Serum high-density lipoprotein cholesterol levels as a prognostic indicator in patients with idiopathic pulmonary arterial hypertension

A peripheral system disease-Pulmonary hypertension

Pulmonary hypertension (PH) is a cardiovascular disorder characterized by substantial morbidity and mortality rates. It is a chronic condition characterized by intricate pathogenesis and uncontrollable factors. We summarized the pathological effects of estrogen, genetics, neuroinflammation, intestinal microbiota, metabolic reorganization, and histone modification on PH. PH is not only a pulmonary vascular disease, but also a systemic disease. The findings emphasize that the onset of PH is not exclusively confined to the pulmonary vasculature, consequently necessitating treatment approaches that extend beyond targeting pulmonary blood vessels. Hence, the research on the pathological mechanism of PH is not limited to target organs such as pulmonary vessels, but also focuses on exploring other fields (such as estrogen, genetics, neuroinflammation, intestinal microbiota, metabolic reorganization, and histone modification).

Blood Cholesterol and Triglycerides Associate with Right Ventricular Function in Pulmonary Hypertension

Background

Blood lipids are dysregulated in pulmonary hypertension (PH). Lower high-density lipoproteins cholesterol (HDL-C) and low-density lipoproteins cholesterol (LDL-C) are associated with disease severity and death in PH. Right ventricle (RV) dysfunction and failure are the major determinants of morbidity and mortality in PH. This study aims to test the hypothesis that dyslipidemia is associated with RV dysfunction in PH.

Methods

We enrolled healthy control subjects (n=12) and individuals with PH (n=30) (age: 18-65 years old). Clinical characteristics, echocardiogram, 2-[18F] fluoro-2-deoxy-D-glucose positron emission tomography (PET) scan, blood lipids, including total cholesterol (TC), triglycerides (TG), lipoproteins (LDL-C and HDL-C), and N-terminal pro-B type Natriuretic Peptide (NT-proBNP) were determined.

Results

Individuals with PH had lower HDL-C [PH, 41±12; control, 56±16 mg/dL, p<0.01] and higher TG to HDL-C ratio [PH, 3.6±3.1; control, 2.2±2.2, p<0.01] as compared to controls. TC, TG, and LDL-C were similar between PH and controls. Lower TC and TG were associated with worse RV function measured by RV strain (R=-0.43, p=0.02 and R=-0.37, p=0.05 respectively), RV fractional area change (R=0.51, p<0.01 and R=0.48, p<0.01 respectively), RV end-systolic area (R=-0.63, p<0.001 and R=-0.48, p<0.01 respectively), RV end-diastolic area: R=-0.58, p<0.001 and R=-0.41, p=0.03 respectively), and RV glucose uptake by PET (R=-0.46, p=0.01 and R=-0.30, p=0.10 respectively). NT-proBNP was negatively correlated with TC (R=-0.61, p=0.01) and TG (R=-0.62, p<0.02) in PH.

Conclusion

These findings confirm dyslipidemia is associated with worse right ventricular function in PH.

Impact of reduced apolipoprotein A-I levels on pulmonary arterial hypertension

BACKGROUND

The significance of apolipoprotein A-I (ApoA-I) is the anti-inflammatory functional component of high-density lipoprotein, which needs to be further studied in relation to pulmonary arterial hypertension (PAH). This study aimed to identify the predictive value of ApoA-1 on the risk and prognosis of PAH, as well as the underlying anti-inflammatory mechanism.

METHODS

Proteomic analysis was conducted on lung tissue from 6 PAH patients and 4 lung donors. Prediction of risk and mortality risk factors associated with PAH in 343 patients used logistic analysis and Cox regression analysis, respectively. The protective function of ApoA-I was assessed in human pulmonary arterial endothelial cells (HPAEC), while its anti-inflammatory function was evaluated in THP-1 macrophages.

