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Sharma AK, Khandelwal R, Wolfrum C. Futile cycles: Emerging utility from apparent futility. Cell Metab 2024; 36:1184-1203. [PMID: 38565147 DOI: 10.1016/j.cmet.2024.03.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2024] [Revised: 02/15/2024] [Accepted: 03/11/2024] [Indexed: 04/04/2024]
Abstract
Futile cycles are biological phenomena where two opposing biochemical reactions run simultaneously, resulting in a net energy loss without appreciable productivity. Such a state was presumed to be a biological aberration and thus deemed an energy-wasting "futile" cycle. However, multiple pieces of evidence suggest that biological utilities emerge from futile cycles. A few established functions of futile cycles are to control metabolic sensitivity, modulate energy homeostasis, and drive adaptive thermogenesis. Yet, the physiological regulation, implication, and pathological relevance of most futile cycles remain poorly studied. In this review, we highlight the abundance and versatility of futile cycles and propose a classification scheme. We further discuss the energetic implications of various futile cycles and their impact on basal metabolic rate, their bona fide and tentative pathophysiological implications, and putative drug interactions.
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Affiliation(s)
- Anand Kumar Sharma
- Laboratory of Translational Nutrition Biology, Institute of Food, Nutrition and Health, ETH Zurich, Schwerzenbach, Switzerland.
| | - Radhika Khandelwal
- Laboratory of Translational Nutrition Biology, Institute of Food, Nutrition and Health, ETH Zurich, Schwerzenbach, Switzerland
| | - Christian Wolfrum
- Laboratory of Translational Nutrition Biology, Institute of Food, Nutrition and Health, ETH Zurich, Schwerzenbach, Switzerland.
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2
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Thiagarajan D, Quadri N, Jawahar S, Zirpoli H, Del Pozo CH, López-Díez R, Hasan SN, Yepuri G, Gugger PF, Finlin BS, Kern PA, Gabbay K, Schmidt AM, Ramasamy R. Aldose reductase promotes diet-induced obesity via induction of senescence in subcutaneous adipose tissue. Obesity (Silver Spring) 2022; 30:1647-1658. [PMID: 35894077 DOI: 10.1002/oby.23496] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Revised: 05/09/2022] [Accepted: 05/12/2022] [Indexed: 11/09/2022]
Abstract
OBJECTIVE Aldose reductase (AKR1B1 in humans; Akr1b3 in mice), a key enzyme of the polyol pathway, mediates lipid accumulation in the murine heart and liver. The study objective was to explore potential roles for AKR1B1/Akr1b3 in the pathogenesis of obesity and its complications. METHODS The study employed mice treated with an inhibitor of aldose reductase or mice devoid of Akr1b3 were used to determine their response to a high-fat diet. The study used subcutaneous adipose tissue-derived adipocytes to investigate mechanisms by which AKR1B1/Akr1b3 promotes diet-induced obesity. RESULTS Increased expression of aldose reductase and senescence in the adipose tissue of humans and mice with obesity were demonstrated. Genetic deletion of Akr1b3 or pharmacological blockade of AKRIB3 with zopolrestat reduced high-fat-diet-induced obesity, attenuated markers of adipose tissue senescence, and increased lipolysis. CONCLUSIONS AKR1B1/Akr1b3 modulation of senescence in subcutaneous adipose tissue contributes to aberrant metabolic responses to high-fat feeding. These data unveil new opportunities to target these pathways to combat obesity.
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Affiliation(s)
- Devi Thiagarajan
- Diabetes Research Program, Department of Medicine, New York University Grossman School of Medicine, New York, New York, USA
- Saha Cardiovascular Research Center, Department of Physiology, University of Kentucky, Lexington, Kentucky, USA
| | - Nosirudeen Quadri
- Diabetes Research Program, Department of Medicine, New York University Grossman School of Medicine, New York, New York, USA
| | - Shabnam Jawahar
- Diabetes Research Program, Department of Medicine, New York University Grossman School of Medicine, New York, New York, USA
| | - Hylde Zirpoli
- Diabetes Research Program, Department of Medicine, New York University Grossman School of Medicine, New York, New York, USA
| | - Carmen Hurtado Del Pozo
- Diabetes Research Program, Department of Medicine, New York University Grossman School of Medicine, New York, New York, USA
| | - Raquel López-Díez
- Diabetes Research Program, Department of Medicine, New York University Grossman School of Medicine, New York, New York, USA
| | - Syed Nurul Hasan
- Diabetes Research Program, Department of Medicine, New York University Grossman School of Medicine, New York, New York, USA
| | - Gautham Yepuri
- Diabetes Research Program, Department of Medicine, New York University Grossman School of Medicine, New York, New York, USA
| | - Paul F Gugger
- Diabetes Research Program, Department of Medicine, New York University Grossman School of Medicine, New York, New York, USA
| | - Brian S Finlin
- Center for Clinical and Translational Sciences, University of Kentucky, Lexington, Kentucky, USA
| | - Philip A Kern
- Center for Clinical and Translational Sciences, University of Kentucky, Lexington, Kentucky, USA
| | | | - Ann Marie Schmidt
- Diabetes Research Program, Department of Medicine, New York University Grossman School of Medicine, New York, New York, USA
| | - Ravichandran Ramasamy
- Diabetes Research Program, Department of Medicine, New York University Grossman School of Medicine, New York, New York, USA
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3
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Stratton MT, Albracht-Schulte K, Harty PS, Siedler MR, Rodriguez C, Tinsley GM. Physiological responses to acute fasting: implications for intermittent fasting programs. Nutr Rev 2022; 80:439-452. [PMID: 35142356 DOI: 10.1093/nutrit/nuab094] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Intermittent fasting (IF) is a dietary strategy that involves alternating periods of abstention from calorie consumption with periods of ad libitum food intake. There is significant interest in the body of literature describing longitudinal adaptations to IF. Less attention has been given to the acute physiological responses that occur during the fasting durations that are commonly employed by IF practitioners. Thus, the purpose of this review was to examine the physiological responses - including alterations in substrate metabolism, systemic hormones, and autophagy - that occur throughout an acute fast. Literature searches were performed to locate relevant research describing physiological responses to acute fasting and short-term starvation. A single fast demonstrated the ability to alter glucose and lipid metabolism within the initial 24 hours, but variations in protein metabolism appeared to be minimal within this time frame. The ability of an acute fast to elicit significant increases in autophagy is still unknown. The information summarized in this review can be used to help contextualize existing research and better inform development of future IF interventions.
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Affiliation(s)
- Matthew T Stratton
- Energy Balance and Body Composition Laboratory; Department of Kinesiology and Sport Management, Texas Tech University, Lubbock, Texas, USA
| | - Kembra Albracht-Schulte
- Energy Balance and Body Composition Laboratory; Department of Kinesiology and Sport Management, Texas Tech University, Lubbock, Texas, USA
| | - Patrick S Harty
- Energy Balance and Body Composition Laboratory; Department of Kinesiology and Sport Management, Texas Tech University, Lubbock, Texas, USA
| | - Madelin R Siedler
- Energy Balance and Body Composition Laboratory; Department of Kinesiology and Sport Management, Texas Tech University, Lubbock, Texas, USA
| | - Christian Rodriguez
- Energy Balance and Body Composition Laboratory; Department of Kinesiology and Sport Management, Texas Tech University, Lubbock, Texas, USA
| | - Grant M Tinsley
- Energy Balance and Body Composition Laboratory; Department of Kinesiology and Sport Management, Texas Tech University, Lubbock, Texas, USA
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4
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Abstract
Altered metabolic activity contributes to the pathogenesis of a number of diseases, including diabetes, heart failure, cancer, fibrosis and neurodegeneration. These diseases, and organismal metabolism more generally, are only partially recapitulated by cell culture models. Accordingly, it is important to measure metabolism in vivo. Over the past century, researchers studying glucose homeostasis have developed strategies for the measurement of tissue-specific and whole-body metabolic activity (pathway fluxes). The power of these strategies has been augmented by recent advances in metabolomics technologies. Here, we review techniques for measuring metabolic fluxes in intact mammals and discuss how to analyse and interpret the results. In tandem, we describe important findings from these techniques, and suggest promising avenues for their future application. Given the broad importance of metabolism to health and disease, more widespread application of these methods holds the potential to accelerate biomedical progress.
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Affiliation(s)
- Caroline R Bartman
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA
- Department of Chemistry, Princeton University, Princeton, NJ, USA
| | - Tara TeSlaa
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA
- Department of Chemistry, Princeton University, Princeton, NJ, USA
| | - Joshua D Rabinowitz
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA.
- Department of Chemistry, Princeton University, Princeton, NJ, USA.
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5
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In-vivo metabolic studies of regional adipose tissue. Cardiovasc Endocrinol Metab 2019; 7:75-79. [PMID: 31646288 DOI: 10.1097/xce.0000000000000154] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Accepted: 02/20/2018] [Indexed: 11/26/2022]
Abstract
The accumulation of abdominal adipose tissue has long been associated with adverse cardiovascular outcomes. Paradoxically, increased gluteofemoral adipose tissue, which is predominantly subcutaneous fat, seems to play a protective role. There has been significant scientific interest in understanding how abdominal and gluteofemoral depots confer opposing metabolic risks. However, the study of regional adipose physiology in vivo remains challenging. We discuss some of the methodologies used. We focus specifically on the arteriovenous difference technique and present some insights into gluteofemoral adipose physiology.
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6
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Perry RJ, Shulman GI. The Role of Leptin in Maintaining Plasma Glucose During Starvation. POSTDOC JOURNAL : A JOURNAL OF POSTDOCTORAL RESEARCH AND POSTDOCTORAL AFFAIRS 2018; 6:3-19. [PMID: 29682594 PMCID: PMC5909716 DOI: 10.14304/surya.jpr.v6n3.2] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
For 20 years it has been known that concentrations of leptin, a hormone produced by the white adipose tissue (WAT) largely in proportion to body fat, drops precipitously with starvation, particularly in lean humans and animals. The role of leptin to suppress the thyroid and reproductive axes during a prolonged fast has been well defined; however, the impact of leptin on metabolic regulation has been incompletely understood. However emerging evidence suggests that, in starvation, hypoleptinemia increases activity of the hypothalamic-pituitary-adrenal axis, promoting WAT lipolysis, increasing hepatic acetyl-CoA concentrations, and maintaining euglycemia. In addition, leptin may be largely responsible for mediating a shift from a reliance upon glucose metabolism (absorption and glycogenolysis) to fat metabolism (lipolysis increasing gluconeogenesis) which preserves substrates for the brain, heart, and other critical organs. In this way a leptin-mediated glucose-fatty acid cycle appears to maintain glycemia and permit survival in starvation.
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Affiliation(s)
- Rachel J Perry
- Department of Internal Medicine, Yale University School of Medicine
| | - Gerald I Shulman
- Department of Internal Medicine, Yale University School of Medicine
- Department of Cellular & Molecular Physiology, Yale University School of Medicine
- Howard Hughes Medical Institute
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7
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Pyle L, Bergman BC, Nadeau KJ, Cree-Green M. Modeling changes in glucose and glycerol rates of appearance when true basal rates of appearance cannot be readily determined. Am J Physiol Endocrinol Metab 2016; 310:E323-31. [PMID: 26714848 PMCID: PMC4773652 DOI: 10.1152/ajpendo.00368.2015] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Accepted: 12/17/2015] [Indexed: 11/22/2022]
Abstract
Advancing diabetes care requires accurate physiological assessments. Hyperinsulinemic clamps with stable isotope tracers can simultaneously measure insulin's ability to suppress lipolysis and hepatic glucose release. Traditionally, these methods require an assessment of basal glucose and glycerol rate of appearance (Ra). Basal Ra is challenging to measure in insulin-dependent diabetes, where exogenous insulin required to maintain normoglycemia can raise peripheral insulin concentrations sufficiently to suppress basal Ra. Thus we identified two alternative statistical approaches to describe changes in glucose and glycerol Ra that are less reliant on basal assessments. Sixteen youths (4 type 1 diabetic, 4 type 2 diabetic, 4 lean controls, and 4 obese nondiabetic) underwent a four-phase ("basal" and 10, 16, and 80 mU·m(2)·min(-1)) hyperinsulinemic euglycemic clamp with glucose and glycerol tracers. Glucose and glycerol Ra were calculated per phase. A statistical method, the standard two-stage (STS) algorithm, was applied to the individual log insulin vs. Ra curves to calculate a single predicted Ra value. A population-based mixed-effects model (MEM) compared the group average Ra with log insulin curves and described individual deviations from group means and was used to calculate individual predicted Ra. Both models were applied to the participant data, and predicted Ras at the mean insulin concentration per phase (10 for glycerol, 16 for glucose) were calculated, with good agreement between observed and predicted values. In our data set, the MEM was better able to detect group differences. Both STS and MEM can model lipolysis and endogenous glucose release in insulin-dependent states when basal Ra cannot be accurately measured.
