title: Methylated trivalent arsenicals are potent inhibitors of glucose stimulated insulin secretion by murine pancreatic islets.
abstract: 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 (MAs(III)) and dimethylarsinite (DMAs(III)), 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), MAs(III) or DMAs(III) inhibited glucose-stimulated insulin secretion (GSIS), but not basal insulin secretion. MAs(III) and DMAs(III) were more potent than iAs(III) as GSIS inhibitors with estimated IC(50)≤0.1 μM. 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), MAs(III) or DMAs(III) could be reversed by a 24-hour incubation of the islets in arsenic-free medium. These results suggest that the insulin producing pancreatic β-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.
authors.affiliation: Department of Nutrition, Gillings School of Global Public Health, 2302 MHRC, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7461, USA.
authors.forename: Christelle
authors.initials: C
authors.lastname: Douillet
authors.forename: Jenna
authors.initials: J
authors.lastname: Currier
authors.forename: Jesse
authors.initials: J
authors.lastname: Saunders
authors.forename: Wanda M
authors.initials: WM
authors.lastname: Bodnar
authors.forename: Tomáš
authors.initials: T
authors.lastname: Matoušek
authors.forename: Miroslav
authors.initials: M
authors.lastname: Stýblo
mesh_terms: D000818:Animals; D001152:Arsenicals / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D002478:Cells, Cultured; D005947:Glucose / Q000037:antagonists & inhibitors* / Q000494:pharmacology*; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects* / Q000378:metabolism*; D008297:Male; D008745:Methylation; D051379:Mice; D008810:Mice, Inbred C57BL
chemical_list: D001152:Arsenicals; D007328:Insulin; D005947:Glucose