Recombinant Human Insulin-like Growth factor-I Research Articles

Are the Effects of Oral and Vaginal Contraceptives on Bone Formation in Young Women Mediated via the Growth Hormone-IGF-I Axis?

Purpose: Combined hormonal contraceptive therapy has been associated with negative bone mineral density outcomes that may be route-dependent [i.e., combined oral contraception (COC) vs. contraceptive vaginal ring (CVR)] and involve the hepatic growth hormone (GH)/insulin-like growth factor-I (IGF-I) axis. The objective of the pilot study was to assess the impact of route of contraceptive administration on IGF-I and procollagen type I N-terminal propeptide (PINP) responses to an IGF-I Generation Test. We hypothesized that the peak rise in IGF-I and PINP concentration and area under the curve (AUC) would be attenuated following COC, but not CVR, use.Methods: Healthy, premenopausal women not taking hormonal contraception were recruited. Women were enrolled in the control group (n = 8) or randomly assigned to COC (n = 8) or CVR (n = 8) for two contraceptive cycles. IGF-I Generation Tests were used as a probe to stimulate IGF-I release and were completed during the pre-intervention and intervention phases. Serum IGF-I and PINP were measured during both IGF-I Generation Tests. The study was registered at ClinicalTrials.gov (NCT02367833).Results: Compared to the pre-intervention phase, peak IGF-I concentration in response to the IGF-I Generation Test in the intervention phase was suppressed in the COC group (p < 0.001), but not the CVR or Control groups (p > 0.090). Additionally, compared to the pre-intervention phase, PINP AUC during the intervention phase was suppressed in both COC and CVR groups (p < 0.001), while no difference was observed in the control group (p = 0.980).Conclusion: These data suggest that changes in recombinant human GH-stimulated hepatic IGF-I synthesis in response to combined hormonal contraception (CHC) use are dependent on route of CHC administration, while the influence on PINP is route-independent. Future research is needed to expand these results with larger randomized control trials in all age ranges of women who utilize hormonal contraception.Clinical Trial Registration: www.ClinicalTrials.gov registration NCT02367833.

A rationale for the treatment of short stature in children with the combination of recombinant human growth hormone (rhGH) and recombinant human insulin-like growth factor-I (rhIGF-I)

Both rhGH and rhIGF-I are signaling molecules with the capacity to restore the rate of growth in certain subsets of slowly growing children. In some instances, heights attained at or near the time of cessation of linear growth are indistinguishable from the height distribution of the community as a whole or from the height distribution expected based on the heights of biological parents. The GH: IGF-I signaling system is sequential, forming a continuous loop wherein GH will stimulate production of IGF-I and IGF-I will inhibit production of GH. This feature suggests that a deficiency of GH will be accompanied by a deficiency of IGF-I and that treatment of GH deficiency with rhGH will restore IGF-I and the subnormal growth of combined GH: IGF-I deficiency. Although logical, this proposition is not always true. rhGH and rhIGF-I are distinct polypeptides, with distinct cell surface receptors and distinct intracellular signaling pathways both capable of amplifying distinct, yet overlapping, patterns of gene replication, protein synthesis and metabolic activities. These features suggest that neither treatment with rhGH nor rhIGF-I alone will invariably recapitulate the combined activities of the GH: IGF-I system, At the present time, this proposition appears both logical and true. The possibility that combined rhGH and rhIGF-I treatment can accomplish that which neither monotherapy can has been examined in gene knock-out experiments in animals and direct comparisons of GH, IGF-I and combined GH: IGF- treatments in animals and in children with short stature, normal GH and low IGF-I (primary IGF-I deficiency). In these experimental models, the growth rates with combined rhGH and rhIGF-I treatment exceed those of either monotherapy. The extent to which this proposition can be generalized to various short stature populations remains to be determined.

