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Hall KD, Farooqi IS, Friedman JM, Klein S, Loos RJF, Mangelsdorf DJ, O'Rahilly S, Ravussin E, Redman LM, Ryan DH, Speakman JR, Tobias DK. The energy balance model of obesity: beyond calories in, calories out. Am J Clin Nutr 2022; 115:1243-1254. [PMID: 35134825 PMCID: PMC9071483 DOI: 10.1093/ajcn/nqac031] [Citation(s) in RCA: 120] [Impact Index Per Article: 60.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Accepted: 02/02/2022] [Indexed: 02/06/2023] Open
Abstract
A recent Perspective article described the "carbohydrate-insulin model (CIM)" of obesity, asserting that it "better reflects knowledge on the biology of weight control" as compared with what was described as the "dominant energy balance model (EBM)," which fails to consider "biological mechanisms that promote weight gain." Unfortunately, the Perspective conflated and confused the principle of energy balance, a law of physics that is agnostic as to obesity mechanisms, with the EBM as a theoretical model of obesity that is firmly based on biology. In doing so, the authors presented a false choice between the CIM and a caricature of the EBM that does not reflect modern obesity science. Here, we present a more accurate description of the EBM where the brain is the primary organ responsible for body weight regulation operating mainly below our conscious awareness via complex endocrine, metabolic, and nervous system signals to control food intake in response to the body's dynamic energy needs as well as environmental influences. We also describe the recent history of the CIM and show how the latest "most comprehensive formulation" abandons a formerly central feature that required fat accumulation in adipose tissue to be the primary driver of positive energy balance. As such, the new CIM can be considered a special case of the more comprehensive EBM but with a narrower focus on diets high in glycemic load as the primary factor responsible for common obesity. We review data from a wide variety of studies that address the validity of each model and demonstrate that the EBM is a more robust theory of obesity than the CIM.
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Affiliation(s)
- Kevin D Hall
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health
| | - I Sadaf Farooqi
- Wellcome-MRC Institute of Metabolic Science, University of Cambridge
| | | | - Samuel Klein
- Washington University School of Medicine in St Louis
| | - Ruth J F Loos
- Washington University School of Medicine in St Louis.,Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen
| | | | - Stephen O'Rahilly
- Wellcome-MRC Institute of Metabolic Science, University of Cambridge
| | | | | | | | - John R Speakman
- Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzen, China, and the University of Aberdeen, Aberdeen, United Kingdom
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Basolo A, Magno S, Santini F, Ceccarini G. Ketogenic Diet and Weight Loss: Is There an Effect on Energy Expenditure? Nutrients 2022; 14:nu14091814. [PMID: 35565778 PMCID: PMC9105638 DOI: 10.3390/nu14091814] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Revised: 04/23/2022] [Accepted: 04/24/2022] [Indexed: 02/01/2023] Open
Abstract
A dysregulation between energy intake (EI) and energy expenditure (EE), the two components of the energy balance equation, is one of the mechanisms responsible for the development of obesity. Conservation of energy equilibrium is deemed a dynamic process and alterations of one component (energy intake or energy expenditure) lead to biological and/or behavioral compensatory changes in the counterpart. The interplay between energy demand and caloric intake appears designed to guarantee an adequate fuel supply in variable life contexts. In the past decades, researchers focused their attention on finding efficient strategies to fight the obesity pandemic. The ketogenic or “keto” diet (KD) gained substantial consideration as a potential weight-loss strategy, whereby the concentration of blood ketones (acetoacetate, 3-β-hydroxybutyrate, and acetone) increases as a result of increased fatty acid breakdown and the activity of ketogenic enzymes. It has been hypothesized that during the first phase of KDs when glucose utilization is still prevalent, an increase in EE may occur, due to increased hepatic oxygen consumption for gluconeogenesis and for triglyceride-fatty acid recycling. Later, a decrease in 24-h EE may ensue due to the slowing of gluconeogenesis and increase in fatty acid oxidation, with a reduction of the respiratory quotient and possibly the direct action of additional hormonal signals.
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Carpentier AC. 100 th anniversary of the discovery of insulin perspective: insulin and adipose tissue fatty acid metabolism. Am J Physiol Endocrinol Metab 2021; 320:E653-E670. [PMID: 33522398 DOI: 10.1152/ajpendo.00620.2020] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Insulin inhibits systemic nonesterified fatty acid (NEFA) flux to a greater degree than glucose or any other metabolite. This remarkable effect is mainly due to insulin-mediated inhibition of intracellular triglyceride (TG) lipolysis in adipose tissues and is essential to prevent diabetic ketoacidosis, but also to limit the potential lipotoxic effects of NEFA in lean tissues that contribute to the development of diabetes complications. Insulin also regulates adipose tissue fatty acid esterification, glycerol and TG synthesis, lipogenesis, and possibly oxidation, contributing to the trapping of dietary fatty acids in the postprandial state. Excess NEFA flux at a given insulin level has been used to define in vivo adipose tissue insulin resistance. Adipose tissue insulin resistance defined in this fashion has been associated with several dysmetabolic features and complications of diabetes, but the mechanistic significance of this concept is not fully understood. This review focusses on the in vivo regulation of adipose tissue fatty acid metabolism by insulin and the mechanistic significance of the current definition of adipose tissue insulin resistance. One hundred years after the discovery of insulin and despite decades of investigations, much is still to be understood about the multifaceted in vivo actions of this hormone on adipose tissue fatty acid metabolism.
