Abstract 414: Putative Role of MicroRNA-143 in Modulating Natriuretic Peptide Signaling via Down-regulation of the Expression of Natriuretic Peptide Receptor 3

Cardiac natriuretic peptides (NPs) play important roles in the regulation of intravascular blood volume and vascular tone. Among other clearance mechanisms, bio-active circulating NPs are removed by the clearance receptor, Natriuretic Peptide Receptor 3 (NPR3). We hypothesized that the level of NPR3 could be modulated by microRNAs (miRNAs) resulting in changes in the bioactivity of NPs. We have previously reported a cluster of miRNAs potentially regulating NPR3 expression. To extend these findings, expression of the microRNAs concerned was examined in multiple platforms, including plasma from a clinical heart failure cohort, in the rat myocardial infarction model, and in a human cardiac derived cell line subjected to hypoxic challenge.

Results: miR-143 was up-regulated in peripheral blood in heart failure patients compared with controls. The binding of miR-143 to the 3’UTR of NPR3 m RNA was verified by luciferase reporter assay. Antagomir-based silencing of miR-143 enhanced NPR3 expression in human derived cardiac cells. Elevation of miR-143 and down-regulation of NPR3 levels were observed in hypoxia treated cells and in the myocardium from the rat myocardial infarction model. Taken together, these findings suggest miR-143 may be involved in the down-regulation of NPR3 which in turn may provide more cardiac protective bioactivity from NPs in heart failure, myocardial hypoxic stress and in myocardial infarction. In summary, NPR3 is negatively regulated by miR-143, pointing to the therapeutic potential of miR-143 to beneficially enhance NP responses.

Abstract 54: MicroRNA Let-7d-3p in Heart Failure

Circulating microRNA (miRNAs) levels are dysregulated in heart failure (HF) suggesting possible diagnostic and prognostic applications. In addition, miRNAs may yield insights into the pathophysiology of HF and provide targets for therapeutic intervention. We sought to identify the diagnostic utility of miRNAs in HF and to further investigate selected miRNAs as potential targets for therapeutic intervention. We hypothesized that distinct dysregulated circulating miRNAs in HF may be potential therapeutic targets to improve outcomes for HF.

Methods: Plasma from 338 well-characterized HF patients and 208 age-matched controls were collected for qPCR based miRNA profiling. Selected miRNAs of interest were further investigated using myocyte cell line, H9C2 and primary neonatal rat ventricular cardiomyocytes, NRVM.

Results: Seventy-four miRNAs (AUC>0.65, p<0.001) were significantly dysregulated for discrimination of HF from non-HF controls on receiver-operator analysis. Seven miRNAs of interest were selected for further investigation. Of these, let-7d-3p had the most up regulated miRNA fold change=1.32 (p<0.001 after FDR). Functional screening using mimic transfection demonstrated that let-7d-3p mimic increased CCK-8 activity and decreased LDH release in both H9C2 and NRVM during hypoxia. By in silico target prediction (miRDB, microRNA.org and Targetscan) and qPCR, mRNA targets YY1, KLF9, KLF12 and MEX3C were identified as candidate targets for let-7d-3p and were significantly downregulated by let-7d-3p mimic. This suggests that let-7d-3p may play a role in signaling pathways pertinent to cardiac development (YY1), cell proliferation/survival (KLF9 and KLF12) and adiposity (Mex3c).

Conclusions: We identified miRNAs that were dysregulated in clinical HF and our preliminary data on let-7d-3p suggests roles in the pathophysiology of HF that warrant further investigation.

Abstract 265: Identification of MicroRNA in an Ovine Model of Heart Failure

Introduction: The sheep ( Ovis aries ) provides a large animal model in cardiovascular research including heart failure (HF). However, microRNA (miR) related work in the sheep model has been limited due to a paucity of information regarding oar-miR. The aim of this study was to identify novel oar-miRs in myocardium and examine their regulation in HF and HF recovery.

Methods: Heart tissue was harvested from sheep undergoing 1. HF induced by rapid left ventricular (LV) pacing at 225bpm for 14 days, 2. HF recovery (HF-R) after discontinuation of pacing for an additional 14 days and 3. Sham. LV miRs were examined using next generation deep sequencing (NGS), miR array and stem-loop qPCR. Sequences were aligned with miRBase v20.0 and mapped to ovine genome and miRBase Mature BLAST search engine. Plasma was collected to assess natriuretic peptides (ANP and BNP).