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Affiliation(s)
- Laura Pyle
- Department of Pediatrics, and Department of Biostatistics and Informatics, Colorado School of Public Health, Aurora, Colorado
| | - Bryan C Bergman
- Division of Endocrinology and Metabolism, Department of Medicine, Anschutz Medical Campus, Aurora, Colorado
| | - Kristen J Nadeau
- Division of Pediatric Endocrinology, Center for Women's Health Research, Anschutz Medical Campus, Aurora, Colorado; and
| | - Melanie Cree-Green
- Division of Pediatric Endocrinology, Center for Women's Health Research, Anschutz Medical Campus, Aurora, Colorado; and
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Yin F, Sancheti H, Liu Z, Cadenas E. Mitochondrial function in ageing: coordination with signalling and transcriptional pathways. J Physiol 2015; 594:2025-42. [PMID: 26293414 DOI: 10.1113/jp270541] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2015] [Accepted: 08/13/2015] [Indexed: 12/14/2022] Open
Abstract
Mitochondrial dysfunction entailing decreased energy-transducing capacity and perturbed redox homeostasis is an early and sometimes initiating event in ageing and age-related disorders involving tissues with high metabolic rate such as brain, liver and heart. In the central nervous system (CNS), recent findings from our and other groups suggest that the mitochondrion-centred hypometabolism is a key feature of ageing brains and Alzheimer's disease. This hypometabolic state is manifested by lowered neuronal glucose uptake, metabolic shift in the astrocytes, and alternations in mitochondrial tricarboxylic acid cycle function. Similarly, in liver and adipose tissue, mitochondrial capacity around glucose and fatty acid metabolism and thermogenesis is found to decline with age and is implicated in age-related metabolic disorders such as obesity and type 2 diabetes mellitus. These mitochondrion-related disorders in peripheral tissues can impact on brain functions through metabolic, hormonal and inflammatory signals. At the cellular level, studies in CNS and non-CNS tissues support the notion that instead of being viewed as autonomous organelles, mitochondria are part of a dynamic network with close interactions with other cellular components through energy- or redox-sensitive cytosolic kinase signalling and transcriptional pathways. Hence, it would be critical to further understand the molecular mechanisms involved in the communication between mitochondria and the rest of the cell. Therapeutic strategies that effectively preserves or improve mitochondrial function by targeting key component of these signalling cascades could represent a novel direction for numerous mitochondrion-implicated, age-related disorders.
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Affiliation(s)
- Fei Yin
- Pharmacology & Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, CA, 90089-9121, USA
| | - Harsh Sancheti
- Pharmacology & Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, CA, 90089-9121, USA
| | - Zhigang Liu
- Pharmacology & Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, CA, 90089-9121, USA
| | - Enrique Cadenas
- Pharmacology & Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, CA, 90089-9121, USA
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9
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Karbowska J, Kochan Z. Effects of DHEA on metabolic and endocrine functions of adipose tissue. Horm Mol Biol Clin Investig 2015; 14:65-74. [PMID: 25436721 DOI: 10.1515/hmbci-2013-0009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Accepted: 04/30/2013] [Indexed: 11/15/2022]
Abstract
Dehydroepiandrosterone (DHEA) and its sulfate ester, DHEAS, are the major circulating adrenal steroids and serve as substrates for sex hormone biosynthesis. DHEA is effectively taken up by adipose tissue, where the concentrations of free DHEA are four to ten times higher than those found in the circulation. DHEA reduces adipose tissue mass and inhibits the proliferation and differentiation of adipocytes; it may also protect against obesity by lowering the activity of stearoyl-CoA desaturase 1 in fat cells. Recent studies demonstrate that DHEA stimulates triacylglycerol hydrolysis in adipose tissue by increasing the expression and activity of adipose triglyceride lipase and hormone-sensitive lipase, the key enzymes of lipolysis. DHEA has been shown to modulate insulin signaling pathways, enhance glucose uptake in adipocytes, and increase insulin sensitivity in patients with DHEA deficiency or abnormal glucose tolerance. Additionally, by suppressing the activity of 11β-hydroxysteroid dehydrogenase 1 in adipocytes, DHEA may promote intra-adipose inactivation of cortisol to cortisone. Several studies have demonstrated that DHEA may also regulate the expression and secretion of adipokines such as leptin, adiponectin, and resistin. The effects of DHEA on adipokine expression in adipose tissue are depot-specific, with visceral fat being the most responsive. The mechanisms underlying DHEA actions in adipose tissue are still unclear; however, they involve nuclear receptors such as androgen receptor and peroxisome proliferator-activated receptors γ and α. Because clinical trials investigating the effects of DHEA failed to yield consistent results, further studies are needed to clarify the role of DHEA in the regulation of human adipose tissue physiology.
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Affiliation(s)
- Joanna Karbowska
- Department of Biochemistry, Medical University of Gdansk, Gdansk, Poland.
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10
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Lankelma J, Kooi B, Krab K, Dorsman JC, Joenje H, Westerhoff HV. A reason for intermittent fasting to suppress the awakening of dormant breast tumors. Biosystems 2014; 127:1-6. [PMID: 25448890 DOI: 10.1016/j.biosystems.2014.11.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Revised: 10/25/2014] [Accepted: 11/01/2014] [Indexed: 12/21/2022]
Abstract
For their growth, dormant tumors, which lack angiogenesis may critically depend on gradients of nutrients and oxygen from the nearest blood vessel. Because for oxygen depletion the distance from the nearest blood vessel to depletion will generally be shorter than for glucose depletion, such tumors will contain anoxic living tumor cells. These cells are dangerous, because they are capable of inducing angiogenesis, which will "wake up" the tumor. Anoxic cells are dependent on anaerobic glucose breakdown for ATP generation. The local extracellular glucose concentration gradient is determined by the blood glucose concentration and by consumption by cells closer to the nearest blood vessel. The blood glucose concentration can be lowered by 20-40% during fasting. We calculated that glucose supply to the potentially hazardous anoxic cells can thereby be reduced significantly, resulting in cell death specifically of the anoxic tumor cells. We hypothesize that intermittent fasting will help to reduce the incidence of tumor relapse via reducing the number of anoxic tumor cells and tumor awakening.
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Affiliation(s)
- Jan Lankelma
- Department of Molecular Cell Physiology, VU University, De Boelelaan 1085, Room G-226a, 1081 HV Amsterdam, The Netherlands.
| | - Bob Kooi
- Department of Theoretical Biology, VU University, De Boelelaan 1085, 1081HV Amsterdam, The Netherlands
| | - Klaas Krab
- Department of Molecular Cell Physiology, VU University, De Boelelaan 1085, Room G-226a, 1081 HV Amsterdam, The Netherlands
| | - Josephine C Dorsman
- Department of Clinical Genetics, VU University Medical Center, Van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands
| | - Hans Joenje
- Department of Clinical Genetics, VU University Medical Center, Van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands
| | - Hans V Westerhoff
- Department of Molecular Cell Physiology, VU University, De Boelelaan 1085, Room G-226a, 1081 HV Amsterdam, The Netherlands; Synthetic Systems Biology, SILS, University of Amsterdam and Manchester Centre for Integrative Systems Biology, The University of Manchester, UK
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11
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Bornø A, Foged L, van Hall G. Glucose and glycerol concentrations and their tracer enrichment measurements using liquid chromatography tandem mass spectrometry. JOURNAL OF MASS SPECTROMETRY : JMS 2014; 49:980-988. [PMID: 25303387 DOI: 10.1002/jms.3407] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Revised: 05/26/2014] [Accepted: 06/01/2014] [Indexed: 06/04/2023]
Abstract
The present study describes a new liquid chromatography tandem mass spectrometry method for high-throughput quantification of glucose and glycerol in human plasma using stable isotopically labeled internal standards and is suitable for simultaneous measurements of glucose and glycerol enrichments in connection to in vivo metabolic studies investigating glucose turnover and lipolytic rate. Moreover, in order to keep up with this new fast analysis, simple derivatization procedures have been developed. Prior to analysis, glucose and glycerol were derivatized using benzoyl chloride in order to form benzoylated derivatives via new simplified fast procedures. For glucose, two internal standards were evaluated, [U-(13) C(6)]glucose and [U-(13) C(6), D(7)]glucose, and for glycerol, [U-(13) C(3), D(8)]glycerol was used. The method was validated by means of calibration curves, quality control samples, and plasma samples spiked with [6,6-D(2)]glucose, [U-(13) C(6)]glucose, and [1,1,2,3,3-D(5)]glycerol in order to test accuracy, precision, and recovery of the method. Moreover, post preparative and freeze-thaw sample stability were tested. The correlation of calibration curves for the glucose concentration were r(2) = 0.9998 for [U-(13) C(6)]glucose and r(2) = 0.9996 for [U-(13) C(6), D(7)]glucose, and r(2) = 0.9995 for the glycerol concentration. Interday accuracy for glucose using [U-(13) C(6)]glucose and glycerol determined in spiked plasma were respectively 103.5% and 106.0%, and the coefficients of variation were 2.0% and 9.7%, respectively. After derivatization, plasma samples were stable for at least 14 days. In conclusion, we have developed and validated a novel, accurate, and sensitive high-throughput liquid chromatography tandem mass spectrometry method for simultaneous determination of glucose and glycerol concentrations and enrichment of infused tracers most commonly used in human metabolic kinetic studies.
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Affiliation(s)
- Andreas Bornø
- Clinical Metabolomics Core Facility (CMCF), Rigshospitalet, section 7652, Ole Maaløesvej 26, 2100, Copenhagen Ø, Denmark
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12
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Mennes E, Dungan CM, Frendo-Cumbo S, Williamson DL, Wright DC. Aging-associated reductions in lipolytic and mitochondrial proteins in mouse adipose tissue are not rescued by metformin treatment. J Gerontol A Biol Sci Med Sci 2013; 69:1060-8. [PMID: 24127429 DOI: 10.1093/gerona/glt156] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Mitochondrial enzyme expression is reduced in adipose tissue from old mice, yet little is known regarding mechanisms that could be mediating, or interventions that could be used, to reverse these changes. The purpose of this study was to examine the relationship between lipolytic and fatty acid reesterification enzymes, 5' adenosine monophosphate-activated protein kinase and mitochondrial proteins in adipose tissue from young versus old mice. A second aim was to determine whether metformin treatment could rescue the age-associated decline in adipose tissue mitochondrial proteins. Approximately 22-month-old male C57BL/6 mice were fed a diet with or without 0.5% metformin for 8 weeks. Compared with young mice (~11 wk of age), the protein content/phosphorylation of hormone-sensitive lipase, adipose tissue triglyceride lipase, and phosphoenolpyruvate carboxykinase were reduced in old mice. This was paralleled by increases in the plasma nonesterified fatty acid:glycerol ratio and reductions in adipose tissue 5' adenosine monophosphate-activated protein kinase activity and select mitochondrial proteins in old mice. There were no differences in these variables when comparing adipose tissue from young and 6-month-old mice. While metformin improved glucose homeostasis, it did not increase 5' adenosine monophosphate-activated protein kinase phosphorylation or mitochondrial enzymes. Our findings demonstrate a co-ordinated down regulation of lipolytic, reesterification, and mitochondrial enzymes in adipose tissue with aging that is unresponsive to metformin treatment.
