高浓度葡萄糖对PDX-1表达和胰岛素分泌功能的影响

目的 探讨高浓度葡萄糖（Glu）对PDX-1表达的影响及其与胰岛素（Ins）分泌的关系。方法 分别测定SD大鼠胰岛细胞基础和Glu刺激后Ins分泌量、细胞内Ins含量、细胞内PDX-1 mRNA和蛋白的表达水平。结果 1．高糖刺激3天后，基础和Glu刺激后Ins分泌量、细胞内Ins含量及PDX-1蛋白表达水平均明显降低（P〈0．01）。2．在高糖环境下，延长培养时间可显著加强高糖对PDX-1蛋白表达的抑制作用。3．纠正高糖环境3天后可部分逆转高糖对PDX-1蛋白表达的抑制作用。结论 高浓度Glu对PDX-1蛋白表达的抑制是Glu毒性作用的机制之一，纠正高糖3天后可部分逆转高糖对PDX-1蛋白表达的抑制作用，恢复Ins分泌功能。     

血管紧张素Ⅱ对RIN-m细胞PDX-1 mRNA及蛋白表达的影响

目的 探讨血管紧张素Ⅱ(ATⅡ) 对胰十二指肠同源盒1(PDX-1)表达的影响及其与胰岛素(Ins) 分泌的关系.方法 测定RIN-m细胞在基础、ATⅡ及氯沙坦作用下Ins 分泌量、细胞内Ins 含量及细胞内PDX-1 mRNA 和蛋白的表达水平.结果 在100nmol/L ATⅡ作用下, 葡萄糖刺激后Ins 分泌量、细胞内Ins 含量及PDX-1表达水平均明显降低(P均<0.05).上述作用可被ATⅡ受体阻滞剂氯沙坦部分逆转.结论 抑制PDX-1表达水平可能是ATⅡ影响胰岛β细胞Ins合成及分泌的机制之一.     

波动性高糖对INS-1细胞凋亡及凋亡相关基因表达的影响

目的探讨波动性高糖对INS-1细胞凋亡及凋亡相关基因表达的影响及其分子机制。方法将INS-1细胞随机分为三组。正常对照组(NG):含5.5 mmol/L葡萄糖;持续高糖组(SHG):含33.3 mmol/L葡萄糖;波动性高糖组(IHG):含5.5 mmol/L或33.3 mmol/L葡萄糖,每24 h交替换液1次,均培养3 d。3 d后检测各组INS-1细胞活性及凋亡百分率,胰岛素分泌量,Bcl-2相关X蛋白(Bax)、细胞色素C(CytC)和天冬氨酸特异性半胱氨酸蛋白酶-3(Caspase-3)蛋白表达水平以及胰岛素(insulin)和胰岛十二指肠同源盒-1(PDX-1)mRNA表达水平。结果与NG组相比,SHG组与IHG组凋亡率均明显升高,细胞活性明显降低,Bax、CytC及Caspase-3表达明显增强,胰岛素分泌量及insulin、PDX-1 mRNA表达水平均明显降低(P均<0.01);与SHG组相比,IHG组细胞活性及胰岛素分泌量明显降低,凋亡率及Caspase-3明显增加(P均<0.01),Bax、CytC表达水平与insulin及PDX-1 mRNA表达水平均未见统计学差异。结论波动性高糖能导致胰岛细胞凋亡增加和功能障碍,其机制可能与上调Bax、CytC、Caspase-3及降低insulin与PDX-1基因表达等相关。     

沙奎那韦致大鼠INS-1细胞胰岛素抵抗

目的探讨HIV-1蛋白酶抑制剂沙奎那韦对大鼠INS-1细胞内胰岛素信号转导通路及β细胞功能的影响。方法INS-1细胞经10μmol／L沙奎那韦处理48h后,台盼蓝染色计数细胞,MTT试验评估沙奎那韦对细胞活力的影响,Western印迹法测定100nmol／L胰岛素刺激的细胞裂解产物中的胰岛素信号转导蛋白的含量及其磷酸化,免疫酶标法测定20mmol／L葡萄糖刺激的胰岛素释放量,并用细胞内DNA含量标准化。结果沙奎那韦处理后,INS-1细胞内胰岛素刺激的胰岛素受体底物1（IRS-1）及IRS-2酪氨酸磷酸化和Akt—Thr^308磷酸化分别降低了60％、66％和55％,基础胰岛素分泌速率和葡萄糖刺激的胰岛素释放速率分别下降了39％和49％。结论沙奎那韦可损害胰岛β细胞内胰岛素信号的转导,导致β细胞自身胰岛素抵抗,这一作用可能影响胰岛β细胞功能。     

