Abstract
SLC30A8 encodes the secretory granule-resident and largely endocrine pancreas-restricted zinc transporter ZnT8. Interest in this gene product was sparked amongst diabetologists in 2007 when the first genome-wide association study for type 2 diabetes identified polymorphisms in SLC30A8 as affecting disease risk. Thus, the common polymorphism rs13266634 was associated with lowered beta cell function and a 14% increase in diabetes abundance per risk (C) allele. This non-synonymous variant encodes a tryptophan-to-arginine switch at position 325 in the protein’s intracellular carboxy-terminal domain, resulting in reduced zinc transport activity and, consequently, decreased intragranular zinc levels. Whereas insulin secretion from isolated islets is most often increased in mice inactivated for Slc30a8, null animals usually show impaired glucose tolerance and lowered circulating insulin. Since Slc30a8 null animals display little, if any, zinc secretion from islets, the lower plasma insulin levels could be explained by increased hepatic clearance as a result of lowered local zinc levels, or less efficient insulin action on target tissues. Despite the emerging consensus on the role of ZnT8 in glucose homeostasis, a recent genetic study in humans has unexpectedly identified loss-of-function SLC30A8 mutants that are associated with protection from diabetes. Here, we attempt to reconcile these apparently contradictory findings, implicating (1) differing degrees of inhibition of ZnT8 activity in carriers of common variants vs rare loss-of-function forms, (2) effects dependent on age or hypoxic beta cell stress. We propose that these variables conspire to affect both the size and the direction of the effect of SLC30A8 risk alleles in man.
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Abbreviations
- GWAS:
-
Genome-wide association study
- LoF:
-
Loss-of-function
- MT:
-
Metallothionein
- PC:
-
Prohormone convertase
- SNP:
-
Single nucleotide polymorphism
- ZnT:
-
Zinc transporter
- ZiP:
-
Zinc importer
References
Maret W (2013) Zinc biochemistry: from a single zinc enzyme to a key element of life. Adv Nutr 4:82–91
Dodson G, Steiner D (1998) The role of assembly in insulin’s biosynthesis. Curr Opin Struct Biol 8:189–194
Emdin SO, Dodson GG, Cutfield JM, Cutfield SM (1980) Role of zinc in insulin biosynthesis. Some possible zinc-insulin interactions in the pancreatic B cell. Diabetologia 19:174–182
Hutton JC, Penn EJ, Peshavaria M (1983) Low-molecular-weight constituents of isolated insulin-secretory vesicles. Bivalent cations, adenine nucleotides and inorganic phosphate. Biochem J 210:297–305
Vinkenborg JL, Nicolson TJ, Bellomo EA, Koay MS, Rutter GA, Merkx M (2009) Genetically encoded FRET sensors to monitor intracellular Zn2+ homeostasis. Nat Methods 6:737–740
Carroll RJ, Hammer RE, Chan SJ, Swift HH, Rubenstein AH, Steiner DF (1988) A mutant human proinsulin is secreted from islets of Langerhans in increased amounts via an unregulated pathway. Proc Natl Acad Sci U S A 85:8943–8947
Chausmer AB (1998) Zinc, insulin and diabetes. J Am Coll Nutr 17:109–115
Sladek R, Rocheleau G, Rung J et al (2007) A genome-wide association study identifies novel risk loci for type 2 diabetes. Nature 445:881–885
Chimienti F, Devergnas S, Favier A, Seve M (2004) Identification and cloning of a beta-cell-specific zinc transporter, ZnT-8, localized into insulin secretory granules. Diabetes 53:2330–2337
Lichten LA, Cousins RJ (2009) Mammalian zinc transporters: nutritional and physiologic regulation. Annu Rev Nutr 29:153–176
Gerber PA, Bellomo EA, Hodson DJ et al (2014) Hypoxia lowers SLC30A8/ZnT8 expression and free cytosolic Zn2+ in pancreatic beta cells. Diabetologia 57:1635–1644
