Human Protein and Amino Acid Requirements

Human protein and amino acid nutrition encompasses a wide, complex, frequently misunderstood, and often contentious area of clinical research and practice. This tutorial explains the basic biochemical and physiologic principles that underlie our current understanding of protein and amino acid nutrition. The following topics are discussed: (1) the identity, measurement, and essentiality of nutritional proteins; (2) the definition and determination of minimum requirements; (3) nutrition adaptation; (4) obligatory nitrogen excretion and the minimum protein requirement; (5) minimum versus optimum protein intakes; (6) metabolic responses to surfeit and deficient protein intakes; (7) body composition and protein requirements; (8) labile protein; (9) N balance; (10) the principles of protein and amino acid turnover, including an analysis of the controversial indicator amino acid oxidation technique; (11) general guidelines for evaluating protein turnover articles; (12) amino acid turnover versus clearance; (13) the protein content of hydrated amino acid solutions; (14) protein requirements in special situations, including protein‐catabolic critical illness; (15) amino acid supplements and additives, including monosodium glutamate and glutamine; and (16) a perspective on the future of protein and amino acid nutrition research. In addition to providing practical information, this tutorial aims to demonstrate the importance of rigorous physiologic reasoning, stimulate intellectual curiosity, and encourage fresh ideas in this dynamic area of human nutrition. In general, references are provided only for topics that are not well covered in modern textbooks.     

复合氨基酸输液对烧伤病人血浆游离氨基酸浓度的影响

复合氨基酸输液对烧伤病人血浆游离氨基酸浓度的影响黎君支，王怀宾，赵有，郭振荣，盛志勇（北京军医进修学院创伤外科中心，三○四医院，１０００２７）关键词：烧伤，复合氨基酸注射液血浆氨基酸ＥｆｆｅｃｔｏｆＣｏｍｐｏｓｉｔｅＡｍｉｎｏＡｃｉｄＴｒａｎｓｆｕｓ...     

山东省二十一种蝗虫蛋白质、氨基酸含量分析

昆虫作为陆地现存种最多的一类生物 ,是地球上尚待进一步开发利用的自然资源 ,对于昆虫资源的开发利用越来越受到世界各国的重视。据统计 ,目前已确定可供食用的昆虫约 3 65 0种之多 ,其中大约有 3 70多种进行了开发和利用 [1 ]。昆虫作为食物营养丰富 ,蛋白质含量有的占干物质的 5 0 %以上 ,并且含有多种人体必需氨基酸 ,尤其是具有低脂肪、低胆固醇、肉质肌纤维多、易吸收的特点 ,有望成为未来的高蛋白资源。本文研究对山东西部地区的二十一种蝗虫[2 ,3] 蛋白质 ,氨基酸含量的分析研究 ,为进一步开发利用提供依据。1　材　料　与　方　法1…     

正常和营养不良儿童血浆游离氨基酸含量

<正> 正常人体血浆游离氨基酸(简称血浆氨基酸)浓度对于氨基酸代谢缺陷性疾病,肝、肾等疾病的诊断与治疗以及对儿童营养状况的评价有参考意义。我们于1985年9月～1986年6月对251名正常儿童和39例营养不良儿童测定了15种血浆氨基酸含量。 对象与方法     

Maternal Low Quality Protein Diet Alters Plasma Amino Acid Concentrations of Weaning Rats

Several studies have indicated the influence of a maternal low protein diet on the fetus. However, the effect of a maternal low quality protein diet on fetal growth and development is largely unknown. Wistar rats (11 weeks old) were mated and maintained on either a chow diet with 20% casein (n = 6) as the control group (C), or a low quality protein diet with 20% wheat gluten (n = 7) as the experimental group (WG) through gestation and lactation. Maternal body weights were similar in both groups throughout the study. Birth weights were not influenced by maternal diet and offspring body weights during lactation were similar between the groups. Offspring’s plasma amino acid profiles showed that plasma methionine, glutamine and lysine were significantly lower and aspartic acid, ornithine and glycine-proline were significantly higher in the WG. Plant based protein comprises an important part of protein intake in developing countries. It is well-known that these diets can be inadequate in terms of essential amino acids. The current study shows differential effects of a maternal low quality protein diet on the offspring’s plasma amino acids. Future studies will examine further aspects of the influence of maternal low quality protein diets on fetal growth and development.     

