Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.10.1 (ERK)
95,504 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Metformin (1,1-dimethylbiguanide; MET) is used in the treatment of type 2 diabetes mellitus. MET's antihyperglycemic action depends at least in part on its inhibitory effect on hepatic gluconeogenesis. As to gluconeogenesis from amino acids (e.g. L-alanine), this is associated with an inhibition of L-alanine uptake into hepatocytes. Since this uptake is mediated by an electrogenic transport mechanism, the aim of the present study was to investigate whether MET has an influence on the liver cell membrane potential which might explain its inhibitory effect on L-alanine uptake. The experiments were performed in vivo in anesthetized rats and in vitro using superfused mouse liver slices with the conventional microelectrode technique. In vivo, MET (160 mg/kg intraperitoneally (i.p.)) significantly depolarized (dV) the liver cell membrane by 6 mV. MET (1 mmol/l) also depolarized the liver cell membrane in vitro (e.g. 15 min after start of superfusion: dV=8 mV). MET's effect was at least partly reversible. Glucagon (10(-7) mol/l), which hyperpolarized the liver cell membrane, abolished MET's effect. Further, the MET-induced depolarization was completely absent during superfusion with low Cl(-) ([Cl(-)]=27 mmol/l) medium, and significantly attenuated by the Cl(-) channel blocker NPPB (25 micromol/l). While MET's effect was only somewhat attenuated by blockade of the Na(+)/K(+)/2Cl(-) cotransporter or by superfusion with (HCO(-)(3)-free) HEPES buffer, the carboanhydrase blocker acetazolamide (1 mmol/l) or blockade of the HCO(-)(3)/Cl(-) exchanger by DIDS (100 micromol/l), which, however, also blocks Cl(-) channels, abolished its effect. The depolarization of the liver cell membrane by MET was unaffected by a blockade of K(+) channels with Ba(2+), a blockade of the Na(+)/K(+) pump or superfusion with low Na(+) medium ([Na(+)]=26 mmol/l). According to these results, the MET-induced depolarization of the liver cell membrane could be due to an activation of the Cl(-)/HCO(-)(3) exchanger and thus depend on intracellular HCO(-)(3) formation. This activation could then lead to a disturbance of the equilibrium between intra- and extracellular Cl(-) and therefore to an enhanced Cl(-) efflux via Cl(-) channels. It is plausible that the depolarizing effect induced by MET is associated with its inhibitory effect on gluconeogenesis by inhibiting uptake of L-alanine and other amino acids into hepatocytes.
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PMID:Depolarization of the liver cell membrane by metformin. 1147 89

1 Metformin lowers blood glucose levels in type 2 diabetic patients. To evaluate the insulin sensitizing action of metformin on skeletal muscle cells, we have used C2C12 skeletal muscle cells differentiated in chronic presence or absence of insulin. 2 Metformin was added during the last 24 h of differentiation of the C2C12 myotubes. Insulin-stimulated tyrosine phosphorylation of insulin receptor (IR) and insulin receptor substrate-1 (IRS-1) was determined. 3 Chronic insulin treatment resulted in 60 and 40% reduction in insulin-stimulated tyrosine phosphorylation of IR and IRS-1, respectively. Treatment with metformin was able to increase the tyrosine phosphorylation of IR and IRS-1 by 100 and 90% respectively. 4 Chronic insulin treatment drastically reduced (45%) insulin-stimulated phosphatidyl inositol 3-kinase (PI 3-kinase) activity. Metformin treatment restored PI 3-kinase activity in insulin-resistant myotubes. 5 Insulin-stimulated glucose uptake was impaired in chronically insulin-treated myotubes. Metformin increased basal glucose uptake to significant levels (P<0.05), but metformin did not increase insulin-stimulated glucose transport. 6 All the three mitogen-activated protein kinases (MAPK) were activated by insulin in sensitive myotubes. The activation of p38 MAPK was impaired in resistant myotubes, while ERK and JNK were unaffected. Treatment with metformin enhanced the basal activation levels of p38 in both sensitive and resistant myotubes, but insulin did not further stimulate p38 activation in metformin treated cells. 7 Treatment of cells with p38 inhibitor, SB203580, blocked insulin- and metformin-stimulated glucose uptake as well as p38 activation. 8 Since the effect of metformin on glucose uptake corresponded to p38 MAPK activation, this suggests the potential role p38 in glucose uptake. 9 These data demonstrate the direct insulin sensitizing action of metformin on skeletal muscle cells.
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PMID:Metformin enhances insulin signalling in insulin-dependent and-independent pathways in insulin resistant muscle cells. 1223 52

