert signaling character (redox signaling), or damaging character (oxidative stress) on cardiac tissue depending on their concentration and/or reactivity. The steady state of ROS concentration is determined by the interplay between its production (mitochondrial, cytosolic, and sarcolemmal enzymes) and ROS defense enzymes (mitochondria, cytosol). Recent studies suggest that ROS regulation is different in the left and right ventricle of the heart, specifically by a different activity of superoxide dismutase (SOD). Mitochondrial ROS defense seems to be lower in right ventricular tissue compared to left ventricular tissue. In this review we summarize the current evidence for heart chamber specific differences in ROS regulation that may play a major role in an observed inability of the right ventricle to compensate for cardiac stress such as pulmonary hypertension. Based on the current knowledge regimes to increase ROS defense in right ventricular tissue should be in the focus for the development of future therapies concerning right heart failure.

A role for calcium in resistin transcriptional activation in diabetic hearts

The adipokine resistin has been proposed to link obesity, insulin resistance and diabetes. We have previously reported that diabetic hearts express high levels of resistin while overexpression of resistin in adult rat hearts gives rise to a phenotype resembling diabetic cardiomyopathy. The transcriptional regulation of resistin in diabetic cardiac tissue is currently unknown. This study investigated the mechanism of resistin upregulation and the role of Serca2a in its transcriptional suppression. We demonstrate that restoration of Ca²⁺ homeostasis in diabetic hearts, through normalization of Serca2a function genetically and pharmacologically, suppressed resistin expression via inhibition of NFATc. H9c2 myocytes stimulated with high-glucose concentration or Ca²⁺ time-dependently increased NFATc and resistin expression while addition of the Ca²⁺ chelator BAPTA-AM attenuated this effect. NFATc expression was enhanced in hearts from ob/ob diabetic and from cardiac-specific Serca2a^−/− mice. Similarly, NFATc increased resistin expression in myocytes cultured in low glucose while the NFATc inhibitor VIVIT blocked glucose-induced resistin expression, suggesting that hyperglycemia/diabetes induces resistin expression possibly through NFATc activation. Interestingly, overexpression of Serca2a or VIVIT mitigated glucose-stimulated resistin and NFATc expression and enhanced AMPK activity, a downstream target of resistin signaling. NFATc direct activation of resistin was verified by resistin promoter luciferase activity and chromatin-immunoprecipitation analysis. Interestingly, activation of Serca2a by a novel agonist, CDN1163, mirrored the effects of AAV9-Serca2a gene transfer on resistin expression and its promoter activity and AMPK signaling in diabetic mice. These findings parse a role for Ca²⁺ in resistin transactivation and provide support that manipulation of Serca2a-NFATc-Resistin axis might be useful in hyper-resistinemic conditions.

The role of pericardial adipose tissue in the heart of obese minipigs

BACKGROUND

Pericardial adipose tissue (PAT) volume is highly associated with the presence and severity of cardiometabolic diseases, but the underlying mechanism is unknown. We previously demonstrated that a high-fat diet (HFD) induced metabolic dysregulation, cardiac fibrosis and accumulation of more PAT in minipigs. This study used our obese minipig model to investigate the characteristics of PAT and omental visceral fat (VAT) induced by a HFD, and the potential link between PAT and HFD-related myocardial fibrosis.

MATERIALS AND METHODS

Five-month-old Lee-Sung minipigs were made obese by feeding a HFD for 6 months.

RESULTS

The HFD induced dyslipidemia, cardiac fibrosis and more fat accumulation in the visceral and pericardial depots. The HFD changes the fatty acid composition in the adipose tissue by decreasing the portion of linoleic acid in the VAT and PAT. No arachidonic acid was detected in the VAT and PAT of control pigs, whereas it existed in the same tissues of obese pigs fed the HFD. Compared with the control pigs, elevated levels of malondialdehyde and TNFα were exhibited in the plasma and PAT of obese pigs. HFD induced greater size of adipocytes in VAT and PAT. Higher levels of GH, leptin, OPG, PDGF, resistin, SAA and TGFβ were observed in obese pig PAT compared to VAT.

