Serum Levels of Free Insulin-Like Growth Factor (IGF)-I in Normal Children

Serum levels of free insulin-like growth factor (IGF)-I were measured by immunoradiometric assay (IRMA) in fasting sera of 137 normal boys and 120 normal girls aged from 8 to 15 yr to study relationships between free IGF-I levels and ages, total IGF-I, IGF binding protein (IGFBP)-1, IGFBP-3, and acid-labile subunit (ALS) levels. In both sexes, serum free IGF-I levels and the ratios of free IGF-I to total IGF-I were significantly higher in the pubertal age groups than in the prepubertal age groups. Serum levels of free IGF-I showed a significant positive correlation with those of total IGF-I, IGFBP-3 and ALS, while they showed a significant negative correlation with those of IGFBP-1. These observations suggest that increase in serum free IGF-I levels during puberty is caused by a dramatic increase in total IGF-I, rather than IGFBP-3, and a decrease in IGFBP-1. Also, high free IGF-I levels may play an important role in pubertal growth spurt.     

Messenger RNA encoding the insulin-like growth factors and their binding proteins, in women with fibroids, pretreated with luteinizing hormone-releasing hormone agonists

The primary objective of this study was to suggest a possiblemechanism of action of luteinizing hormone-releasing hormoneagonist (LHRHa) on fibroids. This was performed by investigatinginsulin-like growth factor (IGF)-I, IGF-II and IGF binding protein(IGFBP)-1, -2 and -3 mRNA expression in uterine fibroids fromwomen rendered hypo-oestrogenic by LHRHa, using Northern blotanalysis. Nine women with fibroids, who were rendered hypo-oestrogenicfrom at least 4 months pretreatment with LHRHa therapy priorto undergoing myomectomy were investigated. Our results showedthat IGF-I, IGF-II, IGFBP-2 and -3 mRNAs were expressed in uterinefibroids, and that IGFBP-1 mRNA or protein was not detectedin fibroids. Western ligand blotting showed the presence ofIGFBP-2 and -3 proteins, and when compared with a group of womenwith fibroids not treated with LHRHa (B.J.Vollenhoven et al.,1993, J. Clin. Endocrinol Metab., 76, 1106–1110) we foundthat there was no difference in the relative abundance for eachof the factors between the two groups of women. Therefore, LHRHaact to decrease fibroid size via induction of a hypo-oestrogenicstate rather than by changes in the IGFs and their IGFBPs.     

Identification and Validation of Nutrient State-Dependent Serum Protein Mediators of Human CD4+ T Cell Responsiveness

Intermittent fasting and fasting mimetic diets ameliorate inflammation. Similarly, serum extracted from fasted healthy and asthmatic subjects’ blunt inflammation in vitro, implicating serum components in this immunomodulation. To identify the proteins orchestrating these effects, SOMAScan technology was employed to evaluate serum protein levels in healthy subjects following an overnight, 24-h fast and 3 h after refeeding. Partial least square discriminant analysis identified several serum proteins as potential candidates to confer feeding status immunomodulation. The characterization of recombinant IGFBP1 (elevated following 24 h of fasting) and PYY (elevated following refeeding) in primary human CD4⁺ T cells found that they blunted and induced immune activation, respectively. Furthermore, integrated univariate serum protein analysis compared to RNA-seq analysis from peripheral blood mononuclear cells identified the induction of IL1RL1 and MFGE8 levels in refeeding compared to the 24-h fasting in the same study. Subsequent quantitation of these candidate proteins in lean versus obese individuals identified an inverse regulation of serum levels in the fasted subjects compared to the obese subjects. In parallel, IL1RL1 and MFGE8 supplementation promoted increased CD4⁺ T responsiveness to T cell receptor activation. Together, these data show that caloric load-linked conditions evoke serological protein changes, which in turn confer biological effects on circulating CD4⁺ T cell immune responsiveness.     

Purification from Transformed Mouse Fibroblast of a Cell Growth Inhibitor which is an IGF-Binding Protein

Abstract

From medium conditioned by 3T3 cells, we had previously purified an inhibitory factor of Mr 45 kDa which we termed IDF45 (inhibitory diffusible factor). The protein was able to 100% inhibit stimulation induced in CEF by 1% calf serum and to reversibly prevent cell growth. We then demonstrated that IDF45 was an IGF-binding protein. Our results suggested that IDF45 was a bifunctional molecule able to bind IGF and to inhibit DNA synthesis stimulated by this hormone, but also to inhibit stimulation of DNA synthesis induced by another growth factor in serum. Indeed, its N terminal amino acid sequence has great homology with that of IGFBP-3 and IDF45 is now proposed to be named IGFBP-3 (mouse IGF binding protein). Present results show that Ha-ras transfected 3T3 cells (EJ cells), like 3T3 cells, secrete a mIGFBP-3 molecule. In addition, transfected cells secrete a doublet of an IGF-binding protein (IGFBP-28) of Mr 28 kDa which is not secreted by untransformed 3T3 cells. IGFBP-28 has been purified and characterized in this work. Various results suggest that IGFBP-28 is not a degradation product of mIGFBP-3. Its N terminal amino acid sequence was different from that of mIGFBP-3. IGFBP-28 inhibited DNA synthesis stimulated by IGF-I, but much more IGFBP-28 protein than mIGFBP-3 was required to prevent this stimulation. In agreement with this result, IGFBP-28 has low affinity for IGF-I. In contrast, IGFBP-28 has high affinity for IGF-II. Like mIGFBP-3, IGFBP-28 was able to inhibit the stimulation induced by serum in CEF and to reversibly prevent growth, though with a specific activity lower than that of mIGFBP-3. It has also the capacity to inhibit stimulation of DNA synthesis induced by high molecular weight serum proteins depleted in IGF-I and II.

