胰升血糖素与肝源性胰岛素抵抗

肝源性IR是T2DM重要发病基础之一,机制主要为受体缺陷及信号转导异常。作为对抗胰岛素的重要激素,胰升血糖素在糖尿病发病中起重要作用。与健康人群比,糖尿病患者或动物存在胰岛素异常分泌,也存在胰升血糖素异常高分泌。胰升血糖素在肝源性IR中的作用主要为抑制肝糖原合成及糖酵解,促进肝糖原分解、糖异生及脂肪分解。     

胰升血糖素样肽1的研究进展

胰升血糖素样肽1(Glucagon like peptidel，GLP-1)是一种肠促胰岛素，具有其促进胰岛素释放、延缓胃排空、降低胰升血糖素和降低食欲等生理作用，为2型糖尿病的治疗提供了一个非常好的前景。它在降低血糖的同时不会增加体重，且可能在促进胰岛细胞增殖和改善胰岛素敏感性方面发挥作用。目前，该类药物正在研发之中。现将其进展综述如下。     

胰升血糖素样肽-1受体激动剂在2型糖尿病合并心血管疾病管理中的作用

T2DM患者常合并多重心血管危险因素,如血脂异常、高血压以及治疗过程中常伴发的低血糖、体重增加等.因此,T2DM患者是心血管疾病的高危人群.为降低T2DM的心血管风险,应控制血糖、血压、血脂、体重等指标.胰升血糖素样肽-1（GLP-1）受体激动剂在动物、细胞研究及临床试验中均显示具有心血管保护作用,可用于T2DM合并心血管疾病的管理.     

胰升血糖素样肽1对胰岛β细胞脂性凋亡的拮抗作用及机制

目的观察棕榈酸盐对胰岛β细胞凋亡及胰腺衍生因子（PANDER）的影响,并观察胰升血糖素样肽1（GLP-1）对其的干预。方法培养β-TC3细胞分别以PA、PA＋GLP-1以及空白处理24h,以MTT法、Annexin-V／PI荧光染色流式细胞术、Tunel荧光染色法检测细胞凋亡,以RT—PCR法测定PANDER mRNA的表达。结果PA浓度达0．25mmol／L时细胞存活率开始显著下降,并随浓度上升逐渐下降（P〈0．05）。GLP-1能显著拮抗PA致胰岛口细胞凋亡;PA能明显增加PANDER mRNA的水平,而GLP-1能显著抑制PA对PANDER的作用。结论PA在诱导胰岛B细胞凋亡的同时刺激PANDER表达,GLP-1拮抗PA致胰岛β细胞凋亡及PANDER的表达;PANDER可能是GLP-1拮抗胰岛B细胞脂性凋亡的靶点之一。     

胰升血糖素样肽-1治疗的胰腺外作用研究进展

随着研究的不断深入,人们发现胰升血糖素样肽-1 （GLP-1）不仅可以刺激胰岛β细胞分泌胰岛素调节血糖,还可保护肝脏、肾脏功能,调节脂类代谢,降低心血管危险因素,影响及保护中枢神经系统等.本文就GLP-1胰腺外作用的最新研究进展进行系统综述.     

胰升血糖素样肽-1促进内浆网应激脂肪细胞内脏脂肪素的表达

目的 探讨胰升血糖素样肽-1（GLP-1）对内质网应激状态下脂肪细胞内脏脂肪素表达的调节作用。 方法 3T3-L1分化成熟的脂肪细胞,经Tg诱导建立内质网应激模型。脂肪细胞经Tg和/或GLP-1孵育后,收集细胞用于总RNA的提取,收集细胞液用于ELISA分析。定量PCR检测内脏脂肪素转录水平,ELISA检测其分泌水平。内质网应激发生通过测定sXBP-1表达水平增加来判断。使用细胞核因子κB（NF-κB）特异阻断剂PDTC预处理30 min,观察NF-κB在GLP-1调节内脏脂肪素表达中的作用。 结果 Tg诱导后sXBP-1表达增加,内脏脂肪素表达下降并呈剂量依赖性;同时给予GLP-1处理后,内脏脂肪素表达增加;PDTC降低内脏脂肪素基础水平,并未阻断GLP-1作用。 结论 GLP-1提升内质网应激状态下脂肪细胞内脏脂肪素的表达。     