棕熊熊掌氨基酸成分的分析

<正> 熊掌为我国传统的名贵食品,我国东北地区民间流传“熊冬季是靠用舌舔其掌而生存”。有关熊掌的组织结构已有报道,但对其营养价值尚未能充分阐明。我们在以往研究熊掌组织结构的基础上,对熊掌中氨基酸的成分又作了进一步的分析研究,旨在开辟人造营养食品的新途径,并为熊掌加工利用提供资料。     

蛋白质营养价值评价——氨基酸比值系数法

氨基酸比值系数法是基于氨基酸平衡理论设计的评价蛋白质营养价值的方法。本文介绍了氨基酸比值系数(RC)和比值系数分(SRC)的计算和意义。RC用于判定限制氨基酸和计算限制氨基酸的强化量,SRC用于评价蛋白质营养价值。SRC与生物价(BV)之问有高度的相关性(P<0.001)。与FAO氨基酸模式计算的化学分相比,SRC比化学分接近BV(P<0.05)。文章讨论了RC法的优缺点。     

Protein Quality in Infant Formulas Marketed in Brazil: Assessments on Biodigestibility,Essential Amino Acid Content and Proteins of Biological Importance

Infant formulas, designed to provide similar nutritional composition and performance to human milk, are recommended when breastfeeding is not enough to provide for the nutritional needs of children under 12 months of age. In this context, the present study aimed to assess the protein quality and essential amino acid content of both starting (phase 1) and follow-up (phase 2) formulas from different manufacturers. The chemical amino acid score and protein digestibility corrected by the amino acid score were calculated. The determined protein contents in most formulas were above the maximum limit recommended by FAO and WHO guidelines and at odds with the protein contents declared in the label. All infant formulas contained lactoferrin (0.06 to 0.44 g·100 g⁻¹) and α-lactalbumin (0.02 to 1.34 g·100 g⁻¹) below recommended concentrations, whereas ĸ-casein (8.28 to 12.91 g·100 g⁻¹), α-casein (0.70 to 2.28 g·100 g⁻¹) and β-lactoglobulin (1.32 to 4.19 g·100 g⁻¹) were detected above recommended concentrations. Essential amino acid quantification indicated that threonine, leucine and phenylalanine were the most abundant amino acids found in the investigated infant formulas. In conclusion, infant formulas are still unconforming to nutritional breast milk quality and must be improved in order to follow current global health authority guidelines.     

三种昆虫蛋白质、氨基酸和脂肪酸的比较研究

昆虫作为一类重要的动物性营养源,日益受到人们的重视。有些种类昆虫已被采捕利用。作为食物[1,2]、饲料[3]或药物原料[4,5]。有关直翅目昆虫营养成分的研究,迄今仅见对个别蝗虫种类的报道[6,7]:对多数昆虫的分析研究尚待进行。本研究选择棉蝗、优雅蝈螽和蟋蟀为实验昆虫,分别代表直翅目蝗总科、螽斯总科和蟋蟀总科,分析其体内蛋白质、氨基酸和肪脂酸的组成与含量,评价其营养价值,为科学开发昆虫食品资源提供依据。1　材　料　与　方　法1.1　材料　　实验昆虫:　棉蝗(Chondracrisrosea,俗称油蚂蚱),优雅蝈螽(Gampsocleisgrationsa俗称蝈蝈…     

The Effects of Dietary Sulfur Amino Acid Deficiency on Rat Brain Glutathione Concentration and Neural Damage in Global Hemispheric Hypoxia-Ischemia

Abstract

Primary brain injury in stroke is followed by an excitotoxic cascade, oxidative stress and further neural damage. Glutathione is critical and depleted in oxidative stress. Since cysteine is limiting in glutathione synthesis, this study investigated the effect of dietary sulfur amino acid (SAA) deficiency on neural damage in a rat model of global hemispheric hypoxia-ischemia (GHHI). Animals were fed with SAA deficient ("deficient") or control diet for 3 days, subjected to right common carotid artery ligation and hypoxia, and diet continued for 3 more days. Histologically evaluated neural damage at 7 days post hypoxia-ischemia was greater in "deficient" rats, shown by mean (±SEM) global and hippocampal grid scores of 2.5±0.7 and 34.9±9.3%, respectively, vs. controls' scores of 0.1±0.1 and 0.1±0.1%, respectively. Mean brain (±SEM) reduced glutathione was not different between groups at 6 h post hypoxia-ischemia, but was decreased in "deficient" animals 3 days later in neocortex (1.46 μmoles/g wet weight±0.05 vs. 1.67±0.04 in controls) and thalamus (1.60 μmoles/g wet weight±0.05 vs. 1.78±0.03 in controls). Administration of a cysteine precursor to "deficient" animals did not ameliorate neural damage. These findings suggest that well-nourished but not "deficient" animals tolerate a mild brain insult. The decline in brain glutathione in the "deficient" animals may be one of several contributing mechanisms.     

