Impaired endothelium-dependent vasodilator response in patients with pulmonary fibrosis

The association between non-high-density lipoprotein cholesterol to high-density lipoprotein cholesterol ratio and pulmonary function: evidence from NHANES 2007-2012

Background

This research aims to explore the potential association between lung function and the ratio of non-high-density lipoprotein cholesterol (NHL) to high-density lipoprotein cholesterol (NHHR). Previous research has shown that lipid metabolism imbalance is closely linked to cardiovascular disease, however, there is a lack of information regarding its impact on lung function.

Methods

This research used information from the National Health and Nutrition Examination Survey (NHANES) spanning the years 2007 to 2012, including a large-scale sample of 9,498 adults aged 20 years and older. A cross-sectional study employing multivariable regression models was aimed at examining the relevance between NHHR and indicators of lung function (FEV1, FVC, and FEV1/FVC). Adjustments were made for a wide range of confounding factors, encompassing race, gender, age, BMI, smoking status, physical activity, diabetes, alcohol consumption, and education level. Data analysis included categorizing NHHR into quartiles and using trend tests to evaluate dose-response relationships between NHHR quartiles and lung function. Sensitivity analyses were conducted by excluding participants with asthma and COPD to ensure the reliability of the results.

Results

The results manifested a significant correlation between decreased FEV1 and FVC values and elevated NHHR, most notably within the highest quartile of NHHR (Q4), where the association was most pronounced. Additionally, trend test results indicated a significant linear negative correlation between NHHR and both FEV1 and FVC. However, the correlation between FEV1/FVC and NHHR showed a nonlinear U-shaped pattern. Suggesting differential impacts of NHHR on various lung function indicators. The findings' robustness was shown by sensitivity analysis, which revealed that even after omitting people with asthma and COPD, the negative correlation between NHHR and FEV1 and FVC remained significant.

Conclusion

This research emphasizes the significance of tracking lipid levels in evaluating respiratory health and offers early evidence in favor of NHHR as a probable biomarker for respiratory function. Further longitudinal research has occasion to prove the causal relationship between NHHR and lung function and to explore its underlying biological mechanisms.

The prognostic role of high-density lipoprotein cholesterol/C-reactive protein ratio in idiopathic pulmonary fibrosis

BACKGROUND

The prognosis of idiopathic pulmonary fibrosis (IPF) patients is highly heterogeneous. Abnormalities in lipids and their metabolism play an important role in the development of IPF.

AIM

To investigate the value of lipid parameters, C-reactive protein (CRP) and high-density lipoprotein cholesterol/C-reactive protein (HDL-C/CRP) ratio levels in the prognosis of IPF patients.

DESIGN

An observational cohort study.

METHODS

We collected baseline data of non-IPF controls and IPF patients, and IPF patients were followed up for 4 years. All-cause death or lung transplantation and IPF-related death were the outcome events. Receiver operating characteristic curves and Cox proportional hazards models were used to analyze the predictive effect of lipid parameters, CRP and HDL-C/CRP ratio on the prognosis of IPF patients.

RESULTS

IPF patients had lower HDL-C, HDL-C/CRP ratio and higher CRP compared to non-IPF controls. IPF patients who died or underwent lung transplantation were older and had worse pulmonary function, lower HDL-C, HDL-C/CRP ratio and higher CRP compared with surviving patients. HDL-C/CRP ratio was better than HDL-C and CRP in predicting all-cause death or lung transplantation. IPF patients with low HDL-C/CRP ratio had shorter survival times. The HDL-C/CRP ratio and diffusing capacity for carbon monoxide(DLCO)% of predicted were independent protective factors for all-cause death or lung transplantation and IPF-related death in IPF patients, while age and gender-age-physiology (GAP) Stage ≥ 2 (HR = 4.927) were independent risk factors for all-cause death or lung transplantation. Age > 65 years (HR = 3.533) was an independent risk factor for IPF-related death.

CONCLUSION

HDL-C/CRP ratio was a valid predictor of clinical outcomes in IPF patients, including all-cause death or lung transplantation and IPF-related death.

