scholarly journals Insulin-like growth factor binding protein-5 modulates muscle differentiation through an insulin-like growth factor-dependent mechanism.

1996 ◽  
Vol 133 (3) ◽  
pp. 683-693 ◽  
Author(s):  
P L James ◽  
C E Stewart ◽  
P Rotwein
Keyword(s):  
Extracellular Matrix ◽  
Growth Factor ◽  
Myogenic Differentiation ◽  
Muscle Differentiation ◽  
Insulin Like Growth Factor ◽  
Factor Binding ◽  
Igf I ◽  
Sense Orientation ◽  
High Level

The insulin-like growth factor binding proteins (IGFBPs) are a family of six secreted proteins which bind to and modulate the actions of insulin-like growth factors-I and -II (IGF-I and -II). IGFBP-5 is more conserved than other IGFBPs characterized to date, and is expressed in adult rodent muscle and in the developing myotome. We have shown previously that C2 myoblasts secrete IGFBP-5 as their sole IGFBP. Here we use these cells to study the function of IGFBP-5 during myogenesis, a process stimulated by IGFs. We stably transfected C2 cells with IGFBP-5 cDNAs under control of a constitutively active promoter. Compared with vector-transfected control cells, C2 myoblasts expressing the IGFBP-5 transgene in the sense orientation exhibit increased IGFBP-5 levels in the extracellular matrix during proliferation, and subsequently fail to differentiate normally, as assessed by both morphological and biochemical criteria. Compared to controls, IGFBP-5 sense myoblasts show enhanced survival in low serum medium, remaining viable for at least four weeks in culture. By contrast, myoblasts expressing the IGFBP-5 antisense transcript differentiate prematurely and more extensively than control cells. The inhibition of myogenic differentiation by high level expression of IGFBP-5 could be overcome by exogenous IGFs, with des (1-3) IGF-I, an analogue with decreased affinity for IGFBP-5 but normal affinity for the IGF-I receptor, showing the highest potency. These results are consistent with a model in which IGFBP-5 blocks IGF-stimulated myogenesis, and indicate that sequestration of IGFs in the extracellular matrix could be a possible mechanism of action. Our observations also suggest that IGFBP-5 normally inhibits muscle differentiation, and imply a role for IGFBP-5 in regulating IGF action during myogenic development in vivo.

Insulin‐like growth factor binding protein 2 (IGFBP‐2) separates hypertrophic and hyperplastic effects of growth hormone (GH)/IGF‐I excess on adrenocortical cells in vivo

2002 ◽  
Vol 16 (13) ◽  
pp. 1721-1731 ◽  
Author(s):  
Andreas Hoeflich ◽  
Matthias M. Weber ◽  
Thomas Fisch ◽  
Sabine Nedbal ◽  
Christian Fottner ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Growth Factor ◽  
Binding Protein ◽  
Insulin Like Growth Factor ◽  
Adrenocortical Cells ◽  
Factor Binding ◽  
Igf I

scholarly journals Extracellular matrix contains insulin-like growth factor binding protein-5: potentiation of the effects of IGF-I.

1993 ◽  
Vol 121 (3) ◽  
pp. 679-687 ◽  
Author(s):  
J I Jones ◽  
A Gockerman ◽  
W H Busby ◽  
C Camacho-Hubner ◽  
D R Clemmons
Keyword(s):  
Extracellular Matrix ◽  
Growth Factors ◽  
Growth Factor ◽  
Cellular Growth ◽  
Insulin Like Growth Factor ◽  
Factor Binding ◽  
Fetal Fibroblasts ◽  
Igf I ◽  
Biologic Effects ◽  
Ionic Basis

