Perchlorate exposure does not induce obesity or non-alcoholic fatty liver disease in zebrafish

Perchlorate is a water-soluble contaminant found throughout the United States and many other countries. Perchlorate competitively inhibits iodide uptake at the sodium/iodide symporter, reducing thyroid hormone synthesis, which can lead to hypothyroidism and metabolic syndromes. Chronic perchlorate exposure induces hepatic steatosis and non-alcoholic fatty liver disease (NAFLD) in developing threespine stickleback (Gasterosteus aculeatus). We hypothesized that perchlorate would also induce zebrafish (Danio rerio) to develop phenotypes consistent with NAFLD and to accumulate lipids throughout the body. We exposed zebrafish embryos to four concentrations of perchlorate treated water (10μg/L, 10mg/L, 30mg/L, and 100mg/L) and a control (0mg/L) over the course of 133 days. Adult zebrafish were euthanized, sectioned, H&E and Oil Red-O stained, and analyzed for liver morphology and whole body lipid accumulation. In a representative section of the liver, we counted the number of lipid droplets and measured the area of each droplet and the total lipid area. For whole body analysis, we calculated the ratio of lipid area to body area within a section. We found that zebrafish exposed to perchlorate did not differ in any measured liver variables or whole body lipid area when compared to controls. In comparison to stickleback, we see a trend that control stickleback accumulate more lipids in their liver than do control zebrafish. Differences between the species indicate that obesogenic effects due to perchlorate exposure are not uniform across fish species, and likely are mediated by evolutionary differences related to geographic location. For example, high latitude fishes such as stickleback evolved to deposit lipid stores for over-winter survival, which may lead to more pronounced obesogenic effects than seen in tropical fish such as zebrafish. Copyright: This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Health impacts of perchlorate and pesticide exposure: Protocol for community-engaged research to evaluate environmental toxicants in a US border community

Background: The Northern Arizona University (NAU) Center for Health Equity Research (CHER) is conducting community-engaged health research involving “environmental scans” in Yuma County in collaboration with community health stakeholders, including the Yuma Regional Medical Center (YRMC), Regional Center for Border Health, Inc. (RCBH), Campesinos Sin Fronteras (CSF), Yuma County Public Health District, and government agencies and nongovernmental organizations (NGOs) working on border health issues. The purpose of these efforts is to address community-generated environmental health hazards identified through ongoing coalitions among NAU, and local health care and research institutions. Objective: We are undertaking joint community/university efforts to examine human exposures to perchlorate and agricultural pesticides. This project also includes the parallel development of a new animal model for investigating the mechanisms of toxicity following a “one health” approach. The ultimate goal of this community-engaged effort is to develop interventions to reduce exposures and health impacts of contaminants in Yuma populations. Methods: All participants completed the informed consent process, which included information on the purpose of the study, a request for access to health histories and medical records, and interviews. The interview included questions related to (1) demographics, (2) social determinants of health, (3) health screening, (4) occupational and environmental exposures to perchlorate and pesticides, and (5) access to health services. Each participant provided a hair sample for quantifying the metals used in pesticides, urine sample for perchlorate quantification, and blood sample for endocrine assays. Modeling will examine the relationships between the concentrations of contaminants and hormones, demographics and social determinants of health, and health status of the study population, including health markers known to be impacted by perchlorate and pesticides. Results: We recruited 323 adults residing in Yuma County during a 1-year pilot/feasibility study. Among these, 147 residents were patients from either YRMC or RCBH with a primary diagnosis of thyroid disease, including hyperthyroidism, hypothyroidism, thyroid cancer, or goiter. The remaining 176 participants were from the general population but with no history of thyroid disorder. The pilot study confirmed the feasibility of using the identified community-engaged protocol to recruit, consent, and collect data from a difficult-to-access, vulnerable population. The demographics of the pilot study population and positive feedback on the success of the community-engaged approach indicate that the project can be scaled up to a broader study with replicable population health findings. Conclusions: Using a community-engaged approach, the research protocol provided substantial evidence regarding the effectiveness of designing and implementing culturally relevant recruitment and dissemination processes that combine laboratory findings and public health information. Future findings will elucidate the mechanisms of toxicity and the population health effects of the contaminants of concern, as well as provide a new animal model to develop precision medicine capabilities for the population. International Registered Report Identifier (IRRID): DERR1-10.2196/15864. ©Robert Trotter II, Julie Baldwin, Charles Loren Buck, Mark Remiker, Amanda Aguirre, Trudie Milner, Emma Torres, Frank Arthur von Hippel.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Case studies on longitudinal mercury content in humpback whale (Megaptera novaeangliae) baleen

