LKB1-AMPK信号通路与胰岛素抵抗

腺苷酸活化蛋白激酶（AMP—activated protein kinase，AMPK）广泛存在于各种真核细胞中，被认为是真核生物的“细胞能量调节器”，受AMP／ATP比值的调节。一磷酸腺苷（AMP）与AMPK-7调节亚基相结合，启动上游激酶LKB1磷酸化AMPK一口催化亚基，从而致使AMPK活化，开启分解代谢途径产生ATP，同时关闭合成代谢途径以减少ATP消耗。新近的研究发现二甲双胍类和噻唑烷二酮类（TZDs）抗糖尿病药物可以激活AMPK，     

二甲双胍对2型糖尿病大鼠脂肪组织中AMPKα2表达的影响

目的观察二甲双胍对2型糖尿病大鼠脂肪组织中腺苷酸活化蛋白激酶α2（AMPKα2）表达及对糖、脂代谢的影响,探讨其改善血糖、血脂的可能机制。方法高脂饮食伴一次性腹腔注射链脲佐菌素的方法制备2型糖尿病大鼠模型,造模成功后随机分为模型组和治疗组,后者给予盐酸二甲双胍灌胃治疗。测定大鼠治疗前后的体质量,实验末测定各组大鼠肾周及睾周脂肪重量,并检测各组空腹血糖（FBG）、胰岛素（FINS）、TC、TG、HDL、LDL水平,计算大鼠脂体比、胰岛素敏感指数（ISI）。同时以半定量RT-PCR检测脂肪组织AMPKα2 mRNA的表达。结果与模型组比较,治疗组脂肪组织AMPKα2的表达及血清FINS、HDL、ISI增高,FBG、TC、TG、LDL降低,P均〈0.05。结论二甲双胍可能通过上调2型糖尿病大鼠脂肪组织AMPKα2表达,调节机体糖、脂代谢,改善胰岛素敏感性。     

小檗碱的降糖作用独立于AMPK的信号通路

目的：研究小檗碱的降糖作用是否依赖于单磷酸腺苷激活蛋白激酶（AMPK）信号途径。方法培养HepG2细胞和C2C12细胞,给予不同浓度小檗碱处理。葡萄糖消耗实验和乳酸生成实验用于检测小檗碱的降糖以及刺激糖酵解的作用。AMPK抑制剂化合物C（Compound C,CC）和显性失活突变型AMPK,即腺病毒负显性AMPK（Ad-DN-AMPK）腺病毒用于抑制AMPK的表达和活性。Western印迹法用于检测AMPK以及乙酰辅酶A羧化酶（ACC）磷酸化水平,以评估AMPK通路的活性。结果小檗碱显著刺激了HepG2细胞和C2C12细胞的葡萄糖消耗和乳酸生成,并表现出剂量依赖性的药物作用。5和10μmol/L的小檗碱显著增加AMPK及其下游蛋白ACC的磷酸化水平。CC和Ad-DN-AMPK腺病毒转染能明显抑制细胞内AMPK信号通路的活性。然而,在AMPK活性被抑制的条件下,小檗碱依然能够显著增加细胞的葡萄糖消耗和乳酸生成。结论小檗碱通过刺激糖酵解而上调细胞的糖代谢,该作用无需AMPK信号通路的参与。即使在AMPK的表达或者活性被抑制的情况下,小檗碱依然能够发挥显著的降糖作用。     

腺苷酸活化蛋白激酶与心肌缺血再灌注损伤

心肌缺血再灌注损伤（MIRI）是指缺血期处于可逆损伤的心肌细胞恢复血液供应后产生更为严重的损伤,主要包括炎症反应、内皮细胞损伤、血流障碍、心肌细胞坏死和凋亡所致心肌梗死面积的扩大、再灌注心律失常、心肌顿抑及冠状微循环障碍等病理生理变化.腺苷酸活化蛋白激酶（5-adenosine monophosphate activated kinase,AMPK）通过调节多种代谢途径控制着心脏能量的供求平衡.AMPK不仅控制葡萄糖和脂类的摄入、储存和利用,还能调节多种代谢酶的活性以及离子通道的开放和相关基因的表达[1].AMPK还能够调节缺血再灌注过程中心肌能量代谢,降低缺血性损伤和心肌凋亡.因此,AMPK被认为是能量应激下心肌细胞代谢调节的关键激酶.     

