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Beghini M, Wagner T, Luca AC, Metz M, Kaltenecker D, Spirk K, Hackl MT, Haybaeck J, Moriggl R, Kautzky-Willer A, Scherer T, Fürnsinn C. Adipocyte STAT5 deficiency does not affect blood glucose homeostasis in obese mice. PLoS One 2021; 16:e0260501. [PMID: 34818373 PMCID: PMC8612524 DOI: 10.1371/journal.pone.0260501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Accepted: 11/10/2021] [Indexed: 11/18/2022] Open
Abstract
The aim of this study was to investigate whether the lack of signal transducer and activator of transcription 5 (STAT5) in mature adipocytes of obese mice (Stat5Adipoq mice) improves glucose and lipid metabolism as previously observed in lean mice. Male Stat5Adipoq mice and their wild type (WT) littermates were fed high-fat diet (HFD). Effects of adipocyte STAT5 deficiency on adiposity as well as on glucose and lipid metabolism were determined under ad libitum feeding and after weight loss induced by calorie restriction. Compared to WT mice, obese Stat5Adipoq mice showed modestly accelerated weight gain and blunted depletion of fat stores under calorie restriction (reduction in % body fat after 3 weeks: WT, -9.3±1.1, vs Stat5Adipoq, -5.9±0.8, p = 0.04). No differences were observed between Stat5Adipoq and WT mice with regard to parameters of glucose and lipid metabolism including basal glycaemia, glucose tolerance, and plasma triglycerides. In conclusion, STAT5 deficiency in the adipocyte of HFD-fed obese mice was associated with increased fat accumulation. In contrast to previous findings in lean mice, however, lipid accumulation was not associated with any improvement in glucose and lipid metabolism. Our results do not support adipocyte STAT5 as a promising target for the treatment of obesity-associated metabolic derangements.
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Affiliation(s)
- Marianna Beghini
- Division of Endocrinology & Metabolism, Department of Medicine III, Medical University of Vienna, Vienna, Austria
| | - Theresia Wagner
- Division of Endocrinology & Metabolism, Department of Medicine III, Medical University of Vienna, Vienna, Austria
| | - Andreea Corina Luca
- Division of Endocrinology & Metabolism, Department of Medicine III, Medical University of Vienna, Vienna, Austria
| | - Matthäus Metz
- Division of Endocrinology & Metabolism, Department of Medicine III, Medical University of Vienna, Vienna, Austria
| | - Doris Kaltenecker
- Institute of Animal Breeding and Genetics, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Katrin Spirk
- Division of Endocrinology & Metabolism, Department of Medicine III, Medical University of Vienna, Vienna, Austria
- Institute of Animal Breeding and Genetics, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Martina Theresa Hackl
- Division of Endocrinology & Metabolism, Department of Medicine III, Medical University of Vienna, Vienna, Austria
| | - Johannes Haybaeck
- Institute of Pathology, Neuropathology and Molecular Pathology, Medical University of Innsbruck, Innsbruck, Austria
- Diagnostic & Research Center for Molecular Biomedicine, Institute of Pathology, Medical University of Graz, Graz, Austria
| | - Richard Moriggl
- Institute of Animal Breeding and Genetics, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Alexandra Kautzky-Willer
- Division of Endocrinology & Metabolism, Department of Medicine III, Medical University of Vienna, Vienna, Austria
| | - Thomas Scherer
- Division of Endocrinology & Metabolism, Department of Medicine III, Medical University of Vienna, Vienna, Austria
| | - Clemens Fürnsinn
- Division of Endocrinology & Metabolism, Department of Medicine III, Medical University of Vienna, Vienna, Austria
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Amatruda M, Gembillo G, Giuffrida AE, Santoro D, Conti G. The Aggressive Diabetic Kidney Disease in Youth-Onset Type 2 Diabetes: Pathogenetic Mechanisms and Potential Therapies. ACTA ACUST UNITED AC 2021; 57:medicina57090868. [PMID: 34577791 PMCID: PMC8467670 DOI: 10.3390/medicina57090868] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2021] [Revised: 08/21/2021] [Accepted: 08/22/2021] [Indexed: 02/07/2023]
Abstract
Youth-onset Type 2 Diabetes Mellitus (T2DM) represents a major burden worldwide. In the last decades, the prevalence of T2DM became higher than that of Type 1 Diabetes Mellitus (T1DM), helped by the increasing rate of childhood obesity. The highest prevalence rates of youth-onset T2DM are recorded in China (520 cases/100,000) and in the United States (212 cases/100,000), and the numbers are still increasing. T2DM young people present a strong hereditary component, often unmasked by social and environmental risk factors. These patients are affected by multiple coexisting risk factors, including obesity, hyperglycemia, dyslipidemia, insulin resistance, hypertension, and inflammation. Juvenile T2DM nephropathy occurs earlier in life compared to T1DM-related nephropathy in children or T2DM-related nephropathy in adult. Diabetic kidney disease (DKD) is T2DM major long term microvascular complication. This review summarizes the main mechanisms involved in the pathogenesis of the DKD in young population and the recent evolution of treatment, in order to reduce the risk of DKD progression.
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Affiliation(s)
- Michela Amatruda
- Unit of Pediatric Nephrology with Dialysis, AOU Policlinic G Martino, University of Messina, 98125 Messina, Italy;
| | - Guido Gembillo
- Unit of Nephrology and Dialysis, Department of Clinical and Experimental Medicine, University of Messina, 98125 Messina, Italy; (G.G.); (A.E.G.); (D.S.)
- Department of Biomedical and Dental Sciences and Morpho-functional Imaging, University of Messina, 98125 Messina, Italy
| | - Alfio Edoardo Giuffrida
- Unit of Nephrology and Dialysis, Department of Clinical and Experimental Medicine, University of Messina, 98125 Messina, Italy; (G.G.); (A.E.G.); (D.S.)
| | - Domenico Santoro
- Unit of Nephrology and Dialysis, Department of Clinical and Experimental Medicine, University of Messina, 98125 Messina, Italy; (G.G.); (A.E.G.); (D.S.)
| | - Giovanni Conti
- Unit of Pediatric Nephrology with Dialysis, AOU Policlinic G Martino, University of Messina, 98125 Messina, Italy;
- Correspondence:
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Eum JY, Lee GB, Yi SS, Kim IY, Seong JK, Moon MH. Lipid alterations in the skeletal muscle tissues of mice after weight regain by feeding a high-fat diet using nanoflow ultrahigh performance liquid chromatography-tandem mass spectrometry. J Chromatogr B Analyt Technol Biomed Life Sci 2020; 1141:122022. [PMID: 32062368 DOI: 10.1016/j.jchromb.2020.122022] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 01/10/2020] [Accepted: 02/06/2020] [Indexed: 12/20/2022]
Abstract
This study investigated lipid alterations in muscle tissues [gastrocnemius (Gas) and soleus (Sol)] of mice under different diet programs (weight gain, weight maintenance, weight regain, and controls) by nanoflow ultrahigh pressure liquid chromatography-electrospray ionization-tandem mass spectrometry. Since overloaded lipids in the skeletal muscle tissues by excessive fat accumulation are related to insulin resistance leading to type II diabetes mellitus, analysis of lipid alteration in muscle tissues with respect to high-fat diet (HFD) is important to understand obesity related diseases. A total of 345 individual lipid species were identified with their molecular structures, and 184 lipids were quantified by selected reaction monitoring method. Most triacylglycerol (TG) and phosphatidylethanolamine (PE) species displayed a significant (>2-fold, p < 0.01) increase in both the Gas and Sol and to a larger degree in the Gas. However, lipid classes involved in insulin resistance and anti-inflammatory response, including lysophosphatidylcholine (18:0), diacylglycerol (16:0_18:1, 16:0_18:2, and 18:1_18:1), ceramide (d18:1/24:0 and d18:1/24:1), and phosphatidylinositol (18:0/20:4), showed a significant accumulation in the Sol exclusively after HFD treatment. In addition, the lipid profiles were not significantly altered in mice that were fed HFD only for the last 4 weeks (weight gain group), suggesting that consuming HFD in the younger age period can be more effective in the Gas. This study reveals that lipid classes related to insulin resistance accumulated more in the Sol than in the Gas following HFD treatment and the weight regain program perturbed lipid profiles of the Sol to a greater extent than that by the other diet programs, confirming that the Sol tissue is more influenced by HFD than Gas.
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Affiliation(s)
- Jung Yong Eum
- Department of Chemistry, Yonsei University, Seoul 03722, Republic of Korea
| | - Gwang Bin Lee
- Department of Chemistry, Yonsei University, Seoul 03722, Republic of Korea
| | - Sun Shin Yi
- Department of Biomedical Laboratory Science, College of Biomedical Sciences, Soonchunhyang University, Asan, Republic of Korea; Korea Mouse Phenotyping Center, Seoul National University, Seoul, Republic of Korea
| | - Il Yong Kim
- Korea Mouse Phenotyping Center, Seoul National University, Seoul, Republic of Korea; Laboratory of Developmental Biology and Genomics, Research Institute for Veterinary Science, and BK21 Program for Creative Veterinary Science, College of Veterinary Medicine, Interdisciplinary Program for Bioinformatics, and BIO-MAX Institute, Seoul National University, Seoul, Republic of Korea
| | - Je Kyung Seong
- Korea Mouse Phenotyping Center, Seoul National University, Seoul, Republic of Korea; Laboratory of Developmental Biology and Genomics, Research Institute for Veterinary Science, and BK21 Program for Creative Veterinary Science, College of Veterinary Medicine, Interdisciplinary Program for Bioinformatics, and BIO-MAX Institute, Seoul National University, Seoul, Republic of Korea.
| | - Myeong Hee Moon
- Department of Chemistry, Yonsei University, Seoul 03722, Republic of Korea.
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Mamdooh N, Kasabri V, Al‐Hiari Y, Almasri I, Al‐Alawi S, Bustanji Y. Evaluation of selected commercial pharmacotherapeutic drugs as potential pancreatic lipase inhibitors and antiproliferative compounds. Drug Dev Res 2018; 80:310-324. [DOI: 10.1002/ddr.21499] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Revised: 10/25/2018] [Accepted: 10/26/2018] [Indexed: 11/11/2022]
Affiliation(s)
- Noor Mamdooh
- School of PharmacyUniversity of Jordan Amman Jordan
| | | | | | - Ihab Almasri
- Pharmaceutical Chemistry DepartmentAl‐Azhar University Gaza Palestinian Territory
| | | | - Yasser Bustanji
- School of PharmacyUniversity of Jordan Amman Jordan
- Hamdi Mango Centre for Scientific ResearchUniversity of Jordan Amman Jordan
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Han YH, Kwon SY, Kim J, Na CJ, Choi S, Min JJ, Bom HS, Kim YC, Oh IJ, Chae HJ, Lim ST, Sohn MH, Jeong HJ. A phase II clinical trial to investigate the effect of pioglitazone on (18)F-FDG uptake in malignant lesions. EJNMMI Res 2015; 5:50. [PMID: 26408008 PMCID: PMC4583556 DOI: 10.1186/s13550-015-0128-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Accepted: 09/13/2015] [Indexed: 01/18/2023] Open
Abstract
BACKGROUND We found that (18)F-2-fluoro-2-deoxy-D-glucose ((18)F-FDG) uptake in malignant lesion was enhanced, and it was decreased in the inflammatory lesion after the use of peroxisome proliferator activated receptor-γ (PPAR-γ) agonist in our previous preclinical study. The purpose of this study was to investigate the effect of PPAR-γ agonist on malignant lesions in clinical (18)F-FDG positron emission tomography/computed tomography (PET/CT) imaging. METHODS Forty-three patients were enrolled in this prospective study. We received the approval for the investigator-initiated trials for a phase II human clinical trial from the Korean Food and Drug Administration. On the first day, (18)F-FDG PET/CT images were acquired from patients without administration of pioglitazone (PIO), which is a PPAR-γ agonist. On the next day, (18)F-FDG PET/CT images were acquired once again from the same patients after administration of PIO. We measured the (18)F-FDG uptake in malignant lesions or inflammatory lesions from two (18)F-FDG PET/CT images. Four different PET parameters were used to compare between the two studies: SUVmax, SUVmean, average activity over 30 % of the isocontour (isocontour, Bq/mL), and isocontour-mediastinal activity (Bq/mL). Additionally, we classified the patients into two groups: the responder or non-responder group according to the presence of PIO effect on skeletal muscle. Furthermore, PET parameters of malignant lesions were analyzed based on the type of malignancy and were compared with those of inflammatory lesions. RESULTS All four PET parameters of malignant lesions in the responder group showed increasing patterns after the use of PIO. In the subgroup analysis, the similar pattern was observed in gastrointestinal cancer. In hepatobiliary and pancreatic cancer, SUVmean and isocontour showed statistically significant increase in the presence of PIO. On the other hand, in the non-responder group, all four PET parameters showed decreasing patterns in both malignant and inflammatory lesions after the use of PIO. There was no statistically significant difference in PET parameters of malignant lesions in the non-responder group. CONCLUSIONS In this study, we found that PIO had the potential to increase (18)F-FDG uptake of malignant lesions in the patients who showed PIO effect on skeletal muscle. Contrary to our preclinical studies, clinical results had limitations to evaluate malignant lesions in non-responder group. Further larger-scale studies are necessary to elucidate the potential role of PIO on (18)F-FDG uptake in malignant or inflammatory lesions. TRIAL REGISTRATION The test for safety and effectiveness of the new efficacy of Pioglitazone to diagnose the malignant tumor and inflammation in F-18 FDG positron emission tomography (PET) study, 12029.