Addition of insulin-like growth factor I (IGF-I) and reduced glutathione (GSH) to cryopreserved boar semen

The objective of this study was to evaluate the effect of adding reduced glutathione (GSH) to a boar semen freezing extender supplemented with insulin-like growth factor I (IGF-I) or anti-IGF-I. Eight ejaculates from eight boars were extended to obtain insemination doses, which were supplemented with either recombinant human IGF-I (30 ng/mL) or anti-IGF-I (60 ng/mL) shortly after extension. After 24 h of liquid storage at 17 °C, the semen was frozen with or without GSH (5 mM) in the freezing extender for a total of six treatments. Osmotic resistance and acrosome integrity was greater in fresh semen (P < 0.05) soon after adding IGF-I or the anti-IGF-I antibody. After 24 h of cooling, the supplementation with these compounds resulted in an increased (P < 0.05) percentage of sperm with relatively greater mitochondrial activity and reduced the percentage of cells with relatively greater concentrations of superoxide. After thawing, there was a reduction (P < 0.05) in the percentage and fluorescence intensity of sperm with greater quantities of superoxide and peroxide only in samples treated with GSH + IGF-I and GSH + anti-IGF-I. The addition of GSH (alone or in combination with IGF-I or anti-IGF-I), however, reduced the percentage of sperm with an intact acrosome (P < 0.05). The same effect was not observed with IGF-I or anti-IGF-I alone. In conclusion, the addition of IGF-I or anti-IGF-I improved the quality of fresh or liquid-stored semen. Using GSH in the freezing extender improved the antioxidant potential of frozen semen only in combination with IGF-I or an anti-IGF-I antibody.

Effect and mechanism of adipocyte co-culture on aquaporin-9 expression in HepG2 cells

