NREP Bridges TGF-ß Signaling and Lipid Metabolism in the Epigenetic Reprogramming of NAFLD in the Offspring of Insulin-Resistant Parents

Nonalcoholic fatty liver disease (NAFLD) prevalence is increasing worldwide and few studies have associated maternal diabetes and birth weights with increased risk for NAFLD. We used an unique non-dietary model, manifesting hyperglycemia and hyperinsulinemia-two hallmarks of gestational and type 2 diabetes. We aimed to determine the genetic and epigenetic effects of paternal vs. maternal genetic insulin resistance on the developmental programming in the offspring of the liver-specific insulin receptor knockout (LIRKO) mice. Male control F1 offspring from father LIRKO (FL), mother LIRKO (ML) or control mothers and fathers (C) were weaned on a chow or high-fat-diet (HFD) and followed for 3 months. FL and ML showed impaired growth and body weight composition. FL and ML developed hepatic steatosis compared to C when challenged with HFD and exhibited increased hepatic expression of lipogenesis-associated genes. Hepatic transcriptomic and genome-wide DNA methylation analyses of FL and ML on chow diet presented enriched-pathways associated with TGF-β signaling and lipid synthesis. FL and ML hepatic NREP mRNA levels were decreased 50% (p<0.05) on HFD compared to C. In-vivo and in-vitro modeling of hepatic steatosis in HepG2 and human primary hepatocytes decreased NREP mRNA and protein levels. Knock-down experiments performed in HepG2 cells revealed that NREP acts by regulating triglyceride and cholesterol synthesis transcriptional network via regulation of ATP-citrate lyase (ACL) in a phospho-AKT dependent manner. Finally, reduced NREP mRNA levels in patients with hepatic steatosis by 40% (p<0.05) and recent preclinical trials implicating ACL in NAFLD highlight the translation relevance of our findings. These data suggest that prenatal insulin resistance epigenetically regulates a novel gene, NREP, that has detrimental effects on metabolic adaptation and transcriptional regulation of hepatic metabolism in the development of NAFLD.