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Affiliation(s)
- Yeon-Hee Han
- Department of Nuclear Medicine, Research Institute of Clinical Medicine of Chonbuk National University-Biomedical Research Institute of Chonbuk National University Hospital, Cyclotron Research Center, Molecular Imaging and Therapeutic Medicine Research Center, Chonbuk National University Medical School and Hospital, Jeonju, Jeonbuk, Republic of Korea.
| | - Seong Young Kwon
- Department of Nuclear Medicine, Chonnam National University Hwasun Hospital, Hwasun-gun, Jeonnam, Republic of Korea.
| | - Jeonghun Kim
- Department of Nuclear Medicine, Research Institute of Clinical Medicine of Chonbuk National University-Biomedical Research Institute of Chonbuk National University Hospital, Cyclotron Research Center, Molecular Imaging and Therapeutic Medicine Research Center, Chonbuk National University Medical School and Hospital, Jeonju, Jeonbuk, Republic of Korea.
| | - Chang Ju Na
- Department of Nuclear Medicine, Research Institute of Clinical Medicine of Chonbuk National University-Biomedical Research Institute of Chonbuk National University Hospital, Cyclotron Research Center, Molecular Imaging and Therapeutic Medicine Research Center, Chonbuk National University Medical School and Hospital, Jeonju, Jeonbuk, Republic of Korea.
| | - Sehun Choi
- Department of Nuclear Medicine, Research Institute of Clinical Medicine of Chonbuk National University-Biomedical Research Institute of Chonbuk National University Hospital, Cyclotron Research Center, Molecular Imaging and Therapeutic Medicine Research Center, Chonbuk National University Medical School and Hospital, Jeonju, Jeonbuk, Republic of Korea.
| | - Jung-Joon Min
- Department of Nuclear Medicine, Chonnam National University Hwasun Hospital, Hwasun-gun, Jeonnam, Republic of Korea.
| | - Hee-Seung Bom
- Department of Nuclear Medicine, Chonnam National University Hwasun Hospital, Hwasun-gun, Jeonnam, Republic of Korea.
| | - Young-Chul Kim
- Lung and Esophageal Cancer Clinic, Chonnam National University Hwasun Hospital, Hwasun-gun, Jeonnam, Republic of Korea.
| | - In-Jae Oh
- Lung and Esophageal Cancer Clinic, Chonnam National University Hwasun Hospital, Hwasun-gun, Jeonnam, Republic of Korea.
| | - Han-Jung Chae
- Department of Pharmacology, Chonbuk National University Medical School, Jeonju, Jeonbuk, Republic of Korea.
| | - Seok Tae Lim
- Department of Nuclear Medicine, Research Institute of Clinical Medicine of Chonbuk National University-Biomedical Research Institute of Chonbuk National University Hospital, Cyclotron Research Center, Molecular Imaging and Therapeutic Medicine Research Center, Chonbuk National University Medical School and Hospital, Jeonju, Jeonbuk, Republic of Korea.
| | - Myung-Hee Sohn
- Department of Nuclear Medicine, Research Institute of Clinical Medicine of Chonbuk National University-Biomedical Research Institute of Chonbuk National University Hospital, Cyclotron Research Center, Molecular Imaging and Therapeutic Medicine Research Center, Chonbuk National University Medical School and Hospital, Jeonju, Jeonbuk, Republic of Korea.
| | - Hwan-Jeong Jeong
- Department of Nuclear Medicine, Research Institute of Clinical Medicine of Chonbuk National University-Biomedical Research Institute of Chonbuk National University Hospital, Cyclotron Research Center, Molecular Imaging and Therapeutic Medicine Research Center, Chonbuk National University Medical School and Hospital, Jeonju, Jeonbuk, Republic of Korea.
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Kokil GR, Veedu RN, Ramm GA, Prins JB, Parekh HS. Type 2 diabetes mellitus: limitations of conventional therapies and intervention with nucleic acid-based therapeutics. Chem Rev 2015; 115:4719-43. [PMID: 25918949 DOI: 10.1021/cr5002832] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Ganesh R Kokil
- †School of Pharmacy, Pharmacy Australia Centre of Excellence, The University of Queensland, Brisbane, QLD 4102, Australia
| | - Rakesh N Veedu
- §Center for Comparative Genomics, Murdoch University, 90 South Street, Murdoch, WA 6150, Australia.,∥Western Australian Neuroscience Research Institute, Perth, WA 6150, Australia.,‡School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane QLD 4072 Australia
| | - Grant A Ramm
- ⊥The Hepatic Fibrosis Group, QIMR Berghofer Medical Research Institute, Brisbane, QLD 4006, Australia.,#Faculty of Medicine and Biomedical Sciences, The University of Queensland, Brisbane, QLD 4006, Australia
| | - Johannes B Prins
- ∇Mater Research Institute, The University of Queensland, Brisbane, QLD 4101, Australia
| | - Harendra S Parekh
- †School of Pharmacy, Pharmacy Australia Centre of Excellence, The University of Queensland, Brisbane, QLD 4102, Australia
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HUBER SOPHIE, VALENTE SERGIO, CHAIMBAULT PATRICK, SCHOHN HERVÉ. Evaluation of Δ2-pioglitazone, an analogue of pioglitazone, on colon cancer cell survival: Evidence of drug treatment association with autophagy and activation of the Nrf2/Keap1 pathway. Int J Oncol 2014; 45:426-38. [DOI: 10.3892/ijo.2014.2408] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Accepted: 03/06/2014] [Indexed: 11/06/2022] Open
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Mohamed WR, El Sherbiny GA, Zaki HF, El Sayed ME. Possible modulation of the antidiabetic effect of rosiglitazone by buspirone. ACTA ACUST UNITED AC 2012. [DOI: 10.1016/j.bfopcu.2012.04.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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9
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Reduced plasma nonesterified fatty acid levels and the advent of an acute lung injury in mice after intravenous or enteral oleic acid administration. Mediators Inflamm 2012; 2012:601032. [PMID: 22529526 PMCID: PMC3317028 DOI: 10.1155/2012/601032] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2011] [Revised: 11/12/2011] [Accepted: 11/13/2011] [Indexed: 01/11/2023] Open
Abstract
Although exerting valuable functions in living organisms, nonesterified fatty acids (NEFAs) can be toxic to cells. Increased blood concentration of oleic acid (OLA) and other fatty acids is detected in many pathological conditions. In sepsis and leptospirosis, high plasma levels of NEFA and low albumin concentrations are correlated to the disease severity. Surprisingly, 24 h after intravenous or intragastric administration of OLA, main NEFA levels (OLA inclusive) were dose dependently decreased. However, lung injury was detected in intravenously treated mice, and highest dose killed all mice. When administered by the enteral route, OLA was not toxic in any tested conditions. Results indicate that OLA has important regulatory properties on fatty acid metabolism, possibly lowering circulating fatty acid through activation of peroxisome proliferator-activated receptors. The significant reduction in blood NEFA levels detected after OLA enteral administration can contribute to the already known health benefits brought about by unsaturated-fatty-acid-enriched diets.
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L-carnitine supplementation to diet: a new tool in treatment of nonalcoholic steatohepatitis--a randomized and controlled clinical trial. Am J Gastroenterol 2010; 105:1338-45. [PMID: 20068559 DOI: 10.1038/ajg.2009.719] [Citation(s) in RCA: 156] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
OBJECTIVES Nonalcoholic steatohepatitis (NASH) is a known metabolic disorder of the liver. No treatment has been conclusively shown to improve NASH or prevent disease progression. The function of L-carnitine to modulate lipid profile, glucose metabolism, oxidative stress, and inflammatory responses has been shown. The aim of this study was to evaluate the effects of L-carnitine's supplementation on regression of NASH. METHODS In patients with NASH and control subjects, we randomly dispensed one 1-g L-carnitine tablet after breakfast plus diet and one 1 g tablet after dinner plus diet for 24 weeks or diet alone at the same dosage and regimen. We evaluated liver enzymes, lipid profile, fasting plasma glucose, C-reactive protein (CRP), tumor necrosis factor (TNF)-alpha, homeostasis model assessment (HOMA)-IR, body mass index, and histological scores. RESULTS At the end of the study, L-carnitine-treated patients showed significant improvements in the following parameters: aspartate aminotransferase (P=0.000), alanine aminotransferase (ALT) (P=0.000), gamma-glutamyl-transpeptidase (gamma-GT) (P=0.000), total cholesterol (P=0.000), low-density lipoprotein (LDL) (P=0.000), high-density lipoprotein (HDL) (P=0.000), triglycerides (P=0.000), glucose (P=0.000), HOMA-IR (P=0.000), CRP (P=0.000), TNF-alpha (P=0.000), and histological scores (P=0.000). CONCLUSIONS L-carnitine supplementation to diet is useful for reducing TNF-alpha and CRP, and for improving liver function, glucose plasma level, lipid profile, HOMA-IR, and histological manifestations of NASH.