Results: Three miR libraries were generated from NGS and a total of 619 miRs were detected. Of these, 93 were oar-miRs; 49 novel miRs (high confidence) mapped to ovine genome and perfectly aligned to mature miRs in other organisms (miRBase v20.0); 69 putative novel miRs (high confidence) that mapped to ovine genome and aligned partially to mature miRs of other species in miRBase v20.0; 168 miRs (low confidence) that mapped to ovine genome but unaligned to any known mature miRs; and 240 miRs (low confidence) that were unmapped to the sheep genome but aligned to either miRBase mature hsa-/mmu-/rno-miRs. Plasma BNP and ANP increased 19-folds and 18- folds respectively in HF, and returned to baseline in HF-R. MiR levels in HF model were examined using miR array. About 1000 miRs were detected from array and at least 301 of them were overlapped with NGS data. Using miR array profiling followed by stem-loop qPCR validation, we found that myocardial enriched miR-133b-3p, miR-208b-3p, miR-21-5p and miR-125a-5p, -125b-5p, -126-3p, -210-3p, and 29a-3p were significantly upregulated in HF (p<0.05 vs. Sham). All trended downwards towards baseline levels during recovery (HF-R) but only miR-210 was significant (p<0.001 vs. HF).

Conclusion: We identified 118 novel oar-miRs with high confidence and 408 potential oar-miRs, which is a solid foundation for miR function studies using sheep models. We also identified miR changes in HF and HF-R.

Abstract 100: Discovery of Cardiac Fibroblast Enriched microRNAs and Their Pivotal Roles in the Regulation of Cardiac Remodeling and Fibrosis

Cardiac fibroblast (cFB) responses to cardiac injury or overload directly contribute to deterioration of cardiac function in heart failure. MicroRNAs (miR) target multiple genes in cell signaling networks and are likely to have pivotal regulatory roles with respect to cFB function. To date cFB enriched miRs have not been reported. We have identified cFB enriched miRs which we hypothesize direct cFB proliferation and differentiation. Neonatal and adult rat cardiomyocytes (CM) and cFBs were isolated and cultured. In vivo and in vitro cardiac ischemic models comprised coronary artery ligation induced myocardial infarction (MI) in rats and cultured cFB exposed to hypoxia. RNA and protein were extracted for miR microarray, qPCR and Western Blot. Adult cFB transfected with miR mimics were tested for CCK-8 proliferation assay. Fifteen dysregulated miRs were selected from array profiles and qPCR validation. Among them miR-31, -199a, -214 and -222 were highly expressed in adult cFBs 10-90 folds vs. CM. CM specific miR-208a and 133a were undetectable in cFB. Neonatal cells showed directionally concordant but less pronounced differences. In early MI, cardiac miR-31 was up-regulated >30 fold vs. Sham (infarct), others increased 6-12 folds. All changes were ranked infarct>border>remote area. As a control, non-cFB enriched miR-125a remained unchanged. Hypoxia treatment of cFB in vitro up-regulated miR-31 but not the other miRs. Functional study by mimic transfection revealed differential roles of the miRs. MiR-31 increased cFB proliferation in CCK8 assay. MiR-199a and -222 had opposite effects. MiR-199a, but not miR-222, reversed the pro-fibrotic effects of TGF-β. MiR-199a reduced mRNA and protein expression of alpha smooth muscle actin (α-SMA), a myoFB differentiation marker and connective tissue growth factor (CTGF), a predicted target (miRDB). Conversely miR-31 increased α-SMA and CTGF. We provide the first report of 4 cFB enriched miRs and demonstrated their pro- vs. anti-fibrotic roles in vitro (miR-31 vs. miR-199 and -222 respectively). In early MI, the increase of pro-fibrotic miR-31 was predominant, whilst other miR dysregulation was secondary to cFB proliferation. cFB enriched miRs determine cFB fate and progression of cardiac fibrosis/remodeling.

Abstract 318: Targeting of Tp53inp1 by Mir-221 to Reduce P62-mediated Autophagy is Cardioprotective in Ischemia / Reperfusion Injury

Purpose: Tumor protein 53-induced nuclear protein 1 (Tp53inp1) acts as a tumor suppressor by inducing cell death. Tp53inp1 mRNA is a predicted target of miR-221. Whether targeting Tp53inp1 plays a role in miR-221-mediated cardioprotection has not been investigated. We hypothesized that miRNA-221 directly targets Tp53inp1 to reduce ischemia/reperfusion (I/R)-induced autophagy.

