Role and mechanism of rosiglitazone on the impairment of insulin secretion induced by free fatty acids on isolated rat islets

Background Prolonged exposure of pancreatic β-cells to fatty acids increases basal insulin secretion but inhibits glucose-stimulated insulin secretion. Rosiglitazone is a new antidiabetic agent of the thiazolidinediones. However, the relationship between thiazolidinediones and insulin secretion is highly controversial. The aim of this study is to explore the effect and mechanism of rosiglitazone on insulin secretion of islets under chronic exposure to free fatty acids （FFA）. Methods Pancreatic islets were isolated from the pancreata of male Sprague-Dawley rats by the collagenase digestion and by the dextran gradient centrifugation method. The purified islets were cultured in the presence or absence of rosiglitazone and palmitate for 48 hours. The insulin secretion was measured by radioimmunoassay. The mRNA level of peroxisome proliferator-activated receptor y, uncoupling protein 2 0dCP-2） and insulin were determined by real-time polymerase chain reaction （PCR）. The cell cytotoxicity assay was measured by cell counting kit-8. Results Islets exposed to elevated palmitate for 48 hours showed an increased basal and a decreased glucose-stimulated insulin secretion （P〈0.01）. The mRNA level of UCP-2 was increased by 3.7 fold in the 0.5 mmol/L concentration of palmitate. When islets were cultured with palmitate （0.5 mmol/L） in the presence of rosiglitazone （1.0 pmol/L）, both basal and glucose-stimulated insulin secretion reversed to a pattern of control islets （P〈0.05, P〈0.0 1）. The addition of rosiglitazone in the culture medium decreased the mRNA level of UCP-2 by 2.2 fold, having a statistically significant difference （P〈0.05） as compared with islets cultured with palmitate alone. The cell viability was not affected. Conclusion The protective effects of rosiglitazone on insulin secretion of isolated pancreatic islets under chronic exposure to palmitate might be mediated through the downregulation of UCP-2 expression.     

Regulation of leptin on insulin secretion and sulfonulurea receptor 1 transcription level in isolated rats pancreatic islets

Objective To investigate the regulation of leptin on insulin secretion and expression of ATP-sensitive potassium channel subunit sulfonulurea receptor 1 (SUR1) mRNA, and to determine whether the effects of leptin are mediated through known intracellular signaling transduction.Methods Pancreatic islets were isolated by the collagenase method from male SD rats. The purified islets were incubated with different concentrations of leptin for 2 h in the presence of different concentrations of glucose. Insulin release was measured using radioimmunoassay. Expression of SUR1 mRNA was detected by RT-PCR.Results In the presence of leptin 2 nmol/L, insulin release was significantly inhibited at either 11.1 or 16.7 mmol/L glucose concentration (both P<0.05), but insulin release was not altered at glucose of 5. 6 mmol/L physiological concentration. The dose-response experiment showed that the maximal effect of leptin on insulin secretion achieved at 2 nmol/L. Exposure of islets to 2 nmol/L leptin induced a significan     

