Aortic valve stenosis and atrial fibrillation influence plasma fibulin-1 levels in patients treated with coronary bypass surgery

Fibrotic expression profile analysis reveals repurposed drugs with potential anti-fibrotic mode of action

Fibrotic diseases cover a spectrum of systemic and organ-specific maladies that affect a large portion of the population, currently without cure. The shared characteristic these diseases feature is their uncontrollable fibrogenesis deemed responsible for the accumulated damage in the susceptible tissues. Idiopathic Pulmonary Fibrosis, an interstitial lung disease, is one of the most common and studied fibrotic diseases and still remains an active research target. In this study we highlight unique and common (i) genes, (ii) biological pathways and (iii) candidate repurposed drugs among 9 fibrotic diseases. We identify 7 biological pathways involved in all 9 fibrotic diseases as well as pathways unique to some of these diseases. Based on our Drug Repurposing results, we suggest captopril and ibuprofen that both appear to slow the progression of fibrotic diseases according to existing bibliography. We also recommend nafcillin and memantine, which haven't been studied against fibrosis yet, for further wet-lab experimentation. We also observe a group of cardiomyopathy-related pathways that are exclusively highlighted for Oral Submucous Fibrosis. We suggest digoxin to be tested against Oral Submucous Fibrosis, since we observe cardiomyopathy-related pathways implicated in Oral Submucous Fibrosis and there is bibliographic evidence that digoxin may potentially clear myocardial fibrosis. Finally, we establish that Idiopathic Pulmonary Fibrosis shares several involved genes, biological pathways and candidate inhibiting-drugs with Dupuytren's Disease, IgG4-related Disease, Systemic Sclerosis and Cystic Fibrosis. We propose that treatments for these fibrotic diseases should be jointly pursued.

Relationship between the Plasma Fibulin-1 Levels, Pulse Wave Velocity, and Vascular Age in Asymptomatic Hyperuricemia

Fibulin-1 (FBLN-1), an elastin-associated extracellular matrix protein, has been found in blood and may play a role in the pathophysiological processes leading to cardiovascular disease (CVD). We aimed to investigate the relationship between fibulin-1 levels and the risk of CVD by evaluating vascular age derived from the Framingham Heart Study and brachial-ankle Pulse Wave Velocity (baPWV) in patients with asymptomatic hyperuricemia (AHU). In total, 66 patients with AHU and 66 gender- and age-matched healthy individuals were enrolled. The plasma fibulin-1 levels were measured by immunochemistry. Patients with AHU presented significantly higher vascular age [median (interquartile range): 54 (22) vs. 48 (14) years, P=0.01] and baPWV [mean±SD: 1373±223 vs. 1291±177 cm/s, P=0.02] than the healthy subjects; however, no significant difference was observed in the plasma fibulin-1 level between the patients with AHU and healthy subjects [median (interquartile range): 4018 (3838) vs. 3099 (3405) ng/mL, P=0.31]. A correlation between fibulin-1 levels and baPWV was observed only in patients with AHU (r=0.29, P=0.02); and there was also a suggestively statistically significant correlation between fibulin-1 levels and vascular age (r=0.22, P=0.08). However, these associations were rendered insignificant after adjustments for potential confounders. In healthy subjects, no correlation was observed between fibulin-1 levels and CVD risk. This study reveals that plasma fibulin-1 levels may reflect the CVD risk in patients with AHU, but the relationship is not robust.

Atrial matrix remodeling in atrial fibrillation patients with aortic stenosis

BACKGROUND

This study aimed to evaluate atrium extracellular matrix remodeling in atrial fibrillation (AF) patients with severe aortic stenosis, through histological fibrosis quantification and extracellular matrix gene expression analysis, as well as serum quantification of selected protein targets.

METHODS

A posthoc analysis of a prospective study was performed in a cohort of aortic stenosis patients. Between 2014 and 2019, 56 patients with severe aortic stenosis submitted to aortic valve replacement surgery in a tertiary hospital were selected.

RESULTS

Fibrosis was significantly increased in the AF group when compared to sinus rhythm (SR) patients (p = 0.024). Moreover, cardiomyocyte area was significantly higher in AF patients versus SR patients (p = 0.008). Conversely, collagen III gene expression was increased in AF patients (p = 0.038). TIMP1 was less expressed in the atria of AF patients. MMP16/TIMP4 ratio was significantly decreased in AF patients (p = 0.006). TIMP1 (p = 0.004) and TIMP2 (p = 0.012) were significantly increased in the serum of AF patients. Aortic valve maximum (p = 0.0159) and mean (p = 0.031) gradients demonstrated a negative association with serum TIMP1.

CONCLUSIONS

Atrial fibrillation patients with severe aortic stenosis present increased atrial fibrosis and collagen type III synthesis, with extracellular matrix remodelling demonstrated by a decrease in the MMP16/TIMP4 ratio, along with an increased serum TIMP1 and TIMP2 proteins.

