Influence of dietary protein on insulin-like growth factor binding proteins in the chicken

We determined the effect of dietary protein on the distribution of insulin-like growth factor (IGF) binding proteins in chicken plasma. Three groups of male broilers (n=6 per group) were fed (ad libitum) isocaloric diets containing 12, 21 or 30% dietary protein. Birds were fed respective diets beginning at 7 days of age and killed at 28 days. No differences were observed between adequate (21%) and high (30%) protein intakes for any of the parameters investigated (growth criteria, plasma levels of IGF-I, growth hormone or IGF-binding proteins). Feeding protein deficient diets (12%) resulted in a 34% decrease in body weight, 17% decrease in feed intake and a 39% increase in feed/gain ratio. IGF-binding proteins in plasma samples were separated by SDS-PAGE and transferred to nitrocellulose sheets. Nitrocellulose blots were probed with [¹²⁵I]chicken IGF-II. Four regions of binding activity corresponding to 70, 43, 30 and 24 kDa were observed in all samples. Birds consuming 12% dietary group protein had less than 50% of the 43-kDa binding activity of birds consuming 21 or 30% dietary protein. The 30-kDa binding activity was 42% lower in the 12% dietary protein group compared to birds consuming adequate protein. In contrast, 70- and 24-kDa binding activities were not influenced by dietary protein. Chickens consuming 12% dietary protein had higher levels of growth hormone and lower levels of IGF-I than those consuming 21 or 30% dietary protein. These data indicate that in chickens, the circulating levels of at least two independent IGF-binding proteins are influenced by dietary protein.     

In vivo processed fragments of IGF binding protein-2 copurified with bioactive IGF-II

Proteolysis of insulin-like growth factor binding proteins (IGFBPs), the major carrier of insulin-like growth factors (IGFs) in the circulation, is an essential mechanism to regulate the bioavailability and half-live of IGFs. Screening for peptides in human hemofiltrate, stimulating the survival of PC-12 cells, resulted in the isolation of C-terminal IGFBP-2 fragments and intact IGF-II co-eluting during the chromatographic purification procedure. The IGFBP-2 fragments exhibited molecular masses of 12.7 and 12.9kDa and started with Gly169 and Gly167, respectively. The fragments were able to bind both IGFs. The stimulatory effect of the purified fraction on the survival of the PC-12 cells could be assigned exclusively to IGF-II, since it was abolished by the addition of neutralizing IGF-II antibodies. We suggest that in the circulation IGF-II is not only complexed with intact IGFBP but also with processed IGFBP-2 fragments not impairing the biological activity of IGF-II.     

Insulin-like growth factor I receptor is expressed at normal levels in Nijmegen breakage syndrome cells

Curcumin (diferuloylmethane) is a major component of food flavoring turmeric (Curcuma longa), and has been reported to be anticarcinogenic and anti-inflammatory. Although curcumin was shown to have antioxidant properties, its exact antioxidant nature has not been fully investigated. In this report we have investigated the possible antioxidant properties of curcumin using EPR spectroscopic techniques. Curcumin was found to inhibit the (1)O(2)-dependent 2,2,6,6-tetramethylpiperidine N-oxyl (TEMPO) formation in a dose-dependent manner. (1)O(2) was produced in a photosensitizing system using rose bengal as sensitizer, and was detected as TEMP-(1)O(2) adducts by electron paramagnetic resonance (EPR) spectroscopic techniques using TEMP as a spin-trap. Curcumin at 2.75 microM caused 50% inhibition of TEMP-(1)O(2) adduct formation. However, curcumin only marginally inhibited (24% maximum at 80 microM) reduction of ferricytochrome c in a xanthine-xanthine oxidase system demonstrating that it is not an effective superoxide radical scavenger. Additionally, there was minor inhibition of DMPO-OH adduct formation by curcumin (solubilized in ethanol) when an ethanol control was included in the EPR spin-trapping study, suggesting that curcumin may not be an effective hydroxyl radical scavenger. Together these data demonstrate that curcumin is able only to effectively quench singlet oxygen at very low concentration in aqueous systems.     