Objective: To observe the effect of differentiated mature adipocytes on hepatic steatosis and aquaporin-9 (AQP9) expressions in HepG2 cells and further explore its possible mechanism of action. Methods: Human preadipocytes were cultured and differentiated to full maturity. HepG2 cells were co-cultured with non-differentiated adipocytes and differentiated mature adipocytes for 48 h, and then labeled as control group and experimental group. Oil red O staining and intracellular triglyceride content were performed on co-cultured HepG2 cells and simultaneous changes in phosphatidylinositol 3-kinase (PI3K) - serine/threonine kinase (Akt) signaling pathway, and AQP9 mRNA and protein levels were detected. The experimental group was co-cultured with recombinant human insulin-like growth factor-I (IGF-I), with the addition of 100ng/ml PI3K-Akt pathway agonist, labeled as experimental group + IGF-I group. The activation of PI3K-Akt pathway was verified by Western blotting (WB). The expression of AQP9 was detected by RT-q PCR and WB. The recombinant lentivirus LV-AQP9 or empty-loaded virus LV-PWPI was transfected with HepG2 cells by recombinant lentiviral transfection tecnique, and labeled as HepG2-AQP9 and HepG2-PWPI. The transfection efficiency was assessed by confocal laser scanning microscopy and RT-qPCR and WB detected the change of AQP9 expression level after virus transfection. Afterwards, the stable over-expressed HepG2-AQP9 cells and the empty-loaded HepG2-PWPI cells were co-cultured with differentiated mature adipocytes for 48h, and labeled as HepG2-AQP9 co-culture group, and then intracellular triglyceride content were detected with Oil red O staining. Finally, IGF-I was added to the HepG2-AQP9 co-culture group, which was recorded as HepG2-AQP9 co-culture + IGF-I group. Intracellular triglyceride content was detected with Oil red O staining, and WB verified PI3K-Akt signaling pathway activation and changes in AQP9 mRNA and protein levels. A t-test was used to compare the two independent samples. Results: The intracellular lipid droplets and triglyceride content (0.052 ± 0.005) in the experimental group was increased significantly than the control group (0.033 ± 0.003) (t= 5.225,P= 0.006), suggesting that adipocyte co-culture had induced steatosis in HepG2 cells. RT-qPCR and WB results indicated that the expression levels of AQP9 mRNA (3.615 ± 0.330) and protein levels (0.072 ± 0.005) in the experimental group were significantly higher than the control group (t= 13.708, 11.225,P= 0.005, < 0.001). WB results showed that the expression level of phosphorylated Akt (p-Akt) protein (0.116±0.003) in the experimental group was significantly lower than the control group (0.202 ± 0.003) (t= 27.136,P< 0.001). The total Akt protein was constant, and the p-Akt/total Akt (0.182 ± 0.017)was significantly lower than the control group (0.327 ± 0.019) (t= 2.431,P= 0.001), suggesting that adipocyte co-culture had inhibited PI3K- Akt signaling pathway in HepG2 cells and up-regulated the expression level of AQP9. WB results indicated that the expression level of p-Akt protein (0.194 ± 0.021) in the experimental group + IGF-I group was significantly higher than the experimental group (0.132 ± 0.003) (t= 5.082,P= 0.007). The total Akt protein was constant, and the p-Akt/total Akt (0.281 ± 0.009) was significantly higher than the control group (0.184 ± 0.132) (t= 10.311,P< 0.001). Simultaneously, RT-qPCR and WB results indicated that the expression levels of AQP9 mRNA (0.327 ± 0.347) and protein levels (0.042 ± 0.004) in the experimental group + IGF-I group were significantly lower than the experimental group (t= 33.573, 5.598,P< 0.001, 0.005), suggesting that adipocyte co-culture had possibility to regulate the expression level of AQP9 through the PI3K-Akt pathway. Confocal laser microscopy analysis showed that the transfection efficiency was more than 90%. RT-q PCR and WB results indicated that the expression levels of AQP9 mRNA and protein levels (0.373 ± 0.221) in HepG2-AQP9 group were significantly higher than HepG2-PWPI group (t=14.953, 28.931,P= 0.002 and 0.000), suggesting that the stable overexpression of AQP9 cell line was successfully constructed. The intracellular lipid droplets and triglyceride content in HepG2-AQP9 co-culture group was significantly increased (t= 5.478, 5.369,P= 0.005) than HepG2-PWPI co-culture group and HepG2-AQP9 co-culture+ IGF-I group, suggesting that the increased expression of AQP9 had promoted HepG2 steatosis in co-cultured adipocytes. WB results showed the expression levels of p-Akt protein (0.168 ± 0.006) and p-Akt/total Akt (0.265±0.009) in HepG2-AQP9 co-culture + IGF-1 group was significantly increased (t= 16.311, 8.769,P< 0.001) than HepG2-AQP9 co-culture group, while the expression levels of AQP9 mRNA (0.327 ± 0.034) and protein (0.375 ± 0.025) was significantly decreased (t= 33.573, 9.146,P< 0.001 and 0.001). Conclusion: Adipocytes co-culture can induce steatosis in HepG2 cells, and may participate in inhibiting PI3K-Akt signaling pathway to upregulate the expression of AQP9 in steatotic HepG2 cells.

First-in-man study with a novel PEGylated recombinant human insulin-like growth factor-I

ObjectiveThis study is a first time assessment of safety and tolerability, pharmacokinetics, and pharmacodynamics of RO5046013 in human, in comparison with unmodified rhIGF-I. DesignThe study was conducted as a single-center, randomized, double-blinded, placebo-controlled, single ascending dose, parallel group study in a clinical research unit in France. A total of 62 healthy volunteers participated in this clinical trial. RO5046013 was given as single subcutaneous injection, or as intravenous infusion over 48h, at ascending dose levels. The active comparator rhIGF-I was administered at 50μg/kg subcutaneously twice daily for 4days. Safety and tolerability, pharmacokinetics, and pharmacodynamics of RO5046013 were evaluated. ResultsPEGylation resulted in long exposure to RO5046013 with a half-life of 140–200h. Exposure to RO5046013 increased approximately dose proportionally. RO5046013 was safe and well tolerated at all doses, injection site erythema after SC administration was the most frequent observed AE. No hypoglycemia occurred. Growth hormone (GH) secretion was almost completely suppressed with rhIGF-I administration, whereas RO5046013 caused only a modest decrease in GH at the highest dose given IV. ConclusionsPEGylation of IGF-I strongly enhances half-life, reduces the negative GH feedback and hypoglycemia potential, and therefore offers a valuable alternative to rhIGF-I in treatment of relevant diseases.

