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

Growth hormone (GH) plays an important role in regulation of animal growth, metabolism and lactation[1]. Numerous studies have shown that exogenous somatotropin (ST) can increase average daily weight gain, improve feed efficiency, stimulate protein deposition and muscle growth and decrease lipid accretion rate[1]. The original somatomedin hypothesis suggested that the effect of GH on postnatal growth was mediated by insulin-like growth hormone factor 1 (IGF-I) which was thought to be deriv…     

Change from a hard to soft diet alters the expression of insulin-like growth factors,their receptors,and binding proteins in association with atrophy in adult mouse masseter muscle

To study the role of insulin-like growth factors (IGFs) in the atrophy of mouse masseter muscle in response to a change from a hard to a soft diet, we analyzed the amounts of mRNA and the immunolocalization for IGF-I, IGF-II, their receptors (IGFRs), and binding proteins (IGFBPs). Sixteen male ICR mice were fed a hard diet after weaning; they were divided into two groups at 6 months of age and fed a hard or a soft diet for 1 week. The soft diet treatment decreased masseter weight by 19% (P<0.01) and the minimal diameter of masseter myofibers by 19% (P<0.01), verifying that a soft diet led to atrophy of mouse masseter muscle. The soft diet treatment induced a 30% reduction in the amount of IGF-I mRNA (P<0.05) in preparations of whole masseter tissues. Immunohistochemical findings suggested that a reduction in the expression of IGF-I protein took place in the neural tissues, not in the masseter myofibers. The soft diet treatment induced a 56% decrease in IGF-II mRNA (P<0.05), a 21% increase in IGFR2 mRNA (P<0.01), and a 38% decrease in IGFBP5 mRNA (P<0.01). Immunohistochemical results suggested that these changes at the protein level occurred in the masseter myofibers. No significant or marked difference in the mRNA amount or immunostaining pattern for IGFR1, IGFBP3, IGFBP4, or IGFBP6 was found between the soft and hard diet groups. No IGFBP1 or IGFBP2 mRNA was detected. Thus, IGF-I, IGF-II, IGFR2, and IGFBP5 seem to play a role in the atrophy of mouse masseter muscle in response to the change from a hard to a soft diet in an autocrine and/or paracrine manner.Part of the present study was supported by a grant-in-aid for funding scientific research (no. 13671955), Bio-ventures and High-Technology Research Center, from the Ministry of Education, Culture, Sports, Science, and Technology of Japan     

Effects of cadmium and zinc on plasma levels of growth hormone, insulin-like growth factor I, and insulin-like growth factor-binding protein 3

Humans are constantly exposed to cadmium (Cd) as a result of the increase in air pollution and cigaret use. Zinc (Zn), which is an essential element for the metabolism of and the constituent of many enzymes, causes growth retardation in the deficiency status so at present it is often added to the diet without measuring blood levels of this element. We also aimed to observe the effects of both Cd and Zn on the plasma levels of growth hormone (GH), insulin-like growth factor I(IGF-I), and insulin-like growth factor-binding protein 3 (IGFBP-3) in this study. For this purpose, 27 young Wistar albino male rats were divided into three groups. The first group was given 50 mg/L of CdCl₂, the second group received 500 mg/L of ZnSO₄, and the third group, as a control, received only drinking water for 1 mo. At the end of this period, plasma GH, IGF-I, and IGFBP-3 of the animals were analyzed in the blood obtained. The significance between groups was evaluated with the Mann-Whitney U-test. According to our results, levels of IGF-I and IGFBP-3 in the Cd-administered group were significantly lower than those of controls (p<0.05 and p<0.01 respectively). No statistically significant difference was observed between Zn administered and control groups in terms of all three parameters. These results show that although the addition of Zn to the diet of healthy rats had no effect on the levels of GH, IGF-I, and IGFBP-3, Cd addition lowered the levels of IGF-I and IGFBP-3 but did not change the levels of GH compared to controls.     

