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Am J Physiol Heart Circ Physiol 294: H198-H204, 2008. First published October 26, 2007; doi:10.1152/ajpheart.00281.2007
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Cardioprotection in female rats subjected to chronic volume overload: synergistic interaction of estrogen and phytoestrogens

Jason D. Gardner, Gregory L. Brower, Tetyana G. Voloshenyuk, and Joseph S. Janicki

Department of Cell and Developmental Biology and Anatomy, University of South Carolina School of Medicine, Columbia, South Carolina

Submitted 6 March 2007 ; accepted in final form 25 October 2007


   ABSTRACT
TOP
 ABSTRACT
METHODS
 RESULTS
 DISCUSSION
 GRANTS
 REFERENCES
 
Intact female rats fed a high-phytoestrogen diet are protected against adverse left ventricular (LV) remodeling induced by chronic volume overload. We hypothesized that both phytoestrogens and ovarian hormones, particularly estrogen, are necessary for this dietary-induced cardioprotection. To test this hypothesis, eight groups of female rats were studied; rats were fed either a high-phytoestrogen (+phyto) or phytoestrogen-free diet. Groups included sham-operated rats, intact rats with fistula (Fist), ovariectomized rats with fistula (Fist-OX), and Fist-OX rats treated with estrogen (EST). Myocardial function and remodeling were assessed after 8 wk of volume overload using a blood-perfused isolated heart apparatus. Fist-OX rats developed significant ventricular dilatation and increased compliance vs. intact Fist rats, which were associated with a significant decrease in contractility. Estrogen treatment prevented pulmonary edema and attenuated LV hypertrophy and dilatation but did not maintain contractility. However, dietary phytoestrogens completely prevented LV dilatation in both the Fist+phyto and Fist-OX+EST+phyto groups but had no effect on LV remodeling in the Fist-OX+phyto group. Contractility was significantly greater in the estrogen-treated rats fed the phytoestrogen diet than in those treated with estrogen alone. Dietary phytoestrogens did not affect LV or uterine mass, serum estrogen, LV estrogen receptor expression, or cardiac function in sham animals. These data indicate that estrogen is not solely responsible for the cardioprotection exhibited by intact females and that phytoestrogens can work synergistically with ovarian hormones to attenuate ventricular remodeling induced by chronic volume overload in female rats.

hormones; heart failure; remodeling; diet; physiology; hypertrophy; fistula

BY FAILING TO PROVIDE EVIDENCE of estrogen-mediated cardioprotection, recent hormone replacement therapy trials have generated controversy, causing many women to seek alternatives to these drug therapies (19, 22, 41). Of particular interest are the phytoestrogenic compounds present in soybean products, which are thought to contribute to the cardioprotection reported in many Asian cultures (5). We have previously reported sex differences in myocardial remodeling and incidence of heart failure using the rat aortocaval (AV) fistula model of chronic volume overload (16). The hearts of intact female rats developed concentric compensatory remodeling in response to the volume overload, resulting in a beneficial increase in their left ventricular (LV) mass-to-volume ratio (M/V). The observation that this cardioprotective remodeling is lost after ovariectomy suggests that it is dependent on estrogen or other ovarian hormones (8). We have also demonstrated that intact female rats fed a diet containing phytoestrogens were more effectively protected against the ventricular dilatation and reduced systolic function that occurs after fistula-induced chronic volume overload (17). However, it is not known whether these soy-derived phytoestrogens, which are known to interact with estrogen receptors, work in concert with estrogen to modulate cardiac remodeling. Accordingly, the purpose of this study was to determine the contribution of both dietary phytoestrogens and estrogen to the cardioprotection exhibited by female rats in response to chronic volume overload.


   METHODS
TOP
 ABSTRACT
 METHODS
RESULTS
 DISCUSSION
 GRANTS
 REFERENCES
 
Studies were performed with 8-wk-old female Sprague-Dawley (Harlan Hsd:SD) rats weighing ~200 g at surgery. Rats were housed under standard environmental conditions and maintained on rat chow (see Dietary data for details) and tap water ad libitum. All experimental procedures were approved by our Institution's Animal Care and Use Committee. Anesthesia for surgical procedures was induced with xylazine (7 mg/kg) and ketamine (62 mg/kg) administered by intraperitoneal injection. Postoperative analgesia was provided by buprenorphine HCl (0.025 mg/kg sc) administered to the rats at the time of surgery. At the experimental endpoint, animals were anesthetized with pentobarbital sodium (50 mg/kg ip). A total of eight groups of age-matched female rats were studied as follows: sham-operated controls fed a phytoestrogen-free or high-phytoestrogen diet (sham and sham+phyto rats, respectively), intact rats with fistula fed a phytoestrogen-free or high-phytoestrogen diet (Fist and Fist+phyto rats, respectively), ovariectomized rats with fistula fed a phytoestrogen-free or high-phytoestrogen diet (Fist-OX and Fist-OX+phyto rats, respectively), and ovariectomized rats with fistula treated with estrogen and fed a phytoestrogen-free or high-phytoestrogen diet (Fist-OX+EST and Fist-OX+EST+phyto rats, respectively).

Dietary data. Animals were fed either a casein-based phytoestrogen-free rat chow (Purina Mills test diet 5K96) with <1.0 ppm total isoflavones or a high-phytoestrogen diet (Purina Mills RMH 3000) with a total isoflavone content of 417 ± 76 ppm (aglycone units), 196 ± 33 ppm genistein, and 183 ± 7 ppm daidzein. The crude protein content of these diets is similar (~19–22%). Rats were fed their respective diets for 1 wk before the fistula surgery and throughout the 8-wk experimental protocol.

