Injection Of Insulin-like Growth factor-I Research Articles

Modification of Carp (Osphronemus Gouramy) Growth with Insulin-Like Growth Factor-I Recombinant Mouse in Vivo

Osphronemus gouramy consumption is increasing every year, which causes a high number of inquiries for this fish, which cannot be offset sufficiently by the amount of production. The growth rate of O. gouramy is relatively slow, so achieving the required consumption is relatively long. Quality improvement of productivity by improving the ability of cell metabolism to intake fish feed through hormone injection recombinant mouse insulin-like growth factor-I (IGF-I) is expected to spur growth so that fish production can be increased. This study aims to determine the effect of the hormone IGF-I recombinant mouse on the increased growth of O. gouramy. The benefits of this research are expected to deliver the benefits of science in the form of scientific information to the public in general and fish farmers, especially about the effect of the hormone recombinant mouse IGF-I on the growth of O. gouramy. The research method is carried out experimentally by using a completely randomized design (RAL); this study uses 80 O. gouramy was divided into 4 treatments P0: without hormone injections of IGF-I, P1: injected with the hormone IGF-I at a dose of 10 ng/ml, P2: injected with the hormone IGF-I at a dose of 20 ng/ml and P3: injected with the hormone at a dose of 40 ng/ml each of 5 replicates each test 4 tail O. gouramy. The hormone IGF-I recombinant mouse is done by injection. The treatment with hormone injection of recombinant mouse IGF-I. The parameters measured were growth. The results showed that the treatment hormone injection of recombinant mouse IGF-I with different doses gave significant differences (p <0.05); weight growth (P0: 0 ng/ml = 7,23 gram ± 0,37-gram dan P3: 40 ng/ml = 26,35 gram ± 1,89 gram.); length growth (P0 : 0 ng/ml = 5,76 cm ± 0,38 cm dan P3: 40 ng/ml = 7,93 cm ± 0,07 cm). The conclusion is that recombinant mouse IGF-I increased the growth by increasing in weight and length of O. gouramy, and improvement of the growth occurred in the treatment injection of the dose: 40 ng/ml.

The influence of IGF-Ⅰ on the expression of Myf5 and TGF-β1 in medial rectus muscle of cat model with strabismus

Objective: To observe the influence of exogenous insulin-like growth factor-Ⅰ(IGF-Ⅰ) on the expression of myocyte differentiation factor 5 (Myf5) and transforming growth factor β1(TGF-β1) in medial rectus muscle of cat model with strabismus. Methods: Experiment research. Twenty-seven kittens which were in sensitive period of visual development (4-6 weeks old), were randomly divided into experimental, control and blank control groups by random numbers table method. Each experimental group was further divided into 3 sub-groups (4 weeks, 8 weeks and 12 weeks) based on drug intervention time, hence 3 kittens in each sub-group. The control group and the blank control group were also divided into 3 sub-groups respectively. Exotropia treatment models were set up through surgical methods and injection of IGF-Ⅰ(0.05 ml,0.1 g/L). The internal rectus muscles of 4 weeks sub-group, 8 weeks sub-group and 12 weeks sub-group were taken respectively after the treatment model had been set up. The internal rectus muscles of the control group and the blank control group were also taken according to corresponding time. The expressions of Myf5 and TGF-β1 were tested with immunohistochemistry staining method, and optical density analysis method were employed to measure the average optical density value. The expression of Myf5 and TGF-β1 was analyzed by Kruskal-Wallis and Bonferroni test. The correlation between the expression of Myf5 and TGF-β1 and the time of drug intervention was analyzed by simple linear regression. Results: (1) In the experimental group, the expression of the Myf5 of the 4 weeks sub-group, 8 weeks sub-group and 12 weeks sub-group were 33.34±17.16, 39.24±15.25 and 47.70±19.39, which were higher than the control group (21.30±7.44, 19.43±4.75, 4.82±2.66) and the blank control group (18.95±6.59, 18.00±7.29, 5.86±2.61) at the same time point, and the differences were statistically significant in 8 weeks sub-group and 12 weeks sub-group (χ(2)=21.864, 31.814, both P<0.01). The expression of Myf5 in the experimental group increased with the extension of IGF-Ⅰ intervention time (R(2)=0.99, P<0.05). But there were negative correlation between expression of Myf5 and drug intervention times in the control group and the blank control group (R(2)=0.81, 0.80, both P<0.05). (2) In the experimental group, the expression of the TGF-β1 of the 4 weeks sub-group, 8 weeks sub-group and 12 sub-weeks group were 0.80±0.12, 0.53±0.09, 0.42±0.08, which were higher than the control group (1.91±0.23, 2.30±1.03, 1.82±0.72) and the blank control group (2.01±0.31, 2.62±1.11, 1.83±0.67) at the same time point, and the differences were statistically significant (χ(2)=30.801, 40.278, 35.177, all P<0.01). The expression of TGF-β1 in the experimental group decreased with the extension of IGF-Ⅰintervention time (R(2)=0.83, P<0.05). The average optical density value regression equation of TGF-β1 in the sterile water control group and the blank control group was 0.04 and 0.06, respectively, and the fitting degree was very poor. Therefore, there was no correlation trend with time. Conclusions: Exogenic IGF-Ⅰ could enhance the expression of Myf5 in medial rectus muscle of cat model with strabismus. Exogenic IGF-Ⅰ could inhibit the expression of TGF-β1 in medial rectus muscle of cat model with strabismus. Repeated injection of exogenous IGF-Ⅰ may continuously enhance the expression of Myf5 and inhibit the expression of TGF-β1. (Chin J Ophthalmol, 2018, 54: 375-382).