Boesgaard TW, Zilinskaite J, Vanttinen M et al (2008) The common SLC30A8 Arg325Trp variant is associated with reduced first-phase insulin release in 846 non-diabetic offspring of type 2 diabetes patients-the EUGENE2 study. Diabetologia 51:816–820
Cauchi S, Del GS, Choquet H et al (2010) Meta-analysis and functional effects of the SLC30A8 rs13266634 polymorphism on isolated human pancreatic islets. Mol Genet Metab 100:77–82
Kirchhoff K, Machicao F, Haupt A et al (2008) Polymorphisms in the TCF7L2, CDKAL1 and SLC30A8 genes are associated with impaired proinsulin conversion. Diabetologia 51:597–601
Nicolson TJ, Bellomo EA, Wijesekara N et al (2009) Insulin storage and glucose homeostasis in mice null for the granule zinc transporter ZnT8 and studies of the type 2 diabetes-associated variants. Diabetes 58:2070–2083
Lemaire K, Ravier MA, Schraenen A et al (2009) Insulin crystallization depends on zinc transporter ZnT8 expression, but is not required for normal glucose homeostasis in mice. Proc Natl Acad Sci U S A 106:14872–14877
Tamaki M, Fujitani Y, Hara A et al (2013) The diabetes-susceptible gene SLC30A8/ZnT8 regulates hepatic insulin clearance. J Clin Invest 123:4513–4524
Wenzlau JM, Juhl K, Yu L et al (2007) The cation efflux transporter ZnT8 (Slc30A8) is a major autoantigen in human type 1 diabetes. Proc Natl Acad Sci U S A 104:17040–17045
Wenzlau JM, Moua O, Sarkar SA et al (2008) SlC30A8 is a major target of humoral autoimmunity in type 1 diabetes and a predictive marker in prediabetes. Ann N Y Acad Sci 1150:256–259
Weijers RN (2010) Three-dimensional structure of beta-cell-specific zinc transporter, ZnT-8, predicted from the type 2 diabetes-associated gene variant SLC30A8 R325W. Diabetol Metab Syndr 2:33
Chao Y, Fu D (2004) Thermodynamic studies of the mechanism of metal binding to the Escherichia coli zinc transporter YiiP. J Biol Chem 279:17173–17180
Kim I, Kang ES, Yim YS et al (2010) A low-risk ZnT-8 allele (W325) for post-transplantation diabetes mellitus is protective against cyclosporin A-induced impairment of insulin secretion. Pharmacogenomics J 11:191–198
Davidson HW, Wenzlau JM, O’Brien RM (2014) Zinc transporter 8 (ZnT8) and beta cell function. Trends Endocrinol Metab 25:415–424
Valentine RA, Jackson KA, Christie GR, Mathers JC, Taylor PM, Ford D (2007) ZnT5 variant B is a bidirectional zinc transporter and mediates zinc uptake in human intestinal Caco-2 cells. J Biol Chem 282:14389–14393
Hoch E, Lin W, Chai J, Hershfinkel M, Fu D, Sekler I (2012) Histidine pairing at the metal transport site of mammalian ZnT transporters controls Zn2+ over Cd2+ selectivity. Proc Natl Acad Sci U S A 109:7202–7207
Pound LD, Sarkar SA, Benninger RK et al (2009) Deletion of the mouse Slc30a8 gene encoding zinc transporter-8 results in impaired insulin secretion. Biochem J 421:371–376
Pound LD, Sarkar SA, Ustione A et al (2012) The physiological effects of deleting the mouse slc30a8 gene encoding zinc transporter-8 are influenced by gender and genetic background. PLoS One 7:e40972
Wijesekara N, Dai FF, Hardy AB et al (2010) Beta cell specific ZnT8 deletion in mice causes marked defects in insulin processing, crystallisation and secretion. Diabetologia 53:1656–1668
Hardy AB, Wijesekara N, Genkin I et al (2012) Effects of high-fat diet feeding on Znt8-null mice: differences between beta-cell and global knockout of Znt8. Am J Physiol Endocrinol Metab 302:E1084–E1096
Rutter GA (2010) Think zinc: new roles for zinc in the control of insulin secretion. Islets 2:1–2
Quarterman J, Mills CF, Humphries WR (1966) The reduced secretion of, and sensitivity to insulin in zinc-deficient rats. Biochem Biophys Res Commun 25:354–358
Coulston L, Dandona P (1980) Insulin-like effect of zinc on adipocytes. Diabetes 29:665–667
Haase H, Maret W (2005) Protein tyrosine phosphatases as targets of the combined insulinomimetic effects of zinc and oxidants. Biometals 18:333–338
