Glycogen storage disease type la (GSD-Ia) is caused by a deficiency in glucose-6-phosphatase-alpha (G6Pase-alpha or G6PC), a key enzyme in endogenous glucose production. This autosomal recessive disorder is characterized by impaired glucose homeostasis and long-term complications of hepatocellular adenoma/carcinoma (HCA/HCC). We have shown that hepatic G6Pase-alpha deficiency-mediated steatosis leads to defective autophagy that is frequently associated with carcinogenesis. We now show that hepatic G6Pase-alpha deficiency also leads to enhancement of hepatic glycolysis and hexose monophosphate shunt (HMS) that can contribute to hepatocarcinogenesis. The enhanced hepatic glycolysis is reflected by increased lactate accumulation, increased expression of many glycolytic enzymes, and elevated expression of c-Myc that stimulates glycolysis. The increased HMS is reflected by increased glucose-6 phosphate dehydrogenase activity and elevated production of NADPH and the reduced glutathione. We have previously shown that restoration of hepatic G6Pase-alpha expression in G6Pase-alpha-deficient liver corrects metabolic abnormalities, normalizes autophagy, and prevents HCA/HCC development in GSD-Ia. We now show that restoration of hepatic G6Pase-alpha expression normalizes both glycolysis and HMS in GSD-Ia. Moreover, the HCA/HCC lesions in L-G6pc-/- mice exhibit elevated levels of hexokinase 2 (HK2) and the M2 isoform of pyruvate kinase (PKM2) which play an important role in aerobic glycolysis and cancer cell proliferation. Taken together, hepatic G6Pase-alpha deficiency causes metabolic reprogramming, leading to enhanced glycolysis and elevated HMS that along with impaired autophagy can contribute to HCA/HCC development in GSD-Ia. Published by Elsevier Inc.