Insulin-like growth factor I and its binding protein-3 are regulators of lactation and maternal responsiveness

Adaptation to motherhood includes maternal behaviour and lactation during the postpartum period. The major organizing centres of maternal behaviour and lactation are located in the hypothalamic medial preoptic area (MPOA) and the arcuate nucleus, respectively. Insulin-like growth factor I (IGF-I) is an effector of the growth hormone axis; however, its function in the brain is largely unexplored. We identified increased maternal IGF binding protein-3 (IGFBP-3) expression in preoptic rat microarray data and confirmed it by RT-PCR. In situ hybridization histochemistry showed markedly elevated IGFBP-3 expression in the MPOA and the arcuate nucleus in rat dams. Prolonged intracerebroventricular injection of IGF-I or antagonism of brain IGFBP-3 with an inhibitor (NBI-31772) using osmotic minipumps increased pup retrieval time, suggesting reduced maternal motivation. Suckling-induced prolactin release and pup weight gain were also suppressed by IGF-I, suggesting reduced lactation. In addition, IGF-I-induced tyrosine hydroxylase expression and its specific phosphorylation in tuberoinfundibular dopaminergic neurons suppress prolactin secretion. Thus, IGF-I may inhibit both behavioural and lactational alterations in mothers. Neurons in the MPOA and arcuate nuclei express IGFBP-3 during the postpartum period to neutralize IGF-I effects. IGFBP-3 can prevent the blockade of maternal behaviour and lactation exerted by IGF-I, suggesting a novel modulatory mechanism underlying the behavioural and hormonal effects during central maternal adaptations.

Tendon protein synthesis rate in classic Ehlers-Danlos patients can be stimulated with insulin-like growth factor-I.

The classic form of Ehlers-Danlos syndrome (cEDS) is an inherited connective tissue disorder, where mutations in type V collagen-encoding genes result in abnormal collagen fibrils. Thus the cEDS patients have pathological connective tissue morphology and low stiffness, but the rate of connective tissue protein turnover is unknown. We investigated whether cEDS affected the protein synthesis rate in skin and tendon, and whether this could be stimulated in tendon tissue with insulin-like growth factor-I (IGF-I). Five patients with cEDS and 10 healthy, matched controls (CTRL) were included. One patellar tendon of each participant was injected with 0.1 ml IGF-I (Increlex, Ipsen, 10 mg/ml) and the contralateral tendon with 0.1 ml isotonic saline as control. The injections were performed at both 24 and 6 h prior to tissue sampling. The fractional synthesis rate (FSR) of proteins in skin and tendon was measured with the stable isotope technique using a flood-primed continuous infusion over 6 h. After the infusion one skin biopsy and two tendon biopsies (one from each patellar tendon) were obtained. We found similar baseline FSR values in skin and tendon in the cEDS patients and controls [skin: 0.005 ± 0.002 (cEDS) and 0.007 ± 0.002 (CTRL); tendon: 0.008 ± 0.001 (cEDS) and 0.009 ± 0.002 (CTRL) %/h, mean ± SE]. IGF-I injections significantly increased FSR values in cEDS patients but not in controls (delta values: cEDS 0.007 ± 0.002, CTRL 0.001 ± 0.001%/h). In conclusion, baseline protein synthesis rates in connective tissue appeared normal in cEDS patients, and the patients responded with an increased tendon protein synthesis rate to IGF-I injections.

