Plasminogen Receptors Promote Lipoprotein(a) Uptake by Enhancing Surface Binding and Facilitating Macropinocytosis.

BACKGROUND: High levels of Lp(a) (lipoprotein(a)) are associated with multiple forms of cardiovascular disease. Lp(a) consists of an apoB100-containing particle attached to the plasminogen homologue apo(a). The pathways for Lp(a) clearance are not well understood. We previously discovered that the plasminogen receptor PlgRKT (plasminogen receptor with a C-terminal lysine) promoted Lp(a) uptake in liver cells. Here, we aimed to further define the role of PlgRKT and to investigate the role of 2 other plasminogen receptors, annexin A2 and S100A10 (S100 calcium-binding protein A10) in the endocytosis of Lp(a). METHODS: Human hepatocellular carcinoma (HepG2) cells and haploid human fibroblast-like (HAP1) cells were used for overexpression and knockout of plasminogen receptors. The uptake of Lp(a), LDL (low-density lipoprotein), apo(a), and endocytic cargos was visualized and quantified by confocal microscopy and Western blotting. RESULTS: The uptake of both Lp(a) and apo(a), but not LDL, was significantly increased in HepG2 and HAP1 cells overexpressing PlgRKT, annexin A2, or S100A10. Conversely, Lp(a) and apo(a), but not LDL, uptake was significantly reduced in HAP1 cells in which PlgRKT and S100A10 were knocked out. Surface binding studies in HepG2 cells showed that overexpression of PlgRKT, but not annexin A2 or S100A10, increased Lp(a) and apo(a) plasma membrane binding. Annexin A2 and S100A10, on the other hand, appeared to regulate macropinocytosis with both proteins significantly increasing the uptake of the macropinocytosis marker dextran when overexpressed in HepG2 and HAP1 cells and knockout of S100A10 significantly reducing dextran uptake. Bringing these observations together, we tested the effect of a PI3K (phosphoinositide-3-kinase) inhibitor, known to inhibit macropinocytosis, on Lp(a) uptake. Results showed a concentration-dependent reduction confirming that Lp(a) uptake was indeed mediated by macropinocytosis. CONCLUSIONS: These findings uncover a novel pathway for Lp(a) endocytosis involving multiple plasminogen receptors that enhance surface binding and stimulate macropinocytosis of Lp(a). Although the findings were produced in cell culture models that have limitations, they could have clinical relevance since drugs that inhibit macropinocytosis are in clinical use, that is, the PI3K inhibitors for cancer therapy and some antidepressant compounds.

Childhood Social Isolation as a Predictor of Retinal Neuronal Thickness in Middle Age: A Lifecourse Birth Cohort Study.

OBJECTIVE: We investigated whether childhood social isolation was associated with retinal neural layer changes in adulthood, and whether this association was independent of other childhood or adulthood risk factors, including adult social isolation. METHODS: Participants were members of the Dunedin Multidisciplinary Health and Development Study, a longitudinal population-based birth cohort from Aotearoa New Zealand ( n = 1037), born 1972 to 1973 and followed until age 45 years, with 94% of the living cohort still participating. Social isolation was recorded prospectively at ages 5, 7, 9, and 11 years, from teacher and parent report. Retinal nerve fiber layer (RNFL) and ganglion cell-inner plexiform layer thicknesses were measured via optical coherence tomography at age 45 years. RESULTS: Childhood social isolation was associated with thinner average RNFL ( B = -0.739, p = .02), nasal RNFL ( B = -1.118, p = .005), and inferior RNFL ( B = -1.524, p = .007), although only nasal RNFL remained significant after adjustment. These associations were not fully explained by other psychosocial or physical health risk factors in childhood or adulthood, nor were they mediated by adult loneliness or social support. CONCLUSIONS: Childhood social isolation was an independent predictor of RNFL thickness in middle age. Highlighting prospective links between childhood psychosocial adversity and retinal neuronal measures will help to inform future research into the utility of retinal neuronal thickness as a biomarker for neurodegeneration.

Diabetes induces dysregulation of microRNAs associated with survival, proliferation and self-renewal in cardiac progenitor cells.

