Current Pharmaceutical Design, 2005, 11, 2063-2073 2063

Management of the Menopausal Disturbances and Oxidative Stress

Francesco Pansini1,*, Gioacchino Mollica1 and Carlo M. Bergamini2

1
Gynaecologic-Obstetric Clinic and Menopause-Osteoporosis Centre and 2Department of Biochemistry and Molecular
Biology and Interdisciplinary Centre for the Study of Inflammation, University of Ferrara Medical School, Ferrara,
Italy

Abstract: Women frequently seek gynaecologic medical advice at menopause and require pharmacologic interventions to
control subjective vasomotor complaints and to prevent late severe organic complications, which may effect the
genitourinary tract, the skeletal, the cardiovascular and the nervous system. Depending on the severity of the presentation
and the involvement of additional systems beyond the reproductive tract, physicians have several distinct therapies
available, which should be carefully evaluated and administered in a “patient-personalised” fashion: they include organ-
oriented drugs, available for selective treatment in patients which do not display major direct endocrine symptoms, as well
as endocrine therapies (administration of native estrogens; or synthetic selective hormonal drugs, i.e. SERMs and
SEEMs). Much interest is now focusing on new kinds of plant estrogen-like compounds, mostly isoflavones, which by
one hand display estrogen-like (or antagonistic) effects, by the other are powerful antioxidising agents.
In our survey, we discuss extensively the enormous amount of data available in the literature, underlining by one side that
most of the formulations currently in use for the overall therapy of menopausal complaints have structure features also
characteristic of antioxidising agents, by the other that there are wide evidences of increased oxidative damage occurs in
women during the postmenopausal life. These observations suggest the possibility of a contribution of antioxidising
activity of the administered drugs to the beneficial clinical effects on the patients, in agreement with the demonstrated
estrogen intrinsic antioxidising activity in vitro. This stresses the requirement of further basic and clinical studies on the
relevance of oxidative damage during postmenopausal female life.
Key Words: Menopause; Climacteric syndrome; Hormone therapy; SERM; SEEM; Phytoestrogens; Oxidative damage.

INTRODUCTION patients is occasionally not immediately evident, but the

clinician should direct much of his attention to substantiate
Climacteric is defined as the critical transitional phase of
their roles, to assume the most appropriate therapeutic and
the reproductive life in women from the fertile to unfertile behavioural interventions.
status. It is characterised by an initial instability of endocrine
ovarian function and subsequently the drop of ovarian
Table 1. Non Hormonal Determinants in Menopausal
hormones production and definitive loss of endometrial Complaints
cycling. This phase of female life is followed by established
menopause, which is frequently associated with severe
pathologic states, linked to both the increase in age and the • Genetics
long-lasting absence of endogenous hormones. • Ageing
Research during the last years has clearly documented
• Relational Life
that ovarian steroids regulate both genital and extra-genital
functions. For these reasons any modification of ovarian • Environmental Factors
hormone secretion can effect several districts with different
• Behavioural Factors
severity in the clinical picture depending on entity of
hormonal changes and individual receptivity. Clinical • Associated Pathologies
disturbances can involve the genitourinary tract, the
cardiovascular, the skeletal system, as well as Central
Nervous System (CNS) related functions [1]. CURRENTLY AVAILABLE THERAPEUTIC
APPROACHES
This multifaced pattern of clinical presentation is mainly
related to the declining levels of steroid hormones, notably In this emerging “patient-tailored” approach, it must be
estrogens. However, other factors, as summarised in Table 1, underlined that exogenous estrogens can usually effectively
can variably contribute to the clinical presentation. Their restore the clinical status and/or prevent late complications
contribution to the severity of clinical picture in individual when indicated, but other therapeutic interventions can be
initiated in relation to specific clinical presentation and
*Address correspondence to this author at the Gynaecologic-Obstetric
individual needs. In the large variety of therapeutic appro-
Clinic and Menopause-Osteoporosis Centre University of Ferrara Medical aches currently available for menopause, a few general
School, Ferrara, Italy; E-mail: pan@unife.it categories can be distinguished as detailed in Table 2.

1381-6128/05 $50.00+.00 © 2005 Bentham Science Publishers Ltd.

