RESUMEN
Genistein (Gen), the primary isoflavone in soy, has been shown to adversely affect various endocrine-mediated endpoints in rodents and humans. Soy formula intake by human infants has been associated with early age at menarche and decreased female-typical behavior in girls. Adipose deposition and expansion are also hormonally regulated and Gen has been shown to alter these processes. However, little is known about the impact of early-life soy intake on metabolic homeostasis in adulthood. The current study examined the impact of early-life Gen exposure on adulthood body composition (by magnetic resonance imaging) and the molecular signals mediating adipose expansion. From postnatal day (PND) 1 to 22, rat pups were daily orally dosed with 50mg/kg Gen to mimic blood Gen levels in human infants fed soy formula. Female but not male Gen-exposed rats had increased fat/lean mass ratio, fat mass, adipocyte size and number, and decreased muscle fiber perimeter. PND22 Gen-exposed females, but not males, had increased expression of adipogenic factors, including CCAAT/enhancer binding protein alpha (Cebpα), CCAAT/enhancer binding protein beta (Cebpß), and peroxisome proliferator-activated receptor gamma (Pparγ). Furthermore, Wingless-related MMTV integration site 10b (Wnt10b), a critical regulator of adipogenic cell fate determination, was hypermethylated and had decreased expression in adipose of PND22 Gen-exposed females. These data suggest that developmental Gen exposure in rats has gender-specific effects on adiposity that closely parallel the effects of a postweaning high-fat diet and underscore the importance of considering timing of exposure and gender when establishing safety recommendations for early-life dietary Gen intake.
Asunto(s)
Adiposidad/efectos de los fármacos , Genisteína/toxicidad , Obesidad/inducido químicamente , Fitoestrógenos/toxicidad , Caracteres Sexuales , Administración Oral , Animales , Animales Recién Nacidos , Composición Corporal , Proteína alfa Potenciadora de Unión a CCAAT/biosíntesis , Proteína beta Potenciadora de Unión a CCAAT/biosíntesis , Femenino , Masculino , Obesidad/metabolismo , Ratas , Ratas Sprague-Dawley , Proteínas Wnt/biosíntesisRESUMEN
Human CCAAT/enhancer-binding protein delta (CEBPD) has been reported as a tumor suppressor because it both induces growth arrest involved in differentiation and plays a crucial role as a regulator of pro-apoptotic gene expression. In this study, CEBPD gene expression is down-regulated, and "loss of function" alterations in CEBPD gene expression are observed in cervical cancer and hepatocellular carcinoma. Suppressor of zeste 12 (SUZ12), a component of the polycomb repressive complex 2 (PRC2), silences CEBPD promoter activity, enhancing the methylation of exogenous CEBPD promoter through the proximal CpG islands. Moreover, this molecular approach is consistent with the opposite mRNA expression pattern between SUZ12 and CEBPD in cervical cancer and hepatocellular carcinoma patients. We further demonstrated that Yin-Yang-1 (YY1) physically interacts with SUZ12 and can act as a mediator to recruit the polycomb group proteins and DNA methyltransferases to participate in the CEBPD gene silencing process. Taking these results into consideration, we not only demonstrate the advantage of SUZ12-silenced CEBPD expression in tumor formation but also clarify an in vivo evidence for YY1-mediated silencing paths of SUZ12 and DNA methyltransferases on the CEBPD promoter.
Asunto(s)
Proteína beta Potenciadora de Unión a CCAAT/biosíntesis , Carcinoma Hepatocelular/metabolismo , Metilasas de Modificación del ADN/metabolismo , Regulación Neoplásica de la Expresión Génica , Silenciador del Gen , Complejos Multiproteicos/metabolismo , Proteínas Supresoras de Tumor/biosíntesis , Neoplasias del Cuello Uterino/metabolismo , Factor de Transcripción YY1/metabolismo , Proteína beta Potenciadora de Unión a CCAAT/genética , Carcinoma Hepatocelular/genética , Proteínas Portadoras/genética , Proteínas Portadoras/metabolismo , Metilasas de Modificación del ADN/genética , Femenino , Regulación Neoplásica de la Expresión Génica/genética , Células HeLa , Humanos , Masculino , Complejos Multiproteicos/genética , Proteínas de Neoplasias , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Complejo Represivo Polycomb 2 , Regiones Promotoras Genéticas/genética , Factores de Transcripción , Proteínas Supresoras de Tumor/genética , Neoplasias del Cuello Uterino/genética , Factor de Transcripción YY1/genéticaRESUMEN
CCAAT/enhancer-binding protein beta (C/EBPbeta) can function as a repressor or as an activator of human papillomavirus (HPV) gene expression, depending on which cell type the experiments are conducted. In this report, it was shown that within primary human foreskin keratinocyte cells (HFK) the activity of C/EBPbeta can be switched from that of a repressor of HPV11 expression to an activator by mutating a single promoter-proximal consensus YY1-binding site within the HPV11 upstream regulatory region (URR). It was shown that in HFK cells, exogenous expression of C/EBPbeta significantly activates the expression of mutant HPV11 URR reporter plasmids that contain deletions which overlap a 127 bp region (-269 to -142). Inclusive in this region are binding sites for multiple transcription factors, including AP1, YY1 and C/EBPalpha. Only mutation of the YY1 site resulted in the switch in phenotype, indicating that C/EBPbeta represses HPV11 expression in these cells via YY1 binding. The level of YY1 activity was also measured in HFK cells transfected with a C/EBPbeta expression plasmid and a significant increase in YY1 activity as compared with mock-transfected cells was found. C33A cells, which exhibit activation of wild-type HPV11 gene expression with exogenous C/EBPbeta co-expression, failed to demonstrate C/EBPbeta-induced YY1 activation. It was concluded that in HFK cells, exogenous C/EBPbeta induces the activity of YY1, which, in turn, can repress HPV11 URR expression through the promoter-proximal YY1-binding site.