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Woolcott OO, Richey JM, Kabir M, Chow RH, Iyer MS, Kirkman EL, Stefanovski D, Lottati M, Kim SP, Harrison LN, Ionut V, Zheng D, Hsu IR, Catalano KJ, Chiu JD, Bradshaw H, Wu Q, Kolka CM, Bergman RN. Corrections: High-Fat Diet-Induced Insulin Resistance does not Increase Plasma Anandamide Levels or Potentiate Anandamide Insulinotropic Effect in Isolated Canine Islets. PLoS One 2015; 10:e0131033. [PMID: 26075612 PMCID: PMC4468268 DOI: 10.1371/journal.pone.0131033] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
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Woolcott OO, Richey JM, Kabir M, Chow RH, Iyer MS, Kirkman EL, Stefanovski D, Lottati M, Kim SP, Harrison LN, Ionut V, Zheng D, Hsu IR, Catalano KJ, Chiu JD, Bradshaw H, Wu Q, Bergman RN. High-fat diet-induced insulin resistance does not increase plasma anandamide levels or potentiate anandamide insulinotropic effect in isolated canine islets. PLoS One 2015; 10:e0123558. [PMID: 25855974 PMCID: PMC4391925 DOI: 10.1371/journal.pone.0123558] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Accepted: 03/05/2015] [Indexed: 01/09/2023] Open
Abstract
Background Obesity has been associated with elevated plasma anandamide levels. In addition, anandamide has been shown to stimulate insulin secretion in vitro, suggesting that anandamide might be linked to hyperinsulinemia. Objective To determine whether high-fat diet-induced insulin resistance increases anandamide levels and potentiates the insulinotropic effect of anandamide in isolated pancreatic islets. Design and Methods Dogs were fed a high-fat diet (n = 9) for 22 weeks. Abdominal fat depot was quantified by MRI. Insulin sensitivity was assessed by the euglycemic-hyperinsulinemic clamp. Fasting plasma endocannabinoid levels were analyzed by liquid chromatography-mass spectrometry. All metabolic assessments were performed before and after fat diet regimen. At the end of the study, pancreatic islets were isolated prior to euthanasia to test the in vitro effect of anandamide on islet hormones. mRNA expression of cannabinoid receptors was determined in intact islets. The findings in vitro were compared with those from animals fed a control diet (n = 7). Results Prolonged fat feeding increased abdominal fat content by 81.3±21.6% (mean±S.E.M, P<0.01). In vivo insulin sensitivity decreased by 31.3±12.1% (P<0.05), concomitant with a decrease in plasma 2-arachidonoyl glycerol (from 39.1±5.2 to 15.7±2.0 nmol/L) but not anandamide, oleoyl ethanolamide, linoleoyl ethanolamide, or palmitoyl ethanolamide. In control-diet animals (body weight: 28.8±1.0 kg), islets incubated with anandamide had a higher basal and glucose-stimulated insulin secretion as compared with no treatment. Islets from fat-fed animals (34.5±1.3 kg; P<0.05 versus control) did not exhibit further potentiation of anandamide-induced insulin secretion as compared with control-diet animals. Glucagon but not somatostatin secretion in vitro was also increased in response to anandamide, but there was no difference between groups (P = 0.705). No differences in gene expression of CB1R or CB2R between groups were found. Conclusions In canines, high-fat diet-induced insulin resistance does not alter plasma anandamide levels or further potentiate the insulinotropic effect of anandamide in vitro.