Neuroprotective efficacy of subcutaneous insulin-like growth factor-I administration in normotensive and hypertensive rats with an ischemic stroke

The aim of this study was to test the insulin-like growth factor-I (IGF-I) as a neuroprotective agent in a rat model for ischemic stroke and to compare its neuroprotective effects in conscious normotensive and spontaneously hypertensive rats. The effects of subcutaneous IGF-I injection were investigated in both rat strains using the endothelin-1 rat model for ischemic stroke. Motor-sensory functions were measured using the Neurological Deficit Score. Infarct size was assessed by Cresyl Violet staining. Subcutaneous administration of IGF-I resulted in significantly reduced infarct volumes and an increase in motor-sensory functions in normotensive rats. In these rats, IGF-I did not modulate blood flow in the striatum and had no effect on the activation of astrocytes as assessed by GFAP staining. In hypertensive rats, the protective effects of IGF-I were smaller and not always significant. Furthermore, IGF-I significantly reduced microglial activation in the cortex of hypertensive rats, but not in normotensive rats. More detailed studies are required to find out whether the reduction by IGF-I of microglial activation contributes to an impairment IGF-I treatment efficacy. Indeed, we have shown before that microglia in hypertensive rats have different properties compared to those in control rats, as they exhibit a reduced responsiveness to ischemic stroke and lipopolysaccharide.

IGF-I redirects doublecortin-positive cell migration in the normal adult rat brain

The migration of subventricular zone (SVZ)-derived neural precursor cells through the rostral migratory stream (RMS) to the olfactory bulb is tightly regulated by local micro-environmental cues. Insulin-like Growth Factor-I (IGF-I) can stimulate the migration of several neuronal cell types and acts as a ‘departure’ factor in the avian SVZ. To establish whether IGF-I can also act as a migratory factor for adult neuronal precursor cells in vivo, in addition to its well established role in precursor cell proliferation and differentiation, we used AAV2-mediated gene transfer to produce ectopic expression of IGF-I in the normal adult rat striatum. We then assessed whether the expression of IGF-I would recruit SVZ-derived neuronal precursor cells from the RMS into the striatum. Ectopic expression of IGF-I in the normal adult rat brain significantly increased the number of doublecortin (Dcx)-positive cells and the extent of their migration into the striatum 4 and 8weeks after AAV2–IGF-I injection but did not promote neuronal differentiation. In vitro migration assays confirmed that IGF-I is an inducer of migration and directs SVZ-derived adult neuronal precursor cell migration by both chemotaxis and chemokinesis. These results demonstrate that overexpression of IGF-I in the normal adult rat brain can override the normal cues directing precursor cell migration along the RMS and can redirect precursor cell migration into a non-neurogenic region. Enhanced expression of IGF-I following brain injury may therefore act as a diffusible factor mediating precursor cell migration to areas of neuronal cell damage.

Effects of sequential injections of hepatocyte growth factor and insulin-like growth factor-I on adult rabbit extraocular muscle

To determine whether hepatocyte growth factor (HGF) and insulin-like growth factor-I (IGF-I) have synergistic effects in promoting extraocular muscle fiber growth and force generation. A superior rectus muscle of adult rabbits was treated with either a single injection of HGF or sequential injections of HGF followed 1 week later by IGF-I. One week after HGF alone and 1 week after the IGF-I injection, the superior rectus muscles from treated and control orbits were examined for alterations in force generation as well as changes in myofiber size. Injection of HGF alone did not result in changes to muscle force, specific tension, or myofiber cross-sectional area; however, it did result in a significant increase in numbers of satellite cells. Sequential injection of HGF and IGF-I resulted in significantly increased force, specific tension, and myofiber cross-sectional areas as well as increased numbers of satellite cells. Preinjection with HGF augments the treatment effect of IGF-I. This synergistic effect is likely a result of HGF-induced activation of satellite cells and should allow a reduction in IGF-I dosing required to produce a given increase in extraocular muscle force generation.

