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Approaches to Measuring the Activity of Major Lipolytic and Lipogenic Enzymes In Vitro and Ex Vivo. Int J Mol Sci 2022; 23:ijms231911093. [PMID: 36232405 PMCID: PMC9570359 DOI: 10.3390/ijms231911093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 09/14/2022] [Accepted: 09/16/2022] [Indexed: 11/17/2022] Open
Abstract
Since the 1950s, one of the goals of adipose tissue research has been to determine lipolytic and lipogenic activity as the primary metabolic pathways affecting adipocyte health and size and thus representing potential therapeutic targets for the treatment of obesity and associated diseases. Nowadays, there is a relatively large number of methods to measure the activity of these pathways and involved enzymes, but their applicability to different biological samples is variable. Here, we review the characteristics of mean lipogenic and lipolytic enzymes, their inhibitors, and available methodologies for assessing their activity, and comment on the advantages and disadvantages of these methodologies and their applicability in vivo, ex vivo, and in vitro, i.e., in cells, organs and their respective extracts, with the emphasis on adipocytes and adipose tissue.
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Glycerol-3-phosphate phosphatase operates a glycerol shunt in pancreatic β-cells that controls insulin secretion and metabolic stress. Mol Metab 2022; 60:101471. [PMID: 35272070 PMCID: PMC8972011 DOI: 10.1016/j.molmet.2022.101471] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Revised: 02/20/2022] [Accepted: 03/03/2022] [Indexed: 11/23/2022] Open
Abstract
Objective The recently identified glycerol-3-phosphate (Gro3P) phosphatase (G3PP) in mammalian cells, encoded by the PGP gene, was shown to regulate glucose, lipid and energy metabolism by hydrolyzing Gro3P and to control glucose-stimulated insulin secretion (GSIS) in β-cells, in vitro. However, whether G3PP regulates β-cell function and insulin secretion in vivo is not known. Methods We now examined the role of G3PP in the control of insulin secretion in vivo, β-cell function and glucotoxicity in inducible β-cell specific G3PP-KO (BKO) mice. Inducible BKO mice were generated by crossing floxed-G3PP mice with Mip-Cre-ERT (MCre) mice. All the in vivo studies were done using BKO and control mice fed normal diet and the ex vivo studies were done using pancreatic islets from these mice. Results BKO mice, compared to MCre controls, showed increased body weight, adiposity, fed insulinemia, enhanced in vivo GSIS, reduced plasma triglycerides and mild glucose intolerance. Isolated BKO mouse islets incubated at high (16.7 mM), but not at low or intermediate glucose (3 and 8 mM), showed elevated GSIS, Gro3P content as well as increased levels of metabolites and signaling coupling factors known to reflect β-cell activation for insulin secretion. BKO islets also showed reduced glycerol release and increased O2 consumption and ATP production at high glucose only. BKO islets chronically exposed to elevated glucose levels showed increased apoptosis, reduced insulin content and decreased mRNA expression of β-cell differentiation markers, Pdx-1, MafA and Ins-2. Conclusions The results demonstrate that β-cells are endowed with a “glycerol shunt”, operated by G3PP that regulates β-cell metabolism, signaling and insulin secretion in vivo, primarily at elevated glucose concentrations. We propose that the glycerol shunt plays a role in preventing insulin hypersecretion and excess body weight gain and contributes to β-cell mass preservation in the face of hyperglycemia. G3PP operates a glycerol shunt in β-cells to remove excess glucose as glycerol. Inducible β-cell specific G3PP-KO (BKO) mice show hyperinsulinemia. BKO mice show enhanced body weight and glucose induced insulin secretion. BKO isolated islets show elevated insulin secretion only at high glucose. Chronic exposure of BKO isolated islets to high glucose enhances glucotoxicity.
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Colson C, Batrow PL, Gautier N, Rochet N, Ailhaud G, Peiretti F, Amri EZ. The Rosmarinus Bioactive Compound Carnosic Acid Is a Novel PPAR Antagonist That Inhibits the Browning of White Adipocytes. Cells 2020; 9:cells9112433. [PMID: 33171828 PMCID: PMC7695189 DOI: 10.3390/cells9112433] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 11/03/2020] [Accepted: 11/04/2020] [Indexed: 12/24/2022] Open
Abstract
Thermogenic brown and brite adipocytes convert chemical energy from nutrients into heat. Therapeutics that regulate brown adipocyte recruitment and activity represent interesting strategies to control fat mass such as in obesity or cachexia. The peroxisome proliferator-activated receptor (PPAR) family plays key roles in the maintenance of adipose tissue and in the regulation of thermogenic activity. Activation of these receptors induce browning of white adipocyte. The purpose of this work was to characterize the role of carnosic acid (CA), a compound used in traditional medicine, in the control of brown/brite adipocyte formation and function. We used human multipotent adipose-derived stem (hMADS) cells differentiated into white or brite adipocytes. The expression of key marker genes was determined using RT-qPCR and western blotting. We show here that CA inhibits the browning of white adipocytes and favors decreased gene expression of thermogenic markers. CA treatment does not affect β-adrenergic response. Importantly, the effects of CA are fully reversible. We used transactivation assays to show that CA has a PPARα/γ antagonistic action. Our data pinpoint CA as a drug able to control PPAR activity through an antagonistic effect. These observations shed some light on the development of natural PPAR antagonists and their potential effects on thermogenic response.
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Affiliation(s)
- Cécilia Colson
- Université Côte d’Azur, CNRS, Inserm, iBV, 06103 Nice, France; (C.C.); (P.-L.B.); (N.G.); (N.R.); (G.A.)
| | - Pierre-Louis Batrow
- Université Côte d’Azur, CNRS, Inserm, iBV, 06103 Nice, France; (C.C.); (P.-L.B.); (N.G.); (N.R.); (G.A.)
| | - Nadine Gautier
- Université Côte d’Azur, CNRS, Inserm, iBV, 06103 Nice, France; (C.C.); (P.-L.B.); (N.G.); (N.R.); (G.A.)
| | - Nathalie Rochet
- Université Côte d’Azur, CNRS, Inserm, iBV, 06103 Nice, France; (C.C.); (P.-L.B.); (N.G.); (N.R.); (G.A.)
| | - Gérard Ailhaud
- Université Côte d’Azur, CNRS, Inserm, iBV, 06103 Nice, France; (C.C.); (P.-L.B.); (N.G.); (N.R.); (G.A.)
| | - Franck Peiretti
- Aix Marseille Université, INSERM, INRAE, C2VN, 13007 Marseille, France;
| | - Ez-Zoubir Amri
- Université Côte d’Azur, CNRS, Inserm, iBV, 06103 Nice, France; (C.C.); (P.-L.B.); (N.G.); (N.R.); (G.A.)
- Correspondence: ; Tel.: +33-493-37-70-82; Fax: +33-493-81-70-58
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Lamontagne J, Al-Mass A, Nolan CJ, Corkey BE, Madiraju SRM, Joly E, Prentki M. Identification of the signals for glucose-induced insulin secretion in INS1 (832/13) β-cells using metformin-induced metabolic deceleration as a model. J Biol Chem 2017; 292:19458-19468. [PMID: 28972173 DOI: 10.1074/jbc.m117.808105] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 09/13/2017] [Indexed: 12/23/2022] Open
Abstract
Metabolic deceleration in pancreatic β-cells is associated with inhibition of glucose-induced insulin secretion (GIIS), but only in the presence of intermediate/submaximal glucose concentrations. Here, we used acute metformin treatment as a tool to induce metabolic deceleration in INS1 (832/13) β-cells, with the goal of identifying key pathways and metabolites involved in GIIS. Metabolites and pathways previously implicated as signals for GIIS were measured in the cells at 2-25 mm glucose, with or without 5 mm metformin. We defined three criteria to identify candidate signals: 1) glucose-responsiveness, 2) sensitivity to metformin-induced inhibition of the glucose effect at intermediate glucose concentrations, and 3) alleviation of metformin inhibition by elevated glucose concentrations. Despite the lack of recovery from metformin-induced impairment of mitochondrial energy metabolism (glucose oxidation, O2 consumption, and ATP production), insulin secretion was almost completely restored at elevated glucose concentrations. Meeting the criteria for candidates involved in promoting GIIS were the following metabolic indicators and metabolites: cytosolic NAD+/NADH ratio (inferred from the dihydroxyacetone phosphate:glycerol-3-phosphate ratio), mitochondrial membrane potential, ADP, Ca2+, 1-monoacylglycerol, diacylglycerol, malonyl-CoA, and HMG-CoA. On the contrary, most of the purine and nicotinamide nucleotides, acetoacetyl-CoA, H2O2, reduced glutathione, and 2-monoacylglycerol were not glucose-responsive. Overall these results underscore the significance of mitochondrial energy metabolism-independent signals in GIIS regulation; in particular, the candidate lipid signaling molecules 1-monoacylglycerol, diacylglycerol, and malonyl-CoA; the predominance of KATP/Ca2+ signaling control by low ADP·Mg2+ rather than by high ATP levels; and a role for a more oxidized state (NAD+/NADH) in the cytosol during GIIS that favors high glycolysis rates.
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Affiliation(s)
- Julien Lamontagne
- From the Molecular Nutrition Unit and Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l'Université de Montréal (CRCHUM), Montréal, Québec H2X 0A9, Canada
| | - Anfal Al-Mass
- From the Molecular Nutrition Unit and Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l'Université de Montréal (CRCHUM), Montréal, Québec H2X 0A9, Canada.,the Department of Medicine, McGill University, Montréal, Québec H4A 3J1, Canada
| | - Christopher J Nolan
- the Department of Endocrinology, Canberra Hospital and the Medical School, Australian National University, Canberra ACT 2605, Australia, and
| | - Barbara E Corkey
- the Department of Medicine, Obesity Research Center, Boston University School of Medicine, Boston, Massachusetts 02118
| | - S R Murthy Madiraju
- From the Molecular Nutrition Unit and Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l'Université de Montréal (CRCHUM), Montréal, Québec H2X 0A9, Canada
| | - Erik Joly
- From the Molecular Nutrition Unit and Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l'Université de Montréal (CRCHUM), Montréal, Québec H2X 0A9, Canada
| | - Marc Prentki
- From the Molecular Nutrition Unit and Montreal Diabetes Research Center, Centre de Recherche du Centre Hospitalier de l'Université de Montréal (CRCHUM), Montréal, Québec H2X 0A9, Canada, .,the Departments of Nutrition and Biochemistry, Université de Montréal, Montréal, Québec H3T 1J4, Canada
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Mugabo Y, Zhao S, Lamontagne J, Al-Mass A, Peyot ML, Corkey BE, Joly E, Madiraju SRM, Prentki M. Metabolic fate of glucose and candidate signaling and excess-fuel detoxification pathways in pancreatic β-cells. J Biol Chem 2017; 292:7407-7422. [PMID: 28280244 DOI: 10.1074/jbc.m116.763060] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Revised: 03/06/2017] [Indexed: 12/28/2022] Open
Abstract
Glucose metabolism promotes insulin secretion in β-cells via metabolic coupling factors that are incompletely defined. Moreover, chronically elevated glucose causes β-cell dysfunction, but little is known about how cells handle excess fuels to avoid toxicity. Here we sought to determine which among the candidate pathways and coupling factors best correlates with glucose-stimulated insulin secretion (GSIS), define the fate of glucose in the β-cell, and identify pathways possibly involved in excess-fuel detoxification. We exposed isolated rat islets for 1 h to increasing glucose concentrations and measured various pathways and metabolites. Glucose oxidation, oxygen consumption, and ATP production correlated well with GSIS and saturated at 16 mm glucose. However, glucose utilization, glycerol release, triglyceride and glycogen contents, free fatty acid (FFA) content and release, and cholesterol and cholesterol esters increased linearly up to 25 mm glucose. Besides being oxidized, glucose was mainly metabolized via glycerol production and release and lipid synthesis (particularly FFA, triglycerides, and cholesterol), whereas glycogen production was comparatively low. Using targeted metabolomics in INS-1(832/13) cells, we found that several metabolites correlated well with GSIS, in particular some Krebs cycle intermediates, malonyl-CoA, and lower ADP levels. Glucose dose-dependently increased the dihydroxyacetone phosphate/glycerol 3-phosphate ratio in INS-1(832/13) cells, indicating a more oxidized state of NAD in the cytosol upon glucose stimulation. Overall, the data support a role for accelerated oxidative mitochondrial metabolism, anaplerosis, and malonyl-CoA/lipid signaling in β-cell metabolic signaling and suggest that a decrease in ADP levels is important in GSIS. The results also suggest that excess-fuel detoxification pathways in β-cells possibly comprise glycerol and FFA formation and release extracellularly and the diversion of glucose carbons to triglycerides and cholesterol esters.
