Adiponectin decreases pulmonary arterial remodeling in murine models of pulmonary hypertension

Extrapulmonary manifestations of pulmonary arterial hypertension

INTRODUCTION

Extrapulmonary manifestations of pulmonary arterial hypertension (PAH) may play a critical pathobiological role and a deeper understanding will advance insight into mechanisms and novel therapeutic targets. This manuscript reviews our understanding of extrapulmonary manifestations of PAH.

AREAS COVERED

A group of experts was assembled and a complimentary PubMed search performed (October 2023 - March 2024). Inflammation is observed throughout the central nervous system and attempts at manipulation are an encouraging step toward novel therapeutics. Retinal vascular imaging holds promise as a noninvasive method of detecting early disease and monitoring treatment responses. PAH patients have gut flora alterations and dysbiosis likely plays a role in systemic inflammation. Despite inconsistent observations, the roles of obesity, insulin resistance and dysregulated metabolism may be illuminated by deep phenotyping of body composition. Skeletal muscle dysfunction is perpetuated by metabolic dysfunction, inflammation, and hypoperfusion, but exercise training shows benefit. Renal, hepatic, and bone marrow abnormalities are observed in PAH and may represent both end-organ damage and disease modifiers.

EXPERT OPINION

Insights into systemic manifestations of PAH will illuminate disease mechanisms and novel therapeutic targets. Additional study is needed to understand whether extrapulmonary manifestations are a cause or effect of PAH and how manipulation may affect outcomes.

Adiponectin and Asthma: Knowns, Unknowns and Controversies

Adiponectin is an adipokine associated with the healthy obese phenotype. Adiponectin increases insulin sensitivity and has cardio and vascular protection actions. Studies related to adiponectin, a modulator of the innate and acquired immunity response, have suggested a role of this molecule in asthma. Studies based on various asthma animal models and on the key cells involved in the allergic response have provided important insights about this relation. Some of them indicated protection and others reversed the balance towards negative effects. Many of them described the cellular pathways activated by adiponectin, which are potentially beneficial for asthma prevention or for reduction in the risk of exacerbations. However, conclusive proofs about their efficiency still need to be provided. In this article, we will, briefly, present the general actions of adiponectin and the epidemiological studies supporting the relation with asthma. The main focus of the current review is on the mechanisms of adiponectin and the impact on the pathobiology of asthma. From this perspective, we will provide arguments for and against the positive influence of this molecule in asthma, also indicating the controversies and sketching out the potential directions of research to complete the picture.

Metabolics of PH - an update

PURPOSE OF REVIEW

While there has been a longstanding interest in metabolic disease in pulmonary hypertension, publications in the last several years have translated basic science findings to human disease and even led to recently published studies of metabolic therapy in pulmonary arterial hypertension that are discussed here.

RECENT FINDINGS

Progress has been made in four key areas including mechanisms of insulin resistance in pulmonary arterial hypertension, the role of obesity in pulmonary vascular disease, novel clinical trials targeting metabolism in pulmonary hypertension, and the role of metabolism in chronic thromboembolic pulmonary hypertension.

SUMMARY

: Insulin resistance in pulmonary arterial hypertension is primarily in the lipid axis. There are systemic manifestations of insulin resistance including right ventricular lipotoxicity. Obesity is associated with elevation of right ventricular systolic pressure even in a healthy population and therapies in pulmonary arterial hypertension that target metabolism hold promise for improving exercise, right ventricular function, and visceral adiposity. Finally, there are emerging data that chronic thromboembolic pulmonary hypertension is similarly characterized by metabolic alterations, though the specific metabolites may be different from pulmonary arterial hypertension.

Adipokines and Metabolic Regulators in Human and Experimental Pulmonary Arterial Hypertension

Pulmonary hypertension (PH) is associated with meta-inflammation related to obesity but the role of adipose tissue in PH pathogenesis is unknown. We hypothesized that adipose tissue-derived metabolic regulators are altered in human and experimental PH. We measured circulating levels of fatty acid binding protein 4 (FABP-4), fibroblast growth factor -21 (FGF-21), adiponectin, and the mRNA levels of FABP-4, FGF-21, and peroxisome proliferator-activated receptor γ (PPARγ) in lung tissue of patients with idiopathic PH and healthy controls. We also evaluated lung and adipose tissue expression of these mediators in the three most commonly used experimental rodent models of pulmonary hypertension. Circulating levels of FABP-4, FGF-21, and adiponectin were significantly elevated in PH patients compared to controls and the mRNA levels of these regulators and PPARγ were also significantly increased in human PH lungs and in the lungs of rats with experimental PH compared to controls. These findings were coupled with increased levels of adipose tissue mRNA of genes related to glucose uptake, glycolysis, tricarboxylic acid cycle, and fatty acid oxidation in experimental PH. Our results support that metabolic alterations in human PH are recapitulated in rodent models of the disease and suggest that adipose tissue may contribute to PH pathogenesis.

PVAT targets VSMCs to regulate vascular remodelling: angel or demon

Vascular remodelling refers to abnormal changes in the structure and function of blood vessel walls caused by injury, and is the main pathological basis of cardiovascular diseases such as atherosclerosis, hypertension, and pulmonary hypertension. Among them, the neointimal hyperplasia caused by abnormal proliferation of vascular smooth muscle cells (VSMCs) plays a key role in the pathogenesis of vascular remodelling. Perivascular adipose tissue (PVAT) can release vasoactive substances to target VSMCs and regulate the pathological process of vascular remodelling. Specifically, PVAT can promote the conversion of VSMCs phenotype from contraction to synthesis by secreting visfatin, leptin, and resistin, and participate in the development of vascular remodelling-related diseases. Conversely, it can also inhibit the growth of VSMCs by secreting adiponectin and omentin to prevent neointimal hyperplasia and alleviate vascular remodelling. Therefore, exploring and developing new drugs or other treatments that facilitate the beneficial effects of PVAT on VSMCs is a potential strategy for prevention or treatment of vascular remodelling-related cardiovascular diseases.

Role of adipokines in systemic sclerosis pathogenesis

Systemic sclerosis (SSc) is a chronic autoimmune connective tissue disease with manifestations in multiple organs, including the skin, lung, heart, joints, gastrointestinal tract, kidney, and liver. Its pathophysiology is characterized by inflammation, fibrosis, and vascular damage, with an increased expression of numerous cytokines, chemokines, and growth factors. However, besides these growth factors and cytokines, another group of molecules may be involved in the pathogenesis of SSc: the adipokines. Adipokines are proteins with metabolic and cytokine-like properties, which were originally found to be expressed by adipose tissue. However, their expression is not limited to this tissue, and they can also be found in other organs. Therefore, this review will describe the current knowledge regarding adipokines in the context of SSc and try to elucidate their potential role in the pathogenesis of SSc.