Method: Myoblast H9c2 cells underwent 16 hours 0.2% O 2 hypoxia followed by 2 hours re-oxygenation (H-R, simulating I/R). H9c2 were transfected with miRNA-221 mimic (25 nmol) and scrambled mimic control (miR-221 and MC). Cell count/viability, WST assay, cell injury-induced LDH release, and GFP-LC3 labeled autophagosome formation were measured. Cells were collected for RT-qPCR and western blot (WB) analyses. pCMV-Myc-Tp53inp1 and pcDNA3.1-Flag-p62 plasmids were cloned and transfected into H9c2 for recovery and immuno-precipitation (IP) studies. The effects of miRNA-221 inhibitor in H9c2 were also assessed.

Results: miR-221 significantly reduced H-R injury as indicated by higher cell count/viability and WST activity, and reduced LDH (miR-221 vs. MC p<0.05). qPCR confirmed that (1) miRNA-221 expression was reduced in H-R; (2) RISC-loaded (IP pull-down Ago-2) miRNA-221 increased by ~80 fold and reduced by 95% following mimic and inhibitor transfection respectively; (3) Increased Tp53inp1 following H-R was reversed by miR-221. miR-221 inhibited H-R induced autophagosome formation (GFP-LC3). WB indicated (1) increase of LC3-I/II ratio and p62, indicators of reduced autophagy, and (2) decrease of Tp53inp1 by miR-221. IP pull-down Myc-Tp53inp1 indicated the formation of p62-Tp53inp1 complex. The protective effect of miR-221 was abolished by Tp53inp1 overexpression (pCMV-Myc-Tp53inp1 and miRNA-221 mimic co-transfection). The protective effect was corroborated in neonatal rat ventricular myocytes (NRVM). MiRNA-221 inhibitor induced reverse effects.

Conclusion: The cardioprotection of miR-221 entails direct targeting of Tp53inp1 which reducing p62-Tp53inp1 complex formation and inhibiting H-R-induced autophagy.

Abstract 319: Mirna-125b Reduces Ischemia / Reperfusion (i/r)-induced Apoptosis Through Targeting Multiple Targets in Intrinsic and Extrinsic Apoptosis Pathways

Apoptosis is mediated through extrinsic and intrinsic pathways, both play a role in ischemia/reperfusion (I/R) injury. Predicted targets for miRNA-125b include extrinsic pathway mediators Traf6 and Tnfrsf1b, and intrinsic mitochondria regulators Bcl-2 family pro-apoptotic effectors Bak1 and BH3-only facilitators Bim, Bmf, Puma. We hypothesized that miRNA-125b directly targets multiple genes to reduce I/R-induced apoptosis. Myoblast H9c2 cells underwent 16 hours 0.2% O 2 hypoxia followed by 2 hours re-oxygenation (H-R, simulating I/R) and were transfected with miRNA-125b mimic vs. scrambled mimic control (25 nmol, miR-125b-M vs. MC) and miR-125b inhibitor vs. inhibitor control (miR-125b-I vs. IC). Cell count/viability, WST assay, cell injury-induced LDH release and apoptotic marker Casp3/7 were measured. Cells were trypsinized for assessment of apoptosis (7-AAD and annexin V double staining) and lysed for RT-qPCR and western blot (WB) analyses. pCMV-Myc-Bak1 plasmids were cloned and transfected into H9c2 for recovery studies. The effects were verified in neonatal rat ventricular myocytes (NRVM). miRNA-125b-M significantly reduced H-R injury as indicated by higher cell count/viability and WST activity, and reduced LDH (miR-125b-M vs. MC p<0.05). qPCR confirmed that (1) miR-125b expression was reduced in H-R; (2) RISC-loaded (immunoprecipitation pull-down Ago-2) miR-125b increased by ~35 fold and reduced to ~3% following mimic and inhibitor transfection respectively; (3) multiple apoptosis-related genes were reduced by miR-125b-M, Bak1, Bmf, Bim, Puma, Traf6 and Tnfrsf1b. All changes were confirmed by WB. Luciferase reporter assays indicated miR-125b bound to the 3’-UTR of all genes tested except Traf6. Total apoptotic cell numbers and Casp3/7 release were significantly reduced by miR-125b-M. The protective effect of miRNA-125b was partially abolished by Bak1 overexpression (pCMV-Myc-Bak1 and miR-125b co-transfection). Protective effects of miRNA-125b were further verified in NRVM. MiRNA-125b inhibitor reversed protective effects and target changes at mRNA and protein level. miR-125b is powerfully cardioprotective in I/R injury due to directly targeting multiple genes in the extrinsic and intrinsic apoptotic pathways.

