New players in high fat diet-induced obesity: LETM1 and CTMP

Objective

Obesity contributes to insulin resistance and is a risk factor for diabetes. C-terminal modulator protein (CTMP) and leucine zipper/EF-hand-containing transmembrane protein 1 (LETM1) have been reported to influence the phosphoinositide 3-kinase (PI3K)/protein kinase B (PKB) signaling pathway via the modulation of PKB activity, a key player for insulin signaling. However, it remains unclear whether CTMP and LETM1 are associated with PI3K/PKB signaling in mouse models of obesity.

Materials/Methods

To address this question, we used two different mouse models of obesity, including high-fat diet (HFD)-induced diabetic mice and genetically modified obese mice (ob/ob mice). The levels of insulin-signaling molecules in these mice were determined by immunohistochemical and Western blot analyses. The involvement of CTMP and LETM1 in PI3K/PKB signaling was investigated in HEK293 cells by transient transfection and adenovirus-mediated infection.

Results

We found that the levels of insulin receptor, phosphorylated PKB, and LETM1 were lower and the level of CTMP was higher in the adipose tissue of obese mice on an HFD compared to lean mice on a chow diet. Similar results were obtained in ob/ob mice. In HEK293 cells, the activation of PKB increased the LETM1 level, and inhibition of PKB increased the CTMP level. The overexpression of CTMP suppressed the insulin-induced increase in PKB phosphorylation, which was abrogated by co-overexpression with LETM1.

Conclusion

These results suggest that CTMP and LETM1 may participate in impaired insulin signaling in the adipose tissue of obese mice, raising the possibility that these parameters may serve as new candidate biomarkers or targets in the development of new therapeutic approaches for diabetes.     

PI3K/PKB信号通路在TGF-β_1诱导人肝星状细胞表达骨桥蛋白中的作用

目的:研究磷脂酰肌醇3-激酶/蛋白激酶B(PI3K/PKB)信号通路在转化生长因子β1(TGF-β1)诱导人肝星状细胞表达骨桥蛋白(OPN)的调控作用。方法:体外培养LX-2人肝星状细胞株,予TGF-β1(终浓度2.5、5、10、20μg/L)刺激24 h或予TGF-β1(终浓度10μg/L)刺激12 h、24 h、48 h;先经PI3K/PKB信号通路特异性抑制剂wortmannin(0.1μmol/L)预处理1 h,再予10μg/L TGF-β1刺激24 h,收集细胞,采用real-time PCR及Western blotting法检测OPN表达情况。结果:TGF-β1能够促进LX-2细胞表达OPN,在一定浓度和时间范围内,其表达量随着TGF-β1浓度和时间的增加而增加,呈剂量和时间依赖性关系;经wortmannin预处理再予TGF-β1刺激的LX-2细胞,与对照组相比,OPN表达受到明显抑制(P0.01)。结论:TGF-β1对LX-2人肝星状细胞OPN表达具有诱导作用,此作用可能受PI3K/PKB信号通路的调控。     

