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Chu X, Wu S, Raju R. NLRX1 Regulation Following Acute Mitochondrial Injury. Front Immunol 2019; 10:2431. [PMID: 31736938 PMCID: PMC6830126 DOI: 10.3389/fimmu.2019.02431] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Accepted: 09/30/2019] [Indexed: 12/17/2022] Open
Abstract
Several metabolic, cardiovascular, and neurological disorders are characterized by mitochondrial dysfunction followed by dysregulation of cellular energetics. Mitochondria play an important role in ATP production and cell death regulation. NLRX1, a mitochondria-targeted protein, is known to negatively regulate innate immunity, and cell death responses. However, the role of this protein in cellular homeostasis following mitochondrial injury is not well-understood. To understand the mechanisms underlying the effect of acute injury in regulating NLRX1 signaling pathways, we used an in vitro model of mitochondrial injury wherein, rat pulmonary microvascular endothelial cells were subjected to sodium azide treatment or glucose starvation. Both sodium azide and glucose starvation activated NF-κB and TBK1 associated innate immune response. Moreover, increased TBK1, IKK, IκB, and TRAF6 were recruited to mitochondria and interacted with NLRX1. Depletion of endogenous NLRX1 resulted in exacerbated NF-κB and TBK1 associated innate immune response and apoptosis. Our results suggest that NLRX1 participates in the regulation of innate immune response in mitochondria, and plays an important role in the maintenance of cellular homeostasis following acute mitochondrial injury. We propose that the mitochondrial recruitment of inflammatory mediators and their interaction with NLRX1 are protective responses to maintain cellular homeostasis following injury.
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Affiliation(s)
- Xiaogang Chu
- Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta University, Augusta, GA, United States
| | - Songwei Wu
- Department of Anesthesiology and Perioperative Medicine, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Raghavan Raju
- Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta University, Augusta, GA, United States
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Sanders J, Scholz M, Merutka I, Biron D. Distinct unfolded protein responses mitigate or mediate effects of nonlethal deprivation of C. elegans sleep in different tissues. BMC Biol 2017; 15:67. [PMID: 28844202 PMCID: PMC5572162 DOI: 10.1186/s12915-017-0407-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Accepted: 07/24/2017] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND Disrupting sleep during development leads to lasting deficits in chordates and arthropods. To address lasting impacts of sleep deprivation in Caenorhabditis elegans, we established a nonlethal deprivation protocol. RESULTS Deprivation triggered protective insulin-like signaling and two unfolded protein responses (UPRs): the mitochondrial (UPRmt) and the endoplasmic reticulum (UPRER) responses. While the latter is known to be triggered by sleep deprivation in rodent and insect brains, the former was not strongly associated with sleep deprivation previously. We show that deprivation results in a feeding defect when the UPRmt is deficient and in UPRER-dependent germ cell apoptosis. In addition, when the UPRER is deficient, deprivation causes excess twitching in vulval muscles, mirroring a trend caused by loss of egg-laying command neurons. CONCLUSIONS These data show that nonlethal deprivation of C. elegans sleep causes proteotoxic stress. Unless mitigated, distinct types of deprivation-induced proteotoxicity can lead to anatomically and genetically separable lasting defects. The relative importance of different UPRs post-deprivation likely reflects functional, developmental, and genetic differences between the respective tissues and circuits.
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Affiliation(s)
- Jarred Sanders
- Genetics, Genomics, and Systems Biology, The University of Chicago, Chicago, IL, 60637, USA.