2064 Current Pharmaceutical Design, 2005, Vol. 11, No. 16 Pansini et al.

Table 2. Therapeutic Approaches for Menopause endometrium during normal physiological cycling [6]. The
non-genomic mechanism is probably particularly relevant in
Hormonal Therapy:
clinical events involving the cardiovascular/vasomotor and
the nervous system [7, 8].
Native ovarian steroid hormones (estradiol/progesterone-
At the menopausal transition, levels of the main “repro-
progestogens/testosterone)
ductive” estrogen, 17 β−estradiol, drop from mean values of
Therapies with selective estrogenic activity: the cycling life (100-250 pg/ml) to less than 10 pg/ml, thus
losing the ability to saturate receptors and to stimulate target
• Native hormones: estriol
cells. This is accompanied by sustained levels of gono-
• Drugs: dotropins, particularly FSH, so that it is a common practice
- SERMs (Selective Estrogen Receptor Modulators: e.g. to define a clinically established menopausal state making
raloxifene) reference to the levels of circulating FSH (in the clinical
- SEEMs (Selective Estrogen Enzyme Modulators: e.g. practice a threshold value of 40 IU/L is usually adopted as
tibolone) indicative of menopausal status). This situation leads to a
functional deficiency of estrogenic activity. This is partially
• Active substances/extracts from plants (e. g. “phytoestrogens”, relieved by the remaining circulating estrogen (notably
Cimicifuga racemosa extract) estrone), produced prevalently in the adipose tissue rather
Therapies without estrogenic activity: than in the ovary, or by trace amounts of androgens,
testosterone, androstenedione and dihydroepiandrostene-
• Drugs: dione sulphate, usually secreted also in females before and
alendronate, risedronate, clodronate, PTH (osteoporosis) after menopause. Recent data indicate that androgen secre-
statins (hypercholesterolemia) tion has beneficial effect on women well-being both during
tolterodine (bladder instability) reproductive and postmenopausal life [3].
• Local products: These endocrine modifications are obviously associated
vaginal lubrificants, skin/vaginal Vitamin E with tissue changes of ageing. The strictly endocrine
menopausal symptoms involve, as mentioned above, the
Other therapies: genito-urinary tract (with mucosae trophic dysregulation and
• Psycho-therapy specific symptoms like dysuria, urgency, vaginal dryness and
dyspareunia), the cardiovascular system (with derangements
• “Alternative Medicine”: acupuncture, homeopathy, music-therapy,
in vessel physiology and blood cholesterol and increased risk
colour-therapy, art-therapy
of hypertension, hypercholesterolaemia and ischaemic heart
disease), the skeleton (with progressive loss of bone mineral
The following discussion will face in depth with the content, osteopaenia, and finally osteoporosis with the
advantages and disadvantages of hormonal/pharmacological disabilitating fractures) and the central nervous system (with
therapies. degenerative lesions and derangement in neuronal trans-
mission and neurovegetative, emotional, cognitive and
Hormone Therapy (HT) neuromuscular symptoms with possibly increased risk of
Parkinson-like complaints and Alzheimer’s disease) [9-12].
Hormone Therapy (HT), previously called Hormone
The role of the HT is well-established in relieving the
Replacement Therapy (HRT), represents the straight-forward
endocrine menopausal symptoms. Short-medium term hor-
attempt to restore the natural ovarian steroid hormones
monal treatment is usually required to control vasomotor
secretion to eliminate or minimise modifications and
symptoms (e.g. hot flashes), which are intrinsically transient.
alterations consequent to the ovarian endocrine deficiency.
Estrogens act through interaction with either of two distinct Long-term treatments are required to control other meno-
mechanisms: the first, genomic, involves intracellular pausal complaints (e.g. those involving urogenital tract) and
receptors (type α- and type β-receptor) and brings about for prevention of the late severe skeletal and cardiovascular
induced synthesis of specific proteins, the second, non- diseases, when indicated.
genomic, involves direct modulations at the target cell At this purpose, we must immediately underline that
membrane. recent scientific evidences [13, 14] have shed doubts on the
efficacy of HT in the secondary prevention of cardiovascular
The genomic effects have been dealt in detail in several
reviews available in the literature and the interested reader is disease, while most biological evidences (in both humans
referred to them for on extensive discussion of basic and and experimental animals) agree in revealing positive effects
clinical biology [2, 3]. Membrane specific effects have been on blood cholesterol parameters. Moreover, doubts are also
recognised only recently and are still incompletely under- emerged for the efficacy of HT in the primary prevention of
stood. They are related to rapid effects [4] and are clearly cardiovascular (CV) disease [15, 16]. Further controlled
exerted through the occupancy of membrane associated clinical prospective trials in healthy earlier postmenopausal
women are expected to confirm definitively the several
receptors coupled to G-protein, which trigger activation of
signal transduction machineries [5]. To give just a single biological evidences for the cardiovascular protective effect
example, we have ourselves demonstrated a few years ago of estrogens, to solve these unforeseen discrepancies
the relevance of cyclic AMP in the metabolic regulation of between the expected biological action and the clinical
outcome. In any case, HT, when administered as long-lasting
Management of the Menopausal Disturbances and Oxidative Stress Current Pharmaceutical Design, 2005, Vol. 11, No. 16 2065

