主要内容：人I型糖尿病中的关键免疫细胞；糖尿病与免疫系统“杀手细胞”；锻炼通过诱生PGC1-α促进脂肪代谢和血糖平衡；单层细胞视网膜色素上皮组织被激活成多能干细胞；鉴别出涉及精子成熟过程的一种新的非编码RNA；饮食中补充叶绿素对癌症的化学预防作用。

　　焦点动态：糖尿病与免疫系统“杀手细胞”。

1. 人I型糖尿病中的关键免疫细胞
【动态】
　　I型糖尿病患者胰岛β细胞被破坏与胰岛自身反应性T细胞之间的直接联系从未被证明，对诊断后的疾病进程也所知无几。最近美国科学家的研究第一次对此有了直接的证据。冷冻胰腺样本来自病程在1周到超过50年的45例死亡患者的遗体捐赠，14个非糖尿病患者对照样本，5个有自身抗体的非糖尿病患者样本，2个孕期糖尿病患者样本，以及6例II型糖尿病患者样本。系统检查样本的组织切片是否存在有足够胰岛素的β细胞、CD8阳性的胰岛病变和I型HLA 过度表达。最后，对表达HLA-A2的样本的连续切片用四聚体染色法针对6种已知确定的与I型糖尿病有关的胰岛自身抗原进行CD8 T细胞反应性检查。在临床确诊后最长达8年的分组患者胰岛样本中单一和多种CD8 T细胞反应性都检测到了。I型糖尿病特有的I型HLA 过度表达和胰岛炎等病理特征存在于一小部分病程很长的患者中。在受影响的器官中，胰岛病变持续存在，表现为不同程度的浸润和β细胞丢失。该研究为人体胰岛自身反应性提供了第一个直接证据并强调了发病历程的异质性和长期性。

【点评】
　　该研究第一次在人体组织中确证了触发I型糖尿病胰腺损坏的特定免疫系统T细胞。其发现在人体上验证了老鼠实验中发现的一些重要的疾病特征并为打断疾病进程提供了切入点。

【参考论文】
J Exp Med. 2012 Jan 3. [Epub ahead of print]
Demonstration of islet-autoreactive CD8 T cells in insulitic lesions from recent onset and long-term type 1 diabetes patients
Coppieters KT, Dotta F, Amirian N, et al.
A direct association of islet-autoreactive T cells with β cell destruction in human pancreatic islets from type1 diabetes (T1D) patients has never been demonstrated, and little is known about disease progression after diagnosis. Frozen pancreas samples were obtained from 45 cadaveric T1D donors with disease durations ranging from 1 wk to >50 yr, 14 nondiabetic controls, 5 nondiabetics with islet autoantibodies, 2 cases of gestational diabetes, and 6 T2D patients. Sections were systematically analyzed for the presence of insulin-sufficient β cells, CD8(+) insulitic lesions, and HLA class I hyperexpression. Finally, consecutive sections from HLA-A2-expressing individuals were probed for CD8 T cell reactivity against six defined islet autoantigens associated with T1D by in situ tetramer staining. Both single and multiple CD8 T cell autoreactivities were detected within individual islets in a subset of patients up to 8 yr after clinical diagnosis. Pathological features such as HLA class I hyperexpression and insulitis were specific for T1D and persisted in a small portion of the patients with longstanding disease. Insulitic lesions consistently presented in a multifocal pattern with varying degrees of infiltration and β cell loss across affected organs. Our observations provide the first direct proof for islet autoreactivity within human islets and underscore the heterogeneous and chronic disease course.
 
