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      miR-378 Activates the Pyruvate-PEP Futile Cycle and Enhances Lipolysis to Ameliorate Obesity in Mice

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          Abstract

          Obesity has been linked to many health problems, such as diabetes. However, there is no drug that effectively treats obesity. Here, we reveal that miR-378 transgenic mice display reduced fat mass, enhanced lipolysis, and increased energy expenditure. Notably, administering AgomiR-378 prevents and ameliorates obesity in mice. We also found that the energy deficiency seen in miR-378 transgenic mice was due to impaired glucose metabolism. This impairment was caused by an activated pyruvate-PEP futile cycle via the miR-378-Akt1-FoxO1-PEPCK pathway in skeletal muscle and enhanced lipolysis in adipose tissues mediated by miR-378-SCD1. Our findings demonstrate that activating the pyruvate-PEP futile cycle in skeletal muscle is the primary cause of elevated lipolysis in adipose tissues of miR-378 transgenic mice, and it helps orchestrate the crosstalk between muscle and fat to control energy homeostasis in mice. Thus, miR-378 may serve as a promising agent for preventing and treating obesity in humans.

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          Highlights

          • Systemically administering AgomiR-378 prevents and ameliorates obesity in mice

          • miR-378 transgenic mice show energy deficiency due to impaired glucose metabolism

          • The impairment is caused by miR-378-activated pyruvate-PEP futile cycle in muscle

          • miR-378 governs energy homeostasis by increased lipolysis via targeting Scd1 in fat

          Futile cycles are generally regarded as energetically wasteful processes that are avoided in metabolic pathways. Zhang et al. demonstrate miR-378-activated pyruvate-phosphoenolpyruvate futile cycle plays a regulatory benefit for the energy homeostasis by orchestrating inter-organ crosstalk between skeletal muscle and fat in mice, resulting its implication in preventing and treating obesity.

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          Most cited references31

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          Role for stearoyl-CoA desaturase-1 in leptin-mediated weight loss.

          Leptin elicits a metabolic response that cannot be explained by its anorectic effects alone. To examine the mechanism underlying leptin's metabolic actions, we used transcription profiling to identify leptin-regulated genes in ob/ob liver. Leptin was found to specifically repress RNA levels and enzymatic activity of hepatic stearoyl-CoA desaturase-1 (SCD-1), which catalyzes the biosynthesis of monounsaturated fatty acids. Mice lacking SCD-1 were lean and hypermetabolic. ob/ob mice with mutations in SCD-1 were significantly less obese than ob/ob controls and had markedly increased energy expenditure. ob/ob mice with mutations in SCD-1 had histologically normal livers with significantly reduced triglyceride storage and VLDL (very low density lipoprotein) production. These findings suggest that down-regulation of SCD-1 is an important component of leptin's metabolic actions.
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            Control of mitochondrial metabolism and systemic energy homeostasis by microRNAs 378 and 378*.

            Obesity and metabolic syndrome are associated with mitochondrial dysfunction and deranged regulation of metabolic genes. Peroxisome proliferator-activated receptor γ coactivator 1β (PGC-1β) is a transcriptional coactivator that regulates metabolism and mitochondrial biogenesis through stimulation of nuclear hormone receptors and other transcription factors. We report that the PGC-1β gene encodes two microRNAs (miRNAs), miR-378 and miR-378*, which counterbalance the metabolic actions of PGC-1β. Mice genetically lacking miR-378 and miR-378* are resistant to high-fat diet-induced obesity and exhibit enhanced mitochondrial fatty acid metabolism and elevated oxidative capacity of insulin-target tissues. Among the many targets of these miRNAs, carnitine O-acetyltransferase, a mitochondrial enzyme involved in fatty acid metabolism, and MED13, a component of the Mediator complex that controls nuclear hormone receptor activity, are repressed by miR-378 and miR-378*, respectively, and are elevated in the livers of miR-378/378* KO mice. Consistent with these targets as contributors to the metabolic actions of miR-378 and miR-378*, previous studies have implicated carnitine O-acetyltransferase and MED13 in metabolic syndrome and obesity. Our findings identify miR-378 and miR-378* as integral components of a regulatory circuit that functions under conditions of metabolic stress to control systemic energy homeostasis and the overall oxidative capacity of insulin target tissues. Thus, these miRNAs provide potential targets for pharmacologic intervention in obesity and metabolic syndrome.
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              LTB4 causes macrophage–mediated inflammation and directly induces insulin resistance in obesity

              Chronic inflammation is a key component of obesity–induced insulin resistance and plays a central role in metabolic disease. In this study, we found that the major insulin target tissues, liver, muscle and adipose tissue exhibit increased levels of the chemotactic eicosanoid LTB4 in obese high fat diet (HFD) mice compared to lean chow fed mice. Inhibition of the LTB4 receptor, Ltb4r1, through either genetic or pharmacologic loss of function results in an anti–inflammatory phenotype with protection from systemic insulin resistance and hepatic steatosis in the setting of both HFD–induced and genetic obesity. Importantly, in vitro treatment with LTB4 directly enhanced macrophage chemotaxis, stimulated inflammatory pathways in macrophages, promoted de novo hepatic lipogenesis, decreased insulin stimulated glucose uptake in L6 myocytes, increased gluconeogenesis, and impaired insulin–mediated suppression of hepatic glucose output (HGO) in primary mouse hepatocytes. This was accompanied by decreased insulin stimulated Akt phosphorylation and increased Irs1 and Irs2 serine phosphorylation and all of these events were Gαi and Jnk dependent. Taken together, these observations elucidate a novel role of LTB4/Ltb4r1 in the etiology of insulin resistance in hepatocytes and myocytes, and shows that in vivo inhibition of Ltb4r1 leads to robust insulin sensitizing effects.
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                Author and article information

                Contributors
                Journal
                EBioMedicine
                EBioMedicine
                EBioMedicine
                Elsevier
                2352-3964
                11 March 2016
                March 2016
                11 March 2016
                : 5
                : 93-104
                Affiliations
                [a ]The State Key Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and School of Basic Medicine, Peking Union Medical College, Beijing 100005, PR China
                [b ]Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Centre for Biospectroscopy and Metabonomics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, PR China
                [c ]Gladstone Institute of Cardiovascular Disease and Roddenberry Center for Stem Cell Biology and Medicine at Gladstone, San Francisco, CA 94158, USA
                Author notes
                [* ]Corresponding author. dhzhu@ 123456pumc.edu.cn
                [1]

                Co-first authors.

                Article
                S2352-3964(16)30031-7
                10.1016/j.ebiom.2016.01.035
                4816830
                27077116
                1c8f6c12-5cf3-4b26-acf7-a5290b27e398
                © 2016 The Authors

                This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

                History
                : 13 November 2015
                : 25 January 2016
                : 28 January 2016
                Categories
                Research Paper

                mir-378,futile cycle,lipolysis,energy homeostasis,obesity,scd1
                mir-378, futile cycle, lipolysis, energy homeostasis, obesity, scd1

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