Mastro Laurel M, Adams Amanda A, Urschel Kristine L
Departments of Animal and Food Sciences, College of Agriculture, Food and the Environment, University of Kentucky, Lexington, KY 40546.
Am J Vet Res. 2014 Jul;75(7):658-67. doi: 10.2460/ajvr.75.7.658.
To compare whole-body phenylalanine kinetics and the abundance of factors in signaling pathways associated with skeletal muscle protein synthesis and protein breakdown between horses with pituitary pars intermedia dysfunction (PPID) and age-matched control horses without PPID.
12 aged horses (6 horses with PPID and 6 control horses; mean age, 25.0 and 25.7 years, respectively).
Plasma glucose, insulin, and amino acids concentrations were determined before and 90 minutes after feeding. Gluteal muscle biopsy samples were obtained from horses 90 minutes after feeding, and the abundance and activation of factors involved in signaling pathways of muscle protein synthesis and breakdown were determined. The next day, horses received a priming dose and 2 hours of a constant rate infusion of (13)C sodium bicarbonate followed by a priming dose and 4 hours of a constant rate infusion of 1-(13)C phenylalanine IV; whole-body protein synthesis was determined.
Plasma glucose and insulin concentrations were higher after feeding than they were before feeding for both groups of horses; however, no significant postprandial increase in plasma amino acids concentrations was detected for either group. Phenylalanine flux, oxidation, release from protein breakdown, and nonoxidative disposal were not significantly different between groups. No significant effect of PPID status was detected on the abundance or activation of positive or negative regulators of protein synthesis or positive regulators of protein breakdown.
Results of this study suggested that whole-body phenylalanine kinetics and the postprandial activation of signaling pathways that regulate protein synthesis and breakdown in muscles were not affected by PPID status alone in aged horses.
比较垂体中间叶功能障碍（PPID）马与年龄匹配的无PPID对照马之间的全身苯丙氨酸动力学以及与骨骼肌蛋白质合成和蛋白质分解相关信号通路中各因子的丰度。
12匹老龄马（6匹患有PPID的马和6匹对照马；平均年龄分别为25.0岁和25.7岁）。
在喂食前和喂食后90分钟测定血浆葡萄糖、胰岛素和氨基酸浓度。在喂食后90分钟从马身上获取臀肌活检样本，并测定参与肌肉蛋白质合成和分解信号通路的各因子的丰度和活性。第二天，给马静脉注射首剂和持续输注2小时的（13）C碳酸氢钠，随后静脉注射首剂和持续输注4小时的1-（13）C苯丙氨酸；测定全身蛋白质合成情况。
两组马喂食后血浆葡萄糖和胰岛素浓度均高于喂食前；然而，两组均未检测到餐后血浆氨基酸浓度有显著升高。两组之间苯丙氨酸通量、氧化、蛋白质分解释放和非氧化代谢无显著差异。未检测到PPID状态对蛋白质合成的正或负调节因子或蛋白质分解的正调节因子的丰度或活性有显著影响。
本研究结果表明，在老龄马中，全身苯丙氨酸动力学以及调节肌肉蛋白质合成和分解的信号通路的餐后激活不受PPID状态单独影响。