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Affiliation(s)
- Elise Mennes
- Department of Human Health and Nutritional Sciences, University of Guelph, Ontario, Canada
| | - Cory M Dungan
- Department of Exercise and Nutrition Sciences, University at Buffalo, The State University of New York
| | - Scott Frendo-Cumbo
- Department of Human Health and Nutritional Sciences, University of Guelph, Ontario, Canada
| | - David L Williamson
- Department of Exercise and Nutrition Sciences, University at Buffalo, The State University of New York
| | - David C Wright
- Department of Human Health and Nutritional Sciences, University of Guelph, Ontario, Canada
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13
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Coker RH, Hays NP, Williams RH, Xu L, Wolfe RR, Evans WJ. Bed rest worsens impairments in fat and glucose metabolism in older, overweight adults. J Gerontol A Biol Sci Med Sci 2013; 69:363-70. [PMID: 23902932 DOI: 10.1093/gerona/glt100] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND The effects of bed rest on the dysregulation of fatty acid and glucose metabolism have not been addressed in the older population. OBJECTIVE We examined the effect of 10 days of bed rest on fatty acid kinetics and hepatic and peripheral insulin resistance in aging. METHODS We utilized an octreotide, basal glucagon replacement, multistage insulin infusion, and the concomitant infusion of [6,6 (2)H₂]glucose to derive insulin-mediated suppression of glucose production and insulin-stimulated glucose disposal in nine older, overweight individuals (body mass index 28.1 ± 1.7 kg m(-2); 39.9% ± 1.9% fat). During the multistage insulin infusion, we also infused [1-(13)C]palmitate to examine free fatty acid rate of appearance (R(a)). RESULTS Body weight, % body fat, and energy metabolism did not change with bed rest. There was a significant decrease (-2291 ± 316 cm(3)) in visceral fat, and no change in abdominal subcutaneous fat with bed rest. Insulin-mediated suppression of glucose production was modest prior to bed rest and was further reduced (>15% ± 2%) by bed rest. There was also a minor decrease in the insulin-mediated suppression of free fatty acid R(a) after bed rest and, as a consequence, a small variation in plasma free fatty acid from pre- to post-bed rest in the first stage of the multistage insulin infusion. There was also a significant bed rest-induced decline (>2.0 ± 0.6 mg kg FFM(-1) min(-1)) in insulin-stimulated glucose disposal. CONCLUSIONS Preexisting impairments in insulin sensitivity are worsened by bed rest and seem linked to alterations in the regulation of free fatty acid in older, overweight individuals.
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Affiliation(s)
- Robert H Coker
- Center for Alaska Native Health Research, Institute of Arctic Biology, 311 Irving I, Box 757000, University of Alaska Fairbanks, Fairbanks, AK 99775-7000.
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14
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Soeters MR, Soeters PB, Schooneman MG, Houten SM, Romijn JA. Adaptive reciprocity of lipid and glucose metabolism in human short-term starvation. Am J Physiol Endocrinol Metab 2012; 303:E1397-407. [PMID: 23074240 DOI: 10.1152/ajpendo.00397.2012] [Citation(s) in RCA: 100] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The human organism has tools to cope with metabolic challenges like starvation that are crucial for survival. Lipolysis, lipid oxidation, ketone body synthesis, tailored endogenous glucose production and uptake, and decreased glucose oxidation serve to protect against excessive erosion of protein mass, which is the predominant supplier of carbon chains for synthesis of newly formed glucose. The starvation response shows that the adaptation to energy deficit is very effective and coordinated with different adaptations in different organs. From an evolutionary perspective, this lipid-induced effect on glucose oxidation and uptake is very strong and may therefore help to understand why insulin resistance in obesity and type 2 diabetes mellitus is difficult to treat. The importance of reciprocity in lipid and glucose metabolism during human starvation should be taken into account when studying lipid and glucose metabolism in general and in pathophysiological conditions in particular.
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Affiliation(s)
- Maarten R Soeters
- Department of Endocrinology and Metabolism, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
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Karbowska J, Kochan Z. Fat-reducing effects of dehydroepiandrosterone involve upregulation of ATGL and HSL expression, and stimulation of lipolysis in adipose tissue. Steroids 2012; 77:1359-65. [PMID: 22951290 DOI: 10.1016/j.steroids.2012.08.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/12/2012] [Accepted: 08/07/2012] [Indexed: 12/31/2022]
Abstract
Dehydroepiandrosterone (DHEA) reduces body fat in rodents and humans, and increases glycerol release from isolated rat epididymal adipocytes and human visceral adipose tissue explants. It suggests that DHEA stimulates triglyceride hydrolysis in adipose tissue; however, the mechanisms underlying this action are still unclear. We examined the effects of DHEA on the expression of adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL), the key enzymes of lipolysis, in rat epididymal white adipose tissue (eWAT). Male Wistar rats were fed a diet containing 0.6% DHEA for 2 weeks and eWAT was analyzed for mRNA and protein expression of ATGL and HSL, as well as mRNA expression of peroxisome proliferator-activated receptor γ 2 (PPARγ2) and its downstream target fatty acid translocase (FAT). Glycerol release from eWAT explants and serum free fatty acids (FFA) were also measured. Rats that received DHEA gained less weight, had 23% lower eWAT mass and 31% higher serum FFA levels than controls. Cultured explants of eWAT from DHEA-treated rats released 81% more glycerol than those from control rats. DHEA administration upregulated ATGL mRNA (1.62-fold, P<0.05) and protein (1.78-fold, P<0.05) expression as well as augmented HSL mRNA levels (1.36-fold, P<0.05) and Ser660 phosphorylation of HSL (2.49-fold, P<0.05). PPARγ2 and FAT mRNA levels were also increased in DHEA-treated rats (1.61-fold, P<0.05 and 2.16-fold, P<0.05; respectively). Moreover, ATGL, HSL, and FAT mRNA levels were positively correlated with PPARγ2 expression. This study demonstrates that DHEA promotes lipid mobilization in adipose tissue by increasing the expression and activity of ATGL and HSL. The effects of DHEA appear to be mediated, at least in part, via PPARγ2 activation, which in turn upregulates ATGL and HSL gene expression.
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Affiliation(s)
- Joanna Karbowska
- Department of Biochemistry, Medical University of Gdansk, Debinki 1, 80-211 Gdansk, Poland.
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16
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Extended-release niacin acutely suppresses postprandial triglyceridemia. Am J Med 2012; 125:1026-35. [PMID: 22840917 PMCID: PMC4170918 DOI: 10.1016/j.amjmed.2012.03.017] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/07/2012] [Revised: 03/21/2012] [Accepted: 03/21/2012] [Indexed: 01/15/2023]
Abstract
OBJECTIVE Postprandial triglyceridemia predicts cardiovascular events. Niacin might lower postprandial triglycerides by restricting free fatty acids. Immediate-release niacin reduced postprandial triglycerides, but extended-release niacin failed to do so when dosed the night before a fat challenge. The study aims were to determine whether extended-release niacin dosed before a fat challenge suppresses postprandial triglycerides and whether postprandial triglycerides are related to free fatty acid restriction. METHODS A double-blinded, placebo-controlled, random-order crossover experiment was performed, in which healthy volunteers took 2 g extended-release niacin or placebo 1 hour before heavy cream. We sampled blood over 12 hours and report triglycerides and free fatty acid as means ± standard deviation for incremental area under the curve (AUC) and nadir. RESULTS By combining 43 fat challenges from 22 subjects, postprandial triglycerides incremental AUC was +312 ± 200 mg/dL*h on placebo versus +199 ± 200 mg/dL*h on extended-release niacin (33% decrease, P=.02). The incremental nadir for free fatty acid was -0.07 ± 0.15 mmol/L on placebo versus -0.27 ± 0.13 mmol/L on extended-release niacin (P<.0001), and free fatty acid incremental AUC decreased from +2.9 ± 1.5 mmol/L*h to +1.5 ± 1.5 mmol/L*h on extended-release niacin (20% decrease, P=.0015). The incremental AUC for triglycerides was strongly related to the post-dose decrease in free fatty acid (r = +0.58, P=.0007). CONCLUSIONS Given right before a fat meal, even a single dose of extended-release niacin suppresses postprandial triglyceridemia. This establishes that postprandial triglycerides suppression is an acute pharmacodynamic effect of extended-release niacin, probably the result of marked free fatty acid restriction. Further study is warranted to determine whether mealtime dosing would augment the clinical efficacy of extended-release niacin therapy.
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Vaidyanathan V, Bastarrachea RA, Higgins PB, Voruganti VS, Kamath S, DiPatrizio NV, Piomelli D, Comuzzie AG, Parks EJ. Selective cannabinoid-1 receptor blockade benefits fatty acid and triglyceride metabolism significantly in weight-stable nonhuman primates. Am J Physiol Endocrinol Metab 2012; 303:E624-34. [PMID: 22761159 PMCID: PMC3468508 DOI: 10.1152/ajpendo.00072.2012] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The goal of this study was to determine whether administration of the CB₁ cannabinoid receptor antagonist rimonabant would alter fatty acid flux in nonhuman primates. Five adult baboons (Papio Sp) aged 12.1 ± 4.7 yr (body weight: 31.9 ± 2.1 kg) underwent repeated metabolic tests to determine fatty acid and TG flux before and after 7 wk of treatment with rimonabant (15 mg/day). Animals were fed ad libitum diets, and stable isotopes were administered via diet (d₃₁-tripalmitin) and intravenously (¹³C₄-palmitate, ¹³C₁-acetate). Plasma was collected in the fed and fasted states, and blood lipids were analyzed by GC-MS. DEXA was used to assess body composition and a hyperinsulinemic euglycemic clamp used to assess insulin-mediated glucose disposal. During the study, no changes were observed in food intake, body weight, plasma, and tissue endocannabinoid concentrations or the quantity of liver-TG fatty acids originating from de novo lipogenesis (19 ± 6 vs. 16 ± 5%, for pre- and posttreatment, respectively, P = 0.39). However, waist circumference was significantly reduced 4% in the treated animals (P < 0.04), glucose disposal increased 30% (P = 0.03), and FFA turnover increased 37% (P = 0.02). The faster FFA flux was consistent with a 43% reduction in these fatty acids used for TRL-TG synthesis (40 ± 3 vs. 23 ± 4%, P = 0.02) and a twofold increase in TRL-TG turnover (1.5 ± 0.9 vs. 3.1 ± 1.4 μmol·kg⁻¹·h⁻¹, P = 0.03). These data support the potential for a strong effect of CB₁ receptor antagonism at the level of adipose tissue, resulting in improvements in fasting turnover of fatty acids at the whole body level, central adipose storage, and significant improvements in glucose homeostasis.
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Affiliation(s)
- Vidya Vaidyanathan
- Center for Human Nutrition, University of Texas Southwestern Medical Center, Dallas, TX 75390-9052, USA
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18
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Banerjee KK, Ayyub C, Sengupta S, Kolthur-Seetharam U. dSir2 deficiency in the fatbody, but not muscles, affects systemic insulin signaling, fat mobilization and starvation survival in flies. Aging (Albany NY) 2012; 4:206-23. [PMID: 22411915 PMCID: PMC3348481 DOI: 10.18632/aging.100435] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Sir2 is an evolutionarily conserved NAD+ dependent protein. Although, SIRT1 has been implicated to be a key regulator of fat and glucose metabolism in mammals, the role of Sir2 in regulating organismal physiology, in invertebrates, is unclear. Drosophila has been used to study evolutionarily conserved nutrient sensing mechanisms, however, the molecular and metabolic pathways downstream to Sir2 (dSir2) are poorly understood. Here, we have knocked down endogenous dSir2 in a tissue specific manner using gene-switch gal4 drivers. Knockdown of dSir2 in the adult fatbody leads to deregulated fat metabolism involving altered expression of key metabolic genes. Our results highlight the role of dSir2 in mobilizing fat reserves and demonstrate that its functions in the adult fatbody are crucial for starvation survival. Further, dSir2 knockdown in the fatbody affects dilp5 (insulin-like-peptide) expression, and mediates systemic effects of insulin signaling. This report delineates the functions of dSir2 in the fatbody and muscles with systemic consequences on fat metabolism and insulin signaling. In conclusion, these findings highlight the central role that fatbody dSir2 plays in linking metabolism to organismal physiology and its importance for survival.
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Affiliation(s)
- Kushal Kr Banerjee
- Tata Institute of Fundamental Research Department of Biological Sciences, Tata Institute of Fundamental Research, Colaba, Mumbai, India
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19
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Weber JM, Reidy SP. Extending food deprivation reverses the short-term lipolytic response to fasting: role of the triacylglycerol/fatty acid cycle. ACTA ACUST UNITED AC 2012; 215:1484-90. [PMID: 22496284 DOI: 10.1242/jeb.062992] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The effects of short-term food deprivation on lipid metabolism are well documented, but little is known about prolonged fasting. This study monitored the kinetics of glycerol (rate of appearance, R(a) glycerol) and non-esterified fatty acids (R(a) NEFA) in fasting rabbits. Our goals were to determine whether lipolysis is stimulated beyond values seen for short-term fasting, and to characterize the roles of primary (intracellular) and secondary (with transit through the circulation) triacylglycerol/fatty acid cycling (TAG/FA cycling) in regulating fatty acid allocation to oxidation or re-esterification. R(a) glycerol (9.62±0.72 to 15.29±0.96 μmol kg(-1) min(-1)) and R(a) NEFA (18.05±2.55 to 31.25±1.93 μmol kg(-1) min(-1)) were stimulated during the first 2 days of fasting, but returned to baseline after 4 days. An initial increase in TAG/FA cycling was followed by a reduction below baseline after 6 days without food, with primary and secondary cycling contributing to these responses. We conclude that the classic activation of lipolysis caused by short-term fasting is abolished when food deprivation is prolonged. High rates of re-esterification may become impossible to sustain, and TAG/FA cycling could decrease to reduce its cost to 3% of total energy expenditure. Throughout prolonged fasting, fatty acid metabolism gradually shifts towards increased oxidation and reduced re-esterification. Survival is achieved by pressing fuel selection towards the fatty acid dominance of energy metabolism and by slowing substrate cycles to assist metabolic suppression. However, TAG/FA cycling remains active even after prolonged fasting, suggesting that re-esterification is a crucial mechanism that cannot be stopped without harmful consequences.