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Effects of rosiglitazone on intramyocellular lipid accumulation in Psammomys obesus. Biochim Biophys Acta Mol Basis Dis 2010; 1802:235-9. [DOI: 10.1016/j.bbadis.2009.10.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2009] [Revised: 10/01/2009] [Accepted: 10/02/2009] [Indexed: 11/19/2022]
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Crouthamel MC, Kahana JA, Korenchuk S, Zhang SY, Sundaresan G, Eberwein DJ, Brown KK, Kumar R. Mechanism and management of AKT inhibitor-induced hyperglycemia. Clin Cancer Res 2009; 15:217-25. [PMID: 19118049 DOI: 10.1158/1078-0432.ccr-08-1253] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
PURPOSE Insulin-like growth factor-I receptor and phosphoinositide 3-kinase/AKT/mammalian target of rapamycin pathways are among the most active areas of drug discovery in cancer research. However, due to their integral roles in insulin signaling, inhibitors targeting these pathways often lead to hyperglycemia and hyperinsulinemia. We investigated the mechanism of hyperglycemia induced by GSK690693, a pan-AKT kinase inhibitor in clinical development, as well as methods to ameliorate these side effects. EXPERIMENTAL DESIGN The effect of GSK690693 on blood glucose, insulin, and glucagon levels was characterized in mice. We then evaluated the effects of commonly prescribed antidiabetic agents on GSK690693-induced hyperglycemia. The mechanism of blood glucose increase was evaluated using fasting and tracer uptake studies and by measuring liver glycogen levels. Finally, approaches to manage AKT inhibitor-induced hyperglycemia were designed using fasting and low carbohydrate diet. RESULTS We report that treatment with antidiabetic agents does not significantly affect GSK690693-induced hyperglycemia in rodents. However, administration of GSK690693 in mice significantly reduces liver glycogen (approximately 90%), suggesting that GSK690693 may inhibit glycogen synthesis and/or activate glycogenolysis. Consistent with this observation, fasting before drug administration reduces baseline liver glycogen levels and attenuates hyperglycemia. Further, GSK690693 also inhibits peripheral glucose uptake and introduction of a low-carbohydrate (7%) or 0% carbohydrate diet after GSK690693 administration effectively reduces diet-induced hyperglycemia in mice. CONCLUSIONS The mechanism of GSK690693-induced hyperglycemia is related to peripheral insulin resistance, increased gluconeogenesis, and/or hepatic glycogenolysis. A combination of fasting and low carbohydrate diet can reduce the magnitude of hyperglycemia induced by an AKT inhibitor.
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Sheng L, Qian Z, Shi Y, Yang L, Xi L, Zhao B, Xu X, Ji H. Crocetin improves the insulin resistance induced by high-fat diet in rats. Br J Pharmacol 2008; 154:1016-24. [PMID: 18469847 PMCID: PMC2451043 DOI: 10.1038/bjp.2008.160] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2008] [Revised: 03/13/2008] [Accepted: 03/19/2008] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND AND PURPOSE The amelioration of insulin resistance by treatment with crocetin is closely related to the hypolipidaemic effect. The present study is designed to clarify the insulin-sensitizing mechanism of crocetin by elucidating the mechanism of regulation of lipid metabolism by crocetin. EXPERIMENTAL APPROACH Rats given a high-fat diet were treated with crocetin for 6 weeks before hyperinsulinaemic-euglycaemic clamp. 14C-palmitate was used as tracer to track the fate of non-esterified fatty acids or as substrate to measure beta-oxidation rate. Triglyceride clearance in plasma and lipoprotein lipase activity in tissues were tested. Content of lipids in plasma and tissues was determined. Real-time PCR was used to assay the level of mRNA from genes involved in non-esterified fatty acid and triglyceride uptake and oxidation. KEY RESULTS Crocetin prevented high-fat-diet induced insulin resistance (increased clamp glucose infusion rate), raised hepatic non-esterified fatty acid uptake and oxidation, accelerated triglyceride clearance in plasma, enhanced lipoprotein lipase activity in liver, and reduced the accumulation of detrimental lipids (DAG and long-chain acyl CoA) in liver and muscle. Genes involved in hepatic lipid metabolism which are regulated by peroxisome proliferator-activated receptor-alpha, were modulated to accelerate lipid uptake and oxidation. CONCLUSIONS AND IMPLICATIONS Through regulating genes involved in lipid metabolism, crocetin accelerated hepatic uptake and oxidation of non-esterified fatty acid and triglyceride, and reduced lipid availability to muscle, thus decreasing lipid accumulation in muscle and liver, and consequently improving sensitivity to insulin.
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Affiliation(s)
- L Sheng
- Department of Pharmacology, China Pharmaceutical University Nanjing, PR China
| | - Z Qian
- Department of Pharmacology, China Pharmaceutical University Nanjing, PR China
| | - Y Shi
- Department of Pharmacology, China Pharmaceutical University Nanjing, PR China
| | - L Yang
- Department of Pharmacology, China Pharmaceutical University Nanjing, PR China
| | - L Xi
- Department of Medicine and Physiology, University of Toronto Toronto, Canada
| | - B Zhao
- Department of Pharmacology, China Pharmaceutical University Nanjing, PR China
| | - X Xu
- Department of Pharmacology, China Pharmaceutical University Nanjing, PR China
| | - H Ji
- Department of Pharmacology, China Pharmaceutical University Nanjing, PR China
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Gaborit B, Andreelli F. Mécanismes de l’action antidiabétique des thiazolidinediones. NUTR CLIN METAB 2008. [DOI: 10.1016/j.nupar.2007.12.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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15
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Carmona MC, Louche K, Lefebvre B, Pilon A, Hennuyer N, Audinot-Bouchez V, Fievet C, Torpier G, Formstecher P, Renard P, Lefebvre P, Dacquet C, Staels B, Casteilla L, Pénicaud L. S 26948: a new specific peroxisome proliferator activated receptor gamma modulator with potent antidiabetes and antiatherogenic effects. Diabetes 2007; 56:2797-808. [PMID: 17704298 DOI: 10.2337/db06-1734] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE Rosiglitazone displays powerful antidiabetes benefits but is associated with increased body weight and adipogenesis. Keeping in mind the concept of selective peroxisome proliferator-activated receptor (PPAR)gamma modulator, the aim of this study was to characterize the properties of a new PPARgamma ligand, S 26948, with special attention in body-weight gain. RESEARCH DESIGN AND METHODS We used transient transfection and binding assays to characterized the binding characteristics of S 26948 and GST pull-down experiments to investigate its pattern of coactivator recruitment compared with rosiglitazone. We also assessed its adipogenic capacity in vitro using the 3T3-F442A cell line and its in vivo effects in ob/ob mice (for antidiabetes and antiobesity properties), as well as the homozygous human apolipoprotein E2 knocking mice (E2-KI) (for antiatherogenic capacity). RESULTS S 26948 displayed pharmacological features of a high selective ligand for PPARgamma with low potency in promoting adipocyte differentiation. It also displayed a different coactivator recruitment profile compared with rosiglitazone, being unable to recruit DRIP205 or PPARgamma coactivator-1 alpha. In vivo experiments showed that S 26948 was as efficient in ameliorating glucose and lipid homeostasis as rosiglitazone, but it did not increase body and white adipose tissue weights and improved lipid oxidation in liver. In addition, S 26948 represented one of the few molecules of the PPARgamma ligand class able to decrease atherosclerotic lesions. CONCLUSIONS These findings establish S 26948 as a selective PPARgamma ligand with distinctive coactivator recruitment and gene expression profile, reduced adipogenic effect, and improved biological responses in vivo.
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Lessard SJ, Rivas DA, Chen ZP, Bonen A, Febbraio MA, Reeder DW, Kemp BE, Yaspelkis BB, Hawley JA. Tissue-specific effects of rosiglitazone and exercise in the treatment of lipid-induced insulin resistance. Diabetes 2007; 56:1856-64. [PMID: 17440174 DOI: 10.2337/db06-1065] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Both pharmacological intervention (i.e., thiazolidinediones [TZDs]) and lifestyle modification (i.e., exercise training) are clinically effective treatments for improving whole-body insulin sensitivity. However, the mechanism(s) by which these therapies reverse lipid-induced insulin resistance in skeletal muscle is unclear. We determined the effects of 4 weeks of rosiglitazone treatment and exercise training and their combined actions (rosiglitazone treatment and exercise training) on lipid and glucose metabolism in high-fat-fed rats. High-fat feeding resulted in decreased muscle insulin sensitivity, which was associated with increased rates of palmitate uptake and the accumulation of the fatty acid metabolites ceramide and diacylglycerol. Impairments in lipid metabolism were accompanied by defects in the Akt/AS160 signaling pathway. Exercise training, but not rosiglitazone treatment, reversed these impairments, resulting in improved insulin-stimulated glucose transport and increased rates of fatty acid oxidation in skeletal muscle. The improvements to glucose and lipid metabolism observed with exercise training were associated with increased AMP-activated protein kinase alpha1 activity; increased expression of Akt1, peroxisome proliferator-activated receptor gamma coactivator 1, and GLUT4; and a decrease in AS160 expression. In contrast, rosiglitazone treatment exacerbated lipid accumulation and decreased insulin-stimulated glucose transport in skeletal muscle. However, rosiglitazone, but not exercise training, increased adipose tissue GLUT4 and acetyl CoA carboxylase expression. Both exercise training and rosiglitazone decreased liver triacylglycerol content. Although both interventions can improve whole-body insulin sensitivity, our results show that they produce divergent effects on protein expression and triglyceride storage in different tissues. Accordingly, exercise training and rosiglitazone may act as complementary therapies for the treatment of insulin resistance.
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Affiliation(s)
- Sarah J Lessard
- School of Medical Sciences, RMIT University, P.O. Box 71, Bundoora, Victoria 3083, Australia
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Abstract
Vitamin A signaling occurs through nuclear receptors recognizing diverse forms of retinoic acid (RA). The retinoic acid receptors (RARs) bind all-trans RA and its 9-cis isomer (9-cis RA). They convey most of the activity of RA, particularly during embryogenesis. The second subset of receptors, the rexinoid receptors (RXRs), binds 9-cis RA only. However, RXRs are obligatory DNA-binding partners for a number of nuclear receptors, broadening the spectrum of their biological activity to the corresponding nuclear receptor-signaling pathways. The present chapter more particularly focuses on RXR-containing transcriptional complexes for which RXR is not only a structural component necessary for DNA binding but also acts as a ligand-activated partner. After positioning RXR among the nuclear receptor superfamily in the first part, we will give an overview of three major signaling pathways involved in metabolism, which are sensitive to RXR activation: LXR:RXR, FXR:RXR, and PPAR:RXR. The third and last part is focused on RXR signaling and its potential role in metabolic regulation. Indeed, while the nature of the endogenous ligand for RXR is still in question, as we will discuss herein, a better understanding of RXR activities is necessary to envisage the potential therapeutic applications of synthetic RXR ligands.
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Affiliation(s)
- Béatrice Desvergne
- Center for Integrative Genomics, Building Génopode, University of Lausanne, CH-1015 Lausanne, Switzerland
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18
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Abstract
The clinical efficacy of currently available thiazolidinediones (TZDs) in improving glycaemic control and ameliorating several risk factors for cardiovascular disease (linked to their insulin-sensitising actions as well as direct vascular effects) is well established. Treatment-associated weight gain, however, which has been identified as a class effect of the TZDs, is seen in a number of patients. The magnitude of weight gain correlates in part with improved metabolic control, i.e. better responders are more prone to increases in body weight. The cardiovascular risk associated with obesity appears to be depot specific; while peripheral obesity is associated with a low risk of cardiovascular complications, central obesity confers a greater degree of risk. Evidence is reviewed that increases in body weight associated with TZD treatment are associated with neutral effects (or even, decreases) in visceral fat, the adipose depot that is associated with central obesity.
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Affiliation(s)
- J Wilding
- Diabetes and Endocrinology Clinical Research Group, Department of Medicine, Clinical Sciences Centre,University Hospital Aintree, Liverpool, UK.
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Abstract
Insulin resistance and obesity is a common health problem in the industrialized world. As a result of the availability of high-calorie food and a reduction in energy expenditure, maladaptive metabolic processes may interfere with the action of insulin and increase susceptibility for the development of atherosclerotic cardiovascular diseases. With the advent of peroxisome proliferator-activated receptors (PPARs), the mechanisms of this maladaptation and its relationship to insulin resistance syndrome components have become less obscure, promising new therapeutic approaches for this common problem. In this review we first focus on the molecular structure and cellular mechanisms of action of these receptors and then discuss how PPAR-gamma, a PPAR isoform, provides a link between adiposity, insulin resistance, and atherosclerosis.
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Affiliation(s)
- Alper Kepez
- Cardiology Department, Hacettepe University Faculty of Medicine, Ankara, Turkey.
