My research goal is to understand the pathophysiology of HFpEF (Heart Failure with preserved Ejection Fraction)and identify its therapeutic targets. Compelling evidence suggests that the pathophysiology of HFpEF in menand women is distinct leading to differential phenotypes responses to treatment and a potential need for sex-specific therapeutic intervention. Studying sex differences in HFpEF is an essential step toward establishing apersonalized therapeutic strategy.Women in HFpEF are typically in their postmenopausal state. Although women comprise the majority of HFpEFpatients the preclinical study of female HFpEF pathogenesis is limited due to a lack of animal models. Femalemice both cycling (premenopausal) and non-cycling (induced by ovariectomy) resist HFpEF development. Oneof the novelties of my proposed work is to use a new female HFpEF-like model induced by ovary-intactmenopause (by VCD (Vinyl Cyclohexene Dioxide) injection) combined with metabolic stress. The VCD-postmenopausal differs from the ovariectomized (OVX) model since it retains residual ovarian stroma analogousto natural menopause in women. VCD mice subjected to metabolic stress develop robust HFpEF phenotype.In addition to estrogen deficiency women with natural menopause also experience relative androgen excess(RAE) due to the remaining androgen-producing capacity of the residual ovaries. Clinical studies show that ahigh androgen/estrogen ratio (not a low level of estrogen alone) is associated with increased cardiovascular risksin women. Androgens suppress NP (Natriuretic Peptide) production from atrial cells a critical activator of cGMP-PKG signaling. Importantly a deficiency of myocardial cGMP-PKG activity was reported to underlie myofilamentdysfunction in HFpEF.My proposed work focuses on myofilament-based alterations that are responsible for mechanical dysfunction inHFpEF. Aim 1 will focus on sex-specific myofilament alterations. The diastolic function will be evaluated at thein vivo LV the myocardium and single cardiomyocyte levels. Diastolic stiffness relaxation kinetics crossbridgekinetics myofilament Ca2+ sensitivity and Ca2+ release-reuptake kinetics will be investigated. Passive sarcomerestiffness and the stiffness contribution of ECM (extracellular matrix) will be measured. Myofilament(phospho)proteomics transcriptomics activity assay protein and RNA studies etc. will investigate the signalingpathways associated with these mechanical changes. Aim 2 will elucidate the role of RAE and anti-androgenseffect on diastolic function in postmenopausal HFpEF. The impact of RAE will be studied in 2 postmenopausalmodels: 1) the OVX model (low estrogens and low androgens); and 2) the VCD model (low estrogens and normalandrogens). The contribution of RAE will be revealed through the inhibition of 5-reductase (by anti-androgens).I anticipate that this proposed work will advance our knowledge of the sarcomere-based alterations in HFpEFand provide potential insight to alleviate diastolic dysfunction in a sex-specific manner.