LRP16 gene protects mouse insulinoma MIN6 cells against fatty acid-induced apoptosis through Akt/FoxO1 signaling

Background  Pancreatic b cells are susceptible to fatty acid-induced apoptosis. The 17b-estradiol (E2) protects pancreatic b cells from apoptosis, mediated by the estrogen receptor-a (ERa). The mRNA level and promoter activity of leukemia-related protein (LRP) 16 were significantly increased by E2 in ER-a and LRP16 was a co-activator of ER-a. The aim of the study was to assess the effects of LRP16 on fatty acid-induced apoptosis in MIN6 cells.

Methods  Cells with over-expressing LRP16 were obtained by lipidosome transfection. Insulin content and glucose-stimulated insulin secretion (GSIS) were examined by radioimmunoassay. Western blotting was applied to detect protein expression. Apoptosis was detected by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and flow cytometry. The forkhead boxO1 (FoxO1) subcellular localization was determined by immunocytochemical analysis.

Results  MIN6-LRP16 cells with overexpression of LRP16 were successfully established, and protein expression of LRP16 was 2.29-fold of that of control cells (MIN6-3.1, P <0.05). Insulin content and GSIS in MIN6-LRP16 were substantially increased compared with those in control cells. When cells were stimulated with glucose, increased phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 and serine-threonine kinase (Akt) were observed in MIN6-LRP16. When cells were under palmitate pressure, the TUNEL-positive rate in MIN6-LRP16 was (17.0±0.5)%, while it in MIN6-3.1 was (22.0±0.4)%. In palmitate-treated cells, attenuated Akt phosphorylation was observed, but the attenuation in Akt activity was partially restored in MIN6-LRP16 cells. Meanwhile, nuclear localization of FoxO1 in MIN6-LRP16 was apparently reduced compared with that in control cells.

Conclusions  LRP16 regulated insulin content and GSIS in MIN6 cells by ERK1/2 and Akt activated way. Meanwhile, LRP16 overexpression protected MIN6 cells from fatty acid-induced apoptosis by partially restoring Akt phosphorylation and inhibiting FoxO1 nuclear redistribution. Therefore, LRP16 played important roles not only in insulin content and GSIS but also in the antilipotoxic effect mediated by Akt /FoxO1 signaling.

     

LRP16基因通过上调GLUT-2促进MIN6细胞胰岛素分泌

目的：探讨LRP16基因对MIN6细胞葡萄糖刺激胰岛素分泌的影响及其可能机制。方法：用Super-Fect脂质体转染法建立稳定过表达LRP16基因的MIN6细胞株,以转染空质粒的MIN6细胞株作为对照。检测两组细胞的增殖、胰岛素分泌及GLUT-2蛋白的表达情况。结果：过表达组的增殖与对照组相比无显著差别（P〉0．05）;在0mmol／L、3mmol／L、30mmol／L葡萄糖刺激下,过表达组的胰岛素分泌量分别为对照组的2．26倍、2．19倍和2．16倍（P〈0．05）;westernblot显示过表达组GLUT-2蛋白量比对照组显著上调（P〈0．05）。结论：过表达LRP16基因不能促进MIN6细胞增殖,但可以通过上调GLUT-2促进胰岛素分泌。表明LRP16基因促进胰岛素分泌的作用不依赖细胞增殖,而依赖细胞对葡萄糖摄取的增加。     

