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:2.7.11.31 (AMP-activated protein kinase)
13,065 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Exercise increases glucose transport into skeletal muscle via a pathway that is poorly understood. We investigated the role of endogenously produced reactive oxygen species (ROS) in contraction-mediated glucose transport. Repeated contractions increased 2-deoxyglucose (2-DG) uptake roughly threefold in isolated, mouse extensor digitorum longus (fast-twitch) muscle. N-Acetylcysteine (NAC), a non-specific antioxidant, inhibited contraction-mediated 2-DG uptake by approximately 50% (P < 0.05 versus control values), but did not significantly affect basal 2-DG uptake or the uptake induced by insulin, hypoxia or 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR, which mimics AMP-mediated activation of AMP-activated protein kinase, AMPK). Ebselen, a glutathione peroxidase mimetic, also inhibited contraction-mediated 2-DG uptake (by almost 60%, P < 0.001 versus control values). Muscles from mice overexpressing Mn2+-dependent superoxide dismutase, which catalyses H2O2 production from superoxide anions, exhibited a approximately 25% higher rate of contraction-mediated 2-DG uptake versus muscles from wild-type control mice (P < 0.05). Exogenous H2O2 induced oxidative stress, as judged by an increase in the [GSSG]/[GSH + GSSG] (reduced glutathione + oxidized glutathione) ratio to 2.5 times control values, and this increase was substantially blocked by NAC. Similarly, NAC significantly attenuated contraction-mediated oxidative stress as judged by measurements of glutathione status and the intracellular ROS level with the fluorescent indicator 5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein (P < 0.05). Finally, contraction increased AMPK activity and phosphorylation approximately 10-fold, and NAC blocked approximately 50% of these changes. These data indicate that endogenously produced ROS, possibly H2O2 or its derivatives, play an important role in contraction-mediated activation of glucose transport in fast-twitch muscle.
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PMID:Role of reactive oxygen species in contraction-mediated glucose transport in mouse skeletal muscle. 1680 55

AMP-activated protein kinase influences cellular metabolism, glucose-regulated gene expression, and insulin secretion of pancreatic beta cells. Its sustained activation by culture at low glucose concentrations or in the presence of 5-aminoimidazole-4-carboxamide riboside (AICAR) was shown to trigger apoptosis in beta cells. This study shows that both low glucose- and AICAR-induced apoptosis are associated with increased formation of mitochondrial superoxide-derived radicals and decreased mitochondrial activity. Mitochondrial dysfunction was reflected by an increased oxidized state of the mitochondrial flavins (FMN/FAD) but not of NAD(P)H. It was accompanied by suppression of glucose oxidation and glucose-induced insulin secretion, while palmitate oxidation appeared unaffected. When the cellular accumulation of superoxide-derived radicals was quenched by the ROS scavengers vitamin E, N-acetylcysteine, or the SOD-mimetic compound MnTBAP, apoptosis was significantly inhibited. Both low glucose and AICAR also elevated the expression of BH3-domain-only Bcl-2 antagonists, and induced caspase-3 activation, causing caspase-dependent truncation of Bcl-2. Overexpression of recombinant human Bcl-2 prevented caspase-3 activation, endogenous Bcl-2 processing, and apoptosis, but did not attenuate oxygen radical formation, AMPK activation, or JNK phosphorylation. We conclude that apoptosis by prolonged AMPK activation in beta cells results from enhanced production of mitochondria-derived oxygen radicals and onset of the intrinsic mitochondrial apoptosis pathway, followed by caspase activation and Bcl-2 cleavage which may amplify the death signal.
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PMID:Increased oxygen radical formation and mitochondrial dysfunction mediate beta cell apoptosis under conditions of AMP-activated protein kinase stimulation. 1715 94