| | - Monika Scholz
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL, 60637, USA
| | - Ilaria Merutka
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL, 60637, USA
| | - David Biron
- Genetics, Genomics, and Systems Biology, The University of Chicago, Chicago, IL, 60637, USA.,Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL, 60637, USA.,Department of Physics, The University of Chicago, Chicago, IL, 60637, USA
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Wei W, Lu Y, Hao B, Zhang K, Wang Q, Miller AL, Zhang LR, Zhang LH, Yue J. CD38 Is Required for Neural Differentiation of Mouse Embryonic Stem Cells by Modulating Reactive Oxygen Species. Stem Cells 2015; 33:2664-73. [DOI: 10.1002/stem.2057] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Accepted: 04/27/2015] [Indexed: 11/12/2022]
Affiliation(s)
- Wenjie Wei
- Department of Biomedical Sciences; City University of Hong Kong; Hong Kong China
| | - Yingying Lu
- Department of Biomedical Sciences; City University of Hong Kong; Hong Kong China
| | - Baixia Hao
- Division of Life Science and State Key Laboratory of Molecular Neuroscience; The Hong Kong University of Science and Technology; Hong Kong China
| | - Kehui Zhang
- State Key Laboratory of Natural and Biomimetic Drugs; School of Pharmaceutical Sciences; Peking University; Beijing China
| | - Qian Wang
- Department of Biomedical Sciences; City University of Hong Kong; Hong Kong China
| | - Andrew L. Miller
- Division of Life Science and State Key Laboratory of Molecular Neuroscience; The Hong Kong University of Science and Technology; Hong Kong China
| | - Liang-Ren Zhang
- State Key Laboratory of Natural and Biomimetic Drugs; School of Pharmaceutical Sciences; Peking University; Beijing China
| | - Li-He Zhang
- State Key Laboratory of Natural and Biomimetic Drugs; School of Pharmaceutical Sciences; Peking University; Beijing China
| | - Jianbo Yue
- Department of Biomedical Sciences; City University of Hong Kong; Hong Kong China
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Han J, Yi J, Liang F, Jiang B, Xiao Y, Gao S, Yang N, Hu H, Xie WF, Chen W. X-3, a mangiferin derivative, stimulates AMP-activated protein kinase and reduces hyperglycemia and obesity in db/db mice. Mol Cell Endocrinol 2015; 405:63-73. [PMID: 25681564 DOI: 10.1016/j.mce.2015.02.008] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Revised: 01/12/2015] [Accepted: 02/06/2015] [Indexed: 12/19/2022]
Abstract
Diabetes mellitus is a major health concern, affecting nearly 10% of the population. Here we describe a potential novel therapeutic agent for this disease, X-3, a derivative of mangiferin. Therapeutic administration of X-3 significantly and dose-dependently reduced plasma glucose and triglycerides in db/db mice following 8 week-treatments. Treatment with X-3 dose-dependently increased the number of insulin-positive β-cell mass. Importantly, X-3 did not cause any death or signs of toxicity in acute toxicity studies. Study of mechanism of action revealed that X-3 increased glucose uptake in parallel with increased phosphorylation of AMP-activated protein kinase (AMPK) in 3T3-L1 cells. It activates AMPK in both LKB1-dependent and -independent manner. Furthermore, administration of X-3 resulted in activation of AMPK and its downstream target, acetyl-CoA carboxylase (ACC) in the hypothalamus, liver, muscle and adipose tissues of C57BL/6 mice. An 80 mg/kg X-3 was more potent than metformin at 500 mg/kg in the hypothalamus, and interscapular fat tissues, potent than MF at the same dose in the liver. Thus, we conclude that X-3 is a promising new class of AMPK activating drug, and can potentially be used in the treatment of type 2 diabetes.
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Affiliation(s)
- Jun Han
- Department of Gastroenterology, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Jia Yi
- Department of Pharmacy, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Fengying Liang
- Department of Pharmacy, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Bo Jiang
- Department of Pharmacy, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Ying Xiao
- Department of Pharmacy, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Shouhong Gao
- Department of Pharmacy, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Na Yang
- Department of Pharmacy, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Honggang Hu
- Department of Organic Chemistry, School of Pharmacy, Second Military Medical University, Shanghai, China
| | - Wei-Fen Xie
- Department of Gastroenterology, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Wansheng Chen
- Department of Pharmacy, Changzheng Hospital, Second Military Medical University, Shanghai, China.
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Pitman RT, Fong JT, Billman P, Puri N. Knockdown of the fat mass and obesity gene disrupts cellular energy balance in a cell-type specific manner. PLoS One 2012; 7:e38444. [PMID: 22675562 PMCID: PMC3367022 DOI: 10.1371/journal.pone.0038444] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2012] [Accepted: 05/08/2012] [Indexed: 11/19/2022] Open
Abstract
Recent studies suggest that FTO variants strongly correlate with obesity and mainly influence energy intake with little effect on the basal metabolic rate. We suggest that FTO influences eating behavior by modulating intracellular energy levels and downstream signaling mechanisms which control energy intake and metabolism. Since FTO plays a particularly important role in adipocytes and in hypothalamic neurons, SH-SY5Y neuronal cells and 3T3-L1 adipocytes were used to understand how siRNA mediated knockdown of FTO expression alters cellular energy homeostasis. Cellular energy status was evaluated by measuring ATP levels using a luminescence assay and uptake of fluorescent glucose. FTO siRNA in SH-SY5Y cells mediated mRNA knockdown (−82%), increased ATP concentrations by up to 46% (P = 0.013) compared to controls, and decreased phosphorylation of AMPk and Akt in SH-SY5Y by −52% and −46% respectively as seen by immunoblotting. In contrast, FTO siRNA in 3T3-L1 cells decreased ATP concentration by −93% (p<0.0005), and increased AMPk and Akt phosphorylation by 204% and 70%, respectively suggesting that FTO mediates control of energy levels in a cell-type specific manner. Furthermore, glucose uptake was decreased in both SH-SY5Y (−51% p = 0.015) and 3T3-L1 cells (−30%, p = 0.0002). We also show that FTO knockdown decreases NPY mRNA expression in SH-SY5Y cells (−21%) through upregulation of pSTAT3 (118%). These results provide important evidence that FTO-variant linked obesity may be associated with altered metabolic functions through activation of downstream metabolic mediators including AMPk.
