PEG-蛋白质类药物的体内代谢与安全性评价

PEG-蛋白质可以有效地延长蛋白质药物半衰期,可以减缓蛋白的排泄速度,并提高蛋白质的抗酶解能力,以此来增加PEG-蛋白质的稳定性和溶解性,降低免疫原性,延长蛋白质类药物在体内的生物活性,对其药物动力学和药效学性质进行改善.但是在实际应用过程中,由于方法学的限制,PEG-蛋白质类药物在进行代谢、组织分布和安全排泄等研究时,无法得到正确的体内代谢与安全性评价.本文通过对PEG-蛋白质体内组织分布与排泄方法的研究,对PEG的代谢与安全性的研究以及对PEG-蛋白质类药物动物和临床应用的安全性的研究,得到了正确的PEG-蛋白药物的体内代谢与安全性评价.     

稳定性同位素示踪技术的蛋白质代谢动力学研究

同位素示踪技术是公认的用于研究蛋白质代谢动力学的最佳方法。起初,由于放射性同位素具有方便、经济、检测技术成熟等优点而得到广泛应用,但因它的放射性限制了在人体代谢研究中的应用。随着稳定性同位素标记技术的成熟和质谱分析技术的发展和普及,稳定性同位素被广泛用于人体代谢动力学研究中。以下就稳定性同位素用于研究蛋白质代谢动力学中的基本原理、方法、检测手段和应用作一综述。     

创伤和感染应激对蛋白质代谢率的影响

创伤和感染均可刺激机体产生应激反应,使各器官、组织等代谢失衡。一些处理方案可有效地减轻不良应激对机体代谢的负面效应。以下着重阐述创伤和感染应激对蛋白质代谢的影响,并介绍相关的处理方法。     

稳定核素技术在蛋白质代谢研究中的应用

本文介绍了稳定核素技术在蛋白质代谢研究中的应用原理、主要方法、研究现状等。稳定核素标记的氨基酸仅作为氨基氮的载体，将一定量的标记物带入体内，测定同一氨基酸在体内不同质量的原子百分比，计算出蛋白质的流量，合成率和分解率，解决了仅用氮平衡不能解决的问题，使蛋白质代谢的研究工作得到了进一步的深入。近年来，研究者们已将该技术用于蛋白质消化、吸收和代谢研究中，并开始用于脂肪、糖、维生素和矿物质的代谢研究。     

胰岛素在蛋白质代谢中的作用研究进展

胰岛素具有促进组织蛋白质合成,抑制蛋白质分解的作用.但这一作用往往受到严重感染、创伤等高代谢状态和其他一些激素的影响.作者就胰岛素在蛋白质代谢中的作用机制和影响胰岛素作用的因素作如下综述.     

蛋白质组学及其在脑科学研究中的应用

蛋白质组（proteome）是指细胞或组织所表达的全部蛋白质的集合体，而蛋白质组学（proteomics）则是指研究蛋白质组的科学。2001年人类基因组计划的顺利完成，标志着后基因组时代的到来，转录组学、蛋白质组学以及代谢组学蓬勃发展。但是，蛋白质才是生物体执行功能的直接载体，使得蛋白质组学的研究尤显重要。而脑在解剖、组织、细胞以及分子水平的复杂性，为利用蛋白质组学的高通量、高效率分析技术提供了良好的切入点。     

人肺腺癌组织的血清蛋白质组学研究

目的采用以肿瘤免疫学与蛋白质组学研究技术有机地结合为基础的血清蛋白质组学研究体系(SERPA)筛选肺腺癌相关抗原。方法应用SERPA对4例人肺腺癌组织进行研究,分析肺腺癌组织总蛋白分别与肺腺癌患者的自身血清以及正常对照血清反应的W estern b lot图谱,识别鉴定差异反应的蛋白质。结果获得了分辨率较高的人肺腺癌组织与患者的自身血清以及正常对照血清的W estern b lot图谱,共识别27±5个差异反应的蛋白质。对其中的部分差异蛋白质点进行了肽质指纹图分析,鉴定出一些与细胞生长增殖、细胞代谢、细胞周期调控、信号转导等有关的肺腺癌相关抗原。结论本研究为进一步筛选用于肺腺癌诊断、治疗和预后评估的肺腺癌分子标志物奠定了坚实的基础。     

~(15)N-甘氨酸示踪法在运动动物蛋白质代谢实验中的应用

目的：用稳定性同位素技术观察运动对动物体内蛋白质代谢的影响。方法：游泳动物为运动模型，用１５Ｎ－甘氨酸作为示踪剂，进行蛋白质代谢实验。结果：运动使动物的蛋白质流率、分解率均增高；心肌的蛋白质合成时间加快，合成量降低；使肝脏的蛋白质合成功能增强，分解速度降低。结论：用１５Ｎ－甘氨酸示踪法研究运动对蛋白质代谢的影响，所得结果准确可靠。     

