The inhibition of apoptosis in EL4 lymphoma cells overexpressing growth hormone

The antiapoptotic action of exogenous growth hormone (GH) has been reported for several lymphoid cell lines; however, the potential role of endogenous GH in apoptosis has not been thoroughly investigated. This study was designed to investigate the effects of endogenous GH on apoptosis induced by methyl methanesulfonate (MMS) in a T cell lymphoma overexpressing GH (GHo). The results of these experiments have shown that in EL4 lymphoma cells, overexpression of GH sustained viability after exposure to MMS compared to control cells. The extent of DNA fragmentation measured by ladder formation on agarose gels was reduced in GHo cells following treatment with MMS, when compared to control cells. Adding exogenous GH to control cells and treatment of GHo cells with antibodies to GH had no effect on MMS-induced DNA ladder formation. In further studies, DNA microarray analysis suggested a marked decrease in the constitutive expression of bax, BAD, and caspases 3, 8, and 9 in GHo cells compared to controls. In addition, after treatment with MMS, the activities of caspases 2, 3, 6, 8, and 9 were all lower than control in GHo cells. Western blot analysis detected an increase in Bcl-2 while the levels of nuclear factor kappa B (NFkappaB) remained unchanged in GHo cells. Treatment of EL4 cells with antisense deoxyoligonucleotides to GH and specific inhibitors of NFkappaB (SN-50) increased DNA fragmentation. GHo cells show increased levels of phosphorylated Akt and GSK-3, suggesting inactivation of this proapoptotic protein. The results, taken together with our previous data which showed increased nitric oxide formation in GHo cells, suggest a possible mechanism for the antiapoptotic effects of endogenous GH through the production of nitric oxide and support the idea that endogenous GH may play an important role in the survival of lymphocytes exposed to stressful stimuli.     

The production of nitric oxide in EL4 lymphoma cells overexpressing growth hormone

Growth hormone (GH) is produced by immunocompetent cells and has been implicated in the regulation of a multiplicity of functions in the immune system involved in growth and activation. However, the actions of endogenous or lymphocyte GH and its contribution to immune reactivity when compared with those of serum or exogenous GH are still unclear. In the present study, we overexpressed lymphocyte GH in EL4 lymphoma cells, which lack the GH receptor (GHR), to determine the role of endogenous GH in nitric oxide (NO) production and response to genotoxic stress. Western blot analysis demonstrated that the levels of GH increased approximately 40% in cells overexpressing GH (GHo) when compared with cells with vector alone. The results also show a substantial increase in NO production in cells overexpressing GH that could be blocked by N(G)-monomethyl-L-arginine (L-NMMA), an L-arginine analogue that competitively inhibits all three isoforms of nitric oxide synthase (NOS). No evidence was obtained to support an increase in peroxynitrite in cells overexpressing GH. Overexpression of GH increased NOS activity, inducible nitric oxide synthase (iNOS) promoter activity, and iNOS protein expression, whereas endothelial nitric oxide synthase and neuronal nitric oxide synthase protein levels were essentially unchanged. In addition, cells overexpressing GH showed increased arginine transport ability and intracellular arginase activity when compared with control cells. GH overexpression appeared to protect cells from the toxic effects of the DNA alkylating agent methyl methanesulfonate. This possibility was suggested by maintenance of the mitochondrial transmembrane potential in cells overexpressing GH when compared with control cells that could be blocked by L-NMMA. Taken together, the data support the notion that lymphocyte GH, independently of the GH receptor, may play a key role in the survival of lymphocytes exposed to stressful stimuli via the production of NO.     

