The Study And Its Mechanism About Palmitic Acid Induce Dairy Cow Oxidative Stress

Perinatal management is a key constraint to the profitability of dairy farms.One of the core contents of perinatal group management is controling and adjusting the negative energy balance（NEB）of perinatal dairy cows.When NEB appears in dairy cows,the content of nonesterified fatty acids（NEFAs）in plasma increases,and a large amount of lipids accumulate in the body,resulting in metabolic stress,oxidative stress,ketosis,fatty liver and subacute inflammation.Until now,the mechanism that NEFA causes oxidative stress in dairy cows has not been elucidated.It has been reported that palmitic acid PA is the main component of NEFA,and the PA content apparently increases in the presence of NEB in dairy cows.Therefore,what this experiment is about to explore is whether PA can induce oxidative stress in perinatal dairy cows.The study inclued three levels:mitochondria level,cell level,and cow body level.The mitochondrial membrane potential was detected by Rhodamine 123,the malondialdehyde content was detected by thiobarbituric acid method,the H2O2 level was detected by FOX method,the glutathione content was detected by DTNB method,and the mechanism of PA induced mitochondrial oxidative stress in calf liver was investigated.MTT assay was used to detect cytotoxicity,DCFH-DA probe was used to detect ROS,TBA was used to detect MDA,ELISA was used to detect GSH,and Western blot was used to detect the expression of nuclear factor-κB（NF-κB）.To study the mechanisms of oxidative stress and inflammatory reaction;The PA content were detected by gas chromatography,detection of NEFA and BHBA were detected by automatic biochemical analyzer,detection of GSH by DTNB,detection of haptoglobin in serum by o-dianisidine colorimetric assay by MDA,DTNB,To investigate the correlation between PA and oxidative stress and inflammation in the body.The following results were obtained:1.With the increasing of the concentration of PA,the content of MDA in calf liver mitochondria induced by PA increases,the H2O2 content,MMP reduced,the content of GSH reduced,and they all showed a concentration depending effects.2.With the increase of PA concentration,the activity of rat hepatocytes was decreased,ROS increased,MDA content increased,H2O2 content increased,GSH content decreased,NF-κB phosphorylation protein level increased significantly,and all showed concentration dependenting effects.3.The content of PA in plasma of ketosis dairy cows was significantly higher than that of young dairy cows and healthy dairy cows;the content of NEFA,BHBA and MDA in plasma of ketosis dairy cows was significantly higher than that of young dairy cows and healthy dairy cows;but GSH was lower than that of young dairy cows and healthy dairy cows;ketones The Hp content of diseased cows was significantly higher than that of young dairy cows and healthy dairy cows.The content of PA was positively correlated with the contents of NEFA,BHBA,MDA and Hp,and negatively correlated with the content of GSH.Conclusion:PA induces mitochondrial MDA,H₂O₂ content in yak liver,oxidative stress environment dramaticly increases,GSH is consumed a lot,and it ultimately leads to mitochondrial oxidative damage.PA-induced increase in ROS and MDA content in BRL-3A hepatocytes reduced GSH content and exacerbated oxidative stress in BRL-3A cells.At the same time,oxidative stress environment may further lead to phosphorylation of NF-κB and activation of downstream inflammatory response.Compared with young dairy cows and healthy dairy cows,plasma levels of NEFA,BHBA,PA and MDA in perinatal dairy cows with ketosis increased,and GSH level decreased.In the ketotic cows,PA is associated with ketosis in the peripheral blood and is associated with oxidative stress in the body and is also associated with subacute inflammation in the body.