Effects of fatty acid regulation on visfatin gene expression in adipocytes

Background The levels of long-term elevated serum or intracellular free fatty acid （FFA） induce insulin resistance associated with central obesity. The insulin-mimetic protein visfatin is preferentially produced by visceral adipose tissues and has been implicated in obesity and insulin resistance. To identify that FFA is capable of inducing insulin resistance and to clarify the role of FFA on visfatin, we examined the effect of monounsaturated FFA oleate （C 18： 1） and saturated FFA palmitate （C 16：0） on glucose transport and visfatin gene expression in cultured 3T3-L1 adipocytes or preadipocytes. Methods FFA-free DMEM/F12, 0.125 mmol/L, 0.5 mmol/1 and 1.0 mmol/L oleate or palmitate was added to cultured 3T3-L1 adipocytes or preadipocytes and incubated overnight. Glucose transport was assessed as 3H- 2-deoxy-glucose uptake. Total RNA was extracted and subjected to RT-PCR for the measurement of visfatin mRNA levels. Statistical comparisons between control group and other groups were performed with the two-tailed paired t test, and one-way ANOVA was used to compare the mean values among the groups. Results Insulin increased specific membrane glucose transport in 3T3-L1 preadipocytes. Upregulation was evident from 15 minutes to 1 hour exposure to insulin. However, after 6-hour exposure to insulin, there was a downregulation in the response to insulin. Dose response studies demonstrated that 2-deoxy glucose transport was increased by 336% at 50 nmol/L insulin （P〈0.01）, and reached a maximal effect at 100 nmol/L insulin （P〈0.01）. Oleate and palmitate treatment did not influence basal glucose transport （without insulin stimulation）, whereas insulin-stimulated glucose transport was inhibited after overnight oleate and palmitate treatment in preadipocytes and adipocytes. In 3T3-L1 preadipocytes, insulin resistance could be achieved at 0.125 mmol/L oleate or palmitate （P〈0.05, respectively）, and the inhibition was dose dependent. In adipocytes, the inhibition was noted at 0.5 mmol/L oleate or 1.0 mmol/L palmitate. Visfatin mRNA expression increased during differentiation more than 1.5-fold. Bovine serum albumin （BSA） did not influence visfatin mRNA expression compared with the control group. Dose-response studies demonstrated that addition of 0.125 mmol/L oleate and palmitate to 3T3-L1 adipocytes decreased visfatin mRNA expression significantly （78%, 77%, respectively, relative to untreated control, P〈0.05）, and further to 65% （relative to untreated control, P〈0.05） and 55% （relative to untreated control, P〈0.01） at 1.0 mmol/L FFA. Furthermore, the suppression on preadipocytes was similar to that of adipocytes, which reached a maximal reduction of 44% （oleate, P〈0.05） and 47% （palmitate, P〈0.05） at 1.0 mmol/L FFA. Conclusions Oleic acid and palmitic acid may induce insulin resistance in 3T3-L1 adipocytes and preadipocytes. Downregulation of visfatin mRNA may contribute to impair insulin sensitivity caused by oleate and palmitate.     

Leptin Regulated Insulin Secretion via Stimulating IRS2-associated Phosphoinositide 3-kinase Activity in the isolated Rat Pancreatic Islets

Leptin,theproductofob gene,isa peptidehor-mone secreted by adipocytes thatacts in the hypotha-lamus and playsa centralrole in regulation of feedingbehavior and energy homeostasis[1] .It has recentlybeen confirmed that leptin receptor(OB- R) m RNAand protein were expressed in rat pancreaticβ- cells,indicating thatleptin may directly regulate insulin se-cretion.Several groups have addressed this question,but the results were controversial[2 ,3] .Up to now,the molecular mechanism by which lept…     

白藜芦醇对高糖高脂处理的原代人脐静脉血管内皮细胞E-选择素表达及NO分泌的影响

目的：探讨白藜芦醇对高糖、高脂培养人原代脐静脉血管内皮细胞E-选择素mRNA表达及胰岛素刺激的一氧化氮（NO）分泌的影响。方法：原代培养人脐静脉内皮细胞,以0．1μmol／L白藜芦醇预处理4h后,以高糖（33．3mmol／L葡萄糖）＋高脂（棕榈酸0．5mmol／L）DMEM培养基培养24h,以RT—PCR法检测培养细胞E-选择素的表达。部分细胞经100nmol／L胰岛素刺激25min后,以硝酸还原酶法检测培养上清NO的含量。结果：与正常对照组相比．高糖高脂培养使内皮细胞E-选择素的表达升高,同时胰岛素刺激的NO分泌降低。而白藜芦醇预处理可以明显降低E-选择素的表达,并明显促进胰岛素对内皮细胞NO分泌的刺激作用。结论：白藜芦醇可以改善高糖、高脂诱导的血管内皮细胞胰岛素刺激的NO分泌作用,并可降低E-选择素表达,保护内皮细胞的功能,从而可能在糖尿病动脉粥样硬化的防治中具有广阔的前景。     