AIMS/HYPOTHESIS: Diabetes mellitus causes a progressive loss of functional efficacy in stem cells, including cardiac progenitor cells (CPCs). The underlying molecular mechanism is still not known. MicroRNAs (miRNAs) are small, non-coding RNA molecules that regulate genes at the post-transcriptional level. We aimed to determine if diabetes mellitus induces dysregulation of miRNAs in CPCs and to test if in vitro therapeutic modulation of miRNAs would improve the functions of diabetic CPCs. METHODS: CPCs were isolated from a mouse model of type 2 diabetes (db/db), non-diabetic mice and human right atrial appendage heart tissue. Total RNA isolated from mouse CPCs was miRNA profiled using Nanostring analysis. Bioinformatic analysis was employed to predict the functional effects of altered miRNAs. MS analysis was applied to determine the targets, which were confirmed by western blot analysis. Finally, to assess the beneficial effects of therapeutic modulation of miRNAs in vitro and in vivo, prosurvival miR-30c-5p was overexpressed in mouse and human diabetic CPCs, and the functional consequences were determined by measuring the level of apoptotic cell death, cardiac function and mitochondrial membrane potential (MMP). RESULTS: Among 599 miRNAs analysed in mouse CPCs via Nanostring analysis, 16 miRNAs showed significant dysregulation in the diabetic CPCs. Using bioinformatics tools and quantitative real-time PCR (qPCR) validation, four altered miRNAs (miR-30c-5p, miR-329-3p, miR-376c-3p and miR-495-3p) were identified to play an important role in cell proliferation and survival. Diabetes mellitus significantly downregulated miR-30c-5p, while it upregulated miR-329-3p, miR-376c-3p and miR-495-3p. MS analysis revealed proapoptotic voltage-dependent anion-selective channel 1 (VDAC1) as a direct target for miR-30c-5p, and cell cycle regulator, cyclin-dependent protein kinase 6 (CDK6), as the direct target for miR-329-3p, miR-376c-3p and miR-495-3p. Western blot analyses showed a marked increase in VDAC1 expression, while CDK6 expression was downregulated in diabetic CPCs. Finally, in vitro and in vivo overexpression of miR-30c-5p markedly reduced the apoptotic cell death and preserved MMP in diabetic CPCs via inhibition of VDAC1. CONCLUSIONS/INTERPRETATION: Our results demonstrate that diabetes mellitus induces a marked dysregulation of miRNAs associated with stem cell survival, proliferation and differentiation, and that therapeutic overexpression of prosurvival miR-30c-5p reduced diabetes-induced cell death and loss of MMP in CPCs via the newly identified target for miR-30c-5p, VDAC1.

Long-chain acylcarnitine 18:1 acutely increases human atrial myocardial contractility and arrhythmia susceptibility.

Long-chain acylcarnitines (LCACs) are known to directly alter cardiac contractility and electrophysiology. However, the acute effect of LCACs on human cardiac function is unknown. We aimed to determine the effect of LCAC 18:1, which has been associated with cardiovascular disease, on the contractility and arrhythmia susceptibility of human atrial myocardium. Additionally, we aimed to assess how LCAC 18:1 alters Ca2+ influx and spontaneous Ca2+ release in vitro. Human right atrial trabeculae (n = 32) stimulated at 1 Hz were treated with LCAC 18:1 at a range of concentrations (1-25 µM) for a 45-min period. Exposure to the LCAC induced a dose-dependent positive inotropic effect on myocardial contractility (maximal 1.5-fold increase vs. control). At the 25 µM dose (n = 8), this was paralleled by an enhanced propensity for spontaneous contractions (50% increase). Furthermore, all LCAC 18:1 effects on myocardial function were reversed following LCAC 18:1 washout. In fluo-4-AM-loaded HEK293 cells, LCAC 18:1 dose dependently increased cytosolic Ca2+ influx relative to vehicle controls and the short-chain acylcarnitine C3. In HEK293 cells expressing ryanodine receptor (RyR2), this increased Ca2+ influx was linked to an increased propensity for RyR2-mediated spontaneous Ca2+ release events. Our study is the first to show that LCAC 18:1 directly and acutely alters human myocardial function and in vitro Ca2+ handling. The metabolite promotes proarrhythmic muscle contractions and increases contractility. The exploratory findings in vitro suggest that LCAC 18:1 increases proarrhythmic RyR2-mediated spontaneous Ca2+ release propensity. The direct effects of metabolites on human myocardial function are essential to understand cardiometabolic dysfunction.NEW & NOTEWORTHY For the first time, the fatty acid metabolite, long-chain acylcarnitine 18:1, is shown to acutely increase the arrhythmia susceptibility and contractility of human atrial myocardium. In vitro, this was linked to an influx of Ca2+ and an enhanced propensity for spontaneous RyR2-mediated Ca2+ release.