CONCLUSION

This study demonstrated the similarities and dissimilarities between PAT and VAT under HFD stimulus. In addition, this study suggested that alteration in PAT contributed to the myocardial damage.

Plasma leptin, but not resistin, TNF-α and adiponectin, is associated with echocardiographic parameters of cardiac remodeling in patients with coronary artery disease

The aim of this research was to assess the relationship between plasma adiponectin, leptin, resistin, tumor necrosis factor alpha (TNF-α) levels and echocardiographic parameters of ventricular remodeling in patients with coronary artery disease, without acute myocardial infarction. The study population consisted of 49 patients with echocardiographic measurements performed. After adjustment for age, gender, body mass index, systolic and diastolic blood pressure, and glycaemia, adiponectin was statistically significant associated with interventricular septum thickness (β = -0.304), left ventricular posterior wall thickness (β = -0.402), left ventricular end diastolic diameter (LVEDD; β = 0.385) and left ventricular relative wall thickness (β = -0.448, p < .05 for all). The associations were no longer significant when only patients without diabetes were included in the analysis. Leptin was associated with LVEDD (β = -0.354) and left ventricular relative wall thickness (β = 0.385, p < .05 for all). No associations between resistin, TNF-α and echocardiographic left ventricular parameters assessed were found in these patients. In conclusion, in patients with coronary artery disease and without acute myocardial infarction leptin may represent a potential mechanism of adverse cardiac remodeling. Resistin and TNF-α might not be involved in ventricular remodeling in these patients.

Exploring the Crosstalk between Adipose Tissue and the Cardiovascular System

Obesity is a clinical entity critically involved in the development and progression of cardiovascular disease (CVD), which is characterised by variable expansion of adipose tissue (AT) mass across the body as well as by phenotypic alterations in AT. AT is able to secrete a diverse spectrum of biologically active substances called adipocytokines, which reach the cardiovascular system via both endocrine and paracrine routes, potentially regulating a variety of physiological and pathophysiological responses in the vasculature and heart. Such responses include regulation of inflammation and oxidative stress as well as cell proliferation, migration and hypertrophy. Furthermore, clinical observations such as the “obesity paradox,” namely the fact that moderately obese patients with CVD have favourable clinical outcome, strongly indicate that the biological “quality” of AT may be far more crucial than its overall mass in the regulation of CVD pathogenesis. In this work, we describe the anatomical and biological diversity of AT in health and metabolic disease; we next explore its association with CVD and, importantly, novel evidence for its dynamic crosstalk with the cardiovascular system, which could regulate CVD pathogenesis.

Human mesenchymal stem cells attenuate pulmonary hypertension induced by prenatal lipopolysaccharide treatment in rats

Intra-amniotic injection of lipopolysaccharide (LPS) induces pulmonary hypertension in newborn rats. This study was designed to test whether human mesenchymal stem cells (MSCs) reduce pulmonary hypertension and alleviate cardiac hypertrophy in prenatal LPS-treated rats. Pregnant Sprague-Dawley rats were injected intraperitoneally with LPS (0.5 mg/kg per day) or untreated on gestational days 20 and 21. Human MSCs (3×10(5) cells and 1×10(6) cells) in 0.03 mL of normal saline (NS) were transplanted intratracheally on postnatal day 5. Four study groups were considered: normal, LPS+NS, LPS+MSCs (3×10(5) cells), and LPS+MSCs (1×10(6) cells). On postnatal day 14, lung and heart tissues were collected for measuring the arterial medial wall thickness (MWT) and β-myosin heavy chain (β-MHC) level as markers of pulmonary hypertension and cardiac hypertrophy, respectively. The LPS+NS group exhibited a significantly higher right ventricle (RV)/[left ventricle (LV)+ interventricular septum (IVS)] thickness ratio and MWT, a greater cardiomyocyte width, a greater number of cardiomyocyte nuclei per squared millimeter, and higher β-MHC expression than those observed in the normal group. Human MSC transplantation (3×10(5) cells and 1×10(6) cells) in LPS-treated rats reduced MWT and the RV/(LV+IVS) thickness ratio to normal levels. This improvement in right ventricular hypertrophy was accompanied by a decrease in toll-like receptor 4 (TLR4), nuclear factor-κB, and tumor necrosis factor-α expression in the heart. Intratracheal human MSCs transplantation can attenuate pulmonary hypertension and right ventricular hypertrophy in prenatal LPS-treated rats; this attenuation may be associated with suppression of TLR4 expression via paracrine pathways.

