Sex-Dependent Cardiac Responses to β3-Adrenergic Receptor Activation in a Murine Model of Heart Failure with...

Background: Brown adipose tissue (BAT) is increasingly recognized as an endocrine organ that releases bioactive factors (batokines) with cardioprotective properties. Activation of BAT is primarily mediated by the β3-adrenergic receptor (β3-AR). Here, we investigated whether pharmacological activation of β3-AR using mirabegron modulates cardiac remodelling in a murine model of heart failure with preserved ejection fraction (HFpEF) induced by metabolic and hypertensive stress (MHS). Methods: Male and female C57BL/6J mice were exposed to MHS (angiotensin II + high-fat diet) for 28 days, with or without mirabegron treatment (2 mg/kg/day). Cardiac structure and function were assessed by echocardiography, and molecular and histological analyses were performed on cardiac and BATs. Results: Mirabegron attenuated several features of cardiac remodelling in males, including cardiac hypertrophy, left atrial enlargement, and left ventricular dilation. These effects were associated with reduced expression of genes related to hypertrophy and fibrosis. In contrast, it was shown that females exhibited a less pronounced response pattern. BAT mass and thermogenic gene expression (Ucp1) increased more markedly in males than in females, suggesting differential BAT responsiveness between sexes. Conclusions: β3-AR activation is associated with sex-dependent cardiac responses in this HFpEF model, with more pronounced protective effects in males. These findings are consistent with a potential contribution of BAT activation to cardiac remodelling, although causality was not directly demonstrated in the present study.