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SLC30A3 responds to glucose- and zinc variations in beta-cells and is critical for insulin production and in vivo glucose-metabolism during beta-cell stress.

Smidt K, Jessen N, Petersen AB, Larsen A, Magnusson N, Jeppesen JB, Stoltenberg M, Culvenor JG, Tsatsanis A, Brock B, Schmitz O, Wogensen L, Bush AI, Rungby J - PLoS ONE (2009)

Bottom Line: In INS-1E cells 2 mM glucose down-regulated ZnT-3 and up-regulated ZnT-5 expression relative to 5 mM. 16 mM glucose increased ZnT-3 and decreased ZnT-8 expression.ZnT-3, which is pivotal in the development of cellular changes as also seen in type 2 diabetes (e.g. amyloidosis in Alzheimer's disease) but not previously described in beta-cells, is present in this cell type, up-regulated by glucose in a concentration dependent manner and up-regulated by zinc depletion which by contrast decreased ZnT-3 protein levels.Knock-down of the ZnT-3 gene lowers insulin secretion in vitro and affects in vivo glucose metabolism after streptozotocin treatment.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology, University of Aarhus, Arhus, Denmark.

ABSTRACT

Background: Ion transporters of the Slc30A- (ZnT-) family regulate zinc fluxes into sub-cellular compartments. beta-cells depend on zinc for both insulin crystallization and regulation of cell mass.

Methodology/principal findings: This study examined: the effect of glucose and zinc chelation on ZnT gene and protein levels and apoptosis in beta-cells and pancreatic islets, the effects of ZnT-3 knock-down on insulin secretion in a beta-cell line and ZnT-3 knock-out on glucose metabolism in mice during streptozotocin-induced beta-cell stress. In INS-1E cells 2 mM glucose down-regulated ZnT-3 and up-regulated ZnT-5 expression relative to 5 mM. 16 mM glucose increased ZnT-3 and decreased ZnT-8 expression. Zinc chelation by DEDTC lowered INS-1E insulin content and insulin expression. Furthermore, zinc depletion increased ZnT-3- and decreased ZnT-8 gene expression whereas the amount of ZnT-3 protein in the cells was decreased. Zinc depletion and high glucose induced apoptosis and necrosis in INS-1E cells. The most responsive zinc transporter, ZnT-3, was investigated further; by immunohistochemistry and western blotting ZnT-3 was demonstrated in INS-1E cells. 44% knock-down of ZnT-3 by siRNA transfection in INS-1E cells decreased insulin expression and secretion. Streptozotocin-treated mice had higher glucose levels after ZnT-3 knock-out, particularly in overt diabetic animals.

Conclusion/significance: Zinc transporting proteins in beta-cells respond to variations in glucose and zinc levels. ZnT-3, which is pivotal in the development of cellular changes as also seen in type 2 diabetes (e.g. amyloidosis in Alzheimer's disease) but not previously described in beta-cells, is present in this cell type, up-regulated by glucose in a concentration dependent manner and up-regulated by zinc depletion which by contrast decreased ZnT-3 protein levels. Knock-down of the ZnT-3 gene lowers insulin secretion in vitro and affects in vivo glucose metabolism after streptozotocin treatment.

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High-dose streptozotocin for three days in ZnT-3−/− knockout mice and control mice.Following a series of low-dose exposures (see Fig. 8) ZnT-3−/− knock-out mice and control mice were treated with 200 mg/kg/day. A) Non-fasting morning blood glucose levels. Salt indicates sham saline injections. Data are mean and SEM (*p<0.01). B) Intraperitoneal glucose tolerance test in ZnT-3−/− knockout mice and control mice after high-dose streptozotozin. Blood glucose concentrations were measured before and 15, 30, 60 and 120 minutes after the glucose injection. Significantly higher AUC0–120 in knock-out vs WT mice (p<0.01). N = 5 for ZnT-3−/− and n = 4 for wild type.
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pone-0005684-g009: High-dose streptozotocin for three days in ZnT-3−/− knockout mice and control mice.Following a series of low-dose exposures (see Fig. 8) ZnT-3−/− knock-out mice and control mice were treated with 200 mg/kg/day. A) Non-fasting morning blood glucose levels. Salt indicates sham saline injections. Data are mean and SEM (*p<0.01). B) Intraperitoneal glucose tolerance test in ZnT-3−/− knockout mice and control mice after high-dose streptozotozin. Blood glucose concentrations were measured before and 15, 30, 60 and 120 minutes after the glucose injection. Significantly higher AUC0–120 in knock-out vs WT mice (p<0.01). N = 5 for ZnT-3−/− and n = 4 for wild type.

Mentions: Knocking out ZnT-3 affected in vivo glucose metabolism after low- and high-dose streptozotocin, most significantly following severe β-cell stress. There were no significant differences in body weights when comparing knock-out and wild-type mice. Fasting blood glucose levels were unaffected by ZnT-3 knock-out, data not shown, thus under normal circumstances glucose metabolism after knock down resembles that of the wild-type. After a single series of low-dose streptozotozin (50 mg/kg/day for 5 days) all mice, knock-out and wild-type, remained non-diabetic with a slight increase in fasting glucose levels in the knock-out group (p<0.01) (Fig. 8). IPGTTs showed no difference when measuring AUC for glucose. Repeated courses of low-dose streptozotocin did not cause diabetes in either group and their IPGTTs were similar. High-dose streptozotocin (200 mg/kg/day for 3 days) resulted in significantly higher glucose levels in the knock-out group both while non-fasting and after IPGTT (p<0.01 for both comparisons) (Fig. 9).