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Affiliation(s)
- Jean-Michel Weber
- Biology Department, University of Ottawa, 30 Marie Curie, Ottawa, Ontario, Canada K1N 6N5.
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20
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Polak J, Kotrc M, Wedellova Z, Jabor A, Malek I, Kautzner J, Kazdova L, Melenovsky V. Lipolytic effects of B-type natriuretic peptide 1-32 in adipose tissue of heart failure patients compared with healthy controls. J Am Coll Cardiol 2011; 58:1119-25. [PMID: 21884948 DOI: 10.1016/j.jacc.2011.05.042] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/17/2011] [Revised: 05/03/2011] [Accepted: 05/31/2011] [Indexed: 12/21/2022]
Abstract
OBJECTIVES Our goal was to examine the role of B-type natriuretic peptide (BNP) in lipolysis regulation in heart failure (HF) patients. BACKGROUND Enhanced adipose tissue lipolysis can contribute to myocardial lipid overload, insulin resistance, and cachexia in advanced HF. Natriuretic peptides were recently recognized to stimulate lipolysis in healthy subjects. METHODS Ten nondiabetic HF patients (New York Heart Association functional class III, 50% nonischemic etiology) and 13 healthy subjects (control subjects) of similar age, sex, and body composition underwent a microdialysis study of subcutaneous abdominal adipose tissue. Four microdialysis probes were simultaneously perfused with 0.1 μM BNP(1-32,) 10 μM BNP(1-32), 10 μM norepinephrine (NE) or Ringer's solution. Outgoing dialysate glycerol concentration (DGC) was measured as an index of lipolysis. RESULTS Spontaneous lipolysis was higher in HF patients compared with control subjects (DGC: 189 ± 37 μmol/l vs. 152 ± 35 μmol/l, p < 0.01). Response to NE was similar (p = 0.35) in HF patients and control subjects (DGC increase of 1.7 ± 0.2-fold vs. 1.7 ± 0.4-fold). BNP(1-32) 10 μM markedly increased lipolysis in both HF patients and control subjects (DGC increase of 2.8 ± 0.5-fold vs. 3.2 ± 0.3-fold), whereas the response to 0.1 μM BNP(1-32) was more pronounced in HF patients (p = 0.02). In HF patients, spontaneous lipolysis positively correlated with insulin resistance and the response to BNP(1-32) negatively correlated with adiposity. CONCLUSIONS BNP(1-32) exerts strong lipolytic effects in humans. Despite marked elevation of plasma immunoreactive BNP, the responsiveness of adipose tissue to BNP(1-32) is not attenuated in HF, possibly reflecting a deficiency of endogenous bioactive BNP. Lipolytic effects of BNP can contribute to excessive fatty acid mobilization in advanced HF.
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Affiliation(s)
- Jan Polak
- Department of Cardiology, Institute of Clinical and Experimental Medicine, IKEM, Videnska 1958/9, Prague, Czech Republic
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21
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Bastarrachea RA, Veron SM, Vaidyanathan V, Garcia-Forey M, Voruganti VS, Higgins PB, Parks EJ. Protocol for the measurement of fatty acid and glycerol turnover in vivo in baboons. J Lipid Res 2011; 52:1272-1280. [PMID: 21415122 PMCID: PMC3090248 DOI: 10.1194/jlr.d012385] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2010] [Revised: 03/15/2011] [Indexed: 01/22/2023] Open
Abstract
Recognition of the strength of nonhuman primate models in investigating metabolic disorders has resulted in an expanded need for in vivo research techniques. We studied adipose metabolism in 10 baboons (13.0 ± 4.2 years old, 29.5 ± 5.5 kg). Part 1 evaluated the effect of different sedatives on the rate of appearance of plasma free fatty acids (RaFFA), assessed using ¹³C₄-labeled palmitate infusion (7 µmol/kg/min). Animals, were studied with no sedation, with complete isoflurane sedation, and with minimal midazolam infusion (0.04 mg/kg/h), with the last scheme allowing for the most consistent values and animals that were visually more calm. In Part 2, RaFFA and RaGlycerol (D₅-glycerol, 5 mg/kg lean body mass/h) were measured. From midnight to 0300, flux fell and came to a steady state between 0500 and 0700 h (RaFFA, 39.4 ± 29.8 μmol/kg fat mass/min; and RaGlycerol, 26.9 ± 7.3 μmol/kg/min). The RaFFA-to-RaGlycerol ratio was 1.5 ± 0.8 (49% reesterification). The decline in turnover throughout the night reflects natural circadian processes and was mirrored by reductions in FFA and glycerol to 0.62 and ± 0.14 and 0.16 and ± 0.03 mmol/l, respectively. The concurrent changes in both FFA and glycerol kinetics indicate physiologic validity of the method. These techniques will support needed research to determine mechanisms by which treatments act upon the adipocyte in vivo.
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Affiliation(s)
- Raul A Bastarrachea
- Department of Genetics, Texas Biomedical Research Institute, San Antonio, TX
| | - Sonya M Veron
- Center for Human Nutrition, University of Texas Southwestern Medical Center, Dallas, TX
| | - Vidya Vaidyanathan
- Center for Human Nutrition, University of Texas Southwestern Medical Center, Dallas, TX
| | - Maggie Garcia-Forey
- Department of Genetics, Texas Biomedical Research Institute, San Antonio, TX
| | - V Saroja Voruganti
- Department of Genetics, Texas Biomedical Research Institute, San Antonio, TX
| | - Paul B Higgins
- Department of Genetics, Texas Biomedical Research Institute, San Antonio, TX
| | - Elizabeth J Parks
- Center for Human Nutrition, University of Texas Southwestern Medical Center, Dallas, TX.
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22
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Iozzo P, Bucci M, Roivainen A, Någren K, Järvisalo MJ, Kiss J, Guiducci L, Fielding B, Naum AG, Borra R, Virtanen K, Savunen T, Salvadori PA, Ferrannini E, Knuuti J, Nuutila P. Fatty acid metabolism in the liver, measured by positron emission tomography, is increased in obese individuals. Gastroenterology 2010; 139:846-56, 856.e1-6. [PMID: 20685204 DOI: 10.1053/j.gastro.2010.05.039] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2010] [Revised: 04/14/2010] [Accepted: 05/20/2010] [Indexed: 02/08/2023]
Abstract
BACKGROUND & AIMS Hepatic lipotoxicity results from and contributes to obesity-related disorders. It is a challenge to study human metabolism of fatty acids (FAs) in the liver. We combined (11)C-palmitate imaging by positron emission tomography (PET) with compartmental modeling to determine rates of hepatic FA uptake, oxidation, and storage, as well as triglyceride release in pigs and human beings. METHODS Anesthetized pigs underwent (11)C-palmitate PET imaging during fasting (n = 3) or euglycemic hyperinsulinemia (n = 3). Metabolic products of FAs were measured in arterial, portal, and hepatic venous blood. The imaging methodology then was tested in 15 human subjects (8 obese subjects); plasma (11)C-palmitate kinetic analyses were used to quantify systemic and visceral lipolysis. RESULTS In pigs, PET-derived and corresponding measured FA fluxes (FA uptake, esterification, and triglyceride FA release) did not differ and were correlated with each other. In human beings, obese subjects had increased hepatic FA oxidation compared with controls (mean +/- standard error of the mean, 0.16 +/- 0.01 vs 0.08 +/- 0.01 micromol/min/mL; P = .0007); FA uptake and esterification rates did not differ between obese subjects and controls. Liver FA oxidation correlated with plasma insulin levels (r = 0.61, P = .016), adipose tissue (r = 0.58, P = .024), and systemic insulin resistance (r = 0.62, P = .015). Hepatic FA esterification correlated with the systemic release of FA into plasma (r = 0.71, P = .003). CONCLUSIONS PET imaging can be used to measure FA metabolism in the liver. By using this technology, we found that obese individuals have increased hepatic oxidation of FA, in the context of adipose tissue insulin resistance, and increased FA flux from visceral fat. FA flux from visceral fat is proportional with the mass of the corresponding depot.
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Affiliation(s)
- Patricia Iozzo
- Turku PET Centre, and Department of Medicine, University of Turku, Turku, Finland.
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Magkos F, Mohammed BS, Patterson BW, Mittendorfer B. Free fatty acid kinetics in the late phase of postexercise recovery: importance of resting fatty acid metabolism and exercise-induced energy deficit. Metabolism 2009; 58:1248-55. [PMID: 19500809 PMCID: PMC2728784 DOI: 10.1016/j.metabol.2009.03.023] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2008] [Accepted: 03/05/2009] [Indexed: 10/20/2022]
Abstract
Free fatty acid (FFA) availability increases several-fold during exercise and remains significantly elevated for at least 3 to 6 hours after exercise cessation. Little, however, is known regarding the duration of the postexercise rise in FFA flux. In the present study, we used stable isotope-labeled palmitate infusion to examine fatty acid metabolism in 27 healthy untrained men and women (age, 29 +/- 7 years; body mass index, 25 +/- 4 kg/m2) between 13 to 16 hours and 21 to 24 hours after a single bout of moderate-intensity endurance exercise (1-2 hours at 60% of peak oxygen consumption), performed in the evening, and after a time-matched resting trial. Postabsorptive FFA rate of appearance (Ra) and FFA concentration in plasma were significantly greater after exercise than rest throughout the recovery period (P < .015), but the exercise-induced increases declined from approximately 40% at 13 to 16 hours to approximately 10% at 21 to 24 hours postexercise (P = .001). The magnitude of the exercise-induced increase in plasma FFA concentration was proportional to the increase in FFA Ra. Correlation analysis demonstrated that exercise-induced changes in plasma FFA Ra at 13 to 16 hours are (1) negatively associated with resting plasma FFA Ra and (2) positively associated with the net energy expenditure of exercise and the exercise-induced changes in whole-body fat oxidation rate (all P values < .05). In multivariate stepwise linear regression analysis, baseline plasma FFA Ra (P < or = .008) and net energy expenditure of exercise (P < or = .005) independently predicted the exercise-induced change in plasma FFA Ra at 13 to 16 hours. We conclude that the exercise-induced increase in FFA mobilization is (1) long-lived, persisting for 12 to 24 hours after exercise, with a progressive decline with time; (2) greater in subjects with low than high resting plasma FFA availability; and (3) greater after exercise with high than low energy demand.
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Affiliation(s)
- Faidon Magkos
- Washington University School of Medicine, St. Louis, MO, USA
- Department of Nutrition and Dietetics, Harokopio University, Athens, Greece
| | | | | | - Bettina Mittendorfer
- Washington University School of Medicine, St. Louis, MO, USA
- Corresponding author: Bettina Mittendorfer, Ph.D., Washington University School of Medicine, Division of Geriatrics & Nutritional Science, 660 South Euclid Avenue; Campus Box 8031, St. Louis, MO 63110; USA, Phone: (314) 362 8450, Fax: (314) 362 8230, E-mail:
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Magkos F, Mittendorfer B. Stable isotope-labeled tracers for the investigation of fatty acid and triglyceride metabolism in humans in vivo. ACTA ACUST UNITED AC 2009; 4:215-230. [PMID: 20161007 DOI: 10.2217/clp.09.9] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Understanding lipid metabolism and its regulation requires information on the rates at which lipids are produced within the body, absorbed (dietary lipids) into the body, transported within the body, and utilized by various tissues. This article focuses on the use of stable isotope-labeled tracers for the quantitative evaluation of major pathways of fatty acid and triglyceride metabolism in humans in vivo. Adipose tissue lipolysis and free fatty acid appearance in plasma, fatty acid tissue uptake and oxidation, and hepatic very low-density lipoprotein triglyceride secretion are among the metabolic pathways that can be studied by using stable isotope labeled tracers, and will be discussed in detail. The methodology has been in use for many years and is constantly being refined. A variety of tracers and analytical approaches are available and can be used; knowing the advantages, assumptions, and limitations of each is essential for the planning of studies and the interpretation of data, which can provide unique insights into human lipid metabolism.