Surgical procedures. Infrarenal AV fistula was created in rats as previously described (9). Briefly, a ventral abdominal laparotomy was performed to expose the aorta and caudal vena cava. An 18-gauge needle was inserted into the exposed abdominal aorta below the renal arteries and advanced into the vena cava to create the fistula. The needle was withdrawn, and the aortic puncture site was sealed with cyanoacrylate. Abdominal musculature and skin incisions were closed by standard techniques with absorbable suture and autoclips, respectively. For the ovariectomy study groups, the ovaries were isolated, the ovarian pedicles were ligated, and the ovaries were excised. Ovariectomies were performed 5 days before the fistula surgery. Estrogen was administered via subcutaneous time-release pellets (0.25 mg total, 60-day release; Innovative Research of America, Sarasota, FL), which delivered a dose of ~0.02 mg·kg–1·day–1 and were implanted at the time of ovariectomy (13). Plasma samples from each animal were assayed for estrogen content using a commercial radioimmunoassay (Coat-a-Count kit; DPC, Los Angeles, CA).

Experimental protocol. All rats were studied at 8 wk after creation of the AV fistula. This time period was chosen because, in previous studies with male rats, a significant number of rats have been shown to develop symptomatic congestive heart failure (CHF) by 8 wk postfistula (9, 16). Results from the sham, Fist, and Fist+phyto groups have been previously published and are included herein for comparison purposes (9, 17). At the experimental endpoint, each rat was weighed and anesthetized; after laparotomy, fistula patency was visually confirmed. Rats were then attached to a ventilator, and, after thoracotomy to expose the heart, cardiac output was measured using a Doppler flow probe (model 3SB; Transonic Systems, Ithaca, NY). A perfusion cannula was then introduced into the aorta, and the heart was removed and attached to a perfusion apparatus (see Assessment of ventricular size and function below). After completion of the functional studies, the atria and great vessels were removed, and the LV (including septum) and right ventricle (RV) were separated and weighed. Lung and uterine weights, after removal of the ovaries, were also measured.

Assessment of ventricular size and function. LV volume and function were evaluated with a blood-perfused isolated heart preparation as previously described (9, 16, 17). Briefly, arterial blood from the carotid artery of a support rat was pumped to a pressurized reservoir for retrograde perfusion of the experimental heart. Coronary perfusion pressure was maintained at 100 ± 5 mmHg. The coronary venous effluent was collected and returned to the support rat through a jugular vein catheter. Before extirpation of the heart from the anesthetized rat, the carotid arteries were ligated, and a cannula was inserted into the thoracic aorta and secured with a silk ligature. The heart was then quickly removed from the chest and attached to the apparatus. LV developed pressure was continuously recorded with a pressure transducer attached to a latex balloon inserted through the mitral valve orifice into the LV chamber. Once the heart developed stable isovolumetric contractions, the balloon volume that produced an LV end-diastolic pressure (LVEDP) of 0 mmHg (V0) was determined. V0 was then increased in 5- to 10-µl increments from this point until an LVEDP of 25 mmHg was attained. The balloon was then evacuated, and this procedure was repeated until a minimum of three consistent runs were obtained.

Western blot analysis of estrogen receptor expression. Total proteins were extracted from LV tissue and homogenized with protease inhibitor cocktail (Pierce). Protein concentrations were determined (Bio-Rad), and equal samples were then separated by 10% SDS-PAGE and transferred onto nitrocellulose membranes (Amersham). Membranes were blocked with 5% nonfat milk in TBS and 0.01% Tween 20 for 1 h at room temperature and then incubated with rabbit anti-estrogen receptor (ER)-{alpha} polyclonal antibody (MC-20; Santa Cruz). After incubation with primary antibody, the membranes were rinsed in TBS containing 0.01% Tween 20 and incubated for 1 h in the 5% milk buffer with peroxidase-coupled donkey anti-rabbit IgG (Santa Cruz). Immunoreaction signals were visualized with enhanced chemiluminescence (Pierce) by exposure to hyperfilm (RPI). Ponceau-S staining was used to confirm equal loading and for normalization of ER-{alpha} signal. Densitometry analysis was performed with a Kodak molecular image station 2000MM. Although several commercial antibodies were tried, none provided the specificity needed to allow repeatable measurement of LV ER-β expression.

Data and statistical analysis. The end-diastolic and peak isovolumetric pressures were determined after each increase in V0 (ADInstruments chart version 5, Colorado Springs, CO). Further processing and statistical analyses were performed with GraphPad analysis software (GraphPad 4.0; Prism, San Diego, CA). LV volumes were adjusted to account for the volume displaced by the balloon material. Pressure-volume relations generated for the balloon alone indicated that the balloon's contribution to LVEDP was negligible over the experimental LV volume range. Diastolic LV pressure-volume data were fitted with a third-order polynomial regression, and V0 for each pressure-volume curve was calculated. With the use of this regression equation, LV end-diastolic volumes (LVEDVs) were calculated at discrete LVEDP intervals (each 2.5 mmHg) for graphical comparison. Systolic LV pressure-volume data were fitted with linear regression, and the slopes of these relations were used as indexes of intrinsic chamber contractility (i.e., neurohormonal influence removed). Linear relations were statistically compared by analysis of covariance. Grouped data comparisons were made by one-way ANOVA, and comparisons of discrete data points on nonlinear relations were analyzed by two-way ANOVA. When a significant F-ratio (P < 0.05) was obtained, intergroup comparisons were made with a modified t-test and Bonferroni bounds. Statistical significance was taken to be P < 0.05/k, where k is equal to the number of groups compared (35). To evaluate the interaction of the estrogen and phytoestrogen treatments, a two-way ANOVA was performed on the ovariectomized groups.