总体蛋白质代谢研究中稳定同位素技术的应用

稳定同位素不具有放射性,使用安全,适于人体营养学研究。本文介绍了稳定同位素示踪技术在总体蛋白质代谢研究中的应用原理、主要方法,并对不同方法的优缺点进行了比较,同时分析了内脏器官对稳定同位素标记的氨基酸的代谢作用。     

进入医学影像诊断水平的PET-CT

PET的全称是正电子发射体层成像，它是采用正电子放射性核素与人体内某些代谢活性物质结合，来反映不同组织器官内的局部血流量、氧利用率、葡萄糖和蛋白质代谢等指标，达到无创伤性诊断疾病的目的。如肿瘤组织对葡萄糖的摄取远远大于正常组织，这在肿瘤组织部位会形成浓聚灶，PET可以定量研究其浓聚程度，实现对肿瘤组织与正常组织的区分。     

瘦素、肥胖与青春期发育

瘦素是由肥胖基因编码的一种分泌型的蛋白质,其作用主要在于调节体重、脂肪和能量代谢。青春期的发动需要一定量的体重或是体脂的贮存,瘦素可能是脂肪组织发出的给生殖系统一种特殊的代谢信号。现就瘦素与肥胖及青春期发育关系的研究进展作以综述。     

感染机体糖代谢异常机制的研究进展

本文从肝的糖代谢、周围组织葡萄糖摄取和利用三个方面对感染机体糖代谢异常机制的研究进展进行综述。在感染的不同代谢阶段肝糖原生成变化，可能与肝细胞膜激素信息系统改变有关。周围组织胰岛素抵抗导致了葡萄糖摄取和转运障碍，炎症细胞糖酵解增加可能是引起感染机体高乳酸血症的主要原因。     

肿瘤与营养

目的 探讨肿瘤病人的营养状况和肿瘤与营养的关系，为肿瘤病人营养提供基础。方法 回顾性复习近10年来国内外有关献20余篇。结果 50％恶性肿瘤病人存在蛋白营养不良。肿瘤病人的代谢以无氧酵解为主，血浆高密度脂蛋白水平低，使用脂肪乳时应慎重；在蛋白质供谢中某种特定氨基酸（asparagine天冬酰氨酸methionine蛋氨酸）作为必需氨基酸，谷氨酰胺－谷氨酸、亮氨酸、组氨酸及牛磺酸浓度低，免疫球蛋白和Ｔ淋巴细胞活性下降。营养支持，可以改善病人的营养状况，提高对手术和化疗的耐受性；精氨酸强化的肠外营养提高机体的体液和细胞免疫力。体外试验肿瘤细胞，应用hGH能够诱导肿瘤细胞分化，促使静止期细胞群进入增殖周期，为提高肿瘤对细胞周期时相特异性药物的敏感性提供了基础。结论 对第１例肿瘤病人都应该进行营养评价并予适当的营养支持。     

Dietary induction of rat liver fatty acid binding protein

Fatty acid binding protein (FABP) present in liver, myocardium, intestine and adipose tissue is involved in the intercellular metabolism of long chain fatty acids. It is known that lipogenic enzymes respond to dietary manipulation, so in the present study we investigated the possible changes induced by high carbohydrate and high fat diets on FABP. The binding activity for [¹⁴C] palmitoyl CoA to FABP fraction was 120% and 148% of control in response to high carbohydrate and high fat diets respectively. These changes in FABP concentration indicate involvement of this protein in the regulation of fatty acid metabolism within the cell. fatty acid binding protein, metabolism     

Differential response of protein metabolism in splanchnic organs and muscle to pectin feeding

The aim of the present study was to determine whether the addition of soluble fibre in the diet affected protein metabolism in the intestinal tissues, some visceral organs and in skeletal muscle. A diet supplemented with pectin (80 g/kg) was fed to young growing rats and the effect on organ mass and protein metabolism in liver, spleen, small and large intestines and gastrocnemius muscle was monitored and compared with the control group. Protein synthesis rates were determined by measuring [13C]valine incorporation in tissue protein. In the pectin-fed rats compared with the controls, DM intake and body weight gain were reduced (9 and 20 %, respectively) as well as gastrocnemius muscle, liver and spleen weights (6, 14 and 11 %, respectively), but the intestinal tissues were increased (64 %). In the intestinal tissues all protein metabolism parameters (protein and RNA content, protein synthesis rate and translational efficiency) were increased in the pectin group. In liver the translational efficiency was also increased, whereas its protein and RNA contents were reduced in the pectin group. In gastrocnemius muscle, protein content, fractional and absolute protein synthesis rates and translational efficiency were lower in the pectin group. The stimulation of protein turnover in intestines and liver by soluble fibre such as pectins could be one of the factors that explain the decrease in muscle turnover and whole-body growth rate.     

