Identification of a novel subset of hepatocytes that are simultaneously gluconeogenic and de novo lipogenic in the fed state and are naturally insulin resistant

It is generally accepted that hepatic gluconeogenesis, the synthesis of glucose from other carbon substrates (i.e.: glycerol, pyruvate, amino acids), is active in the fasted state and inactive in the fed state. In contrast, de novo lipogenesis (synthesis of fatty acids) is active in the fed state and is inactive in the fasted state. However, RNAPII ChIP-seq demonstrated that periportal but not pericentral hepatocytes display a basal (fed state) transcriptional activation of gluconeogenic genes that correlated with the basal level of gluconeogenic mRNA expression. Targeted single cell RNA-seq, HCR RNA-FISH, and PrimeFlow identified a subpopulation of periportal hepatocytes (approximately 10% of total hepatocytes) that simultaneously co-express both gluconeogenic and lipogenic genes in the fed state. These dual-positive hepatocytes identified in normal mouse livers are also present in human hepatocytes from humanized mouse livers. Spatial metabolic imaging coupled with stable isotope tracing analyses at the single cell level demonstrated that these individual hepatocytes simultaneously undergo both gluconeogenesis and de novo lipogenesis. Euglycemic-hyperinsulinemic clamps coupled with PrimeFlow analyses further demonstrated that this novel hepatocyte subpopulation is naturally insulin resistant. Moreover, high-fat diet-induced insulin resistance and hepatic steatosis were accompanied by an increase in the number of these dual-positive hepatocytes, suggesting a paradigm shift in our understanding of how the liver becomes insulin resistant. Taken together, these data demonstrate the existence of a unique, naturally insulin-resistant subset of mouse and human periportal hepatocytes that have the capacity to simultaneously undergo both gluconeogenesis and de novo lipogenesis.