RESULTS

In the lung tissues of patients with PAH, 168 differentially expressed proteins were associated with lipid metabolism according to GO and KEGG enrichment analysis. A protein-protein interaction network identified ApoA-I as a key protein associated with PAH. Lower ApoA-I levels were independent risk factors for PAH and displayed a stronger predictive value for PAH mortality. Plasma interleukin 6 (IL-6) levels were positively correlated with risk stratification and was higher in PAH patients with lower ApoA-I levels. ApoA-I was downregulated in lung tissues of MCT-induced rats. ApoA-I could reduce IL-6-induced pro-proliferative and pro-migratory abilities of HPAEC and inhibit secretion of IL-6 from macrophages, which is compromised under hypoxic conditions.

CONCLUSION

Our study identified the significance of ApoA-I as a biomarker for predicting the survival outcome of PAH patients, which might relate to its altered anti-inflammatory properties.

The Impact of Abnormal Lipid Metabolism on the Occurrence Risk of Idiopathic Pulmonary Arterial Hypertension

The aim was to determine whether lipid molecules can be used as potential biomarkers for idiopathic pulmonary arterial hypertension (IPAH), providing important reference value for early diagnosis and treatment. Liquid chromatography-mass spectrometry-based lipidomic assays allow for the simultaneous detection of a large number of lipids. In this study, lipid profiling was performed on plasma samples from 69 IPAH patients and 30 healthy controls to compare the levels of lipid molecules in the 2 groups of patients, and Cox regression analysis was used to identify meaningful metrics, along with receiver operator characteristic curves to assess the ability of the lipid molecules to predict the risk of disease in patients. Among the 14 lipid subclasses tested, 12 lipid levels were significantly higher in IPAH patients than in healthy controls. Free fatty acids (FFA) and monoacylglycerol (MAG) were significantly different between IPAH patients and healthy controls. Logistic regression analysis showed that FFA (OR: 1.239, 95%CI: 1.101, 1.394, p < 0.0001) and MAG (OR: 3.711, 95%CI: 2.214, 6.221, p < 0.001) were independent predictors of IPAH development. Among the lipid subclasses, FFA and MAG have potential as biomarkers for predicting the pathogenesis of IPAH, which may improve the early diagnosis of IPAH.

Biomarkers in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a severe medical condition characterized by elevated pulmonary vascular resistance (PVR), right ventricular (RV) failure, and death in the absence of appropriate treatment. The progression and prognosis are strictly related to the etiology, biochemical parameters, and treatment response. The gold-standard test remains right-sided heart catheterization, but dynamic monitoring of systolic pressure in the pulmonary artery is performed using echocardiography. However, simple and easily accessible non-invasive assays are also required in order to monitor this pathology. In addition, research in this area is in continuous development. In recent years, more and more biomarkers have been studied and included in clinical guidelines. These biomarkers can be categorized based on their associations with inflammation, endothelial cell dysfunction, cardiac fibrosis, oxidative stress, and metabolic disorders. Moreover, biomarkers can be easily detected in blood and urine and correlated with disease severity, playing an important role in diagnosis, prognosis, and disease progression.

Decreased low‑density lipoprotein and the presence of pulmonary arterial hypertension among newly diagnosed drug‑naïve patients with systemic lupus erythematosus: D‑dimer as a mediator

Pulmonary arterial hypertension (PAH) is commonly associated with systemic lupus erythematosus (SLE). The present study investigated the relationship between coagulation and changes in lipid parameters in newly-diagnosed patients with SLE in the presence of PAH and whether the coagulation parameters were mediators between lipids and PAH presence. A total of 301 subjects scheduled for new-onset drug-naïve SLE were consecutively enrolled. Baseline data for patients without PAH and with PAH were gathered and compared. Coagulation and lipid parameters were compared across patients without lipid regulating and anticoagulation medications. Multivariable logistic regression model was applied to examine potential predictors of PAH in SLE. The relationships between them were examined using Spearman's correlation analysis. The relationship between coagulation index and lipids with SLE-PAH was evaluated using mediation analysis. Female patients accounted for 88.0% of the 301 subjects, and the average age was 32 years (range, 25-45 years). A total of 40 patients (13.3%) had PAH, and the average pulmonary artery systolic pressure (sPAP) was 55.825±26.67 mmHg. Patients with PAH were older and had higher levels of fibrin/fibrinogen degradation products (FDP), D-dimer, C-reactive protein, lower levels of complement 3, complement 4 and 25-hydroxy vitamin D3 compared with the non-PAH group. Multivariable logistic regression analysis showed that age and D-dimer were independent predictor factors for PAH. Among patients without lipid regulating and anticoagulation medications, patients in the PAH group had higher levels of D-dimer and FDP, and lower low-density lipoprotein (LDL) levels compared with patients without PAH. There was also a positive relationship between sPAP and D-dimer and FDP, and a negative relationship between sPAP and total cholesterol and LDL. Mediation analysis indicated that 25.61% of the effect of low LDL on PAH presence in systemic lupus erythematosus was mediated by D-dimer. Overall, the effect of low LDL on SLE-PAH appeared to be mediated by D-dimer, which mediated 25.61% of this effect.