Recombinant adiponectin protects the newborn rat lung from lipopolysaccharide-induced inflammatory injury

Preterm infants are at high risk for developing bronchopulmonary dysplasia and pulmonary hypertension from inflammatory lung injury. In adult models, adiponectin (APN)—an adipocyte‐derived hormone—protects the lung from inflammatory injury and pulmonary vascular remodeling. Cord blood APN levels in premature infants born < 26 weeks gestation are 5% of the level in infants born at term. We previously reported the expression profile of APN and its receptors in neonatal rat lung homogenates during the first 3 weeks of postnatal development. Here, we characterize the expression profile of APN and its receptors in specific lung cells and the effects of exogenous recombinant APN (rAPN) on lipopolysaccharide‐(LPS)‐induced cytokine and chemokine production in total lung homogenates and specific lung cells. In vitro, rAPN added to primary cultures of pulmonary artery smooth muscle cells attenuated the expression of LPS‐induced pro‐inflammatory cytokines while increasing the expression of anti‐inflammatory cytokines. In vivo, intraperitoneal rAPN (2 mg/kg), given 4 hr prior to intrapharyngeal administration of LPS (5 mg/kg) to newborn rats at postnatal day 4, significantly reduced gene and protein expression of the pro‐inflammatory cytokine IL‐1ß and reduced protein expression of the chemokines monocyte chemoattractant protein (MCP‐1) and macrophage inflammatory protein‐1 alpha (MIP‐1α) in the lung. LPS‐induced histopathological changes in the lung were also decreased. Moreover, rAPN given 20 hr after intrapharyngeal LPS had a similar effect on lung inflammation. These findings suggest a role for APN in protecting the lung from inflammation during early stages of lung development.

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.

Relation of visceral fat and haemodynamics in adults with Fontan circulation

Being overweight is associated with reduced functional capacity in Fontan patients. Increased adiposity leads to accumulation of epicardial and intra-abdominal visceral fat, which produce proinflammatory cytokines and may affect endothelial function. This retrospective study to evaluate the association between visceral fat and Fontan haemodynamics included 23 Fontan patients >18 years old with MRI and catheterization data available. Epicardial fat volume indexed to body surface area was measured by cardiac MRI, and intra-abdominal visceral fat thickness and subcutaneous fat thickness were derived from abdominal MRI. Stepwise regression models were used to determine univariable and multivariable associations between fat measures and haemodynamics. Mean age was 28.2 ± 9.5 years and body mass index was 26 ± 4 kg/m2. Mean central venous pressure was 13 ± 3 mmHg and pulmonary vascular resistance index was 1.23WU·m2 (interquartile range: 0.95-1.56). Epicardial fat volume was associated with age (r2 = 0.37, p = 0.002), weight (r2 = 0.26, p = 0.013), body mass index (r2 = 0.27, p = 0.011), and intra-abdominal visceral fat (r2 = 0.30, p = 0.018). Subcutaneous fat thickness did not relate to these measures. There was modest correlation between epicardial fat volume and pulmonary vascular resistance (r2 = 0.27, p = 0.02) and a trend towards significant correlation between intra-abdominal fat thickness and pulmonary vascular resistance (r2 = 0.21, p = 0.06). Subcutaneous fat thickness was not associated with Fontan haemodynamics. In multivariable analysis, including age and visceral fat measures, epicardial fat was independently correlated with pulmonary vascular resistance (point estimate 0.13 ± 0.05 per 10 ml/m2 increase, p = 0.03). In conclusion, in adults with Fontan circulation, increased visceral fat is associated with higher pulmonary vascular resistance. Excess visceral fat may represent a therapeutic target to improve Fontan haemodynamics.

Obesity, estrogens and adipose tissue dysfunction - implications for pulmonary arterial hypertension

Obesity is a prevalent global public health issue characterized by excess body fat. Adipose tissue is now recognized as an important endocrine organ releasing an abundance of bioactive adipokines including, but not limited to, leptin, adiponectin and resistin. Obesity is a common comorbidity amongst pulmonary arterial hypertension patients, with 30% to 40% reported as obese, independent of other comorbidities associated with pulmonary arterial hypertension (e.g. obstructive sleep apnoea). An 'obesity paradox' has been observed, where obesity has been associated with subclinical right ventricular dysfunction but paradoxically may confer a protective effect on right ventricular function once pulmonary hypertension develops. Obesity and pulmonary arterial hypertension share multiple pathophysiological mechanisms including inflammation, oxidative stress, elevated leptin (proinflammatory) and reduced adiponectin (anti-inflammatory). The female prevalence of pulmonary arterial hypertension has instigated the hypothesis that estrogens may play a causative role in its development. Adipose tissue, a major site for storage and metabolism of sex steroids, is the primary source of estrogens and circulating estrogens levels which are elevated in postmenopausal women and men with pulmonary arterial hypertension. This review discusses the functions of adipose tissue in both health and obesity and the links between obesity and pulmonary arterial hypertension. Shared pathophysiological mechanisms and the contribution of specific fat depots, metabolic and sex-dependent differences are discussed.

Effect of Obesity on Pulmonary Vascular Hemodynamics

CONTEXT

Obesity-related pulmonary arterial hypertension (PAH) is associated with hypoxia and metabolic abnormalities. Although right heart catheterization is the gold standard method for the diagnosis of PAH, Doppler echocardiography is more common. On the other hand, there is no definite echocardiographic parameter for PAH diagnosis. Novel echocardiographic parameter, pulmonary pulse transit time (pPTT), is assumed to be a surrogate marker for the assessment of PAH.

AIMS

The aim was to evaluate whether pPTT might be valuable for evaluating pulmonary vascular hemodynamics in obese patients.

SETTINGS AND DESIGN

A cross-sectional observational study.

METHODS

A total of 130 consecutive obese patients and 50 controls were included. Obese patients were divided into three groups according to body mass index (BMI): 25 < BMI <30 kg/m2 formed Group 1, 30 < BMI <35 kg/m2 formed Group 2, and 35

STATISTICAL ANALYSIS USED

Intergroup differences were analyzed with analysis of variance or Kruskal-Wallis test. Pearson's or Spearman's correlation analysis was used for correlation, multivariate logistic regression analysis, and regression.

