Journal
TOXICOLOGY AND APPLIED PHARMACOLOGY
Volume 267, Issue 1, Pages 11-15Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.taap.2012.12.007
Keywords
Arsenic; Diabetes; Isolated pancreatic islets; beta-Cells; Insulin secretion
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Funding
- NIH [5R01 ES015326]
- Ministry of Education, Youth and Sports of the Czech Republic Kontakt II program [LH12040]
- AS CR institutional fund [RVO: 68081715]
- UNC Nutrition Obesity Research Center
- National Institute of Diabetes and Digestive and Kidney Diseases [DK056350]
- Center for Environmental Health and Susceptibility
- National Institute of Environmental Health Sciences [P30ES010126]
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Epidemiologic evidence has linked chronic exposure to inorganic arsenic (iAs) with an increased prevalence of diabetes mellitus. Laboratory studies have identified several mechanisms by which iAs can impair glucose homeostasis. We have previously shown that micromolar concentrations of arsenite (iAs(III)) or its methylated trivalent metabolites, methylarsonite (MAsIII) and dimethylarsinite (DMAsIII), inhibit the insulin-activated signal transduction pathway, resulting in insulin resistance in adipocytes. Our present study examined effects of the trivalent arsenicals on insulin secretion by intact pancreatic islets isolated from C57BL/6 mice. We found that 48-hour exposures to low subtoxic concentrations of iAs(III), MAsIII or DMAsIII inhibited glucosestimulated insulin secretion (GSIS), but not basal insulin secretion. MAsIII and DMAsIII were more potent than iAs(III) as GSIS inhibitors with estimated IC50 <= 0.1 mu M. The exposures had little or no effects on insulin content of the islets or on insulin expression, suggesting that trivalent arsenicals interfere with mechanisms regulating packaging of the insulin transport vesicles or with translocation of these vesicles to the plasma membrane. Notably, the inhibition of GSIS by iAs(III), MAsIII or DMAsIII could be reversed by a 24-hour incubation of the islets in arsenic-free medium. These results suggest that the insulin producing pancreatic beta-cells are among the targets for iAs exposure and that the inhibition of GSIS by low concentrations of the methylated metabolites of iAs may be the key mechanism of iAs-induced diabetes. (C) 2012 Elsevier Inc. All rights reserved.
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