Disease relevance of IGF1

• Significant associations (P < 0.0125) were found between VDR and bone mineral content of the humerus at 35 weeks of age; between IGF1 and SPP1 and 5-week body weight; and between INS and 55-week body weight [1].
• CONCLUSIONS: The elevated IGFBP levels and reduced IGF-1 levels on days 5 and 6 of incubation are congruent with an overall reduction in the bioavailability of IGF-1 during this period and correlate with the decreased embryo weight observed in the alcohol-treated embryos [2].
• Insulin-like growth factor-1 (IGF-I), an endocrine and autocrine/paracrine factor that enhances collagen synthesis and bone matrix formation by osteoblasts, has been implicated in the coupling of bone formation with bone resorption [3].
• Embryonic chick skeletal muscle undergoes profound hypertrophy in response to ectopic IGF-I resulting in two- to three-fold increase in total muscle mass [4].
• However, with longer term undernutrition, IGF-I was not decreased in dwarf chickens [5].

High impact information on IGF1

• Expression of the ovalbumin gene in chicken oviduct explant cultures requires the presence of a somatomedin-like peptide hormone in addition to estrogen [6].
• A somatomedin-like peptide hormone is required during the estrogen-mediated induction of ovalbumin gene transcription [6].
• IGF-I was detectable in fibroblasts, whereas IGF-II mRNA was expressed by neurons, glia, and fibroblasts [7].
• Insulin-like growth factors (IGF1 and IFG2) are candidates for muscle-derived sprouting activity, because (a) they induce neurite growth from peripheral neurons in vitro; and (b) their mRNA levels in adult skeletal muscle increase severalfold after denervation or paralysis [8].
• Neuroretina at days 6-8 of embryonic development (E6-E8) expressed proinsulin/insulin and insulin-like growth factor I (IGF-I) mRNAs as well as insulin receptor and IGF type I receptor mRNAs [9].

Chemical compound and disease context of IGF1

• Daily injections of 2500 micrograms corticosterone/kg body weight, in both lines, depressed mean concentrations of plasma prolactin, T3 and somatomedin C and body weight [10].
• Increasing dietary protein (compared to increasing dietary fat) increased body weights, IGF-I, T4 and decreased lipogenesis, malic enzyme activity, and T3 [11].
• 6. In conclusion, the improvement in body weight gain caused by dietary L-carnitine supplementation was achieved when chicks were given their dietary protein requirement, which may be partially explained by an increase in plasma IGF-I concentration [12].
• The bone uncoupling (in formation and resorption) associated with vitamin B6 deficiency seems to be due to secondary hypercortisolism and (or) another unknown factors but not related to a change in bone modulators such as IGF-1 and eicosanoids [13].
• One of the most interesting observations was that the type of reciprocal cross had highly significant effects on body weight at hatch and on plasma concentrations of glucose, cholesterol, insulin, and IGF-I, but it had no significant effect on body weight at 56 days of age [14].

Biological context of IGF1

• However, these associations were not simultaneously found in both strains suggesting that they might have been produced by linkage disequilibrium with another mutation located in the IGF1 locus or another linked gene [15].
• In chick embryo retinas, cultured in serum-free medium lacking L-glutamine, IGF-I, IGF-II and insulin induced apoptotic DNA fragmentation and cell death, IGF-I being the most efficacious compound [16].
• In mammals, IGF-I gene expression is complicated, as the single-copy gene is transcribed and processed into multiple mRNAs that encode at least two peptide precursors [17].
• Chicken embryos are a suitable model for studying the role of insulin, insulin-like growth factors I and II (IGF-I and IGF-II), and their receptors in embryogenesis [18].
• Hybrid genes containing at least 0.6 kb of IGF-I enhanced expression of luciferase after transfection into SK-N-MC cells, a human line that synthesizes IGF-I mRNA [17].

Anatomical context of IGF1

• However, the concentration of seminal IGF-I in dwarf cocks was similar to that of their normal siblings, indicating that IGF-I might be produced and acted independently in testis [19].
• The concentrations of GH and IGF-I in serum and seminal plasma were measured with RIA and ELISA, respectively [19].
• IGF-I and IGF-II mRNA was found to be expressed in E7 sympathetic ganglia during the period of neurogenesis [7].
• In the chicken, as in rats and humans, IGF-I mRNA is synthesized in multiple tissues, including liver, brain, skeletal muscle, and heart.(ABSTRACT TRUNCATED AT 250 WORDS)[20]
• Pelvic cartilages secreted in vitro both IGF-I and IGF-II and a 32-34 kD IGFBP [21].

