Is there a link between dietary phytoestrogens and reproductive health in men? A meta-analysis of data from the USA and China

Food flavonoid ligand structure/estrogen receptor-α affinity relationships - toxicity or food functionality?

In silico molecular modelling is used to study interactions between flavonoid phytoestrogens and estrogen receptor (ER)α. Twenty flavonoids from foods were studied; e.g., genistein from soy, naringenin from grapefruit, phloretin from pears, chrysin from oyster mushrooms. These potential ligands' molecular attributes and their spatial arrangements that favour binding to the ligand binding cleft (LBC) of ERα are identified, and Docking Scores calculated. The Docking Score order is the same as the estrogenicity order for 8 of the flavonoids studied in detail. The number and position of flavonoid ring hydroxyls influence the Docking Scores which might relate to ERα's bio-activity. Hydrophobic interactions between ligands and ERα are also important; the number of rotatable CC bonds in ligands likely affects the magnitude of hydrophobic interactions and ligand fit. Our findings suggest that flavonoids with diverse structural features could have different binding energies and binding affinities with ERα, which might confer different functionalities and toxicities.

Soy isoflavone consumption and age at pubarche in adolescent males

PURPOSE

Isoflavones have estrogenic properties that may adversely affect pubertal development of boys. We examined if soy isoflavone consumption is associated with age at pubarche (first onset of pubic hair) in a male population with a wide range of soy intake.

METHODS

Boys aged 12-18 years (n = 248) who attended schools around Adventist universities in Southern California and Michigan self-reported their age at pubarche. Intake of soy isoflavones was assessed using a validated Web-based food frequency questionnaire; consumption levels were designated as low, moderate, and high. Descriptives, time-to-event analysis, and Cox proportional hazards regression that controlled for confounders were performed.

RESULTS

Energy-adjusted mean intakes were 0.8-54.9 mg/d for total isoflavones, 0.4-22.1 mg/d for daidzein, and 0.4-28.0 mg/d for genistein. Moderate and high total soy isoflavone intake were significantly associated with earlier adjusted median age at pubarche: 12.58 years [RR (95% CI): 1.58 (1.06, 2.36)] for moderate and 12.50 years [RR (95% CI): 1.63 (1.03, 2.60)] for high vs. 13.00 years for low consumers. Similarly, daidzein and genistein consumption was also significantly associated with age at pubarche. No significant associations were found for facial hair for any of the isoflavones.

CONCLUSIONS

Age at pubarche in this male population widely exposed to soy is within the reported range for boys' pubarcheal age; moderate/high consumers tend to have it earlier compared to low consumers. Further studies are needed to ascertain that substantial exposure to soy isoflavones does not adversely affect pubertal development of boys.

Intimate estrogen receptor-α/ligand relationships signal biological activity

How does estrogen receptor-α bind its natural ligands - estrogens? How can other molecules mimic estrogens and elicit different estrogenic responses? The answers lie in a complex and intimate chemical biology between ligands and receptor. This delicate interaction at the ligand binding cleft signals, via conformational change, exposure of a specific new charge topography at a second site (Activation Function-2). This, in turn, attracts a regulatory protein which modulates gene expression and controls biological activity.