胰岛素样生长因子1和成纤维细胞生长因子7与毛乳头细胞的生长*

背景：毛乳头细胞凝集性生长与其诱导毛发生长有关。毛乳头细胞分泌的多种生长因子如胰岛素样生长因子1、成纤维细胞生长因子7可能对毛乳头细胞生长具有重要的影响。 目的：观察正常人毛乳头细胞的增长与生长方式与胰岛素样生长因子1、成纤维细胞生长因子7的相关性。 方法：采用二步酶消化法分离培养毛乳头细胞,免疫组化法和流式细胞仪分别检测两种生长因子在凝集性与非凝集性生长的毛乳头细胞中的表达,MTT法检测2.5~100 μg/L质量浓度胰岛素样生长因子1对人毛乳头细胞增殖的影响。 结果与结论：胰岛素样生长因子1与成纤维细胞生长因子7均表达于细胞胞浆,但表达量随时间减弱,其中第3代明显比第9代毛乳头细胞中成纤维细胞生长因子7的表达强烈(P < 0.05)。与对照组相比,不同质量浓度胰岛素样生长因子1均有明显促进毛乳头细胞增殖的作用(P < 0.05),其中以2.5 μg/L最为显著。提示毛乳头细胞的凝集性生长状态的改变可能与胰岛素样生长因子1、成纤维细胞生长因子7表达下降有关,胰岛素样生长因子1可明显刺激毛乳头细胞增殖。     

RNA interference affects tumorigenicity and expression of insulin-like growth factor-1, insulin-like growth factor-1 receptor, and basic fibroblast growth factor-2 in rat C6 glioma cells

BACKGROUND： Human gliomas are more likely to express basic fibroblast growth factor-2 （FGF-2） insulin-like growth factor-1（IGF-1）, and IGF-1 receptor （IGF-1R） than normal brain tissue. These factors activate signal transduction systems of Ras/MAPK and PI3K/Akl, which promote glioma growth. OBJECTIVE： To utilize RNA interference （RNAi） technique to down-regulate FGF-2, IGF-1, and IGF-1R gene expression, and to investigate the effects of these genes on rat C6 glioma cells, as well as the feasibility of RNAi for treating glioma. DESIGN, TIME AND SETTING： This neurooncological, randomized, controlled, in vivo and in vitro experiment, which used RNAi methodology, was performed at the Laboratory of Molecular Biology, Institute of Biochemistry, Chinese Academy of Sciences between August 2005 and February 2008. MATERIALS： Rat C6 cell lines were purchased from Shanghai Institute of Cellular Biology Affiliated to Chinese Academy of Sciences. Small interfering RNA （siRNA） was synthesized by Shanghai GenePharma. Anti-IGF-1, anti-IGF-1R, anti-FGF-2, anti-mouse and anti-rabbit IgG G1-HRP antibodies were provided by Santa Cruz Biotechnology, USA. Four to six week-old BALB/c nude mice were purchased from the Laboratory Animal Center, Chinese Academy of Sciences. METHODS： C6 glioma cells were transfected with siRNA, which was chemically synthesized in vitro to correspond to endogenous FGF-2, IGF-1, and IGF-1R genes. The inhibition ratio of targeting mRNA expression was detected by semiquantitative RT-PCR, and protein expression was determined by Western blot analysis. C6 glioma cell proliferation was observed using a growth curve C6 glioma cell apoptosis rate and cell cycle were detected by flow cytometry. C6 glioma cell growth regression was observed by transwell migration assay. In addition, nude mouse subcutaneous tumor models were used in this study. For studying the anti-tumor effects of IGF-1 and IGF-1R siRNA, two blank control groups, with six mice each, were set up： A （2.5 μg siRNA was injected one week after C6 cells were inoculated, Le., when tumor volume reached 8 mm × 8 mm） and B （siRNA was injected at the same time with C6 cells were inoculated. To study the effects of FGF-2 siRNA, the groups consisted of a blank control group, negative control group, 2.6 μg siRNA group, 4 μg siRNA group, and 5.3 μg siRNA group, with six mice each. MAIN OUTCOME MEASURES： mRNA and protein inhibition ratio of FGF-2, IGF-1, and IGF-1 R; C6 glioma cell proliferation, apoptosis, and cycle growth arrest; C6 glioma cell growth regression and subcutaneous tumorigenicity rates. RESULTS： All siRNA constructs proved to be effective. After 48 hours, transfection of 200 nmol/L siRNA resulted in a FGF-2 or IGF-1R gene inhibition ratio 〉 80% and an IGF-1 gene inhibition ratio of approximately 70%. Protein expression levels for FGF-2, IGF-1, and IGF-1R decreased in a dose-dependent manner following siRNA transfection, with an inhibition rate 〉 85%, 60%, and 50%, respectively. C6 glioma cell proliferation and apoptosis rates increased in proportion to siRNA. The apoptosis rate of C6 glioma cells induced by FGF-2, IGF-1, and IGF-1R siRNA was 39.96%, 15.07% and 22.47%, respectively （P 〈 0.01）. Transfection of 200 nmol/L IGF or IGF-1R siRNA for 48 hours suppressed C6 glioma cell migration. At 30 days after intratumoral injection of 2.6, 4, and 5.3 tJg FGF-2 siRNA, tumor growth regression rate of FGF-2 siRNA was 56%, 67%, and 86%, respectively. The tumor growth regression rate was 71.88% and 45.71%, respectively, when IGF-1 or IGF-1R siRNA was intratumorally injected 1 week after C6 glioma cell transplantation. When IGF-1 or IGF-1 R siRNA was intratumorally injected during C6 glioma cell transplantation, the tumor growth regression rate was 78.13% and 74.29%, respectively. CONCLUSION： siRNA transfection downregulated gene expression of FGF-2, IGF-1, and IGF-1R In addition, siRNA treatment markedly suppressed glioma cell proliferation, growth, and migration, and concomitantly reduced subcutaneous tumorigenicity.     

