Foxa1-deficient mice exhibit impaired insulin secretion due to uncoupled oxidative phosphorylation

Area of Science:

• Endocrinology
• Molecular Biology
• Metabolic Regulation

Background:

• Foxa1 (hepatic nuclear factor 3alpha) is crucial for early development and glucose homeostasis.
• Foxa1-/- mice exhibit growth retardation, hypoglycemia, and glucose intolerance.
• The precise mechanism of glucose intolerance in Foxa1 deficiency remains unclear.

Purpose of the Study:

• To investigate the mechanism underlying glucose intolerance in Foxa1-/- mice.
• To elucidate the role of Foxa1 in pancreatic beta-cell function and insulin secretion.
• To identify the molecular pathways affected by Foxa1 deficiency in beta-cells.

Main Methods:

• Islet perifusion experiments to assess glucose-stimulated insulin release.
• Measurement of pancreatic insulin and glucagon content.
• Analysis of calcium influx in beta-cells.
• Assessment of intracellular ATP levels and mitochondrial function.
• Chromatin immunoprecipitation assays to determine transcriptional targets.

Main Results:

• Foxa1-/- islets showed reduced glucose-stimulated insulin release and lower insulin/glucagon content.
• Beta-cells from Foxa1-/- mice had impaired calcium influx, indicating upstream defects in insulin secretion.
• Intracellular ATP levels were significantly lower in Foxa1-/- islets.
• Increased expression of uncoupling protein 2 (UCP2) in Foxa1-deficient islets led to partially uncoupled mitochondria.
• UCP2 was identified as a direct transcriptional target of Foxa1.

Conclusions:

• Foxa1 plays a novel role in regulating oxidative phosphorylation in pancreatic beta-cells.
• Foxa1 deficiency impairs beta-cell function through reduced ATP synthesis and increased UCP2 expression.
• These findings provide new insights into the molecular mechanisms of glucose intolerance and diabetes.