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Watadani R, Kotoh J, Sasaki D, Someya A, Matsumoto K, Maeda A. 10-Hydroxy-2-decenoic acid, a natural product, improves hyperglycemia and insulin resistance in obese/diabetic KK-Ay mice, but does not prevent obesity. J Vet Med Sci 2017; 79:1596-1602. [PMID: 28740028 PMCID: PMC5627335 DOI: 10.1292/jvms.17-0348] [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] [Indexed: 12/11/2022] Open
Abstract
10-Hydroxy-2-decenoic acid (10H2DA) is a fatty acid found in royal jelly (RJ). In healthy mice, it activates 5’-AMP-activated protein kinase (AMPK) and increases glucose transporter 4 (GLUT4) translocation. Therefore, we examined
whether 10H2DA has a potential therapeutic effect against type 2 diabetes in obese/diabetic KK-Ay mice. 10H2DA (3 mg/kg body weight) was administered to female KK-Ay mice for 4 weeks by oral gavage. Phenotypes for body weight,
plasma glucose by oral glucose tolerance test and insulin levels were measured. mRNA and protein levels were determined using qRT-PCR and Western blot analyses, respectively. Long-term administration of 10H2DA significantly
improved hyperglycemia and insulin resistance in KK-Ay mice, but did not prevent obesity. 10H2DA increased the expression of phosphorylated AMPK (pAMPK) protein in skeletal muscles; however, this expression did not correlate with
increased GLUT4 translocation. Furthermore, 10H2DA neither enhanced the expression of adiponectin receptor mRNA nor activated the insulin signaling cascade, such as GSK-3β phosphorylation, in the liver. We found that
10H2DA-treated mice had a significant increase in the expression of peroxisome proliferator-activated receptor gamma coactivator 1 alpha (Pgc-1α) mRNA in skeletal muscles compared with non-treated group
(P=0.0024). These findings suggest that 10H2DA is involved in the improvement of type 2 diabetes, at least in part via activation of Pgc-1α expression, but does not prevent obesity.
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Affiliation(s)
- Risa Watadani
- Department of Animal Medical Sciences, Faculty of Life Sciences, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-ku, Kyoto 603-8555, Japan
| | - Jun Kotoh
- Department of Animal Medical Sciences, Faculty of Life Sciences, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-ku, Kyoto 603-8555, Japan
| | - Daiki Sasaki
- Department of Animal Medical Sciences, Faculty of Life Sciences, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-ku, Kyoto 603-8555, Japan
| | - Azusa Someya
- Department of Animal Medical Sciences, Faculty of Life Sciences, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-ku, Kyoto 603-8555, Japan
| | - Kozo Matsumoto
- Department of Animal Medical Sciences, Faculty of Life Sciences, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-ku, Kyoto 603-8555, Japan
| | - Akihiko Maeda
- Department of Animal Medical Sciences, Faculty of Life Sciences, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-ku, Kyoto 603-8555, Japan
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2
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Kristensen JM, Treebak JT, Schjerling P, Goodyear L, Wojtaszewski JFP. Two weeks of metformin treatment induces AMPK-dependent enhancement of insulin-stimulated glucose uptake in mouse soleus muscle. Am J Physiol Endocrinol Metab 2014; 306:E1099-109. [PMID: 24644243 PMCID: PMC4971810 DOI: 10.1152/ajpendo.00417.2013] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Metformin-induced activation of the 5'-AMP-activated protein kinase (AMPK) has been associated with enhanced glucose uptake in skeletal muscle, but so far no direct causality has been examined. We hypothesized that an effect of in vivo metformin treatment on glucose uptake in mouse skeletal muscles is dependent on AMPK signaling. Oral doses of metformin or saline treatment were given to muscle-specific kinase dead (KD) AMPKα2 mice and wild-type (WT) littermates either once or chronically for 2 wk. Soleus and extensor digitorum longus muscles were used for measurements of glucose transport and Western blot analyses. Chronic treatment with metformin enhanced insulin-stimulated glucose uptake in soleus muscles of WT (∼45%, P < 0.01) but not of AMPK KD mice. Insulin signaling at the level of Akt protein expression or Thr(308) and Ser(473) phosphorylation was not changed by metformin treatment. Insulin signaling at the level of Akt and TBC1D4 protein expression as well as Akt Thr(308)/Ser(473) and TBC1D4 Thr(642)/Ser(711) phosphorylation were not changed by metformin treatment. Also, protein expressions of Rab4, GLUT4, and hexokinase II were unaltered after treatment. The acute metformin treatment did not affect glucose uptake in muscle of either of the genotypes. In conclusion, we provide novel evidence for a role of AMPK in potentiating the effect of insulin on glucose uptake in soleus muscle in response to chronic metformin treatment.
