AIM To investigate the effect of metformin on activated hepatic stellate cells(HSCs) and the possible signaling pathways involved. METHODS A fibrotic mouse model was generated by intraperitoneal injection of carbon te...AIM To investigate the effect of metformin on activated hepatic stellate cells(HSCs) and the possible signaling pathways involved. METHODS A fibrotic mouse model was generated by intraperitoneal injection of carbon tetrachloride(CCl_4) and subsequent treatment with or without metformin. The level of fibrosis was detected by hematoxylin-eosin staining, Sirius Red staining, and immunohistochemistry. The HSC cell line LX-2 was used for in vitro studies. The effect of metformin on cell proliferation(CCK8 assay),motility(scratch test and Transwell assay), contraction(collagen gel contraction assay), extracellular matrix(ECM) secretion(Western blot), and angiogenesis(ELISA and tube formation assay) was investigated. We also analyzed the possible signaling pathways involved by Western blot analysis.RESULTS Mice developed marked liver fibrosis after intraperitoneal injection with CCl_4 for 6 wk. Metformin decreased the activation of HSCs, reduced the deposition of ECM, and inhibited angiogenesis in CCl_4-treated mice. Platelet-derived growth factor(PDGF) promoted the fibrogenic response of HSCs in vitro, while metformin inhibited the activation, proliferation, migration, and contraction of HSCs, and reduced the secretion of ECM. Metformin decreased the expression of vascular endothelial growth factor(VEGF) in HSCs through inhibition of hypoxia inducible factor(HIF)-1α in both PDGF-BB treatment and hypoxic conditions, and it down-regulated VEGF secretion by HSCs and inhibited HSC-based angiogenesis in hypoxic conditions in vitro. The inhibitory effects of metformin on activated HSCs were mediated by inhibiting the Akt/mammalian target of rapamycin(m TOR) and extracellular signal-regulated kinase(ERK) pathways via the activation of adenosine monophosphate-activated protein kinase(AMPK).CONCLUSION Metformin attenuates the fibrogenic response of HSCs in vivo and in vitro, and may therefore be useful for the treatment of chronic liver diseases.展开更多
Background The renoprotective mechanisms of adenosine monophosphate （AMP）-activated protein kinase （AMPK） agonist-metformin have not been stated clearly.We hypothesized that metformin may ameliorate inflammation v...Background The renoprotective mechanisms of adenosine monophosphate （AMP）-activated protein kinase （AMPK） agonist-metformin have not been stated clearly.We hypothesized that metformin may ameliorate inflammation via AMPK interaction with critical inflammatory cytokines The aim of this study was to observe the effects of metformin on expression of nuclear factor-κB （NF-κB）,monocyte chemoattractant protein-1 （MCP-1）,intercellular adhesion molecule-1 （ICAM-1） and transforming growth factor-beta 1 （TGF-β1） induced by high glucose （HG） in cultured rat glomerular mesangial cells （MCs）.Methods MCs were cultured in the medium with normal concentration glucose （group NG,5.6 mmol/L）,high concentration glucose （group HG,25 mmol/L） and different concentrations of metformin （group M1,M2,M3）.After 48-hour exposure,the supernatants and MCs were collected.The expression of NF-κB,MCP-1,ICAM-1,and TGF-β1 mRNA was analyzed by real time polymerase chain reaction.Westem blotting was used to detect the expression of AMPK,phospho-Thr-172 AMPK （p-AMPK）,NF-κB p65,MCP-1,ICAM-1,and TGF-β1 protein.Results After stimulated by HG,the expression of NF-κB,MCP-1,ICAM-1,TGF-β1 mRNA and protein of MCs in group HG increased significantly compared with group NG （P ＜0.05）.Both genes and protein expression of NF-κB,MCP-1,ICAM-1,TGF-β1 of MCs induced by high glucose were markedly reduced after metformin treatment in a dose-dependent manner （P ＜0.05）.The expression of p-AMPK increased with the rising of metformin concentration,presenting the opposite trend,while the level of total-AMPK protein was unchanged with exposure to HG or metformin.Conlusion Metformin can suppress the expression of NF-κB,MCP-1,ICAM-1 and TGF-β1 of glomerular MCs induced by high glucose via AMPK activation,which may partlv contribute to its reno-protection.展开更多