Local administration of insulin‐like growth factor‐I(IGF‐I) stimulates tendon collagen synthesis in humans

Collagen is the predominant structural protein in tendons and ligaments, and can be controlled by hormonal changes. In animals, injections of insulin-like growth factor I (IGF-I) has been shown to increase collagen synthesis in tendons and ligaments and to improve structural tissue healing, but the effect of local IGF-I administration on tendon collagen synthesis in human has not been studied. The purpose of this study was to study whether local injections of IGF-I would have a stimulating effect on tendon collagen synthesis. Twelve healthy nonsmoking men [age 62 ± 1 years (mean ± SEM), BMI 27 ± 1] participated. Two injections of either human recombinant IGF-I (0.1 mL Increlex©) or saline (control) into each patellar tendon were performed 24-h apart, respectively. Tendon collagen fractional synthesis rate (FSR) was measured by stable isotope technique in the hours after the second injection. Simultaneously, interstitial peritendinous (IGF-I) and [procollagen type I N-terminal propeptide (PINP)], as a marker for type I collagen synthesis, were determined by microdialysis technique. Tendon collagen FSR and PINP were significantly higher in the IGF-I leg compared with the control leg (P < 0.05). In conclusion, local IGF-I administration can directly enhance tendon collagen synthesis both within and around the human tendon tissue.

Intralesional injection of insulin-like growth factor-I for treatment of superficial digital flexor tendonitis in Thoroughbred racehorses: 40 cases (2000–2004)

OBJECTIVE-To evaluate outcome after intralesional injection of insulin-like growth factor-I (IGF-I) for treatment of superficial digital flexor (SDF) tendonitis in Thoroughbred racehorses. DESIGN-Retrospective case series. ANIMALS-40 Thoroughbred racehorses. PROCEDURES-Medical records of racehorses with SDF tendonitis treated within 13 weeks after injury by intralesional injection of IGF-I (25 or 50 μg every other day for 4 or 5 treatments) were reviewed. Outcome was determined via analysis of race records, owner follow-up, and examination. RESULTS-Mean age of the horses was 3.1 years (range, 2 to 7 years), and time from injury to treatment ranged from 8 to 90 days. Mean ± SD approximate lesion length on admission was 15.6 ± 6.0 cm, and mean percentage cross-sectional area of the tendon affected was 26 ± 18%. Twenty-six of the 40 horses underwent desmotomy of the accessory ligament of the SDF tendon. Echolucency was reduced in 23 of 26 horses by the end of the treatment period. Twenty-one of 34 (62%) horses for which race data were available raced at least once after treatment, including 10 (30%) horses that raced between 1 and 4 times and 11 horses (32%) that raced ≥ 5 times. Thirteen of 28 (46%) horses had a recurrence of tendonitis or developed tendonitis elsewhere. CONCLUSIONS AND CLINICAL RELEVANCE-Results suggested that in Thoroughbred racehorses with SDF tendonitis, intralesional injection of IGF-I led to a decrease in ultrasonographic lesion severity, but treated horses had only a moderate prognosis for return to racing.

Effects of insulin‐like growth factor‐I administration on in vivo regulation of urea synthesis in normal subjects and patients with cirrhosis

The anabolic effects of insulin-like growth factor-I (IGF-I) may involve a decrease of hepatic nitrogen (N) clearance, but this has never been studied in humans. Patients with cirrhosis have low levels of IGF-I and might benefit from IGF-I therapy. Conversely, a possible decrease in hepatic N clearance by IGF-I could increase the risk of hepatic encephalopathy. To examine the effects of 1-week IGF-I administration on the functional hepatic N clearance (FHNC), viz. the linear slope of the relationship between blood-α-amino-N concentration and urea-N synthesis rate as controlled by an infusion of alanine. A randomized sequence-crossover placebo-controlled study. Eight healthy volunteers and eight patients with alcoholic cirrhosis received injections of saline or IGF-I twice daily (50 μg/kg) for 7 days. IGF-I levels at baseline were lower in the patients than those in the controls. The IGF-I treatment normalized patient levels and caused an increase in the controls to supra-physiological levels. FHNC was lower in patients compared with healthy subjects (23.0 vs 36.5 L/h, P=0.03). IGF-I treatment reduced FHNC by 30% in healthy subjects (from 36.5 to 25.7 L/h, P = 0.02), whereas no effect was found in the patients. IGF-I downregulates urea synthesis in normal subjects. This may be part of the explanation behind the anabolic effects of IGF-I. The normalization of IGF-I in cirrhosis patients without an effect on urea synthesis implies that the patients were resistant to IGF-I with regard to reduction of hepatic amino-N elimination. IGF-I treatment of cirrhosis patients evidently carries no risk of N accumulation.

