Effects of L-carnosine on NIT-1 islet cells

AIM: To investigate the protective effect of L-carnosine on insulin secretion, proliferation and apoptosis of β-cells impaired by high glucose. METHODS: NIT-1 cells were pre-treated with glucose at concentrations of 11.1 mmol/L (control level) and 33.3 mmol/L (high level) for 72 h, and then the cells were stimulated with various concentrations of glucose (0, 5 and 25 mmol/L) and/or L-carnosine (0, 1 and 20 mmol/L). The level of insulin in the medium was measured by radioimmunoassay. To detect the effect of L-carnosine on proliferation and apoptosis, NIT-1 cells were divided into 4 groups according to different culture conditions for 72 h: group C (with 11.1 mmol/L glucose), group H (with 33.3 mmol/L glucose), group H+A (with 33.3 mmol/L glucose+ 1 mmol/L L-carnosine) and group H+B (with 33.3 mmol/L glucose +20 mmol/L L-carnosine). Proliferous or apoptotic cells were identified by BrdU labeling and flow cytometry (labeling with annexin V-FITC/PI),respectively. Total RNA was extracted and the mRNA expression of caspase-3 and bcl-2 was measured by RT-PCR. The caspase-3 activity was also checked by fluorometric assay kit. RESULTS: The insulin in high-level glucose group was lower than that in control-level glucose group. L-carnosine at concentration of 20 mmol/L notably increased the insulin secretion of the cells pre-treated with glucose at control level or high level. The proliferation and apoptosis were both increased in group H compared with group C, but the total cell counts declined because the apoptotic rate was higher than the proliferation rate. L-carnosine at concentration of 1 mmol/L significantly increased the proliferation rate and decreased the apoptotic rate. The mRNA level of caspase-3 was decreased and the mRNA level of bcl-2 was increased after the cells were treated with L-carnosine at concentration of 1 mmol/L. L-carnosine at concentrations of both 1 mmol/L and 20 mmol/L significantly decreased the caspase-3 activity. CONCLUSION: L-carnosine at high level directly stimulates insulin secretion in NIT-1 cells, and L-carnosine at normal level promotes the cell proliferation and inhibits apoptosis induced by high concentration of glucose. Caspsase-3 and Bcl-2 may be partly involved in this process.     

Inhibitory effect of 5-fluorouracil on ultra-microstructure and insulin secretion of pancreatic β cells

AIM: To investigate the molecular mechanisms of β cell dysfunction induced by 5-fluorouracil (5-FU) in islet β cell line (NIT-1 cells). METHODS: The NIT-1 cells were treated with different concentrations of 5-FU. The content of insulin in the culture medium was determined by radioimmunoassay. Cell apoptosis was observed by flow cytometry with annexin V/PI staining. The ultra-microstructural changes of NIT-1 cells were observed under transmission electron microscope. The expression of pancreatic and duodenal homeobox protein 1(PDX-1) at mRNA and protein levels in NIT-1 cells was examined by RT-PCR and Western blotting, respectively. RESULTS: Exposed to the low glucose concentration (5.6 mmol/L), insulin secretion in NIT-1 cells was not significantly decreased following a 24 h treatment with 5.0 to 40.0 mg/L 5-FU (P>0.05). On the contrary, the high glucose (16.7 mmol/L)-stimulated insulin secretion in NIT-1 cells was inhibited by 5.0 to 40.0 mg/L of 5-FU in a dose-dependent manner after 24 h of incubation (P<0.01). The apoptosis rate of NIT-1 cells was significantly increased as compared to those in the control levels(P<0.05). The structural changes of mitochondria were the main apoptotic changes under transmission electron microscope. Significant down-regulation of PDX-1 expression at mRNA and protein levels was observed in NIT-1 cells treated with 5-FU at the concentration of 10.0 mg/L to 40.0 mg/L(P<0.05).CONCLUSION: 5-FU inhibits the insulin secretion in islet β cell induced by high glucose. A relative deficiency in insulin secretion following 5-FU treatment is related to the changes of β cell ultra-microstructure and the reduction of β cell numbers, by which an increase in apoptosis of pancreatic β cells is induced. Down-regulation of PDX-1 expression may play a pivotal role in increasing the apoptosis of pancreatic β cells induced by 5-FU in high-glucose condition.     