Beyond its antidiabetic activity justifying its use in the treatment of the type 2 diabetes, metformin (MET [dimethylguanidine, Glucophage]) has been shown to exhibit antioxidant properties in vitro, which could contribute to limit the deleterious vascular complications of diabetes. We investigated whether MET, at the pharmacological level of 10 -5 mol/L, was able to modulate intracellular production of reactive oxygen species (ROS) both in quiescent bovine aortic endothelial cells (BAECs) and in BAECs stimulated by a short incubation with high levels of glucose (30 mmol/L, 2 hours) or angiotensin II (10 -7 mol/L, 1 hour). Intracellular ROS production was measured by fluorescence of the DCF (2,7-dichlorodihydrofluorescein) probe. Our results showed that MET was able to reduce the intracellular production of ROS in both nonstimulated BAECs (-20%, P < .05) and BAEC stimulated by high levels of glucose or angiotensin II (-28% and -72%, respectively, P < .01). Experiments performed in the presence of the nicotinamide adenine dinucleotide phosphate [NAD(P)H] oxidase inhibitor apocynin or the respiratory mitochondrial chain inhibitor rotenone indicated that MET exerted its effect partly through an inhibition of the formation of ROS produced mainly by NAD(P)H oxidase and also, to a lesser extent, by the respiratory mitochondrial chain.
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PMID:Metformin decreases intracellular production of reactive oxygen species in aortic endothelial cells. 1593 22

The aim of this study was to evaluate the comparative effects of rosiglitazone and metformin on metabolic parameters in recently diagnosed type 2 Greek diabetic patients. A total of 41 drug-naive individuals, with recently diagnosed type 2 diabetes, were randomized in 3 groups: DIET, diet alone; ROSI, diet plus rosiglitazone; and MET, diet plus metformin. Anthropometric indexes, blood pressure, hematological and biochemical parameters were estimated at baseline and after 18 weeks of treatment. We observed a significant decrease of fasting glucose (FBG) (p<0.001), glycated haemoglobin (HbA1c) (ROSI: p=0.001, MET: p<0.001), homeostasis model assessment for insulin resistance (HOMA-IR) (ROSI: p=0.006, MET: p =0.009) and glutamic pyruvic transaminase (SGPT) (ROSI: p=0.004, MET: p=0.003) in both ROSI and MET groups. Metformin significantly reduced fasting insulin (p=0.04), body weight (p=0.026), body mass index (BMI) (p=0.022), waist circumference (p=0.022) and gamma glutamyl transpeptidase (gamma-GT) (p=0.039), while rosiglitazone decreased blood pressure (systolic: p = 0.05, mean: p = 0.03) and alkaline phosphatase (ALP) (p =0.001) compared to baseline values. Combined intervention with rosiglitazone and diet led to a slight, not significant, weight loss. Rosiglitazone and metformin are equaly effective in controling diabetes, decreasing insulin resistance and improving liver function. However, considering the more favorable effects of metformin on body composition and its documented cost-effectiveness, it seems to be preferable in newly diagnosed Greek diabetic patients.
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PMID:Metabolic effects of rosiglitazone and metformin in Greek patients with recently diagnosed type 2 diabetes. 1821 Jul 65

The exposure-response properties of metformin were characterized in 12 subjects with type 2 diabetes mellitus. The time course of drug concentration and effects on fasting plasma glucose and lactic acid concentrations were used from a study in which subjects received 500 mg of metformin twice daily for 5 days followed by 850 mg twice daily for 5 days. Pharmacokinetic sampling included morning trough concentrations obtained on days 7 to 9 and rich sampling (15 time points) on day 10. Fasting plasma glucose and lactic acid concentrations were measured on days 0 to 10 and served as biomarkers of therapeutic effect and tolerability, respectively. A population pharmacokinetic/pharmacodynamic analysis was conducted using nonlinear mixed effects modeling. Metformin pharmacokinetics were described using a 1-compartment model with first-order absorption. Population mean estimates (relative standard error [RSE]) of clearance (CL/F) and volume of distribution were 79.0 L.h(-1) (6.8%) and 648 L (13.8%), respectively. Covariate analyses revealed that creatinine clearance (CL(CR)) significantly influenced metformin CL/F [CL/F = 79.0.(CL(CR)/80)(0.822)]. An indirect response model was applied to describe the antihyperglycemic effect of metformin. Population mean estimates (RSE) of baseline fasting plasma glucose and the drug concentration producing half-maximal effect were 241 mg.dL(-1) (4.6%) and 4.23 mg.L(-1) (31.0%). An empirical linear model was used to describe a slight progressive increase in fasting lactic acid during metformin treatment with an estimated slope coefficient (RSE) of 0.0005 mM.mL.ng(-1) (38.1%). Model evaluation by predictive check and nonparametric bootstrap analysis suggested that the proposed model is robust, and parameter values were estimated with good precision. Simulations suggested that the clinical utility of metformin was maintained over the dose range evaluated with respect to fasting plasma glucose and lactic acid response.
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PMID:Population exposure-response modeling of metformin in patients with type 2 diabetes mellitus. 1837 28

