高蛋白膳食对限食大鼠肠屏障功能的保护作用

目的:探讨高蛋白膳食对限食大鼠肠屏障功能的保护作用。方法:Wistar雄性大鼠,按体重随机分成五组:正常对照组,喂15%酪蛋白合成饲料,自由摄食;限食1组和2组分别按正常对照组摄食量的50%和30%对喂15%酪蛋白合成饲料;补蛋白1组和2组分别按正常对照组摄食量的50%和30%对喂30%酪蛋白合成饲料。实验2w后处死大鼠,取血和小肠组织进行检测。结果:补蛋白组与相应的限食组肠粘膜都有损伤,但前者损害较轻。限食组肠粘膜蛋白和DNA含量低于正常对照组,且有低于相应补蛋白组的趋势。限食组血清二胺氧化酶(DAO)活性、D-木糖水平比正常对照组显著升高,而补蛋白组则有高于正常对照组,低于相应的限食组的趋势。与正常对照组比,补蛋白组和限食组肠粘膜DAO活性都降低,但补蛋白组高于或显著高于相应的限食组。结论:高蛋白膳食能减轻限食对肠粘膜组织结构和功能的损害,对肠屏障功能有保护作用。     

高蛋白膳食对限食大鼠肠道抗氧化功能的影响

目的探讨高蛋白膳食对限食大鼠肠抗氧化功能的影响。方法Wistar雄性大鼠,按体重随机分成五组:正常对照组,喂15%酪蛋白合成饲料,自由摄食;限食1和2组分别按正常对照组摄食量的50%和30%对喂15%酪蛋白合成饲料;补蛋白1和2组分别按正常对照组摄食量的50%和30%对喂30%酪蛋白合成饲料。实验2w后处死大鼠,取血和小肠组织进行检测。结果与相应限食组相比,补蛋白组血清SOD以及肠粘膜和肝脏的SOD、GSH-Px活性均有升高的趋势,并且肠粘膜MDA和血清MDA含量显著下降。结论高蛋白膳食能改善机体及肠粘膜的氧化还原状态,减轻自由基的氧化应激损伤,对限食大鼠肠道抗氧化功能有保护作用。     

高蛋白膳食对限食大鼠肠免疫功能的保护作用

目的探讨高蛋白膳食对限食大鼠肠免疫功能的保护作用,为高蛋白膳食防治限食引起的肠免疫功能损伤提供理论基础。方法 Wistar雄性大鼠,按体质量随机分成5组,分别为正常对照组(喂15%酪蛋白合成饲料并自由摄食)、限食1组和2组(分别按正常对照组摄食量的50%和30%对喂15%酪蛋白合成饲料);补蛋白1组和2组(分别按正常对照组摄食量的50%和30%对喂30%酪蛋白合成饲料)。实验2周后处死大鼠,取血和小肠组织检测小肠细菌移位率、血清内毒素及肠粘膜中SIgA水平。结果正常对照组未发生细菌移位,补蛋白1组的细菌移位率为25%,显著低于相应的限食1组(50%),差异有显著性(P0.05)。补蛋白1组和2组的血清内毒素水平分别为(283.0±15.1)、(332.5±21.6)EU/L,均显著低于相应的限食组(341.2±29.1)、(434.2±24.3)EU/L,差异有显著性(P0.05),但均显著高于正常对照组(16.3±3.0)EU/L,差异有显著性(P0.01)。补蛋白1、2组肠粘膜SIgA水平均显著高于相应的限食组,差异有显著性(P0.05),但均显著低于正常对照组,差异有显著性(P0.05)。结论提高膳食中的蛋白质比例能增强肠道的免疫功能,减少细菌移位的发生,从而降低肠源性感染的机率。     

