Ctcfl is a Fasting-Induced Epigenetic Regulator of Lipid Metabolism and Ketogenesis in the Liver

Engaging regulatory mechanisms mediating physiologic adaptations to fasting may be a potential tool for obesity and T2D. We previously demonstrated SGLT2i induce a fasting-like transcriptional program in liver, and identified Ctcfl (CCTC-binding factor (CTCF)-like) as a top-ranking transcript upregulated in SGLT2i-treated C57BL/6J mice (↑1.5-fold, p=0.01). Ctcfl was also upregulated 2.5-fold with fasting vs. fed littermates. We hypothesize Ctcfl mediates fasting-related transcriptional modulation via dynamic epigenetic regulation of chromatin accessibility. To identify drivers of Ctcfl expression, we studied AML12 hepatocytes, demonstrating key roles for AMPK activation and mTOR inhibition as upstream regulators. Moreover, in vivo inhibition of mTOR or insulin receptor increased hepatic Ctcfl expression (~2-fold), while insulin suppressed Ctcfl by ~50% within 3h. siRNA knockdown (KD) of Ctcfl indicates Ctcfl regulates transcriptional mediators of fasting (e.g. Hnf4, Srebf, Chrebp, Pgc1α), lipid/carbohydrate metabolism, and mitochondrial biogenesis. Single-cell RNAseq in Ctcfl-KD cells revealed distinct populations, enriched in mTOR, insulin signaling and Tfeb targets. Conversely, human CTCFL overexpression resulted in repression of regulators of lipid metabolism (Fas) and ketogenesis (Hmgcs2). In vivo liver-specific knockdown of Ctcfl, using N-acetyl galactosamine-conjugated siRNA, did not modulate body weight but increased circulating β-hydroxybutyrate and reduced respiratory quotient in the fasted state, suggesting shift to increased lipid utilization. Thus, we demonstrate Ctcfl is upregulated with fasting and fasting-like stimuli, including SGLT2i and AMPK activation, and repressed by refeeding, insulin signaling, and mTor pathways. Ctcfl can mediate a transcriptional program which may regulate lipid and ketone metabolism while acting as a “brake” to limit aberrant ketogenesis, potentially via alterations in chromatin accessibility. Disclosure V.Efthymiou: None. L.Poulos: None. L.Straub: None. V.Navarrete: None. B.Ozturk: None. S.Osataphan: None. J.I.Chimene-weiss: None. M.Patti: Consultant; MBX Biosciences, AstraZeneca, Hanmi Pharm. Co., Ltd., Other Relationship; Fractyl Health, Inc. Funding Swiss National Foundation; National Institutes of Health (R01DK106193)