Direct effects of adipokines on the heart: focus on adiponectin

Immune mediators in heart-lung communication

It is often the case that serious, end-stage manifestations of disease result from secondary complications in organs distinct from the initial site of injury or infection. This is particularly true of diseases of the heart-lung axis, given the tight anatomical connections of the two organs within a common cavity in which they collectively orchestrate the two major, intertwined circulatory pathways. Immune cells and the soluble mediators they secrete serve as effective, and targetable, messengers of signals between different regions of the body but can also contribute to the spread of pathology. In this review, we discuss the immunological basis of interorgan communication between the heart and lung in various common diseases, and in the context of organ crosstalk more generally. Gaining a greater understanding of how the heart and lung communicate in health and disease, and viewing disease progression generally from a more holistic, whole-body viewpoint have the potential to inform new diagnostic approaches and strategies for better prevention and treatment of comorbidities.

Association between Triglyceride-Glucose Index and risk of all-cause and cardiovascular mortality in adults with prior cardiovascular disease: a cohort study using data from the US National Health and Nutrition Examination Survey, 2007-2018

OBJECTIVE

The association between the Triglyceride-Glucose (TyG) Index and mortality rates in patients with cardiovascular disease (CVD) remains unclear. This study investigates the association between the TyG index and the incidence of all-cause and CVD-specific mortality among individuals with a history of CVD.

DESIGN

Population-based cohort study.

SETTING

Data were sourced from the US National Health and Nutrition Examination Survey (2007-2018) and linked mortality data, with follow-up continuing until 31 December 2019.

PARTICIPANTS

The study population comprised 3422 individuals aged 20 years or older with a documented history of CVD.

OUTCOME MEASURES

We examined the association between the TyG index and the risk of all-cause and cardiovascular mortality.

RESULTS

Over a median follow-up of 5.79 years, 1030 deaths occurred, including 339 due to CVD. Cox regression analysis, adjusted for multiple confounders, showed that individuals in the highest TyG index quartile, compared with those in the lowest, had HRs of 0.76 (95% CI: 0.60 to 0.96) for all-cause mortality and 0.58 (95% CI: 0.39 to 0.89) for CVD mortality. There was a significant inverse relationship between higher TyG index levels and lower mortality risks. For each unit increase in the TyG index, the adjusted HRs for all-cause and CVD mortality decreased by 18% (HR 0.82; 95% CI: 0.71 to 0.94) and 27% (HR 0.73; 95% CI: 0.57 to 0.92), respectively.

CONCLUSIONS

TyG index values are negatively associated with all-cause and CVD mortality risks among individuals with previous CVD. Further interventional studies are needed to clarify the impact of TyG levels on cardiovascular health.

Recent Advances in Pre-Clinical Development of Adiponectin Receptor Agonist Therapies for Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is caused by genetic mutations in the cytoskeletal-sarcolemmal anchor protein dystrophin. Repeated cycles of sarcolemmal tearing and repair lead to a variety of secondary cellular and physiological stressors that are thought to contribute to weakness, atrophy, and fibrosis. Collectively, these stressors can contribute to a pro-inflammatory milieu in locomotor, cardiac, and respiratory muscles. Given the many unwanted side effects that accompany current anti-inflammatory steroid-based approaches for treating DMD (e.g., glucocorticoids), there is a need to develop new therapies that address inflammation and other cellular dysfunctions. Adiponectin receptor (AdipoR) agonists, which stimulate AdipoR1 and R2 isoforms on various cell types, have emerged as therapeutic candidates for DMD due to their anti-inflammatory, anti-fibrotic, and pro-myogenic properties in pre-clinical human and rodent DMD models. Although these molecules represent a new direction for therapeutic intervention, the mechanisms through which they elicit their beneficial effects are not yet fully understood, and DMD-specific data is limited. The overarching goal of this review is to investigate how adiponectin signaling may ameliorate pathology associated with dystrophin deficiency through inflammatory-dependent and -independent mechanisms and to determine if current data supports their future progression to clinical trials.

Epicardial Adipose Tissue and Heart Failure, Friend or Foe?

Heart failure (HF) management guidelines recommend individualized assessments based on HF phenotypes. Adiposity is a known risk factor for HF. Recently, there has been an increased interest in organ-specific adiposity, specifically the role of the epicardial adipose tissue (EAT), in HF risk. EAT is easily assessable through various imaging modalities and is anatomically and functionally connected to the myocardium. In pathological conditions, EAT secretes inflammatory cytokines, releases excessive fatty acids, and increases mechanical load on the myocardium, resulting in myocardial remodeling. EAT plays a pathophysiological role in characterizing both HF with reduced ejection fraction (HFrEF) and HF with preserved ejection fraction (HFpEF). In HFrEF, EAT volume is reduced, reflecting an impaired metabolic reservoir, whereas in HFpEF, the amount of EAT is associated with worse biomarker and hemodynamic profiles, indicating increased EAT activity. Studies have examined the possibility of therapeutically targeting EAT, and recent studies using sodium glucose cotransporter 2 inhibitors have shown potential in reducing EAT volume. However, further research is required to determine the clinical implications of reducing EAT activity in patients with HF.

Ischemia-induced cardiac dysfunction is exacerbated in adiponectin-knockout mice due to impaired autophagy flux

Strategies to enhance autophagy flux have been suggested to improve outcomes in cardiac ischemic models. We explored the role of adiponectin in mediating cardiac autophagy under ischemic conditions induced by permanent coronary artery ligation. We studied the molecular mechanisms underlying adiponectin's cardio-protective effects in adiponectin knockout (Ad-KO) compared with wild-type (WT) mice subjected to ischemia by coronary artery ligation and H9c2 cardiomyocyte cell line exposed to hypoxia. Systemic infusion of a cathepsin-B activatable near-infrared probe as a biomarker for autophagy and detection via noninvasive three-dimensional fluorescence molecular tomography combined with computerized tomography to quantitate temporal changes, indicated increased activity in the myocardium of WT mice after myocardial infarction which was attenuated in Ad-KO. Seven days of ischemia increased myocardial adiponectin accumulation and elevated ULK1/AMPK phosphorylation and autophagy assessed by Western blotting for LC3 and p62, an outcome not observed in Ad-KO mice. Cell death, assessed by TUNEL analysis and the ratio of Bcl-2:Bax, plus cardiac dysfunction, measured using echocardiography with strain analysis, were exacerbated in Ad-KO mice. Using cellular models, we observed that adiponectin stimulated autophagy flux in isolated primary adult cardiomyocytes and increased basal and hypoxia-induced autophagy in H9c2 cells. Real-time temporal analysis of caspase-3/7 activation and caspase-3 Western blot indicated that adiponectin suppressed activation by hypoxia. Hypoxia-induced mitochondrial reactive oxygen species production and cell death were also attenuated by adiponectin. Importantly, the ability of adiponectin to reduce caspase-3/7 activation and cell death was not observed in autophagy-deficient cells generated by CRISPR-mediated deletion of Atg7. Collectively, our data indicate that adiponectin acts in an autophagy-dependent manner to attenuate cardiomyocyte caspase-3/7 activation and cell death in response to hypoxia in vitro and ischemia in mice.

Probiotics as potential treatments to reduce myocardial remodelling and heart failure via the gut-heart axis: State-of-the-art review

Probiotics are considered to represent important modulators of gastrointestinal health through increased colonization of beneficial bacteria thus altering the gut microflora. Although these beneficial effects of probiotics are now widely recognized, emerging evidence suggests that alterations in the gut microflora also affect numerous other organ systems including the heart through a process generally referred to as the gut-heart axis. Moreover, cardiac dysfunction such as that seen in heart failure can produce an imbalance in the gut flora, known as dysbiosis, thereby further contributing to cardiac remodelling and dysfunction. The latter occurs by the production of gut-derived pro-inflammatory and pro-remodelling factors which exacerbate cardiac pathology. One of the key contributors to gut-dependent cardiac pathology is trimethylamine N-oxide (TMAO), a choline and carnitine metabolic by-product first synthesized as trimethylamine which is then converted into TMAO by a hepatic flavin-containing monooxygenase. The production of TMAO is particularly evident with regular western diets containing high amounts of both choline and carnitine. Dietary probiotics have been shown to reduce myocardial remodelling and heart failure in animal models although the precise mechanisms for these effects are not completely understood. A large number of probiotics have been shown to possess a reduced capacity to synthesize gut-derived trimethylamine and therefore TMAO thereby suggesting that inhibition of TMAO is a factor mediating the beneficial cardiac effects of probiotics. However, other potential mechanisms may also be important contributing factors. Here, we discuss the potential benefit of probiotics as effective therapeutic tools for attenuating myocardial remodelling and heart failure.

