含硫氨基酸的抗氧化作用

抗氧化剂是维持动物体内自由基平衡和稳定的重要物质。甲硫氨酸(Met)和半胱氨酸(Cys) 是组成蛋白质的2种含硫氨基酸,基于其独特的结构,在动物体内起着与动物营养与免疫相关的重要生理功能,而其抗氧化能力越来越受关注。综述了蛋白质Met残基的氧化还原作用和含硫氨基酸的代谢产物谷胱甘肽(GSH)的抗氧化作用。     

高同型半胱氨酸血症治疗研究进展

同型半胱氨酸是蛋氨酸代谢的中间产物,其代谢异常所导致的高同型半胱氨酸血症已被许多研究相继证实与心脑血管疾病、外周血管疾病、神经系统退行性疾病、糖尿病、妊娠高血压综合征、肝硬化、慢性肾病相关。本文将简要介绍高同型半胱氨酸血症及其发病机制,重点综述利用叶酸、维生素B6、B12、甜菜碱、阿托伐他汀、异黄酮、牛磺酸和某些中药治疗方面取得的新进展,同时分析各个治疗方案可能存在的问题。     

重组BHMT对高同型半胱氨酸血症大鼠的影响

目的探讨重组BHMT对大鼠HHcy血症的防治作用。方法用含2%蛋氨酸(methionine,Met)饲料诱发HHcy的大鼠,经尾静脉注射BHMT后,观察模型大鼠血浆中同型半胱氨酸(homocysteine,Hcy)浓度、LDH酶活性及HDL/LDL的影响。结果重组BHMT能将HHcy组大鼠血浆中Hcy浓度(23.70±6.75)μmol/L显著降低为(14.61±2.80)μmol/L(P<0.05),LDH酶活性由(209.57±10.22)U/L降低为(225.04±30.47)U/L(P<0.05),对脂蛋白HDL/LDL基本没有影响。结论重组BHMT对高同型半胱氨酸血症有一定的治疗作用。     

高蛋氨酸饲料喂养的大鼠高同型半胱氨酸血症模型的实验研究

探讨高蛋氨酸饲料诱导高同型半胱氨酸血症的适应剂量及其对相关代谢的影响.选择质量分数1%、2%和3%蛋氨酸饲料喂饲大鼠,高压液相色谱法测定血清同型半胱氨酸、半胱氨酸和还原形谷胱甘肽含量.结果表明饲料中1%蛋氨酸可以使血清同型半胱氨酸水平升高且无生长抑制等毒副作用,2%和3%蛋氨酸饲料喂养大鼠后出现摄食量减少和生长抑制等毒...     

高同型半胱氨酸对动脉粥样硬化形成的作用

同型半胱氨酸是甲硫氨酸的中间代谢产物,高同型半胱氨酸血症已成为动脉粥样硬化的一种独立危险因素,探讨高同型半胱氨酸血症形成的原因及同型芈胱氨酸致动脉粥样硬化的机制,有助于动脉粥样硬化的防治.     

阻断消耗途径提高毕赤酵母工程菌S-腺苷甲硫氨酸产量

【背景】S-腺苷甲硫氨酸(S-adenosyl-L-methionine, SAM)作为所有生物体内的重要中间代谢物,不仅可作为膳食补充剂,还具有良好的临床应用价值。【目的】将毕赤酵母重组菌GS115/DS16的SAM消耗途径阻断,进一步提高SAM的产量。【方法】分别敲除毕赤酵母重组菌GS115/DS16的S-腺苷同型半胱氨酸水解酶基因sah1、S-腺苷甲硫氨酸脱羧酶基因spe2和L-甲硫氨酰tRNA合酶基因msm1,构建工程菌G/Dsah、G/Dspe和G/Dmsm。检测3个工程菌的生长和SAM产量,以及L-Met添加量对SAM积累的影响。【结果】与出发菌GS115/DS16相比,工程菌G/Dsah、G/Dspe和G/Dmsm的单位菌体SAM产量分别提高了29.3%、55.6%和24.8%,其生长无显著差异。L-Met添加量优化后(0.06%),G/Dsah和G/Dmsm单位菌体的SAM产量分别提高了26.4%和28.9%。【结论】构建的毕赤酵母工程菌可用于SAM的工业化生产,该代谢工程策略可用于改进其他化学品的生产。     