therapy, seems to be associated with a limited increase in the The second category, SEEMs, includes selective estrogen
risk of breast cancer, venous thromboembolic disease and compounds capable themselves to modulate the intracellular
stroke, and careful attention must be kept in the recording the action of endogenous estrogen favouring the transformation
anamnestic risk for each of these pathologies before pres- of the more effective estrogenic molecules (e.g. estradiol)
cribing HT [17]. into less estrogenic compounds (like estrone) [27, 28].
Much concern is spreading among both physicians and An example of this action are the effects of SEEM
patients in relation to the increased risk of neoplastic tibolone on the enzymes of the estrogen pathway (17 beta
diseases, as late adverse effects of the chronic endocrine HSD, sulphotransferase and sulphatase) [29]. Women treated
treatment. The hormonal dependence of the breast and with tibolone have a low degree of endometrial and breast
endometrial tumours is clinically clear, and is basically tissue stimulation due to the drug-induced modulation of the
related to the biological function of ovarian sex steroids, intracellular estrogen metabolising enzymes to buffer
which stimulates proliferation of normal, as well as of estrogen content and estrogenic activity in these tissues [30,
transformed endometrial and mammary tissues. In the case 31]. It must be reminded that local management of estrogen
of endometrium, progesterone, used sequentially in the HT is conversely an important risk factor in the development of
in combination with estrogen, physiologically limits the pro- neoplasia [32].
proliferative effects of the estrogen, resulting into menstrua- The benefits of tibolone in the treatment of menopausal
tion and cell shedding. Not so clear is the role of proges- syndrome include osteoprotective, vasomotor and neuro-
terone for the breast, where it is suspected not to be vegetative effects. Conversely, a modest risk of venous
protective but actually to represent an important carcinogenic thromboembolism, a decrease of HDL cholesterol, possibly
factor [18-20]. This issue is certainly, together with the through interference with the function of liver lipoprotein
frequency of unexpected and unpleasant vaginal bleeding, lipase [33] and the appearance of virilization signs are
the main reason for which women discontinue HT, thus possible side effects [34].
limiting the clinically relevant efficacy in menopausal
complaints. New specific SERMs and SEEMs are expected for the
treatment of specific menopausal conditions.
Therapies with Selective Estrogen Activity Some active compounds extract from edible and not
edible plants have demonstrated both SEEM and SERM
As stated above, about 50% of women who initiated HT
activities. Phytoestrogens extracted from several plant
discontinue it after the 1st year of the treatment [21]. This
sources (e.g. soy, red clover and Cimicifuga racemosa)
high discontinuity rate appears due to problems related to
represent the more notable of these compounds presently
uterine and breast stimulation. This situation prompted
available. Several epidemiological, biological and animal
research to discover molecules with ideal pharmacological
scientific evidences support their role in the treatment of
profiles, able to act as estrogen receptor agonists in positive vasomotor disturbances, protection of osteoporosis and
“districts” but devoid of the ability to stimulate growth cardiovascular disease. Clinical evidences have been accu-
promoting effects onto the breast or the endometrium, or
mulated for beneficial effects of phytoestrogens, particularly
even better able to act as estrogen receptor antagonists in
in relation to cardiovascular diseases for control of LDL-
these tissues. This context has led to the synthesis and
cholesterol [35], lipoprotein oxidation [36] and menopausal
clinical use of the Selective Estrogen Receptor Modulators
vasomotor disturbances [37]. At present however it is clear
(SERMs) and of the Selective Estrogen Enzyme Modulator
that more robust clinical trials are expected to confirm these
(SEEM) molecules.
benefits [38-40].
The first category of compounds, the SERMs, includes
drugs that specifically interact with alpha or beta estrogenic Therapies without Estrogenic Activity
receptors, acting as selective estrogens. They should ideally Therapies without Estrogenic Activity represent a
be able to activate estrogen-signalling pathways in the rational first therapeutic option for the treatment of specific
skeleton and in the cardiovascular tissue, without stimulating menopausal conditions (like osteoporosis, hypercholestero-
the reproductive tract. In the clinics, Clomiphene was the laemia) when truly estrogen-deprivation endocrine symp-
first SERM to be developed and utilised in therapies related toms, such as vasomotor and urogenital disturbances, are
to infertility, while Tamoxifen was the second SERM lacking. In this perspective, alendronate and risedronate are
approved for the treatment of hormone responsive breast the main therapeutic options for osteoporosis, while statins
cancer. Later on Raloxifene was the first SERM selectively and tolterodine are the main options for the treatment of
used as osteoprotective in the prevention and the treatment of postmenopausal hypercholesterolemia and bladder instabi-
osteoporosis [22] with additional benefits on cholesterol lity, respectively. These specific therapies are without
metabolism and on breast cancer protection [23, 24]. Hot additional general benefit and include possible side-effects.
flushes and venous thromboembolic risk are possible side- Clinical experimental trials are now in progress to define in
effects [25]. Novel compounds are continuously developed detail clinical situations where use of these different
by the pharma-industries. The newest one, but actually its approaches might be superior in comparison to HT [41, 42].
receptor spectrum activity has not been yet defined is
estrene, which has proved as an effective osteoprotective ESTROGEN DEPRIVATION AND OXIDATIVE
agent against ovariectomy- induced osteopenia in experi- STRESS.
mental animal, without evidence of endometrial and breast
activation [26]. The formation of intracellular reactive oxygen and
reactive nitrogen species (respectively, ROS and RNS) has
2066 Current Pharmaceutical Design, 2005, Vol. 11, No. 16 Pansini et al.