Epicardial adipose tissue and cardiac lipotoxicity: A review

Epicardial adipose tissue (EAT) has morphological and physiological contiguity with the myocardium and coronary arteries, making it a visceral fat deposit with some unique properties. Under normal circumstances, EAT exhibits biochemical, mechanical, and thermogenic cardioprotective characteristics. Under clinical processes, epicardial fat can directly impact the heart and coronary arteries by secreting proinflammatory cytokines via vasocrine or paracrine mechanisms. It is still not apparent what factors affect this equilibrium. Returning epicardial fat to its physiological purpose may be possible by enhanced local vascularization, weight loss, and focused pharmacological therapies. This review centers on EAT's developing physiological and pathophysiological dimensions and its various and pioneering clinical utilities.

Prognostic value of ventricle epicardial fat volume by cardiovascular magnetic resonance in chronic heart failure

The purpose of this study is to explore the prognostic values of ventricle epicardial fat volume (EFV) calculated by cardiac magnetic resonance in patients with chronic heart failure (CHF). A total of 516 patients with CHF (left ventricular ejection fraction ≤ 50%) were recruited, and 136 (26.4%) of whom experienced major adverse cardiovascular events (MACE) within median follow-up of 24 months. The target marker-EFV was found to be associated with MACE in both univariate and multivariable analysis adjusted for various clinical variables (p < 0.01), regardless as a continuous variable and categorized by X-tile program. EFV also showed promising predictive ability, with an area under the curve of 0.612, 0.618, and 0.687 for the prediction of 1-year, 2-year, and 3-year MACE, respectively. In conclusion, EFV could be a useful prognostic marker for CHF patients, helping to identify individuals at greater risk of MACE.

Constant-moderate versus high-intensity interval training on heart adiponectin levels in high-fat fed mice: a preventive and treatment approach

CONTEXT

Research has described that adiponectin plays a key role in cardiomyocytes metabolism, however, the effects of exercise during obesity on cardiac adiponectin levels is unclear.

OBJECTIVE

To investigate the effects of constant-moderate endurance (END) and high-intensity interval training (HIIT), on heart adiponectin levels in mice.

MATERIAL AND METHODS

Two experiments were conducted: (1) preventive (EX1): 10 week-old male mice were fed standard (CHOW) or high-fat diet (HFD;45% fat) and simultaneously trained with END and HIIT for 10 weeks; (2) Treatment (EX2): after 10 weeks of dietary intervention, another cohort of 10 week-old mice were trained by both programmes for 10 weeks.

RESULTS

In EX1, END and HIIT decreased low-molecular weight adiponectin (∼0.5-fold; p < 0.05) and increased GLUT4 levels (∼2-fold; p < .05). In EX2, HFD significantly decreased high-molecular weight adiponectin (∼0.7-fold; p < .05), and END reversed this change.Discussion and conclusion: HFD and exercise influence heart adiponectin isoforms and therefore might impact cardiomyocyte metabolism.

Role of Adiponectin in Cardiovascular Diseases Related to Glucose and Lipid Metabolism Disorders

Lifestyle changes have led to increased incidence of cardiovascular disease (CVD); therefore, potential targets against CVD should be explored to mitigate its risks. Adiponectin (APN), an adipokine secreted by adipose tissue, has numerous beneficial effects against CVD related to glucose and lipid metabolism disorders, including regulation of glucose and lipid metabolism, increasing insulin sensitivity, reduction of oxidative stress and inflammation, protection of myocardial cells, and improvement in endothelial cell function. These effects demonstrate the anti-atherosclerotic and antihypertensive properties of APN, which could aid in improving myocardial hypertrophy, and reducing myocardial ischemia/reperfusion (MI/R) injury and myocardial infarction. APN can also be used for diagnosing and predicting heart failure. This review summarizes and discusses the role of APN in the treatment of CVD related to glucose and lipid metabolism disorders, and explores future APN research directions and clinical application prospects. Future studies should elucidate the signaling pathway network of APN cardiovascular protective effects, which will facilitate clinical trials targeting APN for CVD treatment in a clinical setting.

Metabolic Acidosis and Cardiovascular Disease in CKD

Rationale & Objective

Metabolic acidosis related to chronic kidney disease (CKD) is associated with an accelerated decline in glomerular filtration rate (GFR) and the development of end-stage kidney disease. Whether metabolic acidosis is associated with cardiovascular (CV) events in patients with CKD is unclear.

Study Design

Retrospective cohort study.

Setting & Participants

The Optum De-identified Electronic Health Records Dataset, 2007–2017, was used to generate a cohort of patients with non-dialysis-dependent CKD who had at least 3 estimated GFR < 60 mL/min/1.73 m². Patients with metabolic acidosis (serum bicarbonate 12 to <22 mEq/L) or normal serum bicarbonate (22‒29 mEq/L) at baseline were identified by 2 consecutive measurements 28‒365 days apart.

Predictor

Serum bicarbonate as a continuous variable.

Outcome

Primary outcome was a composite of major adverse cardiovascular events (MACE+). Secondary outcomes included individual components of the composite outcome.

Analytical Approach

Cox proportional hazards models to evaluate the association between 1-mEq/L increments in serum bicarbonate and MACE+.

Results

A total of 51,558 patients were evaluated, 34% had metabolic acidosis. The median follow-up period was 3.9–4.5 years, depending on the outcome assessed. The adjusted hazard ratio (HR) for MACE+ was 0.964 (95% CI, 0.961–0.968). For the individual components of incident heart failure (HF), stroke, myocardial infarction (MI), and CV death, HRs were 0.98 (95% CI, 0.97–0.98), 0.98 (95% CI, 0.97–0.99), 0.96 (95% CI, 0.96–0.97), and 0.94 (95% CI, 0.93–0.94), respectively, for every 1-mEq/L increase in serum bicarbonate.

Limitations

Possible residual confounding.

Conclusions

Metabolic acidosis in CKD is associated with an increased risk of MACE+ as well as the individual components of incident HF, stroke, MI, and CV death. Randomized controlled trials evaluating treatments for the correction of metabolic acidosis in CKD to prevent CV events are needed.

Associations of body size and composition with subclinical cardiac dysfunction in older individuals: the cardiovascular health study

BACKGROUND

Focused studies in younger to middle-aged populations have demonstrated a relationship between obesity and adverse cardiac mechanics. We examined whether measures of overall and central adiposity are associated with cardiac mechanics, assessed by speckle-tracking echocardiography, in an older population without prevalent coronary heart disease or heart failure.

METHODS

Body composition was measured by anthropometry, bioelectrical impedance, and dual-energy x-ray absorptiometry among participants in the Cardiovascular Health Study, a population-based cohort of adults aged 65 years or older. Systolic and diastolic cardiac mechanics were measured with speckle-tracking analysis of echocardiograms. Multi-variable adjusted linear regression models were used to investigate associations of body composition measures and cardiac mechanics.

RESULTS

Mean age for the 3525 included participants was 72.6 years, 39% were male, and 10% were black. Mean body-mass index (BMI) was 26.3 ± 4.4 kg/m², waist circumference (WC) was 93.2 ± 12.9 cm, and waist-to-hip ratio was 0.92 ± 0.09. In fully adjusted analyses, all adiposity measures were associated with worse LV longitudinal strain, LV early diastolic strain rate, and left atrial reservoir strain; however, associations were strongest for WC and BMI (p < 0.001). When both BMI and WC were included in the same model, only WC remained associated with each cardiac strain measure.

CONCLUSION

In this cross-sectional study of older adults, central obesity was most robustly associated with impaired left ventricular systolic and diastolic strain as well as left atrial strain. The adverse effects of central obesity appear to extend even into older age.

Cardiometabolic impacts of saturated fatty acids: are they all comparable?

In last decades, a phenomenon named nutrition transition has been observed in many countries around the world. It has been characterised by increased consumption of fat-rich diets, predisposing to cardiometabolic diseases and high prevalence of the obesity. In the dietary recommendations cited to prevent metabolic diseases, there is a consensus to decrease intake of saturated fatty acids (SFA) to less than 10% of total energy intake, as recommended by the Food Safety Authorities. However, fatty acids of different chain lengths may exhibit different cardiometabolic effects. Thus, our major aim was to review the cardiometabolic effects of different classes of SFA according to carbon chain length, i.e. short-, medium- and long-chains. The review emphasises that not all SFA may have harmful cardiometabolic effects since short- and medium-chain SFA can provide beneficial health effects and participate to the prevention of metabolic disorders.