Background Metformin has become a cornerstone in the treatment of patients with type-2 diabetes. Accumulated evidence suggests that metformin supports direct cardiovascular effects. The present study aimed to investig...Background Metformin has become a cornerstone in the treatment of patients with type-2 diabetes. Accumulated evidence suggests that metformin supports direct cardiovascular effects. The present study aimed to investigate if metformin has beneficial effects on primary cardiomyocytes damaged by H2O2, and reveal the potential mechanism of action of metformin. Methods Cardiomyocytes were incubated in the presence of 100μmol/L H2O2 for 12 hours. Cardiomyocytes were pretreated with metformin at different concentrations and time and with aminoimidazole carboxamide ribonucleotide （AICAR） （500μmol/L）, an adenosine monophophate （AMP）-activated protein kinase （AMPK） agonist for 60 minutes before the addition of H2O2. Other cells were preincubated with compound C （an AMPK antagonist, 20μmol/L） for 4 hours. The viability and apoptosis of cells were analyzed. AMPK, endothelial nitric oxide synthase （eNOS）, and transforming growth factor （TGF）-β1 were analyzed using immunblotting. Results Metformin had antagonistic effects on the influences of H2O2 on cell viability and attenuated oxidative stress-induced apoptosis. Metformin also increased phosphorylation of AMPK and eNOS, and reduced the expression of TGF-β1, basic fibroblast growth factor （bFGF）, and tumor necrosis factor （TNF）-α. Conclusions Metformin has beneficial effects on cardiomyocytes, and this effect involves activation of the AMPK-eNOS pathway. Metformin may be potentially beneficial for the treatment of heart disease.展开更多
Background Non-alcoholic fatty liver disease （NAFLD） is a complex disorder and has been closely linked to obesity.The fat mass and obesity-associated （FTO） gene is a newly discovered gene related to obesity,which ...Background Non-alcoholic fatty liver disease （NAFLD） is a complex disorder and has been closely linked to obesity.The fat mass and obesity-associated （FTO） gene is a newly discovered gene related to obesity,which enhances oxidative stress and tipogenesis in NAFLD.The forkhead transcription factor O1 （FoxO1） is another important gene involved in NAFLD,which causes lipid disorders when insulin resistance appears in the liver.However,the interactions between FTO and FoxO1 during the pathogenesis of NAFLD have not been fully elucidated.This study was designed to identify the relationship between these two factors that are involved in the development of NAFLD.Methods This study includes two parts referred to as animal and cell experiments.Twelve female SPF C57BL/6 mice were fed a high-fat diet to serve as an NAFLD animal model.Aspartate aminotransferase （AST）,alanine aminotransferase （ALT）,total triglyceride （TG）,total cholesterol （TC）,alkaline phosphatase （ALP）,high-density lipoprotein （HDL）,and low-density lipoprotein （LDL） were measured.Immunohistochemical analysis was used to detect the expression and histological localization of FTO,FoxO1,and adenosine monophosphate （AMP）-activated protein kinase （AMPK）.The L02 cells were exposed to high fat for 24,48,or 72 hours.Oil red O staining was used to detect intracellular lipid droplets.Reverse transcription-polymerase chain reaction was used for analyzing the levels of FTO and FoxO1 mRNA.Results At the end of 10 weeks,ALP,ALT,AST,and LDL were significantly increased （P ＜0.01）,while TC and TG were also significantly higher （P ＜0.05）.In addition,HDL was significantly decreased （P ＜0.05）.The FTO and FoxO1 proteins were weakly expressed in the control group,but both FTO and FoxO1 were expressed significantly higher （P ＜0.01） in the experimental group,and the expression of the two factors was significantly correlated.AMPK in the high-fat group showed a low level of correlation with FTO,but not with FoxO1展开更多