Central IGF-I Receptors in the Brain are Instrumental to Neuroprotection by Systemically Injected IGF-I in a Rat Model for Ischemic Stroke.

Insulin-like growth factor I (IGF-I) is a neuroprotective agent in animal models of ischemic stroke. The purpose of this study was to determine whether systemically injected IGF-I exerts its neuroprotective action by binding to IGF-I receptors in the brain after crossing the blood-brain barrier, or via peripheral effects. To differentiate the central effects of IGF-I from systemic effects, ischemic stroke was induced in conscious male Wistar Kyoto rats by the injection of endothelin-1 adjacent to the middle cerebral artery in the right hemisphere, while either the IGF-I receptor antagonist JB-1 or vehicle was introduced into the right lateral ventricle. Intravenous injection of recombinant human (rh)IGF-I resulted in 50% reduction in infarct size, which was counteracted by the central administration of JB-1. Furthermore, rhIGF-I was detected in both the ischemic and nonischemic hemisphere. Systemically injected rhIGF-I passes the blood-brain barrier and protects neurons via IGF-I receptors in the brain in rats with an ischemic stroke.

Potency of Full-Length MGF to Induce Maximal Activation of the IGF-I R Is Similar to Recombinant Human IGF-I at High Equimolar Concentrations.

AimsTo compare full-length mechano growth factor (full-length MGF) with human recombinant insulin-like growth factor-I (IGF-I) and human recombinant insulin (HI) in their ability to activate the human IGF-I receptor (IGF-IR), the human insulin receptor (IR-A) and the human insulin receptor-B (IR-B), respectively. In addition, we tested the stimulatory activity of human MGF and its stabilized analog Goldspink-MGF on the IGF-IR.MethodsThe effects of full-length MGF, IGF-I, human mechano growth factor (MGF), Goldspink-MGF and HI were compared using kinase specific receptor activation (KIRA) bioassays specific for IGF-I, IR-A or IR-B, respectively. These assays quantify activity by measuring auto-phosphorylation of the receptor upon ligand binding.ResultsIGF-IR: At high equimolar concentrations maximal IGF-IR stimulating effects generated by full-length MGF were similar to that of IGF-I (89-fold vs. 77-fold, respectively). However, EC50 values of IGF-I and full-length MGF for the IGF-I receptor were 0.86 nmol/L (95% CI 0.69–1.07) and 7.83 nmol/L (95% CI: 4.87–12.58), respectively. No IGF-IR activation was observed by human MGF and Goldspink-MGF, respectively. IR-A/IR-B: At high equimolar concentrations similar maximal IR-A stimulating effects were observed for full -length MGF and HI, but maximal IR-B stimulation achieved by full -length MGF was stronger than that by HI (292-fold vs. 98-fold). EC50 values of HI and full-length MGF for the IR-A were 1.13 nmol/L (95% CI 0.69–1.84) and 73.11 nmol/L (42.87–124.69), respectively; for IR-B these values were 1.28 nmol/L (95% CI 0.64–2.57) and 35.10 nmol/L (95% 17.52–70.33), respectively.ConclusionsFull-length MGF directly stimulates the IGF-IR. Despite a higher EC50 concentration, at high equimolar concentrations full-length MGF showed a similar maximal potency to activate the IGF-IR as compared to IGF-I. Further research is needed to understand the actions of full-length MGF in vivo and to define the physiological relevance of our in vitro findings.

Effect of insulin-like growth factor-I during the early postnatal period in intrauterine growth-restricted rats.

