Effect of growth hormone administration to mature miniature Brahman cattle treated with or without insulin on circulating concentrations of insulin-like growth factor-I and other metabolic hormones and metabolites

Previously, we determined that a primary cause of proportional stunted growth in a line of Brahman cattle was related to an apparent refractoriness in metabolic response to GH in young animals. The objective of this study was to determine the effect of administration of GH, insulin (INS), and GH plus INS to mature miniature Brahman cows (n = 6; 9.7 ± 2.06 y; 391 ± 48.6 kg) and bulls (n = 8; 9.4 ± 2.00 y; 441 ± 54.0 kg) on circulating concentrations of metabolic hormones and metabolites, primarily IGF-I and IGF-I binding proteins. We hypothesized that IGF-I secretion could be enhanced by concomitant administration of exogenous GH and INS, and neither alone would be effective. Animals were allotted to a modified crossover design that included four treatments: control (CON), GH, INS, and GH + INS. At the start of the study, one-half of the cattle were administered GH (Posilac; 14-d slow release) and the other one-half served as CON for 7 d. Beginning on day 8, and for 7 d, INS (Novolin L) was administered (0.125 IU/kg BW) twice daily (7:00 AM and 7:00 PM) to all animals; hence, the INS and GH + INS treatments. Cattle were rested for 14 d and then were switched to the reciprocal crossover treatments. Blood samples were collected at 12-hour intervals during the study. Compared with CON, GH treatment increased (P < 0.01) mean plasma concentrations of GH (11.1 vs 15.7 ± 0.94 ng/mL), INS (0.48 vs 1.00 ± 0.081 ng/mL), IGF-I (191.3 vs 319.3 ± 29.59 ng/mL), and glucose (73.9 vs 83.4 ± 2.12 mg/dL) but decreased (P < 0.05) plasma urea nitrogen (14.2 vs 11.5 ± 0.75 mg/dL). Compared with INS, GH + INS treatment increased (P < 0.05) mean plasma concentration of INS (0.71 vs 0.96 ± 0.081 ng/mL), IGF-I (228.7 vs 392.3 ± 29.74 ng/mL), and glucose (48.1 vs 66.7 ± 2.12 mg/dL), decreased (P < 0.01) plasma urea nitrogen (13.6 vs 10.4 ± 0.76 mg/dL), and did not affect GH (13.5 vs 12.7 ± 0.95 ng/mL). In the miniature Brahman model, both the GH and GH + INS treatments dramatically increased circulating concentrations of IGF-I in mature cattle, suggesting that this line of Brahman cattle is capable of responding to bioactive GH.     

酶制剂对雏鹅组织中胰岛素样生长因子的影响

18只 7日龄的杂交雏鹅 ,随机分成试验和对照两组 ,饲以大麦基础日粮 ,试验组日粮中添加 0 .1%的Biokyowa酶制剂。测定 2 1日龄血液、肝脏和肌肉中的IGF -I含量。添加粗酶制剂后 ,肝脏和肌肉中的IGF -Ⅰ分别较对照高18.2 3% (P <0 .0 1)和 2 2 .79% (P <0 .0 1) ,而血浆中IGF -I水平却较对照低 9.0 4 % (P <0 .0 5 )。结果提示 :酶制剂能促使肝脏合成IGF -I,血液中与IGFBP结合的IGF -I大量释放 ,从而显著提高肌肉中的IGF -I水平 ,加速了肌肉的生长。     

朗德鹅肌肉生成抑制因子基因（MSTN）的克隆及其表达量与日粮能量、血清IGF-I和GH的关系

 【目的】采用反转录－聚合酶链反应（RT-PCR）技术,克隆朗德鹅肌肉生成抑制因子基因（MSTN）,研究MSTN基因表达和日粮能量及其部分血清激素含量的相互关系,了解MSTN的功能,为水禽分子营养和分子育种提供基础资料。【方法】从朗德鹅（Anser anser）的腿肌中抽提总RNA,用两步法RT-PCR扩增出MSTN基因的cDNA编码序列,以pGEM-T Vector为载体,将该片段克隆到大肠杆菌（Escherichia coli）中。通过筛选阳性克隆,双酶切鉴定后测序;以MSTN基因的克隆为基础,以β-actin为内标,构建优化的半定量RT-PCR方法,研究高中低（A:13.38MJ•kg-1、B:12.13MJ•kg-1、C:10.87MJ•kg-1）3种不同能量对朗德鹅21日龄和70日龄2个时期,肌肉组织MSTN基因表达的差异;同时用放免法测定21、70日龄的血清GH和IGF-I浓度。【结果】克隆朗德鹅MSTN基因cDNA的部分序列,其片段大小为1 128bp,编码375个氨基酸组成的多肽,与已发表的鸡、鸭、鹅的MSTN 核苷酸相似性分别为94%、94%、99%;氨基酸的相似性分别为98%、97%、98%;21日龄时,朗德鹅公鹅、母鹅MSTN表达量差异不显著;70日龄时朗德鹅公鹅MSTN的表达量情况为能量A＞C＞B,朗德鹅母鹅MSTN的表达量情况为C＞B＞A;对于朗德鹅21～70日龄阶段的生长,MSTN基因的表达量和血清IGF-I的变化基本一致;与血清GH含量之间并不存在很大关联,GH和能量的高低呈正相关。【结论】日粮能量对21日龄后朗德鹅MSTN基因的表达有影响,且MSTN基因表达量和血清IGF-I具有相关性,和血清GH无较大相关性。     