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Affiliation(s)
- André C Carpentier
- Division of Endocrinology, Department of Medicine, Centre de recherche du CHUS, Université de Sherbrooke, Sherbrooke, Quebec, Canada
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Kitaoka K, Takeuchi M, Tsuboi A, Minato S, Kurata M, Tanaka S, Kazumi T, Fukuo K. Increased Adipose and Muscle Insulin Sensitivity Without Changes in Serum Adiponectin in Young Female Collegiate Athletes. Metab Syndr Relat Disord 2017; 15:246-251. [PMID: 28318384 PMCID: PMC5485219 DOI: 10.1089/met.2017.0011] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Effects of endurance training on adipose insulin sensitivity in association with body composition, circulating adipokines, and markers of inflammation have been studied less in young Asian subjects. METHODS Adipose insulin sensitivity/resistance was compared between 170 female Japanese collegiate athletes and 311 nonathletes (18-24 years), who underwent measurements of serum adipokines, markers of insulin sensitivity, inflammation, and dual-energy X-ray absorptiometry. Two separate subsamples of two groups of women underwent either a 75-gram oral glucose tolerance test or a standardized meal test, but not both. RESULTS As compared with nonathletes, athletes, characterized by higher skeletal muscle mass and lower percentage of body fat (both P < 0.001), had lower adipose insulin resistance (IR) (a product of fasting insulin and nonesterified fatty acid (NEFA) and lower leptin/adiponectin ratio (both P < 0.001). Although athletes had lower postmeal/postglucose insulinemia (P = 0.009 and 0.01, respectively), the two groups did not differ in postmeal percentage NEFA suppression and postmeal/postglucose glycemia, suggesting increased insulin sensitivity in adipose tissue and skeletal muscle, respectively. Serum leptin (P < 0.001) and tumor necrosis factor-α (P = 0.01) were lower in athletes, whereas adiponectin and homeostasis model assessment IR did not differ. CONCLUSIONS Endurance training was associated with increased insulin sensitivity in adipose tissue as well as skeletal muscle without changes in circulating adiponectin even in young, normal-weight Japanese women.
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Affiliation(s)
- Kaori Kitaoka
- 1 Research Institute for Nutrition Sciences, Mukogawa Women's University , Nishinomiya, Japan .,2 Department of Welfare and Nutrition, Faculty of Health Welfare, Kansai University of Welfare Sciences , Osaka, Japan
| | - Mika Takeuchi
- 3 Department of Food Sciences and Nutrition, School of Human Environmental Sciences, Mukogawa Women's University , Nishinomiya, Japan
| | - Ayaka Tsuboi
- 1 Research Institute for Nutrition Sciences, Mukogawa Women's University , Nishinomiya, Japan
| | - Satomi Minato
- 1 Research Institute for Nutrition Sciences, Mukogawa Women's University , Nishinomiya, Japan .,4 Graduate School of Human Science and Environment, University of Hyogo , Himeji, Japan
| | - Miki Kurata
- 1 Research Institute for Nutrition Sciences, Mukogawa Women's University , Nishinomiya, Japan .,3 Department of Food Sciences and Nutrition, School of Human Environmental Sciences, Mukogawa Women's University , Nishinomiya, Japan
| | - Shigehiro Tanaka
- 5 Department of Health and Sports Sciences, Mukogawa Women's University , Nishinomiya, Japan
| | - Tsutomu Kazumi
- 1 Research Institute for Nutrition Sciences, Mukogawa Women's University , Nishinomiya, Japan .,6 Division of Diabetes, Department of Medicine, Kohnan Kakogawa Hospital , Kakogawa, Japan
| | - Keisuke Fukuo
- 1 Research Institute for Nutrition Sciences, Mukogawa Women's University , Nishinomiya, Japan .,3 Department of Food Sciences and Nutrition, School of Human Environmental Sciences, Mukogawa Women's University , Nishinomiya, Japan
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Hall KD, Chen KY, Guo J, Lam YY, Leibel RL, Mayer LE, Reitman ML, Rosenbaum M, Smith SR, Walsh BT, Ravussin E. Energy expenditure and body composition changes after an isocaloric ketogenic diet in overweight and obese men. Am J Clin Nutr 2016; 104:324-33. [PMID: 27385608 PMCID: PMC4962163 DOI: 10.3945/ajcn.116.133561] [Citation(s) in RCA: 215] [Impact Index Per Article: 26.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 06/06/2016] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND The carbohydrate-insulin model of obesity posits that habitual consumption of a high-carbohydrate diet sequesters fat within adipose tissue because of hyperinsulinemia and results in adaptive suppression of energy expenditure (EE). Therefore, isocaloric exchange of dietary carbohydrate for fat is predicted to result in increased EE, increased fat oxidation, and loss of body fat. In contrast, a more conventional view that "a calorie is a calorie" predicts that isocaloric variations in dietary carbohydrate and fat will have no physiologically important effects on EE or body fat. OBJECTIVE We investigated whether an isocaloric low-carbohydrate ketogenic diet (KD) is associated with changes in EE, respiratory quotient (RQ), and body composition. DESIGN Seventeen overweight or obese men were admitted to metabolic wards, where they consumed a high-carbohydrate baseline diet (BD) for 4 wk followed by 4 wk of an isocaloric KD with clamped protein. Subjects spent 2 consecutive days each week residing in metabolic chambers to measure changes in EE (EEchamber), sleeping EE (SEE), and RQ. Body composition changes were measured by dual-energy X-ray absorptiometry. Average EE during the final 2 wk of the BD and KD periods was measured by doubly labeled water (EEDLW). RESULTS Subjects lost weight and body fat throughout the study corresponding to an overall negative energy balance of ∼300 kcal/d. Compared with BD, the KD coincided with increased EEchamber (57 ± 13 kcal/d, P = 0.0004) and SEE (89 ± 14 kcal/d, P < 0.0001) and decreased RQ (-0.111 ± 0.003, P < 0.0001). EEDLW increased by 151 ± 63 kcal/d (P = 0.03). Body fat loss slowed during the KD and coincided with increased protein utilization and loss of fat-free mass. CONCLUSION The isocaloric KD was not accompanied by increased body fat loss but was associated with relatively small increases in EE that were near the limits of detection with the use of state-of-the-art technology. This trial was registered at clinicaltrials.gov as NCT01967563.
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Affiliation(s)
- Kevin D Hall
- National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD;
| | - Kong Y Chen
- National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD
| | - Juen Guo
- National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD
| | - Yan Y Lam
- Pennington Biomedical Research Center, Baton Rouge, LA
| | | | | | - Marc L Reitman
- National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD
| | | | - Steven R Smith
- The Translational Research Institute for Metabolism and Diabetes, Orlando, FL
| | | | - Eric Ravussin
- Pennington Biomedical Research Center, Baton Rouge, LA
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Umpleby AM. HORMONE MEASUREMENT GUIDELINES: Tracing lipid metabolism: the value of stable isotopes. J Endocrinol 2015; 226:G1-10. [PMID: 26047888 DOI: 10.1530/joe-14-0610] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 06/04/2015] [Indexed: 01/14/2023]
Abstract
Labelling molecules with stable isotopes to create tracers has become a gold-standard method to study the metabolism of lipids and lipoproteins in humans. There are a range of techniques which use stable isotopes to measure fatty acid flux and oxidation, hepatic fatty synthesis, cholesterol absorption and synthesis and lipoprotein metabolism in humans. Stable isotope tracers are safe to use, enabling repeated studies to be undertaken and allowing studies to be undertaken in children and pregnant women. This review provides details of the most appropriate tracers to use, the techniques which have been developed and validated for measuring different aspects of lipid metabolism and some of the limitations of the methodology.