Insulin-like growth factor-I (IGF-I) is essential for perinatal growth and development; low serum IGF-I has been observed during intrauterine growth restriction (IUGR). We investigated the effects of recombinant human (rh) IGF-I in IUGR rats during the early postnatal period. Intrauterine growth restriction was induced by bilateral uterine artery ligation in pregnant rats. IUGR pups were divided into two groups injected daily with rhIGF-I (2 mg/kg; IUGR/IGF-I, n = 16) or saline (IUGR/physiologic saline solution (PSS), n = 16) from postnatal day (PND) 7 to 13. Maternal sham-operated pups injected with saline were used as controls (control, n = 16). Serum IGF-I and IGF binding proteins (IGFBP) 3 and 5 were measured on PND25. The expression of Igf-i, IGF-I receptor (Igf-ir), Igfbp3, and 5 mRNA in the liver and brain was measured using real-time polymerase chain reaction on PND25. Immunohistochemical staining of the liver for IGF expression was performed. Mean bodyweight on PND3 and PND25 in the IUGR pups (IUGR/IGF-I and IUGR/PSS) was significantly lower than that of the control pups. Serum IGF-I and hepatic Igf-ir mRNA in the IUGR pups were significantly lower than those in the control pups. In the IUGR/IGF-I group, hepatic Igfbp3 mRNA and liver immunohistochemical staining were increased. In the IUGR/PSS and control pups, there were no significant differences between these two groups in serum IGFBP3 and IGFBP5, hepatic Igf-i and Igfbp-5 mRNA, or brain Igf mRNA. No benefits on body and brain weight gain but an effective increase in hepatic IGFBP-3 was observed after treatment with 2 mg/kg rhIGF-I during the early postnatal period.

Recombinant IGF-I: Past, present and future

Normal linear growth in humans requires GH and IGF-I. Diminished GH action resulting in reduced availability of IGF-I and IGF-binding proteins is the hallmarks of GH Insensitivity Syndromes (GHIS). The deficiencies are the perceived mechanisms for the growth failure of affected patients and the therapeutic targets for the restoration of normal growth. Early treatment attempts with pituitary-derived GH had limited effects in GHIS patients. Recombinant human insulin-like growth factor-I (rhIGF-I) treatment initially provides accelerated growth to GHIS children and provides substantial benefit. But, in general, catch up growth is less substantial with rhIGF-I treatment of GHIS than with rhGH treatment of GH Deficiency. Few classic GHIS patients have reached heights in the normal range (height SD score between −2.0 SD and +2.0 SD) with rhIGF-I monotherapy. A potential explanation is that while rhIGF-I treatment increases circulating concentrations of IGF-1 and IGFBP-3, such treatment reduces endogenous GH levels by negative feedback inhibition of pituitary GH release. In as much as both GH and IGF-I are required for good catch up growth, the loss of any residual GH signaling during IGF-I monotherapy in GHIS patients may attenuate possible catch up growth. Consistent with this explanation is the finding that, as predicted by the preclinical studies by Ross Clark, combination of rhGH & rhIGF-1 provides better growth responses than rhIGF-1 monotherapy in prepubertal children with short stature and low IGF-I levels despite normal stimulated GH responses. In the future, rhGH and rhIGF-I combination therapy can potentially improve growth outcomes over that seen with rhIGF-I monotherapy in all GHIS patients except in those with a total lack of functional GH signaling. Future alternative treatments for GHIS subjects may also include the use of post-growth hormone receptor signaling agonists which restore both GH signaling and IGF-I exposures or the addition of long-acting rhGH species to rhIGF-I. Additional etiologic factors for the growth failure in GHIS should be considered if the growth deficits of GHIS do not resolve with treatment.

Development and characterization of an enzyme-linked DNA aptamer-magnetic bead-based assay for human IGF-I in serum

DNA aptamer sequences were selected and screened for affinity against recombinant human insulin-like growth factor-I (rhIGF-I) using an ELISA-like aptamer-based assay (ELASA). When the top four aptamers were paired against one another in all possible sandwich assay combinations using capture aptamers on magnetic beads (MBs), one sandwich combination appeared superior. This combination produced a reliably sensitive assay with a probable limit of detection<16ng/mL even in human serum. The assay did not require separation of rhIGF-I from IGF binding proteins (IGFBP) in human serum, suggesting that the capture and reporter aptamers may bind an exposed IGF-I epitope in the IGF-I–IGFBP complex.

Insulin-Like Growth Factor I Inhibits Alveolar Bone Loss Following Tooth Extraction in Rats.

