Pulmonary arterial hypertension is linked to insulin resistance and reversed by peroxisome proliferator-activated receptor-gamma activation

Increasing quality of life in pulmonary arterial hypertension: is there a role for nutrition?

Pulmonary arterial hypertension (PAH) is a progressive disease primarily affecting the pulmonary vasculature and heart. PAH patients suffer from exercise intolerance and fatigue, negatively affecting their quality of life. This review summarizes current insights in the pathophysiological mechanisms underlying PAH. It zooms in on the potential involvement of nutritional status and micronutrient deficiencies on PAH exercise intolerance and fatigue, also summarizing the potential benefits of exercise and nutritional interventions. Pubmed/Medline, Scopus, and Web of Science were searched for publications on pathophysiological mechanisms of PAH negatively affecting physical activity potential and nutritional status, and for potential effects of interventions involving exercise or nutritional measures known to improve exercise intolerance. Pathophysiological processes that contribute to exercise intolerance and impaired quality of life of PAH patients include right ventricular dysfunction, inflammation, skeletal muscle alterations, and dysfunctional energy metabolism. PAH-related nutritional deficiencies and metabolic alterations have been linked to fatigue, exercise intolerance, and endothelial dysfunction. Available evidence suggests that exercise interventions can be effective in PAH patients to improve exercise tolerance and decrease fatigue. By contrast, knowledge on the prevalence of micronutrient deficiencies and the possible effects of nutritional interventions in PAH patients is limited. Although data on nutritional status and micronutrient deficiencies in PAH are scarce, the available knowledge, including that from adjacent fields, suggests that nutritional intervention to correct deficiencies and metabolic alterations may contribute to a reduction of disease burden.

Bariatric surgery in patients with pulmonary hypertension

BACKGROUND

Data regarding the outcomes of bariatric surgery in patients with pulmonary hypertension (PH) is limited. The aim of this study was to review our experience on bariatric surgery in patients with PH.

SETTING

An academic medical center.

METHODS

Patients with PH who underwent either a primary or revisional bariatric surgery between 2005 and 2015 and had a preoperative right ventricle systolic pressure (RVSP) ≥35 mm Hg were included.

RESULTS

Sixty-one patients met the inclusion criteria. Fifty (82%) were female with the median age of 58 years (interquartile range [IQR] 49-63). The median body mass index was 49 kg/m² (IQR 43-54). Procedures performed included the following: Roux-en-Y gastric bypass (n = 33, 54%), sleeve gastrectomy (n = 24, 39%), adjustable gastric banding (n = 3, 5%), and banded gastric plication (n = 1, 2%). Four patients (7%) underwent revisional bariatric procedures. Median operative time and length of stay was 130 minutes (IQR 110-186) and 3 days (IQR 2-5), respectively. The 30-day complication rate was 16% (n = 10) with pulmonary complications noted in 4 patients. There was no 30-day mortality. One-year follow-up was available in 93% patients (n = 57). At 1 year, median body mass index and excess weight loss were 36 kg/m² (IQR 33-41) and 51% (IQR 33-68), respectively. There was significant improvement in the RVSP after bariatric surgery at a median follow-up of 22 months (IQR 10-41). The median RVSP decreased from 44 (IQR 38-53) to 40 mm Hg (IQR 28-54) (P = .03).

CONCLUSION

Bariatric surgery can be performed without prohibitive complication rates in patients with PH. In our experience, bariatric patients with PH achieved significant weight loss and improvement in RVSP.

Role of cardiac inflammation in right ventricular failure

Right ventricular failure (RVF) is the main determinant of mortality in patients with pulmonary arterial hypertension (PAH). Although the exact pathophysiology underlying RVF remains unclear, inflammation may play an important role, as it does in left heart failure. Perivascular pulmonary artery and systemic inflammation is relatively well studied and known to contribute to the initiation and maintenance of the pulmonary vascular insult in PAH. However, less attention has been paid to the role of cardiac inflammation in RVF and PAH. Consistent with many other types of heart failure, cardiac inflammation, triggered by systemic and local stressors, has been shown in RVF patients as well as in RVF animal models. RV inflammation likely contributes to impaired RV contractility, maladaptive remodelling and a vicious circle between RV and pulmonary vascular injury. Although the potential to improve RV function through anti-inflammatory therapy has not been tested, this approach has been applied clinically in left ventricular failure patients, with variable success. Because inflammation plays a dual role in the development of both pulmonary vascular pathology and RVF, anti-inflammatory therapies may have a potential double benefit in patients with PAH and associated RVF.

Plasma levels of high density lipoprotein cholesterol and outcomes in chronic thromboembolic pulmonary hypertension

Background

High Density Lipoprotein Cholesterol (HDL-C) has various anti-inflammatory, anti-atherogenic, anti-oxidant and anti-coagulant properties that improve vascular function. The utility of HDL-C as a biomarker of severity and predictor of survival was described in patients with pulmonary arterial hypertension (PAH). No prior study has assessed the utility of HDL-C in patients with Chronic Thromboembolic Pulmonary Hypertension (CTEPH).

Objectives

We aim to measure HDL-C levels in CTEPH patients and compare it to those in PAH patients and controls and determine HDL-C associations with markers of disease severity, hemodynamics and mortality in CTEPH.

Methods

We retrospectively included patients with CTEPH, identified from the Cleveland Clinic Pulmonary Hypertension Registry. All patients had right heart catheterization (RHC) and imaging studies consistent with CTEPH. We collected demographics, co-morbidities, baseline laboratory data including plasma HDL-C, six-minute walk test (6MWT), echocardiography and RHC. HDL-C levels were compared to a cohort of patients with cardiovascular risk factors and a previously published PAH cohort.

Results

HDL-C levels were available for 90 patients with CTEPH (age: 57.4±13.9 years; female 40%), 69 patients with PAH (age: 46.7±12.8 years; female 90%) and 254 control subjects (age: 56.7±13 years; female 48%). HDL-C levels in CTEPH patients were lower compared to controls and higher compared to PAH patients (median, IQR: CTEPH: 44, 34–57 mg/dl; PAH: 35.3, 29–39 mg/dl; Control: 49, 40–60 mg/dl; p < 0.01 for both pairwise comparisons). In CTEPH, higher HDL-C was associated with decreased prevalence of right ventricular dilation on echocardiography (p = 0.02). 57 patients with CTEPH underwent pulmonary thromboendarterectomy, higher HDL-C was associated with a larger decrement in postoperative pulmonary vascular resistance (PVR) (r = 0.37, p = 0.049). HDL-C was not associated with mortality or other markers of disease severity.

Conclusions

HDL-C levels in CTEPH patients were lower compared to control subjects, but higher compared to PAH patients. Higher HDL-C in CTEPH was associated with less right ventricular dilation and greater decrement in postoperative PVR. These data suggest that HDL-C may be a useful marker of small vessel disease in CTEPH.

Metabolic reprogramming of the urea cycle pathway in experimental pulmonary arterial hypertension rats induced by monocrotaline

Background

Pulmonary arterial hypertension (PAH) is a rare systemic disorder associated with considerable metabolic dysfunction. Although enormous metabolomic studies on PAH have been emerging, research remains lacking on metabolic reprogramming in experimental PAH models. We aim to evaluate the metabolic changes in PAH and provide new insight into endogenous metabolic disorders of PAH.

Method

A single subcutaneous injection of monocrotaline (MCT) (60 mg kg^− 1) was used for rats to establish PAH model. Hemodynamics and right ventricular hypertrophy were adopted to evaluate the successful establishment of PAH model. Plasma samples were assessed through targeted metabolomic profiling platform to quantify 126 endogenous metabolites. Orthogonal partial least squares discriminant analysis (OPLS-DA) was used to discriminate between MCT-treated model and control groups. Metabolite Set Enrichment Analysis was adapted to exploit the most disturbed metabolic pathways.

Results

Endogenous metabolites of MCT treated PAH model and control group were well profiled using this platform. A total of 13 plasma metabolites were significantly altered between the two groups. Metabolite Set Enrichment Analysis highlighted that a disruption in the urea cycle pathway may contribute to PAH onset. Moreover, five novel potential biomarkers in the urea cycle, adenosine monophosphate, urea, 4-hydroxy-proline, ornithine, N-acetylornithine, and two candidate biomarkers, namely, O-acetylcarnitine and betaine, were found to be highly correlated with PAH.

Conclusion

The present study suggests a new role of urea cycle disruption in the pathogenesis of PAH. We also found five urea cycle related biomarkers and another two candidate biomarkers to facilitate early diagnosis of PAH in metabolomic profile.