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Affiliation(s)
- Yves Mugabo
- From the Montreal Diabetes Research Center and Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montréal, Québec H2X 0A9, Canada.,Departments of Nutrition, Biochemistry and Molecular Medicine, Faculty of Medicine, University of Montréal, Montreal, Québec H3C 3J7, Canada, and
| | - Shangang Zhao
- From the Montreal Diabetes Research Center and Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montréal, Québec H2X 0A9, Canada.,Departments of Medicine and Human Genetics, McGill University, Montreal, Québec H3A 1B1, Canada
| | - Julien Lamontagne
- From the Montreal Diabetes Research Center and Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montréal, Québec H2X 0A9, Canada
| | - Anfal Al-Mass
- From the Montreal Diabetes Research Center and Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montréal, Québec H2X 0A9, Canada.,Departments of Medicine and Human Genetics, McGill University, Montreal, Québec H3A 1B1, Canada
| | - Marie-Line Peyot
- From the Montreal Diabetes Research Center and Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montréal, Québec H2X 0A9, Canada
| | - Barbara E Corkey
- Department of Medicine, Obesity Research Center, Boston University School of Medicine, Boston, Massachusetts 02118
| | - Erik Joly
- From the Montreal Diabetes Research Center and Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montréal, Québec H2X 0A9, Canada
| | - S R Murthy Madiraju
- From the Montreal Diabetes Research Center and Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montréal, Québec H2X 0A9, Canada
| | - Marc Prentki
- From the Montreal Diabetes Research Center and Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montréal, Québec H2X 0A9, Canada, .,Departments of Nutrition, Biochemistry and Molecular Medicine, Faculty of Medicine, University of Montréal, Montreal, Québec H3C 3J7, Canada, and
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Stefan-van Staden RI, Diaconeasa AG, Stanciu-Gavan C. Fast Screening of Tissue Samples for Glycogen. J Pharm Biomed Anal 2017; 135:16-19. [DOI: 10.1016/j.jpba.2016.12.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Revised: 12/03/2016] [Accepted: 12/08/2016] [Indexed: 10/20/2022]
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Identification of a mammalian glycerol-3-phosphate phosphatase: Role in metabolism and signaling in pancreatic β-cells and hepatocytes. Proc Natl Acad Sci U S A 2016; 113:E430-9. [PMID: 26755581 DOI: 10.1073/pnas.1514375113] [Citation(s) in RCA: 73] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Obesity, and the associated disturbed glycerolipid/fatty acid (GL/FA) cycle, contribute to insulin resistance, islet β-cell failure, and type 2 diabetes. Flux through the GL/FA cycle is regulated by the availability of glycerol-3-phosphate (Gro3P) and fatty acyl-CoA. We describe here a mammalian Gro3P phosphatase (G3PP), which was not known to exist in mammalian cells, that can directly hydrolyze Gro3P to glycerol. We identified that mammalian phosphoglycolate phosphatase, with an uncertain function, acts in fact as a G3PP. We found that G3PP, by controlling Gro3P levels, regulates glycolysis and glucose oxidation, cellular redox and ATP production, gluconeogenesis, glycerolipid synthesis, and fatty acid oxidation in pancreatic islet β-cells and hepatocytes, and that glucose stimulated insulin secretion and the response to metabolic stress, e.g., glucolipotoxicity, in β-cells. In vivo overexpression of G3PP in rat liver lowers body weight gain and hepatic glucose production from glycerol and elevates plasma HDL levels. G3PP is expressed at various levels in different tissues, and its expression varies according to the nutritional state in some tissues. As Gro3P lies at the crossroads of glucose, lipid, and energy metabolism, control of its availability by G3PP adds a key level of metabolic regulation in mammalian cells, and G3PP offers a potential target for type 2 diabetes and cardiometabolic disorders.
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8
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Rydén M, Bäckdahl J, Petrus P, Thorell A, Gao H, Coue M, Langin D, Moro C, Arner P. Impaired atrial natriuretic peptide-mediated lipolysis in obesity. Int J Obes (Lond) 2015; 40:714-20. [PMID: 26499437 DOI: 10.1038/ijo.2015.222] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Revised: 09/10/2015] [Accepted: 09/28/2015] [Indexed: 11/09/2022]
Abstract
BACKGROUND Catecholamines and natriuretic peptides (NPs) are the only hormones with pronounced lipolytic effects in human white adipose tissue. Although catecholamine-induced lipolysis is well known to be impaired in obesity and insulin resistance, it is not known whether the effect of NPs is also altered. METHODS Catecholamine- and atrial NP (ANP)-induced lipolysis was investigated in abdominal subcutaneous adipocytes in vitro and in situ by microdialysis. RESULTS In a cohort of 122 women, both catecholamine- and ANP-induced lipolysis in vitro was markedly attenuated in obesity (n=87), but normalized after substantial body weight loss (n=52). The impairment of lipolysis differed between the two hormones when expressing lipolysis per lipid weight, the ratio of stimulated over basal (spontaneous) lipolysis rate or per number of adipocytes. Thus, while the response to catecholamines was lower when expressed as the former two measures, it was higher when expressed per cell number, a consequence of the significantly larger fat cell size in obesity. In contrast, although ANP-induced lipolysis was also attenuated when expressed per lipid weight or the ratio stimulated/basal, it was similar between non-obese and obese subjects when expressed per cell number suggesting that the lipolytic effect of ANP may be even more sensitive to the effects of obesity than catecholamines. Obesity was characterized by a decrease in the protein expression of the signaling NP A receptor (NPRA) and a trend toward increased levels of the clearance receptor NPRC. The impairment in ANP-induced lipolysis observed in vitro was corroborated by microdialysis experiments in situ in a smaller cohort of lean and overweight men. CONCLUSIONS ANP- and catecholamine-induced lipolysis is reversibly attenuated in obesity. The pro-lipolytic effects of ANP are relatively more impaired compared with that of catecholamines, which may in part be due to specific changes in NP receptor expression.
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Affiliation(s)
- M Rydén
- Department of Medicine-H7, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden
| | - J Bäckdahl
- Department of Medicine-H7, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden
| | - P Petrus
- Department of Medicine-H7, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden
| | - A Thorell
- Department of Surgery, Karolinska Institutet, Ersta Hospital, Stockholm, Sweden
| | - H Gao
- Department of of Biosciences and Nutrition, Karolinska Institutet, Stockholm, Sweden
| | - M Coue
- INSERM, UMR1048, Obesity Research Laboratory, Institute of Metabolic and Cardiovascular Diseases, Toulouse, France.,University of Toulouse, UMR1048, Paul Sabatier University, France
| | - D Langin
- INSERM, UMR1048, Obesity Research Laboratory, Institute of Metabolic and Cardiovascular Diseases, Toulouse, France.,University of Toulouse, UMR1048, Paul Sabatier University, France.,Department of Clinical Biochemistry, Toulouse University Hospitals, Toulouse, France
| | - C Moro
- INSERM, UMR1048, Obesity Research Laboratory, Institute of Metabolic and Cardiovascular Diseases, Toulouse, France.,University of Toulouse, UMR1048, Paul Sabatier University, France
| | - P Arner
- Department of Medicine-H7, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden
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Iglesias J, Lamontagne J, Erb H, Gezzar S, Zhao S, Joly E, Truong VL, Skorey K, Crane S, Madiraju SRM, Prentki M. Simplified assays of lipolysis enzymes for drug discovery and specificity assessment of known inhibitors. J Lipid Res 2015; 57:131-41. [PMID: 26423520 DOI: 10.1194/jlr.d058438] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Indexed: 12/25/2022] Open
Abstract
Lipids are used as cellular building blocks and condensed energy stores and also act as signaling molecules. The glycerolipid/ fatty acid cycle, encompassing lipolysis and lipogenesis, generates many lipid signals. Reliable procedures are not available for measuring activities of several lipolytic enzymes for the purposes of drug screening, and this resulted in questionable selectivity of various known lipase inhibitors. We now describe simple assays for lipolytic enzymes, including adipose triglyceride lipase (ATGL), hormone sensitive lipase (HSL), sn-1-diacylglycerol lipase (DAGL), monoacylglycerol lipase, α/β-hydrolase domain 6, and carboxylesterase 1 (CES1) using recombinant human and mouse enzymes either in cell extracts or using purified enzymes. We observed that many of the reported inhibitors lack specificity. Thus, Cay10499 (HSL inhibitor) and RHC20867 (DAGL inhibitor) also inhibit other lipases. Marked differences in the inhibitor sensitivities of human ATGL and HSL compared with the corresponding mouse enzymes was noticed. Thus, ATGListatin inhibited mouse ATGL but not human ATGL, and the HSL inhibitors WWL11 and Compound 13f were effective against mouse enzyme but much less potent against human enzyme. Many of these lipase inhibitors also inhibited human CES1. Results describe reliable assays for measuring lipase activities that are amenable for drug screening and also caution about the specificity of the many earlier described lipase inhibitors.
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Affiliation(s)
- Jose Iglesias
- Molecular Nutrition Unit and Montreal Diabetes Research Center, CRCHUM, Montréal, Québec, Canada H2X 0A9 Departments of Nutrition, Biochemistry, and Molecular Medicine, Université de Montréal, Montréal, Québec, Canada H2X 0A9
| | - Julien Lamontagne
- Molecular Nutrition Unit and Montreal Diabetes Research Center, CRCHUM, Montréal, Québec, Canada H2X 0A9 Departments of Nutrition, Biochemistry, and Molecular Medicine, Université de Montréal, Montréal, Québec, Canada H2X 0A9
| | - Heidi Erb
- Molecular Nutrition Unit and Montreal Diabetes Research Center, CRCHUM, Montréal, Québec, Canada H2X 0A9 Departments of Nutrition, Biochemistry, and Molecular Medicine, Université de Montréal, Montréal, Québec, Canada H2X 0A9
| | - Sari Gezzar
- Molecular Nutrition Unit and Montreal Diabetes Research Center, CRCHUM, Montréal, Québec, Canada H2X 0A9 Departments of Nutrition, Biochemistry, and Molecular Medicine, Université de Montréal, Montréal, Québec, Canada H2X 0A9
| | - Shangang Zhao
- Molecular Nutrition Unit and Montreal Diabetes Research Center, CRCHUM, Montréal, Québec, Canada H2X 0A9 Departments of Nutrition, Biochemistry, and Molecular Medicine, Université de Montréal, Montréal, Québec, Canada H2X 0A9
| | - Erik Joly
- Molecular Nutrition Unit and Montreal Diabetes Research Center, CRCHUM, Montréal, Québec, Canada H2X 0A9 Departments of Nutrition, Biochemistry, and Molecular Medicine, Université de Montréal, Montréal, Québec, Canada H2X 0A9
| | | | | | - Sheldon Crane
- NuChem Therapeutics, Montréal, Québec, Canada, H4P 2R2
| | - S R Murthy Madiraju
- Molecular Nutrition Unit and Montreal Diabetes Research Center, CRCHUM, Montréal, Québec, Canada H2X 0A9 Departments of Nutrition, Biochemistry, and Molecular Medicine, Université de Montréal, Montréal, Québec, Canada H2X 0A9
| | - Marc Prentki
- Molecular Nutrition Unit and Montreal Diabetes Research Center, CRCHUM, Montréal, Québec, Canada H2X 0A9 Departments of Nutrition, Biochemistry, and Molecular Medicine, Université de Montréal, Montréal, Québec, Canada H2X 0A9
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10
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A 3-D organoid kidney culture model engineered for high-throughput nephrotoxicity assays. Biomaterials 2012; 33:4700-11. [DOI: 10.1016/j.biomaterials.2012.02.063] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2011] [Accepted: 02/29/2012] [Indexed: 01/17/2023]
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11
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Adler-Wailes DC, Guiney EL, Wolins NE, Yanovski JA. Long-term ritonavir exposure increases fatty acid and glycerol recycling in 3T3-L1 adipocytes as compensatory mechanisms for increased triacylglycerol hydrolysis. Endocrinology 2010; 151:2097-105. [PMID: 20228169 PMCID: PMC2869264 DOI: 10.1210/en.2009-1364] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Lipodystrophy with high nonesterified fatty acid (FA) efflux is reported in humans receiving highly active antiretroviral therapy (HAART) to treat HIV infection. Ritonavir, a common component of HAART, alters adipocyte FA efflux, but the mechanism for this effect is not established. To investigate ritonavir-induced changes in FA flux and recycling through acylglycerols, we exposed differentiated murine 3T3-L1 adipocytes to ritonavir for 14 d. FA efflux, uptake, and incorporation into acylglycerols were measured. To identify a mediator of FA efflux, we measured adipocyte triacylglycerol lipase (ATGL) transcript and protein. To determine whether ritonavir-treated adipocytes increased glycerol backbone synthesis for FA reesterification, we measured labeled glycerol and pyruvate incorporation into triacylglycerol (TAG). Ritonavir-treated cells had increased FA efflux, uptake, and incorporation into TAG (all P < 0.01). Ritonavir increased FA efflux without consistently increasing glycerol release or changing TAG mass, suggesting increased partial TAG hydrolysis. Ritonavir-treated adipocytes expressed significantly more ATGL mRNA (P < 0.05) and protein (P < 0.05). Ritonavir increased glycerol (P < 0.01) but not pyruvate (P = 0.41), utilization for TAG backbone synthesis. Consistent with this substrate utilization, glycerol kinase transcript (required for glycerol incorporation into TAG backbone) was up-regulated (P < 0.01), whereas phosphoenolpyruvate carboxykinase transcript (required for pyruvate utilization) was down-regulated (P < 0.001). In 3T3-L1 adipocytes, long-term ritonavir exposure perturbs FA metabolism by increasing ATGL-mediated partial TAG hydrolysis, thus increasing FA efflux, and leads to compensatory increases in FA reesterification with glycerol and acylglycerols. These changes in FA metabolism may, in part, explain the increased FA efflux observed in ritonavir-associated lipodystrophy.
