High-Casein Diet Suppresses Guanidinoacetic Acid-Induced Hyperhomocysteinemia and Potentiates the Hypohomocysteinemic Effect of Serine in Rats

To determine the effect of dietary protein level on experimental hyperhomocysteinemia, rats were fed 10% casein (10C) and 40% casein (40C) diets with or without 0.5% guanidinoacetic acid (GAA) for 14 d. In addition, rats were fed 10C + 0.75% methionine (10CM) and 40C + 0.75% methionine (40CM) diets with or without 2.5% serine for 14 d to determine the relationship between the dietary protein level and intensity of the hypohomocysteinemic effect of serine. GAA supplementation markedly increased the plasma homocysteine concentration in rats fed with the 10C diet, whereas it did not increase the plasma homocysteine concentration in rats fed with the 40C diet. Although serine supplementation significantly suppressed the methionine-induced enhancement of plasma homocysteine concentration, the decreased plasma homocysteine concentration was significantly lower in rats fed with the 40CM diet than in rats fed with the 10CM diet. The hepatic cystathionine β-synthase and betaine-homocysteine S-methyltransferase activities were significantly higher in rats fed with the 40C or 40CM diet than in rats fed with the 10C or 10CM diet, irrespective of supplementation with GAA and serine. These results indicate that the high-casein diet was effective for both suppressing GAA-induced hyperhomocysteinemia and potentiating the hypohomocysteinemic effect of serine, probably through the enhanced activity of homocysteine-metabolizing enzymes.     

甲硫氨酸诱导高Hcy血症的抗氧化作用研究

为探讨甲硫氨酸在诱导高Hcy血症过程中的抗氧化作用,将Wistar大鼠随机分为正常组和1%甲硫氨酸组,喂养6周后,采用高效液相色谱法测定血清中同型半胱氨酸(Hcy)和谷胱甘肽含量(GSH),全自动氨基酸分析仪测定蛋氨酸和牛磺酸含量,转氨酶活性采用试剂盒测定。肝组织丙二醛(MDA)含量采用硫代巴比妥酸法,黄嘌呤氧化酶法和比色法测定肝组织超氧化物歧化酶(SOD)活性、总抗氧化能力(FRAP值)和还原性谷胱甘肽含量。结果表明,1%甲硫氨酸组血清Hcy和牛磺酸含量分别为3.56±0.68μmol·L-1和568.68±57.02μmol·L-1,较正常组显著升高(p<0.05)。1%甲硫氨酸组肝组织GSH含量和SOD活性分别为132.19±25.49mg·g-1和6.86±1.46U·mg-1,较正常组103.97±16.30mg·g-1和5.01±1.24U·mg-1显著升高(p<0.05)。1%甲硫氨酸组较正常组肝组织FRAP值亦升高而MDA含量降低。结果表明,甲硫氨酸在诱导高Hcy血症过程中同时具有抗氧化作用。     

苯丙酮尿症(PKU)患者血清的氨基酸定量分析(英文)

目的 PKU患者血清中游离氨基酸组成及定量分析。方法 应用日立835-50型氨基酸自动分析仪进行测定。结果 七例PKU患者血清中Phe患者血清中Phe (1.5480.080) 和Glu (0.4680.098) 的含量分别为正常组Phe (0.1070.014) 和Glu (0.1330.046) 的15倍和3.5倍,差异非常显著 (p<0.001)。Arg (0.0330.046) 为正常组 (0.1130.025) 的1/4 (p<0.001)。但患者血清中Tyr (0.0500.016) 与正常值 (0.0470.008) 相比则无显著性差异 (p>0.05)。结论 用氨基酸分析方法可准确测定PKU血清中各种氨基酸含量,为PKU诊断提供了可靠的数据: 并发现除Phe外,还有Arg的异常降低及Glu的异常升高,其发生机理及临床意义有待进一步研究。     