Metabolic Status in Patients with Operable vs. Inoperable Left-to-Right Shunts

BACKGROUND Previous studies have shown the prognostic value of insulin resistance, hyperuricemia, and dyslipidemia in clinical outcome of pulmonary arterial hypertension. Whether these metabolic derangements are different between operable and inoperable left-to-right shunts is unknown. MATERIAL AND METHODS Our study included 116 patients with left-to-right shunts (76 with atrial septal defect and 40 with ventricular septal defect) with or without pulmonary arterial hypertension. Operability of defect closure were assessed by cardiac catheterization and patients were subdivided into an operable group or an inoperable group. The metabolic status, including prediabetes, hyperuricemia, dyslipidemia, hypertension and obesity, were compared between groups. RESULTS Patients receiving defect correction had a lower HbA1c (B: 5.52±0.49 vs. 5.71±0.41, p=0.042) and uric acid (C: 358±105 vs. 406±126, p=0.029) but a higher HDLC (D: 1.21±0.33 vs. 1.08±0.22, p=0.017) and BMI (A: 20.4±3.9 vs. 18.8±3.1, p=0.023). Patients in the inoperable group had a higher prevalence of prediabetes (58% vs. 41%, p=0.076), hyperuricemia (37.2% vs. 21.9, p=0.106), dyslipidemia (74% vs. 56%, p=0.049) but a lower prevalence of hypertension (13.9% vs. 30.1%, p=0.049) and obesity (4.6% vs. 12.3%, p=0.301). According to logistic regression, only HbA1c (1.76 (0.53, 2.99), HR (95% CI), p=0.005) remained significant for pulmonary vascular resistance. CONCLUSIONS Although prediabetes, hyperuricemia, and dyslipidemia were all more prevalent in patients with inoperable left-to-right shunts, only prediabetes was found to be significantly associated with higher pulmonary vascular resistance.

Emerging therapeutics in pulmonary hypertension

Pulmonary hypertension (PH) is a progressive and often fatal illness presenting with nonspecific symptoms of dyspnea, lower extremity edema, and exercise intolerance. Pathologically, endothelial dysfunction leads to abnormal intimal and smooth muscle proliferation along with reduced apoptosis, resulting in increased pulmonary vascular resistance and elevated pulmonary pressures. PH is subdivided into five World Health Organization groups based on the disease pathology and specific cause. While there are Food and Drug Administration-approved medications for the treatment of pulmonary arterial hypertension (PAH; Group 1 PH), as well as for chronic thromboembolic PH (Group 4 PH), the morbidity and mortality remain high. Moreover, there are no approved therapies for other forms of PH (Groups 2, 3, and 5) at present. New research has identified molecular targets that mediate vasodilation, anti-inflammatory, and antifibrotic changes within the pulmonary vasculature. Given that PAH is the most commonly studied form of PH worldwide and because recent studies have led to better mechanistic understanding of this devastating disease, in this review we attempt to provide an updated overview of new therapeutic approaches under investigation for the treatment of PH, with a particular focus on PAH, as well as to offer guidelines for future investigations.

Abnormal Glucose Metabolism and High-Energy Expenditure in Idiopathic Pulmonary Arterial Hypertension

RATIONALE

Insulin resistance has emerged as a potential mechanism related to the pathogenesis of idiopathic pulmonary arterial hypertension (IPAH). However, direct measurements of insulin and glucose metabolism have not been performed in patients with IPAH to date.

OBJECTIVES

To perform comprehensive metabolic phenotyping of humans with IPAH.

METHODS

We assessed plasma insulin and glucose, using an oral glucose tolerance test and estimated insulin resistance, and β-cell function in 14 patients with IPAH and 14 control subjects matched for age, sex, blood pressure, and body mass index. Body composition (dual-energy X-ray absorptiometry), inflammation (CXC chemokine ligand 10, endothelin-1), physical fitness (6-min walk test), and energy expenditure (indirect calorimetry) were also assessed.

MEASUREMENTS AND MAIN RESULTS

Patients with IPAH had a higher rate of impaired glucose tolerance (57 vs. 14%; P < 0.05) and reduced glucose-stimulated insulin secretion compared with matched control subjects (IPAH: 1.31 ± 0.76 μU/ml⋅mg/dl vs. control subjects: 2.21 ± 1.27 μU/ml⋅mg/dl; P < 0.05). Pancreatic β-cell function was associated with circulating endothelin-1 (r = -0.71, P < 0.01) and CXC chemokine ligand 10 (r = -0.56, P < 0.05). Resting energy expenditure was elevated in IPAH (IPAH: 32 ± 3.4 vs. control subjects: 28.8 ± 2.9 kcal/d/kg fat-free mass; P < 0.05) and correlated with the plasma glucose response (r = 0.51, P < 0.01). Greater insulin resistance was associated with reduced 6-minute walk distance (r = 0.55, P < 0.05).

CONCLUSIONS

Independent of age, sex, blood pressure, and body mass index, patients with IPAH have glucose intolerance, decreased insulin secretion in response to glucose, and elevated resting energy expenditure. These abnormalities are associated with circulating markers of inflammation and vascular dysfunction.

Exercise training in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is characterized by a continuous increase in pre-capillary pulmonary vascular resistance (PVR) with a progressive reduction of cardiac output (CO). Similar to what occurs in left heart failure (HF), this represents the initial phase of a syndrome characterized by the progressive development of dyspnea and fatigue with increasing deterioration of exercise tolerance. Although the therapies introduced in the last two decades have determined a significant improvement of the clinical conditions of PAH patients, they have a little impact on exercise capacity and prognosis. However, as previously demonstrated for HF, recent pilot studies have reported that physical and respiratory rehabilitation may have a specific role in the management of PAH. Despite potential risks, so far all studies agree that exercise training (ET) improves exercise capacity, quality of life (QoL), muscle function and pulmonary circulation. We will review the pathophysiological mechanisms underlying the functional incompetence of PAH patients, the effects of ET on clinical and functional parameters, the selection criteria for inclusion of patients in a training program, the suggested monitoring of beneficial effects or possible side effects induced by ET. Finally, we discuss of the possible exercise induced amelioration of prognosis in PAH.

Prostanoid EP4 agonist L-902,688 activates PPARγ and attenuates pulmonary arterial hypertension

Prostacyclin agonists that bind the prostacyclin receptor (IP) to stimulate cAMP synthesis are effective vasodilators for the treatment of idiopathic pulmonary arterial hypertension (IPAH), but this signaling may occur through nuclear peroxisome proliferator-activated receptor-γ (PPARγ). There is evidence of scant IP and PPARγ expression but stable prostanoid EP₄ receptor (EP₄) expression in IPAH patients. Both IP and EP₄ functionally couple with stimulatory G protein (G_s), which activates signal transduction. We investigated the effect of an EP₄-specific agonist on pulmonary arterial remodeling and its regulatory mechanisms in pulmonary arterial smooth muscle cells (PASMCs). Immunoblotting evealed IP, EP₄, and PPARγ expression in human pulmonary arterial hypertension (PAH) and monocrotaline (MCT)-induced PAH rat lung tissue. Isolated PASMCs from MCT-induced PAH rats (MCT-PASMCs) were treated with L-902,688, a selective EP₄ agonist, to investigate the anti-vascular remodeling effect. Scant expression of IP and PPARγ but stable expression of EP₄ was observed in IPAH patient lung tissues and MCT-PASMCs. L-902,688 inhibited IP-insufficient MCT-PASMC proliferation and migration by activating PPARγ in a time- and dose-dependent manner, but these effects were reversed by AH-23848 (an EP₄ antagonist) and H-89 [a protein kinase A (PKA) inhibitor], highlighting the crucial role of PPARγ in the activity of this EP₄ agonist. L-902,688 attenuated pulmonary arterial remodeling in hypoxic PAH mice and MCT-induced PAH rats; therefore, we conclude that the selective EP₄ agonist L-902,688 reverses vascular remodeling by activating PPARγ. This study identified a novel EP₄-PKA-PPARγ pathway, and we propose EP₄ as a potential therapeutic target for PAH.

Pulmonary endothelial cell DNA methylation signature in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a severe and incurable pulmonary vascular disease. One of the primary origins of PAH is pulmonary endothelial dysfunction leading to vasoconstriction, aberrant angiogenesis and smooth muscle cell proliferation, endothelial-to-mesenchymal transition, thrombosis and inflammation. Our objective was to study the epigenetic variations in pulmonary endothelial cells (PEC) through a specific pattern of DNA methylation. DNA was extracted from cultured PEC from idiopathic PAH (n = 11), heritable PAH (n = 10) and controls (n = 18). DNA methylation was assessed using the Illumina HumanMethylation450 Assay. After normalization, samples and probes were clustered according to their methylation profile. Differential clusters were functionally analyzed using bioinformatics tools. Unsupervised hierarchical clustering allowed the identification of two clusters of probes that discriminates controls and PAH patients. Among 147 differential methylated promoters, 46 promoters coding for proteins or miRNAs were related to lipid metabolism. Top 10 up and down-regulated genes were involved in lipid transport including ABCA1, ABCB4, ADIPOQ, miR-26A, BCL2L11. NextBio meta-analysis suggested a contribution of ABCA1 in PAH. We confirmed ABCA1 mRNA and protein downregulation specifically in PAH PEC by qPCR and immunohistochemistry and made the proof-of-concept in an experimental model of the disease that its targeting may offer novel therapeutic options. In conclusion, DNA methylation analysis identifies a set of genes mainly involved in lipid transport pathway which could be relevant to PAH pathophysiology.