Protein turnover and requirements in the healthy and frail elderly

There are as yet no definitive data that warrant the establishment of evidence-based dietary protein recommendations for the elderly. We reviewed the relevance of the new 2002 recommended protein intake of 0.80 g/kg body weight.d for adults to healthy and frail elderly persons. We found that data from published nitrogen balance studies indicate that, a higher protein intake of 1.0 - 1.3 g/k.d is required to maintain nitrogen balance in the healthy elderly, which may be explained by their lower energy intake and impaired insulin action during feeding compared with young persons. Although it needs to be confirmed, a decrease in efficiency of protein utilization with aging may also dictate a higher protein-intake recommendation. Measures of the dynamic aspects of protein metabolism done in the postabsorptive state have shown no change in whole body protein turnover per unit of active metabolic tissue with aging. However, the contribution of muscle protein to wholebody protein metabolism was significantly reduced in the elderly, and explained by their reduced muscle mass and lower rates of myofibrillar protein turnover. Consequently, the contribution of nonmuscle protein, especially that of visceral tissue whose rates of protein turnover are known to be more rapid was proportionally greater with aging. It is conceivable that higher protein consumption rates could compensate for the decrease in availability of muscle amino acids and spare the muscle mass. Despite a paucity of data on the frail elderly population, we present a rationale to justify a greater protein intake of at least equivalent to that of their healthy counterparts. We propose that higher protein intakes for the elderly, and especially the frail population, than those presently recommended may minimize the sarcopenia of aging and thereby protect against some of the health risks of aging.     

An integrative approach to in-vivo protein synthesis measurement: from whole tissue to specific proteins

PURPOSE OF REVIEW: In-vivo estimation of protein turnover by stable isotopes in animals and humans has provided much relevant information on metabolic regulation and alterations for decades. While it was first appreciated at the whole body level in the 1970s and 1980s, new approaches have allowed inter-organ or tissue protein turnover rates to be measured, notably the incorporation rate of a labelled amino acid in muscle. These technical improvements have recently been completed by new isolation methods for the study of protein synthesis rates in various muscle and hepatic protein fractions in different blood cells or tissues such as bone and skin. RECENT FINDINGS: This new insight into tissue protein synthesis opens the door for exploration of single proteins, which may be fully achievable in the near future through the combination of proteomics analysis and technical progress in mass spectrometry. This is, therefore, a new area in which not only quantitative but also qualitative changes in specific proteins will be considered for a fully integrative approach to assessing protein metabolism in physiology and disease. SUMMARY: To understand the mechanisms by which protein metabolism is altered during physiopathological situations, it is of importance to measure the effect on specific proteins rather than on the body as a whole. Procedures are currently under development with the aim of isolating individuals proteins and to measure their synthesis rates by isotopic methods. Such technical progress is needed to gain a better understanding of the regulation of protein metabolism in situations in which loss of body protein mass occurs.     

Mathematical integration of protein metabolism in growing lambs

A mathematical integration of whole-body protein synthesis and degradation based on protein metabolism in 10 individual tissues in growing lambs is described. The tissues represented are adipose, central nervous system (CNS), gastrointestinal tract (GIT), heart, kidney, liver, muscle, pancreatic and salivary glands (PSG), reticuloendothelial system (RES) and skin, together with a blood pool of amino acids. The fluxes represented in the equations are generally assumed to follow simple or modified mass-action kinetics. The fractional rates for protein synthesis in each tissue were calculated from published values for lambs, where these were available, or alternatively derived using assumptions based on data obtained with rats. The initial protein content of each tissue and the fractional degradation rate were assigned values calculated using data from a slaughter experiment. The model was used to examine whole-body protein synthesis at different rates of growth and to compare the relative contributions of each tissue. The GIT (25-26%) and skin (23-26%) had the highest contributions to total protein synthesis, followed by muscle (21-26%), liver (13-14%), RES (6-7%) and PSG (3-6%), while adipose, CNS, heart and kidney together contributed less than 5%. These values agree reasonably well with experimental values, and thus the model can be used to examine the effect of different growth rates on protein metabolism and its associated energy costs.     

Anabolic and catabolic mediators of intestinal protein turnover: a new experimental approach

Studies on regulation of protein turnover in skeletal muscle have revealed the important contributions of protein synthesis and catabolism to tissue protein balance, and have identified a host of specific anabolic and catabolic stimuli and biochemical mechanisms that regulate these processes. This knowledge is critical to current efforts designed to promote anabolism and limit atrophy. Of the tissues with a potentially large contribution to whole-body amino acid metabolism, protein turnover of the intestine stands out as being poorly understood. The intestine is subject to complexities in regulation of its metabolism that are not apparent for other tissues. The study of intestinal protein turnover also entails some important technical challenges. We recently developed an in-situ experimental system for study of intestinal mucosal protein synthesis with the following unique features: multiple observations within an animal; controlled delivery of nutritional stimuli to the apical side, basolateral side, or both; and luminal delivery of tracer in a flooding dose for determination of protein synthesis. We have begun to use the system to test the specific roles of individual luminal nutrients in regulation of mucosal protein synthesis. We have also used protease gene expression as an index of potential regulation of catabolic pathways.