2. 糖尿病与免疫系统“杀手细胞”
【动态】
　　T细胞受体（TCR）通过在有主要组织相容性复合物（MHC）分子的情况下结合细胞表面存在的外源性多肽来协调指挥免疫反应。有效的机体免疫需要能够识别所有可能的外源性多肽-MHC分子，否则会有存在免疫漏洞的风险致使病原体能够迅速进化并利用此漏洞。目前还不清楚不到108种的人体TCR是如何针对以MHC的复合物分子（超过1015种多肽-MHC分子）呈现的从20种生肽氨基酸产生的众多不同多肽成功提供免疫保护。一种可能是T细胞免疫包含了极高水平的受体简并性，使得每种TCR能够识别多种多肽。但是，这种TCR简并性的程度从未被充分量化过。英国科学家最近通过一项综合实验和数学分析表明源于患者的一种与I型糖尿病病理相关的自体免疫CD8+ T 细胞系在一种MHC-I分子存在的情况下能够识别超过一百万种十肽。发现大量多肽是比野生型参照物源于前胰岛素的多肽（ALWGPDPAAA）更好的TCR激动剂。来自超过108种多肽的 RQFGPDFPTI 肽比参照物效力强100倍，而在10个位置的氨基酸中只有7号氨基酸不同。量化这种以前未曾留意的高水平的 CD8+ T 细胞交叉反应性代表了向了解适应性免疫的系统要求迈出的重要一步并突显了TCR简并很可能是自体免疫疾病的致病因素。

【点评】
　　该研究第一次证明人体杀手T细胞会无意中摧毁生产胰岛素的细胞并因此有可能更新我们对I型糖尿病的认识。

【参考论文】
Journal of Biological Chemistry, 2011; 287 (2): 1168 DOI: 10.1074/jbc.M111.289488
A Single Autoimmune T Cell Receptor Recognizes More Than a Million Different Peptides   
L. Wooldridge, J. Ekeruche-Makinde, H. A. van den Berg, et al.  
The T cell receptor (TCR) orchestrates immune responses by binding to foreign peptides presented at the cell surface in the context of major histocompatibility complex (MHC) molecules. Effective immunity requires that all possible foreign peptide-MHC molecules are recognized or risks leaving holes in immune coverage that pathogens could quickly evolve to exploit. It is unclear how a limited pool of <108 human TCRs can successfully provide immunity to the vast array of possible different peptides that could be produced from 20 proteogenic amino acids and presented by self-MHC molecules (>1015 distinct peptide-MHCs). One possibility is that T cell immunity incorporates an extremely high level of receptor degeneracy, enabling each TCR to recognize multiple peptides. However, the extent of such TCR degeneracy has never been fully quantified. Here, we perform a comprehensive experimental and mathematical analysis to reveal that a single patient-derived autoimmune CD8+ T cell clone of pathogenic relevance in human type I diabetes recognizes >one million distinct decamer peptides in the context of a single MHC class I molecule. A large number of peptides that acted as substantially better agonists than the wild-type “index” preproinsulin-derived peptide (ALWGPDPAAA) were identified. The RQFGPDFPTI peptide (sampled from >108 peptides) was >100-fold more potent than the index peptide despite differing from this sequence at 7 of 10 positions. Quantification of this previously unappreciated high level of CD8+ T cell cross-reactivity represents an important step toward understanding the system requirements for adaptive immunity and highlights the enormous potential of TCR degeneracy to be the causative factor in autoimmune disease.

3. 锻炼通过诱生PGC1-α促进脂肪代谢和血糖平衡
【动态】
　　锻炼对哺乳动物的很多器官和系统有益，一些最为熟知的对肌肉的作用是通过转录助激活因子PPAR-γ 和PGC1-α介导的。美国科学家最近在老鼠实验中发现肌肉中PGC1-α的表达刺激了一种新发现的激素鸢尾素即膜蛋白FNDC5的表达增加。在细胞培养以及动物实验中鸢尾素作用于白色脂肪细胞刺激UCP1表达和广泛的棕色脂肪样发育程序。在老鼠和人锻炼可以诱导生产鸢尾素，血液中鸢尾素水平小幅升高能够增加老鼠的能量消耗但不改变运动量或食量。结果可以改善肥胖和血糖平衡。以超重同时有糖尿病前期症状的不常运动的老鼠为实验对象，哈佛大学的科学家发现这些老鼠接受鸢尾素注射后体内白色脂肪向棕色脂肪转化的基因被激活。鸢尾素还能提高高脂饮食老鼠的葡萄糖耐受能力。注射鸢尾素十天后，老鼠的血糖和胰岛素水平改善，这能阻止糖尿病发作，帮助减肥。鸢尾素可能能够用于治疗人体代谢疾病和其他能够通过锻炼改善的疾病。