RESULTS

Statistically significant reduction in pPTT was detected as early as in the first group (361.24 ± 25.54 vs. 391.26 ± 15.07; P = 0.015) and continued throughout Groups 2 and 3 (299.92 ± 35.10 vs. 391.26 ± 15.07; P < 0.0001, and 245.46 ± 11.25 vs. 391.26 ± 15.07; P < 0.0001, respectively). There was a strong negative correlation between pPTT and BMI (r = -0.848, P = 0.001). On linear regression analysis, BMI was found to be an independent risk factor for pPTT (confidence interval: -9.164-6.379, β = -0.525, P = 0.0001).

CONCLUSION

The results of this study suggest that obesity leads to an increase in PAH, and pPTT allows noninvasive determination of the pulmonary hemodynamics in obese patients. pPTT might be a useful parameter in terms of predicting pulmonary hemodynamics and vascular alterations in obese patients. Further studies are warranted to evaluate the association between obesity and PAH.

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Key Words

• Obesity
• pulmonary pulse transit time
• pulmonary vascular hemodynamics

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Affiliation(s)

Mustafa Duran Department of Cardiology, Konya Education and Research Hospital, Konya, Turkey
Murat Ziyrek Department of Cardiology, Konya Education and Research Hospital, Konya, Turkey

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Metabolic syndrome, neurohumoral modulation, and pulmonary arterial hypertension

Pulmonary vascular disease, including pulmonary arterial hypertension (PAH), is increasingly recognized to be affected by systemic alterations including up-regulation of the renin-angiotensin-aldosterone system and perturbations to metabolic pathways, particularly glucose and fat metabolism. There is increasing preclinical and clinical data that each of these pathways can promote pulmonary vascular disease and right heart failure and are not simply disease markers. More recently, trials of therapeutics aimed at neurohormonal activation or metabolic dysfunction are beginning to shed light on how interventions in these pathways may affect patients with PAH. This review will focus on underlying mechanistic data that supports neurohormonal activation and metabolic dysfunction in the pathogenesis of PAH and right heart failure as well as discussing early translational data in patients with PAH.

A multifaceted investigation into molecular associations of chronic thromboembolic pulmonary hypertension pathogenesis

Purpose

Chronic thromboembolic pulmonary hypertension is characterized by incomplete thrombus resolution following acute pulmonary embolism, leading to pulmonary hypertension and right ventricular dysfunction. Conditions such as thrombophilias, dysfibrinogenemias, and inflammatory states have been associated with chronic thromboembolic pulmonary hypertension, but molecular mechanisms underlying this disease are poorly understood. We sought to characterize the molecular and functional features associated with chronic thromboembolic pulmonary hypertension using a multifaceted approach.

Methods

We utilized functional assays to compare clot lysis times between chronic thromboembolic pulmonary hypertension patients and multiple controls. We then performed immunohistochemical characterization of tissue from chronic thromboembolic pulmonary hypertension, pulmonary arterial hypertension, and healthy controls, and examined RNA expression patterns of cultured lymphocytes and pulmonary arterial specimens. We then confirmed RNA expression changes using immunohistochemistry, immunofluorescence, and Western blotting in pulmonary arterial tissue.

Results

Clot lysis times in chronic thromboembolic pulmonary hypertension patients are similar to multiple controls. Chronic thromboembolic pulmonary hypertension endarterectomized tissue has reduced expression of both smooth muscle and endothelial cell markers. RNA expression profiles in pulmonary arteries and peripheral blood lymphocytes identified differences in RNA transcript levels related to inflammation and growth factor signaling, which we confirmed using immunohistochemistry. Gene expression data also suggested significant alterations in metabolic pathways, and immunofluorescence and Western blot experiments confirmed that unglycosylated CD36 and adiponectin expression were increased in chronic thromboembolic pulmonary hypertension versus controls.

Conclusions

Our data do not support impaired clot lysis underlying chronic thromboembolic pulmonary hypertension, but did demonstrate distinct molecular patterns present both in peripheral blood and in pathologic specimens of chronic thromboembolic pulmonary hypertension patients suggesting that altered metabolism may play a role in chronic thromboembolic pulmonary hypertension pathogenesis.

Pulmonary Hypertension and Obesity: Focus on Adiponectin

Pulmonary hypertension is an umbrella term including many different disorders causing an increase of the mean pulmonary arterial pressure (mPAP) ≥ 25 mmHg. Recent data revealed a strong association between obesity and pulmonary hypertension. Adiponectin is a protein synthetized by the adipose tissue with pleiotropic effects on inflammation and cell proliferation, with a potential protective role on the pulmonary vasculature. Both in vivo and in vitro studies documented that adiponectin is an endogenous modulator of NO production and interferes with AMP-activated protein kinase (AMPK) activation, mammalian target of rapamycin (mTOR), and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κβ) signaling preventing endothelial dysfunction and proliferation. Furthermore, adiponectin ameliorates insulin resistance by mediating the biological effects of peroxisome proliferator-activated receptor-gamma (PPARγ). Therefore, adiponectin modulation emerged as a theoretical target for the treatment of pulmonary hypertension, currently under investigation. Recently, consistent data showed that hypoglycemic agents targeting PPARγ as well as renin–angiotensin system inhibitors and mineralocorticoid receptor blockers may influence pulmonary hemodynamics in different models of pulmonary hypertension.

Adipokine expression in systemic sclerosis lung and gastrointestinal organ involvement

OBJECTIVES

The immunomodulatory properties of adipokines have previously been reported in autoimmune disorders. Less is known about the role of adipokines in systemic sclerosis (SSc). Lung and gastrointestinal tract are frequently involved in SSc; therefore, these organs were analyzed for adipokine expression as well as pulmonary samples of patients suffering from idiopathic pulmonary fibrosis (IPF) as comparison.

METHODS

Gastric samples (antrum, corpus) of SSc were analyzed immunohistochemically for adiponectin, resistin and visfatin compared with non-SSc related gastritis. Inflammatory cells were quantified in gastric samples and correlated with adipokine expression. Lung samples of SSc, IPF and healthy controls were also analyzed. Protein levels of lung tissue lysates and bronchoalveolar lavages (BAL) in minor fibrotic stages were measured by ELISA.

