Data_Sheet_1_Impact of a High Protein Intake on the Plasma Metabolome in Elderly Males: 10 Week Randomized Dietary Intervention.docx

High protein diets may improve the maintenance of skeletal muscle mass in the elderly, although it remains less clear what broader impact such diets have on whole body metabolic regulation in the elderly. Non-targeted polar metabolomics analysis using HILIC HPLC-MS was used to profile the circulating plasma metabolome of elderly men (n = 31; 74.7 ± 4.0 years) who were randomized to consume for 10 weeks a diet designed to achieve either protein (RDA; 0.8·g−1·kg−1) or that doubled this recommend intake (2RDA; 1.6.g.kg−1). A limited number of plasma metabolites (n = 24) were significantly differentially regulated by the diet. These included markers of protein anabolism, which increased by the 2RDA diet, including; urea, creatine, and glutarylcarnitine. Whilst in response to the RDA diet; glutamine, glutamic acid, and proline were increased, relative to the 2RDA diet (p < 0.05). Metaboanalyst identified six major metabolic pathways to be influenced by the quantity of protein intake, most notably the arginine and proline pathways. Doubling of the recommended protein intake in older males over 10 weeks exerted only a limited impact on circulating metabolites, as determined by LC-MS. This metabolomic response was almost entirely due to increased circulating abundances of metabolites potentially indicative of altered protein anabolism, without evidence of impact on pathways for metabolic health.
Trial Registration: This trial was registered on 3rd March 2016 at the Australia New Zealand Clinical Trial Registry (www.anzctr.org.au) at ACTRN 12616000310460.

高蛋白饮食或可改善老年人骨骼肌量的维持，但目前尚不清楚此类饮食对老年人全身代谢调控的更广泛影响。本研究采用亲水作用色谱-质谱联用（HILIC HPLC-MS）技术开展非靶向极性代谢组学分析，对31名老年男性（年龄74.7±4.0岁）的循环血浆代谢组进行表征。受试者被随机分为两组，分别遵循为期10周的饮食方案：一组达到推荐蛋白质摄入量（RDA；0.8 g·kg⁻¹·d⁻¹），另一组摄入为推荐量两倍的蛋白质（2RDA；1.6 g·kg⁻¹·d⁻¹）。

研究发现，仅少量血浆代谢物（n=24）的水平因饮食干预发生显著差异调控。其中，2RDA组的蛋白质合成代谢标志物水平升高，包括尿素、肌酸及戊二酰肉碱；而相较于2RDA组，RDA组的谷氨酰胺、谷氨酸及脯氨酸水平显著升高（p<0.05）。

代谢组学分析软件MetaboAnalyst鉴定出6条主要代谢通路受蛋白质摄入量的影响，其中最为显著的为精氨酸与脯氨酸代谢通路。为期10周的干预后，老年男性蛋白质摄入量翻倍仅对循环代谢物产生有限影响，该结论通过液相色谱-质谱（LC-MS）分析得以验证。该代谢组学响应几乎完全源于潜在反映蛋白质合成代谢改变的循环代谢物丰度升高，未发现对代谢健康相关通路产生影响的证据。

试验注册：本试验于2016年3月3日在澳大利亚新西兰临床试验注册中心（www.anzctr.org.au）完成注册，注册号为ACTRN 12616000310460。