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

ABSTRACT: 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.

ORGANISM(S): Danio rerio

PROVIDER: GSE55229 | GEO | 2014/02/21

SECONDARY ACCESSION(S): PRJNA238932

REPOSITORIES: GEO

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Project description:Background: Exposure to dichlorvos (DDVP), an organophosphorus pesticide, is known to result in neurotoxicity as well as other metabolic perturbations. However, the molecular causes of DDVP toxicity are poorly understood, especially in cells other than neurons and muscle cells. To obtain a better understanding of the process of non-neuronal DDVP toxicity, we exposed zebrafish to different concentrations of DDVP, and investigated the resulting changes in liver histology and gene transcription. Results: Functional enrichment analysis of genes affected by DDVP exposure identified a number of processes involved in energy utilization and stress response in the liver. The abundance of transcripts for proteins involved in glucose metabolism was profoundly affected, suggesting that carbon flux might be diverted toward the pentose phosphate pathway to compensate for elevated demand for energy and reducing equivalents for detoxification. Strikingly, many transcripts for molecules involved in Î²-oxidation and fatty acid synthesis were down-regulated. We found increases in message levels for molecules involved in reactive oxygen species responses as well as ubiquitination, proteasomal degradation, and autophagy. To ensure that the effects of DDVP on energy metabolism were not simply a consequence of poor feeding because of neuromuscular impairment, we fasted fish for 29 or 50 h and analyzed liver gene expression in them. The patterns of gene expression for energy metabolism in fasted and DDVP-exposed fish were markedly different.â Conclusion: We observed coordinated changes in the expression of a large number of genes involved in energy metabolism and responses to oxidative stress. These results argue that an appreciable part of the effect of DDVP is on energy metabolism and is regulated at the message level. Although we observed some evidence of neuromuscular impairment in exposed fish that may have resulted in reduced feeding, the alterations in gene expression in exposed fish cannot readily be explained by nutrient deprivation. Dichlorvos induced changes in gene expression in zebrafish were measured after 24 h exposures. A total of 20 arrays were processed with 4 replicates for each exposure condition (low, mid, and high) and 4 replicates for each of 2 control sets. Also, fasting induced changes in gene expression in zebrafish were measured after 24 hours fasting and 50 hours fasting. A total of 12 arrays were processed with 4 replicates for each exposure condition (no fasting, 24h fasting, 50h fasting).

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

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