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Affiliation(s)
- A Margot Umpleby
- Diabetes and Metabolic MedicineFaculty of Health and Metabolic Sciences, University of Surrey, Leggett Building, Daphne Jackson Road, Manor Park, Guildford GU2 7WG, UK
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Abreu-Vieira G, Hagberg CE, Spalding KL, Cannon B, Nedergaard J. Adrenergically stimulated blood flow in brown adipose tissue is not dependent on thermogenesis. Am J Physiol Endocrinol Metab 2015; 308:E822-9. [PMID: 25738783 DOI: 10.1152/ajpendo.00494.2014] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Accepted: 02/26/2015] [Indexed: 01/24/2023]
Abstract
Brown adipose tissue (BAT) thermogenesis relies on blood flow to be supplied with nutrients and oxygen and for the distribution of the generated heat to the rest of the body. Therefore, it is fundamental to understand the mechanisms by which blood flow is regulated and its relation to thermogenesis. Here, we present high-resolution laser-Doppler imaging (HR-LDR) as a novel method for noninvasive in vivo measurement of BAT blood flow in mice. Using HR-LDR, we found that norepinephrine stimulation increases BAT blood flow in a dose-dependent manner and that this response is profoundly modulated by environmental temperature acclimation. Surprisingly, we found that mice lacking uncoupling protein 1 (UCP1) have fully preserved BAT blood flow response to norepinephrine despite failing to perform thermogenesis. BAT blood flow was not directly correlated to systemic glycemia, but glucose injections could transiently increase tissue perfusion. Inguinal white adipose tissue, also known as a brite/beige adipose tissue, was also sensitive to cold acclimation and similarly increased blood flow in response to norepinephrine. In conclusion, using a novel noninvasive method to detect BAT perfusion, we demonstrate that adrenergically stimulated BAT blood flow is qualitatively and quantitatively fully independent of thermogenesis, and therefore, it is not a reliable parameter for the estimation of BAT activation and heat generation.
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Affiliation(s)
- Gustavo Abreu-Vieira
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden; and
| | - Carolina E Hagberg
- Department of Cell and Molecular Biology, Karolinska Institute, Stockholm, Sweden
| | - Kirsty L Spalding
- Department of Cell and Molecular Biology, Karolinska Institute, Stockholm, Sweden
| | - Barbara Cannon
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden; and
| | - Jan Nedergaard
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden; and
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Ramos-Roman MA, Lapidot SA, Phair RD, Parks EJ. Insulin activation of plasma nonesterified fatty acid uptake in metabolic syndrome. Arterioscler Thromb Vasc Biol 2012; 32:1799-808. [PMID: 22723441 DOI: 10.1161/atvbaha.112.250019] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
OBJECTIVE Insulin control of fatty acid metabolism has long been deemed dominated by suppression of adipose lipolysis. The goal of the present study was to test the hypothesis that this single role of insulin is insufficient to explain observed fatty acid dynamics. METHODS AND RESULTS Fatty acid kinetics were measured during a meal tolerance test and insulin sensitivity assessed by intravenous glucose tolerance test in overweight human subjects (n=15; body mass index, 35.8 ± 7.1 kg/m(2)). Non-steady state tracer kinetic models were formulated and tested using ProcessDB software. Suppression of adipose fatty acid release, by itself, could not account for postprandial nonesterified fatty acid concentration changes, but adipose suppression combined with insulin activation of fatty acid uptake was consistent with the measured data. The observed insulin K(m) for nonesterified fatty acid uptake was inversely correlated with both insulin sensitivity of glucose uptake (intravenous glucose tolerance test insulin sensitivity; r=-0.626; P=0.01) and whole body fat oxidation after the meal (r=-0.538; P=0.05). CONCLUSIONS These results support insulin regulation of fatty acid turnover by both release and uptake mechanisms. Activation of fatty acid uptake is consistent with the human data, has mechanistic precedent in cell culture, and highlights a new potential target for therapies aimed at improving the control of fatty acid metabolism in insulin-resistant disease states.
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Affiliation(s)
- Maria A Ramos-Roman
- Department of Internal Medicine, UT Southwestern Medical Center, Dallas, TX 75390-9052, USA
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Lambadiari V, Mitrou P, Maratou E, Raptis A, Raptis SA, Dimitriadis G. Increases in muscle blood flow after a mixed meal are impaired at all stages of type 2 diabetes. Clin Endocrinol (Oxf) 2012; 76:825-30. [PMID: 21950653 DOI: 10.1111/j.1365-2265.2011.04211.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVE In type 2 diabetes, although the impairment of postprandial muscle blood flow response is well established, information on the effect of this impairment on glucose uptake and lipid metabolism is controversial. DESIGN Postprandial forearm blood flow responses and metabolic parameters were assessed in a cross-sectional study of subjects at various stages of insulin resistance. PATIENTS Eleven healthy subjects (CONTROLS), 11 first-degree relatives of type-2 diabetics (RELATIVES), 10 patients with impaired glucose tolerance (IGT), 10 diabetic patients with postprandial hyperglycaemia (DMA), and 13 diabetic patients with both fasting and postprandial hyperglycaemia (DMB). MEASUREMENTS All subjects received a meal. Blood was drawn from a forearm deep vein and the radial artery at specific time-points during a period of 360 min for measurements of glucose, insulin, triglycerides and nonesterified-fatty acids. Forearm muscle blood flow was measured with strain-gauge plethysmography. Glucose uptake and ISI Index were calculated. RESULTS Peak-baseline muscle blood flow was higher in CONTROLS (3.32 ± 0.4) than in RELATIVES (0.53 ± 0.29), IGT (0.82 ± 0.2), DMA (1.44 ± 0.34), DMB (1.23 ± 0.35 ml/min/100 ml tissue), P < 0.001. Glucose uptake (AUC(0-360,) μmol/100 ml tissue) was higher in CONTROLS (1023 ± 132) than in RELATIVES (488 ± 42), IGT (458 ± 43), DMA (347 ± 63), DMB (543 ± 53), P < 0.001. ISI index, postprandial triglycerides and nonesterified-fatty acids behaved in a similar way. Peak-baseline muscle blood flow correlated positively with glucose uptake (r = 0.440, P = 0.001) and ISI index (r = 0.397, P = 0.003), and negatively with postprandial triglycerides (r = -0.434, P = 0.001) and nonesterified-fatty acids (r = -0.370, P = 0.005). CONCLUSIONS These results suggest that increase in muscle blood flow after a meal is impaired at all stages of type-2 diabetes. This defect influences glucose uptake and is associated with impaired lipid metabolism in the postprandial state.