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Affiliation(s)
- Orison O. Woolcott
- Diabetes and Obesity Research Institute, Cedars-Sinai Medical Center, Los Angeles, California, United States of America
- * E-mail:
| | - Joyce M. Richey
- Department of Physiology and Biophysics, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
| | - Morvarid Kabir
- Diabetes and Obesity Research Institute, Cedars-Sinai Medical Center, Los Angeles, California, United States of America
| | - Robert H. Chow
- Department of Physiology and Biophysics, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
| | - Malini S. Iyer
- Diabetes and Obesity Research Institute, Cedars-Sinai Medical Center, Los Angeles, California, United States of America
| | - Erlinda L. Kirkman
- Department of Animal Resources, University of Southern California, Los Angeles, California, United States of America
| | - Darko Stefanovski
- Diabetes and Obesity Research Institute, Cedars-Sinai Medical Center, Los Angeles, California, United States of America
| | - Maya Lottati
- Department of Physiology and Biophysics, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
| | - Stella P. Kim
- Diabetes and Obesity Research Institute, Cedars-Sinai Medical Center, Los Angeles, California, United States of America
| | - L. Nicole Harrison
- Department of Physiology and Biophysics, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
| | - Viorica Ionut
- Diabetes and Obesity Research Institute, Cedars-Sinai Medical Center, Los Angeles, California, United States of America
| | - Dan Zheng
- Department of Physiology and Biophysics, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
| | - Isabel R. Hsu
- Department of Physiology and Biophysics, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
| | - Karyn J. Catalano
- Department of Physiology and Biophysics, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
| | - Jenny D. Chiu
- Department of Physiology and Biophysics, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
| | - Heather Bradshaw
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, United States of America
| | - Qiang Wu
- Diabetes and Obesity Research Institute, Cedars-Sinai Medical Center, Los Angeles, California, United States of America
| | - Richard N. Bergman
- Diabetes and Obesity Research Institute, Cedars-Sinai Medical Center, Los Angeles, California, United States of America
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Kim SP, Woolcott OO, Hsu IR, Stefanoski D, Harrison LN, Zheng D, Lottati M, Kolka C, Catalano KJ, Chiu JD, Kabir M, Ionut V, Bergman RN, Richey JM. CB(1) antagonism restores hepatic insulin sensitivity without normalization of adiposity in diet-induced obese dogs. Am J Physiol Endocrinol Metab 2012; 302:E1261-8. [PMID: 22374758 PMCID: PMC3361982 DOI: 10.1152/ajpendo.00496.2011] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The endocannabinoid system is highly implicated in the development of insulin resistance associated with obesity. It has been shown that antagonism of the CB(1) receptor improves insulin sensitivity (S(I)). However, it is unknown whether this improvement is due to the direct effect of CB(1) blockade on peripheral tissues or secondary to decreased fat mass. Here, we examine in the canine dog model the longitudinal changes in S(I) and fat deposition when obesity was induced with a high-fat diet (HFD) and animals were treated with the CB(1) antagonist rimonabant. S(I) was assessed (n = 20) in animals fed a HFD for 6 wk to establish obesity. Thereafter, while HFD was continued for 16 additional weeks, animals were divided into two groups: rimonabant (1.25 mg·kg(-1)·day(-1) RIM; n = 11) and placebo (n = 9). Euglycemic hyperinsulinemic clamps were performed to evaluate changes in insulin resistance and glucose turnover before HFD (week -6) after HFD but before treatment (week 0) and at weeks 2, 6, 12, and 16 of treatment (or placebo) + HFD. Magnetic resonance imaging was performed to determine adiposity- related changes in S(I). Animals developed significant insulin resistance and increased visceral and subcutaneous adiposity after 6 wk of HFD. Treatment with RIM resulted in a modest decrease in total trunk fat with relatively little change in peripheral glucose uptake. However, there was significant improvement in hepatic insulin resistance after only 2 wk of RIM treatment with a concomitant increase in plasma adiponectin levels; both were maintained for the duration of the RIM treatment. CB(1) receptor antagonism appears to have a direct effect on hepatic insulin sensitivity that may be mediated by adiponectin and independent of pronounced reductions in body fat. However, the relatively modest effect on peripheral insulin sensitivity suggests that significant improvements may be secondary to reduced fat mass.
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Affiliation(s)
- Stella P Kim
- Dept. of Physiology and Biophysics, Univ. of Southern California Keck School of Medicine, 1333 San Pablo St. MMR 626, Los Angeles, CA 90033, USA.
