An insulin-degrading enzyme inhibitor decreases amylin degradation, increases amylin-induced cytotoxicity, and increases amyloid formation in insulinoma cell cultures

Robert G. Bennett, Frederick G. Hamel, William C. Duckworth

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77 Scopus citations


Amylin (islet amyloid polypeptide) is the chief component of the islet amyloid found in type 2 diabetes, and amylin fibril precursors may be cytotoxic to pancreatic β-cells. Little is known about the prevention of amylin aggregation. We investigated the role of insulin-degrading enzyme (IDE) in amylin degradation, amyloid deposition, and cytotoxicity in RIN-m5F insulinoma cells. Human 125I-labeled amylin degradation was inhibited by 46 and 65% with the addition of 100 nmol/l human amylin or insulin, respectively. 125I-labeled insulin degradation was inhibited with 100 nmol/l human amylin, rat amylin, and insulin (by 50, 50, and 73%, respectively). The IDE inhibitor bacitracin inhibited amylin degradation by 78% and insulin degradation by 100%. Amyloid staining by Congo red fluorescence was detectable at 100 nmol/l amylin and was pronounced at 1,000 nmol/l amylin treatment for 48 h. Bacitracin treatment markedly increased staining at all amylin concentrations. Bacitracin with amylin caused a dramatic decrease in cell viability compared with amylin alone (68 and 25%, respectively, at 10 nmol/l amylin). In summary, RIN-m5F cells degraded both amylin and insulin through a common proteolytic pathway. IDE inhibition by bacitracin impaired amylin degradation, increased amyloid formation, and increased amylin-induced cytotoxicity, suggesting a role for IDE in amylin clearance and the prevention of amylin aggregation.

Original languageEnglish (US)
Pages (from-to)2315-2320
Number of pages6
Issue number9
StatePublished - Sep 1 2003


ASJC Scopus subject areas

  • Internal Medicine
  • Endocrinology, Diabetes and Metabolism

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