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Affiliation(s)
- Faidon Magkos
- Center for Human Nutrition, Washington University School of Medicine, St. Louis, MO, USA
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25
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Lavoie F, Frisch F, Brassard P, Normand-Lauzière F, Cyr D, Gagnon R, Drouin R, Baillargeon JP, Carpentier AC. Relationship between total and high molecular weight adiponectin levels and plasma nonesterified fatty acid tolerance during enhanced intravascular triacylglycerol lipolysis in men. J Clin Endocrinol Metab 2009; 94:998-1004. [PMID: 19066306 DOI: 10.1210/jc.2008-1021] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
CONTEXT Increased plasma nonesterified fatty acid (NEFA) appearance during enhanced intravascular triacylglycerol (TG) lipolysis is a marker of metabolic adipose tissue dysfunction and may lead to the development of insulin resistance. The relationship between total and high molecular weight (HMW) adiponectin levels, NEFA appearance, and total TG lipolytic capacity has not been previously studied in humans. OBJECTIVES Our objective was to determine whether total and HMW adiponectin plasma levels are associated with plasma NEFA level and appearance, and with total TG lipolytic rate during enhanced intravascular TG lipolysis in men. DESIGN This was a cross-sectional metabolic study. SETTING The study was performed at an academic clinical research center. PARTICIPANTS There were 15 healthy men (mean +/- sd body mass index 25.5 +/- 4.7 kg/m(2)) aged 21-50 yr (mean +/- sd 31.1 +/- 10.2) without first-degree relatives with type 2 diabetes included in the study. INTERVENTIONS Pancreatic clamps and iv infusion of stable isotopic tracers ([1,1,2,3,3-(2)H(5)]glycerol and [U-(13)C]palmitate) were performed, whereas intravascular TG lipolysis was clamped by iv infusion of heparin plus Intralipid at low (fasting) and high insulin levels. Total and HMW adiponectin levels were measured using an ELISA. MAIN OUTCOME MEASURES Levels of total and HMW adiponectin, palmitate appearance (plasma palmitate appearance rate), and glycerol appearance (plasma glycerol appearance rate) were calculated. RESULTS During heparin plus Intralipid infusion, total and HMW adiponectin was inversely correlated with plasma palmitate appearance rate (r = -0.65; P = 0.01), but this association was lost when expressed per nonlean weight. Adiponectin levels were positively associated with plasma glycerol appearance rate per nonlean weight (r = 0.71 and r = 0.66, respectively; P < or = 0.01). CONCLUSIONS Increased adipose tissue mass likely explains the association between low adiponectin and reduced NEFA tolerance. Adiponectin level is a marker of total TG lipolytic rate per adipose tissue mass in men.
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Affiliation(s)
- F Lavoie
- Department of Medicine, Division of Endocrinology, Centre Hospitalier Universitaire de Sherbrooke, Québec, Canada J1H 5N4
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Selberg O, McMillan DC, Preston T, Carse H, Shenkin A, Burns HJ. Palmitate turnover and its response to glucose infusion in weight-losing cancer patients. Clin Nutr 2008; 9:150-6. [PMID: 16837347 DOI: 10.1016/0261-5614(90)90047-v] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/1989] [Accepted: 08/24/1989] [Indexed: 11/15/2022]
Abstract
Palmitate turnover in weight-stable control subjects (n = 4) and weight-losing patients with progressive malignant disease (n = 4) has been determined. Measurements were made after an overnight fast and during glucose infusion (3.5 mg/kg/min). Turnover rates were calculated from plateau isotopic enrichment of palmitate in plasma during a continuous infusion of 1-13C palmitate. Palmitate turnover was higher in the cancer group before (180%) and during glucose loading (170%) compared with the control group. Palmitate turnover was reduced during glucose administration by approximately 34% in both groups. Plasma concentration of insulin was decreased and of cortisol was increased in the cancer group compared with the control group before and during glucose infusion. We conclude that cancer patients with weight loss have increased rates of fatty acid turnover indicative of enhanced mobilisation of body fat stores. Altered plasma concentrations of insulin and cortisol may mediate this effect. Nonetheless, even at more advanced stages of cachexia cancer patients have normal control mechanisms for inhibiting fatty acid turnover following administration of carbohydrate.
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Affiliation(s)
- O Selberg
- University Department of Surgery, Glasgow Royal Infirmary, Glasgow G4 0SF, UK
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27
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Brassard P, Frisch F, Lavoie F, Cyr D, Bourbonnais A, Cunnane SC, Patterson BW, Drouin R, Baillargeon JP, Carpentier AC. Impaired plasma nonesterified fatty acid tolerance is an early defect in the natural history of type 2 diabetes. J Clin Endocrinol Metab 2008; 93:837-44. [PMID: 18182453 PMCID: PMC2266943 DOI: 10.1210/jc.2007-1670] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT Abnormal plasma nonesterified fatty acid (NEFA) metabolism may play a role in the development of type 2 diabetes. OBJECTIVES Our objectives were to demonstrate whether there is a defect in insulin-mediated suppression of plasma NEFA appearance (RaNEFA) and oxidation (OxNEFA) during enhanced intravascular triacylglycerol lipolysis early in the natural history of type 2 diabetes, and if so, to determine whether other mechanisms than reduced insulin-mediated suppression of intracellular lipolysis are involved. DESIGN These are cross-sectional studies. SETTING The studies were performed at an academic clinical research center. PARTICIPANTS Nine healthy subjects with both parents with type 2 diabetes (FH+) and nine healthy subjects with no first-degree relatives with type 2 diabetes (FH-) with similar anthropometric features were included in the studies. INTERVENTIONS Pancreatic clamps and iv infusion of stable isotopic tracers ([1,1,2,3,3-(2)H5]-glycerol and [U-(13)C]-palmitate or [1,2-(13)C]-acetate) were performed while intravascular triacylglycerol lipolysis was simultaneously clamped by iv infusion of heparin plus Intralipid at low (fasting) and high insulin levels. Oral nicotinic acid (NA) was used to inhibit intracellular lipolysis. MAIN OUTCOME MEASURES RaNEFA and OxNEFA were determined. RESULTS During heparin plus Intralipid infusion at high plasma insulin levels, and despite similar intravascular lipolytic rates, FH+ had higher RaNEFA and OxNEFA than FH- (RaNEFA: 17.4+/-6.3 vs. 9.2+/-4.2; OxNEFA: 4.5+/-1.8 vs. 2.3+/-1.5 micromol/kg lean body mass/min), independent of NA intake, gender, age, and body composition. In the presence of NA, insulin-mediated suppression of RaNEFA was still observed in FH-, but not in FH+. CONCLUSIONS Increased RaNEFA and OxNEFA during intravascular lipolysis at high insulin levels occur early in the natural history of type 2 diabetes.
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Affiliation(s)
- P Brassard
- Department of Medicine, Division of Endocrinology, Centre hospitalier universitaire de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4
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Bisschop PH, Ackermans MT, Endert E, Ruiter AFC, Meijer AJ, Kuipers F, Sauerwein HP, Romijn JA. The effect of carbohydrate and fat variation in euenergetic diets on postabsorptive free fatty acid release. Br J Nutr 2007. [DOI: 10.1079/bjn2002578] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Diet composition and energy content modulate free fatty acid (FFA) release. The aim of this study was to evaluate the dose–response effects of euenergetic variations in dietary carbohydrate and fat content on postabsorptive FFA release. The rate of appearance (Ra) of palmitate was measured by infusion of [2,2-2H2]palmitate after an overnight fast in six healthy men on three separate occasions, i.e. after 7 d on euenergetic control, high-carbohydrate and high-fat diets. The protein content and composition was identical for each diet. Postabsorptive plasma fatty acid concentrations were not different between the high-carbohydrate and control diets (0·36 (SE 0·07) V. 0·43 (se 0·04) mmol/l), but were increased after the high-fat diet (0·75 (se 0·09) mmol/l, (P<0·01 compared with the other diets). Ra palmitate was not different between the high-carbohydrate and control diets (1·36 (se 0·20) v. 1·47 (se 0·15) μmol/kg per min). However, Ra palmitate was increased to 2·36 (se 0·26) μmol/kg per min after the high-fat diet (P<0·01 compared with the other diets). The fatty acid flux and whole-body fat oxidation were not affected by the high-carbohydrate diet compared with the control diet, but were increased by 67 and 47 % respectively, on the high-fat diet (P<0·01 compared with the other diets). A euenergetic high-fat diet results in increased postabsorptive FFA release and fat oxidation, whereas a euenergetic high-carbohydrate diet does not affect these variables of fat metabolism.
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Carpentier AC, Frisch F, Brassard P, Lavoie F, Bourbonnais A, Cyr D, Giguère R, Baillargeon JP. Mechanism of insulin-stimulated clearance of plasma nonesterified fatty acids in humans. Am J Physiol Endocrinol Metab 2007; 292:E693-701. [PMID: 17062840 DOI: 10.1152/ajpendo.00423.2006] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Insulin increases plasma nonesterified fatty acid (NEFA) clearance in humans, but whether this is independent of change in plasma NEFA appearance is currently unknown. Nine nondiabetic men (age: 28+/-3 yr, body mass index: 27.2+/-1.7 kg/m2) underwent euglycemic clamps to maintain low (LINS) vs. high (HINS) physiological insulin levels for 6 h. An intravenous infusion of heparin+Intralipid (HI) was performed during 4 of the 6 h of the clamps (in the last 4 h at LINS and in the first 4 h at HINS), whereas saline infusion (SAL) was administered in the remaining 2 h to modulate plasma NEFA levels independently of plasma insulin levels. Four experimental conditions were obtained in each individual: LINS with saline (LINS/SAL) and with HI infusion (LINS/HI) and HINS with saline (HINS/SAL) and with HI infusion (HINS/HI). Plasma palmitate appearance during HINS/SAL was lower than during the three other experimental conditions (P<0.05). In contrast, plasma linoleate appearance, as expected, was increased by HI independently of insulin level (P<0.02). Plasma palmitate clearance during HINS/SAL was higher than LINS/SAL and LINS/HI (P<0.008), and this increase was blunted during HINS/HI. We observed a linear decrease in plasma palmitate clearance with increasing plasma NEFA appearance independent of insulin levels. Plasma NEFA levels increased exponentially with increase in plasma NEFA appearance. We conclude that insulin stimulates plasma NEFA clearance by reducing the endogenous appearance rate of NEFA. The relationship between plasma NEFA level and appearance rate is nonlinear.
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Affiliation(s)
- André C Carpentier
- Division of Endocrinology, Department of Medicine, Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, Quebec, Canada J1H 5N4.
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Aberg W, Thörne A, Olivecrona T, Nordenström J. Fat oxidation and plasma removal capacity of an intravenous fat emulsion in elderly and young men. Nutrition 2006; 22:738-43. [PMID: 16815487 DOI: 10.1016/j.nut.2006.04.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2005] [Revised: 04/20/2006] [Accepted: 04/23/2006] [Indexed: 11/25/2022]
Abstract
OBJECTIVE We explored metabolic and thermogenic responses to exogenous fat in relation to age as a basis for a rational design of parenteral nutrition in elderly patients. METHODS Ten healthy elderly men (70-78 y of age, body mass index 21-27 kg/m(2)) and 10 healthy young men (19-45 y of age, body mass index 19-26 kg/m(2)) were studied with a hypertriglyceridemic clamp (primed infusion of a long-chain triacylglycerol emulsion to reach and stabilize at a triacylglycerol concentration of 4 mmol/L for 180 min). Continuous indirect calorimetry was carried out in the basal state and throughout the study period. RESULTS The infusion rates required to maintain plasma triacylglycerol levels at 4 mmol/L were similar in elderly and young individuals (mean +/- SEM 0.201 +/- 0.027 versus 0.203 +/- 0.014 mmol/min, not significant). Plasma concentrations of free fatty acids and beta-OH-butyrate were higher in the elderly before the infusion and increased in a similar manner in both groups during infusion. Energy expenditure at baseline was higher in the young than in the elderly (79 +/- 2 versus 64 +/- 3 kcal/h; P < 0.001), although the respiratory quotient was similar in the two groups (0.80 +/- 0.01 versus 0.78 +/- 0.01, not significant). During lipid administration there was a similar increase in energy expenditure in the old and young individuals (+9.0 +/- 1.3% versus +6.0 +/- 1.8%, not significant). Lipid infusion resulted in similar increments in fat oxidation in the young and elderly (23.9 +/- 7.0% versus 15.1 +/- 4.9%, respectively, not significant). Plasma lipoprotein lipase activity was almost three times higher in the young than in the elderly subjects (0.23 +/- 0.02 versus 0.65 +/- 0.09 mU/mL, respectively, P < 0.001). During lipid infusion, a similar increment (four- to five-fold) in plasma lipoprotein lipase activity was noted in the two groups. CONCLUSIONS Elderly healthy men have a similar capacity as young healthy men to clear and oxidize a high triacylglycerol load administered as a hypertriglyceridemic clamp.