   RESULTS
TOP
 ABSTRACT
 METHODS
 RESULTS
DISCUSSION
 GRANTS
 REFERENCES
 
Group-averaged cardiac output and LV, RV, lung, uterine, and body weights for the combined sham and 8-wk Fist groups are listed in Table 1. Because there were no significant differences in parameters between the two sham-operated groups (sham and sham+phyto), these groups were combined for presentation. Cardiac output was significantly increased four- to fivefold in the fistula animals, confirming the successful creation of fistula and chronic volume overload conditions. LV and RV weights were significantly increased for all of the Fist groups relative to sham controls, consistent with our previous results (16). Also, collagen volume fraction, as measured by picrosirius red staining of fixed LV midventricular sections, was not significantly different between groups (data not shown). Successful excision of ovarian tissue was confirmed by a substantial 86% decrease (P < 0.05) in uterine weights in the ovariectomized rats, as well as a significant 67% reduction in serum estrogen levels relative to results in sham rats (Fig. 1). Estrogen replacement sustained uterine weights in ovariectomized rats (31% reduction vs. Sham) and resulted in serum estrogen levels comparable to those for the intact groups. The phytoestrogen content of the diet had no effect on uterine weights or serum estrogen levels. LV ER-{alpha} expression was significantly reduced in the Fist-OX group (P < 0.05 vs. Sham) and maintained in rats treated with estrogen (Fig. 2). The intact rats with fistula fed a high-phytoestrogen diet had greater LV ER-{alpha} expression than their counterparts fed a phytoestrogen-free diet (P < 0.01), whereas expression in sham animals was not affected by diet (data not shown). Although this dietary phytoestrogen-induced increase in ER-{alpha} expression was also evident in the ovariectomized rats and ovariectomized rats treated with estrogen, these differences did not reach significance.


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  		Table 1. Cardiac output and heart, lung, uterine, and body weights at 8 wk postfistula

 

Figure 1
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  		Fig. 1. Serum 17β-estradiol levels as determined by radioimmunoassay. Samples were collected at the 8-wk postfistula endpoint. Sham, sham-operated control; Fist, fistula; OX, ovariectomized; EST, estrogen treated; phyto, high-phytoestrogen diet. *P < 0.05.

 

Figure 2
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  		Fig. 2. Representative Western blots (top) and group-averaged graph (bottom) of left ventricular estrogen receptor (ER)-{alpha} protein expression. *P < 0.05 vs. Sham; {dagger}P < 0.05 vs. Fist-OX.

 
Hormonal effects on cardiac remodeling and function. The Fist-OX group developed significant hypertrophy relative to the sham group (113%); however, this increase was not different from the intact Fist group. Estrogen replacement in the ovariectomized rats attenuated this LV hypertrophy (20% less than that of Fist-OX; P < 0.05). Estrogen treatment also significantly attenuated the RV hypertrophy in the Fist-OX+EST animals (28% less than that of Fist-OX). Lung weights in the Fist and Fist-OX rats were significantly increased relative to sham controls, with the greatest increase (68%) occurring in the Fist-OX group. Estrogen replacement prevented this increase in lung weight in the ovariectomized rats postfistula (Fist-OX+EST vs. sham; P = not significant). Rats were classified to have CHF if they developed a rapid increase in body weight (>50 g/wk) and displayed lethargy and labored respiration; this condition was confirmed at the experimental endpoint by lung weights exceeding 2 g and the presence of ascites. With the use of these criteria, 27% of the intact Fist animals and 75% of Fist-OX group developed CHF. In contrast, only one of the Fist-OX+EST animals developed CHF.

Group differences in the average LVEDP-LVEDV relationship are depicted in Fig. 3A and summarized in Table 2. Structural dilatation of the LV resulting from enlarged chamber dimensions was assessed by the change in unstressed LV volume (V0). In the absence of altered compliance, this remodeling would characteristically result in a parallel rightward shift of the LVEDP-LVEDV relationship. Both intact and ovariectomized females developed significant structural dilatation of the LV postfistula, with the ovariectomized group developing a substantially greater degree of LV chamber dilatation (43% and 67% increases relative to sham control, respectively). Although this LV dilatation was significantly attenuated by estrogen treatment (23% decrease relative to Fist-OX), the Fist-OX+EST rats still developed LV dilatation that was comparable to that of the intact females (28% increase, Fist-OX+EST vs. Sham; P < 0.05). In addition to structural dilatation, changes in compliance, as measured by the volume required to increase LVEDP from 0 to 25 mmHg, occurred as a result of sustained volume overload. Increased compliance is represented as a nonparallel rightward shift of the LVEDP-LVEDV relation. Hearts from Fist and Fist-OX rats exhibited significant increases in ventricular chamber compliance, but the absence of ovarian hormones exacerbated this increase in compliance nearly fourfold (134% and 426% relative to Sham, respectively). Estrogen replacement significantly attenuated this development of increased chamber compliance in the Fist-OX+EST group (203% relative to Sham; P = not significant vs. Fist, P < 0.05 vs. Fist-OX).