Comparison of platinum chromium everolimus-eluting stent with cobalt chromium everolimus-eluting stent in unselected patients undergoing percutaneous coronary intervention

OBJECTIVE

The recent PLATINUM trial has demonstrated that the use of the new generation platinum chromium everolimus-eluting stents (PtCr-EES) yield clinical outcomes similar to those obtained by the use of cobalt chromium everolimus-eluting stents (CoCr-EES) in selected patients with 1 or 2 de novo coronary artery lesions. This study aimed to compare the safety and efficacy of the PtCr-EES and CoCr-EES in unselected patients from a real-life single-center registry.

PATIENTS AND METHODS

  From July 2009 through November 2010, 788 consecutive patients in our institution with symptomatic coronary artery disease who were treated with the CoCr-EES (n = 410) or PtCr-EES (n = 378) were enrolled into this study. The primary endpoint of the study was target-lesion failure (TLF) at 12-month follow-up and the secondary endpoints were major adverse cardiovascular events and stent thrombosis.

RESULTS

The prevalence of TLF in the PtCr-EES group (4.5%) was similar to that in the CoCr-EES group (3.9%). In addition, there were no significant differences in the 12-month rates of cardiac death (2.1% vs. 1.5%), myocardial infarction (2.4% vs. 3.9%), ischemia-driven target lesion revascularization (2.4% vs. 2.2%), and definite or probable stent thrombosis (0.5% vs. 1.5%, all p > 0.05).

CONCLUSIONS

At 12-month follow-up, the PtCr-EES is comparable in safety and efficacy to the CoCr-EES in unselected patients with coronary artery diseases.

High plasma thiocyanate levels are associated with enhanced myeloperoxidase-induced thiol oxidation and long-term survival in subjects following a first myocardial infarction

Elevated levels of myeloperoxidase (MPO) are associated with poor cardiovascular outcomes. MPO uses H2O2 to generate oxidants including HOCl and HOSCN, from chloride and thiocyanate (SCN(-)) ions, respectively. SCN(-) is the preferred substrate. Elevation of this anion decreases HOCl generation and increases HOSCN formation, a thiol-specific oxidant. Such changes are of potential relevance to people with elevated SCN(-) levels, such as smokers. In this retrospective study, we examined whether elevated plasma MPO and SCN(-) levels increased thiol oxidation as a result of increased HOSCN formation, and impacted on long-term survival in 176 subjects (74 non-smokers, 46 smokers, and 56 previous smokers) hospitalized after a first myocardial infarction. Plasma thiols were not significantly altered in smokers compared to non-smokers or past smokers. However, significant positive correlations were detected between SCN(-) levels and MPO-induced thiol loss in the total population (r = 0.19, P = 0.020) and smokers alone (r = 0.58, P < 0.0001). Twelve-year all-cause mortality data indicate that above median MPO is significantly associated with higher mortality, but below-median MPO and above-median SCN(-) results in increased survival, compared to below-median SCN(-). Cox proportional hazard analysis showed a significant decrease in mortality for each 1 μM increase in SCN(-) (0.991; P = 0.040). Subject age was, as expected, a strong predictor of subject survival. Overall these data suggest that subjects with below-median MPO and above-median SCN(-) have better long-term survival, and that elevated plasma levels of SCN(-) might be protective in at least some populations.

Genetic markers of repolarization and arrhythmic events after acute coronary syndromes

BACKGROUND

There is a genetic contribution to the risk of ventricular arrhythmias in survivors of acute coronary syndromes (ACS). We wished to explore the role of 33 candidate single nucleotide polymorphisms (SNPs) in prolonged repolarization and sudden death in patients surviving ACS.

METHODS

A total of 2,139 patients (1680 white ethnicity) surviving an admission for ACS were enrolled in the prospective Coronary Disease Cohort Study. Extensive clinical, echocardiographic, and neurohormonal data were collected for 12 months, and clinical events were recorded for a median of 5 years. Each SNP was assessed for association with sudden cardiac death (SCD)/cardiac arrest (CA) and prolonged repolarization at 3 time-points: index admission, 1 month, and 12 months postdischarge.

RESULTS

One hundred six SCD/CA events occurred during follow-up (6.3%). Three SNPs from 3 genes (rs17779747 [KCNJ2], rs876188 [C14orf64], rs3864180 [GPC5]) were significantly associated with SCD/CA in multivariable models (after correction for multiple testing); the minor allele of rs17779747 with a decreased risk (hazard ratio [HR] 0.68 per copy of the minor allele, 95% CI 0.50-0.92, P = .012), and rs876188 and rs386418 with an increased risk (HR 1.52 [95% CI 1.10-2.09, P = .011] and HR 1.34 [95% CI 1.04-1.82, P = .023], respectively). At 12 months postdischarge, rs10494366 and rs12143842 (NOS1AP) were significant predictors of prolonged repolarization (HR 1.32 [95% CI 1.04-1.67, P = .022] and HR 1.30 [95% CI 1.01-1.66, P = .038], respectively), but not at earlier time-points.