低糖状态对大鼠增食欲素及受体的影响

目的　研究急性葡萄糖水平的下降对大鼠下丘脑及培养胰岛细胞中增食欲素 (orexin)及其受体(OX1 R、OX2 R)的影响。方法　应用单次皮下注射胰岛素并伴 (或不伴 )禁食的方法 ,构建急性低血糖大鼠模型 ;体外原代培养胰岛细胞并调整培养液的葡萄糖浓度 (8 3mmol L及 2 8mmol L) ;应用反转录 -聚合酶链反应 (RT PCR)检测下丘脑组织和胰岛细胞中orexin系统的变化。结果　在胰岛素 (伴禁食 )诱导的急性低血糖大鼠模型中 ,下丘脑orexin的mRNA表达较对照组增加约 1 5 0 % (P <0 0 1 ) ,OX1 R的mRNA表达减少 30 % (P <0 0 1 ) ,但是OX2 R的mRNA表达没有明显变化 (P >0 0 5 ) ;在培养胰岛细胞体外实验中 ,培养基中葡萄糖浓度由 8 3降至 2 8mmol L ,6h后胰岛细胞的orexinmRNA表达增加 1 0 0 % (P <0 0 1 ) ,而OX1 RmRNA表达对培养基中葡萄糖浓度的急性波动不敏感。结论　急性葡萄糖水平降低将刺激大鼠下丘脑中orexin的表达 ,其受体的变化相反 ;进食将会抑制orexin系统的这一反应。体外实验中发现培养胰岛细胞在葡萄糖浓度改变时发生类似变化     

EFFECTS OF ACUTE HYPOGLYCEMIA ON THE OREXIN SYSTEM IN RAT

OREXIN isa kind of new neuropeptideisolated from rathypothalamus, which involvedin many physiologicalregulationprogressesvia orexin1receptor(OX R )and orexin2 receptor(OX R ).The physio- 1 2logicalfunctionoforexinisstillnotcompletelyknown ,butitisidentifiedthatorexinis involvedinmany physiologicalprogressesuchasfeeding,sleep,and stress.1However ,itisstillunknown abouttheregulationoforexinsystemby hypo-thalamus,theregulationtopancreasby orexinsystem,and the regulationbetween orexin,bloodglu…     

胰岛素信号通路在高游离脂肪酸所致的β细胞功能紊乱中的作用及机制

目的:观察血浆游离脂肪酸(FFA)水平升高对β细胞胰岛素分泌功能的影响,探讨β细胞胰岛素信号通路在其中所起的作用及其机制. 方法: 将8周龄雄性SD大鼠随机分为脂肪乳输注组(FFA组,13只)和生理盐水输注组(NS组,12只).分别输注48 h,检测以下指标:(1)采血检测胰岛素, FFA水平;(2)正常血糖高胰岛素钳夹实验,评价外周组织胰岛素抵抗程度;(3)静脉葡萄糖耐量实验,评价活体胰岛β细胞分泌功能;(4)胰岛细胞表面灌注实验,评价离体胰岛β细胞动态分泌功能;(5)采用实时荧光定量PCR方法检测肌肉中胰岛素受体底物-1(IRS-1)、胰岛素受体底物-2(IRS-2)mRNA表达的变化;(6)用实时荧光定量PCR方法检测胰岛细胞IRS-1,IRS-2和葡萄糖转运子-2(Glut-2)mRNA表达的变化.结果:(1)FFA组血中胰岛素水平比NS组增高[(24.44±1.25) mIU/L vs (18.09±1.37) mIU/L,P＜0.05],FFA水平也显著高于NS组[(1.39±0.18) mmol/L vs (0.64±0.10) mmol/L,P＜0.001];(2)FFA刺激后,离体和活体的胰岛β细胞分泌功能均增强;(3)FFA组葡萄糖输注率(GIR)较NS组明显降低(P＜0.05),提示存在明显的外周胰岛素抵抗;(4)FFA组肌肉IRS-1 mRNA表达比NS组降低87.7%,IRS-2表达降低50.7%(P＜0.05);(5) FFA组胰岛细胞IRS-1 mRNA表达增加29.3%(P＜0.05),IRS-2及Glut-2分别增加345.1%和536.4%(P＜0.01).结论:血浆FFA水平短期升高,造成外周胰岛素抵抗的同时,对β细胞胰岛素分泌有刺激作用,此时胰岛细胞胰岛素信号通路分子基因表达增加.     