Insulin-like growth factor binding proteins (IGFBPs) have been shown to serve as carrier proteins for the insulin-like growth factors (IGFs) and to modulate their biologic effects. Since extracellular matrix (ECM) has been shown to be a reservoir for IGF-I and IGF-II, we examined the ECM of cultured human fetal fibroblasts and found that IGFBP-5 was incorporated intact into ECM, while mostly inert proteolytic fragments were found in the medium. In contrast, two other forms of IGFBP that are secreted by these cells were either present in ECM in minimal amounts (IGFBP-3) or not detected (IGFBP-4). Likewise, when purified IGFBPs were incubated with ECM, IGFBP-5 bound preferentially. IGFBP-5 was found to bind to types III and IV collagen, laminin, and fibronectin. Increasing salt concentrations inhibited the binding of IGFBP-5 to ECM and accelerated the release of IGFBP-5 from ECM, suggesting an ionic basis for this interaction. ECM-associated IGFBP-5 had a sevenfold decrease in affinity for IGF-I compared to IGFBP-5 in solution. Furthermore, when IGFBP-5 was present in cell culture substrata, it potentiated the growth stimulatory effects of IGF-I on fibroblasts. When IGFBP-5 was present only in the medium, it was degraded to a 22-kD fragment and had no effect on IGF-I-stimulated growth. We conclude that IGFBP-5 is present in fibroblast ECM, where it is protected from degradation and can potentiate the biologic actions of IGF-I. These findings provide a molecular explanation for the association of the IGF's with the extracellular matrix, and suggest that the binding of the IGF's to matrix, via IGFBP-5, may be important in mediating the cellular growth response to these growth factors.

Stimulation of hepatic insulin-like growth factor-binding protein-1 and -3 gene expression by octreotide in rats

1995 ◽  
Vol 147 (3) ◽  
pp. 545-551 ◽  
Author(s):  
A Flyvbjerg ◽  
A G P Schuller ◽  
J W van Neck ◽  
C Groffen ◽  
H Ørskov ◽  
...  
Keyword(s):  
Growth Factor ◽  
Binding Protein ◽  
Somatostatin Analogue ◽  
Insulin Like Growth Factor ◽  
Human Hepatoma Cells ◽  
Factor Binding ◽  
Igf I ◽  
Clinical Experiments ◽  
Igfbp 3

Abstract It has recently been demonstrated in various clinical experiments that native somatostatin and its long-acting analogues increase circulating levels of insulin-like growth factor-binding protein-1 (IGFBP-1) within 1–2 h, independent of effects on circulating insulin or glucose levels. Using human hepatoma cells in vitro the somatostatin analogue, octreotide, has been shown to increase IGFBP-1 mRNA within 24 h indicative of a direct stimulatory effect of octreotide on IGFBP-1 synthesis. In order to ascertain whether octreotide acutely stimulates IGFBP-1 mRNA in vivo, placebo or two doses of octreotide were injected subcutaneously into three groups of rats. One hour after saline or octreotide administration, liver, kidney and serum were obtained for the measurement of IGFBPs-1 to -6 mRNA in tissue and IGFBPs and IGF-I in serum. Octreotide increased liver IGFBP-1 (562%) and IGFBP-3 (23%) mRNA expression with a concomitant rise in the circulating 30 kDa (106%) and 38–42 kDa (23%) IGFBPs. No detectable changes were seen in other liver IGFBP transcripts, other circulating IGFBPs or in any of the kidney IGFBP transcripts. Serum IGF-I increased by 37% in the animals receiving the high octreotide dose. No concomitant changes were observed in glucose or insulin levels. These data show that octreotide acutely stimulates hepatic IGFBP-1 and -3 mRNA in vivo in rats. The stimulating effect on IGFBP-3 presents a possible hitherto unknown form of regulation of IGFBP-3 whilst the effect on IGFBP-1 indicates that the stimulatory effect of octreotide on circulating IGFBP-1 described in clinical trials may be due to increased hepatic production. The present findings may be of importance in the clinical use of octreotide. Journal of Endocrinology (1995) 147, 545–551

Influence of insulin-like growth factor-binding protein-2 on plasma clearance and transfer of insulin-like growth factors-I and -II from plasma into mammary-derived lymph and milk of goats

1996 ◽  
Vol 150 (1) ◽  
pp. 121-127 ◽  
Author(s):  
C G Prosser ◽  
J Schwander
Keyword(s):  
Growth Factors ◽  
Growth Factor ◽  
Plasma Clearance ◽  
Binding Protein ◽  
Plasma Concentrations ◽  
Insulin Like Growth Factor ◽  
Factor Binding ◽  
Lactating Goats ◽  
Igf I ◽  
Insulin Like Growth Factors

