Reduced Insulin Exocytosis in Human Pancreatic β-Cells With Gene Variants Linked to Type 2 Diabetes

  1. Lena Eliasson1
  1. 1Lund University Diabetes Centre, Department of Clinical Sciences Malmo, Lund University, Malmo, Sweden
  2. 2Oxford Centre for Diabetes, Endocrinology, and Metabolism, University of Oxford, Churchill Hospital, Oxford, U.K.
  3. 3Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
  4. 4Key Laboratory of Hormones and Development, Ministry of Health, China, Metabolic Diseases Hospital, Tianjin Medical University, Tianjin, China
  5. 5Oxford National Institute for Health Research Biomedical Research Centre, Churchill Hospital, Oxford, U.K.
  6. 6Nuffield Department of Surgery, University of Oxford, Oxford, U.K.
  7. 7Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, U.K.
  1. Corresponding author: Anders H. Rosengren, anders.rosengren{at}med.lu.se, or Lena Eliasson, lena.eliasson{at}med.lu.se.

Abstract

The majority of genetic risk variants for type 2 diabetes (T2D) affect insulin secretion, but the mechanisms through which they influence pancreatic islet function remain largely unknown. We functionally characterized human islets to determine secretory, biophysical, and ultrastructural features in relation to genetic risk profiles in diabetic and nondiabetic donors. Islets from donors with T2D exhibited impaired insulin secretion, which was more pronounced in lean than obese diabetic donors. We assessed the impact of 14 disease susceptibility variants on measures of glucose sensing, exocytosis, and structure. Variants near TCF7L2 and ADRA2A were associated with reduced glucose-induced insulin secretion, whereas susceptibility variants near ADRA2A, KCNJ11, KCNQ1, and TCF7L2 were associated with reduced depolarization-evoked insulin exocytosis. KCNQ1, ADRA2A, KCNJ11, HHEX/IDE, and SLC2A2 variants affected granule docking. We combined our results to create a novel genetic risk score for β-cell dysfunction that includes aberrant granule docking, decreased Ca2+ sensitivity of exocytosis, and reduced insulin release. Individuals with a high risk score displayed an impaired response to intravenous glucose and deteriorating insulin secretion over time. Our results underscore the importance of defects in β-cell exocytosis in T2D and demonstrate the potential of cellular phenotypic characterization in the elucidation of complex genetic disorders.

Footnotes

  • Received October 27, 2011.
  • Accepted February 26, 2012.

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  1. Diabetes vol. 61 no. 7 1726-1733
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