血浆氨基酸水平在肝癌患者中的变化及与 Child-pugh分级的关系

目的 探讨血浆氨基酸水平在肝细胞癌患者中的变化及与Child-pugh分级的关系.方法 2010年3月-2011年3月86例肝癌患者作为肝癌组,并根据Child-pugh分级进一步分为A级组34例,B级组31例和C级组21例;另选择50例健康者作为对照组,采用日立835氨基酸分析仪检测血浆中的氨基酸水平.结果 肝癌组缬氨酸、亮氨酸、异亮氨酸、精氨酸、苯丙氨酸、酪氨酸、色氨酸和蛋氨酸和支链氨基酸/芳香氨基酸水平分别为(235.6±29.8)、(125.2±39.6)、(58.7±19.3)、(45.2±18.7)、(148.2±25.6)、(113.2±25.3)、(54.3±13.8)、(49.2±16.5)、(2.1±0.7)μmol/L,而对照组分别为(278.2±37.6)、(164.2±54.6)、(94.5±26.2)、(92.5±29.2)、(112.9±18.5)、(79.7±18.2)、(19.3±8.9)、(23.4±7.2)、(3.3±1.2)μmol/L,两组比较差异有统计学意义(P＜0.05),并且,随着Child-pugh分级的增加,缬氨酸、亮氨酸、异亮氨酸、精氨酸和支链氨基酸/芳香氨基酸水平逐渐降低(P＜0.05),苯丙氨酸、酪氨酸、色氨酸和蛋氨酸水平逐渐升高(P＜0.05);而两组牛磺酸、天门冬氨酸、苏氨酸和谷氨酸水平比较,差异无统计学意义.结论 肝癌患者血浆中存在严重的氨基酸代谢紊乱,通过了解氨基酸代谢在肝癌中的变化规律有助于对肝癌的诊断及治疗.     

半饥饿状态下血浆、肝脏游离氨基酸浓度变化的比较

目的　观察比较半饥饿状态下血浆、肝脏游离氨基酸浓度的变化及其意义。方法雄性 Wistar大鼠 ,半量限食造成半饥饿模型 ,实验 4w后采空腹血和肝脏测定游离氨基酸浓度。结果　动物半饥饿后 ,血浆游离非必需氨基酸浓度下降幅度大于必需氨基酸浓度的下降幅度 ,芳香族氨基酸、支链氨基酸、精氨酸、蛋氨酸下降幅度大于 40 % ;肝脏游离氨基酸中丝氨酸、谷氨酸的浓度下降幅度大于 80 % ,亮氨酸、异亮氨酸、赖氨酸的浓度下降幅度大于 40 %。结论　半饥饿后 ,血浆、肝脏大多数游离氨基酸浓度显著下降 ,但是 ,两者的变化不尽一致     

结肠癌组织游离氨基酸与肿瘤体积相关性研究

目的：探讨结肠癌生长对氨基酸代谢的影响以及对某些氨基酸的特殊需求。方法：采用反相高压液相色谱技术测定18例结肠癌病人肿瘤组织20种游离氨基酸含量，与肿瘤体积进行相关性和多元逐步回归分析。结果：结肠癌组织中谷氨酰胺、蛋氨酸、精氨酸、苏氨酸、缬氨酸、亮氨酸、苯丙氨酸、天冬酰胺、丝氨酸含量较正常结肠粘膜组织明显增加（P＜0．05），而丙氨酸、色氨酸含量较正常结肠粘膜组织明显减少（P＜0．05）。结肠癌组织游离谷氨酰胺、蛋氨酸、精氨酸、缬氨酸、亮氨酸、天冬酰胺、丝氨酸与肿瘤体积呈明显正相关。结论：随着结肠癌生长，肿瘤特别需求谷氨酰胺、蛋氨酸、精氨酸、缬氨酸、亮氨酸、天冬酰胺、丝氨酸，这为结肠癌病人氨酸酸营养液的组成提供了参考资料。     

