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Authors

  • O'Harte, Finbarr
  • Hunter, Kerry
  • Gault, Victor
  • Irwin, Nigel
  • Green, Brian D.
  • Greer, Brett
  • Harriott, Patrick
  • Bailey, Clifford J.
  • Flatt, Peter

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Antagonistic effects of two novel GIP analogs, (Hyp(3))GIP and (Hyp(3)) GIPLys(16)PAL, on the biological actions of GIP and longer-term effects in diabetic ob/ob mice

Date

01-06-2007

Abstract

This study examines the actions of the novel enzyme- resistant, NH2- terminally modified GIP analog ( Hyp(3)) GIP and its fatty acid- derivatized analog ( Hyp(3)) GIPLys(16)PAL. Acute effects are compared with the established GIP receptor antagonist ( Pro(3)) GIP. All three peptides exhibited DPP IV resistance, and significantly inhibited GIP stimulated cAMP formation and insulin secretion in GIP receptor- transfected fibroblasts and in clonal pancreatic BRIN- BD11 cells, respectively. Likewise, in obese diabetic ob/ob mice, intraperitoneal administration of GIP analogs significantly inhibited the acute antihyperglycemic and insulinreleasing effects of native GIP. Administration of once daily injections of ( Hyp(3)) GIP or ( Hyp(3)) GIPLys(16)PAL for 14 days resulted in significantly lower plasma glucose levels ( P < 0.05) after ( Hyp3) GIP on days 12 and 14 and enhanced glucose tolerance ( P < 0.05) and insulin sensitivity ( P < 0.05 to P < 0.001) in both groups by day 14. Both ( Hyp(3)) GIP and ( Hyp(3)) GIPLys(16)PAL treatment also reduced pancreatic insulin ( P < 0.05 to P < 0.01) without affecting islet number. These data indicate that ( Hyp3) GIP and ( Hyp(3)) GIPLys(16)PAL function as GIP receptor antagonists with potential for ameliorating obesity- related diabetes. Acylation of ( Hyp(3)) GIP to extend bioactivity does not appear to be of any additional benefit.