CRIM1, a novel gene encoding a cysteine-rich repeat protein, is developmentally regulated and implicated in vertebrate CNS development and organogenesis

Development of the vertebrate central nervous system is thought to be controlled by intricate cell-cell interactions and spatio-temporally regulated gene expressions. The details of these processes are still not fully understood. We have isolated a novel vertebrate gene, CRIM1/Crim1, in human and mouse. Human CRIM1 maps to chromosome 2p21 close to the Spastic Paraplegia 4 locus. Crim1 is expressed in the notochord, somites, floor plate, early motor neurons and interneuron subpopulations within the developing spinal cord. CRIM1 appears to be evolutionarily conserved and encodes a putative transmembrane protein containing an IGF-binding protein motif and multiple cysteine-rich repeats similar to those in the BMP-associating chordin and sog proteins. Our results suggest a role for CRIM1/Crim1 in CNS development possibly via growth factor binding.     

Insulin-like growth factor I prevents the development of sensitivity to kainate neurotoxicity in cerebellar granule cells

This study reports that insulin-like growth factor I (IGF-I) prevents cerebellar granule cells from developing sensitivity to kainate neurotoxicity. Sensitivity to kainate neurotoxicity normally develops 5-6 days after switching cultures to a serum-free medium containing 25 mM K(+). Addition of either IGF-I or insulin to the serum-free medium at the time of the switch prevented the development of sensitivity to kainate, whereas brain-derived neurotrophic factor, neurotrophin-3, neurotrophin-4, and nerve growth factor did not. The dose-response curves indicated IGF-I was more potent than insulin, favoring the assignment of the former as the physiological protective agent. The phosphatidylinositol 3-kinase (PI 3-K) inhibitors wortmannin (10-100 nM) and LY 294002 (0.3-1 microM) abolished the protection afforded by IGF-I. The p70 S6 kinase (p70(S6k)) inhibitor rapamycin (5-50 nM:) also abolished the protection afforded by IGF-I. The activities of both enzymes decreased in cultures switched to serum-free medium but increased when IGF-I was included; wortmannin (100 nM) lowered the activity of PI 3-K from 2 to 5 days after medium switch, whereas rapamycin (50 nM) prevented the increase observed for p70(S6k) activity over the same interval. The mitogen-activated protein kinase kinase inhibitor U 0126 and the mitogen-activated protein kinase inhibitor SB 203580 did not abolish IGF-I protection. Kainate neurotoxicity was not prevented by Joro spider toxin; therefore, the development of kainate neurotoxicity could not be explained by the formation of calcium-permeable alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate receptors. These results indicate that IGF-I functions through a signal transduction pathway involving PI 3-K and p70(S6k) to prevent the development of sensitivity to kainate neurotoxicity in cerebellar granule cells.     

胰岛素样生长因子-1、转化生长因子-beta1 水平变化在过敏性紫癜患儿肾损害的临床意义

目的：探讨胰岛素样生长因子-1（IGF-1）、转化生长因子-beta1（TGF-beta1）水平变化在过敏性紫癜患儿肾损害发病机制中作用。 方法：选取HSP患儿30 例、HSPN患儿30 例和30 例健康儿童为对照组,分别采血,用化学发光法检测各组标本IGF-1 浓度,采用 双抗体一步夹心法酶联免疫吸附试验检测各组TGF-茁1 浓度;同时用全自动生化仪检测各组患儿血清Cys C、BUN、SCr 水平。结 果：血IGF-1、TGF-beta1 的水平HSPN组、HSP组与对照组患儿比较,差异均有统计学意义（P<0.05）。血清Cys C 水平对照组、HSP 组与HSPN 组患儿比较,差异有统计学意义（P<0.05）。采用直线相关分析HSPN 组的血清Cys C 水平与血IGF-1、TGF-beta1 水平 比较,存在正相关（r=0.759、r=0.802,均P<0.05）,血IGF-1 与TGF-beta1 也存在正相关（r=0.850,P<0.05）。结论：血IGF-1、TGF-beta1 共同 参与紫癜性肾炎发病,其水平变化与病理损害程度相关。     