绵羊肌肉IGF-I.基因表达的发育性变化研究

生长激素（GH）在动物体内主要有两种作用方式：（1）GH与肝脏等靶器官上的GHR结合,产生胰岛素样生长因子（IGF）,随后IGF以内分泌方式进入血液,与胰岛素样生长因子结合蛋白（IGFBP）结合后到达靶器官,作用于胰岛素样生长因子受体（IGFR）,从而调节动物生长发育。②GH直接作用于靶器官GHR,通过旁分泌或自分泌IGF直接影响细胞的代谢,从而调节机体的生长发育。GH可作用于骨骼肌GHR,产生旁分泌或自分泌的IGF-I调节肌肉的生长发育,或直接影响细胞的代谢。笔者采用实时定量PCR法,以处于生长发育早期的雄性哈萨克羊和雄性新疆细毛羊为研究对象,检测了IGF-I基因在肌肉中表达情况。     

Ontogeny of IGF-I responsiveness to bGH in young lambs

The ontogeny of hepatic growth hormone (GH) receptors (GHR), as measured by responses of both plasma insulin-like growth factor-I (IGF-I) and hepatic GHR to an exogenous bGH stimulus, was examined using sheep of different ages (Days 1-7, 14-21, 28-35, and 56-63 of life, and yearlings). The IGF-I response to bGH was first examined in yearling sheep using two doses of bGH (0.1 and 0.2 mg/kg LW/d). Based on these results, lambs in four groups up to Day 63 of life were treated for 5 d with bGH (n = 10) at a dose of 0.15 mg/kg LW/d or with saline (n = 10). Jugular blood samples were taken once daily on Days - 1, 4, and 5 of treatment. bGH treatment in lambs up to Day 63 of life had little effect on plasma concentrations of GH, insulin, glucose or urea, but significantly (P < 0.05) increased circulating concentrations of IGF-I at all ages and of NEFA at Day 62/63 of life. In contrast, bGH treatment at either dose in yearlings significantly increased these parameters, except for plasma urea concentrations which were decreased in bGH-treated yearlings. However, the responses of plasma IGF-I concentration to bGH stimulus in lambs up to Day 63 of life were small compared to those in yearling sheep. Consistent with this, bGH treatment failed to affect hepatic GH binding in young lambs, but up-regulated it in yearling sheep. Furthermore, basal (unstimulated) GH binding did not differ between sheep of 7 vs. 63 vs. 365 d of age, despite the greater IGF-I responses to bGH in the latter group. It is suggested that hepatic GHR in lambs up to Day 63 of life are not fully functional compared to the situation in yearlings.     

A novel phenotype for Laron dwarfism in miniature Bos indicus cattle suggests that the expression of growth hormone receptor 1A in liver is required for normal growth

Mutations within the growth hormone receptor (GHR) gene that lead to an inactivated or truncated GHR protein cause abnormal growth and small adult size in a variety of species (Laron dwarfism). We studied a line of miniature Bos indicus cattle that have phenotypic (small mature size) and endocrine (increased blood growth hormone and decreased blood insulin-like growth factor-I concentrations) similarities to Laron dwarfs. Liver mRNA from miniature and control cattle was used to amplify a cDNA within the coding region of the GHR. The miniature cattle had GHR mRNA size (determined by Northern blot) and cDNA sequence that were similar to control cattle and, therefore, were unlike most Laron dwarf genotypes in which the GHR gene is mutated. Amounts of mRNA from liver as well as muscle (superficial neck and longissimus) were analyzed by ribonuclease protection assay for IGF-I, total GHR, GHR 1A (inducible, liver-specific GHR mRNA), and GHR 1B (constitutive GHR mRNA). Four control and five miniature bulls were tested. As expected, liver IGF-I mRNA was decreased in the miniature cattle (approximately 12% of control; P < 0.01). The amount of the total GHR as well as GHR 1A mRNA were also decreased in liver (17% and 19% of control, respectively; P < 0.01). Other GHR mRNA, including GHR 1B mRNA, were similar for miniature and control cattle. In muscle, there was a tendency (P < 0.10) for decreased IGF-I mRNA and increased GHR mRNA in miniature compared with control cattle. In summary, a novel phenotype for Laron dwarfism in Bos indicus cattle was associated with underexpression of GHR 1A mRNA, but not other GHR mRNA variants in liver. In addition to decreased GHR 1A mRNA, the miniature cattle had decreased liver IGF-I mRNA. Full expression of GHR 1A in liver, therefore, may be required for full liver IGF-I expression and normal growth.     