目的探讨单磷酸腺苷活化蛋白激酶(adenosine monophosphate-activated protein kinase,AMPK)在低剂量二乙基亚硝胺(diethylnitrosamine,DEN)合并高脂饮食诱导的大鼠肝癌前病变发生中的作用及其机制。方法体内实验采用腹腔注射DEN(30 mg/...目的探讨单磷酸腺苷活化蛋白激酶(adenosine monophosphate-activated protein kinase,AMPK)在低剂量二乙基亚硝胺(diethylnitrosamine,DEN)合并高脂饮食诱导的大鼠肝癌前病变发生中的作用及其机制。方法体内实验采用腹腔注射DEN(30 mg/kg)合并高脂饮食饲喂大鼠16周诱导肝癌前病变模型,通过HE染色、Western blotting、Real-time PCR、免疫组织化学等方法观察谷胱甘肽S转移酶(glutathione S-transferase-π,GST-π)、固醇调节元件结合蛋白1c(sterol regulatory element binding protein-1c,SREBP-1c)、脂肪酸合成酶(fatty acid synthase,FAS)、乙酰辅酶A羧化酶(acetyl-Co A carboxylase,ACC)、硬脂酰辅酶A去饱和酶1(stearoyl-Co A desaturase 1,SCD1)及AMPK、p-AMPK的表达变化;体外实验观察AMPK对棕榈酸(palmitic acid,PA)诱导的大鼠H4IIE细胞脂质代谢的影响。结果与单纯DEN处理组比较,DEN+高脂组大鼠肝细胞脂肪变性、气球样变、伴有炎性细胞浸润及小灶性坏死;GST-π表达水平增高;三酰甘油(triglyceride,TG)及SREBP-1c、FAS、ACC、SCD1表达水平上升;p-AMPK水平下降。AMPK通过抑制SREBP-1c的表达水平降低棕榈酸诱导的H4IIE细胞内脂质合成。结论 AMPK可能通过抑制SREBP-1c的表达水平参与大鼠肝癌前病变的形成。展开更多
The adenosine monophosphate-activated protein kinase (AMPK) and p70 ribosomal S6 kinase-1 pathway may serve as a key signaling flow that regulates energy metabolism; thus, this pathway becomes an attractive target for...The adenosine monophosphate-activated protein kinase (AMPK) and p70 ribosomal S6 kinase-1 pathway may serve as a key signaling flow that regulates energy metabolism; thus, this pathway becomes an attractive target for the treatment of liver diseases that result from metabolic derangements. In addition, AMPK emerges as a kinase that controls the redox-state and mitochondrial function, whose activity may be modulated by antioxidants. A close link exists between fuel metabolism and mitochondrial biogenesis. The relationship between fuel metabolism and cell survival strongly implies the existence of a shared signaling network, by which hepatocytes respond to challenges of external stimuli. The AMPK pathway may belong to this network. A series of drugs and therapeutic candidates enable hepatocytes to protect mitochondria from radical stress and increase cell viability, which may be associated with the activation of AMPK, liver kinase B1, and other molecules or components. Consequently, the components downstream of AMPK may contribute to stabilizing mitochondrial membrane potential for hepatocyte survival. In this review, we discuss the role of the AMPK pathway in hepatic energy metabolism and hepatocyte viability. This information may help identify ways to prevent and/or treat hepatic diseases caused by the metabolic syndrome. Moreover, clinical drugs and experimental therapeutic candidates that directly or indirectly modulate the AMPK pathway in distinct manners are discussed here with particular emphasis on their effects on fuel metabolism and mitochondrial function.展开更多
基金Supported by National Natural Science Foundation of China,No.81370590
文摘AIM To investigate the effect of metformin on activated hepatic stellate cells(HSCs) and the possible signaling pathways involved. METHODS A fibrotic mouse model was generated by intraperitoneal injection of carbon tetrachloride(CCl_4) and subsequent treatment with or without metformin. The level of fibrosis was detected by hematoxylin-eosin staining, Sirius Red staining, and immunohistochemistry. The HSC cell line LX-2 was used for in vitro studies. The effect of metformin on cell proliferation(CCK8 assay),motility(scratch test and Transwell assay), contraction(collagen gel contraction assay), extracellular matrix(ECM) secretion(Western blot), and angiogenesis(ELISA and tube formation assay) was investigated. We also analyzed the possible signaling pathways involved by Western blot analysis.RESULTS Mice developed marked liver fibrosis after intraperitoneal injection with CCl_4 for 6 wk. Metformin decreased the activation of HSCs, reduced the deposition of ECM, and inhibited angiogenesis in CCl_4-treated mice. Platelet-derived growth factor(PDGF) promoted the fibrogenic response of HSCs in vitro, while metformin inhibited the activation, proliferation, migration, and contraction of HSCs, and reduced the secretion of ECM. Metformin decreased the expression of vascular endothelial growth factor(VEGF) in HSCs through inhibition of hypoxia inducible factor(HIF)-1α in both PDGF-BB treatment and hypoxic conditions, and it down-regulated VEGF secretion by HSCs and inhibited HSC-based angiogenesis in hypoxic conditions in vitro. The inhibitory effects of metformin on activated HSCs were mediated by inhibiting the Akt/mammalian target of rapamycin(m TOR) and extracellular signal-regulated kinase(ERK) pathways via the activation of adenosine monophosphate-activated protein kinase(AMPK).CONCLUSION Metformin attenuates the fibrogenic response of HSCs in vivo and in vitro, and may therefore be useful for the treatment of chronic liver diseases.
