GSK-3β at the Crossroads in Regulating Protein Synthesis and Lipid Deposition in Zebrafish

In this study, the mechanism by which GSK-3β regulates protein synthesis and lipid deposition was investigated in zebrafish (Danio rerio). The vector of pEGFP-N1-GSK-3β was constructed and injected into the muscle of zebrafish. It was found that the mRNA and protein expression of tuberous sclerosis complex 2 (TSC2) was significantly increased. However, the mRNA and protein expression of mammalian target of rapamycin (mTOR), p70 ribosomal S6 kinase 1 (S6K1), and 4E-binding protein 1 (4EBP1) was significantly decreased by the pEGFP-N1-GSK-3β vector in the muscle of zebrafish. In addition, the mRNA and protein expression of β-catenin, CCAAT/enhancer binding protein α (C/EBPα), and peroxisome proliferators-activated receptor γ (PPARγ) was significantly decreased, but the mRNA expression of fatty acid synthase (FAS), acetyl-CoA carboxylase (ACC), ATP-citrate lyase (ACL), and HMG-CoA reductase (HMGCR) was significantly increased by the pEGFP-N1-GSK-3β vector. The activity of FAS, ACC, ACL, and HMGCR as well as the content of triglyceride (TG), total cholesterol (TC), and nonesterified fatty acids (NEFA) were significantly increased by the pEGFP-N1-GSK-3β vector in the muscle of zebrafish. The content of free amino acids Arg, Lys, His, Phe, Leu, Ile, Val, and Thr was significantly decreased by the pEGFP-N1-GSK-3β vector. The results indicate that GSK-3β may participate in regulating protein synthesis via TSC2/mTOR signaling and regulating lipid deposition via β-catenin in the muscle of zebrafish (Danio rerio).