title: Dose-dependent effects of isoflavone exposure during early lifetime on the rat mammary gland: Studies on estrogen sensitivity, isoflavone metabolism, and DNA methylation.
abstract: METHODS
  Isoflavone (ISO) exposure during adolescence modulates 17β-estradiol (E2) sensitivity of the adult mammary gland. The present study investigated the dose dependency of these effects focusing on proliferation, estrogen receptor dependent and independent gene expression, as well as DNA methylation and ISO metabolism.
  
  
  RESULTS
  Female Wistar rats were lifelong exposed to an ISO-depleted diet or to diets enriched with a soy ISO extract (ISO-rich diet (IRD)) causing plasma concentrations as observed minimally (IRDlow) and maximally (IRDhigh) in Asian women. The extract was characterized by both phytochemical analysis and E-Screen. Rats were ovariectomized at postnatal day (PND) 80 and treated with E2 from PND94 to 97. In contrast to uterine response, body weight and visceral fat mass were affected by ISO. In the mammary gland, both E2-induced proliferation (proliferating cell nuclear antigen staining) and estrogen receptor activation (progesterone receptor staining) were significantly reduced by IRDhigh but not by IRDlow, which however attenuated Gdf15 mRNA expression. DNA methylation analysis revealed significant differences in the promoter regions of Aldhl1, Extl1, and WAP between IRDhigh and ISO-depleted diet.
  
  
  CONCLUSIONS
  Lifelong exposure to ISO results in dose-dependent differential effects on proliferation, gene expression, and DNA methylation in rat mammary glands. Yet, a decrease in estrogen responsiveness was only achieved by IRDhigh.
authors.affiliation: German Sports University Cologne, Köln, Germany.
authors.forename: Tina
authors.initials: T
authors.lastname: Blei
authors.forename: Sebastian T
authors.initials: ST
authors.lastname: Soukup
authors.forename: Katja
authors.initials: K
authors.lastname: Schmalbach
authors.forename: Maria
authors.initials: M
authors.lastname: Pudenz
authors.forename: Frank Josef
authors.initials: FJ
authors.lastname: Möller
authors.forename: Björn
authors.initials: B
authors.lastname: Egert
authors.forename: Nadine
authors.initials: N
authors.lastname: Wörtz
authors.forename: Anne
authors.initials: A
authors.lastname: Kurrat
authors.forename: Dennis
authors.initials: D
authors.lastname: Müller
authors.forename: Günter
authors.initials: G
authors.lastname: Vollmer
authors.forename: Clarissa
authors.initials: C
authors.lastname: Gerhäuser
authors.forename: Leane
authors.initials: L
authors.lastname: Lehmann
authors.forename: Sabine E
authors.initials: SE
authors.lastname: Kulling
authors.forename: Patrick
authors.initials: P
authors.lastname: Diel
mesh_terms: D000818:Animals; D001835:Body Weight / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D019175:DNA Methylation / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004967:Estrogens / Q000378:metabolism*; D005260:Female; D006801:Humans; D007529:Isoflavones / Q000097:blood / Q000494:pharmacology*; D020738:Leptin / Q000097:blood; D061986:MCF-7 Cells; D008321:Mammary Glands, Animal / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D011960:Receptors, Estrogen / Q000235:genetics / Q000378:metabolism; D013025:Glycine max / Q000737:chemistry; D014599:Uterus / Q000187:drug effects
chemical_list: D004967:Estrogens; D007529:Isoflavones; D020738:Leptin; D011960:Receptors, Estrogen
keywords: Epigenetics; Isoflavones; Mammary gland; Phase-II metabolism; Proliferation