Effect of kainic acid treatment on insulin-like growth factor-2 receptors in the IGF2-deficient adult mouse brain

Insulin-like growth factor-2 (IGF2) is a member of the insulin gene family with known neurotrophic properties. The actions of IGF2 are mediated via the IGF type 1 and type 2 receptors as well as through the insulin receptors, all of which are widely expressed throughout the brain. Since IGF2 is up-regulated in the brain after injury, we wanted to determine whether the absence of IGF2 can lead to any alteration on brain morphology and/or in the response of its receptor binding sites following a neurotoxic insult. No morphological differences were observed between the brains of IGF2 knockout (IGF2(-/-)) and wild-type control (IGF2(+/+)) mice. However, our in vitro receptor autoradiography results indicate that IGF2(-/-) mice had lower endogenous levels of [(125)I]IGF1 and [(125)I]insulin receptor binding sites in the hippocampus and cerebellum as compared to IGF2(+/+) mice, while endogenous [(125)I]IGF2 receptor binding showed a decrease only in the cerebellum. Seven days after kainic acid administration, the [(125)I]insulin receptor binding sites were significantly decreased in all brain regions of the IGF2(+/+) mice, while the levels of [(125)I]IGF1 and [(125)I]IGF2 binding sites were decreased only in select brain areas. The IGF2(-/-) mice, on the other hand, showed increased [(125)I]IGF1 and [(125)I]IGF2 and [(125)I]insulin receptor binding sites in selected regions such as the hippocampus and cerebellum. These results, taken together, suggest that deletion of IGF2 gene does not affect gross morphology of the brain but does selectively alter endogenous [(125)I]IGF1, [(125)I]IGF2 and [(125)I]insulin receptor binding sites and their response to neurotoxicity.     

Final height and insulin-like growth factor-1 in children with medulloblastoma treated with growth hormone

Purpose

Medulloblastoma is a highly malignant childhood brain tumor. Survival from medulloblastoma is increasing. This study was performed to examine growth outcomes, insulin-like growth factor-1(IGF-1), and response to growth hormone (GH) treatment in children with medulloblastoma.