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Abstract
OBJECTIVE Obesity causes insulin resistance, which has been interpreted as reduced downstream insulin signaling. However, changes in access of insulin to sensitive tissues such as skeletal muscle may also play a role. Insulin injected directly into skeletal muscle diffuses rapidly through the interstitial space to cause glucose uptake. When insulin resistance is induced by exogenous lipid infusion, this interstitial diffusion process is curtailed. Thus, the possibility exists that hyperlipidemia, such as that seen during obesity, may inhibit insulin action to muscle cells and exacerbate insulin resistance. Here we asked whether interstitial insulin diffusion is reduced in physiological obesity induced by a high-fat diet (HFD). RESEARCH DESIGN AND METHODS Dogs were fed a regular diet (lean) or one supplemented with bacon grease for 9-12 weeks (HFD). Basal insulin (0.2 mU x min(-1) x kg(-1)) euglycemic clamps were performed on fat-fed animals (n = 6). During clamps performed under anesthesia, five sequential doses of insulin were injected into the vastus medialis of one hind limb (INJ); the contralateral limb (NINJ) served as a control. RESULTS INJ lymph insulin showed an increase above NINJ in lean animals, but no change in HFD-fed animals. Muscle glucose uptake observed in lean animals did not occur in HFD-fed animals. CONCLUSIONS Insulin resistance induced by HFD caused a failure of intramuscularly injected insulin to diffuse through the interstitial space and failure to cause glucose uptake, compared with normal animals. High-fat feeding prevents the appearance of injected insulin in the interstitial space, thus reducing binding to skeletal muscle cells and glucose uptake.
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Affiliation(s)
- Cathryn M. Kolka
- From the Department of Physiology and Biophysics, University of Southern California, Los Angeles, California
| | - L. Nicole Harrison
- From the Department of Physiology and Biophysics, University of Southern California, Los Angeles, California
| | - Maya Lottati
- From the Department of Physiology and Biophysics, University of Southern California, Los Angeles, California
| | - Jenny D. Chiu
- From the Department of Physiology and Biophysics, University of Southern California, Los Angeles, California
| | - Erlinda L. Kirkman
- From the Department of Physiology and Biophysics, University of Southern California, Los Angeles, California
| | - Richard N. Bergman
- From the Department of Physiology and Biophysics, University of Southern California, Los Angeles, California
- Corresponding author: Richard N. Bergman,
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Richey JM, Woolcott OO, Stefanovski D, Harrison LN, Zheng D, Lottati M, Hsu IR, Kim SP, Kabir M, Catalano KJ, Chiu JD, Ionut V, Kolka C, Mooradian V, Bergman RN. Rimonabant prevents additional accumulation of visceral and subcutaneous fat during high-fat feeding in dogs. Am J Physiol Endocrinol Metab 2009; 296:E1311-8. [PMID: 19366874 PMCID: PMC3833919 DOI: 10.1152/ajpendo.90972.2008] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
We investigated whether rimonabant, a type 1 cannabinoid receptor antagonist, reduces visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) in dogs maintained on a hypercaloric high-fat diet (HHFD). To determine whether energy expenditure contributed to body weight changes, we also calculated resting metabolic rate. Twenty male dogs received either rimonabant (1.25 mg.kg(-1).day(-1), orally; n = 11) or placebo (n = 9) for 16 wk, concomitant with a HHFD. VAT, SAT, and nonfat tissue were measured by magnetic resonance imaging. Resting metabolic rate was assessed by indirect calorimetry. By week 16 of treatment, rimonabant dogs lost 2.5% of their body weight (P = 0.029), whereas in placebo dogs body weight increased by 6.2% (P < 0.001). Rimonabant reduced food intake (P = 0.027), concomitant with a reduction of SAT by 19.5% (P < 0.001). In contrast with the VAT increase with placebo (P < 0.01), VAT did not change with rimonabant. Nonfat tissue remained unchanged in both groups. Body weight loss was not associated with either resting metabolic rate (r(2) = 0.24; P = 0.154) or food intake (r(2) = 0.24; P = 0.166). In conclusion, rimonabant reduced body weight together with a reduction in abdominal fat, mainly because of SAT loss. Body weight changes were not associated with either resting metabolic rate or food intake. The findings provide evidence of a peripheral effect of rimonabant to reduce adiposity and body weight, possibly through a direct effect on adipose tissue.