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Affiliation(s)
- Jonas Møller Kristensen
- Molecular Physiology Group, August Krogh Centre, Department of Nutrition, Exercise and Sport Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jonas T Treebak
- Molecular Physiology Group, August Krogh Centre, Department of Nutrition, Exercise and Sport Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Peter Schjerling
- Institute of Sports Medicine, Department of Orthopedic Surgery M, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark; and
| | - Laurie Goodyear
- Research Division, Joslin Diabetes Center and Department of Medicine, Harvard Medical School, Boston, Massachusetts
| | - Jørgen F P Wojtaszewski
- Molecular Physiology Group, August Krogh Centre, Department of Nutrition, Exercise and Sport Sciences, University of Copenhagen, Copenhagen, Denmark;
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3
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Hoffman NJ, Penque BA, Habegger KM, Sealls W, Tackett L, Elmendorf JS. Chromium enhances insulin responsiveness via AMPK. J Nutr Biochem 2014; 25:565-72. [PMID: 24725432 DOI: 10.1016/j.jnutbio.2014.01.007] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Revised: 01/02/2014] [Accepted: 01/24/2014] [Indexed: 12/19/2022]
Abstract
Trivalent chromium (Cr(3+)) is known to improve glucose homeostasis. Cr(3+) has been shown to improve plasma membrane-based aspects of glucose transporter GLUT4 regulation and increase activity of the cellular energy sensor 5' AMP-activated protein kinase (AMPK). However, the mechanism(s) by which Cr(3+) improves insulin responsiveness and whether AMPK mediates this action is not known. In this study we tested if Cr(3+) protected against physiological hyperinsulinemia-induced plasma membrane cholesterol accumulation, cortical filamentous actin (F-actin) loss and insulin resistance in L6 skeletal muscle myotubes. In addition, we performed mechanistic studies to test our hypothesis that AMPK mediates the effects of Cr(3+) on GLUT4 and glucose transport regulation. Hyperinsulinemia-induced insulin-resistant L6 myotubes displayed excess membrane cholesterol and diminished cortical F-actin essential for effective glucose transport regulation. These membrane and cytoskeletal abnormalities were associated with defects in insulin-stimulated GLUT4 translocation and glucose transport. Supplementing the culture medium with pharmacologically relevant doses of Cr(3+) in the picolinate form (CrPic) protected against membrane cholesterol accumulation, F-actin loss, GLUT4 dysregulation and glucose transport dysfunction. Insulin signaling was neither impaired by hyperinsulinemic conditions nor enhanced by CrPic, whereas CrPic increased AMPK signaling. Mechanistically, siRNA-mediated depletion of AMPK abolished the protective effects of CrPic against GLUT4 and glucose transport dysregulation. Together these findings suggest that the micronutrient Cr(3+), via increasing AMPK activity, positively impacts skeletal muscle cell insulin sensitivity and glucose transport regulation.
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Affiliation(s)
- Nolan J Hoffman
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Brent A Penque
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Kirk M Habegger
- Department of Biochemistry and Molecular Biology, Center for Diabetes Research, Indiana University School of Medicine, Indianapolis, IN 46202, USA; Department of Medicine - Endocrinology, Diabetes & Metabolism University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Whitney Sealls
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Lixuan Tackett
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Jeffrey S Elmendorf
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN 46202, USA; Department of Biochemistry and Molecular Biology, Center for Diabetes Research, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
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4
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Fellmann L, Nascimento AR, Tibiriça E, Bousquet P. Murine models for pharmacological studies of the metabolic syndrome. Pharmacol Ther 2012. [PMID: 23178510 DOI: 10.1016/j.pharmthera.2012.11.004] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Metabolic syndrome has been described as the association of insulin resistance, hypertension, hyperlipidemia and obesity. Its prevalence increased dramatically, mainly in developed countries. Animal models are essential to understand the pathophysiology of this syndrome. This review presents the murine models of metabolic syndrome the most often used in pharmacological studies. The most common metabolic syndrome models exhibit a non-functional leptin pathway, or metabolic disorders induced by high fat diets. In a first part, and after a short introduction on leptin, its receptor and mechanism of action, we provide a detailed description of each model: SHROB, SHHF, JCR:LA-cp, Zucker, ZDF, Wistar Ottawa Karlsburg W, and Otsuka Long-Evans Tokushima Fatty rats, ob/ob, db/db, agouti yellow and Mc4R KO mice. The second part of this review is dedicated to metabolic syndrome models obtained by high fat feeding.
