Diabetes Abolishes the Cardioprotective Effect of Estrogen on Systolic Cardiac Function

Abstract

The present study evaluated the role of female sex hormones on the adverse effects of diabetes in cardiac function. Adult female Sprague‐Dawley rats (10 weeks‐old) were submitted to ovariectomy. One week later, diabetes was induced with a single dose of streptozotocin (65 mg/kg, i.p) without insulin replacement. After 4 weeks cardiac function was evaluated by echocardiography (Vevo 2100, VisualSonics, Toronto, Ontario, Canada) in intact controls (CTL); diabetics (STZ); ovariectomized (OVX); and OVX with diabetes (OVX‐STZ). Diabetes and OVX alone or in combination did not affect systolic blood pressure. While OVX animals exhibited a higher LV weight: tibia length ratio (LVW/TL; 18%; vs CTL; p<0.05), LVW/TL was particularly reduced in the diabetic animals (STZ: 14%; OVX‐STZ: 11%; vs CTL; p<0.05). However, the relative wall thickness was decreased in OVX and diabetic animals (STZ: 21%; OVX: 18%; OVX‐STZ: 21%; vs CTL; p<0.05). The ejection fraction (EF) and fractional shortening (FS) were decreased in OVX, respectively (65% ± 1% vs 72 % ± 2% in CTL; 37± 1% vs 43 ± 2% in CTL). The systolic function was markedly reduced by the same magnitude in both STZ (EF: 66± 1%; FS: 38 % ± 1%) and OVX‐STZ (EF: 65± 2%; FS: 37± 1%) relative to CTL. These data indicate that diabetes removes the cardioprotective effect of estrogen on cardiac function independently of alterations in blood pressure.