CONCLUSION

Three SNPs were associated with SCD/CA. Repolarization time was associated with variation in the NOS1AP gene. This study demonstrates a possible role for SNPs in risk stratification for arrhythmic events after ACS.

Code blue: Acinetobacter baumannii, a nosocomial pathogen with a role in the oral cavity

Actinetobacter baumannii is an important nosocomial pathogen that can cause a wide range of serious conditions including pneumonia, meningitis, necrotizing fasciitis and sepsis. It is also a major cause of wound infections in military personnel injured during the conflicts in Afghanistan and Iraq, leading to its popular nickname of 'Iraqibacter'. Contributing to its success in clinical settings is resistance to environmental stresses such as desiccation and disinfectants. Moreover, in recent years there has been a dramatic increase in the number of A. baumannii strains with resistance to multiple antibiotic classes. Acinetobacter baumannii is an inhabitant of oral biofilms, which can act as a reservoir for pneumonia and chronic obstructive pulmonary disease. Subgingival colonization by A. baumannii increases the risk of refractory periodontitis. Pathogenesis of the organism involves adherence, biofilm formation and iron acquisition. In addition, A. baumannii can induce apoptotic cell death in epithelial cells and kill hyphal forms of Candida albicans. Virulence factors that have been identified include pili, the outer membrane protein OmpA, phospholipases and extracellular polysaccharide. Acinetobacter baumannii can sense blue light through a blue-light sensing using flavin (BLUF) domain protein, BlsA. The resulting conformational change in BlsA leads to changes in gene expression, including virulence genes.

Abstract 107: MicroRNA-31: A Novel Therapeutic Target for Ischemic Heart Disease

MicroRNAs (miRNA), small sequences of non-coding RNA which interact with complementary sequences on the 3’untranslated region of target messenger RNAs to modulate translation, have a pivotal role in the development of the heart and its response to injury. Myocardial infarction (MI) triggers a dynamic miRNA response with the potential of yielding therapeutic targets. Following miRNA array profiling in rat hearts 2, 7 and 14 days after MI induced by coronary ligation, we identified a progressive time-dependent up-regulation of miR-31 compared to sham rats. Increase of miR-31 in heart tissue in the acute and subacute phases after MI (up to 90-fold) was also detected by Real-Time PCR (P=0.02 at day 2; P<0.0001 at days 7 and 14, vs. sham). We found that miR-31 has a repressive effect on tissue mRNA expression of cardiac troponin-T (TNNT2), E2F transcription factor 6 (E2F6) and mineralocorticoid receptor (NR3C2). Reporter gene assays showed that miR-31 targets the 3′UTR of these genes, with a marked repressive effect on TNNT2. In vitro, exposure to hypoxia significantly induced the expression of miR-31 in neonatal rat cardiomyocytes (nRCM), rat cardiac fibroblasts (nRCF) and cardiomyoblasts (H9C2) and suppressed the expression of TNNT2, E2F6 and NR3C2 in nRCM and H9C2 cells, and of E2F6 and NR3C2 in nRCF. LNA-based oligonucleotide inhibition of miR-31(miR-31i) in vitro reversed its repressive effect on translation from target genes. Therapeutic modulation of miR-31 expression in vivo after MI via subcutaneous administration of miR-31i (25mg/Kg/q2w) in rats, led to cardiac repression of miR-31 and subsequent enhanced expression of target genes. Also, miR-31i led to preservation of cardiac function and structure by day 14 after treatment. An absolute 10% improvement in left ventricular (LV) ejection fraction (EF) was observed in miR-31i-treated rats from day 2 to 16 after MI, while control rats that received scrambled LNA inhibitor or placebo displayed 23% deterioration in EF (n=6-8/group, P<0.0001). We conclude that miR-31 induction after MI is deleterious to cardiac function and plays an important role in adverse remodeling, while its therapeutic inhibition in vivo ameliorates cardiac dysfunction and prevents the development of post-ischemic heart failure.

Differences in late cardiovascular mortality following acute myocardial infarction in three major Asian ethnic groups

AIM

the purpose of this study was to investigate differences in long-term mortality following acute myocardial infarction (AMI) in patients from three major ethnicities of Asia.