been implicated in the pathogenesis of several diseases. ROS logical concentrations [47]. The antioxidative properties of
include hydroxyl radicals (OH.), superoxide anion (O2.-), estradiol have been more definitely appreciated in the case of
hydrogen peroxide (H2O2) and as well as the nitrogen vascular biology and of lipid metabolism [48, 49], but it is
centered nitric oxide (NO) (43, 44). When present in excess, conceivable that they are exerted also in other districts. For
ROS and their bioproducts may cause oxidative damage and instance animal evidences demonstrate that estrogen
be cytotoxic to cells. These oxidants can also act as sub- deprivation after ovariectomy induces an alteration in redox
cellular messengers in gene regulatory and signal trans- state that may be responsible for the decreased release of NO
duction pathways. and therefore the decrease in systemic vascular conductance
Under normal conditions, cells have well-developed [50, 51].
antioxidant systems that minimise the perturbations caused The chemical structure of estrogens enables them to act
by ROS. However, when ROS generation is increased to an as free-radical scavengers preventing oxidative damage. The
extent that overcomes the cellular antioxidants, then tissue key structural element of estrogen molecule required for
damage is produced by oxidative stress. Therefore, oxidative antioxidant effect is the presence of a phenolic ring in the A
stress may be viewed as a continuous battle between position. Under this aspect estrogens can be ascribed to the
inducers (pro-oxidants) and protective factors (antioxidants). class of the Polycyclic Phenolic Compounds (PPCs), mole-
Because ROS are partially reduced products of oxygen, they cules capable to intercalate into the cellular and mitochon-
have a high chemical reactivity with other bio-macro- drial membranes where they interrupt lipid peroxidation, a
molecules that may lead to lipid peroxidation, and oxidation free radical-induced chain reaction that undermines mem-
of DNA, RNA and proteins. Due to this reactivity, oxidative brane integrity or alternatively to integrate into circulating
stress is thought to play an important contributory role in the lipoproteins to exert in the microenvironment the antioxi-
pathogenesis of numerous degenerative and chronic diseases dative action, either directly or through poorly defined
in postmenopause. lipophilic derivatives [52].
Antioxidants are substances that either directly or
ANTIOXIDANT ACTIVITY OF ESTABLISHED
indirectly protect cells against the adverse oxidative effects
PHARMACOLOGIC THERAPIES IN MENOPAUSE
of xenobiotics, toxicants, drugs, and carcinogens. From a
functional point of view, antioxidants can be divided into All therapies commonly used in menopause can present
three general categories: (i) Nutritional (low molecular benefits and risks. Some of these therapies present as
weight compounds ingested by the diet such as vitamin C, E, additional benefit antioxidant activity (Table 3). The
carotenoids, flavonoids, plant and wine phenolics); (ii) therapeutic agents that demonstrate anti-oxidant activity are
Endogenous antioxidants (such as glutathione, albumin, all characterised by the presence of a phenolic ring, a key
bilirubin, uric acid); (iii) Enzymes that specifically meta- structural element required for cell protection against
bolise ROS precursors (such as catalase, superoxide oxidative stress, and can be classified as PPCs. It must be
dismutase, glutathione peroxidase, peroxiredoxins). kept in mind that the antioxidant activity of PPCs is greatly
Studies have documented that estrogens are potent amplified when cellular content in glutathione is high and
antioxidants and decrease LDL oxidation in vitro and in vivo predominantly in the reduced state. Glutathione is a small
[45, 46]. This concept was raised by studies which employed molecule composed of 3 amino acids that operate in cells
pharmacological concentrations, but it has been appreciated with several enzymes, such as glutathione peroxidase and
more recently that 17β-estradiol is active even at physio- glutathione reductase, to scavenge reactive free radicals, in

Table 3. Benefit, Risk and Antioxidant Activity of the Main Menopausal Therapies

Antioxidant
Therapy Benefit Risk
activity

Hot flushes, urogenital atrophy, Breast cancer

HT YES
osteoporosis CV and TEV

Low HDL
Hot flushes, urogenital atrophy, CV (?), TEV
Tibolone ?
Osteoporosis Virilization signs
Breast cancer (?)

Raloxifene Osteoporosis, Breast cancer risk TEV, hot flushes YES

Gastro-esophageal
Alendronate, Risedronate Osteoporosis NO
Irritation

Cholesterol (?), Hot flushes (?)

Phytoextracts Not assessed YES
Breast cancer risk (?)

HT = Hormonal Therapy; CV=Cardiovascular; TEV=Thrombo-Embolic Venous;

Management of the Menopausal Disturbances and Oxidative Stress Current Pharmaceutical Design, 2005, Vol. 11, No. 16 2067