抵抗素对内皮细胞一氧化氮生成的影响及其AMPK信号机制

目的研究抵抗素对人脐静脉内皮细胞（HUVEC）一氧化氮生成的影响及其信号机制。方法不同浓度人抵抗素（0-100ng／ml）干预HUVEC24h。DAF-2DA染色,激光共聚焦显微镜观察各组一氧化氮生成改变,Western-Blot检测各组eNOS、AMPK磷酸化水平改变。结果15、50、100ng／ml抵抗素干预HUVEC24h后,3组的一氧化氮生成分别为4．014-0．69、3．76±0．71、3．73±0．45,与对照组一氧化氮生成（4．89±0．58）相比显著降低（P〈0.05）;50ng／ml组添加AMPK特异激动剂A／CAR后,一氧化氮生成（5．08±0．70）显著升高（P〈0.01）。各抵抗素干预组的AMPK和eNOS磷酸化水平均明显降低;而添加AMPK特异激动剂AICAR后,伴随AMPK的激活,eNOS磷酸化水平也显著增高（P〈0．05）。结论抵抗素在内皮细胞可通过对AMPK的抑制进而导致eNOS失调,降低内皮一氧化氮的生成。     

抵抗素对内皮细胞活性氧生成及AMPK磷酸化水平的影响

目的探讨抵抗素对内皮细胞功能影响的作用机制。方法体外培养人脐静脉内皮细胞,50、100ng/ml抵抗素干预24h,分别检测活性氧（ROS）生成和腺苷酸活化蛋白激酶（AMPK）磷酸化水平,并应用AICAR激活AMPK观察其对内皮ROS生成的影响。结果50、100ng/ml抵抗素作用组与对照组相比,内皮细胞AMPK磷酸化水平明显下降,而ROS生成无明显改变;50ng/ml抵抗素作用组加用AICAR干预后,AMPK磷酸化水平显著增高,同时伴ROS生成显著降低。结论抵抗素可影响内皮细胞功能,其机制可能通过抑制内皮细胞AMPK的磷酸化水平,参与内皮细胞炎症过程的调节,激活内皮AMPK,减少ROS生成,对内皮损伤起保护性作用。     

AMPK与肥胖

能量代谢平衡失调是肥胖发生的主要原因。腺苷酸激活蛋白激酶(AMPK)信号通路是调节细胞能量状态的中心环节,其激活后磷酸化下游的信号分子,关闭消耗ATP的合成代谢途径,开启产生ATP的分解代谢途径,被称为"细胞能量调节器",在增加骨骼肌对葡萄糖的摄取、增强胰岛素敏感性、增加脂肪酸氧化以及调节基因转录等方面发挥重要作用。在整体水平,AMPK通过激素和细胞因子如瘦素、脂联素和ghrelin等调节能量的摄入和消耗。研究AMPK与肥胖的关系,将为AMPK作为防治肥胖的新靶点提供可靠的理论基础和应用依据。     

AMPK-能量代谢感受器与可激活AMPK相关的药物研究进展

单磷酸腺苷活化蛋白激酶（AMPK）可以感受细胞能量代谢变化,调节细胞的葡萄糖、脂肪酸的代谢过程。AMPK与细胞生长、生存和多种代谢信号途径关系密切,研究发现AMPK信号途径涉及炎症、肿瘤和代谢疾病。本文综述AMPK的功能与炎症、肿瘤、代谢类疾病的关系和诸如水杨酸、二甲双胍等药物激活AMPK的研究进展。     

下丘脑能量信号通路通过调节Kiss1神经元对青春期发育的影响研究进展

青春期的启动主要受下丘脑能量信号通路的调控。下丘脑能量信号通路瘦素、腺苷酸活化蛋白激酶（AMPK）、G蛋白偶联受体54(GPR54)具有启动青春期发育和调控机体能量平衡的功能。Kiss1是刺激性成熟的主要内分泌因子,是调控下丘脑促性腺激素释放激素（GnRH）神经元的重要作用元件和下丘脑—垂体—性腺（HPG）轴成熟的调节因子,Kiss1作为GPR54的天然配体,与GPR54结合后调节GnRH分泌,对青春期发育起关键作用;瘦素是一种能量代谢的负反馈调节激素,下丘脑Kiss1神经元表达瘦素受体,介导瘦素对生殖系统产生影响;AMPK是重要的下丘脑能量感受器,在能量缺乏的条件下,AMPK被激活,抑制Kiss1 mRNA表达,在调节能量平衡及生殖方面起关键作用。机体能量代谢与青春期启动信号通路之间关系密切,研究青春期启动过程中调节能量平衡的信号通路,可以为治疗青春期发育异常和能量代谢失衡提供新治疗靶点。     

脂毒性及其防治的一个关键靶点——AMPK

当过多摄人的能量超出了脂肪组织的贮存容量时,脂质溢出进入胰腺、肝脏及骨骼肌等非脂肪组织贮存,诱发胰岛素抵抗,损伤胰岛β细胞功能,导致2型糖尿病及其并发症的发生。运动,饮食控制及激活“代谢总开关”一磷酸腺苷活化蛋白激酶(AMPK)的药物,二甲双胍、罗格列酮可促进外周组织的脂质氧化,降低脂质的异位堆积,阻止或延缓2型糖尿病的发生。因此,AMPK可能成为防治脂毒性的关键靶点。     