Obesity in the absence of comorbidities is not related to clinically meaningful left ventricular hypertrophy

Obesity is associated with the development of left ventricular (LV) hypertrophy. Whether obesity in in the absence of comorbidities can cause LV hypertrophy to an extent which could create diagnostic uncertainty with pathological states (such as hypertrophic cardiomyopathy) is unknown. We used cine cardiovascular magnetic resonance imaging to precisely measure LV wall thickness in the septum and lateral wall in 764 people with body mass indices ranging from 18.5 kg/m2 to 59.2 kg/m2 in the absence of major comorbidities. Obesity was related to LV wall thickness across the cohort (basal septum r 0.30, P < 0.001 and basal lateral wall r 0.18, P < 0.001). Although no participant had hypertension, these associations remained highly significant after controlling for systolic blood pressure (all P < 0.01). Each 10 kg/m2 increase in BMI was associated with an increase in basal septal wall thickness of 1.0 mm males and 0.8 mm in females, with no statistically significant difference between genders (P = 0.1). Even in class 3 obesity (BMI > 40 kg/m2), no LV wall thickness > 13.4 mm in males or > 12.7 mm in females was observed in this cohort. We confirm that obesity in the absence of comorbidities is associated with LV hypertrophy, and establish that the magnitude of this change is modest even in severe obesity. LV hypertrophy > 14 mm cannot safely be attributed to obesity alone and alternative diagnoses should be considered.

Impact of PCSK9 on CTRP9-Induced Metabolic Effects in Adult Rat Cardiomyocytes

The adipocytokine adiponectin and its structural homologs, the C1q/TNF-related proteins (CTRPs), increase insulin sensitivity, fatty acid oxidation and mitochondrial biogenesis. Adiponectin- and CTRP-induced signal transduction has been described to involve the adiponectin receptors and a number of co-receptors including the Low density lipoprotein receptor-related protein 1 (LRP1). LRP1 is another target of the proprotein convertase subtilisin/kexin-9 (PCSK9) in addition to the LDL-receptor (LDL-R). Here, we investigated the influence of PCSK9 on the metabolic effects of CTRP9, the CTRP with the highest homology to adiponectin. Knockdown of LRP1 in H9C2 cardiomyoblasts blunts the effects of CTRP9 on signal transduction and mitochondrial biogenesis, suggesting its involvement in CTRP9-induced cellular effects. Treatment of adult rat cardiomyocytes with recombinant PCSK9 but not knockdown of endogenous PCSK9 by siRNA results in a strong reduction in LRP1 protein expression and subsequently reduces the mitochondrial biogenic effect of CTRP9. PCSK9 treatment (24 h) blunts the effects of CTRP9-induced signaling cascade activation (AMP-dependent protein kinase, protein kinase B). In addition, the stimulating effects of CTRP9 on cardiomyocyte mitochondrial biogenesis and glucose metabolism (GLUT-4 translocation, glucose uptake) are largely blunted. Basal fatty acid (FA) uptake is strongly reduced by exogenous PCSK9, although protein expression of the PCSK9 target CD36, the key regulator of FA transport in cardiomyocytes, is not altered. In addition, only minor effects of PCSK9 were observed on CTRP9-induced FA uptake or the expression of genes involved in FA metabolism or uptake. Finally, this CTRP9-induced increase in CD36 expression occurs independent from LRP1 and LDL-R. In conclusion, PCSK9 treatment influences LRP1-mediated signaling pathways in cardiomyocytes. Thus, therapeutic PCSK9 inhibition may provide an additional benefit through stimulation of glucose metabolism and mitochondrial biogenesis in addition to the known lipid-lowering effects. This could be an important beneficial side effect in situations with impaired mitochondrial function and reduced metabolic flexibility thereby influencing cardiac function.

High plasma adiponectin is associated with increased pulmonary blood flow and reduced right ventricular function in patients with pulmonary hypertension

BACKGROUND

Adiponectin is a biomarker closely related to heart failure. However, its role in pulmonary hypertension remains unclear. In this study, we investigated the association between adiponectin and hemodynamic abnormalities, right ventricular function in patients with congenital heart disease associated pulmonary hypertension (CHD-PH).

METHODS

Patients with CHD-PH were enrolled in this cross-sectional study. Linear regression analysis was performed to assess the association between adiponectin, N-terminal pro-Brain Natriuretic Peptide (NT-proBNP) and different clinical parameters. Results were depicted as beta-estimates(ß) with 95%-confidence intervals (95% CI). In addition, mediation and receiver operating characteristic curve analyses were used to analyze the relationships among adiponectin, NT-proBNP and right ventricular function.

RESULTS

A total of 86 CHD-PH patients were included. The overall mean adiponectin concentration was 7.9 ± 5.8 μg/ml. Log adiponectin was positively correlated with pulmonary circulation index (ß = 2.2, 95% CI 0.5, 4.0), log NT-proBNP (ß = 0.22, 95% CI 0.04, 0.41) and inversely with the tricuspid annular plane systolic excursion (TAPSE, ß = -4.7, 95% CI -8.6, - 0.8). The mediation analysis revealed the association between NT-proBNP and TAPSE was fully mediated by adiponectin (total effect c = - 5.4, 95% CI -9.4, - 1.5, p = 0.013; direct effect c' = - 3.7, 95% CI -7.5, 0.1, p = 0.067). Additionally, the efficiency of adiponectin for detecting right ventricular dysfunction was not inferior to NT-proBNP (AUC = 0.84, 95% CI 0.67-1.00 vs AUC = 0.74, 95% CI 0.51-0.97, p = 0.23).

CONCLUSIONS

Adiponectin is closely correlated with pulmonary blood flow and right ventricular function and may be a valuable biomarker for disease assessment in patients with pulmonary hypertension.

The roles of epicardial adipose tissue in heart failure

Heart failure is a growing health problem resulting in the decreased life expectancy of patients and severely increased the healthcare burden. Penetrating research on the pathogenesis and regulation mechanism of heart failure is important for treatment of heart failure. Epicardial adipose tissue (EAT) has been demonstrated as not only a dynamic organ with biological functions but also an inert lipid store with regulating systemic metabolism. EAT mediates physiological and pathophysiological processes of heart failure by regulating adipogenesis, cardiac remodeling, insulin resistance, cardiac output, and renin angiotensin aldosterone system (RAAS). Moreover, EAT secretes a wide range of adipokines, adrenomedullin, adiponectin, and miRNAs through paracrine, endocrine, and vasocrine pathways, which involve in various extracellular and intracellular mechanism of cardiac-related cells in the progress of cardiovascular disease especially in heart failure. Nevertheless, mechanisms and roles of EAT on heart failure are barely summarized. Understanding the regulating mechanisms of EAT on heart failure may give rise to novel therapeutic targets and will open up innovative strategies to myocardial injury as well as in heart failure.

Adiponectin ameliorates lung injury induced by intermittent hypoxia through inhibition of ROS-associated pulmonary cell apoptosis

PURPOSE

Obstructive sleep apnea hypopnea syndrome has been reported to be associated with pulmonary hypertension (PH). Adiponectin (Ad) has many protective roles in the human body, including its function as an anti-inflammatory and an anti-oxidant, as well as its role in preventing insulin resistance and atherosclerosis. This study aimed to investigate the molecular mechanism of chronic intermittent hypoxia (CIH)-induced pulmonary injury and the protective role of Ad in experimental rats.

METHODS

Thirty male Sprague-Dawley rats were randomly divided into three groups with 10 rats in each group: normal control (NC) group, CIH group, and CIH + Ad group. Rats in the NC group were kept breathing room air for 12 weeks. Rats in the CIH group were intermittently exposed to a hypoxic environment for 8 h/day for 12 weeks. Rats in the CIH + Ad group received 10 μg Ad twice weekly via intravenous injection. After 12 weeks of CIH exposure, we detected the pulmonary function, pulmonary artery pressure, lung histology, pulmonary cell apoptosis, pulmonary artery endothelial cell apoptosis, mitochondrial membrane potential (MMP), and reactive oxygen species (ROS) level. We also analyzed expression proteins involved in the mitochondria-, endoplasmic reticulum (ER) stress-, and Fas receptor-associated pulmonary apoptosis pathways, as well as the SIRT3/SOD2 pathway.

RESULTS

CIH exposure for 12 weeks did not lead to abnormal pulmonary function, PH, or pulmonary artery endothelial cell apoptosis. However, we observed a significant increase in the rate of pulmonary cell apoptosis, the expression of proteins involved in mitochondria-, ER stress-, and Fas receptor-associated pulmonary apoptosis pathways, and the generation of ROS in the CIH group compared with the NC group. In contrast, the MMP and protein expressions of SIRT3/SOD2 pathway were significantly decreased in the CIH group compared with the NC group. Ad supplementation in the CIH + Ad group partially improved these changes induced by CIH.

CONCLUSION

Even though CIH did not cause abnormal pulmonary function or PH, early lung injury was detected at the molecular level in rats exposed to CIH. Treatment with Ad ameliorated the pulmonary injury by activating the SIRT3/SOD2 pathway, reducing ROS generation, and inhibiting ROS-associated lung cell apoptosis.