Differential serum lipid distribution in IPAH and CHD-PAH patients

Lipid homeostasis is dysregulated in pulmonary arterial hypertension (PAH). A decrease in serum high- and low-density lipoprotein cholesterol (HDL-C and LDL-C) is significantly associated with the worse prognosis of PAH. However, no study has investigated the differential distribution of lipids in various PAH subtypes. We enrolled 190 patients in this retrospective study, which includes 20 patients with congenital heart disease without PAH (CHD-nonPAH), 101 patients with PAH associated with congenital heart disease (CHD-PAH), 69 patients with idiopathic PAH (IPAH) and 81 healthy controls. Laboratory parameters such as liver and renal function, serum lipids, C-reactive protein, N-terminal pro-brain natriuretic peptide (NT-proBNP), echocardiography, right heart catheterization and 6-min walk distance (6MWD) were performed. All types of cholesterol including HDL-C, LDL-C and total cholesterol (CHOL) were significantly lower in IPAH patients in association with right heart function. Although LDL-C and CHOL were lower in CHD-PAH, they were not associated with disease severity or heart failure. Thus, we conclude that IPAH and CHD-PAH patients exhibited a differential distribution pattern of serum lipids.

Liver abnormalities in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a cardiopulmonary disease with high mortality. In recent years, it has been recognized that PAH is a multi-organ system disease, involving the systemic circulation, kidneys, skeletal muscles, and the central nervous system, among others. Right heart failure produces congestive hepatopathy, a disease state that has direct consequences on liver biochemistry, histology, and systemic glucose and lipid metabolism. This article aims to summarize the consequences of congestive hepatopathy with an emphasis on liver biochemistry, histology, and PAH-targeted therapy. Furthermore, PAH-specific changes in glucose and lipid metabolism will be discussed.

Plasma irisin levels are associated with hemodynamic and clinical outcome in idiopathic pulmonary arterial hypertension patients

Irisin has been considered to reflect oxidative stress. This study aimed to show whether plasma irisin levels are correlated with hemodynamic dysfunction and predict the clinical outcome of patients with idiopathic pulmonary arterial hypertension (IPAH). A total of 68 adult IPAH patients were prospectively recruited in the present study. Plasma irisin levels were measured by the ELISA method in enrolled IPAH patients. Baseline clinical characteristics, and hemodynamic and clinical outcome were compared according to different plasma irisin levels. IPAH patients were divided into high irisin group (irisin ≥ 7.3 μg/ml) and low irisin group (irisin < 7.3 μg/ml) according to median values of irisin levels. Total plasma cholesterol levels (P = 0.027) and low-density lipoprotein cholesterol (LDL-C) levels (P = 0.042) were higher in high irisin group and were positively correlated with plasma irisin levels. IPAH patients in low irisin group had a significantly higher mean pulmonary artery pressure (mPAP, P = 0.047), systolic pulmonary artery pressure (sPAP, P = 0.022), systolic right-ventricular pressure (sRVP, P = 0.007), mean right atrial pressure (mRAP, P = 0.043), and systolic right atrial pressure (sRAP, P = 0.020). mRAP, sRAP, and diastolic right atrial pressure (dRAP) were negatively correlated with plasma irisin levels. Low irisin group predicts adverse hemodynamic status and poor free of event survival rate (P = 0.030, log-rank test). Multivariate analysis indicates plasma irisin levels to be an independent predictor of prognosis in IPAH patients after adjusting for related covariates (HR 0.786; 95% CI 0.584, 0.957; P = 0.038). Plasma irisin levels may serve as a novel biomarker in IPAH patients for hemodynamic severity assessment and clinical outcome evaluation.

