天冬酰胺对脂多糖刺激断奶仔猪生长性能以及下丘脑-垂体-肾上腺轴Toll样受体4和核苷酸结合寡聚化结构域信号通路的影响

Effects of Asparagine on Growth Performance and Toll-Like Receptor 4 and Nucleotide Binding Oligomerization Domain Signaling Pathways of Hypothalamus-Pituitary-Adrenal Axis of Weaned Piglets Challenged by Lipopolysaccharide

本试验旨在研究天冬酰胺(Asn)对脂多糖(LPS)刺激断奶仔猪生长性能和下丘脑-垂体-肾上腺(HPA)轴的Toll样受体4(TLR4)和核苷酸结合寡聚化结构域(NOD)信号通路关键基因mRNA表达的影响。试验选取24头健康的(21±2)日龄"杜×长×大"断奶仔猪[(8.12±0.56) kg],按体重相近原则随机分为4组,分别为:1)对照组(基础饲粮); 2) LPS组(基础饲粮+LPS); 3) LPS+0.5%Asn组(基础饲粮+0.5%Asn+LPS); 4) LPS+1.0%Asn组(基础饲粮+1.0%Asn+LPS)。每组6个重复,每个重复1头猪。试验第20天,LPS组、LPS+0.5%Asn组和LPS+1.0%Asn组的试验猪注射100μg/kg BW的LPS,对照组试验猪则注射等量的生理盐水。试验期为20 d。结果表明,与对照组相比,LPS刺激以及饲粮中添加Asn对LPS刺激断奶仔猪的生长性能没有显著影响(P>0.05)。LPS刺激可以显著提高HPA轴中TLR4、髓样分化蛋白88(MyD88)、NOD2、受体相互作用丝氨酸/苏氨酸蛋白激酶2(RIP2)和核转录因子-κB (NF-κB)的mRNA表达量(P<0.05)。饲粮中添加Asn可以显著降低下丘脑中NF-κB的mRNA表达量(线性,P<0.05),并有降低肾上腺中TLR4和NOD2的mRNA表达量的趋势(线性,P<0.10)。此外,饲粮中添加Asn可以显著降低垂体中肿瘤坏死因子受体相关因子6(TRAF6)的mRNA表达量(二次,P<0.05),显著增加了肾上腺中RIP2的mRNA表达量(线性,P <0.05;二次,P <0.05)。由此可见,Asn虽然对LPS刺激仔猪的生长性能没有现在影响,但其可通过降低下丘脑NF-κB的mRNA表达量,而对下丘脑TLR4信号通路具有一定的抑制作用。

This study was conducted to investigate the effects of asparagine(Asn)on growth performance and key gene mRNA expression in toll like receptor 4(TLR4)and nucleotide binding oligomerization domain(NOD)signal pathways of the hypothalamus-hypophysis-adrenal(HPA)axis of weaned piglets challenged by lipopolysaccharide(LPS).Twenty-four healthy(21±2)-old-day weaning piglets(Duroc×Landrace×Yorkshire)with a body weight of(8.12+0.56)kg were selected and randomly divided into 4 groups:1)control group(basal diet),2)LPS group(basal diet+LPS);3)LPS+0.5%Asn group(basal diet+0.5%Asn+LPS);4)LPS+1%Asn group(basal diet+1.0%Asn+LPS).There were 6 replicates in each group and 1 pig in each replicate.On day 20,pigs in LPS group,LPS+0.5%Asn group and LPS+1%Asn group were injected with 100μg/kg BW LPS,and pigs in the control group were injected with the same amount of saline.The experiment lasted for 20 days.The results showed that compared with the control group,LPS challange and dietary Asn supplementation had no significant effects on the growth performance of weaned piglets challenged by LPS(P >0.05).LPS challenge significantly increased the mRNA expression of TLR4,myeloid differentiation factor 88(MyD88),NOD2,receptor-interacting protein serine/threonine kinases 2(RIP2)and nuclear factor-κB(NF-κB)mRNA expression in the HPA axis(P<0.05).Dietary Asn supplementation could significantly decrease the mRNA expression of NF-κB in hypothalamus(linear,P<0.05),and had a tendency to decrease the mRNA expression of TLR4 and NOD2 in adrenal(linear,P<0.10).In addition,dietary Asn supplementation decreased the mRNA expression of tumor necrosis factor-associated factor 6(TRAF6)in hypophysis(linear,P<0.05),and significantly increased the mRNA expression of RIP2 in adrenal(linear,P<0.05;quadratic,P<0.05).The results suggest that although Asn had no significant effects on the growth performance of weaned piglets challenged by LPS,but it can inhibit TLR4 signal pathway via decreasing the mRNA expression of NF-κB in hypothalamus.