Towards identification of novel putative biomarkers for infective endocarditis by serum proteomic analysis

INTRODUCTION

Infective endocarditis (IE) has high mortality, partly due to delayed diagnosis. No biomarker can identify IE in patients with fever and clinical picture of infection. To find putative biomarkers we analyzed serum levels of two proteins found in cardiac valves, fibulin-1 (n=696) and osteoprotegerin (n=689) among patients on clinical suspicion of IE. Proteomic analyses were performed in 24 patients with bacteremia, 12 patients with definite IE and 12 patients with excluded IE.

METHODS

Fibulin-1 and osteoprotegerin were studied by enzyme linked immunosorbent assay (ELISA). Proteomic analyses were conducted by 2-dimensional polyacrylamid gel electrophoresis (2D-PAGE) and label-free quantitative liquid chromatography - tandem mass spectrometry (LFQ LC-MS/MS). Controls for 2D 2D-PAGE and LFQ LC-MS/MS had bacteremia and excluded IE.

RESULTS

Osteoprotegerin levels were significantly increased in IE patients compared with non-IE patients. Fibulin-1 showed no difference. 2D-PAGE showed significant differences of 6 proteoforms: haptoglobin, haptoglobin-related protein, α-2-macroglobulin, apolipoprotein A-I and ficolin-3. LFQ LC-MS/MS analysis revealed significant level changes of 7 proteins: apolipoprotein L1, complement C1q subcomponent B and C, leukocyte immunoglobulin-like receptor subfamily A member 3, neuropilin-2, multimerin-1 and adiponectin.

CONCLUSIONS

The concentration changes in a set of proteoforms/proteins suggest that stress and inflammation responses are perturbed in patients with IE compared to patients with bacteremia without IE.

Is cardiovascular disease in patients with diabetes associated with serum levels of MMP-2, LOX, and the elastin degradation products ELM and ELM-2?

BACKGROUND

Diabetes mellitus type 2 (T2DM) is a significant risk factor for the development of cardiovascular diseases (CVDs). In a previous microarray study of internal mammary arteries from patients with and without T2DM, we observed several elastin-related genes with altered mRNA-expression in diabetic patients, namely matrix metalloproteinase 2 (MMP-2), lysyl oxidase (LOX) and elastin itself. In this study we investigate whether the serum concentrations of elastin-related proteins correlate to signs of CVD in patients with T2DM.

METHODS

Blood samples from 302 type 2 diabetic patients were analysed for MMP-2, LOX, and the elastin degradation products ELM and ELM2. The results were investigated for correlations to signs of CVD in different vascular territories, as determined by myocardial perfusion scintigraphy, carotid artery thickness and ankle-brachial blood pressure index.

RESULTS

T2DM patients with peripheral arterial disease (low ankle-brachial index) (PAD) display higher levels of MMP-2 and ELM compared to patients without PAD. However, none of the proteins or degradation products correlated with myocardial ischemia or a combined measure of CVD-signs, including myocardial ischemia, increased carotid thickness and decreased ankle-brachial blood pressure.

CONCLUSIONS

Our results suggest that the diabetic environment affects the circulating amounts of MMP-2 and ELM in patients with PAD. However, the same connection could not be seen in diabetic patients with CVD broadly identified in three vascular territories. LOX and ELM-2 did not correlate to any type of CVD. Overall, serum levels of elastin-related molecules are only remotely related to CVD in type 2 diabetes.

Galectin-3 and fibulin-1 in systolic heart failure - relation to glucose metabolism and left ventricular contractile reserve

Background

Heart failure (HF) patients with diabetes (DM) have an adverse prognosis and reduced functional capacity, which could be associated with cardiac fibrosis, increased chamber stiffness and reduced left ventricular (LV) contractile reserve. Galectin-3 (Gal-3) and fibulin-1 are circulating biomarkers potentially reflecting cardiac fibrosis. We hypothesize that plasma levels of Gal-3 and fibulin-1 are elevated in HF patients with DM and are associated with reduced LV contractile reserve in these patients.

Methods

A total of 155 patients with HF with reduced ejection fraction underwent a low-dose dobutamine echocardiography and blood sampling for biomarker measurements. Patients were classified according to history of DM and an oral glucose tolerance test (OGTT) as: normal glucose tolerance (NGT) (n = 70), impaired glucose tolerance (IGT) (n = 25) and DM (n = 60).

Results

Galectin-3 levels were elevated in DM patients as compared to non-diabetic patients (P = 0.02), while higher fibulin-1 levels were observed in HF patients with IGF and DM (P = 0.07). Reduced LV contractile reserve was associated with increasing Gal-3 levels (β = −0.19, P = 0.03) although, this association was attenuated after adjustment for estimated glomerular filtration rate (P = 0.66). Fibulin-1 was not associated with LV contractile reserve (P = 0.71).

Conclusions

Galectin-3 and fibulin-1 levels were elevated in HF patients with impaired glucose metabolism. However, reduced LV contractile reserve among HF patients with DM does not to have an independent impact on plasma Gal-3 and fibulin-1 levels.