多基因修饰小鼠诱导多潜能干细胞分化为胰岛素分泌细胞

目的观测胰岛素转录关键调控因子胰腺十二指肠同源框蛋白1(PDX-1)、神经分化因子1(NeuroD1)及肌腱膜纤维肉瘤癌基因同系物A(MafA)对小鼠诱导多潜能干细胞(iPS细胞)分化为胰岛素分泌细胞的作用。方法筛选鉴定小鼠胚胎成纤维细胞(MEFs)重编程的iPS细胞。以重组腺病毒Ad-mPDX-1-IRES-GFP、Ad-mNeuroD1-IRES-GFP、Ad-mMafA-IRES-GFP联合感染小鼠iPS细胞,体外培养后以RT-PCR检测胰岛B细胞功能基因表达;免疫荧光检测胰岛素蛋白表达及定位;ELISA检测不同糖浓度(0、5、10、20、30、40mmol/L)下胰岛素的分泌量。结果起源于MEFs的iPS细胞能形成边缘光整的致密克隆,表达干性基因Nanog、Rex-1、SSEA-1,并能在体内外分化为三胚层组织,显示MEFs被成功地重编程为iPS细胞。Ad-PDX-1-IRES-GFP、Ad-mNeuroD-IRES-GFP、Ad-mMafA-IRES-GFP感染的小鼠iPS细胞能分化为胰岛类B细胞,RT-PCR结果显示其胰岛B细胞功能基因的表达与小鼠胰岛B细胞株MIN6相似。免疫荧光检测可见胰岛类B细胞内有胰岛素表达。ELISA检测结果显示胰岛类B细胞对不同浓度葡萄糖有较好的反应性。结论胰岛素转录关键调控因子PDX-1、NeuroD1和MafA三者能协同作用,使小鼠iPS细胞分化为具有显著胰岛素合成和分泌能力的胰岛素分泌细胞。     

Akt信号通路在胰岛β细胞功能中的研究进展

PI3K是调节Akt活性的重要分子。生长因子通过Akt通路将信号传递至细胞内,对细胞的多种生物功能起调节作用。Akt共有3种亚型,它们均表达于胰岛β细胞。在胰岛β细胞中Akt以依赖于PI3K的方式被激活。大量研究发现,Akt信号通路在调节胰岛β细胞增殖、凋亡、胰岛素分泌、再生中起着重要的作用,现对Akt信号通路在胰岛β细胞功能中研究的新进展予以综述。     

Visfatin通过线粒体途径抑制胰岛β细胞凋亡

目的 探讨内脏脂肪素（visfatin）对棕榈酸诱导胰岛β细胞凋亡的影响。 方法 小鼠胰岛β细胞株MIN6体外传代培养,进入对数生长期后进行实验。MTT法检测不同浓度visfatin（0~10-7 mol/L）作用24~72 h后MIN6细胞活力变化。流式细胞术检测0.5 mmol/L棕榈酸和(或)10-8 mol/L visfatin处理24 h后MIN6细胞凋亡率的变化;Western blotting检测MIN6抗凋亡蛋白bcl-2、bax、激活型caspase-3和胞质细胞色素C表达的变化。 结果 Visfatin作用24~48 h,MIN6细胞活力呈剂量依赖性增加（P<0.05）。流式细胞仪检测发现,10-8 mol/L visfatin处理24 h可明显降低棕榈酸诱导的细胞凋亡率（P<0.05）;Western blotting结果表明,10-8 mol/L visfatin可显著抑制棕榈酸引起的细胞内源性bcl-2表达的下调及激活型caspase-3和胞质细胞色素C表达的上调（P<0.05）。 结论 Visfatin可促进胰岛β细胞增殖,并通过细胞内线粒体途径抑制由棕榈酸诱导的胰岛β细胞凋亡。     