游离脂肪酸对βTc6细胞PDX-1表达及胰岛素分泌能力的影响

目的 探讨游离脂肪酸对胰岛β细胞胰-十二指肠同源盒因子-1(PDX-1)的表达及相应的β细胞增殖活性和胰岛素分泌功能变化的影响.方法 0.25～1.00 mmol/L游离脂肪酸干预小鼠胰岛素瘤细胞系βTc6细胞24～48 h,应用RT-PCR法检测转录因子PDX-1 mRNA表达,四甲基偶氮唑盐法检测细胞的增殖活性,放射免疫法检测葡萄糖刺激的胰岛素分泌水平,并观察细胞形态变化.结果 经0.25～1.00 mmol/L游离脂肪酸干预24 h,βTc6细胞PDX-1 mRNA的转录逐步增加,但随着干预时间进一步延长至48 h,PDX-1 mRNA的转录逐渐回落,特别是用1.00 mmoL/L游离脂肪酸干预48 h后,βTc6细胞PDX-1 mRNA的表达低于空白对照组.经过0.50～1.00 mmol/L游离脂肪酸24～48 h的干预之后,βTc6细胞形态学上呈现凋亡趋势,细胞增殖活力以及葡萄糖刺激的胰岛素分泌功能降低,而0.25 mmol/L游离脂肪酸24 h的干预未见此类现象.结论 短时间低浓度的游离脂肪酸干预可介导β细胞转录因子PDX-1的表达上调,对β细胞的增殖活性和胰岛素分泌能力无明显影响;而长时间高浓度的游离脂肪酸干预则将导致PDX-1 mRNA的表达下调,并使β细胞的增殖活性和胰岛素分泌能力受损.     

葡萄糖对血管内皮细胞小凹蛋白1和血管内皮生长因子表达的影响

为了探讨高浓度葡萄糖损伤血管内皮细胞及其对小凹蛋白-1和血管内皮生长因子表达的影响。将人脐静脉内皮细胞株ECV304．分别培养在对照组和含5.5mmol／L、11.1mmol／L、22.0mmol／L、33.0mmol／L葡萄糖的培养基中。经葡萄糖培养24h后，噻唑蓝法测定细胞增殖活性，硝酸还原酶法测定培养上清液中一氧化氮浓度，免疫组织化学和免疫印迹方法检测细胞中小凹蛋白-1和血管内皮生长因子的表达。结果发现，随着葡萄糖浓度的增加，内皮细胞增殖活性呈浓度依赖性抑制(r=-0.776，P=0.000)；一氧化氮浓度呈浓度依赖性增加(r=0.698，P=0.000)；小凹蛋白-1和血管内皮生长因子为棕黄色颗粒，主要分布于胞浆中；血管内皮生长因子的表达呈浓度依赖性增加(r=0.645，P=0.009)；小凹蛋白-1的表达也呈浓度依赖性增加(r=0.808，P=0.000)。提示高糖可诱导血管内皮细胞的血管内皮生长因子和小凹蛋白-1的表达，此变化可能与糖尿病患者高糖致血管病变有关。     

高脂状态下Exendin-4对胰岛βTc6细胞内胰-十二指肠同源盒-1表达、细胞增殖功能及胰岛素分泌能力的干预作用

目的探讨Exendin-4在高脂状态下是否具有抗脂毒性及其相关机制是否涉及胰-十二指肠同源盒(PDX)-1。方法不同浓度的Exendin-4培育βTc6细胞不同时间,再应用1 mmol/L游离脂肪酸(FFA)干预24 h,检测细胞内PDX-1表达及增殖能力和胰岛素分泌功能。结果 1Exendin-4干预6 h,各组细胞PDX-1表达、细胞增殖能力和胰岛素分泌功能均未见明显改善;2当Exendin-4干预延长至12~24 h,随着干预浓度增高,细胞内PDX-1逐渐升高,细胞增殖能力和胰岛素分泌功能明显好转。结论高脂状态下适宜浓度的Exendin-4干预一定时限可上调β细胞内PDX-1的表达,并改善细胞增殖功能及胰岛素分泌能力。     