RESULTS

Lung sections of donor parenchyma showed significantly stronger adiponectin signals as IPF and SSc (donor vs. IPF: p < 0.0001). In SSc and IPF, resistin and visfatin were increased within immune cell infiltrates, but overall no difference in expression for resistin or visfatin compared to controls was observed. In BAL and lung protein lysates of early stages of fibrosis, adiponectin and visfatin were not reduced in IPF and SSc compared to controls. In gastric samples collected by standard endoscopic gastric biopsy, adiponectin was also significantly reduced in SSc- compared to non-SSc gastritis (p = 0.049) while resistin and visfatin were comparable although deeper fibrotic layers were not included in the respective samples. Adiponectin-positive tissues showed higher amounts of CD4⁺ but not CD8⁺ T cells. Controls showed no correlation between CD4⁺ T cells and resistin, whereas SSc showed significantly more CD4⁺ T cells in resistin-negative tissues.

CONCLUSION

Adipokines are expressed in gastric and lung samples of patients with SSc and in lung samples affected by IPF. Prominently, adiponectin levels were reduced in fibrotic SSc gastritic tissue as well as in IPF and SSc lung tissue. Consequently, adiponectin expression seems to be associated with fibrotic progression in the context of SSc and IPF.

Pulmonary vascular dysfunction in metabolic syndrome

Metabolic syndrome is a critically important precursor to the onset of many diseases, such as cardiovascular disease, and cardiovascular disease is the leading cause of death worldwide. The primary risk factors of metabolic syndrome include hyperglycaemia, abdominal obesity, dyslipidaemia, and high blood pressure. It has been well documented that metabolic syndrome alters vascular endothelial and smooth muscle cell functions in the heart, brain, kidney and peripheral vessels. However, there is less information available regarding how metabolic syndrome can affect pulmonary vascular function and ultimately increase an individual's risk of developing various pulmonary vascular diseases, such as pulmonary hypertension. Here, we review in detail how metabolic syndrome affects pulmonary vascular function.

A current view of G protein-coupled receptor - mediated signaling in pulmonary hypertension: finding opportunities for therapeutic intervention

Pathological vascular remodeling is observed in various cardiovascular diseases including pulmonary hypertension (PH), a disease of unknown etiology that has been characterized by pulmonary artery vasoconstriction, right ventricular hypertrophy, vascular inflammation, and abnormal angiogenesis in pulmonary circulation. G protein-coupled receptors (GPCRs) are the largest family in the genome and widely expressed in cardiovascular system. They regulate all aspects of PH pathophysiology and represent therapeutic targets. We overview GPCRs function in vasoconstriction, vasodilation, vascular inflammation-driven remodeling and describe signaling cross talk between GPCR, inflammatory cytokines, and growth factors. Overall, the goal of this review is to emphasize the importance of GPCRs as critical signal transducers and targets for drug development in PH.

Chronic Intermittent Hypoxia in Premature Infants: The Link Between Low Fat Stores, Adiponectin Receptor Signaling and Lung Injury

Premature infants have chronic intermittent hypoxia (CIH) that increases morbidity, and the youngest and the smallest premature infants are at the greatest risk. The combination of lung injury from inflammation/oxidative stress causing low functional residual capacity combined with frequent short apneas leads to CIH. Adiponectin (APN) is an adipose-derived adipokine that protects the lung from inflammation and oxidative stress. Premature and small for gestational age (SGA) infants have minimal body fat and low levels of circulating APN. To begin to understand the potential role of APN in lung protection during lung development, we characterized the developmental profile of APN and APN receptors (AdipoR1 and AdipoR2) protein and mRNA expression in the newborn rat lung at fetal day (FD) 19, and postnatal days (PD) 1, 4, 7, 10, 14, 21, and 28. Protein levels in lung homogenates were measured by western blot analyses; relative mRNA expression was detected by quantitative PCR (qPCR); and serum high molecular weight (HMW) APN was measured using enzyme-linked immunosorbent assay (ELISA). Results: APN protein and mRNA levels were lowest at FD19 and PD1, increased 2.2-fold at PD4, decreased at PD10, and then increased again at PD21. AdipoR1 protein and mRNA levels peaked at PD1, followed by a threefold drop by PD4, and remained low until PD21. AdipoR2 protein and mRNA levels also peaked at PD1, but remained high at PD4, followed by a 1.7-fold drop by PD10 that remained low by PD21. Serum APN levels detected by ELISA did not differ from PD4 to PD28. To date, this is the first report characterizing APN and APN receptor protein and mRNA expression in the rat lung during development. The developmental stage of the newborn rat lung models that of the premature human infant; both are in the saccular stage of lung development. In the newborn rat lung, alveolarization begins at PD4, peaks at PD10, and ends at PD21. Importantly, we found that AdipoR1 receptor protein and mRNA expression is lowest during lung alveolarization (PD4 to PD21). Thus, we speculate that low levels of AdipoR1 during lung alveolarization contributes to the increased susceptibility to developing acute lung edema and chronic lung injury such as bronchopulmonary dysplasia (BPD) in premature human infants.

Combination treatment of adipose-derived stem cells and adiponectin attenuates pulmonary arterial hypertension in rats by inhibiting pulmonary arterial smooth muscle cell proliferation and regulating the AMPK/BMP/Smad pathway

The present study aimed to assess the effects of therapy with adiponectin (APN) gene-modified adipose-derived stem cells (ADSCs) on pulmonary arterial hypertension (PAH) in rats and the underlying cellular and molecular mechanisms. ADSCs were successfully isolated from the rats and characterized. ADSCs were effectively infected with the green fluorescent protein (GFP)-empty (ADSCs-V) or the APN-GFP (ADSCs-APN) lentivirus and the APN expression was evaluated by ELISA. Sprague-Dawley rats were administered monocrotaline (MCT) to develop PAH. The rats were treated with MCT, ADSCs, ADSCs-V and ADSCs-APN. Then ADSCs-APN in the lung were investigated by confocal laser scanning microscopy and western blot analysis. Engrafted ADSCs in the lung were located around the vessels. Mean pulmonary arterial pressure (mPAP) and the right ventricular hypertrophy index (RVHI) in the ADSCs-APN-treated mice were significantly decreased as compared with the ADSCs and ADSCs-V treatments. Pulmonary vascular remodeling was assessed. Right ventricular (RV) function was evaluated by echocardiography. We found that pulmonary vascular remodeling and the parameters of RV function were extensively improved after ADSCs-APN treatment when compared with ADSCs and ADSCs-V treatment. Pulmonary artery smooth muscle cells (PASMCs) were isolated from the PAH rats. The antiproliferative effect of APN on PASMCs was assayed by Cell Counting Kit-8. The influence of APN and specific inhibitors on the levels of bone morphogenetic protein (BMP), adenosine monophosphate activated protein kinase (AMPK), and small mothers against decapentaplegia (Smad) pathways was detected by western blot analysis. We found that APN suppressed the proliferation of PASMCs isolated from the PAH rats by regulating the AMPK/BMP/Smad pathway. This effect was weakened by addition of the AMPK inhibitor (compound C) and BMP2 inhibitor (noggin). Therefore, combination treatment with ADSCs and APN effectively attenuated PAH in rats by inhibiting PASMC proliferation and regulating the AMPK/BMP/Smad pathway.

