Effect of a high-fat diet on lipid metabolism and KLF15-TWIST2 signaling pathway gene expression levels in zebrafish (Danio rerio)
Lipids are important constituents and energy storage substances in fish,and their main role is oxidative energy supply. Excessive lipid levels in the feed affect the normal physiological metabolism of fish. KLF15 is an important regulator and effector of intra-and inter-organ metabolic processes,playing a key role in promoting fat synthesis and storage. TWIST2 is a conserved basic helix-loop-helix (b-HLH) transcription factor that serves as a molecular switch to activate or repress target genes through direct or indirect mechanisms,regulating pathways involved in inflammation,energy homeostasis,and metabolic disorders. The expression patterns of KLF15 with TWIST2 play important roles in many aquatic animals. This study aimed to investigate the role of the KLF15-TWIS2 signaling pathway in lipid metabolism in zebrafish (Danio rerio). Zebrafish larvae were randomly divided into a normal-fat diet (NFD) group and a high-fat diet (HFD) group 5 days after fertilization. The NFD group was fed a basal diet and the HFD group was fed an HFD. After 7 consecutive days of feeding,zebrafish litters from the NFD and HFD groups were homogenized in an ice bath to collect samples,centrifuged to extract the supernatant and measured to analyse changes in lipid metabolism-related indexes and the expression characteristics of the KLF15-TWIST2 signaling pathway. Physiological indices and antioxidant enzyme activities as well as histological observations were used to determine whether an HFD caused lipid metabolism disorders. The expression levels of KLF15,TWIST2,and genes related to lipid metabolism (SREBP,FASN,ACC1,DGAT2,CEBPα,CPT1,ATGL,LPL,SCD,and HSL) were detected by fluorescence quantitative PCR and their correlations were analyzed. An HFD caused a significant (P<0.01) increase in total cholesterol,triglyceride,and low-density lipoprotein-cholesterol content in zebrafish. A significant (P<0.05) increase in superoxide dismutase activity and a significant (P<0.001) decrease in glutathione peroxidase activity were observed in zebrafish in the HFD group compared to those in the NFD group,and a large accumulation of lipids was observed. Intake of an HFD significantly increased the expression level of KLF15 (P<0.001),but significantly decreased the expression level of TWIST2 (P<0.05). The expression levels of lipid-synthesis-related genes,SREBP,FASN,ACC1,DGAT2,and CEBPα were significantly increased (P<0.05),while the expression level of the lipolysis gene ATGL was significantly decreased (P<0.05). Meanwhile,fatty acid oxidation genes PPARα,CPT1,LPL,LXPα showed a significantly higher expression level trend (P<0.05). The expression levels of members of the KLF15-TWIST2 signaling pathway were significantly correlated with the expression levels of SREBP,FASN,ACC1,ATGL,DGAT2,CEBPα,PPARα,and LPL. These results suggested that an HFD led to excessive lipid accumulation and tissue damage and lipid metabolism disorders in zebrafish,and that the KLF15-TWIST2 signaling pathway may regulate lipid metabolism through its involvement in fatty acid synthesis,transport,β-oxidation,catabolism and lipoprotein synthesis. The present study explored the role of the KLF15-TWIST2 signaling pathway in lipid metabolism in fish,which is of great significance for understanding the health of fish.
万方数据
维普