Activation of the cardiac non-neuronal cholinergic system prevents the development of diabetes-associated cardiovascular complications.

BACKGROUND: Acetylcholine (ACh) plays a crucial role in the function of the heart. Recent evidence suggests that cardiomyocytes possess a non-neuronal cholinergic system (NNCS) that comprises of choline acetyltransferase (ChAT), choline transporter 1 (CHT1), vesicular acetylcholine transporter (VAChT), acetylcholinesterase (AChE) and type-2 muscarinic ACh receptors (M2AChR) to synthesize, release, degrade ACh as well as for ACh to transduce a signal. NNCS is linked to cardiac cell survival, angiogenesis and glucose metabolism. Impairment of these functions are hallmarks of diabetic heart disease (DHD). The role of the NNCS in DHD is unknown. The aim of this study was to examine the effect of diabetes on cardiac NNCS and determine if activation of cardiac NNCS is beneficial to the diabetic heart. METHODS: Ventricular samples from type-2 diabetic humans and db/db mice were used to measure the expression pattern of NNCS components (ChAT, CHT1, VAChT, AChE and M2AChR) and glucose transporter-4 (GLUT-4) by western blot analysis. To determine the function of the cardiac NNCS in the diabetic heart, a db/db mouse model with cardiac-specific overexpression of ChAT gene was generated (db/db-ChAT-tg). Animals were followed up serially and samples collected at different time points for molecular and histological analysis of cardiac NNCS components and prosurvival and proangiogenic signaling pathways. RESULTS: Immunoblot analysis revealed alterations in the components of cardiac NNCS and GLUT-4 in the type-2 diabetic human and db/db mouse hearts. Interestingly, the dysregulation of cardiac NNCS was followed by the downregulation of GLUT-4 in the db/db mouse heart. Db/db-ChAT-tg mice exhibited preserved cardiac and vascular function in comparison to db/db mice. The improved function was associated with increased cardiac ACh and glucose content, sustained angiogenesis and reduced fibrosis. These beneficial effects were associated with upregulation of the PI3K/Akt/HIF1α signaling pathway, and increased expression of its downstream targets-GLUT-4 and VEGF-A. CONCLUSION: We provide the first evidence for dysregulation of the cardiac NNCS in DHD. Increased cardiac ACh is beneficial and a potential new therapeutic strategy to prevent or delay the development of DHD.

Obesity and All Cause Mortality Following Acute Coronary Syndrome (ANZACS-QI 53).

BACKGROUND: Some studies have suggested a lower mortality in obese subjects with cardiovascular disease. The aim of this study was to evaluate the relationship between body mass index (BMI) and outcomes in patients with acute coronary syndrome (ACS). METHODS: The study included 13,742 patients undergoing coronary angiography for ACS between 2012 and 2016 from the All New Zealand Acute Coronary Syndrome-Quality Improvement (ANZACS-QI) registry. Patients were categorised by BMI (kg/m2) as: underweight <18.5, normal 18.5 to <25, overweight 25 to <30, mildly obese 30 to <35, moderately obese 35 to <40, and severely obese ≥40. The primary endpoint of the study was all cause mortality with secondary endpoints of cardiovascular disease (CVD) and non-CVD mortality within 4 years of discharge. RESULTS: Unadjusted all cause mortality was lowest in the mildly obese but no different to normal or overweight after adjustment for multiple confounders. Adjusted all cause mortality was higher in the moderately (hazard ratio [HR] 1.39, 95% CI: 1.10-1.75) and severely obese (2.06, 95% CI: 1.57-2.70) compared to the mildly obese. Non-CVD mortality (HR 1.58, 95% CI: 1.12-2.23) was the major contributor to higher all cause mortality in moderately obese patients. Both CVD mortality (HR 2.36, 95% CI: 1.67-3.32) and non-CVD mortality (HR 1.67, 95% CI: 1.07-2.61) contributed to higher all cause mortality in the severely obese. CONCLUSIONS: Moderate and severe obesity is associated with worse survival post ACS influenced by higher non-CVD mortality in moderate/severe obesity and higher CVD mortality in severe obesity.

Nonsynonymous SNPs in LPA homologous to plasminogen deficiency mutants represent novel null apo(a) alleles.