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20
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Koopman R, Manders RJF, Jonkers RAM, Hul GBJ, Kuipers H, van Loon LJC. Intramyocellular lipid and glycogen content are reduced following resistance exercise in untrained healthy males. Eur J Appl Physiol 2005; 96:525-34. [PMID: 16369816 DOI: 10.1007/s00421-005-0118-0] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/29/2005] [Indexed: 12/22/2022]
Abstract
Resistance exercise has recently been shown to improve whole-body insulin sensitivity in healthy males. Whether this is accompanied by an exercise-induced decline in skeletal muscle glycogen and/or lipid content remains to be established. In the present study, we determined fibre-type-specific changes in skeletal muscle substrate content following a single resistance exercise session. After an overnight fast, eight untrained healthy lean males participated in a approximately 45 min resistance exercise session. Muscle biopsies were collected before, following cessation of exercise, and after 30 and 120 min of post-exercise recovery. Subjects remained fasted throughout the test. Conventional light and (immuno)fluorescence microscopy were applied to assess fibre-type-specific changes in intramyocellular triacylglycerol (IMTG) and glycogen content. A significant 27+/-7% net decline in IMTG content was observed in the type I muscle fibres (P<0.05), with no net changes in the type IIa and IIx fibres. Muscle glycogen content decreased with 23+/-6, 40+/-7 and 44+/-7% in the type I, IIa and IIx muscle fibres, respectively (P<0.05). Fibre-type-specific changes in intramyocellular lipid and/or glycogen content correlated well with muscle fibre-type oxidative capacity. During post-exercise recovery, type I muscle fibre lipid content returned to pre-exercise levels within 120 min. No changes in muscle glycogen content were observed during recovery. We conclude that intramyocellular lipid and glycogen stores are readily used during resistance exercise and this is likely associated with the reported increase in whole-body insulin sensitivity following resistance exercise.
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Affiliation(s)
- René Koopman
- Department of Human Biology, Maastricht University, P.O. Box 616, 6200, Maastricht, The Netherlands.
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21
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Phillips SA, Choe CC, Ciaraldi TP, Greenberg AS, Kong APS, Baxi SC, Christiansen L, Mudaliar SR, Henry RR. Adipocyte differentiation-related protein in human skeletal muscle: relationship to insulin sensitivity. ACTA ACUST UNITED AC 2005; 13:1321-9. [PMID: 16129713 DOI: 10.1038/oby.2005.160] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
OBJECTIVE To determine whether adipocyte differentiation-related protein (ADRP), a lipid droplet-associated protein that binds to and sequesters intracellular fatty acids, is 1) expressed in human skeletal muscle and 2) differentially regulated in human skeletal muscle obtained from obese non-diabetic (OND) and obese diabetic (OD) subjects. RESEARCH METHODS AND PROCEDURES Ten OND subjects and 15 OD subjects underwent a weight loss or pharmacological intervention program to improve insulin sensitivity. Anthropometric data, hemoglobin A(1C), fasting glucose, lipids, and glucose disposal rate were determined at baseline and at completion of studies. Biopsies of the vastus lateralis muscle (SkM) were obtained in the fasting state from OND and OD subjects. Protein expression was determined by Western blotting. RESULTS ADRP was highly expressed in SkM from OND (4.4 +/- 1.54 AU/10 microg, protein, n = 10) and OD (5.02 +/- 1.33 AU/10 microg, n = 12) subjects. OND subjects undergoing weight loss had decreased triglyceride levels and improved insulin action. SkM ADRP content increased with weight loss from 5.14 +/- 2.15 AU/10 microg to 9.92 +/- 1.57 AU/10 microg (p < 0.025). OD subjects were treated with either troglitazone or metformin, together with glyburide, for 3 to 4 months. Both treatments attained similar levels of glycemic control. OD subjects with lower baseline ADRP content (2.85 +/- 1.07 AU/10 microg, n = 6) displayed up-regulation of ADRP expression (to 9.27 +/- 2.76 AU/10 microg, p < 0.025). DISCUSSION ADRP is the predominant lipid droplet-associated protein in SkM, and low ADRP expression is up-regulated in circumstances of improved glucose tolerance. Up-regulation of ADRP may act to sequester fatty acids as triglycerides in discrete lipid droplets that could protect muscle from the detrimental effects of fatty acids on insulin action and glucose tolerance.
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Affiliation(s)
- Susan A Phillips
- Veterans Affairs San Diego Healthcare System, San Diego, CA 92161, USA
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22
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Benton CR, Han XX, Febbraio M, Graham TE, Bonen A. Inverse relationship between PGC-1alpha protein expression and triacylglycerol accumulation in rodent skeletal muscle. J Appl Physiol (1985) 2005; 100:377-83. [PMID: 16223979 DOI: 10.1152/japplphysiol.00781.2005] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
PGC-1alpha is a key regulator of tissue metabolism, including skeletal muscle. Because it has been shown that PGC-1alpha alters the capacity for lipid metabolism, it is possible that PGC-1alpha expression is regulated by the intramuscular lipid milieu. Therefore, we have examined the relationship between PGC-1alpha protein expression and the intramuscular fatty acid accumulation in hindlimb muscles of animals in which the capacity for fatty acid accumulation in muscle is increased (Zucker obese rat) or reduced [FAT/CD36 null (KO) mice]. Rates of palmitate incorporation into triacylglycerols were determined in perfused red (RG) and white gastrocnemius (WG) muscles of lean and obese Zucker rats and in perfused RG and WG muscles of FAT/CD36 KO and wild-type (WT) mice. In obese Zucker rats, the rate of palmitate incorporation into triacylglycerol depots in RG and WG muscles were 28 and 24% greater than in lean rats (P < 0.05). In FAT/CD36 KO mice, the rates of palmitate incorporation into triacylglycerol depots were lower in RG (-50%) and WG muscle (-24%) compared with the respective muscles in WT mice (P < 0.05). In the obese animals, PGC-1alpha protein content was reduced in both RG (-13%) and WG muscles (-15%) (P < 0.05). In FAT/CD36 KO mice, PGC-1alpha protein content was upregulated in both RG (+32%, P < 0.05) and WG muscles (+50%, P < 0.05). In conclusion, from studies in these two animal models, it appears that PGC-1alpha protein expression is inversely related to components of intramuscular lipid metabolism, because 1) PGC-1alpha protein expression is downregulated when triacylglycerol synthesis rates, an index of intramuscular lipid metabolism, are increased, and 2) PGC-1alpha protein expression is upregulated when triacylglycerol synthesis rates are reduced. Therefore, we speculate that the intramuscular lipid sensing may be involved in regulating the protein expression of PGC-1alpha in skeletal muscle.
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Affiliation(s)
- Carley R Benton
- Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada
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23
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van Loon LJC, Manders RJF, Koopman R, Kaastra B, Stegen JHCH, Gijsen AP, Saris WHM, Keizer HA. Inhibition of adipose tissue lipolysis increases intramuscular lipid use in type 2 diabetic patients. Diabetologia 2005; 48:2097-107. [PMID: 16096823 DOI: 10.1007/s00125-005-1889-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/19/2005] [Accepted: 04/18/2005] [Indexed: 10/25/2022]
Abstract
AIMS/HYPOTHESIS In the present study, we investigated the consequences of adipose tissue lipolytic inhibition on skeletal muscle substrate use in type 2 diabetic patients. MATERIALS AND METHODS We studied ten type 2 diabetic patients under the following conditions: (1) at rest; (2) during 60 min of cycling exercise at 50% of maximal workload capacity and subsequent recovery. Studies were done under normal, fasting conditions (control trial: CON) and following administration of a nicotinic acid analogue (low plasma non-esterified fatty acid trial: LFA). Continuous [U-13C]palmitate and [6,6 -2H2]glucose infusions were applied to quantify plasma NEFA and glucose oxidation rates, and to estimate intramuscular triacylglycerol (IMTG) and glycogen use. Muscle biopsies were collected before and after exercise to determine net changes in lipid and glycogen content specific to muscle fibre type. RESULTS Following administration of the nicotinic acid analogue (Acipimox), the plasma NEFA rate of appearance was effectively reduced, resulting in lower NEFA concentrations in the LFA trial (p<0.001). Plasma NEFA oxidation rates were substantially reduced at rest, during exercise and subsequent recovery in the LFA trial. The lower plasma NEFA oxidation rates were compensated by an increase in IMTG and endogenous carbohydrate use (p<0.05). Plasma glucose disposal rates did not differ between trials. In accordance with the tracer data, a greater net decline in type I muscle fibre lipid content was observed following exercise in the LFA trial (p<0.05). CONCLUSIONS/INTERPRETATION This study shows that plasma NEFA availability regulates IMTG use, and that adipose tissue lipolytic inhibition, in combination with exercise, could be an effective means of augmenting intramuscular lipid and glycogen use in type 2 diabetic patients in an overnight fasted state.
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Affiliation(s)
- L J C van Loon
- Department of Movement Sciences, Nutrition and Toxicology Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands.
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24
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van Loon LJC, Goodpaster BH. Increased intramuscular lipid storage in the insulin-resistant and endurance-trained state. Pflugers Arch 2005; 451:606-16. [PMID: 16155759 DOI: 10.1007/s00424-005-1509-0] [Citation(s) in RCA: 152] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2005] [Revised: 07/28/2005] [Accepted: 08/19/2005] [Indexed: 01/06/2023]
Abstract
Numerous studies have reported a strong correlation between intramuscular triacylglycerol (IMTG) content and insulin resistance. However, the proposed relationship between IMTG accumulation and skeletal muscle insulin resistance is not unambiguous, as trained athletes have been shown to be markedly insulin sensitive despite an elevated IMTG storage. Though the latter has often been attributed to differences in muscle fibre type composition and/or structural characteristics of the intramyocellular lipid deposits, recent studies have failed to provide such evidence. The greater insulin sensitivity despite an elevated IMTG deposition in the endurance-trained state has often been described as a metabolic paradox. However, divergent metabolic events are responsible for the greater IMTG content in the endurance-trained versus insulin-resistant states. The greater IMTG storage in the trained athlete represents an adaptive response to endurance training, allowing a greater contribution of the IMTG pool as a substrate source during exercise. In contrast, elevated IMTG stores in the obese and/or type 2 diabetes patient seem to be secondary to a structural imbalance between plasma free fatty acid availability, fatty acid (FA) storage and oxidation. Therefore, the reported correlation between IMTG content and insulin resistance does not represent a functional relationship, as it is strongly influenced by training status and/or habitual physical activity. It can be argued that the ratio between IMTG content and muscle oxidative capacity represents a more accurate marker of insulin resistance. Interventions to augment mitochondrial density and/or function are likely to improve the balance between FA uptake and oxidation and should be applied to prevent and/or treat insulin resistance.
