title: Supplemental dietary racemic equol has modest benefits to bone but has mild uterotropic activity in ovariectomized rats.
abstract: Soy isoflavones and their metabolites, with estrogenic activity, have been considered candidates for reducing postmenopausal bone loss. In this study, we examined the effect of dietary equol, a bioactive metabolite of the soy isoflavone daidzein, on equol tissue distribution, bone parameters, and reproductive tissue activity using an adult ovariectomized (OVX) rat model. An 8-wk feeding study was conducted to compare 4 dietary treatments of equol (0, 50, 100, 200 mg/kg diet) in 6-mo-old OVX female Sprague-Dawley rats. A dose response increase in tissue equol concentrations was observed for serum, liver, kidney, and heart, and a plateau occurred at 100 mg equol/kg diet for intestine. In OVX rats receiving 200 mg equol/kg diet, femoral calcium concentration was greater than those receiving lower doses but was still less than SHAM (P < 0.05), and other bone measures were not improved. Tibia calcium concentrations were lower in OVX rats receiving 100 and 200 mg equol/kg diet compared with the OVX control rats. Trabecular bone mineral density of tibia was also lower in equol-fed OVX rats. At this dietary equol intake, uterine weight was higher (P < 0.05) than in other OVX groups but lower than the SHAM-operated intact rats. The 200 mg/kg diet dose of dietary equol significantly increased proliferative index in the uterine epithelium. Dietary equol had no stimulatory effect on mammary gland epithelium. We conclude that in OVX rats, a dietary equol dose that had modest effect on bone also exerts mild uterotropic effects.
authors.affiliation: Department of Foods and Nutrition, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Leecole L
authors.initials: LL
authors.lastname: Legette
authors.forename: Berdine R
authors.initials: BR
authors.lastname: Martin
authors.forename: Mohammad
authors.initials: M
authors.lastname: Shahnazari
authors.forename: Wang-Hee
authors.initials: WH
authors.lastname: Lee
authors.forename: William G
authors.initials: WG
authors.lastname: Helferich
authors.forename: Junqi
authors.initials: J
authors.lastname: Qian
authors.forename: David J
authors.initials: DJ
authors.lastname: Waters
authors.forename: Alireza
authors.initials: A
authors.lastname: Arabshahi
authors.forename: Stephen
authors.initials: S
authors.lastname: Barnes
authors.forename: Jo
authors.initials: J
authors.lastname: Welch
authors.forename: David G
authors.initials: DG
authors.lastname: Bostwick
authors.forename: Connie M
authors.initials: CM
authors.lastname: Weaver
mesh_terms: D000818:Animals; D015519:Bone Density / Q000187:drug effects*; D001842:Bone and Bones / Q000737:chemistry; D002118:Calcium / Q000032:analysis; D019587:Dietary Supplements; D060754:Equol; D005260:Female; D007529:Isoflavones / Q000494:pharmacology*; D007928:Lethal Dose 50; D009929:Organ Size; D010052:Ovariectomy; D048789:Phytoestrogens / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014599:Uterus / Q000033:anatomy & histology / Q000187:drug effects*
chemical_list: C007610:4',7-dihydroxy-3,4-dihydroisoflavone; D007529:Isoflavones; D048789:Phytoestrogens; D060754:Equol; D002118:Calcium