Objective: Recently, we reported that long-term intake of a water-soluble extract from culture medium of Ganoderma lucidum mycelia (WER) reduced hyperglycemia and enhanced glucose transporter-4 (GLUT4) translocation to the plasma membrane in skeletal muscles and adipose tissue in KK-A^y mice, a type 2 diabetic animal model with obesity. In the present study, we investigated the effect of WER on hepatic carbohydrate metabolism.
Methods: Female KK-A^y mice were given free access to water and high-fat food containing 0.5% WER for 8 weeks, and blood glucose levels were assessed every week. At the end of the experimental period, the expression and activities of sugar metabolic enzymes in the liver were determined by Real Time RT-PCR and each activity measurement method. Also, the amount of glycogen was measured by anthrone-sulfuric acid method. Furthermore, the expression level of GLUT2 and activation of AMP kinase (AMPK) and glycogen synthase kinase 3β (GSk3β) was also determined by western blot analysis.
Results: The mice with the high-fat ingestion showed a gradual increase in the levels of blood glucose and body weight. In the WER-treated mice, the blood glucose level was suppressed after 2 weeks of intake. The gene expression and enzyme activities of both glucose-6-phosphatase and phosphoenolpyruvate carboxykinase were suppressed, whereas those of glucokinase were increased in the mice with WER intake and pioglitazone administration. The accumulation of glycogen was increased. Moreover the expression of GLUT2 and phosphorylation levels of AMPK and GSk3β were also increased in the mice with WER intake.
Conclusion: These results indicate that WER affects hepatic carbohydrate metabolism, which may derive from the suppression of gluconeogenesis through the modulation of related enzymes and enhancement of glucose uptake, glycolysis and glycogen synthesis.