Methods

Retrospective analysis of 34 children treated with GH for medulloblastoma was performed. We evaluated serum IGF-1 and insulin-like growth factor binding protein-3 concentrations. Further, we examined growth status and changes with GH treatment according to treatment modality.

Results

GH deficiency was observed in 28 patients (82 %). The initial height at the start of GH treatment was ?2.35?±??1.53 standard deviation score (SDS) and increased to ?1.85?±??1.28 SDS by 1 year, ?1.64?±??1.46 SDS by 2 years, and ?1.42?±??1.49 SDS by 3 years after GH treatment. The final height was ?1.54?±??1.06 SDS. Gender, surgical method, tumor location, tumor size, and type of radiation did not correlate with height gain. A younger age at the initiation of GH treatment correlated with height gain. The initial serum IGF-1 concentration was ?1.73?±??0.42 and increased significantly to ?0.74?±??0.21 SDS by 1 year after GH treatment. The serum IGF-1 SDS increment correlated significantly with height gain.

Conclusions

Beginning GH treatment at a younger age was an important prognostic factor for growth outcome. Serum IGF-1 increment correlated with height gain during GH treatment. Thus, early GH treatment and analysis of serum IGF-1 might be helpful for improving final height or growth outcome.     

Chromaffin cells express two types of insulin-like growth factor receptors

The receptor binding, internalization and tyrosine kinase activation of insulin-like growth factors, IGF-I and IGF-II have been investigated in cultured adult bovine chromaffin cells. IGF-I receptor alpha-subunits (Mr approximately 130,000) bound IGF-I and IGF-II with identical affinity (Kd approximately 1 nM) and insulin with about 1000 times lower affinity. IGF-II receptors (Mr approximately 250,000) bound IGF-II with a Kd of 0.5 nM, IGF-I with about 10 times lower affinity and insulin with greater than 10,000 times lower affinity. The amounts of IGF-I and IGF-II receptors on the cell surface were 8 x 10(4) and 4 x 10(4) sites per cell, respectively. Insulin bound to a specific receptor with Kd approximately 2 nM and the amount of receptors was 1.5 x 10(4) sites per cell. IGF-I and IGF-II stimulated tyrosine kinase activity and autophosphorylation of the IGF-I receptor beta-subunit (Mr approximately 94,000) with equal potency (ED50 approximately 1 nM), whereas insulin was approximately 5 times less potent. Both IGF-I and IGF-II were internalized after their binding to cell surface receptors. Mannose-6-phosphate, which binds to the IGF-II receptor, did not alter the binding or internalization of IGF-II. It is concluded that IGF-I and IGF-II can exert their biological effects in chromaffin cells by activation of the IGF-I receptor tyrosine kinase or by interaction with the IGF-II receptor.     