Abnormal levels of apolipoprotein A-I in chronic thromboembolic pulmonary hypertension

Recent studies have shown low high-density lipoprotein cholesterol (HDL-C) and dysregulated lipid metabolism in chronic thromboembolic pulmonary hypertension (CTEPH). Apolipoprotein A-I (ApoA-I) is the major protein component of HDL-C and mediates most of its functions. We hypothesize that ApoA-1 and its oxidative state might be more sensitive biomarkers in CTEPH. Plasma levels of HDL-C, ApoA-I, paraoxonase-1 enzyme activity (PON1), and the oxidized dysfunctional ApoA-I (oxTrp72-ApoA-I) were measured in patients with CTEPH and compared to those in healthy controls. Association with markers of disease severity in CTEPH was assessed. We included a total of 61 patients with CTEPH (age: 61.2 ± 15 years; male 52.5%) and 28 control subjects (age: 60.1 ± 8 years; male 59.3%). When adjusting for age, sex, body mass index, and statin use, ApoA-I was lower in CTEPH compared to controls (CTEPH:125.2 ± 27 mg/dl; control:158.3 ± 29.4 mg/dl; p < 0.001), but HDL-C levels were not statistically different. There were no significant differences in PON and oxTrp72-ApoA-I/ApoA-I ratio. In exploratory analyses, ApoA-I was associated with mean right atrial pressure (rs = -0.32, p = 0.013) and N-terminal pro B-type natriuretic peptide (rs = -0.31, p = 0.038). There were no significant associations between HDL-C, PON1, or oxTrp72-ApoA-I/ApoA-I ratio and markers of disease severity. We conclude that ApoA-I is a more sensitive biomarker than HDL-C in CTEPH, and may be associated with right heart dysfunction.

Relative incidence and predictors of pulmonary arterial hypertension complicating type 2 diabetes: The Fremantle Diabetes Study Phase I

AIMS

To determine the relative incidence and predictors of pulmonary arterial hypertension (PAH) in type 2 diabetes.

METHODS

Hospitalizations for/with and death from/with PAH, and all-cause mortality, were ascertained from validated databases for participants from the longitudinal, community-based Fremantle Diabetes Study Phase I (FDS1; n = 1287) and age-, sex- and zip code-matched people without diabetes (n = 5153) between entry (1993-1996) and end-2017. Incidence rates (IRs) and IR ratios (IRRs) were calculated. Cox proportional hazards and competing risk models generated cause-specific (cs) and subdistribution (sd) hazard ratios (HRs) for incident PAH.

RESULTS

In the pooled cohort (mean age 64.0 years, 49% males), 49 (3.8%) of the type 2 diabetes participants and 133 (2.6%) of those without diabetes developed PAH during 106,556 person-years of follow-up (IRs (95% CI) 262 (194-346) and 151 (127-179) /100,000 person-years, respectively; IRR 1.73 (1.22-2.42), P = 0.001). Type 2 diabetes was associated with an unadjusted csHR of 1.97 (1.42-2.74) and sdHR of 1.44 (1.04-2.00) (P ≤ 0.03); after adjustment for age, sex, and co-morbidities, these were 1.43 (0.83-2.47) and 1.36 (0.97-1.91), respectively (P ≥ 0.07).

CONCLUSIONS

Type 2 diabetes is associated with an increased risk of PAH but this is no longer significant after adjustment for other explanatory variables and the competing risk of death.

Serum High-Density Lipoprotein Cholesterol is Significantly Associated with the Presence and Severity of Pulmonary Arterial Hypertension: A Retrospective Cross-Sectional Study

INTRODUCTION

To explore the relationship between serum high-density lipoprotein cholesterol (HDL-C) levels and the presence and severity of pulmonary arterial hypertension (PAH).