高同型半胱氨酸血症与内皮祖细胞凋亡

内皮祖细胞在内皮损伤后的修复中起重要作用.高同型半胱氨酸血症作为动脉粥样硬化的一个独立危险因素,可影响外周血内皮祖细胞的数量和功能,导致内皮功能障碍.在其引起内皮祖细胞损伤的机制中,凋亡扮演了重要角色.本文就高同型半胱氨酸血症对内皮祖细胞凋亡的影响及机制的研究进展进行了综述.     

高同型半胱氨酸血症致动脉粥样硬化的细胞分子机制

同型半胱氨酸（homocysteine,Hcy)是蛋氨酸代谢途径产生的含硫氨基酸,其代谢紊乱可以诱导高同型半胱氨酸血症的发生,已被临床及流行病学资料证实为动脉粥样硬化发病的独立危险因子。Hcy通过激活二酰甘油－蛋白激酶C－（DAG－PKC）及丝裂素活化蛋白激酶（MAPK）途径,诱导相关基因的表达,促进细胞钙化,启动脂质过氧化应激,从而损伤心血管系统。金属硫蛋白,牛磺酸,L－精氨酸作为内源性小分子物质,成为继维生素B6,B12之后控制和治疗高同型半胱氨酸血症的新途径。     

警惕高同型半胱氨酸血症

血清同型半胱氨酸浓度增高使老年人容易发生骨折,也使患心脏病的危险性增加。现认为,可能是由于高水平的同型半胱氨酸能抑制胶原蛋白的交联,而亚甲基四氢叶酸还原酶（MTHFR）有TT突变基因型的患者．因为此酶的活性降低,通常伴有同型半胱氨酸水平增高和叶酸水平降低。此外,雌二醇能通过增强抗氧化剂系统以防止高同型半胱氨酸血症引起的动脉粥样硬化症。故服用B族维生素和应用雌激素替代疗法是有益的。     

高同型半胱氨酸血症促进大鼠血管钙化

目的:在大鼠血管钙化模型上,探讨高同型半胱氨酸血症对血管钙化的影响及其作用机制.方法:用维生素D3加尼古丁诱导大鼠血管钙化模型,并给以高蛋氨酸饮食六周诱导大鼠高同型半胱氨酸血症,用高效液相色谱法检测血浆总同型半胱氨酸(Hcy)水平;采用血管组织vonKossa染色、钙含量测定、碱性磷酸酶(ALP)活性和骨钙素(OC)含量测定以判断血管钙化程度,同时测定血浆脂质共轭烯(Diene键)含量反映其脂质过氧化水平.结果:钙化组大鼠血管yon Kossa染色可见大量黑色颗粒沉积,其血管的钙含量,碱性磷酸酶活性及骨钙素含量分别较对照组增加8.09倍、45.57%和2.81倍(P＜0.01).高蛋氨酸饮食的钙化组大鼠血管内钙含量较单纯钙化组增高了34.29%,而碱性磷酸酶活性及骨钙素含量则较单纯的钙化组降低29.13%和74.69%(P＜0.01).钙化组大鼠血浆脂质共轭烯含量与对照组比较无显著性差异,单纯高蛋氨酸饮食和钙化加高蛋氨酸饮食大鼠血浆脂质共轭烯含量较对照组增加了1.93和2.89倍(P＜0.01),而钙化加高蛋氨酸饮食大鼠血浆脂质共轭烯含量较单纯高蛋氨酸饮食大鼠又增加了32.90%(P＜0.01).结论:高同型半胱氨酸血症可以促进血管的钙化,可能与其所致的脂质过氧化程度增强有关.     