Plasma lipoprotein (a) [Lp(a)] levels are largely determined by variation in the LPA gene, which codes for apo(a). Genome-wide association studies (GWASs) have identified nonsynonymous variants in LPA that associate with low Lp(a) levels, although their effect on apo(a) function is unknown. We investigated two such variants, R990Q and R1771C, which were present in four null Lp(a) individuals, for structural and functional effects. Sequence alignments showed the R990 and R1771 residues to be highly conserved and homologous to each other and to residues associated with plasminogen deficiency. Structural modeling showed both residues to make several polar contacts with neighboring residues that would be ablated on substitution. Recombinant expression of the WT and R1771C apo(a) in liver and kidney cells showed an abundance of an immature form for both apo(a) proteins. A mature form of apo(a) was only seen with the WT protein. Imaging of the recombinant apo(a) proteins in conjunction with markers of the secretory pathway indicated a poor transit of R1771C into the Golgi. Furthermore, the R1771C mutant displayed a glycosylation pattern consistent with ER, but not Golgi, glycosylation. We conclude that R1771 and the equivalent R990 residue facilitate correct folding of the apo(a) kringle structure and mutations at these positions prevent the proper folding required for full maturation and secretion. To our knowledge, this is the first example of nonsynonymous variants in LPA being causative of a null Lp(a) phenotype.

Inotropic and lusitropic, but not arrhythmogenic, effects of adipocytokine resistin on human atrial myocardium.

The adipocytokine resistin is released from epicardial adipose tissue (EAT). Plasma resistin and EAT deposition are independently associated with atrial fibrillation. The EAT secretome enhances arrhythmia susceptibility and inotropy of human myocardium. Therefore, we aimed to determine the effect of resistin on the function of human myocardium and how resistin contributes to the proarrhythmic effect of EAT. EAT biopsies were obtained from 25 cardiac surgery patients. Resistin levels were measured by ELISA in 24-h EAT culture media (n = 8). The secretome resistin concentrations increased over the culture period to a maximal level of 5.9 ± 1.2 ng/mL. Coculture with ß-adrenergic agonists isoproterenol (n = 4) and BRL37344 (n = 13) had no effect on EAT resistin release. Addition of resistin (7, 12, 20 ng/mL) did not significantly increase the spontaneous contraction propensity of human atrial trabeculae (n = 10) when given alone or in combination with isoproterenol. Resistin dose-dependently increased trabecula-developed force (maximal 2.9-fold increase, P < 0.0001), as well as the maximal rates of contraction (2.6-fold increase, P = 0.002) and relaxation (1.8-fold increase, P = 0.007). Additionally, the postrest potentiation capacity of human trabeculae was reduced at all resistin doses, suggesting that the inotropic effect induced by resistin might be due to altered sarcoplasmic reticulum Ca2+ handling. EAT resistin release is not modulated by common arrhythmia triggers. Furthermore, exogenous resistin does not promote arrhythmic behavior in human atrial trabeculae. Resistin does, however, induce an acute dose-dependent positive inotropic and lusitropic effect.

Acute interaction between human epicardial adipose tissue and human atrial myocardium induces arrhythmic susceptibility.

Epicardial adipose tissue (EAT) deposition has a strong clinical association with atrial arrhythmias; however, whether a direct functional interaction exists between EAT and the myocardium to induce atrial arrhythmias is unknown. Therefore, we aimed to determine whether human EAT can be an acute trigger for arrhythmias in human atrial myocardium. Human trabeculae were obtained from right atrial appendages of patients who have had cardiac surgery (n = 89). The propensity of spontaneous contractions (SCs) in the trabeculae (proxy for arrhythmias) was determined under physiological conditions and during known triggers of SCs (high Ca2+, ß-adrenergic stimulation). To determine whether EAT could trigger SCs, trabeculae were exposed to superfusate of fresh human EAT, and medium of 24 h-cultured human EAT treated with ß1/2 (isoproterenol) or ß3 (BRL37344) adrenergic agonists. Without exposure to EAT, high Ca2+ and ß1/2-adrenergic stimulation acutely triggered SCs in, respectively, 47% and 55% of the trabeculae that previously were not spontaneously active. Acute ß3-adrenergic stimulation did not trigger SCs. Exposure of trabeculae to either superfusate of fresh human EAT or untreated medium of 24 h-cultured human EAT did not induce SCs; however, specific ß3-adrenergic stimulation of EAT did trigger SCs in the trabeculae, either when applied to fresh (31%) or cultured (50%) EAT. Additionally, fresh EAT increased trabecular contraction and relaxation, whereas media of cultured EAT only increased function when treated with the ß3-adrenergic agonist. An acute functional interaction between human EAT and human atrial myocardium exists that increases the propensity for atrial arrhythmias, which depends on ß3-adrenergic rather than ß1/2-adrenergic stimulation of EAT.

