Effects of organic and inorganic contaminants and their mixtures on metabolic health and gene expression in developmentally exposed zebrafish.

Organic and inorganic chemicals co-occur in household dust, and these chemicals have been reported to have endocrine and metabolic disrupting effects. Although there is increasing study of chemical mixtures, the effects of complex mixtures representing concentrations found in household dust and other environmental matrices have not been well studied and their potential metabolism disrupting effects are thus poorly understood. Previous research has demonstrated high potency adipogenic effects of residential household dust extracts using in vitro adipogenesis assays. More recent research simplified this to a mixture relevant to household dust and comprising common co-occurring organic and inorganic contaminants, finding that these complex combinations often exhibited additive or even synergistic effects in cell models. This study aimed to translate our previous in vitro observation to an in vivo model, the developing zebrafish, to evaluate the metabolic effects of early exposure to organic and inorganic chemicals individually and in mixtures. Zebrafish embryos were exposed from 1 day post-fertilization (dpf) to 6 dpf, then metabolic energy expenditure, swimming behavior, and gene expression were measured. Globally, we observed that most mixtures did not reflect the effects of individual chemicals; the brominated flame retardant mixture produced a less potent effect when compared with individual chemicals, whereas the poly- and perfluoroalkyl substances and inorganic mixtures seemed to have a more potent effect than the individual chemicals. Finally, the environmental mixture, mimicking household dust proportions, was less potent than the inorganic chemical mix alone. Additional work is necessary to better understand the mixture effect of inorganic and organic chemicals combined.