Effects of berberine on the apoptosis of NIT-1 cells induced by high glucose and saturated fatty acids

AIM: To investigate the effects of berberine on the apoptosis of NIT-1 cells induced by high glucose and saturated fatty acid. METHODS: The influence of berberine at different concentrations on NIT-1 cells cultured with or without high glucose and saturated fatty acid were determined and compared using MTT colorimeric assay. The cell apoptotic rate was also determined by flow cytometry assay and in situ TUNEL method. RESULTS: The effects of berberine at different concentrations on NIT-1 cells showed dose-dependent, low dose (≤5 μmol/L) had dispensable cytotoxicity; meanwhile, high dose showed distinct effects. On the other hand, low dose of berberine alleviated the apoptosis in NIT-1 cells induced by high glucose and saturated fatty acid, when adding berberine to cell medium. CONCLUSION: Berberine inhibited the apoptosis of NIT-1 cells induced by high glucose and saturated fatty acid.     

Effects of insulin and glucose on secretion of tissue-type plasminogen activator and its inhibitor-1 in hypoxic vascular endothelial cells

AIM: To study the effects of insulin and glucose on tissue-type plamingen activator (tPA) and its inhibitor-1 (PAI-1) secretion in cultured human endothelial cells. METHODS: Human endothelial cell line ECV-304 was cultured with glucose and/or insulin at different concentrations with or without hypoxic exposure. RESULTS: The tPA, PAI-1 secretion and ratio of tPA/PAI-1 increased in endothelial cells during hypoxia. Insulin and glucose increased the tPA and PAI-1 secretion in endothelial cells exposed to hypoxia, and increase in tPA/PAI-1 ratio was also observed at 4 h and 8 h. CONCLUSION: Hypoxia stimulates the release of tPA and PAI-1. Insulin and glucose also stimulate the tPA and PAI-1 secretion during hypoxia.     

Gene transfer and expression of recombined human proinsulin in hepatoma cells of rats

AIM:To explore the recombined human proinsulin gene containing glucose reaction element (GLRE) expression in transfected CBRH7919 cells. METHODS:The packaged retrovirus encoding genetically modified human proinsulin PLXSN-(GLRE)3-BP-1MpINS3 and PLXSN-(GLRE)3-BP-1MpINS2 were transfected into CBRH7919 cells. Insulin values in cells after transient and steady expression screened by G418 at different glucose levels were detected. Chromosome DNA was isolated from transfected and untransfected cells and polymerase chain reaction (PCR) was performed. PCR products were analyzed by electrophoresis. RESULTS:38 h after transfection, at the glucose levels of 0-25 mmol/L, the levels of insulin produced by cells including PLXSN-(GLRE)3-BP-1MpINS3 were (3.57±0.21)U/L, (5.30±0.20)U/L, (16.27±0.87)U/L, (23.23±1.12)U/L, respectively (P<0.05). One month after transfection, under above glucose levels, insulin values were (3.57±0.21)U/L, (5.30±0.20)U/L, (16.27±0.87)U/L, (23.23±1.12)U/L (P<0.05). CBRH7919 cells including PLXSN-(GLRE)3-BP-1MpINS2 secreted detectable insulin value at the level of 25 mmol/L, they were (2.10±0.23)U/L and (2.05±0.17)U/L, respectively. PCR products of transfected cells showed target band, but control cells did not. CONCLUSIONS:Recombined proinsulin gene was transfected successfully in CBRH7919 cells. The cells combined human proinsulin gene has the ability of producing insulin with increase in glucose concentration in vitro.     

ABA对葡萄花色苷合成相关基因表达的影响

以京优葡萄为试材．研究果实成熟过程中果皮花色苷含量及其生物合成相关酶基因和转录因子转录水平的变化．同时研究不同浓度ABA处理对花色苷含量和相关基因转录水平的影响。结果表明,葡萄果实发育进入着色期,CHSs、CHIs基因家族中的CHS3、CH12和UFGT、MybAJ、MybAl-2随花色苷合成而大量表达,其转录水平与花...     

