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The AMPK agonist AICAR, but not metformin, prevents inflammation-associated cachectic muscle wasting

ABSTRACT: Activation of AMPK has been associated with pro-atrophic signaling in muscle. However, AMPK also has anti-inflammatory effects, suggesting that in cachexia, a syndrome of inflammatory-driven muscle wasting, AMPK activation could be beneficial. Here we show that the AMPK agonist AICAR suppresses IFNγ/TNFα-induced atrophy, while the mitochondrial inhibitor, metformin, does not. IFNγ/TNFα impair mitochondrial oxidative respiration in myotubes and promote a metabolic shift to aerobic glycolysis, similarly to metformin. In contrast, AICAR partially restored metabolic function. The effects of AICAR were prevented by the AMPK inhibitor Compound C and were reproduced with A-769662, a specific AMPK activator. AICAR and A-769662 co-treatment was found to be synergistic, suggesting that the anti-cachectic effects of these drugs are mediated through AMPK activation. AICAR spared muscle mass in mouse models of cancer and LPS induced atrophy. Together, our findings suggest a dual function for AMPK during inflammation-driven atrophy, wherein it can play a protective role when activated exogenously early in disease progression, but may contribute to anabolic suppression and atrophy when activated later through mitochondrial dysfunction and subsequent metabolic stress.

SUBMITTER: Mr. Derek, T Hall

PROVIDER: S-SCDT-EMM-2017-08307 | biostudies-other |

REPOSITORIES: biostudies-other

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The AMPK agonist 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR), but not metformin, prevents inflammation-associated cachectic muscle wasting.

Project description:Activation of AMPK has been associated with pro-atrophic signaling in muscle. However, AMPK also has anti-inflammatory effects, suggesting that in cachexia, a syndrome of inflammatory-driven muscle wasting, AMPK activation could be beneficial. Here we show that the AMPK agonist AICAR suppresses IFN?/TNF?-induced atrophy, while the mitochondrial inhibitor metformin does not. IFN?/TNF? impair mitochondrial oxidative respiration in myotubes and promote a metabolic shift to aerobic glycolysis, similarly to metformin. In contrast, AICAR partially restored metabolic function. The effects of AICAR were prevented by the AMPK inhibitor Compound C and were reproduced with A-769662, a specific AMPK activator. AICAR and A-769662 co-treatment was found to be synergistic, suggesting that the anti-cachectic effects of these drugs are mediated through AMPK activation. AICAR spared muscle mass in mouse models of cancer and LPS induced atrophy. Together, our findings suggest a dual function for AMPK during inflammation-driven atrophy, wherein it can play a protective role when activated exogenously early in disease progression, but may contribute to anabolic suppression and atrophy when activated later through mitochondrial dysfunction and subsequent metabolic stress.

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Chronic Treatment with the AMPK Agonist AICAR Prevents Skeletal Muscle Pathology but Fails to Improve Clinical Outcome in a Mouse Model of Severe Spinal Muscular Atrophy.

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Project description:Activation of interstitial myofibroblasts and excessive production of extracellular matrix proteins are common pathways that contribute to chronic kidney disease. In a number of tissues, AMP-activated kinase (AMPK) activation has been shown to inhibit fibrosis. Here, we examined the inhibitory effect of the AMPK activator, 5-aminoimidazole-4-carboxyamide ribonucleoside (AICAR), on renal fibrosis in vivo and TGF-β1-induced renal fibroblasts activation in vitro. A unilateral ureteral obstruction (UUO) model was induced in male BALB/c mice. Mice with UUO were administered AICAR (500 mg/Kg/day) or saline intraperitoneally 1 day before UUO surgery and daily thereafter. Both kidneys were harvested 7 days after surgery for further analysis. For the in vitro studies, NRK-49F rat fibroblasts were pre-incubated with AICAR before TGF-β1 stimulation. The inhibitory effects of AICAR on signaling pathways down-stream of TGF-β1 were analyzed. In UUO model mice, administration of AICAR attenuated extracellular matrix protein deposition and the expression of α-smooth muscle actin (α-SMA), type I collagen and fibronectin. Pre-incubation of NRK-49F cells with AICAR inhibited TGF-β1-induced myofibroblast activation. Silencing of AMPKα1 by siRNA or by blocking AMPK activation with Compound C diminished the inhibitory effect of AICAR. Moreover, the inhibitory effects of AICAR on TGF-β1-mediated myofibroblast activation were associated with down-regulation of ERK 1/2 and STAT3. Our results suggest that AICAR reduces tubulointerstitial fibrosis in UUO mice and inhibits TGF-β1-induced kidney myofibroblast activation. AMPK activation by AICAR may have therapeutic potential for the treatment of renal tubulointerstitial fibrosis.

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AMPK agonist AICAR improves cognition and motor coordination in young and aged mice.