Adiponectin is an endogenous anti-fibrotic mediator and therapeutic target

Skin fibrosis in systemic sclerosis (SSc) is accompanied by attrition of dermal white adipose tissue (dWAT) and reduced levels of circulating adiponectin. Since adiponectin has potent regulatory effects on fibroblasts, we sought to assess adiponectin signaling in SSc skin biopsies, and evaluate fibrosis in mice with adiponectin gain- and loss-of-function mutations. Furthermore, we investigated the effects and mechanism of action of agonist peptides targeting adiponectin receptors in vitro and in vivo. We found that adiponectin pathway activity was significantly reduced in a subset of SSc skin biopsies. Mice lacking adiponectin mounted an exaggerated dermal fibrotic response, while transgenic mice with constitutively elevated adiponectin showed selective dWAT expansion and protection from skin and peritoneal fibrosis. Adiponectin receptor agonists abrogated ex vivo fibrotic responses in explanted normal and SSc fibroblasts and in 3D human skin equivalents, in part by attenuating focal adhesion complex assembly, and prevented and reversed experimentally-induced organ fibrosis in mice. These results implicate aberrant adiponectin pathway activity in skin fibrosis, identifying a novel function for this pleiotropic adipokine in regulation of tissue remodeling. Restoring adiponectin signaling in SSc patients therefore might represent an innovative pharmacological strategy for intractable organ fibrosis.

Asthma and obesity

The problem of modern medicine is to optimize the treatment of patients with comorbidity, whose number has been growing steadily in recent years. The concurrence of asthma and obesity determines the severity of disease, low-level control, and resistance to basic therapy in conjunction with more frequent use of β-agonists for relief of symptoms, and frequent hospitalizations for a disease exacerbation. Currently, there are only a few known pathogenetic components that are responsible for the negative impact of visceral obesity on the course of asthma.

Pulmonary hypertension in patients with heart failure and preserved ejection fraction: differential diagnosis and management

The most common cause of pulmonary hypertension (PH) due to left heart disease (LHD) was previously rheumatic mitral valve disease. However, with the disappearance of rheumatic fever and an aging population, nonvalvular LHD is now the most common cause of group 2 PH in the developed world. In this review, we examine the challenge of investigating patients who have PH and heart failure with preserved ejection fraction (HF-pEF), where differentiating between pulmonary arterial hypertension (PAH) and PH-LHD can be difficult, and also discuss the entity of combined precapillary and postcapillary PH. Given the proven efficacy of targeted therapy for the treatment of PAH, there is increasing interest in whether these treatments may benefit selected patients with PH associated with HF-pEF, and we review current trial data.

The adiponectin levels and asthma control in non-obese children with asthma

OBJECTIVE

To determine the relationship between adiponectin levels and asthma control in non-obese asthmatic children.

METHODS

Eighty-two children with asthma who had been followed up in a single center were included. The control group included 28 children with no evidence of allergic disease. Adiponectin levels were analyzed in all children. Additionally, skin prick tests and pulmonary function tests were also performed in patients.

RESULTS

Three groups were designated with respect to asthma control as; well-controlled group (n = 28), partially controlled group (n = 34) and uncontrolled group (n = 20). There was no significant difference of gender, age, height, weight, BMI and adiponectin levels between study and control groups (p > 0.05). The duration of illness, presence of atopy and sensitivities to mite, pollens, dander and cockroaches were similar between the groups (p > 0.05). Adiponectin, FEV1, FVC, and FEV1/FVC levels were significantly lower in uncontrolled group (p < 0.05). Sensitivity to Alternaria alternata was significantly higher in the uncontrolled group (p < 0.05). In logistic regression analysis, as dependent parameter, adiponectin, FEV1, FVC and FEV1/FVC levels were found to be statistically significant for uncontrolled asthma.

CONCLUSION

Adiponectin levels in non-obese asthmatics were not different from controls. Lower levels of adiponectin were associated with uncontrolled asthma. Low adiponectin level can therefore be used as an indicator of uncontrolled asthma.

Impaired right ventricular hemodynamics indicate preclinical pulmonary hypertension in patients with metabolic syndrome

Background

Metabolic disease can lead to intrinsic pulmonary hypertension in experimental models. The contributions of metabolic syndrome (MetS) and obesity to pulmonary hypertension and right ventricular dysfunction in humans remain unclear. We investigated the association of MetS and obesity with right ventricular structure and function in patients without cardiovascular disease.

Methods and Results

A total of 156 patients with MetS (mean age 44 years, 71% women, mean body mass index 40 kg/m²), 45 similarly obese persons without MetS, and 45 nonobese controls underwent echocardiography, including pulsed wave Doppler measurement of pulmonary artery acceleration time (PAAT) and ejection time. Pulmonary artery systolic pressure was estimated from PAAT using validated equations. MetS was associated with lower tricuspid valve e′ (right ventricular diastolic function parameter), shorter PAAT, shorter ejection time, and larger pulmonary artery diameter compared with controls (P<0.05 for all). Estimated pulmonary artery systolic pressure based on PAAT was 42±12 mm Hg in participants with MetS compared with 32±9 and 32±10 mm Hg in obese and nonobese controls (P for ANOVA <0.0001). After adjustment for age, sex, hypertension, diabetes, body mass index, and triglycerides, MetS remained associated with a 20‐ms–shorter PAAT (β=−20.4, SE=6.5, P=0.002 versus obese). This association persisted after accounting for left ventricular structure and function and after exclusion of participants with obstructive sleep apnea.

Conclusions

MetS is associated with abnormal right ventricular and pulmonary artery hemodynamics, as shown by shorter PAAT and subclinical right ventricular diastolic dysfunction. Estimated pulmonary artery systolic pressures are higher in MetS and preclinical metabolic heart disease and raise the possibility that pulmonary hypertension contributes to the pathophysiology of metabolic heart disease.