香蕉WAT1基因的鉴定及表达分析

【目的】基于香蕉基因组数据筛选Walls are thin 1(WAT1)基因,分析它们的序列及表达特性。【方法】以拟南芥WAT1为参考序列,通过本地Blast筛选获得香蕉WAT1基因,分析其核苷酸、启动子及编码蛋白特性,并利用实时定量PCR技术研究其在不同组织部位、不同激素和逆境胁迫处理下的表达情况。【结果】筛选获得5个香蕉WAT1基因(命名为MaWAT1-1~5)。蛋白亚细胞定位预测结果显示,MaWAT1-1、MaWAT1-2、MaWAT1-4主要定位在液泡和细胞膜上,MaWAT1-3主要定位在细胞质和细胞膜,MaWAT1-5定位在细胞膜和叶绿体。基因结构分析和系统进化树分析均将MaWAT1s分为两组,MaWAT1-1、MaWAT1-2、MaWAT1-4聚为一组(含6个外显子和5个内含子),MaWAT1-3和MaWAT1-5归为一组(含7个外显子和6个内含子)。启动子顺式作用元件分析结果显示:MaWAT1s启动子含有大量激素和胁迫响应相关元件。实时定量PCR结果显示,MaWAT1-4在叶片中表达量最高,MaWAT1-1在根和假茎中表达量最高,其余均在根中表达量最高;大多数MaWAT1s的表达受GA3、SA、盐胁迫和干旱等显著诱导,受高温显著抑制,同时部分成员的表达受IAA、ABA、JA、低温、机械损伤和枯萎病影响显著。【结论】MaWAT1s的表达受多种激素和逆境影响显著,可能在香蕉生长发育和抗逆防御反应中发挥着重要作用。     

Effect of insulin on the SGK1 expression and extracellular matrix synthesis in human mesangial cells cultured in high glucose

AIM:To study the effect of insulin on the serum and glucocorticoid-inducible kinase 1 (SGK1) expression and extracellular matrix synthesis in human glomerular mesangial cells (HMC) cultured in high glucose. METHODS:The HMCs were cultured in the presence of 5.5 or 25 mmol/L glucose with or without 100 nmol/L insulin (i.e. NG, HG, NI and HI groups). 4 h latter, expressions of SGK1, insulin receptor substrate-1 (IRS1) and IRS2 in corresponding groups were detected by immunofluorescence or examined by Western blotting. The phosphorylation of IRS1 and IRS2 was measured by immunoprecipitation. 24 h latter, connective tissue growth factor(CTGF) and fibronectin (FN) were also examined by RT-PCR and ELISA, respectively. RESULTS:Compared with NG, the SGK1 protein expression in HG, NI and HI groups was significantly higher (P<0.01). High glucose mainly caused IRS2 protein and its phosphorylation level increase (P<0.01). When treated with 100 nmol/L insulin, IRS1 protein and its phosphorylation in HI group apparently elevated while slight inhibition of IRS2 protein expression and its phosphorylation were observed (HI vs HG, P<0.05). High glucose enhanced the expression of CTGF and FN, and insulin strengthened this effect.CONCLUSION:Insulin and high glucose up-regulate the expression of SGK1 in mesangial cells through different target molecular pathways and ultimately enhance ECM synthesis. The effect of insulin is highly associated with IRS1 signaling cascades.     

The related gene expression in mesenchymal stem cells differentiating to neuron-like cells

AIM: To analyze neuron-related gene expression before and after mesenchymal stem cells (MSCs) differentiating into neuron-like cells. METHODS: MSCs were induced to neuron-like cells with β-mercaptoethanol. Before inducement and at 8 h after inducement, the total RNA was extracted, then the expression of microtubule-associated protein-2 (MAP-2), growth -associated protein -43 (GAP-43), NSE, nestin and neurofilament (NF) mRNA were detected with RT-PCR. RESULTS: NSE mRNA expressed before and after inducement, MAP-2, GAP-43, nestin and NF mRNA only expressed after inducement. CONCLUSION: The differentiation of MSCs into neuron-like cells may be related to MAP-2, GAP-43, nestin and NF expression.     