Associations between plasma fibulin-1, pulse wave velocity and diabetes in patients with coronary heart disease

BACKGROUND

Diabetes is related to increased risk of cardiovascular disease, and arterial stiffness and its consequences may be the factor connecting the two. Arterial stiffness is often measured by carotid-femoral pulse wave velocity (cf-PWV), but no plasma biomarker reflecting arterial stiffness is available. Fibulin-1 is an extracellular matrix protein, up-regulated in arterial tissue and in plasma in patients with type 2 diabetes. We aimed to evaluate the association between plasma fibulin-1 and arterial stiffness measured by cf PWV in a group of patients with diabetes, and one without, all undergoing coronary artery bypass grafting.

METHODS

Pulse wave velocity (PWV) and pulse wave analysis including augmentation index (Aix75) was measured in 273 patients, who subsequently underwent a coronary by-pass operation. Plasma samples were drawn and information was gathered on diabetes status, HbA1c, lipids, medication, body mass index, co-morbidities and smoking status. Carotid artery intima-media thickness, as well as estimation of carotid artery plaque burden, and distal blood pressure was also obtained.

RESULTS

Sixty three patients had diabetes, and this group had significantly higher levels of plasma fibulin-1, PWV and Aix75, compared to the 210 patients who did not have diabetes. In univariate analysis fibulin-1 and pulse wave velocity were not correlated in either group whereas fibulin-1 in patients without diabetes was correlated to Aix75.

CONCLUSION

Fibulin-1 and arterial stiffness indices are not directly related in patients with cardiac disease, despite the fact that both measures are increased among patients with diabetes.

Total and isoform-specific quantitative assessment of circulating fibulin-1 using selected reaction monitoring MS and time-resolved immunofluorometry

PURPOSE

Targeted proteomics using SRM-MS combined with stable-isotope dilution has emerged as a promising quantitative technique for the study of circulating protein biomarkers. The purpose of this study was to develop and characterize robust quantitative assays for the emerging cardiovascular biomarker fibulin-1 and its circulating isoforms in human plasma.

EXPERIMENTAL DESIGN

We used bioinformatics analysis to predict total and isoform-specific tryptic peptides for absolute quantitation using SRM-MS. Fibulin-1 was quantitated in plasma by nanoflow-LC-SRM-MS in undepleted plasma and time-resolved immunofluorometric assay (TRIFMA). Both methods were validated and compared to a commercial ELISA (CircuLex). Molecular size determination was performed under native conditions by SEC analysis coupled to SRM-MS and TRIFMA.

RESULTS

Absolute quantitation of total fibulin-1, isoforms -1C, and -1D was performed by SRM-MS. Fibulin-1C was the most abundant isoform in plasma. Circulating fibulin-1 isoforms were homo -or hetero multimeric complexes (range 318-364 kDa). Good correlation was obtained between SRM-MS and TRIFMA but not CircuLex.

CONCLUSIONS AND CLINICAL RELEVANCE

For biomarker studies using smaller cohorts, SRM-MS provides an alternative measure of total and specific fibulin-1 isoforms in undepleted plasma. For larger cohorts TRIFMA provides a faster platform for fibulin-1 quantitation in plasma. While the correlation between these methods was acceptable, low correlation was obtained between the commercial CircuLex assay and SRM-MS or TRIFMA.

Fibulins and their role in cardiovascular biology and disease

Fibulins are a group of extracellular matrix proteins of which many are present in high amounts in the cardiovascular system. They share common biochemical properties and are often found in relation to basement membranes or elastic fibers. Observations in humans with specific mutations in fibulin genes, together with results from genetically engineered mice and data from human cardiovascular tissue suggest that the fibulin family of proteins play important functional roles in the cardiovascular system. Moreover, fibulin-1 circulates in high concentrations in plasma and may function as a cardiovascular disease marker.

DNA methylation in cardiac fibrosis: new advances and perspectives

Cardiac fibrosis is characterized by net accumulation of extracellular matrix (ECM) proteins in the cardiac interstitium, and contributes to both systolic and diastolic dysfunction in many cardiac pathophysiologic conditions. More specifically, cardiac fibroblasts are activated by a variety of pathological stimuli, thereby undergoing proliferation, differentiation to myofibroblasts, and production of various cytokines and ECM proteins. Thus, understanding the biological processes of cardiac fibroblasts will provide novel insights into the underlying mechanisms of cardiac fibrosis. DNA methylation is an important epigenetic mechanism, which often occurs in response to environmental stimuli and is crucial in regulating gene expression. The aberrant methylation of CpG island promoters of selected genes is the prominent epigenetic mechanism by which gene transcription can be effectively silenced. Aberrant hypermethylation of a few selected genes such as RASSF1A plays an important role in facilitating fibrotic fibroblast activation and in driving fibrosis. In this review we will discuss the mechanisms of DNA methylation and their implications for cardiac fibroblasts activation and fibrosis. Control of DNA methylation may serve as a new strategy for anti-fibrotic therapy.