Adipose tissue derived ceramides regulate myocardial redox state and predict cardiovascular outcomes

Background

Obesity is linked to both dysfunctional adipose tissue (AT) and heart failure, but the exact mechanisms mediating these associations are unknown. Although ceramides biosynthesis is dysregulated in obesity, their role as mediators of obesity-induced myocardial dysfunction is unclear.

Purpose

We investigate the causal role of AT-derived ceramides in the regulation of myocardial redox state and explore their role in predicting cardiovascular outcomes.

Methods

The study population included a total of 880 patients undergoing cardiac surgery. A panel of 20 sphingolipids was measured in plasma as well as in biopsies of subcutaneous AT (ScAT), thoracic AT (ThAT) and epicardial AT (EpAT) and their secretome, obtained from a subgroup of n=48. Myocardial redox state was measured using lucigenin chemiluminescence and the contribution of NOXs, uncoupled nitric oxide synthases and mitochondrial oxidases in O2•– production was quantified. The cohort was followed up for a median of 8.3 years. Genome-wide genetic analysis was done using the UK Biobank array. A total of 99,524 SNPs within 50kb of 110 genes involved in sphingolipid biosynthesis were analysed to identify genetic variants that could predict CVD outcomes using cis-Mendelian Randomisation. The underlying mechanisms were then explored further, using differentiated H9c2 cardiomyocytes in vitro and human right atrial tissue ex vivo.

Results

The production and secretion of C16:0-ceramide (CerC16) was higher in visceral AT (EpAT and ThAT) compared to ScAT (p<0.0001). Patients with high plasma levels of CerC16 and its derivative C16:0-glucosylceramide (GlcC16) had higher myocardial O2•– production vs those with low/int. levels (p<0.05 for both) (A). To test the causality of this association, we performed a targeted single-SNP analysis for the genetic prediction of GlcC16 levels demonstrating that rs112572487, an intronic variant in UGCG (an enzyme that catalyses glucosylceramide formation from ceramides), was the top hit (B). Indeed, those with the rs112572487 minor allele (G) displayed significantly increased myocardial NOX-derived O2•– (C) and plasma GlcC16 levels (D) vs those without. Exogenous CerC16 (20nM) induced NOX-derived O2•– production in H9c2 cardiomyocytes, an effect prevented by the UGCG inhibitor D-PDMP (E), suggesting that GlcC16 is a modifiable regulator of myocardial NOX-O2•–. Importantly, high plasma GlcC16 levels were associated with a higher risk of cardiac death and/or heart failure (adj. HR=2.128 [95% CI: 1.101, 4.115], p=0.025, for high vs low/int. levels), a relationship also seen with rs112572487 (F).

Conclusions

We demonstrate for the first time, that AT-derived ceramides are causally related with dysregulated myocardial redox signalling and adverse cardiovascular disease outcomes in patients with advanced atherosclerosis. As such, GlcC16 may be an important therapeutic target for the prevention and treatment of cardiovascular complications in obesity and diabetes.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): The British Heart FoundationBritish Heart Foundation Chair Award

Direct effects of canagliflozin on human myocardial redox signalling: a novel role for SGLT1 inhibition

Background

Recent clinical trials have demonstrated a role for sodium glucose cotransporter 2 (SGLT2) inhibitors in improving cardiovascular outcomes in heart failure patients, but the underlying mechanisms remain unknown. We investigated the direct effects of canagliflozin, a non-selective SGLT1/SGLT2 inhibitor on myocardial redox signalling in humans.

Methods

Study 1 included 364 patients undergoing cardiac surgery. Human right atrial appendage biopsies, obtained during surgery, were used to quantify the sources of superoxide (O2.-) and the gene expression of inflammation, fibrosis and myocardial stretch markers. In Study 2, myocardial biopsies from 51 patients were used ex vivo to study the direct effects of canagliflozin on O2.- generation and understand its role in controlling the activity of NADPH-oxidases and uncoupled nitric oxide synthase (NOS). Finally, we used differentiated H9C2 and human primary cardiomyocytes (hCM) to further characterise the key regulatory mechanisms (Study 3).