克山病患者及健康人血清游离氨基酸与蛋白质含量分析

对克山病病区健康人35例、克山病人38例的17种血清游离氨基酸与蛋白质含量进行了分析,并以非病区健康人31例作对照,发现病区居民血清游离氨基酸总量、必需氨基酸、非必需氨基酸及血清蛋白质显著降低。病区健康人苏氨酸、脯氨酸、胱氨酸、异亮氨酸、酪氨酸及色氨酸降低;克山病人苏氨酸、脯氨酸、丙氨酸、胱氨酸、缬氨酸、异亮氨酸、亮氨酸、酪氨酸、赖氨酸、组氨酸及色氨酸降低。结果表明,病区居民血中处于低氨基酸低蛋白状态,此可能是克山病发病的重要条件之一。     

牛磺酸、羟脯氨酸、色氨酸和鸟氨酸的测定

近几年来 ,牛磺酸、羟脯氨酸、鸟氨酸在强化食品、人体营养等方面的研究和应用越来越深入、广泛 ,因而对这些氨基酸进行测定的要求也越来越迫切。目前 ,国内很多分析单位所拥有的日立 835 5 0型氨基酸分析仪所提供的标准分析程序只能测定 17种蛋白质氨基酸 ,随机所带的氨基酸混合标准液中也只有这 17种氨基酸 ,即门冬氨酸、苏氨酸、丝氨酸、谷氨酸、甘氨酸、丙氨酸、胱氨酸、缬氨酸、蛋氨酸、异亮氨酸、亮氨酸、酪氨酸、苯丙氨酸、赖氨酸、组氨酸、精氨酸、脯氨酸 ,见图1。如要测定其他氨基酸 ,一般来说就要启用体液分析程序 ,其分析时间和…     

高蛋氨酸饲料对大鼠氨基酸代谢的影响

目的：研究高蛋氨酸饲料对大鼠生长及体内蛋白质、氨基酸代谢的影响。方法：SD大鼠20只，随机分为两组，即高蛋氨酸组（M组）和对照组（C组）各10只。M组每天给予含3％蛋氨酸的饲料，动态测量体重，分别在0、4、8、12周眼眶取血测血清氨基酸，并在12周处死动物，测肝的游离氨基酸含量。结果：高蛋氨酸在4周时，即出现高同型半胱氨酸血症、高蛋氨酸血症；12周时血清苏氨酸、缬氨酸、亮氨酸、苯丙氨酸含量明显下降，脯氨酸、 精氨酸和丙氨酸血清含量均有显著增高。肝内七种必需氨基酸含量实验组均显著高于对照组，而非必需氨基酸则实验组含量明显低于对照组。同时，实验组大鼠体重增长缓慢。结论：高蛋氨酸饲料能影响血清、肝的游离氨基酸含量，抑制大鼠生长。     

弥漫大B细胞淋巴瘤患者血清氨基酸谱的靶向代谢组学研究

目的 探究弥漫大B淋巴瘤（dffuse large B lymphoma,DLBCL）患者与正常人是否存在不同血清氨基酸谱。方法 使用超高效液相色谱-串联质谱（ultra performance liquid chromatography-tandem mass,UPLC-MS/MS）技术对上述DLBCL组患者和对照组进行靶向氨基酸定量分析。结果 在DLBCL组肌氨酸、丙氨酸、2-氨基丁酸、丝氨酸、异亮氨酸、鸟氨酸、苯丙氨酸、酪氨酸比对照组呈上升趋势（P<0.05）,赖氨酸、甘氨酸、苏氨酸、亮氨酸、天冬酰胺、组氨酸、瓜氨酸、缬氨酸、色氨酸呈下降趋势（P<0.05）;PLS-DA模型及ROC曲线下面积筛选出肌氨酸区分DLBCL与对照组能力最强;肌氨酸和赖氨酸可作为联合血清标志物,提高诊断准确率。结论 DLBCL患者血清氨基酸谱发生明显改变,肌氨酸可以作为DLBCL的血清标志物,肌氨酸、赖氨酸联合氨基酸有望成为诊断工具。     

