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Reidy PT, Monnig JM, Pickering CE, Funai K, Drummond MJ. Preclinical rodent models of physical inactivity-induced muscle insulin resistance: challenges and solutions. J Appl Physiol (1985) 2020; 130:537-544. [PMID: 33356986 DOI: 10.1152/japplphysiol.00954.2020] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Physical inactivity influences the development of muscle insulin resistance yet is far less understood than diet-induced muscle insulin resistance. Progress in understanding the mechanisms of physical inactivity-induced insulin resistance is limited by a lack of an appropriate preclinical model of muscle insulin resistance. Here, we discuss differences between diet and physical inactivity-induced insulin resistance, the advantages and disadvantages of the available rodent inactivity models to study insulin resistance, and our current understanding of the mechanisms of muscle insulin resistance derived from such preclinical inactivity designs. The burgeoning rise of health complications emanating from metabolic disease presents an alarming issue with mounting costs for health care and a reduced quality of life. There exists a pressing need for more complete understanding of mechanisms behind the development and progression of metabolic dysfunction. Since lifestyle modifications such as poor diet and lack of physical activity are primary catalysts of metabolic dysfunction, rodent models have been formed to explore mechanisms behind these issues. Particularly, the use of a high-fat diet has been pervasive and has been an instrumental model to gain insight into mechanisms underlying diet-induced insulin resistance (IR). However, physical inactivity (and to some extent muscle disuse) is an often overlooked and much less frequently studied lifestyle modification, which some have contended is the primary contributor in the initial development of muscle IR. In this mini-review we highlight some of the key differences between diet- and physical inactivity-induced development of muscle IR and propose reasons for the sparse volume of academic research into physical inactivity-induced IR including infrequent use of clearly translatable rodent physical inactivity models.
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Affiliation(s)
- Paul T Reidy
- Department of Kinesiology and Health, Miami University, Oxford, Ohio
| | - Jackie M Monnig
- Department of Kinesiology and Health, Miami University, Oxford, Ohio
| | | | - Katsuhiko Funai
- Departments of Physical Therapy and Athletic Training, University of Utah, Salt Lake City, Utah
| | - Micah J Drummond
- Departments of Physical Therapy and Athletic Training, University of Utah, Salt Lake City, Utah
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Reidy PT, Mahmassani ZS, McKenzie AI, Petrocelli JJ, Summers SA, Drummond MJ. Influence of Exercise Training on Skeletal Muscle Insulin Resistance in Aging: Spotlight on Muscle Ceramides. Int J Mol Sci 2020; 21:ijms21041514. [PMID: 32098447 PMCID: PMC7073171 DOI: 10.3390/ijms21041514] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Revised: 02/04/2020] [Accepted: 02/07/2020] [Indexed: 12/15/2022] Open
Abstract
Intramuscular lipid accumulation has been associated with insulin resistance (IR), aging, diabetes, dyslipidemia, and obesity. A substantial body of evidence has implicated ceramides, a sphingolipid intermediate, as potent antagonists of insulin action that drive insulin resistance. Indeed, genetic mouse studies that lower ceramides are potently insulin sensitizing. Surprisingly less is known about how physical activity (skeletal muscle contraction) regulates ceramides, especially in light that muscle contraction regulates insulin sensitivity. The purpose of this review is to critically evaluate studies (rodent and human) concerning the relationship between skeletal muscle ceramides and IR in response to increased physical activity. Our review of the literature indicates that chronic exercise reduces ceramide levels in individuals with obesity, diabetes, or hyperlipidemia. However, metabolically healthy individuals engaged in increased physical activity can improve insulin sensitivity independent of changes in skeletal muscle ceramide content. Herein we discuss these studies and provide context regarding the technical limitations (e.g., difficulty assessing the myriad ceramide species, the challenge of obtaining information on subcellular compartmentalization, and the paucity of flux measurements) and a lack of mechanistic studies that prevent a more sophisticated assessment of the ceramide pathway during increased contractile activity that lead to divergences in skeletal muscle insulin sensitivity.
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Affiliation(s)
- Paul T. Reidy
- Department of Kinesiology and Health, Miami University, 420 S Oak St, Oxford, OH 45056, USA;
| | - Ziad S. Mahmassani
- Departments of Physical Therapy and Athletic Training, University of Utah, 520 Wakara Way, Salt Lake City, UT 84018, USA; (Z.S.M.); (A.I.M.); (J.J.P.)
| | - Alec I. McKenzie
- Departments of Physical Therapy and Athletic Training, University of Utah, 520 Wakara Way, Salt Lake City, UT 84018, USA; (Z.S.M.); (A.I.M.); (J.J.P.)
| | - Jonathan J. Petrocelli
- Departments of Physical Therapy and Athletic Training, University of Utah, 520 Wakara Way, Salt Lake City, UT 84018, USA; (Z.S.M.); (A.I.M.); (J.J.P.)
| | - Scott A. Summers
- Department of Nutrition and Integrative Physiology, University of Utah, 250 1850 E, Salt Lake City, UT 84112, USA;
| | - Micah J. Drummond
- Departments of Physical Therapy and Athletic Training, University of Utah, 520 Wakara Way, Salt Lake City, UT 84018, USA; (Z.S.M.); (A.I.M.); (J.J.P.)