Tracking adiponectin biodistribution via fluorescence molecular tomography indicates increased vascular permeability after streptozotocin-induced diabetes

Adiponectin, a highly abundant polypeptide hormone in plasma, plays an important role in the regulation of energy metabolism in a wide variety of tissues, as well as providing important beneficial effects in diabetes, inflammation, and cardiovascular disease. To act on target tissues, adiponectin must move from the circulation to the interstitial space, suggesting that vascular permeability plays an important role in regulating adiponectin action. To test this hypothesis, fluorescently labeled adiponectin was used to monitor its biodistribution in mice with streptozotocin-induced diabetes (STZD). Adiponectin was, indeed, found to have increased sequestration in the highly fenestrated liver and other tissues within 90 min in STZD mice. In addition, increased myocardial adiponectin was detected and confirmed using computed tomography (CT) coregistration. This provided support of adiponectin delivery to affected cardiac tissue as a cardioprotective mechanism. Higher adiponectin content in the STZD heart tissues was further examined by ex vivo fluorescence molecular tomography (FMT) imaging, immunohistochemistry, and Western blot analysis. In vitro mechanistic studies using an endothelial monolayer on inserts and three-dimensional microvascular networks on microfluidic chips further confirmed that adiponectin flux was increased by high glucose. However, in the in vitro model and mouse heart tissue, high glucose levels did not change adiponectin receptor levels. An examination of the tight junction (TJ) complex revealed a decrease in the TJ protein claudin (CLDN)-7 in high glucose-treated endothelial cells, and the functional significance of this change was underscored by increased endothelium permeability upon siRNA-mediated knockdown of CLDN-7. Our data support the idea that glucose-induced effects on permeability of the vascular endothelium contribute to the actions of adiponectin by regulating its transendothelial movement from blood to the interstitial space. These observations are physiologically significant and critical when considering ways to harness the therapeutic potential of adiponectin for diabetes.

Biomarkers in diagnosing and treatment of acute heart failure

Acute heart failure (AHF) is a complex disorder involving different pathophysiological pathways. In recent years, there is an increased focus on biomarkers that help with diagnosis, risk stratification and disease monitoring of AHF. Finding a reliable set of biomarkers not only improves morbidity and mortality but it can also potentially reveal the new targets of therapy. In this paper, we have reviewed the biomarkers found useful for the diagnosis as well as for risk stratification and prognostication in patients with AHF. We have discussed the established biomarkers for AHF including cardiac troponins and natriuretic peptides and emerging biomarkers including adiponectin, mi-RNA, sST2, Gal-3, MR-proADM, OPG, CT-proAVP and H-FABP for the purposes of making diagnosis, their use as a guide of therapy or for determination of prognosis.

Organ crosstalk: the potent roles of inflammation and fibrotic changes in the course of organ interactions

BACKGROUND

Organ crosstalk can be defined as the complex and mutual biological communication between distant organs mediated by signaling factors. Normally, crosstalk helps to coordinate and maintain homeostasis, but sudden or chronic dysfunction in any organ causes dysregulation in another organ. Many signal molecules, including cytokines and growth factors, are involved in the metabolic dysregulation, and excessive or inappropriate release of these molecules leads to organ dysfunction or disease (e.g., obesity, type 2 diabetes).

AIM AND METHOD

The aim of this review is to reveal the impact of organ crosstalk on the pathogenesis of diseases associated with organ interactions and the role of inflammatory and fibrotic changes in the organ dysfunction. After searching in MEDLINE, PubMed and Google Scholar databases using 'organ crosstalk' as a keyword, studies related to organ crosstalk and organ interaction were compiled and examined.

CONCLUSION

The organ crosstalk and the functional integration of organ systems are exceedingly complex processes. Organ crosstalk contributes to metabolic homeostasis and affects the inflammatory response, related pathways and fibrotic changes. As in the case of interactions between adipose tissue and intestine, stimulation of inflammatory mechanisms plays an active role in the development of diseases including insulin resistance, obesity, type 2 diabetes and hepatic steatosis. The increased level of knowledge about the 'crosstalk' between any organ and distant organs will facilitate the early diagnosis of the disease as well as the management of the treatment practices in the short- and long-term organ dysfunction.

Obese phenotype and natriuretic peptides in patients with heart failure with preserved ejection fraction

The results of several recent experimental studies using animal models and clinical trials suggested that obesity is not merely an epiphenomenon or a prominent comorbidity in patients with heart failure (HF). Indeed, recent studies suggest that obesity is intimately involved in the pathogenesis of HF with preserved ejection fraction (HFpEF). The most recent studies indicate that approximately 50% of HF patients have HFpEF. As standard pharmacological treatment usually shows only a weak or even neutral effect on primary outcomes in patients with HFpEF, treatment strategies targeted to specific groups of HFpEF patients, such as those with obesity, may increase the likelihood of reaching substantial clinical benefit. Considering the well-known inverse relationship between body mass index (BMI) values and B-type natriuretic peptide (BNP) levels, it is theoretically conceivable that the measurement of natriuretic peptides, using cutoff values adjusted for age and BMI, should increase diagnostic and prognostic accuracy in HFpEF patients. However, further experimental studies and clinical trials are needed to differentiate and better understand specific mechanisms of the various HFpEF phenotypes, including obese HFpEF.

Visceral obesity, but not central obesity, is associated with cardiac remodeling in subjects with suspected metabolic syndrome

BACKGROUND AND AIMS

Metabolic syndrome (MetS) is a cluster of multiple risk factors including central obesity that may lead to cardiac damage and cardiovascular events. We investigated whether visceral obesity induces cardiac structural and functional remodeling independently from central obesity and other risk factors in subjects with suspected MetS.

METHODS AND RESULTS

We studied 229 participants with suspected MetS. Visceral fat area (VFA) was measured by bioelectrical impedance analysis. Left ventricular (LV) mass index, early diastolic velocity of mitral annulus (e'), and LV global longitudinal strain (GLS) were measured by echocardiography. Subjects were categorized into high and low VFA group (VFA_h and VFA_l). MetS was more prevalent in the VFA_h than in the VFA_l (p = 0.004). The VFA_h had a higher waist circumference (WC) than the VFA_l (p < 0.001). LV mass index was higher, but e' and GLS were lower in the VFA_h than in VFA_l (all p < 0.05). VFA was well correlated with blood pressure, fasting blood glucose, triglyceride, high-sensitivity C-reactive protein and adiponectin (all p < 0.05). VFA was correlated to LV mass index, e', and GLS (all p < 0.05) and was independently associated with GLS after adjustment for other risk factors, including WC (p = 0.005).

CONCLUSIONS

Visceral obesity assessed by VFA was well correlated with parameters of MetS. Visceral obesity, but not central obesity measured by WC, was independently associated with structural and functional cardiac remodeling in subjects with suspected MetS. It suggests that visceral obesity should be considered as an important risk factor for cardiac damage in dysmetabolic subjects.

TRIAL REGISTRATION

NCT02077530 (date of registration: November 1, 2013).

An adiponectin-S1P axis protects against lipid induced insulin resistance and cardiomyocyte cell death via reduction of oxidative stress

BACKGROUND

Adiponectin exerts several beneficial cardiovascular effects, however their specific molecular mechanisms require additional understanding. This study investigated the mechanisms of adiponectin action in the heart during high fat diet (HFD) feeding or in palmitate (PA) treated H9c2 cardiomyoblasts.

METHODS

6-week-old male adiponectin knock out (Ad-KO) mice were fed chow or 60% HFD for 6 weeks then received saline or recombinant adiponectin (3μg/g body weight) for an additional 2 weeks. After acute insulin stimulation (4 U/kg), tissue and serum samples were collected for analysis. H9c2 cardiomyocytes were treated ±0.1 mM PA, the adiponectin receptor agonist AdipoRon, or the antioxidant MnTBAP then assays to analyze reactive oxygen species (ROS) production and cell death were conducted. To specifically determine the mechanistic role of S1P, gain and loss of function studies were conducted with adding S1P to cells or the inhibitors THI and SKI-II, respectively.

RESULTS

HFD feeding induced cardiac insulin resistance in Ad-KO mice, which was reversed following replenishment of normal circulating adiponectin levels. In addition, myocardial total triglyceride was elevated by HFD and lipidomic analysis showed increased levels of ceramides and sphingosine-1-phosphate (S1P), with only the latter being corrected by adiponectin administration. Similarly, treatment of H9C2 cardiomyoblasts with PA led to a significant increase of intracellular S1P but not in conditioned media whereas AdipoRon significantly increased S1P production and secretion from cells. AdipoRon or the antioxidant MnTBAP significantly reduced PA-induced cell death. Gain and loss of function studies suggested S1P secretion and autocrine receptor activation mediated the effect of AdipoRon to attenuate PA-induced ROS production and cell death.