促酰化蛋白受体C5L2在前脂肪细胞分化过程和脂肪酸负荷下的表达研究

目的 观察3T3-L1前脂细胞分化和游离脂肪酸（FFA）对3T3-L1（前）脂肪细胞C5L2基因和蛋白表达的影响。方法采用逆转录（RT）-PCR和流式细胞仪检测不同分化时段和FFA处理后（前）脂肪细胞C5L2mRNA和蛋白表达。结果 3T3-L1脂肪细胞C512mRNA表达呈分化依赖性增加,而C5L2蛋白表达水平在分化早期显著增强,诱导分化6hC5L2蛋白表达增加了21％（61％±18％VS51％±15％,P〈0．05）;分化12h达高峰,增加了38％（70％±12％VS51％±15％,P〈0．01）;分化3d基本恢复至0d水平。在3T3-L1成熟脂肪细胞,0．5mmol／L和1．0mmol／L油酸分别抑制46％（0．58±0．21 vs 1．08±0．46,P〈0．05）和84％（0．18±0．04VS1．08±0．46,P〈0．05）C5L2 mRNA表达,而0．125mmol／L油酸即能显著下调36％（35％±8％vs54％±7％,P〈0．01）C5L2蛋白表达。低浓度棕榈酸均能明显抑制C5L2mRNA和蛋白的表达,1．0mmol／L时c512mRNA和蛋白表达分别减少了41％（0．57±0．28vs0．97±0．41,P〈0．05）和55％（24％±13％VS54％±7％,P〈0．01）。油酸和棕榈酸对前脂肪细胞C512表达差异无统计学意义。结论促酰化蛋白／C5L2途径参与了脂肪细胞分化的调控过程。C512mRNA和蛋白表达的下调可能参与了油酸和棕榈酸诱导的成熟脂肪细胞胰岛素抵抗的发生。     

游离脂肪酸对大鼠肝细胞瘦素受体基因、蛋白表达及酪氨酸磷酸化的影响

目的 :探讨游离脂肪酸 (FFA)是否会对大鼠肝细胞瘦素 (leptin)受体的基因、蛋白表达及酪氨酸磷酸化产生一定的影响。　方法 :分离、培养新生Sprague Dawley大鼠肝细胞 ,分别与软脂酸 (0 .2 5mmol/L)或油酸 (0 .12 5mmol/L)孵育 12、2 4和 36h ,提取蛋白后用Western印迹法检测瘦素受体的蛋白水平。用RT PCR检测肝细胞内瘦素受体RNA含量的变化。应用免疫沉淀法检测瘦素受体的酪氨酸磷酸化程度。　结果 :软脂酸和油酸孵育后大鼠肝细胞瘦素受体的蛋白表达水平在孵育 12和 2 4h后无显著变化 ,在孵育 36h后显著下调 (P <0 .0 5 ) ;瘦素受体的RNA水平在孵育 12h后无显著变化 ,孵育 2 4和 36h后显著下调 (P <0 .0 5 ) ;瘦素受体的酪氨酸磷酸化程度在孵育 12h后无显著变化 ,孵育 2 4和 36h后显著下调 (P <0 .0 5 )。　结论 :FFA可对大鼠肝细胞瘦素受体的基因、蛋白表达水平及磷酸化程度产生一定的抑制作用 ,这可能是FFA导致胰岛素抵抗的机制之一。     