抑制LRP16增加Hela细胞对足叶乙甙的敏感性

目的 探明LRP16的表达与化疗药物足叶乙甙所诱导的肿瘤细胞凋亡是否产生作用以及可能的分子机制.方法 首先将抑制LRP16表达的小干扰RNA,control,siRNA,siRNA-374(抑制率90％),siRNA-668(抑制率60％),对照分别转染入Hela细胞内,并通过足叶乙甙处理的细胞而导致DNA损伤.之后用CCK-8检测细胞活力;用流式细胞技术测定抑制LRP16的表达对Hela细胞凋亡率的影响;通过RT-PCR检测抑制LRP16表达之后核转录因子-κ B(nuclear factor-κ B,NF-κ B)凋亡相关的下游靶基因的mRNA水平.结果 在足叶乙甙(100μmol)的作用下,抑制LRP16的表达能够明显抑制细胞的增长(P＜0.05),并呈浓度依赖性,同时增加细胞的凋亡率(P＜0.05).RT-PCR结果显示,下调LRP16的表达减弱NF-κB的转录活性,进而对其下游靶基因的水平进行调节.结论 LRP16在足叶乙甙导致的凋亡起重要作用,而且可能是通过下调NF-κ B的活性来发挥化疗药物抵抗效应.我们的实验结果初步证实抑制LRP16增加Hela细胞对足叶乙甙的敏感性.     

Effects of High Concentration Glucose on the Expression of NF-κB, Bax and Cytochrome C and Apoptosis of Islet Cells in Mice

The roles of NF-kappaB （NF-κB） expression, Bax activity and cytochrome C （Cyt C） release, apoptosis of islet cells induced by high concentration glucose were explored in vitro. Pancreatic islet cells, which were isolated from Kunming mice, were cultured with different concentrations of glucose in DMEM, and divided into the following groups： G1, G2, G3, G4, G5, and G6 groups, corresponding to the glucose concentrations of 5.6, 7.8, 11.1, 16.7, 22.5, and 27.6 mmol/L, respectively. After culture for 120 h, insulin secretion was evaluated by radioimmunoassay, and the NF-rd3 expression was detected by immunocytochemistry. Bax activity and Cyt C release were measured by immunofluorescence, and apoptosis was examined by Hoechst33342 assay. The results showed that in GI, G2 and G3 groups, insulin secretion was enhanced with the increase of glucose concentration, and the NF-κB expression was also increased （P〈0.05）, but Bax activity, Cyt C release and apoptosis rate showed no significant difference among them. However, in G4, G5, and G6 groups, apoptosis rate of islet cells, NF-rd3 expression, Bax activity, and Cyt C release were all significantly increased, and insulin secretion was impaired as compared with G1, G2, and G3 groups （P〈0.05）. It was concluded that the exposure of islet cells to high glucose could induce islet cells apoptosis as well as impaired insulin secretion. The NF-κB signaling pathway and mitochondria pathway in islet cells might play some roles in the progressive loss of islet cells in diabetes. The inhibition of the NF-κB expression could be an effective strategy for protecting pancreatic islet cells.     

Exendin-4对IL-1β诱导小鼠胰岛β细胞凋亡的保护作用

目的探讨GLP-1受体激动剂Exendin-4对细胞因子IL-1β诱导的小鼠胰岛β细胞株MIN6细胞凋亡的保护作用。方法体外培养小鼠胰岛β细胞株MIN6细胞,用不同浓度(5,10,20,40ng/mL)IL-1β作用24h,噻唑兰还原(MTT)法观察不同浓度IL-1β作用后细胞存活率;Hoechst-PI荧光染色法观测细胞凋亡形态;后以Exendin-4(100nmol/L)预处理细胞24h,观察Exendin-4对IL-1β诱导的MIN6细胞凋亡的保护作用。结果 MTT显示IL-1β(5～40ng/mL)作用24h后,MIN6细胞的增殖率明显下降,并呈现一定的量效关系;Hoechst-PI染色荧光显微镜检测证实随着IL-1β浓度的增高,MIN6细胞的凋亡率亦增加。Exendin-4预先处理24h后可以抑制IL-1β诱导的β细胞凋亡。结论 GLP-1受体激动剂Exendin-4可以显著抑制IL-1β诱导MIN6细胞的凋亡,提示Exendin-4对IL-1β诱导的MIN6细胞的凋亡具有保护作用。     

Modulatory Effects of EPA and DHA on Proliferation and Apoptosis of Pancreatic Cancer Cells