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Affiliation(s)
- Wiveca Aberg
- Department of Surgery, Karolinska University Hospital-Solna, Stockholm, Sweden
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Abstract
There is an epidemic of obesity, insulin resistance and cardiovascular disease. Adipose tissue plays a major metabolic role and produces hormones with important physiological effects. In vitro studies remove regulatory factors, such as blood flow, making results difficult to interpret, and animal studies cannot necessarily be extrapolated to humans. Fortunately, adipose tissue can be studied in vivo with microdialysis, adipose tissue vein cannulation, measurement of blood flow using 133Xenon washout, stable isotope tracers and biopsies. In vivo studies have shown that adipose tissue is an efficient buffer against the postprandial flux of non-esterified fatty acids (NEFA) in the circulation, protecting other tissues. When there is excess adipose tissue, this buffering effect may be impaired. The postprandial blood flow response is also reduced, potentially causing an atherogenic lipid profile and atheroma. A systems biology approach, combining in vivo techniques with genomics, proteomics and metabolomics, will clarify links between adipose tissue and vascular disease.
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Affiliation(s)
- Lucinda Km Summers
- The Academic Unit of Molecular Vascular Medicine, University of Leeds, Clarendon Way, Leeds, LS2 9JT, UK.
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Carpentier AC, Frisch F, Cyr D, Généreux P, Patterson BW, Giguère R, Baillargeon JP. On the suppression of plasma nonesterified fatty acids by insulin during enhanced intravascular lipolysis in humans. Am J Physiol Endocrinol Metab 2005; 289:E849-56. [PMID: 15972273 DOI: 10.1152/ajpendo.00073.2005] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
During the fasting state, insulin reduces nonesterified fatty acid (NEFA) appearance in the systemic circulation mostly by suppressing intracellular lipolysis in the adipose tissue. In the postprandial state, insulin may also control NEFA appearance through enhanced trapping into the adipose tissue of NEFA derived from intravascular triglyceride lipolysis. To determine the contribution of suppression of intracellular lipolysis in the modulation of plasma NEFA metabolism by insulin during enhanced intravascular triglyceride lipolysis, 10 healthy nonobese subjects underwent pancreatic clamps at fasting vs. high physiological insulin level with intravenous infusion of heparin plus Intralipid. Nicotinic acid was administered orally during the last 2 h of each 4-h clamp to inhibit intracellular lipolysis and assess insulin's effect on plasma NEFA metabolism independently of its effect on intracellular lipolysis. Stable isotope tracers of palmitate, acetate, and glycerol were used to assess plasma NEFA metabolism and total triglyceride lipolysis in each participant. The glycerol appearance rate was similar during fasting vs. high insulin level, but plasma NEFA levels were significantly lowered by insulin. Nicotinic acid significantly blunted the insulin-mediated suppression of plasma palmitate appearance and oxidation rates by approximately 60 and approximately 70%, respectively. In contrast, nicotinic acid did not affect the marked stimulation of palmitate clearance by insulin. Thus most of the insulin-mediated reduction of plasma NEFA appearance and oxidation can be explained by suppression of intracellular lipolysis during enhanced intravascular triglyceride lipolysis in healthy humans. Our results also suggest that insulin may affect plasma NEFA clearance independently of the suppression of intracellular lipolysis.
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Affiliation(s)
- André C Carpentier
- Division of Endocrinology, Centre hospitalier universitaire de Sherbrooke, Sherbrooke, Quebec, Canada J1H 5N4.
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Coppack SW, Chinkes DL, Miles JM, Patterson BW, Klein S. A multicompartmental model of in vivo adipose tissue glycerol kinetics and capillary permeability in lean and obese humans. Diabetes 2005; 54:1934-41. [PMID: 15983192 DOI: 10.2337/diabetes.54.7.1934] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Lipolysis of adipose tissue triglycerides releases glycerol. Twenty-four volunteers, of whom 6 were obese and 13 were women, received a primed-constant infusion of 2H5-glycerol for 120 min during postabsorptive steady-state conditions. Arterial, abdominal venous, and interstitial (microdialysis) samples were taken, and a four-compartment model was applied to assess subcutaneous abdominal adipose tissue glycerol kinetics. Adipose tissue blood flow was measured using 133Xe washout. Venous glycerol concentrations (median 230 micromol/l [interquartile range 210-268]) were consistently greater than those of arterial blood (69.1 micromol/l [56.5-85.5]), while glycerol isotopic enrichments (tracer-to-tracee ratio) were greater in arterial blood (8.34% [7.44-10.1]) than venous blood (2.34% [1.71-2.69], P < 0.01). Microdialysate glycerol enrichment was 1.44% (1.11-1.79), indicating incomplete permeability of glycerol between capillary blood and interstitium. Calculated interstitial glycerol concentrations were between 270 micromol/l (256-350) and 332 micromol/l (281-371) (examining different boundary conditions). The calculated capillary diffusion capacity (ps) was between 2.21 ml . 100 g tissue(-1) . min(-1) (1.31-3.13) and 3.09 ml . 100 g tissue(-1) . min(-1) (1.52-4.90) and correlated inversely with adiposity (Rs< or = -0.45, P < 0.05). Our results support previous estimates of interstitial glycerol concentration within adipose tissue and reveal capillary diffusion capacity is reduced in obesity.
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Affiliation(s)
- Simon W Coppack
- Diabetes & Metabolic Medicine, St. Bartholomew's and The London School of Medicine, London, UK.
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Mohammed BS, Fields DA, Mittendorfer B, Coggan AR, Klein S. Are peristaltic pumps as reliable as syringe pumps for metabolic research? Assessment of accuracy, precision, and metabolic kinetics. Metabolism 2004; 53:875-8. [PMID: 15254880 DOI: 10.1016/j.metabol.2004.02.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Syringe pumps are traditionally used to infuse tracers in metabolic research because they are perceived to be more accurate and precise than peristaltic pumps. This study evaluated the accuracy (actual v programmed infusion rate) and precision (reproducibility of infusion) of a peristaltic pump (Gemini PC 2; IMED, San Diego, CA) and a syringe pump (Model 22; Harvard Apparatus, Natick, MA) for metabolic research. In one protocol, saline delivery was measured in vitro in 5 trials at 4 flow rates: 3, 30, 150, and 300 mL/h. In the second protocol, basal glycerol rate of appearance (Ra) was determined in vivo in 5 women on 2 consecutive days. On day 1, [2-(13C)]glycerol was infused with 1 pump and [1,1,2,3,3-(2H5)]glycerol with the other. On day 2, the opposite pattern was used. The accuracy of the 2 pumps was the same (error approximately 2%). In addition, both the syringe and the peristaltic pumps were very precise, with coefficients of variation (CV) <1% at all flow rates. Glycerol Ra values were the same when tracer was infused with either a syringe or peristaltic pump on day 1 and day 2: 4.1 +/- 1.7 (syringe pump) and 4.2 +/- 1.9 (peristaltic pump) micromol. kg fat mass (FM)(-1). min(-1) on day 1; 4.2 +/- 1.2 (syringe pump) and 4.2 +/- 1.3 (peristaltic pump) micromol. kg FM(-1). min(-1) on day 2. These data demonstrate that both syringe and peristaltic pumps are very accurate and precise across a large range of flow rates. Moreover, the assessment of in vivo substrate kinetics in human subjects is the same when either pump is used to infuse isotope tracers.
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Affiliation(s)
- B Selma Mohammed
- Division of Geriatrics and Nutritional Sciences and Center for Human Nutrition, Washington University School of Medicine, St Louis, MO, USA
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Strawford A, Antelo F, Christiansen M, Hellerstein MK. Adipose tissue triglyceride turnover, de novo lipogenesis, and cell proliferation in humans measured with 2H2O. Am J Physiol Endocrinol Metab 2004; 286:E577-88. [PMID: 14600072 DOI: 10.1152/ajpendo.00093.2003] [Citation(s) in RCA: 228] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The turnover of adipose tissue components (lipids and cells) and the pathways of adipose lipid deposition have been difficult to measure in humans. We apply here a (2)H(2)O long-term labeling technique for concurrent measurement of adipose-triglyceride (TG) turnover, cell (DNA) proliferation, and de novo lipogenesis (DNL). Healthy subjects drank (2)H(2)O (70 ml/day) for 5-9 wk. Subcutaneous adipose tissue aspirates were taken (gluteal, thigh, and flank depots). Deuterium incorporation into TG glycerol (representing all-source TG synthesis), TG palmitate (representing DNL, by mass isotopomer distribution analysis), and DNA (representing cell proliferation) was measured by gas chromatography-mass spectrometry. Subjects tolerated the protocol well, and body (2)H(2)O enrichments were stable. Mean TG-glycerol fractional synthesis was 0.12 (i.e., 12%) with a range of 0.03-0.32 after 5 wk and 0.20 (range 0.08-0.49) after 9 wk (TG half-life 200-270 days). Label decay measurements 5-8 mo after discontinuing (2)H(2)O gave similar turnover estimates. Net lipolysis (TG turnover) was 50-60 g/day. DNL contribution to adipose-TG was 0.04 after 9 wk, representing approximately 20% of newly deposited TG. Cell proliferation was 0.10-0.17 after 9 wk (half-life 240-425 days). In summary, long-term (2)H(2)O administration to human subjects allows measurement of the dynamics of adipose tissue components. Turnover of all elements is slow, and DNL contributes approximately 20% of new TG.
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Affiliation(s)
- A Strawford
- Department of Nutritional Sciences & Toxicology, 119 Morgan Hall, University of California at Berkeley, CA 94720-3104, USA
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Kalderon B, Mayorek N, Ben-Yaacov L, Bar-Tana J. Adipose tissue sensitization to insulin induced by troglitazone and MEDICA 16 in obese Zucker rats in vivo. Am J Physiol Endocrinol Metab 2003; 284:E795-803. [PMID: 12488241 DOI: 10.1152/ajpendo.00368.2002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The putative role played by insulin sensitizers in modulating adipose tissue lipolysis in the fasting state was evaluated in obese conscious Zucker rats treated with troglitazone or beta,beta'-tetramethylhexadecanedioic acid (MEDICA 16) and compared with nontreated lean and obese animals. The rates of appearance (R(a)) of glycerol and free fatty acid (FFA), primary intra-adipose reesterification, and secondary reuptake of plasma FFA in adipose fat were measured using constant infusion of stable isotope-labeled [(2)H(5)]glycerol, [2,2-(2)H(2)]palmitate, and radioactive [(3)H]palmitate. The overall lipolytic flux (R(a) glycerol) was increased 1.7- and 1.4-fold in obese animals treated with troglitazone or MEDICA 16, respectively, resulting in increased FFA export (R(a) FFA) in the troglitazone-treated rats. Primary intra-adipose reesterification of lipolysis-derived fatty acids was enhanced twofold by insulin sensitizers, whereas reesterification of plasma fatty acids was unaffected by either treatment. Despite the unchanged R(a) FFA in MEDICA 16 or the increased R(a) FFA induced by troglitazone, very low density lipoprotein production rates were robustly curtailed. Total adipose tissue reesterification, used as an estimate of glucose conversion to glyceride-glycerol, was increased 1.9-fold by treatment with the insulin sensitizers. Our results indicate that, in the fasting state, insulin sensitizers induce, in vivo, a significant activation rather than suppression of adipose tissue lipolysis together with stimulation of glucose conversion to glyceride-glycerol.
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Affiliation(s)
- Bella Kalderon
- Department of Human Nutrition and Metabolism, Hebrew University Medical School, Jerusalem, Israel 91120.