CONCLUSION

Our data establish adiponectin signaling-mediated increase in S1P secretion as a mechanism via which HFD or PA induced cardiomyocyte lipotoxicity, leading to insulin resistance and cell death, is attenuated.

Examining the Potential of Developing and Implementing Use of Adiponectin-Targeted Therapeutics for Metabolic and Cardiovascular Diseases

Cardiometabolic diseases encompass those affecting the heart and vasculature as well as other metabolic problems, such as insulin resistance, diabetes, and non-alcoholic fatty liver disease. These diseases tend to have common risk factors, one of which is impaired adiponectin action. This may be due to reduced bioavailability of the hormone or resistance to its effects on target tissues. A strong negative correlation between adiponectin levels and cardiometabolic diseases has been well-documented and research shown that adiponectin has cardioprotective, insulin sensitizing and direct beneficial metabolic effects. Thus, therapeutic approaches to enhance adiponectin action are widely considered to be desirable. The complexity of adiponectin structure and function has so far made progress in this area less than ideal. In this article we will review the effects and mechanism of action of adiponectin on cardiometabolic tissues, identify scenarios where enhancing adiponectin action would be of clinical value and finally discuss approaches via which this can be achieved.

A different effect of obesity on ECG in premenopausal and postmenopausal women

Both obesity and menopause are significant cardiovascular risk factors. In postmenopausal women the protective effect of estrogens is reduced and menopause is frequently associated with occurrence of other significant cardiovascular factors including obesity. This study was focused on evaluating the effect of obesity on the QRS complex in pre- and postmenopausal women. We present results of analysis of 199 electrocardiograms of pre- and postmenopausal women analyzed in relation to the body mass index within normal limits (BMI 20 to 24.9 kg/m²) and obesity (BMI > 30 kg/m²), respectively. Obesity in premenopausal women and menopause significantly affected both the electrical axis (EA) and maximum QRS spatial vector magnitude (QRSmax). The highest QRSmax and electrical axis values were observed in premenopausal lean women, and they were significantly higher as than in the premenopausal obese women, postmenopausal lean and obese women (QRSmax: 1.66 ± 0.4 mV, 1.17 ± 0.35 mV, 1.4 ± 0.46 mV, and 1.35 ± 0.39 mV, resp.). (EA: 56.4 ± 18.0°, 38.22 ± 18.38°, 45.82 ± 18.63°, and 36.75 ± 17.51°). The differences between obese premenopausal women, lean and obese postmenopausal women were not statistically significant. These differences were reflected in 12-lead ECG amplitude. The presence of additional cardiovascular risk factors did not affect the ECG parameters. Obesity significantly affected QRS complex in premenopausal women. This effect was comparable with the effect of menopause. Because all QRS complex changes were within normal limits, these results suggest that ECG evaluation in women should go beyond traditional diagnostic categories and consider the relationship between ECG changes and two cardiovascular risk factors - obesity and menopause.

Adiponectin is valuable in the diagnosis of acute heart failure with renal insufficiency

Acute heart failure (AHF) is a major public health issue due to its high incidence and poor prognosis; thus, efficient and timely diagnosis is critical for improving the prognosis and lowering the mortality rate. Amino-terminal pro-brain natriuretic peptide (NT-proBNP) is widely used in the diagnosis of AHF; however, its efficacy is controversial in diagnosing AHF with renal insufficiency. There were numerous studies reporting the association of adiponectin (ADPN) and heart diseases. Therefore, the present study aimed to investigate whether ADPN is helpful in identifying AHF with renal insufficiency. A total of 407 participants (218 AHF patients and 189 controls) were enrolled into the current study. The plasma levels of ADPN and NT-proBNP were measured using a sandwich enzyme-linked immunosorbent assay and an electrochemiluminescence immunoassay, respectively. In addition, these levels were compared among the various New York Health Association classes, as well as the ischemic and non-ischemic AHF cases. The correlation between the two biomarkers and the renal function was analyzed by Spearman's correlation, while the diagnostic efficiency of ADPN and NT-proBNP was evaluated in AHF patients with and without renal insufficiency. The results revealed that NT-proBNP exhibited a higher diagnostic efficiency as compared with ADPN in patients without renal insufficiency [area under the receiver operating characteristic curve (AUC), 0.905 vs. 0.775]. By contrast, the ADPN presented a better diagnostic value in comparison with NT-proBNP in AHF with renal insufficiency (AUC, 0.872 vs. 0.828). Therefore, a combination of these two biomarkers may provide an excellent efficacy in the diagnosis of AHF with renal insufficiency (AUC, 0.904; sensitivity, 71.2%; specificity, 98.3%). In conclusion, ADPN is a valuable biomarker for diagnosing AHF, particularly in patients with impaired renal function.

The evolving role of adiponectin as an additive biomarker in HFrEF

Heart failure (HF) is a growing health problem. Despite improved management and outcome, the number of patients with HF is expected to keep rising in the following years. In recent research, adiponectin was shown to exert beneficial effects in the cardiovascular system, but the protein was also implicated in the development and progression of HF. The objective of this review is to provide an overview of current knowledge on the role of adiponectin in HF with reduced ejection fraction. We discuss the cardioprotective and (anti-) inflammatory actions of adiponectin and its potential use in clinical diagnosis and prognosis.

The Effect of Omega-3 on Circulating Adiponectin in Adults With Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Whether consumption of omega-3 affects circulating adiponectin has not been established. The objective of this study was to evaluate the effect of omega-3 (food or supplement) on circulating adiponectin in patients with type 2 diabetes through a systematic review of meta-analyses of randomized controlled trials. PubMed, Scopus and Web of Science were searched for relevant studies through May 2016. Two researchers screened and abstracted the literature independently. Pooled estimates were obtained using the random-effects models. Overall, omega-3 increased adiponectin by 0.57 µg/mL (95% confidence interval [CI] 0.15 to 1.31; p=0.01, I-square=74.2% p for heterogeneity <0.001). The source of observed heterogeneity was explored by subgroup analyses. In subgroup analyses, adiponectin levels increased only in those who had consumed omega-3 for more than 8 weeks. This systematic review and meta-analysis of randomized, placebo-controlled clinical trials suggests that omega-3 in patients with type 2 diabetes increases circulating adiponectin. These findings support the potentially beneficial effects of dietary omega-3 in patients with type 2 diabetes on pathways related to adiponectin metabolism.

Cardiometabolic Traits and Systolic Mechanics in the Community

BACKGROUND

Obesity and cardiometabolic dysfunction are associated with increased risk of heart failure and other cardiovascular diseases. We sought to examine the association of cardiometabolic traits with left ventricular (LV) cardiac mechanics. We hypothesized that specific obesity-related phenotypes are associated with distinct aspects of LV strain.

METHODS AND RESULTS

We evaluated the associations of obesity-related phenotypes, including central adiposity, diabetes mellitus, insulin resistance, and circulating adipokine concentrations with echocardiographic measures of LV mechanical function among participants of the Framingham Heart Study Offspring and Third Generation cohorts. Among 6231 participants, the mean age was 51±16 years, and 54% were women. Greater body mass index was associated with worse LV longitudinal strain, radial strain (apical view), and longitudinal synchrony (multivariable-adjusted P<0.0001). After accounting for body mass index, we found that central adiposity, as measured by waist circumference, was associated with worse global longitudinal strain and synchrony (P≤0.006). Measures of insulin resistance, dyslipidemia, and diabetes mellitus also were associated with distinct aspects of LV mechanical function. Circulating leptin concentrations were associated with global longitudinal and radial strain (apical view, P<0.0001), whereas no such association was found with leptin receptor, adiponectin, or C-reactive protein.

CONCLUSIONS

Our findings highlight the association of central obesity and related cardiometabolic phenotypes above and beyond body mass index with subclinical measures of LV mechanical function. Interestingly, obesity-related traits were associated with distinct aspects of LV mechanics, underscoring potential differential effects along specific LV planes of deformation. These findings may shed light onto obesity-related cardiac remodeling and heart failure.

Myocardial Adiponectin Isoform Shift in Dogs with Congestive Heart Failure-A Comparison to Hibernating Brown Bears (Ursus arctos horribilis)

Adiponectin is the most abundant plasma adipokine, and is well known for its role in energy homeostasis and cardiac protection. In humans with dilated cardiomyopathy, myocardial adiponectin protein expression is reduced compared to normal hearts and has been implicated in the pathology of cardiomyopathy. Serum adiponectin levels are often conflicting, with higher levels associated with poor survival in humans with congestive heart failure (CHF). We evaluated adiponectin serum concentrations and myocardial protein expression in dogs with naturally occurring myxomatous mitral valve disease and CHF. We compared the findings to active and hibernating brown bears as bears are adapted to endure an extreme period of low cardiac output during their annual hibernation. Bears exhibited largely the active high-molecular weight (HMW) versus the low-molecular weight isoforms of myocardial adiponectin (HMW:LMW = 6.3) during both the active period and hibernation, while healthy dogs exhibited a more balanced mix of isoforms. Dogs with CHF expressed predominately HMW isoforms of adiponectin (HMW:LMW = 12.5), appearing more similar to bears. In contrast to humans, serum adiponectin was significantly lower in dogs with CHF and lowest levels in the severest CHF class. In both dogs and bears, myocardial adiponectin was expressed independent of circulating adiponectin concentrations, suggesting a local regulatory mechanism within the heart.