罗格列酮对高糖诱导RIN-m细胞凋亡的作用及其机制探讨

目的探讨罗格列酮对高糖诱导的RIN-m细胞凋亡作用及其机制。方法采用分别含5.5 mmol/L葡萄糖、33.3 mmol/L葡萄糖、5.5 mmol/L葡萄糖＋10μmol/L罗格列酮及33.3 mmol/L葡萄糖＋50μmol/L罗格列酮的培养液培养RIN-m细胞。以放射免疫法检测胰岛素分泌水平。以流式细胞仪及TUNEL法检测RIN-m细胞凋亡情况。同时行免疫细胞化学染色,半定量分析Bcl-2和Bax的表达。RT-PCR检测胰腺十二指肠同源盒-1（PDX-1）mRNA表达。结果长期高糖可导致RIN-m细胞胰岛素分泌功能下降、凋亡率增加2.7倍（P〈0.05）。罗格列酮可以增加高糖环境下RIN-m细胞胰岛素的分泌、降低RIN-m细胞凋亡率（P〈0.05）。长期高糖可以降低RIN-m细胞Bcl-2/Bax的比例,并下调PDX-1 mRNA表达（P〈0.05）。10μmol/L罗格列酮即可增加高糖环境下RIN-m细胞Bcl-2/Bax表达的比例及上调PDX-1 mRNA表达（P均〈0.05）。结论罗格列酮对RIN-m细胞有直接的保护作用,这种保护作用可能与罗格列酮增加了Bcl-2/Bax表达比例和上调PDX-1 mRNA表达,进而抑制RIN-m细胞凋亡有关。     

Ghrelin抑制胰岛β细胞胰岛素释放的机制探讨

目的探讨ghrelinx对小鼠胰腺β细胞株NIT-1细胞胰岛素释放的影响及其作用机制。方法NIT1细胞与不同浓度ghrelin和高浓度葡萄糖孵育后，放免法测定上清液胰岛素含量，RTPCR法检测葡萄糖转运子2（GluT2）、胰十二指肠同源盒-1（PDX-1）、含两个跨膜区的内向整流钾通道（Kir6．2）及磺酰脲受体1（SUR-1）等基因的表达。NIT-1细胞与不同浓度ghrelin孵育不同时间后，MTT法检测细胞增殖情况。结果（1）10^-9mol／L至10^-7mol／L ghrelin呈剂量依赖性抑制NIT-1细胞高浓度葡萄精刺激的胰岛素释放；（2）10^-7mol／L ghrelin硅著降低Kir6．2mRNA的表达，但对GluT2、PDX-1及SUR-1 mRNA的表达无明显的效应；（3）Ghrelin对NIT-1细胞的增殖无垃著影响。结论Ghrelin可抑制胰岛β细胞高浓度葡萄糖刺激的胰岛素释放，该效应可能是由于下调ATP敏感性钾通道组成成分Kir6．2基因的表达所致。     

高糖高棕榈酸培养对β细胞脂质含量及脂肪酸转位酶表达的影响

目的研究高糖高棕榈酸（PA）培养对β细胞脂质含量及脂肪酸转位酶（FAT/CD36）表达的影响。方法NIT-1细胞分别以5mmol/L葡萄糖（NC组）、25mmol/L葡萄糖（HG组）、0.25mmol/LPA＋5mmol/L葡萄糖（HP组）及0.25mmol/LPA＋25mmol/L葡萄糖（GP组）培养24h后,测定细胞内甘油三酯（TG）含量、胰岛素分泌以及FAT/CD36 mRNA与蛋白的表达。结果（1）与NC组比较,各处理组细胞内TG含量增加,而葡萄糖刺激的胰岛素分泌下降,以GP组变化最明显。（2）在高糖孵育下,HG组和GP组FAT/CD36 mRNA与蛋白表达均较NC组显著增加（P〈0.01）,但HP和GP组与相应的葡萄糖组比较,FAT/CD36表达无明显变化。结论在高棕榈酸的环境下,高糖可进一步促进β细胞脂质沉积,抑制葡萄糖刺激的胰岛素分泌;其中高糖上调脂肪酸转位酶表达可能是其重要机制之一。     