Influence of Branched-Chain Amino Acid Supplementation on Urinary Protein Metabolite Concentrations after Swimming

Objective: The influence of branched-chain amino acid (BCAA) supplementation on urinary urea nitrogen, hydroxyproline (HP), and 3-methylhistidine (3MH) concentrations after 25 min of breast stroke exercise (65–70% maximum heart rate reserved, 65–70% HRRmax) followed by a 600 m crawl stroke competition was investigated in a double-blind, counter-balanced study.

Methods: Male university students (19–22 years old) majoring in physical education participated in the study. Based on the previous swimming time of a 600 m crawl stroke, the participants were divided into two groups: placebo (n = 9, BMI = 24.2 ± 2.1 kg/m²; 12 g of glucose/day; in capsules) and BCAA (n = 10, BMI = 22.7 ± 1.5 kg/m²; 12 g of BCAAs/day; in capsules: leucine 54%, isoleucine 19%, valine 27%) groups. The participants maintained a regular dietary intake (except the prescribed breakfast on day 15) and exercise activity at a moderate/low intensity (60–70% HRRmax, swimming and rowing, ～1.5 hour/day) during the 15-day study. A prescribed exercise program was performed on day 15. Urinary and blood samples were collected before, during, and after the prescribed exercise for the measurements of the urinary urea nitrogen, HP, and 3MH concentrations in urine, as well as the glucose, lactate, glutamine, alanine, and BCAA concentrations in plasma.

Results: Two weeks of dietary supplementation did not induce any changes in the plasma glucose and total BCAA concentrations of either group, nor in the urinary urea nitrogen, HP, and 3MH concentrations in urine. On day 15, after 25 min of breast stroke exercise and a 600 m crawl stroke competition, plasma glucose concentration decreased significantly (p < 0.05) whereas plasma lactate concentration increased significantly (p < 0.05) in both groups. The exercise program prescribed in the study did not affect urinary urea nitrogen, HP, and 3MH concentrations. Twenty hours after the competition, however, a significant increase in the concentrations of urinary urea nitrogen, HP, and 3MH was found in the placebo group (p < 0.05), but not in the BCAA group.

Conclusions: The results obtained in this study suggest that swimming induced muscle proteolysis was prevented by BCAA supplementation. The mechanism could be attributed to the availability of ammonia provided by the oxidation of supplemented BCAAs during exercise.     

实验性兔多器官衰竭时血浆游离氨基酸浓度的变化

<正> 我们以创伤和感染后多系统器官衰竭(MSOF)的动物模型,研究某些氨基酸的变化特征,对MSOF的病因研究和防治提供有意义的依据。 1 材料和方法 1.1 以兔为多器官衰竭模型,(38只大耳白兔),以胃管饲入大肠杆菌(011B4约3×10~(12)个/kg)后,用Wigger’s法造成失血性休克(5.332kPa维持1小时),休克末     

四种扇贝氨基酸和脂肪酸含量分析

四种扇贝氨基酸和脂肪酸含量分析段德麟，王远红，汪贻生，薛长湖，徐家敏（青岛海洋大学食品工程系，青岛２６６００３）关键词扇贝，氨基酸，脂肪酸ＡｎａｌｙｓｅｓｏｆＡｍｉｎｏＡｃｉｄａｎｄＦａｔｔｙＡｃｉｄＣｏｎｔｅｎｔｓｏｆＦｏｕｒＳｐｅｃｉｅｓｏｆＳｃ...     

Effects of Egg White Protein Supplementation on Muscle Strength and Serum Free Amino Acid Concentrations

The aim of this study was to evaluate the effects of egg white protein compared to carbohydrate intake prior to exercise on fat free mass (FFM), one repetition maximum (1RM) muscle strength and blood biochemistry in female athletes. Thirty healthy female collegiate athletes were recruited for this study and matched by sport type, body fat percentage and 1RM leg curl muscle strength. Participants were randomly divided into two groups: protein group (15.0 g egg white protein; 75 kcal) and carbohydrate group (17.5 g maltodextrin, 78 kcal). Supplements were administered daily at the same time in a double-blind manner prior to training during an 8-week period. Measurements were performed before and after the 8-week regimen. The mean dietary energy intake did not change throughout the study period. FFM and 1RM assessments (i.e., leg curl, leg extension, squat, and bench press) increased in both groups. Furthermore, serum urea and serum citrulline levels after the 8-week regimen increased significantly only in the protein group. Our findings indicated that compared to the carbohydrate supplement, the protein supplement was associated with some changes in protein metabolites but not with changes in body composition or muscle strength.     