Flannick J, Thorleifsson G, Beer NL et al (2014) Loss-of-function mutations in SLC30A8 protect against type 2 diabetes. Nat Genet 46:357–363
Kang ES, Kim MS, Kim YS et al (2008) A polymorphism in the zinc transporter gene SLC30A8 confers resistance against posttransplantation diabetes mellitus in renal allograft recipients. Diabetes 57:1043–1047
Kim BJ, Kim YH, Kim S et al (2000) Zinc as a paracrine effector in pancreatic islet cell death. Diabetes 49:367–372
Chimienti F, Jourdan E, Favier A, Seve M (2001) Zinc resistance impairs sensitivity to oxidative stress in HeLa cells: protection through metallothioneins expression. Free Radic Biol Med 31:1179–1190
Zeggini E, Weedon MN, Lindgren CM et al (2007) Replication of genome-wide association signals in U.K. samples reveals risk loci for type 2 diabetes. Science 316:1336–1341
Scott LJ, Mohlke KL, Bonnycastle LL et al (2007) A genome-wide association study of type 2 diabetes in Finns detects multiple susceptibility variants. Science 316:1341–1345
da Silva Xavier G, Bellomo EA, McGinty JA, French PM, Rutter GA (2013) Animal models of GWAS-identified type 2 diabetes genes. J Diabetes Res 2013:906590
Kahn SE, Zraika S, Utzschneider KM, Hull RL (2009) The beta cell lesion in type 2 diabetes: there has to be a primary functional abnormality. Diabetologia 52:1003–1012
van Hoek M, Dehghan A, Witteman JC et al (2008) Predicting type 2 diabetes based on polymorphisms from genome-wide association studies: a population-based study. Diabetes 57:3122–3128
Lango H, Palmer CN, Morris AD et al (2008) Assessing the combined impact of 18 common genetic variants of modest effect sizes on type 2 diabetes risk. Diabetes 57:3129–3135
Nature Medicine (2013) Of men, not mice. Nat Med 19:379
da Silva Xavier G, Loder MK, McDonald A et al (2009) TCF7L2 regulates late events in insulin secretion from pancreatic islet beta-cells. Diabetes 58:894–905
da Silva Xavier G, Mondragon A, Sun G et al (2012) Abnormal glucose tolerance and insulin secretion in pancreas-specific Tcf7l2 null mice. Diabetologia 55:2667–2676
White CR, Seymour RS (2003) Mammalian basal metabolic rate is proportional to body mass2/3. Proc Natl Acad Sci U S A 100:4046–4049
Tamaki M, Fujitani Y, Uchida T, Hirose T, Kawamori R, Watada H (2009) Downregulation of ZnT8 expression in pancreatic beta-cells of diabetic mice. Islets 1:124–128
Acknowledgements
We thank Professor Mark McCarthy (University of Oxford, UK) for useful discussion.
Funding
GAR thanks the MRC (UK) for Programme grant MR/J0003042/1, the BBSRC (UK) for a Project grant (BB/J015873/1) the Royal Society for a Wolfson Research Merit Award and the Wellcome Trust for a Senior Investigator Award (WT098424AIA). The work leading to this publication has received support from the Innovative Medicines Initiative Joint Undertaking under grant agreement n° 155005 (IMIDIA), resources of which are composed of financial contribution from the European Union’s Seventh Framework Programme (FP7/2007-2013) and EFPIA companies’ in kind contribution (to GAR).
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There is no duality of interest associated with this manuscript.
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Both authors were responsible for the conception and design of the manuscript, drafting the article and revising it critically for important intellectual content. Both authors approved the version to be published.
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Rutter, G.A., Chimienti, F. SLC30A8 mutations in type 2 diabetes. Diabetologia 58, 31–36 (2015). https://doi.org/10.1007/s00125-014-3405-7
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DOI: https://doi.org/10.1007/s00125-014-3405-7