Upregulation of microRNA-532 enhances cardiomyocyte apoptosis in the diabetic heart.

Type 2 diabetes has a strong association with the development of cardiovascular disease, which is grouped as diabetic heart disease (DHD). DHD is associated with the progressive loss of cardiovascular cells through the alteration of molecular signalling pathways associated with cell death. In this study, we sought to determine whether diabetes induces dysregulation of miR-532 and if this is associated with accentuated apoptosis. RT-PCR analysis showed a significant increase in miR-532 expression in the right atrial appendage tissue of type 2 diabetic patients undergoing coronary artery bypass graft surgery. This was associated with marked downregulation of its anti-apoptotic target protein apoptosis repressor with caspase recruitment domain (ARC) and increased TUNEL positive cardiomyocytes. Further analysis showed a positive correlation between apoptosis and miR-532 levels. Time-course experiments in a mouse model of type 2 diabetes showed that diabetes-induced activation of miR-532 occurs in the later stage of the disease. Importantly, the upregulation of miR-532 preceded the activation of pro-apoptotic caspase-3/7 activity. Finally, inhibition of miR-532 activity in high glucose cultured human cardiomyocytes prevented the downregulation of ARC and attenuated apoptotic cell death. Diabetes induced activation of miR-532 plays a critical role in accelerating cardiomyocytes apoptosis. Therefore, miR-532 may serve as a promising therapeutic agent to overcome the diabetes-induced loss of cardiomyocytes.

Both Small and Large Infrarenal Aortic Size is Associated with an Increased Prevalence of Ischaemic Heart Disease.

OBJECTIVE: Past studies have suggested a potential "J shaped" relationship between infrarenal aortic diameter and both cardiovascular disease (CVD) prevalence and all cause mortality. However, screening programmes have focused primarily on large (aneurysmal) aortas. In addition, aortic diameter is rarely adjusted for body size, which is particularly important for women. This study aimed to investigate specifically the relationship between body size adjusted infrarenal aortic diameter and baseline prevalence of CVD. METHODS: A retrospective analysis was performed on a total of 4882 elderly (>50 years) participants (mean age 69.4 ± 8.9 years) for whom duplex ultrasound to assess infrarenal abdominal aortic diameters had been performed. History of CVDs, including ischaemic heart disease (IHD), and associated risk factors were collected at the time of assessment. A derivation cohort of 1668 participants was used to select cut offs at the lower and upper 12.5% tails of the aortic size distributions (aortic size index of <0.84 and >1.2, respectively), which was then tested in a separate cohort. RESULTS: A significantly elevated prevalence of CVD, and specifically IHD, was observed in participants with both small and large aortas. These associations remained significant following adjustment for age, sex, diabetes, hypertension, dyslipidaemia, obesity (body mass index), and smoking. CONCLUSION: The largest and smallest infrarenal aortic sizes were both associated with prevalence of IHD. In addition to identifying those with aneurysmal disease, it is hypothesised that screening programmes examining infrarenal aortic size may also have the potential to improve global CVD risk prediction by identifying those with small aortas.

Associations between lung and endothelial function in early middle age.

BACKGROUND AND OBJECTIVE: Chronic lung disease is associated with impaired endothelial function and this may be a risk factor for poor cardiovascular health. It is unknown if there is an association between lung and endothelial function in the general population. We investigated associations between lung and endothelial function in a population-based cohort of 38-year-old men and women. METHODS: Systemic endothelial function was measured using peripheral arterial tonometry to calculate the Framingham reactive hyperaemia index. Lung function was assessed using spirometry, plethysmographic lung volumes, airway conductance and gas transfer. Associations between lung and endothelial function were assessed with and without adjustment for potential confounding factors using regression analyses. RESULTS: Sex modified the association between lung and endothelial function. Among women, lower values of pre- and post-bronchodilator spirometry, total lung capacity and functional residual capacity (FRC) were associated with worse endothelial function (P < 0.05). These associations persisted after adjustment for smoking, asthma diagnoses, fitness and body mass index. Associations were weaker among men: only FRC, airway conductance and post-bronchodilator forced expiratory volume in 1 s (FEV1 )/forced vital capacity (FVC) ratios were associated with endothelial function. Endothelial function was not associated with gas transfer in either sex. CONCLUSION: Lower lung volumes and airflow obstruction are associated with endothelial dysfunction among women. There is weaker evidence for an association between airway and endothelial function in men. These findings may partly explain the increased risk of cardiovascular disease among people with poor lung function, but suggest that there are sex differences in this association.

