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Sucralose Affects Thyroid Hormone Signaling in American Bullfrog [Rana (Lithobates) catesbeiana] Tadpoles

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Nonnutritive sweeteners used in food and beverage products are widespread, persistent aquatic pollutants. Despite this, their impact on aquatic organisms, particularly vertebrates, is not well-studied. Recent findings in rodents suggest sucralose, a chlorinated disaccharide, alters thyroid hormone (TH) metabolism. Because amphibian tadpole metamorphosis is TH-dependent, we hypothesized sucralose may alter signaling for this postembryonic developmental process. The present study used the American bullfrog, Rana (Lithobates) catesbeiana, as a sensitive, environmentally relevant model for testing TH disruption in the absence and presence of thyroxine (T4), a hormone that induces metamorphosis. Premetamorphic R. catesbeiana tadpoles were immersed in 1-, 15-, and 32-mg/L sucralose solutions ± 5 nM (3.9 µg/L) thyroxine (T4) for 48 h. RNA transcripts encoding thyroid hormone receptors alpha and beta (thra and thrb) and TH-induced basic region leucine zipper protein (thibz) were analyzed in four tissues: back skin, liver, olfactory epithelium, and tail fin, using reverse transcription quantitative real-time PCR (RT-qPCR). We found that sucralose altered the expression of fundamental TH-response genes involved in anuran metamorphosis in a tissue- and TH-status dependent manner. As organochlorines induce xenobiotic metabolism, we isolated and characterized three novel R. catesbeiana gene transcripts involved in xenobiotic metabolism: pregnane X receptor (nr1i2), constitutive androstane receptor (nr1i3), and cytochrome p450 3a4 (cyp3a4). We analyzed their expression using RT-qPCR and found evidence of their modulation by sucralose. To our knowledge, these data are the first to show xenobiotic and thyroid-disrupting activities in amphibians and further investigations into cumulative effects of environmental sucralose exposure are warranted.

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The authors thank Emily Koide, Jessica Round, and Lorissa Corrie for their technical assistance and helpful discussions and Dr. Jun Han at the University of Victoria-Genome BC Proteomics Centre for his mass spectrometry expertise.


This research was supported by a Natural Sciences and Engineering Research Council (NSERC) Discovery Grant RGPIN-2018-03816 to CCH.

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Correspondence to Caren C. Helbing.

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The authors declare that they have no conflict of interest.

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Care and use of animals was approved by the University of Victoria Animal Care Committee: Protocols #2015-028 and #2019-025.

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Abbott, E.A., Helbing, C.C. Sucralose Affects Thyroid Hormone Signaling in American Bullfrog [Rana (Lithobates) catesbeiana] Tadpoles. Arch Environ Contam Toxicol 80, 735–744 (2021).

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