Effects Of Amino Acid Deficiency On The Expression Of Protein Metabolism Related Genes In Lactating Mice

When there was a lack of amino acid，mammary gland epithelial cells and muscle cellsshowed distinct reaction. Blood amino acid extraction increased in mammary gland epithelialcells, in order to meet the need of protein synthesis, peripheral tissue cells degradated to setfree amino acids into blood circulation. Therefore, lactating requirement was prior to maintainrequirement in the amino acid nutrition distribution. The mechanism of the differences wasnot clear.This study was intended to take Kunming small white mice for research materials,observed in different amino acids deficiency environment when they were post partum. Wecollected blood, mammary tissue and muscle tissue. Radioactive immunity method was usedto test blood hormone levels. Blood glucose level was measured by automatic biochemicalanalyzer. The gene expression of characteristic protein and ubiquitin-proteolytic enzymecomplex pathway in mammary and muscle tissue was analysed by real-time PCR. The proteinlevel of mTOR pathway and aminio acid carrier in mammary and muscle tissue was analysedby western-blotting.The results indicated that:(1) Stress of protein or energy in the diet had significantlyinfluence on β-casein and MHC2expression（P<0.01，P<0.05）. The β-casein mRNAexpression quantity increased in the treatment groups，especially the energy provided onlygroup(P<0.01), followed by the starved group. Other groups also rised but had no statisticaldifference. There was no significant effect on α-actin mRNA expression in muscle tissue（P>0.05）although there was a downward tendency, especially the starved group. Meanwhilethe MHC2αmRNA expression decreased（P<0.05）, no statistical difference among the groups.(2) The mRNA expression of PolyUbc, C2and E214k were increased and had significantdifference between treatment groups (P <0.01). This indicated that lack of protein or energyin the diet could strengthen muscle protein breakdown.(3) Compared with normal control group, IGF-1in the treatment group were lower (P <0.01)，but there was no significantdifference between treatment groups. There was a significant influence on PRL content (P <0.01), it increased in all the groups except the starved group, the protein provided group risedmost but differences between groups were not statistically significant.(4) The treatmentinfluenced the mTOR pathway phosphorylation level in casein synthesis significantly (P <0.05). Each treatment group made p70S6K phosphorylation levels rose, but compared withthe group only supplied with protein, the starved group and enery group rose more. Theexpression of Lys and Arg carrier CAT1in mammary tissue increased(P<0.05), comparedwith protein group, the starved and energy group rose less. The phosphorylation level ofmTOR pathway factor mTOR and4EBP1increased although no significant difference.(5)The phosphorylation level of signal factor p70S6K of mTOR pathway in muscle tissueincreased in all the treatment except the group only supplied with inadequate protein, but theyall rose less than in mammary. Moreover, the phosphorylation level of mTOR and4EBP1alsohas a rising trend which were less than in mammary. The expression of Met carrier ASCT2alldecreased(P<0.05), biggest drop in the starved group.