This study was undertaken to characterize the ubiquitin proteasome system (UPS) response to varied dietary protein intake, energy deficit (ED), and consumption of a mixed meal. A randomized, controlled trial of 39 adults consuming protein at 0.8 (recommended dietary allowance [RDA]), 1.6 (2×-RDA), or 2.4 (3×-RDA) g · kg(-1) · d(-1) for 31 d. A 10-d weight maintenance (WM) period was followed by 21 d of 40% ED. Ubiquitin (Ub)-mediated proteolysis and associated gene expression were assessed in the postabsorptive (fasted) and postprandial (fed; 480 kcal, 20 g protein) states after WM and ED by using muscle biopsies, fluorescence-based assays, immunoblot analysis, and real-time qRT-PCR. In the assessment of UPS responses to varied protein intakes, ED, and feeding, the RDA, WM, and fasted measures served as appropriate controls. ED resulted in the up-regulation of UPS-associated gene expression, as mRNA expression of the atrogenes muscle RING finger-1 (MuRF1) and atrogin-1 were 1.2- and 1.3-fold higher (P<0.05) for ED than for WM. However, mixed-meal consumption attenuated UPS-mediated proteolysis, independent of energy status or dietary protein, as the activities of the 26S proteasome subunits β1, β2, and β5 were lower (P<0.05) for fed than for fasted. Muscle protein ubiquitylation was also 45% lower (P<0.05) for fed than for fasted, regardless of dietary protein and energy manipulations. Independent of habitual protein intake and despite increased MuRF1 and atrogin-1 mRNA expression during ED, consuming a protein-containing mixed meal attenuates Ub-mediated proteolysis.

译文

:这项研究的目的是表征泛素蛋白酶体系统(UPS)对各种饮食蛋白质摄入量,能量缺乏症(ED)和混合餐的摄入量的反应。一项随机,对照试验,对39位摄入蛋白质的成人进行了研究,他们的蛋白质摄入量分别为0.8(建议的膳食允许量[RDA]),1.6(2×-RDA)或2.4(3×-RDA)g·kg(-1)·d(-1) 31天维持体重10天(WM),然后进行21天40%ED。通过使用肌肉活检,基于荧光的测定,免疫印迹分析和免疫印迹,在WM和ED后评估了吸收后(禁食)和餐后(进食; 480 kcal,20 g蛋白)状态下泛素(Ub)介导的蛋白水解和相关基因表达。实时定量RT-PCR。在评估UPS对各种蛋白质摄入量,ED和进食的反应时,RDA,WM和禁食措施可作为适当的对照。 ED导致UPS相关基因表达上调,因为ED的质子肌RING RING-1(MuRF1)和atrogin-1的mRNA表达比WM高1.2倍和1.3倍(P <0.05)。 。然而,由于进食的26S蛋白酶体亚基β1,β2和β5的活性比禁食的低(P <0.05),因此混合膳食的消耗减弱了UPS介导的蛋白水解,而与能量状态或膳食蛋白质无关。进食的肌肉蛋白质泛素化水平也比禁食的肌肉蛋白质泛素化水平低45%(P <0.05),而与饮食蛋白质和能量操作无关。与习惯性蛋白质摄入无关,尽管在ED期间MuRF1和atrogin-1 mRNA表达增加,但食用含蛋白质的混合粉会减弱Ub介导的蛋白水解作用。

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