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Affiliation(s)
- Lyne Fellmann
- Laboratory of Neurobiology and Cardiovascular Pharmacology, EA4438, Faculty of Medicine, University of Strasbourg, France
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5
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Gaster M. Fibre Type Dependent Expression of Glucose Transporters in Human Skeletal Muscles. APMIS 2008. [DOI: 10.1111/j.1600-0463.2007.apmv115s121.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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6
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Horvath EM, Tackett L, McCarthy AM, Raman P, Brozinick JT, Elmendorf JS. Antidiabetogenic effects of chromium mitigate hyperinsulinemia-induced cellular insulin resistance via correction of plasma membrane cholesterol imbalance. Mol Endocrinol 2007; 22:937-50. [PMID: 18165437 DOI: 10.1210/me.2007-0410] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Previously, we found that a loss of plasma membrane (PM) phosphatidylinositol 4,5-bisphosphate (PIP2)-regulated filamentous actin (F-actin) structure contributes to insulin-induced insulin resistance. Interestingly, we also demonstrated that chromium picolinate (CrPic), a dietary supplement thought to improve glycemic status in insulin-resistant individuals, augments insulin-regulated glucose transport in insulin-sensitive 3T3-L1 adipocytes by lowering PM cholesterol. Here, to gain mechanistic understanding of these separate observations, we tested the prediction that CrPic would protect against insulin-induced insulin resistance by improving PM features important in cytoskeletal structure and insulin sensitivity. We found that insulin-induced insulin-resistant adipocytes display elevated PM cholesterol with a reciprocal decrease in PM PIP2. This lipid imbalance and insulin resistance was corrected by the cholesterol-lowering action of CrPic. The PM lipid imbalance did not impair insulin signaling, nor did CrPic amplify insulin signal transduction. In contrast, PM analyses corroborated cholesterol and PIP2 interactions influencing cytoskeletal structure. Because extensive in vitro study documents an essential role for cytoskeletal capacity in insulin-regulated glucose transport, we next evaluated intact skeletal muscle from obese, insulin-resistant Zucker (fa/fa) rats. Because insulin resistance in these animals likely involves multiple mechanisms, findings that cholesterol-lowering restored F-actin cytoskeletal structure and insulin sensitivity to that witnessed in lean control muscle were striking. Also, experiments using methyl-beta-cyclodextrin to shuttle cholesterol into or out of membranes respectively recapitulated the insulin-induced insulin-resistance and protective effects of CrPic on membrane/cytoskeletal interactions and insulin sensitivity. These data predict a PM cholesterol basis for hyperinsulinemia-associated insulin resistance and importantly highlight the reversible nature of this abnormality.
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Affiliation(s)
- Emily M Horvath
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Center for Diabetes Research, Indianapolis, Indiana 46202, USA
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7
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Suwa M, Egashira T, Nakano H, Sasaki H, Kumagai S. Metformin increases the PGC-1α protein and oxidative enzyme activities possibly via AMPK phosphorylation in skeletal muscle in vivo. J Appl Physiol (1985) 2006; 101:1685-92. [PMID: 16902066 DOI: 10.1152/japplphysiol.00255.2006] [Citation(s) in RCA: 153] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
AMP-activated protein kinase (AMPK), which was activated by an antihyperglycemic drug metformin, has been hypothesized to mediate metabolic adaptations. The purposes of the present study were 1) to confirm whether acute metformin administration induced AMPK phosphorylation and 2) to determine whether chronic metformin treatment increased the peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC-1alpha) protein expression, glycolytic and oxidative enzyme activities, and cytochrome c and glucose transporter-4 (GLUT4) protein expressions in the rat soleus and red and white gastrocnemius muscles. The single oral administration of metformin (300 mg/kg body wt) enhanced the AMPK phosphorylation at 5 and/or 6 h after treatment. In the chronic study, rats were fed either normal chow or chow containing 1% metformin for 14 days. Metformin treatment resulted in a mean daily metformin intake of 631 mg.kg body wt(-1).day(-1). Metformin increased the PGC-1alpha content in all three muscles. Metformin increased the hexokinase activity in the white gastrocnemius, the citrate synthase activity in all three muscles, and the beta-hydroxyacyl-CoA dehydrogenase activity in the soleus. The cytochrome c protein content in the soleus muscle also increased. The GLUT4 content was unchanged by metformin. These results suggest that metformin enhances the PGC-1alpha expression and mitochondrial biogenesis possibly at least in part via AMPK phosphorylation in the skeletal muscle. Metformin has thus been proposed to possibly ameliorate insulin resistance, at least partially, by means of such metabolic effects.