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Affiliation(s)
- Ryan T. Pitman
- Department of Biomedical Sciences, University of Illinois College of Medicine, Rockford, Illinois, United States of America
| | - Jason T. Fong
- Department of Biomedical Sciences, University of Illinois College of Medicine, Rockford, Illinois, United States of America
| | - Penny Billman
- Department of Biomedical Sciences, University of Illinois College of Medicine, Rockford, Illinois, United States of America
| | - Neelu Puri
- Department of Biomedical Sciences, University of Illinois College of Medicine, Rockford, Illinois, United States of America
- * E-mail:
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Naidoo N. Roles of endoplasmic reticulum and energetic stress in disturbed sleep. Neuromolecular Med 2012; 14:213-9. [PMID: 22527792 DOI: 10.1007/s12017-012-8179-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Accepted: 03/23/2012] [Indexed: 11/26/2022]
Abstract
Sleep disturbances are contributing factors to health risk for several diseases including hypertension, diabetes, obesity, depression, and stroke. On a molecular level, sleep disturbances that incur sleep loss and sleep fragmentation result in cellular stress, inflammation, and an impaired immune system. It has been hypothesized that sleep deprivation or prolonged waking leads to increased energy demand and thus energetic stress. Sleep loss and sleep fragmentation are also known to lead to cellular stress specifically endoplasmic reticulum (ER) stress. This review will summarize the current knowledge of the roles of ER and energetic stress during sleep loss and fragmentation that are characteristics of many sleep disturbances. Sleep research pertinent to these specific pathways will be discussed.
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Affiliation(s)
- Nirinjini Naidoo
- Center for Sleep and Circadian Neurobiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
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Devraj K, Klinger ME, Myers RL, Mokashi A, Hawkins RA, Simpson IA. GLUT-1 glucose transporters in the blood-brain barrier: differential phosphorylation. J Neurosci Res 2011; 89:1913-25. [PMID: 21910135 DOI: 10.1002/jnr.22738] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Revised: 06/13/2011] [Accepted: 06/16/2011] [Indexed: 11/11/2022]
Abstract
Glucose is the primary metabolic fuel for the mammalian brain, and a continuous supply is required to maintain normal CNS function. The transport of glucose across the blood-brain barrier (BBB) into the brain is mediated by the facilitative glucose transporter GLUT-1. Prior studies (Simpson et al. [2001] J Biol Chem 276:12725-12729) had revealed that the conformations of the GLUT-1 transporter were different in luminal (blood facing) and abluminal (brain facing) membranes of bovine cerebral endothelial cells, based on differential antibody recognition. This study has extended these observations and, by using a combination of 2D-PAGE/Western blotting and immunogold electron microscopy, determined that these different conformations are exhibited in vivo and arise from differential phosphorylation of GLUT-1 and not from alternative splicing or altered O- or N-linked glycosylation.