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Affiliation(s)
- Vaia Lambadiari
- 2nd Department of Internal Medicine, Research Institute and Diabetes Center, Attikon University Hospital, Athens University Medical School, Athens, Greece
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Sotornik R, Brassard P, Martin E, Yale P, Carpentier AC, Ardilouze JL. Update on adipose tissue blood flow regulation. Am J Physiol Endocrinol Metab 2012; 302:E1157-70. [PMID: 22318953 DOI: 10.1152/ajpendo.00351.2011] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
According to Fick's principle, any metabolic or hormonal exchange through a given tissue depends on the product of the blood flow to that tissue and the arteriovenous difference. The proper function of adipose tissue relies on adequate adipose tissue blood flow (ATBF), which determines the influx and efflux of metabolites as well as regulatory endocrine signals. Adequate functioning of adipose tissue in intermediary metabolism requires finely tuned perfusion. Because metabolic and vascular processes are so tightly interconnected, any disruption in one will necessarily impact the other. Although altered ATBF is one consequence of expanding fat tissue, it may also aggravate the negative impacts of obesity on the body's metabolic milieu. This review attempts to summarize the current state of knowledge on adipose tissue vascular bed behavior under physiological conditions and the various factors that contribute to its regulation as well as the possible participation of altered ATBF in the pathophysiology of metabolic syndrome.
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Affiliation(s)
- Richard Sotornik
- Diabetes and Metabolism Research Group, Division of Endocrinology, Department of Medicine, Centre Hospitalier, Universitaire de Sherbrooke, Université de Sherbrooke, Sherbrooke, Quebec, Canada
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Frayn KN, Humphreys SM. Metabolic characteristics of human subcutaneous abdominal adipose tissue after overnight fast. Am J Physiol Endocrinol Metab 2012; 302:E468-75. [PMID: 22167523 PMCID: PMC3287351 DOI: 10.1152/ajpendo.00527.2011] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Subcutaneous abdominal adipose tissue is one of the largest fat depots and contributes the major proportion of circulating nonesterified fatty acids (NEFA). Little is known about aspects of human adipose tissue metabolism in vivo other than lipolysis. Here we collated data from 331 experiments in 255 healthy volunteers over a 23-year period, in which subcutaneous abdominal adipose tissue metabolism was studied by measurements of arterio-venous differences after an overnight fast. NEFA and glycerol were released in a ratio of 2.7:1, different (P < 0.001) from the value of 3.0 that would indicate no fatty acid re-esterification. Fatty acid re-esterification was 10.2 ± 1.4%. Extraction of triacylglycerol (TG) (fractional extraction 5.7 ± 0.4%) indicated intravascular lipolysis by lipoprotein lipase, and this contributed 21 ± 3% of the glycerol released. Glucose uptake (fractional extraction 2.6 ± 0.3%) was partitioned around 20-25% for provision of glycerol 3-phosphate and 30% into lactate production. There was release of lactate and pyruvate, with extraction of the ketone bodies 3-hydroxybutyrate and acetoacetate, although these were small numerically compared with TG and glucose uptake. NEFA release (expressed per 100 g tissue) correlated inversely with measures of fat mass (e.g., with BMI, r(s) = -0.24, P < 0.001). We examined within-person variability. Systemic NEFA concentrations, NEFA release, fatty acid re-esterification, and adipose tissue blood flow were all more consistent within than between individuals. This picture of human adipose tissue metabolism in the fasted state should contribute to a greater understanding of adipose tissue physiology and pathophysiology.
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Affiliation(s)
- Keith N Frayn
- Oxford Centre for Diabetes, Endocrinology & Metabolism, Churchill Hospital, Oxford OX3 7LJ, UK.
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Identification of diacylglycerol acyltransferase inhibitors from Rosa centifolia petals. Lipids 2011; 46:691-700. [PMID: 21538210 DOI: 10.1007/s11745-011-3559-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2010] [Accepted: 03/14/2011] [Indexed: 01/12/2023]
Abstract
Diacylglycerol acyltransferase (DGAT) catalyzes the final step of triacylglycerol (TAG) synthesis, and is considered as a potential target to control hypertriglyceridemia or other metabolic disorders. In this study, we found that the extract of rose petals suppressed TAG synthesis in cultured cells, and that the extract showed DGAT inhibitory action in a dose-dependent manner. Fractionation of the rose extract revealed that the DGAT inhibitory substances in the extract were ellagitannins; among them rugosin B, and D, and eusupinin A inhibited DGAT activity by 96, 82, and 84% respectively, at 10 μM. These substances did not inhibit the activities of other hepatic microsomal enzymes, glucose-6-phosphatase and HMG-CoA reductase, or pancreatic lipase, suggesting that ellagitannins inhibit DGAT preferentially. In an oral fat load test using mice, postprandial plasma TAG increase was suppressed by rose extract; TAG levels 2 h after the fat load were significantly lower in mice administered a fat emulsion containing rose extract than in control mice (446.3 ± 33.1 vs 345.3 ± 25.0 mg/dL, control vs rose extract group; P < 0.05). These results suggest that rose ellagitannins or rose extract could be beneficial in controlling lipid metabolism and used to improve metabolic disorders.
