Zheng Liufeng, Zuo Fangrui, Zhao Shengjun, He Pingli, Wei Hongkui, Xiang Quanhang, Pang Jiaman, Peng Jian
1Department of Animal Nutrition and Feed Science,College of Animal Science and Technology,Huazhong Agricultural University,Wuhan 430070,People's Republic of China.
2Department of Feed Science,Wuhan Polytechnic University,Wuhan 430070,People's Republic of China.
Br J Nutr. 2017 Apr;117(7):911-922. doi: 10.1017/S0007114517000757. Epub 2017 Apr 27.
Branched-chain amino acids (BCAA) have been clearly demonstrated to have anabolic effects on muscle protein synthesis. However, little is known about their roles in the regulation of net AA fluxes across skeletal muscle in vivo. This study was aimed to investigate the effect and related mechanisms of dietary supplementation of BCAA on muscle net amino acid (AA) fluxes using the hindlimb flux model. In all fourteen 4-week-old barrows were fed reduced-protein diets with or without supplemental BCAA for 28 d. Pigs were implanted with carotid arterial, femoral arterial and venous catheters, and fed once hourly with intraarterial infusion of p-amino hippurate. Arterial and venous plasma and muscle samples were obtained for the measurement of AA, branched-chain α-keto acids (BCKA) and 3-methylhistidine (3-MH). Metabolomes of venous plasma were determined by HPLC-quadrupole time-of-flight-MS. BCAA-supplemented group showed elevated muscle net fluxes of total essential AA, non-essential AA and AA. As for individual AA, muscle net fluxes of each BCAA and their metabolites (alanine, glutamate and glutamine), along with those of histidine, methionine and several functional non-essential AA (glycine, proline and serine), were increased by BCAA supplementation. The elevated muscle net AA fluxes were associated with the increase in arterial and intramuscular concentrations of BCAA and venous metabolites including BCKA and free fatty acids, and were also related to the decrease in the intramuscular concentration of 3-MH. Correlation analysis indicated that muscle net AA fluxes are highly and positively correlated with arterial BCAA concentrations and muscle net BCKA production. In conclusion, supplementing BCAA to reduced-protein diet increases the arterial concentrations and intramuscular catabolism of BCAA, both of which would contribute to an increase of muscle net AA fluxes in young pigs.
支链氨基酸（BCAA）已被明确证明对肌肉蛋白质合成具有合成代谢作用。然而，关于它们在体内调节骨骼肌净氨基酸通量中的作用却知之甚少。本研究旨在使用后肢通量模型研究饮食中补充BCAA对肌肉净氨基酸（AA）通量的影响及相关机制。将14头4周龄的公猪分为两组，分别饲喂含或不含补充BCAA的低蛋白日粮28天。给猪植入颈动脉、股动脉和静脉导管，每小时经动脉内输注对氨基马尿酸一次。采集动脉和静脉血浆及肌肉样本，用于测定氨基酸、支链α-酮酸（BCKA）和3-甲基组氨酸（3-MH）。通过高效液相色谱-四极杆飞行时间质谱法测定静脉血浆的代谢组。补充BCAA组的总必需氨基酸、非必需氨基酸和氨基酸的肌肉净通量升高。就单个氨基酸而言，补充BCAA可增加每种BCAA及其代谢产物（丙氨酸、谷氨酸和谷氨酰胺）以及组氨酸、蛋氨酸和几种功能性非必需氨基酸（甘氨酸、脯氨酸和丝氨酸）的肌肉净通量。肌肉净氨基酸通量的升高与BCAA的动脉和肌肉内浓度以及包括BCKA和游离脂肪酸在内的静脉代谢产物的增加有关，也与肌肉内3-MH浓度的降低有关。相关性分析表明，肌肉净氨基酸通量与动脉BCAA浓度和肌肉净BCKA生成高度正相关。总之，在低蛋白日粮中补充BCAA可增加BCAA的动脉浓度和肌肉内分解代谢，这两者都有助于增加幼猪的肌肉净氨基酸通量。