Oestrogen inhibition reverses pulmonary arterial hypertension and associated metabolic defects

Increased oestrogen is a strong epidemiological risk factor for development of pulmonary arterial hypertension (PAH) in patients, associated with metabolic defects. In addition, oestrogens drive penetrance in mice carrying mutations in bone morphogenetic protein receptor type II (BMPR2), the cause of most heritable PAH. The goal of the present study was to determine whether inhibition of oestrogens was effective in the treatment of PAH in these mice.The oestrogen inhibitors fulvestrant and anastrozole were used in a prevention and treatment paradigm in BMPR2 mutant mice, and tamoxifen was used for treatment. In addition, BMPR2 mutant mice were crossed onto oestrogen receptor (ESR)1 and ESR2 knockout backgrounds to assess receptor specificity. Haemodynamic and metabolic outcomes were measured.Oestrogen inhibition both prevented and treated PAH in BMPR2 mutant mice. This was associated with reduction in metabolic defects including oxidised lipid formation, insulin resistance and rescue of peroxisome proliferator-activated receptor-γ and CD36. The effect was mediated primarily through ESR2, but partially through ESR1.Our data suggest that trials of oestrogen inhibition in human PAH are warranted, and may improve pulmonary vascular disease through amelioration of metabolic defects. Although fulvestrant and anastrozole were more effective than tamoxifen, tamoxifen may be useful in premenopausal females, because of a reduced risk of induction of menopause.

Mechanisms of Lipid Accumulation in the Bone Morphogenetic Protein Receptor Type 2 Mutant Right Ventricle

RATIONALE

In heritable pulmonary arterial hypertension with germline mutation in the bone morphogenetic protein receptor type 2 (BMPR2) gene, right ventricle (RV) dysfunction is associated with RV lipotoxicity; however, the underlying mechanism for lipid accumulation is not known.

OBJECTIVES

We hypothesized that lipid accumulation in cardiomyocytes with BMPR2 mutation occurs owing to alterations in lipid transport and impaired fatty acid oxidation (FAO), which is exacerbated by a high-lipid (Western) diet (WD).

METHODS

We used a transgenic mouse model of pulmonary arterial hypertension with mutant BMPR2 and generated a cardiomyocyte cell line with BMPR2 mutation. Electron microscopy and metabolomic analysis were performed on mouse RVs.

MEASUREMENTS AND MAIN RESULTS

By metabolomics analysis, we found an increase in long-chain fatty acids in BMPR2 mutant mouse RVs compared with controls, which correlated with cardiac index. BMPR2-mutant cardiomyocytes had increased lipid compared with controls. Direct measurement of FAO in the WD-fed BMPR2-mutant RV showed impaired palmitate-linked oxygen consumption, and metabolomics analysis showed reduced indices of FAO. Using both mutant BMPR2 mouse RVs and cardiomyocytes, we found an increase in the uptake of (14)C-palmitate and fatty acid transporter CD36 that was further exacerbated by WD.

CONCLUSIONS

Taken together, our data suggest that impaired FAO and increased expression of the lipid transporter CD36 are key mechanisms underlying lipid deposition in the BMPR2-mutant RV, which are exacerbated in the presence of dietary lipids. These findings suggest important features leading to RV lipotoxicity in pulmonary arterial hypertension and may point to novel areas of therapeutic intervention.

Clinical and Biological Insights Into Combined Post- and Pre-Capillary Pulmonary Hypertension

BACKGROUND

Pulmonary hypertension (PH) is a common and morbid complication of left heart disease with 2 subtypes: isolated post-capillary pulmonary hypertension (Ipc-PH) and combined post-capillary and pre-capillary pulmonary hypertension (Cpc-PH). Little is known about the clinical or physiological characteristics that distinguish these 2 subphenotypes or if Cpc-PH shares molecular similarities to pulmonary arterial hypertension (PAH).

OBJECTIVES

The goal of this study was to test the hypothesis that the hemodynamic and genetic profile of Cpc-PH would more closely resemble PAH than Ipc-PH.

METHODS

Vanderbilt University's electronic medical record linked to a DNA biorepository was used to extract demographic characteristics, clinical data, invasive hemodynamic data, echocardiography, and vital status for all patients referred for right heart catheterization between 1998 and 2014. Shared genetic variants between PAH and Cpc-PH compared with Ipc-PH were identified by using pre-existing single-nucleotide polymorphism data.

RESULTS

A total of 2,817 patients with PH (13% Cpc-PH, 52% Ipc-PH, and 20% PAH) were identified. Patients with Cpc-PH were on average 6 years younger, with more severe pulmonary vascular disease than patients with Ipc-PH, despite similar comorbidities and prevalence, severity, and chronicity of left heart disease. After adjusting for relevant covariates, the risk of death was similar between the Cpc-PH and Ipc-PH groups (hazard ratio: 1.14; 95% confidence interval: 0.96 to 1.35; p = 0.15) when defined according to diastolic pressure gradient. We identified 75 shared exonic single-nucleotide polymorphisms between Cpc-PH and PAH enriched in pathways involving cell structure, extracellular matrix, and immune function. These genes are expressed, on average, 32% higher in lungs relative to other tissues.

CONCLUSIONS

Patients with Cpc-PH develop pulmonary vascular disease similar to patients with PAH, despite younger age and similar prevalence of obesity, diabetes mellitus, and left heart disease compared with patients with Ipc-PH. An exploratory genetic analysis in Cpc-PH identified genes and biological pathways in the lung known to contribute to PAH pathophysiology, suggesting that Cpc-PH may be a distinct and highly morbid PH subphenotype.

Emerging Roles of Apolipoprotein E and Apolipoprotein A-I in the Pathogenesis and Treatment of Lung Disease

Emerging roles are being recognized increasingly for apolipoproteins in the pathogenesis and treatment of lung diseases on the basis of their ability to suppress inflammation, oxidative stress, and tissue remodeling, and to promote adaptive immunity and host defense. Apolipoproteins, such as apolipoprotein E (apoE) and apolipoprotein A-I (apoA-I), are important components of lipoprotein particles that facilitate the transport of cholesterol, triglycerides, and phospholipids between plasma and cells. ApoE-containing lipoprotein particles are internalized into cells by low-density lipoprotein receptors (LDLRs), whereas apoA-I can interact with the ATP-binding cassette subfamily A member 1 (ABCA1) transporter to efflux cholesterol and phospholipids out of cells. ApoE and apoA-I also mediate receptor-independent effects, such as binding to and neutralizing LPS. Both apoE and apoA-I are expressed by lung cells, which allows apoE/LDLR- and apoA-I/ABCA1-dependent pathways to modulate normal lung health and the pathogenesis of respiratory diseases, including asthma, acute lung injury, cancer, emphysema, pulmonary fibrosis, and pulmonary hypertension. Data from human studies and research using experimental murine model systems have shown that both apoE and apoA-I pathways play primarily protective roles in lung biology and respiratory disease. Furthermore, apolipoprotein mimetic peptides, corresponding to the LDLR-binding domain of apoE or the class A amphipathic α-helical structure of apoA-I, have antiinflammatory and antioxidant effects that attenuate the severity of lung disease in murine models. Thus, the development of inhaled apolipoprotein mimetic peptides as a novel treatment paradigm could represent a significant advance for patients with respiratory disease who do not respond to current therapies.

Peroxisome Proliferator-Activated Receptor γ Regulates the V-Ets Avian Erythroblastosis Virus E26 Oncogene Homolog 1/microRNA-27a Axis to Reduce Endothelin-1 and Endothelial Dysfunction in the Sickle Cell Mouse Lung

Pulmonary hypertension (PH), a serious complication of sickle cell disease (SCD), causes significant morbidity and mortality. Although a recent study determined that hemin release during hemolysis triggers endothelial dysfunction in SCD, the pathogenesis of SCD-PH remains incompletely defined. This study examines peroxisome proliferator-activated receptor γ (PPARγ) regulation in SCD-PH and endothelial dysfunction. PH and right ventricular hypertrophy were studied in Townes humanized sickle cell (SS) and littermate control (AA) mice. In parallel studies, SS or AA mice were gavaged with the PPARγ agonist, rosiglitazone (RSG), 10 mg/kg/day, or vehicle for 10 days. In vitro, human pulmonary artery endothelial cells (HPAECs) were treated with vehicle or hemin for 72 hours, and selected HPAECs were treated with RSG. SS mice developed PH and right ventricular hypertrophy associated with reduced lung levels of PPARγ and increased levels of microRNA-27a (miR-27a), v-ets avian erythroblastosis virus E26 oncogene homolog 1 (ETS1), endothelin-1 (ET-1), and markers of endothelial dysfunction (platelet/endothelial cell adhesion molecule 1 and E selectin). HPAECs treated with hemin had increased ETS1, miR-27a, ET-1, and endothelial dysfunction and decreased PPARγ levels. These derangements were attenuated by ETS1 knockdown, inhibition of miR-27a, or PPARγ overexpression. In SS mouse lung or in hemin-treated HPAECs, activation of PPARγ with RSG attenuated reductions in PPARγ and increases in miR-27a, ET-1, and markers of endothelial dysfunction. In SCD-PH pathogenesis, ETS1 stimulates increases in miR-27a levels that reduce PPARγ and increase ET-1 and endothelial dysfunction. PPARγ activation attenuated SCD-associated signaling derangements, suggesting a novel therapeutic approach to attenuate SCD-PH pathogenesis.