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Buijs MM, Burggraaf J, Wijbrandts C, de Kam ML, Frölich M, Cohen AF, Romijn JA, Sauerwein HP, Meinders AE, Pijl H. Blunted lipolytic response to fasting in abdominally obese women: evidence for involvement of hyposomatotropism. Am J Clin Nutr 2003; 77:544-50. [PMID: 12600841 DOI: 10.1093/ajcn/77.3.544] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Abdominal obesity is associated with a blunted lipolytic response to fasting that may contribute to the preservation of adipose tissue mass. OBJECTIVE To further explore the pathophysiology of blunted lipolysis during fasting in obesity, we simultaneously measured lipolysis and distinct neuroendocrine regulatory hormones in abdominally obese and normal-weight (NW) women. DESIGN Eight abdominally obese [x +/- SD body mass index (BMI; in kg/m(2)): 32.1 +/- 2.6] and 6 NW (BMI: 22.7 +/- 1.5) women were studied during the last 8 h of a 20-h fast. The glycerol appearance rate and the serum and plasma concentrations of insulin, leptin, cortisol, and growth hormone were measured regularly. RESULTS At 13 h of fasting, the mean (+/-SD) glycerol appearance rate corrected for fat mass was greater in NW women than in obese women (7.2 +/- 1.0 and 5.1 +/- 0.6 micro mol.kg(-1).min(-1), respectively; P = 0.001). After a 20-h fast, lipolysis increased to 8.9 +/- 1.5 mmol.kg(-1).min(-1) in NW women (23%), whereas it did not change significantly in obese women (-2%). Fasting decreased insulin concentrations by approximately 30% in both groups, but it did not induce significant changes in leptin concentrations. Mean cortisol concentrations and urinary catecholamine excretion were comparable in both groups. However, mean plasma growth hormone concentrations were higher in NW women than in obese women (1.81 +/- 0.98 compared with 0.74 +/- 0.52 mU/L; P = 0.046). The relative change in lipolysis tended to correlate with mean plasma growth hormone concentrations (r = 0.515, P = 0.059). CONCLUSION Abdominal obesity-associated hyposomatotropism may be involved in the blunted increase in lipolysis during fasting.
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Affiliation(s)
- Madelon M Buijs
- Department of General Internal Medicine, Leiden University Medical Center, Leiden, Netherlands.
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Bernard SF, Fayolle C, Robin JP, Groscolas R. Glycerol and NEFA kinetics in long-term fasting king penguins: phase IIversusphase III. J Exp Biol 2002; 205:2745-54. [PMID: 12151380 DOI: 10.1242/jeb.205.17.2745] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARYIn spontaneously fasting birds such as penguins, below a body mass threshold corresponding to the phase II—phase III transition, a metabolic and hormonal shift occurs and feeding behaviour is stimulated(`refeeding signal'). The major aim of this study was to determine whether a decrease in non-esterified fatty acid (NEFA) release from adipose tissue could be a component of this signal. Lipolytic fluxes and primary triacylglycerol:fatty acid (TAG:FA) cycling were determined in vivoin breeding, fasting king penguins (Aptenodytes patagonicus) using continuous infusions of 2-[3H]glycerol and 1-[14C]palmitate under field conditions. In phase II (after approximately 8 days of fasting, large fat stores, body protein spared, N=8), the rate of appearance (Ra) of glycerol and of NEFA were 5.7±0.8 and 10.5±0.4 μmol kg-1min-1, respectively, and the percentage of primary TAG:FA cycling was 41±7%. In phase III (after approximately 25 days of fasting, fat stores reduced by fourfold, increased body protein catabolism, N=9), Ra glycerol kg-1 body mass remained unchanged,whereas Ra glycerol kg-1 fat mass and Ra NEFA kg-1 body mass were increased by 2.8-fold and 1.5-fold, respectively. Increased Ra glycerol kg-1 fat mass was possibly the result of a 3.5-fold increase in circulating glucagon, the increased Ra NEFA kg-1 body mass being attributable to decreased primary TAG:FA cycling. Thus, triggering of the refeeding signal that redirects the behavior of fasting, incubating penguins from incubation towards the search for food after entrance into phase III cannot be ascribed to a reduction in lipolytic fluxes and NEFA availability.
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Affiliation(s)
- S F Bernard
- Centre d'Ecologie et Physiologie Energétiques, Centre National de la Recherche Scientifique, 67087 Strasbourg, France
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Lange KHW, Lorentsen J, Isaksson F, Simonsen L, Juul A, Christensen NJ, Kjaer M, Bülow J. Subcutaneous abdominal adipose tissue lipolysis during exercise determined by arteriovenous measurements in older women. J Am Geriatr Soc 2002; 50:275-81. [PMID: 12028209 DOI: 10.1046/j.1532-5415.2002.50059.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVES To characterize the lipolytic response in the subcutaneous abdominal adipose tissue in older women to endurance exercise. DESIGN Cross-sectional exercise study. SETTING Exercise laboratory, Copenhagen, Denmark. PARTICIPANTS Seven healthy, older women (mean age +/- standard error = 75 +/- 2 years); weight: 67.8 +/- 4.9 kg; body fat: 40 +/- 3; maximal oxygen uptake (VO2max): 1.43 +/- 0.07 L.min 1). MEASUREMENTS Body composition (dual energy x-ray absorptiometry (DEXA)), maximal oxygen uptake (VO2max, maximal cycling test), lipolytic response to exercise (arterial and adipose tissue venous catheterization at rest and during 60 minutes of continuous cycling at a load corresponding to 60 of VO2max), adipose tissue blood flow (ATBF) (133Xenon (133Xe) washout), oxygen consumption and respiratory exchange ratio during exercise (indirect calorimetry), whole blood glycerol, plasma nonesterified fatty acids (NEFA), lactate, glucose, epinephrine, norepinephrine, insulin, serum growth hormone, and hematocrit. RESULTS Glycerol and NEFA mobilization rates increased by 250 and 180, respectively, from rest to exercise. This was achieved primarily by an increase in veno-arterial differences, because ATBF did not increase significantly. NEFA:glycerol mobilization ratio was about two at rest and remained at that level during exercise, indicating significant local reesterification in both conditions. After an initial decrease, arterial plasma NEFA concentration increased significantly, by 26, indicating that NEFA delivery exceeded muscle uptake. CONCLUSIONS Older women are capable of prompt and substantial increase in subcutaneous abdominal adipose tissue glycerol and NEFA mobilization rates in response to moderate acute endurance exercise. The lipolytic response matches skeletal muscle NEFA uptake, and decreased ability to mobilize fat during exercise is therefore not likely to cause increased fat mass with advancing age.
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Cogo PE, Carnielli VP, Rosso F, Cesarone A, Giordano G, Faggian D, Plebani M, Barreca A, Zacchello F. Protein turnover, lipolysis, and endogenous hormonal secretion in critically ill children. Crit Care Med 2002; 30:65-70. [PMID: 11902289 DOI: 10.1097/00003246-200201000-00010] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
OBJECTIVES The catabolic state is a major contributor to morbidity and mortality of critical illness and may be related to endocrine changes. We studied whether protein and lipid turnover correlate with insulin and growth and thyroid hormone plasma levels in critically ill infants. DESIGN Prospective clinical study. SETTING Pediatric intensive care unit. PATIENTS Twelve critically ill children and ten age-matched controls. MEASUREMENTS We measured lipolysis and protein turnover by infusing albumin-bound uniformly 13C palmitic acid and 2H3-leucine for 3 hrs and 2H5-glycerol for 5 hrs to critically ill infants. Simultaneously, we measured serum growth hormones, insulin, C-peptide, thyroid-stimulating hormone, T4, T3, albumin, retinol binding protein (RBP), and prealbumin. Hormone and serum protein levels were also measured in six children when recovered from critical illness. Ten healthy age-matched children served as controls for hormone serum levels comparison. RESULTS Palmitic acid and glycerol turnover were 5.6 +/- 2.2 micromol/kg/min and 12.2 +/- 7.3 micromol/kg/min, respectively, whereas alpha-ketoisocaproic turnover was 4.9 +/- 2.8 micromol/kg/min. Alpha-ketoisocaproic turnover positively correlated (R = 0.7, p = .03) with duration of pediatric intensive care unit admission and with prealbumin and RBP serum levels (R = 0.9, p = .001). Insulin-like growth factor binding protein (IGFBP)-2 was significantly higher and IGFBP-3 was significantly lower in critically ill children (p = .03 and p = .04 vs. recovery phase, respectively). No other hormonal differences were found. Serum albumin was significantly lower in sick children. We found a significant correlation between prealbumin and RBP and IGFBP-3 (R = 0.6, p = 0.03 and R = 0.6, p = .04, respectively). Alpha-ketoisocaproic turnover positively correlated with IGFBP-1 (R = 0.79, p = .01) and did not correlate with insulin-like growth factor I (R = -0.5, p = .15 [not significant]) No other correlations were found. Lipid turnover measurements did not correlate with any endogenous hormone levels or with duration of critical illness. CONCLUSION Protein turnover but not lipolysis correlated with a persisting critically ill condition, serum prealbumin, RBP, and plasma IGFBP-1.
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Affiliation(s)
- Paola E Cogo
- Department of Pediatrics, Azienda Ospedaliera of Padova, Italy.
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Jensen MD, Chandramouli V, Schumann WC, Ekberg K, Previs SF, Gupta S, Landau BR. Sources of blood glycerol during fasting. Am J Physiol Endocrinol Metab 2001; 281:E998-1004. [PMID: 11595656 DOI: 10.1152/ajpendo.2001.281.5.e998] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To determine the source(s) of blood and very low density lipoprotein (VLDL)-triglyceride glycerol during fasting, four men ingested (2)H(2)O from 14 to 20 h into a 60-h fast to achieve ~0.5% body water enrichment. At 60 h of fasting, glycerol flux was measured using [2-(14)C]glycerol. Blood was taken for measurement of (2)H enrichment at carbon 6 of glucose and at carbon 3 of free glycerol and VLDL-triglyceride glycerol. (2)H enrichment of the 2 hydrogens bound to carbon 3 of VLDL-triglyceride glycerol was 105 +/- 2% of the (2)H enrichment of the 2 hydrogens bound to carbon 6 of glucose, indicating isotopic equilibrium between hepatic glyceraldehyde 3-P and glycerol 3-P. The (2)H enrichment of the 2 hydrogens bound to carbon 3 of free glycerol was 17 +/- 3% of VLDL-triglyceride glycerol, indicating that a significant percentage of free glycerol in blood originated from the hydrolysis of circulating VLDL-triglyceride or a pool of glycerol with similar (2)H enrichment. Glycerol flux was 6.3 +/- 1.1 micromol. kg(-1). min(-1). Glycerol appearing from nonadipose tissue sources was then approximately 1.1 micromol. kg(-1). min(-1). Seven other subjects were fasted for 12, 42, and 60 h. A small percentage of glycerol in the circulation after 12 h of fasting was enriched with (2)H. The enrichment of the 2 hydrogens bound to carbon 3 of free glycerol in the longer periods of fasting was approximately 16% of the enrichment of the 2 hydrogens bound to carbon 6 of glucose. Therefore, as much as 15-20% of systemic glycerol turnover during fasting is not from lipolysis of adipose tissue triglyceride.
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Affiliation(s)
- M D Jensen
- Endocrine Research Unit, Mayo Clinic, Rochester, Minnesota 55905, USA
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Abstract
UNLABELLED Compared with men, women appear to have a decreased sympathetic nervous system (SNS) response to stress. The two manifestations where the sexual dimorphism has been the most pronounced involve the response of the SNS to fluid shifts and fuel metabolism during exercise. The objectives of this study were to investigate whether a similar sexual dimorphism was found in the response to spaceflight. To do so, we compared catecholamine excretion by male and female astronauts from two similar shuttle missions, Spacelab Life Sciences 1 (SLS1, 1991) and 2 (SLS2, 1993) for evidence of sexual dimorphism. To evaluate the variability of the catecholamine response in men, we compared catecholamine excretion from the two SLS missions against the 1996 Life and Microgravity Sciences Mission (LMS) and the 1973 Skylab missions. RESULTS No gender- or mission-dependent changes were found with epinephrine. Separating out the SLS1/2 data by gender shows that norepinephrine excretion was essentially unchanged with spaceflight in women (98 +/- 10%; n = 3) and substantially decreased with the men (41 +/- 9%; n = 4, P < 0.05). Data are a percentage of mean preflight value +/- SE. Comparisons among males demonstrated significant mission effects on norepinephrine excretion. After flight, there was a transient increase in norepinephrine but no evidence of any gender-specific effects. We conclude that norepinephrine excretion during spaceflight is both mission and gender dependent. Men show the greater response, with at least three factors being involved, a response to microgravity, energy balance, and the ratio of carbohydrate to fat in the diet.
