含赖氨酸二肽对奶牛乳蛋白合成和乳腺氨基酸转运相关基因表达的影响

试验旨在研究含赖氨酸二肽对奶牛乳腺组织中乳蛋白合成和氨基酸转运的影响。在体外培养的奶牛乳腺组织培养液中添加不同含赖氨酸二肽(赖氨酸-赖氨酸(KK)、赖氨酸—组氨酸(KH)、赖氨酸—苯丙氨酸(KF)、赖氨酸—亮氨酸(KL)和赖氨酸—苏氨酸(KT)),分别等量取代培养液中0、5%、10%、15%和20%的游离赖氨酸(赖氨酸总浓度为210μg/mL)进行培养,试验结束后收集乳腺组织用于基因表达检测。结果显示,同游离氨基酸替代量为0组相比,KH替代Lys比例为15%,KF替代比例为10%,KK、KL和KT替代比例为5%时,α_s1酪蛋白(CSN1S1)mRNA丰度最高(P<0.05);KK替代Lys比例为5%、10%、15%和20%,KH替代比例为10%和15%,KF替代比例为15%,KL替代比例为5%、20%及KT替代比例为5%、10%和15%时,均显著促进了奶牛乳腺组织中小肽转运载体2(SLC15A2)的基因表达(P<0.05);KH替代Lys比例为15%,KK、KL替代比例分别为10%,KF、KT替代比例分别为5%时,赖氨酸转运载体B⁰⁺(SLC6A14)的mRNA丰度最高(P<0.05);KH替代Lys的15%、20%,KK替代比例为5%、10%和15%,KL替代比例为5%和10%时,显著促进了雷帕霉素靶蛋白(mTOR)基因的表达(P<0.05)。结果提示,奶牛乳腺摄取赖氨酸二肽能促进氨基酸的吸收和乳蛋白的合成。

Effects of Lysine Dipeptides on the Expression of Genes Related to Milk Protein Synthesis and Amino Acid Transporters in Bovine Mammary Tissue

The study was carried out to investigate the effects of various lysine (Lys) dipeptides on gene expression related to milk protein and amino acid transporters in bovine mammary tissue.Mammary tissues were obtained from midlactating Holstein dairy cows and cultured under lactogenic hormones (prolactin, hydrocortisone and insulin) with different ratios of various Lys-peptide (Lys-Lys (KK), Lys-His (KH), Lys-Phe (KF), Lys-Leu (KL)and Lys-Thr (KT)).They isometrically substituted 0, 5%, 10%, 15% and 20% of free Lys (total concentration of Lys was 210 μg/mL), respectively.After 48 h treatment, mammary tissues were harvested for gene expression analysis by Real-time PCR.The results showed that:Compared with the free Lys group with no Lys substitution, when the KH replaced Lys at ratio of 15%, the KF replacement ratio was 10%, KK, KL and KT replacement ratio was 5%, the CSN1S1 mRNA abundance were the highest (P<0.05);When the KK replaced Lys at ratios of 5%, 10%, 15% and 20%, KH replacement ratios were 10% and 15%, KF replacement ratio was 15%, KL replacement ratios were 5% and 20% and KT replacement ratios were 5%, 10% and 15%, the SLC15A2 gene expression was significantly enhanced (P<0.05); when the KH replaced lysine at ratio of 15%, KK and KL replacement ratio was 10%, KF and KT replacement ratio was 5%, the abundance of SLC6A14⁺ mRNA was the highest (P<0.05);When the KH replaced Lys at ratio of 15% and 20%, KK replacement ratios were 5%, 10% and 15%, KL replacement ratio was 5% and 10%, the mRNA abundance of mTOR was significantly increased (P<0.05).The results indicated that the Lys dipeptides might be able to promote amino acid uptake and milk protein related gene expression in bovine mammary gland tissues.