Loos Caroline M M, McLeod Kyle R, Vanzant Eric S, Stratton Sophie A, Bohannan Adam D, Coleman Robert J, van Doorn David A, Urschel Kristine L
Department of Animal and Food Sciences, University of Kentucky, Lexington, KY, United States.
Equivado Consultancy B.V., Utrecht, Netherlands.
Front Vet Sci. 2022 Aug 1;9:896220. doi: 10.3389/fvets.2022.896220. eCollection 2022.
The objective of the study was to characterize the temporal changes of phosphorylation patterns of mTOR signaling proteins in response to two dietary protein sources in insulin dysregulated (ID, = 8) and non-ID ( = 8) horses. Horses were individually housed and fed timothy grass hay and 2 daily concentrate meals so that protein was the first limiting nutrient and the total diet provided 120% of daily DE requirements for maintenance. On sample days, horses randomly received 0.25 g CP/kg BW of a pelleted alfalfa (AP) or commercial protein supplement (PS). Blood samples were collected before and 30, 60, 90, 120, 150, 180, 210, 240, 300, 360, 420, and 480 min post feeding and analyzed for plasma glucose, insulin and amino acid (AA) concentrations. G muscle samples were obtained before and 90, 180, and 300 min after feeding and analyzed for relative abundance of phosphorylated mTOR pathway components using western immunoblot analysis. There was no effect of protein source on postprandial glucose and insulin responses ( ≥ 0.14) but consumption of PS elicited a 2 times larger AUC for essential AA (EAA), greater peak concentrations of EAA and a shorter time to reach peak EAA concentrations compared to AP. Abundance of phosphorylated mTOR ( = 0.08) and rpS6 ( = 0.10) tended to be ~1.5-fold greater after consumption of PS at 90 min compared to AP. Dephosphorylation patterns differed between protein sources and was slower for AP compared to PS. ID horses had a 2 times greater ( = 0.009) AUC and 3 times higher postprandial peak concentrations ( < 0.0001) for insulin compared to non-ID horses after consumption of both treatment pellets, but EAA responses were similar between groups ( = 0.53). Insulin status did not affect rpS6 or mTOR phosphorylation after consumption of either protein source ( ≥ 0.35), but phosphorylated rpS6 abundance was twice as high in ID compared to non-ID horses ( = 0.007). These results suggest that the consumption of higher quality protein sources may result in greater postprandial activation of the mTOR pathway compared to equal amounts of a forage-based protein source. Moreover, ID does not impair postprandial activation of mTOR and rpS6 proteins in horses following a protein-rich meal.
本研究的目的是描述胰岛素调节异常（ID，n = 8）和非ID（n = 8）马匹在对两种膳食蛋白质来源做出反应时，mTOR信号蛋白磷酸化模式的时间变化。马匹单独饲养，饲喂提摩西草干草和每日两顿精料，使蛋白质成为第一限制营养素，且总日粮提供维持所需每日消化能需求的120%。在采样日，马匹随机接受0.25 g CP/kg体重的颗粒苜蓿（AP）或商业蛋白质补充剂（PS）。在喂食前以及喂食后30、60、90、120、150、180、210、240、300、360、420和480分钟采集血样，分析血浆葡萄糖、胰岛素和氨基酸（AA）浓度。在喂食前以及喂食后90、180和300分钟采集G肌肉样本，使用western免疫印迹分析来分析mTOR信号通路磷酸化成分的相对丰度。蛋白质来源对餐后葡萄糖和胰岛素反应没有影响（P≥0.14），但与AP相比，食用PS后必需氨基酸（EAA）的曲线下面积（AUC）大2倍，EAA的峰值浓度更高，达到EAA峰值浓度的时间更短。与AP相比，在90分钟时食用PS后，磷酸化mTOR（P = 0.08）和rpS6（P = 0.10）的丰度往往高约1.5倍。蛋白质来源之间的去磷酸化模式不同，与PS相比，AP的去磷酸化速度较慢。在食用两种处理颗粒后，ID马匹的胰岛素AUC比非ID马匹大2倍（P = 0.009），餐后峰值浓度高3倍（P < 0.0001），但两组之间的EAA反应相似（P = 0.53）。食用任何一种蛋白质来源后，胰岛素状态均不影响rpS6或mTOR的磷酸化（P≥0.35），但与非ID马匹相比，ID马匹中磷酸化rpS6的丰度是其两倍（P = 0.007）。这些结果表明，与等量的基于草料的蛋白质来源相比，食用更高质量的蛋白质来源可能导致餐后mTOR信号通路的激活程度更高。此外，ID并不损害富含蛋白质餐食后马匹中mTOR和rpS6蛋白的餐后激活。
