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Obesity is increasing worldwide, particularly in rural communities, where people are likely exposed to high levels of pesticides. We here investigated whether six commonly used agricultural pesticides on corn and soy fields have adipogenic activity and act as obesogens. Exposure to two pesticides, the herbicides acetochlor and metolachlor, induced adipogenesisin vitroin mouse 3T3-L1 preadipocytes. The most potent compound, acetochlor, was selected for further studies in zebrafish. Acetochlor exposure caused morphological malformations and lethality in zebrafish larvae with an EC₅₀of 7.8 µM and an LC₅₀of 12 µM. Acetochlor exposure also resulted in lipid accumulation is zebrafish larvae when simultaneously fed a high cholesterol diet. To decipher the molecular mechanisms behind acetochlor action, we preformed transcriptomic and targeted lipidomic analysis of exposed animals. The combined omics results suggested that acetochlor exposure increased Nrf2 activity in response to reactive oxygen species, as well as induced lipid peroxidation and ferroptosis. We further discovered that acetochlor structurally shares a chloroacetamide group with known inhibitors of glutathione peroxidase 4 (GPX4). Computational docking analysis suggested that acetochlor covalently binds to the active site of GPX4. Consequently, Gpx4 activity was efficiently repressed by acetochlor, and lipid peroxidation was increased in zebrafish. We propose that acetochlor disrupts lipid homeostasis by inhibiting Gpx4, resulting in accumulation of lipid peroxidation, 4-hydroxynonenal, and reactive oxygen species in the cells, which in turn activate Nrf2. Because metolachlor, among other acetanilide herbicides, also contain the chloroacetamide group, inhibition of Gpx4 activity may represent a novel, common molecular initiating event of obesogens.

Synopsis

Rural populations have a high prevalence of metabolic disease and are highly exposed to pesticides. This study reports that the herbicide acetochlor, heavily used on soy and corn fields, inhibits an enzyme that protects from oxidation of lipids in the cell membrane, oxidative stress and a type of cell death called ferroptosis, features that are linked to metabolic disruption and obesity.