Frailty in Elderly Patients Undergoing Cardiac Surgery Increases Hospital Stay and 12-Month Readmission Rate.

BACKGROUND: Cardiac surgery risk scoring systems predict operative mortality but not outcomes related to preoperative frailty. The aim of this study was to assess frailty in a cohort of older cardiac surgery patients as a predictor of postoperative outcomes. METHODS: Prospective data was collected on patients 65 years of age and older undergoing cardiac surgery between September 2015 and October 2016 at Dunedin Hospital. Frailty was assessed with the Edmonton frail scale and five-metre gait speed. The primary endpoint was length of hospital stay. Secondary outcomes included postoperative complications, major adverse events, death and 12-month readmission rate. RESULTS: Among the 96 patients, median age was 74 (interquartile range 10.5) and 65 (68%) were males. Of the sample 64 (67%) were scored as not frail, 22 (23%) as vulnerable, and 10 (10%) as frail. The median (interquartile range) postoperative days' stay were: not frail 6 (2), vulnerable 9.5 (8), and frail 15 (13). Survival analysis adjusting for EuroSCORE II, age, sex and surgery type showed that greater Edmonton Frail Scale scores were independently predictive of longer post-surgery hospital stay with a hazard ratio for discharge of 0.83 (95% confidence interval 0.76-0.91, p<0.001) per point. The Edmonton Frail Scale score was associated with the 12-month post discharge number of readmissions (adjusted incidence rate ratio 1.24 (95% confidence interval 1.13-1.37, p<0.001) per point. CONCLUSIONS: The Edmonton Frail Scale score predicts length of hospital stay post cardiac surgery and 12-month readmission rate in patients older than 65 years of age.

Variant ASGR1 Associated with a Reduced Risk of Coronary Artery Disease.

BACKGROUND: Several sequence variants are known to have effects on serum levels of non-high-density lipoprotein (HDL) cholesterol that alter the risk of coronary artery disease. METHODS: We sequenced the genomes of 2636 Icelanders and found variants that we then imputed into the genomes of approximately 398,000 Icelanders. We tested for association between these imputed variants and non-HDL cholesterol levels in 119,146 samples. We then performed replication testing in two populations of European descent. We assessed the effects of an implicated loss-of-function variant on the risk of coronary artery disease in 42,524 case patients and 249,414 controls from five European ancestry populations. An augmented set of genomes was screened for additional loss-of-function variants in a target gene. We evaluated the effect of an implicated variant on protein stability. RESULTS: We found a rare noncoding 12-base-pair (bp) deletion (del12) in intron 4 of ASGR1, which encodes a subunit of the asialoglycoprotein receptor, a lectin that plays a role in the homeostasis of circulating glycoproteins. The del12 mutation activates a cryptic splice site, leading to a frameshift mutation and a premature stop codon that renders a truncated protein prone to degradation. Heterozygous carriers of the mutation (1 in 120 persons in our study population) had a lower level of non-HDL cholesterol than noncarriers, a difference of 15.3 mg per deciliter (0.40 mmol per liter) (P=1.0×10(-16)), and a lower risk of coronary artery disease (by 34%; 95% confidence interval, 21 to 45; P=4.0×10(-6)). In a larger set of sequenced samples from Icelanders, we found another loss-of-function ASGR1 variant (p.W158X, carried by 1 in 1850 persons) that was also associated with lower levels of non-HDL cholesterol (P=1.8×10(-3)). CONCLUSIONS: ASGR1 haploinsufficiency was associated with reduced levels of non-HDL cholesterol and a reduced risk of coronary artery disease. (Funded by the National Institutes of Health and others.).

Early dysregulation of cardiac-specific microRNA-208a is linked to maladaptive cardiac remodelling in diabetic myocardium.