Influence of periurethral injection of insulin-like growth factor-I on the expression of IGF-I and IGF-II mRNA following urethral sphincter muscle injury in female rats

Objective To investigate the effect of periurethral injection of insulin-like growth factor(IGF)-Ⅰ on the expression of IGF-Ⅰ and IGF-Ⅱ mRNA during regeneration period following urethral sphincter muscle injury in female rats. Methods Model of urethral sphincter muscle injury was made in female virgin SD rats (n=50) by intravaginal balloon inflation. Then the rats were divid-ed randomly into treatment group (n= 25) and control group (n= 25), treatment group accepted peri-urethral injection of 1.0μg human IGF-Ⅱ to the middle urethral muscle, control group accepted nor-mal saline injection. Five rats in each group were sacrificed at 2, 4, 6, 8, 14 day respectively and the whole urethra specimens were processed for RT-PCR to detect the expression of IGF-Ⅰ ,Ⅱ mRNA. A normal control group (n = 5) was set without intravaginal balloon inflation and injection. Results The expression of IGF-Ⅰ mRNA in control group increased at day 4, 6, 8, 14, the IGF-Ⅰ/β-actin ra-tios were 0. 58±0.15, 1.73±0.31, 2.30±0.29, 0. 46±0. 06. The expression of IGF-Ⅰ mRNA in treatment group increased at all time points, as 0. 69±0.21, 1.45±0.17, 2.25±0.45, 2.90±0.49, 1.92±0. 31. The difference was significant on day 4, 14(P<0.01), and day 8 (P<0.05) compared with the control group. The expression of IGF-Ⅱ mRNA in control group increased at day 4, 6, 8, as 0.42±0. 14, 1.51±0. 59, 1.31±1.04. The expression of IGF-Ⅱ mRNA in treatment group in-creased at day 4, 6, 8, 14, as 1.04±0.23, 1.94±0.29, 1.75±0.41, 0. 81±0.15. The significant difference was noted on day 4 (P<0. 01)compared with the control group. No expression of IGF-Ⅰand Ⅱ mRNA in the normal control group. Conclusions The expression of endogenous IGF-Ⅰ and IGF-Ⅱ mRNA was up-regulated by periurethral injection of IGF-Ⅰ during regeneration period follow-ing urethral sphincter muscle injury in female rat. Our findings suggest that IGF-Ⅰ facilitates the re-generation of the urethral muscles and may play a role in treatment of stress urinary incontinence in-duced by urethral sphincter muscle dysfunction. Key words: Insulin-like growth factor; Urethral sphincter muscle; Injury; Stress urinaryincontience

Regulation of REDD1 by insulin‐like growth factor‐I in skeletal muscle and myotubes

Insulin-like growth factor-I (IGF-I) is a major anabolic hormone for skeletal muscle and a potent stimulus for protein synthesis and translation initiation. Recent studies suggest that translation can be inhibited by over expression of the mammalian target of rapamycin (mTOR) repressor REDD1. The purpose of the present study was to determine whether IGF-I alters the expression of REDD1 and whether this is associated with a concomitant change in protein synthesis in vitro. Subcutaneous injection of IGF-I or intravenous delivery of insulin for 3-4 h increased REDD1 mRNA in skeletal muscle 7-10-fold. A threefold increase in REDD1 was observed when C2C12 myotubes were treated with IGF-I. REDD1 protein continued to be expressed for up to 24 h after addition of IGF-I to cells. Withdrawal of IGF-I from myotubes lead to a rapid loss of REDD1 protein content. IGF-I-induced REDD1 mRNA and protein expression were prevented by inhibitors of transcription and translation. IGF-I had an additive effect with dexamethasone (Dex) on REDD1 protein content in myotubes. The PI3K inhibitor LY294002 blocked IGF-I but not Dex induced REDD1. IGF-I also stimulated REDD1 promoter activity. Although REDD1 protein was elevated 5-6 h after addition of IGF-I to myotubes, protein synthesis measured during this 1 h window was paradoxically greater in myotubes expressing more REDD1. In contrast to the IGF-I induced increase in REDD1 mRNA, REDD2 mRNA was decreased by IGF-I. We conclude that IGF-I stimulates REDD1 expression in skeletal muscle and myotubes but under these conditions the REDD1 response is not sufficient to repress protein synthesis.

