Regulatory Mechanism Of α-lipoic Acid On Meat Quality And Antioxidant Of Tan Lamb

Due to the ban on grassland grazing and the pursuit of farming efficiency,the current farming method of Tan lamb usually adopts housing and high concentrate fattening,which eventually causes the deterioration of meat quality after slaughter.The aim of this experiment was to investigate the effect of adding α-lipoic acid(α-LA)to the diet on the quality and antioxidant capacity of lamb meat.Eighteen 4month-old Tan lamb in good health and similar body condition were randomly divided into three groups:control(Con),low-dose(600 mg/kg α-lipoic acid,LS)and high-dose(900 mg/kg α-lipoic acid,HS).The biceps femoris of beach goats were collected to determine meat quality,antioxidant properties and mitochondrial function.The main results of the study are as follows:(1)Meat quality results showed that the addition of both low and high doses of α-lipoic acid significantly increased the pH45min value and reduced the b*45min and L*48h values(P<0.05)compared with the control group;the low dose of α-lipoic acid significantly increased the pH48h value(P<0.05)and significantly reduced the shear force(P<0.05).The high dose of α-lipoic acid significantly reduced the a*45min and a*48h values(P<0.05);however,there was no significant difference in pH24h values,drip loss and cooking loss between the groups(P>0.05).A total of 41 volatile compounds were detected in the meat,including butyraldehyde,n-valeraldehyde,hexanal,heptanal,trans-2-pentenal,benzaldehyde,2-heptanone,2-octanone,2-nonanone and acetone.The levels of benzaldehyde,2-heptanone,acetone and heptanal in lamb were significantly lower in the low and high dose α-lipoic acid groups than in the control group(P<0.05).The addition of α-lipoic acid to the diet could improve the pH45min value and tenderness of Tan lamb,reduce the b*45min and L*48h values,and thus improve the meat quality.(2)The results of antioxidant properties showed that compared with the control group,low and high doses of α-lipoic acid can significantly reduce the Malondialdehyde(MDA)content of Tan lamb(P<0.05),and improve the total antioxidant capacity(T-AOC),free radicalscav-engingactivity(RSA)and antioxidant capacity.High dose of α-lipoic acid can significantly increase the activity of superoxidedismutase(SOD)(P<0.05).Further,three groups of Tan lamb samples were deeply sequenced based on transcriptomics technology,and 986 differential genes were identified.Genes are differentially enriched in six KEGG pathways,including glutathione metabolism,p53 signaling pathway and cytochrome P450.Finally,21 genes related to antioxidation were identified,including monoamine oxidase B,glutathione peroxidase 7 and glutathione S-transferase Mul.Low and high doses of α-lipoic acid can up-regulate the expression of antioxidant enzymes related genes and down-regulate the expression of oxidase related genes.RT-PCR was used to verify the results of transcriptome sequencing,and it was found that the expression trends of four target genes were basically consistent with the results of transcriptome sequencing.On the whole,adding α-lipoic acid to diet can activate antioxidant pathway,up-regulate the expression of antioxidant enzyme gene,and finally improve the antioxidant performance of Tan lamb muscle.(3)The results showed that compared with the control group,both low and high doses of α-lipoic acid significantly increased the expression level of MyHC Ⅱa mRNA and decreased the expression level of MyHC Ⅱb and Ⅱx(P<0.05),thus increasing the mitochondrial content in the muscles of Tan lambs.The addition of α-lipoic acid significantly reduced mitochondrial swelling,MTPT open state,ROS content and Caspase-3 activity(P<0.05),increased ATP content in mitochondria(P<0.05),increased Cyt-c reduction level(P<0.05)and improved mitochondrial function.In conclusion:dietary supplementation of α-lipoic acid could maintain the content and function of mitochondria in the muscle of Tan lamb,increase the ATP content in mitochondria,reduce the level of ROS,enhance the expression and activity of antioxidant enzyme genes,thus inhibiting the oxidation of muscle tissue and thus improving the quality of Tan lamb meat.