The novel molecular mechanism of pulmonary fibrosis: insight into lipid metabolism from reanalysis of single-cell RNA-seq databases

Pulmonary fibrosis (PF) is a severe pulmonary disease with limited available therapeutic choices. Recent evidence increasingly points to abnormal lipid metabolism as a critical factor in PF pathogenesis. Our latest research identifies the dysregulation of low-density lipoprotein (LDL) is a new risk factor for PF, contributing to alveolar epithelial and endothelial cell damage, and fibroblast activation. In this study, we first integrative summarize the published literature about lipid metabolite changes found in PF, including phospholipids, glycolipids, steroids, fatty acids, triglycerides, and lipoproteins. We then reanalyze two single-cell RNA-sequencing (scRNA-seq) datasets of PF, and the corresponding lipid metabolomic genes responsible for these lipids' biosynthesis, catabolism, transport, and modification processes are uncovered. Intriguingly, we found that macrophage is the most active cell type in lipid metabolism, with almost all lipid metabolic genes being altered in macrophages of PF. In type 2 alveolar epithelial cells, lipid metabolic differentially expressed genes (DEGs) are primarily associated with the cytidine diphosphate diacylglycerol pathway, cholesterol metabolism, and triglyceride synthesis. Endothelial cells are partly responsible for sphingomyelin, phosphatidylcholine, and phosphatidylethanolamines reprogramming as their metabolic genes are dysregulated in PF. Fibroblasts may contribute to abnormal cholesterol, phosphatidylcholine, and phosphatidylethanolamine metabolism in PF. Therefore, the reprogrammed lipid profiles in PF may be attributed to the aberrant expression of lipid metabolic genes in different cell types. Taken together, these insights underscore the potential of targeting lipid metabolism in developing innovative therapeutic strategies, potentially leading to extended overall survival in individuals affected by PF.

Lipid metabolism in idiopathic pulmonary fibrosis: From pathogenesis to therapy

Idiopathic pulmonary fibrosis (IPF) is a chronic irreversible interstitial lung disease characterized by a progressive decline in lung function. The etiology of IPF is unknown, which poses a significant challenge to the treatment of IPF. Recent studies have identified a strong association between lipid metabolism and the development of IPF. Qualitative and quantitative analysis of small molecule metabolites using lipidomics reveals that lipid metabolic reprogramming plays a role in the pathogenesis of IPF. Lipids such as fatty acids, cholesterol, arachidonic acid metabolites, and phospholipids are involved in the onset and progression of IPF by inducing endoplasmic reticulum stress, promoting cell apoptosis, and enhancing the expression of pro-fibrotic biomarkers. Therefore, targeting lipid metabolism can provide a promising therapeutic strategy for pulmonary fibrosis. This review focuses on lipid metabolism in the pathogenesis of pulmonary fibrosis.

Atorvastatin and ezetimibe protect against hypercholesterolemia-induced lung oxidative stress, inflammation, and fibrosis in rats

Background

Hypercholesterolemia is a major risk factor for interstitial lung disease (ILD). Atorvastatin and ezetimibe are antilipemic drugs that have pleiotropic effects. However, their effects on pulmonary fibrosis prevention and the mechanisms underlying hypercholesterolemia have not been fully investigated. This study aimed to evaluate the individual effects of atorvastatin and ezetimibe on lung inflammation and fibrosis in high-cholesterol diet (HCD)-fed rats.

Materials and methods

Male Sprague-Dawley rats were divided into four groups — standard diet (S), standard diet + 1% cholesterol (SC), standard diet + 1% cholesterol with 30 mg/kg/day atorvastatin (SCA), and standard diet + 1% cholesterol with 10 mg/kg/day ezetimibe (SCE). At the end of an 8-week dietary schedule, serum lipid parameters and the levels of lung oxidative stress, inflammatory cytokines, and fibrotic mediators were determined.

Results

Atorvastatin and ezetimibe treatment remarkably reduced serum lipid profiles with reversed pulmonary histological alterations, in addition to reducing the levels of lung oxidative stress, inflammation, and fibrosis in hypercholesterolemic rats.

Conclusion

Atorvastatin and ezetimibe treatment showed a protective effect against hypercholesterolemia-induced pulmonary fibrosis in rats. This information appears potentially useful in the prevention of PF in a hypercholesterolemia model; however, further rigorous investigations are needed to prove their clinical utility on antifibrosis.