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.     

Influence of exercise duration on serum insulin-like growth factor and its binding proteins in athletes

The changes in circulating concentrations of insulin-like growth factors during exercise have to date remained incomplete in their documentation. Therefore, we examined in 25 healthy athletes the effects of three different durations of three types of exercise – incremental ergometer cycling exercise (ICE), long-distance Nordic ski race (NSR) and a treadmill-simulated soccer game (TSG) lasting 20 min, 3 h, and 2 × 45 min separated by a 15-min half-time rest respectively, on plasma concentrations of growth hormone ([GH]), insulin-like growth factor-1 ([IGF-I]) and its binding proteins 1 and 3 ([IGFBP-1], [IGFBP-3]). Compared to baseline, serum [GH] increased by 15.2-fold after ICE (P < 0.001), 2.9-fold after NSR (P < 0.01) and 4.6-fold after TSG. Serum [IGF-I] rose by 11.9% after ICE (P < 0.001), while it decreased by −14.6% after NSR (P < 0.001) and was unchanged after TSG. Serum [IGFBP-1] was slightly increased (1.7-fold) after ICE (P < 0.01), but increased markedly (11.8-fold) after NSR (P < 0.001) and by 6.3-fold after the second session of TSG (P < 0.01) (it remained unchanged at the end of the first period of TSG, i.e. after 45-min exercise). The [IGFBP-3] increased by 14.7% after ICE (P < 0.001) and by 6% after TSG (P < 0.05) while it did not change after NSR. From our results it would appear that [IGFBP-1] increase to bind free IGF and hinder their insulin-like action during long-term exercise (lasting beyond 45 min). It is suggested that IGFBP-1 might thus contribute both to preventing hypoglycaemic action of IGF and to facilitating glucose uptake by muscle cells when muscle glycogen stores become deplete. Accepted: 27 May 1998     

Effects of dietary amylose and amylopectin ratio on growth performance,meat quality,postmortem glycolysis and muscle fibre type transformation of finishing pigs

The present study was conducted to investigate the effects of dietary amylose and amylopectin ratio on growth performance, meat quality, postmortem glycolysis and muscle fibre type transformation of finishing pigs. Twenty-four barrows (Duroc × Landrace × Yorkshire) with an average initial body weight of 61.7 ± 2.01 kg were randomly assigned to four dietary treatments with amylose: amylopectin ratios of 1:1 (HD), 1:2 (MD), 1:3 (CD) and 1:4 (LD). The results showed that the average daily weight gain of finishing pigs tended to reduce with the ratio of amylose and amylopectin decreased (p = 0.09). Diet LD increased the pH_24h value and decreased the shear force in longissimus dorsi (LM) compared with diet HD (p < 0.05). Diet LD decreased the lactate content and the HK-2 mRNA abundance and increased the mRNA abundance of ATP5B in LM compared with diet HD (p < 0.05). Higher mRNA abundance of MyHC I and lesser abundance of MyHC IIb in LM were found in pigs fed diet CD and LD than those fed diet HD (p < 0.05). Furthermore, pigs fed diet LD had higher mRNA abundances of PGC-1α and PPAR δ in LM than other groups (p < 0.05). These results suggested that diet with low amylose and amylopectin ratio could improve meat quality of finishing pigs via delaying muscle glycolysis capacity and shifting muscle fibre types.     