Alveolar bone is often lost after tooth extraction. Few studies have assessed the longitudinal changes in bone volume that occur within these extraction sites. To investigate the longitudinal morphological changes in extraction sockets following sustained continuous subcutaneous infusion of human recombinant insulin-like growth factor I (IGF-I). Fourteen rats were subjected to right mandibular first molar extraction. Experimental rats (n = 7) received a continuous subcutaneous infusion of human recombinant IGF-I (320 mg/day) for 3 weeks by osmotic minipump. Control animals were treated with saline via the same method (n = 7). All rats were then housed for an additional 3 weeks. Micro-CT scanning was performed immediately after tooth extraction and at 1, 2, 3, and 6 weeks after extraction. New bone formation was markedly higher in the IGF-I-treated group as compared with the control group. The loss in alveolar ridge height in the IGF-I group was significantly lower than that in the control group at each time point after extraction on the buccal side and at 2, 3, and 6 weeks on the lingual side. IGF-I treatment increases the volume of newly formed bone and reduces the loss in alveolar ridge height following tooth extraction.

P.11.15 Recombinant human insulin-like growth factor-I (IGF-I) therapy in Duchenne Muscular Dystrophy (DMD): A 6-month prospective randomized controlled trial

Glucocorticoids (GC) delay motor decline in DMD, but cause significant endocrine adverse effects. IGF-I offers potential as a therapeutic agent; it may improve or preserve muscle function and counter GC effects of growth failure and insulin resistance. To determine if IGF-I therapy (1) improves or preserves muscle function and (2) improves linear growth in DMD. Prospective randomized controlled trial of IGF-I therapy in pre-pubertal, ambulatory, GC-treated DMD boys (n = 17) compared to controls (GC alone, n = 21). IGF-I 160 mcg/kg was given daily subcutaneously for 6 months. Primary motor outcome was 6-min walk distance (6MWD), and endocrine outcomes were height velocity and change in height SD score (ΔHtSDS). Other outcomes included changes in timed motor tests, cardiopulmonary function, insulin sensitivity and safety. The difference of 6MWD between control and IGF-I groups at 6 months was 8.5 ± 7.0 m (mean ± SEM, p > 0.5). There were no significant differences between groups for changes in cardiopulmonary and other motor functional outcomes. Height velocity in IGF-I treated subjects was double that of controls at 6 months (6.5 ± 0.4 vs. 3.3 ± 0.3 cm/yr, p In this first study of IGF-I therapy in DMD boys, 6 months of daily IGF-I significantly increased height velocity and HtSDS compared to controls, but there was no difference in motor functional outcomes.

Insulin-like growth factor-I (IGF-I) misuse in athletes and potential methods for detection

To athletes, insulin-like growth factor-I (IGF-I) is an attractive performance-enhancing drug, particularly as an alternative to growth hormone (GH) because IGF-I mediates many of the anabolic actions of GH. IGF-I has beneficial effects on muscle protein synthesis and glycogen storage that could enhance performance in several sporting disciplines. Recombinant human IGF-I (rhIGF-I) is used in clinical practice, but a variety of IGF-I compounds and IGF-I analogues are also advertised on the internet and many have been available on the black market for several years. Although methods for detecting GH misuse are now well established and there have been several cases in which athletes have tested positive for GH, no test is yet in place for detecting IGF-I misuse. The GH-2004 research group has been investigating methods for detection of IGF-I misuse and a test is being developed on the basis of the principles of the successful GH-2000 marker method, in which markers from the IGF axis and markers of collagen and bone turnover are used to detect GH misuse. Commercial immunoassays for these markers have been validated for anti-doping purposes but new methods, including IGF-I measurement by use of mass spectrometry, should improve the performance of the tests and help in the detection of athletes who are doping with these peptide hormones.

