Metabolic and transcriptional adaptations improve physical performance of zebrafish

Background: Obesity is a worldwide public health problem with increasing prevalence and affects 80% of diabetes mellitus type 2 cases. Zebrafish (Danio rerio) are an established model organism for studying obesity and diabetes including diabetic microvascular complications. We aimed to determine whether physical activity is an appropriate tool to examine training effects in zebrafish and to analyse metabolic and transcriptional processes in trained zebrafish. Methods: A 2- and 8-weeks experimental training phase protocol with adult zebrafish in a swim tunnel system was established. We examined zebrafish basic characteristics before and after training such as body weight, body length and maximum speed and considered overfeeding as an additional parameter in the 8-weeks training protocol. Ultimately, the effects of training and overfeeding on blood glucose, muscle core metabolism and liver gene expression using RNA-Seq were investigated. Results: Zebrafish maximum speed was correlated with body length and was significantly increased after 2 weeks of training. Maximum swim speed further increased after 8 weeks of training in both the normalfed and the overfed groups, but training was found not to be sufficient in preventing weight gain in overfed fish. Metabolome and transcriptome profiling in trained fish exhibited increased blood glucose levels in the short-term and upregulated energy supply pathways in the long-term. Conclusion: Swim training is a valuable tool to study effects of physical activity in zebrafish, which is accompanied by metabolic and transcriptional adaptations. total RNA sequencing was performed with 24 zebrafish liver samples (ABTL strain), including 6 control fish, 6 overfed fish, 6 trained fish, 6 trained and overfed fish