Obesity-related pulmonary arterial hypertension in rats correlates with increased circulating inflammatory cytokines and lipids and with oxidant damage in the arterial wall but not with hypoxia

Obesity is causally linked to a number of comorbidities, including cardiovascular disease, diabetes, renal dysfunction, and cancer. Obesity has also been linked to pulmonary disorders, including pulmonary arterial hypertension (PAH). It was long believed that obesity-related PAH was the result of hypoventilation and hypoxia due to the increased mechanical load of excess body fat. However, in recent years it has been proposed that the metabolic and inflammatory disturbances of obesity may also play a role in the development of PAH. To determine whether PAH develops in obese rats in the absence of hypoxia, we assessed pulmonary hemodynamics and pulmonary artery (PA) structure in the diet-resistant/diet-induced obesity (DR/DIO) and Zucker lean/fatty rat models. We found that high-fat feeding (DR/DIO) or overfeeding (Zucker) elicited PA remodeling, neomuscularization of distal arterioles, and elevated PA pressure, accompanied by right ventricular (RV) hypertrophy. PA thickening and distal neomuscularization were also observed in DIO rats on a low-fat diet. No evidence of hypoventilation or chronic hypoxia was detected in either model, nor was there a correlation between blood glucose or insulin levels and PAH. However, circulating inflammatory cytokine levels were increased with high-fat feeding or calorie overload, and hyperlipidemia and oxidant damage in the PA wall correlated with PAH in the DR/DIO model. We conclude that hyperlipidemia and peripheral inflammation correlate with the development of PAH in obese subjects. Obesity-related inflammation may predispose to PAH even in the absence of hypoxia.

Pulmonary and cardiac function in asymptomatic obese subjects and changes following a structured weight reduction program: a prospective observational study

BACKGROUND

The prevalence of obesity is rising. Obesity can lead to cardiovascular and ventilatory complications through multiple mechanisms. Cardiac and pulmonary function in asymptomatic subjects and the effect of structured dietary programs on cardiac and pulmonary function is unclear.

OBJECTIVE

To determine lung and cardiac function in asymptomatic obese adults and to evaluate whether weight loss positively affects functional parameters.

METHODS

We prospectively evaluated bodyplethysmographic and echocardiographic data in asymptomatic subjects undergoing a structured one-year weight reduction program.

RESULTS

74 subjects (32 male, 42 female; mean age 42±12 years) with an average BMI 42.5±7.9, body weight 123.7±24.9 kg were enrolled. Body weight correlated negatively with vital capacity (R = -0.42, p<0.001), FEV1 (R = -0.497, p<0.001) and positively with P 0.1 (R = 0.32, p = 0.02) and myocardial mass (R = 0.419, p = 0.002). After 4 months the study subjects had significantly reduced their body weight (-26.0±11.8 kg) and BMI (-8.9±3.8) associated with a significant improvement of lung function (absolute changes: vital capacity +5.5±7.5% pred., p<0.001; FEV1+9.8±8.3% pred., p<0.001, ITGV+16.4±16.0% pred., p<0.001, SR tot -17.4±41.5% pred., p<0.01). Moreover, P0.1/Pimax decreased to 47.7% (p<0.01) indicating a decreased respiratory load. The change of FEV1 correlated significantly with the change of body weight (R = -0.31, p = 0.03). Echocardiography demonstrated reduced myocardial wall thickness (-0.08±0.2 cm, p = 0.02) and improved left ventricular myocardial performance index (-0.16±0.35, p = 0.02). Mitral annular plane systolic excursion (+0.14, p = 0.03) and pulmonary outflow acceleration time (AT +26.65±41.3 ms, p = 0.001) increased.

CONCLUSION

Even in asymptomatic individuals obesity is associated with abnormalities in pulmonary and cardiac function and increased myocardial mass. All the abnormalities can be reversed by a weight reduction program.

Regulation of adipocyte lipolysis

In adipocytes the hydrolysis of TAG to produce fatty acids and glycerol under fasting conditions or times of elevated energy demands is tightly regulated by neuroendocrine signals, resulting in the activation of lipolytic enzymes. Among the classic regulators of lipolysis, adrenergic stimulation and the insulin-mediated control of lipid mobilisation are the best known. Initially, hormone-sensitive lipase (HSL) was thought to be the rate-limiting enzyme of the first lipolytic step, while we now know that adipocyte TAG lipase is the key enzyme for lipolysis initiation. Pivotal, previously unsuspected components have also been identified at the protective interface of the lipid droplet surface and in the signalling pathways that control lipolysis. Perilipin, comparative gene identification-58 (CGI-58) and other proteins of the lipid droplet surface are currently known to be key regulators of the lipolytic machinery, protecting or exposing the TAG core of the droplet to lipases. The neuroendocrine control of lipolysis is prototypically exerted by catecholaminergic stimulation and insulin-induced suppression, both of which affect cyclic AMP levels and hence the protein kinase A-mediated phosphorylation of HSL and perilipin. Interestingly, in recent decades adipose tissue has been shown to secrete a large number of adipokines, which exert direct effects on lipolysis, while adipocytes reportedly express a wide range of receptors for signals involved in lipid mobilisation. Recently recognised mediators of lipolysis include some adipokines, structural membrane proteins, atrial natriuretic peptides, AMP-activated protein kinase and mitogen-activated protein kinase. Lipolysis needs to be reanalysed from the broader perspective of its specific physiological or pathological context since basal or stimulated lipolytic rates occur under diverse conditions and by different mechanisms.

Scleroderma-related lung disease: are adipokines involved pathogenically?

Scleroderma is a systemic autoimmune disease of unknown etiology whose characteristic features include endothelial cell dysfunction, fibroblast proliferation, and immune dysregulation. Although almost any organ can be pathologically involved in scleroderma, lung complications including interstitial lung disease (ILD) and pulmonary arterial hypertension (PAH) are the leading cause of death in patients with this condition. Currently, the molecular mechanisms leading to development of scleroderma-related lung disease are poorly understood; however, the systemic nature of this condition has led many to implicate circulating factors in the pathogenesis of some of its organ impairment. In this article we focus on a new class of circulating factors derived from adipose-tissue called adipokines, which are known to be altered in scleroderma. Recently, the adipokines adiponectin and leptin have been found to regulate biological activity in endothelial, fibroblast, and immune cell types in lung and in many other tissues. The pleiotropic nature of these circulating factors and their functional activity on many cell types implicated in the pathogenesis of ILD and PAH suggest these hormones may be mechanistically involved in the onset and/or progression of scleroderma-related lung diseases.