Interactions among the branched-chain amino acids and their effects on methionine utilization in growing pigs: effects on nitrogen retention and amino acid utilization

An experiment was conducted to investigate the effects of branched-chain amino acid (BCAA) interactions on their utilization by growing pigs and the effects of excessive amounts of BCAA (leucine, isoleucine, valine) on the utilization of methionine. A semipurified diet containing 100 g crude protein/kg with a balanced amino acid pattern was prepared using casein supplemented with free amino acids. Three further diets were made by reducing the concentration of methionine + cyst(e)ine, valine or isoleucine by 20%. Each of these four diets was then supplemented with leucine (50% excess) or a mixture of BCAA (50% excess of each but excluding the limiting amino acid). All diets were isoenergetic and were made isonitrogenous by replacement of glutamic and aspartic acids. The twelve diets were given to twenty-four growing pigs (30-40 kg) in three periods according to a randomized block design. Each period lasted 8 d and N retention was measured during the last 5 d of each period. Reducing dietary methionine, valine or isoleucine reduced the utilization of N (N retained/N digested) by approximately 20% (P < 0.05). Adding leucine to the isoleucine-limiting diet decreased the utilization of N by 9% (P < 0.05). This was reversed by simultaneous addition of valine. Excess leucine in a valine-deficient diet did not significantly reduce N utilization. In methionine-limiting diets an excess of either leucine alone or of all three BCAA increased the utilization of N by 8% (P < 0.05).     

Dietary casein and soybean protein affect the concentrations of serum cholesterol, triglyceride and free amino acids in rats.

This work was undertaken to investigate the concentrations of free amino acids in blood after food was withheld from growing, male Wistar rats fed cholesterol-free, low fat (1 g corn oil/100 g) diets with casein or soybean protein for 2 wk. A diet containing 22.5 or 23.5 g/100 g of soybean protein was hypocholesterolemic compared with a diet containing 20.0 g casein/100 g diet. A comparison of serum amino acids in soybean protein-fed vs. casein-fed rats showed that, whereas concentrations of many amino acids were lower in the soybean protein-fed rats compared with the casein-fed groups, glycine was the only amino acid having a higher concentration. Further, alanine was significantly lower in the soybean protein-fed rats compared with the casein-fed rats, and the protein-induced differences in glycine and alanine concentrations of unfed rats were reproducible. When diets containing 15.0% casein or 30.0% soybean protein, a casein diet supplemented with glycine and a soybean protein diet supplemented with methionine were compared, the changes in serum glycine and alanine correlated with the changes in serum cholesterol. Concentrations of several amino acids, particularly valine, leucine and tyrosine, also changed when serum cholesterol concentrations varied, but these effects could not be explained by our experiments. The results suggest that a change in serum concentration of glycine and alanine of unfed rats may be related to the change in serum cholesterol concentration.     

Effect of diets supplemented with amino acids on intestinal sucrase and leucine aminopeptidase activities in rats.

In order to investigate the relationship between dietary amino acids and protein, and activities of intestinal sucrase [EC 3.2.1.26] and leucine aminopeptidase [EC 3.4.11.1, LAPase] in rats, the effect of supplementation of amino acids into a protein-free diet and a low casein diet containing sucrose as the carbohydrate source on these enzyme activities was studied. The segmental weights of the small intestine and its mucosa of rats fed the protein-free diet supplemented with L-methionine or with L-methionine and L-threonine at 0.1 or 0.2% levels were significantly higher than those of rats fed the protein-free diet or one supplemented with L-glutamic acid, but there was no difference in the segmental activities of the sucrase and LAPase among rats fed these diets. On the other hand, the supplementation of methionine or methionine plus threonine to the 5% or 10% casein diet produced remarkable increases in the segmental weights of the small intestine and its mucosa as well as in the segmental activities of the sucrase and LAPase. There was no difference between the segmental sucrase activity of rats fed the 10% casein diet supplemented with 0.2% methionine ad libitum and that of rats fed this diet under restricted feeding conditions, although the segmental LAPase activity was affected by the amount of food consumed.     