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Affiliation(s)
- Kavi Devraj
- Department of Neural and Behavioral Sciences, College of Medicine, Pennsylvania State University, Hershey, Pennsylvania 17033, USA
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TONG HL, GAO XJ, LI QZ, LIU J, LI N, WAN ZY. Metabolic Regulation of Mammary Gland Epithelial Cells of Dairy Cow by Galactopoietic Compound Isolated from Vaccariae segetalis. ACTA ACUST UNITED AC 2011. [DOI: 10.1016/s1671-2927(11)60100-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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9
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Gaskin FS, Kamada K, Zuidema MY, Jones AW, Rubin LJ, Korthuis RJ. Isoform-selective 5'-AMP-activated protein kinase-dependent preconditioning mechanisms to prevent postischemic leukocyte-endothelial cell adhesive interactions. Am J Physiol Heart Circ Physiol 2011; 300:H1352-60. [PMID: 21239628 DOI: 10.1152/ajpheart.00944.2010] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We previously demonstrated that preconditioning induced by ethanol consumption at low levels [ethanol preconditioning (EPC)] or with 5-aminoimidazole-4-carboxamide 1-β-d-ribofuranoside (AICAR-PC) 24 h before ischemia-reperfusion prevents postischemic leukocyte-endothelial cell adhesive interactions (LEI) by a mechanism that is initiated by nitric oxide formed by endothelial nitric oxide synthase. Recent work indicates that 1) ethanol increases the activity of AMP-activated protein kinase (AMPK) and 2) AMPK phosphorylates endothelial nitric oxide synthase at the same activation site seen following EPC (Ser1177). In light of these observations, we postulated that the heterotrimeric serine/threonine kinase, AMPK, may play a role in triggering the development of the anti-inflammatory phenotype induced by EPC. Ethanol was administered to C57BL/6J mice by gavage in the presence or absence of AMPK inhibition. Twenty-four hours later, the numbers of rolling and adherent leukocytes in postcapillary venules of the small intestine were recorded using an intravital microscopic approach. Following 45 min of ischemia, LEI were recorded after 30 and 60 min of reperfusion or at equivalent time points in control animals. Ischemia-reperfusion induced a marked increase in LEI relative to sham-operated control mice. The increase in LEI was prevented by EPC, an effect that was lost with AMPK inhibition during the period of ethanol exposure. Studies conducted in AMPK α(1)- and α(2)-knockout mice suggest that the anti-inflammatory effects of AICAR are not dependent on which isoform of the catalytic α-subunit is present because a deficiency of either isoform results in a loss of protection. In sharp contrast, EPC appears to be triggered by an AMPK α(2)-isoform-dependent mechanism.
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Affiliation(s)
- F Spencer Gaskin
- Departments of Medical Pharmacology and Physiology, University of Missouri, Columbia, 65212, USA
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Nikonova EV, Naidoo N, Zhang L, Romer M, Cater JR, Scharf MT, Galante RJ, Pack AI. Changes in components of energy regulation in mouse cortex with increases in wakefulness. Sleep 2010; 33:889-900. [PMID: 20614849 DOI: 10.1093/sleep/33.7.889] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
STUDY OBJECTIVES Increases in ATP production machinery have been described in brain after 3 h of sleep deprivation. Whether this is sustained with longer durations of extended wakefulness is unknown. We hypothesized that energy depletion could be a mechanism leading to difficulty maintaining wakefulness and assessed changes in components of the electron transport chain. DESIGN Protein levels of key subunits of complexes IV and V of the electron transport chain (COXI, COXIV, ATP5B) and uncoupling protein 2 (UCP2) in isolated mitochondria by Westerns in mouse cerebral cortex after 3 and 12 h of sleep deprivation were compared to that in control mice. Activity of complex IV enzyme and relevant transcription factors-Nrf1, Nrf2 (Gabp), and phosphorylation of AMP-dependent kinase (AMPK)-were also assessed. PARTICIPANTS 8-10 week old C57BL/6J male mice (n = 91). INTERVENTIONS 3, 6, and 12 h of sleep deprivation. MEASUREMENTS AND RESULTS After both 3 and 12 h of sleep deprivation, complex IV proteins and enzyme activity were significantly increased. The complex V catalytic subunit was significantly increased after 12 h of sleep deprivation only. Increased levels of UCP2 protein after 12 h of sleep deprivation suggests that there might be alterations in the ATP/AMP ratio as wakefulness is extended. That phosphorylation of AMPK is increased after 6 h of sleep deprivation supports this assertion. The increase in Nrf1 and Nrf2 (Gabp) mRNA after 6 h of sleep deprivation provides a mechanism by which there is up-regulation of key proteins. CONCLUSIONS There are complex dynamic changes in brain energy regulation with extended wakefulness.