Function and Dysfunction of Adipose Tissue

Adipose tissue is an endocrine organ which is responsible for postprandial uptake of glucose and fatty acids, consequently producing a broad range of adipokines controlling several physiological functions like appetite, insulin sensitivity and secretion, immunity, coagulation, and vascular tone, among others. Many aspects of adipose tissue pathophysiology in metabolic diseases have been described in the last years. Recent data suggest two main factors for adipose tissue dysfunction: accumulation of nonesterified fatty acids and their secondary products and hypoxia. Both of these factors are thought to be on the basis of low-grade inflammatory activation, further increasing metabolic dysregulation in adipose tissue. In turn, inflammation is involved in the inhibition of substrate uptake, alteration of the secretory profile, stimulation of angiogenesis, and recruitment of further inflammatory cells, which creates an inflammatory feedback in the tissue and is responsible for long-term establishment of insulin resistance.

Peroxisome Proliferator-Activated Receptor α Reduces Endothelin-1-Caused Cardiomyocyte Hypertrophy by Inhibiting Nuclear Factor-κB and Adiponectin

Peroxisome proliferator-activated receptor α (PPARα) plays a role in the pathogenesis of cardiac hypertrophy, although its underlying mechanism remains unclear. The purpose of this study was to evaluate the effect of PPARα activation on endothelin-1- (ET-1-) caused cardiomyocyte hypertrophy and explore its underlying mechanisms. Human cardiomyocytes (HCMs) were cultured with or without ET-1, whereafter the inhibitory effects of fenofibrate, a PPARα activator, on cell size and adiponectin protein were tested. We examined the activation of extracellular signal-regulated kinase (ERK) and p38 proteins caused by ET-1 and the inhibition of the ERK and p38 pathways on ET-1-induced cell size and adiponectin expression. Moreover, we investigated the interaction of PPARα with adiponectin and nuclear factor-κB (NF-κB) by electrophoretic mobility shift assays and coimmunoprecipitation. ET-1 treatment significantly increased cell size, suppressed PPARα expression, and enhanced the expression of adiponectin. Pretreatment with fenofibrate inhibited the increase in cell size and enhancement of adiponectin expression. ET-1 significantly activated the ERK and p38 pathways, whereas PD98059 and SB205380, respectively, inhibited them. Our results suggest that activated PPARα can decrease activation of adiponectin and NF-κB and inhibit ET-1-induced cardiomyocyte hypertrophy.

Endothelin-1-Induced Cell Hypertrophy in Cardiomyocytes is Improved by Fenofibrate: Possible Roles of Adiponectin

Aim: Previous studies demonstrated that endothelin-1 (ET-1) can significantly increase the cell size and stimulate adiponectin expression in cultured human cardiomyocytes (HCM). The aim of the present study was to investigate the effects of fenofibrate, a peroxisome proliferator-activated receptor-α (PPARα) activator, on cell hypertrophy and adiponectin expression in vitro and in a rat model of daunorubicin-induced cardiomyopathy.

Methods: The cultured human cardiomyocytes (HCM) were stimulated with or without ET-1. The cell size and the protein expressions of PPARα and adiponectin were tested by confocal Immunofluorescence study and Western blot, respectively. To study the effects of PPARα activation on ET-1-induced cell hypertrophy and adiponectin protein synthesis, HCM were pretreated with fenofibrate or small interfering RNA (siRNA) of PPARα. Echocardiographic parameters were measured and immunohistochemistry study of myocardial adiponectin expression was conducted in the in vivo study.

Results: ET-1 significantly increased the cell size, dose-dependently suppressed the expression of PPARα, and enhanced the expression of adiponectin; whereas, such an increase of cell size and enhancement of adiponectin expression were inhibited by the pre-treatment with fenofibrate. Addition of siRNA of PPARα abolished the effects of fenofibrate. Moreover, we found that fenofibrate treatment can significantly improve the left ventricular function and reverse the myocardial expression of adiponectin.

Conclusions: Our study shows that fenofibrate may protect against ET-1-induced cardiomyocyte hypertrophy and enhanced adiponectin expression through modulation of PPARα expression in vitro and limitation of daunorubicin cardiotoxicity in vivo, suggesting a novel mechanistic insight into the role of PPARα and adiponectin in cardiac hypertrophy and heart failure.

Cellular, structural and functional cardiac remodelling following pressure overload and unloading

BACKGROUND

The cardiac remodelling process in advanced heart failure due to pressure overload has not been clearly defined but likely involves mechanisms of cardiac fibrosis and cardiomyocyte hypertrophy. The aim of this study was to examine pressure overload (PO)-induced cardiac remodelling processes and their reversibility after unloading in both humans with heart failure and a mouse model of PO induced by aortic constriction.

METHODS & RESULTS

Speckle tracking echocardiography showed PO-induced cardiac dysfunction in mice was reversible after removal of aortic constriction to unload. Masson's Trichrome staining suggested that PO-induced myocardial fibrosis was reversible, however detailed analysis of 3-dimensional collagen architecture by scanning electron microscopy demonstrated that matrix remodelling was not completely normalised as a disorganised network of thin collagen fibres was evident. Analysis of human left ventricular biopsy samples from HF patients revealed increased presence of large collagen fibres which were greatly reduced in paired samples from the same individuals after unloading by left ventricular assist device implantation. Again, an extensive network of small collagen fibres was still clearly seen to closely surround cardiomyocytes after unloading. Other features of PO-induced remodelling including increased myofibroblast content, cardiomyocyte disarray and hypertrophy were largely reversed upon unloading in both humans and mouse model. Previous work in humans demonstrated that receptors for adiponectin, an important mediator of cardiac fibrosis and hypertrophy, decreased in heart failure patients and returned to normal after unloading. Here we provide novel data showing a similar trend for adiponectin receptor adaptor protein APPL1, but not APPL2 isoform.

CONCLUSIONS

LV unloading diminishes PO-induced cardiac remodelling and improves function. These findings add new insights into the cardiac remodelling process, and provide novel targets for future pharmacologic therapies.

Crosstalk between the heart and peripheral organs in heart failure

Mediators from peripheral tissues can influence the development and progression of heart failure (HF). For example, in obesity, an altered profile of adipokines secreted from adipose tissue increases the incidence of myocardial infarction (MI). Less appreciated is that heart remodeling releases cardiokines, which can strongly impact various peripheral tissues. Inflammation, and, in particular, activation of the nucleotide-binding oligomerization domain-like receptors with pyrin domain (NLRP3) inflammasome are likely to have a central role in cardiac remodeling and mediating crosstalk with other organs. Activation of the NLRP3 inflammasome in response to cardiac injury induces the production and secretion of the inflammatory cytokines interleukin (IL)-1β and IL-18. In addition to having local effects in the myocardium, these pro-inflammatory cytokines are released into circulation and cause remodeling in the spleen, kidney, skeletal muscle and adipose tissue. The collective effects of various cardiokines on peripheral organs depend on the degree and duration of myocardial injury, with systematic inflammation and peripheral tissue damage observed as HF progresses. In this article, we review mechanisms regulating myocardial inflammation in HF and the role of factors secreted by the heart in communication with peripheral tissues.

Healthspan and longevity can be extended by suppression of growth hormone signaling

Average and maximal lifespan are important biological characteristics of every species, but can be modified by mutations and by a variety of genetic, dietary, environmental, and pharmacological interventions. Mutations or disruption of genes required for biosynthesis or action of growth hormone (GH) produce remarkable extension of longevity in laboratory mice. Importantly, the long-lived GH-related mutants exhibit many symptoms of delayed and/or slower aging, including preservation of physical and cognitive functions and resistance to stress and age-related disease. These characteristics could be collectively described as "healthy aging" or extension of the healthspan. Extension of both the healthspan and lifespan in GH-deficient and GH-resistant mice appears to be due to multiple interrelated mechanisms. Some of these mechanisms have been linked to healthy aging and genetic predisposition to extended longevity in humans. Enhanced insulin sensitivity combined with reduced insulin levels, reduced adipose tissue, central nervous system inflammation, and increased levels of adiponectin represent such mechanisms. Further progress in elucidation of mechanisms that link reduced GH action to delayed and healthy aging should identify targets for lifestyle and pharmacological interventions that could benefit individuals as well as society.