小鼠多能干细胞诱导的功能性胰岛素分泌细胞对1型糖尿病小鼠的治疗作用研究

目的探讨小鼠多能干细胞(iPSCs)经改良7步法诱导生成胰岛素分泌细胞(ISCs)的可行性及其对T1DM小鼠的治疗作用。方法分离和提取小鼠胚胎成纤维细胞,通过体外诱导构建小鼠i PSCs。小鼠iPSCs经改良的7步诱导法转化为小鼠ISCs。免疫荧光检测小鼠ISCs的胰十二指肠同源盒1(PDX-1)、胰岛素和C-P表达。流式细胞术检测小鼠ISCs的C-P表达以评估小鼠ISCs的分化率。ELISA法检测高浓度(23.3 mmol/L)和正常浓度(5.5 mmol/L)葡萄糖刺激下小鼠ISCs的胰岛素分泌水平。将小鼠ISCs移植到T1DM模型小鼠左肾包膜下,ELISA法检测小鼠血糖和胰岛素分泌水平。结果小鼠iPSCs经7步法诱导生成小鼠ISCs的PDX-1、胰岛素和C-P免疫荧光检测阳性;流式细胞术结果显示,小鼠ISCs的分化率为35.2%。ELISA结果显示,与小鼠iPSCs比较,小鼠ISCs在5.5、23.3 mmol/L葡萄糖浓度下的胰岛素分泌水平均升高[(0.82±0.49)vs(9.45±1.32)mIU/L,(2.38±0.67)vs(27.86±3.45)mIU/L,P<0.05];在小鼠ISCs中,23.3 mmol/L葡萄糖浓度胰岛素分泌水平高于5.5 mmol/L葡萄糖浓度[(27.86±3.45)vs(9.45±1.32)mIU/L,P<0.05]。小鼠ISCs移植后第3~12周,ISCs组血糖水平降低(P<0.05或P<0.01),胰岛素分泌水平升高(P<0.05或P<0.01)。结论小鼠iPSCs经改良的7步诱导法可有效转化为成熟的小鼠ISCs,且小鼠ISCs对T1DM小鼠有降低血糖、提升胰岛素分泌水平的作用。     

Dexamethasone suppresses phospholipase C activation and insulin secretion from isolated rat islets

Dexamethasone inhibits insulin secretion from isolated islets. In the present experiments, possible underlying biochemical mechanisms responsible for defective secretion were explored. Dexamethasone (1 micromol/L) had no immediate deleterious effect on 15 mmol/L glucose-induced insulin release from perifused rat islets. However, a 3-hour preincubation period with 1 micromol/L dexamethasone resulted in parallel reductions in both the first (64%) and second phases (74%) of 15 mmol/L glucose-induced insulin secretion monitored during a dynamic perifusion. When measured after the perifusion, there were no differences in insulin content or in the capacity of control or dexamethasone-treated islets to use glucose. Dexamethasone (1 micromol/L) preexposure also reduced phorbol ester- and potassium-induced secretion. In additional experiments, islets were labeled for 3 hours with 3H-inositol in the presence or absence of 1 micromol/L dexamethasone. The steroid did not affect total 3H-inositol incorporation during the labeling period. However, the capacity of 15 mmol/L glucose, 30 mmol/L KCl, and 100 micromol/L carbachol to activate phospholipase C (PLC), monitored by the accumulation of labeled inositol phosphates, was significantly reduced in dexamethasone-pretreated islets. Inclusion of the nuclear glucocorticoid receptor antagonist RU486 (mifepristone, 10 micromol/L) abolished the adverse effects of dexamethasone on both glucose-induced inositol phosphate accumulation and insulin secretion. Quantitative Western blot analyses revealed that the islet contents of PLCdelta1, PLCbeta1, beta2, beta3, and protein kinase C alpha were unaffected by dexamethasone pretreatment. These findings demonstrate that dexamethasone pretreatment impairs insulin secretion via a genomic action and that impaired activation of the PLC/protein kinase C signaling system is involved in the evolution of its inhibitory effect on secretion.     