MKR转基因小鼠糖尿病发病特点的初步探讨

目的观察骨骼肌胰岛素样生长因子-1受体及胰岛素受体的功能缺失(Mouse overexpressing adominant-negative IGF-I receptor specifically in muscle,MKR mouse)转基因2型糖尿病小鼠的血糖及其生长情况。方法由美国国立卫生研究院(NIH)授权使用引进的MKR鼠,经自然交配后繁殖的子代作为研究对象,制备尾组织基因组DNA,经聚合酶链反应得到扩增产物,1%琼脂糖凝胶电泳观察鉴定。同时对MKR鼠子代出生后的血糖、体重、胰岛素定时检测。同期采用昆明种小鼠或C57野生型小鼠进行对照。结果MKR鼠所有子代鼠均会出现长度为330 bp的DNA片段,表明该MKR鼠后代能稳定遗传。新生MKR鼠自出生3周开始,即出现显著的血糖增高,5周以后血糖则较稳定地维持在高水平。与对照组小鼠同期的血糖比较,差异具有非常显著性意义(P<0.01)。其体重增长随年龄的增长而减慢,至4月龄时体重基本稳定,但无下降趋势。MKR鼠在2月龄时即表现出显著的高胰岛素血症及糖耐量低下,与对照组小鼠同期比较,亦具有非常显著性意义(P<0.01)。MKR鼠在生长过程中无自然死亡发生。结论MKR鼠是至今为止一种非常良好的2型糖尿病的动物模型。     

Specific Activation of Insulin-like Growth Factor-1 Receptor by Ginsenoside Rg5 Promotes Angiogenesis and Vasorelaxation

Ginsenoside Rg5 is a compound newly synthesized during the steaming process of ginseng; however, its biological activity has not been elucidated with regard to endothelial function. We found that Rg5 stimulated in vitro angiogenesis of human endothelial cells, consistent with increased neovascularization and blood perfusion in a mouse hind limb ischemia model. Rg5 also evoked vasorelaxation in aortic rings isolated from wild type and high cholesterol-fed ApoE^−/− mice but not from endothelial nitric-oxide synthase (eNOS) knock-out mice. Angiogenic activity of Rg5 was highly associated with a specific increase in insulin-like growth factor-1 receptor (IGF-1R) phosphorylation and subsequent activation of multiple angiogenic signals, including ERK, FAK, Akt/eNOS/NO, and G_i-mediated phospholipase C/Ca²⁺/eNOS dimerization pathways. The vasodilative activity of Rg5 was mediated by the eNOS/NO/cGMP axis. IGF-1R knockdown suppressed Rg5-induced angiogenesis and vasorelaxation by inhibiting key angiogenic signaling and NO/cGMP pathways. In silico docking analysis showed that Rg5 bound with high affinity to IGF-1R at the same binding site of IGF. Rg5 blocked binding of IGF-1 to its receptor with an IC₅₀ of ∼90 nmol/liter. However, Rg5 did not induce vascular inflammation and permeability. These data suggest that Rg5 plays a novel role as an IGF-1R agonist, promoting therapeutic angiogenesis and improving hypertension without adverse effects in the vasculature.     

Resveratrol improves cognitive function in mice by increasing production of insulin-like growth factor-I in the hippocampus

We examined whether resveratrol increases insulin-like growth factor-I (IGF-I) production in the hippocampus by stimulating sensory neurons in the gastrointestinal tract, thereby improving cognitive function in mice. Resveratrol increased calcitonin gene-related peptide (CGRP) release from dorsal root ganglion (DRG) neurons isolated from wild-type (WT) mice. Increases in tissue levels of CGRP, IGF-I, and IGF-I mRNA and immunohistochemical expression of IGF-I were observed in the hippocampus at 3 weeks after oral administration of resveratrol in WT mice. Significant enhancement of angiogenesis and neurogenesis was observed in the dentate gyrus of the hippocampus in these animals (P<.01). Improvement of spatial learning in the Morris water maze was observed in WT mice after administration of resveratrol. None of the effects of resveratrol observed in WT mice were seen after resveratrol administration in CGRP-knockout (CGRP^−/−) mice. Although red wine containing 20 mg/L of resveratrol produced effects similar to those of resveratrol administrationl in WT mice, neither red wine containing 3.1 mg/L of resveratrol nor white wine exhibited such effects in WT mice. Resveratrol was undetectable in the hippocampus of WT mice administered resveratrol and red wine containing 20 mg/L of resveratrol. These observations strongly suggest that resveratrol increases hippocampal IGF-I production via sensory neuron stimulation in the gastrointestinal tract, thereby improving cognitive function in mice.