FitoestrogeniFitoestrogeni

DNA pol a

Cyclins E,A

B-Myb

Estrogen Receptor

Estrogen Receptors

http://www.bio.cmu.edu/Courses/BiochemMols/ER/#ERchime

Estrogen Receptors• ER-

– Uterus, testis, pituitary, ovary, epididymis, and adrenal gland.

• ER- (Kuiper et al. 1996)– brain, kidney, prostrate, ovary, lung, bladder, intestine, and

epididymis.– 88% identity with rat ER-

identity with human ER-

• Membrane localized ER (Pietras and Szego, 1997)

• ER and differ in C-terminal ligand binding domains and N-terminal transactivation domains. Highest homology in DNA binding domain.

Regulation of ER activity by coactivators and corepressors

Hall et al. 2001. J. Biol. Chem., 276: 36869-36872

ER effects on different cell types

Estrogen has multiple effects

Ligand Induces a Conformational Change in the LBD that Repositions helix 12

No Ligand Agonist

NR Antagonists Alter the Position of Helix 12

No Ligand Agonist(ER)

Antagonist(ER)

Phytoestrogens

Aherne and O’Brien, 2002. Nutrition 18:75-81.

Benassayag, et al., 2002. J. Chromatogr.B 777:233-248.

Comparison of binding affinities and transactivation of estrogen and phytoestrogens

Belcher & Zsarnovszky, 2001. J. Pharmacol. Exp. Therap. 299:408-414

Dietary Sources of Phytoestrogens

Pytoestrogens in humans• Fitoestrogeni hanno una attivita’ piu’ debole di quella degli

estrogeni circolanti (17--estradiol or estrone).• Fitoestrogeni possono legarsi alla sex steroid binding

protein (SBP) e -feroprotein (AFP) e circolare.• Fitoestrogeni sono coniugati nel fegato (da

sulfotransferasi and UDP-glucoronyosyl transferasi), circolano nel plasma ed escreti nelle urine.

• Livelli di Fitoestrogeni sono piu’ alti nei fluidi dei dotti prostatici e mammari di quelli del plasma.

• Le urine dei vegetariani possono contenere 1000 volte piu’ Fitoestrogeni che estrogeni totali.

• Fitoestrogeni hanno effetti inibitori a 0.5-50M che sono livelli simili alle urine.

Fitoestrogeni (PEs) della Soia• Genistein, daidzein, coumesterol, and equol si legano e

transattivano ER and (0.1-10M)• Genistetin ha una affinita’ piu’ alta per ER.• Soia PEs influenzano la progressione del ciclo cellulare,

crescita e differenziamento. Hanno attivita’ antiossidanti.

• Antioxidant, anti‑apoptosis, anti‑inflammatory, anti-cancer, and anti‑invasive.• Reduces Cu-induced LDL oxidation by binding to LDL via a glycosidic ether bond. Increases HDL cholesterol. Inhibits platelet activation.• Ameliorates neuronal damage due to ethanol consumption. Probably via antioxidant effect. Minimizes effects of NOS activity by ehtanol. Inhibits ethanol-induced arachidonic acid release and cycloxygenase activity.Anti-ageing role?• inhibitory effects on cancer initiation, growth promotion progression and angiogenesis in model systems. • The anti‑proliferative activity of resveratrol is mediated by p38-MAPKs via p53 mediated inhibition. Resveratrol may inhibit apoptosis induced by oxidized lipoproteins through inhibition of NF-B and AP-1 pathways.• Resveratrol inhibits protein kinase C, Akt, and FAK activities in ER (+) breast cancer cells.

Red wine phytoestrogens:Resveratrol, quercetin, and anthocyanins

Genistein

• Both estrogenic and anti-estrogenic effects

• Inhibitor of tyrosine kinases• 20-fold higher binding affinity for ER-

than ER- (Makela et al. 1999)

Synonyms: 4',5,7-Trihydroxyisoflavone;

Synonyms: 4',5,7-Trihydroxyisoflavone;

Synonyms: 4',5,7-Trihydroxyisoflavone;

4',5,7-Trihydroxyisoflavone

Phytoestrogens in Human Health

• Cancer preventive• Post-menopausal supplement• Prevention of osteoporosis• Cardiovascular health• Fertility• Breast enhancement

References: Kurzer, 2003. J. Nutr. 133: 1983S-1986S.

Benassayag, et al., 2002. J. Chromatogr.B 777:233-248.

Cancer preventive• Benefits to human breast and uterine cancer

controversial.• Genistein can be carcinogenic in uterine cancer at

neonatal exposure.• Cancer protective in animal studies, especially when

exposed during breast development.• Isoflavonoids and lignans stimulate proliferation of ER+

breast cancer cells.• Inhibit cell growth at high concentrations and in ER (-)

breast cancer cells. • Therefore, ER may have cancer protective effect.• Anti-angiogenic effects of genistein, daidzein, and

biochanin A may contribute to antitumor activity.• Anti-oxidants in vitro and in vivo.

Post-menopausal therapy

• In 2002, the Women’s Health Initiative (WHI) trial of estrogen/progestin therapy was halted midtrial due to high incidence of breast cancer and cardiovascular disease.

• Consumption of 30mg/d soy isoflavones may reduce hot flashes by 30-50%.

Prevention of osteoporosis

• Isoflavone intake increases bone mineral density.

• Can be useful in preventing post-menopausal osteoporosis.

• Diets rich in phytoestrogens can protect long-term bone loss (Setchell & Lydeking-Olsen, 2003. Am. J. Clin. Nutr. 78:593S-609S) .

Cardiovascular health

• Average intake of 47g/day soy protein results in 9% decrease in total cholesterol,13% decrease in LDL cholesterol, and a trend towards HDL cholesterol.

• Flavanoids decrease platelet aggregation.• Genistein-induced inhibition of growth factor

activity can interfere with platelet and thrombin action.

Effects on fertility (premenopausal)

• Interferes with menstrual cycle (delay)Reduced LH and FSH and progesterone.• Male rodents exposed to PEs in early life:

impaired semen quality, congenital malformations, testicular cancer

(coumesterol, delay in mating)