Results

SGLT1 was abundantly expressed in the human myocardial biopsies and hCM whilst SGLT2 was barely detectable. SGLT1 expression levels were positively correlated with basal O2.- production and the expression of natriuretic peptides, proinflammatory cytokines and pro-fibrotic markers in human myocardial biopsies from study 1. Incubation of human myocardium with canagliflozin significantly reduced basal and NADPH-oxidase-derived O2.- via AMP kinase (AMPK)-mediated suppression of GTP-activation and consequent reduction of membrane translocation of Rac1, an NADPH-oxidase subunit. This resulted in reduced oxidation and increased bioavailability of tetrahydrobiopterin, the nitric oxide synthase (NOS) co-factor essential for enzymatic coupling, leading to improved NOS coupling. These findings were replicated in hCM, where canagliflozin was shown to regulate AMP/ATP ratio, which could be upstream of AMPK activation. The effects of canagliflozin were significantly attenuated by knocking-down SGLT1 in hCM. Transcriptional profiling of hCM treated with canagliflozin revealed that canagliflozin had striking effects on myocardial redox signalling, causing suppression of apoptotic and inflammatory pathways in the human heart.

Conclusions

We demonstrate for the first time in humans that canagliflozin suppresses myocardial NADPH-oxidase activity and improves NOS coupling through an SGLT1/AMPK/Rac1-mediated pathway, leading to global anti-inflammatory and anti-apoptotic effects in the human myocardium. These findings provide a mechanistic basis for the beneficial effects of SGLT1/2 inhibitors in patients with heart failure.

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): 1. British Heart Foundation (FS/16/15/32047 and PG/13/56/30383 to CA, CH/16/1/32013 to KC, and Centre of Research Excellence award RG/13/1/30181), 2. The Japanese Heart Rhythm Society-European Heart Rhythm Association fellowship grant sponsored by Biotronik.

A novel arterial redox-specific machine learning-derived radiomic signature of perivascular adipose tissue predicts cardiac mortality from routine CCTA

Background

Vascular oxidative stress is involved in inflammation and atherogenesis. Vascular inflammation induces spatial changes in perivascular adipose tissue (PVAT) composition, which can be detected by radiomic analysis of coronary computed tomography angiography (CCTA) images.

Purpose

To explore the association of arterial oxidative stress with long-term risk of major adverse cardiovascular events (MACE). To develop a radiomic signature to identify high oxidative stress non-invasively using CCTA. Finally, to assess the ability of this signature to predict future cardiac risk.

Methods

Arm 1 included 272 patients undergoing cardiac surgery. Segments of internal mammary artery (IMA) were used for ex-vivo quantification of NADPH-stimulated and Vas2870 (pan-NOX inhibitor) inhibitable superoxide production by lucigenin-enhanced chemiluminescence. Eighty-two of these patients with CCTA scans available constituted Arm 2. Peri-IMA PVAT was segmented and used to extract 1,616 radiomic features, which, after filtering (40 final features), were utilised to train extreme gradient boosting, a machine learning algorithm, to predict high arterial oxidative stress. Arm 3 included a nested cohort of 308 participants (41 suffering cardiac death and 267 matched controls) from the CRISP-CT (Cardiovascular RISk Prediction using Computed Tomography) study to externally validate the redox-specific signature developed in Arm 2 for cardiac risk prediction.

Results

Over a median follow-up of 40 months, 18 (6.6%) MACE (cardiovascular death, non-fatal myocardial infarction, and stroke) occurred in Arm 1. High arterial NADPH-stimulated superoxide was independently associated with MACE risk (Adj. HR[95% CI]: 1.61 [1.04–2.53] per SD, p=0.03, adjusted for age, sex, diabetes, hypertension, hyperlipidemia, smoking, obesity, and plasma TNFa). Unsupervised hierarchical clustering of radiomic features from peri-IMA PVAT segments in Arm 2 identified two distinct clusters (A) that differed in NADPH stimulated (p=0.01) and Vas2870 inhibitable (p=0.04) IMA superoxide (B), supporting the hypothesis that PVAT mapping can capture changes corresponding to differential levels of underlying vascular redox state. This prompted the development of a radiomic signature specific to PVAT alterations associated with high vascular oxidative stress, which was validated in Arm 3 (AUC:0.61, p=0.026, C). The novel signature was able to stratify cardiac risk in the validation set, independently of the Fat Attenuation Index, epicardial adipose tissue volume, high-risk plaque features, and obstructive CAD (Adj. HR [95% CI]:2.56 [1.35–4.87], p=0.004, D).

