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Abstract Title:

Arsenic modifies serotonin metabolism through glucuronidation in pancreaticβ-cells

Abstract Source:

Am J Physiol Endocrinol Metab. 2019 03 1 ;316(3):E464-E474. Epub 2018 Dec 18. PMID: 30562058

Abstract Author(s):

Christopher M Carmean, Norihide Yokoi, Harumi Takahashi, Okechi S Oduori, Christie Kang, Akiko Kanagawa, Andrew G Kirkley, Guirong Han, Michael Landeche, Shihomi Hidaka, Miki Katoh, Robert M Sargis, Susumu Seino

Article Affiliation:

Christopher M Carmean

Abstract:

In arsenic-endemic regions of the world, arsenic exposure correlates with diabetes mellitus. Multiple animal models of inorganic arsenic (iAs, as As) exposure have revealed that iAs-induced glucose intolerance manifests as a result of pancreaticβ-cell dysfunction. To define the mechanisms responsible for this β-cell defect, the MIN6-K8 mouse β-cell line was exposed to environmentally relevant doses of iAs. Exposure to 0.1-1 µM iAs for 3 days significantly decreased glucose-induced insulin secretion (GIIS). Serotonin and its precursor,5-hydroxytryptophan (5-HTP), were both decreased. Supplementation with 5-HTP, which loads the system with bioavailable 5-HTP and serotonin, rescued GIIS, suggesting that recovery of this pathway was sufficient to restore function. Exposure to iAs was accompanied by an increase in mRNA expression ofUDP-glucuronosyltransferase 1 family, polypeptide a6a (Ugt1a6a), a phase-II detoxification enzyme that facilitates the disposal of cyclic amines, including serotonin, via glucuronidation. Elevated Ugt1a6a and UGT1A6 expression levels were observed in mouse and human islets, respectively, following 3days of iAs exposure. Consistent with this finding, the enzymatic rate of serotonin glucuronidation was increased in iAs-exposed cells. Knockdown by siRNA of Ugt1a6a during iAs exposure restored GIIS in MIN6-K8 cells. This effect was prevented by blockade of serotonin biosynthesis, suggesting thatthe observed iAs-induced increase in Ugt1a6a affects GIIS by targeting serotonin or serotonin-related metabolites. Although it is not yet clear exactly which element(s) of the serotonin pathway is/are most responsible for iAs-induced GIIS dysfunction, this study provides evidence that UGT1A6A, acting on the serotonin pathway, regulates GIIS under both normal and pathological conditions.

Study Type : In Vitro Study
Additional Links
Problem Substances : Arsenic : CK(352) : AC(103)

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