Figure 3
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  		Fig. 3. Group-averaged left ventricular (LV) end-diastolic pressure-volume relationships from blood-perfused isolated heart analyses: comparison of hormonal (A) and dietary (B) effects.

 

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  		Table 2. Diastolic and systolic cardiac functional parameters from isolated hearts

 
Figure 4A depicts the influence of ovarian hormones on the average LV M/V postfistula. The intact Fist animals developed a significant increase in LV M/V over the full range of LVEDP compared with the sham group, whereas the Fist-OX group did not. However, the Fist-OX+EST group developed significantly increased LV M/V, which was comparable to that of the intact Fist group. The effects of volume overload-induced ventricular remodeling on systolic function were assessed with the linear systolic LV pressure-volume relations (slopes reported in Table 2), previously validated by Suga et al. (43) as an accurate index of LV chamber contractility. Chamber contractility was markedly reduced in hearts from intact females postfistula relative to sham-operated controls (39% reduction vs. Sham; P < 0.05). However, ovariectomized females postfistula had a much greater reduction in the slope of the systolic pressure-volume relation (77% reduction vs. Sham; P < 0.05), which was only partially attenuated by estrogen replacement (64% reduction relative to Sham; P < 0.05).


Figure 4
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  		Fig. 4. Group-averaged ratio of LV mass to LV end-diastolic volume (EDV) vs. LV end-diastolic pressure: comparison of hormonal (A) and dietary (B) effects.

 
Dietary effects on cardiac remodeling and function. As can be seen in Table 1, the high-phytoestrogen diet did not appreciably affect the extent of LV or RV hypertrophy in the Fist+phyto or Fist-OX+phyto groups (74% and 123% increase in LV mass, respectively, vs. Sham; P < 0.05). Although the phytoestrogen diet did not prevent the significant increases in lung weights developed by the Fist-OX+phyto rats, lung weights in the intact Fist+phyto group were not significantly different from those of control. Furthermore, although 75% of the Fist-OX+phyto rats developed CHF, none of the Fist+phyto group and only one of the Fist-OX+EST+phyto rats developed CHF.

A plot of the LVEDP-LVEDV relationship in Fig. 3B depicts the effects of dietary phytoestrogens on the group-averaged diastolic function of isolated hearts (parameters summarized in Table 2). Although the high-phytoestrogen diet did not prevent the chamber dilatation and increased compliance developed by the ovariectomized females (i.e., Fist-OX+phyto; P = not significant vs. Fist-OX), the diet did prevent both the dilatation and increased compliance in the intact Fist+phyto group. This is reflected by the LVEDP-LVEDV relation of the Fist+phyto group being identical to that of the sham group. Likewise, dilatation was prevented and increased compliance was markedly attenuated (P < 0.05 vs. Fist-OX) in the Fist-OX+EST+phyto group, indicating that estrogen and phytoestrogens act synergistically to prevent volume overload-induced adverse ventricular remodeling. Phytoestrogen diet did not alter the LV M/V in the Fist-OX+phyto group from that seen in the Fist-OX group (Fig. 4B). However, the intact females with fistula fed a high-phytoestrogen diet developed a marked increase in LV M/V relative to the intact females fed a phytoestrogen-free diet (P < 0.05). Much like the Fist+phyto group, the combined treatments of phytoestrogen and estrogen produced a comparable increase in LV M/V for the Fist-OX+EST+phyto group (P < 0.05 vs. Fist-OX, Fist, and sham groups).

LV chamber contractility was maintained in hearts from intact Fist+phyto rats (P = not significant vs. Sham; Table 2). Although this phytoestrogen-derived cardioprotection was not evident in the Fist-OX+phyto females (78% reduction in contractility vs. Sham), the combined treatments of high-phytoestrogen diet and estrogen replacement did significantly improve the intrinsic contractility of the Fist-OX+EST+phyto group vs. estrogen treatment alone (40 vs. 64% reduction relative to Sham). However, contractility remained significantly impaired in both of the estrogen-treated groups compared with the sham and Fist+phyto hearts. Statistical analysis of the LV dilatation (i.e., V0) and chamber contractility of the four ovariectomized groups determined that the interaction of the phytoestrogen and estrogen treatments was significant.


   DISCUSSION
TOP
 ABSTRACT
 METHODS
 RESULTS
 DISCUSSION
GRANTS
 REFERENCES
 
Although premenopausal women are essentially protected from cardiovascular disease, the development of CHF in postmenopausal women is exacerbated, with a greater incidence than that shown in age-matched men (18, 21, 24). Historically, this sex-specific cardioprotection has been attributed to estrogen (34); however, this assumption has been refuted by results from clinical trials, including the Heart and Estrogen/Progestin Replacement Study, which reported no cardiovascular benefit of hormone replacement therapy (3, 19). The typical Western diet contains minimal soy phytoestrogens (14, 15, 46), but the emergent use of dietary supplements based on the supposition that they are beneficial is of concern because little is known about how these compounds affect the heart's ability to respond to stress (11). Although we have previously demonstrated that dietary phytoestrogens provide cardioprotection to intact female rats and contribute to sex differences in ventricular remodeling induced by volume overload, these studies did not address the influence of estrogen or the possibility of interactions between phytoestrogens and estrogen (16, 17). Thus the purpose of the present study was to test the hypothesis that dietary phytoestrogens, in conjunction with estrogen, prevent adverse myocardial remodeling induced by chronic volume overload.