Do single or sequential measurements of leptin and adiponectin in plasma have prognostic value in pulmonary arterial hypertension?

Leptin (a neuroendocrine peptide that enhances metabolism and acts on the hypothalamus to suppress appetite) and adiponectin (a protein that has insulin-sensitizing, anti-inflammatory, and antiproliferative properties) are involved in the pathobiology of pulmonary arterial hypertension (PAH). We hypothesized that plasma leptin and adiponectin as well as the leptin/adiponectin ratio are abnormal in PAH patients and their levels track with disease severity and functional changes during follow-up. We tested this hypothesis in a cohort of patients included in the 16-week, international, multicenter, double-blind, placebo-controlled FREEDOM-C2 study. Blood was collected at baseline and week 16 in 178 out of 310 randomized patients with PAH. Baseline plasma leptin and adiponectin concentrations were 25 ± 31 ng/mL and 7.8 ± 6.1 ug/mL, respectively. Leptin, adiponectin, and leptin/adiponectin (mean ± SD) changes at 16 week were of small magnitude. Leptin at baseline was significantly associated with older age, higher BMI, higher Borg dyspnea index, and lower NT-pro BNP. Women had higher levels of leptin than men (30.5 ± 33.2 versus 7.2 ± 6.4 ng/mL), even when adjusting for background therapy and etiology (linear regression: β = 21.8, P < 0.001). Adiponectin was negatively associated with BMI and positively associated with NT-pro BNP. Changes in leptin, adiponectin, and leptin/adiponectin ratio adjusted for weight at 16 weeks did not predict functional class, distance walk in 6 min or survival at one, two, three, or four years. Plasma leptin and adiponectin at baseline and their change at 16-week do not appear to significantly impact prognosis in PAH.

Puerarin Protects against Cardiac Fibrosis Associated with the Inhibition of TGF-β1/Smad2-Mediated Endothelial-to-Mesenchymal Transition

Background

Puerarin is a kind of flavonoids and is extracted from Chinese herb Kudzu root. Puerarin is widely used as an adjuvant therapy in Chinese clinics. But little is known about its effects on regulating cardiac fibrosis.

Methods

Mice were subjected to transverse aorta constriction (TAC) for 8 weeks; meanwhile puerarin was given 1 week after TAC. Cardiac fibrosis was assessed by pathological staining. The mRNA and protein changes of CD31 and vimentin in both animal and human umbilical vein endothelial cells (HUVECs) models were detected. Immunofluorescence colocalization of CD31 and vimentin and scratch test were carried out to examine TGF-β1-induced changes in HUVECs. The agonist and antagonist of peroxisome proliferator-activated receptor-γ (PPAR-γ) were used to explore the underlying mechanism.

Results

Puerarin mitigated TAC-induced cardiac fibrosis, accompanied with suppressed endothelial-to-mesenchymal transition (EndMT). The consistent results were achieved in HUVECs model. TGF-β1/Smad2 signaling pathway was blunted and PPAR-γ expression was upregulated in puerarin-treated mice and HUVECs. Pioglitazone could reproduce the protective effect in HUVECs, while GW9662 reversed this effect imposed by puerarin.

Conclusion

Puerarin protected against TAC-induced cardiac fibrosis, and this protective effect may be attributed to the upregulation of PPAR-γ and the inhibition of TGF-β1/Smad2-mediated EndMT.

Development of a Mouse Model of Metabolic Syndrome, Pulmonary Hypertension, and Heart Failure with Preserved Ejection Fraction

Pulmonary hypertension (PH) associated with heart failure with preserved ejection fraction (PH-HFpEF; World Health Organization Group II) secondary to left ventricular (LV) diastolic dysfunction is the most frequent cause of PH. It is an increasingly recognized clinical complication of the metabolic syndrome. To date, no effective treatment has been identified, and no genetically modifiable mouse model is available for advancing our understanding for PH-HFpEF. To develop a mouse model of PH-HFpEF, we exposed 36 mouse strains to 20 weeks of high-fat diet (HFD), followed by systematic evaluation of right ventricular (RV) and LV pressure-volume analysis. The HFD induces obesity, glucose intolerance, insulin resistance, hyperlipidemia, as well as PH, in susceptible strains. We observed that certain mouse strains, such as AKR/J, NON/shiLtJ, and WSB/EiJ, developed hemodynamic signs of PH-HFpEF. Of the strains that develop PH-HFpEF, we selected AKR/J for further model validation, as it is known to be prone to HFD-induced metabolic syndrome and had low variability in hemodynamics. HFD-treated AKR/J mice demonstrate reproducibly higher RV systolic pressure compared with mice fed with regular diet, along with increased LV end-diastolic pressure, both RV and LV hypertrophy, glucose intolerance, and elevated HbA1c levels. Time course assessments showed that HFD significantly increased body weight, RV systolic pressure, LV end-diastolic pressure, biventricular hypertrophy, and HbA1c throughout the treatment period. Moreover, we also identified and validated 129S1/SvlmJ as a resistant mouse strain to HFD-induced PH-HFpEF. These studies validate an HFD/AKR/J mouse model of PH-HFpEF, which may offer a new avenue for testing potential mechanisms and treatments for this disease.

New-Onset Diabetes Mellitus After Heart Transplantation - Incidence, Risk Factors and Impact on Clinical Outcome

BACKGROUND

New-onset diabetes mellitus (DM) can occur as a serious complication after heart transplantation, but the comparative data on its clinical impact on survival and on transplant-related adverse events are limited.Methods and Results:We reviewed a total of consecutive 391 patients aged ≥17 years undergoing isolated orthotopic heart transplantation at the present institution from 1992 to 2013. The entire cohort was divided into 3 groups: (1) no diabetes (n=257); (2) pre-existing DM (n=46); and (3) new-onset DM (n=88). Early and long-term clinical outcomes were compared across the 3 groups. Early death occurred in 8 patients (2.0%). Of the 345 non-diabetic patients before transplantation, 88 (25.5%) developed new-onset DM postoperatively. During follow-up, 83 (21.2%) died. On time-varying Cox analysis, new-onset DM was associated with increased risk for overall death (HR, 2.11; 95% CI: 1.26-3.55) and tended to have a greater risk for severe chronic kidney disease (HR, 1.77; 95% CI: 0.94-3.44). Compared with the no-diabetes group, the new-onset DM group had a worse survival rate (P=0.035), but a similar survival rate to that of the pre-existing DM group (P=0.364).

CONCLUSIONS

New-onset DM has a negative effect on long-term survival and kidney function after heart transplantation. Further studies are warranted to evaluate the relevance of early diagnosis and timely control of new-onset DM to improve long-term survival.

Severe pulmonary hypertension in aging female apolipoprotein E-deficient mice is rescued by estrogen replacement therapy

Background

Apolipoprotein E (ApoE) is a multifunctional protein, and its deficiency leads to the development of atherosclerosis in mice. Patients with pulmonary hypertension (PH) have reduced expression of ApoE in lung tissue. ApoE is known to inhibit endothelial and smooth muscle cell proliferation and has anti-inflammatory and anti-platelet aggregation properties. Young ApoE-deficient mice have been shown to develop PH on high fat diet. The combined role of female sex and aging in the development of PH has not been investigated before. Here, we investigated the development of PH in young and middle-aged (MA) female ApoE-deficient mice and explored the role of exogenous estrogen (E2) replacement therapy for the aging females.

Methods

Wild type (WT) and ApoE-deficient female mice (Young and MA) were injected with a single intraperitoneal dose of monocrotaline (MCT, 60 mg/kg). Some ApoE-deficient MA female mice that received MCT were also treated with subcutaneous E2 pellets (0.03 mg/kg/day) from day 21 to 30 after MCT injection. Direct cardiac catheterization was performed terminally to record right ventricular systolic pressure (RVSP). Right ventricular (RV), left ventricular (LV), and interventricular septum (IVS) were dissected and weighed. Lung sections were examined using trichrome and immunofluorescence staining. Western blot analyses of lung and RV lysates were performed.

