Effect of recombinant growth hormone on expression of growth hormone receptor,insulin-like growth factor mRNA and serum level of leptin in growing pigs

Sixteen Large White × Landrace castrated male pigs were allotted into treatment and control group. The treatment group was injected intramuscularly with recombinant porcine growth hormone (rpGH, 4 mg d⁻¹) and the control group with vehicle for 28 days. Animals were slaughtered 4 h after final injection for liver, longissimus dorsi (LD) muscle and blood sampling. Serum concentration of insulin-like growth factor 1 (IGF-I) and leptin were determined by RIA. The total RNA was extracted from tissues to measure the abundance of growth hormone receptor (GHR), IGF-I mRNA by RT-PCR with 18S rRNA internal standard. Results showed that rpGH enhanced the average daily weight gain by 26.1% (P < 0.05), the serum IGF-I concentration by 70.94% (P < 0.01), decreased serum leptin by 34.8% (P < 0.01). The relative abundance of GHR and IGF-I mRNA in liver were increased by 24.45% (P < 0.05) and 45.30% (P < 0.01), respectively, but no difference of GHR (P > 0.05) and IGF-I mRNA (P > 0.05) in LD between GH treated and control group was found. These results suggest that rpGH can up-regulate hepatic GHR and IGF-I gene expression and improve animal growth. However the effect of rpGH on GHR and IGF-I gene expression are tissue-specific.     

The regulation of IGF-1 by leptin in the pig is tissue specific and independent of changes in growth hormone

A combination of in vivo and in vitro experiments were performed to determine the extent to which exogenous leptin regulates serum growth hormone (GH) and insulin-like growth factor I (IGF-1) concentrations, and the abundance of IGF-1 mRNA in major peripheral tissues. Initially (Experiment 1), a recombinant human leptin analog was administered i.m. to young growing pigs (approximately 27 kg body weight) for 15 days at 0 (control), 0.003, 0.01 and 0.03 mg. kg(-1). day(-1). Although there was no sustained effect of leptin on serum GH, there was a reduction (P < 0.02) in serum IGF-1 at the intermediate dose that paralleled a decrease (P < 0.09) in hepatic IGF-1 expression. Leptin, at these doses, did not reduce feed intake (P > 0.57), nor was there an effect of leptin on dietary nitrogen retention (P > 0.97). In a second experiment, pigs were injected with vehicle or a higher dose of leptin (0.05 mg. kg(-1). day(-1)) for 14 days. A third treatment group was injected with vehicle and pair-fed to the intake of the group treated with leptin. In this study, exogenous leptin resulted in a sustained increase in serum leptin (P < 0.0001) and reduction in feed intake of approximately 30% (P < 0.0001). Serum IGF-1 was depressed in both the leptin-treated and pair-fed groups, relative to the group allowed ad-libitum intake (P < 0.01). Furthermore, there was no difference among treatments in the relative abundance of IGF-1 mRNA in skeletal muscle (P > 0.42) or adipose tissue (P > 0.26), and liver mRNA abundance was actually increased (P < 0.01) by leptin, despite the lower feed intake. Finally, to determine whether leptin altered the secretion of IGF-1 by isolated pig hepatocytes, primary cultures were incubated with leptin for 24 to 48 hr (Experiment 3). Leptin (100 nM) caused a sharp reduction (P < 0.0001) in dexamethasone-induced IGF-1 secretion at 24 hr (47% reduction) and at 48 hr (40% reduction). Collectively, these data indicate that leptin may regulate hepatic IGF-1 production in the pig, independent of GH, but that hepatocyte sensitivity to leptin may be depend on dose and in vitro vs. in vivo conditions.     

