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The role of a newly discovered pancreatic islet peptide in the control of insulin secretion

K.W. Stewart,1 A.R.J. Phillips,2,3,4 L. Whiting3 and G.J.S. Cooper,3,4,5 1School of Engineering, Science & Primary Industries, Waikato Institute of Technology, Hamilton, New Zealand, 2Department of Surgery, University of Auckland, Auckland 3240, New Zealand, 3School of Biological Sciences, University of Auckland, Auckland 1010, New Zealand, 4Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, Auckland 1010, New Zealand and 5Centre for Advanced Discovery and Experimental Therapeutics, University of Manchester, Manchester M15 6BG, UK.

A peptide was discovered in the pancreatic islets of STZ-diabetic rats by direct tissue imaging of individual islets using MALDI-TOF mass spectrometry (Stewart et al., 2011). The peptide is similar in structure to glicentin-related pancreatic polypeptide (GRPP) and has initially been called GRPP-like peptide (GRPP-LP). GRPP-LP was synthesized and the effect of both GRPP and GRPP-LP on insulin secretion were tested in an isolated rat pancreatic perfusion preparation. Both peptides markedly attenuated the secretion of insulin in response to a 20 mM glucose infusion. When considered with results from another similar study showing enhanced glucose-induced insulin secretion with glicentin 12-69, which encompasses the GRPP sequence (Yanaihara et al., 1985), these novel findings raise the possibility of a pancreatic control mechanism involving peptides from glicentin.

Stewart, K.W., Phillips, A.R., Whiting, L., Jullig, M., Middleditch, M.J., and Cooper, G.J. (2011). A simple and rapid method for identifying and semi-quantifying peptide hormones in isolated pancreatic islets by direct-tissue matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Rapid Communications in Mass Spectrometry 25, 3387-3395.

Yanaihara, C., Matsumoto, T., Hong, Y.M., and Yanaihara, N. (1985). Isolation and chemical characterization of glicentin C-terminal hexapeptide in porcine pancreas. FEBS Letters 189, 50-56.