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Affiliation(s)
- Elena V Nikonova
- Center for Sleep and Respiratory Neurobiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-3403, USA
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Jing M, Cheruvu VK, Ismail-Beigi F. Stimulation of glucose transport in response to activation of distinct AMPK signaling pathways. Am J Physiol Cell Physiol 2008; 295:C1071-82. [PMID: 18701654 DOI: 10.1152/ajpcell.00040.2008] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
AMP-activated protein kinase (AMPK) plays a critical role in the stimulation of glucose transport in response to hypoxia and inhibition of oxidative phosphorylation. In the present study, we examined the signaling pathway(s) mediating the glucose transport response following activation of AMPK. Using mouse fibroblasts of AMPK wild type and AMPK knockout, we documented that the expression of AMPK is essential for the glucose transport response to both azide and 5-aminoimidazole-4-carboxamide-1-beta-d-ribofuranoside (AICAR). In Clone 9 cells, the stimulation of glucose transport by a combination of azide and AICAR was not additive, whereas there was an additive increase in the abundance of phosphorylated AMPK (p-AMPK). In Clone 9 cells, AMPK wild-type fibroblasts, and H9c2 heart cells, azide or hypoxia selectively increased p-ERK1/2, whereas, in contrast, AICAR selectively stimulated p-p38; phosphorylation of JNK was unaffected. Azide's effect on p-ERK1/2 abundance and glucose transport in Clone 9 cells was partially abolished by the MEK1/2 inhibitor U0126. SB 203580, an inhibitor of p38, prevented the phosphorylation of p38 and the glucose transport response to AICAR and, unexpectedly, to azide. Hypoxia, azide, and AICAR all led to increased phosphorylation of Akt substrate of 160 kDa (AS160) in Clone 9 cells. Employing small interference RNA directed against AS160 did not inhibit the glucose transport response to azide or AICAR, whereas the content of P-AS160 was reduced by approximately 80%. Finally, we found no evidence for coimmunoprecipitation of Glut1 and p-AS160. We conclude that although azide, hypoxia, and AICAR all activate AMPK, the downstream signaling pathways are distinct, with azide and hypoxia stimulating ERK1/2 and AICAR stimulating the p38 pathway.
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Affiliation(s)
- Ming Jing
- Dept. of Medicine, Case Western Reserve Univ., 10900 Euclid Ave., Cleveland, OH 44106-4951, USA
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12
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Jensen TE, Schjerling P, Viollet B, Wojtaszewski JFP, Richter EA. AMPK alpha1 activation is required for stimulation of glucose uptake by twitch contraction, but not by H2O2, in mouse skeletal muscle. PLoS One 2008; 3:e2102. [PMID: 18461163 PMCID: PMC2346549 DOI: 10.1371/journal.pone.0002102] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2008] [Accepted: 03/20/2008] [Indexed: 12/29/2022] Open
Abstract
Background AMPK is a promising pharmacological target in relation to metabolic disorders partly due to its non-insulin dependent glucose uptake promoting role in skeletal muscle. Of the 2 catalytic α-AMPK isoforms, α2 AMPK is clearly required for stimulation of glucose transport into muscle by certain stimuli. In contrast, no clear function has yet been determined for α1 AMPK in skeletal muscle, possibly due to α-AMPK isoform signaling redundancy. By applying low-intensity twitch-contraction and H2O2 stimulation to activate α1 AMPK, but not α2 AMPK, in wildtype and α-AMPK transgenic mouse muscles, this study aimed to define conditions where α1 AMPK is required to increase muscle glucose uptake. Methodology/Principal Findings Following stimulation with H2O2 (3 mM, 20 min) or twitch-contraction (0.1 ms pulse, 2 Hz, 2 min), signaling and 2-deoxyglucose uptake were measured in incubated soleus muscles from wildtype and muscle-specific kinase-dead AMPK (KD), α1 AMPK knockout or α2 AMPK knockout mice. H2O2 increased the activity of both α1 and α2 AMPK in addition to Akt phosphorylation, and H2O2-stimulated glucose uptake was not reduced in any of the AMPK transgenic mouse models compared with wild type. In contrast, twitch-contraction increased the activity of α1 AMPK, but not α2 AMPK activity nor Akt or AS160 phosphorylation. Glucose uptake was markedly lower in α1 AMPK knockout and KD AMPK muscles, but not in α2 AMPK knockout muscles, following twitch stimulation. Conclusions/Significance These results provide strong genetic evidence that α1 AMPK, but not α2 AMPK, Akt or AS160, is necessary for regulation of twitch-contraction stimulated glucose uptake. To our knowledge, this is the first report to show a major and essential role of α1 AMPK in regulating a physiological endpoint in skeletal muscle. In contrast, AMPK is not essential for H2O2-stimulated muscle glucose uptake, as proposed by recent studies.
