Ablation of AMP-activated protein kinase α1 and α2 from mouse pancreatic beta cells and RIP2.Cre neurons suppresses insulin release in vivo
AMP-activated protein kinase (AMPK) is an evolutionarily conserved enzyme and a target of glucose-lowering agents, including metformin. However, the precise role or roles of the enzyme in controlling insulin secretion remain uncertain.
The catalytic α1 and α2 subunits of AMPK were ablated selectively in mouse pancreatic beta cells and hypothalamic neurons by breeding Ampkα1 [also known as Prkaa1]-knockout mice, bearing floxed Ampkα2 [also known as Prkaa2] alleles (Ampkα1 −/− ,α2 fl/fl ,), with mice expressing Cre recombinase under the rat insulin promoter (RIP2). RIP2 was used to express constitutively activated AMPK selectively in beta cells in transgenic mice. Food intake, body weight and urinary catecholamines were measured using metabolic cages. Glucose and insulin tolerance were determined after intraperitoneal injection. Beta cell mass and morphology were analysed by optical projection tomography and confocal immunofluorescence microscopy, respectively. Granule docking, insulin secretion, membrane potential and intracellular free Ca2+ were measured with standard techniques.
Trigenic Ampkα1 −/− ,α2 fl/fl expressing Cre recombinase and lacking both AMPKα subunits in the beta cell, displayed normal body weight and increased insulin sensitivity, but were profoundly insulin-deficient. Secreted catecholamine levels were unchanged. Total beta cell mass was unaltered, while mean islet and beta cell volume were reduced. AMPK-deficient beta cells displayed normal glucose-induced changes in membrane potential and intracellular free Ca2+, while granule docking and insulin secretion were enhanced. Conversely, βAMPK transgenic mice were glucose-intolerant and displayed defective insulin secretion.
Inhibition of AMPK activity within the beta cell is necessary, but not sufficient for stimulation of insulin secretion by glucose to occur. AMPK activation in extrapancreatic RIP2.Cre-expressing cells might also influence insulin secretion in vivo.
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- Ablation of AMP-activated protein kinase α1 and α2 from mouse pancreatic beta cells and RIP2.Cre neurons suppresses insulin release in vivo
Volume 53, Issue 5 , pp 924-936
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- Beta cell
- Insulin secretion
- Industry Sectors
- Author Affiliations
- 1. Section of Cell Biology, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Faculty of Medicine, Imperial College London, Sir Alexander Fleming Building, Exhibition Road, South Kensington, London, SW7 2AZ, UK
- 2. Photonics Group, Department of Physics, Imperial College London, London, UK
- 3. AstraZeneca, Alderley Edge, UK
- 4. Cambridge Institute of Medical Research, Cambridge, UK
- 5. Charing Cross Hospital, Imperial College London, London, UK
- 6. Electron Microscopy Centre, Imperial College London, London, UK
- 7. Institut Cochin, Université Paris Descartes, CNRS (UMR 8104), Paris, France
- 8. Inserm, U1067, Paris, France