Saturday, November 30, 2013

Phytoestrogens: Good, Bad, or Indifferent?

Or who the heck knows? Most of the studies I've gone through seem to be seeking a relationship between phytoestrogens and menopause or phytoestrogens and breast cancer.

Preread notes: Aromatase inhibitors used in the treatment of endo act by keeping aromatase from converting androgen to estrogen.  Genistein and daidzein is in soy. Naringenin is in grapefruit, orange juice, and limes.  Chrysin is in honey (yummy). Zearalenone is a mycotoxin (toxin produced by a fungus) found on maize, wheat, barley, sorghum and rye.

And a little review about estrogen receptors (ER): endo lesion growth seems to be mediated mostly through ERα.                   

Okay. Let's dive on in!

"Dietary phytoestrogens have been reported to inhibit aromatase activity in placental microsomes, but the effects in the human endometrium are unknown. Aromatase, the rate-limiting enzyme in the conversion of androgens to estrogens, has recently been shown to be expressed in the endometrium of women with endometriosis and is thought to play a role in the pathophysiology of this disease. Therefore, the objective of this study was to screen dietary phytoestrogens for their ability to inhibit aromatase activity in human endometrial stromal cells (ESC) and identify potential novel therapeutic agents for the treatment of endometriosis. The inhibition of aromatase activity by direct interaction with the dietary phytoestrogens genistein, daidzein, chrysin, and naringenin was tested in a cell free assay. Furthermore, test compound effects on aromatase activity in ESC cultures were also examined. Genistein and daidzein were inactive in the human recombinant aromatase assay whereas naringenin and chrysin inhibited aromatase activity. However, genistein (1 nM to 1 mM) stimulated aromatase activity in ESC whereas other phytoestrogens had no effect. Immunopositive aromatase cells were demonstrated in genistein-treated ESC but not in untreated control cultures. Taken together, our data suggest that genistein can increase aromatase activity in ESC likely via increased enzyme expression."

SO, according to this, naringenin and chrysin (found in grapefruits, orange & tangerine juice, limes, and honey) have aromatase inhibiting effects, so they keep androgens from being turned into estrogen. However, genistein (soy) increased the aromatase enzymes turning androgen into estrogen.  Let's go a little deeper.

Does dietary consumption have that big of an impact on endometriosis? The study below suggests not:

"Endometriosis is a disease in which uterine tissue proliferates in extrauterine sites. Using a surgical model to simulate endometriosis, we explored the potential for the phytoestrogen genistein, by injection and diet, to sustain endometriosis in rats. Uterine tissue was attached to intestinal mesentery of 8-week-old Sprague Dawley rats. After 3 weeks, the rats were ovariectomized and the implants measured. Following 3 weeks of daily injections or exposure to dietary genistein, animals were necropsied and implants located and measured. Injections of genistein (50 and 16.6 μg/g BW) or estrone (1 μg/rat) sustained the implants; injection of sesame oil (vehicle for estrone), dimethylsulfoxide (DMSO; vehicle for genistein), or genistein at 5.0 μg/g BW did not sustain implants. Dietary genistein (250 or 1000 mg genistein/kg AIN-76A diet) did not support the implants. In ovary-intact rats exposed to 250 mg genistein/kg AIN-76A diet, implant size was not altered, compared to control-fed animals. To assess estrogenic actions of genistein, we measured uterine estrogen receptor alpha (ER-α) and progesterone receptor (PR) isoforms A and B by Western blot analyses. Injections of estrone or genistein (50 or 16.6 μg/g BW) significantly reduced uterine ER-α compared to vehicle-treated animals. PR (B) was significantly increased by all injected doses of genistein or estrone and by the higher dietary dose (1000 mg genistein/kg AIN-76A). PR (A) was significantly increased by injected doses of genistein (16.6 and 5.0 μg/g BW). We conclude that pharmacologic injections, but not dietary physiological concentrations of genistein, support surgically induced endometriosis in rats. Our results suggest a critical role for ER modulation and genistein bioavailability in the maintenance of the implants."

Then there's studies showing that phytoestrogens act as anti-estrogens too:

"Results: Endometrial glandular cells responded to stimulation with genistein and daidzein by alteration of both ERα- and ERβ-mRNA expression. The effects were time- and dose-dependent....We could detect a decrease in ERα- and an increase in ERβ-mRNA expression after stimulation with tested phytoestrogens. Our results are in line with findings that phytoestrogens act as anti-estrogens in organs expressing more ERα and as estrogens in ERβ-presenting organs."