High levels of dietary amino and branched-chain alpha-keto acids alter plasma and brain amino acid concentrations in rats

Plasma and brain amino acid and plasma branched-chain alpha-keto acid (BCKA) concentrations were measured in rats fed diets containing high levels of individual amino and alpha-keto acids. Consumption of a low-protein (9% casein) diet high in leucine or alpha-ketoisocaproate depressed plasma concentrations of isoleucine and valine and their respective keto acids, alpha-keto-beta-methylvalerate and alpha-ketoisovalerate. High dietary levels of alpha-keto-beta-methylvalerate or alpha-ketoisovalerate (but not of isoleucine or valine) depressed plasma concentrations of the other BCKA and their respective branched-chain amino acids (BCAA). Consumption of a low protein, high phenylalanine diet depressed plasma concentrations of both BCAA and BCKA. Brain large neutral amino acid pools of rats fed all low-protein, high-amino acid diets were depleted. Consumption of diets high in individual BCKA increased brain concentrations of aromatic amino acids. In this study of rats allowed to feed for only 6 h/d, elevated brain phenylalanine concentration was associated with a significant depression of food intake, whereas elevated brain BCAA concentrations were not. Also, elevated plasma BCKA concentrations, comparable with those observed in maple syrup urine disease, were accompanied by elevations in concentrations of aromatic amino acids in brain but not in plasma.     

The branched-chain amino acid antagonism in chicks

The effects of dietary supplements of branched-chain amino acids on growth, food consumption and metabolism in chicks were investigated. When an adequate diet contained 1.20, 1.60, 2.25, 3.75, or 5.00% leucine, increasing leucine content caused reduced food consumption and weight gains, coupled with impaired efficiency of food utilization. When the diet deficient in branched-chain amino acids contained 0.98, 1.46, 2.25, 3.75, or 5.00% leucine, increasing leucine resulted in increased food consumption and reduced efficiency of food utilization when levels of leucine up to 3.75% were fed. Excess leucine depressed plasma concentrations of isoleucine and valine. Excesses of isoleucine or valine caused smaller depressions of concentrations of the other two branched-chain amino acids. All these effects were seen during the first 8 days of experiment, after which they diminished or disappeared. Muscle branched-chain amino acid aminotransferase (BCAT) (L-leucine:2-oxoglutarate aminotransferase, EC 2.6.1.6) activity was increased in chicks fed excess leucine but not in those fed excess isoleucine or valine. Hepatic alpha-ketoisocaproic dehydrogenase (KADH) (2-oxoisocaproate:lipoate oxidoreductase, EC 1.2.4.3) activity and muscle polyribosomal aggregation were unaffected by diet. When chicks were fed diets containing either 0.98 or 2.25% leucine, production of 14CO2 from [1-14C]isoleucine and [1-14C]valine was increased in chicks fed the higher level of leucine. The increase was small in both cases, representing approximately 2% of consumed isoleucine and valine. Increased production of 14CO2 was observed within 12 hours of feeding excess leucine; however, BCAT increased only after 2 to 4 days. No differences were seen in excreted 14C or in the relative distribution of 14C along the small intestine. We conclude that the chick is able to adapt in part to excesses of dietary leucine and that the branched-chain amino acid antagonism may involve increased catabolism of the limiting branched-chain amino acids.     