Effects of a dietary crude fibre concentrate on growth in weaned piglets

Many fibre sources can help the adaptation of piglets at weaning, improving the growth. In this study, the effects of a dietary crude fibre concentrate (CFC) on piglet’s growth was investigated. From 31 to 51 days of age, 108 weaned piglets (D×(Lw×L)), had access to two isofibrous, isoenergetic and isonitrogenous diets, supplemented with 1% of CFC (CFC group) or not (control (CON) group). From days 52 to 64 all piglets received the same starter diet. During the dietary treatment period the CFC group showed higher average daily gain, average daily feed intake and feed efficiency (P<0.001) than CON group. At 64 days of age, BW was higher in CFC group compared with CON group (P<0.001). Blood samples were collected at days 31, 38, 45 and 52 of age. From days 31 to 52 significant differences in the somatotropic axis between groups were observed. In particular, growth hormone levels were higher only at the end of the 1^st week of dietary treatment (P<0.05) in CFC group animals compared with CON group animals. The IGF-I trend was similar between groups even if the IGF-I levels were higher in the CFC group than CON group 1 week after starting treatment (P<0.01). The IGF-binding protein 3 (IGFBP-3) levels were higher in the first 2 weeks of dietary treatment and lower in the 3^rd week in CON group compared with CFC group (P<0.01). Specifically, the IGFBP-3 profile was consistent with that of IGF-I in CFC group but not in CON group. At the same time, an increase of leptin in CFC compared with CON group was observed (P<0.05). Piglets fed the CFC diet showed a lower diarrhoea incidence (P<0.05) and a lower number of antibiotic interventions (P<0.05) than CON diet from 31 to 51 days of age. Pig-major acute-phase protein plasma level (P<0.01) and interleukin-6 gene expression (P<0.05) were higher in CON group than CFC group at the end of 1^st week of dietary treatment. In conclusion, this study showed that CFC diet influences the hormones related to energy balance enhancing the welfare and growth of piglets. Furthermore, the increase in feed intake during 3 weeks of dietary treatment improved the feed efficiency over the entire post-weaning period.     

Influence of equine growth hormone,insulin-like growth factor-I and its interaction with gonadotropins on in vitro maturation and cytoskeleton morphology in equine oocytes

In horses, successful in vitro fertilization procedures are limited by our inability to consistently mature equine oocytes by in vitro methods. Growth hormone (GH) is an important regulator of female reproduction in mammals, playing an important role in ovarian function, follicular growth and steroidogenesis. The objectives of this research were to investigate: the effects of equine growth hormone (eGH) and insulin-like growth factor-I (IGF-I) on the in vitro maturation (IVM) of equine oocytes, and the effects of eGH in addition to estradiol (E₂), gonadotropins (FSH and LH) and fetal calf serum (FCS) on IVM. We also evaluated the cytoskeleton organization of equine oocytes after IVM with eGH. Equine oocytes were aspirated from follicles <30 mm in diameter and matured for 30 h at 38.5°C in air with 5% CO₂. In experiment 1, selected cumulus–oocyte complexes (COCs) were randomly allocated as follows: (a) control (no additives); (b) 400 ng/ml eGH; (c) 200 ng/ml IGF-I; (d) eGH + IGF-I; and (e) eGH + IGF-I + 200 ng/ml anti-IGF-I. In addition to these treatment groups, we also added 1 μg/ml E₂, 5 IU/ml FSH, 10 IU/ml LH and 10% FCS in vitro (experiment 2). Oocytes were stained with markers for microtubules (anti-α-tubulin antibody), microfilaments (AlexaFluor 488 Phalloidin) and chromatin (TO-PRO₃-iodide) and assessed via confocal microscopy. No difference was observed when eGH and IGF-I was added into our IVM system. However, following incubation with eGH alone (40%) and eGH, E₂, gonadotropins and FCS (36.6%) oocytes were classified as mature v. 17.6% of oocytes in the control group (P < 0.05). Matured equine oocytes showed that a thin network of filaments concentrated within the oocyte cortex and microtubules at the metaphase spindle showed a symmetrical barrel-shaped structure, with chromosomes aligned along its midline. We conclude that the use of E₂, gonadotropins and FCS in the presence of eGH increases the number of oocytes reaching oocyte competence.     