Effects of insulin on VEGF expression in cultured retinal Müller cells

AIM: To investigate the effect of insulin on the expression of vascular endothelial growth factor(VEGF) in cultured rabbit retinal Müller cells. METHODS: Immunocytochemical method and ELISA were used to assay the change of VEGF expression in cultured Müller cells in vitro at different insulin concentrations in qualitative and quantitative ways. RESULTS: VEGF expression in retinal Müller cells was enhanced markedly by insulin. CONCLUSION: Insulin at high concentration enhances VEGF expression in cultured Müller cells, which may be one of factors that insulin accelerates the progress of diabetic retinopathy.     

Influence of obesity on first-phase insulin secretion in individuals with different glucose tolerance

AIM: To explore the influence of obesity on the first-phase insulin secretion in the individuals with different glucose tolerance. METHODS: Thirty-eight subjects with normal glucose tolerance without family history of diabetes (normal control,NC), 32 subjects with normal glucose tolerance (NGT) who were the first-degree relatives of type 2 diabetic patients, 67 patients with impaired glucose regulation (IGR) and 35 newly-diagnosed type 2 diabetic patients (T2DM) were enrolled in the study. The patients in the 4 groups were further divided into 2 subgroups: overweight/obesity and normal weight subgroups. All subjects received oral glucose-insulin release test (OG-IRT) and intravenous glucose tolerance test (IVGTT). Acute insulin response at 3~5 min (AIR3-5) was used to reflect first-phase insulin secretion,and insulin sensitivity index (ISI) was used to reflect insulin sensitivity. The influence of obesity on the islet β-cell function and insulin sensitivity in the individuals with different glucose tolerance was observed. RESULTS: The level of AIR3-5 in NC overweight/obesity subgroup was significantly higher than that in normal weight subgroup (P<0.05), while there was no significant difference between other subgroups (P>0.05). No significant difference in the level of ISI between the patients of IGR in overweight/obesity subgroup and normal weight subgroup was observed, while in the other 3 overweight/obesity subgroups, ISI was lower than that in normal weight subgroups (P<0.05). ISI was negatively correlated with body mass index and waist circumference in all groups (P<0.05). ISI was also positively correlated with AIR3-5 in NC group and negatively correlated in the other 3 groups (P<0.05). CONCLUSION: The impact of obesity on insulin secretion is not the same in the subjects with different glucose tolerance. With the aggravation of insulin resistance, the first-phase insulin secretion in the subjects with normal glucose tolerance without family history of diabetes increases for compensation, while that in the normal glucose tolerance subjects who are the first-degree relatives of type 2 diabetic patients, the patients with impaired glucose regulation and the type 2 diabetic patients could not increase for compensation.     

Effects of rs5418 site variation in SLC2A4 promoter region on gene expression

AIM: To investigate the effect of G/A mutation in rs5418 site of solute carrier family 2,facilitated glucose transporter,member 4 protein(SLC2A4) promoter region on gene expression. METHODS: The core promoter region of SLC2A4 gene was amplified by PCR. Mutant and wild-type recombinant expression vectors containing promoter of SLC2A4 gene were constructed by recombinant gene technique and the strategy of site-directed mutagenesis. Recombinant vectors were transfected into HEK293T cells by lipofectamine and the expression activity of the reporter gene in the recombinant expression vectors with different alleles was detected by a dual-luciferase reporter assay system. RESULTS: The 716-bp SLC2A4 promoter was amplified and the recombinant expression vectors pGL3-SLC2A4-prom(A) and pGL3-SLC2A4-prom(G) were successfully constructed. The luciferase reporter vector containing SLC2A4 promoter with rs5418-A alleles produced significantly higher relative luciferase activity (19.49±4.41) than that with rs5418-G allele (13.04±4.45; P<0.05). CONCLUSION: The G→A variation of rs5418 site in SLC2A4 promoter region increases the expression of SLC2A4 gene,thereby affecting the gene function.     