Osteo-promoting effects of insulin-like growth factor I (IGF-I) in a mouse model of type 1 diabetes

ObjectiveUsing a streptozotocin (STZ)-induced mouse model of type 1 diabetes (T1D), we have previously demonstrated that long-term diabetes inhibits regenerative bone formation during tibial distraction osteogenesis (DO) and perturbs skeletal integrity by decreasing cortical thickness, bone mineral density and bone's resistance to fracture. Because long-standing T1D is also associated with a deficiency of insulin-like growth factor I (IGF-I), we examined the effects of systemic IGF-I treatment on skeletal microarchitecture and strength, as well as on bone formation in diabetic mice. Research design and methodsStreptozotocin-induced diabetic or control mice were treated with recombinant human IGF-I (rhIGF-I, 1.5mg/kg/day as subcutaneous infusion) or vehicle throughout a 14day DO procedure. Thereafter, trunk blood was assayed for glucose, insulin, rhIGF-I, mouse IGF-I and leptin. Bone formation in distracted tibiae was quantified. Effects on cortical bone strength and trabecular bone architecture were assessed by μCT analysis and three-point bend testing of contralateral femurs. ResultsNew bone formation during DO was reduced in diabetic mice but significantly improved with rhIGF-I treatment. The contralateral femurs of diabetic mice demonstrated significant reductions in trabecular thickness, yield strength and peak force of cortical bone, which were improved with rhIGF-I treatment. rhIGF-I also reduced intracortical porosity in control mice. However, treatment with rhIGF-I did not normalize serum glucose, or correct concurrent deficiencies of insulin or leptin seen in diabetes. ConclusionsThese findings demonstrate that despite persistent hyperglycemia, rhIGF-I promoted new bone formation and improved biomechanical properties of bone in a model of T1D, suggesting that it may be useful as a fracture preventative in this disease.

Adult and Near-Adult Height in Patients with Severe Insulin-Like Growth Factor-I Deficiency after Long-Term Therapy with Recombinant Human Insulin-Like Growth Factor-I

Background: Treatment with recombinant human insulin-like growth factor-I (IGF-I) stimulates linear growth in children with severe IGF-I deficiency (IGFD). Aims: To evaluate the efficacy and safety of treatment with IGF-I in patients with severe IGFD treated until adult or near-adult height. Methods: Twenty-one children with severe IGFD were treated until adult or near-adult height under a predominantly open-label design. All patients were naive to IGF-I. Recombinant human IGF-I was administered subcutaneously in doses between 60 and 120 µg/kg twice daily. Nine patients received additional therapy with gonadotropin- releasing hormone (GnRH) analog for a mean period of 2.9 ± 1.8 years. Results: Mean duration of treatment was 10.0 years. Mean height velocity increased from 3.1 cm/year prior to treatment to 7.4 cm/year during the first year of treatment. Height velocities during the subsequent years were lower, but remained above baseline for up to 12 years. Cumulative mean Δ height SD score at (near) adult height was +2. The observed mean gain in height was 13.4 cm more than had been expected without treatment. The adult height achieved by the patients also treated with GnRH analog was not different from those who received IGF-I therapy alone. There were no new safety signals identified in these patients, a subset of those previously reported. Conclusion: Long-term therapy with IGF-I improves adult height of patients with severe IGFD. Most patients did not bring their heights into the normal adult range.

Adult and Near-Adult Height in Patients with Severe Insulin-Like Growth Factor-I Deficiency after Long-Term Therapy with Recombinant Human Insulin-Like Growth Factor-I

Adult and Near-Adult Height in Patients with Severe Insulin-Like Growth Factor-I Deficiency after Long-Term Therapy with Recombinant Human Insulin-Like Growth Factor-I

The Time Course Effects of Electroacupuncture on Promoting Skeletal Muscle Regeneration and Inhibiting Excessive Fibrosis after Contusion in Rabbits