不同胰升血糖素样肽1受体激动剂类药物心血管结局研究差异及其在临床治疗中的指导意义

动脉粥样硬化性心血管疾病(ASCVD)是T2DM患者重要的伴发疾病和主要死因。在DM新药研发规则的影响下,新型DM药物的心血管结局研究(CVOT)数据不断涌现。7项针对胰升血糖素样肽1受体激动剂(GLP-1 RA)类药物的CVOT,因研究目的不同,采用不同的研究设计来验证不同的科学假设,全面证明GLP-1 RA类药物心血管安全性的同时,显示出某些药物的心血管保护作用。GLP-1 RA类药物临床证据使其在DM管理中的地位上升,为DM患者高血糖管理和心血管疾病防治提供新的解决方案。     

黄芪甲甙对类胰升血糖素肽-1作用的研究

目的　应用放射免疫分析方法研究黄芪甲甙对类胰升血糖素肽 - 1的作用。方法　用三种不同浓度黄芪甲甙溶液给 Wistar大鼠腹腔注射 ,并于 3、4、5 w后取血测定大鼠血浆中黄芪甲甙的含量。结果　经过统计学处理发现 ,经黄芪甲甙作用 ,大鼠血浆中类胰升血糖素肽 - 1含量各实验组与对照组相比存在显著差异 (P<0 .0 5) ,并随着作用时间的延长 ,分泌作用增加。结论　黄芪甲甙具有促进类胰升血糖素肽 - 1分泌的作用。     

胰升糖素样肽1对胰岛β细胞作用的研究进展

胰升糖素样肽1(GLP-1)是由小肠内L细胞分泌的肠道促胰岛激素,GLP-1与其特异性受体GLP-1受体(GLP-1R)结合后可激活腺苷酸环化酶,生成cAMP,并激活蛋白激酶A及鸟嘌呤核苷酸交换因子(GEF)信号途径,另外GLP-1还可通过不同的方式激活钙调蛋白通路及丝裂原活化蛋白激酶和磷脂酰肌醇3激酶通路,产生多种生理效应.GLP-1可促进胰岛素的1相和2相分泌,增加胰岛素的合成,此外GLP-1还可促进胰岛β细胞的增殖及分化,减少β细胞凋亡,减轻内质网应激对β细胞的损伤作用,增加β细胞存活.     

胰升血糖素样肽1对非酒精性脂肪性肝病大鼠氧化应激损伤的干预

目的 通过建立大鼠非酒精性脂肪性肝病(NAFLD)模型,观察胰升血糖素样肽1(GLP-1)对NAFLD大鼠氧化应激损伤的干预效应.方法 60只雄性SD大鼠分为正常饮食组(NC组,n=15)和高脂饮食组(HF组,n=45),12周末评估NAFLD模型的建立.NC组给予等渗盐水干预,HF组再分为等渗盐水组(NS组,n=10),低剂量GLF-1组(LG组,n=10),中剂量GLP-1组(MG组,n=10),高剂量GLP-1组(HG组,n=10),给予等渗盐水及不同剂量(50μg/kg,100μg/kg,200 μg/kg) GLP-1进行干预,4周后检测血清生物化学指标(甘油三酯、总胆固醇、高密度脂蛋白、低密度脂蛋白、ALT、AST),肝组织超氧化物歧化酶、丙二醛及细胞色素氧化酶P450 2E1 (CYP2E1)mRNA和蛋白含量.两个样本均数比较采用t检验或近似t检验,多个样本均数比较采用LSD检验或Dunnett T3检验.结果 NS组超氧化物歧化酶水平较NC组显著降低[(165.81±11.64) U/mg对比(192.89±16.53) U/mg,P＜ 0.05],丙二醛水平显著升高[(7.30±1.79)nmol/mg对比(3.10±1.30)nmol/mg,P＜0.05],CYP2E1 mRNA及蛋白含量亦明显升高(P＜0.05).经过GLP-1干预后,与NS组比较,LG、MG、HG组大鼠肝组织超氧化物歧化酶水平呈升高趋势[(171.44±9.80) U/mg对比(177.66±14.77)对比(186.17±15.43) U/mg,仅HG组,P＜0.05],MDA水平明显降低[(5.16±1.45)nmol/mg对比(4.08±1.22) nmol/mg对比(3.31±1.14)nmol/mg,P＜0.05],CYP2E1 mRNA和蛋白水平亦呈降低趋势(CYP2E1 mRNA含量仅HG组差异有统计学意义,P＜0.05;CYP2E1蛋白含量在MG、HG组差异均有统计学意义,P值均＜0.05). 结论 GLP-1可改善肝组织脂质沉积,减轻NAFLD大鼠氧化应激损伤.     

