Role of AMPK in pancreatic beta cell function

Pharmacological activation of AMP activated kinase (AMPK) by metformin has proven to be a beneficial therapeutic approach for the treatment of type II diabetes. Despite improved glucose regulation achieved by administration of small molecule activators of AMPK, the potential negative impact of enhanced AMPK activity on insulin secretion by the pancreatic beta cell is an important consideration. In this review, we discuss our current understanding of the role of AMPK in central functions of the pancreatic beta cell, including glucose-stimulated insulin secretion (GSIS), proliferation, and survival. In addition we discuss the controversy surrounding the role of AMPK in insulin secretion, underscoring the merits and caveats of methods used to date.     

PPARs与动脉粥样硬化关系的研究进展

过氧化物酶体增殖物激活受体(PPARs)是一类由配体激活的核转录因子,属于Ⅱ型核受体超家族的成员。通过与位于某些基因上游的特异DNA反应元件(peroxisome prolifer-ator responsive element,PPRE)相互作用而调控靶基因的表达。PPARs在血管、心脏组织均有表达,参与调节糖脂代谢、炎症、细胞凋亡、平滑肌迁移和增殖等病理过程。而这些病理改变贯穿了动脉粥样硬化(AS)发生、发展的全过程,现综述核受体PPARs与AS关系的研究进展。     

含小鼠PPRE反应元件报告质粒的转化扩增

目的对含小鼠过氧化物酶体增殖物反应元件（PPRE）报告质粒p4×PPRE-luc进行体外转化和扩增，为基于PPAR为靶标的药物筛选分子平台的建立提供高纯度、高丰度的报告载体。方法取p4×PPRE-luc质粒转化DH5α感受态菌，再接种到含氨苄青霉素的LB琼脂培养板进行抗性筛选培养，挑取阳性克隆菌落进行培养后抽提质粒，紫外分光光度计测定提取质粒的纯度和浓度，并取样进行琼脂糖凝胶电泳验证。结果经转化后获得了抗氨苄青霉素的阳性克隆菌落，挑取阳性克隆并经培养后提取的p4×PPRE—luc质粒其A260/A280=1．84，浓度为750ng／μl。结论成功转化并扩增了p4×PPRE—luc质粒，为基于PPAR为靶标的药物筛选分子平台的建立提供了高纯度、高浓度的报告质粒。     

PPARγC161→T基因多态性对代谢综合征和膳食因素的影响

目的 探讨过氧化物酶体增殖物激活受体γ(peroxisome proliferator-activated receptorsgamma,PPARγ)基因C161→T多态性在人群中的分布及其与代谢综合征和膳食因素的关系.方法 从血凝块中提取DNA,用聚合酶链反应和限制性片段长度多态性方法(PCR·RFLP)检测上海224例成年代谢综合征人群以及224名对照人群的PPARγ基因C161→T位点多态性;对研究对象进行体格,检查、膳食调查及血清生化指标测定.结果 CC、CT和TT三种基因型的频率分别为32.4%、49.6%和18.0%,符合Hardy-Weinberg定律.代谢综合征人群和正常组人群的基因型CC、CT和TT及等位基因C和T构成比差异无统计学意义,三种基因型及等位基因C和T在性别上差异无统计学意义.三种基因型人群中体质指数、腰围和臀围差异有统计学意义,其中CT基因型的水平最高.代谢综合征人群不同基因型人群中,蛋白质与血清甘油三酯水平的负相关性有统计学意义.结论 PPARγ基因C161→T位点多态性与体质指数、腰围和臀围有关;该位点多态性可能会影响膳食对血清甘油三酯的易感性.     

PPAR-γ在多囊卵巢综合征大鼠脂肪组织中的表达及意义

目的:探讨过氧化物酶增殖物激活受体-γ(PPAR-γ)在多囊卵巢及正常大鼠脂肪组织中的表达及在多囊卵巢综合征(PCOS)发病中的作用。方法:应用脱氢表雄酮(DHEA)皮下注射23天龄SD雌性大鼠20天,建立PCOS大鼠模型,应用免疫组织化学技术对PPAR-γ在PCOS大鼠和对照组大鼠脂肪组织的表达强度变化进行研究。结果:PCOS大鼠模型建立成功;PPAR-γ在PCOS组脂肪组织基质细胞上的表达强度(102.7656±11.15510)明显低于对照组(146.3264±4.93102),P<0.001。结论:PPAR-γ在多囊卵巢大鼠发病中起着重要作用。     

Effect of ligand of peroxisome proliferator-activated receptor γ on the biological characters of hepatic stellate cells

