George Krasopoulos

Adiponectin as a Link Between Type 2 Diabetes and Vascular NADPH Oxidase Activity in the Human Arterial Wall: The Regulatory Role of Perivascular Adipose Tissue

Oxidative stress plays a critical role in the vascular complications of type 2 diabetes. We examined the effect of type 2 diabetes on NADPH oxidase in human vessels and explored the mechanisms of this interaction. Segments of internal mammary arteries (IMAs) with their perivascular adipose tissue (PVAT) and thoracic adipose tissue were obtained from 386 patients undergoing coronary bypass surgery (127 with type 2 diabetes). Type 2 diabetes was strongly correlated with hypoadiponectinemia and increased vascular NADPH oxidase–derived superoxide anions (O2˙−). The genetic variability of the ADIPOQ gene and circulating adiponectin (but not interleukin-6) were independent predictors of NADPH oxidase–derived O2˙−. However, adiponectin expression in PVAT was positively correlated with vascular NADPH oxidase–derived O2˙−. Recombinant adiponectin directly inhibited NADPH oxidase in human arteries ex vivo by preventing the activation/membrane translocation of Rac1 and downregulating p22phox through a phosphoinositide 3-kinase/Akt-mediated mechanism. In ex vivo coincubation models of IMA/PVAT, the activation of arterial NADPH oxidase triggered a peroxisome proliferator–activated receptor-γ–mediated upregulation of the adiponectin gene in the neighboring PVAT via the release of vascular oxidation products. We demonstrate for the first time in humans that reduced adiponectin levels in individuals with type 2 diabetes stimulates vascular NADPH oxidase, while PVAT “senses” the increased NADPH oxidase activity in the underlying vessel and responds by upregulating adiponectin gene expression. This PVAT-vessel interaction is identified as a novel therapeutic target for the prevention of vascular complications of type 2 diabetes.

Mutual Regulation of Epicardial Adipose Tissue and Myocardial Redox State by PPAR-γ/Adiponectin Signalling.

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Detecting human coronary inflammation by imaging perivascular fat

Adipocyte size and lipid content in perivascular adipose tissue are inversely associated with coronary inflammation and atherosclerotic plaque burden in human patients. Picturing plaques and imaging inflammation To determine risk of future coronary artery disease, calcium content in vascular plaques is typically evaluated by coronary calcium scoring, which uses computerized tomography (CT) imaging. To detect inflammation and subclinical coronary artery disease (soft, noncalcified plaques), Antonopoulos et al. developed an alternative metric called the perivascular CT fat attenuation index (FAI). The perivascular FAI uses CT imaging of adipose tissue surrounding the coronary arteries to assess adipocyte size and lipid content. Larger, more mature adipocytes exhibit greater lipid accumulation, which is inversely associated with the FAI. Inflammation reduces lipid accumulation and slows preadipocyte differentiation. Imaging pericoronary fat in human patients after myocardial infarction revealed that unstable plaques had larger perivascular FAIs than stable plaques and that the FAI was greatest directly adjacent to the inflamed coronary artery. The perivascular FAI may be a useful, noninvasive method for monitoring vascular inflammation and the development of coronary artery disease. Early detection of vascular inflammation would allow deployment of targeted strategies for the prevention or treatment of multiple disease states. Because vascular inflammation is not detectable with commonly used imaging modalities, we hypothesized that phenotypic changes in perivascular adipose tissue (PVAT) induced by vascular inflammation could be quantified using a new computerized tomography (CT) angiography methodology. We show that inflamed human vessels release cytokines that prevent lipid accumulation in PVAT-derived preadipocytes in vitro, ex vivo, and in vivo. We developed a three-dimensional PVAT analysis method and studied CT images of human adipose tissue explants from 453 patients undergoing cardiac surgery, relating the ex vivo images with in vivo CT scan information on the biology of the explants. We developed an imaging metric, the CT fat attenuation index (FAI), that describes adipocyte lipid content and size. The FAI has excellent sensitivity and specificity for detecting tissue inflammation as assessed by tissue uptake of 18F-fluorodeoxyglucose in positron emission tomography. In a validation cohort of 273 subjects, the FAI gradient around human coronary arteries identified early subclinical coronary artery disease in vivo, as well as detected dynamic changes of PVAT in response to variations of vascular inflammation, and inflamed, vulnerable atherosclerotic plaques during acute coronary syndromes. Our study revealed that human vessels exert paracrine effects on the surrounding PVAT, affecting local intracellular lipid accumulation in preadipocytes, which can be monitored using a CT imaging approach. This methodology can be implemented in clinical practice to noninvasively detect plaque instability in the human coronary vasculature.

