The antipsychotic drug olanzapine altered lipid metabolism in the common carp (Cyprinus carpio L.): Insight from the gut microbiota-SCFAs-liver axis

Olanzapine (OLA) is a common drug used to treat schizophrenia and has recently come under increasing scrutiny as an emerging contaminant. However, its impact on lipid metabolism in fish and its mechanisms of action are not well understood. In this study, common carp were exposed to 0, 10, 100, and 250 μM OLA for 60 days. The results indicated that OLA exposure increased weight gain, total cholesterol (TC), low-density lipoprotein (LDL), and triglycerides (TG) and decreased high-density lipoprotein (HDL). In addition, lipids accumulated in the liver of the common carp. To explore the underlying mechanisms of action, gut microbiota, short-chain fatty acids (SCFAs), liver transcripts, and genes related to lipid metabolism were measured. It was discovered that OLA exposure altered the common carp gut microbiota composition and increased the abundance of SCFA-producing bacteria. Correspondingly, this study showed that OLA exposure increased the levels of SCFAs, which are highly relevant to the development of lipid accumulation. Transcriptome sequencing results indicated that OLA exposure could change lipid metabolism signalling pathways, including steroid biosynthesis, the PPAR signalling pathway, asglycerophospholipid metabolism, glycerolipid metabolism, and fatty acid metabolic pathways of the common carp. Additionally, OLA exposure interrupted lipid metabolism by means of significant upregulation of lipid synthesis-related genes, including pparγ, srebp1, and fas. OLA exposure also resulted in significant lipolysis-related gene downregulation, including cpt, lpl, hsl, and pparα. The results of this study indicated that contamination of aquatic environments with OLA alters lipid metabolism in common carp. In addition, the underlying mechanism might be due in part to the modulation of the gut microbiota-SCFA-PPAR signalling pathway.