AIM: To study the effect of rosiglitazone, which is a ligand of peroxisome proliferator-activated receptor gamma (PPARgamma), on the expression of PPARgamma in hepatic stellate cells (HSCs) and on the biological characteristics of HSCs. METHODS: The activated HSCs were divided into three groups: control group, 3 micromol/L rosiglitazone group, and 10 micromol/L rosiglitazone group. The expression of PPARgamma, alpha-smooth muscle actin (alpha-SMA), and type I and III collagen was detected by RT-PCR, Western blot and immunocytochemical staining, respectively. Cell proliferation was determined with methylthiazolyltetrazolium (MTT) colorimetric assay. Cell apoptosis was demonstrated with flow cytometry. RESULTS: The expression of PPARgamma at mRNA and protein level markedly increased in HSCs of 10 micromol/L rosiglitazone group (t value was 10.870 and 4.627 respectively, P<0.01 in both). The proliferation of HSCs in 10 micromol/L rosiglitazone group decreased significantly (t = 5.542, P<0.01), alpha-SMA expression level and type I collagen synthesis ability were also reduced vs controls (t value = 10.256 and 14.627 respectively, P<0.01 in both). The apoptotic rate of HSCs significantly increased in 10 micromol/L rosiglitazone group vs control (chi(2) = 16.682, P<0.01). CONCLUSION: By increasing expression of PPARgamma in activated HSCs, rosiglitazone, an agonist of PPARgamma, decreases alpha-SMA expression and type I collagen synthesis, inhibits cell proliferation, and induces cell apoptosis.     

Troglitazone attenuates hypoxia-induced injury in cultured term human trophoblasts

OBJECTIVE: The purpose of this study was to test the hypothesis that the thiazolidinedione troglitazone, a peroxisome proliferator activated receptor-gamma ligand, attenuates hypoxia-induced trophoblast injury. STUDY DESIGN: Cytotrophoblasts from 4 term human placentas were cultured in the presence or absence of 10 mumol/L troglitazone in either 20% oxygen (standard conditions) or 1% oxygen (hypoxic conditions) for variable periods before cell harvest. Medium beta-human chorionic gonadotropin and human placental lactogen were analyzed by enzyme-linked immunosorbent assay. Apoptosis was quantified by cytokeratin-18 cleavage products staining; p53 expression was examined by Western blot analysis. RESULTS: beta-human chorionic gonadotropin and human placental lactogen levels were >/=2-fold higher in troglitazone-exposed cells at 16 hours of hypoxia, compared with vehicle control cells ( P <.05). The apoptotic index was reduced by >/=30% ( P <.001), and the expression of p53 was 2-fold lower ( P <.02) in troglitazone-exposed cells under hypoxia for 24 hours of low oxygen. CONCLUSION: Troglitazone attenuates the influence of acute hypoxia on cultured term human trophoblasts.     

Dietary clofibrate inhibits induction of hepatic antioxidant enzymes by chronic estradiol in female ACI rats

Excess production of H₂O₂ has been implicated in oncogenesis. The object of the present study was twofold: first, to determine the influence of chronic estradiol (E₂) on the activities of selected hepatic antioxidant enzymes in female ACI rats, a strain that is highly sensitive to the induction of estrogen dependent mammary tumors; secondly, to evaluate the actions of dietary clofibrate, a peroxisome proliferator, on activities of these enzymes in control and E₂-treated ACI rats. Enzymes selected for study were: NAD(P)H quinone oxidoreductase (NQO1), glutathione S-transferase (GST) and glutathione peroxidase (GPx). Cytosolic catalase (CAT) was also measured as an index of peroxisome proferation in control and E_2- treated animals. E₂ was administered chronically over 6 and 12 week periods from cholesterol pellet implants containing either 1 or 3 mg E₂. Animals were fed AIN-76A diets with or without 0.4% clofibrate over the experimental period. NQO1 and GST but not GPx were induced to varying degrees (NQO1 about 300%, and GST about 45–97%) by chronic E₂-treatment. E₂-induced increases in these activities were completely prevented in rats exposed to dietary clofibrate. Dietary clofibrate also caused slight but significant reductions in baseline activities of NQO1, GST and GPx in control animals. Serum E₂ levels, increased approximately 540% in a dose-dependent manner, and were not altered by dietary clofibrate. It is concluded that chronic E2 treatment markedly induces several important hepatic antioxidant enzymes in female ACI rats, and induction of these activities by E2 is inhibited completely by dietary clofibrate. Both of these actions have the potential to markedly influence the profile of E₂ metabolites exported from the liver to E₂ sensitive extrahepatic tissues and influence the initiation and progression of hormone-dependent tumors.