Effects of Various Amino Acids on Methionine-Induced Hyperhomocysteinemia in Rats

Rats were fed diets supplemented with 1% L-methionine with and without 2.5% various amino acids for 7 d to determine what amino acids other than glycine, serine, and cystine can suppress methionine-induced hyperhomocysteinemia. L-Glutamic acid, L-histidine, and L-arginine significantly suppressed methionine-induced enhancement of plasma homocysteine concentrations, but the mechanisms underlying the effect of these amino acids are thought not to be identical.     

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.     

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.     

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。     

血浆同型半胱氨酸水平升高与动脉粥样硬化

心血管疾病已成为当今全球性致残与致死的最重要原因之一。目前确定的冠心病的危险因素主要包括高龄、血脂异常、高血压、糖尿病、吸烟、肥胖症。大量的临床试验及流行病学研究已经证实血浆同型半胱氨酸水平升高是心血管疾病的一个独立的危险因素。健康人的血浆同型半胱氨酸水平为5～10μmol／L。血浆同型半胱氨酸水平严重升高的主要原因是胱硫醚-β-合成酶(cystathionine-β-synthase,CBS)基因的缺陷。CBS基因缺陷的纯合体可导致血浆同型半胱氨酸水平升高至100～500μmol／L。血浆同型半胱氨酸水平严重升高的病人通常伴随神经系统异常、早发性的动脉粥样硬化。叶酸、维生素B6和B12治疗能降低血浆同型半胱氨酸的水平并改善血管内皮功能、减少经皮冠状动脉腔内成形术(percutaneou stransluminal coronary angioplasty,PTCA)术后并发症。迄今为止,血浆同型半胱氨酸水平升高引起心血管疾病的发病机制并未完全明了,目前认为主要与以下几个方面有关：(1)内皮细胞损伤及功能障碍。我们实验室在CBS基因敲除的小鼠模型上证实血浆同型半胱氨酸水平升高能抑制eNOS的活性,导致主动脉内皮功能的障碍。我们还在细胞模型上证实了同型半胱氨酸能显著抑制内皮细胞的增殖。(2)KH固醇和甘油三脂生物合成代谢异常。我们实验室在apoE、CBS双基因敲除的小鼠模型上证实血浆同型半胱氨酸水平升高能改变肝脏的脂肪代谢,增加巨噬细胞对修饰LDL的摄取,从而导致胆固醇脂和甘油三脂在血管壁的堆积,促进主动脉粥样斑块的形成。(3)刺激血管平滑肌细胞增殖。此外还发现同型半胱氨酸能激活蛋白激酶C信号途径,促进胶原蛋白的合成,抑制弹性蛋白和胶原蛋白的交联。(4)激活血栓形成。(5)激活单核细胞。目前认为同型半胱氦酸主要通过以下几个化学机制致病;(1)自氧化产生活性氧。同型半胱氨酸在自氧化的过程中能产生大量的活性氧,从而引起血液中脂蛋白和细胞膜脂质的过氧化损伤,并进一步引起内皮功能的障碍。(2)在腺苷的参与下形成SAH,一种甲基转移抑制剂,导致细胞内的低甲基化。(3)与一氧化氮结合形成亚硝酰物。(4)参与蛋白质的合成。总之,我们和其他实验室的研究结果均表明同型半胱氨酸不仅与动脉粥样硬化相关,而且具有致病效应。尽管补充叶酸、维生素B6和B12等治疗能降低血浆同型半胱氨酸的水平,但是否能降低心血管疾病的风险仍有待于大量的动物研究及临床试验。     

槲皮素对甲硫氨酸负载大鼠氨基酸代谢的影响

为探讨槲皮素对甲硫氨酸(Met)负载大鼠氨基酸代谢的影响,将Wistar大鼠24只随机分为3组,即对照组、1％甲硫氨酸组以及1％甲硫氨酸和0.5％槲皮素组,喂养6周后,采用高压液相色谱法测定血清中半胱氨酸含量,全自动氨基酸分析仪测定血清中其他氨基酸含量.结果显示,1％甲硫氨酸干预后除对牛磺酸产生显著影响外,对其他氨基酸没有明显影响.0.5％槲皮素干预后,血清必需氨基酸苏氨酸、缬氨酸含量较1％ Met组显著升高(p＜0.05),牛磺酸、缬氨酸、亮氨酸和异亮氨酸较对照组亦显著升高(p＜0.05),而血清丝氨酸和脯氨酸含量较对照组显著降低(p＜0.05).结果表明,槲皮素可能加强甲硫氨酸转硫化代谢途径.     

