Profiling hepatic microRNAs in zebrafish: Fluoxetine exposure mimics a fasting response that targets AMP-activated protein kinase (AMPK). Danio rerio

Recent evidence has suggested that fluoxetine, a serotonin-reuptake inhibitor and emerging environmental contaminant, can have non-targeted effects on metabolism in fish exposed to this waterborne pollutant. Using the highest, environmentally relevant, detectable level of fluoxetine (540 ng/L) we examined the impact of fluoxetine on the miRNA profile in the liver of zebrafish that were both fed and fasted for a period of 7 days. These results were further compared to the miRNA profile of zebrafish fasted and fed for 7 days, which were not exposed to fluoxetine. Results indicated that several miRNA that were involved with downregulating genes/pathways in response to fasting were also upregulated in fish exposed to fluoxetine, irrespective to fasting or feeding. These results suggest fluoxetine can have non-targeted effects on metabolic pathways mediated through miRNA expression. Furthermore, specific miRNA (dre-let-7d & dre-miR-140-5p) were found to target the catalytic subunit (AMPKa1 & AMPKa2, respectively) of AMP-Kinase, a master regulator of metabolism. Using predictive software and qPCR validation, combined with the expression profile of these two miRNA, we were able to establish a significant relationship between the expression of these specific miRNA to the downregulation of AMPKa subunit under the influence of 540 ng/L fluoxetine. Overall design: Adult, female zebrafish were either fed or fasted for 7 days with and without the presense of 540 ng/L fluoxetine, and livers extracted and miRNA purified for miRNA microaary experiment.