title: Dietary soy effects on mammary gland development during the pubertal transition in nonhuman primates.
abstract: While epidemiologic studies suggest that soy intake early in life may reduce breast cancer risk, there are also concerns that exposure to soy isoflavones during childhood may alter pubertal development and hormonal profiles. Here, we assessed the effect of a high-soy diet on pubertal breast development, sex hormones, and growth in a nonhuman primate model. Pubertal female cynomolgus monkeys were randomized to receive a diet modeled on a typical North American diet with one of two protein sources for approximately 4.5 years: (i) casein/lactalbumin (CL, n = 12, as control) or (ii) soy protein isolate with a human equivalent dose of 120 mg/d isoflavones (SOY, n = 17), which is comparable to approximately four servings of soy foods. Pubertal exposure to the SOY diet did not alter onset of menarche, indicators of growth and pubertal progression, or circulating estradiol and progesterone concentrations. Greater endometrial area was seen in the SOY group on the first of four postmenarchal ultrasound measurements (P < 0.05). There was a subtle effect of diet on breast differentiation whereby the SOY group showed higher numbers of differentiated large-sized lobular units and a lower proportion with immature ducts following menarche (P < 0.05). Numbers of small lobules and terminal end buds and mammary epithelial cell proliferation did not differ by diet. Expression of progesterone receptor was lower in immature lobules of soy-fed animals (P < 0.05). Our findings suggest that consumption of soy starting before menarche may result in modest effects consistent with a more differentiated breast phenotype in adulthood.
authors.affiliation: Department of Pathology, Section on Comparative Medicine, Wake Forest School of Medicine, Winston-Salem, NC 27157, USA. fdewi@wakehealth.edu
authors.forename: Fitriya N
authors.initials: FN
authors.lastname: Dewi
authors.forename: Charles E
authors.initials: CE
authors.lastname: Wood
authors.forename: Cynthia J
authors.initials: CJ
authors.lastname: Lees
authors.forename: Cynthia J
authors.initials: CJ
authors.lastname: Willson
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Register
authors.forename: Janet A
authors.initials: JA
authors.lastname: Tooze
authors.forename: Adrian A
authors.initials: AA
authors.lastname: Franke
authors.forename: J Mark
authors.initials: JM
authors.lastname: Cline
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics*; D049109:Cell Proliferation / Q000187:drug effects; D004032:Diet; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D007124:Immunoenzyme Techniques; D007529:Isoflavones / Q000097:blood / Q000494:pharmacology*; D008252:Macaca fascicularis; D008321:Mammary Glands, Animal / Q000166:cytology* / Q000187:drug effects; D011627:Puberty / Q000187:drug effects* / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013025:Glycine max / Q000378:metabolism*
chemical_list: D007529:Isoflavones; D012333:RNA, Messenger