Insulin Storage and Glucose Homeostasis in Mice Null for the Granule Zinc Transporter ZnT8 and Studies of the Type 2 Diabetes–Associated Variants
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Open Access
- 19 June 2009
- journal article
- research article
- Published by American Diabetes Association in Diabetes
- Vol. 58 (9), 2070-2083
- https://doi.org/10.2337/db09-0551
Abstract
OBJECTIVE Zinc ions are essential for the formation of hexameric insulin and hormone crystallization. A nonsynonymous single nucleotide polymorphism rs13266634 in the SLC30A8 gene, encoding the secretory granule zinc transporter ZnT8, is associated with type 2 diabetes. We describe the effects of deleting the ZnT8 gene in mice and explore the action of the at-risk allele. RESEARCH DESIGN AND METHODS Slc30a8 null mice were generated and backcrossed at least twice onto a C57BL/6J background. Glucose and insulin tolerance were measured by intraperitoneal injection or euglycemic clamp, respectively. Insulin secretion, electrophysiology, imaging, and the generation of adenoviruses encoding the low- (W325) or elevated- (R325) risk ZnT8 alleles were undertaken using standard protocols. RESULTS ZnT8−/− mice displayed age-, sex-, and diet-dependent abnormalities in glucose tolerance, insulin secretion, and body weight. Islets isolated from null mice had reduced granule zinc content and showed age-dependent changes in granule morphology, with markedly fewer dense cores but more rod-like crystals. Glucose-stimulated insulin secretion, granule fusion, and insulin crystal dissolution, assessed by total internal reflection fluorescence microscopy, were unchanged or enhanced in ZnT8−/− islets. Insulin processing was normal. Molecular modeling revealed that residue-325 was located at the interface between ZnT8 monomers. Correspondingly, the R325 variant displayed lower apparent Zn2+ transport activity than W325 ZnT8 by fluorescence-based assay. CONCLUSIONS ZnT8 is required for normal insulin crystallization and insulin release in vivo but not, remarkably, in vitro. Defects in the former processes in carriers of the R allele may increase type 2 diabetes risks.This publication has 52 references indexed in Scilit:
- TCF7L2 Regulates Late Events in Insulin Secretion From Pancreatic Islet β-CellsDiabetes, 2009
- Glucose Sensing in L Cells: A Primary Cell StudyCell Metabolism, 2008
- Mouse Pancreatic Endocrine Cell Transcriptome Defined in the Embryonic Ngn3-Null MouseDiabetes, 2008
- Insights into the Mode of Action of a Putative Zinc Transporter CzrB in Thermus thermophilusStructure, 2008
- The cation efflux transporter ZnT8 (Slc30A8) is a major autoantigen in human type 1 diabetesProceedings of the National Academy of Sciences, 2007
- MolProbity: all-atom contacts and structure validation for proteins and nucleic acidsNucleic Acids Research, 2007
- Zinc transporter 2 (SLC30A2) can suppress the vesicular zinc defect of adaptor protein 3-depleted fibroblasts by promoting zinc accumulation in lysosomesExperimental Cell Research, 2007
- A genome-wide association study identifies novel risk loci for type 2 diabetesNature, 2007
- New developments in the understanding of the cation diffusion facilitator familyJournal of Industrial Microbiology & Biotechnology, 2005
- Modeller: Generation and Refinement of Homology-Based Protein Structure ModelsMethods in enzymology, 2003