- Correspondence:
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Qi-Deficiency Related Increases in Disease Susceptibility Are Potentially Mediated by the Intestinal Microbiota. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2018; 2018:1304397. [PMID: 30425748 PMCID: PMC6218746 DOI: 10.1155/2018/1304397] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/14/2018] [Accepted: 10/02/2018] [Indexed: 12/24/2022]
Abstract
Qi-deficiency (QX) is thought to promote the body's susceptibility to disease, but the underlying mechanism through which this occurs is not clear. We surveyed the traditional Chinese medicine constitution (TCMC) of healthy college students to identify those that were PH (balanced TCMC constitution) and QX (unbalanced TCMC constitution). We then used high-throughput sequencing of the 16SrRNA V3-4 region in fecal microbiota samples to identify differences between those obtained from PH and QX individuals. Our results demonstrated that the alpha diversity of QX samples was significantly lower than that of PH samples (p < 0.05) and that beta diversity was remarkably different in QX and PH samples. Four and 122 bacterial taxa were significantly overrepresented in QX and PH groups, respectively. The genera Sphingobium, Clostridium, and Comamonas were enriched in the QX group and had a certain pathogenic role. The QX group also showed a statistically significant lack of probiotics and anti-inflammatory bacteria such as Bifidobacterium and Bdellovibrio. The functional potential of QX bacterial taxa was reduced in fatty acid metabolism and butanoate metabolism. We contend that the imbalanced intestinal microbiota in QX and the following functional changes in metabolism influence immunity and energy metabolism, which could increase susceptibility to disease.
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Machado FSM, Zhang Z, Su Y, de Goede P, Jansen R, Foppen E, Coimbra CC, Kalsbeek A. Time-of-Day Effects on Metabolic and Clock-Related Adjustments to Cold. Front Endocrinol (Lausanne) 2018; 9:199. [PMID: 29755411 PMCID: PMC5932155 DOI: 10.3389/fendo.2018.00199] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Accepted: 04/10/2018] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND Daily cyclic changes in environmental conditions are key signals for anticipatory and adaptive adjustments of most living species, including mammals. Lower ambient temperature stimulates the thermogenic activity of brown adipose tissue (BAT) and skeletal muscle. Given that the molecular components of the endogenous biological clock interact with thermal and metabolic mechanisms directly involved in the defense of body temperature, the present study evaluated the differential homeostatic responses to a cold stimulus at distinct time-windows of the light/dark-cycle. METHODS Male Wistar rats were subjected to a single episode of 3 h cold ambient temperature (4°C) at one of 6 time-points starting at Zeitgeber Times 3, 7, 11, 15, 19, and 23. Metabolic rate, core body temperature, locomotor activity (LA), feeding, and drinking behaviors were recorded during control and cold conditions at each time-point. Immediately after the stimulus, rats were euthanized and both the soleus and BAT were collected for real-time PCR. RESULTS During the light phase (i.e., inactive phase), cold exposure resulted in a slight hyperthermia (p < 0.001). Light phase cold exposure also increased metabolic rate and LA (p < 0.001). In addition, the prevalence of fat oxidative metabolism was attenuated during the inactive phase (p < 0.001). These metabolic changes were accompanied by time-of-day and tissue-specific changes in core clock gene expression, such as DBP (p < 0.0001) and REV-ERBα (p < 0.01) in the BAT and CLOCK (p < 0.05), PER2 (p < 0.05), CRY1 (p < 0.05), CRY2 (p < 0.01), and REV-ERBα (p < 0.05) in the soleus skeletal muscle. Moreover, genes involved in substrate oxidation and thermogenesis were affected in a time-of-day and tissue-specific manner by cold exposure. CONCLUSION The time-of-day modulation of substrate mobilization and oxidation during cold exposure provides a clear example of the circadian modulation of physiological and metabolic responses. Interestingly, after cold exposure, time-of-day mostly affected circadian clock gene expression in the soleus muscle, despite comparable changes in LA over the light-dark-cycle. The current findings add further evidence for tissue-specific actions of the internal clock in different peripheral organs such as skeletal muscle and BAT.