Methionine and Serine Synergistically Suppress Hyperhomocysteinemia Induced by Choline Deficiency,but Not by Guanidinoacetic Acid,in Rats Fed a Low Casein Diet

The effects of dietary supplementation with 0.5% methionine, 2.5% serine, or both on hyperhomocysteinemia induced by deprivation of dietary choline or by dietary addition of 0.5% guanidinoacetic acid (GAA) were investigated in rats fed a 10% casein diet. Hyperhomocysteinemia induced by choline deprivation was not suppressed by methionine alone and was only partially suppressed by serine alone, whereas it was completely suppressed by a combination of methionine and serine, suggesting a synergistic effect of methionine and serine. Fatty liver was also completely prevented by the combination of methionine and serine. Compared with methionine alone, the combination of methionine and serine decreased hepatic S-adenosylhomocysteine and homocysteine concentrations and increased hepatic betaine and serine concentrations and betaine-homocysteine S-methyltransferase activity. GAA-induced hyperhomocysteinemia was partially suppressed by methionine alone, but no interacting effect of methionine and serine was detected. In contrast, GAA-induced fatty liver was completely prevented by the combination of methionine and serine. These results indicate that a combination of methionine and serine is effective in suppressing both hyperhomocysteinemia and fatty liver induced by choline deprivation, and that methionine alone is effective in suppressing GAA-induced hyperhomocysteinemia partially.     

束缚应激对大鼠同型半胱氨酸代谢的影响

为了探讨束缚应激对大鼠血清含硫氨基酸代谢的影响,根据同型半胱氨酸(Hcy)水平,将32只雄性Wistar大鼠分为对照组(control)、束缚应激组(RS)、1%蛋氨酸组(1%Met)和1%蛋氨酸+束缚应激组(1%Met+RS)。采用高压液相色谱法检测血清中的Hcy、半胱氨酸(Cys)和还原型谷胱甘肽(GSH)含量,采用全自动氨基酸分析仪测定血清中蛋氨酸(Met)和牛磺酸(Tau)含量。结果显示,RS组大鼠血清Hcy、Cys和GSH含量随着束缚时间延长而降低,且较对照组和1%蛋氨酸组有显著性差异(p<0.05);RS组大鼠血清Met和Tau含量较对照组和1%蛋氨酸组则显著升高(p<0.05)。束缚应激可能降低血清抗氧化能力和总Hcy水平。     

高蛋氨酸饮食对大鼠血管内皮细胞分泌功能的影响

目的:探讨高蛋氨酸饮食对大鼠血管内皮细胞分泌功能的影响。方法:雄性Wistar大鼠随机分为正常饮食对照组(对照组)和高蛋氨酸饮食组(高蛋氨酸组)。对照组喂饲普通饲料,高蛋氨酸组大鼠喂饲含3%蛋氨酸的饲料,共8周。采用高效液相色谱法测定大鼠血浆同型半胱氨酸含量,以MDA、SOD、NO/ET和t-PA/PAI平衡等指标建立研究平台和内皮功能评价体系,同时以扫描电镜观察主动脉弓血管内皮细胞形态。结果:与对照组相比,高蛋氨酸组血浆Hcy含量显著高于对照组,是对照组的2倍以上;血浆MDA和SOD活力显著升高(P<0.05),t-PA/PAI-1和NO/ET比值均显著降低(P<0.05)。扫描电镜显示高蛋氨酸组大鼠内皮细胞呈典型虫蛀样损害,伴有附壁血栓形成和脂质沉积。结论:高蛋氨酸饮食可诱发大鼠高半胱氨酸血症,Hcy可通过氧化应激机制损伤血管内细胞分泌功能,血浆NO/ET和t-PA/PAI-1系统失衡。     

Cooperative Effects Between Arginine and Glutamic Acid in the Amino Acid‐Catalyzed Aldol Reaction

Catalysis of the aldol reaction between cyclohexanone and 4‐nitrobenzaldehyde by mixtures of L‐Arg and of L‐Glu in wet dimethyl sulfoxide (DMSO) takes place with higher enantioselectivity (up to a 7‐fold enhancement in the anti‐aldol for the 1:1 mixture) than that observed when either L‐Glu or L‐Arg alone are used as the catalysts. These results can be explained by the formation of a catalytically active hydrogen‐bonded complex between both amino acids, and demonstrate the possibility of positive cooperative effects in catalysis by two different α‐amino acids. Chirality 28:599–605, 2016. © 2016 Wiley Periodicals, Inc.     