Project description:Normal aging can result in a decline of memory and muscle function. Exercise may prevent or delay these changes. However, aging-associated frailty can preclude physical activity. In young sedentary animals, pharmacological activation of AMP-activated protein kinase (AMPK), a transcriptional regulator important for muscle physiology, enhanced spatial memory function, and endurance. In the present study we investigated effects of AMPK agonist 5-aminoimidazole-4-carboxamide riboside (AICAR) on memory and motor function in young (5- to 7-wk-old) and aged (23-mo-old) female C57Bl/6 mice, and in young (4- to 6-wk-old) transgenic mice with muscle-specific mutated AMPK α2-subunit (AMPK-DN). Mice were injected with AICAR (500 mg/kg) for 3-14 d. Two weeks thereafter animals were tested in the Morris water maze, rotarod, and open field. Improved water maze performance and motor function were observed, albeit at longer duration of administration, in aged (14-d AICAR) than in young (3-d AICAR) mice. In the AMPK-DN mice, the compound did not enhance behavior, providing support for a muscle-mediated mechanism. In addition, microarray analysis of muscle and hippocampal tissue derived from aged mice treated with AICAR revealed changes in gene expression in both tissues, which correlated with behavioral effects in a dose-dependent manner. Pronounced up-regulation of mitochondrial genes in muscle was observed. In the hippocampus, genes relevant to neuronal development and plasticity were enriched. Altogether, endurance-related factors may mediate both muscle and brain health in aging, and could play a role in new therapeutic interventions.

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The AMPK agonist AICAR inhibits the growth of EGFRvIII-expressing glioblastomas by inhibiting lipogenesis.

Project description:The EGFR/PI3K/Akt/mTOR signaling pathway is activated in many cancers including glioblastoma, yet mTOR inhibitors have largely failed to show efficacy in the clinic. Rapamycin promotes feedback activation of Akt in some patients, potentially underlying clinical resistance and raising the need for alternative approaches to block mTOR signaling. AMPK is a metabolic checkpoint that integrates growth factor signaling with cellular metabolism, in part by negatively regulating mTOR. We used pharmacological and genetic approaches to determine whether AMPK activation could block glioblastoma growth and cellular metabolism, and we examined the contribution of EGFR signaling in determining response in vitro and in vivo. The AMPK-agonist AICAR, and activated AMPK adenovirus, inhibited mTOR signaling and blocked the growth of glioblastoma cells expressing the activated EGFR mutant, EGFRvIII. Across a spectrum of EGFR-activated cancer cell lines, AICAR was more effective than rapamycin at blocking tumor cell proliferation, despite less efficient inhibition of mTORC1 signaling. Unexpectedly, addition of the metabolic products of cholesterol and fatty acid synthesis rescued the growth inhibitory effect of AICAR, whereas inhibition of these lipogenic enzymes mimicked AMPK activation, thus demonstrating that AMPK blocked tumor cell proliferation primarily through inhibition of cholesterol and fatty acid synthesis. Most importantly, AICAR treatment in mice significantly inhibited the growth and glycolysis (as measured by (18)fluoro-2-deoxyglucose microPET) of glioblastoma xenografts engineered to express EGFRvIII, but not their parental counterparts. These results suggest a mechanism by which AICAR inhibits the proliferation of EGFRvIII expressing glioblastomas and point toward a potential therapeutic strategy for targeting EGFR-activated cancers.

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p38 MAPK links oxidative stress to autophagy-related gene expression in cachectic muscle wasting.

Project description:Oxidative stress is a primary trigger of cachectic muscle wasting, but the signaling pathway(s) that links it to the muscle wasting processes remains to be defined. Here, we report that activation of p38 mitogen-activated protein kinase (MAPK) (phosphorylation) and increased oxidative stress (trans-4-hydroxy-2-nonenal protein modification) in skeletal muscle occur as early as 8 h after lipopolysaccharide (1 mg/kg) and 24 h after dexamethasone (25 mg/kg) injection (intraperitoneal) in mice, concurrent with upregulation of autophagy-related genes, Atg6, Atg7, and Atg12. Treating cultured C2C12 myotubes with oxidant hydrogen peroxide (4 h) resulted in increased p38 phosphorylation and reduced FoxO3 phosphorylation along with induced Atg7 mRNA expression without activation of NF-kappaB or FoxO3a transcriptional activities. Furthermore, inhibition of p38alpha/beta by SB202190 blocked hydrogen peroxide-induced atrophy with diminished upregulation of Atg7 and atrogenes [muscle atrophy F-box protein (MAFbx/Atrogin-1), muscle ring finger protein 1 (MuRF-1), and Nedd4]. These findings provide direct evidence for p38alpha/beta MAPK in mediating oxidative stress-induced autophagy-related genes, suggesting that p38alpha/beta MAPK regulates both the ubiquitin-proteasome and the autophagy-lysosome systems in muscle wasting.

| S-EPMC2838571 | biostudies-literature

Muscle contractions, AICAR, and insulin cause phosphorylation of an AMPK-related kinase.