Lipid metabolism and signaling in cardiac lipotoxicity

The heart balances uptake, metabolism and oxidation of fatty acids (FAs) to maintain ATP production, membrane biosynthesis and lipid signaling. Under conditions where FA uptake outpaces FA oxidation and FA sequestration as triacylglycerols in lipid droplets, toxic FA metabolites such as ceramides, diacylglycerols, long-chain acyl-CoAs, and acylcarnitines can accumulate in cardiomyocytes and cause cardiomyopathy. Moreover, studies using mutant mice have shown that dysregulation of enzymes involved in triacylglycerol, phospholipid, and sphingolipid metabolism in the heart can lead to the excess deposition of toxic lipid species that adversely affect cardiomyocyte function. This review summarizes our current understanding of lipid uptake, metabolism and signaling pathways that have been implicated in the development of lipotoxic cardiomyopathy under conditions including obesity, diabetes, aging, and myocardial ischemia-reperfusion. This article is part of a Special Issue entitled: Heart Lipid Metabolism edited by G.D. Lopaschuk.

Cardiomyocyte Antihypertrophic Effect of Adipose Tissue Conditioned Medium from Rats and Its Abrogation by Obesity is Mediated by the Leptin to Adiponectin Ratio

White adipocytes are known to function as endocrine organs by secreting a plethora of bioactive adipokines which can regulate cardiac function including the development of hypertrophy. We determined whether adipose tissue conditioned medium (ATCM) generated from the epididymal regions of normal rats can affect the hypertrophic response of cultured rat ventricular myocytes to endothelin-1 (ET-1) administration. Myocytes were treated with ET-1 (10 nM) for 24 hours in the absence or presence of increasing ATCM concentrations. ATCM supressed the hypertrophic response to ET-1 in a concentration-dependent manner, an effect enhanced by the leptin receptor antagonist and attenuated by an antibody against the adiponectin AdipoR1 receptor. Antihypertrophic effects were also observed with ATCM generated from perirenal-derived adipose tissue. However, this effect was absent in ATCM from adipose tissue harvested from corpulent JCR:LA-cp rats. Detailed analyses of adipokine content in ATCM from normal and corpulent rats revealed no differences in the majority of products assayed, although a significant increase in leptin concentrations concomitant with decreased adiponectin levels was observed, resulting in a 11 fold increase in the leptin to adiponectin ratio in ATCM from JCR:LA-cp. The antihypertrophic effect of ATCM was associated with increased phosphorylation of AMP-activated protein kinase (AMPK), an effect abrogated by the AdipoR1 antibody. Moreover, the antihypertrophic effect of ATCM was mimicked by an AMPK activator. There was no effect of ET-1 on mitogen-activated protein kinase (MAPK) activities 24 hour after its addition either in the presence or absence of ATCM. Our study suggests that adipose tissue from healthy subjects exerts antihypertrophic effects via an adiponectin–dependent pathway which is impaired in obesity, most likely due to adipocyte remodelling resulting in enhanced leptin and reduced adiponectin levels.

Nutrient sensing and utilization: Getting to the heart of metabolic flexibility

A central feature of obesity-related cardiometabolic diseases is the impaired ability to transition between fatty acid and glucose metabolism. This impairment, referred to as "metabolic inflexibility", occurs in a number of tissues, including the heart. Although the heart normally prefers to metabolize fatty acids over glucose, the inability to upregulate glucose metabolism under energetically demanding conditions contributes to a pathological state involving energy imbalance, impaired contractility, and post-translational protein modifications. This review discusses pathophysiologic processes that contribute to cardiac metabolic inflexibility and speculates on the potential physiologic origins that lead to the current state of cardiometabolic disease in an obesogenic environment.

Adiponectin is required for cardiac MEF2 activation during pressure overload induced hypertrophy

Cardiomyocyte (CM) hypertrophy and increased heart mass in response to pressure overload are associated with hyper-activation of the myocyte enhancer factor-2 (MEF2) family of transcriptional regulators, and concomitant initiation of the fetal gene program. Adiponectin, an adipokine that is reduced in individuals with obesity and diabetes, has been characterized both as a negative regulator or permissive factor in cardiac hypertrophy. We therefore sought to analyze temporal regulation of MEF2 activity in response to pressure overload (PO) and changes in adiponectin status. To address this we crossed a well characterized transgenic MEF2 "sensor" mouse (MEF2-lacZ) with adiponectin null mice (Ad-KO) to create compound MEF2 lacZ/Ad-KO mice. Initially, we established that transverse aortic banding induced PO in wild-type (WT) mice increased heart mass and CM hypertrophy from 1 to 4weeks following surgery, indicated by increased CM diameter and heart weight/tibia length ratio. This was associated with cardiac dysfunction determined by echocardiography. Hypertrophic changes and dysfunction were observed in Ad-KO mice 4weeks following surgery. MEF2 lacZ activity and endogenous ANF mRNA levels, used as indicators of hypertrophic gene activation, were both robustly increased in WT mice after MTAB but attenuated in the Ad-KO background. Furthermore, activation of the pro-hypertrophic molecule p38 was increased following MTAB surgery in WT mice, but not in Ad-KO animals, and treatment of primary isolated CM with recombinant adiponectin induced p38 phosphorylation in a time dependent manner. Adiponectin also increased MEF2 activation in primary cardiomyocytes, an effect attenuated by p38 MAPK inhibition. In conclusion, our data indicate that robust hypertrophic MEF2 activation in the heart in vivo requires a background of adiponectin signaling and that adiponectin signaling in primary isolated CM directly enhances MEF2 activity through activation of p38 MAPK. We conclude that adiponectin is required for full induction of cardiomyocyte MEF2 activation, thus contributing to the myocardial hypertrophic gene expression program in response to PO.

Pressure Overload-Induced Cardiac Dysfunction in Aged Male Adiponectin Knockout Mice Is Associated With Autophagy Deficiency

Heart failure is a leading cause of death, especially in the elderly or obese and diabetic populations. Various remodeling events have been characterized, which collectively contribute to the progression of heart failure. Of particular interest, autophagy has recently emerged as an important determinant of cardiac remodeling and function. Here, we used aged, 13-month-old, male adiponectin knockout (Ad-KO) or wild-type (wt) mice subjected to aortic banding to induce pressure overload (PO). Cardiac strain analysis using speckle tracking echocardiography indicated significant dysfunction at an earlier stage in Ad-KO than wt. Analysis of autophagy by Western blotting for Light Chain 3 or microtubule-associated proteins 1B and Sequestosome 1 together with transmission electron microscopy of left ventricular tissue indicated a lack of PO-induced cardiac autophagy in Ad-KO compared with wt mice. Associated with this was mitochondrial degeneration and evidence of enhanced endoplasmic reticulum stress. Western blotting for Light Chain 3 or microtubule-associated proteins 1B, examination of flux using tandem fluoresent tagged-Light Chain 3, and analysis of lysosomal activity in H9c2 cardiac myoblasts treated with adiponectin indicated that adiponectin enhanced autophagy flux. In conclusion, adiponectin directly stimulates autophagic flux and the lack of autophagy in response to PO in aged mice lacking adiponectin may contribute to cellular events which exacerbate the development of cardiac dysfunction.

Temporal and Molecular Analyses of Cardiac Extracellular Matrix Remodeling following Pressure Overload in Adiponectin Deficient Mice

Adiponectin, circulating levels of which are reduced in obesity and diabetes, mediates cardiac extracellular matrix (ECM) remodeling in response to pressure overload (PO). Here, we performed a detailed temporal analysis of progressive cardiac ECM remodelling in adiponectin knockout (AdKO) and wild-type (WT) mice at 3 days and 1, 2, 3 and 4 weeks following the induction of mild PO via minimally invasive transverse aortic banding. We first observed that myocardial adiponectin gene expression was reduced after 4 weeks of PO, whereas increased adiponectin levels were detected in cardiac homogenates at this time despite decreased circulating levels of adiponectin. Scanning electron microscopy and Masson’s trichrome staining showed collagen accumulation increased in response to 2 and 4 weeks of PO in WT mice, while fibrosis in AdKO mice was notably absent after 2 weeks but highly apparent after 4 weeks of PO. Time and intensity of fibroblast appearance after PO was not significantly different between AdKO and WT animals. Gene array analysis indicated that MMP2, TIMP2, collagen 1α1 and collagen 1α3 were induced after 2 weeks of PO in WT but not AdKO mice. After 4 weeks MMP8 was induced in both genotypes, MMP9 only in WT mice and MMP1α only in AdKO mice. Direct stimulation of primary cardiac fibroblasts with adiponectin induced a transient increase in total collagen detected by picrosirius red staining and collagen III levels synthesis, as well as enhanced MMP2 activity detected via gelatin zymography. Adiponectin also enhanced fibroblast migration and attenuated angiotensin-II induced differentiation to a myofibroblast phenotype. In conclusion, these data indicate that increased myocardial bioavailability of adiponectin mediates ECM remodeling following PO and that adiponectin deficiency delays these effects.