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Affiliation(s)
- Frederico Sander Mansur Machado
- Department of Endocrinology and Metabolism, Academic Medical Center, University of Amsterdam, Amsterdam, Netherlands
- Hypothalamic Integration Mechanisms, Netherlands Institute for Neuroscience, Amsterdam, Netherlands
- Department of Physiology and Biophysics, Biological Sciences Institute, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Zhi Zhang
- Department of Endocrinology and Metabolism, Academic Medical Center, University of Amsterdam, Amsterdam, Netherlands
- Hypothalamic Integration Mechanisms, Netherlands Institute for Neuroscience, Amsterdam, Netherlands
- Laboratory of Endocrinology, Department of Clinical Chemistry, Academic Medical Centre, University of Amsterdam, Amsterdam, Netherlands
| | - Yan Su
- Hypothalamic Integration Mechanisms, Netherlands Institute for Neuroscience, Amsterdam, Netherlands
- Laboratory of Endocrinology, Department of Clinical Chemistry, Academic Medical Centre, University of Amsterdam, Amsterdam, Netherlands
| | - Paul de Goede
- Hypothalamic Integration Mechanisms, Netherlands Institute for Neuroscience, Amsterdam, Netherlands
- Laboratory of Endocrinology, Department of Clinical Chemistry, Academic Medical Centre, University of Amsterdam, Amsterdam, Netherlands
| | - Remi Jansen
- Hypothalamic Integration Mechanisms, Netherlands Institute for Neuroscience, Amsterdam, Netherlands
- Laboratory of Endocrinology, Department of Clinical Chemistry, Academic Medical Centre, University of Amsterdam, Amsterdam, Netherlands
| | - Ewout Foppen
- Department of Endocrinology and Metabolism, Academic Medical Center, University of Amsterdam, Amsterdam, Netherlands
- Laboratory of Endocrinology, Department of Clinical Chemistry, Academic Medical Centre, University of Amsterdam, Amsterdam, Netherlands
| | - Cândido Celso Coimbra
- Department of Physiology and Biophysics, Biological Sciences Institute, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Andries Kalsbeek
- Department of Endocrinology and Metabolism, Academic Medical Center, University of Amsterdam, Amsterdam, Netherlands
- Hypothalamic Integration Mechanisms, Netherlands Institute for Neuroscience, Amsterdam, Netherlands
- Laboratory of Endocrinology, Department of Clinical Chemistry, Academic Medical Centre, University of Amsterdam, Amsterdam, Netherlands
- *Correspondence: Andries Kalsbeek,
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Hrometz SL, Ebert JA, Grice KE, Nowinski SM, Mills EM, Myers BJ, Sprague JE. Potentiation of Ecstasy-induced hyperthermia and FAT/CD36 expression in chronically exercised animals. Temperature (Austin) 2017; 3:557-566. [PMID: 28090559 PMCID: PMC5198810 DOI: 10.1080/23328940.2016.1166310] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Revised: 03/10/2016] [Accepted: 03/10/2016] [Indexed: 11/16/2022] Open
Abstract
Fatal hyperthermia as a result of 3,4-methylenedioxymethamphetamine (MDMA) use involves non-esterified free fatty acids (NEFA) and the activation of mitochondrial uncoupling proteins (UCP). NEFA gain access into skeletal muscle via specific transport proteins, including fatty acid translocase (FAT/CD36). FAT/CD36 expression is known to increase following chronic exercise. Previous studies have demonstrated the essential role of NEFA and UCP3 in MDMA-induced hyperthermia. The aims of the present study were to use a chronic exercise model (swimming for two consecutive hours per day, five days per wk for six wk) to increase FAT/CD36 expression in order to: 1) determine the contribution of FAT/CD36 in MDMA (20 mg/kg, s.c.)-mediated hyperthermia; and 2) examine the effects of the FAT/CD36 inhibitor, SSO (sulfo-N-succinimidyl oleate), on MDMA-induced hyperthermia in chronic exercise and sedentary control rats. MDMA administration resulted in hyperthermia in both sedentary and chronic exercise animals. However, MDMA-induced hyperthermia was significantly potentiated in the chronic exercise animals compared to sedentary animals. Additionally, chronic exercise significantly reduced body weight, increased FAT/CD36 protein expression levels and reduced plasma NEFA levels. The FAT/CD36 inhibitor, SSO (40 mg/kg, ip), significantly attenuated the hyperthermia mediated by MDMA in chronic exercised but not sedentary animals. Plasma NEFA levels were elevated in sedentary and exercised animals treated with SSO prior to MDMA suggesting attenuation of NEFA uptake into skeletal muscle. Chronic exercise did not alter skeletal muscle UCP3 protein expression levels. In conclusion, chronic exercise potentiates MDMA-mediated hyperthermia in a FAT/CD36 dependent fashion.
