Ablation of AMP-activated protein kinase alpha 1 and alpha 2 from mouse pancreatic beta cells and RIP2.Cre neurons suppresses insulin release in vivo

• Published in: Diabetologia 2010-05, Vol.53 (5), p.924-936
• Main Authors: Sun, G, Tarasov, AI, McGinty, J, McDonald, A, Silva Xavier, G, Gorman, T, Marley, A, French, P M, Parker, H, Gribble, F, Reimann, F, Prendiville, O, Carzaniga, R, Viollet, B, Leclerc, I, Rutter, G A
• Format: Article
• Language: English
• ISSN: 0012-186X; 1432-0428
• DOI: 10.1007/s00125-010-1692-1

Aims/hypothesis: 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. Methods: The catalytic alpha 1 and alpha 2 subunits of AMPK were ablated selectively in mouse pancreatic beta cells and hypothalamic neurons by breeding Ampk alpha 1 [also known as Prkaa1]-knockout mice, bearing floxed Ampk alpha 2 [also known as Prkaa2] alleles (Ampk alpha 1 super( -/-), alpha 2 super(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 Ca super(2+) were measured with standard techniques. Results: Trigenic Ampk alpha 1 super(-/-), alpha 2 super( fl/fl) expressing Cre recombinase and lacking both AMPK alpha 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 Ca super(2+), while granule docking and insulin secretion were enhanced. Conversely, beta AMPK transgenic mice were glucose-intolerant and displayed defective insulin secretion. Conclusions/interpretation: 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.