Results

In WT female mice, the severity of PH was similar between young and MA mice as RVSP was not significantly different (RVSP = 38.2 ± 1.2 in young vs. 40.5 ± 8.3 mmHg in MA, p < 0.05). In ApoE-deficient mice, MA females developed significantly severe PH (RVSP = 63 ± 10 mmHg) compared to young females (RVSP; 36 ± 3 mmHg, p < 0.05 vs. MA female). ApoE-deficient MA females also developed more severe RV hypertrophy compared to young females (RV hypertrophy index (RV/[LV + IVS]) = 0.53 ± 0.06 vs. 0.33 ± 0.01, p < 0.05). ApoE-deficient MA female mice manifested increased peripheral pulmonary artery muscularization and pulmonary fibrosis. E2 treatment of MA female ApoE-deficient mice resulted in a significant decrease in RVSP, reversal of pulmonary vascular remodeling, and RV hypertrophy. In MA female ApoE-deficient mice with PH, only the expression of ERβ in the lungs, but not in RV, was significantly downregulated, and it was restored by E2 treatment. The expression of ERα was not affected in either lungs or RV by PH. GPR30 was only detected in the RV, and it was not affected by PH in MA female ApoE-deficient mice.

Conclusions

Our results suggest that only aging female ApoE-deficient but not WT mice develop severe PH compared to younger females. Exogenous estrogen therapy rescued PH and RV hypertrophy in aging female ApoE-deficient mice possibly through restoration of lung ERβ.

Kidney dysfunction in patients with pulmonary arterial hypertension

Pulmonary arterial hypertension (PH) and chronic kidney disease (CKD) both profoundly impact patient outcomes, whether as primary disease states or as co-morbid conditions. PH is a common co-morbidity in CKD and vice versa. A growing body of literature describes the epidemiology of PH secondary to chronic kidney disease and end-stage renal disease (ESRD) (WHO group 5 PH). But, there are only limited data on the epidemiology of kidney disease in group 1 PH (pulmonary arterial hypertension [PAH]). The purpose of this review is to summarize the current data on epidemiology and discuss potential disease mechanisms and management implications of kidney dysfunction in PAH. Kidney dysfunction, determined by serum creatinine or estimated glomerular filtration rate, is a frequent co-morbidity in PAH and impaired kidney function is a strong and independent predictor of mortality. Potential mechanisms of PAH affecting the kidneys are increased venous congestion, decreased cardiac output, and neurohormonal activation. On a molecular level, increased TGF-β signaling and increased levels of circulating cytokines could have the potential to worsen kidney function. Nephrotoxicity does not seem to be a common side effect of PAH-targeted therapy. Treatment implications for kidney disease in PAH include glycemic control, lifestyle modification, and potentially Renin-Angiotensin-Aldosterone System (RAAS) blockade.

PPARγ attenuates hypoxia-induced hypertrophic transcriptional pathways in the heart

Chronic hypoxia-induced pulmonary hypertension (PH) is characterized by increased pressure and resistance in the pulmonary vasculature and hypertrophy of the right ventricle (RV). The transcription factors, nuclear factor activated T-cells (NFAT), and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB/p65) contribute to RV hypertrophy (RVH). Because peroxisome proliferator-activated receptor gamma (PPARγ) activation attenuates hypoxia-induced PH and RVH, we hypothesized that PPARγ inhibits activation of RV hypertrophic transcriptional signaling mechanisms. C57BL/6J mice were exposed to normoxia (21% O₂) or hypoxia (10% O₂) for 21 days. During the final 10 days of exposure, selected mice were treated with the PPARγ ligand, pioglitazone. RV systolic pressure (RVSP) and RVH were measured, and NFATc2 and NF-kB/p65 protein levels were measured in RV and LV nuclear and cytosolic fractions. Cardiomyocyte hypertrophy was assessed with wheatgerm agglutinin staining. NFAT activation was also examined with luciferase reporter mice and analysis of protein levels of selected transcriptional targets. Chronic-hypoxia increased: (1) RVH, RVSP, and RV cardiomyocyte hypertrophy; (2) NFATc2 and NF-κB activation in RV nuclear homogenates; (3) RV and LV NFAT luciferase activity; and (4) RV protein levels of brain natriuretic peptide (BNP) and β-myosin heavy chain (β-MyHC). Treatment with pioglitazone attenuated hypoxia-induced increases in both RV and LV NFAT luciferase activity. Chronic hypoxia caused sustained RV NFATc2 and NF-κB activation. Pioglitazone attenuated PH, RVH, cardiomyocyte hypertrophy, and activation of RV hypertrophic signaling and also attenuated LV NFAT activation. PPARγ favorably modulates signaling derangements in the heart as well as in the pulmonary vascular wall.

Hypoxia-induced pulmonary hypertension in type 2 diabetic mice

Hypoxia-induced pulmonary hypertension (HPH) is a progressive disease that is mainly caused by chronic exposure to high altitude, chronic obstructive lung disease, and obstructive sleep apnea. The increased pulmonary vascular resistance and increased pulmonary arterial pressure result in increased right ventricular afterload, leading to right heart failure and increased morbidity. There are several clinical reports suggesting a link between PH and diabetes, insulin resistance, or obesity; however, it is unclear whether HPH is associated with diabetes as a progressive complication in diabetes. The major goal of this study is to examine the effect of diabetic "preconditioning" or priming effect on the progression of HPH and define the molecular mechanisms that explain the link between diabetes and HPH. Our data show that HPH is significantly enhanced in diabetic mice, while endothelium-dependent relaxation in pulmonary arteries is significantly attenuated in chronically hypoxic diabetic mice (DH). In addition, we demonstrate that mouse pulmonary endothelial cells (MPECs) isolated from DH mice exhibit a significant increase in mitochondrial reactive oxygen species (ROS) concentration and decreased SOD2 protein expression. Finally, scavenging mitochondrial ROS by mitoTempol restores endothelium-dependent relaxation in pulmonary arteries that is attenuated in DH mice. These data suggest that excessive mitochondrial ROS production in diabetic MPECs leads to the development of severe HPH in diabetic mice exposed to hypoxia.

Novel methods in pulmonary hypertension phenotyping in the age of precision medicine (2015 Grover Conference series)

Among pulmonary vascular diseases, pulmonary hypertension (PH) is the best studied and has been the focus of our work. The current classification of PH is based on a relatively simple combination of patient characteristics and hemodynamics. This leads to inherent limitations, including the inability to customize treatment and the lack of clarity from a more granular identification based on individual patient phenotypes. Accurate phenotyping of PH can be used in the clinic to select therapies and determine prognosis and in research to increase the homogeneity of study cohorts. Rapid advances in the mechanistic understanding of the disease, improved imaging methods, and innovative biomarkers now provide an opportunity to define novel PH phenotypes. We have recently shown that altered metabolism may affect nitric oxide levels and protein glycosylation, the peripheral circulation (which may provide insights into the response to therapy), and exhaled-breath analysis (which may be useful in disease evaluation). This review is based on a talk presented during the 2015 Grover Conference and highlights the relevant literature describing novel methods to phenotype pulmonary arterial hypertension patients by using approaches that involve the pulmonary and systemic (peripheral) vasculature. In particular, abnormalities in metabolism, the pulmonary and peripheral circulation, and exhaled breath in PH may help identify phenotypes that can be the basis for a precision-medicine approach to PH management. These approaches may also have a broader scope and may contribute to a better understanding of other diseases, such as asthma, diabetes, and cancer.

Independent predictors of developing pulmonary hypertension in heart failure with reduced versus preserved ejection fraction

OBJECTIVES

To investigate the different clinical and echocardiographic predictors of evolving PH in patients with heart failure with and without reduced ejection fraction.

METHODS AND RESULTS

The study included 153 heart failure patients with reduced ejection fraction (HFrEF) (n = 89) and preserved ejection fraction (HFpEF) (n = 64) both of which were subdivided into 2 subgroups according to the presence of PH. All patients were subjected to detailed clinical assessment and full transthoracic echocardiogram. There were significant differences between the 2 HFrEF subgroups regarding systolic BP, presence of diabetes, dyslipidemia, diuretics usage, all LV parameters, LAD, LAV and LAV indexed to BSA, E/A ratio, DT and severity of TR. Using multivariate analysis, the presence of diabetes (P = 0.04), diuretics usage (P = 0.04), LAV (P = 0.007) and TR grade (P < 0.001) were significant independent predictors for the development of PH among HFrEF patients. There were significant differences between the 2 HFpEF subgroups regarding presence of hypertension, diuretics usage, LAD, LAA, TR severity. Using multivariate analysis, only diuretics usage (P = 0.02) and TR grade (P < 0.0001) were significant independent predictors for the development of PH among HFpEF patients.

CONCLUSION

Neither the decrease in EF among HFrEF patients nor the DD grade in HFpEF patients act as independent predictor for evolving PH. Common independent predictors for evolving PH in both HFrEF and HFpEF patients are TR grade and use of diuretics. Other independent predictors in HFrEF and not HFpEF patients are the presence of diabetes and increased LAV.

