Article

Diabetologia

, Volume 53, Issue 7, pp 1415-1427

First online:

Differences between amyloid toxicity in alpha and beta cells in human and mouse islets and the role of caspase-3

  • E. LawAffiliated withDivision of Pharmacology and Toxicology, Faculty of Pharmaceutical Sciences, University of British Columbia
  • , S. LuAffiliated withDivision of Pharmacology and Toxicology, Faculty of Pharmaceutical Sciences, University of British Columbia
  • , T. J. KiefferAffiliated withDepartment of Cellular and Physiological Sciences, Faculty of Medicine, University of British ColumbiaDepartment of Surgery, Faculty of Medicine, University of British Columbia
  • , G. L. WarnockAffiliated withDepartment of Surgery, Faculty of Medicine, University of British Columbia
  • , Z. AoAffiliated withDepartment of Surgery, Faculty of Medicine, University of British Columbia
  • , M. WooAffiliated withDepartment of Medicine, University of Toronto, Ontario Cancer Institute, St Michael’s Hospital
  • , L. MarzbanAffiliated withDivision of Pharmacology and Toxicology, Faculty of Pharmaceutical Sciences, University of British Columbia Email author 

Abstract

Aims/hypothesis

Type 2 diabetes is characterised by decreased beta cell mass and islet amyloid formation. Islet amyloid formed by aggregation of human islet amyloid polypeptide (hIAPP) is associated with beta cell apoptosis. We used human and transgenic mouse islets in culture to examine whether deletion of caspase-3 protects islets from apoptosis induced by endogenously produced and exogenously applied hIAPP and compared hIAPP toxicity in islet alpha and beta cells.

Methods

Human and wild-type or caspase-3 knockout mouse islet cells were treated with hIAPP. Rat insulinoma INS-1 cells were similarly cultured with hIAPP and the amyloid inhibitor Congo Red or caspase-3 inhibitor. Human and hIAPP-expressing caspase-3 knockout mouse islets were cultured to form amyloid fibrils and assessed for beta and alpha cell apoptosis, beta cell function and caspase-3 activation.

Results

hIAPP-treated INS-1 cells had increased caspase-3 activation and apoptosis, both of which were reduced by inhibitors of amyloid or caspase-3. Similarly, hIAPP-treated human and mouse islet beta cells had elevated active caspase-3- and TUNEL-positive cells, whereas mouse islet cells lacking caspase-3 had markedly lower beta cell but comparable alpha cell apoptosis. During culture, human islets that formed amyloid had higher active caspase-3- and TUNEL-positive beta cells than those without detectable amyloid. Finally, cultured hIAPP-expressing mouse islets lacking caspase-3 had markedly lower beta cell apoptosis than those expressing caspase-3, associated with an increase in islet beta cell/alpha cell ratio, insulin content and glucose response.

Conclusions/interpretation

Prevention of caspase-3 activation protects islet beta cells from apoptosis induced by fibrillogenesis of endogenously secreted and exogenously applied hIAPP. Islet beta cells are more susceptible to hIAPP toxicity than alpha cells cultured under the same conditions.

Keywords

Alpha cell apoptosis Amylin Amyloid Beta cell apoptosis Caspase-3 Islet amyloid polypeptide Type 2 diabetes