Effects Of Adiponectin And Substrates Of Gluconeogenesis On Liver Gluconeogenesis Of Starved Yaks

Yak is endemic species living in the Qinghai-Tibetan Plateau,which could adapt the specific natural environment of plateau.Yaks are important means of production and livelihood to the local pastoralists for survival,and have great impacts in local social,economic and cultural.However,since the severe plateau environmental conditions,primitive grazing methods,and the long period of grass withered(April to September),the starvation became inevitable problem that Yak must facing in cold season.Gluconeogenesis is the typical characteristics of carbohydrate metabolism in ruminants.When ruminants are under the starvation conditions,Gluconeogenic pathway of the propanoic acid fermentated in rumen from feeds is blocked,and the precursor substance of gluconeogenesis are altered in liver.Some studies have reported that adiponectin is one of the most abundant protein expression in adipose tissue,played an important role in the regulation of energy balance and insulin sensitivity.The efficiency of gluconeogenesis of difference precursor substances and the potential mechanism are still unclear.The Jiulong yak were used in this study to explore the effect of starvation on gluconeogenesis under the premise of starvation models.The study is designed by three parts:Part I:Eight yaks,which were healthy,in good growth condition andconsistent in body weight(90.75±8.66kg)were selected and were randomLyallocated into two groups(the control vs starvation group).The starvation group was dealing with fasting.Blood samples were collectedthrough jugular vein on day 1,3,5,7 respectively.The results showed as following:Yaks live weight decreased significantly after starvation(P<0.05).The content of glucose was decreased(P<0.05).The content of NEFA and TG were risen significantly(P<0.05).The substances of gluconeogenesis propionic acid and lactic acid was decreased(P<0.05)while the content of glycerol,glucogenic amino acid and beta-hydroxybutyric acid were promoted significantly(P<0.05).The concentration of PC,FBP,PEPCK and G-6-P were promoted significantly(P<0.05).The content of APN,GN in serum were all promoted significantly(P<0.05)while the INS was decresed.The results indicate that yaks use the energy stored in the body after starvation,the starvation models was successfully established.Part II:After the starvation experiment,the primary cultured hepatocytes from two group yak were incubated with propanoic acid,glycerine,alanine,beta-hydroxybutyrate for 12h.The result showed that the glucose consumption and gluconeogenesis in starvation group were rose significantly(P<0.05).The expression and activities of PC,FBP,PEPCK and G-6-Pase were up-regulated by the substances of gluconeogenesis(P<0.05).Propanoic acid treatment is the most efficient precursor in control group,while the beta-hydroxybutyrate is the most efficient precursor instarvation group.Part ?:Propanoic acid and beta-hydroxybutyrate were selected as the basal content of control group and starvation group medium respectively.Hepatocytes cultured in vitro were treated with APN and BML-275(an AMPKa inhibitor)for 12 h,including 4 groups,control group,APN group,BML group and BML+APN group.The mRNA,total protein were extracted and then were detected by various methods.The results showed that except the mRNA of AdipoRl and ATP in starvation group hepatocytes were decreased,the AdipoR2 and other transcription factors such as APPL1,FoxO1,HNF-4?,TORC2,CREB,GLUT4,PGC-la were rose significantly(P<0.05).APN significantly increased the mRNA levels of two adiponectin receptors and protein expression of AMPKa(P<0.05).The mRNA of FoxO1?HNF-4? were decreased significantly in control group(P<0.05).The mRNA of PGC-la were decreased significantly in starvation group(P<0.05)while the TORC2,CREB,GLUT4 were increased significantly(P<0.05).In conclusion,yak live weight decreased significantly after fasting.The content of GLU decreased significantly.The content of NEFA and TG were risen.Body will regulate GN,INS to maintain glucose homeostasis.Starvation up-regulated the expression of APN.Meanwhile,the substance of gluconeogenesis was changed from propionic acid to glycerine,alanine,beta-hydroxybutyrate,fasting promotes the expression of key enzymes of gluconeogenesis,in order to promote gluconeogenesis,improve the synthesis of GLU to maintain the body's glucose homeostasis.The propanoic acid is the most efficient precursor of gluconeogenesis in control group,while the beta-hydroxybutyrate is the most efficient precursor in starvation group.In normal group,APN activates the AMPKa signaling pathway,subsequently control FoxO1,HNF4? expression level and finally reducing gluconeogenesis in yak hepatocytes cultured in vitro,while the pathway could change into PGC-1??TORC2?CREB in starvation group.