METHODS AND RESULTS

We studied 15,151 patients hospitalized for AMI with a median follow-up of 7.3 years (maximum 12 years) in six publicly-funded hospitals in Singapore from 2000-2005. Overall and cause-specific cardiovascular (CV) mortality until 2012 were compared among three major ethnic groups that represent large parts of Asia: Chinese, Malay and Indian. Relative survival of all three ethnic groups was compared with a contemporaneous background reference population using the relative survival ratio (RSR) method. The median global registry of acute coronary events score was highest among Chinese, followed by Malay and Indians: 144 (25th percentile 119, 75th percentile 173), 138 (115, 167), and 131 (109, 160), respectively, p<0.0001; similarly, in-hospital mortality was highest among Chinese (9.8%) followed by Malay (7.6%) and Indian (6.4%) patients. In contrast, 12-year overall and cause-specific CV mortality was highest among Malay (46.2 and 32.0%) followed by Chinese (43.0 and 27.0%) and Indian (35.9 and 25.2%) patients, p<0.0001. The five-year RSR was lowest among Malay (RSR 0.69) followed by Chinese (RSR 0.73) and Indian (RSR 0.79) patients, compared with a background reference population (RSR 1.00).

CONCLUSIONS

We observed strong inter-Asian ethnic disparities in long-term mortality after AMI. Malay patients had the most discordant relationship between baseline risk and long-term mortality. Intensified interventions targeting Malay patients as a high-risk group are necessary to reduce disparities in long-term outcomes.

Hyperuricaemia and gout in New Zealand rural and urban Māori and non-Māori communities

BACKGROUND

There are few current data on the prevalence of hyperuricaemia and gout in New Zealand, particularly among the indigenous Māori population.

AIMS

To determine the prevalence of gout and hyperuricaemia in rural and urban Māori and non-Māori community samples and describe the treatment and comorbidities of participants with gout.

METHODS

Participants aged 20-64 years were recruited by random selection from the electoral roll. Māori samples were selected from among those identified as being of Māori descent on the roll and who self-identified as being of Māori ethnicity at interview. Personal medical history, blood pressure, anthropometrics, fasting lipids, glucose, HbA1c and urate were recorded.

RESULTS

There were 751 participants. Mean serum urate (SU) was 0.30 mmol/L (0.06-0.69 mmol/L). Māori had a significantly higher prevalence of hyperuricaemia (SU > 0.40 mmol/L) compared with non-Māori (17.0% vs 7.5%, P = 0.0003). A total of 57 participants had a history of gout, with a higher prevalence in Māori compared with non-Māori (10.3% vs 2.3%, P < 0.0001). Of the participants, 18/57 (31.6%) with gout were receiving urate-lowering therapy, but in 38.9%, SU was >0.36 mmol/L. Participants with gout were more likely to have metabolic syndrome, diabetes, cardiac disease or hypertension.

CONCLUSIONS

Gout and hyperuricaemia were more prevalent in Māori, and participants with gout were more likely to have comorbidities. There was not a higher overall adjusted cardiovascular disease risk in Māori participants with gout. Despite the high prevalence of gout, management remains suboptimal.

Impact of age, phenotype and cardio-renal function on plasma C-type and B-type natriuretic peptide forms in an adult population

CONTEXT

In contrast to the cardiac hormones, atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP), variations in plasma concentrations of C-type natriuretic peptide (CNP) in healthy adults are ill-defined, limiting their clinical application.

OBJECTIVE

Our objective was to define the effect of age, phenotype (gender, height, BMI), and cardiac and renal function on plasma CNPs in an adults population without renal or cardiovascular disease.

DESIGN AND SETTING

This was a prospective cross-sectional observational study of adult volunteers, aged 21-80 years, randomly selected from the electoral roll.

SUBJECTS AND METHODS

Plasma CNP and its associated aminoterminal propeptide (NTproCNP) were measured in 258 subjects and related to age, gender, height and plasma creatinine. Subgroup analyses seeking associations with cardiac function (plasma BNP and NTproBNP) and bone turnover bone-specific alkaline phosphatase (bALP) were also determined.

RESULTS

Plasma concentrations of CNPs in men continued to decline from adolescent values to reach a nadir in the 5th decade after which values increased. Similar but less marked changes occurred in women. In both sexes, NTproCNP was inversely and independently correlated with height. In contrast to B-type natriuretic peptides (BNPs), NTproCNP was higher in men, significantly related to creatinine and positively related to bALP.

