Wang, Thomas J.

Moritz F Sinner, 2012 Finalist and Presenting Author

Introduction: Through degradation of the cardio- and renal-protective second messenger cyclic GMP, phosphodiesterase-9 (PDE9) excess may contribute to cardiomyocyte hypertrophy, fibrosis, and renal dysfunction, common features in heart failure with preserved ejection fraction (HFpEF) development and progression. Hypothesis: Selective PDE9 inhibition with IMR-687 mitigates an adverse cardiac and renal phenotype in mouse models of HFpEF. Methods: Cardiac and renal responses to IMR-687 (60 mg/kg, 100 mg/kg) compared with vehicle were examined over 6-8 weeks in 3 adult male mouse models of HFpEF (1.5 mg/kg/d angiotensin-II infusion [ang-II]; uninephrectomy + 0.30 ug/h d-aldosterone infusion + 1% NaCl drinking water [neph-aldo]; and db/db [db]). Phenotyping included wheat germ agglutinin staining for cardiomyocyte cross-sectional area (CSA); RT-PCR for myocardial PDE9, natriuretic peptide, inflammatory and fibrosis marker transcript abundances; ELISA for plasma natriuretic peptides; and urinary albumin to creatinine ratio (UACR). Results: IMR-687 reduced median cardiomyocyte size (CSA) by 54, 58, and 35% compared with vehicle in the ang-II, neph-aldo, and db models, respectively; p < 0.003 for all. Myocardial PDE9, NPPA, NPPB, COL3A1, and IL-1β expression were decreased by IMR-687 in all models (Table). Median plasma BNP levels (pg/mL) were lower in IMR-687 vs. vehicle treated mice in all models (ang-II: 2376 vs. 5757; neph-aldo: 1216 vs. 1860; db: 830 vs. 1216); p < 0.007 for all, with similar findings for ANP (Table). UACR was lower in IMR-687 compared with vehicle treated mice in all models (Table). Heart rate and blood pressure did not differ between IMR-687 and vehicle treated mice. Conclusion: Selective PDE9 inhibition with IMR-687 was effective for prevention and treatment of cardiac hypertrophy and renal dysfunction in 3 different preclinical models of HFpEF. IMR-687 may be a promising candidate therapy for testing in clinical trials of human HFpEF.

Heart failure with preserved ejection fraction (HFpEF), a major public health problem that is rising in prevalence, is associated with high morbidity and mortality and is considered to be the greatest unmet need in cardiovascular medicine today because of a general lack of effective treatments. To address this challenging syndrome, the National Heart, Lung, and Blood Institute convened a working group made up of experts in HFpEF and novel research methodologies to discuss research gaps and to prioritize research directions over the next decade. Here, we summarize the discussion of the working group, followed by key recommendations for future research priorities. There was uniform recognition that HFpEF is a highly integrated, multiorgan, systemic disorder requiring a multipronged investigative approach in both humans and animal models to improve understanding of mechanisms and treatment of HFpEF. It was recognized that advances in the understanding of basic mechanisms and the roles of inflammation, macrovascular and microvascular dysfunction, fibrosis, and tissue remodeling are needed and ideally would be obtained from (1) improved animal models, including large animal models, which incorporate the effects of aging and associated comorbid conditions; (2) repositories of deeply phenotyped physiological data and human tissue, made accessible to researchers to enhance collaboration and research advances; and (3) novel research methods that take advantage of computational advances and multiscale modeling for the analysis of complex, high-density data across multiple domains. The working group emphasized the need for interactions among basic, translational, clinical, and epidemiological scientists and across organ systems and cell types, leveraging different areas or research focus, and between research centers. A network of collaborative centers to accelerate basic, translational, and clinical research of pathobiological mechanisms and treatment strategies in HFpEF was discussed as an example of a strategy to advance research progress. This resource would facilitate comprehensive, deep phenotyping of a multicenter HFpEF patient cohort with standardized protocols and a robust biorepository. The research priorities outlined in this document are meant to stimulate scientific advances in HFpEF by providing a road map for future collaborative investigations among a diverse group of scientists across multiple domains.