Associations of IGF1 with chemical compounds

• As in the rat and human genes, the mature 70-amino acid IGF-I molecule is encoded within exons 2 and 3, while exons 1 and 4 contain NH2- and COOH-terminal extension peptides, respectively, and untranslated sequences [17].
• In response to insulin, IGF-I, or IGF-II, an 87K membrane-associated protein (pp87) became phosphorylated on tyrosine in a rapid, dose-dependent manner [22].
• Pretreatment of neurons with lovastatin (2 micrograms/ml), an inhibitor of ras isoprenylation, completely blocked the activation of p21ras by insulin and IGF-I [23].
• The percentage carcass protein for ad libitum-fed breeders was positively correlated to IGF-I, T4, T3, insulin/glucagon M ratio, and insulin [24].
• The T4 was the most important hormone for predicting the percentage carcass fat in ad libitum-fed pullets, and IGF-I was the most important hormone for predicting the percentage carcass fat in feed-restricted pullets [24].

Physical interactions of IGF1

• The developmental patterns of [125I]IGF-I and [125I]IGF-II binding to brain were similar, and IGF-I showed approximately a 2-fold higher binding than IGF-II; there was a sharp increase from days 3 to 6, and a subsequent gradual fall during the second and third weeks of ontogeny [25].
• We suggest that the interaction of a somatomedin with its membrane-bound receptor generates an intracellular signal that interacts specifically with the ovalbumin gene [6].

Regulatory relationships of IGF1

• We conclude that insulin and IGF-I activate p21ras in fetal chick forebrain neurons by increasing the amount of GTP bound to p21ras [23].
• Finally, BMP-7 stimulated G cell proliferation, but BMP-4 inhibited TGF-alpha+ IGF-I- and/or FSH-stimulated G cell proliferation, suggesting a role in the control of follicular growth during development [26].
• Insulin-like growth factor I (IGF-I) and insulin regulate expression of the endogenous delta 1-crystallin gene in embryonic lens cells that express receptors for both peptides [27].
• IGF-1 regulates transcription of the fatty acid synthase gene [28].
• In contrast, TGF-alpha inhibited basal and LH- and IGF-I-stimulated progesterone production [29].

Other interactions of IGF1

• Half-maximal responses required 0.2 nM IGF2 or IGF1, or 20 nM insulin [8].
• The results indicate an increase in IGF-1 (P < 0.01) and a decrease in IGFBP-2 (P < 0.05) mRNA expression in slow muscle of the stimulated group compared with the control group [30].
• The serum GH in the dwarf cocks was significantly higher than their normal siblings (P < 0.05), whereas the serum IGF-I in the dwarf cocks was very low [19].
• Thereafter, plasma concentrations of IGF-I declined with decreases (P < 0.05) between Days 14.5 and 15.5 and between Days 16.5 and 17.5 of incubation [31].
• By day 8 of incubation, IGF-1 levels were significantly higher and the 30 kDa IGFBP levels were significantly lower in the alcohol-treated group compared with vehicles [2].

Analytical, diagnostic and therapeutic context of IGF1

• The pattern of IGF-I gene expression appears to be simpler in chickens than in mammals, since a single predominant mRNA of 2.6 kilobases can be detected in liver polyadenylated RNA on Northern blots [20].
• Chicken IGF-I (cIGF-I) has been measured using a radioimmunoassay with a human IGF-I (hIGF-I) standard and an antibody raised against hIGF-I [32].
• To determine whether binding proteins in chicken plasma can artifactually interfere with IGF-I measurements as they do in mammals, chicken plasma was fractionated by molecular sieve chromatography at acid pH [32].
• To explore the function of IGF1 in olfactory system in the chick, we infused IGF1 at the lesion site 0 and 12 h after olfactory axotomy [33].
• No IGF-I gene expression was detected in cell cultures at any time point [34].

References