Molecular cloning, expression analysis of insulin-like growth factor I (IGF-I) gene and IGF-I serum concentration in female and male Tongue sole (Cynoglossus semilaevis)

Insulin-like growth factor I (IGF-I) is a polypeptide hormone that regulates growth during all stages of development in vertebrates. To examine the mechanisms of the sexual growth dimorphism in the Tongue sole (Cynoglossus semilaevis), molecular cloning, expression analysis of IGF-I gene and IGF-I serum concentration analysis were performed. As a result, the IGF-I cDNA sequence is 911 bp, which contains an open reading frame (ORF) of 564 bp encoding a protein of 187 amino acids. The sex-specific tissue expression was analyzed by using 14 tissues from females, normal males and extra-large male adults. The IGF-I mRNA was predominantly expressed in liver, and the IGF-I expression levels in females and extra-large males were 1.9 and 10.2 times as much as those in normal males, respectively. Sex differences in IGF-I mRNA expressions at early life stages were also examined by using a full-sib family of C. semilaevis, and the IGF-I mRNA was detected at all of the 27 sampling points from 10 to 410 days old. An increase in IGF-I mRNA was detected after 190 day old fish. The significantly higher levels of IGF-I mRNA in females were observed after 190 days old in comparison with males (P < 0.01). The IGF-I concentrations in serum of mature individuals were detected by ELISA. The IGF-I level in the serum of females was approximately two times as much as that of males. Consequently, IGF-I may play an important role in the endocrine regulation of the sexually dimorphic growth of C. semilaevis.     

Selection for superior growth advances the onset of puberty and increases reproductive performance in ewe lambs

The reproductive efficiency of the entire sheep flock could be improved if ewe lambs go through puberty early and produce their first lamb at 1 year of age. The onset of puberty is linked to the attainment of critical body mass, and therefore we tested whether it would be influenced by genetic selection for growth rate or for rate of accumulation of muscle or fat. We studied 136 Merino ewe lambs with phenotypic values for depth of eye muscle (EMD) and fat (FAT) and Australian Sheep Breeding Values at post-weaning age (200 days) for live weight (PWT), eye muscle depth (PEMD) and fat depth (PFAT). First oestrus was detected with testosterone-treated wethers and then entire rams as the ewes progressed from 6 to 10 months of age. Blood concentrations of leptin and IGF-I were measured to test whether they were related to production traits and reproductive performance (puberty, fertility and reproductive rate). In total, 97% of the lambs reached first oestrus at average weight 39.4 ± 0.4 kg (mean ± s.e.m.) and age 219 days (range 163 to 301). Age at first oestrus decreased with increases in values for PWT (P < 0.001), and concentrations of IGF-I (P < 0.05) and leptin (P < 0.01). The proportion of ewe lambs that achieved puberty was positively related with increases in values for EMD (P < 0.01), FAT (P < 0.05) or PWT (P < 0.01), and 75% of the ewe lambs were pregnant at average weight 44.7 ± 0.5 kg and age 263 days (range 219 to 307). Ewe lambs that were heavier at the start of mating were more fertile (P < 0.001) and had a higher reproductive rate (P < 0.001). Fertility and reproductive rate were positively correlated with increases in values for EMD (P < 0.01), FAT (P < 0.05), PWT (P < 0.01) and leptin concentration (P < 0.01). Fertility, but not reproductive rate, increased as values for PFAT increased (P < 0.05). Leptin concentration increased with increases in values for EMD (P < 0.001), FAT (P < 0.001), PWT (P < 0.001), PEMD (P < 0.05) and PFAT (P < 0.05). Many of these relationships became non-significant when PWT or live weight was added to the statistical model. We conclude that selection for genetic potential for growth can accelerate the onset of puberty and increase fertility and reproductive rate of Merino ewe lambs. The metabolic hormones, IGF-I and leptin, might act as a physiological link between the growing tissues and the reproductive axis.     

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.     