In vitro pancreas duodenal homeobox-1 enhances the differentiation of pancreatic ductal epithelial cells into insulin-producing cells

AIM: To observe whether pancreatic and duodenal homeobox factor-1 enhances the differentiation of pancreatic ductal epithelial cells into insulin-producing cells in vitro. METHODS: Rat pancreatic tissue was submitted to digestion by collegenase, ductal epithelial cells were separated by density gradient centrifugation and then cultured in RPMI1640 medium with 10% fetal bovine serum. After 3-5 passages, the cells were incubated in a six-well plate for 24 h before transfection of recombination plasmid XlHbox8VP16. Lightcycler quantitative real-time RT-PCR was used to detect the expression of PDX-1 and insulin mRNA in pancreatic epithelial cells. The expression of PDX-1 and insulin protein was analyzed by Western blotting. Insulin secretion was detected by radioimmunoassay. Insulin- producing cells were detected by dithizone-staining. RESULTS: XlHbox8 mRNA was expressed in pancreatic ductal epithelial cells. PDX-1 and insulin mRNA as well as PDX-1 and insulin protein were signifi cantly increased in the transfected group. The production and insulin secretion of insulin-producing cells differentiated from pancreatic ductal epithelial cells were higher than those of the untransfected cells in vitro with a significant difference (1.32 ± 0.43 vs 3.48 ± 0.81, P < 0.01 at 5.6 mmol/L; 4.86 ± 1.15 vs 10.25 ± 1.32, P < 0.01 at 16.7 mmol/L). CONCLUSION: PDX-1 can differentiate rat pancreaticductal epithelial cells into insulin-producing cells in vitro. In vitro PDX-1 transfection is a valuable strategy for increasing the source of insulin-producing cells.     

Inhibition of insulin gene expression by long-term exposure of pancreatic beta cells to palmitate is dependent on the presence of a stimulatory glucose concentration

Long-term exposure of pancreatic beta cells to elevated levels of fatty acids (FAs) impairs glucose-induced insulin secretion. However, the effects of FAs on insulin gene expression are controversial. We hypothesized that FAs adversely affect insulin gene expression only in the presence of elevated glucose concentrations. To test this hypothesis, isolated rat islets were cultured for up to 1 week in the presence of 2.8 or 16.7 mmol/L glucose with or without 0.5 mmol/L palmitate. Insulin release, insulin content, and insulin mRNA levels were determined at the end of each culture period. Palmitate increased insulin release at each time point independently of the glucose concentration. In contrast, insulin content was unchanged in the presence of palmitate at 2.8 mmol/L glucose, but was markedly decreased in the presence of 0.5 mmol/L palmitate and 16.7 mmol/L glucose after 2, 3, and 7 days of culture. In the presence of a basal concentration of glucose, insulin mRNA levels were transiently increased by palmitate at 24 hours but were unchanged thereafter. In contrast, palmitate significantly inhibited the stimulatory effects of 16.7 mmol/L glucose on insulin mRNA levels after 2, 3, and 7 days. To determine whether the inhibitory effect of palmitate on glucose-stimulated insulin mRNA levels was associated with decreased insulin promoter activity, HIT-T15 cells were cultured for 24 hours in 11.1 mmol/L glucose in the presence or absence of palmitate, and insulin gene promoter activity was measured in transient transfection experiments using the insulin promoter-reporter construct INSLUC. INSLUC activity was decreased more than 2-fold after 24 hours of exposure to 0.5 mmol/L palmitate. We conclude that long-term exposure of pancreatic beta cells to palmitate decreases insulin gene expression only in the presence of elevated glucose concentrations, in part through inhibition of insulin gene promoter activity.     