In aerobic conditions, the heart preferentially oxidizes fatty acids. However, during metabolic stress, glucose becomes the major energy source, and enhanced glucose uptake has a protective effect on heart function and cardiomyocyte survival. Thus abnormal regulation of glucose uptake may contribute to the development of cardiac disease in diabetics. Ketone bodies are often elevated in poorly controlled diabetics and are associated with increased cellular oxidative stress. Thus we sought to determine the effect of the ketone body beta-hydroxybutyrate (OHB) on cardiac glucose uptake during metabolic stress. We used 2,4-dinitrophenol (DNP), an uncoupler of the mitochondrial oxidative chain, to mimic hypoxia in cardiomyocytes. Our data demonstrated that chronic exposure to OHB provoked a concentration-dependent decrease of DNP action, resulting in 56% inhibition of DNP-mediated glucose uptake at 5 mM OHB. This was paralleled by a diminution of DNP-mediated AMP-activated protein kinase (AMPK) and p38 MAPK phosphorylation. Chronic exposure to OHB also increased reactive oxygen species (ROS) production by 1.9-fold compared with control cells. To further understand the role of ROS in OHB action, cardiomyocytes were incubated with H(2)O(2). Our results demonstrated that this treatment diminished DNP-induced glucose uptake without altering activation of the AMPK/p38 MAPK signaling pathway. Incubation with the antioxidant N-acetylcysteine partially restored DNP-mediated glucose but not AMPK/p38 MAPK activation. In conclusion, these results suggest that ketone bodies, through inhibition of the AMPK/p38 MAPK signaling pathway and ROS overproduction, regulate DNP action and thus cardiac glucose uptake. Altered glucose uptake in hyperketonemic states during metabolic stress may contribute to diabetic cardiomyopathy.
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PMID:Ketone bodies alter dinitrophenol-induced glucose uptake through AMPK inhibition and oxidative stress generation in adult cardiomyocytes. 1722 64

This study investigated the effect of N-acetylcysteine on plasma adiponectin, renal adiponectin receptors, lipid metabolism and oxidative stress in streptozotocin-induced diabetic rats. Metabolic parameters, plasma adiponectin level, renal protein expression of adiponectin receptors were analyzed in controls and diabetic rats treated with or without N-acetylcysteine in drinking water for 8 weeks. Plasma lipid, creatinine and free 5-F(2t)-isoprostane levels, urine protein excretion rate, mesangial matrix expansion index, and protein expression of renal connective tissue growth factor (CTGF) were increased in diabetic rats. The decreased plasma adiponectin levels and renal protein expression of adiponectin receptor 1 were accompanied by the decreased renal phosphorylation of adenosine monophosphate (AMP)-activated protein kinase (AMPK)-alpha (Thr172) and protein expression of phospho-acetyl coenzyme A carboxylase (ACC) (Ser79) which led to the increased renal triglyceride levels in diabetic rats. There was no difference in the protein expression of renal adiponectin receptor 2 between control and diabetic rats. N-acetylcysteine treatment attenuated the increased oxidative stress, plasma and renal lipids, urine protein excretion rate, mesangial matrix expansion index, and protein expression of renal CTGF, but did not affect plasma adiponectin levels, renal protein expression of adiponectin receptor 1, phosphorylation of AMPK-alpha (Thr172) and renal protein expression of phospho-ACC (Ser79) in diabetic rats. These results suggested that the decreased plasma adiponectin and renal adiponectin receptor 1 result in the increased renal triglyceride that stimulates renal CTGF expression leading to the renal hypertrophy and the deteriorated renal function in the diabetic rats. N-acetylcysteine treatment attenuates the increased oxidative stress, but has no effect on the decreased plasma adiponectin and renal adiponectin receptor 1 in diabetic rats, indicating that oxidative stress may not contribute to the decreased plasma adiponectin and renal adiponectin receptor 1 protein expression in diabetic rats.
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PMID:Effect of N-acetylcysteine on plasma adiponectin and renal adiponectin receptors in streptozotocin-induced diabetic rats. 1727 Jan 71

Recent studies suggest that the AMP-activated protein kinase (AMPK) acts as a major energy sensor and regulator in adipose tissues. The objective of this study was to investigate the role of AMPK in nicotine-induced lipogenesis and lipolysis in 3T3L1 adipocytes. Exposure of 3T3L1 adipocytes to smoking-related concentrations of nicotine increased lipolysis and inhibited fatty acid synthase (FAS) activity in a time- and dose-dependent manner. The effects of nicotine on FAS activity were accompanied by phosphorylation of both AMPK (Thr(172)) and acetyl-CoA carboxylase (ACC; Ser(79)). Nicotine-induced AMPK phosphorylation appeared to be mediated by reactive oxygen species based on the finding that nicotine significantly increased superoxide anions and 3-nitrotyrosine-positive proteins, exogenous peroxynitrite (ONOO(-)) mimicked the effects of nicotine on AMPK, and N-acetylcysteine (NAC) abolished nicotine-enhanced AMPK phosphorylation. Inhibition of AMPK using either pharmacologic (insulin, compound C) or genetic means (overexpression of dominant negative AMPK; AMPK-DN) abolished FAS inhibition induced by nicotine or ONOO(-). Conversely, activation of AMPK by pharmacologic (nicotine, ONOO(-), metformin, and AICAR) or genetic (overexpression of constitutively active AMPK) means inhibited FAS activity. Notably, AMPK activation increased threonine phosphorylation of FAS, and this effect was blocked by adenovirus encoding dominant negative AMPK. Finally, AMPK-dependent FAS phosphorylation was confirmed by (32)P incorporation into FAS in adipocytes. Taken together, our results strongly suggest that nicotine, via ONOO(-) activates AMPK, resulting in enhanced threonine phosphorylation and consequent inhibition of FAS.
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PMID:Nicotine-induced activation of AMP-activated protein kinase inhibits fatty acid synthase in 3T3L1 adipocytes: a role for oxidant stress. 3192 73