BACKGROUND: The diabetic heart undergoes remodelling contributing to an increased incidence of heart failure in individuals with diabetes at a later stage. The molecular regulators that drive this process in the diabetic heart are still unknown. METHODS: Real-time (RT) PCR analysis was performed to determine the expression of cardiac specific microRNA-208a in right atrial appendage (RAA) and left ventricular (LV) biopsy tissues collected from diabetic and non-diabetic patients undergoing coronary artery bypass graft surgery. To determine the time-dependent changes, cardiac tissue were collected from type 2 diabetic mice at different age groups. A western blotting analysis was conducted to determine the expression of contractile proteins α- and ß-myosin heavy chain (MHC) and thyroid hormone receptor-α (TR-α), the negative regulator of ß-MHC. To determine the beneficial effects of therapeutic modulation of miR-208a, high glucose treated adult mouse HL-1 cardiomyocytes were transfected with anti-miR-208a. RESULTS: RT-PCR analysis showed marked upregulation of miR-208a from early stages of diabetes in type 2 diabetic mouse heart, which was associated with a marked increase in the expression of pro-hypertrophic ß-MHC and downregulation of TR-α. Interestingly, upregulation of miR-208a preceded the switch of α-/ß-MHC isoforms and the development of diastolic and systolic dysfunction. We also observed significant upregulation of miR-208a and modulation of miR-208a associated proteins in the type 2 human diabetic heart. Therapeutic inhibition of miR-208a activity in high glucose treated HL-1 cardiomyocytes prevented the activation of ß-MHC and hence the hypertrophic response. CONCLUSION: Our results provide the first evidence that early modulation of miR-208a in the diabetic heart induces alterations in the downstream signaling pathway leading to cardiac remodelling and that therapeutic inhibition of miR-208a may be beneficial in preventing diabetes-induced adverse remodelling of the heart.

Recycling of Apolipoprotein(a) After PlgRKT-Mediated Endocytosis of Lipoprotein(a).

RATIONALE: Lipoprotein(a) [Lp(a)] is a low-density lipoprotein-like lipoprotein and important cardiovascular risk factor whose cognate receptor and intracellular fate remains unknown. OBJECTIVE: Our study aimed to determine the intracellular trafficking pathway for Lp(a) and the receptor responsible for its uptake in liver cells. METHODS AND RESULTS: Human hepatoma cells were treated with Lp(a) purified from human plasma and Lp(a) uptake studied using Western blot analysis and intracellular localization of Lp(a) by confocal microscopy. Lp(a) was maximally internalized by 2 hours and was detected by an antiapo(a) antibody to be localized to Rab5-positive early endosomes, the trans-Golgi network, and subsequently Rab11-positive recycling endosomes. In human hepatoma cells, the apo(a) component from the internalized Lp(a) was resecreted back into the cellular media, whereas the low-density lipoprotein component was localized to the lysosomal compartment. Lp(a) internalization was reduced 0.35-fold in HAP1 and 0.33-fold in human hepatoma cells in which the plasminogen receptor (KT) was knocked out. Conversely, Lp(a) internalization was enhanced 2-fold in HAP1 and 1.6-fold in human hepatoma cells in which plasminogen receptor (KT) was overexpressed, showing for the first time the role of a specific plasminogen receptor in Lp(a) uptake. CONCLUSIONS: The novel findings that Lp(a) is internalized by the plasminogen receptor, plasminogen receptor (KT), and the apo(a) component is recycled may have important implications for the catabolism and function of Lp(a).

Meta-Analysis of Genome-Wide Association Studies for Abdominal Aortic Aneurysm Identifies Four New Disease-Specific Risk Loci.

RATIONALE: Abdominal aortic aneurysm (AAA) is a complex disease with both genetic and environmental risk factors. Together, 6 previously identified risk loci only explain a small proportion of the heritability of AAA. OBJECTIVE: To identify additional AAA risk loci using data from all available genome-wide association studies. METHODS AND RESULTS: Through a meta-analysis of 6 genome-wide association study data sets and a validation study totaling 10 204 cases and 107 766 controls, we identified 4 new AAA risk loci: 1q32.3 (SMYD2), 13q12.11 (LINC00540), 20q13.12 (near PCIF1/MMP9/ZNF335), and 21q22.2 (ERG). In various database searches, we observed no new associations between the lead AAA single nucleotide polymorphisms and coronary artery disease, blood pressure, lipids, or diabetes mellitus. Network analyses identified ERG, IL6R, and LDLR as modifiers of MMP9, with a direct interaction between ERG and MMP9. CONCLUSIONS: The 4 new risk loci for AAA seem to be specific for AAA compared with other cardiovascular diseases and related traits suggesting that traditional cardiovascular risk factor management may only have limited value in preventing the progression of aneurysmal disease.