AMPK - Activated Protein Kinase and its Role in Energy Metabolism of the Heart

Adenosine monophosphate - activated kinase (AMPK) plays a key role in the coordination of the heart's anabolic and catabolic pathways. It induces a cellular cascade at the center of maintaining energy homeostasis in the cardiomyocytes.. The activated AMPK is a heterotrimeric protein, separated into a catalytic α - subunit (63kDa), a regulating β - subunit (38kDa) and a γ - subunit (38kDa), which is allosterically adjusted by adenosine triphosphate (ATP) and adenosine monophosphate (AMP). The actual binding of AMP to the γ - subunit is the step which activates AMPK. AMPK serves also as a protein kinase in several metabolic pathways of the heart, including cellular energy sensoring or cardiovascular protection. The AMPK cascade represents a sensitive system, activated by cellular stresses that deplete ATP and acts as an indicator of intracellular ATP/AMP. In the context of cellular stressors (i.e. hypoxia, pressure overload, hypertrophy or ATP deficiency) the increasing levels of AMP promote allosteric activation and phosphorylation of AMPK. As the concentration of AMP begins to increase, ATP competitively inhibits further phosphorylation of AMPK. The increase of AMP may also be induced either from an iatrogenic emboli, percutaneous coronary intervention, or from atherosclerotic plaque rupture leading to an ischemia in the microcirculation. To modulate energy metabolism by phosphorylation and dephosphorylation is vital in terms of ATP usage, maintaining transmembrane transporters and preserving membrane potential. In this article, we review AMPK and its role as an important regulatory enzyme during periods of myocardial stress, regulating energy metabolism, protein synthesis and cardiovascular protection.     

AMPK-能量代谢感受器与可激活AMPK相关的药物研究进展

单磷酸腺苷活化蛋白激酶(AMPK)可以感受细胞能量代谢变化,调节细胞的葡萄糖、脂肪酸的代谢过程。AMPK与细胞生长、生存和多种代谢信号途径关系密切,研究发现AMPK信号途径涉及炎症、肿瘤和代谢疾病。本文综述AMPK的功能与炎症、肿瘤、代谢类疾病的关系和诸如水杨酸、二甲双胍等药物激活AMPK的研究进展。     

Adenosine 5'-monophosphate-activated protein kinase regulation of fatty acid oxidation in skeletal muscle

AMP-activated protein kinase (AMPK) is master regulator of energy balance through suppression of ATP-consuming anabolic pathways and enhancement of ATP-producing catabolic pathways. AMPK is activated by external metabolic stresses and subsequently orchestrates a complex downstream signaling cascade that mobilizes the cell for efficient energy production. AMPK has emerged as a key kinase driving lipid oxidation in skeletal muscle, and this function has important implications for exercise adaptations as well as metabolic defects associated with obesity.     

The regulation of AMP-activated protein kinase by upstream kinases

AMP-activated protein kinase (AMPK) is the downstream component of a protein kinase cascade that plays a major role in maintaining energy homoeostasis. Within individual cells, AMPK is activated by a rise in the AMP/ATP ratio that occurs following a fall in ATP levels. AMPK is also regulated by the adipokines, adiponectin and leptin, hormones that are secreted from adipocytes. AMPK regulates a wide range of metabolic pathways, including fatty acid oxidation, fatty acid synthesis, glycolysis and gluconeogenesis. In peripheral tissues, activation of AMPK leads to responses that are beneficial in counteracting the deleterious effects that arise in the metabolic syndrome. Recent studies have demonstrated that modulation of AMPK activity in the hypothalamus plays a role in feeding. A decrease in hypothalamic AMPK activity is associated with decreased feeding, whereas activation of AMPK leads to increased food intake. Furthermore, signalling pathways occurring in the hypothalamus lead to changes in AMPK activity in peripheral tissues, such as skeletal muscle, via the sympathetic nervous system. AMPK, therefore, provides a mechanism for monitoring changes in energy metabolism within individual cells and at the level of the whole body. Activation of AMPK requires phosphorylation of threonine 172 (Thr-172) within the catalytic subunit. Recent studies have shown that both LKB1 and Ca(2+)/calmodulin-dependent protein kinase kinase-beta (CaMKKbeta) play important roles in phosphorylating and activating AMPK. In addition, there is evidence that AMPK can be activated by other upstream kinases, although the physiological significance of this is not clear at present. This review focuses on the role of LKB1 and CaMKKbeta in the regulation of AMPK.     