Histology of extraocular muscle after direct injection of insulin-likegrowth factor-I

目的 探讨局部注射胰岛素样生长因子Ⅰ(IGF-Ⅰ)后眼外肌组织学变化,评估局部用药对眼部组织的安全性.方法 7只成年新西兰大白兔,双眼上直肌随机注射0.05mL(10μg)IGF-Ⅰ或0.05mL生理盐水,1周后获取上直肌行组织病理学检查.结果 实验组和对照组眼球巩膜及色素膜未见明显炎性细胞浸润;实验组眶层纤维周径(120.24±30.76)μm与对照组(108.48±25.64)μm比较差异有统计学意义(t=6.734,P=0.000).2组球层眼外肌肌纤维周径差异无统计学意义(t=1.527,P=0.127).实验组的球层和眶层纤维大细胞和小细胞的比例与对照组差异有统计学意义.实验组球层和眶层眼外肌活化卫星细胞的比例较对照组均显著提高;2组眼外肌球层肌纤维的活化卫星细胞比例较眶层显著提高.结论 局部注射10μg IGF-Ⅰ对眼部组织无明显不良反应,局部应用对眼外肌和眼球是安全的.IGF-Ⅰ能使眼外肌肌纤维快速增生,激活肌卫星细胞.球层和眶层眼外肌肌纤维对IGF-Ⅰ的反应可能有所不同。

Increased Extraocular Muscle Strength with Direct Injection of Insulin-like Growth Factor-I

Previous work has demonstrated the effectiveness of insulin-like growth factor (IGF)-II in increasing force generation in extraocular muscle (EOM). Studies in the literature have suggested that IGF-I would be even more effective than IGF-II. This study was performed to assess the effects on muscle mass and force generation of IGF-I injection in adult rabbit superior rectus muscle. Adult rabbits received a single injection of IGF-I at one of several doses into one superior rectus muscle. One week after treatment, the rabbits were euthanatized, and the superior rectus muscle from each orbit was removed. Force generation was measured using an in vitro apparatus, and injected muscles were compared with the contralateral control. A second group of animals were injected similarly, and the muscles were examined at 1 week for changes in cross-sectional area of individual myofibers. EOMs demonstrate significant numbers of cells expressing the IGF receptor. After the EOMs were injected with IGF-I, there were significant increases both in muscle force generation and cross-sectional area at all doses tested in this study. Doses of 10 and 25 microg IGF-I were most effective. Direct muscular injection of IGF-I effectively increases EOM force generation without the potential biomechanical hazards of surgery such as permanently altered muscle length or insertional position on the globe.

Elevated plasma free fatty acids decrease basal protein synthesis, but not the anabolic effect of leucine, in skeletal muscle

Elevations in free fatty acids (FFAs) impair glucose uptake in skeletal muscle. However, there is no information pertaining to the effect of elevated circulating lipids on either basal protein synthesis or the anabolic effects of leucine and insulin-like growth factor I (IGF-I). In chronically catheterized conscious rats, the short-term elevation of plasma FFAs by the 5-h infusion of heparin plus Intralipid decreased muscle protein synthesis by approximately 25% under basal conditions. Lipid infusion was associated with a redistribution of eukaryotic initiation factor (eIF)4E from the active eIF4E.eIF4G complex to the inactive eIF4E.4E-BP1 complex. This shift was associated with a decreased phosphorylation of eIF4G but not 4E-BP1. Lipid infusion did not significantly alter either the total amount or phosphorylation state of mTOR, TSC2, S6K1, or the ribosomal protein S6 under basal conditions. In control rats, oral leucine increased muscle protein synthesis. This anabolic response was not impaired by lipid infusion, and no defects in signal transduction pathways regulating translation initiation were detected. In separate rats that received a bolus injection of IGF-I, lipid infusion attenuated the normal redistribution of eIF4E from the active to inactive complex and largely prevented the increased phosphorylation of 4E-BP1, eIF4G, S6K1, and S6. This IGF-I resistance was associated with enhanced Ser(307) phosphorylation of insulin receptor substrate-1 (IRS-1). These data indicate that the short-term elevation of plasma FFAs impairs basal protein synthesis in muscle by altering eIF4E availability, and this defect may be related to impaired phosphorylation of eIF4G, not 4E-BP1. Moreover, hyperlipidemia impairs IGF-I action but does not produce leucine resistance in skeletal muscle.

