title: Proglucagon Promoter Cre-Mediated AMPK Deletion in Mice Increases Circulating GLP-1 Levels and Oral Glucose Tolerance.
abstract: BACKGROUND
  Enteroendocrine L-cells synthesise and release the gut hormone glucagon-like peptide-1 (GLP-1) in response to food transit. Deletion of the tumour suppressor kinase LKB1 from proglucagon-expressing cells leads to the generation of intestinal polyps but no change in circulating GLP-1 levels. Here, we explore the role of the downstream kinase AMP-activated protein kinase (AMPK) in these cells.
  
  
  METHODS
  Loss of AMPK from proglucagon-expressing cells was achieved using a preproglucagon promoter-driven Cre (iGluCre) to catalyse recombination of floxed alleles of AMPKα1 and α2. Oral and intraperitoneal glucose tolerance were measured using standard protocols. L-cell mass was measured by immunocytochemistry. Hormone and peptide levels were measured by electrochemical-based luminescence detection or radioimmunoassay.
  
  
  RESULTS
  Recombination with iGluCre led to efficient deletion of AMPK from intestinal L- and pancreatic alpha-cells. In contrast to mice rendered null for LKB1 using the same strategy, mice deleted for AMPK displayed an increase (WT: 0.05 ± 0.01, KO: 0.09±0.02%, p<0.01) in L-cell mass and elevated plasma fasting (WT: 5.62 ± 0.800 pg/ml, KO: 14.5 ± 1.870, p<0.01) and fed (WT: 15.7 ± 1.48pg/ml, KO: 22.0 ± 6.62, p<0.01) GLP-1 levels. Oral, but not intraperitoneal, glucose tolerance was significantly improved by AMPK deletion, whilst insulin and glucagon levels were unchanged despite an increase in alpha to beta cell ratio (WT: 0.23 ± 0.02, KO: 0.33 ± 0.03, p<0.01).
  
  
  CONCLUSIONS
  AMPK restricts L-cell growth and GLP-1 secretion to suppress glucose tolerance. Targeted inhibition of AMPK in L-cells may thus provide a new therapeutic strategy in some forms of type 2 diabetes.
authors.affiliation: Department of Cell Biology and Functional Genomics, Imperial College London, London, W12 ONN, United Kingdom.
authors.forename: Sophie R
authors.initials: SR
authors.lastname: Sayers
authors.affiliation: Wellcome Trust - MRC Institute of Metabolic Science, University of Cambridge, Hills Road, Cambridge, CB2 0QQ, United Kingdom.
authors.forename: Frank
authors.initials: F
authors.lastname: Reimann
authors.affiliation: Wellcome Trust - MRC Institute of Metabolic Science, University of Cambridge, Hills Road, Cambridge, CB2 0QQ, United Kingdom.
authors.forename: Fiona M
authors.initials: FM
authors.lastname: Gribble
authors.affiliation: Wellcome Trust - MRC Institute of Metabolic Science, University of Cambridge, Hills Road, Cambridge, CB2 0QQ, United Kingdom.
authors.forename: Helen
authors.initials: H
authors.lastname: Parker
authors.affiliation: Department of Investigative Medicine, Imperial College London, London, W12 ONN, United Kingdom.
authors.forename: Sagen
authors.initials: S
authors.lastname: Zac-Varghese
authors.affiliation: Department of Investigative Medicine, Imperial College London, London, W12 ONN, United Kingdom.
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Bloom
authors.affiliation: INSERM, U1016, Institut Cochin, 75014 Paris, France.|CNRS, UMR8104, 75014 Paris, France.|Université Paris Descartes, Sorbonne Paris Cité, 75014 Paris, France.
authors.forename: Marc
authors.initials: M
authors.lastname: Foretz
authors.affiliation: INSERM, U1016, Institut Cochin, 75014 Paris, France.|CNRS, UMR8104, 75014 Paris, France.|Université Paris Descartes, Sorbonne Paris Cité, 75014 Paris, France.
authors.forename: Benoit
authors.initials: B
authors.lastname: Viollet
authors.affiliation: Department of Cell Biology and Functional Genomics, Imperial College London, London, W12 ONN, United Kingdom.
authors.forename: Guy A
authors.initials: GA
authors.lastname: Rutter
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000235:genetics*; D000818:Animals; D005260:Female; D017353:Gene Deletion; D052216:Glucagon-Like Peptide 1 / Q000097:blood*; D050416:Glucagon-Secreting Cells / Q000166:cytology / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D005951:Glucose Tolerance Test; D007328:Insulin / Q000097:blood; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000166:cytology; D008297:Male; D051379:Mice; D052336:Proglucagon / Q000235:genetics*; D011401:Promoter Regions, Genetic
chemical_list: D007328:Insulin; D052336:Proglucagon; D052216:Glucagon-Like Peptide 1; D055372:AMP-Activated Protein Kinases; D005947:Glucose