Potential novel biomarkers of cardiovascular dysfunction and disease: cardiotrophin-1, adipokines and galectin-3

Cardiovascular disease is one of the main burdens of healthcare systems worldwide. Nevertheless, assessing cardiovascular risk in both apparently healthy individuals and low/high-risk patients remains a difficult issue. Already established biomarkers (e.g. brain natriuretic peptide, troponin) have significantly improved the assessment of major cardiovascular events and diseases but cannot be applied to all patients and in some cases do not provide sufficiently accurate information. In this context, new potential biomarkers that reflect various underlying pathophysiological cardiac and vascular modifications are needed. Also, a multiple biomarker evaluation that shows changes in the cardiovascular state is of interest. This review describes the role of selected markers of vascular inflammation, atherosclerosis, atherothrombosis, endothelial dysfunction and cardiovascular fibrosis in the pathogenesis and prognosis of cardiovascular disease: the potential use of cardiotrophin-1, leptin, adiponectin, resistin and galectin-3 as biomarkers for various cardiovascular conditions is discussed.

Linking resistin, inflammation, and cardiometabolic diseases

Adipose tissue secretes a variety of bioactive substances that are associated with chronic inflammation, insulin resistance, and an increased risk of type 2 diabetes mellitus. While resistin was first known as an adipocyte-secreted hormone (adipokine) linked to obesity and insulin resistance in rodents, it is predominantly expressed and secreted by macrophages in humans. Epidemiological and genetic studies indicate that increased resistin levels are associated with the development of insulin resistance, diabetes, and cardiovascular disease. Resistin also appears to mediate the pathogenesis of atherosclerosis by promoting endothelial dysfunction, vascular smooth muscle cell proliferation, arterial inflammation, and the formation of foam cells. Thus, resistin is predictive of atherosclerosis and poor clinical outcomes in patients with cardiovascular disease and heart failure. Furthermore, recent evidence suggests that resistin is associated with atherogenic dyslipidemia and hypertension. The present review will focus on the role of human resistin in the pathogeneses of inflammation and obesity-related diseases.

Resistin Gene Expression is Downregulated in CD4(+) T Helper Lymphocytes and CD14(+) Monocytes in Rheumatoid Arthritis Responding to TNF-α Inhibition