In order to investigate the effects of eicosapentaenoic acid （EPA） and docosahexaenoic acid （DHA） on the proliferation, apoptosis of pancreatic cancer cell line SW1990 cells and the expression of cyclin E mRNA, the SW1990 cells were treated with different concentrations of EPA or DHA （20, 40, 60 μg/mL） for 0, 12, 24, 36 and 48 h respectively. By using MTF method, the inhibitory effects of EPA or DHA on the cell growth were assayed. Real time PCR was used to detect the expression changes of cyclin E mRNA after the SW1990 cells were treated with 40μg/mL EPA or DHA for different time. Flow cytometry was used to test the changes of apoptostic rate in the SW1990 cells treated with different concentrations of EPA or DHA for 24 h. The results showed that EPA and DHA could inhibit the growth of SW1990 cells in a time- and concentration-dependent manner （P〈0.01）. EPA or DHA could also significantly inhibit the expression of cyclin E mRNA in a time-dependent manner （P〈0.05）. EPA or DHA could induce the apoptosis of SW1990 cells in a concentration-dependent manner （P〈0.01）. It was concluded that ω-3 fatty acid could inhibit the proliferation of pancreatic cancer cell line SW1990 cells and promote their apoptosis. The down-regulation of the cyclin E expression by ω-3 fatty acid might be one of the mechanisms for its anti-tumor effect on pancreatic cancer.     

醛固酮诱导MIN6细胞凋亡及作用机制研究

目的 探讨醛固酮对小鼠胰岛B细胞株MIN6细胞凋亡的影响及可能的作用机制.方法 体外培养的小鼠胰岛B细胞株MIN6分为对照组(加入无血清的DMEM培养基)、醛固酮组(加入10、100、1 000 nmol/L醛同酮进行干预)和醛固酮+拮抗剂组(以100 nmol/L醛固酮和100 nmol/L醛固酮拮抗剂螺内酯共同干预).采用MTT法检测细胞活性;放射免疫分析法检测葡萄糖刺激的胰岛素分泌(GSIS);流式细胞术结合FITC-Annexin V/PI荧光染色检测细胞凋亡;ELISA法检测细胞培养上清液中Caspas-3活性;Western blotting法检测凋亡相关蛋白细胞色素C(Cyt-C)、Bcl-2、Bax和磷酸化蛋白激酶C(p-Akt)的表达.结果 MIN6细胞增殖活性随醛固酮干预浓度的升高而下降,呈现浓度依赖性.在生理糖浓度(5.6 mmol/L)和高葡萄糖浓度(28 mmol/L)环境中,醛固酮组的GSIS均显著低于与对照组(P＜0.01),而醛固酮+拮抗剂组GSIS显著高于醛固酮组(P＜0.01).醛固酮组细胞凋亡率显著高于对照组(P＜0.01),而醛固酮+拮抗剂组细胞凋亡率显著低于醛固酮组(P＜0.01).与对照组比较,醛固酮组Caspase-3活性明显升高,Cyt-C表达上调,Bcl-2/Bax下降,p-Akt表达下调(均P＜0.01);而醛固酮+拮抗剂组对醛固酮组的Caspase-3活性升高及相关蛋白表达异常具有明显抑制作用.结论 醛固酮具有促进MIN6细胞凋亡的作用,其作用机制可能与Cyt-C、Bcl-2、Bax和Akt介导的线粒体信号途径有关.     