Fatty acid nitroalkenes ameliorate glucose intolerance and pulmonary hypertension in high-fat diet-induced obesity

AIMS

Obesity is a risk factor for diabetes and cardiovascular diseases, with the incidence of these disorders becoming epidemic. Pathogenic responses to obesity have been ascribed to adipose tissue (AT) dysfunction that promotes bioactive mediator secretion from visceral AT and the initiation of pro-inflammatory events that induce oxidative stress and tissue dysfunction. Current understanding supports that suppressing pro-inflammatory and oxidative events promotes improved metabolic and cardiovascular function. In this regard, electrophilic nitro-fatty acids display pleiotropic anti-inflammatory signalling actions.

METHODS AND RESULTS

It was hypothesized that high-fat diet (HFD)-induced inflammatory and metabolic responses, manifested by loss of glucose tolerance and vascular dysfunction, would be attenuated by systemic administration of nitrooctadecenoic acid (OA-NO2). Male C57BL/6j mice subjected to a HFD for 20 weeks displayed increased adiposity, fasting glucose, and insulin levels, which led to glucose intolerance and pulmonary hypertension, characterized by increased right ventricular (RV) end-systolic pressure (RVESP) and pulmonary vascular resistance (PVR). This was associated with increased lung xanthine oxidoreductase (XO) activity, macrophage infiltration, and enhanced expression of pro-inflammatory cytokines. Left ventricular (LV) end-diastolic pressure remained unaltered, indicating that the HFD produces pulmonary vascular remodelling, rather than LV dysfunction and pulmonary venous hypertension. Administration of OA-NO2 for the final 6.5 weeks of HFD improved glucose tolerance and significantly attenuated HFD-induced RVESP, PVR, RV hypertrophy, lung XO activity, oxidative stress, and pro-inflammatory pulmonary cytokine levels.

CONCLUSIONS

These observations support that the pleiotropic signalling actions of electrophilic fatty acids represent a therapeutic strategy for limiting the complex pathogenic responses instigated by obesity.

A comprehensive review: the evolution of animal models in pulmonary hypertension research; are we there yet?

Pulmonary hypertension (PH) is a disorder that develops as a result of remodeling of the pulmonary vasculature and is characterized by narrowing/obliteration of small pulmonary arteries, leading to increased mean pulmonary artery pressure and pulmonary vascular resistance. Subsequently, PH increases the right ventricular afterload, which leads to right ventricular hypertrophy and eventually right ventricular failure. The pathophysiology of PH is not fully elucidated, and current treatments have only a modest impact on patient survival and quality of life. Thus, there is an urgent need for improved treatments or a cure. The use of animal models has contributed extensively to the current understanding of PH pathophysiology and the investigation of experimental treatments. However, PH in current animal models may not fully represent current clinical observations. For example, PH in animal models appears to be curable with many therapeutic interventions, and the severity of PH in animal models is also believed to correlate poorly with that observed in humans. In this review, we discuss a variety of animal models in PH research, some of their contributions to the field, their shortcomings, and how these have been addressed. We highlight the fact that the constant development and evolution of animal models will help us to more closely model the severity and heterogeneity of PH observed in humans.

Adiponectin, Leptin, and Resistin in Asthma: Basic Mechanisms through Population Studies

Adipokines, factors produced by adipose tissue, may be proinflammatory (such as leptin and resistin) or anti-inflammatory (such as adiponectin). Effects of these adipokines on the lungs have the potential to evoke or exacerbate asthma. This review summarizes basic mechanistic data through population-based and clinical studies addressing the potential role of adipokines in asthma. Augmenting circulating concentrations of adiponectin attenuates allergic airway inflammation and airway hyperresponsiveness in mice. Murine data is supported by human data that suggest that low serum adiponectin is associated with greater risk for asthma among women and peripubertal girls. Further, higher serum total adiponectin may be associated with lower clinical asthma severity among children and women with asthma. In contrast, exogenous administration of leptin results in augmented allergic airway hyperresponsiveness in mice. Alveolar macrophages obtained from obese asthmatics are uniquely sensitive to leptin in terms of their potential to augment inflammation. Consistent with this basic mechanistic data, epidemiologic studies demonstrate that higher serum leptin is associated with greater asthma prevalence and/or severity and that these associations may be stronger among women, postpubertal girls, and prepubertal boys. The role of adipokines in asthma is still evolving, and it is not currently known whether modulation of adipokines may be helpful in asthma prevention or treatment.

Impact of adiponectin overexpression on allergic airways responses in mice

Obesity is an important risk factor for asthma. Obese individuals have decreased circulating adiponectin, an adipose-derived hormone with anti-inflammatory properties. We hypothesized that transgenic overexpression of adiponectin would attenuate allergic airways inflammation and mucous hyperplasia in mice. To test this hypothesis, we used mice overexpressing adiponectin (Adipo Tg). Adipo Tg mice had marked increases in both serum adiponectin and bronchoalveolar lavage (BAL) fluid adiponectin. Both acute and chronic ovalbumin (OVA) sensitization and challenge protocols were used. In both protocols, OVA-induced increases in total BAL cells were attenuated in Adipo Tg versus WT mice. In the acute protocol, OVA-induced increases in several IL-13 dependent genes were attenuated in Adipo Tg versus WT mice, even though IL-13 per se was not affected. With chronic exposure, though OVA-induced increases in goblet cells numbers per millimeter of basement membrane were greater in Adipo Tg versus WT mice, mRNA abundance of mucous genes in lungs was not different. Also, adiponectin overexpression did not induce M2 polarization in alveolar macrophages. Our results indicate that adiponectin protects against allergen-induced inflammatory cell recruitment to the airspaces, but not development of goblet cell hyperplasia.

Dexfenfluramine and the oestrogen-metabolizing enzyme CYP1B1 in the development of pulmonary arterial hypertension

AIMS

Pulmonary arterial hypertension (PAH) occurs more frequently in women than men. Oestrogen and the oestrogen-metabolising enzyme cytochrome P450 1B1 (CYP1B1) play a role in the development of PAH. Anorectic drugs such as dexfenfluramine (Dfen) have been associated with the development of PAH. Dfen mediates PAH via a serotonergic mechanism and we have shown serotonin to up-regulate expression of CYP1B1 in human pulmonary artery smooth muscle cells (PASMCs). Thus here we assess the role of CYP1B1 in the development of Dfen-induced PAH.