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Affiliation(s)
- Sandra L Hrometz
- Department of Pharmaceutical Sciences, College of Pharmacy, Natural and Health Sciences, Manchester University , Fort Wayne, IN, USA
| | - Jeremy A Ebert
- Department of Pharmaceutical and Biomedical Sciences, The Raabe College of Pharmacy, Ohio Northern University , Ada, OH, USA
| | - Karen E Grice
- Department of Pharmaceutical and Biomedical Sciences, The Raabe College of Pharmacy, Ohio Northern University , Ada, OH, USA
| | - Sara M Nowinski
- Division of Pharmacology and Toxicology, College of Pharmacy, University of Texas at Austin , Austin, TX, USA
| | - Edward M Mills
- Division of Pharmacology and Toxicology, College of Pharmacy, University of Texas at Austin , Austin, TX, USA
| | - Brian J Myers
- Department of Chemistry and Biochemistry, The Getty College of Arts & Sciences, Ohio Northern University ; Ada, OH, USA
| | - Jon E Sprague
- The Ohio Attorney General's Center for the Future of Forensic Science, Bowling Green State University , Bowling Green, OH, USA
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Callahan ZJ, Oxendine M, Wheatley JL, Menke C, Cassell EA, Bartos A, Geiger PC, Schaeffer PJ. Compensatory responses of the insulin signaling pathway restore muscle glucose uptake following long-term denervation. Physiol Rep 2015; 3:3/4/e12359. [PMID: 25896980 PMCID: PMC4425965 DOI: 10.14814/phy2.12359] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
We investigated the role of muscle activity in maintaining normal glucose homeostasis via transection of the sciatic nerve, an extreme model of disuse atrophy. Mice were killed 3, 10, 28, or 56 days after transection or sham surgery. There was no difference in muscle weight between sham and transected limbs at 3 days post surgery, but it was significantly lower following transection at the other three time points. Transected muscle weight stabilized by 28 days post surgery with no further loss. Myocellular cross-sectional area was significantly smaller at 10, 28, and 56 days post transection surgery. Additionally, muscle fibrosis area was significantly greater at 56 days post transection. In transected muscle there was reduced expression of genes encoding transcriptional regulators of metabolism (PPARα, PGC-1α, PGC-1β, PPARδ), a glycolytic enzyme (PFK), a fatty acid transporter (M-CPT 1), and an enzyme of mitochondrial oxidation (CS) with transection. In denervated muscle, glucose uptake was significantly lower at 3 days but was greater at 56 days under basal and insulin-stimulated conditions. Although GLUT 4 mRNA was significantly lower at all time points in transected muscle, Western blot analysis showed greater expression of GLUT4 at 28 and 56 days post surgery. GLUT1 mRNA was unchanged; however, GLUT1 protein expression was also greater in transected muscles. Surgery led to significantly higher protein expression for Akt2 as well as higher phosphorylation of Akt. While denervation may initially lead to reduced glucose sensitivity, compensatory responses of insulin signaling appeared to restore and improve glucose uptake in long-term-transected muscle.
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Affiliation(s)
| | | | - Joshua L Wheatley
- Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, Kansas
| | - Chelsea Menke
- Department of Biology, Miami University, Oxford, Ohio
| | | | - Amanda Bartos
- Department of Biology, Miami University, Oxford, Ohio
| | - Paige C Geiger
- Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, Kansas
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Neels JG, Grimaldi PA. Physiological functions of peroxisome proliferator-activated receptor β. Physiol Rev 2014; 94:795-858. [PMID: 24987006 DOI: 10.1152/physrev.00027.2013] [Citation(s) in RCA: 117] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The peroxisome proliferator-activated receptors, PPARα, PPARβ, and PPARγ, are a family of transcription factors activated by a diversity of molecules including fatty acids and fatty acid metabolites. PPARs regulate the transcription of a large variety of genes implicated in metabolism, inflammation, proliferation, and differentiation in different cell types. These transcriptional regulations involve both direct transactivation and interaction with other transcriptional regulatory pathways. The functions of PPARα and PPARγ have been extensively documented mainly because these isoforms are activated by molecules clinically used as hypolipidemic and antidiabetic compounds. The physiological functions of PPARβ remained for a while less investigated, but the finding that specific synthetic agonists exert beneficial actions in obese subjects uplifted the studies aimed to elucidate the roles of this PPAR isoform. Intensive work based on pharmacological and genetic approaches and on the use of both in vitro and in vivo models has considerably improved our knowledge on the physiological roles of PPARβ in various cell types. This review will summarize the accumulated evidence for the implication of PPARβ in the regulation of development, metabolism, and inflammation in several tissues, including skeletal muscle, heart, skin, and intestine. Some of these findings indicate that pharmacological activation of PPARβ could be envisioned as a therapeutic option for the correction of metabolic disorders and a variety of inflammatory conditions. However, other experimental data suggesting that activation of PPARβ could result in serious adverse effects, such as carcinogenesis and psoriasis, raise concerns about the clinical use of potent PPARβ agonists.
