Effects of Liraglutide on β-cell-specific Glucokinase-deficient Neonatal Mice

The glucagon-like peptide-1 receptor agonist liraglutide is used to treat diabetes. A hallmark of liraglutide is the glucose-dependent facilitation of insulin secretion from pancreatic β-cells. In β-cells, the glycolytic enzyme glucokinase plays a pivotal role as a glucose sensor. However, the role of glucokinase in the glucose-dependent action of liraglutide remains unknown. We first examined the effects of liraglutide on glucokinase haploinsufficient (Gck(+/-)) mice. Single administration of liraglutide significantly improved glucose tolerance in Gck(+/-) mice without increase of insulin secretion. We also assessed the effects of liraglutide on the survival rates, metabolic parameters, and histology of liver or pancreas of β-cell-specific glucokinase-deficient (Gck(-/-)) newborn mice. Liraglutide reduced the blood glucose levels in Gck(-/-) neonates but failed to prolong survival, and all the mice died within 1 wk. Furthermore, liraglutide did not improve glucose-induced insulin secretion in isolated islets from Gck(-/-) neonates. Liraglutide initially prevented increases in alanine aminotransferase, free fatty acids, and triglycerides in Gck(-/-) neonates but not at 4 d after birth. Liraglutide transiently prevented liver steatosis, with reduced triglyceride contents and elevated glycogen contents in Gck(-/-) neonate livers at 2 d after birth. Liraglutide also protected against reductions in β-cells in Gck(-/-) neonates at 4 d after birth. Taken together, β-cell glucokinase appears to be essential for liraglutide-mediated insulin secretion, but liraglutide may improve glycemic control, steatosis, and β-cell death in a glucokinase-independent fashion.