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      Populus balsamifera Extract and Its Active Component Salicortin Reduce Obesity and Attenuate Insulin Resistance in a Diet-Induced Obese Mouse Model

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          Abstract

          Populus balsamifera L. (BP) is a medicinal plant stemming from the traditional pharmacopoeia of the Cree of Eeyou Istchee (CEI—Northern Quebec). In vitro screening studies revealed that it strongly inhibited adipogenesis in 3T3-L1 adipocytes, suggesting potential antiobesity activity. Salicortin was identified, through bioassay-guided fractionation, as the active component responsible for BP's activity. The present study aimed to assess the potential of BP and salicortin at reducing obesity and features of the metabolic syndrome, in diet-induced obese C57Bl/6 mice. Mice were subjected to high fat diet (HFD) for sixteen weeks, with BP (125 or 250 mg/kg) or salicortin (12.5 mg/kg) introduced in the HFD for the last eight of the sixteen weeks. BP and salicortin effectively reduced whole body and retroperitoneal fat pad weights, as well as hepatic triglyceride accumulation. Glycemia, insulinemia, leptin, and adiponectin levels were also improved. This was accompanied by a small yet significant reduction in food intake in animals treated with BP. BP and salicortin (slightly) also modulated key components in signaling pathways involved with glucose regulation and lipid oxidation in the liver, muscle, and adipose tissue. These results confirm the validity of the CEI pharmacopoeia as alternative and complementary antiobesity and antidiabetic therapies.

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          IKK-beta links inflammation to obesity-induced insulin resistance.

          Inflammation may underlie the metabolic disorders of insulin resistance and type 2 diabetes. IkappaB kinase beta (IKK-beta, encoded by Ikbkb) is a central coordinator of inflammatory responses through activation of NF-kappaB. To understand the role of IKK-beta in insulin resistance, we used mice lacking this enzyme in hepatocytes (Ikbkb(Deltahep)) or myeloid cells (Ikbkb(Deltamye)). Ikbkb(Deltahep) mice retain liver insulin responsiveness, but develop insulin resistance in muscle and fat in response to high fat diet, obesity or aging. In contrast, Ikbkb(Deltamye) mice retain global insulin sensitivity and are protected from insulin resistance. Thus, IKK-beta acts locally in liver and systemically in myeloid cells, where NF-kappaB activation induces inflammatory mediators that cause insulin resistance. These findings demonstrate the importance of liver cell IKK-beta in hepatic insulin resistance and the central role of myeloid cells in development of systemic insulin resistance. We suggest that inhibition of IKK-beta, especially in myeloid cells, may be used to treat insulin resistance.
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            Glucose transporters in the 21st Century.

            The ability to take up and metabolize glucose at the cellular level is a property shared by the vast majority of existing organisms. Most mammalian cells import glucose by a process of facilitative diffusion mediated by members of the Glut (SLC2A) family of membrane transport proteins. Fourteen Glut proteins are expressed in the human and they include transporters for substrates other than glucose, including fructose, myoinositol, and urate. The primary physiological substrates for at least half of the 14 Glut proteins are either uncertain or unknown. The well-established glucose transporter isoforms, Gluts 1-4, are known to have distinct regulatory and/or kinetic properties that reflect their specific roles in cellular and whole body glucose homeostasis. Separate review articles on many of the Glut proteins have recently appeared in this journal. Here, we provide a very brief summary of the known properties of the 14 Glut proteins and suggest some avenues of future investigation in this area.
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              The Anti-diabetic drugs rosiglitazone and metformin stimulate AMP-activated protein kinase through distinct signaling pathways.

              AMP-activated protein kinase (AMPK) is activated within the cell in response to multiple stresses that increase the intracellular AMP:ATP ratio. Here we show that incubation of muscle cells with the thiazolidinedione, rosiglitazone, leads to a dramatic increase in this ratio with the concomitant activation of AMPK. This finding raises the possibility that a number of the beneficial effects of the thiazolidinediones could be mediated via activation of AMPK. Furthermore, we show that in addition to the classical activation pathway, AMPK can also be stimulated without changing the levels of adenine nucleotides. In muscle cells, both hyperosmotic stress and the anti-diabetic agent, metformin, activate AMPK in the absence of any increase in the AMP:ATP ratio. However, although activation is no longer dependent on this ratio, it still involves increased phosphorylation of threonine 172 within the catalytic (alpha) subunit. AMPK stimulation in response to hyperosmotic stress does not appear to involve phosphatidylinositol 3-phosphate kinase, protein kinase C, mitogen-activated protein (MAP) kinase kinase, or p38 MAP kinase alpha or beta. Our results demonstrate that AMPK can be activated by at least two distinct signaling mechanisms and suggest that it may play a wider role in the cellular stress response than was previously understood.
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                Author and article information

                Journal
                Evid Based Complement Alternat Med
                Evid Based Complement Alternat Med
                ECAM
                Evidence-based Complementary and Alternative Medicine : eCAM
                Hindawi Publishing Corporation
                1741-427X
                1741-4288
                2013
                27 May 2013
                27 May 2013
                : 2013
                : 172537
                Affiliations
                1Canadian Institutes of Health Research (CIHR) Team in Aboriginal Antidiabetic Medicines, Université de Montréal, P.O. Box 6128, Downtown Station, Montréal, QC, Canada H3C 3J7
                2Natural Health Products and Metabolic Diseases Laboratory, Department of Pharmacology, Université de Montréal, P.O. Box 6128, Downtown Station, Montréal, QC, Canada H3C 3J7
                3Institute of Nutrition and Functional Foods, Université Laval, Quebec City, QC, Canada G1V 0A6
                4Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montreal, QC, Canada H1W 4A4
                5Department of Biology and Center for Research in Biopharmaceuticals and Biotechnology, University of Ottawa, Ottawa, ON, Canada K1N 6N5
                Author notes
                *Lina Musallam: l.musallam@ 123456gmail.com and

                Academic Editor: Ravirajsinh N. Jadeja

                Article
                10.1155/2013/172537
                3678421
                23781256
                f6f275d5-2905-4f68-b985-d2c3e28e9936
                Copyright © 2013 Despina Harbilas et al.

                This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 13 February 2013
                : 8 April 2013
                Funding
                Funded by: 501100000024 Canadian Institutes of Health Research
                Award ID: CTP-79855
                Categories
                Research Article

                Complementary & Alternative medicine
                Complementary & Alternative medicine

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