硫酸脱氢表雄酮刺激MIN6细胞胰岛素分泌的机制研究

目的 初步探讨硫酸脱氢表雄酮(DHEAS)促进MIN6细胞胰岛素分泌的机制.方法 选用小鼠胰岛B细胞株MIN6作为实验对象,在葡萄糖浓度为2.8 mmol/L和16.7 mmol/L的条件下,分别以0.1、1、5、10、50μmol/L的DHEAS干预10 min和24h,采用ELISA法测定细胞培养上清液中胰岛素的含量,应用相关试剂盒检测细胞内三磷酸腺苷(ATP)和二磷酸腺苷(ADP)的生物发光水平及比率(ATP/ADP);采用Real-Time PCR法检测不同浓度DHEAS干预24 h的细胞内葡萄糖激酶(GCK) mRNA的表达.结果 两种葡萄糖浓度条件下,以5、10、50 μmol/L DHEAS干预10 min和24 h的MIN6的细胞培养上清液中胰岛素含量和细胞内ATP/ADP比率显著高于空白对照组(P＜0.05).与空白对照组比较,1、5、10、50 μmol/L DHEAS干预24 h的MIN6细胞内GCK mRNA表达显著上调(p＜0.05).结论 DHEAS可能通过增加ATP/ADP的比率,促进MIN6细胞胰岛素的分泌;干预24 h的效应可能与上调GCK mRNA的表达、促进葡萄糖酵解有关.     

烟酰胺单核苷酸对RIN-m5f细胞中胰岛素分泌及PDX-1和FoxO1基因表达的影响

目的:在细胞水平研究烟酰胺单核苷酸(nicotinamide mononucleotide,NMN)对胰岛素分泌的调节作用及其对与胰岛素分泌相关的重要转录因子胰十二指肠同源盒基因(pancreatic and duodenal homeobox-1,PDX-1)和分叉头框家族转录因子l(forkhead box-con...     

Chronic Hyperinsulinism Induced Down—regulation of Insulin Post—Receptor Signaling Transduction in Hep G2 Cells

Insulin initiates its biological effects first bybinding to its cellular receptor,thereby activatingthe tyrosine kinase in theβ- subunit of the insulinreceptor ( IRβ) .This leads to tyrosine phosphory-lation of several insulin receptor protein substrates( IRS) ,especially IRS- 1 [1,2 ] .Phosphorylated IRS-1 plays a critical role in divergence of the insulinsignal.Phosphorylated IRS- 1 associates with SH2domain proteins,such as the p85 subunit of phos-phatidylinositol 3- kinase ( PI 3-…     

不同途径移植人脐带间充质干细胞治疗糖尿病大鼠

目的观察不同途径移植人脐带间充质干细胞(hUCMSCs)对糖尿病大鼠的治疗效果。方法 60只SD大鼠单次腹腔注射链脲佐菌素(70 mg.kg-1)建立糖尿病模型,成模后随机分为糖尿病模型组、胰腺被膜下移植组、肾被膜下移植组及肝实质内移植组,每组14只;另取10只大鼠为正常对照组。分别于各干细胞移植组大鼠胰腺被膜下、左肾被膜下、肝实质内注射0.5 mL hUCMSCs悬液(1×106个);糖尿病模型组及正常对照组于胰腺被膜下注射生理盐水0.5 mL。移植后动态观察空腹血糖(FBG)、空腹胰岛素(FINS)、体质量变化,6周后处死大鼠,取相关组织行病理学检查及胰岛素、胰十二指肠同源异型盒基因(PDX-1)、巢蛋白mRNA表达测定。结果移植前各组大鼠体质量比较差异无统计学意义(P>0.05);各干细胞移植组及糖尿病模型组大鼠FBG值高于正常对照组(P<0.05),FINS水平低于正常对照组(P<0.05);各干细胞移植组及糖尿病模型组大鼠FBG和FINS水平组间比较差异无统计学意义(P>0.05)。移植5周末,与正常对照组比较,各干细胞移植组及糖尿病模型组大鼠体质量及FINS降低,FBG增高,差异均有统计学意义(P<0.05);与糖尿病模型组比较,各干细胞移植组大鼠体质量及FINS升高,FBG降低,差异均有统计学意义(P<0.05);与胰腺被膜下移植组比较,肾被膜下及肝实质内移植组大鼠体质量降低,FBG升高,FINS水平降低,差异均有统计学意义(P<0.05)。与正常对照组相比,各实验组大鼠平均阳性染色面积均降低(P<0.05);胰腺被膜下移植组阳性染色面积大于糖尿病模型组(P<0.05);所有组织切片均未检测到人胰岛素的表达。与正常对照组比较,胰腺被膜下移植组、糖尿病模型组大鼠胰岛素mRNA表达量均降低(P<0.05),大鼠PDX-1及巢蛋白mRNA表达量均增高(P<0.05)。与糖尿病模型组比较,胰腺被膜下移植组大鼠胰岛素、PDX-1及巢蛋白mRNA表达量均增高(P<0.05)。各实验组均未检测到人胰岛素、PDX-1及巢蛋白mRNA表达。结论不同移植途径对hUCM-SCs治疗糖尿病的效果有影响,胰腺被膜下移植效果优于其他途径。hUCMSCs并未分化为β细胞,但其能够促进内源性胰腺干细胞增殖、分化。     