氨基酸调节基因表达

在哺乳动物中，营养素对基因表达的影响已成为一个重要的研究领域，然而，目前对氨基酸调控基因表达的了解是有限的。本文就氨基酸在调节哺乳动物基因表达和蛋白质更新中的作用作一综述。     

北京市城乡乳母营养状况、乳成分、乳量、及婴儿生长发育关系的研究 Ⅳ.母乳中蛋白质及氨基酸含量

本文报道了北京城区、近郊、远郊及江西某农村91名分娩后1～6个月乳母乳汁中蛋白质及氯基酸含量。结果表明:(1)江西农村乳母每日摄入的蛋白质量远低于北京地区乳母,其乳汁中含氮量亦较北京地区母乳的为低,但氨基酸总量(18种氨基酸之和)则无显著差异。(2)据氨基酸总量得到的每100g母乳中真正蛋白质含量在四个调查点分别为0.98,1.04,1.01和0.96g。(3)母乳蛋白质中多数氨基酸含量在四个调查点无显著差异。江西乳母乳汁中酪、赖及异亮氨酸含量较低。(4)婴儿自出生三个月后,每日从母乳中获得的必需氨基酸量,除组与色氨酸外,均达不到我国暂用的婴儿氨基酸需要量标准,但婴儿体重正常。因此,该标准是否过高值得考虑。     

山东省十二种熟啤酒氨基酸含量

<正> 啤酒中含有各种营养成份,氨基酸是其中之一,国外已有啤酒中氨基酸含量的报告,国内尚未见有其含量报告,食物成份表中也无此项数据。为了获得国内啤酒中氨基酸含量的数据,并为新食物成份表提供参考资料,我们用日立835-50型氨基酸分析仪,对山东省十二个牌号的熟啤酒进行了氨基酸分析。 一、采样:     

斑鰶鱼肉蛋白质氨基酸组成分析及评价

<正>斑鰶鱼(Clupanodom punchtatus)属鲱形目鲱科鰶属,为暖水中、上层小型鱼类,分布于印度、朝鲜、日本及中国沿海。斑鰶鱼具有很强的再生能力,资源丰富且不会因捕获而资源枯竭;但其个体小,多细小骨刺,口感差,脂肪含量高,易氧化变质,限制了其加工适应性。目前关于低值水产品及加工下脚料髙值化利用研究已有较多报道[1-3],但对斑鰶鱼的报道很少[4]。为了合理利用斑鰶鱼,本研究分析其蛋白质构成和氨基酸组分,旨在为合理充分利用提供实验依据。     

德国小蠊成虫血淋巴游离氨基酸的测定

采用离心法收集羽化后不同天数的雌雄虫血淋巴，用意大利ＣＡＢＬＯＥＲＢＡ３Ａ３ｏ型氨基酸自动分析仪测定，共检出１０种氨基酸和１个氨残基，其氨基酸总量及每种氨基酸的含量与成虫性别、不同发育期有密切的关系。     

天麻对铝染毒大鼠大脑皮质氨基酸递质的影响

[目的]探讨天麻对铝染毒大鼠大脑皮质氨基酸类神经递质的影响。[方法]将SD大鼠36只在动物室适应性喂养1周后 ,分成6组 ,腹腔注射生理盐水或AlCl3 溶液0.2ml/d ,60d。每连续注射3d间歇1d ,60d内共计注射45次。在间歇天肌肉注射青链霉素以抗感染。整个染毒期间 ,动物室以自然节律采光 ,温度18～23℃ ,湿度40%～60 % ,清洁 ,安静。所有动物饲以普通饲料 ,自由饮水和进食 ,加天麻组 ,以0.4g/kg体重的剂量在饮水中加入天麻。每周定时称体重一次 ,调整Al的浓度和饮水中天麻的浓度。染毒期结束后 ,将大鼠断头取脑 ,在冰冷的生理盐水中漂洗、去脑膜、用滤纸拭干。取大脑皮质0.2g(湿重 ) ,加浓硝酸1.6ml,高氯酸0.4ml,消化后 ,用去离子水定容至1.5ml,用石墨炉原子吸收光谱法测定脑铝含量。取左侧大脑半球额叶皮质0.1g,用脑组织处理液以1:50( g:ml)作成匀浆 ,用HLPC法测定氨基酸含量。[结果]与生理盐水组相比 ,Al3 +5mg/kg组和Al3+10mg/kg组脑铝含量均显著升高 (P<0.01) ;生理盐水 +天麻组与生理盐水组相比、Al3+5mg/kg+天麻组与Al3+5mg/kg组相比及Al3 +10mg/kg+天麻组与Al3 +10mg/kg组相比 ,大鼠大脑皮质铝含量差异未见统计学意义(P>0.05)。大脑皮质氨基酸含量结果显示 ,与生理盐水组相比 ,Al3+ 5mg/kg组谷氨酸 (G