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Affiliation(s)
- Luc J C van Loon
- Department of Movement Sciences, Nutrition Research Institute Maastricht, Maastricht University, 616, 6200, Maastricht, MD, The Netherlands,
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25
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van Loon LJC, Thomason-Hughes M, Constantin-Teodosiu D, Koopman R, Greenhaff PL, Hardie DG, Keizer HA, Saris WHM, Wagenmakers AJM. Inhibition of adipose tissue lipolysis increases intramuscular lipid and glycogen use in vivo in humans. Am J Physiol Endocrinol Metab 2005; 289:E482-93. [PMID: 15886227 DOI: 10.1152/ajpendo.00092.2005] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study investigates the consequences of inhibition of adipose tissue lipolysis on skeletal muscle substrate use. Ten subjects were studied at rest and during exercise and subsequent recovery under normal, fasting conditions (control trial, CON) and following administration of a nicotinic acid analog (low plasma free fatty acid trial, LFA). Continuous [U-13C]palmitate and [6,6-2H2]glucose infusions were applied to quantify plasma free fatty acid (FFA) and glucose oxidation rates and to estimate intramuscular triacylglycerol (IMTG) and glycogen use. Muscle biopsies were collected to measure 1) fiber type-specific IMTG content; 2) allosteric regulators of hormone-sensitive lipase (HSL), glycogen phosphorylase, and pyruvate dehydrogenase; and 3) the phosphorylation status of HSL at Ser563 and Ser565. Administration of a nicotinic acid analog (acipimox) substantially reduced plasma FFA rate of appearance and subsequent plasma FFA concentrations (P < 0.0001). At rest, this substantially reduced plasma FFA oxidation rates, which was compensated by an increase in the estimated IMTG use (P < 0.05). During exercise, the progressive increase in FFA rate of appearance, uptake, and oxidation was prevented in the LFA trial and matched by greater IMTG and glycogen use. Differential phosphorylation of HSL or relief of its allosteric inhibition by long-chain fatty acyl-CoA could not explain the increase in muscle TG use, but there was evidence to support the contention that regulation may reside at the level of the glucose-fatty acid cycle. This study confirms the hypothesis that plasma FFA availability regulates both intramuscular lipid and glycogen use in vivo in humans.
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Affiliation(s)
- Luc J C van Loon
- Department of Movement Sciences, Maastricht University, PO Box 616, 6200 MD Maastricht, The Netherlands.
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26
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Szanto A, Narkar V, Shen Q, Uray IP, Davies PJA, Nagy L. Retinoid X receptors: X-ploring their (patho)physiological functions. Cell Death Differ 2005; 11 Suppl 2:S126-43. [PMID: 15608692 DOI: 10.1038/sj.cdd.4401533] [Citation(s) in RCA: 207] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Retinoid X receptor (RXR) belongs to a family of ligand-activated transcription factors that regulate many aspects of metazoan life. A class of nuclear receptors requires RXR as heterodimerization partner for their function. This places RXR in the crossroad of multiple distinct biological pathways. This and the fact that the debate on the endogenous ligand requirement for RXR is not yet settled make RXR still an enigmatic transcription factor. Here, we review some of the biology of RXR. We place RXR into the evolution of nuclear receptors, review structural details and ligands of the receptor. Then processes regulated by RXR are discussed focusing on the developmental roles deduced from studies on knockout animals and metabolic roles in diseases such as diabetes and atherosclerosis deduced from pharmacological studies. Finally, aspects of RXR's involvement in myeloid differentiation and apoptosis are summarized along with issues on RXR's suitability as a therapeutic target.
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Affiliation(s)
- A Szanto
- Department of Biochemistry and Molecular Biology, Research Center for Molecular Medicine, University of Debrecen, Nagyerdei krt. 98, Debrecen H-4012, Hungary
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Ding SY, Shen ZF, Chen YT, Sun SJ, Liu Q, Xie MZ. Pioglitazone can ameliorate insulin resistance in low-dose streptozotocin and high sucrose-fat diet induced obese rats. Acta Pharmacol Sin 2005; 26:575-80. [PMID: 15842776 DOI: 10.1111/j.1745-7254.2005.00090.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
AIM To investigate the effect of the peroxisome proliferator-activator receptor (PPAR)-gamma agonist, pioglitazone, on insulin resistance in low-dose streptozotocin and high sucrose-fat diet induced obese rats. METHODS Normal female Wistar rats were injected intraperitoneally with low-dose streptozotocin (STZ, 30 mg/kg) and fed with a high sucrose-fat diet for 8 weeks. Pioglitazone (20 mg/kg) was administered orally to the obese and insulin-resistant rats for 28 d. Intraperitoneal glucose tolerance tests, insulin tolerance tests and gluconeogenesis tests were carried out over the last 14 d. At the end of d 28 of the treatment, serums were collected for biochemical analysis. Glucose transporter 4 (GLUT4) and insulin receptor substrate-1 (IRS-1) protein expression in the liver and skeletal muscle were detected using Western blotting. RESULTS Significant insulin resistance and obesity were observed in low-dose STZ and high sucrose-fat diet induced obese rats. Pioglitazone (20 mg/kg) treatment significantly decreased serum insulin, triglyceride and free fatty acid levels, and elevated high density lipoprotein-cholesterol (HDL-C) levels. Pioglitazone also lowered the lipid contents in the liver and muscles of rats undergoing treatment. Gluconeogenesis was inhibited and insulin sensitivity was improved markedly. The IRS-1 protein contents in the liver and skeletal muscles and the GLUT4 contents in skeletal muscle were elevated significantly. CONCLUSION The data suggest that treatment with pioglitazone improves insulin sensitivity in low-dose STZ and high sucrose-fat diet induced obese rats. The insulin sensitizing effect may be associated with ameliorating lipid metabolism, reducing hyperinsulinemia, inhibiting gluconeogenesis, and increasing IRS-1 and GLUT4 protein expression in insulin-sensitive tissues.
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Affiliation(s)
- Shi-ying Ding
- Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China
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Vasudevan AR, Balasubramanyam A. Thiazolidinediones: a review of their mechanisms of insulin sensitization, therapeutic potential, clinical efficacy, and tolerability. Diabetes Technol Ther 2004; 6:850-63. [PMID: 15684639 DOI: 10.1089/dia.2004.6.850] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The thiazolidinediones (TZDs) rosiglitazone and pioglitazone are newer additions to the antidiabetic armamentarium and are indicated for the treatment of type 2 diabetes mellitus (T2DM) in the United States. The TZDs are peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonists that provide clinically effective glycemic control and unique pharmacologic effects on multiple risk factors for T2DM-related morbidity, including improvement of insulin sensitivity and endothelial dysfunction, reduction of blood pressure, and amelioration of dyslipidemia. Weight gain and fluid retention occur with TZD therapy, especially when they are administered in higher doses and in combination with insulin. Although fluid retention associated with the use of TZDs is generally mild and reversible, these agents should not be used in patients with New York Heart Association Class III or IV heart failure symptoms. The findings of ongoing, long-term, prospective studies will clarify the role of the TZDs in the treatment of T2DM, particularly in terms of the durability of improvements in glycemic control, insulin sensitivity, pancreatic beta- cell function, and cardiovascular health.
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Affiliation(s)
- Abu R Vasudevan
- Division of Diabetes, Endocrinology, and Metabolism, Baylor College of Medicine, Houston, Texas 77030, USA
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30
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Abstract
In addition to obesity, many factors, including the distribution of body fat, contribute to the development of insulin resistance and type 2 diabetes mellitus (T2DM). Lipid contained within skeletal muscle as triglyceride is a parameter of regional fat accumulation thought to be an important link among obesity, insulin resistance, and type 2 diabetes, even in the pediatric population. Intramuscular triglycerides can also be a fuel source for healthy muscle during periods of physical activity. Thus, the balance between storage and efficient utilization of muscle triglycerides is likely a key to a better understanding of the interaction between dysregulated fat and glucose metabolism by muscle in both adults and children. This review examines the evidence that muscle lipid accumulation is linked with insulin resistance and type 2 diabetes of both adults and children. In addition, we explore the potential mechanisms for muscle lipid accumulation as well as the effects of weight loss and physical activity on muscle lipid. Further defining the links between muscle lipid accumulation and insulin action should help develop more effective strategies to prevent or treat type 2 diabetes and other obesity-associated disorders.
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Affiliation(s)
- Bret H Goodpaster
- Division of Endocrinology and Metabolism, Department of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
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31
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Abstract
Globalization and global market have contributed to increased consumption of high-fat, energy-dense diets, particularly rich in saturated fatty acids( SFAs). Polyunsaturated fatty acids (PUFAs) regulate fuel partitioning within the cells by inducing their own oxidation through the reduction of lipogenic gene expression and the enhancement of the expression of those genes controlling lipid oxidation and thermogenesis. Moreover, PUFAs prevent insulin resistance by increasing membrane fluidity and GLUT4 transport. In contrast, SFAs are stored in non-adipocyte cells as triglycerides (TG) leading to cellular damage as a sequence of their lipotoxicity. Triglyceride accumulation in skeletal muscle cells (IMTG) derives from increased FA uptake coupled with deficient FA oxidation. High levels of circulating FAs enhance the expression of FA translocase the FA transport proteins within the myocites. The biochemical mechanisms responsible for lower fatty acid oxidation involve reduced carnitine palmitoyl transferase (CPT) activity, as a likely consequence of increased intracellular concentrations of malonyl-CoA; reduced glycogen synthase activity; and impairment of insulin signalling and glucose transport. The depletion of IMTG depots is strictly associated with an improvement of insulin sensitivity, via a reduced acetyl-CoA carboxylase (ACC) mRNA expression and an increased GLUT4 expression and pyruvate dehydrogenase (PDH) activity. In pancreatic islets, TG accumulation causes impairment of insulin secretion. In rat models, beta-cell dysfunction is related to increased triacylglycerol content in islets, increased production of nitric oxide, ceramide synthesis and beta-cell apoptosis. The decreased insulin gene promoter activity and binding of the pancreas-duodenum homeobox-1 (PDX-1) transcription factor to the insulin gene seem to mediate TG effect in islets. In humans, acute and prolonged effects of FAs on glucose-stimulated insulin secretion have been widely investigated as well as the effect of high-fat diets on insulin sensitivity and secretion and on the development of type 2 diabetes.
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Affiliation(s)
- Melania Manco
- Institute of Internal Medicine, Catholic University, 00168 Rome, Italy.
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Hegarty BD, Furler SM, Oakes ND, Kraegen EW, Cooney GJ. Peroxisome proliferator-activated receptor (PPAR) activation induces tissue-specific effects on fatty acid uptake and metabolism in vivo--a study using the novel PPARalpha/gamma agonist tesaglitazar. Endocrinology 2004; 145:3158-64. [PMID: 15059948 DOI: 10.1210/en.2004-0260] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Agonists of peroxisome proliferator-activated receptors (PPARs) have emerged as important pharmacological agents for improving insulin action. A major mechanism of action of PPAR agonists is thought to involve the alteration of the tissue distribution of nonesterified fatty acid (NEFA) uptake and utilization. To test this hypothesis directly, we examined the effect of the novel PPARalpha/gamma agonist tesaglitazar on whole-body insulin sensitivity and NEFA clearance into epididymal white adipose tissue (WAT), red gastrocnemius muscle, and liver in rats with dietary-induced insulin resistance. Wistar rats were fed a high-fat diet (59% of calories as fat) for 3 wk with or without treatment with tesaglitazar (1 micromol.kg(-1).d(-1), 7 d). NEFA clearance was measured using the partially metabolizable NEFA tracer, (3)H-R-bromopalmitate, administered under conditions of basal or elevated NEFA availability. Tesaglitazar improved the insulin sensitivity of high-fat-fed rats, indicated by an increase in the glucose infusion rate during hyperinsulinemic-euglycemic clamp (P < 0.01). This improvement in insulin action was associated with decreased diglyceride (P < 0.05) and long chain acyl coenzyme A (P < 0.05) in skeletal muscle. NEFA clearance into WAT of high-fat-fed rats was increased 52% by tesaglitazar under basal conditions (P < 0.001). In addition the PPARalpha/gamma agonist moderately increased hepatic and muscle NEFA utilization and reduced hepatic triglyceride accumulation (P < 0.05). This study shows that tesaglitazar is an effective insulin-sensitizing agent in a mild dietary model of insulin resistance. Furthermore, we provide the first direct in vivo evidence that an agonist of both PPARalpha and PPARgamma increases the ability of WAT, liver, and skeletal muscle to use fatty acids in association with its beneficial effects on insulin action in this model.
