Figure 4. Deletion of the β₂AR gene normalizes cardiac contractile response to adrenergic stimulation in HFD mice.

A–C show body weight (A), fasting glucose (B) and insulin concentrations (C) in mice lacking the β₂AR (β₂AR‐KO) after 8 weeks of NC or HFD feeding. ^* P < 0.05 and ^*** P < 0.001 for HFD vs NC. Eight weeks of HFD feeding induces glucose intolerance (D) and mild insulin intolerance (E) when compared with NC control animals. ^*P < 0.05 and ^**P < 0.01 between groups by two‐way repeated‐measures ANOVA with Bonferroni multiple comparisons test. F–H, after 8 weeks of HFD feeding, cardiac contractile function in response to β‐adrenergic stimulation (ISO, 0.2 mg kg⁻¹, i.p.) was examined by echocardiography in the β₂AR‐KO mice. Data show ejection fraction (F) and fractional shortening (G) measured by M‐mode and isovolumetric relaxation time (H) measured by tissue Doppler image mode (n = 8). ^*** P < 0.001 by one‐way ANOVA followed by Tukey's post hoc test.