Rheumatoid arthritis (RA) is caused by complex interactions between immune cells and sustained by Th1 response cytokines. Resistin [resistance to insulin; (RETN)] is an inflammatory cytokine, first discovered in murine adipocytes. In man, RETN is mainly secreted by monocytes. The distinct role of RETN in the immune reaction is uncertain; however, RETN has pro-inflammatory, pro-fibrotic and possibly tolerogenic properties. The aim was to assess the reaction of RETN gene expression to TNF-α inhibition (I) in pathogenetic immune cell subsets in RA, in the context of Th1, inflammatory and regulatory cytokine gene expressions. Accordingly, we measured RETN, IFN-γ, TNF-β, IL-1β, TNF-α, TGF-β and IL-10 gene expressions in CD14(+) monocytes, CD4(+) T helper (Th) lymphocytes (ly), CD8(+) T cytotoxic (Tc) ly and CD19(+) B ly in active RA before and 3 months after start of TNF-αI. Leucocyte subsets were separated by specific monoclonal antibody-covered beads, RNA extracted and levels of RETN, Th1 response, inflammatory and regulatory cytokine mRNAs measured by quantitative reverse transcription-polymerase chain reaction technique. We found that TNF-αI caused a significant downregulation of RETN gene expression in CD14(+) monocytes and CD4(+) Th ly and was unchanged in CD8(+) Tc ly and CD19(+) B ly. Both in active RA and during TNF-αI, RETN mRNA levels were significantly higher in CD14(+) monocytes than in all other examined cell types. In monocytes, fold change in RETN and TGF-β gene expressions upon TNF-αI correlated significantly. Our findings indicate that RETN has pro-inflammatory as well as proresolving roles in active RA.

Can the onset of heart failure be delayed by treating diabetic cardiomyopathy?

The pathophysiology of diabetic cardiomyopathy (DC) is not fully understood. This frequently undiagnosed complication of chronic hyperglycemia leads to heart failure (HF). However, it is suggested that an appropriate metabolic control of diabetes at an early stage of this deleterious disease, is able to inhibit the development and progression of DC to HF. Recently, it has been postulated that myocardial ischaemia plays an important role in the development of this pathology. Results of the antianginal pharmacological treatment and revascularization are unsatisfactory and reveal a gap in our knowledge and current approaches to treating DC. Most recent studies emphasize the ischaemic component of DC as a key target for therapeutic strategies, which could change its unfavorable history. More stress is put on an early diagnosis of coronary artery disease (CAD), promoting prompt revascularization. Choosing the accurate time of surgical revascularization, with the inclusion of the metabolic background, can ensure complete revascularization with better prognosis. This review will focus on the complexity of DC and summarize contemporary knowledge of treatment strategies for patients with diabetes and CAD.

Resistin-induced cardiomyocyte hypertrophy is inhibited by apelin through the inactivation of extracellular signal-regulated kinase signaling pathway in H9c2 embryonic rat cardiomyocytes

It has been reported that resistin induces, whereas apelin inhibits cardiac hypertrophy. However, the underlying molecular mechanisms of apelin inhibiting resistin-induced cardiac hypertrophy remain unclear. The aim of the current study is to investigate the effects of apelin on resistin-induced cardiomyocyte hypertrophy and elucidate the underlying molecular mechanism. H9c2 cells were used in the present study, and cell surface area and protein synthesis were evaluated. Reverse transcription-quantitative polymerase chain reaction was performed to analyze the expression levels of hypertrophic markers, brain natriuretic peptide (BNP) and β-myosin heavy chain (β-MHC). In addition, western blotting was conducted to examine phosphorylation of extracellular signal-regulated kinase (ERK)1/2. Following treatment of H9c2 cells with resistin, cell surface area, protein synthesis, and BNP and β-MHC mRNA expression levels were increased. Subsequent to co-treatment of H9c2 cells with apelin and resistin, lead to the inhibition of resistin-induced hypertrophic effects by apelin. In addition, treatment with resistin increased phosphorylation of ERK1/2, whereas pretreatment with apelin decreased phosphorylation of ERK1/2, which was increased by resistin. These results indicate that resistin-induced cardiac hypertrophy is inhibited by apelin via inactivation of ERK1/2 cell signaling.