In conclusion we have shown that transformation of 3T3 cells with Ha-ras induced the synthesis of a new IGF binding protein in medium conditioned by normal 3T3 cells. Our results suggest that IGFBP-28 like mIGFBP-3 is a bifunctional protein able to inhibit stimulation induced by IGF and by serum proteins different from IGFs.     

胰岛素样生长因子结合蛋白-4对大鼠骨髓间充质干细胞增殖和神经分化的影响

目的探究胰岛素样生长因子结合蛋白4(IGFBP4)对骨髓间充质干细胞(BMSC)增殖和神经分化的影响。方法通过全骨髓贴壁法分离培养BMSCs,免疫荧光检测IGFBP4在P1、P4、P6、P8和P10 BMSCs的表达。取第4代BMSC细胞,分为单纯培养基组和添加IGFBP4组,用CCK8试剂盒检测单纯培养基组和添加IGFBP 4组吸光度值A450 nm。再将BMSC细胞分为3组:neurocult组、EGF+b FGF组、EGF+b FGF+IGFBP4组,每组连续测定7 d,每天6个平行孔,诱导培养基Neuro Cult培养再分别添加EGF+b FGF和EGF+b FGF+IGFBP4,诱导其向神经祖细胞分化,免疫荧光染色检测Nestin和Sox-2表达,并观察神经球数量和细胞增殖活性。结果成功获得原代大鼠BMSCs,可见CD105、CD44和CD90表达,IGFBP4的表达随培养代数而增加,外源IGFBP4能明显抑制BMSCs的增殖(P0.05)。经诱导BMSCs形成的神经球样结构表达Nestin和Sox-2,细胞增殖活性升高(P0.05)。结论 IGFBP4能抑制BMSCs的增殖,促进其向神经祖细胞分化。     

Gene expression and serum levels of insulin-like growth factors (IGFs) and IGF-binding proteins in a case of non-islet cell tumour hypoglycaemia

We describe a case of non-islet cell tumour hypoglycaemia (NICTH) associated with a renal cell carcinoma. Serum insulin-like growth factors (IGFs) (including IGF-II E peptide), IGF-binding proteins (IGFBPs), insulin and C-peptide were measured before and after surgical removal of the tumour. IGFBPs were visualized by Western ligand blotting. Preoperatively 'big' IGF-II and IGFBP-2 levels were raised. IGF-I, IGFBP-1 and IGFBP-3 were low, while insulin, C-peptide and GH were undetectable. These changes were reversed by 2 days postoperatively. Protease assays showed little IGFBP-3 protease activity preoperatively. Preoperatively, neutral chromatography demonstrated most of the immunoassayable IGFBP-3 in a high molecular weight form with a small amount of IGF-II. Most of the IGF-II and big IGF-II eluted in lower molecular weight forms. Postoperative samples showed a shift in IGF-II which became increasingly associated with IGFBP-3 in both low and high molecular weight complexes. By Northern blotting, expression of all species of IGF-II mRNA in the tumour was 10-fold greater than in normal human liver. The tumour did not express IGFBP-1 or IGFBP-2. IGFBP-3 was expressed in small amounts, while the expression of IGFBP-4 was two-fold higher than in liver. In conclusion, we have confirmed high levels of big IGF-II and IGFBP-2 in NICTH, changes which are reversed postoperatively. The IGF-II is derived from the tumour which overexpresses these genes but IGFBP-2 probably arises from extratumour upregulation.     

膜联蛋白A7与IGFBP2结合抑制肝癌细胞增殖

目的 分析膜联蛋白A7(ANXA7)与肝癌发生的相关性及筛选、鉴定ANXA7的相互作用分子,探讨ANXA7在肝癌发生中的机制.方法 通过实时定量PCR法检测48对肝癌与癌旁组织以及多种肝和肝癌细胞株中ANXA7表达量的差异,并通过肝癌细胞ANXA7过表达及特异性干扰抑制分析其对肝癌细胞增殖的影响.采用免疫共沉淀法筛选与ANXA7发生结合的蛋白,并以点突变法分析蛋白质相互作用的关键位点;用蛋白免疫印迹法分析了ANXA7对肝癌相关的重要信号通路中ERK1/2磷酸化水平的影响.结果 ANXA7在肝癌组织与肝癌细胞中均呈下调表达.胰岛素样生长因子结合蛋白2(insulin-like growth factor binding protein 2,IGFBP2)能与ANXA7蛋白发生特异性结合,且IGFBP2上的RGD序列是两者结合的关键位点.肝癌细胞中ANXA7表达上调能抑制肿瘤细胞增殖(P＜0.05),并能使IGFBP2介导的ERK1/2的磷酸化水平降低.下调ANXA7的表达可促进肝癌细胞增殖(P＜0.01),磷酸化ERK1/2的水平升高.结论 ANXA7可能作为一种抑癌基因,通过介导IGFBP2对ERK1/2磷酸化水平的影响参与对肝癌增殖的调控.