Hormonal effects. The compensatory processes and ensuing pattern of myocardial remodeling occurring in the AV fistula model of chronic volume overload mimics those described in humans with CHF (23) and, in male rats, result in the development of myocardial remodeling characterized by eccentric hypertrophy, marked dilatation, increased ventricular compliance, and CHF-related mortality (9). In contrast, intact female rats fed a diet with high-phytoestrogen content develop concentric hypertrophy with no significant ventricular dilatation or alterations in myocardial compliance and minimal mortality (16, 17). These studies, as well as the findings herein, are consistent with the report by Liu et al. (30) in which intact female rats developed significant hypertrophy without progression to heart failure postfistula (unspecified diet). The extent of LV dilatation in ovariectomized females at 8 wk postfistula was comparable to that previously reported in age-matched male rats (i.e., V0 of 497 vs. 472 µl, respectively) (16). The marked ventricular dilatation and pulmonary edema exhibited by the ovariectomized females vs. intact females clearly demonstrate the influence of circulating ovarian hormones on the remodeling of the myocardium postfistula. Estrogen replacement significantly attenuated, but did not prevent, the LV hypertrophy, dilatation, and increased compliance occurring postfistula in the ovariectomized rats. However, it is worth noting that the increase in LV mass is not thought to be pathological but rather represents a necessary adaptation that allows for the normalization of increased wall stress induced by volume overload. Previous findings suggest that failure to adequately increase LV M/V in response to chronic volume overload is indicative of a maladaptive pattern of remodeling that will eventually result in heart failure, as occurs in male rats (16, 23). Figure 4A illustrates that, although intact females successfully increased their LV M/V postfistula relative to sham rats, the ovariectomized females were not able to replicate this response. Because of this inability to normalize the increased wall stress imposed by the volume overload, 75% of the Fist-OX rats developed extensive pulmonary edema, signifying CHF. Estrogen replacement in the Fist-OX group produced a more successful ventricular adaptation in these rats, comparable to that seen in the intact Fist group fed a phytoestrogen-free diet. This positive effect of estrogen treatment on LV remodeling in ovariectomized female rats was similar to that demonstrated by Xu et al. (48).

Although the depressed systolic function in ovariectomized rats was significantly improved by estrogen treatment, it was not maintained at a level comparable to that of intact females. However, despite the relative decrease in systolic function, only one rat in this estrogen-treated group actually developed heart failure. This finding is consistent with that of Beer et al. (6) who found that estrogen treatment of female rats prevented the development of heart failure induced by myocardial infarction. Likewise, estrogen replacement led to improved cardiomyocyte survival in mice after myocardial infarction, and this cardioprotective effect was mediated via activation of the phosphatidylinositol 3-kinase/Akt pathway (39). Sex-specific differences in myocardial Akt activation have been demonstrated and represent a plausible mechanism contributing to cardioprotection in premenopausal women (2, 10). Additionally, our results suggest that the maintenance of estrogen receptor expression in the heart may be key to cardioprotection because the groups with the lowest levels of ER-{alpha} expression developed a greater degree of LV dilatation and increased compliance and CHF.

Dietary effects. Although many laboratories, including our own, have demonstrated the cardioprotective effects of dietary soy compounds, the most striking finding in the present study was the synergism of the combined phytoestrogen and estrogen treatments in preventing adverse remodeling (17, 42, 45, 50). The LV dilatation was completely prevented in both the Fist+phyto and Fist-OX+EST+phyto groups, allowing for the development of an appropriate hypertrophic response (i.e., increased LV M/V). Intact females fed the high phytoestrogen diet developed the greatest increase in LV M/V, and the successful compensatory adaptation of this treatment group is reflected in their ability to sustain both diastolic and systolic performance, as well as the complete absence of symptomatic CHF. These cardioprotected females also had the greatest level of LV ER-{alpha} expression. Contributing to this successful compensation was the prevention of increased ventricular compliance in the Fist+phyto and Fist-OX+EST+phyto groups. In contrast, the inability of ovariectomized females, regardless of diet, to develop appropriate hypertrophy predisposed them to more extensive ventricular dilatation and increased compliance. These findings clearly demonstrate a synergistic cardioprotective effect of the combined estrogen and phytoestrogen treatments contributing to the successful adaptation of these animals to chronic volume overload. Although the cardioprotective effects imparted on LV chamber structure and compliance were striking, the combined treatment of estrogen and phytoestrogens in ovariectomized rats did not fully maintain systolic cardiac function postfistula, as demonstrated in the intact females that were treated with phytoestrogens. This finding suggests that other ovarian-derived factors, in addition to estrogen, work in conjunction with the phytoestrogenic compounds to further enhance cardioprotection.