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Affiliation(s)
- Diane C Adler-Wailes
- Head, Unit on Growth and Obesity, National Institutes of Health, Hatfield Clinical Research Center, Bethesda, Maryland 20892-1103, USA
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Wojtanik KM, Edgemon K, Viswanadha S, Lindsey B, Haluzik M, Chen W, Poy G, Reitman M, Londos C. The role of LMNA in adipose: a novel mouse model of lipodystrophy based on the Dunnigan-type familial partial lipodystrophy mutation. J Lipid Res 2009; 50:1068-79. [PMID: 19201734 DOI: 10.1194/jlr.m800491-jlr200] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We investigated the role of LMNA in adipose tissue by developing a novel mouse model of lipodystrophy. Transgenic mice were generated that express the LMNA mutation that causes familial partial lipodystrophy of the Dunnigan type (FPLD2). The phenotype observed in FPLD-transgenic mice resembles many of the features of human FPLD2, including lack of fat accumulation, insulin resistance, and enlarged, fatty liver. Similar to the human disease, FPLD-transgenic mice appear to develop normally, but after several weeks they are unable to accumulate fat to the same extent as their wild-type littermates. One poorly understood aspect of lipodystrophies is the mechanism of fat loss. To this end, we have examined the effects of the FPLD2 mutation on fat cell function. Contrary to the current literature, which suggests FPLD2 results in a loss of fat, we found that the key mechanism contributing to the lack of fat accumulation involves not a loss, but an apparent inability of the adipose tissue to renew itself. Specifically, preadipocytes are unable to differentiate into mature and fully functional adipocytes. These findings provide insights not only for the treatment of lipodystrophies, but also for the study of adipogenesis, obesity, and insulin resistance.
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Affiliation(s)
- Kari M Wojtanik
- Laboratory of Cellular and Developmental Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
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13
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Birkenfeld AL, Budziarek P, Boschmann M, Moro C, Adams F, Franke G, Berlan M, Marques MA, Sweep FCGJ, Luft FC, Lafontan M, Jordan J. Atrial natriuretic peptide induces postprandial lipid oxidation in humans. Diabetes 2008; 57:3199-204. [PMID: 18835931 PMCID: PMC2584124 DOI: 10.2337/db08-0649] [Citation(s) in RCA: 115] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE Atrial natriuretic peptide (ANP) regulates arterial blood pressure. In addition, ANP has recently been shown to promote human adipose tissue lipolysis through cGMP-mediated hormone-sensitive lipase activation. We hypothesized that ANP increases postprandial free fatty acid (FFA) availability and energy expenditure while decreasing arterial blood pressure. RESEARCH DESIGN AND METHODS We infused human ANP (25 ng . kg(-1) . min(-1)) in 12 men (age 32 +/- 0.8 years, BMI 23.3 +/- 0.4 kg/m(2)) before, during, and 2 h after ingestion of a standardized high-fat test meal in a randomized, double-blind, cross-over fashion. Cardiovascular changes were monitored by continuous electrocardiogram and beat-by-beat blood pressure recordings. Metabolism was monitored through venous blood sampling, intramuscular and subcutaneous abdominal adipose tissue microdialysis, and indirect calorimetry. RESULTS ANP infusion decreased mean arterial blood pressure by 4 mmHg during the postprandial phase (P < 0.01 vs. placebo). At the same time, ANP induced lipolysis systemically (P < 0.05 vs. placebo) and locally in subcutaneous abdominal adipose tissue (P < 0.0001 vs. placebo), leading to a 50% increase in venous glycerol (P < 0.01) and FFA (P < 0.05) concentrations compared with placebo. The increase in FFA availability with ANP was paralleled by a 15% increase in lipid oxidation rates (P < 0.05 vs. placebo), driving a substantial increase in postprandial energy expenditure (P < 0.05 vs. placebo). CONCLUSIONS Our data identify the ANP system as a novel pathway regulating postprandial lipid oxidation, energy expenditure, and concomitantly arterial blood pressure. The findings could have therapeutic implications.
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Affiliation(s)
- Andreas L Birkenfeld
- Experimental and Clinical Research Center, Charité and HELIOS Klinikum, Berlin, Germany
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14
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Moro C, Pillard F, de Glisezinski I, Klimcakova E, Crampes F, Thalamas C, Harant I, Marques MA, Lafontan M, Berlan M. Exercise-induced lipid mobilization in subcutaneous adipose tissue is mainly related to natriuretic peptides in overweight men. Am J Physiol Endocrinol Metab 2008; 295:E505-13. [PMID: 18559985 DOI: 10.1152/ajpendo.90227.2008] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Involvement of sympathetic nervous system and natriuretic peptides in the control of exercise-induced lipid mobilization was compared in overweight and lean men. Lipid mobilization was determined using local microdialysis during exercise. Subjects performed 35-min exercise bouts at 60% of their maximal oxygen consumption under placebo or after oral tertatolol [a beta-adrenergic receptor (AR) antagonist]. Under placebo, exercise increased dialysate glycerol concentration (DGC) in both groups. Phentolamine (alpha-AR antagonist) potentiated exercise-induced lipolysis in overweight but not in lean subjects; the alpha(2)-antilipolytic effect was only functional in overweight men. After tertatolol administration, the DGC increased similarly during exercise no matter which was used probe in both groups. Compared with the control probe under placebo, lipolysis was reduced in lean but not in overweight men treated with the beta-AR blocker. Tertatolol reduced plasma nonesterified fatty acids and insulin concentration in both groups at rest. Under placebo or tertatolol, the exercise-induced changes in plasma nonesterified fatty acids, glycerol, and insulin concentrations were similar in both groups. Exercise promoted a higher increase in catecholamine and ANP plasma levels after tertatolol administration. In conclusion, the major finding of our study is that in overweight men, in addition to an increased alpha(2)-antilipolytic effect, the lipid mobilization in subcutaneous adipose tissue that persists during exercise under beta-blockade is not dependent on catecholamine action. On the basis of correlation findings, it seems to be related to a concomitant exercise-induced rise in plasma ANP when exercise is performed under tertatolol intake and a decrease in plasma insulin.
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Affiliation(s)
- Cedric Moro
- INSERM U858-I2MR, Institut de Médecine Moléculaire de Rangueil, 1 Ave. Jean Poulhès, Toulouse Cedex 4, France
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15
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Burén J, Lai YC, Lundgren M, Eriksson JW, Jensen J. Insulin action and signalling in fat and muscle from dexamethasone-treated rats. Arch Biochem Biophys 2008; 474:91-101. [PMID: 18328801 DOI: 10.1016/j.abb.2008.02.034] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2008] [Revised: 02/18/2008] [Accepted: 02/21/2008] [Indexed: 10/22/2022]
Abstract
Glucocorticoids initiate whole body insulin resistance and the aim of the present study was to investigate effects of dexamethasone on protein expression and insulin signalling in muscle and fat tissue. Rats were injected with dexamethasone (1mg/kg/day, i.p.) or placebo for 11 days before insulin sensitivity was evaluated in vitro in soleus and epitrochlearis muscles and in isolated epididymal adipocytes. Dexamethasone treatment reduced insulin-stimulated glucose uptake and glycogen synthesis by 30-70% in epitrochlearis and soleus, and insulin-stimulated glucose uptake by approximately 40% in adipocytes. 8-bromo-cAMP-stimulated lipolysis was approximately 2-fold higher in adipocytes from dexamethasone-treated rats and insulin was less effective to inhibit cAMP-stimulated lipolysis. A main finding was that dexamethasone decreased expression of PKB and insulin-stimulated Ser(473) and Thr(308) phosphorylation in both muscles and adipocytes. Expression of GSK-3 was not influenced by dexamethasone treatment in muscles or adipocytes and insulin-stimulated GSK-3beta Ser(9) phosphorylation was reduced in muscles only. A novel finding was that glycogen synthase (GS) Ser(7) phosphorylation was higher in both muscles from dexamethasone-treated rats. GS expression decreased (by 50%) in adipocytes only. Basal and insulin-stimulated GS Ser(641) and GS Ser(645,649,653,657) phosphorylation was elevated in epitrochlearis and soleus muscles and GS fractional activity was reduced correspondingly. In conclusion, dexamethasone treatment (1) decreases PKB expression and insulin-stimulated phosphorylation in both muscles and adipocytes, and (2) increases GS phosphorylation (reduces GS fractional activity) in muscles and decreases GS expression in adipocytes. We suggest PKB and GS as major targets for dexamethasone-induced insulin resistance.
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Affiliation(s)
- J Burén
- Department of Public Health and Clinical Medicine, Umeå University Hospital, Umeå, Sweden
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16
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Moro C, Klimcakova E, Lafontan M, Berlan M, Galitzky J. Phosphodiesterase-5A and neutral endopeptidase activities in human adipocytes do not control atrial natriuretic peptide-mediated lipolysis. Br J Pharmacol 2007; 152:1102-10. [PMID: 17906676 PMCID: PMC2095109 DOI: 10.1038/sj.bjp.0707485] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND AND PURPOSE Atrial natriuretic peptide (ANP) stimulates lipolysis in human adipocyte through a cGMP signalling pathway, the regulation of which is poorly known. Since phosphodiesterases (PDE) and neutral endopeptidase (NEP) play a major role in the regulation of the biological effects of natriuretic peptides in the cardiovascular and renal systems, we investigated whether these mechanisms could regulate cGMP signalling and ANP-mediated lipolysis in human adipocytes. EXPERIMENTAL APPROACH The presence of cGMP-specific PDE and NEP in differentiated pre-adipocytes and in mature adipocytes was evaluated by real-time qPCR and Western blot. The effect of non-selective and selective inhibition of these enzymes on ANP-mediated cGMP signalling and lipolysis was determined in isolated mature adipocytes. KEY RESULTS PDE-5A was expressed in both pre-adipocytes and adipocytes. PDE-5A mRNA and protein levels decreased as pre-adipocytes differentiated (10 days). PDE-5A is rapidly activated in response to ANP stimulation and lowers intracellular cGMP levels. Its selective inhibition by sildenafil partly prevented the decline in cGMP levels. However, no changes in baseline- and ANP-mediated lipolysis were observed under PDE-5 blockade using various inhibitors. In addition, NEP mRNA and protein levels gradually increased during the time-course of pre-adipocyte differentiation. Thiorphan, a selective NEP inhibitor, completely abolished NEP activity in human adipocyte membranes but did not modify ANP-mediated lipolysis. CONCLUSIONS AND IMPLICATIONS Functional PDE-5A and NEP activities were present in human adipocytes, however these enzymes did not play a major role in the regulation of ANP-mediated lipolysis.
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Affiliation(s)
- C Moro
- INSERM, U858, Obesity Research Laboratory Toulouse, France
- Louis Bugnard Institute IFR31, Paul Sabatier University Toulouse, France
| | - E Klimcakova
- INSERM, U858, Obesity Research Laboratory Toulouse, France
- Louis Bugnard Institute IFR31, Paul Sabatier University Toulouse, France
| | - M Lafontan
- Louis Bugnard Institute IFR31, Paul Sabatier University Toulouse, France
- INSERM, U858, Avenir Team 1 Toulouse, France
| | - M Berlan
- INSERM, U858, Obesity Research Laboratory Toulouse, France
- Louis Bugnard Institute IFR31, Paul Sabatier University Toulouse, France
- Faculty of Medicine, Laboratory of Medical and Clinical Pharmacology Toulouse, France
| | - J Galitzky
- Louis Bugnard Institute IFR31, Paul Sabatier University Toulouse, France
- INSERM, U858, Avenir Team 1 Toulouse, France
- Author for correspondence:
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17
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Moro C, Pillard F, de Glisezinski I, Crampes F, Thalamas C, Harant I, Marques MA, Lafontan M, Berlan M. Sex differences in lipolysis-regulating mechanisms in overweight subjects: effect of exercise intensity. Obesity (Silver Spring) 2007; 15:2245-55. [PMID: 17890493 DOI: 10.1038/oby.2007.267] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
OBJECTIVE To explore sex differences in the regulation of lipolysis during exercise, the lipid-mobilizing mechanisms in the subcutaneous adipose tissue (SCAT) of overweight men and women were studied using microdialysis. RESEARCH METHODS AND PROCEDURES Subjects matched for age, BMI, and physical fitness performed two 30-minute exercise bouts in a randomized fashion: the first test at 30% and 50% of their individual maximal oxygen uptake (Vo(2max)) and the second test at 30% and 70% of their Vo(2max). RESULTS In both groups, an exercise-dependent increment in extracellular glycerol concentration (EGC) was observed. Whatever the intensity, phentolamine [alpha-adrenergic receptor (AR) antagonist] added to a dialysis probe potentiated exercise-induced lipolysis only in men. In a probe containing phentolamine plus propranolol (beta-AR antagonist), no changes in EGC occurred when compared with the control probe when exercise was performed at 30% and 50% Vo(2max). A significant reduction of EGC (when compared with the control probe) was observed in women at 70% Vo(2max). At each exercise power, the plasma non-esterified fatty acid and glycerol concentrations were higher in women. Exercise-induced increase in plasma catecholamine levels was lower in women compared with men. Plasma insulin decreased and atrial natriuretic peptide increased similarly in both groups. DISCUSSION Overweight women mobilize more lipids (assessed by glycerol) than men during exercise. alpha(2)-Anti-lipolytic effect was functional in SCAT of men only. The major finding is that during low-to-moderate exercise periods (30% and 50% Vo(2max)), lipid mobilization in SCAT relies less on catecholamine-dependent stimulation of beta-ARs than on an increase in plasma atrial natriuretic peptide concentrations and the decrease in plasma insulin.