The aim of this study was to investigate the longitudinal effects of electroacupuncture (EA) on Zusanli (ST36) and Ashi acupoints in promoting skeletal muscle regeneration and inhibiting excessive fibrosis after contusion in rabbits. Sixty rabbits were randomly divided into four groups: normal, contusion, EA, and recombinant human insulin-like growth factor-I (rhIGF-I). An acute skeletal muscle contusion was produced on the right gastrocnemius (GM) by an instrument-based drop-mass technique. EA was performed for 15 minutes every two days with 0.4 mA (2 Hz), and GM injections were executed with rhIGF-I (0.25 mL once a week). Rabbits treated with EA had a higher T-SOD and T-AOC serum activities and lower MDA serum level, the blood perfusion of which was also significantly higher. In the EA group, the diameter of the myofibril was uniform and the arrangement was regular, contrary to the contusion group. The number and diameter of regenerative myofibers and MHC expression were increased in the EA group. EA treatment significantly decreased fibrosis formation and reduced both GDF-8 and p-Smad2/3 expressions in injured muscle. Our data indicate that EA may promote myofiber regeneration and reduce excessive fibrosis by improving blood flow and antioxidant capacities. Additionally, EA may regulate signaling factor expression after contusion.

Phosphatidylinositol 3-Kinase (PI3K) Activity Bound to Insulin-like Growth Factor-I (IGF-I) Receptor, which Is Continuously Sustained by IGF-I Stimulation, Is Required for IGF-I-induced Cell Proliferation

Continuous stimulation of cells with insulin-like growth factors (IGFs) in G(1) phase is a well established requirement for IGF-induced cell proliferation; however, the molecular components of this prolonged signaling pathway that is essential for cell cycle progression from G(1) to S phase are unclear. IGF-I activates IGF-I receptor (IGF-IR) tyrosine kinase, followed by phosphorylation of substrates such as insulin receptor substrates (IRS) leading to binding of signaling molecules containing SH2 domains, including phosphatidylinositol 3-kinase (PI3K) to IRS and activation of the downstream signaling pathways. In this study, we found prolonged (>9 h) association of PI3K with IGF-IR induced by IGF-I stimulation. PI3K activity was present in this complex in thyrocytes and fibroblasts, although tyrosine phosphorylation of IRS was not yet evident after 9 h of IGF-I stimulation. IGF-I withdrawal in mid-G(1) phase impaired the association of PI3K with IGF-IR and suppressed DNA synthesis the same as when PI3K inhibitor was added. Furthermore, we demonstrated that Tyr(1316)-X-X-Met of IGF-IR functioned as a PI3K binding sequence when this tyrosine is phosphorylated. We then analyzed IGF signaling and proliferation of IGF-IR(-/-) fibroblasts expressing exogenous mutant IGF-IR in which Tyr(1316) was substituted with Phe (Y1316F). In these cells, IGF-I stimulation induced tyrosine phosphorylation of IGF-IR and IRS-1/2, but mutated IGF-IR failed to bind PI3K and to induce maximal phosphorylation of GSK3β and cell proliferation in response to IGF-I. Based on these results, we concluded that PI3K activity bound to IGF-IR, which is continuously sustained by IGF-I stimulation, is required for IGF-I-induced cell proliferation.

Subcutaneous administration of rhIGF-I post irradiation exposure enhances hematopoietic recovery and survival in BALB/c mice

It is unclear how to effectively mitigate against irradiation injury. In this study, we studied the capacity of recombinant human insulin-like growth factor-I (rhIGF-I) on hematologic recovery in irradiated BALB/c mice and its possible mechanism. BALB/c mice were injected with rhIGF-I subcutaneously at a dose of 100 μg/kg twice daily for 7 days after total body irradiation. Compared with a saline control group, treatment with rhIGF-I significantly improved the survival of mice after lethal irradiation (7.5 Gy). It was found that treatment with rhIGF-I not only could increase the frequency of Sca-1+ cells in bone marrow harvested at Day 14 after irradiation, but also it could decrease the apoptosis of mononuclear cells induced by irradiation as measured by flow cytometry, suggesting that rhIGF-I may mediate its effects primarily through promoting hematopoietic stem cell/progenitor survival and protecting mononuclear cells from apoptosis after irradiation exposure. Moreover, we have found that rhIGF-I might facilitate thrombopoiesis in an indirect way. Our data demonstrated that rhIGF-I could promote overall hematopoietic recovery after ionizing radiation and reduce the mortality when administered immediately post lethal irradiation exposure.

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.