Conclusion

Increased arterial oxidative stress predicts cardiac risk in patients with advanced atherosclerosis. We present for the first time a novel, non-invasive CCTA imaging biomarker reflecting changes in vascular redox state by radiomic phenotyping of perivascular space, which stratifies cardiac risk beyond standard and newer risk assessment methods.

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): British Heart Foundation, National Institute of Health Research, Oxford Biomedical Research Centre

P6267Novel direct effects of SGLT2 inhibitor, Canagliflozin, on myocardial redox state in humans

Background

Sodium glucose cotransporter 2 (SGLT2) inhibitors are antidiabetic drugs that control plasma glucose levels by inhibiting reabsorption of glucose in kidney. Recent clinical trials have suggested a class effect of SGLT2 inhibitors in preventing hospitalization due to heart failure. However, the underlying mechanism has not been fully elucidated.

Purpose

We investigated the direct effect of the SGLT2 inhibitor, Canagliflozin (Cana), on myocardial redox state in humans.

Methods

The study included 48 patients undergoing cardiac surgery. Fresh myocardial tissues were incubated ex vivo with or without Cana and then used for superoxide quantification and Western immunoblotting. NADPH-oxidases activity was evaluated with NADPH 100μM stimulation, while nitric oxide synthase (NOS) coupling was assessed by using N(ω)-nitro-L-arginine methyl ester (L-NAME, a NOS inhibitor). A human cardiomyocyte (HCM) cell line was also used for in vitro validation of the effects of Cana on myocardium.

Results

Ex vivo incubation of myocardium with Cana significantly reduced baseline (A) and NADPH-oxidase-derived O2·− (B) and improved NOS coupling reflected by positive L-NAME delta O2·− values (C). Regulation of NADPH-oxidases activity by Cana was found to result from reduced GTP-activation (D) and consequent membrane translocation (E) of Rac1, a key subunit of NADPH-oxidases. Cana also reduced tetrahydrobiopterin (BH4) oxidation, increasing its bioavailability (F), which is a key mechanism to improve NOS coupling. Incubation with Cana enhanced phosphorylation of AMPK, and the downstream signalling, ACC (not shown). Additional Compound C, which is inhibitor of AMPK, significantly reversed these effects of Cana (A, B, C, D, E, F). These findings were replicated in HCM (not shown). In line with these, Cana increased the ADP/ATP ratio of cytoplasm in HCM, which could provide an upstream mechanism for AMPK activation.

Conclusions

We demonstrate for the first time in humans, that Cana suppresses myocardial NADPH-oxidases activity and improves NOS coupling through an AMPK-mediated pathway. This could be an underlying mechanism for the cardioprotective effects of SGLT2 inhibitors.

P2709Wnt5a contributes to human atherosclerosis via novel USP17 redox signalling

Background

Wnt5a is a non-canonical Wnt ligand with potential vascular effects, but its mechanistic role in atherosclerosis progression and the underlying downstream mechanisms are poorly explored.

Purpose

To address the hypothesis that Wnt5a induces vascular NADPH-oxidases activity, endothelial dysfunction and detrimental downstream redox signalling which could propagate atherosclerosis in humans.

Methods

Study 1 included 70 patients with coronary artery disease (CAD) versus age- and sex-matched non-CAD controls. Study 2 included 1,003 CAD patients undergoing cardiac surgery; internal mammary artery (IMA) and saphenous vein (SV) segments were harvested and used for ex vivo experiments. Study 3 included 68 individuals undergoing two cardiac computed tomography scans 3–5 years apart; calcified plaque burden was assessed by coronary calcium score (CCS). Superoxide (O2·−) generation was measured by lucigenin chemiluminescence with NADPH 100μM stimulation as indicator of NADPH-oxidases activity. Activation of Rac1, a key NADPH-oxidases subunit, was evaluated by a commercially available kit. Primary vascular smooth muscle cells (VSMCs) and HeLa cells were used for in vitro experiments. Circulating Wnt5a and Sfrp5 (a Wnt5a antagonist) were measured by ELISA in fasting plasma samples.