Effects of dexamethasone on glucose-induced insulin and proinsulin release in low and high insulin responders

We compared the effects of dexamethasone-induced insulin resistance on B-cell secretory performance in 12 low insulin responders (LIR) and in eight high insulin responders (HIR). A hyperglycemic clamp (120 minutes) was performed before and after the subjects had ingested dexamethasone 3 mg x 2 for 2 1/2 days. Fasting levels of blood glucose increased from 4.60 +/- 0.13 to 5.74 +/- 0.23 mmol/L after dexamethasone in LIR and from 4.37 +/- 0.18 to 5.26 +/- 0.13 mmol/L in HIR. Dexamethasone treatment increased fasting levels of total immunoreactive insulin (IRI), C-peptide, and proinsulin, as well as the proinsulin to IRI ratio to a similar degree in LIR and HIR. The amount of glucose infused to uphold hyperglycemia during the clamp decreased by 54% after dexamethasone in LIR and by 46% in HIR. Mean level of stimulated IRI during the clamp increased after dexamethasone by 43% in LIR and by 53% in HIR. Mean level of stimulated C-peptide increased by 11% (not significant) in LIR and by 24% in HIR. Mean level of stimulated proinsulin increased by 86% in LIR and by 93% in HIR. The effects of dexamethasone on insulin secretion varied among individuals, since steroid treatment failed to affect IRI responses to glucose in two LIR and two HIR. The magnitude of dexamethasone effects on secretion was not correlated to pre-dexamethasone insulin sensitivity as assessed by a somatostatin-insulin-glucose infusion test (SIGIT) or by M/I (glucose infused/insulin level) ratios of the control clamp.(ABSTRACT TRUNCATED AT 250 WORDS)     

不同浓度葡萄糖和游离脂肪酸对大鼠骨骼肌细胞株L6细胞胰岛素敏感性和细胞内活性氧的影响

目的研究不同浓度的葡萄糖和游离脂肪酸（FFA）对骨骼肌L6细胞胰岛素敏感性及细胞内活性氧（ROS）的影响。方法L6细胞诱导分化成熟后,分为6组,以5mmol／L葡萄糖为低糖对照组,其中加0．3或1mmol／L的混合FFA为低糖低FFA或低糖高FFA组,以25mmol／L葡萄糖为高糖对照组,其中加0．3和1mmol／L的FFA的培养基为高糖低FFA或高糖高FFA组。干预48h,^3H—D葡萄糖摄取实验（加与不加100nmol／I,胰岛素37℃30rain）验证L6细胞胰岛素敏感性,经荧光探针H2DCFDA观察细胞内ROS含量的变化。结果在5mmol／L葡萄糖组,低糖对照组基础摄糖值为22777．6±6608．7,低糖低FFA组为26027．5±4085．7,低糖高FFA组为146805．1±21099．4。胰岛素刺激后,低糖对照组为76586．5±18450．1,低糖低FFA组为43738土9203．6,低糖高FFA组为32050．6±3362．3,较低糖对照组显著降低（P〈0．01）。在25mmol／L葡萄糖组,基础葡萄糖摄取量为11793．8±551．4,高糖低FFA组11887．3±2082．3高糖高FFA组为13886．1±3872．9,差别无统计学意义（P〉0．05）,但较低糖对照组显著降低（P〈0．01）．加入胰岛素刺激后,高糖对照组为42798．8±9441．5,高糖低FFA组为23946．9±3839．6,高糖高FFA组为13886．1±3872．9,各组之间差别显著（P〈0．01）。对细胞内R0s的研究发现,低糖低FFA组为2234．2±477．2,低糖高FFA组为1969．0±480．9,高糖对照组为1969．0土229．4,高糖低FFA组为2]84．5±734．2,高糖高FFA组为2571．3±96．7,可以显著增加的L6细胞内ROS,与低糖对照组（615．3±244．3）相比差别显著（P〈0．01）。除对照组之外的各组之间差别无统计学意义（P〉0．05）。结论高糖和高FFA可以诱导L6细胞出现氧化应激,同时高糖和高FFA是导致骨骼肌细胞胰岛素抵抗的重要原因之一。