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Affiliation(s)
- Bronwyn D Hegarty
- Diabetes and Obesity Research Program, The Garvan Institute of Medical Research, 384 Victoria Street, Sydney, New South Wales 2010, Australia
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Abstract
Prevention and treatment of type 2 diabetes mellitus (T2DM) and the metabolic syndrome represent a major clinical challenge, because effective strategies such as fat restriction and exercise are difficult to implement into diabetes treatment. Based on the increasing knowledge on the pathogenesis of T2DM, new therapeutic approaches are currently under investigation. Potential targets of new therapeutic approaches include: (i) Inhibition of hepatic glucose production, (ii) stimulation of glucose-dependent insulin secretion, (iii) enhancement of insulin signal transduction, and (iv) reduction of body fat mass. Agonists of glucagon-like-peptide 1 (GLP-1) and antagonists of dipeptidylpeptidase IV, which inactivates GLP-1, stimulate glucose-dependent insulin secretion, improve hyperglycemia and are already tested in clinical trials. In humans, glucagon antagonists and an amylin analogue reduce glucagon-dependent glucose production. The glucose-lowering effect of current modulators of lipid oxidation is not pronounced and their use could be limited by side effects. In addition to clinically approved thiazolidendiones, new agonists of the peroxisome proliferator activator receptor gamma (PPAR gamma) as well as combined PPAR alpha/gamma agonists are developed at present. The direct modulation of insulin signal transduction is still limited to experimental studies.
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MESH Headings
- Animals
- Clinical Trials as Topic
- Diabetes Mellitus, Experimental/drug therapy
- Diabetes Mellitus, Type 2/blood
- Diabetes Mellitus, Type 2/etiology
- Diabetes Mellitus, Type 2/genetics
- Diabetes Mellitus, Type 2/metabolism
- Diabetes Mellitus, Type 2/physiopathology
- Diabetes Mellitus, Type 2/prevention & control
- Diabetes Mellitus, Type 2/therapy
- Dipeptidyl-Peptidases and Tripeptidyl-Peptidases/antagonists & inhibitors
- Forecasting
- Glucagon/antagonists & inhibitors
- Glucagon/therapeutic use
- Glucagon-Like Peptide 1
- Glucose/antagonists & inhibitors
- Glucose/metabolism
- Glycated Hemoglobin/analysis
- Glycogen Synthase Kinase 3/administration & dosage
- Glycogen Synthase Kinase 3/therapeutic use
- Humans
- Hypoglycemic Agents/therapeutic use
- Insulin/genetics
- Insulin/metabolism
- Insulin Secretion
- Lipid Peroxidation
- Metabolic Syndrome/metabolism
- Metabolic Syndrome/therapy
- Mice
- Oxazines/therapeutic use
- Peptide Fragments/therapeutic use
- Phenylpropionates/therapeutic use
- Protein Precursors/therapeutic use
- Rats
- Receptor, Insulin/physiology
- Receptors, Cytoplasmic and Nuclear/metabolism
- Rosiglitazone
- Signal Transduction
- Thiazolidinediones/therapeutic use
- Transcription Factors/metabolism
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Affiliation(s)
- Harald Stingl
- Klinische Abteilung für Endokrinologie und Stoffwechsel, Universitätsklinik für Innere Medizin III, Medizinische Universität Wien, Osterreich
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Chakrabarti R, Misra P, Vikramadithyan RK, Premkumar M, Hiriyan J, Datla SR, Damarla RKB, Suresh J, Rajagopalan R. Antidiabetic and hypolipidemic potential of DRF 2519—a dual activator of PPAR-α and PPAR-γ. Eur J Pharmacol 2004; 491:195-206. [PMID: 15140637 DOI: 10.1016/j.ejphar.2004.03.034] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2004] [Accepted: 03/17/2004] [Indexed: 10/26/2022]
Abstract
We investigated the biological activity of Dr. Reddy's Research Foundation (DRF) 2519, a benzoxazinone analogue of the thiazolidinedione class of compounds. In the in vitro transactivation assay, DRF 2519 showed interesting dual activation of Peroxisome Proliferator Activated Receptor (PPAR) alpha and gamma. In insulin-resistant ob/ob mouse model, DRF 2519 showed significant alleviation of insulin resistance and dyslipidemia, which is better than rosiglitazone. Fatty Zucker rats treated with DRF 2519 showed better reduction of plasma insulin, triglyceride and free fatty acid levels than those treated with rosiglitazone. In addition, these rats were able to clear plasma lipids better when challenged with exogenous lipid (i.v.). DRF 2519 treatment resulted in improved plasma lipid profiles in high-fat-fed Sprague-Dawley rats. Treated rats showed better plasma lipid clearance and hepatic triglyceride secretion. When compared to DRF 2519, fenofibrate was comparatively less efficacious while rosigltiazone showed no activity in these models. In ex vivo studies, DRF 2519 showed induction of liver acyl CoA oxidase mRNA and increase in lipoprotein lipase (LPL) protein expression and activity in adipose tissue. In the in vitro studies, DRF 2519 inhibited the lipid biosynthesis and secretion of apolipoprotein B from human hepatoma (Hep)G2 cells. It also enhanced insulin-induced relaxation of rat aortic smooth muscle. These results indicate that DRF 2519, a dual activator of PPAR-alpha and gamma, could be an interesting development candidate in the management of metabolic disorders and associated complications.
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Affiliation(s)
- Ranjan Chakrabarti
- Discovery Biology, Dr. Reddy's Laboratory-Discovery Research, Bollaram Road, Miyapur, Hyderabad 500 049, India.
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Bennett SMA, Agrawal A, Elasha H, Heise M, Jones NP, Walker M, Wilding JPH. Rosiglitazone improves insulin sensitivity, glucose tolerance and ambulatory blood pressure in subjects with impaired glucose tolerance. Diabet Med 2004; 21:415-22. [PMID: 15089784 DOI: 10.1111/j.1464-5491.2004.01155.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIMS To determine the effects of rosiglitazone on insulin sensitivity, glucose tolerance and ambulatory blood pressure when administered to subjects with persistent impaired glucose tolerance (IGT). METHODS Eighteen subjects with persistent IGT were randomized to receive rosiglitazone 4 mg twice daily or matching placebo for 12 weeks. Evaluation at baseline and at the end of treatment included measurement of whole body insulin sensitivity during a euglycaemic hyperinsulinaemic clamp and deriving an insulin sensitivity index. Changes in glucose and insulin concentration were determined after oral glucose tolerance test (OGTT) and mixed meal tolerance tests, and 24-h ambulatory blood pressure was monitored. RESULTS Rosiglitazone significantly improved the insulin sensitivity index by 2.26 micro g/kg per min per pmol/l relative to placebo (P = 0.0003). Four of nine subjects receiving rosiglitazone reverted to normal glucose tolerance and 5/9 remained IGT, although four of these had improved 2-h glucose values. In the placebo group, 1/9 subjects progressed to Type 2 diabetes and 8/9 remained IGT. Following OGTT and meal tolerance test, glucose and insulin area under curve were reduced over 3 and 4 h, respectively. Compared with placebo, ambulatory blood pressure decreased significantly in the rosiglitazone group by 10 mmHg systolic (P = 0.0066) and 8 mmHg diastolic (P = 0.0126). CONCLUSIONS Consistent with its effects in patients with Type 2 diabetes, rosiglitazone substantially improved whole body insulin sensitivity and the glycaemic and insulinaemic responses to an OGTT and meal tolerance test in subjects with persistent IGT. Furthermore, rosiglitazone reduced systolic and diastolic ambulatory blood pressure in these subjects.
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Affiliation(s)
- S M A Bennett
- Department of Diabetes & Metabolism, Diabetes Resource Centre, University of Newcastle, North Tyneside General Hospital, Rake Lane, North Shields, Tyne & Wear NE29 8NH, Newcastle upon Tyne, UK.
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Rosa G, Manco M, Vega N, Greco AV, Castagneto M, Vidal H, Mingrone G. Decreased muscle acetyl-coenzyme A carboxylase 2 mRNA and insulin resistance in formerly obese subjects. ACTA ACUST UNITED AC 2004; 11:1306-12. [PMID: 14627750 DOI: 10.1038/oby.2003.177] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
OBJECTIVE A relationship between free fatty acids, intramuscular triglycerides (TG(M)s), and insulin resistance is widely accepted. The intracellular level of malonyl-coenzyme A (CoA) was suggested to be the possible link. Acetyl-CoA carboxylase (ACC) is a key enzyme in fatty acid metabolism, catalyzing the synthesis of malonyl-CoA, a fatty acid acyl-chain elongation unit, from acetyl-CoA. We assessed ACC2 mRNA expression variations in skeletal muscle of subjects who have undergone biliopancreatic diversion (BPD) operation. BPD, in fact inducing a massive lipid malabsorption, leads to a reversion of insulin resistance. RESEARCH METHODS AND PROCEDURES Twelve obese women (BMI > 40 kg/m(2)) were enrolled in the study. Body composition, euglycemic-hyperinsulinemic clamp, and muscle biopsies for lipid analysis and reverse transcription-competitive polymerase chain reaction were performed before and 3 years after BPD. RESULTS The average weight loss was around 37%. A significant inverse linear relation was observed between glucose uptake and TG(M) (y = -5.62x - 142.82, R(2) = 0.50, p = 0.01). The reduced amount of ACC2 mRNA directly correlated with both TG(M) (y = 2.11x +69.85, R(2) = 0.70, p = 0.01) and fasting insulin (y = 1.49x + 57.17, R(2) = 0.69, p < 0.01) concentrations. DISCUSSION In conclusion, down-regulation of ACC2 mRNA, induced by the lowering of plasma insulin concentration, is related to improvement of insulin sensitivity. We hypothesize that reduced amount of malonyl-CoA, consequent to reduced ACC2 mRNA, enhancing fatty acid oxidation, causes lowering of the intramyocitic triglyceride depot.
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Affiliation(s)
- Giuseppina Rosa
- Department of Internal Medicine, Consiglio Nazionale delle Richerche (CNR) Center, Catholic University of the Sacred Heart, Largo A. Gemelli 8, 00168 Rome, Italy.
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Shen Q, Cline GW, Shulman GI, Leibowitz MD, Davies PJA. Effects of rexinoids on glucose transport and insulin-mediated signaling in skeletal muscles of diabetic (db/db) mice. J Biol Chem 2004; 279:19721-31. [PMID: 14998989 DOI: 10.1074/jbc.m311729200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Rexinoids and thiazolidinediones (TZDs) are two classes of nuclear receptor ligands that induce insulin sensitization in diabetic rodents. TZDs are peroxisome proliferator-activated receptor gamma (PPARgamma) activators, whereas rexinoids are selective ligands for the retinoid X receptors (RXRs). Activation of both the insulin receptor substrates (IRSs)/Akt and the c-Cbl-associated protein (CAP)/c-Cbl pathways are important in regulating insulin-stimulated glucose transport. We have compared the effects of a rexinoid (LG268) and a TZD (rosiglitazone) on these two signal pathways in skeletal muscle of diabetic (db/db) mice. The results we have obtained show that treatment of db/db mice with either LG268 or rosiglitazone for 2 weeks results in a significant increase in insulin-stimulated glucose transport activity in skeletal muscle. Treatment with LG268 increases insulin-stimulated IRS-1 tyrosine phosphorylation and Akt phosphorylation in skeletal muscle without affecting the activity of the CAP/c-Cbl pathway. In contrast, rosiglitazone increases the levels of CAP expression and insulin-stimulated c-Cbl phosphorylation without affecting the IRS-1/Akt pathway. The effects of LG268 on the IRS-1/Akt pathway were associated with a decrease in the level of IRS-1 Ser(307) phosphorylation. Taken together, these data suggest that rexinoids improve insulin sensitivity via changes in skeletal muscle metabolism that are distinct from those induced by TZDs. Rexinoids represent a novel class of insulin sensitizers with potential applications in the treatment of insulin resistance.