简便快捷的小鼠胰岛分离纯化方法研究

目的 探讨小鼠胰岛分离与纯化的方法.方法 采用多点注射灌注胶原酶法消化胰腺,不连续密度梯度离心联合人工挑取的方法分离、纯化胰岛.双硫腙特异性染色后计算胰岛产量及纯度.葡萄糖刺激后测定培养上清液胰岛素水平检测胰岛功能.结果 (1)每只小鼠采用上述分离、纯化法平均得到(114±15)个胰岛,平均纯度为(77.12±3.23)％,胰岛细胞存活率＞90％; (2)分离、纯化的胰岛培养上清液中胰岛素水平在无糖、低糖(2.8 mmol/L)和高糖(22.2 mmol/L)刺激下分别为(23.80±3.52) mIU/L、 (67.57 ±4.04) mIU/L和(164.32±10.75) mIU/L,各组间比较,差异有统计学意义(P＜0.05).两两比较,低糖组的胰岛素水平为无糖组的2.84倍(P＜ 0.05),高糖组的胰岛素水平为低糖组的2.43倍(P＜0.05),高糖组的胰岛素水平为无糖组的6.90倍(P＜0.05).结论 采用多点注射灌注胶原酶法消化胰腺,不连续密度梯度离心联合人工挑取的方法分离、纯化的小鼠胰岛产量及纯度较高,形态完整,不同浓度葡萄糖刺激后胰岛素分泌反应良好,是一种简便、快捷的小鼠胰岛分离方法.     

大剂量抗氧化剂对高脂饲养大鼠胰岛β细胞分泌功能的影响及机制

目的:探讨大剂量抗氧化剂-N-乙酰半胱氨酸(N-acetyl-l-cysteine,NAC)对高脂饲养大鼠胰岛β细胞分泌功能的影响及可能机制。方法:将59只8周龄SD大鼠随机分为正常饲料组(NC组)、高脂饲料组(HF组)和高脂 NAC组(NAC组)。饲养20周,(1)测血浆及胰腺组织丙二醛(MDA)和还原型谷胱甘肽(GSH)水平;(2)正常血糖高胰岛素钳夹实验,评价外周组织胰岛素抵抗程度;(3)胰岛细胞表面灌注实验,评价离体胰岛β细胞动态分泌功能;(4)实时荧光定量PCR方法比较各组大鼠胰岛素受体底物-1(IRS-1)、胰岛素受体底物-2(IRS-2)和葡萄糖转运子-2(Glut-2)mRNA表达的变化。结果:(1)HF组血浆及胰腺MDA水平明显高于NC组,GSH水平低于NC组,NAC可以改善以上变化;(2)HF组葡萄糖输注率(GIR)比NC组降低(P<0.01),用NAC后GIR明显改善(P<0.01);HF组葡萄糖刺激的胰岛素分泌(GSIS)功能下降,用NAC后可逆转上述变化;(3)HF组胰岛细胞IRS-1、IRS-2、Glut-2mRNA表达降低42.3%、28.1%、22.9%(P均<0.05);NAC组胰岛细胞IRS-1、IRS-2、Glut-2 mRNA表达与HF组相比增加40.2%、30.2%,19.1%(P均<0.05)。结论:大剂量抗氧化干预治疗能改善胰岛细胞胰岛素信号传导,逆转高脂饲养导致的大鼠胰岛细胞分泌功能紊乱,其机制可能与NAC纠正机体氧化及抗氧化失衡有关。     

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.     