A Direct Chemical Interaction between Dynorphin and Excitatory Amino Acids

The endogenous opioid peptide dynorphin A elicits non-opioid receptor-mediated neurotoxic effects. These effects are blocked by pretreatment with N-methyl-D-aspartate (NMDA) receptor antagonists. Herein, the mechanism for the non-opioid effects of dynorphin and related peptides was studied by matrix-assisted laser desorption ionization (MALDI) mass-spectrometry. We observed that both glutamate or aspartate bind non-covalently to dynorphin A and dynorphin 2-17. However, when dynorphin A or dynorphin 2-17 were added to an equimolar mixture of Glutamate and Aspartate, they both complexed preferentially with glutamate. These data may explain the non-opioid physiological effects of dynorphin A and related peptides and indicate that the direct chemical interaction between neurotransmitters should be monitored when studying interactions between different neurochemical systems.     

Effects of Dietary Amino Acids on Brain Amino Acids and Transmitter Amines in Rats with a Portacaval Shunt

The etiologic relationship between disturbances in metabolism of amino acids and amines and hepatic coma was investigated by examining the effects of diets containing various mixtures of amino acids on brain amine metabolism in rats with a portacaval shunt, using a method for simultaneous analysis of amino acids and amines. Rats with a portacaval shunt were fed on four different amino acid compositions with increased amounts of various amino acids suspected to be etiologically related to hepatic coma, such as methionine, phenylalanine, tyrosine, and tryptophan. The animals were killed 4 weeks after operation. During the experimental period, these animals did not become comatose, but exhibited various behavioral abnormalities. Marked increase in the plasma and brain levels of the augmented amino acids, especially methionine and tyrosine, were observed in rats with a portacaval shunt. Brain noradrenaline, dopamine, and serotonin levels were significantly decreased when the brain tyrosine level was increased. These results indicate that in rats with a portacaval shunt the dietary levels of amino acids greatly influence the brain levels of both amino acids and transmitter amines.     

条件必需氨基酸对放射损伤大鼠血浆蛋白的影响

观察条件必需氨基酸对放射损伤大鼠血浆蛋白的影响。以雄性Wistar大鼠 6 9只 ,普通饲料喂养 6天 ,随机分成A、B、C、D四组 ,A、B、C组各 2 0只、D组 9只。A、B、C三组动物均接受 6 .5Gy的γ线全身照射 ,D组动物不照射。照射后在A组饲料中添加 3%精氨酸 +5 %牛磺酸 +1%谷氨酰胺 ;B组饲料中添加与A组等氮量的甘氨酸 (10 .91% ) ;C组及D组仍喂普通饲料。照射后 7及 14天测血浆总蛋白、白蛋白、前白蛋白、纤维结合蛋白。结果显示A组在饲料摄入量、体重及血浆总蛋白、白蛋白、前白蛋白、纤维结合蛋白水平等方面均优于B组及C组。提示饲料中增加条件必需氨基酸含量可以改善进食 ,促进体重恢复及蛋白质合成 ,进而提高受照大鼠应激能力     

In Vitro Release of Endogenous Excitatory Sulfur-Containing Amino Acids from Various Rat Brain Regions