Role of oxidized lipids in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a multifactorial disease characterized by interplay of many cellular, molecular, and genetic events that lead to excessive proliferation of pulmonary cells, including smooth muscle and endothelial cells; inflammation; and extracellular matrix remodeling. Abnormal vascular changes and structural remodeling associated with PAH culminate in vasoconstriction and obstruction of pulmonary arteries, contributing to increased pulmonary vascular resistance, pulmonary hypertension, and right ventricular failure. The complex molecular mechanisms involved in the pathobiology of PAH are the limiting factors in the development of potential therapeutic interventions for PAH. Over the years, our group and others have demonstrated the critical implication of lipids in the pathogenesis of PAH. This review specifically focuses on the current understanding of the role of oxidized lipids, lipid metabolism, peroxidation, and oxidative stress in the progression of PAH. This review also discusses the relevance of apolipoprotein A-I mimetic peptides and microRNA-193, which are known to regulate the levels of oxidized lipids, as potential therapeutics in PAH.

Increased Pyruvate Dehydrogenase Kinase 4 Expression in Lung Pericytes Is Associated with Reduced Endothelial-Pericyte Interactions and Small Vessel Loss in Pulmonary Arterial Hypertension

Reduced endothelial-pericyte interactions are linked to progressive small vessel loss in pulmonary arterial hypertension (PAH), but the molecular mechanisms underlying this disease remain poorly understood. To identify relevant gene candidates associated with aberrant pericyte behavior, we performed a transcriptome analysis of patient-derived donor control and PAH lung pericytes followed by functional genomics analysis. Compared with donor control cells, PAH pericytes had significant enrichment of genes involved in various metabolic processes, the top hit being PDK4, a gene coding for an enzyme that suppresses mitochondrial activity in favor of glycolysis. Given reports that link reduced mitochondrial activity with increased PAH cell proliferation, we hypothesized that increased PDK4 is associated with PAH pericyte hyperproliferation and reduced endothelial-pericyte interactions. We found that PDK4 gene and protein expression was significantly elevated in PAH pericytes and correlated with reduced mitochondrial metabolism, higher rates of glycolysis, and hyperproliferation. Importantly, reducing PDK4 levels restored mitochondrial metabolism, reduced cell proliferation, and improved endothelial-pericyte interactions. To our knowledge, this is the first study that documents significant differences in gene expression between human donor control and PAH lung pericytes and the link between mitochondrial dysfunction and aberrant endothelial-pericyte interactions in PAH. Comprehensive characterization of these candidate genes could provide novel therapeutic targets to improve endothelial-pericyte interactions and prevent small vessel loss in PAH.

Up-regulation of the mammalian target of rapamycin complex 1 subunit Raptor by aldosterone induces abnormal pulmonary artery smooth muscle cell survival patterns to promote pulmonary arterial hypertension

Activation of the mammalian target of rapamycin complex 1 (mTORC1) subunit Raptor induces cell growth and is a downstream target of Akt. Elevated levels of aldosterone activate Akt, and, in pulmonary arterial hypertension (PAH), correlate with pulmonary arteriole thickening, which suggests that mTORC1 regulation by aldosterone may mediate adverse pulmonary vascular remodeling. We hypothesized that aldosterone-Raptor signaling induces abnormal pulmonary artery smooth muscle cell (PASMC) survival patterns to promote PAH. Remodeled pulmonary arterioles from SU-5416/hypoxia-PAH rats and monocrotaline-PAH rats with hyperaldosteronism expressed increased levels of the Raptor target, p70S6K, which provided a basis for investigating aldosterone-Raptor signaling in human PASMCs. Aldosterone (10(-9) to 10(-7) M) increased Akt/mTOR/Raptor to activate p70S6K and increase proliferation, viability, and apoptosis resistance in PASMCs. In PASMCs transfected with Raptor-small interfering RNA or treated with spironolactone/eplerenone, aldosterone or pulmonary arterial plasma from patients with PAH failed to increase p70S6K activation or to induce cell survival in vitro Optimal inhibition of pulmonary arteriole Raptor was achieved by treatment with Staramine-monomethoxy polyethylene glycol that was formulated with Raptor-small interfering RNA plus spironolactone in vivo, which decreased arteriole muscularization and pulmonary hypertension in 2 experimental animal models of PAH in vivo Up-regulation of mTORC1 by aldosterone is a critical pathobiologic mechanism that controls PASMC survival to promote hypertrophic vascular remodeling and PAH.-Aghamohammadzadeh, R., Zhang, Y.-Y., Stephens, T. E., Arons, E., Zaman, P., Polach, K. J., Matar, M., Yung, L.-M., Yu, P. B., Bowman, F. P., Opotowsky, A. R., Waxman, A. B., Loscalzo, J., Leopold, J. A., Maron, B. A. Up-regulation of the mammalian target of rapamycin complex 1 subunit Raptor by aldosterone induces abnormal pulmonary artery smooth muscle cell survival patterns to promote pulmonary arterial hypertension.

Proline-rich tyrosine kinase 2 downregulates peroxisome proliferator-activated receptor gamma to promote hypoxia-induced pulmonary artery smooth muscle cell proliferation

Hypoxia stimulates pulmonary hypertension (PH), in part by increasing the proliferation of human pulmonary artery smooth muscle cells (HPASMCs) via sustained activation of mitogen-activated protein kinase, extracellular signal-regulated kinases 1 and 2 (ERK 1/2), and nuclear factor-kappa B (NF-κB); elevated expression of NADPH oxidase 4 (Nox4); and downregulation of peroxisome proliferator-activated receptor gamma (PPARγ) levels. However, the upstream mediators that control these responses remain largely unknown. We hypothesized that proline-rich tyrosine kinase 2 (Pyk2) plays a critical role in the mechanism of hypoxia-induced HPASMC proliferation. To test this hypothesis, HPASMCs were exposed to normoxia or hypoxia (1% O2) for 72 hours. Hypoxia activated Pyk2 (detected as Tyr402 phosphorylation), and inhibition of Pyk2 with small interfering RNA (siRNA) or tyrphostin A9 attenuated hypoxia-induced HPASMC proliferation. Pyk2 inhibition attenuated ERK 1/2 activation as early as 24 hours after the onset of hypoxia, suggesting a proximal role for Pyk2 in this response. Pyk2 inhibition also attenuated hypoxia-induced NF-κB activation, reduced HPASMC PPARγ messenger RNA levels and activity, and increased NF-κB-mediated Nox4 levels. The siRNA-mediated PPARγ knockdown enhanced Pyk2 activation, whereas PPARγ overexpression reduced Pyk2 activation in HPASMCs, confirming a reciprocal relationship between Pyk2 and PPARγ. Pyk2 depletion also attenuated hypoxia-induced NF-κB p65 activation and reduced PPARγ protein levels in human pulmonary artery endothelial cells. These in vitro findings suggest that Pyk2 plays a central role in the proliferative phenotype of pulmonary vascular wall cells under hypoxic conditions. Coupled with recent reports that hypoxia-induced PH is attenuated in Pyk2 knockout mice, these findings suggest that Pyk2 may represent a novel therapeutic target in PH.

Time-dependent PPARγ Modulation of HIF-1α Signaling in Hypoxic Pulmonary Artery Smooth Muscle Cells

BACKGROUND

Pathogenesis of pulmonary hypertension is complex and involves activation of the transcription factor, hypoxia-inducible factor-1 (HIF-1) that shifts cellular metabolism from aerobic respiration to glycolysis, in part, by increasing the expression of its downstream target pyruvate dehydrogenase kinase-1 (PDK-1), thereby promoting a proliferative, apoptosis-resistant phenotype in pulmonary vascular cells. Activation of the nuclear hormone transcription factor, peroxisome proliferator-activated receptor gamma (PPARγ), attenuates pulmonary hypertension and pulmonary artery smooth muscle cell (PASMC) proliferation. In the current study, we determined whether PPARγ inhibits HIF-1α and PDK-1 expression in human PASMCs.

METHODS

HPASMCs were exposed to normoxia (21% O2) or hypoxia (1% O2) for 2-72 hours ± treatment with the PPARγ-ligand, rosiglitazone (RSG, 10μM).

RESULTS

Compared to normoxia, HIF-1α mRNA levels were elevated in HPASMC at 2 hours hypoxia and reduced to baseline levels by 24-72 hours. HIF-1α protein levels increased following 4 and 8 hours of hypoxia and returned to baseline levels by 24 and 72 hours. PDK-1 protein levels increased following 24 hours hypoxia and remained elevated by 72 hours. RSG treatment at the onset of hypoxia attenuated HIF-1α protein and PDK-1 mRNA and protein levels at 4, 8 and 24 hours of hypoxia, respectively. However, RSG treatment during final 24 hours of 72-hour hypoxia, an intervention that inhibits HPASMC proliferation, failed to prevent hypoxia-induced PDK-1 expression.