METHODS

A total of 177 patients with PAH and 103 patients without pulmonary hypertension (PH) were enrolled in this study. All patients underwent right heart catheterization (RHC) for diagnosing and assessing the severity of PAH. Demographics, comorbidities, and laboratory data including serum HDL-C levels were collected.

RESULTS

Plasma HDL-C levels in patients with PAH were significantly lower compared with patients without PH (1.08 ± 0.36 vs 1.49 ± 0.36, p < 0.001). HDL-C levels positively correlated with cardiac output (r = 0.360, p < 0.001), cardiac index (r = 0.337, p < 0.001), and mixed venous oxygen saturation (r = 0.426, p < 0.001), and negatively with mean pulmonary arterial pressure (r = - 0.529, p < 0.001), right atrial pressure (r = - 0.421, p < 0.001), and pulmonary vascular resistance (r = - 0.583, p < 0.001). Multivariate logistic regression analysis indicated that HDL-C was a significant independent predictor of PAH (OR 0.042, 95% CI 0.006-0.304, p = 0.002). The receiver operating characteristic curve analysis showed that the optimal cutoff value of the serum HDL-C concentration for predicting PAH was 1.32 mmol/L, with a sensitivity of 83.6% and a specificity of 72.8% (area under the curve 0.803, 95% confidence interval 0.750-0.856, p < 0.001).

CONCLUSIONS

Serum HDL-C is a simple biomarker that might be used for prediction and assessment of PAH in Chinese Han ethnicity, and the mechanism underlying the association needs further study.

Prognostic role of traditional cardiovascular risk factors in patients with idiopathic pulmonary arterial hypertension

INTRODUCTION

Metabolic alterations have been recently associated with onset and progression of idiopathic pulmonary arterial hypertension (IPAH). We aimed to determine the prevalence and prognostic role of cardiovascular risk factors in patients with IPAH.

MATERIAL AND METHODS

Between February 2009 and January 2015 we recruited consecutive IPAH patients. Clinical assessment included medical history, fasting glucose, lipid profile, N-terminal pro-brain natriuretic peptide concentration, 6-minute walk test distance, WHO functional class and hemodynamic evaluation. Patients' risk was estimated based on the Swedish PAH Register grading system.

RESULTS

The study group included 61 IPAH patients, and the control group included 2413 Polish residents. When compared to the general population, IPAH patients had lower low-density lipoprotein cholesterol (LDL-C) and a higher triglyceride to high-density lipoprotein cholesterol (TG/HDL-C) ratio. Female patients were characterized by elevated glucose level, higher prevalence of diabetes and lower HDL-C than controls. PAH severity grade correlated positively with age and TG/HDL-C ratio (R = 0.29, p = 0.02) and inversely with LDL-C (R = -0.28, p = 0.03) and HDL-C (R = -0.39, p = 0.02) concentrations. After a follow-up of 48 (23-79) months we recorded 28 deaths in the IPAH group. In the regression analysis lower LDL-C (p = 0.002) and HDL-C (p = 0.0002) levels, and higher TG/HDL-C ratio (p = 0.003) and glucose level (p = 0.003) were associated with all-cause mortality after adjustment for age, sex or PAH severity grade.

CONCLUSIONS

Patients with IPAH are characterized by an altered profile of lipid and glucose metabolism. Lowered levels of LDL-C and HDL-C and increased TG/HDL-C ratio correlate with disease severity and together with elevated plasma glucose level predict poor survival in IPAH.

[Novel Biomarkers of Pulmonary Hypertension]

Pulmonary hypertension (PH) is a clinical syndrome characterized by a progressive increase in pulmonary vascular resistance (PVR), which leads to remodeling of the right ventricle (RV), right heart failure and premature death of patients. Early diagnosis and monitoring of disease progression are crucial for making decisions about the necessary therapy. The gold standard for the diagnosis of pulmonary hypertension is the right heart catheterization. The estimation of systolic pressure in pulmonary artery by means of transthoracic echocardiography is also used for monitoring the course of the disease. At present, there is still a need for non-invasive biomarkers that reflect pathological changes in pulmonary arterial vessels and allow diagnosing of PH. Our review outlines the new data about some biomarkers potentially useful for diagnosis and prognostication of PH. These biomarkers (mid-regional pro-adrenomedullin, carboxyterminal pro-endothelin-1, copeptin, asymmetric dimethylarginine, growth differentiation factor 15, and others) are classified based on their relationship to endothelial cell dysfunction, inflammation, epigenetics, cardiac function, oxidative stress, extracellular matrix. The determination of biomarkers that are of diagnostic value for predicting the severity, progression of PH and response to therapy, in a simple blood test or condensate of exhaled air, can significantly reduce treatment costs and improve PH management.