Up-regulation of miR-31 in human atrial fibrillation begets the arrhythmia by depleting dystrophin and neuronal nitric oxide synthase

Atrial microRNA-31 up-regulation causes dystrophin and nNOS depletion, which in turn contributes to the electrical phenotype of atrial fibrillation. Rhythm remodeling traced to tiny RNA Atrial fibrillation (AF) is characterized by abnormal heart rhythms and can be caused by a variety of risk factors ranging from obesity to diabetes. Although treatments exist, AF is famously able to recur by “remodeling” the heart tissue electrically and structurally to maintain its unsteady beat. Reilly et al. have discovered a small noncoding RNA, miR-31, that is responsible for a string of signals that allow for such remodeling. An increase in miR-31 led to depletion of neuronal nitric oxide synthase (nNOS) and repression of dystrophin (which binds nNOS in muscle cells) in the fibrillating atrial myocardium of both humans and goats. These mechanistic findings were further explored in mice. Because up-regulation of miR-31 and the resulting loss of dystrophin and nNOS in AF are specific to the atrium, it may be possible to target interventions to this remodeling pathway, thus providing a safer therapeutic option for patients with AF than those that are currently available, including ablation and ion channel blockers. Atrial fibrillation (AF) is a growing public health burden, and its treatment remains a challenge. AF leads to electrical remodeling of the atria, which in turn promotes AF maintenance and resistance to treatment. Although remodeling has long been a therapeutic target in AF, its causes remain poorly understood. We show that atrial-specific up-regulation of microRNA-31 (miR-31) in goat and human AF depletes neuronal nitric oxide synthase (nNOS) by accelerating mRNA decay and alters nNOS subcellular localization by repressing dystrophin translation. By shortening action potential duration and abolishing rate-dependent adaptation of the action potential duration, miR-31 overexpression and/or disruption of nNOS signaling recapitulates features of AF-induced remodeling and significantly increases AF inducibility in mice in vivo. By contrast, silencing miR-31 in atrial myocytes from patients with AF restores dystrophin and nNOS and normalizes action potential duration and its rate dependency. These findings identify atrial-specific up-regulation of miR-31 in human AF as a key mechanism causing atrial dystrophin and nNOS depletion, which in turn contributes to the atrial phenotype begetting this arrhythmia. miR-31 may therefore represent a potential therapeutic target in AF.

European real world trans-catheter aortic valve implantation: systematic review and meta-analysis of European national registries

ObjectiveTranscatheter aortic valve implantation (TAVI) has been adopted rapidly in Europe. TAVI national registries can augment understanding of technologies and represent real-world experience, providing further clinical insights. We undertook a meta-analysis of published European national TAVI registries to assess current results following TAVI in Europe.MethodsElectronic databases were searched. The review focused on the comparison of the following TAVI strategies: transfemoral (TF) and transapical (TA) SAPIEN and CoreValve implantation. Individual event rates for outcomes of interest were pooled using a mixed effect model.ResultsSeven European national TAVI registries (UK, Swiss, Belgium, Italy, Spain, France, Germany) were identified, including a total of 9786 patients who received TF-SAPIEN (n = 2885), TA-SAPIEN (n = 2252) and CoreValve (n = 4649) implantation. Pooled incidence of 30-day mortality was 0.08% [95% Confidence Interval (CI): 0.05–0.11], 0.12% [95% CI: 0.07–0.19] and 0.06% [95% CI: 0.03–0.11] for TF-SAPIEN, TA-SAPIEN and CoreValve respectively (test for subgroup difference P = 0.18); there was high heterogeneity across European countries. Pooled incidence of stroke was comparable among the TAVI strategies (test for subgroup difference P = 0.79); the incidence of post-procedural moderate paravalvular leak ≥ 2 (P = 0.9) was similar across groups. CoreValve implantation was associated with an increased risk of pacemaker implantation (0.22 [95% CI: 0.19–0.26]; test for subgroup difference P < 0.0001). The lowest 30-day mortality was associated with TAVI performed in Spain (b coefficient −4.3; P = 0.03), in Italy (b coefficient −2.1; P < 0.0001), in UK (b coefficient −1.95; P = 0.01) and in France (b coefficient −2.8; P = 0.03). The German registry has the highest mortality for every TAVI strategy amongst all other European registries and especially for the TA-SAPIEN group.ConclusionsTransarterial TAVI approaches were associated with a low early mortality regardless of the type of device used. There was marked heterogeneity among European countries for early mortality.