Efflux of various amino acids from rat brain slices was determined under resting or depolarizing conditions. Slices of neocortex, hippocampus, striatum, cerebellum, mesodiencephalon, pons-medulla, and spinal cord were depolarized by K+ (50 mM) or veratrine (33 micrograms/ml). The 4-N,N-dimethylamino-azobenzene-4'-isothiocyanate (DABITC) derivatization method of Chang [Biochem. J. 199, 537-545 (1981)] for HPLC was adapted for analysis of amino acids and peptides in superfusion solutions. It allowed the separation and simultaneous detection of the sulfur-containing amino acids cysteine sulfinic acid (CSA), cysteic acid (CA), homocysteine sulfinic acid (HCSA), and homocysteic acid (HCA) at the picomole level. All four were shown to be released on depolarization in a Ca2+-dependent manner from brain slices. CSA and HCSA were released from cortex, hippocampus, mesodiencephalon, and, for HCSA only, striatum. HCA release, observed in all regions, was most prominent in cortex and hippocampus. CA was slightly increased by depolarization in hippocampus and mesodiencephalon. These sulfur-containing amino acids have been shown to exert an excitatory action on CNS neurons. The fact that these sulfur-containing amino acids are released as endogenous substances from nervous tissue supports the hypothesis that they play a role in CNS neurotransmission.     

The Inhibitory Effects of Various Amino Acids on the Growth of Barley Seedlings

The effect of fifteen amino acids, supplied singly, on the growthof isolated germinating barley embryos in the presence of nitratehas been studied. The L forms of lysine, arginine, tyrosine,proline, threonine, methionine, leucine, and valine at concentrationsof either 1 or 2 mM have been found to inhibit fresh-weightaccumulation. The inhibition by valine is relieved by furtheraddition of isoleucine and that of leucine by the addition ofboth isoleucine and valine. These interrelations have been interpretedas suggesting that leucine and valine can inhibit acetolactateand acetohydrorybutyrate synthesis. The inhibition of tyrosinecan be relieved by phenylalanine and that of lysine by ornithineor arginine. The possible reasons for these interrelationshipsare discussed.     

氨基酸的电分析进展

氨基酸电分析研究是生命科学中令人关注的课题。本文就各种氨基酸电分析化学研究的最新进展进行了综述。主要叙述了电活性氨基酸的直接伏安检测和非电活性氨基酸通过衍生化反应和电致化学发光进行的间接检测 ,并对其前景进行了展望。     

氨基酸对于Monascus ruber生物合成Monacolin K影响的研究

在Monacolin K发酵中添加氨基酸后发现较高质量浓度的氨基酸高度抑制了Monacolin K的产量。0.1 g.L-1的D-甲硫氨酸在发酵第4 d添加可以提高产量30%以上,而L-甲硫氨酸则没有此功能,D,L-甲硫氨酸因D-甲硫氨酸的关系也有一定的增产效果。以甲硫氨酸代替蛋白胨作为主要氮源,则抑制了polyketide途径的前期步骤,因此严重抑制了色素及Monacolin K的生产。另外,发现1 g.L-1的L-苯丙氨酸的添加时间越早越有利于Monacolin K的生产,在起始时添加发酵单位可达135.9 mg.L-1,可能是因为L-苯丙氨酸经过脱氨后,可以进入polyketide途径从而促进了Monacolin K的生产。     

支链氨基酸对运动大鼠氨基酸代谢和运动能力的影响

观察了支链氨基酸(BCAA)对大鼠运动能力和血清游离氨基酸代谢的影响。实验用21只雄性wistar大鼠,随机分为3组:正常组、游泳对照组和游泳补充BCAA组。2个运动组每天游泳训练1h,10天后游泳6h,观察补充BCAA对大鼠游泳运动能力和血清游离氨基酸水平的影响。实验结果表明,补充BCAA可明显提高大鼠游泳存活率,抑制血清中必需氨基酸、非必需氨基酸和总氨基酸水平升高,游泳运动后大鼠的血清中乳酸和LDH的升高幅度有所降低,抑制骨骼肌LDH活力的下降。说明补充BCAA可明显提高大鼠的运动能力,减少运动造成的蛋白质分解     