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Affiliation(s)
- Masataka Suwa
- Institute of Health Science, Kyushu University, Kasuga, Fukuoka 816-8580, Japan.
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8
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Pattar GR, Tackett L, Liu P, Elmendorf JS. Chromium picolinate positively influences the glucose transporter system via affecting cholesterol homeostasis in adipocytes cultured under hyperglycemic diabetic conditions. Mutat Res 2006; 610:93-100. [PMID: 16870493 PMCID: PMC2424232 DOI: 10.1016/j.mrgentox.2006.06.018] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/05/2006] [Indexed: 11/26/2022]
Abstract
Since trivalent chromium (Cr(3+)) enhances glucose metabolism, interest in the use of Cr(3+)as a therapy for type 2 diabetes has grown in the mainstream medical community. Moreover, accumulating evidence suggests that Cr(3+) may also benefit cardiovascular disease (CVD) and atypical depression. We have found that cholesterol, a lipid implicated in both CVD and neurodegenerative disorders, also influences cellular glucose uptake. A recent study in our laboratory shows that exposure of 3T3-L1 adipocytes to chromium picolinate (CrPic, 10 nM) induces a loss of plasma membrane cholesterol. Concomitantly, accumulation of intracellularly sequestered glucose transporter GLUT4 at the plasma membrane was dependent on the CrPic-induced cholesterol loss. Since CrPic supplementation has the greatest benefit on glucose metabolism in hyperglycemic insulin-resistant individuals, we asked here if the CrPic effect on cells was glucose-dependent. We found that GLUT4 redistribution in cells treated with CrPic occurs only in cells cultured under high glucose (25 mM) conditions that resemble the diabetic-state, and not in cells cultured under non-diabetic (5.5 mM glucose) conditions. Examination of the effect of CrPic on proteins involved in cholesterol homeostasis revealed that the activity of sterol regulatory element-binding protein (SREBP), a membrane-bound transcription factor ultimately responsible for controlling cellular cholesterol balance, was upregulated by CrPic. In addition, ABCA1, a major player in mediating cholesterol efflux was decreased, consistent with SREBP transcriptional repression of the ABCA1 gene. Although the exact mechanism of Cr(3+)-induced cholesterol loss remains to be determined, these cellular responses highlight a novel and significant effect of chromium on cholesterol homeostasis. Furthermore, these findings provide an important clue to our understanding of how chromium supplementation might benefit hypercholesterolemia-associated disorders.
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Affiliation(s)
- Guruprasad R Pattar
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Center for Diabetes Research, Indianapolis, IN 46202, United States
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9
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Abstract
A regulação da homeostasia intra e extra-celular da glicose está diretamente relacionada ao controle preciso da expressão dos genes que codificam as diferentes isoformas de proteínas transportadoras de glicose, as quais se expressam de maneira tecido-específica, em conseqüência do padrão de ativação dos fatores transcricionais reguladores de cada gene, em cada tipo celular. A síndrome metabólica (SM) abrange uma grande variedade de alterações fisiopatológicas, todas de repercussões sistêmicas, acometendo os mais distintos territórios do organismo, nos quais alterações nos transportadores de glicose presentes são observadas em maior ou menor grau. A presente revisão abordará as alterações na expressão de transportadores de glicose claramente demonstradas na literatura, cujas repercussões nos fluxos territoriais de glicose auxiliam na compreensão de mecanismos fisiopatológicos da SM, assim como dos tratamentos propostos para esta entidade.
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Affiliation(s)
- Ubiratan Fabres Machado
- Departamento de Fisiologia e Biofísica, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, SP.