LKB1/AMPK pathway mediates resistin-induced cardiomyocyte hypertrophy in H9c2 embryonic rat cardiomyocytes

Resistin has been previously demonstrated to induce cardiac hypertrophy, however, the underlying molecular mechanisms of resistin-induced cardiac hypertrophy remain unclear. Using H9c2 cells, the present study investigated the liver kinase B1 (LKB1)/adenosine monophosphate-activated protein kinase (AMPK) signaling pathway for a potential role in mediating resistin-induced cardiomyocyte hypertrophy. Treatment of H9c2 cells with resistin increased cell surface area, protein synthesis, and expression of hypertrophic marker brain natriuretic peptide and β-myosin heavy chain. Treatment with metformine attenuated these effects of resistin. Furthermore, treatment with resistin decreased phosphorylation of LKB1 and AMPK, whereas pretreatment with metformin increased phosphorylation of LKB1 and AMPK that is reduced by resistin. These results suggest that resistin induces cardiac hypertrophy through the inactivation of the LKB1/AMPK cell signaling pathway.

Sitagliptin decreases ventricular arrhythmias by attenuated glucose-dependent insulinotropic polypeptide (GIP)-dependent resistin signalling in infarcted rats

Myocardial infarction (MI) was associated with insulin resistance, in which resistin acts as a critical mediator. We aimed to determine whether sitagliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor, can attenuate arrhythmias by regulating resistin-dependent nerve growth factor (NGF) expression in postinfarcted rats. Normoglycaemic male Wistar rats after ligating coronary artery were randomized to either vehicle or sitagliptin for 4 weeks starting 24 h after operation. Post-infarction was associated with increased myocardial noradrenaline [norepinephrine (NE)] levels and sympathetic hyperinnervation. Compared with vehicle, sympathetic innervation was blunted after administering sitagliptin, as assessed by immunofluorescent analysis of tyrosine hydroxylase, growth-associated factor 43 and neurofilament and western blotting and real-time quantitative RT-PCR of NGF. Arrhythmic scores in the sitagliptin-treated infarcted rats were significantly lower than those in vehicle. Furthermore, sitagliptin was associated with reduced resistin expression and increased Akt activity. Ex vivo studies showed that glucose-dependent insulinotropic polypeptide (GIP) infusion, but not glucagon-like peptide-1 (GLP-1), produced similar reduction in resistin levels to sitagliptin in postinfarcted rats. Furthermore, the attenuated effects of sitagliptin on NGF levels can be reversed by wortmannin (a phosphatidylinositol 3-kinase antagonist) and exogenous resistin infusion. Sitagliptin protects ventricular arrhythmias by attenuating sympathetic innervation in the non-diabetic infarcted rats. Sitagliptin attenuated resistin expression via the GIP-dependent pathway, which inhibited sympathetic innervation through a signalling pathway involving phosphatidylinositol 3-kinase (PI3K) and Akt protein.

Association between serum resistin level and outcomes in kidney transplant recipients

Resistin is an adipocytokine that is associated with inflammation, coronary artery disease, and other types of cardiovascular disease among patients with normal kidney function. However, little is known about the association of resistin with outcomes in kidney transplant recipients. We collected socio-demographic and clinical parameters, medical and transplant history, and laboratory data from 988 prevalent kidney transplant recipients enrolled in the Malnutrition-Inflammation in Transplant-Hungary Study (MINIT-HU study). Serum resistin levels were measured at baseline. Associations between serum resistin level and death with a functioning graft over a 6-year follow-up period were examined in unadjusted and adjusted models. The mean±SD age of the study population was 51 ± 13 years, among whom 57% were men and 21% were diabetics. Median serum resistin concentrations were significantly higher in patients who died with a functioning graft as compared to those who did not die during the follow-up period (median [IQR]: 22[15-26] vs. 19[14-22] ng/ml, respectively; P < 0.001). Higher serum resistin level was associated with higher mortality risk in both unadjusted and fully adjusted models: HRs (95% CI): 1.33(1.16-1.54) and 1.21(1.01-1.46), respectively. In prevalent kidney transplant recipients, serum resistin was an independent predictor of death with a functioning graft.

