Abstract Body (Do not enter title and authors here): Introduction. After menopause, estrogen levels decline, increasing the prevalence of cardiovascular disease in post-menopausal women. Ca2+ handling alterations have been reported in male cardiometabolic injury (CMI) models, but female-specific mechanisms remain unclear. Ca2+/calmodulin-dependent protein kinase II (CaMKII), a key regulator of calcium homeostasis, shows increased activity in ovariectomized (OVX) models of estrogen deficiency, suggesting a link between estrogen loss and cardiac dysfunction.
Research Questions. We investigated whether estrogen deficiency promotes CaMKII activation, leading to altered Ca2+ handling and cardiac dysfunction in female mice with CMI.
Methods. Four groups of 6-week-old female C57BL/6 mice were studied: (1) SHAM (control surgery), (2) SHAM-CMI (high-fat diet + L-NAME), (3) OVX, and (4) OVX-CMI. Mice were monitored for 18 weeks for body weight, adiposity, blood pressure, glucose metabolism, and echocardiography. At endpoint, cardiomyocytes were isolated to explore calcium handling at the confocal microscope, and heart tissue was analyzed by qPCR and western blot for remodeling and calcium-handling proteins. Data were analyzed with ANOVA and Tukey’s post hoc test (p<0.05).
Results. At 18 weeks, OVX-CMI mice showed increased body weight (SHAM 7.6±0.7 g vs. OVX-CMI 18.3±5.4 g, p=0.04) and adiposity (SHAM 8.8±1.2% vs. OVX-CMI 18.3±3.1%, p=0.03). Fasting glucose was elevated in OVX-CMI (141.2±6.3 mg/dL, p<0.05 vs. other groups), along with worsened diastolic function (E/e’ OVX-CMI 19.1±5.4 vs. SHAM 4.4±2.6, p=0.001; vs. OVX 5.9±3.0, p=0.01). Despite no change in Ca2+-Calmodulin Kinase II (CaMKII) or Phospho-CaMKII levels, phospho-phospholamban at Thr17 (P-PLN-Thr17) expression was reduced (SHAM 2.2±0.3 vs. OVX-CMI 0.38±0.003), suggesting PLN dephosphorylation may enhance SERCA inhibition and impair relaxation. Ca2+ transient amplitude increased with CMI (SHAM 1.9±0.1 ΔF/F0 vs. CMI 3.4±0.1, p=0.0008; vs. OVX-CMI 3.1±0.1, p=0.01), independent of hormonal status.
Conclusion. Estrogen deficiency exacerbates cardiometabolic dysfunction and contributes to diastolic impairment via disrupted PLN signaling. These findings highlight a synergistic effect of estrogen loss and metabolic stress on cardiac remodeling and underscore the need for sex-specific preclinical models to inform targeted therapies.