addition to being itself susceptible of oxidation-reduction by chemical structure of estrogen enables it to act as a free-
a thiol-disulphide exchange. radical scavenger, preventing oxidative damage [60]. It must
also be mentioned that within CNS estrogens can addi-
HT tionally be converted into catechol-estrogens, which have
higher antioxidant ability than the parent compound [60].
All estrogens molecules (native or synthetic) usually Finally, the discovery that estrogen receptor (ER) alpha, not
utilised in the HT have phenol ring in A position of the beta, mediates protection of the brain carried far-reaching
cyclopentaneperhydrophenantrene structure and for this implications for a selective targeting of ERs in the treatment
reason they can be classified as PPCs. The main scientific and prevention of neural dysfunction associated with ageing
evidences of the anti oxidant activity of the estrogens came or brain injury [61].
from neurological, cardiovascular and metabolic fields.
The evidence is now specifically compelling that estro-
Neurological Evidences gens are neuroprotective for the Alzheimer’s disease for the
CNS has an high susceptibility to free radical damage. A oxidative stress via several mechanisms [62]: (i) estrogen
host of unique anatomical, physiological, and biochemical protects PC12 cells expressing mutant presenilin from
characteristics makes the CNS more vulnerable to the effects apoptosis induced by amyloid or serum withdrawal, prevent-
of free radicals: in particular, the level of oxidative metabolic ing and reducing free radical production and preserving
activity is disproportionate to the size of the brain. ROS are cellular ATP pools; (ii) estrogens protect cortical neurons
generated continuously in neurones during metabolism and from hydroxyl radical and amyloid toxicity by moderating
neuronal activity. This is reflected by normal cerebral oxy- intraneuronal free Ca2+ and preserving the function of
gen consumption in conscious young men which amounts to membrane proteins as Na-K-ATPase and glucose trans-
3.5 ml O2 100 g –1 brain min –1 [53]. Thus, in the brain, 2% of porters; (iii) estrogens protect neuroblastoma cells from the
body weight accounts for 20% of the resting total body mitochondrial toxin 3-nitroproprionic acid by preserving
oxygen consumption. Whether damage occurs or further Dym, thereby moderating both ATP depletion and ROS
develops depends on the balance between the generation of production; (iv) estrogen protects spinal cord cultures from
ROS and the activity of cellular antioxidant defences. The mice expressing the human mutant superoxide dismutase
protection in the CNS to oxidation is lower relative to other associated with familial amyotrophic lateral sclerosis against
systems. Specifically, there are lower levels of antioxidants excitotoxicity by preserving mitochondrial function and
(e.g. glutathione) and protective enzyme activity (e.g. reducing radical production; (v) estrogen induces activity of
glutathione peroxidase, catalase and superoxide dismutase) constitutive Nitric Oxide (NO) synthase with a rapid increase
[see 54, and references herein]. Conversely, the CNS of NO synthesis: NO synthase is widespread in the CNS and
contains abundant polyunsaturated fatty membranes. Lipid NO acts as neurotransmitter/neuromodulator. Besides its
membranes are extremely susceptible to free radical- relevance in relation to CNS degenerative diseases [63],
mediated destruction [55]. The cells in the CNS are non- modulation of NO production by estrogens might actually
replicating and it is thus conceivable that their damage might reveal as an important and widespread mechanism also for
have long-lasting effects, despite attempts to vicarage. the rapid non-genomic actions of the hormones.
Postmenopausal estrogen withdrawal constitutes a Cardiovascular Evidences
relevant factor for an increase to a susceptibility of CNS to Several observational studies conducted in the last 20
free radicals in the woman. It is well-know that Alzheimer’s years have clearly suggested that estrogen therapy for
Disease (AD) is a “female disease” and that the incidence postmenopausal women is associated with a lower incidence
increases progressively during the postmenopausal years. of ischaemic disease [64-66]. The most comprehensive of
The observation that preventive treatment with estrogen is these studies, the Nurses’ Health Study, began in 1985 and
accompanied by less incidence of AD reinforced for the key was updated in 2000 [66]. Biological and animal studies
pathogenic role of the postmenopausal estrogen deficiency in elucidated the mechanisms by which estrogen can protect
AD [56, 57]. against heart disease. These mechanisms include endothelial-
In general, there are several clinical and experimental mediated vascular effects, non-endothelial vascular effects,
evidences that estrogens might have neuroprotective favourable lipoprotein effects, possible favourable effects on
properties. Observations in vivo and in vitro, as well the glucose and insulin homeostasis, changes in extracellular
epidemiological studies, lend general support to this concept matrix and plaque stabilisation, and facilitation of collateral
[58]. Firstly, estrogen receptors, which are transcription vessel formation, as detailed in several clinical studies in
factors, might act directly on genes that code for proteins that humans by us and others [67-69]. Recent large controlled
modulate nerve-cell survival, regulating their expression. trials questioned for the cardioprotective effect of estrogen
These proteins might enhance neurotropic support, suppress therapy. The most wide studies are the “Heart and Estrogen/
apoptosis and affect neuronal structure. Secondly, the progestin Replacement Study” (HERS) [70] and the
neuroprotective action of estrogen could also depend on non- “Estrogen Replacement and Atherosclerosis” (ERA) [71]
classical actions of this neurohormone. Indeed, estrogen can investigations, addressed specifically to secondary (not
interact with intracellular signalling pathways that are primary) prevention, and also the large “Women Health
directly linked to the control of neuronal survival, such as the Initiative” (WHI) controlled study [13]. In our opinion it
Mitogen-Activated Protein Kinase (MAPK) pathway, cyclic should be clear that all these studies might be regarded as a
AMP-responsive-element-binding protein (CREB) and secondary prevention trial for the clinical picture of the
phosphatidylinositol 3-kinase (PI3K) [59]. In addition, the patients at the enrolment (mean age 63 years, large
2068 Current Pharmaceutical Design, 2005, Vol. 11, No. 16 Pansini et al.