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Affiliation(s)
- Cédric Moro
- Institut National de la Santé et de la Recherche Médicale U858, Laboratoire de Pharmacologie Médicale et Clinique, Faculté de Médecine, 37 Allées Jules Guesde, 31073 Toulouse, France
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18
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Viswanadha S, Londos C. Optimized conditions for measuring lipolysis in murine primary adipocytes. J Lipid Res 2006; 47:1859-64. [PMID: 16675855 DOI: 10.1194/jlr.d600005-jlr200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The current literature on lipolysis in murine primary adipocytes is rife with experiments performed under conditions not optimized for reproducible and reliable results. Here, we present conditions for optimizing the measurement of lipolysis in murine adipocytes. We demonstrate that adenosine management is of paramount importance in evaluating the lipolytic response under basal and stimulated conditions. Also, adipocyte concentrations in the 10,000-15,000 cells per milliliter range produce a greater increase in stimulated lipolysis than higher concentrations, and the response is further enhanced by agitating the cells.
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Affiliation(s)
- Srikant Viswanadha
- Laboratory of Cellular and Developmental Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-8028, USA
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19
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Kim H, Pennisi PA, Gavrilova O, Pack S, Jou W, Setser-Portas J, East-Palmer J, Tang Y, Manganiello VC, Leroith D. Effect of adipocyte beta3-adrenergic receptor activation on the type 2 diabetic MKR mice. Am J Physiol Endocrinol Metab 2006; 290:E1227-36. [PMID: 16682489 DOI: 10.1152/ajpendo.00344.2005] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The antiobesity and antidiabetic effects of the beta3-adrenergic agonists were investigated on nonobese type 2 diabetic MKR mice after injection with a beta3-adrenergic agonist, CL-316243. An intact response to acute CL-316243 treatment was observed in MKR mice. Chronic intraperitoneal CL-316243 treatment of MKR mice reduced blood glucose and serum insulin levels. Hyperinsulinemic euglycemic clamps exhibited improvement of the whole body insulin sensitivity and glucose homeostasis concurrently with enhanced insulin action in liver and adipose tissue. Treating MKR mice with CL-316243 significantly lowered serum and hepatic lipid levels, in part due to increased whole body triglyceride clearance and fatty acid oxidation in adipocytes. A significant reduction in total body fat content and epididymal fat weight was observed along with enhanced metabolic rate in both wild-type and MKR mice after treatment. These data demonstrate that beta3-adrenergic activation improves the diabetic state of nonobese diabetic MKR mice by potentiation of free fatty acid oxidation by adipose tissue, suggesting a potential therapeutic role for beta3-adrenergic agonists in nonobese diabetic subjects.
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Affiliation(s)
- Hyunsook Kim
- Diabetes Branch, National Institute of Diabetes, Digestive and Kidney Diseases, NIH, Bethesda, MD, USA
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20
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Belhadj-Tahar H, Nassar BB, Sadeg N, Coulais Y. [Monitoring of adipocyte responsiveness by in situ microdialysis in lipodystrophy tissue: adjustment of a glycerol quantification method in small samples]. Acta Clin Belg 2006; 61:143-6. [PMID: 16881564 DOI: 10.1179/acb.2006.023] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
In situ microdialysis allows monitoring of metabolic cellular processes at the tissue level in vivo. In the assessment of physiopathologic alterations seen in lipodystrophy, monitoring of glycerol release is pivotal. Indeed, it allows to quantify the pharmacological responsiveness of subcutaneous adipose tissue in humans. Until now, the small volume of microdialysate collected (5-15 microL/sample) restricted the assessment of glycerol level to the use of the radio-enzymatic method or the reference spectrophotometric microanalysis technique. The aim of this study was to adapt the method of glycerol measurement by iminequinone spectrophotometry colorimetric assay (520 nm) using the following reagent: 0.5 IU Glycerokinase, 1.23 IU glycerophosphate oxidase, 0.98 IU peroxidase, 4.6 mM Mg, 5.4 mM 4-chlorophenol, 0.25 mM 4-aminoantipyrine and 1.4 mM ATP. The assay was setup to run on Olympus AU 2700 automate (15 pL sample volume). The sensitivity of the method was improved by adding a 0.2 mmol triglyceride (TG) solution and 1.5 IU lipase to samples, reducing the limit of free glycerol quantification to 0.020 mmol/L. The analytical repeatability was 2.0% and the reproducibility was 7.9%. The present method thus demonstrated the feasibility of pharmacodynamic exploration of local cutaneous responsiveness in vivo in clinical trials.
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Affiliation(s)
- H Belhadj-Tahar
- Groupe Santé Recherche, Département de Pharmacologie Clinique, 31300 Toulouse, France.
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21
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Moro C, Polak J, Hejnova J, Klimcakova E, Crampes F, Stich V, Lafontan M, Berlan M. Atrial natriuretic peptide stimulates lipid mobilization during repeated bouts of endurance exercise. Am J Physiol Endocrinol Metab 2006; 290:E864-9. [PMID: 16291573 DOI: 10.1152/ajpendo.00348.2005] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Atrial natriuretic peptide (ANP) controls lipolysis in human adipocytes. Lipid mobilization is increased during repeated bouts of exercise, but the underlying mechanisms involved in this process have not yet been delineated. The relative involvement of catecholamine- and ANP-dependent pathways in the control of lipid mobilization during repeated bouts of exercise was thus investigated in subcutaneous adipose tissue (SCAT) by microdialysis. The study was performed in healthy males. Subjects performed two 45-min exercise bouts (E1 and E2) at 50% of their maximal oxygen uptake separated by a 60-min rest period. Extracellular glycerol concentration (EGC), reflecting SCAT lipolysis, was measured in a control probe perfused with Ringer solution and in two other probes perfused with either Ringer plus phentolamine (alpha(1/2)-AR antagonist) or Ringer plus both phentolamine and propranolol (beta-AR antagonist). Plasma epinephrine, plasma glycerol, and EGC were 1.7-, 1.6-, and 1.2-fold higher in E2 than in E1, respectively. Phentolamine potentiated exercise-induced EGC increase during E2 only. Propranolol reduced the lipolytic rate during both E1 and E2 compared with the probe with phentolamine. Plasma ANP concentration increased more during E2 than during E1 and was correlated with the increase in EGC in the probe containing phentolamine plus propranolol. The results suggest that ANP is involved in the control of lipolysis during exercise and that it contributes to stimulation of lipolysis during repeated bouts of exercise.
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Affiliation(s)
- Cédric Moro
- Franco-Czech Laboratory for Clinical Research on Obesity, French Institute of Health and Medical Research (INSERM U586), Toulouse, France.
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22
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Polak J, Moro C, Klimcakova E, Hejnova J, Majercik M, Viguerie N, Langin D, Lafontan M, Stich V, Berlan M. Dynamic strength training improves insulin sensitivity and functional balance between adrenergic alpha 2A and beta pathways in subcutaneous adipose tissue of obese subjects. Diabetologia 2005; 48:2631-40. [PMID: 16273345 DOI: 10.1007/s00125-005-0003-8] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/10/2005] [Accepted: 07/05/2005] [Indexed: 11/27/2022]
Abstract
AIMS/HYPOTHESIS The aim of this study was to investigate whether dynamic strength training modifies the control of lipolysis, with particular attention paid to the involvement of the antilipolytic adrenergic alpha 2A receptor (ADRA2A) pathway. METHODS Twelve obese men (age: 47.4+/-2.8 years; BMI: 32.7+/-0.9) were investigated during a 210-min euglycaemic-hyperinsulinaemic clamp conducted before and after 3 months of dynamic strength training. Before and during the third hour of the clamp, the lipolytic effect of a perfusion of isoproterenol or adrenaline (epinephrine) alone or associated with the ADRA2A antagonist phentolamine was evaluated using the microdialysis method of measuring extracellular glycerol concentration (EGC) in subcutaneous abdominal adipose tissue (SCAAT). In addition, biopsies of SCAAT were carried out before and after training to determine mRNA levels RESULTS The training increased insulin sensitivity in adipose tissue. The decrease of EGC was more pronounced during the clamp conducted after the training period than during the clamp done in pre-training conditions. Before and after the training, catecholamines induced an increase in EGC, the increase being lower during the clamp on each occasion. The isoproterenol-induced increase in EGC was higher after the training. Adrenaline-induced lipolysis was potentiated by phentolamine after but not before the training. There were no training-induced changes in mRNA levels of key genes of the lipolytic pathway in SCAAT. CONCLUSIONS/INTERPRETATION In obese subjects, dynamic strength training improves whole-body and adipose tissue insulin responsiveness. It increases responsiveness to the adrenergic beta receptor stimulation of lipolysis and to the antilipolytic action of catecholamines mediated by ADRA2As.
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MESH Headings
- 3',5'-Cyclic-AMP Phosphodiesterases/genetics
- 3',5'-Cyclic-AMP Phosphodiesterases/physiology
- Adrenergic alpha-2 Receptor Agonists
- Adrenergic alpha-2 Receptor Antagonists
- Adrenergic beta-2 Receptor Agonists
- Adult
- Cyclic Nucleotide Phosphodiesterases, Type 3
- Epinephrine/pharmacology
- Exercise/physiology
- Fatty Acids, Nonesterified/blood
- Glucose Clamp Technique
- Glycerol/analysis
- Glycerol/blood
- Humans
- Insulin/physiology
- Insulin Resistance/physiology
- Isoproterenol/pharmacology
- Lipid Metabolism
- Lipolysis
- Male
- Middle Aged
- Obesity/metabolism
- Obesity/physiopathology
- Phentolamine/pharmacology
- RNA, Messenger/analysis
- Receptors, Adrenergic, alpha-2/genetics
- Receptors, Adrenergic, alpha-2/metabolism
- Receptors, Adrenergic, beta-2/genetics
- Receptors, Adrenergic, beta-2/metabolism
- Sterol Esterase/genetics
- Sterol Esterase/physiology
- Subcutaneous Fat, Abdominal/chemistry
- Subcutaneous Fat, Abdominal/metabolism
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Affiliation(s)
- J Polak
- Franco-Czech Laboratory for Clinical Research on Obesity, French Institute of Health and Medical Research (Inserm U586) and 3rd Faculty of Medicine, Charles University, Prague, Czech Republic
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23
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Sengenès C, Lolmède K, Zakaroff-Girard A, Busse R, Bouloumié A. Preadipocytes in the human subcutaneous adipose tissue display distinct features from the adult mesenchymal and hematopoietic stem cells. J Cell Physiol 2005; 205:114-22. [PMID: 15880450 DOI: 10.1002/jcp.20381] [Citation(s) in RCA: 397] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The stroma-vascular fraction (SVF) of human adipose tissue has recently been described to be composed of endothelial cells identified as CD34+/CD31+ cells, infiltrated/resident macrophages defined as CD14+/CD31+ cells, and a new cell population characterized as CD34+/CD31- cells. To elucidate the cell identity of the adipocyte precursor cells, fluorescent activating cell sorter (FACS) analyses were performed on crude SVF cultured under adipogenic conditions, i.e., serum-deprived medium containing insulin, cortisol, triiodothyronine, and supplemented with a PPARgamma agonist for the first 3 days. The progressive accumulation of lipid droplets was associated with a selective enrichment of the CD34+/CD31- cell population whereas control experiments performed in medium supplemented with 10% serum showed an overall downregulation of the three cell markers without adipogenesis. Among the different cell subsets, the CD34+/CD31- subset was the unique cell fraction able to answer to adipogenic culture conditions. Indeed, a time-dependent expression of adipocyte markers as well as acquisition of adipocyte-typical metabolic activities were observed. In parallel, the gene expression of lipogenic and lipolytic enzymes increased. The ability to differentiate into adipocytes was restricted to cells that did not express the mesenchymal stem cell marker CD105. Furthermore, the CD34+/CD31- cells did not respond to culture conditions used for hematopoietic colony assays. Taken together, the present study demonstrates that adipocyte progenitor cells, i.e., the preadipocytes, are included in the CD34+/CD31- cell fraction, which displays distinct features from the adult mesenchymal and hematopoietic stem cells.