胰淀素对大鼠胰岛素和胰高血糖素分泌的影响

目的研究胰淀素对大鼠胰岛素和胰高血糖素分泌的影响。方法应用胶原酶消化和不连续密度梯度离心技术建立离体大鼠胰岛模型,研究不同浓度胰淀素对胰岛素和胰高血糖素分泌的影响。结果不同浓度的葡萄糖增加胰岛素的分泌,抑制胰高血糖素的分泌,并都呈线性相关。葡萄糖浓度为0、5.6、11.2mmol/L时,孵育1h,胰淀素(10-10~10-5mol/L)显著抑制胰高血糖素的分泌(P<0.05),且胰高血糖素的分泌与胰淀素浓度呈负相关(P<0.01)。葡萄糖浓度为5.6mmol/L时,不同浓度的胰淀素增加胰岛素分泌,而且两者呈正相关(P<0.05);但葡萄糖浓度为11.2和16.7mmol/L时,10-5mol/L胰淀素对胰岛素的分泌有明显抑制作用(P<0.05)。结论胰淀素对胰高血糖素的分泌有直接抑制作用;在葡萄糖浓度为5.6mmol/L时,胰淀素能增加胰岛素分泌,抑制胰高血糖素分泌;高糖时,高浓度的胰淀素抑制胰岛素分泌。     

硫酸脱氢表雄酮对MIN6细胞葡萄糖刺激的胰岛素分泌的影响

目的探讨硫酸脱氢表雄酮(DHEAS)对胰岛β细胞株MIN6葡萄糖刺激的胰岛素分泌的影响。方法以葡萄糖刺激浓度为2.8mmol/L和16.7mmol/L的对数生长期MIN6细胞作为实验对象,分别以1、5、10μmol/LDHEAS干预10min和24h(不同浓度DHEAS组),以5μmol/LDHEAS或与10μmol/L糖皮质激素受体阻断剂RU486联合干预24h(DHEAS和DHEAS+RU486组),设立空白对照组。ELISA法测定细胞培养上清液中胰岛素分泌量,Real-TimePCR检测细胞胰岛素mRNA表达。结果干预后10min和24h时点,5μmol/L和10μmol/LDHEAS组MIN6细胞培养上清液中的胰岛素分泌量均显著高于空白对照组(P<0.05);干预后24h时点,DHEAS+RU486组与DHEAS组MIN6细胞培养上清液中胰岛素分泌量比较差异无统计学意义(P>0.05),但均显著高于空白对照组(P<0.05)。干预后24h时点,5μmol/L和10μmol/LDHEAS组MIN6细胞胰岛素mRNA表达均显著高于空白对照组(P<0.05)。结论 DHEAS对MIN6细胞葡萄糖刺激的胰岛素...     

iPLA2在人胰岛β细胞的表达和对胰岛素分泌功能的影响

目的 探讨Ca2+-非依赖性磷酸脂酶A2(iPLA2)在人胰岛的表达及在胰岛素分泌功能中的作用.方法 正常人胰腺组织切片免疫组织化学染色及人胰岛Western印迹方法检测,观察iPLA2在人胰岛中的表达情况;随机分组对照研究iPLA2选择性抑制剂溴烯醇内酯(BEL)对离体人胰岛的葡萄糖刺激引起胰岛素分泌反应的影响.结果 在人胰岛iPLA2高表达,与抗胰岛素染色分布一致,而外分泌腺很少表达;与对照组相比,BEL处理组胰岛素分泌反应明显减弱(P＜0.01),BEL通过抑制iPLA2活性抑制了葡萄糖刺激引起的离体人胰岛胰岛素分泌.结论 iPLA2在人胰岛β细胞高表达并在葡萄糖刺激胰岛β细胞胰岛素分泌过程起到重要的作用.     