胰岛素样生长因子Ⅰ对大鼠纤维环细胞体外增殖活性影响的量效关系

背景：近年来体外椎间盘髓核和纤维环组织细胞培养技术的建立，特别是软骨组织工程研究的不断深入及自体椎间盘细胞移植修复髓核缺损动物实验的初步成功，为退变椎间盘的形态结构与生理功能的完全再生修复带来了希望。 目的：通过对椎间盘纤维环细胞的培养，观察胰岛素样生长因子Ⅰ对大鼠纤维环细胞体外增殖活性的影响及量效和时效关系。 设计、时间及地点：单一样本观察，于2006-09/2007-01在山西医科大学寄生虫实验室完成。 材料：清洁级1月龄 Wistar系大鼠30只，雌雄不限。 方法：体外分离培养大鼠纤维环细胞。剂量-效应实验：在培养的细胞中分别加入由含体积分数为0.01或0.1的小牛血清HAMF-12配制成的不同浓度的胰岛素样生长因子Ⅰ（0.1，1.0，10，100 μg/L）。以不加生长因子做对照，培养72 h。时间-效应实验：在培养的细胞中分别加入含有最佳效应浓度胰岛素样生长因子Ⅰ体积分数为0.1的小牛血清+F12培养液，分组为对照组和100 μg/L的胰岛素样生长因子Ⅰ组，分别培养1，3，5，7 d。 主要观察指标：①苏木精-伊红、甲苯胺蓝、免疫细胞化学染色分析细胞的生物学特性。②噻唑蓝比色法观察胰岛素样生长因子Ⅰ在体积分数为0.01和0.1的血清浓度下对大鼠纤维环细胞体外增殖的调节作用及其剂量、时间与作用效果的关系。 结果：苏木精-伊红染色细胞多为梭形，有伪足伸出，细胞核为圆形或椭圆形；甲苯胺蓝染色，胞浆为深蓝色；免疫细胞学方法检测表明纤维环细胞有Ⅰ型胶原表达；在体积分数为0.1的血清条件下，胰岛素样生长因子Ⅰ能提高细胞的增殖活性，并且在有效浓度范围内呈剂量效应关系。 结论：胰岛素样生长因子Ⅰ能促进大鼠纤维环细胞的体外增殖，其效应在一定范围内与剂量和时间呈正相关。     

Growth dependence on insulin-like growth factor-1 during the ketogenic diet

Purpose:   To examine the influence of the ketogenic diet (KD) on linear growth and insulin-like growth factor I (IGF-I) levels in children with pharmacotherapy-resistant epilepsy.
Methods:   A prospective study was designed to evaluate growth, serum IGF-I levels, blood β-hydroxybutyric acid (β-OHB), and seizure frequency before and during KD in 22 children (median age 5.5 years). Growth was assessed by measurements of weight, height, body mass index (BMI), and height velocity. Standard deviation scores (SDS) were calculated for all measured parameters as well as for serum IGF-I to eliminate the influence of age- and sex-related differences among patients.
Results:   Fourteen of the 22 patients responded to the KD. Weight, height, BMI, and height velocity decreased significantly during the KD. We found that the KD had profound influence on growth and IGF-I levels. No correlation was found between seizure response and growth alterations. Height velocity correlated negatively with β-OHB during the KD. The slope of the regression of height velocity against IGF-I decreased significantly during the KD.
Conclusions:   Height velocity was most affected in those with pronounced ketosis, which implies that, in clinical practice, the level of ketosis should be related to outcomes in seizure response and growth. Our data indicate that growth disturbances and the decreased sensitivity of growth to similar IGF-I levels during KD are independent of seizure reduction. The metabolic status induced by KD may be the mechanism underlying both alterations of linear growth and seizure reduction.     

Regionally distinct regulation of astroglial neurotransmitter receptors by fibroblast growth factor-2

Fibroblast growth factor (FGF)-2 is an abundant astroglial cytokine. We have previously shown that FGF-2 downregulates gap junctions in primary astroglial cultures (B. Reuss et al., 1998, Glia 22, 19-30). We demonstrate now that FGF-2 induces astroglial dopamine (DA) sensitivity and D1 dopamine-receptor (D1DR) antigen and message in cortical and striatal astroglial cultures. On the functional level 10 micromol/L DA triggered transient increases in astroglial [Ca(2+)](i). In gap-junction-coupled cells, no FGF-2-dependent changes in proportions of DA-responsive cells were observable. However, uncoupling with octanol or 18alpha-glycirrhetinic acid isolated the smaller population of astrocytes intrinsically sensitive to DA which was significantly increased by FGF-2 in cortical and striatal cultures. Administration of DR-specific substances revealed that FGF-2 upregulated D1DR. These results indicate that downregulation of astroglial gap junctions by FGF-2 is accompanied by an upregulation of D1DR and DA sensitivity, adding a new aspect to the role of FGF-2 in the regulation of brain functions.     