Pentoxifylline and insulin-like growth factor-I (IGF-I) abrogate kainic acid-induced cognitive impairment in mice

Hippocampal insults involving neuroimmune mechanisms can impair learning and memory in a variety of tasks. The present study was designed to assess the effect of pentoxifylline, an inhibitor of tumor necrosis factor alpha (TNFα), and insulin-like growth factor-I (IGF-I) on kainate (KA)-induced impairment in spatial memory. Male mice received a subcutaneous injection of a dose of KA (15 mg/kg) that had no cytotoxic effect on hippocampal neurons as confirmed by Fluorojade B staining. This dose resulted in an impairment of spatial memory in a two-trial recognition task 11 days later. Intraperitoneal administration of pentoxifylline (200 mg/kg) abrogated this effect. Repeated intracerebroventricular injection of IGF-I (2 μg/mouse on day 1 followed by 1 μg/mouse on days 2–5) abrogated KA-induced deficits in spatial memory whereas acute IGF-I (2 μg/mouse on day 1 only) had mixed effects. These findings indicate that endogenous TNFα is probably involved in the detrimental effects of kainate on cognition and that exogenous IGF-I can oppose these effects, probably by antagonizing TNFα-induced neurotoxicity.

Reconstruction of erectile reflex circuit by autologous vein graft combined with use of insulin-like growth factor

To explore the feasibility of erectile reflex circuit reconstruction by autologous vein graft combined with the use of insulin-like growth factor-I (IGF-I). 48 male adult Sprague-Dawley rats were randomized into 4 groups of 12 rats: group I (sham-operation group), undergoing operation to identify the bilateral cavernous nerves (CNs) only; group II (bilateral CN ablation group) in which the bilateral CNs of the length of at least 5 mm were ablated; group III (vein graft plus IGF-I group) in which the ablated CNs were repaired by autologous vein graft and IGF-I was injected into the venous cavity; and group IV (vein graft plus normal saline group), in which the ablated CNs were repaired and normal saline was injected instead. Four months later, apomorphine test was performed on each rat, and the erection times during the following half hour were recorded. After that, 4% fluoro-gold was injected into the bilateral corpus cavernosum of penis for each rat after anesthesia. Five days later, the rats were sacrificed and their bilateral major pelvic ganglia were obtained for detection of fluoro-gold by fluorescent microscopy. Apomorphine test showed an erection rate of 92% in group III, significantly higher than those of the group II (0%) and group IV (50%, both P < 0.01), and close to that of the sham-operation group (100%, P > 0.05). The average erection times of the group III was (1.5 +/- 0.8) times, significantly more than those of the group II and group IV [(0.0 +/- 0.0) times and (0.6 +/- 0.7) times respectively, both P < 0.05], but significantly less than that of the sham-operation group [(2.7 +/- 0.9) times, P < 0.05]. Five days after injection of fluoro-gold solution, the number of fluoro-god positively stained neural cells of the group III was 86 +/- 14, significantly more than those of the group II (14 +/- 6) and group IV (46 +/- 14, both P < 0.05), but significantly less than that of the sham-operation group (152 +/- 36, P < 0.05). And the fluoro-gold stained neural cells of the group III was brighter than those of the group II and group IV, but not so bright as those of the sham operation group. Reparation of ablated CNs by autologous vein graft combined with local injection of IGF-I is a new effective method to treat ED following CN injury.

Insulin-like growth factor I is required for vessel remodeling in the adult brain.