prevalence of obese and overweight with a mean Body Mass significant. Another protective mechanism of the estrogens
Index of 28.5 kg/m2, 36% had hypertension, 13% had raised involving lipoproteins is the capability of these hormones to
cholesterol levels requiring medication, 50% were or had reduce the oxidation of LDL. Oxidised LDL play a major
been smokers). As consequence of these studies currently role in the development of atherosclerosis. The oxidation of
HT cannot be advocated for treatment of coronary artery LDL isolated from postmenopausal women is inhibited
disease (secondary prevention). At the same time investi- differentially by various estrogens [78-80]. Not only estra-
gators should be aware that for a definite consensus on the diol or equine estrogens, but also estriol seems to have an
opportunity to start or not to start HT for primary prevention antioxidant action on LDL at least in vitro, although its effect
of cardiovascular disease, results of large prospective is less potent than estradiol [81].
controlled preventive trials in healthy and younger post-
Metabolic Evidences
menopausal women should become available.
It is well documented that coronary heart disease (CHD)
Thus the clinical potential role of estrogens in protecting
is the leading cause of death among women in the western
against cardiovascular disease remains controversial and
world. One of the major predisposing factors for CHD is the
unresolved. However, during this “stand-by” additional
biological evidences are accumulating and corroborate the “metabolic syndrome”, a complex mixture of subtle risk
preventive role of estrogens against cardiovascular risk [72]. markers especially common in postmenopausal women [82,
It is well-known that direct protective effects of estrogens on 83]. This syndrome is characterised by mild abnormalities in
three or more of the following parameters: abdominal girth,
cardiovascular apparatus are mediated by the two estrogen
receptors ERα and ERβ. The receptor mechanism accounts blood pressure, fasting glucose, triglycerides, and HDL
cholesterol. Additional factors common in the metabolic
for the long-term (genomic) effects of estrogens on vascular
syndrome include abnormal markers of inflammation and
tissues. A second mechanism for a direct effect of estrogen
coagulation. Researchers in the field agree in thinking that
on vessels has been recently disclosed [73]. Experimental
the contemporaneous presence of even mild alterations in
studies have shown that physiological levels of estrogen can
several of these parameters is a signal of bad prognosis and
rapidly cause vasodilatation and this effect is largely
mediated by activation of endothelial nitric oxide synthase of increased risk for rapidly evolving cardiovascular
diseases. A special care must be paid to identify individuals
(eNOS) involving mainly ERα and P13-kinase-Akt pathway
with “metabolic syndrome” and to subject them to both
in this rapid activation of eNOS. MAP kinase pathway may
nutritional and pharmacological therapy. In this respect it is
possibly be involved as well. It has been also recently
interesting to note that recent evidences indicate that Free
demonstrated that estrogen inhibits the Angiotensin II (AII)
Fatty Acids (FFA) can play a pathogenic key role in
effects possibly through reduced AII type 1 receptor expres-
metabolic syndrome favouring insulin resistance throughout
sion [74].
involvement of ROS and/or RNS [84, 85]. These radicals
However, despite these biological new evidences, there is could induce macromolecular damage either directly or,
still no compelling demonstration at present that this non- indirectly, by activation of several stress-sensitive pathways
genomic activation of eNOS by estrogen has any physiolo- (such as NF-κB, p38MAPK, JNK/SAPK) [86-88]. In fact,
gical cardioprotective role in women. Are these complex infusion of FFA causes increased oxidative stress as judged
signalling vessel-pathways that underlie, for example, the by increased malondialdehyde levels and a decline in the
pathophysiology of “hot flushes” in the peri-post-meno- plasma reduced/oxidised glutathione ratio [89] In vitro
pausal woman? In fact, positive significant association was evidences also indicate that elevated FFA levels have
found between hot flushes surge and oxidative stress in numerous adverse effects on mitochondrial function,
postmenopausal woman [75]. Animal evidences however including the uncoupling of oxidative phosphorylation [90].
have reported that estrogen protects against endothelial and Estrogen withdrawal consequent to bilateral ovariectomy is
myocardial dysfunction resulting from brief ischaemia/ accompanied by sustained high blood level of FFA, while
reperfusion and that this effect was associated with increased subsequent administration of transdermal estrogens restore
serum NO2 concentration and reduced superoxide anion the physiological levels [91]. On these bases we can prospect
generation in arterial segments after this transient hypoxia that the high incidence of the “metabolic syndrome”, that
[76]. Other evidences suggest that chronic estrogen adminis- often complicates the physiological consequences of
tration is associated with significant decrease in glycoxi- menopause, can be at least in part due to the increase of FFA
dative damage and oxidative stress in the arterial wall, thus levels and the consequent oxidative stress.
attenuating the progression of atherosclerotic lesion [77].
One of the mechanisms whereby estrogen is thought to Raloxifene
benefit the cardiovascular system, is its effects on lipid Raloxifene is a SERM approved in many countries for
levels. It is well known that estrogen administration results the prevention and the treatment of postmenopausal
in both increased high-density lipoprotein (HDL) levels and osteoporosis [92] that acts as estrogen antagonist in breast
decreased levels of low-density lipoprotein (LDL), small and uterus [39], but possibly as agonist in other districts.
dense LDL, and lipoprotein (a) (Lp(a)), both atherogenic This is for instance the case in relation to the metabolism of
lipoproteins [see for instance the discussion by Fellin and lipids, where additional therapeutic benefits of raloxifene
associates in these issues]. Triglycerides levels also tend to arise from the ability to share the cholesterol-lowering
increase in patients receiving estrogen. However, it is not properties of estrogen [93], while displaying conversely a
known whether increased triglyceride levels in women prominent mammary breast protective effect (70% reduction
without hypertriglyceridaemia at baseline are clinically in risk of breast invasive cancer) [24].
Management of the Menopausal Disturbances and Oxidative Stress Current Pharmaceutical Design, 2005, Vol. 11, No. 16 2069

