280-OR: CTCFL Is a Fasting-Induced Epigenetic Regulator That Modulates Lipid and Cholesterol Metabolism in the Liver

Abstract

Physiologic adaptations to fasting ensure health when food intake is limited; engaging these regulatory mechanisms is a potential tool for T2D and obesity. One approach utilizes SGLT2 inhibitors (SGLT2i), which reduce glucose, weight and cardiovascular/renal complications. In preclinical studies, we demonstrated SGLT2i induce a fasting-like transcriptional program in liver, and identified Ctcfl (CCTC-binding factor (CTCF)-like, also known as Boris, or Brother Of Regulator of Imprinting sites), as a top-ranking upregulated transcript in SGLT2i-treated C57BL/6J mice (↑1.5-fold, p=0.017). Ctcfl was also upregulated 2.5-fold with fasting as compared to ad lib-fed littermates. Thus, we hypothesize Ctcfl mediates fasting-related transcription via dynamic epigenetic regulation of chromatin accessibility.To identify drivers of increased Ctcfl expression in the fasting state, we performed in vitro studies in cultured AML12 hepatocytes revealing a key role for AMPK activation and mTOR inhibition as upstream regulators of Ctcfl. Transcriptomic analysis in siRNA-mediated Ctcfl knockdown (KD) vs. wild type (WT) cells indicates Ctcfl regulates critical pathways of lipid/carbohydrate metabolism, mitochondrial biogenesis, and transcriptional mediators of fasting (e.g., Hnf4, Srebf, Chrebp, Pgc1α). Single-cell RNAseq revealed distinct populations in Ctcfl-KD vs. WT cells, with the two largest sub-clusters of Ctcfl-KD cells enriched in genes associated with mTOR and insulin signaling and Tfeb target genes. Conversely, gain-of-function studies via overexpression of human CTCFL resulted in significant repression of key transcription factors and enzymes regulating lipid/cholesterol metabolism and gluconeogenesis (Pgc1α). In conclusion, we demonstrate that AMPK and mTor-mediated pathways regulate Ctcfl, a mediator of fasting-associated lipid and glucose transcriptional programs in the liver, potentially via alterations in chromatin accessibility. Disclosure V. Efthymiou: None. J. I. Chimene-weiss: None. L. Zhou: None. S. Osataphan: None. L. Su: None. M. Patti: Consultant; Self; Cello Health, Fractyl Laboratories, Inc., MBX, Poxel SA, WGBH, Other Relationship; Self; Xeris Pharmaceuticals, Inc., Research Support; Self; Dexcom, Inc.