Although vascular dysfunction is a major suspect in the etiology of several important neurodegenerative diseases, the signals involved in vessel homeostasis in the brain are still poorly understood. We have determined whether insulin-like growth factor I (IGF-I), a wide-spectrum growth factor with angiogenic actions, participates in vascular remodeling in the adult brain. IGF-I induces the growth of cultured brain endothelial cells through hypoxiainducible factor 1 alpha and vascular endothelial growth factor, a canonical angiogenic pathway. Furthermore, the systemic injection of IGF-I in adult mice increases brain vessel density. Physical exercise that stimulates widespread brain vessel growth in normal mice fails to do so in mice with low serum IGF-I. Brain injury that stimulates angiogenesis at the injury site also requires IGF-I to promote perilesion vessel growth, because blockade of IGF-I input by an anti-IGF-I abrogates vascular growth at the injury site. Thus, IGF-I participates in vessel remodeling in the adult brain. Low serum/brain IGF-I levels that are associated with old age and with several neurodegenerative diseases may be related to an increased risk of vascular dysfunction.

Local administration of IGF-I stimulates the growth of mandibular condyle in mature rats.

To evaluate the effects of local injection of insulin-like growth factor I (IGF-I) on the growth of mandibular condyle in mature rats. Sixteen 15 week-old male rats were used in this study. In the experimental group, IGF-I at a concentration of 50 microg/ml was injected into articular capsules of the condyle, while rats in the control group were injected with equal volume of physiological saline. These injections were performed three times at 7 day intervals, and all of the rats were killed on the 7th day after the last injection. Tetracycline and calcein were used for vital staining. After death, the condyles were extracted and undecalcified ground sections were prepared for histological and histomorphometric observations. The thickness of the cartilaginous layer of the condyle, the percentage of bone area in the subchondral cancellous bone layer and the amount of endochondral bone growth in the condyle were measured. The significance of the difference in these measurements between IGF-I and control group was evaluated. An increase in the thickness of the cartilaginous layer, and a decrease in the percentage of bone area in the subchondral cancellous bone layer was recognized in IGF-I treated condyle. The amount of endochondral bone growth in the experimental group was greater than that in the control group. The local injection of IGF-I into mature condyle seemed to reactivate the process of endochondral bone formation and induced actual bone growth in mature condyle.

Improvement of the developmental capacity of oocytes from prepubertal cattle by intraovarian insulin-like growth factor-I application.

The developmental potential of oocytes from prepubertal cattle is decreased, compared with those from their adult counterparts. The aim of the present study was to improve the developmental capacity of oocytes from prepubertal cattle by either systemic application of recombinant bovine somatotropin (rbST) or intraovarian injection of insulin-like growth factor-I (IGF-I). Blastocyst yields and the mRNA expression pattern (relative abundance, RA) of three putative marker genes (i.e., glucose transporter-1, Glut-1; eukaryotic translation initiation factor-1A, eIF1A, and upstream binding factor, UBF) were selected as criteria to determine the success of the treatments. At 6-7 mo of age, 30 healthy Holstein calves were randomly assigned to three experimental groups. The first group served as control and received an intraovarian injection of 0.6 ml acetic acid. The second group received a single s.c. injection of 500 mg of rbST. The third group received an intraovarian injection of 6 microg recombinant human IGF-I. During the following 2 wk, follicles were aspirated four times via transvaginal ultrasound-guided technology. All animals were i.m. injected with 60 mg FSH 48 h prior to each aspiration. The treatments were repeated with the same animals at 9-10, 11-12, and 14-15 mo of age. For comparison, five adult cows were each i.m. injected with 100 mg FSH and underwent oocyte retrieval. The proportion of oocytes considered to be developmentally competent was higher in cows than calves (65% vs. 58%, 50%, 52%) for the control, rbST, and IGF-I groups, respectively. The rate of blastocysts was similar in IGF-I-treated calves and cows (28% and 25%) and was higher (P </= 0.05) than in the controls and the rbST group (11% and 16%). The RA for Glut-1 was lower (P </= 0.05) in two- to four- cell embryos from calves, compared with cows. At the 8- to 16- cell stage, Glut-1 RA was similar in IGF-I-treated calves and cows. The RA for eIF1A was higher (P </= 0.05) in 8- to 16-cell embryos derived from cows than those from the control group. Results show that IGF-I intraovarian injection increased blastocyst yields and mRNA expression of Glut-1 and eIF1A to levels found in embryos produced from adult cows. This treatment may at least partially overcome the developmental deficiency of oocytes derived from calves and could be a step forward toward the use of prepubertal animals in breeding programs aimed at shortening the generation interval.