Effect of exogenous insulin and fasting on growth hormone receptor and IGF-I expression in the pre-ovulatory follicle of ewes

The aim of this study was to investigate the effect of fasting and exogenous insulin administration on the expression of growth hormone receptor (GHR) and IGF-I mRNA in the pre-ovulatory follicle of ewes. Fifteen ewes received an intravaginal progesterone releasing device that was removed 6 days later (day of removal = day 0). On day -2, the ewes were divided into three groups: (i) fasting group (n = 5) that was fasted from day -2 to day 2; (ii) control group (n = 5) that received a maintenance diet; and (iii) insulin group (n = 5) that received insulin injections (0.25 IU/kg) every 12 h from day -2 to day 2 under the same diet as the control group. Follicular samples were obtained on day 2. Fasting increased plasma non-esterified fatty acids concentrations from day -1 to day 2 (P < 0.001). There was no difference (P > 0.05) in the number of follicles, although there was a tendency for an increase in the pre-ovulatory follicle diameter for the insulin group in comparison to the control group (P = 0.12). Thecal GHR mRNA expression was very low and was considered insignificant. Moreover, granulosa cells GHR mRNA expression increased (P < 0.05) in the insulin group. Expression of IGF-I mRNA was not different among groups in both tissues. In conclusion, insulin administration increases GHR mRNA but not IGF-I mRNA expression in granulosa cells of the pre-ovulatory follicle. However, fasting did not change the pattern of GHR/IGF-I mRNA expression in the pre-ovulatory follicle.     

LHRH-A对尼罗罗非鱼生长及生长轴相关基因表达的影响

促性腺激素释放激素(GnRH)的主要作用是刺激脑垂体促性激素(GtH)的释放, 亦可促进鱼类生长激素(GH)的释放。促黄体素释放激素类似物(LHRH-A)是哺乳类GnRH的类似物, 为了分析LHRH-A对尼罗罗非鱼生长调节的作用, 设计了长期和短期2个实验, 采用腹腔注射(剂量0.1 μg/g体重)方法, 分析LHRH-A对尼罗罗非鱼绝对生长率、特定生长率、肝体系数和肥满度的影响, 并应用荧光实时定量PCR方法检测在注射LHRH-A后不同时段(6h、12h、24h、2周)尼罗罗非鱼垂体GH、肝脏GHR和肝脏IGF-I基因的表达变化。结果表明, LHRH-A组尼罗罗非鱼的绝对生长率、特定生长率、肝体系数、肥满度均显著高于对照组(P<0.05); 注射LHRH-A后12h、24h垂体GH mRNA表达水平均显著升高(P<0.05), 2周后恢复到对照组水平; 注射LHRH-A后24h和2周肝脏GHR mRNA表达水平显著上升(P<0.05); 注射LHRH-A后6h肝脏IGF-I mRNA表达水平显著升高(P<0.05), 12h、24h和2周恢复到对照组水平。以上结果提示, LHRH-A可显著上调尼罗罗非鱼生长轴相关基因的表达, 从而促进鱼类的生长。     

Leptin gene expression, circulating leptin, and luteinizing hormone pulsatility are acutely responsive to short-term fasting in prepubertal heifers: relationships to circulating insulin and insulin-like growth factor I(1)

In the present study, we tested the hypothesis that short-term fasting would reduce leptin gene expression, circulating leptin, and LH pulsatility in prepubertal heifers in association with a decrease in circulating concentrations of insulin and insulin-like growth factor I (IGF-I). Twelve prepubertal crossbred heifers (mean +/- SD = 315 +/- 5 kg body weight) were assigned randomly to one of two treatments in two replicates: 1) control; normal feed consumption (n = 6) and 2) fasted; 48 h of total feed restriction (n = 6). Blood samples were collected at 15-min intervals for 8 h on Days 0 and 2 of the experiment and twice on Day 1. Subcutaneous fat samples were collected before treatment onset (Day -1) and at the end of the intensive blood sampling on Day 2. Acute feed restriction markedly reduced leptin mRNA in adipose tissue (P < 0.01) and circulating concentrations of leptin (P < 0.05), IGF-I (P < 0.01), and insulin (P = 0.05) as compared with controls on Day 2. Moreover, the treatment x day interaction (P < 0.076) and within-day contrasts (expressed as a percentage of Day 0 values) revealed that the mean frequency of LH pulses in the fasted group was lower (P < 0.06) than in controls on Day 2. Neither mean concentrations of growth hormone (GH) nor GH secretory dynamics were affected by acute feed restriction. Fasting-mediated decreases in leptin gene expression and circulating leptin, in association with reductions in secretion of IGF-I, insulin, and LH, provide a basis for investigating leptin as a hormone signaling energy status to the central reproductive axis in cattle.     