Mechanisms of PGF2α on the glucose-induced insulin secretion in NIT-1β cells

AIM:To investigate the cellular mechanisms by which PGF₂α promotes glucose-stimulated insulin secretion in NIT-1 beta cells. METHODS:Using the radioimmunoassay (RIA), the amount of the PGF₂α augmentation of glucose stimulated insulin secession was determined in different conditions, and the confocal laser scanning methods by Fluo-3AM as a fluorescent probe were used to analyze the changes of intracellular calcium in NIT-1β cells. RESULTS:At the lower glucose (0, 5.5 mmol/L), PGF₂α (5 μmol/L) failed to potentiate insulin secretion (P>0.05). However, in the presence of 16.5 mmol/L glucose, PGF₂α increased significantly in insulin secretion (P<0.05). Neither the AC inhibitor ddA nor the GC inhibitor Ly-83583 altered PGF₂α-potentiated insulin secretion in the presence of 16.5 mmol/L (P<0.05 or P<0.01). Otherwise, the PLC inhibitor U-73122 and the PKC blocker calphostin C both counteracted the insulinotropic of PGF₂α (P<0.01 or P<0.05). Moreover, exposure of the NIT-1β cells to 5 μmol/L PGF₂α induced a rapid increase of intracellular calcium (P<0.01). The inhibitor, ddA or Ly-83583 had no impact on PGF₂α-induced elevation of the intracellular calcium (P<0.01). Pretreatment of the cells with U-73122 completely prevented the calcium response induced by PGF₂α (P<0.01). CONCLUSION:Efects of PGF₂α was independent of cAMP or cGMP, potentiated glucose (16.5 mmol/L)-induced insulin secretion in NIT-1β cells through stimulation of phospholipase C, which subsequently mediated the elevation of intracellular calcium and activation of protein kinase C.     

Establishment and verification of insulin resistance model in mouse skeletal muscle cells

AIM:To establish a stable and repeatable insulin resistance model of skeletal muscle cells in vitro, so as to promote the exploration of the pathological mechanism of insulin resistance and the development and screening of related drugs. METHODS:C2C12 mouse myoblasts were used to induce differentiation in normal differentiation medium and differentiation medium containing glucose at 40 and 60 mmol/L, respectively. The effects of glucose at different concentrations on cell convergence, fusion and formation of multinucleated myotubes were observed under phase contrast microscope every day. After 1, 3, 5 and 7 d of differentiation, 2-NBDG assay was used to detect the effects of different interventions on C2C12 basal glucose uptake and insulin-stimulated glucose uptake. The effects of different interventions on the protein expression of glucose transporter 4 (GLUT4) after 5 d and 7 d of differentiation were determined by Western blot. The effects of different interventions on the distribution of GLUT4 protein after 5 d of differentiation were detected by immunofluorescence staining. RESULTS:After treated with glucose at 60 mmol/L, the morphological observation showed that high glucose treatment significantly inhibited the growth and differentiation of C2C12 cells after 3 d. High glucose treatment significantly inhibited basal glucose uptake and insulin-stimulated glucose uptake of the C2C12 cells after 5 d and 7 d (P<0.01). No difference between insulin-stimulated GLUT4 expression and basal GLUT4 expression after 5 d and 7 d of high glucose treatment was observed (P>0.05), but there was significant difference between control group and 60 mmol/L group (P<0.05) determined by Western blot. Immunofluorescence staining observation showed that the distribution of GLUT4 protein in the C2C12 cell membrane was significantly decreased after 5 d of high glucose treatment (P<0.01). Glucose treatment (40 mmol/L) also played a role to some extent, but the effect was not as obvious and stable as 60 mmol/L glucose. CONCLUSION:A stable insulin resistance model of mouse skeletal muscle cells in vitro was successfully established by high glucose stimulation. The treatment of glucose at 60 mmol/L for 5 d was the best. Morphological observation and detection of basic and insulin-stimulated glucose uptake and GLUT4 protein expression and distribution evaluates the insulin resistance level of skeletal muscle cells in vitro.     

Relationship between apoptosis,proliferation and expression,mutation of related genes in breast cancer

AIM:To study the relationship between apoptosis, proliferation and expression,mutation of related genes in breast cancer.METHODS:Methods of TUNEL, immunohistochemical S-P and PCR-SSCP were used respectively to study apoptotic index (AI), mitotic index(MI), expression of Bcl-2,p53,c-erbB-2,PCNA,Ki67,TopoⅡ and mutation of p53 in 54 cases of breast cancer.RESULTS:AI and MI were 9.40±3.78 and 5.96±2.36, respectively. There was a significant direct correlation between them(r=0.46.P＜0.01).High expression of Bcl-2,PCNA,Ki67,TopoⅡ coincided with high AI,MI(P＜0.01). High expression of p53,c-erbB-2 and mutation of p53 coincided with high MI(P＜0.01). Type of p53 mutation coincided with AI(P＜0.05).CONCLUSION:Disturbance of gene control between apoptosis and proliferation is related with expression,mutation of related genes in breast cancer.     