Another additional cardioprotective effect of raloxifene diseases and of clinically overt osteopenia and osteoporosis)
comes from the demonstration that it reduces blood pressure in Eastern populations. In careful investigations, it was
levels and improves endothelial dysfunction in male established that these differences are independent of genetic-
spontaneous hypertensive rats. These effects are possibly based grounds but rather correlate with the large assumption
mediated by an increased release of NO from vessel wall and of soy-based diets (with its high content of phytoestrogenic
by the reduction of the vascular production of ROS. This is isoflavones [102]) and the urinary excretion of large amounts
induced by a direct effect of the raloxifene on the membrane- of their metabolic derivatives [103].
bound NAD(P)H oxidase, which is shown to represent a Interest in these findings has grown also in Western
major source of free radicals in the vascular wall [94, 95]. world at the light of the high drop out of women from HT
The evidence [96] that the effect of raloxifene on cellular
(about 50% discontinue hormonal treatment after just one
ROS production is completely blocked by the estrogen
year) particularly because of vaginal bleeding, breast
receptor antagonist ICI 182,780 indicates that the anti-
tenderness and the fear of neoplasia [10]. Treatment with a
oxidant effect of raloxifene is estrogen receptor-mediated.
“natural” product would seem to meet better female accept-
In conclusion, the antioxidant properties of raloxifene on ability than the pharmacologic one, but it must nevertheless
the vessel are demonstrated by the reduction of free radical be clear to both physicians and patients that phytoestrogens
release, the induction of the eNOS/NO system, the improve- can reach tissue concentrations at which several biological
ment of endothelial dysfunction. All these effects induce a processes can definitely be influenced [105, 106], and that
decrease of blood pressure at least in hypertensive rats. they should absolutely not be administered as innocent
compounds, particularly in the case of additional endocrine,
POTENTIAL THERAPEUTIC USEFULLNESS OF immunologic or hormonal antineoplastic therapy [107-109].
PLANT ANTIOXIDANTS IN MENOPAUSE As already stated above, soy as well as many other plants
During the most recent years, an enormous body of (e.g. red clover) contain high amounts of isoflavones
literature has been published on the relevance of a consistent daidsein and genistein, mostly as their glycon derivatives,
intake of phytoestrogenic antioxidating agents (either in the daidzin and genistin. These compounds are powerful
form of traditional foods or of dietary supplementation) on antioxidants (because of their phenolic rings, as referred to
human fitness and well-being. This line of nutritional studies above), but they display also mild estrogenic activity, with
started from epidemiologic evidences of prevalence of comparatively higher affinity [110] for ERβ rather ERα,
morbidity and mortality in different populations and focused since they are relatively similar to estrogens for solubility
mainly on cardiovascular and neoplastic diseases. The main and space-filling organization, despite definitely different
nutritive elements taken in account are represented by plant chemical structure. Studies in experimental animals have
isoflavones, which have proven effective also in the frame of confirmed this general scheme, demonstrating that adminis-
menopausal disturbances, in particular in relation to tration of soy phytoestrogens to ovariectomised monkeys
vasomotor complaints [37] but possibly also for skeletal and protects against estrogen deprivation effects, without
genitourinary disturbances. The list of potential compounds stimulation to both uterus and breast [111], consistently with
in any case is far from complete, since several plants contain a selective stimulation of ERβ.
still unidentified phytoestrogenic compounds. Recent exam- Because of these reasons plant phytoestrogens can
ples are represented by Cimicifuga racemosa and by accumulate beneficial antioxidant activity with possible in
Umbellifera communis. Some of these molecules are very vivo estrogenic (or antiestrogenic) effects, depending on the
interesting as, to cite just a few, red grape resveratrol (which hormonal state of the recipient. In other terms, if they are
beside antioxidant and estrogenic activity is also a potential administered to a woman in the fertile state they are likely
modulator of apoptosis [97]) and ferutinin (from wild estrogen antagonists, (binding to ERs, without being able to
Umbellifera comunis) which is suspected to be a powerful fully transactivate them and antagonising the action of
estrogenic compound, specific for ERα [98, 99]. endogenous hormones) but can conversely behave as
This poses the basis for an “alternative medicine”, whose estrogens when administered to postmenopausal women,
potential clinical usefulness finds the basis in scientific vicariating the actions of the declining endogenous hormones
evidences (we will focus about below) as recognised by a [see ref. 112, for further discussion]. In addition, behaving a
recent health claim for soy foods from the American Food & bit like tibolone, it is likely that phytoestrogens can modulate
Drug Administration [100]. Notable examples are the so- interconversions among the several forms of circulating
called French Paradox (which relates alimentary habits in estrogens (even in the postmenopause), modulating the
France, consumption of red wine and prevalence of cardio- activity of endogenous interconverting hormones.
vascular diseases) and several studies of health epidemiolo-
gical comparison within East Asian populations, between IN VIVO STUDIES WITH PHYTOESTROGENS AND
people maintaining traditional food habits and those WITH PLANT FOODS
converted to Western-type nutrition.
The clinical studies on the effects of plant phytoestrogens
In relation to menopausal complaints, this is particularly (usually soy), stimulated originally by the epidemiological
appreciated in the prevention of cardiovascular diseases and investigations [113], focused mainly on cardiovascular
of postmenopausal osteoporosis [for a recent review see ref. diseases and lipid metabolism, resulting into the notion that
101]. Benefits for menopausal women include a lower alimentation with soy leads to a favourable pattern of serum
frequency of severe subjective and clinically relevant symp- lipoproteins, as compared to control subjects with soy-free
toms (including hot-flashes, incidence of cardiovascular diet, and to a reduced oxidability of circulating lipoproteins.
2070 Current Pharmaceutical Design, 2005, Vol. 11, No. 16 Pansini et al.