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Affiliation(s)
- Jaap G Neels
- Institut National de la Santé et de la Recherche Médicale U 1065, Mediterranean Center of Molecular Medicine (C3M), Team "Adaptive Responses to Immuno-metabolic Dysregulations," Nice, France; and Faculty of Medicine, University of Nice Sophia-Antipolis, Nice, France
| | - Paul A Grimaldi
- Institut National de la Santé et de la Recherche Médicale U 1065, Mediterranean Center of Molecular Medicine (C3M), Team "Adaptive Responses to Immuno-metabolic Dysregulations," Nice, France; and Faculty of Medicine, University of Nice Sophia-Antipolis, Nice, France
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8
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Jordy AB, Serup AK, Karstoft K, Pilegaard H, Kiens B, Jeppesen J. Insulin sensitivity is independent of lipid binding protein trafficking at the plasma membrane in human skeletal muscle: effect of a 3-day, high-fat diet. Am J Physiol Regul Integr Comp Physiol 2014; 307:R1136-45. [PMID: 25163924 DOI: 10.1152/ajpregu.00124.2014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The aim of the present study was to investigate lipid-induced regulation of lipid binding proteins in human skeletal muscle and the impact hereof on insulin sensitivity. Eleven healthy male subjects underwent a 3-day hypercaloric and high-fat diet regime. Muscle biopsies were taken before and after the diet intervention, and giant sarcolemmal vesicles were prepared. The high-fat diet induced decreased insulin sensitivity, but this was not associated with a relocation of FAT/CD36 or FABPpm protein to the sarcolemma. However, FAT/CD36 and FABPpm mRNA, but not the proteins, were upregulated by increased fatty acid availability. This suggests a time dependency in the upregulation of FAT/CD36 and FABPpm protein during high availability of plasma fatty acids. Furthermore, we did not detect FATP1 and FATP4 protein in giant sarcolemmal vesicles obtained from human skeletal muscle. In conclusion, this study shows that a short-term lipid-load increases mRNA content of key lipid handling proteins in human muscle. However, decreased insulin sensitivity after a high-fat diet is not accompanied with relocation of FAT/CD36 or FABPpm protein to the sarcolemma. Finally, FATP1 and FATP4 protein was located intracellularly but not at the sarcolemma in humans.
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Affiliation(s)
- Andreas B Jordy
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
| | - Annette K Serup
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
| | - Kristian Karstoft
- The Centre of Inflammation and Metabolism and The Centre for Physical Activity Research, Department of Infectious Diseases, Rigshospitalet, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark; and
| | - Henriette Pilegaard
- The Centre of Inflammation and Metabolism and The Centre for Physical Activity Research, Department of Infectious Diseases, Rigshospitalet, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark; and CFAS, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Bente Kiens
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark;
| | - Jacob Jeppesen
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
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9
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McArdle Disease and Exercise Physiology. BIOLOGY 2014; 3:157-66. [PMID: 24833339 PMCID: PMC4009758 DOI: 10.3390/biology3010157] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Revised: 02/19/2014] [Accepted: 02/20/2014] [Indexed: 11/17/2022]
Abstract
McArdle disease (glycogen storage disease Type V; MD) is a metabolic myopathy caused by a deficiency in muscle glycogen phosphorylase. Since muscle glycogen is an important fuel for muscle during exercise, this inborn error of metabolism provides a model for understanding the role of glycogen in muscle function and the compensatory adaptations that occur in response to impaired glycogenolysis. Patients with MD have exercise intolerance with symptoms including premature fatigue, myalgia, and/or muscle cramps. Despite this, MD patients are able to perform prolonged exercise as a result of the “second wind” phenomenon, owing to the improved delivery of extra-muscular fuels during exercise. The present review will cover what this disease can teach us about exercise physiology, and particularly focuses on the compensatory pathways for energy delivery to muscle in the absence of glycogenolysis.
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10
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Maione D, Cicero AF, Bacchelli S, Cosentino E, Degli Esposti D, Senaldi R, Strocchi E, D'Addato S, Borghi C. VO2 kinetics in supra-anaerobic threshold constant tests allow the visualization and quantification of the O2 saving after cytochrome c oxidase inhibition by aerobic training or nitrate administration. Physiol Res 2013; 62:671-9. [PMID: 23869892 DOI: 10.33549/physiolres.932484] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
We tested whether the known cytochrome c oxidase (COX) inhibition by nitric oxide (NO) could be quantified by VO(2) kinetics during constant load supra-Anaerobic Threshold (AT) exercises in healthy trained or untrained subjects following aerobic training or nitrate administration. In cycle ergometer constant load exercises supra-AT, identified in previous incremental tests, VO(2) kinetics describe a double exponential curve, one rapid and one appreciably slower, allowing the area between them to be calculate in O(2) l. After training, with increased NO availability, this area decreases in inverse ratio to treatment efficacy. In fact, in 11 healthy subjects after aerobic training for 6-7 weeks, area was decreased on average by 51 %. In 11 untrained subjects, following the assumption of an NO donor, 20 mg isosorbide 5 mononitrate, area was decreased on average by 53 %. In conclusion, supra-AT VO(2) kinetics in constant load exercises permit the quantification of the inhibitory effect NO-dependent on COX after either physical training or nitrate assumption.
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Affiliation(s)
- D Maione
- Medical and Surgical Sciences Department, S. Orsola-Malpighi University Hospital, Bologna, Italy.