Inhibition of G-protein-coupled Receptor Kinase 2 Prevents the Dysfunctional Cardiac Substrate Metabolism in Fatty Acid Synthase Transgenic Mice

Impairment of myocardial fatty acid substrate metabolism is characteristic of late-stage heart failure and has limited treatment options. Here, we investigated whether inhibition of G-protein-coupled receptor kinase 2 (GRK2) could counteract the disturbed substrate metabolism of late-stage heart failure. The heart failure-like substrate metabolism was reproduced in a novel transgenic model of myocardium-specific expression of fatty acid synthase (FASN), the major palmitate-synthesizing enzyme. The increased fatty acid utilization of FASN transgenic neonatal cardiomyocytes rapidly switched to a heart failure phenotype in an adult-like lipogenic milieu. Similarly, adult FASN transgenic mice developed signs of heart failure. The development of disturbed substrate utilization of FASN transgenic cardiomyocytes and signs of heart failure were retarded by the transgenic expression of GRKInh, a peptide inhibitor of GRK2. Cardioprotective GRK2 inhibition required an intact ERK axis, which blunted the induction of cardiotoxic transcripts, in part by enhanced serine 273 phosphorylation of Pparg (peroxisome proliferator-activated receptor γ). Conversely, the dual-specific GRK2 and ERK cascade inhibitor, RKIP (Raf kinase inhibitor protein), triggered dysfunctional cardiomyocyte energetics and the expression of heart failure-promoting Pparg-regulated genes. Thus, GRK2 inhibition is a novel approach that targets the dysfunctional substrate metabolism of the failing heart.

Diabetic cardiomyopathy: is resistin a culprit?

Cardiovascular disease, including heart failure (HF), is the major cause of death in patients with diabetes. A contributing factor to the occurrence of HF in such patients is the development of diabetic cardiomyopathy. Recent evidence demonstrates that perturbations associated with adipokines secretion and signaling result in lusitropic and inotropic defects in diabetic cardiomyopathy. This perspective editorial will discuss the central role of resistin, a recently discovered adipokine, in the maladaptive cardiac phenotype seen in diabetic hearts. Given the pleiotropic effects of resistin, strategies targeting the control of resistin levels may constitute a potentially viable therapeutic utility in patients with diabetes and diabetes-induced cardiovascular diseases.

Adipokines and their receptors: potential new targets in cardiovascular diseases

Adipose tissue is an 'endocrine organ' that influences diverse physiological and pathological processes via adipokines secretion. Strong evidences suggest that epicardial and perivascular adipose tissue can directly regulate heart and vessels' structure and function. Indeed, in obesity there is a shift toward the secretion of adipokines that promote a pro-inflammatory status and contribute to obesity cardiomyopathy. The prospect of modulating adipokines and/or their receptors represents an attractive perspective to the treatment of cardiovascular diseases. In this paper, we described the most important actions of certain adipokines and their receptors that are capable of influencing cardiovascular physiology as well as their possible use as therapeutic targets.

Obesity and coronary microvascular disease - implications for adipose tissue-mediated remote inflammatory response

It is believed that obesity has detrimental effects on the coronary circulation. These include immediate changes in coronary arterial vasomotor responsiveness and the development of occlusive large coronary artery disease. Despite its critical role in regulating myocardial perfusion, the altered behavior of coronary resistance arteries, which gives rise to coronary microvascular disease (CMD) is poorly understood in obesity. A chronic, low-grade vascular inflammation has been long considered as one of the main underlying pathology behind CMD. The expanded adipose tissue and the infiltrating macrophages are the major sources of pro-inflammatory mediators that have been implicated in causing inadequate myocardial perfusion and, in a long term, development of heart failure in obese patients. Much less is known the mechanisms regulating the release of these cytokines into the circulation that enable them to exert their remote effects in the coronary microcirculation. This mini review aims to examine recent studies describing alterations in the vasomotor function of coronary resistance arteries and the role of adipose tissue-derived pro-inflammatory cytokines and adipokines in contributing to CMD in obesity. We provide examples of regulatory mechanisms by which adipokines are released from adipose tissue to exert their remote inflammatory effects on coronary microvessels. We identify some of the important challenges and opportunities going forward.