CONCLUSIONS

Gender- and age-specific changes affect CNPs in adults. Inverse associations of NTproCNP with adult height, positive correlation with creatinine - and in contrast to CNP - no association with BNP are further unique findings distinguishing NTproCNP, which need to be considered in future studies.

Comparative pharmacokinetics and pharmacodynamics of urocortins 1, 2 and 3 in healthy sheep

BACKGROUND AND PURPOSE The urocortin (Ucn) peptides are emerging as potential therapeutic targets for heart disease. However, pharmacokinetic (PK) and pharmacodynamic (PD) data are lacking. Therefore, we investigated the PK/PD for all three Ucns. EXPERIMENTAL APPROACH Seven sheep received 1 µg·kg(-1) boluses of Ucn1, Ucn2 and Ucn3. Population PK/PD models were developed to describe the time course of the haemodynamic effects. RESULTS The population estimate for Ucn1 clearance (0.486 L·h(-1)) was lower than that for Ucn2 (21.7 L·h(-1)) and Ucn3 (220 L·h(-1)), while steady-state volumes of distribution were similar for Ucn1 and Ucn2 (∼8 L) but substantially larger for Ucn3 (23.5 L). Ucn1 disposition was adequately described by a two-compartment model, with a one-compartment model required for Ucn2 and Ucn3. The half-life for Ucn1 was 2.9 h (α phase) and 8.3 h (β phase), and 15.7 and 4.4 min for Ucn2 and Ucn3 respectively. All Ucns produced significant increases in heart rate, cardiac output and left ventricular systolic and mean arterial pressures, and decreases in left atrial pressure and peripheral resistance. Delayed-effect pharmacodynamic models best described the time course of haemodynamic responses, with effects more rapid and less prolonged for Ucn2 and Ucn3 than Ucn1. Similar and physiologically plausible estimated baseline (E(0)) effects were exhibited by all Ucns, whereas EC(50) values were generally greater for Ucn1. CONCLUSIONS AND IMPLICATIONS Relative to Ucn1, both the PK and haemodynamic responses to Ucn2 and Ucn3 occurred more rapidly. Our data provide important comparative information, useful to the rational design of future clinical studies.

Genetic variation in the renin-angiotensin-aldosterone system is associated with cardiovascular risk factors and early mortality in established coronary heart disease

This study examined renin-angiotensin-aldosterone (RAAS) system gene variants for associations with cardiovascular risk factors and outcomes in coronary heart disease. Coronary disease patients (n=1186) were genotyped for 21 single-nucleotide polymorphisms (SNPs) within angiotensinogen (AGT), angiotensin-converting enzyme (ACE), angiotensin-II type-1 receptor (AGTR1) and aldosterone synthase (CYP11B2). Associations with all-cause mortality and cardiovascular readmissions were assessed over a median of 3.0 years. The AGT M235T 'T' allele was associated with a younger age of clinical coronary disease onset (P=0.006), and the AGT rs2478545 minor allele was associated with lower circulating natriuretic peptides (P=0.0001-P=0.001) and E/E(1) (P=0.018). Minor alleles of AGT SNPs rs1926723 and rs11122576 were associated with more frequent history of renal disease (P0.04) and type-2 diabetes (P0.02), higher body mass index (P0.02) and greater mortality (P0.007). AGT rs11568054 minor allele carriers had more frequent history of renal disease (P=0.04) and higher plasma creatinine (P=0.033). AGT rs6687360 minor allele carriers exhibited worse survival (P=0.02). ACE rs4267385 was associated with older clinical coronary disease onset (P=0.008) and hypertension (P=0.013) onset, increased plasma creatinine (P=0.01), yet greater mortality (P=0.044). Less history of hypertension was observed with the AGTR1 rs12685977 minor allele (P=0.039). Genetic variation within the RAAS was associated with cardiovascular risk factors and accordingly poorer survival.