Reactive oxygen species (ROS) play an important role in cellular function via the activation of signaling cascades. ROS have been shown to affect mitochondrial biogenesis, morphology, and function. Their beneficial effects are likely mediated via the upregulation of transcriptional regulators such as peroxisome proliferator-activated receptor-gamma coactivator-1 protein-alpha (PGC-1alpha). However, the ROS signals that regulate PGC-1alpha transcription in skeletal muscle are not understood. Here we examined the effect of H2O2 on the regulation of PGC-1alpha expression, and its relationship to AMPK activation. We demonstrate that 24 h of exogenous H2O2 treatment increased PGC-1alpha promoter activity and mRNA expression. Both effects were blocked with the addition of N-acetylcysteine, a ROS scavenger. These effects were mediated, in part, via upstream stimulatory factor-1/Ebox DNA binding and involved 1) interactions with downstream sequences and 2) the activation of AMPK. Elevated ROS led to the activation of AMPK, likely via a decline in ATP levels. The activation of AMPK using 5-aminoimidazole-4-carboxamide-1-beta-d-ribofuranoside increased PGC-1alpha promoter activity and mRNA levels but reduced ROS production. Thus the net effect of AMPK activation on PGC-1alpha expression was a result of increased transcriptional activation, counterbalanced by reduced ROS production. The effects of H2O2 on PGC-1alpha expression differed depending on the level of ROS within the cell. Low levels of ROS result in reduced PGC-1alpha mRNA in the absence of an effect on PGC-1alpha promoter activation. In contrast, elevated levels of H2O2 induce PGC-1alpha transcription indirectly, via AMPK activation. These data identify unique interactions between ROS and AMPK activation on the expression of PGC-1alpha in muscle cells.
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PMID:Interactions between ROS and AMP kinase activity in the regulation of PGC-1alpha transcription in skeletal muscle cells. 1900 63

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

Dopamine at 100-500 microM has toxic effects on human SH-SY5Y neuroblastoma cells, manifested as apoptotic cell loss and strong autophagy. The molecular mechanisms and types of dopamine-induced cell death are not yet well known. Their identification is important in the study of neurodegenerative diseases that specifically involve dopaminergic neurons. We looked for changes in expression and content of proteins involved in apoptosis and autophagy after dopamine treatment. All the changes found were prevented by avoiding dopamine oxidation with N-acetylcysteine, indicating a key role for the products of dopamine oxidation in dopamine toxicity. As early as 1-2h after treatment we found an increase in hypoxia-inducible factor-1alpha (HIF-1alpha) and an accumulation of ubiquitinated proteins. Proteins regulated by HIF-1alpha and involved in apoptosis and/or autophagy, such as p53, Puma and Bnip3, were subsequently increased. However, apoptotic parameters (caspase-3, caspase-7, PARP) were only activated after 12h of 500muM dopamine treatment. Autophagy, monitored by the LC3-II increase after LC3-I linkage to autophagic vacuoles, was evident after 6h of treatment with both 100 and 500 microM dopamine. The mTOR pathway was inhibited by dopamine, probably due to the intracellular redox changes and energy depletion leading to AMPK activation. However, this mechanism is not sufficient to explain the high LC3-II activation caused by dopamine: the LC3-II increase was not reversed by IGF-1, which prevented this effect when caused by the mTOR inhibitor rapamycin. Our results suggest that the aggregation of ubiquitinated non-degraded proteins may be the main cause of LC3-II activation and autophagy. As we have reported previously, cytosolic dopamine may cause damage by autophagy in neuroblastoma cells (and presumably in dopaminergic neurons), which develops to apoptosis and leads to cell degeneration.
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PMID:Effects of dopamine on LC3-II activation as a marker of autophagy in a neuroblastoma cell model. 1941 Jun 1