Hypoxia-induced mitogenic factor (FIZZ1/RELMα) induces endothelial cell apoptosis and subsequent interleukin-4-dependent pulmonary hypertension

Pulmonary hypertension (PH) is characterized by elevated pulmonary artery pressure that leads to progressive right heart failure and ultimately death. Injury to endothelium and consequent wound repair cascades have been suggested to trigger pulmonary vascular remodeling, such as that observed during PH. The relationship between injury to endothelium and disease pathogenesis in this disorder remains poorly understood. We and others have shown that, in mice, hypoxia-induced mitogenic factor (HIMF, also known as FIZZ1 or RELMα) plays a critical role in the pathogenesis of lung inflammation and the development of PH. In this study, we dissected the mechanism by which HIMF and its human homolog resistin (hRETN) induce pulmonary endothelial cell (EC) apoptosis and subsequent lung inflammation-mediated PH, which exhibits many of the hallmarks of the human disease. Systemic administration of HIMF caused increases in EC apoptosis and interleukin (IL)-4-dependent vascular inflammatory marker expression in mouse lung during the early inflammation phase. In vitro, HIMF, hRETN, and IL-4 activated pulmonary microvascular ECs (PMVECs) by increasing angiopoietin-2 expression and induced PMVEC apoptosis. In addition, the conditioned medium from hRETN-treated ECs had elevated levels of endothelin-1 and caused significant increases in pulmonary vascular smooth muscle cell proliferation. Last, HIMF treatment caused development of PH that was characterized by pulmonary vascular remodeling and right heart failure in wild-type mice but not in IL-4 knockout mice. These data suggest that HIMF contributes to activation of vascular inflammation at least in part by inducing EC apoptosis in the lung. These events lead to subsequent PH.

Human resistin in chemotherapy-induced heart failure in humanized male mice and in women treated for breast cancer

Resistin is a circulating mediator of insulin resistance mainly expressed in human monocytes and responsive to inflammatory stimuli. Recent clinical studies have connected elevated resistin levels with the development and severity of heart failure. To further our understanding of the role of human resistin in heart failure, we studied a humanized mouse model lacking murine resistin but transgenic for the human Retn gene (Hum-Retn mice), which exhibits basal and inflammation-stimulated resistin levels similar to humans. Specifically, we explored whether resistin underlies acute anthracycline-induced cardiotoxicity. Remarkably, doxorubicin (25mg/kg ip) led to a 4-fold induction of serum resistin levels in Hum-Retn mice. Moreover, doxorubicin-induced cardiotoxicity was greater in the Hum-Retn mice than in littermate controls not expressing human resistin (Retn(-/-)). Hum-Retn mice showed increased cardiac mRNA levels of inflammatory and cell adhesion genes compared with Retn(-/-) mice. Macrophages, but not cardiomyocytes, from Hum-Retn mice treated with doxorubicin in vitro showed dramatic induction of hRetn (human resistin) mRNA and protein expression. We also examined resistin levels in anthracycline-treated breast cancer patients with and without cardiotoxicity. Intriguingly, serum resistin levels in women undergoing anthracycline-containing chemotherapy increased significantly at 3 months and remained elevated at 6 months in those with subsequent cardiotoxicity. Further, elevation in resistin correlated with decline in ejection fraction in these women. These results suggest that elevated resistin is a biomarker of anthracycline-induced cardiotoxicity and may contribute in the development of heart failure via its direct effects on macrophages. These results further implicate resistin as a link between inflammation, metabolism, and heart disease.