Objective Natriuretic peptides (NPs) are hormones with cardioprotective effects. NP levels vary by race; however, the pathophysiological consequences of lower NP levels are not well understood. We aimed to quantify the association between NPs and endothelial function as measured by flow-mediated dilation (FMD) and the contribution of NP levels to racial differences in endothelial function. Methods In this cross-sectional study of 2938 Multi-Ethnic Study of Atherosclerosis participants (34% Caucasian, 20% African-American, 20% Asian-American and 26% Hispanic) without cardiovascular disease at baseline, multivariable linear regression models were used to examine the association between serum N-terminal pro-B-type NP (NT-proBNP) and natural log-transformed FMD. We also tested whether NT-proBNP mediated the relationship between race and FMD using the product of coefficients method. Results Among African-American and Chinese-American individuals, lower NT-proBNP levels were associated with lower FMD, β=0.06 (95% CI: 0.03 to 0.09; p<0.001) and β=0.06 (95% CI: 0.02 to 0.09; p=0.002), respectively. Non-significant associations between NT-proBNP and FMD were found in Hispanic and Caucasian individuals. In multivariable models, endothelial function differed by race, with African-American individuals having the lowest FMD compared with Caucasians, p<0.001. Racial differences in FMD among African-Americans and Chinese-Americans were mediated in part by NT-proBNP levels (African-Americans, mediation effect: −0.03(95% CI: −0.05 to −0.01); Chinese-Americans, mediation effect: −0.03(95% CI: −0.05 to −0.01)). Conclusions Lower NP levels are associated with worse endothelial function among African-Americans and Chinese-Americans. A relative NP deficiency in some racial/ethnic groups may contribute to differences in vascular function.

Background: Proteomic approaches allow measurement of thousands of proteins in a single specimen, which can accelerate biomarker discovery. However, applying these technologies to massive biobanks is not currently feasible because of the practical barriers and costs of implementing such assays at scale. To overcome these challenges, we used a “virtual proteomic” approach, linking genetically predicted protein levels to clinical diagnoses in >40 000 individuals. Methods: We used genome-wide association data from the Framingham Heart Study (n=759) to construct genetic predictors for 1129 plasma protein levels. We validated the genetic predictors for 268 proteins and used them to compute predicted protein levels in 41 288 genotyped individuals in the Electronic Medical Records and Genomics (eMERGE) cohort. We tested associations for each predicted protein with 1128 clinical phenotypes. Lead associations were validated with directly measured protein levels and either low-density lipoprotein cholesterol or subclinical atherosclerosis in the MDCS (Malmö Diet and Cancer Study; n=651). Results: In the virtual proteomic analysis in eMERGE, 55 proteins were associated with 89 distinct diagnoses at a false discovery rate q<0.1. Among these, 13 associations involved lipid (n=7) or atherosclerosis (n=6) phenotypes. We tested each association for validation in MDCS using directly measured protein levels. At Bonferroni-adjusted significance thresholds, levels of apolipoprotein E isoforms were associated with hyperlipidemia, and circulating C-type lectin domain family 1 member B and platelet-derived growth factor receptor-β predicted subclinical atherosclerosis. Odds ratios for carotid atherosclerosis were 1.31 (95% CI, 1.08–1.58; P =0.006) per 1-SD increment in C-type lectin domain family 1 member B and 0.79 (0.66–0.94; P =0.008) per 1-SD increment in platelet-derived growth factor receptor-β. Conclusions: We demonstrate a biomarker discovery paradigm to identify candidate biomarkers of cardiovascular and other diseases.

Background In epidemiologic studies, obesity has been associated with reduced natriuretic peptide ( NP ) concentrations. Reduced NP production could impair the ability of obese individuals to respond to salt loads, increasing the risk of hypertension and other disorders. We hypothesized that weight loss enhances NP production before and after salt loading. Methods and Results We enrolled 15 obese individuals (mean BMI 45±5.4 kg/m 2 ) undergoing gastric bypass surgery. Before and 6 months after surgery, subjects were admitted to the clinical research center and administered a large‐volume intravenous saline challenge. Echocardiography and serial blood sampling were performed. From the pre‐operative visit to 6 months after surgery, subjects had a mean BMI decrease of 27%. At the 6‐month visit, N‐terminal pro‐atrial NP (Nt‐pro ANP ) levels were 40% higher before, during, and after the saline infusion, compared with levels measured at the same time points during the pre‐operative visit ( P <0.001). The rise in Nt‐pro‐ ANP induced by the saline infusion (≈50%) was similar both before and after surgery (saline, P <0.001; interaction, P =0.2). Similar results were obtained for BNP and Nt‐pro BNP ; resting concentrations increased by 50% and 31%, respectively, after gastric bypass surgery. The increase in NP concentrations after surgery was accompanied by significant decreases in mean arterial pressure ( P =0.004) and heart rate ( P <0.001), and an increase in mitral annular diastolic velocity ( P =0.02). Conclusion In obese individuals, weight loss is associated with a substantial increase in the “setpoint” of circulating NP concentrations. Higher NP concentrations could contribute to an enhanced ability to handle salt loads after weight loss.