蛋氨酸脑啡肽质量标准研究

建立了蛋氨酸脑啡肽的质量标准。采用液相色谱-质谱联用仪检测蛋氨酸脑啡肽分子量和鉴别蛋氨酸脑啡肽的各氨基酸组成,反相高效液相色谱测定蛋氨酸脑啡肽含量。蛋氨酸脑啡肽分子量为573.7,氨基酸组成为Tyr-Gly-Gly-Phe-Met。蛋氨酸脑啡肽质量浓度在7~280 mg/L(r=0.999 8)内线性关系良好,平均回收率为98.54%,RSD为0.89%。所建立的方法科学,可靠,重复性好。可准确地对蛋氨酸脑啡肽进行定性定量检测。     

蛋氨酸合成方法概述

蛋氨酸是重要的精细化工产品,国内蛋氨酸产业发展落后于国外.总结了蛋氨酸的各种合成方法及生产工艺流程,并且各种方法的优缺点得到了详细的介绍和讨论.     

蛋氨酸羟基类似物对肉鸡骨骼性能和基因表达的影响

本文以雄性罗斯肉鸡为材料,探讨饲粮添加不同蛋氨酸源:蛋氨酸(DLM)、蛋氨酸羟基类似物(HMTBA)和蛋氨酸羟基类似物钙盐(HMTB-Ca)对肉鸡骨骼性能和基因表达的影响。结果表明,HMTBA和HMTB-Ca能提高肉鸡终体重、日增重、血液GSH/GSSG比值、抗氧化酶(CAT)水平、总抗氧化能力(T-AOC)、骨骼长度、重量、骨骼指数(p<0.05)。不同蛋氨酸源对肉仔鸡采食量、料重比和灰分含量影响不显著(p>0.05),HMTBA组骨生长分化因子-5(GDF-5)表达量显著上升(p<0.05)。HMTB-Ca显著提高骨骼强度、钙磷含量,下调金属基质蛋白酶-2(MMP-2)、金属基质蛋白酶-9(MMP-9)的表达水平(p<0.05)。由此可知,采食蛋氨酸羟基类似物及其钙盐饲粮,可提高肉鸡体增重,改善血液氧化还原状态,改善骨骼生长发育,其中HMTB-Ca对骨骼作用更显著。     

Methionine,folic acid and vitamin B12 in growing-finishing pigs: Impact on growth performance and meat quality

Growth performance, metabolic variables, and meat quality were measured in 78 growing-finishing pigs using supplements of 0 (C), or 0.2% of DL-methionine (M), and three combinations of folic acid [mg/kg] and cyanocobalamin [μg/kg], respectively 0 and 0 (V0), 10 and 25 (V1), and 10 and 150 (V2) in a 2 × 3 factorial arrangement. Feed conversion was lower (p = 0.05) in M than in C pigs during the growing period (0–4 weeks). Both V1 and V2 treatments increased plasma vitamin B₁₂ (p < 0.01) and decreased plasma homocysteine (p < 0.01). Plasma 5-methyl-tetrahydrofolates were the lowest, highest and intermediate in V0, V1 and V2 pigs (p < 0.04), respectively. In V2 meat, folates were 32% higher, vitamin B₁₂, 55% higher and homocysteine, 28% lower than in V0 (p < 0.01). Oxidative stability of the fresh meat was similar among treatments during a storage period of 42 days. Therefore, methionine supplements improved growth performance during the growing period. Vitamin supplements interacted with the methionine cycle pathway, increased vitamin content of pork meat but did not improve oxidative stability of the fresh meat during storage.