Thalacker-Mercer Anna E, Fleet James C, Craig Bruce A, Carnell Nadine S, Campbell Wayne W
Department of Foods & Nutrition, Purdue University, West Lafayette, IN 47907, USA.
Am J Clin Nutr. 2007 May;85(5):1344-52. doi: 10.1093/ajcn/85.5.1344.
Inadequate dietary protein intake causes adverse changes in the morphology and function of skeletal muscle. These changes may be reflected in early alterations in muscle messenger RNA levels.
This study assessed whether inadequate protein intake differentially affects skeletal muscle transcript concentrations and expression profiles in older adults.
Twenty-one older men and women (aged 55-80 y) consumed controlled diets that provided 1.2 g protein x kg(-1) x d(-1) (adequate protein) for 1 wk and then were randomly assigned to consume either 0.5 g protein x kg(-1) x d(-1) [inadequate protein (IP) group; n=11] or 1.2 g protein x kg(-1) x d(-1) (control group; n=10) for a second week. RNA was isolated from fasting-state vastus lateralis biopsy samples obtained at the end of each period, and transcript levels in the IP group were measured by using microarray analysis. Changes in selected transcript levels were confirmed by real-time polymerase chain reaction in both groups.
Analysis of variance showed 529 differentially expressed transcripts (P<0.05) after inadequate protein intake. Using the false discovery rate (FDR) correction to adjust for multiple comparisons, we observed that 85 transcripts were differentially expressed: 54 were up-regulated and 31 were down-regulated. The differentially expressed transcripts were in functional classes for immune, inflammatory, and stress responses (predominantly up-regulated); contraction, movement, and development (up-regulated); extracellular connective tissue (up-regulated); energy metabolism (down-regulated); protein synthesis (down-regulated); and proliferation (down-regulated). Diet-related differences in the expression of 9 transcripts were cross-validated by using real-time polymerase chain reaction.
The results document changes in skeletal muscle transcript levels induced by short-term inadequate protein intakes in older humans that might precede adverse metabolic, functional, and structural events, including muscle wasting.
膳食蛋白质摄入不足会导致骨骼肌形态和功能发生不良变化。这些变化可能反映在肌肉信使核糖核酸水平的早期改变上。
本研究评估蛋白质摄入不足是否会对老年人骨骼肌转录本浓度和表达谱产生不同影响。
21名老年男性和女性（年龄55 - 80岁）食用控制饮食，其中提供1.2 g蛋白质·kg⁻¹·d⁻¹（充足蛋白质），持续1周，然后随机分配在第二周食用0.5 g蛋白质·kg⁻¹·d⁻¹[蛋白质摄入不足（IP）组；n = 11]或1.2 g蛋白质·kg⁻¹·d⁻¹（对照组；n = 10）。在每个阶段结束时，从空腹状态的股外侧肌活检样本中分离RNA，并通过微阵列分析测量IP组中的转录本水平。两组均通过实时聚合酶链反应确认选定转录本水平的变化。
方差分析显示，蛋白质摄入不足后有529个差异表达的转录本（P<0.05）。使用错误发现率（FDR）校正进行多重比较调整后，我们观察到85个转录本差异表达：54个上调，31个下调。差异表达的转录本属于免疫、炎症和应激反应（主要上调）；收缩、运动和发育（上调）；细胞外结缔组织（上调）；能量代谢（下调）；蛋白质合成（下调）；以及增殖（下调）等功能类别。通过实时聚合酶链反应交叉验证了9个转录本表达的饮食相关差异。
结果证明了老年人短期蛋白质摄入不足会引起骨骼肌转录本水平的变化，这些变化可能先于包括肌肉萎缩在内的不良代谢、功能和结构事件。