Correcting for Body Surface Area Identifies the True Prevalence of Abdominal Aortic Aneurysm in Screened Women.

OBJECTIVE: Recently, the prevalence of abdominal aortic aneurysm (AAA) using screening strategies based on elevated cardiovascular disease (CVD) risk was reported. AAA was defined as a diameter ≥30 mm, with prevalence of 6.1% and 1.8% in men and women respectively, consistent with the widely reported AAA predominant prevalence in males. Given the obvious differences in body size between sexes this study aimed to re-evaluate the expanded CVD risk based AAA screening dataset to determine the effect of body size on sex specific AAA prevalence. METHODS: Absolute (26 and 30 mm) and relative (aortic size index [ASI] equals the maximum infrarenal aorta diameter (cm) divided by body surface area (m2), ASI ≥ 1.5) thresholds were used to assess targeted AAA screening groups (n = 4115) and compared with a self reported healthy elderly control group (n = 800). RESULTS: Male AAA prevalence was the same using either the 30 mm or ASI ≥1.5 aneurysm definitions (5.7%). In females, AAA prevalence was significantly different between the 30 mm (2.4%) and ASI ≥ 1.5 (4.5%) or the 26 mm (4.4%) thresholds. CONCLUSION: The results suggest the purported male predominance in AAA prevalence is primarily an artefact of body size differences. When aortic size is adjusted for body surface area there is only a modest sex difference in AAA prevalence. This observation has potential implications in the context of the ongoing discussion regarding AAA screening in women.

Myocardial tissue characterisation using echocardiographic deformation imaging.

Myocardial pathology results in significant morbidity and mortality, whether due to primary cardiomyopathic processes or secondary to other conditions such as ischemic heart disease. Cardiac imaging techniques characterise the underlying tissue directly, by assessing a signal from the tissue itself, or indirectly, by inferring tissue characteristics from global or regional function. Cardiac magnetic resonance imaging is currently the most investigated imaging modality for tissue characterisation, but, due to its accessibility, advanced echocardiography represents an attractive alternative. Speckle tracking echocardiography (STE) is a reproducible technique used to assess myocardial deformation at both segmental and global levels. Since distinct myocardial pathologies affect deformation differently, information about the underlying tissue can be inferred by STE. In this review, the current available studies correlating STE deformation parameters with underlying tissue characteristics in humans are examined, with separate emphasis on global and segmental analysis. The current knowledge is placed in the context of integrated backscatter and the future of echocardiographic based tissue characterisation is discussed. The use of these imaging techniques to more precisely phenotype myocardial pathology more precisely will allow the design of translational cardiac research studies and, potentially, tailored management strategies.

All-Cause Mortality Following an Acute Coronary Syndrome: 12-Year Follow-Up of the Comprehensive 2002 New Zealand Acute Coronary Syndrome Audit.

BACKGROUND: To describe the long-term mortality of a complete national cohort of acute coronary syndrome (ACS) patients enrolled in 2002, to compare this with a national age, sex and Maori ethnicity matched population, and to assess the influence of baseline factors on the 12-year mortality. METHODS: We reviewed 721 patients with a discharge diagnosis of an ACS who were enrolled in the first New Zealand ACS audit group cohort over 14days in May 2002. We matched the cohort to the national mortality database using each patient's unique national identity number. RESULTS: Over a median follow-up of 12.7 years of 721 patients discharged with an ACS, overall mortality was 52%: ST-elevation myocardial infarction (STEMI) (58%), non-ST-elevation myocardial infarction (NSTEMI) (61%) and unstable angina pectoris (UAP) (42%) patients, p<0.0001. In an age-adjusted survival model, males had a 29% increased mortality rate compared to females with a hazard ratio of 1.29 (95% CI 1.04, 1.61, p=0.019). Over 12 years there were 339 (47%) deaths, compared to 284 (39%) deaths observed in the matched population. The standardised mortality ratio for patients admitted with an ACS in New Zealand is 1.3 (95% CI 1.2, 1.5) with eight patients per 100 not surviving to 12 years compared to this matched population. CONCLUSIONS: The high mortality rate in this ACS cohort is a stark reminder of the prognostic implications of a presentation with an ACS. It emphasises the on-going need for optimal management of these patients throughout every stage of their initial treatment and subsequent on-going care.