Reproductive safety studies with genistein in rats.

Area of Science:

• Toxicology
• Developmental Biology
• Nutritional Science

Background:

• Genistein is a soy phytoestrogen with potential chemopreventive properties.
• Epidemiological studies suggest reduced cancer rates in populations with high soy intake.
• Concerns exist regarding potential adverse effects of genistein due to its estrogenic activity.

Purpose of the Study:

• To assess the teratogenic and fetal toxic potential of genistein.
• To evaluate genistein's safety profile through in vitro and in vivo studies.
• To determine a no-observed-adverse-effect level (NOAEL) for genistein exposure.

Main Methods:

• In vitro rat whole embryo culture (WEC) assay to screen for fetotoxicity and teratogenicity.
• In vivo oral administration (gavage and dietary admix) in embryo-fetal development studies in rats.
• Maternal and fetal endpoints including body weight, food consumption, mortality, malformations, and variations were assessed.

Main Results:

• In vitro, genistein exhibited teratogenic potential at high concentrations (≥10 µg/mL).
• In vivo studies showed maternal and fetal toxicity at high doses (up to 1000 mg/kg/day), including increased pup mortality and reduced body weights, but no teratogenic effects.
• The NOAEL for maternal and developmental toxicity was determined to be 100 mg/kg/day via dietary admix.

Conclusions:

• Genistein does not demonstrate in vivo teratogenic potential, even at maternally and fetally toxic doses.
• In vitro findings were not predictive of in vivo outcomes.
• A NOAEL of 100 mg/kg/day was established for genistein administered orally via dietary admix.