Epigenetic regulation of a pituitary/liver axis by GH, prolactin, and neonatal steroids

RAMIREZ, MARIA CECILIA; DE LUCA, PAOLA; ORNSTEIN, ANA MARIA; BECU-VILLALOBOS, DAMASIA; BRIE, BELÉN; CATALANO, PAOLO

Congreso; ENDO 2018; 2018

Growth hormone (GH) and prolactin secretion are sexually dimorphic in many species, and impact on sexual dimorphism of hepatic gene expression. Central deletion Dopamine D2 Receptor (D2R) in neuroDrd2KO mice decreases the growth axis, while lactotrope D2R disruption (lacDrd2KO) induces hyperprolactinemia, and neonatal steroids enhance pituitary GH content. We searched for epigenetic alterations such as promoter methylation and specific microRNA expression which might correlate with liver gene sexual dimorphism in female and male mice, as well as in experimental models with low or high GH, and high prolactin levels. We measured promoter methylation levels of hepatic genes using a methylation sensitive restriction enzyme, followed by specific qPCR. MicroRNA expression was measured through stem-loop RT-qPCR. A bioinformatic analysis pointed to the miRNAs mmu-miR-155-5p and mmu-miR-142a-3p as possible modulators of the sexually dimorphic liver genes Cyp7b1 and Prolactin Receptor (Prlr) respectively.Liver mRNA levels of Cyp2a4, Prlr, Hepatocite Nuclear Factor 6 (Hnf6) and Alcohol Dehydrogenase (Adh1) were female predominant, while Cyp7b1 mRNA levels were higher in males. High promoter methylation, which suppresses gene expression, accounted for sex differences in Prlr, Cyp2a4, Hnf6 and Cyp7b1, and reduced mmu-miR-155-5p in males correlated with enhanced Cyp7b1 expression. We next evaluated if these liver genes were epigenetically modified in our models of low GH (neuroDrd2KO), high prolactin (lacDrd2KO), or high GH levels (neonatally androgenized female mice). Liver Cyp7b1 mRNA expression was decreased both in male and female neuroDrd2KO mice, and the decrease correlated with enhanced mmu-miR-155-5p expression. Specific promoter methylation correlated inversely with decreased Prlr, Cyp2a4 and Hnf6 mRNA found in female neuroDrd2KO, and Prlr in androgenized females; but not with increased Prlr in lacDrd2KO females, while mmu-miR-142a-3p could not explain the modifications of Prlr. Furthermore, Cyp2a4 feminization in male neuroDrd2KO mice correlated with decreased methylation of the promoter.Our results demonstrate that specific epigenetic mechanisms participate in sexual dimorphism of distinct liver genes. Furthermore, regulation by GH, but not prolactin, may be achieved in part through specific promoter methylation or miRNA abundance. Mmu-miR-155-5p participates in Cyp7b1 regulation, while promoter methylation modulates the effect of GH on Cyp2a4, Hnf6 and Prlr liver expression.