Palmitate induces ER stress and autophagy in H9c2 cells: implications for apoptosis and adiponectin resistance

The association between obesity and heart failure is well documented and recent studies have indicated that understanding the physiological role of autophagy will be of great significance. Cardiomyocyte apoptosis is one component of cardiac remodeling which leads to heart failure and in this study we used palmitate-treated H9c2 cells as an in vitro model of lipotoxicity to investigate the role of autophagy in cell death. Temporal analysis revealed that palmitate (100 μM) treatment induced a gradual increase of intracellular lipid accumulation as well as apoptotic cell death. Palmitate induced autophagic flux, determined via increased LC3-II formation and p62 degradation as well as by detecting reduced colocalization of GFP with RFP in cells overexpressing tandem fluorescent GFP/RFP-LC3. The increased level of autophagy indicated by these measures were confirmed using transmission electron microscopy (TEM). Upon inhibiting autophagy using bafilomycin we observed an increased level of palmitate-induced cell death assessed by Annexin V/PI staining, detection of active caspase-3 and MTT cell viability assay. Interestingly, using TEM and p-PERK or p-eIF2α detection we observed increased endoplasmic reticulum (ER) stress in response to palmitate. Autophagy was induced as an adaptive response against ER stress since it was sensitive to ER stress inhibition. Palmitate-induced ER stress also induced adiponectin resistance, assessed via AMPK phosphorylation, via reducing APPL1 expression. This effect was independent of palmitate-induced autophagy. In summary, our data indicate that palmitate induces autophagy subsequent to ER stress and that this confers a prosurvival effect against lipotoxicity-induced cell death. Palmitate-induced ER stress also led to adiponecin resistance.

Adiponectin stimulates Rho-mediated actin cytoskeleton remodeling and glucose uptake via APPL1 in primary cardiomyocytes

OBJECTIVE

Adiponectin is known to confer its cardioprotective effects in obesity and type 2 diabetes, mainly by regulating glucose and fatty acid metabolism in cardiomyocytes. Dynamic actin cytoskeleton remodeling is involved in regulation of multiple biological functions, including glucose uptake. Here we investigated in neonatal cardiomyocytes whether adiponectin induced actin cytoskeleton remodeling and if this played a role in adiponectin-stimulated glucose uptake.

MATERIALS/METHODS

Primary cardiomyocytes were treated with full-length and globular adiponectin (fAd and gAd, respectively).

RESULTS

Both fAd and gAd increased RhoA activity, phosphorylation of the Rho/ROCK signaling target cofilin and actin polymerization to form filamentous actin as determined by rhodamine-phallodin immunofluorescence and quantitative analysis of filamentous to globular actin ratio. Scanning electron microscopy also demonstrated structural remodeling. Adiponectin stimulated glucose uptake, was significantly abrogated in the presence of inhibitors of actin cytoskeleton remodeling (cytochalasin D) and Rho/ROCK signaling (C3 transferase, Y27632). We showed that adiponectin increased colocalization of actin and APPL1 and that actin remodeling, phosphorylation of AMPK, p38MAPK and cofilin, glucose uptake and oxidation were all attenuated after siRNA-mediated knockdown of APPL1.

CONCLUSION

We show that adiponectin mediates Rho/ROCK-dependent actin cytoskeleton remodeling to increase glucose uptake and metabolism via APPL1 signaling.

Adiponectin mediated APPL1-AMPK signaling induces cell migration, MMP activation, and collagen remodeling in cardiac fibroblasts

Defects in adiponectin action have been implicated in the development of cardiac dysfunction in obesity and diabetes. Cardiac fibroblasts play an important role in regulating extracellular matrix remodeling yet little is known regarding the direct effects of adiponectin on cardiac fibroblasts. In this study, we first demonstrated temporal relocalization of cellular APPL1 in response to adiponectin in primary cardiac fibroblasts and that siRNA-mediated knockdown of APPL1 attenuated stimulation of AMPK by adiponectin. The cell surface content of MT1-MMP and activation of MMP2 were induced by adiponectin and these responses were dependent on AMPK signaling. Enhanced MMP activity facilitated increased fibroblast migration in response to adiponectin which was also prevented by inhibition of AMPK, with no change in cell proliferation observed. Collagen and elastin immunofluorescence demonstrated reorganization of the extracellular matrix in accordance with increased MMP activity, whereas quantitative mRNA analysis, (3) H-proline incorporation and picrosirius red assays showed no change in intracellular or extracellular total collagen levels in response to adiponectin. In summary, these data are the first to report the adiponectin stimulated APPL1-AMPK signaling axis in cardiac fibroblasts and characterize MT1-MMP translocation, MMP2 activity and cell migration as functional outcomes. These effects may be of significance in heart failure associated with obesity and diabetes.

The role of adiponectin signaling in metabolic syndrome and cancer

The increased prevalence of obesity has mandated extensive research focused on mechanisms responsible for associated clinical complications. Emerging from the focus on adipose tissue biology as a vitally important adipokine is adiponectin which is now believed to mediate anti-diabetic, anti-atherosclerotic, anti-inflammatory, cardioprotective and cancer modifying actions. Adiponectin mediates these primarily beneficial effects via direct signaling effects and via enhancing insulin sensitivity via crosstalk with insulin signaling pathways. Reduced adiponectin action is detrimental and occurs in obesity via decreased circulating levels of adiponectin action or development of adiponectin resistance. This review will focus on cellular mechanisms of adiponectin action, their crosstalk with insulin signaling and the resultant role of adiponectin in cardiovascular disease, diabetes and cancer and reviews data from in vitro cell based studies through animal models to clinical observations.

Altered transendothelial transport of hormones as a contributor to diabetes

The vascular endothelium is a dynamic structure responsible for the separation and regulated movement of biological material between circulation and interstitial fluid. Hormones and nutrients can move across the endothelium either via a transcellular or paracellular route. Transcellular endothelial transport is well understood and broadly acknowledged to play an important role in the normal and abnormal physiology of endothelial function. However, less is known about the role of the paracellular route. Although the concept of endothelial dysfunction in diabetes is now widely accepted, we suggest that alterations in paracellular transport should be studied in greater detail and incorporated into this model. In this review we provide an overview of endothelial paracellular permeability and discuss its potential importance in contributing to the development of diabetes and associated complications. Accordingly, we also contend that if better understood, altered endothelial paracellular permeability could be considered as a potential therapeutic target for diabetes.

Novel fibro-inflammation markers in assessing left atrial remodeling in non-valvular atrial fibrillation

Background

Structural remodeling is associated with the fibroinflammatory process in the atrial extracellular matrix. In the present study we aimed to investigate whether serum levels of new circulating remodeling markers differ in patients with atrial fibrillation (AF) compared to patients with sinus rhythm.

Material/Methods

The study population included 52 patients diagnosed with non-valvular AF and 33 age-matched patients with sinus rhythm. Serum levels of Galectin-3, matrix metalloproteinase-9 (MMP-9), lipocalin-2 (Lcn2/NGAL), N-terminal propeptide of type III procollagen (PIIINP), Hs-Crp, and neutrophil-to-lymphocyte ratio (NLR) were measured. The left atrial volume (LAV) was calculated by echocardiographic method and LAV index was calculated.

Results

Galectin-3, MMP-9, and PIIINP levels were significantly higher in AF patients except NGAL levels (1166 pg/ml (1126–1204) and 1204 pg/ml (1166–1362) p=0.001, 104 (81–179) pg/ml and 404 (162–564) pg/ml p<0.0001, and 1101 (500–1960) pg/ml and 6710 (2370–9950) pg/ml p<0.0001, respectively). The NLR and Hs-CRP levels were also higher in AF (2.1±1.0 and 2.7±1.1 p=0.02 and 4.2±1.9 mg/L and 6.0±4.7 mg/L p=0.04, respectively). In correlation analyses, NLR showed a strongly significant correlation with LAVi, but Hs-CRP did not (p=0.007 r=0.247, Pearson test and p=0.808 r=0.025, Pearson test, respectively). Moreover, Galectin-3, MMP-9, and PIIINP had a strong positive correlation with LAVi (p=0.021 r=640, Spearman test and p=0.004 r=0.319 Pearson test, and p=0.004 r=0.325 Pearson test, respectively).

Conclusions

Novel fibrosis and inflammation markers in AF are correlated with atrial remodeling. Several unexplained mechanisms of atrial remodeling remain, but the present study has taken the first step in elucidating the mechanisms involving fibrosis and inflammation markers.