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Affiliation(s)
- Coralie Sengenès
- Institute of Cardiovascular Physiology, Johann Wolfgang Goethe University, Frankfurt am Main, Germany. coralie@
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24
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Moro C, Pillard F, De Glisezinski I, Harant I, Rivière D, Stich V, Lafontan M, Crampes F, Berlan M. Training enhances ANP lipid-mobilizing action in adipose tissue of overweight men. Med Sci Sports Exerc 2005; 37:1126-32. [PMID: 16015128 DOI: 10.1249/01.mss.0000170124.51659.52] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
PURPOSE This study was designed to evaluate whether a 4-month endurance training program could improve ANP- as well as isoproterenol-mediated (beta-adrenergic receptor agonist) in situ lipolysis and adipose tissue blood flow (ATBF) in the subcutaneous adipose tissue (SCAT) of untrained overweight subjects. METHODS Ten overweight men aged 26.0 +/- 1.4 yr with a mean body mass index of 27.6 +/- 0.2 kg.m(-2), performed aerobic exercise 5 d.wk(-1) for 4 months. Before and after the training period, SCAT responsiveness was investigated in situ during a 60-min infusion of 1 micromol.L(-1) isoproterenol and 10 micromol.L(-1) ANP through microdialysis probes. Plasma metabolic parameters and physical fitness variables were measured as well. RESULTS Endurance training significantly increased fat-free mass and VO2max, while reducing plasma insulin, glucose, NEFA, low density lipoprotein (LDL)-C and the respiratory exchange ratio at rest. Training significantly lowered resting dialysate glycerol levels in SCAT. The lipid-mobilizing effect of ANP was markedly enhanced (by 191%, P < 0.05) after training as was that of isoproterenol (by 145%, P < 0.05). Resting adipose tissue blood flow as well as ANP- and isoproterenol-mediated rise in ATBF was increased after training. CONCLUSION The present study shows that endurance training improves ANP- as well as beta-adrenergic-receptor-mediated lipid mobilization and ATBF in the SCAT of overweight subjects. The recovery of a higher lipolytic efficiency in adipose tissue is an important benefit of a training program in overweight subjects.
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Affiliation(s)
- Cedric Moro
- Franco-Czech Laboratory for Clinical Research on Obesity, Inserm U586, Institut Louis Bugnard, Centre Hospitalier Universitaire de Toulouse, Université Paul Sabatier, Toulouse, France
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25
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Ladeira RB, Freitas MAR, Silva EF, Gontijo NF, Gomes MA. Glycogen as a carbohydrate energy reserve in trophozoites of Giardia lamblia. Parasitol Res 2005; 96:418-21. [PMID: 15940524 DOI: 10.1007/s00436-005-1356-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2004] [Accepted: 03/22/2005] [Indexed: 11/25/2022]
Abstract
Although there is indirect evidence to suggest that glycogen is present in G. lamblia, to date it has not been purified and identified from this organism. In this study, a high molecular weight carbohydrate was purified and characterized and its physiological role as an energetic reserve was established. The monosaccharide constituents of the carbohydrate reserve were identified as glucose by two independent methods: thin layer chromatography and an enzymatic assay. The degree of branching of the molecule was evaluated by comparing its absorbance spectrum in the presence of lugol with spectra of standard solutions of glycogen and starch under the same conditions. The results strongly suggest that glycogen is present in G. lamblia and acts as an energy reserve in trophozoites of this organism.
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Affiliation(s)
- Rodolfo B Ladeira
- Departamento de Parasitologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte, Brazil
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26
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Tavernier G, Jimenez M, Giacobino JP, Hulo N, Lafontan M, Muzzin P, Langin D. Norepinephrine induces lipolysis in beta1/beta2/beta3-adrenoceptor knockout mice. Mol Pharmacol 2005; 68:793-9. [PMID: 15939797 DOI: 10.1124/mol.105.014670] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Catecholamines are major stimulants of adipose tissue metabolism. Norepinephrine and epinephrine act through three subtypes of beta-adrenoceptors (beta-AR) expressed in the adipocytes. The aim of this work was to study the mechanisms of lipid mobilization in beta1/beta2/beta3-AR triple-knockout (beta-less) mice. Glycerol and nonesterified fatty acids released from isolated adipocytes were measured as an index of lipolytic activity. There was no difference between the two genotypes for basal lipolysis and lipolytic response to corticotropin or to agents acting at the adenylyl cyclase and protein kinase A levels. The lipolytic response to norepinephrine and beta-AR agonists was blunted in beta-less mice. However, a residual low-affinity lipolytic effect was observed in the presence of catecholamines and beta3-AR agonists but not of beta1- or beta2-AR agonists. cAMP levels were increased by a beta-AR agonist in white and brown adipocytes of beta-less mice. The residual lipolytic effect was blocked by beta-AR antagonists. It was mediated neither by alpha1- or alpha2-AR nor dopaminergic, serotonergic, and histaminergic by receptors. Bioinformatic analyses do not provide evidence for a fourth beta-AR. We conclude that the residual lipolytic effect observed in beta-less mice can be attributed to an unknown Gs-protein-coupled receptor with low affinity for catecholamines.
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Affiliation(s)
- Geneviève Tavernier
- Unité de Recherches sur les Obésités, Inserm UPS U586, Institut Louis Bugnard IFR31, CHU Rangueil, Bātiment L3, BP 84225, 31432 Toulouse Cedex 4, France.
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27
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Adler-Wailes DC, Liu H, Ahmad F, Feng N, Londos C, Manganiello V, Yanovski JA. Effects of the human immunodeficiency virus-protease inhibitor, ritonavir, on basal and catecholamine-stimulated lipolysis. J Clin Endocrinol Metab 2005; 90:3251-61. [PMID: 15741249 PMCID: PMC1350765 DOI: 10.1210/jc.2004-2194] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Several of the aspartic acid protease inhibitors used to treat HIV infection increase basal lipolysis in adipocytes, but the cellular mechanisms leading to this augmentation are not well understood. We therefore studied the effects of chronic exposure to the HIV protease inhibitor, ritonavir, on the lipolytic cascade in 3T3-L1 adipocytes. Treatment of 3T3-L1 adipocytes with ritonavir for 14 d (during and after differentiation) enhanced basal, isoproterenol (Iso)-stimulated, and cAMP analog-stimulated lipolysis. Enhancement of lipolysis was observed after Iso at concentrations between 0.1 and 10 mum. Despite a significant decrease in cyclic nucleotide phosphodiesterase (PDE)3B activity and protein levels, there were no changes in Iso-stimulated intracellular cAMP, protein kinase A (PKA) expression, or PKA activity. Ritonavir-augmented lipolysis was also observed under conditions that reversed the effect on PDE3B activity via preincubation with 1 mum (-)-N(6)-(2-phenylisopropyl)adenosine. In ritonavir-treated cells, protein expression of the lipid droplet-protective protein, perilipin, was significantly decreased, whereas there was no change in hormone-sensitive lipase. Activation of ERK1/2 by Iso did not play a role in the augmentation. We conclude that ritonavir decreases PDE3B and perilipin protein expression and affects both basal and catecholamine-stimulated lipolysis in 3T3-L1 adipocytes primarily through actions at sites downstream of PKA.
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Key Words
- ap-2, adipocyte fatty acid binding protein
- cat-α, catalytic-α
- dmso, dimethylsulfoxide
- fbs, fetal bovine serum
- haart, highly active antiretroviral therapy
- hsl, hormone-sensitive lipase
- ibmx, isobutylmethylxanthine
- iso, isoproterenol
- krh, krebs/ringer/hepes
- nefa, nonesterified fatty acid
- pde, phosphodiesterase
- peri, perilipin
- pia, (-)-n6-(2-phenylisopropyl)adenosine
- pka, protein kinase a
- pki, protein kinase inhibitor
- sds, sodium dodecyl sulfate
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Affiliation(s)
| | | | | | | | | | | | - Jack A. Yanovski
- Address all correspondence and requests for reprints to: Jack A. Yanovski, National Institutes of Health, Clinical Research Center, Room 1–3330, 10 Center Drive, MSC-1103, Bethesda, Maryland 20892-1103. E-mail:
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Moro C, Polak J, Richterova B, Sengenès C, Pelikanova T, Galitzky J, Stich V, Lafontan M, Berlan M. Differential regulation of atrial natriuretic peptide- and adrenergic receptor-dependent lipolytic pathways in human adipose tissue. Metabolism 2005; 54:122-31. [PMID: 15562390 DOI: 10.1016/j.metabol.2004.07.020] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The aim of the study was to investigate the regulation affecting the recently described atrial natriuretic peptide (ANP)-dependent lipolytic pathway in comparison with the adrenergic lipolytic cascade. We studied in vivo the effect of a euglycemic-hyperinsulinemic clamp on the changes occurring in the extracellular glycerol concentration (EGC) of subcutaneous adipose tissue (SCAT) during ANP or epinephrine perfusion in a microdialysis probe. Homologous desensitization and the incidence of hyperinsulinemia on the ANP- and catecholaminergic-dependent control of lipolysis were also investigated in vitro on fat cells from SCAT. When perfused in SCAT, epinephrine and ANP promoted an increase in EGC; the EGC increase was significantly lower during the clamp. The reduction of epinephrine-induced lipolysis was limited (18%) when phentolamine (an alpha(2)-adrenergic receptor [AR] antagonist) was perfused together with epinephrine. Unlike the effect of epinephrine, the response to ANP observed during the second perfusion was reduced by 32%. The increase in extracellular guanosine 3',5' -cyclic monophosphate concentration, which reflects ANP activity, was also reduced during the second perfusion. Desensitization of the lipolytic effects of ANP was observed in vitro after a 2-hour period of recovery, while the effects of alpha(2)-AR agonist or of epinephrine were unchanged. Insulin was without any effect on ANP-induced lipolysis and alpha(2)-AR-mediated antilipolysis, while it reduced beta-AR-induced lipolysis. The ANP-dependent lipolytic pathway undergoes desensitization in vitro and in situ. Insulin had no inhibitory effect on either ANP- or alpha(2)-AR-dependent pathways, while it counteracted the beta-AR pathway.
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Affiliation(s)
- Cédric Moro
- Unité de Recherches sur les Obésités Inserm U586, Institut Louis Bugnard, Center Hospitalier Universitaire de Toulouse, Université Paul Sabatier, 31062 Toulouse, France
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29
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Kim H, Haluzik M, Gavrilova O, Yakar S, Portas J, Sun H, Pajvani UB, Scherer PE, LeRoith D. Thiazolidinediones improve insulin sensitivity in adipose tissue and reduce the hyperlipidaemia without affecting the hyperglycaemia in a transgenic model of type 2 diabetes. Diabetologia 2004; 47:2215-25. [PMID: 15662559 DOI: 10.1007/s00125-004-1581-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/05/2004] [Accepted: 07/15/2004] [Indexed: 01/08/2023]
Abstract
AIM/HYPOTHESIS The aim of this study was to examine the effects of thiazolidinediones on the MKR mouse model of type 2 diabetes. METHODS Six-week-old wild-type (WT) and MKR mice were fed with or without rosiglitazone or pioglitazone for 3 weeks. Blood was collected from the tail vein for serum biochemistry analysis. Hyperinsulinaemic-euglycaemic clamp analysis was performed to study effects of thiazolidinediones on insulin sensitivity of tissues in MKR mice. Northern blot analysis was performed to measure levels of target genes of PPAR gamma agonists in white adipose tissue and hepatic gluconeogenic genes. RESULTS Thiazolidinedione treatment of MKR mice significantly lowered serum lipid levels and increased serum adiponectin levels but did not affect levels of blood glucose and serum insulin. Hyperinsulinaemic-euglycaemic clamp showed that whole-body insulin sensitivity and glucose homeostasis failed to improve in MKR mice after rosiglitazone treatment. Insulin suppression of hepatic endogenous glucose production failed to improve in MKR mice following rosiglitazone treatment. This lack of change in hepatic insulin insensitivity was associated with no change in the ratio of HMW : total adiponectin, hepatic triglyceride content, and sustained hepatic expression of PPAR gamma and stearoyl-CoA desaturase 1 mRNA. Interestingly, rosiglitazone markedly enhanced glucose uptake by white adipose tissue with a parallel increase in CD36, aP2 and GLUT4 gene expression. CONCLUSIONS/INTERPRETATION These data suggest that potentiation of insulin action on tissues other than adipose tissue is required to mediate the antidiabetic effects of thiazolidinediones in our MKR diabetic mice.
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Affiliation(s)
- H Kim
- Molecular and Cellular Physiology Section, Diabetes Branch, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health, 9000 Rockville Pike, Bldg. 10, Room 8D12, Bethesda, MD 20892-1758, USA
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30
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Haluzik M, Colombo C, Gavrilova O, Chua S, Wolf N, Chen M, Stannard B, Dietz KR, Le Roith D, Reitman ML. Genetic background (C57BL/6J versus FVB/N) strongly influences the severity of diabetes and insulin resistance in ob/ob mice. Endocrinology 2004; 145:3258-64. [PMID: 15059949 DOI: 10.1210/en.2004-0219] [Citation(s) in RCA: 147] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
We studied the effects of genetic background on the phenotype of ob/ob mice, a model of severe obesity, insulin resistance, and diabetes caused by leptin deficiency. Despite a comparable degree of obesity and hyperinsulinemia, C57BL/6J ob/ob mice had much milder hyperglycemia and, surprisingly, normal circulating adiponectin levels despite still-prominent signs of insulin resistance. Hyperinsulinemic-euglycemic clamp revealed relatively less whole-body and muscle insulin resistance in C57BL/6J ob/ob mice, whereas liver insulin resistance tended to be more severe than in FVB/N ob/ob mice. C57BL/6J ob/ob mice had also more rapid clearance of circulating triglycerides and more severe hepatic steatosis. We suggest that strain-related distinction in lipid handling is the most important player in the differences in diabetic phenotype and insulin sensitivity, whereas the impact of circulating adiponectin levels on the overall phenotype of ob/ob mice is less important.