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10
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Klip A, Marette A. Regulation of Glucose Transporters by Insulin and Exercise: Cellular Effects and Implications for Diabetes. Compr Physiol 2001. [DOI: 10.1002/cphy.cp070214] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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11
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Larkin LM, Reynolds TH, Supiano MA, Kahn BB, Halter JB. Effect of aging and obesity on insulin responsiveness and glut-4 glucose transporter content in skeletal muscle of Fischer 344 x Brown Norway rats. J Gerontol A Biol Sci Med Sci 2001; 56:B486-92. [PMID: 11682570 PMCID: PMC2714732 DOI: 10.1093/gerona/56.11.b486] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
This study investigated the metabolic changes with age in the Fischer 344 x Brown Norway rat and its suitability as an animal model of postmaturational insulin resistance. Specifically, we determined whether an age-associated decrease in glucose disposal is associated with diminished whole body insulin responsiveness and/or a decrease in glucose transporter (GLUT-4) protein and mRNA content in medial gastrocnemius muscle of male Fischer 344 x Brown Norway rats of ages 8, 18, and 28 months. Fasting plasma glucose was unchanged with age. There was a significant age effect on visceral adiposity, fasting plasma insulin levels, insulin responsiveness, and GLUT-4 protein content. Insulin responsiveness and GLUT-4 protein were lower in the 18-month-old rats than in the 8-month-old rats. The findings of age-associated increases in visceral adiposity and insulin resistance, and decreases in GLUT-4 in the Fisher 344 x Brown Norway rat, suggest that this rat strain may be an appropriate model for studying the effects of aging on glucose homeostasis.
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Affiliation(s)
- L M Larkin
- Division of Geriatric Medicine, Department of Internal Medicine, University of Michigan, Ann Arbor 48109-0940, USA.
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12
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Santuré M, Pitre M, Gaudreault N, Marette A, Nadeau A, Bachelard H. Effect of metformin on the vascular and glucose metabolic actions of insulin in hypertensive rats. Am J Physiol Gastrointest Liver Physiol 2000; 278:G682-92. [PMID: 10801260 DOI: 10.1152/ajpgi.2000.278.5.g682] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We investigated the long-term effect of metformin treatment on blood pressure, insulin sensitivity, and vascular responses to insulin in conscious spontaneously hypertensive rats (SHR). The rats were instrumented with intravascular catheters and pulsed Doppler flow probes to measure blood pressure, heart rate, and blood flow. Insulin sensitivity was assessed by the euglycemic hyperinsulinemic clamp technique. Two groups of SHR received metformin (100 or 300 mg x kg(-1) x day(-1)) for 3 wk while another group of SHR and a group of Wistar Kyoto (WKY) rats were left untreated. We found that vasodilation of skeletal muscle and renal vasculatures by insulin is impaired in SHR. Moreover, a reduced insulin sensitivity was detected in vivo and in vitro in isolated soleus and extensor digitorum longus muscles from SHR compared with WKY rats. Three weeks of treatment with metformin improves the whole-body insulin-mediated glucose disposal in SHR but has no blood pressure-lowering effect and no influence on vascular responses to insulin (4 mU x kg(-1) x min(-1)). An improvement in insulin-mediated glucose transport activity was detected in isolated muscles from metformin-treated SHR, but in the absence of insulin no changes in basal glucose transport activity were observed. It is suggested that part of the beneficial effect of metformin on insulin resistance results from a potentiation of the hormone-stimulating effect on glucose transport in peripheral tissues (mainly skeletal muscle). The results argue against a significant antihypertensive or vascular effect of metformin in SHR.
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Affiliation(s)
- M Santuré
- Hypertension Research Unit, Department of Physiology, Laval University Hospital Research Center, Sainte-Foy, Quebec, Canada G1V 4G2
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13
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Morris MJ, Tortelli CF, Filippis A, Proietto J. Reduced BAT function as a mechanism for obesity in the hypophagic, neuropeptide Y deficient monosodium glutamate-treated rat. REGULATORY PEPTIDES 1998; 75-76:441-7. [PMID: 9802441 DOI: 10.1016/s0167-0115(98)00100-1] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Neuropeptide Y (NPY) exerts effects on food intake at the level of the paraventricular nucleus (PVN), which receives a dense projection from the arcuate nucleus. Monosodium glutamate (MSG) has been shown to induce hyperadiposity despite hypophagia associated with chemical ablation of the arcuate nucleus. We investigated the mechanism for the excess fat accumulation by studying the time course of changes in brain NPY content, food intake, leptin levels and BAT GLUT4 content after neonatal MSG treatment. Male rat pups were injected with MSG or saline vehicle on days 2, 4, and 6 and examined at 30 and 90 days. Plasma leptin, body mass, length, adipose tissue mass and brown fat GLUT4 were measured and brains dissected for measurement of NPY content. By 30 days, NPY concentrations were reduced in the arcuate nucleus and anterior hypothalamus, and animals tended to be hypophagic. Peripheral adipose tissue levels were less than controls, in line with their low leptin concentrations. At 90 days, MSG treatment was associated with marked reductions in NPY concentrations in several hypothalamic areas, including the PVN and arcuate nucleus, along with increased adiposity and plasma leptin. Animals also displayed marked hypophagia. Levels of GLUT4 transporter were reduced in brown adipose tissue at both ages. The early decrease in brown fat GLUT4 suggests an impairment of the hypothalamic sympathetic input to brown fat which disrupts thermogenesis, contributing to the development of adiposity in the presence of hypophagia.