Association of insulin-like growth factor-1 receptor polymorphism in dementia

There is an increasing interest in how oxidative stress can cause cells to go into apoptosis in both normal ageing and in neurodegenerative disorders. Previous research has implicated insulin-like growth factor-1 (IGF-1) as being involved in the pathogenesis in Alzheimer's disease (AD) by protecting the neurons through reducing neuronal susceptibility to oxidative stress. IGF-1 receptor (IGF-1R) polymorphisms alter cerebral and systemic levels of IGF-1 and may alter the function of the receptor. We genotyped the IGF-1R gene by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) to assess whether this gene polymorphism can be linked to dementia. We used leukocyte DNA from 72 patients with AD, 75 patients with vascular dementia (VaD), 14 patients with mixed dementia (AD+VaD), and a control group consisting of 209 individuals without a history of progressive neurological disorders. Analysis of gene frequency for gender revealed a significant difference between female VaD patients and female controls carrying at least one A allele (OR = 1.8, CI 95% 1.1-2.9, p = 0.02), but not for male patients. In addition, we found a strong tendency to a difference between all cases of female dementia patients and controls carrying the A allele (OR = 1.5, CI 95% 0.99-2.2, p = 0.054). Our results suggest that the A allele of IGF-1R may be involved in the pathogenesis of VaD in females.     

Central opiate modulation of growth hormone and insulin-like growth factor-I

The effects of central administration of morphine-sulfate (MOR:80 μg) and morphine-6-glucuronide (M6G:1 μg) on the growth hormone (GH)/insulin-like growth factor (IGF) system were assessed. MOR and M6G were injected intracerebroventricularly (ICV) in chronically catheterized 24 h fasted rats; time-matched control animals received H₂O (5 μl). MOR increased plasma GH concentrations 3-fold 2 h after ICV injection, and transiently increased the plasma concentration and liver content of IGF-I (60% and 90%, respectively) 30 min after ICV injection. M6G did not produce any significant alterations in plasma GH and IGF-I levels at the time-points measured. Both MOR and M6G increased the concentration of IGF binding protein-1 (IGFBP-1) in plasma and liver 2 h after injection. However, MOR showed 2- to 2.5-fold greater effect than M6G in stimulating plasma and liver IGFBP-1. MOR and M6G produced similar increases in plasma epinephrine (5-fold), norepinephrine (3-fold) and corticosterone (1.5-fold). Neither opiate significantly altered circulating insulin levels. These findings suggest that opiate modulation of GH and IGF may be hormone-independent and centrally modulated. We speculate that differential affinities of MOR and M6G to the different opiate receptor subtypes might be responsible for their distinct effects on GH/IGF-I system.     