Influence of ration level and rearing temperature on hepatic GHR1 and 2, and hepatic and intestinal TRα and TRβ gene expression in late stages of rainbow trout embryos

The study examined whether the early life-history temperature experience of rainbow trout Oncorhynchus mykiss embryos affects subsequent growth and expression of growth-related genes in the growing-up juveniles in response to variations in ration levels. Embryos were reared in a Heath incubator at either 8·5° C (E_8·5) or 6·0° C (E_6·0) until hatching, at which time they were transferred to grow-up tanks supplied with water at 8·5° C. At swim-up, the late stage embryos were subsequently fed a salmonid starter diet at levels of 5, 2 or 0·5% of live body mass per day. The body mass and proximate composition of the juveniles was examined when yolk absorbance was complete (21 days after the fish commenced feeding). Quantitative RT-PCR was used to examine the expression of mRNA encoding for growth hormone receptors 1 and 2 (GHR1 and GHR2) in the liver, and the two isoforms of thyroid hormone receptor (TRα and TRβ) in the liver and intestinal tract. Final body mass and total length, liver and intestinal masses, and total lipid content of the E_8·5 treatment group were directly related to increased ration size. These variables in the E_6·0 treatment group fed the 5% ration were significantly lower than for the comparable E_8·5 treatment group, suggesting an effect of embryo rearing temperature on the subsequent growth of these late stage embryos as they undergo the transition from embryo to early juvenile. Intestinal TRα and TRβ mRNA abundance was directly related to ration size in the E_8·5 treatment group, but not in the E_6·0 treatment group. Conversely, hepatic TRα and TRβ mRNA abundance was significantly affected by ration size only in the E_6·0 group, with TRβ and TRα abundance showing direct and inverse relationships with ration size, respectively. Hepatic GHR1 mRNA abundance was significantly and directly related to ration size in both the E_8·5 and E_6·0 treatment groups, but there were no differences in the abundance of hepatic GHR2 mRNA among any treatments.     

Plasma levels of total and active ghrelin in acromegaly and growth hormone deficiency

Ghrelin is an endogenous growth hormone (GH) secretagogue recently isolated from the stomach. Although it possesses a strong GH releasing activity in vitro and in vivo, its physiological significance in endogenous GH secretion remains unclear. The aim of this study was to characterize plasma ghrelin levels in acromegaly and growth hormone deficiency (GHD). We investigated plasma total and active ghrelin in 21 patients with acromegaly, 9 patients with GHD and 24 age-, sex- and BMI-matched controls. In all subjects, we further assessed the concentrations of leptin, soluble leptin receptor, insulin, IGF-I, free IGF-I and IGFBP-1, 2, 3 and 6. Patients with acromegaly and GHD as well as control subjects showed similar levels of total ghrelin (controls 2.004+/-0.18 ng/ml, acromegalics 1.755+/-0.16 ng/ml, p=0.31, GHD patients 1.704+/-0.17 ng/ml, p=0.35) and active ghrelin (controls 0.057+/-0.01 ng/ml, acromegalics 0.047+/-0.01 ng/ml, p=0.29, GHD patients 0.062+/-0.01 ng/ml, p=0.73). In acromegalic patients plasma total ghrelin values correlated negatively with IGF-I (p<0.05), in GHD patients active ghrelin correlated with IGF-I positively (p<0.05). In the control group, total ghrelin correlated positively with IGFBP-2 (p<0.05) and negatively with active ghrelin (p=0.05), BMI (p<0.05), WHR (p<0.05), insulin (p=0.01) and IGF-I (p=0.05). Plasma active ghrelin correlated positively with IGFBP-3 (p=0.005) but negatively with total ghrelin and free IGF-I (p=0.01). In conclusion, all groups of the tested subjects showed similar plasma levels of total and active ghrelin. In acromegaly and growth hormone deficiency plasma ghrelin does not seem to be significantly affected by changes in GH secretion.     

