Changes in the triglyceride metabolism in the thigh muscle and liver of broilers injected intravenously with angiopoietin-like protein 4

Angiopoietin-like protein 4 (ANGPTL4) is a potential circulating mediator connecting nutritional factors and fat metabolism, however, information is lacking on the exact role of ANGPTL4 on triglyceride metabolism in the thigh muscles and livers of broilers. The objective of this study was to determine the changes in the triglyceride metabolism in the thigh muscles and livers of broilers injected intravenously with ANGPTL4. In experiment 1, 36 male Arbor Acres broilers at 35 days of age were randomly allocated into six treatments with six replicates. The broilers were subjected to intravenous injection of polyhistidine-small ubiquitin-related modifier-ANGPTL4 (His-SUMO-ANGPTL4) once at a dose of 0, 20, 100, 500, 2 500, or 12 500 ng/ kg body weight (BW), respectively. The results showed that the injection of His-SUMO-ANGPTL4 at a dose of 500, 2 500 and 12 500 ng/kg BW decreased (P < 0.05) the broilers' heart-fatty acid-binding protein (H-FABP) mRNA expression in the thigh muscle. All of the His-SUMO- ANGPTL4 broiler injected groups had a lower (P < 0.05) adipocyte-fatty acid-binding protein mRNA expression in the thigh muscle. In experiment 2, 18 male Arbor Acres broilers at 35 days of age were randomly allocated into three treatments with six replicates. The broilers were given an injection of normal saline (NS), His-SUMO, or His-SUMO-ANGPTL4 (500 ng/kg BW) once. The results showed that the broilers receiving an injection of ANGPTL4 at a dose of 500 ng/kg BW decreased (P < 0.05) the H-FABP mRNA expression in the thigh muscle. Besides, the broilers given an injection of ANGPTL4 at a dose of 500 ng/kg BW increased ( P < 0.05) the fatty acid synthase mRNA expression and activity and decreased (P < 0.05) the microsomal triglyceride transfer protein mRNA expression in the liver. However, the concentrations of the high- density lipoprotein, low-density lipoprotein, very low-density lipoprotein, insulin, growth hormone and leptin in the serum were not affected by the ANGPTL4 injection. In conclusion, ANGPTL4 has the ability to change the triglyceride metabolism in the thigh muscles and livers of broilers.