Dynamic Changes Of Plasma GH In Ketosis Cows And Effects Of BHBA On Hepatic Oxidative Stress

Ketosis is a common metabolic disorder during the transition period in cows which is caused by a negative energy balance?NEB?.Studies have shown that endocrine hormones may play an important role in mobilizing the body's reserves during cows NEB.Growth hormone?GH?is a multifunctional endogenous hormone.At present,the research on GH mainly focuses on fat decomposition,inhibition of fat synthesis and oxidation energy supply.However,the dynamic monitoring of GH during the occurrence of natural ketosis in dairy cows has not been reported.Excessive body fat mobilization during ketosis increases the concentration of non-lipidized fatty acid?NEFA?,increases the production of reactive oxygen species?ROS?.The aim of this study was to analyze the oxidative stress and the correlation between various indicators during the onset of ketosis cows by observing the dynamic changes of plasma GH in ketosis cows with natural pathogenesis,and to analyze the key enzymes and GH-related gene mRNA of hepatocyte oxidase in vitro by ?-Hydroxylbutyrate?BHBA?.Frist experiment:Experiment in vivo-Dynamic changes of postpartum GH and other indicators in ketosis cows.For 5 weeks:62 Holstein cows were selected.On the day of delivery to 5 weeks after delivery,blood was collected once a week?6 times in total?and plasma BHBA levels were detected.Ketosis cows(BHBA?1.2 mmol L^-1)were set as experimental groups?SK?,and the selected fetuses and the similar physical conditions of the cows(BHBA<1.0 mmol L^-1)were paired as the control group?NK?.The blood collected at every week while assessing the cow body condition score?BCS?and record milk production?MY?.Finally,12 Holstein cows were selected as the SK group,and 12 cows selected as NK group.The levels of plasma GH and BHBA,NEFA and GLU were monitored dynamically and mapping of cows' dynamics.Simultaneously test the oxidative stress index of the sample[catalase?CAT?,glutathione peroxidase?GSH-Px?,malondialdehyde?MDA?].And analysing the correlation between GH and other indicators.The results showed that GH,BHBA and NEFA in SK group were significantly higher than that of NK group in postpartum 5 weeks?p<0.01?,but GLU in SK group was significantly lower than that of NK group?p<0.01?.The results of correlation analysis showed that GH was positively correlated with BHBA and NEFA?r=0.495,p=0.000;r=0.494,p=0.000?and was significantly negatively correlated with GLU?p=0.000,r=-0.535?.GH was highest in postpartum during 2 weeks,meanwhile,its changes was same as BHBA and NEFA,but GLU was the lowest in the postpartum 2 weeks.MDA level of SK group was significantly higher than that of NK Group?p<0.01?;MY,CAT,BCS and GSH-Px were significantly lower than that of NK group.The correlation showed that GH was positively correlated with MDA?r=0.443,p =0.000?,but GH was negatively correlated with CAT and GSH-Px in SK group?r=-0.597,p=0.000;r=-0.610,p=0.000?.For one day,dynamic monitoring of cows within 12 hours after detection of BHBA 1.2 mmol L'1 was conducted on the next day.The blood collection time was from 10:00 to 20:00,5 times in total every 3 hours.Selected 8 ketosis cows set as experiment group and 8 health cows set as control cows.The blood samples obtained were also tested for GH,BHBA,NEFA,and GLU levels.The results showed that GH,BHBA and NEFA in SK group were significantly higher than that of NK group,and GH in SK group was significantly positively correlated with BHBA and NEFA respectively?r= 0.550,p = 0.000;r=0.663,p = 0.000?,but the GLU in SK group was significantly lower than that of NK group and negatively correlated?r=-0.419,p =0.004?.It was also found that the feeding time affected the plasma levels of each index,that is,the GH level decreased,BHBA,NEFA and GLU increased after 1 h of feeding;GH,BHBA and NEFA had the highest plasma concentration and the lowest GLU after 4 h of feeding.Third experiment:The effects of BHBA on the level of the relative enzymes and GH related gene mRNA expression in hepatocytes in vitro.The changes of the relative antioxidants were determined by subjected different concentrations of BHBA(0,0.6,1.2,3.0 mmol L^-1).The results showed that concentration of SOD,CAT,GSH-Px were decreased and MDA gradually was increased with the increase of BHBA concentration and time?Oh,6h,12h,24h,48h?.The level of mRNA expression of GHR,IGF1,IGF-1R were decreased and CAT,GSH-Px,SOD were decreased.Conclusion:This study demonstrates for the first time that GH levels during postpartum Holstein dairy cows are significantly higher than those of healthy cows,and that GH reaches its highest level level of postpartum 1-2 week.The concentration of GH was significantly higher than that of healthy cows,and concentration of GH had a certain relationship with the time of feeding.High GH levels are significantly associated with high NEFA levels.The level of oxidative stress of ketones cows was higher than that of healthy cows.In vitro experiments showed that the decrease of GHR mRNA level in hepatocytes could down-regulated the level of IGF 1 and IGF-1R mRNA,and the expression of CAT,GSH-Px and SOD mRNA were decreased when BHBA was high concentration.In summary,it can be verified that GH is one of the endocrine bases of ketosis.