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Affiliation(s)
- M J Morris
- Department of Pharmacology, University of Melbourne, Parkville, Victoria, Australia.
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14
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Hirata AE, Andrade IS, Vaskevicius P, Dolnikoff MS. Monosodium glutamate (MSG)-obese rats develop glucose intolerance and insulin resistance to peripheral glucose uptake. Braz J Med Biol Res 1997; 30:671-4. [PMID: 9283637 DOI: 10.1590/s0100-879x1997000500016] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Different levels of insulin sensitivity have been described in several animal models of obesity as well as in humans. Monosodium glutamate (MSG)-obese mice were considered not to be insulin resistant from data obtained in oral glucose tolerance tests. To reevaluate insulin resistance by the intravenous glucose tolerance test (IVGTT) and by the clamp technique, newborn male Wistar rats (N = 20) were injected 5 times, every other day, with 4 g/kg MSG (N = 10) or saline (control; N = 10) during the first 10 days of age. At 3 months, the IVGTT was performed by injecting glucose (0.75 g/kg) through the jugular vein into freely moving rats. During euglycemic clamping plasma insulin levels were increased by infusing 3 mU.kg-1.min-1 of regular insulin until a steady-state plateau was achieved. The basal blood glucose concentration did not differ between the two experimental groups. After the glucose load, increased values of glycemia (P < 0.001) in MSG-obese rats occurred at minute 4 and from minute 16 to minute 32. These results indicate impaired glucose tolerance. Basal plasma insulin levels were 39.9 +/- 4 microU/ml in control and 66.4 +/- 5.3 microU/ml in MSG-obese rats. The mean post-glucose area increase of insulin was 111% higher in MSG-obese than in control rats. When insulinemia was clamped at 102 or 133 microU/ml in control and MSG rats, respectively, the corresponding glucose infusion rate necessary to maintain euglycemia was 17.3 +/- 0.8 mg.kg-1.min-1 for control rats while 2.1 +/- 0.3 mg.kg-1.min-1 was sufficient for MSG-obese rats. The 2-h integrated area for total glucose metabolized, in mg.min.dl-1, was 13.7 +/- 2.3 vs 3.3 +/- 0.5 for control and MSG rats, respectively. These data demonstrate that MSG-obese rats develop insulin resistance to peripheral glucose uptake.
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Affiliation(s)
- A E Hirata
- Departamento de Fisiologia, Universidade Federal de São Paulo, Brasil
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15
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Worm D, Handberg A, Hoppe E, Vinten J, Beck-Nielsen H. Decreased skeletal muscle phosphotyrosine phosphatase (PTPase) activity towards insulin receptors in insulin-resistant Zucker rats measured by delayed Europium fluorescence. Diabetologia 1996; 39:142-8. [PMID: 8635665 DOI: 10.1007/bf00403956] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
In order to measure the phosphotyrosine phosphatase (PTPase) activity in small muscle biopsies, a sandwich-immunofluorescence assay was developed using the phosphorylated human insulin receptor as a substrate, a C-terminal insulin receptor antibody as catching antibody and Europium-labelled anti-phosphotyrosine as detecting antibody. Soluble and particulate muscle fractions were prepared from soleus muscle of obese, diabetic (fa/fa) Zucker rats and their lean littermates (Fa/-). In the soluble muscle fractions of the obese (fa/fa) rats PTPase activity was significantly reduced compared to control (Fa/-) rats (45.2 +/- 2.6% vs 61.3 +/- 4.7%, p < 0.02). This reduction was completely prevented by 24 days of metformin treatment which decreased plasma glucose and plasma insulin levels. In particulate muscle fractions, however, no difference in PTPase activity was found among any groups of rats examined. These results show that the alterations in soluble PTPase activity in the insulin-resistant, diabetic Zucker rat vary with the abnormality in glucose homeostasis.