Effects of dietary excesses of the branched-chain amino acids on growth, food intake and plasma amino acid concentrations of kittens

The effect of excesses of the branched-chain amino acids (BCAA), particularly leucine, on growth, food intake and plasma amino acid concentrations were investigated in kittens. Effects of excess leucine were tested in kittens fed five basal diets that varied in their nitrogen and amino acid contents. Compared to rats, kittens were much less sensitive to excesses of the BCAA. Addition of 10% leucine to basal diets that provided nitrogen just at or below the minimal requirement of kittens resulted in no change or increased growth and food intake of kittens when the isoleucine and valine concentrations in the basal diet were just at or slightly in excess of the kitten's minimal requirements for those amino acids. An adverse effect of leucine added to low nitrogen basal diets was observed only when isoleucine and valine were provided below the kitten's requirement (80% of requirement). When basal diets containing adequate nitrogen (24% amino acids) were tested, the addition of leucine (10%) resulted in an adverse effect when isoleucine and valine were provided at 80% of the kitten's requirement and in mild growth depressions when isoleucine and valine were provided at 1.1 times the requirement. Leucine-induced growth depression was alleviated by the addition of isoleucine and valine at 0.5%, indicating that excess leucine caused a BCAA antagonism or an amino acid imbalance. With the addition of leucine to the basal diets, there were consistent decreases in concentrations of alanine and tyrosine in plasma but no consistent depressions in the concentrations of isoleucine and valine.     

Nutritional and metabolic effects of dietary leucine excess in preruminant lamb

The effects of excess leucine intake on food intake, branched-chain amino acid and branched-chain alpha-keto acid concentrations in plasma and nitrogen retention were investigated in the preruminant lamb. Lambs were fed leucine in excess in either an adequate protein diet [24% of dry matter (DM)] or a low protein diet (15% DM) for 2 d. Increasing the dietary leucine content of 2.3 to 10.6 or 12.6% DM led to a significant decrease in food intake. This depressing effect was not influenced by dietary protein content. Increasing the dietary leucine content from 2.3 to 6.4% DM in an adequate protein diet for a week did not significantly improve nitrogen retention in the preruminant lamb. Plasma leucine and its alpha-keto acid concentrations increased with leucine intake. Plasma valine and isoleucine concentrations were significantly decreased only in lambs fed the highest excess leucine diet. Surprisingly, a maximal 50% decrease of their plasma alpha-keto acid concentrations occurred even in the group fed the lowest excess leucine diet. Our results might be explained by an inhibition of the rate of transamination of valine and isoleucine by high leucine concentration.     

Effects of leucine/isoleucine ratio in amino acid mixture-diets simulating normal and high-lysine maize proteins on growth, nitrogen balance, and tryptophan-niacin metabolism in rats

To re-evaluate nutritive values of opaque-2 (o2) and brittle-2 opaque-2 (bt2o2) maize protein and to re-estimate Gopalan's hypothesis [Lancet, i, 954-957 (1960)] that pathogenesis of pellagra might be related with intake of excess leucine and with chronic consumption of maize or jowar which contains relative high leucine, rats were fed on synthetic diets composed of amino acid mixtures simulating the protein of normal and high-lysine maize, o2 and bt2o2 maize. In order to investigate the effect of intake of excess leucine, leucine was supplemented to o2 and bt2o2 diet at the level of 0.43 and 0.73%, respectively, to adjust the ratio of leucine to isoleucine to that of normal maize protein. Judging from body weight gains and carcass nitrogen of weanling rats fed on these diets, the protein quality (amino acid composition) of bt2o2 maize was 30% superior nutritionally to that of o2 maize, and body composition of bt2o2 diet group were similar to that of casein diet group. Leucine supplementation did not affect these values except for a significant decrease in plasma valine levels. In young adult rats fed on leucine supplemented o2 diet, excretion of urinary nitrogen increased significantly compared with o2 diet alone, suggesting that a slight amino acid imbalance took place. But leucine supplementation altered neither N1-methylnicotinamide level in urine nor total niacin levels in the liver and the brain. These results suggest that supplementation of leucine to a high lysine maize diet did not affect tryptophan and niacin metabolism in rats under these conditions.