SLC30A3 responds to glucose- and zinc variations in beta-cells and is critical for insulin production and in vivo glucose-metabolism during beta-cell stress.

Smidt K, Jessen N, Petersen AB, Larsen A, Magnusson N, Jeppesen JB, Stoltenberg M, Culvenor JG, Tsatsanis A, Brock B, Schmitz O, Wogensen L, Bush AI, Rungby J - PLoS ONE (2009)

High-dose streptozotocin for three days in ZnT-3−/− knockout mice and control mice.Following a series of low-dose exposures (see Fig. 8) ZnT-3−/− knock-out mice and control mice were treated with 200 mg/kg/day. A) Non-fasting morning blood glucose levels. Salt indicates sham saline injections. Data are mean and SEM (*p<0.01). B) Intraperitoneal glucose tolerance test in ZnT-3−/− knockout mice and control mice after high-dose streptozotozin. Blood glucose concentrations were measured before and 15, 30, 60 and 120 minutes after the glucose injection. Significantly higher AUC0–120 in knock-out vs WT mice (p<0.01). N = 5 for ZnT-3−/− and n = 4 for wild type.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2683566&req=5

pone-0005684-g009: High-dose streptozotocin for three days in ZnT-3−/− knockout mice and control mice.Following a series of low-dose exposures (see Fig. 8) ZnT-3−/− knock-out mice and control mice were treated with 200 mg/kg/day. A) Non-fasting morning blood glucose levels. Salt indicates sham saline injections. Data are mean and SEM (*p<0.01). B) Intraperitoneal glucose tolerance test in ZnT-3−/− knockout mice and control mice after high-dose streptozotozin. Blood glucose concentrations were measured before and 15, 30, 60 and 120 minutes after the glucose injection. Significantly higher AUC0–120 in knock-out vs WT mice (p<0.01). N = 5 for ZnT-3−/− and n = 4 for wild type.
Mentions: Knocking out ZnT-3 affected in vivo glucose metabolism after low- and high-dose streptozotocin, most significantly following severe β-cell stress. There were no significant differences in body weights when comparing knock-out and wild-type mice. Fasting blood glucose levels were unaffected by ZnT-3 knock-out, data not shown, thus under normal circumstances glucose metabolism after knock down resembles that of the wild-type. After a single series of low-dose streptozotozin (50 mg/kg/day for 5 days) all mice, knock-out and wild-type, remained non-diabetic with a slight increase in fasting glucose levels in the knock-out group (p<0.01) (Fig. 8). IPGTTs showed no difference when measuring AUC for glucose. Repeated courses of low-dose streptozotocin did not cause diabetes in either group and their IPGTTs were similar. High-dose streptozotocin (200 mg/kg/day for 3 days) resulted in significantly higher glucose levels in the knock-out group both while non-fasting and after IPGTT (p<0.01 for both comparisons) (Fig. 9).

Bottom Line: In INS-1E cells 2 mM glucose down-regulated ZnT-3 and up-regulated ZnT-5 expression relative to 5 mM. 16 mM glucose increased ZnT-3 and decreased ZnT-8 expression.ZnT-3, which is pivotal in the development of cellular changes as also seen in type 2 diabetes (e.g. amyloidosis in Alzheimer's disease) but not previously described in beta-cells, is present in this cell type, up-regulated by glucose in a concentration dependent manner and up-regulated by zinc depletion which by contrast decreased ZnT-3 protein levels.Knock-down of the ZnT-3 gene lowers insulin secretion in vitro and affects in vivo glucose metabolism after streptozotocin treatment.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology, University of Aarhus, Arhus, Denmark.

ABSTRACT

Background: Ion transporters of the Slc30A- (ZnT-) family regulate zinc fluxes into sub-cellular compartments. beta-cells depend on zinc for both insulin crystallization and regulation of cell mass.

Methodology/principal findings: This study examined: the effect of glucose and zinc chelation on ZnT gene and protein levels and apoptosis in beta-cells and pancreatic islets, the effects of ZnT-3 knock-down on insulin secretion in a beta-cell line and ZnT-3 knock-out on glucose metabolism in mice during streptozotocin-induced beta-cell stress. In INS-1E cells 2 mM glucose down-regulated ZnT-3 and up-regulated ZnT-5 expression relative to 5 mM. 16 mM glucose increased ZnT-3 and decreased ZnT-8 expression. Zinc chelation by DEDTC lowered INS-1E insulin content and insulin expression. Furthermore, zinc depletion increased ZnT-3- and decreased ZnT-8 gene expression whereas the amount of ZnT-3 protein in the cells was decreased. Zinc depletion and high glucose induced apoptosis and necrosis in INS-1E cells. The most responsive zinc transporter, ZnT-3, was investigated further; by immunohistochemistry and western blotting ZnT-3 was demonstrated in INS-1E cells. 44% knock-down of ZnT-3 by siRNA transfection in INS-1E cells decreased insulin expression and secretion. Streptozotocin-treated mice had higher glucose levels after ZnT-3 knock-out, particularly in overt diabetic animals.

Conclusion/significance: Zinc transporting proteins in beta-cells respond to variations in glucose and zinc levels. ZnT-3, which is pivotal in the development of cellular changes as also seen in type 2 diabetes (e.g. amyloidosis in Alzheimer's disease) but not previously described in beta-cells, is present in this cell type, up-regulated by glucose in a concentration dependent manner and up-regulated by zinc depletion which by contrast decreased ZnT-3 protein levels. Knock-down of the ZnT-3 gene lowers insulin secretion in vitro and affects in vivo glucose metabolism after streptozotocin treatment.

Show MeSH
Related in: MedlinePlus