Figure 1. Feeding high‐fat diet (HFD) for 8 weeks induces impairment of cardiac functional reserve in response to adrenergic stimulation.

A–C show body weight (A), fasting blood glucose (B) and fasting serum insulin concentrations (C) after 8 weeks of normal chow (NC) or high‐fat diet (HFD) feeding. ^* P < 0.05 and ^** P < 0.01 between HFD and NC groups (n = 10). The HFD induces glucose intolerance (D) and mild insulin intolerance (E) when compared with NC control animals. ^* P < 0.05 and ^** P < 0.01 by two‐way repeated‐measures ANOVA with Bonferroni multiple comparisons test (n = 5–7). F–H, cardiac contractile function of the mice before and after β‐adrenergic stimulation [isoproterenol (ISO), 0.2 mg kg⁻¹, i.p.] was measured by echocardiography after 8 weeks of HFD. Data show ejection fraction (F) and fractional shortening (G) measured by M‐mode, and isovolumetric relaxation time (IVRT; H) measured by tissue Doppler image mode. ^** P < 0.01 and ^*** P < 0.001 (n = 8) by one‐way ANOVA followed by Tukey's post hoc test.