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Affiliation(s)
- Martin Haluzik
- Diabetes Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
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31
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Moro C, Crampes F, Sengenes C, De Glisezinski I, Galitzky J, Thalamas C, Lafontan M, Berlan M. Atrial natriuretic peptide contributes to physiological control of lipid mobilization in humans. FASEB J 2004; 18:908-10. [PMID: 15033935 DOI: 10.1096/fj.03-1086fje] [Citation(s) in RCA: 136] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
In humans, lipid mobilization is considered to depend mainly on sympathetic nervous system activation and catecholamine action. A contribution of ANP was hypothesized because we have previously shown that atrial natriuretic peptide (ANP) is a lipolytic agent on isolated human fat cells. Control of lipid-mobilizing mechanisms was investigated using in situ microdialysis in subcutaneous adipose tissue (SCAT) in healthy young men during two successive exercise bouts performed at 35% and 60% peak oxygen consumption (VO2max) after placebo or acute oral tertatolol (nonselective beta-antagonist) treatment. In placebo-treated subjects, infusion of propranolol in the probe (100 micromol/l) only partially reduced (40%) the increment in extracellular glycerol concentration (EGC) promoted by exercise. Moreover, oral beta-adrenergic receptor blockade did not prevent exercise-induced lipid mobilization in SCAT while exerting fat cell beta-adrenergic receptor blockade. Exercise-induced increase in plasma ANP was potently amplified by oral tertatolol. A positive correlation was found between EGC and plasma ANP levels but also between extracellular cGMP (i.e., index of ANP-mediated lipolysis) and EGC. Thus, we demonstrate that exercise-induced lipid mobilization resistant to local propranolol and lipid-mobilizing action observed under oral beta-blockade is related to the action of ANP. Oral beta-adrenergic receptor blockade, which potentiates exercise-induced ANP release by the heart, may contribute to lipid mobilization in SCAT. The potential relevance of an ANP-related lipid-mobilizing pathway is discussed.
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Affiliation(s)
- Cedric Moro
- Unité de recherches sur les Obésités, Institut National de la Santé et de la Recherche Médicale U586 ,Toulouse, France
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32
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Rodriguez AM, Elabd C, Delteil F, Astier J, Vernochet C, Saint-Marc P, Guesnet J, Guezennec A, Amri EZ, Dani C, Ailhaud G. Adipocyte differentiation of multipotent cells established from human adipose tissue. Biochem Biophys Res Commun 2004; 315:255-63. [PMID: 14766202 DOI: 10.1016/j.bbrc.2004.01.053] [Citation(s) in RCA: 231] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2003] [Indexed: 12/27/2022]
Abstract
In this study multipotent adipose-derived stem cells isolated from human adipose tissue (hMADS cells) were shown to differentiate into adipose cells in serum-free, chemically defined medium. During the differentiation process, hMADS cells exhibited a gene expression pattern similar to that described for rodent clonal preadipocytes and human primary preadipocytes. Differentiated cells displayed the key features of human adipocytes, i.e., expression of specific molecular markers, lipolytic response to agonists of beta-adrenoreceptors (beta2-AR agonist > beta1-AR agonist >> beta3-AR agonist) and to the atrial natriuretic peptide, insulin-stimulated glucose transport, and secretion of leptin and adiponectin. hMADS cells were able to respond to drugs as inhibition of adipocyte differentiation was observed in the presence of prostaglandin F2alpha, tumour necrosis factor-alpha, and nordihydroguaiaretic acid, a natural polyhydroxyphenolic antioxidant. Thus, for the first time, human adipose cells with normal karyotype and indefinite life span have been established. They represent a novel and valuable tool for studies of fat tissue development and metabolism.
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Affiliation(s)
- Anne-Marie Rodriguez
- Institut de Recherche Signalisation, Biologie du Développement et Cancer, UMR 6543 CNRS, Centre de Biochimie, Faculté des Sciences, Parc Valrose, 06108 Nice cedex 2, France
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33
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Sengenes C, Bouloumie A, Hauner H, Berlan M, Busse R, Lafontan M, Galitzky J. Involvement of a cGMP-dependent pathway in the natriuretic peptide-mediated hormone-sensitive lipase phosphorylation in human adipocytes. J Biol Chem 2003; 278:48617-26. [PMID: 12970365 DOI: 10.1074/jbc.m303713200] [Citation(s) in RCA: 191] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Our previous studies have demonstrated that natriuretic peptides (NPs), peptide hormones with natriuretic, diuretic, and vasodilating properties, exert a potent control on the lipolysis in human adipocytes via the activation of the type A guanylyl cyclase receptor (1, 2). In the current study we investigated the intracellular mechanisms involved in the NP-stimulated lipolytic effect in human preadipocytes and adipocytes. We demonstrate that the atrial NP (ANP)-induced lipolysis in human adipocytes was associated with an enhanced serine phosphorylation of the hormone-sensitive lipase (HSL). Both ANP-mediated lipolysis and HSL phosphorylation were inhibited in the presence of increasing concentrations of the guanylyl cyclase inhibitor LY-83583. ANP did not modulate the activity of the cAMP-dependent protein kinase (PKA). Moreover, H-89, a PKA inhibitor, did not affect the ANP-induced lipolysis. On primary cultures of human preadipocytes, the ANP-mediated lipolytic effect was dependent on the differentiation process. On differentiated human preadipocytes, ANP-mediated lipolysis, associated with an increased phosphorylation of HSL and of perilipin A, was strongly decreased by treatment with the inhibitor of the cGMP-dependent protein kinase I (cGKI), Rp-8-pCPT-cGMPS. Thus, ANP-induced lipolysis in human adipocytes is a cGMP-dependent pathway that induces the phosphorylation of HSL and perilipin A via the activation of cGKI. The present study shows that lipolysis in human adipocytes can be controlled by an independent cGKI-mediated signaling as well as by the classical cAMP/PKA pathway.
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Affiliation(s)
- Coralie Sengenes
- Obesity Research Unit, INSERM U 586, Institut Louis Bugnard, Centre Hospitalier Universitaire Rangueil, Université Paul Sabatier, Toulouse, France.
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Moro C, Galitzky J, Sengenes C, Crampes F, Lafontan M, Berlan M. Functional and pharmacological characterization of the natriuretic peptide-dependent lipolytic pathway in human fat cells. J Pharmacol Exp Ther 2003; 308:984-92. [PMID: 14634036 DOI: 10.1124/jpet.103.060913] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A lipolytic pathway involving natriuretic peptides has recently been discovered in human fat cells. Its functional characteristics and the interactions of the atrial natriuretic peptide (ANP)-induced effects with adrenergic and insulin pathways were studied. Characterization of the action of ANP antagonists, i.e., A71915, anantin, S-28-Y (Ser-28-Tyr, a synthesized peptide), and HS-142-1 (a microbial polysaccharide), was performed. Lipolytic assays and intracellular cGMP and cAMP determinations were performed on isolated fat cells. Cell membranes were used for binding studies. At low concentrations ANP and isoproterenol [beta-adrenergic receptor (beta-AR) agonist] exerted additive lipolytic effects. The alpha(2)-AR pathway did not interfere with that of ANP. Lipolytic effects of ANP were unaltered by a 2-h pretreatment of fat cells with insulin, whereas beta-AR-induced lipolysis was reduced. Homologous desensitization occurred for ANP-dependent lipolytic pathways. Dendroapsis natriuretic peptide exhibited a similar maximal effect but a 10-fold higher lipolytic potency than ANP and mini-ANP (the shortest form of ANP). The antagonist A71915 exhibited competitive antagonistic properties with a pA(2) value of 7.51. Anantin displayed noncompetitive antagonism and exerted an inhibitory action on basal and beta-adrenergic receptor-induced lipolytic response. S-28-Y exhibited antagonist potencies toward ANP-induced lipolysis and behaved as a partial lipolytic agonist with a lower pD(2) value (7.4 +/- 0.2) than ANP (9.4 +/- 0.3). HS-142-1 exerted the weakest antagonistic effects. The results demonstrate that ANP-dependent effects do not interfere with beta- and alpha(2)-adrenergic pathways in human fat cells. They are unaffected by insulin pretreatments of fat cells but undergo desensitization. In the search of potent and specific natriuretic peptide receptor-A antagonist, in the human fat cell, A71915 was the only reliable one found.
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Affiliation(s)
- Cedric Moro
- Unité de recherches sur les obésités, Institut National de la Santé et de la Recherche Médicale, Universitaire Rangueil, Toulouse, France
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Rotter V, Nagaev I, Smith U. Interleukin-6 (IL-6) induces insulin resistance in 3T3-L1 adipocytes and is, like IL-8 and tumor necrosis factor-alpha, overexpressed in human fat cells from insulin-resistant subjects. J Biol Chem 2003; 278:45777-84. [PMID: 12952969 DOI: 10.1074/jbc.m301977200] [Citation(s) in RCA: 751] [Impact Index Per Article: 35.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Several studies have shown a relationship between interleukin (IL) 6 levels and insulin resistance. We here show that human subcutaneous adipose cells, like 3T3-L1 cells, are target cells for IL-6. To examine putative mechanisms and cross-talk with insulin, 3T3-L1 adipocytes were cultured for different times with IL-6 and tumor necrosis factor alpha (TNF-alpha). IL-6, in contrast to TNF-alpha, did not increase pS-307 of insulin-receptor substrate (IRS)-1 or JNK activation. However, IL-6, like TNF-alpha exerted long term inhibitory effects on the gene transcription of IRS-1, GLUT-4, and peroxisome proliferator-activated receptor gamma. This effect of IL-6 was accompanied by a marked reduction in IRS-1, but not IRS-2, protein expression, and insulin-stimulated tyrosine phosphorylation, whereas no inhibitory effect was seen on the insulin receptor tyrosine phosphorylation. Consistent with the reduced GLUT-4 mRNA, insulin-stimulated glucose transport was also significantly reduced by IL-6. An important interaction with TNF-alpha was found because TNF-alpha markedly increased IL-6 mRNA and protein secretion. These results show that IL-6, through effects on gene transcription, is capable of impairing insulin signaling and action but, in contrast to TNF-alpha, IL-6 does not increase pS-307 (or pS-612) of IRS-1. The link between IL-6 and insulin resistance in man was further corroborated by the finding that the expression of IL-6, like that of TNF-alpha and IL-8, was markedly increased ( approximately 15-fold) in human fat cells from insulin-resistant individuals. We conclude that IL-6 can play an important role in insulin resistance in man and, furthermore, that it may act in concert with other cytokines that also are up-regulated in adipose cells in insulin resistance.
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Affiliation(s)
- Victoria Rotter
- Department of Internal Medicine, Lundberg Laboratory for Diabetes Research, The Sahlgrenska Academy, Göteborg University, SE-413 45 Göteborg, Sweden
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36
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Stich V, Pelikanova T, Wohl P, Sengenès C, Zakaroff-Girard A, Lafontan M, Berlan M. Activation of alpha2-adrenergic receptors blunts epinephrine-induced lipolysis in subcutaneous adipose tissue during a hyperinsulinemic euglycemic clamp in men. Am J Physiol Endocrinol Metab 2003; 285:E599-607. [PMID: 12900381 DOI: 10.1152/ajpendo.00502.2002] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The aim of this study was to investigate whether hyperinsulinemia modifies adrenergic control of lipolysis, with particular attention paid to the involvement of antilipolytic alpha2-adrenergic receptors (AR). Eight healthy male subjects (age: 23.9 +/- 0.9 yr; body mass index: 23.8 +/- 1.9) were investigated during a 6-h euglycemichyperinsulinemic clamp and in control conditions. Before and during the clamp, the effect of graded perfusions of isoproterenol (0.1 and 1 microM) or epinephrine (1 and 10 microM) on the extracellular glycerol concentration in subcutaneous abdominal adipose tissue was evaluated by using the microdialysis method. Both isoproterenol and epinephrine induced a dose-dependent increase in extracellular glycerol concentration when infused for 60 min through the microdialysis probes before and during hours 3 and 6 of the clamp. The catecholamine-induced increase was significantly lower during the clamp than before it, with the inhibition being more pronounced in hour 6 of the clamp. Isoproterenol (1 microM)-induced lipolysis was reduced by 28 and 44% during hours 3 and 6 of the clamp, respectively, whereas the reduction of epinephrine (100 microM)-induced lipolysis was significantly greater (by 63 and 70%, P < 0.01 and P < 0.04, respectively) during the same time intervals. When epinephrine was infused in combination with 100 microM phentolamine (a nonselective alpha-AR antagonist), the inhibition of epinephrine (10 microM)-induced lipolysis was only of 19 and 40% during hours 3 and 6 of the clamp, respectively. The results demonstrate that, in situ, insulin counteracts the epinephrine-induced lipolysis in adipose tissue. The effect involves 1) reduction of lipolysis stimulation mediated by the beta-adrenergic pathway and 2) the antilipolytic component of epinephrine action mediated by alpha2-ARs.
