title: Insulin storage and glucose homeostasis in mice null for the granule zinc transporter ZnT8 and studies of the type 2 diabetes-associated variants.
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.
  
  
  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 Zn(2+) 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.
authors: Section of Cell Biology, Division of Medicine, Imperial College London, London, U.K.
authors: Tamara J
authors: TJ
authors: Nicolson
authors: Elisa A
authors: EA
authors: Bellomo
authors: Nadeeja
authors: N
authors: Wijesekara
authors: Merewyn K
authors: MK
authors: Loder
authors: Jocelyn M
authors: JM
authors: Baldwin
authors: Armen V
authors: AV
authors: Gyulkhandanyan
authors: Vasilij
authors: V
authors: Koshkin
authors: Andrei I
authors: AI
authors: Tarasov
authors: Raffaella
authors: R
authors: Carzaniga
authors: Katrin
authors: K
authors: Kronenberger
authors: Tarvinder K
authors: TK
authors: Taneja
authors: Gabriela
authors: G
authors: da Silva Xavier
authors: Sarah
authors: S
authors: Libert
authors: Philippe
authors: P
authors: Froguel
authors: Raphael
authors: R
authors: Scharfmann
authors: Volodymir
authors: V
authors: Stetsyuk
authors: Philippe
authors: P
authors: Ravassard
authors: Helen
authors: H
authors: Parker
authors: Fiona M
authors: FM
authors: Gribble
authors: Frank
authors: F
authors: Reimann
authors: Robert
authors: R
authors: Sladek
authors: Stephen J
authors: SJ
authors: Hughes
authors: Paul R V
authors: PR
authors: Johnson
authors: Myriam
authors: M
authors: Masseboeuf
authors: Remy
authors: R
authors: Burcelin
authors: Stephen A
authors: SA
authors: Baldwin
authors: Ming
authors: M
authors: Liu
authors: Roberto
authors: R
authors: Lara-Lemus
authors: Peter
authors: P
authors: Arvan
authors: Frans C
authors: FC
authors: Schuit
authors: Michael B
authors: MB
authors: Wheeler
authors: Fabrice
authors: F
authors: Chimienti
authors: Guy A
authors: GA
authors: Rutter
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D003594:Cytoplasmic Granules / Q000378:metabolism; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology / Q000235:genetics / Q000378:metabolism*; D005089:Exocytosis / Q000502:physiology; D005260:Female; D015870:Gene Expression / Q000502:physiology; D006367:HeLa Cells; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000378:metabolism / Q000473:pathology / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D011110:Polymorphism, Genetic; D012307:Risk Factors; D015032:Zinc / Q000378:metabolism*; D000075703:Zinc Transporter 8
chemical_list: D001786:Blood Glucose; D027682:Cation Transport Proteins; D007328:Insulin; C492522:SLC30A8 protein, human; C516348:Slc30a8 protein, mouse; D000075703:Zinc Transporter 8; D015032:Zinc