Insulin inhibits glucagon secretion by the activation of PI3-kinase in In-R1-G9 cells.

Intracellular mechanisms through which insulin inhibits glucagon secretion remain to be elucidated in glucagon secreting cells. In this study, we confirmed that, in In-R1-G9 cells, a pancreatic alpha cell line, insulin stimulated phosphorylation of insulin receptor substrate-1 (IRS-1) and activated phosphatidylinositol 3-kinase (PI3-kinase). We further studied, using wortmannin, an inhibitor of PI3-kinase, whether the inhibitory effect of insulin on glucagon secretion was mediated through PI3-kinase pathway in these cells. In static incubation studies, insulin significantly inhibited glucagon secretion at 2, 6 and 12 h, which was completely abolished by pretreatment with wortmannin. In perifusion studies, insulin significantly suppressed glucagon secretion after 10 min, which was also blocked by wortmannin. Insulin also reduced glucagon mRNA at 6 and 12 h but not at 2 h. Wortmannin also abolished insulin-induced reduction of glucagon mRNA. Insulin increased the amount of 85 kDa subunit of PI3-kinase in plasma membrane fraction (PM), with a reciprocal decrease of the kinase in cytosol fraction (CY). Insulin also increased PI3-kinase activity in PM, but not in CY. Our results suggest that insulin suppressed glucagon secretion by inhibiting glucagon release and gene expression. Both actions were mediated by activation of PI3-kinase. Recruitment and activation of PI3-kinase in plasma membrane might be relevant at least in part to insulin-induced inhibition of glucagon release.     

Some characteristics of GnRH receptors in rat-pituitary membranes: differences between an agonist and and antagonist

The interaction of gonadotropin-releasing hormone (GnRH) agonists and antagonists with pituitary membranes was studied by using 125I-labeled agonist, [D-Ser(t-Bu)6, des-Gly10-ethylamide]-GnRH, and antagonist [D-pGlu1, D-Phe2, Trp3,6]-GnRH. Their binding was affected differently by cations, and by pretreatment of membranes with proteolytic enzymes and sulfhydryl-blocking reagents. Monovalent cations at millimolar concentrations (10-100 mM) and divalent cations at lower concentrations (0.5-5 mM) reduced more significantly the binding of the agonist than that of the antagonist. Pretreatment of the membranes with trypsin and chymotrypsin abolished the specific binding of both agonist and antagonist, in a dose-response manner, with the former being less affected. Pretreatment of the membranes with sulfhydryl-blocking reagents did not alter the binding of the antagonist but enhanced the binding of the agonist. This enhancement in the specific binding was found to be due to an increase in the apparent affinity of the agonist. These results may suggest that GnRH agonists and antagonists bind differently to the same receptor.     

GLP-1R agonist may activate pancreatic stellate cells to induce rat pancreatic tissue lesion

ObjectiveTo explore the mechanism of GLP-1R agonist-induced rat pancreatic tissue lesion.MethodsThirty SD male rats were divided into three groups, namely GLP-1R agonist experimental group, diabetes-model experimental group and control group. Diabetes-model rats were induced by streptozotocin and high-sugar high-fat diet. GLP-1R agonist group and diabetes-model group were administered with GLP-1R agonist in dose 5 μg/kg each time, twice a day. After 10 weeks of treatment, the amount of matrix metalloproteinase (MMP)-2 and MMP-9, and expression of α-smooth muscle actin (α-SMA) and type III collagen protein in pancreatic tissue were measured.ResultsThe amount of MMP-2 and MMP-9 in GLP-1R agonist group and diabetes-model group were significantly higher than the control group. Compared with the GLP-1R agonist group, the diabetic model group had more severe pathological changes of pancreatic tissue interstitial edema, inflammatory cell infiltration, glandular atrophy and fibrosis, and significantly increased pancreatic tissue MMP-2 and MMP-9 levels, significantly increased α-SMA and collagen III-positive cell counts, all the differences were statistically significant. α-SMA and type III collagen were expressed in all parts of the lesions of GLP-1R agonist group and diabetes-model group. α-SMA can only be observed in the vessel wall in control group, however, in the other two groups, α-SMA can also be observed in pancreatic acinar cell interstitia, in addition to vessel wall.ConclusionsLong-term subcutaneous GLP-1R agonist injection may activate pancreatic stellate cells, causing the expression of α-SMA and collagen III and the amount of MMP-2 and MMP-9 in pancreatic acinar cell interstitial significantly increasing, and thus inducing chronic inflammatory change.     