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Affiliation(s)
- Joyce M Richey
- Dept. of Physiology, Keck School of Medicine, Univ. of Southern California, 1333 San Pablo St., MMR 626, Los Angeles, CA 90033, USA
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Chiu JD, Richey JM, Harrison LN, Zuniga E, Kolka CM, Kirkman E, Ellmerer M, Bergman RN. Direct administration of insulin into skeletal muscle reveals that the transport of insulin across the capillary endothelium limits the time course of insulin to activate glucose disposal. Diabetes 2008; 57:828-35. [PMID: 18223011 DOI: 10.2337/db07-1444] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE Intravenous insulin infusion rapidly increases plasma insulin, yet glucose disposal occurs at a much slower rate. This delay in insulin's action may be related to the protracted time for insulin to traverse the capillary endothelium. An increased delay may be associated with the development of insulin resistance. The purpose of the present study was to investigate whether bypassing the transendothelial insulin transport step and injecting insulin directly into the interstitial space would moderate the delay in glucose uptake observed with intravenous administration of the hormone. RESEARCH DESIGN AND METHODS Intramuscular injections of saline (n = 3) or insulin (n = 10) were administered directly into the vastus medialis of anesthetized dogs. Injections of 0.3, 0.5, 0.7, 1.0, and 3.0 units insulin were administered hourly during a basal insulin euglycemic glucose clamp (0.2mU x min(-1) x kg(-1)). RESULTS Unlike the saline group, each incremental insulin injection caused interstitial (lymph) insulin to rise within 10 min, indicating rapid diffusion of the hormone within the interstitial matrix. Delay in insulin action was virtually eliminated, indicated by immediate dose-dependent increments in hindlimb glucose uptake. Additionally, bypassing insulin transport by direct injection into muscle revealed a fourfold greater sensitivity to insulin of in vivo muscle tissue than previously reported from intravenous insulin administration. CONCLUSIONS Our results indicate that the transport of insulin to skeletal muscle is a rate-limiting step for insulin to activate glucose disposal. Based on these results, we speculate that defects in insulin transport across the endothelial layer of skeletal muscle will contribute to insulin resistance.
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Affiliation(s)
- Jenny D Chiu
- Department of Physiology and Biophysics, University of Southern California, Keck School of Medicine, 1333 San Pablo St., MMR 626, Los Angeles, CA 90033, USA
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Abstract
The nucleosome, the basic fundamental repeating unit of chromatin, contains two H2A/H2B dimers and an H3/H4 tetramer. Modulation of the structure and dynamics of the nucleosome is an important regulation mechanism of DNA-based chemistries in the eukaryotic cell, such as transcription and replication. One means of altering the properties of the nucleosome is by incorporation of histone variants. To provide insights into how histone variants may impact the thermodynamics of the nucleosome, the stability of the heterodimer between the H2A.Z variant and H2B was determined by urea-induced denaturation, monitored by far-UV circular dichroism, intrinsic Tyr fluorescence intensity, and anisotropy. In the absence of stabilizing agents, the H2A.Z/H2B dimer is only partially folded. The stabilizing cosolute, trimethylamine-N-oxide (TMAO) was used to promote folding of the unstable heterodimer. The equilibrium stability of the H2A.Z/H2B dimer is compared to that of the H2A/H2B dimer. The equilibrium folding of both histone dimers is highly reversible and best described by a two-state model, with no detectable equilibrium intermediates populated. The free energies of unfolding, in the absence of denaturant, of H2A.Z/H2B and H2A/H2B are 7.3 kcal mol(-1) and 15.5 kcal mol(-1), respectively, in 1 M TMAO. The H2A.Z/H2B dimer is the least stable histone fold characterized to date, while H2A/H2B appears to be the most stable. It is speculated that this difference in stability may contribute to the different biophysical properties of nucleosomes containing the major H2A and the H2A.Z variant.
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Affiliation(s)
- Brandon J Placek
- School of Molecular Biosciences, Washington State University, Pullman, WA 99164-4660, USA
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