Although there are multiple phytoestrogenic compounds derived from soybeans, a likely candidate mediating these dietary phytoestrogenic effects is genistein. Genistein has been shown to interact with estrogen receptors, preferentially binding to ER-β (26). ER-{alpha} is the predominant isoform expressed in the heart, but ER-β has been implicated as the cardioprotective subtype, on the basis of studies that utilized ER-{alpha} and ER-β knockout mice [reviewed by Harris (20) and Otsuki et al. (37)]. Genistein has been shown to exert both anti-inflammatory and antioxidant effects (29, 33) and can inhibit multiple cellular signaling proteins including MAPK (1, 7, 44), NF-{kappa}B (7), and IL-6 (38). These anti-inflammatory effects are potentially important because observations in our laboratory and others indicate that proinflammatory cytokines are centrally involved in the initial response of the heart to insult (4, 23). It should also be noted that genistein has been shown to inhibit the transcription and activation of matrix metalloproteinases (MMPs) in cancer cells (25, 28, 49). Genistein-mediated MMP inhibition represents a plausible cardioprotective mechanism, as our group (12) has previously demonstrated that MMP inhibition markedly attenuates the adverse cardiac remodeling occurring postfistula.

Summary. The synergistic effects of dietary-derived phytoestrogens and estrogen on remodeling in the ovariectomized female rats were marked and led to complete prevention of the LV dilatation and significant attenuation of the increased LV compliance associated with chronic volume overload. These remarkable and unexpected findings provide a basis for future investigations into the mechanisms underlying the complementary synergistic cardioprotective effects of hormonal and phytoestrogenic compounds. Future studies are warranted to determine 1) the specific phytoestrogen(s) responsible, 2) whether these effects are estrogen receptor mediated, 3) and which key signaling pathways are involved. Until the mechanisms responsible for the loss of premenopausal cardioprotection are resolved, the most effective clinical therapy will remain controversial.


   GRANTS
TOP
 ABSTRACT
 METHODS
 RESULTS
 DISCUSSION
 GRANTS
REFERENCES
 
This study was supported by American Heart Association Grants National 0435298N (J. D. Gardner) and Southeast Affiliate 0160195B (J. D. Gardner), the United Soybean Board, and National Heart, Lung, and Blood Institute Grants HL-073990 and HL-62228 (J. S. Janicki).


   ACKNOWLEDGMENTS
 
We are grateful to Kimberly Jagnandan and Kathryn Oberle for providing technical support.


   FOOTNOTES
 

Address for reprint requests and other correspondence: J. D. Gardner, CDBA-SOM, Univ. of South Carolina, Columbia, SC 29208 (e-mail: jgardner{at}gw.med.sc.edu)

The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.


   REFERENCES
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 ABSTRACT
 METHODS
 RESULTS
 DISCUSSION
 GRANTS
 REFERENCES
 

