Glycogen storage disease type 1a (GSD-1a) is caused by a deficiency in glucose-6-phosphatase-α (G6Pase-α), and is characterized by impaired glucose homeostasis and a high risk of developing hepatocellular adenomas (HCAs). A globally G6Pase-α-deficient (G6pc−/−) mouse model that shows pathological features similar to those of humans with GSD-1a has been developed. These mice show a very severe phenotype of disturbed glucose homeostasis and rarely live beyond weaning. We generated liver-specific G6Pase-α-deficient (LS‑G6pc−/−) mice as an alternative animal model for studying the long-term pathophysiology of the liver and the potential treatment strategies, such as cell therapy. LS‑G6pc−/− mice were viable and exhibited normal glucose profiles in the fed state, but showed significantly lower blood glucose levels than their control littermates after 6 hours of fasting. LS‑G6pc−/− mice developed hepatomegaly with glycogen accumulation and hepatic steatosis, and progressive hepatic degeneration. Ninety percent of the mice analyzed developed amyloidosis by 12 months of age. Finally, 25% of the mice sacrificed at age 10–20 months showed the presence of multiple HCAs and in one case late development of hepatocellular carcinoma (HCC). In conclusion, LS‑G6pc−/− mice manifest hepatic symptoms similar to those of human GSD-1a and, therefore, represent a valid model to evaluate long-term liver pathogenesis of GSD-1a.

TM-induced inactivation of G6PT in these mice leads to a phenotype which mimics that of human GSD1b patients. The conditional mice we have generated represent an excellent tool to study the tissue-specific role of the G6PT gene and the mechanism of long-term complications in GSD1b.

Glycogen storage disease type 1a (GSD-1a) is a rare genetic disease caused by mutations in the catalytic subunit of the enzyme glucose-6-phosphatase-alpha (G6Paseα). The majority of patients develop long-term complications including renal failure and hepatocellular adenoma/carcinoma. The purpose of this study was to ascertain the proteomic changes in the liver of LS-G6pc −/− mice, a murine model of GSD-1a, in comparison with wild type mice to identify potential biomarkers of the pathophysiology of the affected liver. We used liquid chromatography-tandem mass spectrometry (LC-MS/MS) to analyze liver lysates from a total of 20 LS-G6pc −/− and 18 wild type (WT) mice. We compared the proteomic expression profile of LS-G6pc −/− and WT mice. We identified 4138 significantly expressed proteins, 1243 of which were differentially represented. Network and pathway analyses indicate that LS-G6pc −/− livers display an age-dependent modulation of the expression of proteins involved in specific biological processes associated with increased progression of liver disease. Moreover, we found upregulation of proteins involved in the process of tissue inflammation and macrophage polarization toward the M2 phenotype in LS-G6pc −/− mice with adenomas. Our results identify a metabolic reprogramming of glucose-6-P and a pathologic environment in the liver compatible with tumor development and progression.

Our data indicate that bone marrow-derived myelomonocytic cell transplant may represent an effective way to achieve liver reconstitution of highly degenerated livers in newborn animals.

Most patients affected by glycogen storage disease type 1a (GSD1a), an inherited metabolic disorder caused by mutations in the enzyme glucose-6-phosphatase-α (G6Pase-α), develop renal and liver complications, including the development of hepatocellular adenoma/carcinoma. The purpose of this study was to identify potential biomarkers of the pathophysiology of the GSD1a-affected liver. To this end, we used the plasma exosomes of a murine model of GSD1a, the LS-G6pc−/− mouse, to uncover the modulation in microRNA expression associated with the disease. The microRNAs differentially expressed between LS-G6pc−/− and wild-type mice, LS-G6pc−/− mice with hepatocellular adenoma and LS-G6pc−/− mice without adenoma, and LS-G6pc−/− mice with amyloidosis and LS-G6pc−/− mice without amyloidosis were identified. Pathway analysis demonstrated that the target genes of the differentially expressed microRNA were significantly enriched for the insulin signaling pathway, glucose and lipid metabolism, Wnt/β-catenin, telomere maintenance and hepatocellular carcinoma, and chemokine and immune regulation signaling pathways. Although some microRNAs were common to the different pathologic conditions, others were unique to the cancerous or inflammatory status of the animals. Therefore, the altered expression of several microRNAs is correlated with various pathologic liver states and might help to distinguish them during the progression of the disease and the development of late GSD1a-associated complications.

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Type Ib glycogen storage disease (GSD-Ib) is caused by a deficiency in the G6P transporter (G6PT) that translocates G6P from the cytoplasm into the endoplasmic reticulum lumen, where the intraluminal G6P is hydrolyzed to glucose by glucose-6-phosphatase-α (G6Pase-α). Clinically, GSD-Ib patients manifest a metabolic phenotype of impaired blood glucose homeostasis and a long-term risk of hepatocellular adenoma/carcinoma (HCA/HCC). Studies have shown that autophagy deficiency contributes to hepatocarcinogenesis. In this study, we show that G6PT deficiency leads to impaired hepatic autophagy evident from attenuated expression of many components of the autophagy network, decreased autophagosome formation, and reduced autophagy flux. The G6PT-deficient liver displayed impaired SIRT1 and AMP-activated protein kinase (AMPK) signaling, along with reduced expression of SIRT1, forkhead boxO3a (FoxO3a), liver kinase B-1 (LKB1), and the active p-AMPK. Importantly, we show that overexpression of either SIRT1 or LKB1 in G6PT-deficient liver restored autophagy and SIRT1/FoxO3a and LKB1/AMPK signaling. The hepatosteatosis in G6PT-deficient liver decreased SIRT1 expression. LKB1 overexpression reduced hepatic triglycerides levels, providing a potential link between LKB1/AMPK signaling upregulation and the increase in SIRT1 expression. In conclusion, downregulation of SIRT1/FoxO3a and LKB1/AMPK signaling underlies impaired hepatic autophagy which may contribute to HCA/HCC development in GSD-Ib. Understanding this mechanism may guide future therapies.

Glycogen storage disease type Ia (GSDIa) is an inherited metabolic disorder caused by mutations in the enzyme glucose-6-phosphatase-α (G6Pase-α). Affected individuals develop renal and liver complications, including the development of hepatocellular adenoma/carcinoma and kidney failure. The purpose of this study was to identify potential biomarkers of the evolution of the disease in GSDIa patients. To this end, we analyzed the expression of exosomal microRNAs (Exo-miRs) in the plasma exosomes of 45 patients aged 6 to 63 years. Plasma from age-matched normal individuals were used as controls. We found that the altered expression of several Exo-miRs correlates with the pathologic state of the patients and might help to monitor the progression of the disease and the development of late GSDIa-associated complications.