METHODS AND RESULTS

Dfen (5 mg kg(-1) day(-1) PO for 28 days) increased right ventricular pressure and pulmonary vascular remodelling in female mice only. Mice dosed with Dfen showed increased whole lung expression of CYP1B1 and Dfen-induced PAH was ablated in CYP1B1(-/-) mice. In line with this, Dfen up-regulated expression of CYP1B1 in PASMCs from PAH patients (PAH-PASMCs) and Dfen-mediated proliferation of PAH-PASMCs was ablated by pharmacological inhibition of CYP1B1. Dfen increased expression of tryptophan hydroxylase 1 (Tph1; the rate-limiting enzyme in the synthesis of serotonin) in PAH-PASMCs and both Dfen-induced proliferation and Dfen-induced up-regulation of CYP1B1 were ablated by inhibition of Tph1. 17β-Oestradiol increased expression of both Tph1 and CYP1B1 in PAH-PASMCs, and Dfen and 17β-oestradiol had synergistic effects on proliferation of PAH-PASMCs. Finally, ovariectomy protected against Dfen-induced PAH in female mice.

CONCLUSION

CYP1B1 is critical in the development of Dfen-induced PAH in mice in vivo and proliferation of PAH-PASMCs in vitro. CYP1B1 may provide a novel therapeutic target for PAH.

Obesity and pulmonary arterial hypertension: Is adiponectin the molecular link between these conditions?

Pulmonary arterial hypertension (PAH) is a condition of unknown etiology whose pathological features include increased vascular resistance, perivascular inflammatory cell infiltration and pulmonary arteriolar remodeling. Although risk factors for PAH are poorly defined, recent studies indicate that obesity may be an important risk factor for this condition. The mechanisms leading to this association are largely unknown, but bioactive mediators secreted from adipose tissue have been implicated in this process. One of the most important mediators released from adipose tissue is the adipokine adiponectin. Adiponectin is highly abundant in the circulation of lean healthy individuals, and possesses well-described metabolic and antiinflammatory actions. Levels of adiponectin decrease with increasing body mass, and low levels are directly linked to the development of PAH in mice. Moreover, overexpression of adiponectin has been shown to protect mice from developing PAH in response to inflammation and hypoxia. Based on the findings from these studies, it is suggested that the effects of adiponectin are mediated, in part, through its antiinflammatory and antiproliferative properties. In this review, we discuss the emerging evidence demonstrating a role for adiponectin in lung vascular homeostasis and discuss how deficiency in this adipocyte-derived hormone might explain the recent association between obesity and PAH.

Fat, fire and muscle--the role of adiponectin in pulmonary vascular inflammation and remodeling

Pulmonary hypertension is a life-threatening condition that results from a heterogeneous group of diseases, many of which demonstrate characteristic pathologic changes of pulmonary vascular inflammation and remodeling. Recent clinical studies indicate obesity to be a risk factor for the development of pulmonary hypertension; however, the mechanisms leading to this association are unknown. Adipocytes secrete multiple bioactive mediators that can influence inflammation and tissue remodeling, suggesting that adipose tissue may directly influence the pathogenesis of pulmonary hypertension. One of these mediators is adiponectin, a protein with a wide range of metabolic, anti-inflammatory, and anti-proliferative activities. Paradoxically, adiponectin is present in high concentration in the serum of lean healthy individuals, but decreases in obesity. Studies suggest that relative adiponectin-deficiency may contribute to the development of inflammatory diseases in obesity, and recent animal studies implicate adiponectin in the pathogenesis of pulmonary hypertension. Most notably, experimental studies show that adiponectin can reduce lung vascular remodeling in response to inflammation and hypoxia. Moreover, mice deficient in adiponectin develop a spontaneous lung vascular phenotype characterized by age-dependent increases in peri-vascular inflammatory cells and elevated pulmonary artery pressures. Emerging evidence indicates adiponectin's effects are mediated through anti-inflammatory and anti-proliferative actions on cells in the lung. This review aims to synthesize the existing data related to adiponectin's effects on the pulmonary vasculature and to discuss how changes in adiponectin levels might contribute to the development of pulmonary hypertension.

Adiponectin in cardiovascular inflammation and obesity

Inflammation is widely known to play a key role in the development and progression of cardiovascular diseases. It is becoming increasingly evident that obesity is linked to many proinflammatory and obesity-associated cardiovascular conditions (e.g., metabolic syndrome, acute coronary syndrome, and congestive heart failure). It has been observed that adipokines play an increasingly large role in systemic and local inflammation. Therefore, adipose tissue may have a more important role than previously thought in the pathogenesis of several disease types. This review explores the recently described role of adiponectin as an immunomodulatory factor and how it intersects with the inflammation associated with both cardiovascular and autoimmune pathologies.

Eosinophils are necessary for pulmonary arterial remodeling in a mouse model of eosinophilic inflammation-induced pulmonary hypertension

There is increasing evidence that inflammation plays a pivotal role in the pathogenesis of some forms of pulmonary hypertension (PH). We recently demonstrated that deficiency of adiponectin (APN) in a mouse model of PH induced by eosinophilic inflammation increases pulmonary arterial remodeling, pulmonary pressures, and the accumulation of eosinophils in the lung. Based on these data, we hypothesized that APN deficiency exacerbates PH indirectly by increasing eosinophil recruitment. Herein, we examined the role of eosinophils in the development of inflammation-induced PH. Elimination of eosinophils in APN-deficient mice by treatment with anti-interleukin-5 antibody attenuated pulmonary arterial muscularization and PH. In addition, we observed that transgenic mice that are devoid of eosinophils also do not develop pulmonary arterial muscularization in eosinophilic inflammation-induced PH. To investigate the mechanism by which APN deficiency increased eosinophil accumulation in response to an allergic inflammatory stimulus, we measured expression levels of the eosinophil-specific chemokines in alveolar macrophages isolated from the lungs of mice with eosinophilic inflammation-induced PH. In these experiments, the levels of CCL11 and CCL24 were higher in macrophages isolated from APN-deficient mice than in macrophages from wild-type mice. Finally, we demonstrate that the extracts of eosinophil granules promoted the proliferation of pulmonary arterial smooth muscle cells in vitro. These data suggest that APN deficiency may exacerbate PH, in part, by increasing eosinophil recruitment into the lung and that eosinophils could play an important role in the pathogenesis of inflammation-induced PH. These results may have implications for the pathogenesis and treatment of PH caused by vascular inflammation.