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11
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O'Neill HM, Holloway GP, Steinberg GR. AMPK regulation of fatty acid metabolism and mitochondrial biogenesis: implications for obesity. Mol Cell Endocrinol 2013; 366:135-51. [PMID: 22750049 DOI: 10.1016/j.mce.2012.06.019] [Citation(s) in RCA: 241] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/10/2011] [Revised: 03/13/2012] [Accepted: 06/21/2012] [Indexed: 12/25/2022]
Abstract
Skeletal muscle plays an important role in regulating whole-body energy expenditure given it is a major site for glucose and lipid oxidation. Obesity and type 2 diabetes are causally linked through their association with skeletal muscle insulin resistance, while conversely exercise is known to improve whole body glucose homeostasis simultaneously with muscle insulin sensitivity. Exercise activates skeletal muscle AMP-activated protein kinase (AMPK). AMPK plays a role in regulating exercise capacity, skeletal muscle mitochondrial content and contraction-stimulated glucose uptake. Skeletal muscle AMPK is also thought to be important for regulating fatty acid metabolism; however, direct genetic evidence in this area is currently lacking. This review will discuss the current paradigms regarding the influence of AMPK in regulating skeletal muscle fatty acid metabolism and mitochondrial biogenesis at rest and during exercise, and highlight the potential implications in the development of insulin resistance.
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Affiliation(s)
- Hayley M O'Neill
- University of Melbourne, Department of Medicine, St. Vincent's Institute of Medical Research, Melbourne, Victoria, Australia.
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12
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Abstract
Carnitine palmitoyltransferase I has been viewed historically as the sole regulator of fatty acid oxidation. However, we have identified fatty acid translocase/CD36 as an additional control point. Specifically, fatty acid translocase/CD36 seems to have a novel dual mechanism of action with regard to fatty acid oxidation during exercise, influencing transport of lipids across the sarcolemmal membrane and into the mitochondria.
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13
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Stehno-Bittel L. Organ-based response to exercise in type 1 diabetes. ISRN ENDOCRINOLOGY 2012; 2012:318194. [PMID: 23251813 PMCID: PMC3518066 DOI: 10.5402/2012/318194] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/23/2012] [Accepted: 11/14/2012] [Indexed: 12/16/2022]
Abstract
While significant research has clearly identified sedentary behavior as a risk factor for type 2 diabetes and its subsequent complications, the concept that inactivity could be linked to the complications associated with type 1 diabetes (T1D) remains underappreciated. This paper summarizes the known effects of exercise on T1D at the tissue level and focuses on the pancreas, bone, the cardiovascular system, the kidneys, skeletal muscle, and nerves. When possible, the molecular mechanisms underlying the benefits of exercise for T1D are elucidated. The general benefits of increased activity on health and the barriers to increased exercise specific to people with T1D are discussed.
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Affiliation(s)
- Lisa Stehno-Bittel
- Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center, Kansas City, KS 66160, USA
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14
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Yoshida Y, Jain SS, McFarlan JT, Snook LA, Chabowski A, Bonen A. Exercise- and training-induced upregulation of skeletal muscle fatty acid oxidation are not solely dependent on mitochondrial machinery and biogenesis. J Physiol 2012; 591:4415-26. [PMID: 22890711 DOI: 10.1113/jphysiol.2012.238451] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Regulation of skeletal muscle fatty acid oxidation (FAO) and adaptation to exercise training have long been thought to depend on delivery of fatty acids (FAs) to muscle, their diffusion into muscle, and muscle mitochondrial content and biochemical machinery. However, FA entry into muscle occurs via a regulatable, protein-mediated mechanism, involving several transport proteins. Among these CD36 is key. Muscle contraction and pharmacological agents induce CD36 to translocate to the cell surface, a response that regulates FA transport, and hence FAO. In exercising CD36 KO mice, exercise duration (-44%), and FA transport (-41%) and oxidation (-37%) are comparably impaired, while carbohydrate metabolism is augmented. In trained CD36 KO mice, training-induced upregulation of FAO is not observed, despite normal training-induced increases in mitochondrial density and enzymes. Transfecting CD36 into sedentary WT muscle (+41%), comparable to training-induced CD36 increases (+44%) in WT muscle, markedly upregulates FAO to rates observed in trained WT mice, but without any changes in mitochondrial density and enzymes. Evidently, in vivo CD36-mediated FA transport is key for muscle fuel selection and training-induced FAO upregulation, independent of mitochondrial adaptations. This CD36 molecular mechanism challenges the view that skeletal muscle FAO is solely regulated by muscle mitochondrial content and machinery.
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Affiliation(s)
- Yuko Yoshida
- A. Bonen: University of Guelph, Human Health and Nutritional Sciences, Gordon St Bldg 70, Guelph, ON, Canada, N1G 2W1.