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Affiliation(s)
- Thomas E. Jensen
- Molecular Physiology Group, Copenhagen Muscle Research Centre, Department of Exercise and Sport Sciences, Section of Human Physiology, University of Copenhagen, Copenhagen, Denmark
| | - Peter Schjerling
- Copenhagen Muscle Research Centre, Department of Molecular Muscle Biology, Rigshospitalet, Copenhagen, Denmark
- Medical Muscle Research Cluster, Molecular Muscle Biology, Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Benoit Viollet
- Institut Cochin, Université Paris Descartes, CNRS (UMR 8104), Paris, France
- Inserm, U567, Paris, France
| | - Jørgen F. P. Wojtaszewski
- Molecular Physiology Group, Copenhagen Muscle Research Centre, Department of Exercise and Sport Sciences, Section of Human Physiology, University of Copenhagen, Copenhagen, Denmark
| | - Erik A. Richter
- Molecular Physiology Group, Copenhagen Muscle Research Centre, Department of Exercise and Sport Sciences, Section of Human Physiology, University of Copenhagen, Copenhagen, Denmark
- * E-mail:
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Kim SH, Shin EJ, Kim ED, Bayaraa T, Frost SC, Hyun CK. Berberine activates GLUT1-mediated glucose uptake in 3T3-L1 adipocytes. Biol Pharm Bull 2007; 30:2120-5. [PMID: 17978486 DOI: 10.1248/bpb.30.2120] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It has recently been known that berberine, an alkaloid of medicinal plants, has anti-hyperglycemic effects. To explore the mechanism underlying this effect, we used 3T3-L1 adipocytes for analyzing the signaling pathways that contribute to glucose transport. Treatment of berberine to 3T3-L1 adipocytes for 6 h enhanced basal glucose uptake both in normal and in insulin-resistant state, but the insulin-stimulated glucose uptake was not augmented significantly. Inhibition of phosphatidylinositol 3-kinase (PI 3-K) by wortmannin did not affect the berberine effect on basal glucose uptake. Berberine did not augment tyrosine phosphorylation of insulin receptor (IR) and insulin receptor substrate (IRS)-1. Further, berberine had no effect on the activity of the insulin-sensitive downstream kinase, atypical protein kinase C (PKCzeta/lambda). However, interestingly, extracellular signal-regulated kinases (ERKs), which have been known to be responsible for the expression of glucose transporter (GLUT)1, were significantly activated in berberine-treated 3T3-L1 cells. As expected, the level of GLUT1 protein was increased both in normal and insulin-resistant cells in response to berberine. But berberine affected the expression of GLUT4 neither in normal nor in insulin-resistant cells. In addition, berberine treatment increased AMP-activated protein kinase (AMPK) activity in 3T3-L1 cells, which has been reported to be associated with GLUT1-mediated glucose uptake. Together, we concluded that berberine increases glucose transport activity of 3T3-L1 adipocytes by enhancing GLUT1 expression and also stimulates the GLUT1-mediated glucose uptake by activating GLUT1, a result of AMPK stimulation.
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Affiliation(s)
- So Hui Kim
- School of Life and Food Sciences, Handong Global University, Pohang, Kyonbuk, Korea
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Kasturi S, Bederman IR, Christopher B, Previs SF, Ismail-Beigi F. Exposure to azide markedly decreases the abundance of mRNAs encoding cholesterol synthetic enzymes and inhibits cholesterol synthesis. J Cell Biochem 2007; 100:1034-44. [PMID: 17131385 DOI: 10.1002/jcb.21092] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
This study was performed to identify genes that are regulated in the adaptive response to prolonged inhibition of oxidative phosphorylation. Gene microarray analysis in control Clone 9 cells and Clone 9 cells exposed to 5 mM azide for 24 h was carried out as a condition of "Chemical hypoxia." Among several hundred mRNAs whose abundances were either increased or decreased, we noted that the abundance of mRNAs encoding enzymes that catalyze the sequential steps of cholesterol synthesis was decreased; this finding was verified by real-time PCR. Exposure to azide for 24 h markedly inhibited the biosynthesis of cholesterol by approximately 90% and decreased the cellular content of cholesterol by 30%, similar results were observed in HepG2 cells. The abundance of sterol regulatory element binding protein (SREBP)-2 mRNA decreased to 0.37 and 0.25 that of controls after 2 and 24 h exposure, respectively. After 24 h of exposure to azide the precursor and nuclear forms of SREBP-2 protein decreased by approximately 80% and approximately 50%, respectively. Stimulation of AMP-activated protein kinase (AMPK) by AICAR in Clone 9 cells increased the abundance of mRNAs encoding cholesterol biosynthetic enzymes and that of SREBP-1c, and had no effect on SREBP-2 mRNA abundance. We conclude that the decrease in the abundance of multiple mRNAs encoding cholesterol biosynthetic enzymes may be mediated by decreased expression of SREBP-2 mRNA and protein and does not involve stimulation of AMPK. The decrease in SREBP-2 mRNA and protein abundance in the face of decreased cell cholesterol content raises the possibility of a novel regulatory pathway.
