Metformin disrupts Danio rerio metabolism at environmentally relevant concentrations: A full life-cycle study

• Published in: The Science of the total environment Vol. 846; p. 157361
• Main Authors: Barros, Susana, Ribeiro, Marta, Coimbra, Ana M., Pinheiro, Marlene, Morais, Hugo, Alves, Nélson, Montes, Rosa, Rodil, Rosario, Quintana, José Benito, Santos, Miguel M., Neuparth, Teresa
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 10-11-2022
• Subjects: Cell cycle and DNA repair; Full life-cycle exposure; Lipid and energy metabolisms; Metformin environmental concentrations; Zebrafish; Metformin environmental concentrations; Zebrafish; Lipid and energy metabolisms; Full life-cycle exposure; Cell cycle and DNA repair
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2022.157361

Metformin (MET), an anti-diabetic pharmaceutical of large-scale consumption, is increasingly detected in surface waters. However, current knowledge on the long-term effects of MET on non-target organisms is limited. The present study aimed to investigate the effects of MET in the model freshwater teleost Danio rerio, following a full life-cycle exposure to environmentally relevant concentrations (390 to 14 423 ng/L). Considering that the mode of action (MoA) of MET on non-target organisms remains underexplored and that MET may act through similar human pathways, i.e., lipid and energy metabolisms, biochemical markers were used to determine cholesterol and triglycerides levels, as well as mitochondrial complex I activity in zebrafish liver. Also, the hepatosomatic index as an indication of metabolic disruption, and the expression levels of genes involved in MET's putative MoA, i.e. acaca, acadm, cox5aa, idh3a, hmgcra, prkaa1, were determined, the last by qRT-PCR. A screening of mRNA transcripts, associated with lipid and energy metabolisms, and other signaling pathways potentially involved in MET-induced toxicity were also assessed using an exploratory RNA-seq analysis. The findings here reported indicate that MET significantly disrupted critical biochemical and molecular processes involved in zebrafish metabolism, such as cholesterol and fatty acid biosynthesis, mitochondrial electron transport chain and tricarboxylic acid cycle, concomitantly to changes on the hepatosomatic index. Likewise, MET impacted other relevant pathways mainly associated with cell cycle, DNA repair and steroid hormone biosynthesis, here reported for the first time in a non-target aquatic organism. Non-monotonic dose response curves were frequently detected in biochemical and qRT-PCR data, with higher effects observed at 390 and 2 929 ng/L MET treatments. Collectively, the results suggest that environmentally relevant concentrations of MET severely disrupt D. rerio metabolism and other important biological processes, supporting the need to revise the proposed environmental quality standard (EQS) and predicted no-effect concentration (PNEC) for MET.
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•Danio rerio was exposed to metformin for a full generation at low concentrations.•MET affected COX I activity, as well as Chol and TGL content in zebrafish livers.•qRT-PCR and RNA-seq revealed altered mRNA levels of genes involved in metabolism.•MET impacted pathways related to cell cycle, DNA repair and steroid hormone biosynthesis.•Due to MET potential risk to aquatic ecosystems, MET PNEC and EQS should be revised.