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Affiliation(s)
- D Worm
- Diabetes Research Centre, Odense University Hospital, Denmark
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16
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Uphues I, Chern Y, Eckel J. Insulin-dependent translocation of the small GTP-binding protein rab3C in cardiac muscle: studies on insulin-resistant Zucker rats. FEBS Lett 1995; 377:109-12. [PMID: 8543030 DOI: 10.1016/0014-5793(95)01315-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The failure of insulin-regulated recruitment of the GLUT4 glucose transporter in cardiac muscle of obese Zucker rats is associated with alterations of the subcellular distribution of the small-molecular-mass GTP-binding protein rab4A. Here, we show by subcellular fractionation and Western blotting a translocation of the small-molecular-mass GTP-binding protein rab3C from microsomal membranes to plasma membranes in lean control rats following in vivo insulin stimulation. However, in cardiac muscle of obese animals no significant effect of the hormone on the subcellular distribution of rab3C was observed. In GLUT4-enriched membrane vesicles, obtained from cardiac microsomes of the obese group as well as of lean controls, rab3C was not detectable. It is suggested that the altered behaviour of rab3C may contribute to an impaired trafficking of GLUT4 in the insulin-resistant state.
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Affiliation(s)
- I Uphues
- Laboratory of Molecular Cardiology, Diabetes Research Institute, Düsseldorf, Germany
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17
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Uphues I, Kolter T, Goud B, Eckel J. Failure of insulin-regulated recruitment of the glucose transporter GLUT4 in cardiac muscle of obese Zucker rats is associated with alterations of small-molecular-mass GTP-binding proteins. Biochem J 1995; 311 ( Pt 1):161-6. [PMID: 7575448 PMCID: PMC1136133 DOI: 10.1042/bj3110161] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Cardiac ventricular tissue of lean and genetically obese (fa/fa) Zucker rats was used to study the expression, subcellular distribution and insulin-induced recruitment of the glucose transporter GLUT4 and to elucidate possible molecular alterations of the translocation process. Hearts were removed from basal and insulin-treated (20 min) lean and obese Zucker rats, and processed for subcellular fractionation and Western blotting of proteins. In obese rats, the total GLUT4 content in a crude membrane fraction was reduced to 75 +/- 8% (P = 0.019) of lean controls. In contrast, GLUT4 abundance in plasma membranes was not significantly different between lean and obese rats with a concomitant decrease (47 +/- 3%) in the microsomal fraction of obese animals. In plasma membranes of lean animals insulin was found to increase the GLUT4 abundance to 294 +/- 43% of control with a significantly (P = 0.009) reduced effect in the obese group (139 +/- 10% of control). In these animals insulin failed to recruit GLUT4 from the microsomal fraction, whereas the hormone induced a significant decrease (41 +/- 4%) of microsomal GLUT4 in lean controls. In GLUT4-enriched membrane vesicles, obtained from cardiac microsomes of lean rats, a 24 kDa GTP-binding protein could be detected, whereas no significant labelling of this species was observed in GLUT4 vesicles prepared from obese animals. In addition to the translocation of GLUT4, insulin was found to promote the movement of the small GTP-binding protein rab4A from the cytosol (decrease to 61 +/- 13% of control) to the plasma membrane (increase to 177 +/- 19% of control) in lean rats with no effect of the hormone on rab4A redistribution in the obese group. In conclusion, cardiac glucose uptake of insulin-resistant obese Zucker rats is subject to multiple cellular abnormalities involving a reduced expression, altered redistribution and defective recruitment of GLUT4. We show here an association of the latter defect with alterations at the level of small GTP-binding proteins possibly leading to an impaired trafficking of GLUT4 in the insulin-resistant state.
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Affiliation(s)
- I Uphues
- Laboratory of Molecular Cardiology, Diabetes Research Institute, Düsseldorf, Germany
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18
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Rouru J, Koulu M, Peltonen J, Santti E, Hänninen V, Pesonen U, Huupponen R. Effects of metformin treatment on glucose transporter proteins in subcellular fractions of skeletal muscle in (fa/fa) Zucker rats. Br J Pharmacol 1995; 115:1182-7. [PMID: 7582542 PMCID: PMC1908777 DOI: 10.1111/j.1476-5381.1995.tb15022.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
1. The present study was designed to clarify the cellular mechanism through which the antihyperglycaemic drug, metformin, exerts its effects. For this purpose the contents of glucose transporter protein isoforms GLUT1 and GLUT4 were measured in plasma membrane and intracellular membrane fractions of skeletal muscle obtained from genetically obese, insulin-resistant Zucker rats. 2. Hindlimb muscles were dissected from metformin-treated (300 mg kg-1 day-1, p.o., for 12 days) and control rats in basal treatment state, and after acute stimulation with insulin (22 u kg-1, i.p.). Since metformin treatment reduces food intake, we also used a pair-fed control group to investigate the effects of altered insulinaemia per se. Glucose transporter levels were analysed by Western blot and slot blot-techniques. In addition, 2-deoxy-[14C]-glucose uptake in isolated muscle strips was evaluated. 3. No changes were noted in the contents of GLUT1 proteins in any of the subcellular fractions after metformin treatment. The contents of GLUT4 in subcellular fractions were not altered in the basal treatment state. After acute insulin exposure the content of GLUT4 in the intracellular membrane fraction declined significantly in the metformin-treated group, while no significant effect was seen in the plasma membrane fraction. In agreement with these results, metformin treatment did not alter 2-deoxyglucose uptake into isolated muscle strips. 4. In conclusion, the present study does not support the concept that metformin would enhance translocation of glucose transporter proteins from the intracellular compartment to the plasma membrane in skeletal muscle in vivo.