The role of resistin in inflammatory myopathies

Both immune and non-immune mechanisms are involved in muscle damage and dysfunction occurring in idiopathic inflammatory myopathies (IIMs). Crosstalk among inflammatory cells, muscle and endothelial cells is essential in the pathogenesis of IIMs. Resistin, originally described as an adipokine linking obesity and insulin resistance in rodents, has been shown a pro-inflammatory molecule in humans. Besides its direct effect on production of several inflammatory mediators, resistin influences chemotaxis, migration, proliferation, cell survival, endothelial dysfunction and metabolism--all aspects implicated in the pathogenesis of IIMs. Up-regulation of resistin in muscle tissue and elevated serum resistin levels have been recently demonstrated in patients with IIMs. In addition, serum levels of resistin reflected global disease activity, including extramuscular organ involvement, in patients with this disease. However, there are currently not sufficient data to distinguish the features of resistin that cause injury of muscle tissue from those that promote muscle regeneration and repair. The aim of this review is therefore to summarize current knowledge about potential implication of resistin in idiopathic inflammatory myopathies.

Differential patterns of replacement and reactive fibrosis in pressure and volume overload are related to the propensity for ischaemia and involve resistin

Pathological left ventricle (LV) hypertrophy (LVH) results in reactive and replacement fibrosis. Volume overload LVH (VOH) is less profibrotic than pressure overload LVH (POH). Studies attribute subendocardial fibrosis in POH to ischaemia, and reduced fibrosis in VOH to collagen degradation favouring dilatation. However, the mechanical origin of the relative lack of fibrosis in VOH is incompletely understood. We hypothesized that reduced ischaemia propensity in VOH compared to POH accounted for the reduced replacement fibrosis, along with reduced reactive fibrosis. Rats with POH (ascending aortic banding) evolved into either compensated-concentric POH (POH-CLVH) or dilated cardiomyopathy (POH-DCM); they were compared to VOH (aorta-caval fistula). We quantified LV fibrosis, structural and haemodynamic factors of ischaemia propensity, and the activation of profibrotic pathways. Fibrosis in POH-DCM was severe, subendocardial and subepicardial, in contrast with subendocardial fibrosis in POH-CLVH and nearly no fibrosis in VOH. The propensity for ischaemia was more important in POH versus VOH, explaining different patterns of replacement fibrosis. LV collagen synthesis and maturation, and matrix metalloproteinase-2 expression, were more important in POH. The angiotensin II-transforming growth-factor β axis was enhanced in POH, and connective tissue growth factor (CTGF) was overexpressed in all types of LVH. LV resistin expression was markedly elevated in POH, mildly elevated in VOH and independently reflected chronic ischaemic injury after myocardial infarction. In vitro, resistin is induced by angiotensin II and induces CTGF in cardiomyocytes. Based on these findings, we conclude that a reduced ischaemia propensity and attenuated upstream reactive fibrotic pathways account for the attenuated fibrosis in VOH versus POH.

Resistin impairs SIRT1 function and induces senescence-associated phenotype in hepatocytes

Resistin is a cysteine-rich secreted protein which significantly inhibits phosphorylation of AMP-activated protein kinase in both human and mouse hepatocytes. It has been demonstrated that resistin plays an important role in inducing hepatic insulin resistance. However, whether resistin has other unknown influences on hepatocytes still remains poorly studied. Here, we show that recombinant resistin protein significantly reduces expression of SIRT1, attenuates the interaction between SIRT1 and PPARα as well as PGC-1α, and increases PGC-1α acetyl-lysine levels in HepG2 cells. In line with this, resistin treatment weakens the association between SIRT1 and major satellite repeats and alters the transcription level of SIRT1 target genes in mouse primary hepatocytes. Resistin treatment also significantly increases senescence-associated β-galactosidase activity in mouse primary hepatocytes and this effect can be eliminated by co-treatment with the SIRT1 agonists resveratrol and nicotinamide mononucleotide. Our findings suggest that resistin is a negative regulator of SIRT1 in both human hepatoma cell line HepG2 and mouse hepatocytes and that it might also play an important role in the development of senescence-associated liver diseases.