IGF-I及其受体基因在牙鲆胚胎发育过程中的表达图式

胰岛素样生长因子-I(insulin-like growth factor I, IGF-I)是脊椎动物生长发育的重要调控因子, 其生物学功能主要通过与其特异的膜受体(IGF-I receptor, IGF-IR)结合而调节。因此, IGF-I及其受体表达特征的分析对于阐述IGF系统调控的发育过程具有重要的意义。本研究采用荧光实时PCR方法, 以不同发育时期的牙鲆(Paralichthys olivaceus)胚胎为材料, 分析了胰岛素样生长因子-I(IGF-I)及其两种受体基因在鱼类胚胎发育过程中的表达图式。结果显示, 牙鲆IGF-I、IGF-IR-1和IGF-IR-2基因均有母源转录本, 且各基因的表达在胚胎发育的不同阶段具有明显的发育性变化。IGF-I 基因在早期胚胎发育阶段仅有少量的mRNA存在, 而合子基因的表达在晶体出现至出膜前阶段逐步增加。两种IGF-I 受体基因则展现出迥然不同的表达时序。IGF-IR-1 基因在受精卵、卵裂及囊胚期的早期胚胎发育中有相对较少的转录本, 至原肠期其合子基因强烈表达, 且在神经胚、晶体出现、心跳和出膜前各阶段均有高量的表达; 相反, IGF-IR-2 基因在受精卵至原肠期的早期胚胎中有丰富的转录本, 但合子基因的表达在后期胚胎形成中却相对降低, 暗示了二者可能在调节牙鲆胚胎发育中起着不同的作用。

     

藏鸡IGF—I基因的SNPs检测及与生长性状的关联分析

通过PCR-RFLP技术对藏鸡和隐性白羽鸡类胰岛素生长因子-I（IGF-I）基因的5’非翻译区（UTR）的2个位点进行了多态性检测。检测结果显示，该基因具有HinfI和PstI多态现象.测序结果表明，HinfI识别位点发生了A→C突变，PstI识别位点发生了C→T突变，从而在2群体中分别产生了3种基因型，而出现了8种单倍型组合。单倍型组合的x^2检验结果表明，2个品种间存在极显著差异（P〈0．01）。方差分析结果显示，品种对所分析的17个生长发育性状都有显著影响（P〈0．05或P〈0．01），性别对6个生长发育性状有显著影响（P〈0．05或P〈0．01），而基因型或单倍型组合对5个生长发育性状（初生重、2周龄体重和胫围、7周龄体斜长以及16周龄胫围）有显著影响（P〈0．05或P〈0．01）。同时，基因型或单倍型组合与品种之间的互作对鸡的部分生长发育性状也有一定的影响。另外，基因型CT在鸡初生重和7周龄体斜长上显著（P〈0．05）或极显著地（P〈0．01）高于基因型CC和TT，而单倍型组合A＋T／C＋T在鸡初生重、2周龄体重和胫围以及16周龄胫围上显著（P〈0．05）或极显著地（P〈0．01）高于其它6种单倍型组合。     

琅琊鸡IGF-I基因多态性与肉用性的相关性

采用PCR-RFLP技术对琅琊鸡胰岛素样生长因子-I(IGF-I)5'非编码区Pst I酶切位点的多态性与生长发育的相关性进行分析.结果表明,琅琊鸡该位点存在2种等位基因(A和B),基因频率分别为61.7%和38.3%,其中A等位基因是有利基因.从型个体活重、半净膛重和脂肪含量极显著高于BB型(P<0.01),其屠体重、全净膛重、腿肌重和胸肌重显著大于AB型和BB型(P<0.05),其剪切力和失水率也高于BB型(P<0.05,P<0.01).结果表明:等位基因A对琅琊鸡的肌肉产量和品质具有正效应.