Effect of ovariectomy in heart failure-prone SHHF/Mcc-facp rats

Soy diet worsens heart disease in mice

We report that dietary modification from a soy-based diet to a casein-based diet radically improves disease indicators and cardiac function in a transgenic mouse model of hypertrophic cardiomyopathy. On a soy diet, males with a mutation in the alpha-myosin heavy chain gene progress to dilation and heart failure. However, males fed a casein diet no longer deteriorate to severe, dilated cardiomyopathy. Remarkably, their LV size and contractile function are preserved. Further, this diet prevents a number of pathologic indicators in males, including fibrosis, induction of beta-myosin heavy chain, inactivation of glycogen synthase kinase 3beta (GSK3beta), and caspase-3 activation.

Modulation of cardiac mast cell-mediated extracellular matrix degradation by estrogen

There are fundamental differences between males and females with regard to susceptibility to heart disease. Although numerous animal models of heart failure have demonstrated that premenopausal females are afforded cardioprotection and, therefore, fare better in the face of cardiac disease than their male counterparts, many questions as to how this occurs still exist. Recently, we showed that 1) increased mast cell density is associated with adverse ventricular remodeling and 2) chemically induced mast cell degranulation using compound 48/80 resulted in remarkable changes in matrix metalloproteinase (MMP) activity, cardiac collagen structure, and cardiac diastolic function in normal male rats. With the known gender differences in cardiac disease in mind, we sought to examine the effects of chemically induced cardiac mast cell degranulation in isolated, blood-perfused hearts of intact female rats, ovariectomized female rats, and ovariectomized female rats treated with 17β-estradiol. In response to mast cell degranulation, no significant differences in cardiac function, MMP-2 activity, or collagen volume fraction were observed between intact female rats and ovariectomized female rats treated with estrogen. In the ovariectomized female group, a significant rightward shift in the left ventricular pressure-volume relation, accompanied by a marked 133% increase in active MMP-2 values over that in the intact female group, was noted after treatment with compound 48/80 ( P ≤ 0.05), along with a significant reduction in collagen volume fraction below control (0.46 ± 0.23 vs. 0.73 ± 0.13%, P ≤ 0.05). These findings indicate that estrogen's cardioprotective role can be partially mediated by its effects on cardiac mast cells, MMPs, and the extracellular matrix.

Gender modulates activation of renin-angiotensin and endothelin systems in hypertension and heart failure

Sexual dimorphism may occur during the development of hypertension and congestive heart failure (CHF). Male and female spontaneous hypertension heart failure (SHHF) rats with established hypertension, but before CHF (age 5-8 mo) and during cardiac decompensation leading to CHF (age 18-20 mo in male rats and 22-24 mo in female rats), were studied. At 5-8 mo, male SHHF rats showed early activation of the renin-angiotensin system (RAS), as indicated by increased plasma renin activity (PRA) and higher serum angiotensin-converting enzyme activity compared with female rats. The increase in PRA in female rats was delayed compared with males rats, but it reached comparable levels just before CHF. Urinary endothelin excretion was significantly greater in 5- to 8-mo-old female rats compared with age-matched male rats. Urinary endothelin excretion increased in both male and female rats as CHF developed. Plasma atrial natriuretic peptide (ANP) was comparable at both time points, and both genders showed similar, marked increases as CHF developed. In conclusion, male rats show early activation of the RAS, whereas female rats show early activation of the endothelin vasopressor system. During cardiac decompensation, generalized activation of the RAS, endothelin, and ANP systems occurs and is similar in male and female SHHF rats.