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Affiliation(s)
- Sriram Kasturi
- Division of Clinical and Molecular Endocrinology, Department of Medicine, Case Western Reserve University, Cleveland, OH 44106-4951, USA
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Carraway RE, Hassan S. Neurotensin receptor binding and neurotensin-induced growth signaling in prostate cancer PC3 cells are sensitive to metabolic stress. ACTA ACUST UNITED AC 2007; 141:140-53. [PMID: 17289170 DOI: 10.1016/j.regpep.2006.12.027] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2006] [Revised: 12/19/2006] [Accepted: 12/23/2006] [Indexed: 01/03/2023]
Abstract
Neurotensin (NT) stimulates the proliferation of prostate cancer PC3 cells, which express high levels of its G protein-coupled receptor NTS1. To shed light on mechanisms that might serve to coordinate mitogenic responses to metabolic status, we studied the effects of metabolic inhibitors on NTS1 function. We also related these effects to cellular ATP levels and to the activation of AMP-activated protein kinase (AMPK). Glycolytic and mitochondrial inhibitors, at concentrations that reduced cellular ATP levels, altered NT binding to the cells, inhibited NT-induced inositol phosphate formation, and inhibited NT-induced DNA synthesis. For eight of the nine inhibitors, the potencies to alter NT receptor function correlated to the potencies to decrease cellular ATP levels. In keeping with its known role to oppose metabolic stress, AMPK was activated by the metabolic inhibitors. Accordingly, the AMPK activator AICAR elevated cellular ATP levels and produced effects on NTS1 function that were opposite to those for the metabolic inhibitors. These results indicate that metabolic stress inhibited NTS1 function by a mechanism that involved a fall in cellular ATP levels and that was opposed by activation of AMPK. In a broader context, these findings are compatible with the idea that one means by which cells might coordinate mitogenic signaling to metabolic status could involve changes in growth factor receptor function.
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Affiliation(s)
- Robert E Carraway
- Department of Physiology, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, MA 01655, USA.
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Jing M, Ismail-Beigi F. Critical role of 5'-AMP-activated protein kinase in the stimulation of glucose transport in response to inhibition of oxidative phosphorylation. Am J Physiol Cell Physiol 2006; 292:C477-87. [PMID: 16943243 DOI: 10.1152/ajpcell.00196.2006] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
5'-AMP-activated protein kinase (AMPK) functions as an energy sensor to provide metabolic adaptation under conditions of ATP depletion, such as hypoxia and inhibition of oxidative phosphorylation. Whether activation of AMPK is critical for stimulation of glucose transport in response to inhibition of oxidative phosphorylation is unknown. Here we found that treatment of Glut1-expressing Clone 9 cells with sodium azide (5 mM for 2 h) or the AMPK activator 5'-aminoimidazole-4-carboxamide-1-beta-d-ribofuranoside (AICAR, 2 mM for 2 h) stimulated the rate of glucose transport by two- to fourfold. Use of small interference RNA (siRNA) directed against AMPKalpha(1) or AMPKalpha(1) + AMPKalpha(2) (total AMPKalpha) resulted in a significant inhibition of the glucose transport response and the content of phosphorylated AMPKalpha(1) + phosphorylated AMPKalpha(2) (total p-AMPKalpha) and phosphorylated acetyl-CoA carboxylase (p-ACC) in response to azide. Transfection with siRNA directed against AMPKalpha(2) did not affect the glucose transport response. The efficacy of transfection with siRNAs in reducing AMPK content was confirmed by Western blotting. Incubation of cells with compound C, an inhibitor of AMPK, abrogated the glucose transport response and abolished the increase in total p-AMPK in azide-treated or hypoxia-exposed cells. Simultaneous exposure to azide and AICAR did not augment the rate of transport in response to AICAR alone. There was no evidence of coimmunoprecipitation of total p-AMPKalpha with Glut1. However, LKB1 was associated with total p-AMPKalpha. We conclude that activation of AMPK plays both a sufficient and a necessary role in the stimulation of glucose transport in response to inhibition of oxidative phosphorylation.