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Asmar M, Tangaa W, Madsbad S, Hare K, Astrup A, Flint A, Bülow J, Holst JJ. On the role of glucose-dependent insulintropic polypeptide in postprandial metabolism in humans. Am J Physiol Endocrinol Metab 2010; 298:E614-21. [PMID: 19996386 DOI: 10.1152/ajpendo.00639.2009] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We investigated the role of glucose-dependent insulintropic polypeptide (GIP) in the regulation of gastric emptying (GE), appetite, energy intake (EI), energy expenditure (EE), plasma levels of triglycerides (TAG), and free fatty acids (FFA) in humans. First, 20 healthy males received intravenous infusion of GIP (0.8 pmol.kg(-1).min(-1)) or saline for 300 min during and after a fixed meal (protocol 1). GE was measured using paracetamol, appetite sensations using visual analog scales, EE using indirect calorimetry, and EI during a subsequent ad libitum meal (at 300 min). Next, 10 healthy males received intravenous infusions of Intralipid, glucose, or Intralipid plus glucose, with and without GIP (1.5 pmol.kg(-1).min(-1)) for 300 min (protocol 2). In protocol 1, GIP did not have any effect on GE, EI, EE, removal of TAG, or FFA and did not influence the subjective feeling of hunger, satiety, fullness or prospective food consumption compared with saline. In protocol 2, no difference was seen in the plasma TAG on Intralipid + GIP/saline and Intralipid + glucose + GIP/saline days. FFA concentrations were lower on Intralipid + glucose + GIP/saline days (P < 0.05) compared with Intralipid + GIP/saline days and on Intralipid + GIP day (P < 0.004) compared with Intralipid + saline day. Insulin increased on all GIP days compared with saline days (P < 0.05). In conclusion, while confirming its insulinotropic effects, these data suggest that GIP does not affect GE, appetite, energy intake, EE, or the clearance rate of the applied TAG formulation in humans. However, both insulin and GIP lower post-Intralipid FFA concentration, GIP probably via stimulation of insulin secretion, increasing FFA reesterification.
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Affiliation(s)
- Meena Asmar
- Department of Endocrinology, Hvidovre Hospital, Denmark
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Gu L, Zhang GF, Kombu RS, Allen F, Kutz G, Brewer WU, Roe CR, Brunengraber H. Parenteral and enteral metabolism of anaplerotic triheptanoin in normal rats. II. Effects on lipolysis, glucose production, and liver acyl-CoA profile. Am J Physiol Endocrinol Metab 2010; 298:E362-71. [PMID: 19903863 PMCID: PMC2822475 DOI: 10.1152/ajpendo.00384.2009] [Citation(s) in RCA: 41] [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
The anaplerotic odd-medium-chain triglyceride triheptanoin is used in clinical trials for the chronic dietary treatment of patients with long-chain fatty acid oxidation disorders. We previously showed (Kinman RP, Kasumov T, Jobbins KA, Thomas KR, Adams JE, Brunengraber LN, Kutz G, Brewer WU, Roe CR, Brunengraber H. Am J Physiol Endocrinol Metab 291: E860-E866, 2006) that the intravenous infusion of triheptanoin increases lipolysis traced by the turnover of glycerol. In this study, we tested whether lipolysis induced by triheptanoin infusion is accompanied by the potentially harmful release of long-chain fatty acids. Rats were infused with heptanoate +/- glycerol or triheptanoin. Intravenous infusion of triheptanoin at 40% of caloric requirement markedly increased glycerol endogenous R(a) but not oleate endogenous R(a). Thus, the activation of lipolysis was balanced by fatty acid reesterification in the same cells. The liver acyl-CoA profile showed the accumulation of intermediates of heptanoate beta-oxidation and C(5)-ketogenesis and a decrease in free CoA but no evidence of metabolic perturbation of liver metabolism such as propionyl overload. Our data suggest that triheptanoin, administered either intravenously or intraduodenally, could be used for intensive care and nutritional support of metabolically decompensated long-chain fatty acid oxidation disorders.
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Affiliation(s)
- Lei Gu
- Department of Nutrition, Case Western Reserve University, Cleveland, Ohio 44106-4954, USA
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15
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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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16
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Carpentier AC. Postprandial fatty acid metabolism in the development of lipotoxicity and type 2 diabetes. DIABETES & METABOLISM 2008; 34:97-107. [DOI: 10.1016/j.diabet.2007.10.009] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2007] [Revised: 10/19/2007] [Accepted: 10/26/2007] [Indexed: 12/31/2022]
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17
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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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18
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Gormsen LC, Nielsen C, Gjedsted J, Gjedde S, Vestergaard ET, Christiansen JS, Jørgensen JO, Møller N. Effects of free fatty acids, growth hormone and growth hormone receptor blockade on serum ghrelin levels in humans. Clin Endocrinol (Oxf) 2007; 66:641-5. [PMID: 17492951 DOI: 10.1111/j.1365-2265.2007.02786.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND Circulating ghrelin levels are reported to be suppressed by insulin, GH and free fatty acids (FFAs). However, insulin, GH and FFA levels are all interdependent, and it is therefore difficult to delineate their independent effects on ghrelin secretion. OBJECTIVE To isolate and define the impact of GH, GH receptor (GHR) blockade and intravenous FFA infusion on total circulating ghrelin levels during a hyperinsulinaemic glucose clamp with identical insulin levels. DESIGN In a randomized design, eight healthy males each underwent an 8-h hyperinsulinaemic glucose clamp on four occasions together with either: (1) control (saline), (2) intravenous FFA infusion (intralipid/heparin infusion 4 h), (3) a GH bolus (0.5 mg i.v.) or (4) GHR blockade (pegvisomant, 30 mg s.c.). RESULTS Hyperinsulinaemia per se resulted in a decrease in ghrelin concentrations of about 15%. During FFA exposure, ghrelin levels were suppressed by about 22% when compared with saline [area under the curve (AUC)(ghrelin0-240) 122.7 +/- 10.9 vs. 97.6 +/- 13.4 pg/ml/min, P = 0.001], followed by a rebound increase upon discontinuation of the infusion. Furthermore, average ghrelin concentration (AUC(ghrelin)) was significantly inversely correlated to average FFA levels (AUC(FFA)) (r = -0.33, P < 0.05). Neither GH administration nor GHR blockade resulted in significant alterations in total ghrelin levels in the presence of unaltered insulin and FFA levels. CONCLUSIONS Elevation of FFAs by means of an intravenous infusion acutely suppresses ghrelin levels, whereas GH administration and GHR blockade have no detectable effect on ghrelin concentration when insulin and FFA levels are kept fixed.
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Affiliation(s)
- Lars C Gormsen
- Department M (Endocrinology and Diabetes), Aarhus University Hospital, Aarhus C, Denmark.