CONCLUSION

Hypoxia causes transient activation of HPASMC HIF-1α that is attenuated by RSG treatment initiated at hypoxia onset. These findings provide novel evidence that PPARγ modulates fundamental and acute cellular responses to hypoxia through both HIF-1-dependent and HIF-1-independent mechanisms.

The Clinical Significance of HbA1c in Operable Chronic Thromboembolic Pulmonary Hypertension

Background

Glycosylated hemoglobin A1c (HbA1c) has been proposed as an independent predictor of long-term prognosis in pulmonary arterial hypertension. However, the clinical relevance of HbA1c in patients with operable chronic thromboembolic pulmonary hypertension (CTEPH) remains unknown. The aim of the present study was to investigate the clinical significance of HbA1c as a biomarker in CTEPH.

Methods

Prospectively, 102 patients underwent pulmonary endarterectomy (PEA) in our national referral center between March 2013 and March 2014, of which after exclusion 45 patients were analyzed. HbA1c- levels, hemodynamic and exercise parameters were analyzed prior and one-year post-PEA.

Results

45 patients (BMI: 27.3 ± 6.0 kg/m²; age: 62.7 ± 12.3 years) with a mean pulmonary arterial pressure (mPAP) of 43.6 ± 9.4 mmHg, a pulmonary vascular resistance (PVR) of 712.1 ± 520.4 dyn*s/cm⁵, a cardiac index (CI) of 2.4 ± 0.5 l/min/m² and a mean HbA1c-level of 39.8 ± 5.6 mmol/mol were included. One-year post-PEA pulmonary hemodynamic and functional status significantly improved in our cohort. Baseline HbA1c-levels were significantly associated with CI, right atrial pressure, peak oxygen uptake and the change of 6-minute walking distance using linear regression analysis. However, using logistic regression analysis baseline HbA1c-levels were not significantly associated with residual post-PEA PH.

Conclusions

This is the first prospective study to describe an association of HbA1c-levels with pulmonary hemodynamics and exercise capacity in operable CTEPH patients. Our preliminary results indicate that in these patients impaired glucose metabolism as assessed by HbA1c is of clinical significance. However, HbA1c failed as a predictor of the hemodynamic outcome one-year post-PEA.

Metabolic Dysfunction in Pulmonary Arterial Hypertension

Previously considered a disease isolated to the pulmonary circulation, pulmonary arterial hypertension is now being recognized as a systemic disorder that is associated with significant metabolic dysfunction. Numerous animal models have demonstrated the development of pulmonary arterial hypertension following the onset of insulin resistance, indicating that insulin resistance may be causal. Recent publications highlighting alterations in aerobic glycolysis, fatty acid oxidation, and the tricarboxylic acid cycle in the pulmonary circulation and right ventricle have expanded our understanding of the complex pathobiology of this disease. By targeting these derangements in metabolism, numerous researchers are investigating noninvasive techniques to monitor disease activity and therapeutics that address the underlying metabolic condition. In the following review, we will explore pre-clinical and clinical studies investigating the metabolic dysfunction seen in pulmonary arterial hypertension.

SIRT3-AMP-Activated Protein Kinase Activation by Nitrite and Metformin Improves Hyperglycemia and Normalizes Pulmonary Hypertension Associated With Heart Failure With Preserved Ejection Fraction

BACKGROUND

Pulmonary hypertension associated with heart failure with preserved ejection fraction (PH-HFpEF) is an increasingly recognized clinical complication of metabolic syndrome. No adequate animal model of PH-HFpEF is available, and no effective therapies have been identified to date. A recent study suggested that dietary nitrate improves insulin resistance in endothelial nitric oxide synthase null mice, and multiple studies have reported that both nitrate and its active metabolite, nitrite, have therapeutic activity in preclinical models of pulmonary hypertension.

METHODS AND RESULTS

To evaluate the efficacy and mechanism of nitrite in metabolic syndrome associated with PH-HFpEF, we developed a 2-hit PH-HFpEF model in rats with multiple features of metabolic syndrome attributable to double-leptin receptor defect (obese ZSF1) with the combined treatment of vascular endothelial growth factor receptor blocker SU5416. Chronic oral nitrite treatment improved hyperglycemia in obese ZSF1 rats by a process that requires skeletal muscle SIRT3-AMPK-GLUT4 signaling. The glucose-lowering effect of nitrite was abolished in SIRT3-deficient human skeletal muscle cells, and in SIRT3 knockout mice fed a high-fat diet, as well. Skeletal muscle biopsies from humans with metabolic syndrome after 12 weeks of oral sodium nitrite and nitrate treatment (IND#115926) displayed increased activation of SIRT3 and AMP-activated protein kinase. Finally, early treatments with nitrite and metformin at the time of SU5416 injection reduced pulmonary pressures and vascular remodeling in the PH-HFpEF model with robust activation of skeletal muscle SIRT3 and AMP-activated protein kinase.

CONCLUSIONS

These studies validate a rodent model of metabolic syndrome and PH-HFpEF, suggesting a potential role of nitrite and metformin as a preventative treatment for this disease.

Reconciling paradigms of abnormal pulmonary blood flow and quasi-malignant cellular alterations in pulmonary arterial hypertension

In pulmonary arterial hypertension (PAH) structural and functional abnormalities of the small lung vessels interact and lead to a progressive increase in pulmonary vascular resistance and right heart failure. A current pathobiological concept characterizes PAH as a 'quasi-malignant' disease focusing on cancer-like alterations in endothelial cells (EC) and the importance of their acquired apoptosis-resistant, hyper-proliferative phenotype in the process of vascular remodeling. While changes in pulmonary blood flow (PBF) have been long-since recognized and linked to the development of PAH, little is known about a possible relationship between an altered PBF and the quasi-malignant cell phenotype in the pulmonary vascular wall. This review summarizes recognized and hypothetical effects of an abnormal PBF on the pulmonary vascular bed and links these to quasi-malignant changes found in the pulmonary endothelium. Here we describe that abnormal PBF does not only trigger a pulmonary vascular cell growth program, but may also maintain the cancer-like phenotype of the endothelium. Consequently, normalization of PBF and EC response to abnormal PBF may represent a treatment strategy in patients with established PAH.

Metabolic Syndrome and the Lung

A link between metabolic syndrome (MetS) and lung diseases has been observed in several cross-sectional and longitudinal studies. This syndrome has been identified as an independent risk factor for worsening respiratory symptoms, greater lung function impairment, pulmonary hypertension, and asthma. This review will discuss several potential mechanisms to explain these associations, including dietary factors and the effect of adiposity and fat-induced inflammation on the lungs, and the role of other comorbidities that frequently coexist with MetS, such as OSA and obesity. In contrast to the well-known association between asthma and obesity, the recognition that MetS affects the lung is relatively new. Although some controversy remains as to whether MetS is a unique disease entity, its individual components have independently been associated with changes in pulmonary function or lung disease. There is, however, uncertainty as to the relative contribution that each metabolic factor has in adversely affecting the respiratory system; also, it is unclear how much of the MetS-related lung effects occur independently of obesity. In spite of these epidemiological limitations, the proposed mechanistic pathways strongly suggest that this association is likely to be causal. Given the wide prevalence of MetS in the general population, it is imperative that we continue to further understand how this metabolic disorder impacts the lung and how to prevent its complications.

The Role of Hyperglycemia and Insulin Resistance in the Development and Progression of Pulmonary Arterial Hypertension

Pulmonary hypertension is a progressive disorder which often leads to right ventricular failure and death. While the existing classification system for pulmonary hypertension does not account for the impact of diabetes mellitus, evidence is emerging that suggests that diabetes is associated with pulmonary hypertension and that diabetes modifies the course of pulmonary hypertension. There is also growing radiographic, hemodynamic, biochemical, and pathologic data supporting an association between diabetes and pulmonary hypertension. More robust epidemiologic studies are needed to confirm an association between diabetes and pulmonary hypertension and to show that diabetes is a disease modifier in pulmonary hypertension. In addition, evaluating the effects of glucose control in animals with pulmonary hypertension and diabetes (as well as in humans) is warranted.

Nitro-fatty acids in cardiovascular regulation and diseases: characteristics and molecular mechanisms

Electrophilic nitro-fatty acids (NO2-FAs) are endogenously formed by redox reactions of nitric oxide ((.)NO)- and nitrite ((.)NO2)- derived nitrogen dioxide with unsaturated fatty acids. Nitration preferentially occurs on polyunsaturated fatty acids with conjugated dienes under physiological or pathophysiological conditions such as during digestion, metabolism and as adaptive inflammatory processes. Nitro-fatty acids are present in free and esterified forms achieving broad biodistribution in humans and experimental models. Structural, functional and biological characterization of NO2-FAs has revealed clinically relevant protection from inflammatory injury in a number of cardiovascular, renal and metabolic experimental models. NO2-FAs are engaged in posttranslational modifications (PTMs) of a selective redox sensitive pool of proteins and regulate key adaptive signaling pathways involved in cellular homeostasis and inflammatory response. Here, we review and update the biosynthesis, metabolism and signaling actions of NO2-FAs, highlighting their diverse protective roles relevant to the cardiovascular system.