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Affiliation(s)
- T P Stein
- Department of Surgery, University of Medicine and Dentistry of New Jersey-School of Osteopathic Medicine, Stratford, NJ 08084, USA.
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Lange KH, Lorentsen J, Isaksson F, Juul A, Rasmussen MH, Christensen NJ, Bülow J, Kjaer M. Endurance training and GH administration in elderly women: effects on abdominal adipose tissue lipolysis. Am J Physiol Endocrinol Metab 2001; 280:E886-97. [PMID: 11350770 DOI: 10.1152/ajpendo.2001.280.6.e886] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In the present study, the effect of endurance training alone and endurance training combined with recombinant human growth hormone (rhGH) administration on subcutaneous abdominal adipose tissue lipolysis was investigated. Sixteen healthy women [age 75 +/- 2 yr (mean +/- SE)] underwent a 12-wk endurance training program on a cycle ergometer. rhGH was administered in a randomized, double-blinded, placebo-controlled design in addition to the training program. Subcutaneous abdominal adipose tissue lipolysis was estimated by means of microdialysis combined with measurements of subcutaneous abdominal adipose tissue blood flow (ATBF; (133)Xe washout). Whole body fat oxidation was estimated simultaneously by indirect calorimetry. Before and after completion of the training program, measurements were performed both at rest and during 60 min of continuous cycling at a workload corresponding to 60% of pretraining peak oxygen uptake. Endurance training alone did not affect subcutaneous abdominal adipose tissue lipolysis either at rest or during exercise, as reflected by identical levels of interstitial adipose tissue glycerol, subcutaneous abdominal ATBF, and plasma nonesterified fatty acids before and after completion of the training program. Similarly, no effect on subcutaneous abdominal adipose tissue lipolysis was observed when combining endurance training with rhGH administration. However, in both the placebo and the GH groups, fat oxidation was significantly increased during exercise performed at the same absolute workload after completion of the training program. We conclude that the changed lipid metabolism during exercise observed after endurance training alone or after endurance training combined with rhGH administration is not due to alterations in subcutaneous abdominal adipose tissue metabolism in elderly women.
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Affiliation(s)
- K H Lange
- Sports Medicine Research Unit, Bispebjerg Hospital, DK-2400 Copenhagen NV, Denmark.
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Li R, Keymeulen B, Gerlo E. Determination of glycerol in plasma by an automated enzymatic spectrophotometric procedure. Clin Chem Lab Med 2001; 39:20-4. [PMID: 11256795 DOI: 10.1515/cclm.2001.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The plasma concentration of glycerol, the backbone of triglycerides and the end product of triacylglycerol breakdown, is considered to reflect lipolysis in adipose tissue. We evaluated an automated enzymatic procedure for the measurement of glycerol in plasma. The assay was linear up to 250 micromol/l. The detection limit was 8 micromol/l. Recovery averaged 94% from spiked plasma and 104% from diluted plasma. An extensive precision study performed according to the guidelines of the National Committee for Clinical Laboratory Standards showed within-run coefficients of variation between 14.8% and 2.6% for concentrations ranging from 28 micromol/l to 164 micromol/l. The reference range for fasting healthy adult men was 14-69 micromol/l. Glycerol levels were significantly correlated with free fatty acid levels. This automated enzymatic method is rapid and reliable, and provides greater sensitivity or convenience than previously described procedures.
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Affiliation(s)
- R Li
- Department of Clinical Chemistry, Vrije Universiteit Brussel, Belgium
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45
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Abstract
Endogenous triacylglycerols represent an important source of fuel for endurance exercise. Triacylglycerol oxidation increases progressively during exercise; the specific rate is determined by energy requirements of working muscles, fatty acid delivery to muscle mitochondria, and the oxidation of other substrates. The catecholamine response to exercise increases lipolysis of adipose tissue triacylglycerols and, presumably, intramuscular triacylglycerols. In addition, increases in adipose tissue and muscle blood flow decrease fatty acid reesterification and facilitate the delivery of released fatty acids to skeletal muscle. Alterations in fatty acid mobilization and the relative use of adipose and intramuscular triacylglycerols during exercise depend, in large part, on degree of fitness and exercise intensity. Compared with untrained persons exercising at the same absolute intensity, persons who have undergone endurance training have greater fat oxidation during exercise without increased lipolysis. Available evidence suggests that the training-induced increase in fat oxidation is due primarily to increased oxidation of non-plasma-derived fatty acids, perhaps from intramuscular triacylglycerol stores. Fat oxidation is lower in high-intensity exercise than in moderate-intensity exercise, in part because of decreased fatty acid delivery to exercising muscles. Parenteral lipid supplementation during high-intensity exercise increases fat oxidation, but the effect of ingesting long-chain or medium-chain triacylglycerols on substrate metabolism during exercise is less clear. This review discusses the relation between fatty acid mobilization and oxidation during exercise and the effect of endurance training, exercise intensity, and lipid supplementation on these responses.
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Affiliation(s)
- J F Horowitz
- Department of Internal Medicine, Washington University School of Medicine, St Louis, MO 63110-1093, USA
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Mora-Rodriguez R, Coyle EF. Effects of plasma epinephrine on fat metabolism during exercise: interactions with exercise intensity. Am J Physiol Endocrinol Metab 2000; 278:E669-76. [PMID: 10751201 DOI: 10.1152/ajpendo.2000.278.4.e669] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study determined the effects of elevated plasma epinephrine on fat metabolism during exercise. On four occasions, seven moderately trained subjects cycled at 25% of peak oxygen consumption (VO(2 peak)) for 60 min. After 15 min of exercise, subjects were intravenously infused with low (0.96 +/- 0.10 nM), moderate (1.92 +/- 0.24 nM), or high (3.44 +/- 0.50 nM) levels (all P < 0.05) of epinephrine to increase plasma epinephrine above control (Con; 0.59 +/- 0.10 nM). During the interval between 35 and 55 min of exercise, lipolysis [i.e., rate of appearance of glycerol] increased above Con (4.9 +/- 0.5 micromol. kg(-1). min(-1)) with low, moderate, and high (6.5 +/- 0.5, 7.1 +/- 0.8, and 10.6 +/- 1.2 micromol. kg(-1). min(-1), respectively; all P < 0.05) levels of epinephrine despite simultaneous increases in plasma insulin. The release of fatty acid into plasma also increased progressively with the graded epinephrine infusions. However, fatty acid oxidation was lower than Con (11.1 +/- 0.8 micromol. kg(-1). min(-1)) during moderate and high levels (8.7 +/- 0.7 and 8.1 +/- 0.9 micromol. kg(-1). min(-1), respectively; P < 0.05). In one additional trial, the same subjects exercised at 45% VO(2 peak) without epinephrine infusion, which produced a plasma epinephrine concentration identical to low levels. However, lipolysis was lower (i.e., 5.5 +/- 0.6 vs. 6.5 +/- 0.5 micromol. kg(-1). min(-1); P < 0.05). In conclusion, elevations in plasma epinephrine concentration during exercise at 25% of VO(2 peak) progressively increase whole body lipolysis but decrease fatty acid oxidation. Last, increasing exercise intensity from 25 to 45% VO(2 peak) attenuates the lipolytic actions of epinephrine.
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Abstract
This paper reviews the general mechanisms by which leptin acts as a regulator of lipid reserves through changes in food intake, energy expenditure and fuel selection, with an emphasis on its direct effects on cellular lipid metabolism. Briefly, when leptin levels increase, food consumption decreases via modulation of hypothalamic neuropeptides. As well, normal decreases in energy expenditures (e.g. with diurnal cycles or reduced caloric intake) do not occur. This is probably caused by an increase in mitochondrial proton leak mediated by leptin via increases in sympathetic nervous system stimulation and thyroid hormone release. The decrease in caloric input coupled with relatively higher energy expenditure, therefore, leads to negative energy balance. Leptin also changes the fuel source from which ATP is generated. Fuel preference switches from carbohydrate (glucose) to lipid (fatty acids). This effect arises through stimulation of triacylglycerol catabolism by leptin. In vitro studies show that leptin is a potent stimulator of lipolysis and fatty acid oxidation in adipocytes and other cell types. Consequently, leptin is also a regulator of cellular triacylglycerol content. Hormonal regulation of leptin, as well as its role in fasting and seasonal weight gain and energy expenditure are also briefly discussed.
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Affiliation(s)
- S P Reidy
- Department of Biology, University of Ottawa, 30 Marie Curie, Ottawa, Ont., Canada
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Ignjatovic V, Ogru E, Heffernan M, Libinaki R, Lim Y, Ng F. Studies on the use of "slimax", a chinese herbal mixture, in the treatment of human obesity. PHARMACEUTICAL BIOLOGY 2000; 38:30-35. [PMID: 21214436 DOI: 10.1076/1388-0209(200001)3811-bft030] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
A phytochemical preparation known as "Slimax" was administered orally to human volunteers for a six week period, using a double-blind experimental method. This preparation is an aqueous extract of the Chinese medicinal plants Hordeum vulgare , Polygonatum multiflorum , Dimocarpus longan , Ligusticum sinense , Lilium brownii and Zingiber officinale . Treatment with Slimax resulted in a significant decrease in parameters such as body weight, waist and hip circumference, and Body Mass Index (BMI), in all subjects tested. The basis of action was shown to be through modification of lipid metabolism, with significant effects on both the accumulation and the release of lipid from adipose tissue. The experimental results indicate a great potential for the use of this herbal preparation in treatment of human obesity.
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Abstract
The purpose of this study was to examine age-related differences in the magnitude of caffeine-induced thermogenesis and the relationship of aerobic fitness, body composition, and hormone and substrate concentrations to the thermic effect of caffeine in younger and older women. Using a placebo-controlled, double-blind study design, 10 older (50 to 67 years) and 10 younger (21 to 31 years) healthy women who were moderate consumers of caffeine (self-reported intake: younger, 139 +/- 152 mg/d; older, 204 +/- 101 mg/d, NS, mean +/- SD) were characterized for fasting plasma glucose, insulin, free fatty acid (FFA), and caffeine levels, energy expenditure, body composition, anthropometry, aerobic fitness, physical activity, and energy intake. Before and after placebo and caffeine ingestion (5 mg/kg fat-free mass [FFM]), the following variables were measured: fasting plasma glucose, insulin, FFA, and energy expenditure, plasma glucose, insulin, and FFA, and energy expenditure in response to placebo and caffeine ingestion. Caffeine ingestion resulted in similar increases in younger and older women for plasma caffeine (younger, 80 +/- 34 to 5,604 +/- 528 ng/mL, P < .01; older, 154 +/- 134 to 5,971 +/- 867 ng/mL, P < .01) and fatty acids (younger, 294 +/- 118 to 798 +/- 248 micromol/L, P < .01; older, 360 +/- 180 to 727 +/- 310 micromol/L, P < .01), whereas plasma insulin and glucose levels remained unchanged from baseline. Energy expenditure increased following caffeine ingestion in both groups (younger, 15.4%, 1.09 +/- 0.14 to 1.24 +/- 0.13 kcal/min, P < .05; older, 7.8%, 0.98 +/- 0.14 to 1.06 +/- 0.12 kcal/min, P < .05), although there was a blunted thermic response in the older versus younger women (older, 6.9 +/- 5 kcal/90 min; younger, 15.5 +/- 7 kcal/90 min, P < .05). In younger women, the thermic response to caffeine was positively correlated with the waist circumference (r = .70, P < .05) and body weight (r = .91; P < .01), whereas aerobic fitness (r = .77; P < .05) was the only significant correlate in older women. In conclusion, older and younger women increase energy expenditure significantly following caffeine ingestion, but older women have a blunted thermic response compared with younger women. Second, the thermic response to caffeine is positively associated with the body weight and waist circumference in younger women, whereas a positive association with aerobic fitness was observed in older women. Thus, the physiologic determinants of the thermic response to caffeine differ among women of different age groups.
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Affiliation(s)
- P J Arciero
- Department of Exercise Science, Skidmore College, Saratoga Springs, NY 12866-1632, USA
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Patterson BW, Zhao G, Elias N, Hachey DL, Klein S. Validation of a new procedure to determine plasma fatty acid concentration and isotopic enrichment. J Lipid Res 1999. [DOI: 10.1016/s0022-2275(20)32435-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
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