Complex Involvement of the Extracellular Matrix, Immune Effect, and Lipid Metabolism in the Development of Idiopathic Pulmonary Fibrosis

Background and objective: Idiopathic pulmonary fibrosis (IPF) is an aggressive fibrotic pulmonary disease with spatially and temporally heterogeneous alveolar lesions. There are no early diagnostic biomarkers, limiting our understanding of IPF pathogenesis.

Methods: Lung tissue from surgical lung biopsy of patients with early-stage IPF (n = 7), transplant-stage IPF (n = 2), and healthy controls (n = 6) were subjected to mRNA sequencing and verified by real-time quantitative PCR (RT-qPCR), immunohistochemistry, Western blot, and single-cell RNA sequencing (scRNA-Seq).

Results: Three hundred eighty differentially expressed transcripts (DETs) were identified in IPF that were principally involved in extracellular matrix (ECM) remodeling, lipid metabolism, and immune effect. Of these DETs, 21 (DMD, MMP7, POSTN, ECM2, MMP13, FASN, FADS1, SDR16C5, ACAT2, ACSL1, CYP1A1, UGT1A6, CXCL13, CXCL5, CXCL14, IL5RA, TNFRSF19, CSF3R, S100A9, S100A8, and S100A12) were selected and verified by RT-qPCR. Differences in DMD, FASN, and MMP7 were also confirmed at a protein level. Analysis of scRNA-Seq was used to trace their cellular origin to determine which lung cells regulated them. The principal cell sources of DMD were ciliated cells, alveolar type I/II epithelial cells (AT cells), club cells, and alveolar macrophages (AMs); MMP7 derives from AT cells, club cells, and AMs, while FASN originates from AT cells, ciliated cells, and AMs.

Conclusion: Our data revealed a comprehensive transcriptional mRNA profile of IPF and demonstrated that ECM remodeling, lipid metabolism, and immune effect were collaboratively involved in the early development of IPF.

LDLR dysfunction induces LDL accumulation and promotes pulmonary fibrosis

Treatments for pulmonary fibrosis (PF) are ineffective because its molecular pathogenesis and therapeutic targets are unclear. Here, we show that the expression of low-density lipoprotein receptor (LDLR) was significantly decreased in alveolar type II (ATII) and fibroblast cells, whereas it was increased in endothelial cells from systemic sclerosis-related PF (SSc-PF) patients and idiopathic PF (IPF) patients compared with healthy controls. However, the plasma levels of low-density lipoprotein (LDL) increased in SSc-PF and IPF patients. The disrupted LDL-LDLR metabolism was also observed in four mouse PF models. Upon bleomycin (BLM) treatment, Ldlr-deficient (Ldlr-/-) mice exhibited remarkably higher LDL levels, abundant apoptosis, increased fibroblast-like endothelial and ATII cells and significantly earlier and more severe fibrotic response compared to wild-type mice. In vitro experiments revealed that apoptosis and TGF-β1 production were induced by LDL, while fibroblast-like cell accumulation and ET-1 expression were induced by LDLR knockdown. Treatment of fibroblasts with LDL or culture medium derived from LDL-pretreated endothelial or epithelial cells led to obvious fibrotic responses in vitro. Similar results were observed after LDLR knockdown operation. These results suggest that disturbed LDL-LDLR metabolism contributes in various ways to the malfunction of endothelial and epithelial cells, and fibroblasts during pulmonary fibrogenesis. In addition, pharmacological restoration of LDLR levels by using a combination of atorvastatin and alirocumab inhibited BLM-induced LDL elevation, apoptosis, fibroblast-like cell accumulation and mitigated PF in mice. Therefore, LDL-LDLR may serve as an important mediator in PF, and LDLR enhancing strategies may have beneficial effects on PF.

Heterogeneity in Unclassifiable Interstitial Lung Disease. A Systematic Review and Meta-Analysis

RATIONALE

Accurate diagnosis of interstitial lung disease is necessary to identify the most appropriate management strategy and to inform prognosis. Many patients cannot be provided a confident diagnosis, despite an exhaustive search for potential etiologies and review in a multidisciplinary conference, and are consequently labeled with unclassifiable interstitial lung disease.

OBJECTIVES

To systematically review and meta-analyze previous studies reporting on the diagnostic criteria, prevalence, clinical features, and outcome of unclassifiable interstitial lung disease.

