Profiling MicroRNAs to Identify Candidate Posttranscriptional Regulators of Hepatic Glucose Metabolism in Rainbow Trout (Oncorhynchus mykiss)

Abstract

Rainbow trout are an important salmonid species whose poor utilization of dietary carbohydrates spurred research investigating molecular and physiological components of its glucoregulation. Among the environmental factors described to exert robust changes in glucose metabolism in rainbow trout, nutrition and social stress are among the most studied: Diets exceeding 20% of carbohydrates and chronic social stress induce hyperglycemia in adult and juvenile rainbow trout, respectively. Common to both responses is a contribution of hepatic de novo gluconeogenesis, which has been described to evade repression in response to high dietary carbohydrate content and to be stimulated in subordinate rainbow trout. Compared to previous studies investigating the regulation of hepatic gluconeogenesis at the molecular level, the recent publication of the annotated rainbow trout genome has opened novel possibilities to investigate paralogue-specific and posttranscriptional regulation of gluconeogenesis. In this thesis, I identify and describe the regulation of the novel phosphoenolpyruvate carboxykinase paralogue pck2b in rainbow trout and identify specific miRNA candidates predicted to contribute to gene paralogue-specific regulation of gluconeogenesis in nutritional and social contexts using small RNA next generation sequencing, real-time RT-PCR and in silico target prediction approaches. In nutritional and social status experiments, in silico predicted targets of differentially expressed hepatic miRNAs are enriched for gluconeogenesis regulation, suggesting a posttranscriptional component in regulating gluconeogenic transcript abundance. Differentially expressed hepatic miRNAs in both experiments comprise evolutionarily conserved and teleost-specific miRNAs, and are indicative of both environmental factor-specific and common regulation of gluconeogenesis transcripts in rainbow trout liver. Together this work provides novel comparative insight into hepatic miRNA-dependent glucoregulation and identifies several specific candidate miRNAs for future functional validation in hepatic glucoregulation in rainbow trout.