Quantification of contaminant concentrations in baleen whales is important for individual and population level health assessments but is difficult due to large migrations and infrequent resighings. The use of baleen allows for a multiyear retrospective analysis of contaminant concentrations without having to collect repeated samples from the same individual. Here we provide case studies of mercury analysis using cold vapor atomic absorption spectroscopy in three individual humpback whales (Megaptera novaeangliae), a 44.5-year-old female and two males aged ≥35 and 66 years, over approximately three years of baleen growth. Mercury concentrations in the female's baleen were consistently 2–3 times higher than in either male. Age did not affect mercury concentrations in baleen; the younger male had comparable levels to the older male. In the female, mercury concentrations in the baleen did not change markedly during pregnancy but mercury did spike during the first half of lactation. Stable isotope profiles suggest that diet likely drove the female's high mercury concentrations. In conclusion, variations in baleen mercury content can be highly individualistic. Future studies should compare sexes as well as different populations and species to determine how the concentrations of mercury and other contaminants vary by life history parameters and geography. © 2022 The AuthorsOpen access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Evolution and developmental expression of the sodium–iodide symporter (NIS, slc5a5) gene family: Implications for perchlorate toxicology

The vertebrate sodium–iodide symporter (NIS or SLC5A5) transports iodide into the thyroid follicular cells that synthesize thyroid hormone. The SLC5A protein family includes transporters of vitamins, minerals, and nutrients. Disruption of SLC5A5 function by perchlorate, a pervasive environmental contaminant, leads to human pathologies, especially hypothyroidism. Perchlorate also disrupts the sexual development of model animals, including threespine stickleback (Gasterosteus aculeatus) and zebrafish (Danio rerio), but the mechanism of action is unknown. To test the hypothesis that SLC5A5 paralogs are expressed in tissues necessary for the development of reproductive organs, and therefore are plausible candidates to mediate the effects of perchlorate on sexual development, we first investigated the evolutionary history of Slc5a paralogs to better understand potential functional trajectories of the gene family. We identified two clades of slc5a paralogs with respect to an outgroup of sodium/choline cotransporters (slc5a7); these clades are the NIS clade of sodium/iodide and lactate cotransporters (slc5a5, slc5a6, slc5a8, slc5a8, and slc5a12) and the SGLT clade of sodium/glucose cotransporters (slc5a1, slc5a2, slc5a3, slc5a4, slc5a10, and slc5a11). We also characterized expression patterns of slc5a genes during development. Stickleback embryos and early larvae expressed NIS clade genes in connective tissue, cartilage, teeth, and thyroid. Stickleback males and females expressed slc5a5 and its paralogs in gonads. Single-cell transcriptomics (scRNA-seq) on zebrafish sex-genotyped gonads revealed that NIS clade-expressing cells included germ cells (slc5a5, slc5a6a, and slc5a6b) and gonadal soma cells (slc5a8l). These results are consistent with the hypothesis that perchlorate exerts its effects on sexual development by interacting with slc5a5 or its paralogs in reproductive tissues. These findings show novel expression domains of slc5 genes in stickleback and zebrafish, which suggest similar functions across vertebrates including humans, and provide candidates to mediate the effects of perchlorate on sexual development. © 2022 The Authors. Evolutionary Applications published by John Wiley & Sons Ltd.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Predicting future from past: The genomic basis of recurrent and rapid stickleback evolution

Similar forms often evolve repeatedly in nature, raising long-standing questions about the underlying mechanisms. Here, we use repeated evolution in stickleback to identify a large set of genomic loci that change recurrently during colonization of freshwater habitats by marine fish. The same loci used repeatedly in extant populations also show rapid allele frequency changes when new freshwater populations are experimentally established from marine ancestors. Marked genotypic and phenotypic changes arise within 5 years, facilitated by standing genetic variation and linkage between adaptive regions. Both the speed and location of changes can be predicted using empirical observations of recurrence in natural populations or fundamental genomic features like allelic age, recombination rates, density of divergent loci, and overlap with mapped traits. A composite model trained on these stickleback features can also predict the location of key evolutionary loci in Darwin's finches, suggesting that similar features are important for evolution across diverse taxa. © 2021 American Association for the Advancement of Science. All rights reserved.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]