Pharmacodynamic responses of plasma and tissue C-type natriuretic peptide to GH: correlation with linear growth in GH-deficient rats

Studies from genetic modification and spontaneous mutations show that C-type natriuretic peptide (CNP) signalling plays an essential part in postnatal endochondral growth, but measurement of CNP proteins and changes in their abundance in tissues and plasma during normal growth has not been reported. Using rodent pups with GH deficiency, we now describe the pharmacodynamic response of CNP and rat amino-terminal proCNP (NTproCNP) in plasma and tissues, and relate these to changes in linear growth (nose-tail length, tibial length and tibial growth plate width) during the course of 1 week of GH or saline (control) administration. Compared with saline, significant increases in plasma and tissue CNP forms were observed after 24 h in GH-treated pups and before any detectable change in linear growth. Whereas CNP abundance was increased in most tissues (muscle, heart and liver) by GH, enrichment was the greatest in extracts from growth plates and kidney. Plasma and tissue concentrations in GH-treated pups were sustained or further increased at 1 week when strong positive associations were found between plasma NTproCNP and linear growth or tissue concentrations. High content of NTproCNP in kidney tissue strongly correlated with plasma concentrations, which is consistent with previous data showing renal extraction of the peptide. In showing a prompt and significant increase in CNP in tissues driving normal endochondral growth, these findings provide further rationale for CNP agonists in the treatment of growth disorders resistant to current therapies and support the use of CNP concentrations as biomarkers of linear growth.

KCNE5 polymorphism rs697829 is associated with QT interval and survival in acute coronary syndromes patients

INTRODUCTION

The KCNE family is a group of small transmembrane channel proteins involved in potassium ion (K(+)) conductance. The X-linked KCNE5 gene encodes a regulator of the K(+) current mediated by the potassium channel KCNQ1. Polymorphisms in KCNE5 have been associated with altered cardiac electrophysiological properties in human studies. We investigated associations of the common rs697829 polymorphism from KCNE5 with baseline characteristics, baseline electrocardiographic (ECG) measurements, and patient survival in a cohort of post-acute coronary syndromes (ACS) patients (the Coronary Disease Cohort Study cohort).

METHODS AND RESULTS

DNA samples (n = 1,740) were genotyped for rs697829 using a TaqMan assay. Baseline ECG data revealed corrected QT (QTc) interval was associated with rs697829 in male, but not female, patients, being extended in the G genotype group (A 416 ± 1.71; G 431 ± 4.25 ms, P = 0.002). Covariate-adjusted survival was poorest in G genotype patients in Cox proportional hazard modeling of mortality data of males (P(overall) = 0.020). Male patients with G genotype had a hazard ratio of 1.44 (1.11-2.33) for death when compared to the A genotype male patients (P = 0.048) after adjustment for age, baseline log-transformed N-terminal pro-B-type natriuretic peptide (NTproBNP), β-blocker and insulin treatment, QTc interval, history of myocardial infarction, and physical activity score.

CONCLUSION

This study suggests an association between rs697829, a common single nucleotide polymorphism (SNP) from KCNE5, and ECG measurements and survival in postacute ACS patients. Prolonged subclinical QT interval may be a marker of adverse outcome in this group of patients. 

Regional vascular response to ProAngiotensin-12 (PA12) through the rat arterial system

ProAngiotensin-12 (PA12) is the most recent peptide to be identified as a functional component of the renin-angiotensin system (RAS). PA12 is reported to constrict rat coronary arteries and the aorta, dependent upon angiotensin II-converting enzyme 1 (ACE1) and chymase. The current study employed myography to determine the direct vascular effects of PA12 on a range of isolated rat arteries extending from the core to periphery. PA12 significantly constricted the descending thoracic aorta, right and left common carotid arteries, abdominal aorta and superior mesenteric artery, with little effect on the femoral and renal arteries. AngII was found to produce similar responses to PA12 when administered at the same dose. A potency gradient in response to PA12 was clearly apparent, with vessels in closest proximity to the heart responding with the greatest constriction; while constrictive potency was lost further form the heart. Inhibition of ACE1 and chymase both significantly attenuated PA12-induced vasoconstriction, with chymostatin displaying lesser potency. We postulate ACE1 primarily regulates RAS activity within the circulation, while chymase may have an important role in local, tissue-based RAS activity.

Subsidence of uncemented stems in osteoporotic and non-osteoporotic cadaveric femora

The increased use of uncemented stems for hip arthroplasty and of fast-recovery protocols in elderly patients make initial stem stability and resistance to fracture critical factors in osteoporotic bone. In this paper, the subsidence and failure of two uncemented stem designs (M/L Taper and VerSys Fullcoat, Zimmer, Inc, Warsaw, Indiana, USA) in osteoporotic and non-osteoporotic cadaveric femora were compared under simulated walking conditions (axial compression and external rotation). Osteoporotic femora implanted with either stem design failed significantly more frequently than did non-osteoporotic femora. Femora implanted with the M/L stems (seven of ten by 1000 cycles) fractured earlier than did femora implanted with the Fullcoat stem (one of ten by 1000 cycles). The use of early weight-bearing protocols with uncemented stem designs in osteoporotic bone should be approached with caution.