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Affiliation(s)
- Qi Shen
- Department of Integrative Biology and Pharmacology, University of Texas Medical School, 6431 Fannin Street, Houston, TX 77225, USA
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38
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Pégorier JP, Girard J. Thiazolidinediones et insulino-sensibilité : rôle du récepteur nucléaire PPARγ. ANNALES D'ENDOCRINOLOGIE 2004; 65:65-72. [PMID: 15122095 DOI: 10.1016/s0003-4266(04)95633-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- J-P Pégorier
- Institut Cochin, département d'Endocrinologie, INSERM U 567, CNRS UMR 8104, Université Paris V René Descartes, 24, rue du Faubourg Saint Jacques, 75014 Paris, France.
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Rangwala SM, Rhoades B, Shapiro JS, Rich AS, Kim JK, Shulman GI, Kaestner KH, Lazar MA. Genetic modulation of PPARgamma phosphorylation regulates insulin sensitivity. Dev Cell 2003; 5:657-63. [PMID: 14536066 DOI: 10.1016/s1534-5807(03)00274-0] [Citation(s) in RCA: 173] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Obesity-associated diabetes is epidemic in industrialized societies. The nuclear receptor peroxisome proliferator-activated receptor gamma (PPARgamma) is highly expressed in adipose tissue and the presumed molecular target for antidiabetic thiazolidinedione drugs that reverse insulin resistance but also promote weight gain. Phosphorylation reduces the activity of PPARgamma in vitro, but physiological relevance has not been demonstrated. We have studied mice homozygous for a mutation (S112A) that prevents PPARgamma phosphorylation. Surprisingly, the weights and adipose mass of PPARgamma-S112A mice are not greater than wild-type. Remarkably, however, genetic prevention of PPARgamma phosphorylation preserves insulin sensitivity in the setting of diet-induced obesity. Underlying this protection are smaller fat cells, elevated serum adiponectin, and reduced free fatty acid levels. Thus, the phosphorylation state of PPARgamma modulates insulin sensitivity. Compounds that prevent PPARgamma phosphorylation or ligands that induce the conformation of nonphosphorylated PPARgamma may selectively enhance insulin sensitivity without increasing body weight.
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MESH Headings
- Adiponectin
- Adipose Tissue/metabolism
- Adipose Tissue, Brown
- Alanine/genetics
- Amino Acid Substitution
- Animals
- Blood Glucose/metabolism
- Blotting, Southern
- Body Weight
- Cell Size
- Cells, Cultured
- Culture Media, Conditioned/pharmacology
- Dose-Response Relationship, Drug
- Embryo, Mammalian
- Fatty Acids, Nonesterified/blood
- Female
- Gene Expression
- Glucose/metabolism
- Glucose Tolerance Test
- Immunoblotting
- Insulin/metabolism
- Insulin/pharmacology
- Insulin/physiology
- Insulin Resistance
- Intercellular Signaling Peptides and Proteins
- Leptin/blood
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Transgenic/blood
- Mice, Transgenic/genetics
- Mutation
- Obesity/blood
- Obesity/chemically induced
- Phosphorylation
- Proteins/genetics
- Proteins/metabolism
- Receptors, Cytoplasmic and Nuclear/genetics
- Receptors, Cytoplasmic and Nuclear/metabolism
- Receptors, Cytoplasmic and Nuclear/physiology
- Serine/genetics
- Time Factors
- Transcription Factors/genetics
- Transcription Factors/metabolism
- Transcription Factors/physiology
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Affiliation(s)
- Shamina M Rangwala
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
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Yuen VG, Bhanot S, Battell ML, Orvig C, McNeill JH. Chronic glucose-lowering effects of rosiglitazone and bis(ethylmaltolato)oxovanadium(IV) in ZDF rats. Can J Physiol Pharmacol 2003; 81:1049-55. [PMID: 14719040 DOI: 10.1139/y03-094] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The aim of this study was to determine if there was a synergistic or additive effect of a thiazolidinedione derivative (rosiglitazone (ROS)) and a vanadium compound (bis(ethylmaltolato)oxovanadium(IV) (BEOV)) on plasma glucose and insulin levels following chronic oral administration to Zucker diabetic fatty (ZDF) rats. Whole-blood vanadium levels were determined at time 0 and at days 1, 6, and 18. The doses of BEOV (0.1 mmol/kg) and ROS (2.8 µmol/kg) were selected to produce a glucose-lowering effect in 30% (ED30) of animals. Both drugs were administered daily by oral gavage as suspensions in 1% carboxymethylcellulose (CMC) in a volume of 2.5 mL/kg. The total volume administered to all rats was 5 mL/(kg·day). The combination of BEOV and ROS was effective in lowering plasma glucose levels to <9 mmol/L in 60% of fatty animals as compared with 30% for BEOV and 10% for ROS alone. The age-dependent decrease in plasma insulin levels associated with β-cell failure in the ZDF rats did not occur in the BEOV-treated fatty groups. There was no effect of any treatment on body weight; however, there was a significant reduction in both food and fluid intake in fatty groups treated with BEOV. There were no overt signs of toxicity and no mortality in this study. Both BEOV and ROS were effective in lowering plasma glucose levels, as stated above, and there was at least an additive effect when BEOV and ROS were used in combination.Key words: rosigitazone, bis(ethylmaltolato)oxovanadium(IV), diabetes, ZDF rats.
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Affiliation(s)
- Violet G Yuen
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, Canada
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Abstract
Type 2 diabetes mellitus is characterised by insulin resistance as well as progressive pancreatic beta cell dysfunction. The cornerstone of current oral blood-glucose lowering therapy consists of metformin, which primarily lowers hepatic glucose production, and the sulphonylureas that act by stimulating pancreatic beta-cells to secrete insulin. Recently, a novel class of agents, the thiazolidinediones, has been introduced that favourably influence insulin sensitivity and possibly also pancreatic beta-cell function. The thiazolidinediones are synthetic ligands that bind to the nuclear peroxisome proliferator-activated receptor-gamma and exert their action by activating transcription of genes that, among others, regulate adipocyte differentiation and adipogenesis as well as glucose and lipid metabolism. To date, the precise mechanisms underlying the actions of thiazolidinediones are largely unknown. When given as monotherapy or in combination with sulphonylureas, metformin or insulin in patients with type 2 diabetes, the currently available thiazolidinediones (rosiglitazone and pioglitazone) ameliorate glycaemic control, by lowering fasting and postprandial blood glucose levels, and improve insulin sensitivity in placebo-controlled trials. They seem to have differential effects on dyslipidaemia in patients with type 2 diabetes; rosiglitazone increases total cholesterol as well as high-density lipoprotein (HDL) and low-density lipoprotein cholesterol levels and affects plasma triglyceride levels depending on the baseline values, whereas pioglitazone lowers triglycerides and increases HDL cholesterol levels. The adverse events of both agents that occur with greater frequency than in patients treated with placebo are fluid retention and oedema. As demonstrated, mainly in preclinical studies to date, rosiglitazone and pioglitazone possess beneficial effects on other cardiovascular risk factors associated with the insulin resistance syndrome. Thus, these agents were shown to decrease blood pressure, enhance myocardial function and fibrinolysis, as well as possess anti-inflammatory and other beneficial vascular effects. Long-term efficacy and surveillance of this promising class of drugs in patients, however, still need to be demonstrated in outcome trials.
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Affiliation(s)
- Michaela Diamant
- Department of Endocrinology, Diabetes Centre, VU University Medical Centre, Amsterdam, The Netherlands.
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Koh EH, Kim MS, Park JY, Kim HS, Youn JY, Park HS, Youn JH, Lee KU. Peroxisome proliferator-activated receptor (PPAR)-alpha activation prevents diabetes in OLETF rats: comparison with PPAR-gamma activation. Diabetes 2003; 52:2331-7. [PMID: 12941773 DOI: 10.2337/diabetes.52.9.2331] [Citation(s) in RCA: 120] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Lipid accumulation in nonadipose tissues is closely related to the development of type 2 diabetes in obese subjects. We examined the potential preventive effect of peroxisome proliferator-activated receptor (PPAR)-alpha and PPAR-gamma stimulation on the development of diabetes in obese diabetes-prone OLETF rats. Chronic administration of a PPAR-alpha agonist (0.5% [wt/wt] fenofibrate) or a PPAR-gamma agonist (3 mg x kg(-1) x day(-1) rosiglitazone) completely prevented the development of glycosuria. Pancreatic islets from untreated OLETF rats underwent sequential hypertrophy and atrophy, which was completely prevented by chronic fenofibrate treatment. In contrast, rosiglitazone treatment did not affect islet hypertrophy at earlier stages but prevented beta-cell atrophy at later stages. Fenofibrate treatment decreased body weight and visceral fat, whereas rosiglitazone treatment increased body weight. Despite the opposite effects on adiposity, both drugs were equally effective in improving insulin actions in skeletal muscle. Furthermore, both drugs significantly decreased the triglyceride content in the soleus muscle and pancreatic islets. The present study demonstrates that the PPAR-alpha agonist fenofibrate prevents the development of diabetes in OLETF rats by reducing adiposity, improving peripheral insulin action, and exerting beneficial effects on pancreatic beta-cells.
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Affiliation(s)
- Eun Hee Koh
- Division of Endocrinology and Metabolism, Department of Internal Medicine, University of Ulsan College of Medicine, Seoul, Korea
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Hsueh WA, Law R. The central role of fat and effect of peroxisome proliferator-activated receptor-gamma on progression of insulin resistance and cardiovascular disease. Am J Cardiol 2003; 92:3J-9J. [PMID: 12957321 DOI: 10.1016/s0002-9149(03)00610-6] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Recent evidence suggests that progression of insulin resistance parallels progression of atherosclerosis. Fat plays an integral role in the development of type 2 diabetes and vascular injury. The balance of adipose-derived substances, including free fatty acids, tumor necrosis factor-alpha, leptin, adiponectin, and plasminogen activator inhibitor-1, determine both insulin action and the state of vascular inflammation. Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) ligands promote the balance of these substances to enhance insulin-mediated glucose uptake and decrease inflammation. PPAR-gamma ligands reverse the major defect of the insulin resistance syndrome and have important effects that inhibit atherosclerosis, improve endothelial cell function, and attenuate inflammation. Although more research is needed, data suggest that PPAR-gamma ligands may prevent the progression of insulin resistance to diabetes and endothelial dysfunction to atherosclerosis.
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Affiliation(s)
- Willa A Hsueh
- Division of Endocrinology, Diabetes, and Hypertension, University of California-Los Angeles School of Medicine, Los Angeles, California 90095-7073, USA.
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44
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Hegarty BD, Furler SM, Ye J, Cooney GJ, Kraegen EW. The role of intramuscular lipid in insulin resistance. ACTA PHYSIOLOGICA SCANDINAVICA 2003; 178:373-83. [PMID: 12864742 DOI: 10.1046/j.1365-201x.2003.01162.x] [Citation(s) in RCA: 183] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
There is interest in how altered lipid metabolism could contribute to muscle insulin resistance. Many animal and human states of insulin resistance have increased muscle triglyceride content, and there are now plausible mechanistic links between muscle lipid accumulation and insulin resistance, which go beyond the classic glucose-fatty acid cycle. We postulate that muscle cytosolic accumulation of the metabolically active long-chain fatty acyl CoAs (LCACoA) is involved, leading to insulin resistance and impaired insulin signalling or impaired enzyme activity (e.g. glycogen synthase or hexokinase) either directly or via chronic translocation/activation of mediators such as a protein kinase C (particularly PKC theta and epsilon ). Ceramides and diacylglycerols (DAGs) have also been implicated in forms of lipid-induced muscle insulin resistance. Dietary lipid-induced muscle insulin resistance in rodents is relatively easily reversed by manipulations that lessen cytosolic lipid accumulation (e.g. diet change, exercise or fasting). PPAR agonists (both gamma and alpha) also lower muscle LCACoA and enhance insulin sensitivity. Activation of AMP-activated protein kinase (AMPK) by AICAR leads to muscle enhancement (especially glycolytic muscle) of insulin sensitivity, but involvement of altered lipid metabolism is less clear cut. In rodents there are similarities in the pattern of muscle lipid accumulation/PKC translocation/altered insulin signalling/insulin resistance inducible by 3-5-h acute free fatty acid elevation, 1-4 days intravenous glucose infusion or several weeks of high-fat feeding. Recent studies extend findings and show relevance to humans. Muscle cytosolic lipids may accumulate either by increased fatty acid flux into muscle, or by reduced fatty acid oxidation. In some circumstances muscle insulin resistance may be an adaptation to optimize use of fatty acids when they are the predominant available energy fuel. The interactions described here are fundamental to optimizing therapy of insulin resistance based on alterations in muscle lipid metabolism.