Effects of Various Polyunsaturated Fatty Acids on Blood Cholesterol and Eicosanoids in Rats

The hypocholesterolemic efficacy of various polyunsaturated fatty acids was compared in rats given cholesterol-enriched diets with (0.004%) or without indomethacin, the cyclooxygenase inhibitor. Evening primrose oil (EPO, linoleic+ γ-linolenic), safflower oil (SFO, linoleic) or soybean oil (SBO, linoleic + α-linolenic) were added to diets at the 10% level. The serum cholesterol level of the EPO group was consistently lower than the other groups and after 3 weeks, it was significantly different from the SFO group without indomethacin and the SBO group with indomethacin. In rats fed EPO, the aorta tended to produce more prostacyclin whereas the concentration of plasma thromboxane B₂ was much lower than in rats fed SFO or SBO. The effects of indomethacin on these eicosanoids were less evident in rats fed EPO. Thus, in addition to the hypocholesterolemic action of β-linolenic acid (GLA) in preference to linoleic and possibly α-linolenic acid, GLA appears to cultivate an environment suitable for the prevention of carbiovascular disease even in the presence of excess cholesterol in the diet.     

Specificity of Amino Acid Transport in Trypanosoma equiperdum*

Uptake of [¹⁴C] alanine, arginine, glutamic acid and phenylalanine by Trypanosoma equiperdum occurred by both a mediated mechanism and diffusion. Twenty amino acids were studied as inhibitors of absorption of the above amino acids. Results suggested that at least 4 distinct transport loci are involved in amino acid transport. These 4 loci have overlapping affinities for amino acids and seem to be involved, respectively, in the absorption of (a) arginine and phenylalanine; (b) arginine; (c) alanine, phenylalanine, and glutamic acid; (d) glutamic acid. The data also showed that multiple sites for substrate binding occur on each of 2 transport systems.     

Effects of Free Fatty Acids on Synaptosomal Amino Acid Uptake Systems

Abstract: The Na⁺-dependent synaptosomal uptakes of proline, aspartic acid, glutamic acid, and γ-aminobutyric acid were strongly inhibited by monounsaturated fatty acids. With oleic acid, half-maximal inhibition was observed at about 15 μM. The Na⁺-independent uptakes of leucine, phenylalanine, histidine, and valine were less sensitive to inhibition by the unsaturated fatty acids. In contrast, the uptakes of all of these amino acids were unaffected by saturated fatty acids. The inhibition of proline uptake (and that of the other Na⁺-dependent amino acids) by oleic acid was overcome by the addition of serum albumin and the data presented further indicate that the previously reported stimulation of proline uptake by albumin could be related to its fatty acid binding properties.     

氨基酸分析仪测定饲料添加剂——叶酸的方法

用６ｍｏｌ／Ｌ盐酸于１１０℃条件下水解饲料添加剂——叶酸,使之游离出谷氨酸,用氢氧化钠中和调节ｐＨ到２,氨基酸分析仪测定谷氨酸含量,经与标准叶酸水解样品比较,计算出叶酸的纯度。该方法重现性好,变异系数ＣＶ＝０．０８％,平均回收率为９８．３４％,浓度与峰面积呈线性相关,相关系数ｒ＝０．９９８７,可随氨基酸分析同时进行,不需改变任何分析条件。     

氨基酸的消旋研究

在纯乙酸溶剂中,以乙酸酐酰化消旋酪氨酸,消旋温度为90℃,L-酪氨酸和乙酸酐的摩尔比为12,每消旋1gL-酪氨酸时,溶剂乙酸的用量为5mL,效果较好。同样的方法应用于L-脯氨酸,L-苏氨酸,L-缬氨酸,L-赖氨酸,L-半胱氨酸等氨基酸,消旋率均可达到100%。