基金This work was supported by grants from the Natural Science Foundation （No. 11040606M 159） and Natural Science Research Project （No. K J2011A157） of Anhui Province, China.
文摘Background The renoprotective mechanisms of adenosine monophosphate （AMP）-activated protein kinase （AMPK） agonist-metformin have not been stated clearly.We hypothesized that metformin may ameliorate inflammation via AMPK interaction with critical inflammatory cytokines The aim of this study was to observe the effects of metformin on expression of nuclear factor-κB （NF-κB）,monocyte chemoattractant protein-1 （MCP-1）,intercellular adhesion molecule-1 （ICAM-1） and transforming growth factor-beta 1 （TGF-β1） induced by high glucose （HG） in cultured rat glomerular mesangial cells （MCs）.Methods MCs were cultured in the medium with normal concentration glucose （group NG,5.6 mmol/L）,high concentration glucose （group HG,25 mmol/L） and different concentrations of metformin （group M1,M2,M3）.After 48-hour exposure,the supernatants and MCs were collected.The expression of NF-κB,MCP-1,ICAM-1,and TGF-β1 mRNA was analyzed by real time polymerase chain reaction.Westem blotting was used to detect the expression of AMPK,phospho-Thr-172 AMPK （p-AMPK）,NF-κB p65,MCP-1,ICAM-1,and TGF-β1 protein.Results After stimulated by HG,the expression of NF-κB,MCP-1,ICAM-1,TGF-β1 mRNA and protein of MCs in group HG increased significantly compared with group NG （P ＜0.05）.Both genes and protein expression of NF-κB,MCP-1,ICAM-1,TGF-β1 of MCs induced by high glucose were markedly reduced after metformin treatment in a dose-dependent manner （P ＜0.05）.The expression of p-AMPK increased with the rising of metformin concentration,presenting the opposite trend,while the level of total-AMPK protein was unchanged with exposure to HG or metformin.Conlusion Metformin can suppress the expression of NF-κB,MCP-1,ICAM-1 and TGF-β1 of glomerular MCs induced by high glucose via AMPK activation,which may partlv contribute to its reno-protection.
文摘Background Metformin has become a cornerstone in the treatment of patients with type-2 diabetes. Accumulated evidence suggests that metformin supports direct cardiovascular effects. The present study aimed to investigate if metformin has beneficial effects on primary cardiomyocytes damaged by H2O2, and reveal the potential mechanism of action of metformin. Methods Cardiomyocytes were incubated in the presence of 100μmol/L H2O2 for 12 hours. Cardiomyocytes were pretreated with metformin at different concentrations and time and with aminoimidazole carboxamide ribonucleotide （AICAR） （500μmol/L）, an adenosine monophophate （AMP）-activated protein kinase （AMPK） agonist for 60 minutes before the addition of H2O2. Other cells were preincubated with compound C （an AMPK antagonist, 20μmol/L） for 4 hours. The viability and apoptosis of cells were analyzed. AMPK, endothelial nitric oxide synthase （eNOS）, and transforming growth factor （TGF）-β1 were analyzed using immunblotting. Results Metformin had antagonistic effects on the influences of H2O2 on cell viability and attenuated oxidative stress-induced apoptosis. Metformin also increased phosphorylation of AMPK and eNOS, and reduced the expression of TGF-β1, basic fibroblast growth factor （bFGF）, and tumor necrosis factor （TNF）-α. Conclusions Metformin has beneficial effects on cardiomyocytes, and this effect involves activation of the AMPK-eNOS pathway. Metformin may be potentially beneficial for the treatment of heart disease.