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Affiliation(s)
- B D Hegarty
- Garvan Institute of Medical Research, Sydney, Australia
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45
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Hockings PD, Changani KK, Saeed N, Reid DG, Birmingham J, O'Brien P, Osborne J, Toseland CN, Buckingham RE. Rapid reversal of hepatic steatosis, and reduction of muscle triglyceride, by rosiglitazone: MRI/S studies in Zucker fatty rats. Diabetes Obes Metab 2003; 5:234-43. [PMID: 12795656 DOI: 10.1046/j.1463-1326.2003.00268.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
AIM This study aimed to chart the time course and durability of the effects of rosiglitazone, a potent thiazolidinedione-based peroxisome proliferator-activated receptor gamma agonist, on hepatic steatosis and intramyocellular lipid in an animal model of obesity, the Zucker Fatty (ZF) rat. METHODS AND RESULTS Rosiglitazone (3 mg/kg/day p.o.) significantly reduced both liver fat content (by 59%; p < 0.05) and size (11.5%; p < 0.05) in male ZF rats that received between 3 days and 1 week of treatment, and these reductions were maintained for at least 12 weeks. Liver fat content measured by magnetic resonance spectroscopy (MRS) correlated closely and positively with plasma insulin levels (reduced by 89% within a week, r = 0.8) and with postmortem histological fat fractional volume (r = 0.89). Similarly, liver volume measured by magnetic resonance imaging (MRI) correlated closely with postmortem wet weight (r = 0.99). MRS also showed, and numbers of lipid vacuoles counted in transmission electron micrographs confirmed, that rosiglitazone significantly reduced the elevated intramyocellular lipid seen in ZF rat skeletal muscle by at least 40% (p < 0.05). CONCLUSIONS Localized MRS and MRI showed that rosiglitazone reversed the hepatic steatosis, hepatomegaly and intramyocellular lipid, characteristic of the ZF rat, an animal model of obesity.
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Affiliation(s)
- P D Hockings
- Imaging Group, GlaxoSmithKline, Welwyn, Herts., UK.
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46
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Abstract
The metabolic nuclear receptors act as metabolic and toxicological sensors, enabling the organism to quickly adapt to environmental changes by inducing the appropriate metabolic genes and pathways. Ligands for these metabolic receptors are compounds from dietary origin, intermediates in metabolic pathways, drugs, or other environmental factors that, unlike classical nuclear receptor ligands, are present in high concentrations. Metabolic receptors are master regulators integrating the homeostatic control of (a) energy and glucose metabolism through peroxisome proliferator-activated receptor gamma (PPARgamma); (b) fatty acid, triglyceride, and lipoprotein metabolism via PPARalpha, beta/delta, and gamma; (c) reverse cholesterol transport and cholesterol absorption through the liver X receptors (LXRs) and liver receptor homolog-1 (LRH-1); (d) bile acid metabolism through the farnesol X receptor (FXR), LXRs, LRH-1; and (e) the defense against xeno- and endobiotics by the pregnane X receptor/steroid and xenobiotic receptor (PXR/SXR). The transcriptional control of these metabolic circuits requires coordination between these metabolic receptors and other transcription factors and coregulators. Altered signaling by this subset of receptors, either through chronic ligand excess or genetic factors, may cause an imbalance in these homeostatic circuits and contribute to the pathogenesis of common metabolic diseases such as obesity, insulin resistance and type 2 diabetes, hyperlipidemia and atherosclerosis, and gallbladder disease. Further studies should exploit the fact that many of these nuclear receptors are designed to respond to small molecules and turn them into therapeutic targets for the treatment of these disorders.
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Affiliation(s)
- Gordon A Francis
- CIHR Group on Molecular and Cell Biology of Lipids and Department of Medicine, University of Alberta, Edmonton, Alberta, Canada T6G 2S2
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Pickavance LC, Widdowson PS, Foster JR, Williams G, Wilding JPH. Chronic treatment with the thiazolidinedione, MCC-555, is associated with reductions in nitric oxide synthase activity and beta-cell apoptosis in the pancreas of the Zucker Diabetic Fatty rat. Int J Exp Pathol 2003; 84:83-9. [PMID: 12801282 PMCID: PMC2517543 DOI: 10.1046/j.1365-2613.2003.00337.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2002] [Accepted: 02/11/2003] [Indexed: 11/20/2022] Open
Abstract
The Zucker Diabetic Fatty (ZDF) rat is a model of impaired insulin sensitivity arising from hyperphagia owing to a mutation in the leptin receptor. In time, young ZDF rats, which are not initially diabetic, develop impaired pancreatic beta-cell function leading to apoptotic cell death. This results in an inability to fully compensate for the reduction in insulin sensitivity with hypersecretion of insulin. Young, pre-diabetic ZDF rats were treated, over a 4-week period, with the thiazolidinedione compound MCC-555, and the islet morphology studied in comparison to ZDF rats not given MCC-555. In particular, changes in the apoptotic incidence, as measured using TUNEL staining to localize apoptotic cells, were studied over the 4-week period. Changes in the induction of nitric oxide synthase and in the accumulation of nitrate/nitrite within the pancreas were also studied during the time course of administration of MCC-555. The study has demonstrated that the administration of MCC-555 significantly decreases the apoptotic incidence in the islets of Langerhans of pre-diabetic ZDF rats given the compound, as compared to those not given MCC-555, as well as decreasing the accumulation of nitrate/nitrite within the pancreas.
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Affiliation(s)
- Lucy C Pickavance
- Department of Medicine, University of Liverpool, Liverpool, Merseyside, UK.
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48
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Affiliation(s)
- E Shafrir
- Department of Medicine, Diabetes Research Centre, Hadassah University Hospital, Ein Kerem, Jerusalem, 91120 Israel.
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49
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Jucker BM, Schaeffer TR, Haimbach RE, Mayer ME, Ohlstein DH, Smith SA, Cobitz AR, Sarkar SK. Reduction of intramyocellular lipid following short-term rosiglitazone treatment in Zucker fatty rats: an in vivo nuclear magnetic resonance study. Metabolism 2003; 52:218-25. [PMID: 12601636 DOI: 10.1053/meta.2003.50040] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The aim of the study was to characterize the effects of rosiglitazone, an oral insulin sensitizer, on intramyocellular lipid (IMCL) content in tibialis anterior muscle and whole body lipid deposition in Zucker fatty rats using in vivo (1)H nuclear magnetic resonance (NMR) spectroscopy. The IMCL/EMCL (extramyocellular) ratio was significantly lower in the rosiglitazone (FRSG) group at 7, 14, 21, and 28 days of treatment at 3 mg/kg/d (0.04 +/- 0.01, 0.09 +/- 0.03, 0.11 +/- 0.02, and 0.07 +/- 0.02, respectively) versus baseline (0.43 +/- 0.12, P <.01 v all time points), whereas there was no difference in the control (FC) group at these time points (0.31 +/- 0.08, 0.36 +/- 0.08, 0.40 +/- 0.14, and 0.49 +/- 0.18, respectively) versus baseline (0.37 +/- 0.07). Absolute IMCL content was also lower at 28 days in the FRSG (0.41 +/- 0.09 micromol/g) versus FC (2.13 +/- 0.40 micromol/g, P <.005) group. To further characterize the temporal nature of this change, the IMCL/EMCL ratio was examined in the FRSG group on each of the first 4 days of treatment, and a steady decline was observed (0.38 +/- 0.12, 0.21 +/- 0.08, 0.12 +/- 0.04, 0.09 +/- 0.04, 0.05 +/- 0.03 at baseline and days 1, 2, 3, and 4 respectively, P <.05 baseline v all time points). To examine the relationship between IMCL and insulin sensitivity, a euglycemic-hyperinsulinemic clamp and IMCL measurement was performed on 7-day treated FRSG and FC groups. There was a negative correlation between absolute IMCL content and glucose infusion rate (r = -0.47, P <.04). The FRSG and the FC groups had similar whole body lipid content (expressed as a percentage of whole body water content) at baseline (48% +/- 5% and 44% +/- 2%, respectively), but the value was greater in the FRSG group following 28 days of treatment (103% +/- 4 v 84% +/- 6%, respectively, P <.02). In summary, there was a rapid (days) and pronounced reduction ( downward arrow approximately 70%) in IMCL content in tibialis anterior muscle following rosiglitazone treatment. Additionally, the increase in whole body lipid in the FRSG group suggests that there was increased adipocyte lipid storage following long-term rosiglitazone treatment. These results support the hypothesis that rosiglitazone indirectly increases peripheral insulin sensitivity by decreasing adipocyte lipolysis, thereby lowering IMCL content.
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Affiliation(s)
- Beat M Jucker
- Department of Cardiovascular and Urogenital Investigational Biology and Product Support, Laboratory of Animal Sciences, Clinical Development, and Technology Development, GlaxoSmithKline, King of Prussia, PA 19406, USA
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50
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Ye JM, Frangioudakis G, Iglesias MA, Furler SM, Ellis B, Dzamko N, Cooney GJ, Kraegen EW. Prior thiazolidinedione treatment preserves insulin sensitivity in normal rats during acute fatty acid elevation: role of the liver. Endocrinology 2002; 143:4527-35. [PMID: 12446579 DOI: 10.1210/en.2002-220387] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Thiazolidinediones lower lipids, but it is unclear whether this is essential for their insulin-sensitizing action. We investigated relationships between lipid-lowering and insulin-sensitizing actions of a thiazolidinedione. Normal rats were pretreated with or without Pioglitazone (Pio, 3 mg/kg.d) for 2 wk. Insulin sensitivity was assessed by hyperinsulinemic-euglycemic clamp with elevation of free fatty acids (FFA) by Intralipid/heparin infusion over 6 h. In untreated rats insulin sensitivity decreased by 46% over 3-6 h of elevated FFA, whereas it remained normal but with a 50% increase in FFA clearance in Pio-treated rats. After matching plasma FFA, insulin sensitivity was still partially (30%) protected in Pio-treated rats, substantially by maintaining insulin suppressibility of hepatic glucose output. This was associated with lower hepatic long-chain acyl-coenzyme A. Plasma adiponectin was increased 2-fold in Pio-treated rats and was negatively correlated with hepatic glucose output (r2 = 0.70, P < 0.001) and liver long-chain acyl-coenzyme A (r2 = 0.39, P < 0.005). Pio-induced muscle insulin sensitization was largely diminished after matching plasma FFA elevation, but insulin-stimulated protein kinase B phosphorylation was protected. We conclude that thiazolidinediones can protect against lipid-induced insulin resistance with a significant component (mainly liver) of the protective effect not requiring lipid lowering. This may be related to chronic elevation of adiponectin by thiazolidinediones.
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Affiliation(s)
- Ji-Ming Ye
- Garvan Institute of Medical Research, St. Vincent's Hospital, Sydney, New South Wales 2010, Australia.
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