Col4a3-/- Mice on Balb/C Background Have Less Severe Cardiorespiratory Phenotype and SGLT2 Over-Expression Compared to 129x1/SvJ and C57Bl/6 Backgrounds.

Alport syndrome (AS) is a hereditary renal disorder with no etiological therapy. In the preclinical Col4a3-/- model of AS, disease progression and severity vary depending on mouse strain. The sodium-glucose cotransporter 2 (SGLT2) is emerging as an attractive therapeutic target in cardiac/renal pathologies, but its application to AS remains untested. This study investigates cardiorespiratory function and SGLT2 renal expression in Col4a3-/- mice from three different genetic backgrounds, 129x1/SvJ, C57Bl/6 and Balb/C. male Col4a3-/- 129x1/SvJ mice displayed alterations consistent with heart failure with preserved ejection fraction (HFpEF). Female, but not male, C57Bl/6 and Balb/C Col4a3-/- mice exhibited mild changes in systolic and diastolic function of the heart by echocardiography. Male C57Bl/6 Col4a3-/- mice presented systolic dysfunction by invasive hemodynamic analysis. All strains except Balb/C males demonstrated alterations in respiratory function. SGLT2 expression was significantly increased in AS compared to WT mice from all strains. However, cardiorespiratory abnormalities and SGLT2 over-expression were significantly less in AS Balb/C mice compared to the other two strains. Systolic blood pressure was significantly elevated only in mutant 129x1/SvJ mice. The results provide further evidence for strain-dependent cardiorespiratory and hypertensive phenotype variations in mouse AS models, corroborated by renal SGLT2 expression, and support ongoing initiatives to develop SGLT2 inhibitors for the treatment of AS.

Cardiac conduction abnormalities associated with pacemaker implantation after transcatheter aortic valve replacement.

BACKGROUND: Complete heart block is a known complication after transcatheter aortic valve replacement (TAVR), often requiring pacemaker implantation within 24 hours of the procedure. However, clinical markers for delayed progression to complete heart block after TAVR remain unclear. OBJECTIVES: We examined electrocardiographic data that may correlate with delayed progression to complete heart block and need for pacemaker. METHODS: This is a single-center retrospective study of 608 patients who underwent TAVR between April 2008 and June 2017. We excluded 164 (27.0%) patients due to having a pacemaker before the procedure or expiring within 24 hours of the procedure (8, 1.3%). We excluded an additional 50 (8.2%) patients who received a pacemaker within 24 hours of the procedure. Electrocardiograms (EKGs) obtained after the procedure were compared to the preprocedural EKG to detect new changes. RESULTS: Left bundle branch block, intraventricular conduction delay, left anterior fascicular block, and right bundle branch block were the most commonly seen conduction abnormalities after TAVR (25.1%, 10.9%, 7.5%, and 3.6%, respectively). Both left bundle branch block (odds ratio [OR] = 2.77 [95% confidence interval (CI): 1.24-6.22]) and right bundle branch block (OR = 13.2 [95% CI: 4.18-41.70]) carried an increased risk of pacemaker implantation after TAVR. Additionally, ΔPR greater than 40 ms from baseline also carried an increased risk of pacemaker implantation (OR = 3.53 [95% CI: 1.49-8.37]). CONCLUSION: Left bundle branch block, right bundle branch block, and ΔPR greater than 40 ms were all associated with delayed progression to complete heart block and need for pacemaker implantation after TAVR.

A comprehensive review of coronary artery disease in patients with end-stage liver disease.

The prevalence of coronary artery disease has increased in patients with end stage liver disease. In the near future, non-alcoholic steatohepatitis is expected to be the leading cause of end stage liver disease and shares common risk factors with coronary artery disease such as hypertension, hyperlipidemia, obesity and diabetes mellitus. At present, liver transplantation is the only definitive treatment for end stage liver disease, with post-operative mortality associated with the presence of coronary artery disease. Given the high prevalence of cardiovascular disease and the unique balance of pro-thrombotic and antithrombotic factors in patients with end stage liver disease, we sought to discuss the non-invasive and invasive diagnosis, medical and procedural management considerations and pre-transplant evaluation of coronary artery disease in patients with end stage liver disease.

Osteopontin Promotes Left Ventricular Diastolic Dysfunction Through a Mitochondrial Pathway.

BACKGROUND: Patients with chronic kidney disease (CKD) and coincident heart failure with preserved ejection fraction (HFpEF) may constitute a distinct HFpEF phenotype. Osteopontin (OPN) is a biomarker of HFpEF and predictive of disease outcome. We recently reported that OPN blockade reversed hypertension, mitochondrial dysfunction, and kidney failure in Col4a3-/- mice, a model of human Alport syndrome. OBJECTIVES: The purpose of this study was to identify potential OPN targets in biopsies of HF patients, healthy control subjects, and human induced pluripotent stem cell-derived cardiomyocytes (hiPS-CMs), and to characterize the cardiac phenotype of Col4a3-/- mice, relate this to HFpEF, and investigate possible causative roles for OPN in driving the cardiomyopathy. METHODS: OGDHL mRNA and protein were quantified in myocardial samples from patients with HFpEF, heart failure with reduced ejection fraction, and donor control subjects. OGDHL expression was quantified in hiPS-CMs treated with or without anti-OPN antibody. Cardiac parameters were evaluated in Col4a3-/- mice with and without global OPN knockout or AAV9-mediated delivery of 2-oxoglutarate dehydrogenase-like (Ogdhl) to the heart. RESULTS: OGDHL mRNA and protein displayed abnormal abundances in cardiac biopsies of HFpEF (n = 17) compared with donor control subjects (n = 12; p < 0.01) or heart failure with reduced ejection fraction patients (n = 12; p < 0.05). Blockade of OPN in hiPS-CMs conferred increased OGDHL expression. Col4a3-/- mice demonstrated cardiomyopathy with similarities to HFpEF, including diastolic dysfunction, cardiac hypertrophy and fibrosis, pulmonary edema, and impaired mitochondrial function. The cardiomyopathy was ameliorated by Opn-/- coincident with improved renal function and increased expression of Ogdhl. Heart-specific overexpression of Ogdhl in Col4a3-/- mice also improved cardiac function and cardiomyocyte energy state. CONCLUSIONS: Col4a3-/- mice present a model of HFpEF secondary to CKD wherein OPN and OGDHL are intermediates, and possibly therapeutic targets.