Dapagliflozin modulates glucagon secretion in an SGLT2-independent manner in murine alpha cells

AimSGLT2 inhibitors reduce renal glucose uptake through an insulin-independent mechanism. They also increase glucagon concentration, although the extent to which this is due to a direct effect on pancreatic alpha cells remains unclear.MethodsIn the present work, αTC1 cells treated with the SGLT2 inhibitor dapagliflozin (Dapa) were analyzed for glucose transporters, molecular mediators of hormone secretion, glucagon and GLP-1 release, and the effects of somatostatin. Data were validated in murine and human pancreatic islets.ResultsSLC5A2 (the SGLT2-encoding gene) was nearly undetectable in αTC1 cells, not even by a digital PCR technique using different probes. In contrast, SLC5A1 (the SGLT1-encoding gene) was constitutively abundant in αTC1 cells and in islets, and increased with Dapa. This was associated with greater glucagon release, preceded by increased expression of preproglucagon and HNF4α. Looking at the candidate intracellular signalling pathway, reduced PASK and increased AMPK-α2 expression were also detected. GLUT1 and GLUT2, as well as regulators of glucagon release and alpha-cell phenotype (chromogranin A, paired box 6, proprotein convertase 1/2, synaptophysin), were unaffected by Dapa, as were GLP-1 receptor expression and GLP-1 release. Low glucose did not influence the stimulatory effect of Dapa on glucagon release, but was instead almost fully reverted by SLC5A1 silencing. When the effect of Dapa on AMPK and PASK, emerging regulators of lipid and glucose metabolism, was tested, upregulated AMPK-α2 appeared to be involved in molecular signalling.ConclusionOur study has shown that, in αTC1 cells, Dapa acutely upregulates SGLT1 expression and increases glucagon release through an SGLT1-dependent mechanism, with SGLT2 expression virtually undetectable. These results suggest the involvement of SGLT1 in modulating glucagon increases following SGLT2 inhibition.     

Mechanisms of bradykinin-induced glucagon release in clonal alpha-cells In-R1-G9: involvement of Ca(2+)-dependent and -independent pathways

Recent studies suggest striking similarities between polarized protein sorting in thyrocytes and MDCK epithelial cells, including apical trafficking of thyroglobulin (Tg), thyroid peroxidase, and aminopeptidase N; as well as basolateral targeting of heparan sulfate proteoglycans, thrombospondin 1 (TSP1), type 1 5'-deiodinase, sodium-potassium ATPase, and the thyrotropin receptor. In this report, we have firstly expressed in stably transfected MDCK II cells a range of truncation mutants lacking up to 78% of the C-terminus of TSP1; these studies indicate that the N-terminal region containing the heparin binding domain is sufficient for basolateral targeting of TSP1. Secondly, we have stably transfected MDCK II cells with both Tg and sodium-iodide symporter (NIS) cDNAs, obtaining clones that simultaneously express both thyroid-specific proteins at the apical and basolateral cell surfaces, respectively. These studies represent promising early steps towards designing artificial thyrocytes by thyroid gene transfer into MDCK cells.     

Dysregulated plasma glucagon levels in Japanese young adult type 1 diabetes patients

Currently, the clinical dynamics of glucagon need to be revised based on previous data obtained from conventional glucagon radioimmunoassays. In the present study, we evaluated plasma glucagon levels in type 1 diabetes patients using a newly‐developed sandwich enzyme‐linked immunosorbent assay, and its association with clinical parameters and markers of diabetes complications were statistically assessed. The plasma glucagon level in 77 Japanese type 1 diabetes patients was 28.1 ± 17.7 pg/mL, and comparable with that reported previously for type 2 diabetes patients. However, the values were widely spread and did not correlate with plasma glucose values. Additionally, the average glucagon levels in patients in a hypoglycemic state (glucose level <80 mg/dL) did not increase (21.7 ± 12.2 pg/mL). The average glucagon level of patients experiencing hypoglycemia unawareness was significantly lower. Plasma glucagon levels evaluated using the new enzyme‐linked immunosorbent assay were dysregulated in type 1 diabetes patients in respect to plasma glucose levels, suggesting dysregulation of secretion.