Effects of starter feeding and early weaning on GHR mRNA expression in liver and rumen of lambs from birth to 84 days of age

The growth hormone receptor (GHR) is associated with animal growth and development. To investigate such effects on GHR gene expression, a total of 102 Hu lambs were randomly allocated to one of three groups (Group 1: starter diet from 7 d of age, weaning at 56 d of age; Group 2: starter diet from 42 d of age, weaning at 56 d of age; Group 3: starter diet from 7 d of age; weaning at 28 d of age). Six lambs from each group were sacrificed every 14 d to investigate the effects of starter feeding and weaning age on GHR mRNA expression in the liver and rumen. The results revealed that GHR mRNA expression was significantly higher in the liver and rumen (p < 0.05) than in other tissues. Early starter feeding up-regulated hepatic GHR mRNA expression on days 14, 28, 42 and 56 and ruminal GHR mRNA expression on days 28, 42, 70, and 84 (p < 0.05). Early weaning up-regulated hepatic GHR mRNA expression on days 56, 70 and 84 and ruminal GHR mRNA expression on days 42, 56, 70 and 84 (p < 0.05). Dietary and weaning regimes and age affected the hepatic and ruminal GHR mRNA expression.     

尼罗罗非鱼生长激素及其受体的cDNA克隆与mRNA表达的雌雄差异

尼罗罗非鱼(Oreochromis niloticus)雌雄鱼生长差异明显,为了探讨其原因,本文采用RT-PCR方法克隆了尼罗罗非鱼生长激素(Growthhormone,GH)及其受体(Growth hormone receptor,GHR)的cDNA序列,并应用半定量RT-PCR方法比较了雌、雄尼罗罗非鱼垂体GHmRNA、肝脏GHRmRNA、肌肉GHRmRNA的表达差异。序列分析表明:GH开放阅读框为615bp,共编码204个氨基酸;GHR开放阅读框为1908bp,共编码635个氨基酸。以RT-PCR方法研究了GH、GHR在各组织的分布情况,结果表明:GH仅在垂体中检测到有表达,而GHR在所检测的18种组织中均有表达,其中以肝脏、肌肉、性腺、下丘脑、胸腺表达量较高。以半定量RT-PCR方法进一步比较了雌、雄尼罗罗非鱼垂体GHmRNA、肝脏GHRmRNA、肌肉GHRmRNA的表达量,结果表明:雄鱼垂体GHmRNA和肝脏GHRmRNA的表达量均显著高于雌鱼,肌肉GHRmRNA的表达量则无显著差异,推测垂体GHmRNA和肝脏GHRmRNA表达的雌雄差异是尼罗罗非鱼雌雄生长差异的主要原因之一。     

Differential expression of insulin-like growth factor-I and insulin-like growth factor binding protein-1 in the diabetic rat

Summary Multiple factors contribute to the growth retardation which is a characteristic feature of uncontrolled diabetes. In this report we have examined the effects of streptozotocin-induced (STZ) diabetes on expression of insulin-like growth factor-I (IGF-I) and insulin-like growth factor binding protein-1 (IGFBP-1) in various tissues. As early as 7 days after STZ administration there was a modest reduction in IGF-I mRNA abundance. The reduction (10–30%) was of similar magnitude in each of the 7 tissues examined; liver, kidney, lung, diaphragm, quadraceps, heart and adipose tissue. However, the reduction achieved statistical significance only in the lung (p < 0.05) and diaphragm (p < 0.01). A further reduction in IGF-I mRNA abundance was seen in many tissues, 32 and 91 days after STZ administration. In contrast to the decrease in IGF-I mRNA, IGFBP-1 mRNA was significantly increased in the liver and kidney of diabetic rats. IGFBP-1 mRNA was detectable at only very low levels in other tissues but was increased in diabetic rats compared non-diabetic rats. In diabetic rats, a highly significant correlation (R = 0.75, p < 0.001) between hepatic IGFBP-1 mRNA and glucose was observed whereas there was no significant correlation between serum glucose and hepatic IGF-I mRNA abundance (R = 0.24, p = NS). Treatment of diabetic rats with insulin resulted in a small, non significant increase in hepatic and renal IGF-I mRNA and a significant decrease in renal IGFBP-1 mRNA abundance. The observations reported here are consistent with the hypothesis that diminished IGF-I expression and inhibition of available IGF-1 by increased levels of IGFBP-1 may explain the impaired growth seen in diabetic animals.