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19
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Ryber L, Obrink K, Houe N, Frystyk J, Jørgensen JOL. Serum ghrelin levels are suppressed in hypopituitary patients following insulin-induced hypoglycaemia irrespective of GH status. Clin Endocrinol (Oxf) 2006; 65:210-4. [PMID: 16886962 DOI: 10.1111/j.1365-2265.2006.02575.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVE Circulating ghrelin is suppressed during insulin-induced hypoglycaemia in healthy subjects, but it is unknown whether this is determined by feedback inhibition from counter-regulatory hormones. We therefore investigated the impact of GH and cortisol on ghrelin secretion during insulin-induced hypoglycaemia. DESIGN Serum levels of ghrelin, GH, and cortisol were measured in 41 adult patients with suspected hypopituitarism during insulin-induced hypoglycaemia. Based on their peak GH response (cut-off level: 3 microg/l), the patients were divided into a GH-sufficient group (GHS) and a GH-deficient group (GHD). RESULTS The GHS patients (n = 16) were younger (P < 0.01), had lower baseline cortisol levels [255 +/- 37 vs. 372 +/- 38 nmol/l (P = 0.04)], and tended to have a lower body mass index (P = 0.09) as compared to GHD patients (n = 25). By definition, peak GH (microg/l) was higher in GHS patients [15.0 +/- 1.8 vs. 1.0 +/- 0.2 (P < 0.0001)]. The increase in serum cortisol during the ITT (insulin-tolerance test) was higher and occurred later in GHS patients [Cmax (nmol/l): 561 +/- 41 vs. 412 +/- 50 (P = 0.04); Tmax (minutes): 65 +/- 5 vs. 49 +/- 5 (P = 0.03)]. Serum ghrelin levels changed significantly with time during ITT in both groups (P < 0.0001), characterized by a moderate decline during the initial 50-60 min and a return to baseline after 2 h. No significant differences were recorded in AUCghrelin during the ITT between the two groups. No gender differences in ghrelin levels were recorded. CONCLUSIONS (i) Like in healthy subjects serum ghrelin levels are suppressed during an ITT in patients with suspected hypopituitarism. (ii) The suppression of ghrelin was similar in GHD and GHS subjects and was not determined by cortisol. (iii) We hypothesize that insulin rather than hypoglycaemia accounts for ghrelin suppression during an ITT.
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Affiliation(s)
- Louise Ryber
- Medical Department M and Medical Research Laboratories, Clinical Institute, Aarhus University Hospital, Aarhus, Denmark
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20
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Goossens GH, McQuaid SE, Dennis AL, van Baak MA, Blaak EE, Frayn KN, Saris WHM, Karpe F. Angiotensin II: a major regulator of subcutaneous adipose tissue blood flow in humans. J Physiol 2006; 571:451-60. [PMID: 16396927 PMCID: PMC1796792 DOI: 10.1113/jphysiol.2005.101352] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
We investigated the functional roles of circulating and locally produced angiotensin II (Ang II) in fasting and postprandial adipose tissue blood flow (ATBF) regulation and examined the interaction between Ang II and nitric oxide (NO) in ATBF regulation. Local effects of the pharmacological agents (or contralateral saline) on ATBF, measured with 133Xe wash-out, were assessed using the recently developed microinfusion technique. Fasting and postprandial (75 g glucose challenge) ATBF regulation was investigated in nine lean healthy subjects (age, 29 +/- 3 years; BMI, 23.4 +/- 0.7 kg m(-2)) using local Ang II stimulation, Ang II type 1 (AT1) receptor blockade, and angiotensin-converting enzyme (ACE) inhibition. Furthermore, NO synthase (NOS) blockade alone and in combination with AT1 receptor blockade was used to examine the interaction between Ang II and NO. Ang II induced a dose-dependent decrease in ATBF (10(-9)m: -16%, P = 0.04; 10(-7)m: -33%, P < 0.01; 10(-5)m: -53%P < 0.01). Fasting ATBF was not affected by ACE inhibition, but was increased by approximately 55% (P < 0.01) by AT(1) receptor blockade. NOS blockade induced a approximately 30% (P = 0.001) decrease in fasting ATBF. Combined AT1 receptor and NOS blockade increased ATBF by approximately 40% (P = 0.003). ACE inhibition and AT1 receptor blockade did not affect the postprandial increase in ATBF. We therefore conclude that circulating Ang II is a major regulator of fasting ATBF, and a major proportion of the Ang II-induced decrease in ATBF is NO independent. Locally produced Ang II does not appear to regulate ATBF. Ang II appears to have no major effect on the postprandial enhancement of ATBF.
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Affiliation(s)
- G H Goossens
- Department of Human Biology, Nutrition and Toxicology Research Institute Maastricht (NUTRIM), Maastricht University, Maastricht, The Netherlands.
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21
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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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22
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Ravikumar B, Carey PE, Snaar JEM, Deelchand DK, Cook DB, Neely RDG, English PT, Firbank MJ, Morris PG, Taylor R. Real-time assessment of postprandial fat storage in liver and skeletal muscle in health and type 2 diabetes. Am J Physiol Endocrinol Metab 2005; 288:E789-97. [PMID: 15572652 DOI: 10.1152/ajpendo.00557.2004] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Liver and skeletal muscle triglyceride stores are elevated in type 2 diabetes and correlate with insulin resistance. As postprandial handling of dietary fat may be a critical determinant of tissue triglyceride levels, we quantified postprandial fat storage in normal and type 2 diabetes subjects. Healthy volunteers (n = 8) and diet-controlled type 2 diabetes subjects (n = 12) were studied using a novel 13C magnetic resonance spectroscopy protocol to measure the postprandial increment in liver and skeletal muscle triglyceride following ingestion of 13C-labeled fatty acids given with a standard mixed meal. The postprandial increment in hepatic triglyceride was rapid in both groups (peak increment controls: +7.3 +/- 1.5 mmol/l at 6 h, P = 0.002; peak increment diabetics: +10.8 +/- 3.4 mmol/l at 4 h, P = 0.009). The mean postprandial incremental AUC of hepatic 13C enrichment between the first and second meals (0 and 4 h) was significantly higher in the diabetes group (6.1 +/- 1.4 vs. 1.7 +/- 0.6 mmol x l(-1) x h(-1), P = 0.019). Postprandial increment in skeletal muscle triglyceride in the control group was small compared with the diabetic group, the mean 24-h postprandial incremental AUC being 0.2 +/- 0.3 vs. 1.7 +/- 0.4 mmol x l(-1) x h(-1) (P = 0.009). We conclude that the postprandial uptake of fatty acids by liver and skeletal muscle is increased in type 2 diabetes and may underlie the elevated tissue triglyceride stores and consequent insulin resistance.