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Affiliation(s)
- J Rouru
- Department of Pharmacology, University of Turku, Finland
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19
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Galuska D, Nolte LA, Zierath JR, Wallberg-Henriksson H. Effect of metformin on insulin-stimulated glucose transport in isolated skeletal muscle obtained from patients with NIDDM. Diabetologia 1994; 37:826-32. [PMID: 7988785 DOI: 10.1007/bf00404340] [Citation(s) in RCA: 85] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Metformin has been demonstrated to lower blood glucose in vivo by a mechanism which increases peripheral glucose uptake. Furthermore, the therapeutic concentration of metformin has been estimated to be in the order of 0.01 mmol/l. We investigated the effect of metformin on insulin-stimulated 3-0-methylglucose transport in isolated skeletal muscle obtained from seven patients with non-insulin-dependent diabetes mellitus (NIDDM) and from eight healthy subjects. Whole body insulin-mediated glucose utilization was decreased by 45% (p < 0.05) in the diabetic subjects when studied at 8 mmol/l glucose, compared to the healthy subjects studied at 5 mmol/l glucose. Metformin, at concentrations of 0.1 and 0.01 mmol/l, had no effect on basal or insulin-stimulated (100 microU/ml) glucose transport in muscle strips from either of the groups. However, the two control subjects and three patients with NIDDM which displayed a low rate of insulin-mediated glucose utilization (< 20 mumol.kg-1.min-1), as well as in vitro insulin resistance, demonstrated increased insulin-stimulated glucose transport in the presence of metformin at 0.1 mmol/l (p < 0.05). In conclusion, the concentration of metformin resulting in a potentiating effect on insulin-stimulated glucose transport in insulin-resistant human skeletal muscle is 10-fold higher than the therapeutic concentrations administered to patients with NIDDM. Thus, it is conceivable that the hypoglycaemic effect of metformin in vivo may be due to an accumulation of the drug in the extracellular space of skeletal muscle, or to an effect of the drug distal to the glucose transport step.
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Affiliation(s)
- D Galuska
- Department of Clinical Physiology, Karolinska Hospital, Karolinska Institute, Stockholm, Sweden
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Handberg A, Kayser L, Høyer PE, Micheelsen J, Vinten J. Elevated GLUT 1 level in crude muscle membranes from diabetic Zucker rats despite a normal GLUT 1 level in perineurial sheaths. Diabetologia 1994; 37:443-8. [PMID: 8056180 DOI: 10.1007/s001250050130] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Recently, we demonstrated that approximately 60% of GLUT 1 in a crude membrane fraction of rat skeletal muscle originates from perineurial sheaths. To study the in vivo regulation of GLUT 1 expression in different tissues in muscles, we measured the level of GLUT 1 in crude muscle membranes and in perineurial sheaths in diabetic (fa/fa) Zucker rats and lean controls, with and without metformin treatment. The GLUT 1 concentration in perineurial sheaths was identical in all four groups of rats, both when measured by quantitative immunofluorescence and by immunoblotting and densitometry. In a fraction of crude membranes of soleus muscles GLUT 1 expression was more than two-fold higher in (fa/fa) rats than in lean controls (p < 0.005). Metformin treatment significantly elevated GLUT 1 in control rats (p < 0.05) and tended to decrease GLUT 1 in diabetic rats (p < 0.075). The expressions of GLUT 1 and GLUT 4 in crude muscle membranes were inversely correlated (p < 0.01), and GLUT 1 expression correlated positively with fasting glucose (p < 0.05). In conclusion, GLUT 1 expression in perineurial sheaths is unaffected by alterations in glucose homeostasis and by the genes responsible for obesity and diabetes in the Zucker rat. GLUT 1 expression in a crude membrane fraction of soleus muscle is increased in the diabetic animals, likely due to an increased expression in muscle cells proper.
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Affiliation(s)
- A Handberg
- Department of Medical Physiology, Panum Institute, University of Copenhagen, Denmark
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