AMP‐activated protein kinase: a key regulator of energy balance with many roles in human disease

The AMP‐activated protein kinase (AMPK) is a sensor of cellular energy status that regulates cellular and whole‐body energy balance. A recently reported crystal structure has illuminated the complex regulatory mechanisms by which AMP and ADP cause activation of AMPK, involving phosphorylation by the upstream kinase LKB1. Once activated by falling cellular energy status, AMPK activates catabolic pathways that generate ATP whilst inhibiting anabolic pathways and other cellular processes that consume ATP. A role of AMPK is implicated in many human diseases. Mutations in the γ2 subunit cause heart disease due to excessive glycogen storage in cardiac myocytes, leading to ventricular pre‐excitation. AMPK‐activating drugs reverse many of the metabolic defects associated with insulin resistance, and recent findings suggest that the insulin‐sensitizing effects of the widely used antidiabetic drug metformin are mediated by AMPK. The upstream kinase LKB1 is a tumour suppressor, and AMPK may exert many of its antitumour effects. AMPK activation promotes the oxidative metabolism typical of quiescent cells, rather than the aerobic glycolysis observed in tumour cells and cells involved in inflammation, explaining in part why AMPK activators have both antitumour and anti‐inflammatory effects. Salicylate (the major in vivo metabolite of aspirin) activates AMPK, and this could be responsible for at least some of the anticancer and anti‐inflammatory effects of aspirin. In addition to metformin and salicylates, novel drugs that modulate AMPK are likely to enter clinical trials soon. Finally, AMPK may be involved in viral infection: downregulation of AMPK during hepatitis C virus infection appears to be essential for efficient viral replication.     

Folliculin encoded by the BHD gene interacts with a binding protein, FNIP1, and AMPK, and is involved in AMPK and mTOR signaling

Birt-Hogg-Dubé syndrome, a hamartoma disorder characterized by benign tumors of the hair follicle, lung cysts, and renal neoplasia, is caused by germ-line mutations in the BHD(FLCN) gene, which encodes a tumor-suppressor protein, folliculin (FLCN), with unknown function. The tumor-suppressor proteins encoded by genes responsible for several other hamartoma syndromes, LKB1, TSC1/2, and PTEN, have been shown to be involved in the mammalian target of rapamycin (mTOR) signaling pathway. Here, we report the identification of the FLCN-interacting protein, FNIP1, and demonstrate its interaction with 5' AMP-activated protein kinase (AMPK), a key molecule for energy sensing that negatively regulates mTOR activity. FNIP1 was phosphorylated by AMPK, and its phosphorylation was reduced by AMPK inhibitors, which resulted in reduced FNIP1 expression. AMPK inhibitors also reduced FLCN phosphorylation. Moreover, FLCN phosphorylation was diminished by rapamycin and amino acid starvation and facilitated by FNIP1 overexpression, suggesting that FLCN may be regulated by mTOR and AMPK signaling. Our data suggest that FLCN, mutated in Birt-Hogg-Dubé syndrome, and its interacting partner FNIP1 may be involved in energy and/or nutrient sensing through the AMPK and mTOR signaling pathways.     

Targeting AMP-activated protein kinase as a novel therapeutic approach for the treatment of metabolic disorders

In the light of recent studies in humans and rodents, AMP-activated protein kinase (AMPK), a phylogenetically conserved serine/threonine protein kinase, has been described as an integrator of regulatory signals monitoring systemic and cellular energy status. AMP-activated protein kinase (AMPK) has been proposed to function as a 'fuel gauge' to monitor cellular energy status in response to nutritional environmental variations. Recently, it has been proposed that AMPK could provide a link in metabolic defects underlying progression to the metabolic syndrome. AMPK is a heterotrimeric enzyme complex consisting of a catalytic subunit and two regulatory subunits β and γ. AMPK is activated by rising AMP and falling ATP. AMP activates the system by binding to the γ subunit that triggers phosphorylation of the catalytic subunit by the upstream kinases LKB1 and CaMKKβ (calmodulin-dependent protein kinase kinase). AMPK system is a regulator of energy balance that, once activated by low energy status, switches on ATP-producing catabolic pathways (such as fatty acid oxidation and glycolysis), and switches off ATP-consuming anabolic pathways (such as lipogenesis), both by short-term effect on phosphorylation of regulatory proteins and by long-term effect on gene expression. As well as acting at the level of the individual cell, the system also regulates food intake and energy expenditure at the whole body level, in particular by mediating the effects of insulin sensitizing adipokines leptin and adiponectin. AMPK is robustly activated during skeletal muscle contraction and myocardial ischaemia playing a role in glucose transport and fatty acid oxidation. In liver, activation of AMPK results in enhanced fatty acid oxidation as well as decreased glucose production. Moreover, the AMPK system is one of the probable targets for the anti-diabetic drugs biguanides and thiazolidinediones. Thus, the relationship between AMPK activation and beneficial metabolic effects provide the rationale for the development of new therapeutic strategies in metabolic disorders.