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Affiliation(s)
- Vladimir Stich
- Department of Sports Medicine, Third Faculty of Medicine, Charles University, Prague, Czech Republic
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37
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Darimont C, Zbinden I, Avanti O, Leone-Vautravers P, Giusti V, Burckhardt P, Pfeifer AMA, Macé K. Reconstitution of telomerase activity combined with HPV-E7 expression allow human preadipocytes to preserve their differentiation capacity after immortalization. Cell Death Differ 2003; 10:1025-31. [PMID: 12934077 DOI: 10.1038/sj.cdd.4401273] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Overexpression of SV40 T-antigen (SV40 T-Ag) has been widely used to overcome replicative senescence of human primary cells and to promote cell immortalization. However, in the case of certain cell types, such as preadipocytes, the differentiation process of immortalized cells is blocked by SV40 T-Ag expression. In this study, human telomerase reverse transcriptase (hTERT) and papillomavirus E7 oncoprotein (HPV-E7) genes were coexpressed in human preadipocytes to test whether this combination could maintain cell differentiation capacity after immortalization. We demonstrated that the HPV-E7/hTERT expressing preadipocytes displayed an indefinite life span. Interestingly, immortalized cells were diploid and presented no chromosomic alterations. These immortalized cells were able to accumulate and hydrolyze intracellular triglycerides and to express adipocyte markers. These data demonstrate, for the first time, that coexpression of hTERT and HPV-E7 in human preadipocytes allows cells not only to display an indefinite life span but also to retain their capacity to differentiate.
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Affiliation(s)
- C Darimont
- Nestlé Research Center, PO Box 44, Vers-Chez-Les-Blanc, 1000 Lausanne 26, Switzerland.
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38
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Colombo C, Haluzik M, Cutson JJ, Dietz KR, Marcus-Samuels B, Vinson C, Gavrilova O, Reitman ML. Opposite effects of background genotype on muscle and liver insulin sensitivity of lipoatrophic mice. Role of triglyceride clearance. J Biol Chem 2003; 278:3992-9. [PMID: 12456680 DOI: 10.1074/jbc.m207665200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The metabolic phenotype of the A-ZIP/F-1 (AZIP) lipoatrophic mouse is different depending on its genetic background. On both the FVB/N (FVB) and C57BL/6J (B6) backgrounds, AZIP mice have a similarly severe lack of white adipose tissue and comparably increased insulin levels and triglyceride secretion rates. However, on the B6 background, the AZIP mice have less hyperglycemia, lower circulating triglyceride and fatty acid levels, and lower mortality. AZIP characteristics that are more severe on the B6 background include increased liver size and liver triglyceride content. A unifying hypothesis is that the B6 strain has higher triglyceride clearance into the liver, with lower triglyceride levels elsewhere. This may account for the observation that the B6 AZIP mice have less insulin-resistant muscles and more insulin-resistant livers, than do the FVB AZIP mice. B6 wild type, as well as B6 AZIP, mice have increased triglyceride clearance relative to FVB, which may be explained in part by higher serum lipase levels and liver CD36/fatty acid translocase mRNA levels. Thus, it is likely that increased triglyceride clearance in B6, as compared with FVB, mice contributes to the strain differences in insulin resistance and lipid metabolism.
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Affiliation(s)
- Carlo Colombo
- Diabetes Branch, NIDDK, National Institutes of Health, Bethesda, Maryland 20892, USA
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Burén J, Lindmark S, Renström F, Eriksson JW. In vitro reversal of hyperglycemia normalizes insulin action in fat cells from type 2 diabetes patients: is cellular insulin resistance caused by glucotoxicity in vivo? Metabolism 2003; 52:239-45. [PMID: 12601640 DOI: 10.1053/meta.2003.50041] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Chronic hyperglycemia promotes the development of insulin resistance. The aim of this study was to investigate whether cellular insulin resistance is secondary to the diabetic state in human type 2 diabetes. Subcutaneous fat biopsies were taken from 3 age-, sex-, and body mass index (BMI)-matched groups with 10 subjects in each group: type 2 diabetes patients with either good (hemoglobin A(1c) [HbA(1c)] < 7%, G) or poor (HbA(1c) > 7.5%, P) metabolic control and healthy control subjects (C). Insulin action in vitro was studied by measurements of glucose uptake both directly after cell isolation and following a 24-hour incubation at a physiological glucose level (6 mmol/L). The relationship with insulin action in vivo was addressed by employing the euglycemic clamp technique. Freshly isolated fat cells from type 2 diabetes patients with poor metabolic control had approximately 55% lower maximal insulin response (1,000 microU/mL) on glucose uptake (P <.05) compared to C. Cells from P were more insulin-resistant (P <.05) than cells from G at a low (5 microU/mL) but not at a high (1,000 microU/mL) insulin concentration, suggesting insulin insensitivity. However, following 24 hours of incubation at physiological glucose levels, insulin resistance was completely reversed in the diabetes cells and no differences in insulin-stimulated glucose uptake were found among the 3 groups. Insulin sensitivity in vivo assessed with hyperinsulinemic, euglycemic clamp (M-value) was significantly associated with insulin action on glucose uptake in fresh adipocytes in vitro (r = 0.50, P <.01). Fasting blood glucose at the time of biopsy and HbA(1c), but not serum insulin, were negatively correlated to insulin's effect to stimulate glucose uptake in vitro (r = -0.36, P =.064 and r = - 0.41, P <.05, respectively) in all groups taken together. In the in vivo situation, fasting blood glucose, HbA(1c), and serum insulin were all negatively correlated to insulin sensitivity (M-value; r = -0.62, P<.001, r= -0.61, P<.001, and r = -0.56, p <.01, respectively). Cell size, waist-to-hip ration (WHR), and BMI correlated negatively with insulin's effect to stimulate glucose uptake both in vitro (r = -0.55, P <.01, r = -0.54, P <.01, and r = -0.43, P <.05, respectively) and in vivo (r = -0.43, P <.05, r = -0.50, P <.01, and r = -0.36, P <.05, respectively). Multiple regression analyses revealed that adipocyte cell size and WHR independently predicted insulin resistance in vitro. Furthermore, insulin sensitivity in vivo could be predicted by fasting blood glucose and serum insulin levels. We conclude that insulin resistance in fat cells from type 2 diabetes patients is fully reversible following incubation at physiological glucose concentrations. Thus, cellular insulin resistance may be mainly secondary to the hyperglycemic state in vivo.
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Affiliation(s)
- Jonas Burén
- Department of Medicine, Umeå University Hospital, Umeå, Sweden
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Crampes F, Marion-Latard F, Zakaroff-Girard A, De Glisezinski I, Harant I, Thalamas C, Stich V, Rivière D, Lafontan M, Berlan M. Effects of a longitudinal training program on responses to exercise in overweight men. OBESITY RESEARCH 2003; 11:247-56. [PMID: 12582221 DOI: 10.1038/oby.2003.38] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
OBJECTIVE The aim of this study was to determine how training modifies metabolic responses and lipid oxidation in overweight young male subjects. RESEARCH METHODS AND PROCEDURES Eleven overweight subjects were selected for a 4-month endurance training program. Before and after the training period, they cycled for 60 minutes at 50% of their VO(2)max after an overnight fast or 3 hours after eating a standardized meal. Various metabolic and endocrine parameters, and respiratory exchange ratio values were evaluated. RESULTS Exercise-induced plasma norepinephrine concentration increases were similar before and after training in fasted or fed conditions. After food intake, exercise promoted a decrease in plasma glucose and a higher increase in epinephrine than in fasting conditions. The increase in epinephrine after the meal was more marked after training (264 +/- 32 vs. 195 +/- 35 pg/mL). Training lowered the resting plasma nonesterified fatty acids. During exercise, changes in glycerol were similar to those found before training. Lipid oxidation during exercise was higher in fasting than in fed conditions (15.5 +/- 1.4 vs. 22.3 +/- 1.7 g/h). Training did not significantly increase fat oxidation when exercise was performed in fed conditions, but it did in fasting conditions (18.6 +/- 1.4 vs. 27.2 +/- 1.8 g/h). DISCUSSION Endurance training decreased plasma nonesterified fatty acids, cholesterol, and insulin concentrations. Training increased lipid oxidation during exercise, in fasting conditions, and not when exercise was performed after the meal. During exercise in overweight subjects, the fasting condition seems more suited to oxidizing fat and maintaining glucose homeostasis than a 3-hour wait after a standard meal.
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Affiliation(s)
- Francois Crampes
- Department of Adaptation to Exercise, Laboratory of Medical and Clinical Pharmacology, Faculty of Medicine, INSERM Unit 317, Toulouse, France
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Pelat M, Verwaerde P, Galitzky J, Lafontan M, Berlan M, Senard JM, Montastruc JL. High isoproterenol doses are required to activate beta3-adrenoceptor-mediated functions in dogs. J Pharmacol Exp Ther 2003; 304:246-53. [PMID: 12490598 DOI: 10.1124/jpet.102.040691] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The "in vivo" conditions for beta3-adrenoceptors (beta-AR) activation by isoproterenol were investigated in dog. Experiments were carried out in anesthetized dogs using isoproterenol as a nonselective beta-AR agonist. Intravenous infusion of isoproterenol (0.4 nmol/kg/min) induced arterial hypotension and tachycardia with a slight decrease in cutaneous blood flow. At this dose, isoproterenol increased glucose, glycerol, and nonesterified fatty acid plasma levels. The changes in cardiovascular and endocrine-metabolic parameters, induced by the low dose of isoproterenol, were suppressed by pretreatment with nadolol (1 mg/kg, i.v.). After nadolol administration, however, a 10-fold higher dose (4 nmol/kg/min) of isoproterenol was able to induce a decrease in arterial blood pressure with a slight tachycardia and an increase in cutaneous blood flow. This high dose of isoproterenol increased nonesterified fatty acid and glycerol plasma levels but failed to change glucose plasma levels. All these effects were abolished by a pretreatment with nadolol (1 mg/kg, i.v.) plus SR59230A [a selective beta3-adrenoceptor antagonist; (3-(2-ethylphenoxy)-1(1S)-1,2,3,4-tetrahydronaphth-1-ylaminol-(2S)2-propanol oxalate); 1 mg/kg, i.v.]. Moreover, as observed with the high dose of isoproterenol under nadolol pretreatment, an infusion of SR58611A [a selective beta3-adrenoceptor agonist; ((N2S)-7-carbethoxymethoxy-1,2,3,4-tetrahydronaphth-2-yl-(2R)-2-hydroxy-2-chlorophenyl) ethanamine hydrochloride] induces a decrease in mean arterial blood pressure associated with an increase in heart rate, cutaneous blood flow, and nonesterified fatty acid and glycerol plasma levels. These results demonstrate that the in vivo activation of beta3-adrenoceptors requires higher doses of catecholamine than those necessary for beta1- and/or beta2-adrenoceptor stimulation. These results also argue for the lack of a beta3-AR involvement in the control of heart rate and glycogenolysis in dogs.
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Affiliation(s)
- Michel Pelat
- Laboratoire de Pharmacologie Médicale et Clinique, INSERM U317, Faculté de Médecine, Toulouse Cedex, France
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Lucas S, Tavernier G, Tiraby C, Mairal A, Langin D. Expression of human hormone-sensitive lipase in white adipose tissue of transgenic mice increases lipase activity but does not enhance in vitro lipolysis. J Lipid Res 2003; 44:154-63. [PMID: 12518034 DOI: 10.1194/jlr.m200250-jlr200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Hormone-sensitive lipase (HSL) catalyzes the hydrolysis of acylglycerols and cholesteryl esters (CEs). The enzyme is highly expressed in adipose tissues (ATs), where it is thought to play an important role in fat mobilization. The purpose of the present work was to study the effect of a physiological increase of HSL expression in vivo. Transgenic mice were produced with a 21 kb human genomic fragment encompassing the exons encoding the adipocyte form of HSL. hHSL mRNA was expressed at 3-fold higher levels than murine HSL mRNA in white adipocytes. Transgene expression was also observed in brown adipose tissue (BAT) and skeletal muscle. The human protein was detected in ATs of transgenic (Tg) mice. The hydrolytic activities against triacylglycerol (TG), diacylglycerol (DG) analog, and CE were increased in transgenic mouse AT. However, cAMP-inducible adipocyte lipolysis was lower in transgenic animals. In the B6CBA genetic background, transgenic mice up to 14 weeks of age showed lower body weight and fat mass. The phenotype was not observed in older animals and in mice fed a high-fat diet (HFD). In the OF1 genetic background, there was no difference in fat mass of mice fed ad libitum. However, transgenic mice became leaner than their wild-type (WT) littermates after a 4 day calorie restriction. The data show that overexpression of HSL, despite increased lipase activity, does not lead to enhanced lipolysis.