Construction of mouse pdx-1 gene eukaryotic expression vector and its expression in embryonic stem cells

AIM: To clone mouse pdx-1 gene and construct its eukaryotic expression vector for expression of pdx-1 in mouse embryonic stem cells.METHODS: Mouse pdx-1 cDNA fragment was amplified with polymerase chain reaction (PCR) from mouse pancreatic cDNA. The purified fragment was recombinated with a eukaryotic expression vector carrying enhanced green fluorescent protein, pEGFP-N1. The pdx-1 cDNA fragment was inserted into the multi-clone sites of the vector to construct a new plasmid, pEGFP/pdx-1. E.colli strain DH5α was transfected with the new recombinant plasmid to expand it. Plasmid DNA extracted from the expanded DH5α was identifed by cutting with Hind Ⅲ, BamHⅠ nuclease and by DNA sequencing. Identified plasmid DNA was transfected into mouse embryonic stem cell line MESPU13 by carrying with liposome. RESULTS: A 876 bp cDNA fragment was amplified from mouse pancreatic cDNA by PCR and it was inserted into the vector pEGFP-N1 correctly. The fragment was defined to be pdx-1 gene by nuclease digestion and DNA sequencing. Mouse embryonic stem cell line MESPU13 was transfected with the new recombinant plasmid DNA. The green fluorescent protein report gene and pdx-1 gene expressed in transfected mouse embryonic stem cells within 24 h. CONCLUSION: Mouse pdx-1 gene is cloned and its recombinant eukaryotic expression vector carrying green fluorescent protein is constructed successfully. It provides a useful tool for further research on the function of pdx-1.     

Effects of intermittent high glucose on apoptosis and PTEN expression in islet cells

AIM: To investigate whether the increase in PTEN expression is related to apoptosis, and whether it is regulated by reactive oxygen species(ROS). METHODS: The rat islet cells were divided into constant low glucose group (group L), constant high glucose group (group H), glucose fluctuation group (group F), low glucose after high glucose group (group HL) and low glucose after fluctuation group (group FL). The ROS level, apoptotic rate, intracellular calcium, insulin release and PTEN protein expression were analyzed. RESULTS: Compared with groups H and L, the insulin secretion decreased, and intracellular calcium, ROS level, PTEN protein expression and apoptotic rate increased in group F (P<0.05). Compared with group H, the intracellular calcium, ROS level, PTEN protein expression and apoptotic rate in group HL decreased, but were still higher than those in group L (P<0.05). Compared with group F, the intracellular calcium, ROS level, PTEN protein expression and apoptotic rate in group FL decreased, but were still higher than those in group L (P<0.05). CONCLUSION: Glucose fluctuation can cause the apoptosis of islet cells more easily than constant high glucose. This may be related to the change of intracellular calcium and increase in oxidative stress which promotes PTEN expression. The recovery of glucose level to some extent relieves oxidative stress, decrease PTEN expression and reduce cell damage.     

Effect of NP9 on gene expression profile of NPC cell line CNE1

AIM: To identify the gene expression profiles of CNE1 cells stably transfected with NP9 expressing plasmid, and to explore the potential molecular function of NP9 gene.METHODS: CNE1 cells stably expressing NP9 protein and CNE1 cells transfected with empty vector were used as test and control. Differentially expressed genes were screened with high- throughout human genome array. Differential expression of 6 genes was analyzed with quantitative RT-PCR. RESULTS: Of all the 14 500 human genes in array, 266 genes were revealed differential expression between test and control , of which 82 genes (RA>1)were up-regulated in test and 184 genes (RA<1) were down-regulated. 34 genes and 75 genes were found distinctively up-regulation (RA>1.5) and down-regulation (RA<1.5),respectively.CONCLUSION: NP9 expression in CNE1 cells leads to changes of some genes involved in regulation of cell cycle, cell proliferation and differentiation, cell signal transduction, cell adhesion. Some new clues may be provided for further studying the potential function and molecular mechanism of NP9 gene.