Population studies have revealed that treatment with the antidiabetic drug metformin significantly associates with reduced breast cancer risk. Animal studies have shown that metformin suppresses the development of mammary carcinomas in transgenic female mice carrying a HER2 oncogene, but not that of spontaneous tumors. We herein demonstrate that HER2 oncoprotein itself may represent a key cellular target involved in the anti-breast cancer actions of metformin. First, ectopical overexpression of HER2 oncogene significantly enhances metformin-induced breast cancer cell growth inhibition. Second, metformin treatment drastically downregulates HER2 protein levels (up to 85% reduction) in a dose- and time-dependent manner. Metformin-induced inhibition of HER2 take places regardless the molecular mechanism contributing to HER2 overexpression (i.e., human HER2 cDNA exogenously driven by a viral promoter and naturally occurring endogenous HER2 gene amplification). Mechanistically, metformin-induced suppression of HER2 overexpression appears to occur via direct (AMPK-independent) inhibition of p70S6K1 activity. Compound C- and small interference RNA (siRNA)-induced blockade of AMPK activity/expression fail to prevent the anti-HER2 effect of metformin while AMPK hyperactivation following exposure to the AMP analog AICAR is not sufficient to downregulate HER2 expression. HER2-positive breast cancer cells transfected with p70S6K1 siRNA become completely refractory to metformin-induced HER2 suppression. Of note, co-incubation with agents that block reactive oxygen species (ROS) production (e.g., N-acetylcysteine) dramatically enhanced the ability of metformin to decrease HER2 expression. From the perspective of chemoprevention, these findings altogether suggest that metformin might exert a protective mostly confined to the HER2-positive breast cancer subtype. From the perspective of intervention, the presence/absence of molecular hallmarks such as HER2 overexpression and/or p70S6K1 hyperactivation might dictate alternative responses in metformin-based treatment of early breast cancer. The importance of mTOR/p70S6K1-sensed ROS status at mediating the anti-oncogenic effects of metformin might represent a previously unrecognized linkage molecularly connecting its anti-aging and anti-cancer actions.
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PMID:The antidiabetic drug metformin suppresses HER2 (erbB-2) oncoprotein overexpression via inhibition of the mTOR effector p70S6K1 in human breast carcinoma cells. 1910 26

Metformin treatment, now widely prescribed in polycystic ovary syndrome, is aimed at correcting the associated insulin resistance, but it has also been shown to directly inhibit ovarian steroidogenesis. The mechanisms, however, by which metformin inhibits estradiol production in human granulosa cells remains unknown. Granulosa luteal cells were incubated with metformin, insulin, or combined metformin and insulin treatment, and aromatase mRNA expression was quantified using real-time RT-PCR. Enzyme activity was assessed by the conversion of (3)H-androstenedione to estrone and estradiol. Metformin's effect on the expression of specific untranslated first exon aromatase promoters was analyzed using semiquantitative PCR. The involvement of MAPK kinase (MEK)/ERK pathway was investigated by immunoblotting for aromatase, phosphorylated, and total ERK-1,2 from cells cultured as above with/without the MEK inhibitor PD98059. Metformin significantly inhibited basal and insulin-stimulated aromatase mRNA expression, with parallel results from the aromatase activity assay and protein assessment. This suppression was via down-regulation of aromatase promoter II, I.3, and 1.4 expression and was reversed by the addition of PD98059. Involvement of the ERK signaling pathway was demonstrated by the significant increase in phosphorylated ERK-1,2 with the combined metformin and insulin treatment. We have shown for the first time in human granulosa cells that metformin signficantly attenuated basal and insulin-stimulated P450 aromatase mRNA expression and activity, via silencing of key promoters. This occurred by activation of MEK/ERK pathway, which negatively regulated aromatase production. This is an important consideration given metformin's widespread use in polycystic ovary syndrome and may further support a possible therapeutic indication in estrogen-dependent breast tumors.
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PMID:Metformin inhibits aromatase via an extracellular signal-regulated kinase-mediated pathway. 1957 98