5-[5-(2-Nitrophenyl) furfuryliodine]-1,3-diphenyl-2-thiobarbituric acid (UCF-101) is a protease inhibitor which was reported to protect against ischaemic heart damage and apoptosis. This study evaluated the impact of UCF-101 on steptozotocin (STZ)-induced diabetic cardiomyocyte dysfunction. Adult FVB mice were made diabetic with a single injection of STZ (200 mg kg(1)). Two weeks after STZ injection, cardiomyocytes from control and STZ-treated mice were isolated and treated with UCF-101 (20 mum for 1 h). Cardiomyocyte contractile properties were analysed, including peak shortening (PS), maximal velocity of shortening/relengthening (+/-dL/dt), time to PS (TPS) and time to 90% relengthening (TR(90)). Steptozotocin-induced diabetes depressed PS and +/-dL/dt and prolonged TPS and TR(90) in cardiomyocytes, all of which were significantly alleviated by UCF-101. Immunoblotting analysis showed that UCF-101 significantly alleviated STZ-induced loss of phospholamban phosphorylation without affecting sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA2a) and phospholamban. Steptozotocin reduced AMP-activated protein kinase (AMPK) phosphorylation at Thr172 of the catalytic subunit without affecting total AMPK expression, which was restored by UCF-101. Short-term exposure to UCF-101 did not change the expression of X-linked inhibitor of apoptosis protein (XIAP) and Omi stress-regulated endoprotease, high temperature requirement protein A2 (Omi/HtrA2), favouring an apoptosis-independent mechanism. Both the AMPK activator resveratrol and the antioxidant N-acetylcysteine mimicked the UCF-101-induced beneficial effect in STZ-induced diabetic cardiomyocytes. In addition, UCF-101 promoted the phosphorylation of p38 mitogen-activated protein kinases and c-Jun N-terminal kinase (JNK) after 15 min of incubation, while it failed to affect the phosphorylation of extracellular signal-regulated kinase (ERK) and glycogen synthase kinase-3beta (GSK-3beta) within 120 min in H9C2 myoblasts. Taken together, these results indicate that UCF-101 protects against STZ-induced cardiomyocyte contractile dysfunction, possibly via an AMPK-associated mechanism.
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PMID:The protease inhibitor UCF-101 ameliorates streptozotocin-induced mouse cardiomyocyte contractile dysfunction in vitro: role of AMP-activated protein kinase. 2751 Jun 42

Oxidative stress-induced cerebral endothelial cell dysfunction is associated with cerebral microvascular complication of primary diabetic encephaolopathy, a neurodegenerative disorder of long-standing diabetes, but the injury mechanisms are poorly understood. This study sought to determine the contribution of carbonyl (methylglyoxal, MG) stress to human brain endothelial cell (IHEC) apoptosis, the relationship to cellular redox status and mitochondrial membrane potential, and the protection by thiol antioxidant and insulin sensitizers. MG exposure induced IHEC apoptosis in association with perturbed cellular glutathione (GSH) redox status, decreased mitochondrial membrane potential (Deltapsi(m)), activation of caspase-9 and -3, and cleavage of polyADP-ribose polymerase. Insulin sensitizers such as biguanides or AMP-activated protein kinase activator, but not glitazones, afforded cytoprotection through preventing (Deltapsi(m) collapse and activation of caspase-9 that was independent of cellular GSH. Similarly, cyclosporine A prevented Deltapsi(m) collapse, while N-acetylcysteine (NAC) mediated the recovery of cellular GSH redox balance that secondarily preserved Deltapsi(m). Collectively, these results provide mechanistic insights into the role of GSH redox status and mitochondrial potential in carbonyl stress-induced apoptosis of brain endothelial cells, with implications for cerebral microvascular complications associated with primary diabetic encephalopathy. The findings that thiol antioxidant and insulin sensitizers afforded cytoprotection suggest potential therapeutic approaches.
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PMID:Preservation of cellular glutathione status and mitochondrial membrane potential by N-acetylcysteine and insulin sensitizers prevent carbonyl stress-induced human brain endothelial cell apoptosis. 1980 52


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