This paper provides molecular evidence for a liver glyconeogenic pathway, that is, a concomitant activation of hepatic gluconeogenesis and glycogenesis, which could participate in the mechanisms that cope with amino acid excess in high-protein (HP) fed rats. This evidence is based on the concomitant upregulation of phosphoenolpyruvate carboxykinase (PEPCK) gene expression, downregulation of glucose 6-phosphatase catalytic subunit (G6PC1) gene expression, an absence of glucose release from isolated hepatocytes and restored hepatic glycogen stores in the fed state in HP fed rats. These effects are mainly due to the ability of high physiological concentrations of portal blood amino acids to counteract glucagon-induced liver G6PC1 but not PEPCK gene expression. These results agree with the idea that the metabolic pathway involved in glycogen synthesis is dependent upon the pattern of nutrient availability. This nonoxidative glyconeogenic disposal pathway of gluconeogenic substrates copes with amino excess and participates in adjusting both amino acid and glucose homeostasis. In addition, the pattern of PEPCK and G6PC1 gene expression provides evidence that neither the kidney nor the small intestine participated in gluconeogenic glucose production under our experimental conditions. Moreover, the main glucose-6-phosphatase (G6Pase) isoform expressed in the small intestine is the ubiquitous isoform of G6Pase (G6PC3) rather than the G6PC1 isoform expressed in gluconeogenic organs.high-protein diet; glyconeogenesis; glucose 6-phosphatase; phosphoenolpyruvate carboxykinase; liver THE CONSEQUENCES OF HIGH-PROTEIN feeding on the regulation and pathways of glucose disposal through glycogen metabolism and gluconeogenesis remain unclear. High-protein feeding induced both insulin and glucagon secretion in the fed state, associated with the repletion of glycogen stores (3, 45, 52), whereas excess dietary amino acids are metabolized within tissues and the derived nitrogen released into the circulation in the form of glutamine, alanine, serine, and glycine (28, 56). These amino acids are subsequently taken up by the liver, and the nitrogen is converted to urea and glutamine (12,28), the bulk of their carbon skeleton being converted to glucose through hepatic gluconeogenesis (8,29,37,51). This concomitant activation of both glycogen synthesis and gluconeogenesis in the fed state raises the question as to whether the glucose-6-P produced from gluconeogenic amino acid precursors could be directly channeled to glycogen through glycogenesis instead of being excreted as glucose from hepatocytes. This pathway of glyconeogenesis has been discussed over several decades, but despite some evidence during refeeding (49), its significance and molecular basis remain poorly understood (4, 30), and it has not previously been hypothesized under high-protein feeding.It is established that insulin stimulates glycogen synthesis and represses the gluconeogenic production of glucose, whereas glucagon represses glycogen synthesis and stimulates glucose ...