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Affiliation(s)
- Ming Jing
- Clinical and Molecular Endocrinology, Department of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-4951, USA
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Gaskin FS, Kamada K, Yusof M, Korthuis RJ. 5'-AMP-activated protein kinase activation prevents postischemic leukocyte-endothelial cell adhesive interactions. Am J Physiol Heart Circ Physiol 2006; 292:H326-32. [PMID: 16935999 DOI: 10.1152/ajpheart.00744.2006] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Preconditioning (PC) with nitric oxide (NO) donors or agents that increase endothelial NO synthase (eNOS) activity 24 h before ischemia-reperfusion (I/R) prevents postischemic leukocyte rolling (LR) and stationary leukocyte adhesion (LA). Since 5'-AMP-activated protein kinase (AMPK) phosphorylates eNOS at Ser1177, resulting in activation, we postulated that AMPK activation may trigger the development of a preconditioned anti-inflammatory phenotype similar to that induced by NO donors. Wild-type (WT) C57BL/6J and eNOS(-/-) mice were treated with the AMPK agonist 5-aminoimidazole-4-carboxamide 1-beta-d-furanoside (AICAR) 30 min (early AICAR PC) or 24 h (late AICAR PC) before I/R; LR and LA were quantified in single postcapillary venules in the jejunum using intravital microscopy. I/R induced comparable marked increases in LR and LA in WT and eNOS(-/-) mice relative to sham-operated (no ischemia) animals. Late AICAR PC prevented postischemic LR and LA, whereas early AICAR PC prevented LA in WT mice. Late AICAR PC was ineffective in preventing I/R-induced LR but not LA in the eNOS(-/-) mice, and the same pattern was seen in WT animals treated with the NOS inhibitor N(omega)-nitro-l-arginine. Early AICAR PC remained effective in preventing LA in eNOS(-/-) mice. Our results indicate that both early and late PC with an AMPK agonist produces an anti-inflammatory phenotype in postcapillary venules. Since the protection afforded by late AICAR PC on postischemic LR was prevented by NOS inhibition in WT mice and absent in eNOS-deficient mice, it appears that eNOS triggers this protective effect. In stark contrast, antecedent AMPK activation prevented I/R-induced LA by an eNOS-independent mechanism.
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Affiliation(s)
- F Spencer Gaskin
- Dept. of Medical Pharmacology and Physiology, Univ. of Missouri-Columbia, 1 Hospital Dr., Columbia, MO 65212, USA.
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Evans AM. AMP-activated protein kinase underpins hypoxic pulmonary vasoconstriction and carotid body excitation by hypoxia in mammals. Exp Physiol 2006; 91:821-7. [PMID: 16740641 DOI: 10.1113/expphysiol.2006.033514] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
In order to maintain tissue partial pressure of oxygen (P(O(2))) within physiological limits, vital homeostatic mechanisms monitor O(2) supply and respond to a fall in P(O(2)) by altering respiratory and circulatory function, and the capacity of the blood to transport O(2). Two systems that are key to this process in the acute phase are the pulmonary arteries and the carotid bodies. Hypoxic pulmonary vasoconstriction is driven by mechanisms intrinsic to the pulmonary arterial smooth muscle and endothelial cells, and aids ventilation-perfusion matching in the lung by diverting blood flow from areas with an O(2) deficit to those that are rich in O(2). By contrast, a fall in arterial P(O(2)) precipitates excitation-secretion coupling in carotid body type I cells, increases sensory afferent discharge from the carotid body and thereby elicits corrective changes in breathing patterns via the brainstem. There is a general consensus that hypoxia inhibits mitochondrial oxidative phosphorylation in these O(2)-sensing cells over a range of P(O(2)) values that has no such effect on other cell types. However, the question remains as to the identity of the mechanism that underpins hypoxia-response coupling in O(2)-sensing cells. Here, I lay out the case in support of a primary role for AMP-activated protein kinase in mediating chemotransduction by hypoxia.
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Affiliation(s)
- A Mark Evans
- Division of Biomedical Sciences, School of Biology, University of St Andrews, St Andrews, Fife KY16 9TS, UK.
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