Zinc deficiency inhibits the direct growth effect of growth hormone on the tibia of hypophysectomized rats

The effect of zinc deficiency on the direct-growth effect of growth hormone (GH) on tibia growth in hypophysectomized rats was studied. There were three dietary groups. Zinc deficient (ZD) group (0.9 mg/kg diet), control (C) group (66 mg/kg diet) and zinc adequate pair fed (PF) group (66 mg zinc/kg diet). All rats in each group received local infusion of recombinant human-growth hormone (hGH) (1 Μg/d), except for half of the animals in the control group, which were sham-treated, receiving vehicle infusion only. The substances were infused continuously for 13 d by osmotic minipumps through a catheter implanted into the right femoral artery. Food intake was lower and body weight loss was greater in ZD, and PF animals compared with C animals (p < 0.001). Tissuezinc concentration and plasma alkaline-phosphatase activity were decreased (p < 0.05) by dietary-zinc deficiency. GH infusion increased the tibial-epiphyseal width of the treated right limb, but not of the noninfused left limb in C and PF animals. However, in ZD rats, no difference was found between the infused and the noninfused limbs. These results demonstrate that zinc deficiency inhibits the direct-growth effect of GH on long-bone growth.     

Growth and IGF-I response of juvenile Nile tilapia (Oreochromis niloticus) to changes in water temperature and dietary protein level

Water temperature and dietary protein level play an important role in influencing the growth and insulin-like growth factor I (IGF-I) in Nile tilapia juveniles. The combined effect of temperature (20–34 °C) and dietary protein level (25–50%) on the specific growth rate (SGR), feed efficiency (FE), serum IGF-I level and hepatic IGF-I mRNA level was examined under laboratory conditions by employing central composite design and response surface method. Results showed that the linear effects of temperature and dietary protein level on the SGR, FE, serum IGF-I and hepatic IGF-I mRNA level were significant (P<0.05); the quadratic effects of temperature and dietary protein level on the FE and serum IGF-I were significant (P<0.05). The interaction of temperature and dietary protein level on the FE, serum IGF-I and hepatic IGF-I mRNA level all proved significant (P<0.05). The optimal temperature/dietary protein level combination was determined, i.e., 29.9 °C/40.3%, at which the greatest SGR (2.748%/d) and FE (0.775) were simultaneously arrived. Both SGR and FE were linearly correlated with serum IGF-I or hepatic IGF-I mRNA level. These results suggested that optimum combination of temperature and dietary protein level would enhance tilapia growth efficiency and IGF-I would regulate growth and FE.     

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.     

Glucose regulates ghrelin, neuropeptide Y, and the GH/IGF-I axis in the tilapia, Oreochromis mossambicus

In general, a fish's ability to clear glucose is sluggish in relation to mammals, which has lead to the idea that fish are glucose intolerant. It has been reported that circulating glucose levels do fluctuate in response to environmental challenges. Recent reports suggest that glucose may function as a metabolic signal regulating ‘glucosensors’ in the brain in fish, as has been reported in mammals. The current study was designed to investigate the effect of glucose on ghrelin and neuropeptide Y (NPY) signaling in the brain, and on the growth hormone/insulin-like growth factor-I (GH/IGF-I) in the tilapia, Oreochromis mossambicus. Glucose treatment significantly increased plasma and stomach mRNA levels of ghrelin. In the brain, mRNA levels of the ghrelin receptor (GRLN-R) were significantly reduced, whereas NPY mRNA levels were significantly elevated; suggesting that NPY containing neurons may be a “glucosensor” as reported in mammals. Glucose treatment resulted in changes in the GH/IGF-I axis. Liver mRNA levels of both GH receptors (GHR1 and GHR2) were significantly elevated, whereas liver IGF-I mRNA were unaltered by glucose treatment. No change in plasma or pituitary mRNA levels of GH was observed. Glucose significantly reduced plasma IGF-I levels. These data show that glucose regulates endocrine factors involved in appetite, growth, and possibly energy homeostasis, and suggests that glucose may be acting as a signal of metabolic status in fish.