Predictive value of telomere length on outcome following acute myocardial infarction: evidence for contrasting effects of vascular vs. blood oxidative stress

Abstract Aims Experimental evidence suggests that telomere length (TL) is shortened by oxidative DNA damage, reflecting biological aging. We explore the value of blood (BTL) and vascular TL (VTL) as biomarkers of systemic/vascular oxidative stress in humans and test the clinical predictive value of BTL in acute myocardial infarction (AMI). Methods and results In a prospective cohort of 290 patients surviving recent AMI, BTL measured on admission was a strong predictor of all-cause [hazard ratio (HR) [95% confidence interval (CI)]: 3.21 [1.46–7.06], P = 0.004] and cardiovascular mortality (HR [95% CI]: 3.96 [1.65–9.53], P = 0.002) 1 year after AMI (for comparisons of short vs. long BTL, as defined by a T/S ratio cut-off of 0.916, calculated using receiver operating characteristic analysis; P adjusted for age and other predictors). To explore the biological meaning of these findings, BTL was quantified in 727 consecutive patients undergoing coronary artery bypass grafting (CABG), and superoxide (O2.-) was measured in peripheral blood mononuclear cells (PBMNC). VTL/vascular O2.- were quantified in saphenous vein (SV) and mammary artery (IMA) segments. Patients were genotyped for functional genetic polymorphisms in P22ph°x (activating NADPH-oxidases) and vascular smooth muscle cells (VSMC) selected by genotype were cultured from vascular tissue. Short BTL was associated with high O2.- in PBMNC (P = 0.04) but not in vessels, whereas VTL was related to O2.- in IMA (ρ = −0.49, P = 0.004) and SV (ρ = −0.52, P = 0.01). Angiotensin II (AngII) incubation of VSMC (30 days), as a means of stimulating NADPH-oxidases, increased O2.- and reduced TL in carriers of the high-responsiveness P22ph°x alleles (P = 0.007). Conclusion BTL predicts cardiovascular outcomes post-AMI, independently of age, whereas VTL is a tissue-specific (rather than a global) biomarker of vascular oxidative stress. The lack of a strong association between BTL and VTL reveals the importance of systemic vs. vascular factors in determining clinical outcomes after AMI.

Influence of coronary territory on flow profiles of saphenous vein grafts

BackgroundDiffering perfusion of the left and right ventricular coronary territory may influence flow-profiles of saphenous vein grafts (SVGs). We compared flow parameters, measured by transit-time flowmetry (TTFM), in left- and right-sided SVGs during coronary artery by-pass grafting (CABG).MethodsRoutine TTFM measurements were obtained in 167 SVGs to the left territory (55%) and 134 SVGs to the right territory (total of 301 SVGs in 207 patients). The four standard TTFM parameters, [mean graft flow (MGF), pulsatility index (PI), percentage diastolic filling (%DF), and percentage backward flow (%BF)] were compared. Differences in flow parameters were also examined according to surgical technique (on- vs. off-pump).ResultsNo significant difference between coronary territories was found for MGF, PI and %BF. However, a higher %DF was noted in left-sided SVGs in the overall cohort as well as in the on-pump (both p < 0.001) and the off-pump cohorts (p = 0.07). Further, a significantly higher %BF was found in SVGs performed off-pump to the left territory (1.2 ± 2.5 vs. 2.3 ± 3.0, p = 0.023). In a multivariate regression analysis, anastomosing a SVG to the left territory was weakly associated with higher PI (OR = 0.36, p = 0.026) and strongly associated with higher %DF (OR = 5.1, p < 0.001). No significant association was found for MGF, PI, %DF or %BF in either the on-pump nor the off-pump cohorts.ConclusionsAlthough statistically significant, the established differences in TTFM parameters between left- and right-sided vein grafts were small and unlikely to be of clinical relevance.