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Affiliation(s)
- Stéphanie Lucas
- INSERM U317, Institut Louis Bugnard, Centre Hospitalier Universitaire de Rangueil, Université Paul Sabatier, 31403 Toulouse Cedex 4, France
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Sengenès C, Zakaroff-Girard A, Moulin A, Berlan M, Bouloumié A, Lafontan M, Galitzky J. Natriuretic peptide-dependent lipolysis in fat cells is a primate specificity. Am J Physiol Regul Integr Comp Physiol 2002; 283:R257-65. [PMID: 12069952 DOI: 10.1152/ajpregu.00453.2001] [Citation(s) in RCA: 131] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have recently demonstrated that natriuretic peptides (NPs), which are known for regulation of blood pressure via membrane guanylyl cyclase (GC) receptors, are lipolytic in human adipose tissue. In this study, we compared the NP control of lipolysis in adipocytes from humans, nonhuman primates (macaques), rodents (rats, mice, hamsters), and nonrodent mammals (rabbits, dogs). Isolated adipocytes from these species were exposed to increasing concentrations of atrial NP (ANP) or isoproterenol (beta-adrenergic agonist). Although isoproterenol was lipolytic in all of the species, ANP only enhanced lipolysis in human and macaque adipocytes. In primate fat cells, NP-induced lipolysis involved a cGMP-dependent pathway. Binding studies and real-time quantitative PCR assays revealed that rat adipocytes expressed a higher density of NP receptors compared with humans but with a different subtype pattern of expression; type-A GC receptors predominate in human fat cells. This was also confirmed by the weak GC-activity stimulation and the reduced cGMP formation under ANP exposure in rat adipocytes compared with human fat cells. In conclusion, NP-induced lipolysis is a primate specificity, and adipocytes from ANP-nonresponsive species present a predominance of "clearance" receptors and very low expression of "biologically active" receptors.
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Affiliation(s)
- Coralie Sengenès
- INSERM U317, Laboratory of Medical and Clinical Pharmacology, Division of Medicine, National Institute of Health and Medical Research, Unité 317, 37 Allées Jules Guesde, 31073 Toulouse Cedex, France.
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Figueroa JE, Vijayagopal P, Prasad C. Azaftig stimulates in vitro lipolysis by rodent and human adipocytes. Biochem Biophys Res Commun 2002; 293:847-9. [PMID: 12054548 DOI: 10.1016/s0006-291x(02)00300-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Azaftig is an urinary proteoglycan present in some cancer and AIDS patients experiencing weight loss. Administration of azaftig to mice results in weight loss that is associated with loss of fat depot. So far, very little is known about the mechanism underlying loss of fat depot in mice or weight loss in patients excreting azaftig. Augmentation of lipolysis may be one mechanism that can cause reduction of fat depot. Therefore, the present study was designed to examine the effect of azaftig on lipolysis by adipocytes derived from obese rats and humans. Results show a dose-dependent potentiation of lipolysis by azaftig in both rat and human adipocytes.
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Affiliation(s)
- Julio E Figueroa
- Department of Medicine (Sections of Infectious Disease, Cardiology and Endocrinology), and Stanley S. Scott Cancer Center, Box T4M5, LSU Health Sciences Center, 1542 Tulane Ave, New Orleans, LA 70112, USA
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Svensson M, Yu ZW, Eriksson JW. A small reduction in glomerular filtration is accompanied by insulin resistance in type I diabetes patients with diabetic nephrophathy. Eur J Clin Invest 2002; 32:100-9. [PMID: 11895456 DOI: 10.1046/j.1365-2362.2002.00949.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Insulin sensitivity and insulin clearance are compromised in end-stage renal disease but it has not been fully established whether they are altered in earlier stages of diabetic nephropathy. DESIGN We studied three groups of patients with type 1 diabetes; 10 with no sign of nephropathy, 11 with albuminuria (> 20 microg min-1) but normal glomerular filtration rate (GFR) and eight with a small reduction in GFR, (43-73 mL min-1 1.73 m-2). The groups were matched for age (range 36-61 years), body mass index (BMI), diabetes duration and glycaemic control. The euglycaemic hyperinsulinaemic clamp technique was utilized to study insulin sensitivity (M-value) and metabolic clearance rate for insulin. Needle biopsies from abdominal subcutaneous fat tissue were obtained to study insulin binding, insulin degradation, insulin-stimulated glucose uptake and anti-lipolysis in adipocytes in vitro. RESULTS Patients with reduced GFR were more insulin-resistant (M-value 5.7 +/- 0.7 mg kg LBM-1 min-1) than those without nephropathy (9.6 +/- 0.7, P = 0.001) and those with only albuminuria (8.9 +/- 1.2, P = 0.044). In all subjects taken together there was a strong association between insulin sensitivity and GFR (r = 0.46, P = 0.012). Patients with reduced GFR displayed no significant difference in insulin clearance (12.2 +/- 1.6 mL kg-1 min-1) compared to controls (13.8 +/- 1.3) but a slightly lower insulin clearance than patients with only albuminuria (16.6 +/- 1.0, P = 0.027). There were no significant differences between patient groups in the adipocyte studies in vitro, i.e. with respect to insulin binding, insulin degradation and the effects of insulin on glucose uptake and lipolysis. This is compatible with humoral factors causing whole-body insulin resistance and in the group with reduced GFR, we found that serum parathyroid hormone, interleukin-6 and tumour necrosis factor-alpha levels were elevated whereas the morning cortisol was decreased. CONCLUSIONS In type 1 diabetes, the appearance of albuminuria does not seem to alter insulin sensitivity and clearance. A marked insulin resistance but no consistent impairment in insulin clearance seems to accompany progression to a stage with a slight reduction in GFR. These alterations are not accompanied by general defects in insulin target cells. Instead, alterations in the regulation of insulin-antagonistic hormones and cytokines could potentially contribute to the development of insulin resistance in diabetic nephropathy.
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Sengenes C, Stich V, Berlan M, Hejnova J, Lafontan M, Pariskova Z, Galitzky J. Increased lipolysis in adipose tissue and lipid mobilization to natriuretic peptides during low-calorie diet in obese women. Int J Obes (Lond) 2002; 26:24-32. [PMID: 11791143 DOI: 10.1038/sj.ijo.0801845] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2001] [Revised: 04/25/2001] [Accepted: 07/06/2001] [Indexed: 11/09/2022]
Abstract
OBJECTIVE We recently demonstrated that natriuretic peptides (NP) are involved in a pathway inducing lipolysis in human adipose tissue. Atrial NP (ANP) and brain NP (BNP) operate via a cGMP-dependent pathway which does not involve phosphodiesterase-3B inhibition or cAMP. The study was performed to evaluate the effect of ANP on lipid mobilization in obese women and secondly to examine the possible effect of a low-calorie diet (LCD) on the lipolytic response of subcutaneous abdominal fat cells to NP and on the lipid mobilization induced by ANP infusion (1 microg/m(2) min for 60 min). SUBJECTS Ten obese women from 40.5+/-3.4 y old were selected for this study. Their body weight was 96.4+/-5.7 kg and their BMI was 35.3+/-1.7 kg/m(2). They received a 2.5-2.9 MJ/day formula diet for 28 days. DESIGN Before and during the LCD, an adipose tissue biospy was performed for in vitro studies and, moreover, ANP was perfused i.v. to evaluate its lipid mobilizing action in toto and in situ in subcutaneous abdominal adipose tissue (SCAAT) using microdialysis. RESULTS The lipolytic effects of isoproterenol, ANP, BNP and bromo-cGMP (an analogue of cGMP) on fat cells increased by about 80-100% during LCD. The lipid mobilization during i.v. ANP infusion, assessed by plasma non-esterified fatty acids (NEFA) increase was enhanced during the LCD. However, during LCD, ANP infusion induced a biphasic effect on glycerol concentration in plasma and interstitial fluid of SCAAT; a significant increase was observed in glycerol levels during the first 30 min infusion period, followed by a steady decrease. The concentration of glycerol was lower during the post-infusion period than during the baseline period. This effect was stronger in obese subjects submitted to the LCD with a low-carbohydrate composition. Other plasma parameters were weakly increased (noradrenaline) or not modified (insulin, glucose) by ANP infusion and no difference was found before and during LCD treatment. CONCLUSION The present study shows that NP are powerful lipolytic agents in subcutaneous fat cells and that both isoproterenol- and NP-induced lipolysis increase during LCD, in obese women. These changes seem to be associated with an improvement of the lipolytic pathway at a post-receptor level. Moreover, i.v. administration of ANP induced a lipid mobilizing effect which was enhanced by a LCD in these objects.
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Affiliation(s)
- C Sengenes
- INSERM Unité 317, Laboratory of Medical and Clinical Pharmacology, Faculty of Medicine, Toulouse, France
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De Glisezinski I, Marion-Latard F, Crampes F, Berlan M, Hejnova J, Cottet-Emard JM, Stich V, Rivière D. Lack of alpha(2)-adrenergic antilipolytic effect during exercise in subcutaneous adipose tissue of trained men. J Appl Physiol (1985) 2001; 91:1760-5. [PMID: 11568160 DOI: 10.1152/jappl.2001.91.4.1760] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The aim of this study was to investigate the involvement of the antilipolytic alpha(2)-adrenergic receptor pathway in the regulation of lipolysis during exercise in subcutaneous abdominal adipose tissue (SCAAT). Seven trained men and 15 untrained men were studied. With the use of microdialysis, the extracellular glycerol concentration was measured in SCAAT at rest and during 60 min of exercise at 50% of maximal oxygen consumption. One microdialysis probe was perfused with Ringer solution; the other was supplemented with phentolamine (alpha(2)-adrenergic receptor antagonist). No differences in baseline extracellular or plasma glycerol concentrations were found between the two groups. The exercise-induced extracellular and plasma glycerol increase was higher in trained compared with untrained subjects (P < 0.05). Addition of phentolamine to the perfusate enhanced the exercise-induced response of extracellular glycerol in untrained subjects but not in trained subjects. The exercise-induced increase in plasma norepinephrine and epinephrine concentrations and the decrease in plasma insulin were not different in the two groups. These in vivo findings demonstrate higher exercise-induced lipolysis in trained compared with untrained subjects and show that, in trained subjects, the alpha(2)-mediated antilipolytic action is not involved in the regulation of lipolysis in SCAAT during exercise.
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Affiliation(s)
- I De Glisezinski
- Laboratoire des Adaptations de l'Organisme à l'Exercice Musculaire, Centre Hospitalier Universitaire Purpan, 31059 Toulouse Cedex, France
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Galitzky J, Sengenès C, Thalamas C, Marques MA, Senard JM, Lafontan M, Berlan M. The lipid-mobilizing effect of atrial natriuretic peptide is unrelated to sympathetic nervous system activation or obesity in young men. J Lipid Res 2001. [DOI: 10.1016/s0022-2275(20)31162-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Marion-Latard F, De Glisezinski I, Crampes F, Berlan M, Galitzky J, Suljkovicova H, Riviere D, Stich V. A single bout of exercise induces beta-adrenergic desensitization in human adipose tissue. Am J Physiol Regul Integr Comp Physiol 2001; 280:R166-73. [PMID: 11124148 DOI: 10.1152/ajpregu.2001.280.1.r166] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study was designed to assess whether physiological activation of the sympathetic nervous system induced by exercise changes adipose tissue responsiveness to catecholamines in humans. Lipid mobilization in abdominal subcutaneous adipose tissue was studied with the use of a microdialysis method in 11 nontrained men (age: 22. 3 +/- 1.5 yr; body mass index: 23.0 +/- 1.6). Adipose tissue adrenergic sensitivity was explored with norepinephrine, dobutamine (beta(1)-agonist), or terbutaline (beta(2)-agonist) perfused during 30 min through probes before and after 60-min exercise (50% of the maximal aerobic power). The increase in extracellular glycerol concentration during infusion was significantly lower after the exercise when compared with the increase observed before the exercise (P < 0.05, P < 0.02, and P < 0.01, respectively, for norepinephrine, dobutamine, and terbutaline). In a control experiment realized without exercise, no difference in norepinephrine-induced glycerol increase between the two infusions was observed. To assess the involvement of catecholamines in the blunted beta-adrenergic-induced lipolytic response after exercise, adipose tissue adrenergic sensitivity was explored with two 60-min infusions of norepinephrine or epinephrine separated by a 60-min interval. With both catecholamines, the increase in glycerol was significantly lower during the second infusion (P < 0.05). The findings suggest that aerobic exercise, which increased adrenergic activity, induces a desensitization in beta(1)- and beta(2)-adrenergic lipolytic pathways in human subcutaneous adipose tissue.
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Affiliation(s)
- F Marion-Latard
- Laboratory of the Adaptations to Exercise, Purpan University Hospital, 31059 Toulouse Cedex, France
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Yuen VG, McNeill JH. Comparison of the glucose oxidase method for glucose determination by manual assay and automated analyzer. J Pharmacol Toxicol Methods 2000; 44:543-6. [PMID: 11395333 DOI: 10.1016/s1056-8719(01)00117-4] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
In experimental models of diabetes, glucose levels in plasma and blood are commonly determined by colorimetric assay and by automated analyzers based on the glucose oxidase conversion of glucose and O2 to gluconate and H2O2. We have compared the glucose levels obtained by these two methods in control Wistar rats, streptozotocin diabetic Wistar rats, Zucker fa/fa fatty rats and Zucker Diabetic Fatty rats. We found that the manual glucose assay and the glucose analyzer produced comparable values up to concentrations of about 25 mM. Above this level, samples should be diluted.
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Affiliation(s)
- V G Yuen
- Faculty of Pharmaceutical Sciences, University of British Columbia, 2146 East Mall, V6T 1Z3, Vancouver, BC, Canada
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