Mutations in the liver glycogen phosphorylase (Pygl) gene are associated with the diagnosis of glycogen storage disease type VI (GSD‐VI). To understand the pathogenesis of GSD‐VI, we generated a mouse model with Pygl deficiency (Pygl−/−). Pygl−/− mice exhibit hepatomegaly, excessive hepatic glycogen accumulation, and low hepatic free glucose along with lower fasting blood glucose levels and elevated blood ketone bodies. Hepatic glycogen accumulation in Pygl−/− mice increases with age. Masson's trichrome and picrosirius red staining revealed minimal to mild collagen deposition in periportal, subcapsular, and/or perisinusoidal areas in the livers of old Pygl−/− mice (>40 weeks). Consistently, immunohistochemical analysis showed the number of cells positive for alpha smooth muscle actin (α‐SMA), a marker of activated hepatic stellate cells, was increased in the livers of old Pygl−/− mice compared with those of age‐matched wild‐type (WT) mice. Furthermore, old Pygl−/− mice had inflammatory infiltrates associated with hepatic vessels in their livers along with up‐regulated hepatic messenger RNA levels of C‐C chemokine ligand 5 (Ccl5/Rantes) and monocyte chemoattractant protein 1 (Mcp‐1), indicating inflammation, while age‐matched WT mice did not. Serum levels of aspartate aminotransferase and alanine aminotransferase were elevated in old Pygl−/− mice, indicating liver damage. Conclusion: Pygl deficiency results in progressive accumulation of hepatic glycogen with age and liver damage, inflammation, and collagen deposition, which can increase the risk of liver fibrosis. Collectively, the Pygl‐deficient mouse recapitulates clinical features in patients with GSD‐VI and provides a model to elucidate the mechanisms underlying hepatic complications associated with defective glycogen metabolism.

Glycogen storage disease type Ia (GSD‐Ia) is an inherited metabolic disease caused by a deficiency in glucose‐6‐phosphatase‐α (G6Pase‐α or G6PC) which plays a critical role in blood glucose homeostasis by catalyzing the hydrolysis of glucose‐6‐phosphate (G6P) to glucose and phosphate in the terminal step of glycogenolysis and gluconeogenesis. Patients with GSD‐Ia manifest life‐threatening fasting hypoglycemia along with the excessive accumulation of hepatic glycogen and triglycerides which results in hepatomegaly and a risk of long‐term complications such as hepatocellular adenoma and carcinoma (HCA/HCC). The etiology of HCA/HCC development in GSD‐Ia, however, is unknown. Recent studies have shown that the livers in model animals of GSD‐Ia display impairment of autophagy, a cellular recycling process which is critical for energy metabolism and cellular homeostasis. However, molecular mechanisms of autophagy impairment and its involvement in pathogenesis in GSD‐Ia are still under investigation. Here, we summarize the latest advances for signaling pathways implicated in hepatic autophagy impairment and the roles of autophagy in hepatic tumorigenesis in GSD‐Ia. In addition, recent evidence has illustrated that autophagy plays an important role in hepatic metabolism and liver‐directed gene therapy mediated by recombinant adeno‐associated virus (rAAV). Therefore, we highlight the possible role of hepatic autophagy in metabolic control and rAAV‐mediated gene therapy for GSD‐Ia. In this review, we also provide potential therapeutic strategies for GSD‐Ia on the basis of molecular mechanisms underlying hepatic autophagy impairment in GSD‐Ia.