So, according to the above, in organs that have more ERα it can act as an anti-estrogen, but in ERβ they act as estrogens. (The central nervous system, cardiovascular, breast, bone, and urogenital all have both receptors. The lung and GI tract have ERβ, and the liver has ERα.) More so, this action is dependent on how much you get and when you get it. For instance, zearalenone (that little fungus producing toxins on maize, wheat, etc) and resveratrol (think grapes) at high doses act as antagonists on both receptors. Also genistein (soy) can be estrogenic but by acting on the ER sites can interfere with estrogen and over time lessen the response they show to estrogen. This is explored more thoroughly below:

"The soy-derived genistein, coumestrol, and equol displayed a preference for transactivation of ERβ compared to ERα and were 10- to 100-fold less potent than diethylstilbestrol. In contrast, zearalenone was the most potent phytoestrogen tested and activated preferentially ERα. All other phytoestrogens tested, including resveratrol and human metabolites of daidzein and enterolactone, were weak ER agonists. Interestingly, the daidzein metabolites 3′,4′,7-isoflavone and 4′,6,7-isoflavone were superagonists on ERα and ERβ. All phytoestrogens tested showed reduced potencies to activate ERα and ERβ compared to diethylstilbestrol on the estrogen-responsive C3 promoter compared to a consensus estrogen response element indicating a degree of promoter dependency. Zearalenone and resveratrol were antagonistic on both ERα and ERβ at high doses.... Due to activation of the ER, these compounds are referred to as phytoestrogens and have the potential to disrupt estrogenic signaling.... Interestingly, although ERβ shows lower binding affinity for and activation by endogenous estrogens, some xenoestrogens preferentially bind and activate ERβ.... the eventually high doses of dietary phytoestrogens (Bingham et al., 1998) warrant a more thorough analysis of the potential dysregulation of ER action by phytoestrogens.... Nevertheless, estrogenic and/or antiestrogenic activities of phytoestrogens like resveratrol and genistein may reduce but also stimulate estrogen-dependent tumor growth depending on dose and timing of exposure....Binding affinity to ER has been used frequently as a surrogate marker for estrogenicity. However, binding to the ER does not necessarily result in agonistic activity and may lead to antagonistic activity on ERα or ERβ. ...ZEA and COUM were the most potent phytoestrogens on ERα, and COUM, GEN, and equol preferentially activated ERβ....Another measure of estrogenic activity is the efficacy. ZEA, COUM, GEN, equol, and RESV had efficacies that were comparable to DES and E2 (Fig. 3). Therefore, these compounds were considered full agonists. ENL and 6OH-ENL showed markedly lower efficacies than DES and were considered partial agonists....Next to the agonistic activity, the antagonistic activity on ER is important for the characterization of endocrine-active compounds....ZEA that showed dose-dependent antagonistic activity on ERα and ERβ, RESV displayed an inverted U-shaped dose response (Fig. 4). At low doses, RESV increased the DES-induced activity of ERα and ERβ, but at high doses it inhibited activity of ERα and ERβ....Activation of the ER depends on the proper recruitment of coactivators that facilitate the transcription of ER target genes (Tremblay and Giguere, 2002). Recruitment of coactivators may, therefore, also determine the ER subtype–specific activation by phytoestrogens....Thus, these results warrant a cautious evaluation of the use of phytoestrogens to prevent estrogen-dependent diseases and require a thorough analysis of the estrogenic and antiestrogenic properties of these compounds. ... In contrast, ZEA was the most potent phytoestrogen tested and activated preferentially ERα. All other phytoestrogens tested including RESV and the daidzein and ENL metabolites were weak to very weak ER agonists....Beneficial effects on estrogen-related diseases are often attributed to antiestrogenic activities of phytoestrogens (Bingham et al., 1998). Analysis of antagonistic activity on ERα and ERβ revealed that only RESV and ZEA displayed apparent inhibitory properties on both ERα and ERβ transactivation. ...ZEA was a more potent antiestrogen than RESV and lacked any additive agonistic effects with DES on ERα and ERβ, indicating its potential to act as a pure ER antagonist at high doses....Recruitment of coactivators to ERα and ERβ is a prerequisite for ER action, and ER coactivators are also important determinants for tissue-specific estrogen action, since coregulators show a tissue-specific expression profile....We showed that all ER agonists tested enhanced recruitment of coactivators at doses similar to that which induced transactivation. This confirmed that coactivator recruitment is necessary for ER action and that a two-hybrid coactivator assay could serve as surrogate marker for ER activation....These studies showed that ERβ-selective phytoestrogens like genistein were more potent to recruit coactivators to ERβ compared to ERα....The isoflavones showed all pure ER agonistic activity. Thus, these compounds should be regarded as potentially estrogenic and, consequently, as potential endocrine disruptors that may cause elevated cell proliferation leading to estrogen-dependent tumor promotion.... The beneficial effects associated with soy intake are likely due in part to non-ER-mediated effects as described above. But, with regard to the adverse and beneficial ER-mediated effects, the timing of exposure is important....In conclusion, the risks and benefits of estrogenic or antiestrogenic effects depend highly on the target tissue as well as the timing and level of exposure. These latter two factors along with further research on the potential tissue-specific effects of phytoestrogens should aid in the assessment of the real risks and benefits of phytoestrogen-containing diets."