文摘Background Non-alcoholic fatty liver disease （NAFLD） is a complex disorder and has been closely linked to obesity.The fat mass and obesity-associated （FTO） gene is a newly discovered gene related to obesity,which enhances oxidative stress and tipogenesis in NAFLD.The forkhead transcription factor O1 （FoxO1） is another important gene involved in NAFLD,which causes lipid disorders when insulin resistance appears in the liver.However,the interactions between FTO and FoxO1 during the pathogenesis of NAFLD have not been fully elucidated.This study was designed to identify the relationship between these two factors that are involved in the development of NAFLD.Methods This study includes two parts referred to as animal and cell experiments.Twelve female SPF C57BL/6 mice were fed a high-fat diet to serve as an NAFLD animal model.Aspartate aminotransferase （AST）,alanine aminotransferase （ALT）,total triglyceride （TG）,total cholesterol （TC）,alkaline phosphatase （ALP）,high-density lipoprotein （HDL）,and low-density lipoprotein （LDL） were measured.Immunohistochemical analysis was used to detect the expression and histological localization of FTO,FoxO1,and adenosine monophosphate （AMP）-activated protein kinase （AMPK）.The L02 cells were exposed to high fat for 24,48,or 72 hours.Oil red O staining was used to detect intracellular lipid droplets.Reverse transcription-polymerase chain reaction was used for analyzing the levels of FTO and FoxO1 mRNA.Results At the end of 10 weeks,ALP,ALT,AST,and LDL were significantly increased （P ＜0.01）,while TC and TG were also significantly higher （P ＜0.05）.In addition,HDL was significantly decreased （P ＜0.05）.The FTO and FoxO1 proteins were weakly expressed in the control group,but both FTO and FoxO1 were expressed significantly higher （P ＜0.01） in the experimental group,and the expression of the two factors was significantly correlated.AMPK in the high-fat group showed a low level of correlation with FTO,but not with FoxO1
基金Supported by The National Research Foundation of Korea Grant,Funded by the Korea Government(MEST),No.2010-0001706,South Korea
文摘The adenosine monophosphate-activated protein kinase (AMPK) and p70 ribosomal S6 kinase-1 pathway may serve as a key signaling flow that regulates energy metabolism; thus, this pathway becomes an attractive target for the treatment of liver diseases that result from metabolic derangements. In addition, AMPK emerges as a kinase that controls the redox-state and mitochondrial function, whose activity may be modulated by antioxidants. A close link exists between fuel metabolism and mitochondrial biogenesis. The relationship between fuel metabolism and cell survival strongly implies the existence of a shared signaling network, by which hepatocytes respond to challenges of external stimuli. The AMPK pathway may belong to this network. A series of drugs and therapeutic candidates enable hepatocytes to protect mitochondria from radical stress and increase cell viability, which may be associated with the activation of AMPK, liver kinase B1, and other molecules or components. Consequently, the components downstream of AMPK may contribute to stabilizing mitochondrial membrane potential for hepatocyte survival. In this review, we discuss the role of the AMPK pathway in hepatic energy metabolism and hepatocyte viability. This information may help identify ways to prevent and/or treat hepatic diseases caused by the metabolic syndrome. Moreover, clinical drugs and experimental therapeutic candidates that directly or indirectly modulate the AMPK pathway in distinct manners are discussed here with particular emphasis on their effects on fuel metabolism and mitochondrial function.