HDL Cholesterol as a Marker of Disease Severity and Prognosis in Patients with Pulmonary Arterial Hypertension

The impact of high-density lipoprotein (HDL) cholesterol on the development of atherosclerosis and diseases of systemic circulation has been well documented both in experimental and registry studies. Recent discoveries in pulmonary arterial hypertension (PAH) revealed a significant impact of HDL on pulmonary artery vasoreactivity and patients' prognosis. The vasoprotective activity of HDL primarily involves vascular endothelium that also plays a central role in pulmonary arterial hypertension (PAH) pathobiology. However, the exact mechanism in which this lipoprotein fraction exerts its effect in pulmonary circulation is still under investigation. This paper reviews potential vasoprotective mechanisms of HDL in pulmonary circulation and presents current clinical reports on the role of HDL in PAH patients.

Reduced plasma levels of small HDL particles transporting fibrinolytic proteins in pulmonary arterial hypertension

BACKGROUND

Aberrant lipoprotein metabolism has been implicated in experimental pulmonary hypertension, but the relevance to patients with pulmonary arterial hypertension (PAH) is inconclusive.

OBJECTIVE

To investigate the relationship between circulating lipoprotein subclasses and survival in patients with PAH.

METHODS

Using nuclear magnetic resonance spectroscopy, 105 discrete lipoproteins were measured in plasma samples from two cohorts of patients with idiopathic or heritable PAH. Data from 1124 plasma proteins were used to identify proteins linked to lipoprotein subclasses. The physical presence of proteins was confirmed in plasma lipoprotein subfractions separated by ultracentrifugation.

RESULTS

Plasma levels of three lipoproteins from the small high-density lipoprotein (HDL) subclass, termed HDL-4, were inversely related to survival in both the discovery (n=127) and validation (n=77) cohorts, independent of exercise capacity, comorbidities, treatment, N-terminal probrain natriuretic peptide, C reactive protein and the principal lipoprotein classes. The small HDL subclass rich in apolipoprotein A-2 content (HDL-4-Apo A-2) exhibited the most significant association with survival. None of the other lipoprotein classes, including principal lipoprotein classes HDL and low-density lipoprotein cholesterol, were prognostic. Three out of nine proteins identified to associate with HDL-4-Apo A-2 are involved in the regulation of fibrinolysis, namely, the plasmin regulator, alpha-2-antiplasmin, and two major components of the kallikrein-kinin pathway (coagulation factor XI and prekallikrein), and their physical presence in the HDL-4 subfraction was confirmed.

CONCLUSION

Reduced plasma levels of small HDL particles transporting fibrinolytic proteins are associated with poor outcomes in patients with idiopathic and heritable PAH.

Somatic growth and the risks of bronchopulmonary dysplasia and pulmonary hypertension: connecting epidemiology and physiology 1

In the premature infant, poor growth in utero (fetal growth restriction) and in the first weeks of life (postnatal growth restriction) are associated with increased risk for bronchopulmonary dysplasia and pulmonary hypertension. In this review, we summarize the epidemiologic data supporting these associations, present a novel rodent model of postnatal growth restriction, and review 5 promising mechanisms by which poor nutrition may affect the developing lung. These observations support the hypothesis that nutritional and (or) pharmacologic interventions early in life may be able to decrease risk of the pulmonary complications of extreme prematurity.