胰岛素样生长因子1、血小板源性生长因子、转化生长因子β1对

背景：生长因子可调整椎间盘细胞的增殖、分化及基质代谢,用于椎间盘退变的生物学治疗,既往的研究偏重于成骨性生长因子对髓核细胞的作用,对纤维环细胞的研究相对较少。 目的：观察体外培养条件下胰岛素样生长因子1、血小板源性生长因子、转化生长因子β1对人退变纤维环细胞生物学活性的影响。 设计、时间及地点：对照观察实验,于2007-11/2008-12在解放军南京军区福州总医院完成。 材料：腰椎间盘手术患者的纤维环组织。 方法：结合酶消化法和组织块培养法,体外单层培养人退变纤维环原代细胞。传代后通过免疫组织化学染色鉴定细胞。对传3代细胞分别采用不同生长因子干预,分为 100 μg/L胰岛素样生长因子1组、10 μg/L 血小板源性生长因子组、10 μg/L 转化生长因子β1组、100 μg/L 胰岛素样生长因子 1+ 10 μg/L 血小板源性生长因子组、100 μg/L 胰岛素样生长因子1+ 10 μg/L 转化生长因子β1组、10 μg/L 血小板源性生长因子+10 μg/L 转化生长因子β1组、100 μg/L 胰岛素样生长因子1+10 μg/L血小板源性生长因子+10 μg/L 转化生长因子β1组,以不加生长因子为对照组。 主要观察指标：免疫组织化学染色观察传3代细胞。干预3,6 d后,采用MTT法测定传3代细胞增殖,ELISA法测定细胞培养上清液中Ⅰ、Ⅱ型胶原和聚集蛋白聚糖质量浓度。 结果：传3代细胞Ⅰ、Ⅱ型胶原免疫组织化学染色阳性。胰岛素样生长因子1促进人退变纤维环细胞增殖,轻度抑制细胞合成Ⅰ型胶原,促进合成Ⅱ型胶原和聚集蛋白聚糖,促Ⅱ型胶原合成作用轻度强于转化生长因子β1。血小板源性生长因子促进细胞增殖,作用强于胰岛素样生长因子1,其抑制细胞合成Ⅰ型胶原,轻度促进合成Ⅱ型胶原,无促合成聚集蛋白聚糖作用。转化生长因子β1抑制细胞增殖,促进合成Ⅰ、Ⅱ型胶原及聚集蛋白聚糖,促聚集蛋白聚糖合成作用强于胰岛素样生长因子1。多种因子联合作用较单种未见明显优势,未能呈现协同效应。 结论：胰岛素样生长因子1、血小板源性生长因子、转化生长因子β1明显改变人退变纤维环细胞的生物学活性,可应用于对人类椎间盘退变的生物学治疗。     

胰岛素样生长因子1对小鼠成骨细胞增殖和碱性磷酸酶活性的影响

背景：胰岛素样生长因子1是骨形成的调节因子,具有促进有丝分裂、促进成骨等作用。由骨细胞所产生的胰岛素样生长因子1在调节成骨细胞和破骨细胞介导的骨骼重建中起着重要的作用。 目的：观察胰岛素样生长因子1作用后,小鼠成骨细胞的增殖和碱性磷酸酶的表达。 方法：在体外培养的小鼠成骨细胞中分别加入25,50,100及200 μg/L的胰岛素样生长因子1,于培养的第1,2,3,4,5天用Cell Counting Kit-8比色法检测细胞增殖率;用流式细胞仪检测细胞的增殖周期和凋亡率;于培养的第3,6,9天应用酶联免疫法检测细胞内碱性磷酸酶活性。 结果与结论：胰岛素样生长因子1质量浓度在25~200 μg/L时,对小鼠成骨细胞的增殖率有明显的促进作用(P < 0.05),且呈明显的浓度依赖效应。当胰岛素样生长因子1质量浓度在200 μg/L时,能明显提高细胞S期所占的比例。说明胰岛素样生长因子1可加速细胞的增殖活动,以保证参与骨改建的成骨细胞数量而促进骨组织再生。同时,胰岛素样生长因子1在25~200 μg/L时,能显著提高细胞内碱性磷酸酶活性(P < 0.05),促进成骨细胞分化。     

Effect of sericin on diabetic hippocampal growth hormone/insulin-like growth factor 1 axis

Previous studies have shown that sericin extracted from silk cocoon significantly reduces blood glucose levels and protects the nervous system against diabetes mellitus. In this study, a rat type 2 diabetes mellitus model was established by intraperitoneal injection of 25 mg/kg streptozotocin for 3 successive days, following which the rats were treated with sericin for 35 days. After treatment, the blood glucose levels of the diabetic rats decreased significantly, the growth hormone level in serum and its expression in the hippocampus decreased significantly, while the insulin-like growth factor-1 level in serum and insulin-like growth factor-1 and growth hormone receptor expression in the hippocampus increased significantly. The experimental findings indicate that sericin improves disorders of the growth hormone/insulin-like growth factor 1 axis to alleviate hippocampal damage in diabetic rats.