Results

In Study 1, the presence of CAD was independently linked with increased circulating Wnt5a bioavailability (A), which was, in turn, associated with increased IMA NADPH-oxidases activity in Study 2 (B). Recombinant Wnt5a directly stimulated NADPH-oxidases activity (C) via Rac1 activation (not shown) in human IMA, while inducing endothelial dysfunction evidenced by impaired SV endothelium-dependent acetylcholine (Ach) vasorelaxations (D). Transcriptomic analysis in Wnt5a-treated primary VSMCs versus controls identified USP17, a deubiquitinating enzyme implicated in Rac1 activation, as the top differentially regulated hit (not shown). Indeed, Wnt5a stimulated USP17 upregulation in VSMCs which was reversed by PEGylated superoxide dismutase (peg-SOD) 300U/mL (E), suggesting a redox sensitive effect. USP17 knockdown abolished the ability of Wnt5a to induce Rac1 activation in HeLa cells (F). At a clinical level, plasma Wnt5a was a predictor of plaque progression (defined as ΔCCS≥1, G) and new onset calcification (H) in Study 3.

Conclusions

We demonstrate for the first time that Wnt5a is elevated in CAD and causally associated with increased vascular oxidative stress and endothelial dysfunction in humans. We further reveal USP17 to be a novel, previously undescribed, link between Wnt5a, Rac1 activation and NADPH-oxidase activity induction in humans. We finally propose that circulating Wnt5a may have a clinically relevant role in predicting atherosclerosis progression. Our findings identify Wnt5a as rational therapeutic target in vascular disease.

Acknowledgement/Funding

British Heart Foundation; Alexandros S Onassis Public Benefit Foundation

5893Adipose tissue secreted ceramides and related sphingolipids - potential modulators of vascular redox signalling in cardiovascular disease

Background

Adipose tissue (AT) plays a vital role in the modulation of vascular biology via known adipokines and other yet unidentified secreted molecules. Recent technological advances of omics-based approaches have enabled the identification of more metabolites that drive the currently recognised cross talk between the AT and the vasculature.

Purpose

The main aim of this study is to explore the role of AT secreted ceramides on the regulation of vascular superoxide (O2·−) generation in cardiac patients.

Methods

Untargeted metabolic profiling for the secretome of paired thoracic and subcutaneous ATs from 48 patients undergoing cardiac surgery (the Oxford cohort for heart, vessels and fat) along with the subsequent sphingolipids-targeted quantification were performed using liquid-chromatography/mass-spectrometry. Immortalized human aortic endothelial cells (teloHAEC) were treated exogenously with C6-ceramide (CerC6) for 20min and O2·− production was measured using lucigenin-enhanced chemiluminescence.

Results

Metabolomics differential (A) and enrichment analysis (not shown) highlighted the significant differences in sphingolipids secretion levels between the two fat depots. Higher amount of ceramides were produced and secreted from the thoracic depot with C16-ceramide (CerC16) representing the most abundant differentially secreted ceramide (B). Compared to the lowest tertile, the middle and highest tertiles of ceramides in thoracic AT were significantly associated with higher O2·− generation in patients' vessels namely saphenous veins (SV) and internal mammary arteries (IMA) (C). Exogenous treatment of teloHAEC with ceramide increased O2·− generation and eNOS uncoupling evidenced by more negative O2·− after addition of L-NAME, an inhibitor of eNOS (D).

Results Overview

Conclusions

In this study, we demonstrate for the first time that sphingolipids, in particular ceramides, secreted from AT of cardiac patients may modulate their vascular redox state via dysregulating vascular eNOS signalling leading to endothelial dysfunction –a hallmark of cardiovascular disease.

Acknowledgement/Funding

the NovoNordisk Foundation (NNF15CC0018486)

Large-scale discovery of novel genetic causes of developmental disorders

Despite three decades of successful, predominantly phenotype-driven discovery of the genetic causes of monogenic disorders, up to half of children with severe developmental disorders of probable genetic origin remain without a genetic diagnosis. Particularly challenging are those disorders rare enough to have eluded recognition as a discrete clinical entity, those with highly variable clinical manifestations, and those that are difficult to distinguish from other, very similar, disorders. Here we demonstrate the power of using an unbiased genotype-driven approach to identify subsets of patients with similar disorders. By studying 1,133 children with severe, undiagnosed developmental disorders, and their parents, using a combination of exome sequencing and array-based detection of chromosomal rearrangements, we discovered 12 novel genes associated with developmental disorders. These newly implicated genes increase by 10% (from 28% to 31%) the proportion of children that could be diagnosed. Clustering of missense mutations in six of these newly implicated genes suggests that normal development is being perturbed by an activating or dominant-negative mechanism. Our findings demonstrate the value of adopting a comprehensive strategy, both genome-wide and nationwide, to elucidate the underlying causes of rare genetic disorders.