葛根芩连汤对糖尿病大鼠早期视网膜病变影响的实验研究

[目的]探讨葛根芩连汤对糖尿病大鼠早期视网膜病变的治疗作用。[方法]选取45只Wistar大鼠,链脲佐菌素(STZ)腹腔注射,制作糖尿病模型,糖尿病模型建立后随机分为DM组(糖尿病组)、DM+NS组(糖尿病生理盐水注射组)和实验组(DM+葛根芩连汤组)。模型建立后,DM组不做任何处理,实验组给予葛根芩连汤8.2 g/kg,DM+NS组注射等体积的生理盐水。对糖尿病大鼠的空腹血糖、血浆胰岛素、体质量、甘油三酯(TG)和高密度脂蛋白(HDL-C)的含量进行检测,以观察葛根芩连汤降糖降脂功效;通过免疫印迹(Westem blot)法检测视网膜蛋白激酶B(PKB)以及炎性相关因子——细胞间黏附分子-1(ICAM-1)的表达情况;利用苏木-伊红(HE)染色观察各组大鼠的超微结构;采用TUNEL法检测凋亡相关蛋白C-myc的凋亡指数。[结果]与DM组和DM+NS组比较,实验组大鼠空腹血糖明显降低、体质量明显增加,差异有统计学意义(P0.05);与DM组和DM+NS组比较,实验组大鼠血胰岛素含量增加,组间比较差异有统计学意义(P0.05);与DM组和DM+NS组比较,实验组大鼠TG明显降低而HDL-C明显升高(P0.05)。通过Westem blot检测可见与DM组和DM+NS组比较,实验组大鼠PKB的表达明显增加、ICAM-1的表达明显下降,差异有统计学意义(P0.05);光镜下HE染色观察到各组超微结构:DM组可见核固缩、浓染,核膜内陷,染色质边集,凋亡小体出现,实验组变化明显减轻(P0.05);与DM组和DM+NS组比较,实验组中凋亡相关蛋白C-myc明显减少(P0.05)。[结论]葛根芩连汤能够改善大鼠空腹血糖、血浆胰岛素及体质量等的变化,具有较好的降糖降脂作用,能通过增加PKB的表达及抑制糖尿病大鼠视网膜病变的炎症反应减轻或延缓糖尿病的发生和发展。     

ShcC proteins: Brain aging and beyond

To date, most studies of Shc family of signaling adaptor proteins have been focused on the near-ubiquitously expressed ShcA, indicating its relevance to age-related diseases and longevity. Although the role of the neuronal ShcC protein is much less investigated, accumulated evidence suggests its importance for neuroprotection against such aging-associated conditions as brain ischemia and oxidative stress. Here, we summarize more than decade of studies on the ShcC expression and function in normal brain, age-related brain pathologies and immune disorders with a focus on the interactions of ShcC with signaling proteins/pathways, and the possible implications of these interactions for changes associated with aging.     

IGF信号通路关键蛋白IGF1、IGF1R和AKT在原发性肺腺癌中的表达及意义

目的检测IGF信号通路关键蛋白IGF1，IGF1R和AKT在原发性肺腺癌中的表达，探讨其与临床病理学特征和生存时间的关系。方法采用免疫组化方法和免疫印迹技术检测IGF1，IGF1R和AKT在31例原发性肺腺癌及12例良性肺病变组织中的表达。结果IGF1、IGF1R和AKT在肺腺癌中的表达率分别为41．9％（13／31）、67．7％（21／31）和51．6％（16／31），显著高于良性肺组织（P值分别为0．0252、0．0016和0．0071）。IGF1和IGF1R及IGF1和AKT在肺腺癌中表达呈显著相关（P值分别为0．0344和0．0179）。晚期肺癌（Ⅲ＋Ⅳ）IGF1和IGF1R表达显著高于早期（Ⅰ＋Ⅱ）（P值分别为0．0109和0．0303）。IGF1、IGF1R和AKT在伴有淋巴结转移肺癌中的表达显著高于无淋巴结转移肺癌（P值分别为0．0468、0．0490和0．0443）。低分化肺癌中IGF1和IGF1R表达显著高于中或高分化肺癌（P值分别为0．0484和0．0291）。IGF1和IGF1R阳性患者的生存时间显著短于阴性者（IGF1：10比14个月，P=0．0103；IGF1R：13比26个月，P=0．0056）。IGF1和IGF1R是肺腺癌预后的影响因素，AKT无预后意义。结论IGF信号通路关键蛋白IGF1、IGF1R和AKT表达在肺腺癌的发生和发展中可能起重要作用，进一步的研究有望展示其在肺癌预后和治疗方面的意义。     

Cyclic AMP enhances resolution of allergic pleurisy by promoting inflammatory cell apoptosis via inhibition of PI3K/Akt and NF-κB

