Nguyen, T. T.

Abstract Background A genome-wide association study (GWAS) assessing change in left ventricular ejection fraction (LVEF) in dilated cardiomyopathy (DCM), a surrogate marker of morbidity and mortality in heart failure (HF), had not been performed previously and could provide insight into novel biological pathways that could lead to the development of new drugs that might target myocardial recovery. The presence and extent of cardiac fibrosis in DCM is independently associated with myocardial recovery and cardiovascular mortality. Purpose To identify the biological relevance of genetic targets that are associated with change in LVEF in patients with DCM. Methods A GWAS was performed using DNA from 686 patients with recent onset DCM who were on standard HF therapy using change in LVEF at a median of 6 months after initial diagnosis. Cultured human cardiac fibroblasts (HCFs) were used as an in vitro model to study the functional and biological relevance of the gene target identified in the GWAS. Specifically, HCFs were transfected with siRNA by using the Lipofectamine™ RNAiMAX Transfection Reagent for gene knockdown (KD). RNA-seq was performed using the Illumina TruSeq protocol with expression analysis conducted with the EdgeR package. Ingenuity Pathway Analysis was used. Results A single-nucleotide polymorphism, rs11105445(G>A), mapping to the neuron navigator 3 (NAV3) gene (rs11105445, p=2.37E-07; beta 2.74±0.53) was associated with improvement in LVEF. We performed a phenome-wide association study using data from the UK Biobank and demonstrated that genetic variation in NAV3 was significantly associated with HF mortality (p=3.2E-28), highlighting the potential importance of this gene in HF. Using GTEx data we demonstrated that in LV tissue the minor allele A was associated with ↓NAV3 expression (p=0.03) suggesting that ↓NAV3 expression might be associated with improvement in LVEF. We demonstrated that NAV3 KD significantly ↓TGF-β1 mediated HCF transdifferentiation into myofibroblasts, ↓α-smooth muscle actin (ACTA2) and ↓collagen I (COL1A1), therefore NAV3 KD was anti-fibrotic (see Figure 1), 1a. HCFs treated by vehicle/TGF-β1 after KD of NAV3/ctrl, and ACTA2 and COL1A1 were analyzed by qPCR; 1b. Representative immunofluorescence staining for α-SMA (in green), RNA-seq after NAV3 KD followed by pathway analysis suggested that NAV3 exerted its effect by regulating cell cycle related proteins (Figure 2), 2a. Volcano plot shows significant differentially expressed genes identified by RNA-seq analysis (down-regulated in blue, up-regulated in red); 2b. NAV3 KD significantly increased expression of cell cycle related proteins, which was validated by Western blot. Conclusions Decreased expression of NAV3 is associated with myocardial recovery in DCM, most likely due to its anti-fibrotic effect via direct regulation of cell cycle proteins. The role of NAV3 as a novel therapeutic target in DCM needs to be explored. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): Mayo Clinic Center for Individualized MedicineMayo Clinic Department of Cardiovascular Medicine

These studies were conducted to determine whether there are gender-specific regional differences in meal triglyceride fatty acid uptake. Systemic and regional oleate ([3H]oleate) kinetics were measured in nine nonobese men and eight nonobese women before and at the end of a 6-h meal, administered as small frequent feedings to achieve steady-state chylomicronemia. Chylomicron uptake in the splanchnic bed accounted for 71 +/- 15% of meal triglyceride disappearance in men and 20 +/- 7% in women (P < 0.01), whereas leg chylomicron uptake could only account for 12 +/- 2 and 8 +/- 4% (P not significant in men vs. women) of meal triglyceride disappearance. Meal ingestion suppressed (P < 0.05) systemic and regional free fatty acid release in both men and women. Splanchnic nonchylomicron triglyceride release and leg nonchylomicron triglyceride uptake were not significantly different in men and women. In summary, the largest quantitative difference between men and women in fatty acid kinetics during meal ingestion is a substantially greater splanchnic uptake of meal triglyceride fatty acids in men. This could represent greater meal fatty acid storage in visceral adipose tissue.

Abstract The aim of this study was to examine the role of HDL subparticles with apolipoprotein (apo) A-I alone (LpA-I) and with apoA-I and apoA-II (LpA-I/A-II) in predicting coronary artery disease. Concentrations of these HDL subparticles were compared in 184 subjects with angiographically confirmed significant coronary artery disease (>50% stenosis of at least one vessel) and 191 age- and sex-matched control subjects without clinical coronary artery disease. LpA-I and LpA-I/A-II were measured with magnetic beads coated with anti–apoA-II antibodies to separate particles containing apoA-II from plasma. Total plasma cholesterol and triglyceride levels were similar in both groups. Although subjects with coronary artery disease had lower HDL cholesterol, plasma apoA-I, LpA-I, and LpA-I/A-II than age- and sex-matched control subjects without coronary artery disease, plasma apoA-I was the best predictor of coronary artery disease. In conclusion, LpA-I and LpA-I/A-II are lower in subjects with coronary artery disease but do not add to plasma apoA-I in predicting the presence of coronary artery disease.