Effect Of Energy Metabolism Factors On Hepatic Glyconeogenesis In Dairy Cows

The objects of this paper were to study the effect of energy metabolism factors on glyconeogenesis of calf dairy cows. In invitro experiment, liver cells were dissociated from new born calf. Two steps perfusion method was used to isolate liver cells.After culture 72 h, different concentions of leptin, neuropeptide Y, glucagon, insulin and IGF-I into culture fluid, extracted RNA total after incubating 12 h. mRNA abundances of Pyruvate carboxylase (PC) and Phosphoenol pyruvate carboxykinase (PEPCK) were detected through quantity RT-PCR method and enzyme actities of PC and PEPCK were analysised by chromatometry. Leptin concentrations were 0 ng/mL,2.5 ng/mL,5 ng/mL,10 ng/mL,50 ng/mL,100 ng/mL; NPY concentrations were 0 pg/mL,50 pg/mL,100 pg/mL,200 pg/mL,500 pg/mL,1000 pg/mL; GLN concentrations were 0 pg/mL,50 pg/mL,100 pg/mL,200 pg/mL,500 pg/mL,800 pg/mL; INS concentrations were 0μmol/L,5μmol/L,10μmol/L,20μmol/L,50μmol/L,100μmol/L and IGF-I concentrations were 0 ng/mL,10 ng/mL,30 ng/mL,50 ng/mL,100 ng/mL,150 ng/mL variously. The results displayed that leptin, insulin and IGF-I could downregulat PCmRNA and PEPCKmRNA abundances and enzyme activities in liver cells (p<0.05); However, NPY and GLN could upregulat PCmRNA and PEPCKmRNA abundances and enzyme activities in liver cells (p<0.05).In experiment of ketotic cows, PCmRNA and PEPCKmRNA abundances and enzyme activity were detected with the method as described above. In addition, concentration of serum neuroendocrine factors were determined and the interrelation among PCmRNA and PEPCKmRNA abundances, enzyme activities and concentration of neuroendocrine factors. The results shows that serum concentrations of GLU, LP and INS were lower in ketotic cows than those of healthy cows(p<0.05). PCmRNA abundance in ketotic cow was higher than those of healthy cows (p<0.05), but PEPCKmRNA abundance are similar between ketotic and healthy cows (P>0.05). PC and PEPCK enzyme activities were enhanced in liver of ketotic cows (p<0.01). PC mRNA and PEPCKmRNA abundances and enzyme activities are significant difference between normal and ketotic group(p<0.05), indicating that ablity of liver glyconeogenesis was enhanced in ketotic cows. In ketotic cows PC activities and serum concentrations of GLU (R=0.665), LP (R=0.515) and NPY (R=0.788)were positive correlation; PC activities and serum concentrations of GLN and INS were negative correlation,but no significant difference; PEPCK activities and serum concentrations of GLU, LP were positive correlation, but no significant difference; PC activities and serum concentrations of GLN and INS were negative correlation, but no significant difference. PCmRNA abundance and serum concentrations of GLN (p<0.01), LP, NPY (p<0.01) and GLN were negative correlation, but no significant difference in INS. PEPCKmRNA and serum concentrations of GLU (p<0.01), LP (p<0.01), NPY (p<0.01), GLN(p<0.05) and INS (p<0.05) were negative correlation.The results indicates that ability of liver glyconeogenesis are increased in ketotic cows through increasing abundances of PCmRNA and PEPCKmRNA,abd enzyme activies regulated by energy metabolic related facters such as GLU,LP,NPY and so on, in order to alleviate negative enengy balance.But, hepatic glycogen in ketotic cows remains low level , suggesting that increased ability of hepatic glyconeogenesis is still unsatisfied with the energy demand for lactation;so that negative energy balance aggravates,and following ketosis occurs.