Estrogen Promotes Hepatic Synthesis of Long-Chain Polyunsaturated Fatty Acids by Regulating ELOVL5 at Post-Transcriptional Level in Laying Hens
The effect of different levels of corn oil (CO) and flaxseed oil (FO) on growth performance, blood characteristics, fatty acid composition, and expression of lipogenic genes in the liver of broiler chickens was studied. Two hundred forty female Cobb-500 broiler chickens at the age of one day (body weight (BW) = 46 ± 4 g) were fed a corn soybean meal based diet containing 5% CO (LC), 3.75% CO + 1.25% FO (FO1), 2.5% CO + 2.5% FO (FO2) or 5% FO (FC). Chickens fed FO1 diet had better BW gain (P = 0.049) and gain/feed ratio (P = 0.006) than those fed LC and FC diets during days 1–21 of age. However, for the whole experimental period (1–42 days of age), the dietary lipid source had no effect on the growth performance. On day 42 of age, the hepatic percentages of 18:3n-3 (P = 0.001) and 20:5n-3 (P < 0.001) were higher in FC than in LC group, which led to a higher content of total n-3 PUFA and lower n-6/n-3 PUFA ratio. The contents of 18:2n-6 (P < 0.05) and Σ n-6 PUFA (P = 0.009) were lower in FC than in LC group. Chickens fed FO1 and FO2 diets had higher Ca2+-ATPase activity and lower lipoprotein lipase activity than those fed LC and FC diets, whereas activities of lactate dehydrogenase and Na+,K+-ATPase were increased by FO2 than by LC diet (P < 0.05). The relative mRNA expression level of lipin 1 in chickens fed FO2 and FC was higher (P < 0.01) than in those fed LC and FO1 diets. Our results demonstrated that higher levels of FO led to hepatic enrichment of n-3 PUFA content and lower n-6/n-3 PUFA ratios in liver and increased the expression of lipin 1 whereas the expression of lipin 2, NADH dehydrogenase subunit 2, Δ-6 fatty acid desaturase, WD and tetratricopeptide repeats 1, and glyceraldehyde-3-phosphate dehydrogenase was not affected.