Project description:We hypothesized that AMP-activated protein kinase-related kinase 5 (ARK5)/novel kinase family 1 (NUAK1), an AMP-activated protein kinase (AMPK)-related kinase that has been found to be stimulated by protein kinase B (Akt), would be expressed in rat skeletal muscle and activated by electrically elicited contractions, 5-aminoimidazole-4-carboxamide-1-beta-d-ribofuranoside (AICAR), or insulin. We verified expression of ARK5 in muscle through RT-PCR and Western blot. Cross-reactivity of ARK5 immunoprecipitates with antibodies against phospho-AMPK was increased by approximately 30% by muscle contractions and approximately 60% by incubation of muscle with AICAR. AMPK was not detected in the ARK5 immunoprecipitates. Despite the apparent increase in phosphorylation of ARK5 at a site essential to its activation, neither contractions nor AICAR increased ARK5 activity. For muscles from animals injected with saline or insulin, we probed nonimmunoprecipitated samples in sequence for phosphotyrosine (P-Tyr), ARK5, and phosphorylated substrates of Akt (P-AS) and found that the ARK5 band could be precisely superimposed on phosphoprotein bands from the P-Tyr and P-AS blots. In the band corresponding to ARK5, insulin increased P-Tyr content by approximately 45% and cross-reactivity with the antibody against P-AS by approximately threefold. We also detected ARK5 in phosphotyrosine immunoprecipitates. Our data suggest that increased phosphorylation of ARK5 by muscle contractions or exposure to AICAR is insufficient to activate ARK5 in skeletal muscle, suggesting that some other modification (e.g., phosphorylation on tyrosine or by Akt) may be necessary to its activity in muscle.

| S-EPMC1350986 | biostudies-literature

Pharmacological Inhibition of HMGB1 Prevents Muscle Wasting.

Project description:Background: Cachexia is a multifactorial disorder characterized by weight loss and muscle wasting, making up for about 20% of cancer-related death. However, there are no effective drugs to combat cachexia at present. Methods: In this study, the effect of CT26 exosomes on C2C12 myotubes was observed. We compared serum HMGB1 level in cachexia and non-cachexia colon cancer patients. We further explored HMGB1 expression level in CT26 exosome. We added recombinant HMGB1 to C2C12 myotubes to observe the effects of HMGB1 on C2C12 myotubes and detected the expression level of the muscle atrophy-related proteins. Then, we used the HMGB1 inhibitor glycyrrhizin to reverse the effects of HMGB1 on C2C12 myotubes. Finally, HMGB1 inhibitor glycyrrhizin was utilized to relieve cachexia in CT26 cachexia mouse model. Results: Exosomes containing HMGB1 led to muscle atrophy with significantly decreased myotube diameter and increased expression of muscle atrophy-related proteins Atrogin1 and MuRF1. Further, we detected that HMGB1 induced the muscle atrophy mainly via TLR4/NF-κB pathway. Administration of the HMGB1 inhibitor glycyrrhizin could relieve muscle wasting in vitro and attenuate the progression of cachexia in vivo. Conclusion: These findings demonstrate the cachectic role of HMGB1, whether it is soluble form of HMGB1 or secreted from tumor cells as part of exosomes. HMGB1 inhibitor glycyrrhizin might be a promising drug in colon cancer cachexia.

| S-EPMC8637759 | biostudies-literature

AICAR prevents heat-induced sudden death in RyR1 mutant mice independent of AMPK activation.

Project description:Mice with a knock-in mutation (Y524S) in the type I ryanodine receptor (Ryr1), a mutation analogous to the Y522S mutation that is associated with malignant hyperthermia in humans, die when exposed to short periods of temperature elevation (?37 °C). We show here that treatment with 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR) prevents this heat-induced sudden death in this mouse model. The protection by AICAR is independent of AMP-activated protein kinase (AMPK) activation and results from a newly identified action of the compound on mutant Ryr1 to reduce Ca(2+) leak from the sarcoplasmic reticulum to the sarcoplasm. AICAR thus prevents Ca(2+)-dependent increases in the amount of both reactive oxygen species (ROS) and reactive nitrogen species (RNS) that act to further increase resting Ca(2+) concentrations. If unchecked, the temperature-driven increases in resting Ca(2+) concentrations and the amounts of ROS and RNS create an amplifying cycle that ultimately triggers sustained muscle contractions, rhabdomyolysis and death. Although antioxidants are effective in reducing this cycle in vitro, only AICAR prevents heat-induced death in vivo. Our findings suggest that AICAR is probably effective in prophylactic treatment of humans with enhanced susceptibility to exercise- and/or heat-induced sudden death associated with RYR1 mutations.

| S-EPMC3274651 | biostudies-literature

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