Population studies have shown that treatment with the antidiabetic biguanide metformin significantly reduced cancer risk. In our animal studies, metformin delayed the onset of mammary adenocarcinoma (MAC) in transgenic HER-2/neu mice but not the onset of spontaneous mammary tumors in female SHR mice. Pineal hormone also inhibits mammary carcinoma development in HER2/neu transgenic mice as well as in female SHR mice. Here we demonstrated that a combination of metformin and melatonin significantly inhibits growth of transplanted tumors in mice. Metformin (0.5 mg/ml in drinking water) increased mean life span by 8% and MAC latency by 13.2% (p < 0.05) in HER2/neu mice. The treatment with melatonin alone (2 mg/L in drinking water during the night time) or combined treatment with metformin (0.5 mg/ ml in drinking water during the day time) + melatonin (2 mg/L in drinking water during the night time) did not influence mammary carcinogenesis in the mice. The treatment metformin alone inhibited the growth of transplantable HER2 mammary carcinoma in FVB/N male mice by 46% at the 45(th) day after transplantation (p < 0.001). The combined treatment with metformin + melatonin significantly suppressed Ehrlich tumor growth (by 40%, p < 0.001). These results suggest that metformin may be useful in prevention and treatment of breast cancer.
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PMID:Metformin extends life span of HER-2/neu transgenic mice and in combination with melatonin inhibits growth of transplantable tumors in vivo. 2001 87

The relationship between obesity, metabolic syndrome, diabetes and cancer has been recognized for many years. Multiple studies conducted in the last 20 years have identified molecular mechanisms responsible for this phenomenon. Elucidation of the important role of insulin, IGF receptor, mTOR and AMP-activated protein kinase in breast cancer biology has led to the development and subsequent clinical evaluation of novel targeted therapies, including IGF-1 receptor-specific antibodies or tyrosine kinase inhibitors and inhibitors of mTOR. There is also a growing interest in the use of metformin, which has been shown to possess antitumor activity resulting from activation of AMP-activated protein kinase and subsequent inhibiton of mTOR, as well as from decreased circulating insulin levels. Metformin has been shown to inhibit proliferation, invasion and angiogenesis of neoplastic cells and to overcome resistance of breast cancer to chemotherapy, hormonal therapy and HER2 inhibition. Recently, metformin has been demonstrated to inhibit breast cancer stem cell growth and to synergize with chemotherapy in suppression of tumor growth and prolongation of survival of breast tumor-bearing animals. Several currently ongoing Phase II and III clinical studies are evaluating the therapeutic efficacy of metformin in the treatment of early and advanced breast cancer patients.
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PMID:Obesity, hyperinsulinemia and breast cancer: novel targets and a novel role for metformin. 2046 5

Vascular endothelial dysfunction is an early marker of atherosclerosis seen in type 2 diabetes (T2DM). Circulating endothelial progenitor cell (EPC) is involved in the neovasculogenesis and maintenance of vascular homeostasis, whose impairment may have an important role in the pathogenesis of diabetic vasculopathy. This study was performed to investigate the relationship between vascular endothelial function and circulating EPC number in T2DM. A total of 46 newly diagnosed T2DM patients (DM group) and 51 healthy subjects (NG group) were recruited. Metformin was administered to all patients for 16 weeks. Endothelial function was assessed by flow-mediated brachial artery dilatation (FMD). EPC was defined by CD45( low)/CD34(+)/VEGFR2(+) and quantified by flow cytometry. The EPC number in the DM group was significantly lower than that in the NG group (p < 0.001), and improved markedly after treatment (p < 0.001). The results of FMD were consistent with EPC variations among the three groups (p < 0.001). In multivariate regression analysis, the EPC number was an independent risk factor for FMD at baseline (p < 0.05). The absolute changes of EPC number showed significant correlation with the changes of FMD before and after treatment (r = 0.63, p < 0.001). This study demonstrated that the circulating EPC number was related to endothelial function and could be considered as a surrogate biological marker of endothelial function for T2DM.
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PMID:Number of circulating endothelial progenitor cells as a marker of vascular endothelial function for type 2 diabetes. 2051 Dec 92


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