The Hepatokine Adropin Is Regulated by Estrogen

Abstract

Introduction: menopause is associated with weight gain, visceral adiposity and NAFLD. Rodent ovariectomy (OVX) is an accepted model for human menopause. Many OVX studies add high-fat diet or old-age to accentuate deranged phenotype. We have shown OVX alone induced weight gain and changes in liver transcriptome including downregulation of Enho, encoding for the hepatokine adropin (1). Here, we explore changes in VAT cytokine and adipokine genes, hepatic miRNA, and liver triglyceride content induced by OVX, in addition to estrogen’s role in regulation of adropin. Methods: 9-week-old C57BL/6J female mice underwent OVX or sham surgery. Groups of 10 mice were sacrificed at 6- and 12-weeks post-surgery and tissues harvested including mesenteric adipose tissue representing VAT. Liver TG was quantified using Cayman colorimetric assay. In-vitro studies performed in the murine hepatic cell-line, BNL1.ME. Adropin was measured using ELISA. Results: OVX induced adverse inflammatory cytokine & adipokine gene expression in VAT at 6-weeks post-surgery (Il18 1.1 p=0.01, Rares2 2.9, p=0.003, Retn 5.5, p=0.002) and 12-weeks post-surgery (Tnfa 2.3 p<0.001, Cxcl5 1.9 p=0.04). In the liver, OVX induced an increase in TG content at 12 weeks post-surgery (realtive increase vs sham 2.0 p=0.05). Hepatic Enho expression showed a strong inverse coorelation with total body weight gain (r= -0.7 p<0.001) and liver TG content (r=-0.4, p=0.04). In-vitro, estrogen induced an increase in Enho (relative mRNA change vs. growing medium 2.6, p=0.004); though protein level was unchanged, a trend for increased adropin was found in supernatant (relative change vs control 2.2 P=0.09). In-silico analysis of data from OVX mice treated with estrogen showed up-regulation of Enho (relative change vs vehicle, 6 p<0.001). At 6-weeks post-surgery OVX induced changes in hepatic miRNA profile with 48 miRNAs differentially expressed vs SHAM (24 up & 24 down). Integrating data from same sample RNA-SEQ and miRNA-SEQ created a network of differently expressed miRNA with oppositely differently expressed known specific mRNA targets. mIR-29, a known regulator of Enho in liver, was not found to be correlated with Enho expression in this context. Conclusions: OVX alone is sufficient to induce adverse changes in VAT gene expression and liver TG. Hepatic adropin gene expression is regulated by estrogen and its downregulation was strongly correlated to phenotypes relevant to menopause induced metabolic dysfunction, weight gain and increased liver fat. Thus, adropin should be further explored as a novel therapeutic and/or biomarker for menopause induced metabolic dysfunction. (1) Stokar, J., Gurt, I., Cohen-Kfir, E., Yakubovsky, O., Hanna, A., Assayag, E., & Dresner-Pollak, R. (2019). RNA-Seq Analysis of Ovariectomy-Induced Changes in Mouse Liver Reveals New Targets for Menopause-Associated Metabolic Derangement. Journal of the Endocrine Society, 3(Supplement_1), SUN-033.