"We also found that genistein, though estrogenic, can interfere with the effects of estradiol. In addition, prolonged exposure to genistein resulted in a decrease in estrogen receptor mRNA level as well as a decreased response to stimulation by estradiol."
Getting a little strange around here...

Another good point brought up below, is that most tests are done in vitro (think lab) as opposed to in vivo (living human beings like us) and there is a difference.

"Some suspected endocrine disruptors have been shown to interact not only with the ER but also with the androgen receptor or to interfere with steroid hormone synthesis or metabolism (20)....Most suspected endocrine disruptors have been tested in in vitro systems (radioligand competition, transactivation assays) and these tests may underestimate or overestimate their in vivo estrogenic potency. The estrogenic potency of bisphenol A in vitro is 1000- to 5000-fold lower than that of E2, but in vivo bisphenol A was rather effective in stimulating PRL release from the pituitary.... Development of in vivo reporter systems for the assessment of the estrogenic activity of suspected endocrine disruptors might be necessary....The estrogenic potency of compounds is a complicated phenomenon that is the result of a number of factors, such as differential effects on the transactivation functionalities of the receptor, the particular coactivators recruited and the cell- and target gene promoter-context (62)....The reason for these differences in transcriptional activity of the ER subtypes is at the moment unknown, but it might reflect differential expression of transcriptional coactivators or differential stability of the receptor proteins.... Most prominently, phytoestrogens have been suggested to exert strong antiestrogenic effects, thereby inhibiting development of hormone-related cancers (39, 72). In our study, only zearalenone exhibited some antagonistic activity. All other phytoestrogens, including the flavonoids that are present in soy foods, showed only agonistic activity. In previous in vitro studies, involving ERα, only agonistic or at best partial antagonistic activities instead of complete antagonistic activities were reported (36, 37, 38, 75). Several other mechanisms for the proposed chemopreventive effects of flavonoids have been suggested, including induction of cancer cell differentiation, inhibition of protein tyrosine kinases, suppression of angiogenesis, and direct antioxidant effects (41, 76). These alternative mechanisms generally occur at flavonoid concentrations much higher (>5 μm) than the concentrations at which estrogenic effects are detected (<100 nm), and show a different structure-activity relationship; moreover, the effects are observed in cells in the absence of ER expression, and therefore it seems unlikely that all of these effects are ER mediated (41, 77, 78). On the other hand, because both ER subtypes are expressed in bone and the cardiovascular system (4, 79, 80, 81) and given the quite strong estrogenic activity of certain phytoestrogens, the potential beneficial effects of increased food intake of phytoestrogens in the prevention of postmenopausal osteoporosis and cardiovascular diseases should be further investigated (82)."

"These data taken together demonstrate alterations in the ovary following neonatal exposure to genistein. Given that human infants are exposed to high levels of genistein in soy-based foods, this study indicates that the effects of such exposure on the developing reproductive tract warrant further investigation....In summary, we have shown that neonatal genistein exposure produces multiple effects on the morphology and function of the mouse ovary. Furthermore, we have begun to elucidate the mechanisms by which genistein elicits such effects. The ectopic induction of ERα expression in the granulosa cells of the ovary appears to be associated more with the tyrosine-kinase inhibitory properties of genistein rather than its estrogen actions, although indirect effects secondary to estrogenization of the hypothalamic-pituitary axis cannot be ruled out. In contrast, the induction of MOFs in the ovary, which appears to be a direct effect and unrelated to the changes in ERα expression, is dependent on the presence of functional ERβ within the ovary. Future investigations into the mechanisms of the diverse effects of genistein will prove invaluable in evaluating the possible effects of phytoestrogens on reproductive function."