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Affiliation(s)
- B Ravikumar
- School of Clinical Medical Sciences (Diabete)s Medical School, University of Newcastle, UK
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23
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Schenk S, Cook JN, Kaufman AE, Horowitz JF. Postexercise insulin sensitivity is not impaired after an overnight lipid infusion. Am J Physiol Endocrinol Metab 2005; 288:E519-25. [PMID: 15522993 DOI: 10.1152/ajpendo.00401.2004] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
High plasma fatty acid availability and a positive energy balance in sedentary individuals reduce insulin sensitivity. This study's purpose was to determine whether high plasma fatty acid availability and systemic caloric excess after exercise also impair insulin sensitivity. On two separate occasions, seven nonobese women performed 90 min of exercise at approximately 65% peak oxygen uptake. In one trial, a lipid + heparin emulsion (Lipid) was infused overnight to increase plasma fatty acid availability. In the other trial, saline was infused as control. The next morning, a muscle biopsy was taken to measure muscle glycogen and intramuscular triglyceride (IMTG) concentrations. Three hours after the overnight infusion was stopped, insulin sensitivity was assessed with an intravenous glucose tolerance test, using minimal model analysis (Si). During the overnight infusions, plasma fatty acid concentration was approximately fourfold higher [means (SD): 0.84 (0.36) vs. 0.22 (0.09) mmol/l; P = 0.003], and the next morning IMTG concentration was approximately 30% greater [49.2 (6.6) vs. 38.3 (7.7) mmol/kg dry wt; P = 0.036] in Lipid compared with saline. However, muscle glycogen concentration was not different between trials (P = 0.82). Lipid caused a 24-h surplus of approximately 1100 kcal above energy balance (P = 0.00001), whereas energy balance was maintained in saline. Despite these differences in fatty acid and energy availability, Si the morning after exercise was not different between trials (P = 0.72). Thus insulin sensitivity the morning after a single exercise session was not reduced despite overnight exposure to a fourfold increase in plasma fatty acid concentration, elevated IMTG concentration, and systemic delivery of approximately 1,100-kcal excess.
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Affiliation(s)
- Simon Schenk
- Substrate Metabolism Laboratory, Division of Kinesiology, The Univ. of Michigan, 401 Washtenaw Ave., Ann Arbor, MI 48109-2214, USA
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24
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Tan GD, Fielding BA, Currie JM, Humphreys SM, Désage M, Frayn KN, Laville M, Vidal H, Karpe F. The effects of rosiglitazone on fatty acid and triglyceride metabolism in type 2 diabetes. Diabetologia 2005; 48:83-95. [PMID: 15619071 DOI: 10.1007/s00125-004-1619-9] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2004] [Accepted: 11/18/2004] [Indexed: 11/30/2022]
Abstract
AIMS/HYPOTHESIS We investigated the effects of rosiglitazone on NEFA and triglyceride metabolism in type 2 diabetes. METHODS In a double-blind, placebo-controlled, cross-over study of rosiglitazone in diet-treated type 2 diabetic subjects, we measured arteriovenous differences and tissue blood flow in forearm muscle and subcutaneous abdominal adipose tissue, used stable isotope techniques, and analysed gene expression. Responses to a mixed meal containing [1,1,1-(13)C]tripalmitin were assessed. RESULTS Rosiglitazone induced insulin sensitisation without altering fasting NEFA concentrations (-6.6%, p=0.16). Postprandial NEFA concentrations were lowered by rosiglitazone compared with placebo (-21%, p=0.04). Adipose tissue NEFA release was not decreased in the fasting state by rosiglitazone treatment (+24%, p=0.17) and was associated with an increased fasting hormone-sensitive lipase rate of action (+118%, p=0.01). Postprandial triglyceride concentrations were decreased by rosiglitazone treatment (-26%, p<0.01) despite unchanged fasting concentrations. Rosiglitazone did not change concentrations of triglyceride-rich lipoprotein remnants. Adipose tissue blood flow increased with rosiglitazone (+32%, p=0.03). Postprandial triglyceride [(13)C]palmitic acid concentrations were unchanged, whilst NEFA [(13)C]palmitic acid concentrations were decreased (p=0.04). In muscle, hexokinase II mRNA expression was increased by rosiglitazone (+166%, p=0.001) whilst the expression of genes involved in insulin signalling was unchanged. Adipose tissue expression of FABP4, LPL and FAT/CD36 was increased. CONCLUSIONS/INTERPRETATION Rosiglitazone decreases postprandial NEFA and triglyceride concentrations. This may represent decreased spillover of NEFAs from adipose tissue depots. Decreased delivery of NEFAs to the liver may lead to lowered postprandial triglyceride concentrations. Upregulation of hexokinase II expression in muscle may contribute to insulin sensitisation by rosiglitazone.
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Affiliation(s)
- G D Tan
- Oxford Centre for Diabetes Endocrinology and Metabolism, Churchill Hospital, University of Oxford, Oxford, OX3 7LJ, UK.
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25
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Faraj M, Cianflone K. Differential regulation of fatty acid trapping in mouse adipose tissue and muscle by ASP. Am J Physiol Endocrinol Metab 2004; 287:E150-9. [PMID: 15191884 DOI: 10.1152/ajpendo.00398.2003] [Citation(s) in RCA: 26] [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
Acylation-stimulating protein (ASP) is a lipogenic hormone secreted by white adipose tissue (WAT). Male C3 knockout (KO; C3(-/-)) ASP-deficient mice have delayed postprandial triglyceride (TG) clearance and reduced WAT mass. The objective of this study was to examine the mechanism(s) by which ASP deficiency induces differences in postprandial TG clearance and body composition in male KO mice. Except for increased (3)H-labeled nonesterified fatty acid (NEFA) trapping in brown adipose tissue (BAT) of KO mice (P = 0.02), there were no intrinsic tissue differences between wild-type (WT) and KO mice in (3)H-NEFA or [(14)C]glucose oxidation, TG synthesis or lipolysis in WAT, muscle, or liver. There were no differences in WAT or skeletal muscle hydrolysis, uptake, and storage of [(3)H]triolein substrate [in situ lipoprotein lipase (LPL) activity]. ASP, however, increased in situ LPL activity in WAT (+64.8%, P = 0.02) but decreased it in muscle (-35.0%, P = 0.0002). In addition, after prelabeling WAT with [(3)H]oleate and [(14)C]glucose, ASP increased (3)H-lipid retention, [(3)H]TG synthesis, and [(3)H]TG-to-[(14)C]TG ratio, whereas it decreased (3)H-NEFA release, indicating increased NEFA trapping in WAT. Conversely, in muscle, ASP induced effects opposite to those in WAT and increased lipolysis, indicating reduced NEFA trapping within muscle by ASP (P < 0.05 for all parameters). In conclusion, novel data in this study suggest that 1) there is little intrinsic difference between KO and WT tissue in the parameters examined and 2) ASP differentially regulates in situ LPL activity and NEFA trapping in WAT and skeletal muscle, which may promote optimal insulin sensitivity in vivo.