苯丙酸诺龙对胰岛NIT-1细胞Nampt表达和胰岛素分泌的影响

目的：观察雄性激素苯丙酸诺龙(BPN)干预下胰岛NIT-1细胞中烟酰胺磷酸核糖转移酶（Nampt）、胰岛素受体底物-2（IRS-2）和胰岛十二指肠同源盒-1（PDX-1）蛋白表达、细胞周期和胰岛素分泌的变化,探讨高浓度葡萄糖氧化应激状态下BPN对NIT-1细胞Nampt表达和胰岛素信号分子的影响。方法：应用4种不同浓度（5.6、11.1、16.7和27.6mmol•L^-1）葡萄糖培养NIT-1细胞,以10 mg•L^-1 BPN干预NIT-1细胞48 h,以未加BPN处理的相应浓度葡萄糖为对照组。应用Western blotting法检测各组细胞中Nampt、IRS-2 和 PDX-1蛋白表达水平;流式细胞术检测细胞周期;放射免疫法测定细胞胰岛素分泌水平。结果：与相应浓度葡萄糖对照组比较,各BPN处理组NIT-1细胞中Nampt、ISR-2和PDX-1蛋白表达水平增加（P<0.05或P<0.01）;与相应对照组比较,在低糖（5.6 mmol•L^-1）时,BPN能够明显解除细胞G0/G1期阻滞（P<0.01）,在高糖（27.6 mmol•L^-1）时,能够解除细胞的G2/M阻滞（P<0.01）;除正常葡萄糖浓度11.1mmol•L^-1组之外,各处理组细胞的胰岛素分泌水平均明显增加（P<0.01）。结论：BPN能够增加胰岛NIT-1细胞中Nampt、ISR-2和PDX-1蛋白表达水平,NIT-1细胞中Nampt表达与胰岛素信号传导途径的相关分子间可能存在密切关联,雄性激素在一定条件下能够改善胰岛细胞的胰岛素抵抗状态。     

VEGF-B对胰岛β细胞胰岛素分泌和Ca2+、cAMP、ATP含量的影响

目的 观察血管内皮生长因子B(VEGF-B)对胰岛MIN6细胞胰岛素分泌及细胞内Ca²⁺、cAMP和ATP含量的影响,并探讨其作用机制。方法 采用50 ng/mL VEGF-B蛋白在5.5 mM和25 mM葡萄糖条件下处理MIN6细胞,在2 h和24 h时应用ELISA试剂盒检测MIN6细胞的胰岛素分泌,细胞内Ca²⁺、cAMP和ATP含量。应用siRNA抑制MIN6细胞中的VEGF-B 48 h后,在5.5 mM和25 mM葡萄糖条件下检测2 h和24 h时MIN6细胞的胰岛素分泌、细胞内Ca²⁺、cAMP和ATP含量。结果 VEGF-B干预MIN6细胞后胰岛素分泌减少,同时细胞内Ca²⁺、cAMP和ATP含量均减少;抑制VEGF-B后胰岛素分泌增加,细胞内Ca²⁺、cAMP和ATP含量与胰岛素变化趋势一致。结论 VEGF-B可能通过影响Ca²⁺、 cAMP和ATP的含量影响胰岛β细胞胰岛素分泌。