Effects of Soybean Isoflavone on the Growth Performance and Lipid Metabolism of Juvenile Chinese Mitten Crab Eriocheir sinensis

In order to study the effects of soybean isoflavones on the growth performance and lipid metabolism of juvenile Chinese mitten crab, six experimental diets were formulated by gradient supplementation 0%, 0.004% and 0.008% soybean isoflavones at different dietary lipid levels (10% and 15%), which were named to NF-0 group (10% fat and 0% SIF), NF-0.004 group (10% fat and 0.004% SIF), NF-0.008 group (10% fat and 0.008% SIF), HF-0 group (15% fat and 0% SIF), HF-0.004 group (15% fat and 0.004% SIF) and HF-0.008 group (15% fat and 0.008% SIF). All crabs with an initial weight of 0.4 ± 0.03 g were fed for 8 weeks. The results showed that diets supplementation with 0.004% or 0.008% SIF significantly increased the weight gain and specific growth rate of crabs. Diets supplementation with 0.004% or 0.008% SIF significantly reduced the content of non-esterified free fatty acids and triglycerides in the hepatopancreas of crabs at 10% dietary lipid level. Dietary SIF significantly decreased the relative mRNA expressions of elongase of very long-chain fatty acids 6 (elovl6), triglyceride lipase (tgl), sterol regulatory element binding protein 1 (srebp-1), carnitine palmitoyltransferase-1a (cpt-1a), fatty acid transporter protein 4 (fatp4), carnitine palmitoyltransferase-2 (cpt-2), Δ9 fatty acyl desaturase (Δ9 fad), carnitine palmitoyltransferase-1b (cpt-1b), fatty acid binding protein 10 (fabp10) and microsomal triglyceride transfer protein (mttp) in the hepatopancreas of crabs. At 15% dietary lipid level, 0.008% SIF significantly increased the relative mRNA expressions of fatty acid binding protein 3 (fabp3), carnitine acetyltransferase (caat), fatp4, fabp10, tgl, cpt-1a, cpt-1b and cpt-2 and significantly down regulated the relative mRNA expressions of Δ9 fad and srebp-1. In conclusion, SIF can improve the growth and utilization of high-fat diet by inhibiting genes related to lipid synthesis and promoting lipid decomposition in juvenile Chinese mitten crab.