游离脂肪酸对大鼠骨骼肌细胞葡萄糖转运蛋白4和胰岛素信号传导蛋白的影响

目的：观察游离脂肪酸对大鼠骨骼肌细胞葡萄糖转运蛋白4（GLUT4）和胰岛素信号传导蛋白Grb2及ERK2的影响。方法：分离、培养新生Sprague-Dawley大鼠骨骼肌细胞,分别与软脂酸（0．25mmol/L)或油酸（0．125mmol/L)孵育12、24、36h,提取蛋白后用Western印迹法检测GLUT4、Grb2和ERK2的蛋白水平;用斑点印迹杂交法检测骨骼肌细胞内GLUT4 RNA含量的变化。结果：经软脂酸和油酸孵育12、24、36h后,大鼠骨骼肌细胞GLUT4的蛋白和RNA水平均显著降低（P＜0．05）;同时,Grb2和ERK2的蛋白水平也明显下降（P＜0．05）。结论：游离脂肪酸可抑制GLUT4的基因及蛋白表达和降低胰岛素信号传导蛋白Grb2和ERK2的蛋白表达水平,这可能会影响胰岛素的信号传导作用和骨骼肌的葡萄糖摄取,引起骨骼肌的胰岛素抑抗。     

高血糖对体外培养的胎鼠胰岛Pdx-1基因的影响

目的：研究在体外培养时，高血糖对胎鼠胰岛胰和十二指肠同源盒基因-1（Pdx-1)和胰岛素基因的影响。方法：胶原酶法分离胎鼠胰岛，分别在葡萄糖浓度为5.5mmol/L,11.1mmol/L,33.3mmol/L的条件下培养24h。采用胰岛素含量测定、胰岛素释放实验评价胰岛功能；免疫细胞化学染色检测Pdx-1在细胞内的表达；逆转录PCR（RT-PCR）检测Pdx-1和胰岛素mRNA表达水平。结果：高血糖组1（11.1mmol/L)胎鼠单位重量胰岛细胞内胰岛素水平和刺激指数高于低糖组（5.5mmol/L)和高血糖组2（33.3mmol/L)。而且，高血糖组胎鼠胰岛Pdx-1蛋白的核移位率和mRNA表达水平均高于低糖组，但是高糖组2胰岛素mRNA表达低于高血糖组1，与低糖组无显著性差异。结论：高血糖刺激可以促进胎鼠Pdx-1表达和转录活性，可能是影响胰岛功能和β细胞对葡萄糖刺激敏感性增加的原因之一。     

葡萄糖浓度波动对INS-1细胞胰岛素分泌的影响

目的初探葡萄糖浓度波动对大鼠胰岛素瘤INS-1细胞胰岛素分泌功能影响机制。方法将INS-1细胞随机分为正常糖组（5.5 mmol/L葡萄糖培养液培养）、持续高糖组（16.7 mmol/L葡萄糖培养液培养）、波动组（用16.7 mmol/L葡萄糖培养液培养2 h,再换5.5 mmol/L培养3 h,每天重复3次,夜间9 h维持在5.5 mmol/L的培养液中）、N-乙酰半胱氨酸（N-acetyl-L-cysteine,NAC）＋正常糖组、NAC＋持续高糖组、NAC＋波动组,后3组的培养基中均预先负载终浓度为1.0 mmol/L的NAC,余干预措施相同,均干预72 h。荧光素酶方法检测细胞内三磷酸腺苷（adenosine-triphosphate,ATP）含量,放射免疫分析法测定胰岛素分泌水平。结果 INS-1细胞ATP含量及胰岛素分泌水平在持续高糖组及波动组均较正常糖组显著下降,且波动组下降更明显,差异有高度统计学意义（P〈0.01）。NAC＋波动组及NAC＋持续高糖组细胞ATP含量及胰岛素分泌水平分别较波动组及持续高糖组显著增加,差异有统计学意义（P〈0.05）。结论持续性高糖及波动性高糖损伤INS-1细胞的胰岛素分泌可能与减少细胞ATP含量有关,且波动性高糖较前者更严重,氧化应激可能是波动性高糖及持续性高糖导致INS-1细胞ATP减少的机制。