杜仲叶对绵羊脂肪代谢的影响及其机理

为研究杜仲叶对绵羊脂肪代谢和肉品质的影响,本研究随机选择70~80日龄、体重25~30 kg的绵羊(湖羊)30只,平均分为3组,分别为对照组(CTL组,饲粮中不含杜仲叶)、低水平杜仲叶组(EUL1组,饲粮含10%杜仲叶)和高水平杜仲叶组(EUL2组,饲粮含20%杜仲叶),每组10只。预试期15 d,正试期90 d。采集血液,测定血浆脂质代谢分析指标;采集背最长肌,测定营养物质含量;采集肝脏组织,测定脂肪代谢相关酶和核转录因子的mRNA表达水平和蛋白水平。结果表明:1)各组干物质采食量EUL1组EUL2组CTL组,组间差异显著(P0.05)。2)与CTL组相比,EUL2组血浆极低密度脂蛋白(VLDL)、高密度脂蛋白(HDL)、非酯化脂肪酸(NEFA)含量显著升高(P0.05),EUL1和EUL2组血浆低密度脂蛋白(LDL)(0.05≤P0.10)、总胆固醇(TC)(P0.05)含量降低。3)与CTL组相比,EUL1组肌肉粗蛋白质含量、EUL2组肌肉粗脂肪含量显著升高(P0.05),EUL1组肌肉剪切力显著减小(P0.05)。4)与CTL组相比,EUL1组和EUL2组肌肉饱和脂肪酸(SFA)含量略有降低(P0.05),肌肉不饱和脂肪酸(UFA)含量显著升高(P0.05),其中,EUL2组肌肉MUFA、PUFA含量及UFA/SFA显著升高(P0.05)。5)与CTL组相比,杜仲叶能够显著下调肝脏脂肪合成相关酶硬脂酰辅酶A去饱和酶1(SCD1)和核转录因子固醇调节元件结合蛋白1c(SREBP-1c)、过氧化物酶体增生激活受体γ(PPARγ)的mRNA表达水平(P0.05);显著上调肝脏脂肪酸分解相关酶肉毒碱棕榈酰基转移酶1A(CPT1A)、脂蛋白酯酶(LPL)mRNA表达水平显著上调(P0.05);与CTL组相比,EUL2组肝脏SCD1蛋白水平显著下降(P0.05)。结果提示,杜仲叶通过调节脂肪合成和分解相关基因的表达,显著影响绵羊脂肪的代谢和肌肉脂肪酸的组成。

Effects of Eucommia ulmoides Leaves on Sheep Lipid Metabolism and the Mechanism

In order to research the effects of Eucommia ulmoides leaves ( EUL) on sheep lipid metabolism and the mechanism, thirty healthy Hu sheep with the similar age (70 to 80 days of age) and body weight (25 to 30 kg) were randomly divided into three groups with 10 sheep per group, which were control group ( CTL group, diets without EUL) ,low level of EUL group ( EUL1 group, diet containing 10% EUL) , and high lev?el of EUL group ( EUL2 group, diets containing 20% EUL) . The pre?experimental period lasted for 15 d, the formal experiment period lasted for 90 d. Blood was collected to determine plasma lipid metabolism indexes;longissimus dorsi muscle was collected to determine nutrient contents; liver tissue was collected to determine mRNA expression levels and protein levels of enzymes or nuclear factors involved in lipid metabolism. The re?sults showed as follows:1) dry matter intake showed EUL1 grouP>EUL2 grouP>CTL group with significant difference among groups ( P<0.05) . 2) Compared with CTL group, plasma contents of total cholesterol ( TC) (P<0.05), low?density lipoprotein (LDL) (0.05≤P<0.10) were reduced, while plasma contents of very low?density lipoprotein ( VLDL) ( P<0.05) , high?density lipoprotein ( HDL) , non?esterified fatty acid ( NE?FA) in EUL2 group were significantly increased (P<0.05). 3) Compared with CTL group, crude protein content of muscle in EUL1 group, ether extract content of muscle in EUL2 group were significantly increased (P<0.05), but muscle shear force in EUL1 group was significantly reduced (P<0.05). 4) Compared with CTL group, saturated fatty acids ( SFA) content of muscle went down slightly in EUL1 and EUL2 groups ( P>0.05) , while unsaturated fatty acids ( UFA) content was significantly increased in EUL1 and EUL2 groups ( P<0.05) , in which monounsaturated fatty acids ( MUFA) and polyunsaturated fatty acids ( PUFA) contents and UFA/SFA in EUL2 group were significantly increased (P<0.05). 5) Compared with CTL group, EUL could significantly down?regulate mRNA expression levels of lipid synthesis related enzyme [ stearyl CoA desat?urase 1 ( SCD1) ] and nuclear factors [ sterol regulatory element?binding proteins 1c( SREBP?1c) and peroxi?some proliferator?activated receptor γ( PPARγ) ] in liver ( P<0.05) , and could significantly up?regulate mR?NA expression levels of lipid deposition related enzymes [ carnitine palmityl transferase1A ( CPT1A) and li?poproteinesterase ( LPL) ] in liver ( P<0.05); compared with CTL group, liver SCD1 protein level in EUL2 group was significantly decreased ( P<0.05) . These changes indicate that EUL significantly affects lipid metab?olism and muscle fatty acid composition of sheep by regulating gene expressions related to lipid synthesis and deposition.