Influence of external stenting on venous graft flow parameters in coronary artery bypass grafting: a randomized study.

OBJECTIVES Long-term patency of saphenous vein grafts (SVGs) remains a concern after coronary artery bypass grafting. Interventions to overcome this problem include monitoring intraoperative flow profile and, more recently, external stenting of SVGs. It is not known to what extent external stenting changes the perioperative flow characteristics of SVGs. The aim of this study was to assess whether the presence of an external stent affects perioperative graft flow parameters as evaluated by transit time flowmetry. METHODS Thirty-five patients were included from 1 centre participating in a multicentre, randomized clinical trial of external stenting of SVGs. Patients were eligible if scheduled for on-pump multivessel coronary artery bypass grafting including planned SVGs to both the right and the left coronary territories. Each patient received external stenting of a single SVG randomly allocated intraoperatively to either coronary territory. The primary end-points were mean graft flow, pulsatility index, percentage of diastolic filling and percentage of backward flow in stented versus non-stented SVGs. RESULTS External stenting was performed in 17 SVGs supplying the left territory (20 non-stented SVGs for control) and in 18 SVGs supplying the right territory (18 non-stented SVGs for control). No significant difference was found in flow parameters between stented and non-stented SVGs in the overall group or between pre-defined groups of SVGs supplying the right and left territories, respectively. CONCLUSIONS External stenting of SVGs do not affect intraoperative flow parameters significantly. CLINICAL TRIAL REGISTRATION clinicaltrials.gov identifier: NCT02511834.

127 Insulin induces oxidatives stress in the vascular wall of patients with atherosclerosis independently of systemic insulin resistance: the regulatory role of DPP4 inhibition

Background Insulin may have protective roles in vascular cells, but its vascular effects in patients with atherosclerosis are unknown. Dipeptidyl peptidase 4 (DPP4) inhibitors are a class of insulin-sensitising agents that may regulate vascular responses to insulin in humans. We attempted to determine the direct vascular effects of insulin in humans with atherosclerosis, and explore the effect of DPP4 inhibition on vascular insulin signalling. Methods The study included 613 patients undergoing coronary bypass surgery. Vascular segments (internal mammary arteries (IMA), saphenous veins (SV)) were collected and incubated with insulin glargine active metabolite M1 (insulin), insulin degludec (DEG) and human insulin (HI) (1–100 nM as stated), with or without pre-incubation with KR62436 (a DPP4 inhibitor) at 70 µM. Vascular superoxide (O2.-) was quantified by lucigenin chemiluminescence, while nitric oxide bioavailability was evaluated by quantifying the vasorelaxations to acetylcholine. Circulating DPP4 activity was measured in fasting serum using commercially available kits. Downstream signalling was evaluated by Western blotting for protein phosphorylation. Results Insulin increased NADPH-oxidases-derived O2.- in vessels from patients with or without diabetes, an effect reversed in vascular segments from diabetic patients pre-treated with an oral DPP4 inhibitor (A). In contrast, insulin reduced O2.- in vessels of healthy mice used as controls (not shown). Circulating DPP4 activity was associated with increased vascular NADPH-oxidases activity in the study population (not shown), while ex vivo pre-incubation of human vessels with KR62436 (DPP4-i) reversed the effect of insulin on vascular O2.-, supressing NADPH-oxidases activity (B), improving eNOS coupling (C) and ameliorating endothelial dysfunction in human vessels (D). This was a class effect, replicated using DEG and HI (data not shown). DPP4 inhibition improved downstream insulin signalling by reducing insulin receptor substrate 1 (IRS1) phosphorylation at Ser307, a site linked to molecular insulin resistance (E). The vascular effects of DPP4 inhibition may be regulated via AMPK, since DPP4-i increased AMPK Thr172 phosphorylation while AMPK inhibition with compound C reversed the protective vascular effects of DPP4-I (F). Conclusions We demonstrate for the first time that insulin induces oxidative stress and endothelial dysfunction in vascular segments from patients with atherosclerosis, independently of systemic insulin resistance. This may partially explain the inability of insulin treatment to improve cardiovascular outcomes in patients with moderately elevated blood glucose. Pre-treatment with a DPP4 inhibitor restores local insulin sensitivity modulating the vascular responses to insulin. These findings suggest that vascular sensitisation may be crucial when treating of diabetic patients in secondary prevention.