"...genistein has an ERβ-selective affinity and potency but an ERα-selective efficacy."

"Our results demonstrate that ERb can act as a negative
or positive dominant regulator of ER activity. This is
manifested through reduced transcriptional activity at
low concentrations of estradiol (E2); increased antag-
onistic effects of tamoxifen on E2 stimulated activity;
and enhanced agonistic action of the phytoestrogenic
compound genistein....

Estrogen levels vary in females during the menstrual
cycle, pregnancy and at menopause. These fluctuations
may influence the estrogenic activity in tissues contain-
ing ERb. Tissues expressing predominantly ERb could
be expected to be resistant to low levels of E2 with
respect to regulation of ERE-containing genes.
ERb expression may also amplify the
agonistic effect of the isoflavonoid genistein in tissuesthat also express ERa.
The concentrations of genistein required for activation of ERs and in
particular ERb are well within the range of what can
be measured in the circulation of individuals on a diet
rich in isoflavonoids." 

Feeling a little overwhelmed? Me too.

But let's keep going. Men have estrogen receptors too!

 "Results: Using concentrations of genistein that have been detected in sera of Asian men on regular soy-diet we found down-regulation of androgen receptor at both mRNA and protein level. The relative binding affinity to the AR was below 4% when compared to methyltrienologe (R1881) and there was no modulation of AR transcriptional activity by genistein concentrations up to 1 μM. We also demonstrated inhibition of PSA secretion after genistein treatment. As the anti-estrogen ICI 164 384 abolished the inhibitory effect of genistein and ER-β, but not ER-α is expressed in LNCaP cells we postulate that the mechanism of genistein action on androgen receptor is mediated through ER-β.
Conclusion: Using physiological concentrations of genistein we showed AR down-regulation by genistein in prostate cancer cells occurring via ER-β. This likely results in a modified response to hormonal stimuli and may help to explain the low incidence of prostate cancer in the Asian population."

"Emerging data is suggesting that estrogens, in addition to androgens, may also be contributing to the development of prostate cancer (PCa). In view of this notion agents that target estrogens, in addition to androgens, may be a novel approach for PCa chemoprevention and treatment. Thus, the identification and development of non-toxic dietary agents capable of disrupting androgen receptor (AR) in addition to estrogen receptor (ER) could be extremely useful in the management of PCa. Through molecular modeling we found carnosol, a dietary diterpene fits within the ligand binding domain of both AR and ER-α....The major finding of the study is the demonstration that carnosol can modulate both AR and ER-α activity. Using both prostate and breast cancer cell lines that each express AR and ER-α we found carnosol decreases the expression of AR and ER-α in a dose dependent manner. In addition, we have provided evidence that carnosol induces apoptosis in prostate cancer cells, however, further studies are needed to determine if there is any role for the ER-β which has been shown to have pro-apoptotic properties. We have also observed carnosol to be unique to other proposed dual AR and ER-α antagonists (e.g. tamoxifen, toremifene, fulvestrant) in that there is no evidence of carnosol acting as an agonist at the AR or ER-α. When carnosol was administered orally tumor formation was inhibited in athymic nude mice implanted with PCa cells. The attributes of carnosol to simultaneously disrupt AR and ER-α are unique compared to other FDA approved agents and may be further developed or chemically modified to develop a dual AR/ER-α disruptor."   
(carnosol is found in rosemary)

Let's come up for air.

So, in conclusion, it's still not clear. A regular diet of phytoestrogens (eating tofu or soymilk every day, taking pill forms of phytoestrogens) may not be the best thing to do until we have further research, but an occasional/rare bit probably won't hurt you (unless you're sensitive to soy). Like salt, soy is being processed in much of our food these days, so we may be getting more than we realize. Eating less processed food probably a good idea for our health overall, as is getting a variety of foods. Of course, we haven't even talked about xenoestrogens from environmental sources yet. We'll save that for another time. Let's head for the decompression chamber...