Abstract Plasma clearance of insulin-like growth factors-I and -II (IGF-I and -II) and insulin-like growth factor-binding protein-2 (IGFBP-2) from lactating goats (n=4) was determined following a single intravenous injection of the corresponding 125I-labelled human protein. Transfer of these proteins out of the vascular space was monitored by their subsequent appearance in mammary-derived lymph and milk. Clearance of 125I-IGFBP-2 from circulation was 0·37 ± 0·06 ml/min/kg, which is markedly greater than that of 125I-IGF-I or -II (0·11 ± and 0·12 ± 0·01 ml/min/kg respectively). This was also reflected in longer elimination half-lives for IGF-I (353 ± 6 min) and -II (254 ± 8 min) compared with IGFBP-2 (110 ± 9 min). Three hours after injection of the 125I-labelled protein, the plasma:lymph ratio of trichloroacetic acid-precipitable radioactivity was 1·54 ±0·04, 3·3 ±0·6 and 4·1 ±0·4 for IGFBP-2, IGF-I and -II respectively. The form of 125I-IGFBP-2 in lymph was not different from that of plasma. Elevation of plasma concentrations of IGFBP-2 by its intravenous infusion significantly decreased plasma half-life of both IGF-I and -II (251 ± 8 and 198 ±7 min respectively). Although the amount and rate of transfer of IGF into mammary-derived lymph was decreased slightly by IGFBP-2, concentrations eventually obtained were not different from control. However, secretion of IGFs into milk was significantly reduced by IGFBP-2, particularly in the case of IGF-I. These results are consistent with the ability of all three compounds to cross the vascular endothelium intact and of IGFBP-2 to decrease the uptake of IGF by mammary epithelium and subsequent secretion into milk. IGFBP-2 may well have acted to target plasma IGF towards non-mammary tissues, thus explaining the more rapid plasma clearance of IGFs in the presence of elevated IGFBP-2. Journal of Endocrinology (1996) 150, 121–127

Tri-iodothyronine increases insulin-like growth factor binding protein-4 expression in rat hepatocytes

1997 ◽  
Vol 154 (1) ◽  
pp. 155-165 ◽  
Author(s):  
I Demori ◽  
C Bottazzi ◽  
A Voci ◽  
G Gallo ◽  
J-G Scharf ◽  
...  
Keyword(s):  
Growth Factor ◽  
Binding Protein ◽  
Mrna Level ◽  
Insulin Like Growth Factor ◽  
Cultured Hepatocytes ◽  
Adult Rats ◽  
Direct Role ◽  
Factor Binding ◽  
Rat Thyroid

Abstract Previous in vivo studies demonstrated significant variations in insulin-like growth factor binding protein-1 (IGFBP-1), IGFBP-2 and IGFBP-4 hepatic mRNAs and/or serum levels depending on the rat thyroid status. In this study we employed cultured hepatocytes from adult rats to demonstrate a possible direct regulation of these genes by tri-iodothyronine (T3). Northern blot analysis revealed that IGFBP-1 and -4 messages were clearly expressed, whereas IGFBP-2 signal was barely detectable. No significant effects on IGFBP-1 mRNA level or on peptide secretion were detected in T3-cultured hepatocytes. In contrast, significant increases in IGFBP-4 mRNA steady-state levels as well as in IGFBP-4 secretion were observed in hepatocytes cultured for 12–24 h in the presence of T3. The T3 effect on IGFBP-4 transcript levels appears to consist of enhanced gene transcription and is independent of ongoing protein synthesis. The T3-increased IGFBP-4 expression in cultured hepatocytes is consistent with our in vivo experiments demonstrating an increase in hepatic IGFBP-4 mRNA and serum IGFBP-4 levels in T3-treated rats. Furthermore, significant decreases in hepatic IGFBP-4 message and serum IGFBP-4 levels were observed in hypothyroid rats compared with euthyroid controls. Our data establish an important direct role for thyroid hormone in regulating IGFBP-4 expression and consequently IGF activity. Journal of Endocrinology (1997) 154, 155–165

scholarly journals Insulin-like growth factor 1 stimulates the angiogenic activity of adipose tissue–derived microvascular fragments