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

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

Estrogen Metabolite 16α-Hydroxyestrone Exacerbates Bone Morphogenetic Protein Receptor Type II-Associated Pulmonary Arterial Hypertension Through MicroRNA-29-Mediated Modulation of Cellular Metabolism

BACKGROUND

Pulmonary arterial hypertension (PAH) is a proliferative disease of the pulmonary vasculature that preferentially affects women. Estrogens such as the metabolite 16α-hydroxyestrone (16αOHE) may contribute to PAH pathogenesis, and alterations in cellular energy metabolism associate with PAH. We hypothesized that 16αOHE promotes heritable PAH (HPAH) via microRNA-29 (miR-29) family upregulation and that antagonism of miR-29 would attenuate pulmonary hypertension in transgenic mouse models of Bmpr2 mutation.

METHODS AND RESULTS

MicroRNA array profiling of human lung tissue found elevation of microRNAs associated with energy metabolism, including the miR-29 family, among HPAH patients. miR-29 expression was 2-fold higher in Bmpr2 mutant mice lungs at baseline compared with controls and 4 to 8-fold higher in Bmpr2 mice exposed to 16αOHE 1.25 μg/h for 4 weeks. Blot analyses of Bmpr2 mouse lung protein showed significant reductions in peroxisome proliferator-activated receptor-γ and CD36 in those mice exposed to 16αOHE and protein derived from HPAH lungs compared with controls. Bmpr2 mice treated with anti-miR-29 (20-mg/kg injections for 6 weeks) had improvements in hemodynamic profile, histology, and markers of dysregulated energy metabolism compared with controls. Pulmonary artery smooth muscle cells derived from Bmpr2 murine lungs demonstrated mitochondrial abnormalities, which improved with anti-miR-29 transfection in vitro; endothelial-like cells derived from HPAH patient induced pluripotent stem cell lines were similar and improved with anti-miR-29 treatment.

CONCLUSIONS

16αOHE promotes the development of HPAH via upregulation of miR-29, which alters molecular and functional indexes of energy metabolism. Antagonism of miR-29 improves in vivo and in vitro features of HPAH and reveals a possible novel therapeutic target.

Hypothesis: Neuroendocrine Mechanisms (Hypothalamus-Growth Hormone-STAT5 Axis) Contribute to Sex Bias in Pulmonary Hypertension

Pulmonary hypertension (PH) is a disease with high morbidity and mortality. The prevalence of idiopathic pulmonary arterial hypertension (IPAH) and hereditary pulmonary arterial hypertension (HPAH) is approximately two- to four-fold higher in women than in men. Paradoxically, there is an opposite male bias in typical rodent models of PH (chronic hypoxia or monocrotaline); in these models, administration of estrogenic compounds (for example, estradiol-17β [E2]) is protective. Further complexities are observed in humans ingesting anorexigens (female bias) and in rodent models, such as after hypoxia plus SU5416/Sugen (little sex bias) or involving serotonin transporter overexpression or dexfenfluramine administration (female bias). These complexities in sex bias in PH remain incompletely understood. We recently discovered that conditional deletion of signal transducer and activator of transcription 5a/b (STAT5a/b) in vascular smooth muscle cells abrogated the male bias in PH in hypoxic mice and that late-stage obliterative lesions in patients of both sexes with IPAH and HPAH showed reduced STAT5a/b, reduced Tyr-P-STAT5 and reduced B-cell lymphoma 6 protein (BCL6). In trying to understand the significance of these observations, we realized that there existed a well-characterized E2-sensitive central neuroendocrine mechanism of sex bias, studied over the last 40 years, that, at its peripheral end, culminated in species-specific male ("pulsatile") versus female ("more continuous") temporal patterns of circulating growth hormone (GH) levels leading to male versus female patterned activation of STAT5a/b in peripheral tissues and thus sex-biased expression of hundreds of genes. In this report, we consider the contribution of this neuroendocrine mechanism (hypothalamus-GH-STAT5) in the generation of sex bias in different PH situations.

Farnesoid-X-receptor expression in monocrotaline-induced pulmonary arterial hypertension and right heart failure

OBJECTIVE

The farnesoid-X-receptor (FXR) is a metabolic nuclear receptor superfamily member that is highly expressed in enterohepatic tissue and is also expressed in the cardiovascular system. Multiple nuclear receptors, including FXR, play a pivotal role in cardiovascular disease (CVD). Pulmonary arterial hypertension (PAH) is an untreatable cardiovascular system disease that leads to right heart failure (RHF). However, the potential physiological/pathological roles of FXR in PAH and RHF are unknown. We therefore compared FXR expression in the cardiovascular system in PAH, RHF and a control.

METHODS AND RESULTS

Hemodynamic parameters and morphology were assessed in blank solution-exposed control, monocrotaline (MCT)-exposed PAH (4 weeks) and RHF (7 weeks) Sprague-Dawley rats. Real-time reverse transcription polymerase chain reaction (real-time RT-PCR), Western blot (WB), immunohistochemistry (IHC) analysis and immunofluorescence (IF) analysis were performed to assess FXR levels in the lung and heart tissues of MCT-induced PAH and RHF rats. In normal rats, low FXR levels were detected in the heart, and nearly no FXR was expressed in rat lungs. However, FXR expression was significantly elevated in PAH and RHF rat lungs but reduced in PAH and RHF rat right ventricular (RV) tissues. FXR expression was reduced only in RHF rat left ventricular (LV) tissues.

CONCLUSIONS

The differential expression of FXR in MCT-induced PAH lungs and heart tissues in parallel with PAH pathophysiological processes suggests that FXR contributes to PAH.

A Biochemical Approach to Understand the Pathogenesis of Advanced Pulmonary Arterial Hypertension: Metabolomic Profiles of Arginine, Sphingosine-1-Phosphate, and Heme of Human Lung

Pulmonary arterial hypertension (PAH) is a vascular disease characterized by persistent precapillary pulmonary hypertension (PH), leading to progressive right heart failure and premature death. The pathological mechanisms underlying this condition remain elusive. Analysis of global metabolomics from lung tissue of patients with PAH (n = 8) and control lung tissue (n = 8) leads to a better understanding of disease progression. Using a combination of high-throughput liquid-and-gas-chromatography-based mass spectrometry, we showed unbiased metabolomic profiles of disrupted arginine pathways with increased Nitric oxide (NO) and decreased arginine. Our results also showed specific metabolic pathways and genetic profiles with increased Sphingosine-1-phosphate (S1P) metabolites as well as increased Heme metabolites with altered oxidative pathways in the advanced stage of the human PAH lung. The results suggest that PAH has specific metabolic pathways contributing to the vascular remodeling in severe pulmonary hypertension. Profiling metabolomic alterations of the PAH lung has provided a new understanding of the pathogenic mechanisms of PAH, which benefits therapeutic targeting to specific metabolic pathways involved in the progression of PAH.

PPARγ Ligands Attenuate Hypoxia-Induced Proliferation in Human Pulmonary Artery Smooth Muscle Cells through Modulation of MicroRNA-21

Pulmonary hypertension (PH) is a progressive and often fatal disorder whose pathogenesis involves pulmonary artery smooth muscle cell (PASMC) proliferation. Although modern PH therapies have significantly improved survival, continued progress rests on the discovery of novel therapies and molecular targets. MicroRNA (miR)-21 has emerged as an important non-coding RNA that contributes to PH pathogenesis by enhancing vascular cell proliferation, however little is known about available therapies that modulate its expression. We previously demonstrated that peroxisome proliferator-activated receptor gamma (PPARγ) agonists attenuated hypoxia-induced HPASMC proliferation, vascular remodeling and PH through pleiotropic actions on multiple targets, including transforming growth factor (TGF)-β1 and phosphatase and tensin homolog deleted on chromosome 10 (PTEN). PTEN is a validated target of miR-21. We therefore hypothesized that antiproliferative effects conferred by PPARγ activation are mediated through inhibition of hypoxia-induced miR-21 expression. Human PASMC monolayers were exposed to hypoxia then treated with the PPARγ agonist, rosiglitazone (RSG,10 μM), or in parallel, C57Bl/6J mice were exposed to hypoxia then treated with RSG. RSG attenuated hypoxic increases in miR-21 expression in vitro and in vivo and abrogated reductions in PTEN and PASMC proliferation. Antiproliferative effects of RSG were lost following siRNA-mediated PTEN depletion. Furthermore, miR-21 mimic decreased PTEN and stimulated PASMC proliferation, whereas miR-21 inhibition increased PTEN and attenuated hypoxia-induced HPASMC proliferation. Collectively, these results demonstrate that PPARγ ligands regulate proliferative responses to hypoxia by preventing hypoxic increases in miR-21 and reductions in PTEN. These findings further clarify molecular mechanisms that support targeting PPARγ to attenuate pathogenic derangements in PH.