This antioxidative effects is also partly shared by estrogens Additional preparations beside those of soy phytoestro-
[52] and correlates with the presence within these molecules gens are continuously appearing on the market, as phytoes-
of aromatic phenolic groups. These functional groups are trogens from red clover (Trifolium pratense) and extracts
initially esterified to highly apolar derivatives by the LCAT from Cimicifuga racemosa. It is presently impossible to
reaction within HDL, and subsequently transferred from judge on their efficacy for the absence of carefully controlled
HDL to LDL by means of the cholesterol transfer protein. In human clinical trials, which are awaited with interest [see
this way, LDL particles are loaded with appreciable amounts refs 39 and 40, for discussion] at the light of the consistent
of antioxidants which might contribute, along with vitamin results obtained in experimental animals.
A, C and E, to protect LDL from oxidation in the blood
stream. In this way we can understand the observations by CONCLUSIONS
Tikkannen et al [36], who proved that supplementation of
normal diet with soy food bars containing about 20 mg of In this brief review we have discussed the therapeutic
isoflavones for periods as short as two weeks, could approaches now in use for the treatment of menopause, to
significantly delay oxidation of LDL after in vitro challenge relieve the clinical symptoms as well as to prevent the late
with copper salts in human volunteers. In a similar way, 4 metabolic complications, typical of this syndrome. Our goal
has been actually to make clear that there is availability of a
months supplementation of diet of premenopausal women
large panel of treatments and that the clinician must select
with 90 mg of isoflavones significantly delayed oxidability
the most appropriate one in a personalised way on the basis
of circulating LDL during ex vivo copper treatment [35].
of the patient’s clinical presentation and of the health targets
Several unpublished trials are also investigating the effects
of alimentary soy protein preparations with different phyto- to act for, taking in account both the individual needs and the
estrogen content in effecting circulating lipids. The conclu- therapeutic risks of each drug. Appreciation of the
sion they are apparently reaching is that phytoestrogens are therapeutic risk must consider available clinical evidences as
well as the patient’s family and clinical story.
important in a dose-dependent way for the lipid benefits,
promoting reduction in LDL-cholesterol, without effects or Some of these therapies, notably the endocrine general
slight increases in HDL-cholesterol, but only in moderately ones, also display additional possible benefits, particularly in
hypercholesterolemic patients. It is also noteworthy that relation to their antioxidant action, along with the main
efforts to reproduce the effects of soy diets through clinical target. The antioxidant benefit is tightly related to the
administration of extracted isoflavones until now gave poor chemical structure of these molecules, notably to the
results, suggesting that the protein-phytoestrogenic associa- presence of polycyclic phenolic groups. These additional
tion is important, although no explanation is yet available. activity of the endocrine treatments is particularly attractive,
Additional points of interest of phytoestrogens in and its potential and advantages are still incompletely
cardiovascular biology in relation to menopausal diseases are explored, at the light of the emerging evidences of the role of
the control of microcirculation [114] (which might also be oxidative stress for postmenopausal women’s health.
relevant in relation to the tumour preventing activity [115,
116] of phytoestrogens and other plant antioxidants as the ABBREVIATIONS
polyphenols from green tea) and the relief of vasomotor
CNS = Central Nervous System
complaints [37]. Even these topics however are far from
established because of ethical difficulties and of the intrinsic CV = Cardiovascular
instability of these self-limiting clinical symptoms, so that
ER = Estrogen Receptor
large population samples and careful statistical analysis are
required to fully clarify these issues [39]. FFA = Free Fatty Acids
The situation is similarly confused for the other HT = Hormone Therapy
climacteric clinical syndromes, as is the case of neurological NO = Nitric Oxide
and skeletal diseases, although evidences in experimental
animals are quite promising. In the case of bone diseases, for PPC = Phenolic Poly-cyclic Compounds
instance, observational studies demonstrate lower incidence PTH = Parathyroid Hormone
and lower clinical severity in Eastern populations, while
biologic studies suggest that phytoestrogens have intrinsic SEEM = Selective Estrogen Enzyme Modulator
growth promoting activity, stimulating osteoblast activity SERM = Selective Estrogen Receptor Modulator
[117]. These observations are extremely important because
they would introduce completely new weapons against TEV = Thrombo-Embolic Venous
osteoporosis, since, as stated above, all pharmacological
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