title: Glucagon receptor antagonism improves islet function in mice with insulin resistance induced by a high-fat diet.
abstract: OBJECTIVE
  Increased glucagon secretion predicts deterioration of glucose tolerance, and high glucagon levels contribute to hyperglycaemia in type 2 diabetes. Inhibition of glucagon action may therefore be a potential novel target to reduce hyperglycaemia. Here, we investigated whether chronic treatment with a glucagon receptor antagonist (GRA) improves islet dysfunction in female mice on a high-fat diet (HFD).
  
  
  METHODS
  After 8 weeks of HFD, mice were treated with a small molecule GRA (300 mg/kg, gavage once daily) for up to 30 days. Insulin secretion was studied after oral and intravenous administration of glucose and glucagon secretion after intravenous arginine. Islet morphology was examined and insulin secretion and glucose oxidation were measured in isolated islets.
  
  
  RESULTS
  Fasting plasma glucose levels were reduced by GRA (6.0 +/- 0.2 vs 7.4 +/- 0.5 mmol/l; p = 0.017). The acute insulin response to intravenous glucose was augmented (1,300 +/- 110 vs 790 +/- 64 pmol/l; p < 0.001). The early insulin response to oral glucose was reduced in mice on HFD + GRA (1,890 +/- 160 vs 3,040 +/- 420 pmol/l; p = 0.012), but glucose excursions were improved. Intravenous arginine significantly increased the acute glucagon response (129 +/- 12 vs 36 +/- 6 ng/l in controls; p < 0.01), notably without affecting plasma glucose. GRA caused a modest increase in alpha cell mass, while beta cell mass was similar to that in mice on HFD + vehicle. Isolated islets displayed improved glucose-stimulated insulin secretion after GRA treatment (0.061 +/- 0.007 vs 0.030 +/- 0.004 pmol islet(-1) h(-1) at 16.7 mmol/l glucose; p < 0.001), without affecting islet glucose oxidation.
  
  
  CONCLUSIONS
  Chronic glucagon receptor antagonism in HFD-fed mice improves islet sensitivity to glucose and increases insulin secretion, suggesting improvement of key defects underlying impaired glucose tolerance and type 2 diabetes.
authors.affiliation: Department of Clinical Sciences, Lund, Division of Medicine, BMC, B11, Lund University, 221 84, Lund, Sweden. Maria.Sorhede_Winzell@med.lu.se
authors.forename: M Sörhede
authors.initials: MS
authors.lastname: Winzell
authors.forename: C L
authors.initials: CL
authors.lastname: Brand
authors.forename: N
authors.initials: N
authors.lastname: Wierup
authors.forename: U G
authors.initials: UG
authors.lastname: Sidelmann
authors.forename: F
authors.initials: F
authors.lastname: Sundler
authors.forename: E
authors.initials: E
authors.lastname: Nishimura
authors.forename: B
authors.initials: B
authors.lastname: Ahrén
mesh_terms: D000821:Animal Feed; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D004032:Diet; D005260:Female; D005934:Glucagon / Q000378:metabolism; D005951:Glucose Tolerance Test; D007328:Insulin / Q000378:metabolism; D007333:Insulin Resistance; D007515:Islets of Langerhans / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D010100:Oxygen / Q000378:metabolism; D018027:Receptors, Glucagon / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013997:Time Factors
chemical_list: D001786:Blood Glucose; D007328:Insulin; D018027:Receptors, Glucagon; D005934:Glucagon; D010100:Oxygen