Pax6 Haploinsufficiency Causes Abnormal Metabolic Homeostasis by Down-Regulating Glucagon-Like Peptide 1 in Mice

Heterozygosity for the Pax6 allele is associated with impaired glucose tolerance in humans. With a Pax6 mutant mouse model, we found many of the metabolic abnormalities were consistent with the effects of down-regulating the expression of glucagon-like peptide 1 (GLP-1). In addition to impaired glucose tolerance, adult heterozygous mutant mice (Pax6m/+) secreted less insulin responding to glucose and arginine administration compared with control mice. Moreover, Pax6m/+ mice showed increased food intake compared with control mice, although they were resistant to diet-induced fat accumulation. Indeed, levels of circulating GLP-1 and intestinal transcription of Gcg/Proglucagon were dramatically reduced in Pax6m/+ mice. Mutated Pax6 also failed to activate the Gcg/Proglucagon promoter by in vitro transfection assay. Finally, administering the GLP-1 receptor agonist exendin-4 to Pax6m/+ mice largely reversed their abnormal food intake, glycemic excursion, and insulin secretion. Our studies suggested that disru...