【点评】
　　该研究发现了一种与锻炼有关的身体自然生产的物质有明显的潜力预防和治疗糖尿病、肥胖症等代谢疾病。但是在没有最终人体应用结果的情况下，一切都只是可能。

【参考论文】
Nature (2012) doi:10.1038/nature10777
A PGC1-α-dependent myokine that drives brown-fat-like development of white fat and thermogenesis
Pontus Boström, Jun Wu, Mark P. Jedrychowski, et al. 
Exercise benefits a variety of organ systems in mammals, and some of the best-recognized effects of exercise on muscle are mediated by the transcriptional co-activator PPAR-γ co-activator-1 α (PGC1-α). Here we show in mouse that PGC1-α expression in muscle stimulates an increase in expression of FNDC5, a membrane protein that is cleaved and secreted as a newly identified hormone, irisin. Irisin acts on white adipose cells in culture and in vivo to stimulate UCP1 expression and a broad program of brown-fat-like development. Irisin is induced with exercise in mice and humans, and mildly increased irisin levels in the blood cause an increase in energy expenditure in mice with no changes in movement or food intake. This results in improvements in obesity and glucose homeostasis. Irisin could be therapeutic for human metabolic disease and other disorders that are improved with exercise.

4. 单层细胞视网膜色素上皮组织被激活成多能干细胞
【动态】
　　美国科学家最近在在眼睛后部的单层细胞视网膜色素上皮组织里鉴定出中枢神经系统的成体干细胞。这项新研究表明视网膜色素上皮组织也拥有自我更新的干细胞，在合适条件下能被唤醒产生活跃增长的细胞培养物。它们也能够被诱导形成其他细胞类型。此外，这些细胞还有可能能够解释在眼睛其他组织类型中出现的疾病。它们的存在也提示着可能存在某种方法刺激上百万老年性视网膜黄斑退化疾病病人的眼睛受控修复。

【点评】
　　该研究发现并使单层细胞视网膜色素上皮组织干细胞成为可得的来自人体中枢神经系统的多能干细胞用于细胞命运决定、替代治疗以及疾病模型的研究。

【参考论文】
Cell Stem Cell, Volume 10, Issue 1, 88-95, 6 January 2012
Adult Human RPE Can Be Activated into a Multipotent Stem Cell that Produces Mesenchymal Derivatives
Enrique Salero, Timothy A. Blenkinsop, Barbara Corneo, et al.
The retinal pigment epithelium (RPE) is a monolayer of cells underlying and supporting the neural retina. It begins as a plastic tissue, capable, in some species, of generating lens and retina, but differentiates early in development and remains normally nonproliferative throughout life. Here we show that a subpopulation of adult human RPE cells can be activated in vitro to a self-renewing cell, the retinal pigment epithelial stem cell (RPESC) that loses RPE markers, proliferates extensively, and can redifferentiate into stable cobblestone RPE monolayers. Clonal studies demonstrate that RPESCs are multipotent and in defined conditions can generate both neural and mesenchymal progeny. This plasticity may explain human pathologies in which mesenchymal fates are seen in the eye, for example in proliferative vitroretinopathy (PVR) and phthisis bulbi. This study establishes the RPESC as an accessible, human CNS-derived multipotent stem cell, useful for the study of fate choice, replacement therapy, and disease modeling.