  1. Akiyama T, Ishida J, Nakagawa S, Ogawara H, Watanabe S, Itoh N, Shibuya M, Fukami Y. Genistein, a specific inhibitor of tyrosine-specific protein kinases. J Biol Chem 262: 5592–5595, 1987.[Abstract/Free Full Text]
  2. Bae S, Zhang L. Gender differences in cardioprotection against ischemia/reperfusion injury in adult rat hearts: focus on Akt and protein kinase C signaling. J Pharmacol Exp Ther 315: 1125–1135, 2005.[Abstract/Free Full Text]
  3. Barrett-Connor E, Stuenkel C. Hormones and heart disease in women: Heart and Estrogen/Progestin Replacement Study in perspective. J Clin Endocrinol Metab 84: 1848–1853, 1999.[Free Full Text]
  4. Baumgarten G, Knuefermann P, Kalra D, Gao F, Taffet GE, Michael L, Blackshear PJ, Carballo E, Sivasubramanian N, Mann DL. Load-dependent and -independent regulation of proinflammatory cytokine and cytokine receptor gene expression in the adult mammalian heart. Circulation 105: 2192–2197, 2002.[Abstract/Free Full Text]
  5. Beaglehole R. International trends in coronary heart disease mortality and incidence rates. J Cardiovasc Risk 6: 63–68, 1999.[Web of Science][Medline]
  6. Beer S, Reincke M, Kral M, Callies F, Stromer H, Dienesch C, Steinhauer S, Ertl G, Allolio B, Neubauer S. High-dose 17β-estradiol treatment prevents development of heart failure postmyocardial infarction in the rat. Basic Res Cardiol 102: 9–18, 2007.[CrossRef][Web of Science][Medline]
  7. Borras C, Gambini J, Gomez-Cabrera MC, Sastre J, Pallardo FV, Mann GE, Vina J. Genistein, a soy isoflavone, up-regulates expression of antioxidant genes: involvement of estrogen receptors, ERK1/2, and NF-{kappa}B. FASEB J 20: 2136–2138, 2006.[Abstract/Free Full Text]
  8. Brower GL, Gardner JD, Janicki JS. Gender mediated cardiac protection from adverse ventricular remodeling is abolished by ovariectomy. Mol Cell Biochem 251: 89–95, 2003.[CrossRef][Web of Science][Medline]
  9. Brower GL, Janicki JS. Contribution of ventricular remodeling to pathogenesis of heart failure in rats. Am J Physiol Heart Circ Physiol 280: H674–H683, 2001.[Abstract/Free Full Text]
  10. Camper-Kirby D, Welch S, Walker A, Shiraishi I, Setchell KD, Schaefer E, Kajstura J, Anversa P, Sussman MA. Myocardial Akt activation and gender: increased nuclear activity in females vs. males. Circ Res 88: 1020–1027, 2001.[Abstract/Free Full Text]
  11. Cassidy A. Potential risks and benefits of phytoestrogen-rich diets. Int J Vitam Nutr Res 73: 120–126, 2003.[CrossRef][Web of Science][Medline]
  12. Chancey AL, Brower GL, Peterson JT, Janicki JS. Effects of matrix metalloproteinase inhibition on ventricular remodeling due to volume overload. Circulation 105: 1983–1988, 2002.[Abstract/Free Full Text]
  13. Chancey AL, Gardner JD, Murray DB, Brower GL, Janicki JS. Modulation of cardiac mast cell-mediated extracellular matrix degradation by estrogen. Am J Physiol Heart Circ Physiol 289: H316–H321, 2005.[Abstract/Free Full Text]
  14. De Kleijn MJ, Van Der Schouw YT, Wilson PW, Adlercreutz H, Mazur W, Grobbee DE, Jacques PF. Intake of dietary phytoestrogens is low in postmenopausal women in the United States: the Framingham study (1–4). J Nutr 131: 1826–1832, 2001.[Abstract/Free Full Text]
  15. Erdman JW Jr. AHA Science Advisory. Soy protein and cardiovascular disease: a statement for healthcare professionals from the Nutrition Committee of the AHA. Circulation 102: 2555–2559, 2000.[Free Full Text]
  16. Gardner JD, Brower GL, Janicki JS. Gender differences in cardiac remodeling secondary to chronic volume overload. J Card Fail 8: 101–107, 2002.[CrossRef][Web of Science][Medline]
  17. Gardner JD, Brower GL, Janicki JS. Effects of dietary phytoestrogens on cardiac remodeling secondary to chronic volume overload in female rats. J Appl Physiol 99: 1378–1383, 2005.[Abstract/Free Full Text]
  18. Gorodeski GI. Impact of the menopause on the epidemiology and risk factors of coronary artery heart disease in women. Exp Gerontol 29: 357–375, 1994.[CrossRef][Web of Science][Medline]
  19. Grady D, Herrington D, Bittner V, Blumenthal R, Davidson M, Hlatky M, Hsia J, Hulley S, Herd A, Khan S, Newby LK, Waters D, Vittinghoff E, Wenger N. Cardiovascular disease outcomes during 6.8 years of hormone therapy: Heart and Estrogen/Progestin Replacement Study Follow-up (HERS II). JAMA 288: 49–57, 2002.[Abstract/Free Full Text]
  20. Harris HA. Estrogen receptor-β: recent lessons from in vivo studies. Mol Endocrinol 21: 1–13, 2007.[Abstract/Free Full Text]
  21. Hayward CS, Kelly RP, Collins P. The roles of gender, the menopause and hormone replacement on cardiovascular function. Cardiovasc Res 46: 28–49, 2000.[Free Full Text]
  22. Hulley S, Grady D, Bush T, Furberg C, Herrington D, Riggs B, Vittinghoff E. Randomized trial of estrogen plus progestin for secondary prevention of coronary heart disease in postmenopausal women. Heart and Estrogen/progestin Replacement Study (HERS) Research Group. JAMA 280: 605–613, 1998.[Abstract/Free Full Text]
  23. Janicki JS, Brower GL, Gardner JD, Chancey AL, Stewart JA Jr. The dynamic interaction between matrix metalloproteinase activity and adverse myocardial remodeling. Heart Fail Rev 9: 33–42, 2004.[CrossRef][Web of Science][Medline]
  24. Kalin MF, Zumoff B. Sex hormones and coronary disease: a review of the clinical studies. Steroids 55: 330–352, 1990.[CrossRef][Web of Science][Medline]
  25. Kousidou OC, Mitropoulou TN, Roussidis AE, Kletsas D, Theocharis AD, Karamanos NK. Genistein suppresses the invasive potential of human breast cancer cells through transcriptional regulation of metalloproteinases and their tissue inhibitors. Int J Oncol 26: 1101–1109, 2005.[Web of Science][Medline]
