Effects of DHA supplementation on (A) Survival, (B) body weight, (C) feed efficiency. Values are means ± SEMs (n = 3 biological replicates). Means without a common letter are significantly different, P < 0.05.

Effects of DHA supplementation on hepatic lipid metabolism. (A) H&E staining of liver sections of LFD, HFD, and HFDHAs-fed zebrafish for 2 wks. The scale bar is 20 μm. (B) Oil red staining of liver sections of LFD, HFD, and HFDHAs-fed zebrafish for 2 wks. The scale bar is 50 μm. (C) Hepatic TG content of zebrafish fed HFD and HFDHAs for 2 wks. Relative mRNA expression of genes related to (D) lipid synthesis and (E) β-oxidation. Values are means ± SEMs (n = 3-5 biological replicates). Means without a common letter are significantly different, P < 0.05.

Modulation of DHA on lipid metabolism in ZFL cells. (A) Lipid droplets accumulation in ZFL cells with lipid treatment. The scale bar is 20 μm. (B) TG content in ZFL cells treated with CK, OA, and ODHA. (C) Relative mRNA expression of genes related to lipid synthesis and (D) β-oxidation in control and lipid treated ZFL cells. Values are means ± SEMs (n = 5-6 biological replicates). Means without a common letter are significantly different, P < 0.05. *P < 0.05; **P < 0.01. CK, controls; OA, 100 μM oleic acid; ODHA, mix of 50 μM OA and 50 μM DHA.

Effects of DHA on cell growth, cell apoptosis and cell cycle. (A) Growth of ZFL cells treated with DHA for 48 h. (B) Cell apoptosis and (C) cell cycle of ZFL treated with DHA at 24 h. (D) Relative mRNA expression of genes encoding D-type Cyclins in ZFL cells. (E) Relative mRNA expression of genes encoding D-type Cyclins in the liver of LFD, HFD, and HFDHA0.5-fed zebrafish. (F) Relative mRNA expression of genes encoding D-type Cyclins in ZFL cells treated with OA and ODHA. Values are means ± SEMs (n = 3-5 biological replicates). Means without a common letter are significantly different, P < 0.05. *P < 0.05.

Effects of Cyclin D1 knockdown and Cyclin D1-Cdk4 blocking on lipid metabolism. (A) Growth of NC and Cyclin D1-knockdown ZFL cells. (B) Apoptosis of NC and Cyclin D1-knockdown ZFL cells. (C) Efficiency of siRNA targeting cyclin D1 in ZFL cells. (D) Relative mRNA expression of genes related lipid synthesis in ZFL cells with Cyclin D1 knockdown. (E) Relative mRNA expression of genes related β-oxidation in ZFL cells with Cyclin D1 knockdown. Relative mRNA expression of genes related (F) lipid synthesis and (G) lipid β-oxidation in ZFL cells treated with LY2835219. Values are means ± SEMs (n = 3 biological replicates). *P < 0.05; ^**P < 0.01.

Effects of DHA supplementation on lipid metabolism in GF zebrafish. (A) Whole-mount oil red staining in GF zebrafish fed LFD, HFD and HFDHA0.5. The scale bar is 200 μm. (B) Relative mRNA expression of CyclinDs. Relative mRNA expression of (C) lipid synthesis-related, and (D) lipid β-oxidation-related genes. Values are means ± SEMs (n = 4 biological replicates). Means without a common letter are significantly different, P < 0.05.

Effects of DHA supplementation on gut microbial community in zebrafish. (A) PCoA analysis of gut microbiota in HFD- and HFDHA0.5-fed zebrafish. (B) Relative abundance at the phylum level of gut microbial community from HFD- and HFDHA0.5-fed zebrafish (C) Relative abundance at the genus level of gut microbial community from HFD- and HFDHA0.5-fed zebrafish. Values are means ± SEMs (n = 4 biological replicates).

Effects of gut microbiota on lipid metabolism in GF zebrafish. (A) Whole-mount oil red staining in GF zebrafish in LFD, HFD, and HFDHA0.5. The scale bar is 200 μm. (B) Relative mRNA expression of CyclinDs. Relative mRNA expression of (C) lipid synthesis-related, and (D) lipid β-oxidation-related genes. Values are means ± SEMs (n = 4 biological replicates). Means without a common letter are significantly different, P < 0.05.