BIOLOGICALLY-ACTIVE HUMAN ISLET AMYLOID POLYPEPTIDE AMYLIN IN TRANSGENIC MICE/

Objective: Human islet amyloid polypeptide (hIAPP), also named amylin, is a pancreatic beta cell protein implicated in the pathogenesis of p ancreatic islet amyloid formation and type 2 diabetes mellitus. To stu dy the (patho)physiological roles of hIAPP, we have generated transgen ic mice that overexpress hIAPP mRNA, in relation to endogenous mouse I APP (mIAPP) mRNA, in pancreatic beta cells. The biological activity of human and mouse IAPP derived from pancreatic extracts was determined. Methods: Pancreatic and plasma extracts of transgenic and control mic e were analyzed by reversed-phase high-performance liquid chromatograp hy (HPLC) and radioimmunoassay, yielding a separation of hIAPP from mI APP. Biological activity of immunoreactive human and mouse IAPP compon ents derived from pancreatic extracts was assessed by calcitonin recep tor-mediated stimulation of cyclic AMP accumulation in T47D human brea st carcinoma cells. Results: The predominant immunoreactive human and mouse LAPP gene products had the retention times on HPLC analysis of t he corresponding synthetic peptides. The ratio of bioactive over immun oreactive hIAPP and mIAPP was 0.93 +/- 0.18 and 1.19 +/- 0.56 respecti vely. In extracts of two plasma pools from 4 transgenic animals, hIAPP was 4.6- to 7-fold more abundant than mIAPP. Conclusion: This study h as shown that correctly processed hIAPP produced in transgenic mouse p ancreatic beta cells exhibits full biological activity. The results va lidate these transgenic mice for the study of (patho)physiological rol es of hIAPP in vivo.