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Affiliation(s)
- May Faraj
- Mike Rosenbloom Laboratory for Cardiovascular Research, McGill Univ. Health Centre, Royal Victoria Hospital, 687 Pine Ave. West, Montreal, Quebec H3A 1A1, Canada
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26
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Katsanos CS, Grandjean PW, Moffatt RJ. Effects of low and moderate exercise intensity on postprandial lipemia and postheparin plasma lipoprotein lipase activity in physically active men. J Appl Physiol (1985) 2004; 96:181-8. [PMID: 12949025 DOI: 10.1152/japplphysiol.00243.2003] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This study was designed to assess differences in the intensity of exercise to attenuate postprandial lipemia (PPL). Thirteen healthy men (age 23.8 +/- 0.9 yr) participated in three random-ordered trials: in low-(25% peak oxygen consumption; Low) and moderate-intensity (65% peak oxygen consumption; Mod) exercise trials, which were completed 1 h before a high-fat meal (1.3 g fat/kg body mass), and a control (Con), fat meal only, trial. Venous blood samples were obtained before the fat meal, and at 2, 4, 6, 8, and 20 h after the fat meal. PPL in the Mod trial (267 +/- 50 mg.dl-1.8 h) was lower compared with that in either Con (439 +/- 81 mg.dl-1.8 h) or Low (403 +/- 91 mg.dl-1.8 h) trials (P < 0.05), whereas there was no difference in PPL between Con and Low trials (P > 0.05). High-density lipoprotein cholesterol (HDL-C) and HDL subtype 2 cholesterol were not different between or within trials (P > 0.05). Postprandial insulinemia was lower in the Mod trial (20.5 +/- 5.7 microIU.ml-1.8 h; P < 0.05), but not in the Low trial (31.4 +/- 4.7 microIU.ml-1.8 h), compared with that in the Con trial (34.9 +/- 5.0 microIU.ml-1.8 h). Postheparin lipoprotein lipase activity at 8 h was higher in the Low trial compared with that in either Con or Mod trials, whereas there were no differences between trials at 20 h. These results suggest that, when exercise is performed 1 h before a fat meal, only exercise of moderate but not of low intensity attenuates PPL and that this effect is not associated with changes in postheparin lipoprotein lipase activity.
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Affiliation(s)
- Christos S Katsanos
- Metabolism Unit, Shriners Burns Hospital, 815 Market St., Galveston, TX 77550, USA.
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Evans K, Burdge GC, Wootton SA, Clark ML, Frayn KN. Regulation of dietary fatty acid entrapment in subcutaneous adipose tissue and skeletal muscle. Diabetes 2002; 51:2684-90. [PMID: 12196459 DOI: 10.2337/diabetes.51.9.2684] [Citation(s) in RCA: 122] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Using stable isotopic labeling of dietary fatty acids in conjunction with arteriovenous difference measurements, we have assessed the regulation of lipoprotein lipase-derived fatty acid entrapment in subcutaneous adipose tissue and forearm muscle in healthy subjects in the postprandial state. Eight volunteers fasted overnight and were then given a mixed meal containing [ 1-(13)C]palmitic acid and [1-(13)C]oleic acid. At baseline and for 6 h after the meal, blood samples were obtained from an arterialized hand vein and veins draining subcutaneous abdominal adipose tissue and forearm muscle, and arteriovenous differences were calculated. Entrapment of labeled fatty acids released by circulating triacylglycerol hydrolysis was close to 100% at 60 min, decreasing to 10-30% by 360 min. Entrapment of labeled fatty acids in forearm muscle was >100% and did not change with time. This study shows that entrapment of dietary fatty acids in adipose tissue in the postprandial period is a highly regulated process (varying with time) and that this can be studied in humans using stable isotope- labeled fatty acids in combination with measurement of appropriate arteriovenous differences. Also, fatty acid trapping in skeletal muscle is fundamentally different from that in adipose tissue, in that all the fatty acids released by lipoprotein lipase in skeletal muscle are taken up by the tissue.
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Affiliation(s)
- Kevin Evans
- Department of Clinical Chemistry, Staffordshire General Hospital, Stafford, UK.
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Moberg E, Sjöberg S, Hagström-Toft E, Bolinder J. No apparent suppression by insulin of in vivo skeletal muscle lipolysis in nonobese women. Am J Physiol Endocrinol Metab 2002; 283:E295-301. [PMID: 12110534 DOI: 10.1152/ajpendo.00339.2001] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To investigate the antilipolytic effect of insulin in skeletal muscle and adipose tissue in vivo, the rates of glycerol release from the two tissues were compared in 10 nonobese women during a two-step euglycemic hyperinsulinemic clamp. Tissue interstitial glycerol levels were determined by microdialysis, and tissue blood flow was assessed with the (133)Xe clearance technique. Absolute rates of glycerol release were estimated according to Fick's principle. In both adipose tissue and muscle, glycerol levels decreased significantly already during the low insulin infusion rate. The fractional release of glycerol (difference between interstitial glycerol and arterialized venous plasma glycerol) was reduced by more than one-half in adipose tissue (P < 0.0001) in response to insulin, whereas it remained unaltered in skeletal muscle. Muscle blood flow rates increased by 60% (P < 0.02) during insulin infusion; in adipose tissue, blood flow rates did not change significantly in response to insulin. The basal rate of glycerol release from skeletal muscle amounted to approximately 15% of that from adipose tissue. After insulin infusion, the rate of adipose tissue glycerol release was markedly suppressed, whereas in skeletal muscle the rate of glycerol mobilization did not change significantly in response to insulin. It is concluded that insulin does not inhibit the rate of lipolysis in skeletal muscle of nonobese women.
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Affiliation(s)
- Erik Moberg
- Department of Medicine, Huddinge University Hospital, Karolinska Institutet, S-141 86 Stockholm, Sweden
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