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15
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Coen PM, Goodpaster BH. Role of intramyocelluar lipids in human health. Trends Endocrinol Metab 2012; 23:391-8. [PMID: 22721584 PMCID: PMC4908975 DOI: 10.1016/j.tem.2012.05.009] [Citation(s) in RCA: 176] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2012] [Revised: 05/21/2012] [Accepted: 05/22/2012] [Indexed: 11/20/2022]
Abstract
Intramyocellular lipid (IMCL) is predominantly stored as intramuscular triglyceride (IMTG) in lipid droplets and is utilized as metabolic fuel during physical exercise. IMTG is also implicated in muscle insulin resistance (IR) in type 2 diabetes. However, it has become apparent that lipid moieties such as ceramide and diacylglycerol are the likely culprits of IR. This article reviews current knowledge of IMCL-mediated IR and important areas of investigation, including myocellular lipid transport and lipid droplet proteins. Several crucial questions remain unanswered, such as the identity of specific ceramide and diacylglycerol species that mediate IR in human muscle and their subcellular location. Quantitative lipidomics and proteomics of targeted subcellular organelles will help to better define the mechanisms underlying pathological IMCL accumulation and IR.
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Affiliation(s)
- Paul M Coen
- Department of Health and Physical Activity, University of Pittsburgh, Trees Hall Rm 134D, Allequippa Street and Darragh Street, Pittsburgh, PA 15260, USA
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16
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McFarlan JT, Yoshida Y, Jain SS, Han XX, Snook LA, Lally J, Smith BK, Glatz JFC, Luiken JJFP, Sayer RA, Tupling AR, Chabowski A, Holloway GP, Bonen A. In vivo, fatty acid translocase (CD36) critically regulates skeletal muscle fuel selection, exercise performance, and training-induced adaptation of fatty acid oxidation. J Biol Chem 2012; 287:23502-16. [PMID: 22584574 DOI: 10.1074/jbc.m111.315358] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
For ~40 years it has been widely accepted that (i) the exercise-induced increase in muscle fatty acid oxidation (FAO) is dependent on the increased delivery of circulating fatty acids, and (ii) exercise training-induced FAO up-regulation is largely attributable to muscle mitochondrial biogenesis. These long standing concepts were developed prior to the recent recognition that fatty acid entry into muscle occurs via a regulatable sarcolemmal CD36-mediated mechanism. We examined the role of CD36 in muscle fuel selection under basal conditions, during a metabolic challenge (exercise), and after exercise training. We also investigated whether CD36 overexpression, independent of mitochondrial changes, mimicked exercise training-induced FAO up-regulation. Under basal conditions CD36-KO versus WT mice displayed reduced fatty acid transport (-21%) and oxidation (-25%), intramuscular lipids (less than or equal to -31%), and hepatic glycogen (-20%); but muscle glycogen, VO(2max), and mitochondrial content and enzymes did not differ. In acutely exercised (78% VO(2max)) CD36-KO mice, fatty acid transport (-41%), oxidation (-37%), and exercise duration (-44%) were reduced, whereas muscle and hepatic glycogen depletions were accelerated by 27-55%, revealing 2-fold greater carbohydrate use. Exercise training increased mtDNA and β-hydroxyacyl-CoA dehydrogenase similarly in WT and CD36-KO muscles, but FAO was increased only in WT muscle (+90%). Comparable CD36 increases, induced by exercise training (+44%) or by CD36 overexpression (+41%), increased FAO similarly (84-90%), either when mitochondrial biogenesis and FAO enzymes were up-regulated (exercise training) or when these were unaltered (CD36 overexpression). Thus, sarcolemmal CD36 has a key role in muscle fuel selection, exercise performance, and training-induced muscle FAO adaptation, challenging long held views of mechanisms involved in acute and adaptive regulation of muscle FAO.
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Affiliation(s)
- Jay T McFarlan
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario N1G 2W1, Canada
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17
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Jonkers RAM, Dirks ML, Nabuurs CIHC, De Feyter HM, Praet SFE, Nicolay K, van Loon LJC, Prompers JJ. Myofibrillar distribution of succinate dehydrogenase activity and lipid stores differs in skeletal muscle tissue of paraplegic subjects. Am J Physiol Endocrinol Metab 2012; 302:E365-73. [PMID: 22068603 DOI: 10.1152/ajpendo.00270.2011] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Lack of physical activity has been related to an increased risk of developing insulin resistance. This study aimed to assess the impact of chronic muscle deconditioning on whole body insulin sensitivity, muscle oxidative capacity, and intramyocellular lipid (IMCL) content in subjects with paraplegia. Nine subjects with paraplegia and nine able-bodied, lean controls were recruited. An oral glucose tolerance test was performed to assess whole body insulin sensitivity. IMCL content was determined both in vivo and in vitro using (1)H-magnetic resonance spectroscopy and fluorescence microscopy, respectively. Muscle biopsy samples were stained for succinate dehydrogenase (SDH) activity to measure muscle fiber oxidative capacity. Subcellular distributions of IMCL and SDH activity were determined by defining subsarcolemmal and intermyofibrillar areas on histological samples. SDH activity was 57 ± 14% lower in muscle fibers derived from subjects with paraplegia when compared with controls (P < 0.05), but IMCL content and whole body insulin sensitivity did not differ between groups. In muscle fibers taken from controls, both SDH activity and IMCL content were higher in the subsarcolemmal region than in the intermyofibrillar area. This typical subcellular SDH and IMCL distribution pattern was lost in muscle fibers collected from subjects with paraplegia and had changed toward a more uniform distribution. In conclusion, the lower metabolic demand in deconditioned muscle of subjects with paraplegia results in a significant decline in muscle fiber oxidative capacity and is accompanied by changes in the subcellular distribution patterns of SDH activity and IMCL. However, loss of muscle activity due to paraplegia is not associated with substantial lipid accumulation in skeletal muscle tissue.