2019 ◽  
Vol 10 ◽  
pp. 204173141987983 ◽  
Author(s):  
Matthias W Laschke ◽  
Elena Kontaxi ◽  
Claudia Scheuer ◽  
Alexander Heß ◽  
Philipp Karschnia ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
Growth Factor ◽  
Binding Protein ◽  
Insulin Like Growth Factor ◽  
Cellular Composition ◽  
Angiogenic Activity ◽  
Factor Binding ◽  
Factor Expression ◽  
Growth Factor Expression

Angiogenesis in adipose tissue is promoted by insulin-like growth factor 1 signaling. We analyzed whether this regulatory mechanism also improves the angiogenic activity of adipose tissue–derived microvascular fragments. Murine adipose tissue–derived microvascular fragments were cultivated for 24 h in the University of Wisconsin (UW) solution supplemented with vehicle, insulin-like growth factor 1, or a combination of insulin-like growth factor 1 and insulin-like growth factor–binding protein 4. Subsequently, we assessed their cellular composition, viability, proliferation, and growth factor expression. Moreover, cultivated adipose tissue–derived microvascular fragments were seeded onto collagen–glycosaminoglycan scaffolds, which were implanted into dorsal skinfold chambers to study their vascularization and incorporation. Insulin-like growth factor 1 increased the viability and growth factor expression of adipose tissue–derived microvascular fragments without affecting their cellular composition and proliferation. Accordingly, scaffolds containing insulin-like growth factor 1–stimulated adipose tissue–derived microvascular fragments exhibited an enhanced in vivo vascularization and incorporation. These positive insulin-like growth factor 1 effects were reversed by additional exposure of adipose tissue–derived microvascular fragments to insulin-like growth factor–binding protein 4. Our findings indicate that insulin-like growth factor 1 stimulation of adipose tissue–derived microvascular fragments is suitable to improve their vascularization capacity.

Recombinant human insulin-like growth factor: testing the somatomedin hypothesis in hypophysectomized rats

1987 ◽  
Vol 112 (1) ◽  
pp. 123-132 ◽  
Author(s):  
A. Skottner ◽  
R. G. Clark ◽  
I. C. A. F. Robinson ◽  
L. Fryklund
Keyword(s):  
Growth Factor ◽  
Bone Growth ◽  
Body Weight Gain ◽  
Insulin Like Growth Factor ◽  
Recombinant Human Insulin ◽  
Poor Growth ◽  
Igf I ◽  
Hypophysectomized Rats ◽  
Growth Promoting

ABSTRACT The in-vivo biological activity of recombinant methionyl insulin-like growth factor I (met-IGF-I) was demonstrated in hypophysectomized rats by following blood glucose after an i.v. bolus injection of met-IGF-I; a dose-dependent decrease in blood sugar was seen. Membrane transport was studied using the non-metabolizable amino acid α-aminoisobutyric acid; stimulation was obtained with the highest dose used (90 μg/rat). To test the original somatomedin hypothesis, growth studies were performed in hypophysectomized rats. Two or three doses of met-IGF-I were given with three different administration regimes (i.v. or s.c. infusion, or s.c. injections twice daily) for 6 or 8 days. Little growth-promoting activity was observed, with a significant effect on body weight gain obtained only when met-IGF-I was given continuously at the highest dose used (180 μg/day). No effect was seen on the in-vivo uptake of radioactive sulphate into cartilage. Epiphyseal cartilage width increased slightly at the highest dose of met-IGF-I, but only when the hormone was given by infusion. When 180 μg met-IGF-I/day were given by injections, a significant effect on longitudinal bone growth was obtained (90 μm above control). The levels of IGF in the serum were not measurably increased after s.c. administration of met-IGF-I, whereas after i.v. infusion, significantly raised levels were obtained at the higher dose rates (3·0 ± 0·3 and 2·8 ± 0·1 units/ml). Growth hormone was much more effective than met-IGF-I even at 50-fold lower doses. Priming the animals with 10 mu. bovine GH/day followed by combined infusions of GH and met-IGF-I did not reveal any potentiating effects of met-IGF-I in the presence of GH. We conclude that met-IGF-I is a relatively poor growth-promoting agent when given systemically, and that somatomedins are more likely to act as local growth factors rather than as circulating mediators of the growth-promoting effects of GH. J. Endocr. (1987) 112, 123–132

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