5. 鉴别出涉及精子成熟过程的一种新的非编码RNA
【动态】
　　中国科学家的最新研究证实一新长链非编码RNA以小RNA前体分子形式参与调节了精子成熟，他们利用大鼠附睾 cDNA 文库筛选克隆到一个附睾特异的新长链非编码RNA分子(HongrES2)。该RNA分子3’端序列和另一个附睾特异编码基因，羧基酯酶ces7的3’端序列完全同源，并能够在细胞水平下调CES7的蛋白表达。进一步的研究表明，HongrES2能够生成一个23bp的小RNA分子mil-Hongres2，而体内外实验都证明HongrES2对CES7的调节作用即为mil-hongres2对ces7 的直接靶向作用所致。另外该小RNA分子的生成量在正常生理水平很低，受到附睾炎症刺激后短时间内激增，表明其从前体到成熟体的过程受到严格调控；同时观察到如果整体过表达其小分子成熟体，大鼠精子的运动和获能等精子附睾成熟过程均受到影响。这些初期研究结果提示HongrES2以小分子调节RNA的前体形式稳定存在于大鼠附睾组织中，参与维持附睾精子成熟所需特定的微环境。

【点评】
　　该研究有助于加深对精子成熟的相关因子的理解并提高临床不育的分子诊断及治疗水平，还可以调控生殖有效避孕。

【参考论文】 china
PLoS One. 2011;6(10):e26053. Epub 2011 Oct 12.
Identification and characterization of a novel non-coding RNA involved in spermmaturation
Ni MJ, Hu ZH, Liu Q, et al.
A long and ever-expanding roster of small (∼20-30 nucleotides) RNAs has emerged during the last decade, and most can be subsumed under the three main headings of microRNAs (miRNAs), Piwi-interacting RNAs (piRNAs), and short interfering RNAs (siRNAs). Among the three categories, miRNAs is the most quickly expanded group. The most recent number of identified miRNAs is 16,772 (Sanger miRbase, April 2011). However, there are insufficient publications on their primary forms, and no tissue-specific small RNAs precursors have been reported in the epididymis. Here, we report the identification in rats of an epididymis-specific, chimeric, noncoding RNA that is spliced from two different chromosomes (chromosomes 5 and 19), which we named HongrES2. HongrES2 is a 1.6 kb mRNA-like precursor that gives rise to a new microRNA-like small RNA (mil-HongrES2) in rat epididymis. The generation of mil-HongrES2 is stimulated during epididymitis. An epididymis-specific carboxylesterase named CES7 had 100% cDNA sequence homology at the 3'end with HongrES2 and its protein product could be downregulated by HongrES2 via mil-HongrES2. This was confirmed in vivo by initiating mil-HongrES2 over-expression in rats and observing an effect on sperm capacitation.

6. 饮食中补充叶绿素对癌症的化学预防作用
【动态】
　　最近的初步研究发现天然叶绿素可以抑制啮齿类动物和鱼类模型中致癌物的摄取和肿瘤发生，并改变人志愿者体内痕量14C-aflatoxin B1的摄取和生物分布。美国科学家最新研究扩展了这些有前途的发现，他们通过剂量-剂量矩阵设计检测鲑鱼中叶绿素介导的对DBC诱导的DNA化学修饰、肿瘤产生、肿瘤多样性和基因调节变化的影响。矩阵实验起用了12360条虹鳟鱼，分别喂四周0-4000ppm的叶绿素伴以0-225ppm的DBC。结果表明富含叶绿素的蔬菜中所含浓度的叶绿素能够实质性的起到癌症化学预防作用，并提示原理可能是减少致癌物的生物利用度。但是，在超过最佳浓度的DBC存在时，叶绿素的联合处理不能抑制肿瘤发生并明显提高肿瘤多样性。该发现对在不处于确证的线性关系或至少是单一终点剂效范围内的高浓度致癌物条件下进行的化学预防研究与人的关联性提出了疑问。

【点评】
　　该研究表明绿色蔬菜中的叶绿素能够化学预防环境中常见的中等水平的致癌物的致癌作用，但是在很高水平的致癌物存在下，叶绿素反而增加了肿瘤的多样性。该研究结果对于传统实验室针对老鼠和高水平致癌物进行的研究能够提供多准确的关乎健康风险的答案提出了质疑。

【参考论文】
Food and Chemical Toxicology, 2012; 50 (2): 341 DOI: 10.1016/j.fct.2011.10.065  
Cancer chemoprevention by dietary chlorophylls: A 12,000-animal dose–dose matrix biomarker and tumor study
Tammie J. McQuistan, Michael T. Simonich, M. Margaret Pratt, et al.