METHODS

MEDLINE, Embase, and the Cochrane Central Register of Controlled Trials databases were systematically searched for all studies related to unclassifiable interstitial lung disease published before September 1, 2017. Two authors independently screened each citation for eligibility criteria, serially reviewing the title, abstract, and full-text manuscript, and then abstracted data pertaining to the study objectives from eligible studies. Articles were stratified by risk of selection bias, whether the publication stated that patients were reviewed in a multidisciplinary discussion, and by the frequency of surgical lung biopsy. Meta-analyses and meta-regression were performed to calculate the pooled prevalence of unclassifiable interstitial lung disease within an interstitial lung disease population and within specific subgroups to identify reasons for across-study heterogeneity.

RESULTS

The search identified 10,130 unique citations, 313 articles underwent full-text review, and eligibility criteria were met in 88 articles. Twenty-two studies were deemed low risk of selection bias, including 1,060 patients with unclassifiable interstitial lung disease from a total of 10,174 patients with interstitial lung disease. The terminology and definition of unclassifiable interstitial lung disease varied substantially across publications, with inconsistent diagnostic criteria and evaluation processes. The prevalence of unclassifiable interstitial lung disease was 11.9% (95% confidence interval, 8.5-15.6%), with lower prevalence in centers that reported use of a formal multidisciplinary discussion of cases (9.5% vs. 14.5%). Four articles reported survival of unclassifiable interstitial lung disease, with 1-year, 2-year, and 5-year survival of 84% to 89%, 70% to 76%, and 46% to 70%, respectively.

CONCLUSIONS

This systematic review and meta-analysis shows that unclassifiable interstitial lung disease is common but has substantial heterogeneity and inconsistent definitions across interstitial lung disease cohorts. These findings highlight important limitations in multicenter studies of fibrotic interstitial lung disease and the need for a standardized approach to interstitial lung disease diagnostic classification.

Cholesterol, lipoproteins and subclinical interstitial lung disease: the MESA study

We investigated associations of plasma lipoproteins with subclinical interstitial lung disease (ILD) by measuring high attenuation areas (HAA: lung voxels between -600 and -250 Hounsfield units) in 6700 adults and serum MMP-7 and SP-A in 1216 adults age 45-84 without clinical cardiovascular disease in Multi-Ethnic Study of Atherosclerosis. In cross-sectional analyses, each SD decrement in high density lipoprotein cholesterol (HDL-C) was associated with a 2.12% HAA increment (95% CI 1.44% to 2.79%), a 3.53% MMP-7 increment (95% CI 0.93% to 6.07%) and a 6.37% SP-A increment (95% CI 1.35% to 11.13%), independent of demographics, smoking and inflammatory biomarkers. These findings support a novel hypothesis that HDL-C might influence subclinical lung injury and extracellular matrix remodelling.

Integrative Cardiopulmonary Ultrasound for Interstitial Lung Disease Assessment: Correlation between Lung Ultrasound Performance and Cardiac Involvement

The aims of this study were to apply integrative cardiopulmonary ultrasound (thoracic ultrasound) to the evaluation of patients with interstitial lung disease (ILD) and to determine the relationship between lung ultrasound signs and echocardiographic parameters such as systolic pulmonary artery pressure (SPAP) and various right ventricular parameters. ILD patients and healthy controls underwent lung ultrasound (LUS) and echocardiographic tests. In addition to traditional echocardiographic parameters, right ventricular free wall longitudinal strain (RVLS_FW) was measured using 2-D speckle-tracking echocardiography. The degree of pulmonary fibrosis or the disease severity of each ILD patient was scored with a semiquantitative scoring method, taking into account multiple LUS signs. Statistical analyses were performed to compare various parameters between ILD patients with and those without pulmonary hypertension. Correlations between the different parameters were then evaluated, and the LUS scores were used to predict pulmonary hypertension using a receiver operating characteristic curve analysis. Among the 90 patients who qualified for entry into this study, 30% (n = 27) had pulmonary hypertension. The patients with pulmonary hypertension had larger right ventricular dimensions, lower RVLS_FW and higher LUS scores. An effective correlation was found between ILD LUS scores and echocardiographic parameters, especially SPAP (r = 0.735, p < 0.001). The groups were comparable with respect to most echocardiographic parameters, with mild, moderate and severe pulmonary fibrosis, whereas SPAP was significantly higher in the moderate and severe groups. RVLS_FW was obviously reduced in the group with severe pulmonary fibrosis. Although RVLS_FW in the mild pulmonary fibrosis group was in the normal range, it was slightly reduced compared with that of the controls. A cutoff of more than 16 LUS points had 85.2% sensitivity and 80.3% specificity in predicting elevated SPAP (>36 mm Hg). Thoracic ultrasound is useful in the assessment of ILD. As ILD progresses, the structure or function of the right ventricle gradually deteriorates. LUS not only detects lung conditions in ILD, but also indirectly reflects SPAP and right ventricular function. Integrated use of LUS and echocardiography will provide an invaluable point-of-care imaging modality to facilitate the diagnosis, management and treatment of patients with ILD.