Selective and timely induction of apoptosis is an effective means of resolving inflammation. The effects and putative mechanisms by which cyclic AMP (cAMP) modulates leukocyte apoptosis in vivo are still unclear. The present study aims at identifying intracellular pathways underlying the ability of cAMP elevating agents to resolve eosinophilic inflammation in a model of allergic pleurisy in mice. Ovalbumin (OVA) challenge of immunized mice induced eosinophil recruitment that peaked at 24 h and persisted till 48 h. Treatment with the PDE4 inhibitor rolipram, cAMP mimetic db-cAMP or adenylate cyclase activator forskolin, at 24 h after antigen-challenge resulted in profound resolution of eosinophilic inflammation, without a decrease of mononuclear cell numbers. There was a concomitant increase in number of apoptotic cells in the pleural cavity. The effects of rolipram and db-cAMP were inhibited by the PKA inhibitor H89. Inhibition of PI3K/Akt or NF-κB induced resolution of inflammation that was associated with increased apoptosis. OVA-challenge resulted in a time-dependent activation of Akt and NF-κB, which was blocked by treatment with rolipram or PI3K/Akt pathway inhibitors. Thus, cAMP elevating agents resolve established eosinophilic inflammation by inducing leukocyte apoptosis. Mechanistically, the actions of cAMP are dependent on PKA and target a PI3K/Akt-dependent NF-κB survival pathway.     

糖尿病大鼠蛋白激酶B信号传导系统表达的实验研究

目的探讨在糖尿病大鼠胰腺中磷酸化蛋白激酶B（PKB）表达的变化及胰腺β细胞增殖及凋亡的变化。方法向糖尿病大鼠腹腔内注射链脲佐菌素（STZ）,实验中监测血糖,用免疫组化染色法观察胰腺中胰岛素、胰离血糖素、磷酸化PKB的表达,以及胰腺β细胞的增生及凋亡情况。结果糖尿病大鼠胰腺中胰岛素（46．62±4．35）％、磷酸化PKB（22．21±2．73）％的表达水平较对照组[（55．54±4．39）％与（27．37±2．93）％]均降低,而胰高血糖素（22．08±2．72）％的表达水平较对照组（17．27±1．92）％升高,糖尿病组β细胞凋亡率（31．17±2．19）％明显高于对照组（18．90±2．09％）（均P〈0．01）,2组大鼠胰腺β细胞均无明显增生。结论磷酸化PKB在糖尿病大鼠胰腺中的表达水平下降,PKB介导的信号传导系统能促进胰岛素的分泌,减少胰高血糖素的分泌,抑制胰腺β细胞的凋亡。     

Focal adhesion kinase: a potential target in cancer therapy

Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase that plays an important role in signal transduction pathways that are initiated at sites of integrin-mediated cell adhesions and by growth factor receptors. FAK is a key regulator of survival, proliferation, migration and invasion: processes that are all involved in the development and progression of cancer. FAK is also linked to oncogenes at both a biochemical and functional level. Moreover, overexpression and/or increased activity of FAK is common in a wide variety of human cancers, implicating a role for FAK in carcinogenesis. Given the important role of FAK in a large number of processes involved in tumorigenesis, metastasis and survival signalling FAK should be regarded as a potential target in the development of anti-cancer drugs. Therefore, selective inhibitors of FAK need to be developed. Combination of these selective FAK inhibitors with cytotoxic agents could be a very promising anti-cancer therapy.     

The role of integrin-linked kinase (ILK) in cancer progression

Integrin-linked kinase (ILK) is an intracellular protein, which interacts with the cytoplasmic domains of integrin beta1 and beta3 subunits. ILK is a 59kDa protein containing a phosphoinositide phospholipid-binding domain flanked by an N-terminal ankyrin repeat domain and a C-terminal serine/threonine protein kinase domain. Genetic and biochemical evidence have established an essential role of ILK in connecting integrins to the actin cytoskeleton. Apart from integrins, ILK interacts with several adaptor and signaling proteins resulting in its activation and localization to focal adhesion plaques. The kinase activity of ILK is stimulated upon integrin engagement, as well as by growth factors and chemokines in a PI-3Kinase-dependent manner. ILK can mediate the phosphorylation of a variety of intracellular substrates, most notable of which are: protein kinase B (PKB/Akt), glycogen synthase kinase-3 (GSK-3) and myosin light chain. Gain and loss of function strategies have shown that overexpression, and/or constitutive activation of ILK results in oncogenic transformation and progression to invasive and metastatic phenotypes. In addition ILK expression and activity are upregulated in several types of cancers. In this review, we summarize the adaptor and signaling properties of ILK, and also progress in the identification of therapeutic strategies for inhibition of ILK activity.