  26. Kuiper GG, Lemmen JG, Carlsson B, Corton JC, Safe SH, Van der Saag PT, van der BB, Gustafsson JA. Interaction of estrogenic chemicals and phytoestrogens with estrogen receptor β. Endocrinology 139: 4252–4263, 1998.[Abstract/Free Full Text]
  27. Levine RL, Chen SJ, Durand J, Chen YF, Oparil S. Medroxyprogesterone attenuates estrogen-mediated inhibition of neointima formation after balloon injury of the rat carotid artery. Circulation 94: 2221–2227, 1996.[Abstract/Free Full Text]
  28. Li Y, Che M, Bhagat S, Ellis KL, Kucuk O, Doerge DR, Abrams J, Cher ML, Sarkar FH. Regulation of gene expression and inhibition of experimental prostate cancer bone metastasis by dietary genistein. Neoplasia 6: 354–363, 2004.[CrossRef][Web of Science][Medline]
  29. Liang YC, Huang YT, Tsai SH, Lin-Shiau SY, Chen CF, Lin JK. Suppression of inducible cyclooxygenase and inducible nitric oxide synthase by apigenin and related flavonoids in mouse macrophages. Carcinogenesis 20: 1945–1952, 1999.[Abstract/Free Full Text]
  30. Liu Z, Hilbelink DR, Gerdes AM. Regional changes in hemodynamics and cardiac myocyte size in rats with aortocaval fistulas. 2. Long-term effects. Circ Res 69: 59–65, 1991.[Abstract/Free Full Text]
  31. Machens K, Schmidt-Gollwitzer K. Issues to debate on the Women's Health Initiative (WHI) study hormone replacement therapy: an epidemiological dilemma? Hum Reprod 18: 1992–1999, 2003.[Abstract/Free Full Text]
  32. Mendelsohn ME, Karas RH. The time has come to stop letting the HERS tale wag the dogma. Circulation 104: 2256–2259, 2001.[Free Full Text]
  33. Messina MJ. Legumes and soybeans: overview of their nutritional profiles and health effects. Am J Clin Nutr 70: 439S–450S, 1999.[Abstract/Free Full Text]
  34. Mosca L, Collins P, Herrington DM, Mendelsohn ME, Pasternak RC, Robertson RM, Schenck-Gustafsson K, Smith SC Jr, Taubert KA, Wenger NK. Hormone replacement therapy and cardiovascular disease: a statement for healthcare professionals from the American Heart Association. Circulation 104: 499–503, 2001.[Free Full Text]
  35. Motulsky HJ. Intuitive Biostatistics. New York: Oxford Univ. Press, 1995.
  36. Oparil S, Levine RL, Chen SJ, Durand J, Chen YF. Sexually dimorphic response of the balloon-injured rat carotid artery to hormone treatment. Circulation 95: 1301–1307, 1997.[Abstract/Free Full Text]
  37. Otsuki M, Dahlman-Wright K, Gustafsson JA. Cardiovascular roles of estrogen receptors: insights gained from knockout models. Nucl Recept Signal 1: e003, 2003.[Medline]
  38. Paradkar PN, Blum PS, Berhow MA, Baumann H, Kuo SM. Dietary isoflavones suppress endotoxin-induced inflammatory reaction in liver and intestine. Cancer Lett 215: 21–28, 2004.[CrossRef][Web of Science][Medline]
  39. Patten RD, Pourati I, Aronovitz MJ, Baur J, Celestin F, Chen X, Michael A, Haq S, Nuedling S, Grohe C, Force T, Mendelsohn ME, Karas RH. 17β-Estradiol reduces cardiomyocyte apoptosis in vivo and in vitro via activation of phosphoinositide-3 kinase/Akt signaling. Circ Res 95: 692–699, 2004.[Abstract/Free Full Text]
  40. Rosano GM, Webb CM, Chierchia S, Morgani GL, Gabraele M, Sarrel PM, de Ziegler D, Collins P. Natural progesterone, but not medroxyprogesterone acetate, enhances the beneficial effect of estrogen on exercise-induced myocardial ischemia in postmenopausal women. J Am Coll Cardiol 36: 2154–2159, 2000.[Abstract/Free Full Text]
  41. Rossouw JE, Anderson GL, Prentice RL, LaCroix AZ, Kooperberg C, Stefanick ML, Jackson RD, Beresford SA, Howard BV, Johnson KC, Kotchen JM, Ockene J. Risks and benefits of estrogen plus progestin in healthy postmenopausal women: principal results from the Women's Health Initiative randomized controlled trial. JAMA 288: 321–333, 2002.[Abstract/Free Full Text]
  42. Souzeau E, Belanger S, Picard S, Deschepper CF. Dietary isoflavones during pregnancy and lactation provide cardioprotection to offspring rats in adulthood. Am J Physiol Heart Circ Physiol 289: H715–H721, 2005.[Abstract/Free Full Text]
  43. Suga H, Sagawa K, Shoukas AA. Load independence of the instantaneous pressure-volume ratio of the canine left ventricle and effects of epinephrine and heart rate on the ratio. Circ Res 32: 314–322, 1973.[Abstract/Free Full Text]
  44. Thorburn J, Thorburn A. The tyrosine kinase inhibitor, genistein, prevents alpha-adrenergic-induced cardiac muscle cell hypertrophy by inhibiting activation of the Ras-MAP kinase signaling pathway. Biochem Biophys Res Commun 202: 1586–1591, 1994.[CrossRef][Web of Science][Medline]
  45. Tissier R, Waintraub X, Couvreur N, Gervais M, Bruneval P, Mandet C, Zini R, Enriquez B, Berdeaux A, Ghaleh B. Pharmacological postconditioning with the phytoestrogen genistein. J Mol Cell Cardiol 42: 79–87, 2007.[CrossRef][Web of Science][Medline]
  46. Van Der Schouw YT, Kreijkamp-Kaspers S, Peeters PH, Keinan-Boker L, Rimm EB, Grobbee DE. Prospective study on usual dietary phytoestrogen intake and cardiovascular disease risk in Western women. Circulation 111: 465–471, 2005.[Abstract/Free Full Text]
  47. Williams JK, Adams MR. Estrogens, progestins and coronary artery reactivity. Nat Med 3: 273–274, 1997.[CrossRef][Web of Science][Medline]
  48. Xu Y, Arenas IA, Armstrong SJ, Davidge ST. Estrogen modulation of left ventricular remodeling in the aged heart. Cardiovasc Res 57: 388–394, 2003.[Abstract/Free Full Text]
  49. Yan C, Han R. Effects of genistein on invasion and matrix metalloproteinase activities of HT1080 human fibrosarcoma cells. Chin Med Sci J 14: 129–133, 1999.[Medline]
  50. Zhai P, Eurell TE, Cotthaus RP, Jeffery EH, Bahr JM, Gross DR. Effects of dietary phytoestrogen on global myocardial ischemia-reperfusion injury in isolated female rat hearts. Am J Physiol Heart Circ Physiol 281: H1223–H1232, 2001.[Abstract/Free Full Text]




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