Bone mineral density in patients with idiopathic pulmonary fibrosis

BACKGROUND

Decreased bone mineral density (BMD) has been reported in patients with interstitial lung disease. However, BMD has not been evaluated in steroid-naïve patients with idiopathic pulmonary fibrosis (IPF). We aimed to measure vertebral BMD and investigate its relationship with clinical features in steroid-naïve patients with IPF.

METHODS

We recruited 55 consecutive male patients with steroid-naïve IPF; 55 male smokers without chronic obstructive pulmonary disease or interstitial lung disease, matched by age, body mass index, and pack-years of smoking (control smokers); and 27 healthy young adults. Thoracic vertebral BMD was measured by computed tomography (CT). We further investigated the relationship of BMD with clinical features and quantitative CT indices of lung density in patients with IPF.

RESULTS

The thoracic vertebral BMD of patients with IPF was significantly lower than that of control smokers (139.9 ± 28.5 mg/mL vs 160.9 ± 39.5 mg/mL, p < 0.01). Fifteen patients (27.2%) had BMD more than 2.5 SD below the mean BMD of young adults. In patients with IPF, emphysema volume (EV) and its ratio to total lung volume (EV%) had a significantly negative correlation with BMD (r = -0.28, p = 0.04 and r = -0.39, p < 0.01, respectively). In stepwise multiple regression analysis, EV% was an independent explanatory variable for thoracic vertebral BMD.

CONCLUSION

A substantial percentage of steroid-naïve IPF patients had decreased BMD, and a significant association was observed between the extent of emphysema and BMD in IPF.

Prognostic value of cardiovascular magnetic resonance derived right ventricular function in patients with interstitial lung disease

BACKGROUND

Cardiovascular magnetic resonance (CMR) provides non-invasive and more accurate assessment of right ventricular (RV) function in comparison to echocardiography. Recent study demonstrated that assessment of RV function by echocardiography was an independent predictor for mortality in patients with interstitial lung disease (ILD). The purpose of this study was to determine the prognostic significance of CMR derived RV ejection fraction (RVEF) in ILD patients.

METHODS

We enrolled 76 patients with ILD and 24 controls in the current study. By using 1.5 T CMR scanner equipped with 32 channel cardiac coils, we performed steady-state free precession cine CMR to assess the RVEF. RV systolic dysfunction (RVSD) was defined as RVEF ≤45.0% calculated by long axis slices. Pulmonary hypertension (PH) was defined as mean pulmonary artery pressure (mPAP) of more than 25 mmHg at rest in the setting of pulmonary capillary wedge pressure ≤15 mmHg.

RESULTS

The median RVEF was 59.2% in controls (n = 24), 53.8% in ILD patients without PH (n = 42) and 43.1% in ILD patients with PH (n = 13) (p < 0.001 by one-way ANOVA). During a mean follow-up of 386 days, 18 patients with RVSD had 11 severe events (3 deaths, 3 right heart failure, 3 exacerbation of dyspnea requiring oxygen, 2 pneumonia requiring hospitalization). In contrast, only 2 exacerbation of dyspnea requiring oxygen were observed in 58 patients without RVSD. Multivariate Cox regression analysis showed that RVEF independently predicted future events, after adjusting for age, sex and RVFAC by echocardiography (hazard ratio: 0.889, 95% confidence interval: 0.809-0.976, p = 0.014).

CONCLUSIONS

The current study demonstrated that RVSD in ILD patients can be clearly detected by cine CMR. Importantly, low prevalence of PH (17%) indicated that population included many mild ILD patients. CMR derived RVEF might be useful for the risk stratification and clinical management of ILD patients.