Cholesterol Regulation of Pulmonary Endothelial Calcium Homeostasis

Cholesterol is a key structural component and regulator of lipid raft signaling platforms critical for cell function. Such regulation may involve changes in the biophysical properties of lipid microdomains or direct protein-sterol interactions that alter the function of ion channels, receptors, enzymes, and membrane structural proteins. Recent studies have implicated abnormal membrane cholesterol levels in mediating endothelial dysfunction that is characteristic of pulmonary hypertensive disorders, including that resulting from long-term exposure to hypoxia. Endothelial dysfunction in this setting is characterized by impaired pulmonary endothelial calcium entry and an associated imbalance that favors production vasoconstrictor and mitogenic factors that contribute to pulmonary hypertension. Here we review current knowledge of cholesterol regulation of pulmonary endothelial Ca²⁺ homeostasis, focusing on the role of membrane cholesterol in mediating agonist-induced Ca²⁺ entry and its components in the normal and hypertensive pulmonary circulation.

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.

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 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.

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.

Low-density lipoprotein cholesterol and survival in pulmonary arterial hypertension

Low-density lipoprotein cholesterol(LDL-C) is a well established metabolic marker of cardiovascular risk, however, its role in pulmonary arterial hypertension (PAH) has not been determined. Therefore we assessed whether LDL-C levels are altered in PAH patients, if they are associated with survival in this group and whether pulmonary hypertension (PH) reversal can influence LDL-C levels. Consecutive 46 PAH males and 94 females were age matched with a representative sample of 1168 males and 1245 females, respectively. Cox regression models were used to assess the association between LDL-C and mortality. The effect of PH reversal on LDL-C levels was assessed in 34 patients with chronic thromboembolic pulmonary hypertension (CTEPH) undergoing invasive treatment. LDL-C was lower in both PAH (2.6 ± 0.8 mmol/l) and CTEPH (2.7 ± 0.7 mmol/l) patients when compared to controls (3.2 ± 1.1 mmol/l, p < 0.001). In PAH patients lower LDL-C significantly predicted death (HR:0.44/1 mmol/l, 95%CI:0.26-0.74, p = 0.002) after a median follow-up time of 33(21-36) months. In the CTEPH group, LDL-C increased (from 2.6[2.1-3.2] to 4.0[2.8-4.9]mmol/l, p = 0.01) in patients with PH reversal but remained unchanged in other patients (2.4[2.2-2.7] vs 2.3[2.1-2.5]mmol/l, p = 0.51). We concluded that LDL-C level is low in patients with PAH and is associated with an increased risk of death. Reversal of PH increases LDL-C levels.

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.

Prognostic Significance of Biomarkers in Pulmonary Arterial Hypertension

RATIONALE

Pulmonary arterial hypertension (PAH) is a rare progressive disease of the pulmonary vasculature that is characterized by endothelial dysfunction, inflammation, and right ventricular dysfunction.

OBJECTIVES

The main objective was to determine whether endothelial, inflammatory, and cardiac biomarkers would be associated with the World Health Organization functional assessment and survival in patients with PAH.

METHODS

We performed a retrospective cohort study of patients with PAH enrolled in the Randomized Clinical Trial of Aspirin and Simvastatin for Pulmonary Arterial Hypertension (ASA-STAT). Biomarkers (N-terminal fragment of pro-BNP [NT-pro-BNP], von Willebrand factor [vWF], soluble P selectin, C-reactive protein, total and high-density lipoprotein cholesterol, triglycerides, tumor necrosis factor, IL-6, β-thromboglobulin, and thromboxane B2) were measured at baseline. Patients from the study were followed until lung transplantation, death, or August 1, 2013. Ordinal logistic regression and Cox regression analyses were performed.

MEASUREMENTS AND MAIN RESULTS

Sixty-five patients with PAH were enrolled. The mean age was 51 years, and 86% were women. Higher vWF activity, lower high-density lipoprotein cholesterol, and higher thromboxane B2 levels were associated with worse World Health Organization functional class after adjustment for age, sex, and etiology of PAH. Higher NT-pro-BNP levels, lower vWF activity, and lower total cholesterol were associated with an increased risk of death or lung transplant after adjustment for age, sex, etiology of PAH, and 6-minute-walk distance.

