Thick and Thin Filament Dysfunction in Obese Heart Failure with Preserved Ejection Fraction

射血分数保留的肥胖性心力衰竭的粗细丝功能障碍

• 批准号: 10678204
• 负责人: Vivek Pinakin Jani
• 金额: $ 5.27万
• 依托单位: JOHNS HOPKINS UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-05-01 至 2025-04-30
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10678204
• 关键词: Actins; Affect; Basic Science; Biological Assay; Biomechanics; Biopsy; Body mass index; Calcium; Cardiac; Cardiac Myocytes; Cardiovascular Diseases; Cardiovascular system; Cells; Clinical; Complex; Data; Depressed mood; Disease; EFRAC; Enhancers; Enzymes; Exhibits; Exposure to; Filament; Freezing; Functional disorder; Future; Generations; Goals; Head; Heart failure; Human; Hypertension; Hypertrophy; Label; Laboratories; Link; Location; Measures; Mediating; Medicine; Mental Depression; Metabolic syndrome; Microfilaments; Molecular Biology Techniques; Molecular Conformation; Morbidity - disease rate; Muscle Cells; Mutagenesis; Myocardium; Myosin ATPase; Myosin Type I; Obesity; Patients; Pattern; Phenotype; Phosphorylation; Phosphorylation Site; Phosphotransferases; Physicians; Physiologic pulse; Positioning Attribute; Production; Protein Kinase C; Protein phosphatase; Protein-Serine-Threonine Kinases; Proteins; Relaxation; Reporting; Research; Role; Sarcomeres; Scientist; Serine/Threonine Phosphorylation; Site; Skin; Structure; Synchrotrons; Syndrome; Techniques; Test Result; Testing; Thick; Thick Filament; Thin Filament; Thinness; Threonine; Training; Transgenic Organisms; Tropomyosin; Troponin; Troponin I; Ventricular; Work; X ray diffraction analysis; career; comorbidity; effective therapy; heart preservation; mimetics; novel; novel strategies; novel therapeutics; obese patients; pandemic disease; phosphoproteomics; preservation; skills; small molecule; systolic hypertension

PROJECT SUMMARY Heart Failure with Preserved Ejection (HFpEF) is one of the largest unmet needs of all cardiovascular disease. Although it now is the most common form of heart failure, to date, it has little to no specific effective therapy. An obesity pandemic has now changed its phenotype, with obesity and metabolic syndrome now significant drivers of the disease. We recently reported that an obese-HFpEF phenotype exhibits striking depression of right ventricular myocyte tension generation at higher (contraction-related) levels of calcium. Critically, the mechanism by which this occurs is unknown. Myocyte tension is regulated by both the thick filament, consisting of myosin, and the thin filament, consisting of actin, tropomyosin, and cardiac troponins. In the thick filament, approximately half of all myosin heads are in a conformation known as the super-relaxed (SRX) state, and the proportion of myosin in this state is an important regulator of tension. The thin filament regulates tension by altering calcium sensitivity, and one regulator is phosphorylation of cardiac troponin I (cTnI). In exciting new preliminary data, I find that thick filament structure and phosphorylation of myofilament proteins are altered in obese-HFpEF. This proposal derives from these data and aims to elucidate how obesity alters the thick and thin filament in human HFpEF. In Aim 1, I will test the hypothesis that structural inactivation of the thick filament in obese-HFpEF results from an excess of SRX myosin. To assess thick filament structure, I use small angle x-ray diffraction, a technique that leverages the ordered structure of cardiac muscle to quantify distances between sarcomere proteins. This technique is performed at the synchrotron at Argonne National Laboratory, one of few locations globally that can perform the assay, and this proposal describes the first application of this technique to endomyocardial biopsies from human HFpEF patients. While informative, X-ray diffraction on its own cannot prove the presence of excess SRX myosin. For this, I will measure the myosin ATP turnover from single cardiomyocytes from HFpEF patients. I will then explore whether obesity is a driver of excess SRX myosin by measuring both assays in HFpEF patients with both obesity and hypertension/hypertrophy. In Aim 2, I explore the mechanism underlying how hyperphosphorylation alters calcium activated tension. My preliminary data finds that the exposure to enzymatically active protein phosphatase 2A (PP2A) partially reverses the deficit observed in calcium activated tension in obese HFpEF, but the mechanism is unknown. I will test if this is from thick filament activation by measuring x-ray diffraction patterns and myosin ATP turnover after PP2A exposure. I also test if this results from thin filament hyperphosphorylation, specifically at cTnI, in HFpEF. We have identified a novel threonine 181 residue of cTnI to be hyperphosphorylated in HFpEF, but its function is unknown. Phospho-null/mimetic transgenic cTnI Thr181 will be swapped into skinned myocytes from HFpEF patients, and myocyte tension measured. These studies will advance our understanding of the thick and thin filament in HFpEF and could pave the way for new therapies with small molecule sarcomere enhancers that target these mechanisms.

项目总结