CONCLUSIONS

In patients with PAH, lower vWF activity and cholesterol levels and higher NT-pro-BNP levels at baseline were associated with an increased risk of death or transplantation. Clinical trial registered with www.clinicaltrials.gov (NCT00384865).

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.

Novel biomarkers for pulmonary arterial hypertension

Pulmonary arterial hypertension is a deadly disease characterized by elevated pulmonary arterial pressures leading to right ventricular hypertrophy and failure. The confirmatory gold standard test is the invasive right heart catheterization. The disease course is monitored by pulmonary artery systolic pressure measurement via transthoracic echocardiography. A simple non-invasive test to frequently monitor the patients is much needed. Search for a novel biomarker that can be detected by a simple test is ongoing and many different options are being studied. Here we review some of the new and unique pre-clinical options for potential pulmonary hypertension biomarkers. These biomarkers can be broadly categorized based on their association with endothelial cell dysfunction, inflammation, epigenetics, cardiac function, oxidative stress, metabolism,extracellular matrix, and volatile compounds in exhaled breath condensate. A biomarker that can be detected in blood, urine or breath condensate and correlates with disease severity, progression and response to therapy may result in significant cost reduction and improved patient outcomes.

Usefulness of High-Density Lipoprotein Cholesterol to Predict Survival in Pulmonary Arterial Hypertension

It has been suggested that lipoprotein abnormalities may contribute to the pulmonary arteriolar dysfunction observed in pulmonary arterial hypertension (PAH). High-density lipoprotein cholesterol (HDL) has vasodilatory, anti-inflammatory, and endothelial protective properties. We hypothesized that a higher serum HDL level may be advantageous for survival in PAH and that the serum HDL level at diagnosis would be an independent predictor of survival in PAH and be additive to previously validated predictors of survival. This study included all patients with PAH seen at the Mayo Clinic Pulmonary Hypertension Clinic from January 1, 1995, to December 31, 2009, who had a baseline HDL measurement. Mortality was analyzed over 5 years using the Kaplan-Meier method. Univariate and multivariable Cox proportional hazards ratios were calculated to evaluate the relation between baseline HDL level and survival. HDL levels were available for 227 patients. Higher HDL levels were associated with significantly lower mortality. Patients with an HDL >54 mg/dl at diagnosis had a 5-year survival of 59%. By comparison those with an HDL <34 mg/dl had a 5-year survival of 30%. On multivariate analysis, higher HDL was associated with an age-adjusted risk ratio for death of 0.78 (CI 0.67 to 0.91; p <0.01) per 10 mg/dl increase. In conclusion, HDL was an independent predictor of survival in PAH.

NSFC spurs significant basic research progress of respiratory medicine in China

Over the years, research in respiratory medicine has progressed rapidly in China. This commentary narrates the role of the National Natural Science Foundation of China (NSFC) in supporting the basic research of respiratory medicine, summarizes the major progress of respiratory medicine in China, and addresses the main future research directions sponsored by the NSFC.

The beneficial impact of fasudil and sildenafil on monocrotaline-induced pulmonary hypertension in rats: a hemodynamic and biochemical study

Pulmonary arterial hypertension (PAH) still cannot be cured effectively, hence the search for novel treatments continues. The effects of sildenafil (25 mg/kg body weight) and fasudil (30 mg/kg body weight) given alone or in combination, on normalization of right ventricular pressure (RVP), right ventricle mass, as well as the levels of several biomarkers (HDL-C, BNP, VEGF-A), were assessed in a rat model of monocrotaline (MCT)-induced PAH. MCT (60 mg/kg body weight) induced clear PAH in male Wistar rats. After 21 days, a significant decrease in RVP accompanied by a reduction of right ventricular hypertrophy - a significant decrease in the right ventricle/left ventricle plus septum ratio - as a result of sildenafil or fasudil administration was assessed. The administration of fasudil and sildenafil alone or in combination caused a significant decrease in plasma BNP level as compared to MCT-treated rats. Fasudil alone or with sildenafil, but not sildenafil alone, significantly increased HDL-C level as compared to MCT-treated rats. Fasudil and sildenafil given alone or in combination caused a significant increase in plasma VEGF-A level as compared to rats exposed to MCT.