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Affiliation(s)
- Richard A M Jonkers
- Biomedical NMR, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
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18
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Hoshino D, Yoshida Y, Holloway GP, Lally J, Hatta H, Bonen A. Clenbuterol, a β2-adrenergic agonist, reciprocally alters PGC-1 alpha and RIP140 and reduces fatty acid and pyruvate oxidation in rat skeletal muscle. Am J Physiol Regul Integr Comp Physiol 2012; 302:R373-84. [DOI: 10.1152/ajpregu.00183.2011] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Clenbuterol, a β2-adrenergic agonist, reduces mitochondrial content and enzyme activities in skeletal muscle, but the mechanism involved has yet to be identified. We examined whether clenbuterol-induced changes in the muscles' metabolic profile and the intrinsic capacity of mitochondria to oxidize substrates are associated with reductions in the nuclear receptor coactivator PGC-1 alpha and/or an increase in the nuclear corepressor RIP140. In rats, clenbuterol was provided in the drinking water (30 mg/l). In 3 wk, this increased body (8%) and muscle weights (12–17%). In red (R) and white (W) muscles, clenbuterol induced reductions in mitochondrial content (citrate synthase: R, 27%; W, 52%; cytochrome- c oxidase: R, 24%; W, 34%), proteins involved in fatty acid transport (fatty acid translocase/CD36: R, 36%; W, 35%) and oxidation [β-hydroxyacyl CoA dehydrogenase (β-HAD): R, 33%; W, 62%], glucose transport (GLUT4: R, 8%; W, 13%), lactate transport monocarboxylate transporter (MCT1: R, 61%; W, 37%), and pyruvate oxidation (PDHE1α, R, 18%; W, 12%). Concurrently, only red muscle lactate dehydrogenase activity (25%) and MCT4 (31%) were increased. Palmitate oxidation was reduced in subsarcolemmal (SS) (R, 30%; W, 52%) and intermyofibrillar (IMF) mitochondria (R, 17%; W, 44%) along with reductions in β-HAD activity (SS: R, 17%; W, 51%; IMF: R, 20%; W, 57%). Pyruvate oxidation was only reduced in SS mitochondria (R, 20%; W, 28%), but this was not attributable solely to PDHE1α, which was reduced in both SS (R, 21%; W, 20%) and IMF mitochondria (R, 15%; W, 43%). These extensive metabolic changes induced by clenbuterol were associated with reductions in PGC-1α (R, 37%; W, 32%) and increases in RIP140 (R, 23%; W, 21%). This is the first evidence that clenbuterol appears to exert its metabolic effects via simultaneous and reciprocal changes in the nuclear receptor coactivator PGC-1α and the nuclear corepressor RIP140.
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Affiliation(s)
- Daisuke Hoshino
- Department of Sports Sciences, The University of Tokyo, Tokyo, Japan; and
| | - Yuko Yoshida
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Graham P. Holloway
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - James Lally
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Hideo Hatta
- Department of Sports Sciences, The University of Tokyo, Tokyo, Japan; and
| | - Arend Bonen
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
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19
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Holloway GP, Snook LA, Harris RJ, Glatz JFC, Luiken JJFP, Bonen A. In obese Zucker rats, lipids accumulate in the heart despite normal mitochondrial content, morphology and long-chain fatty acid oxidation. J Physiol 2010; 589:169-80. [PMID: 21041527 DOI: 10.1113/jphysiol.2010.198663] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
We aimed to determine whether an increased rate of long-chain fatty acid (LCFA) transport and/or a reduction in mitochondrial oxidation contributes to lipid deposition in hearts, as lipid accumulation within cardiac muscle has been associated with heart failure. In hearts of lean and obese Zucker rats we examined: (a) triacylglycerol (TAG) and mitochondrial content and distribution using transmission electron microscopy (TEM), (b) LCFA oxidation in cardiac myocytes, and in isolated subsarcolemmal (SS) and intermyofibrillar (IMF) mitochondria, and (c) rates of LCFA transport into cardiac vesicles. Compared to lean rats, in obese Zucker rats, lipid droplet size was similar but there were more (P < 0.05) droplets, and TAG esterification rates and contents were markedly increased. TEM analyses and biochemical determinations showed that SS and IMF mitochondria in obese animals did not appear to be different in their appearance, area, density and number, nor in citrate synthase, β-hydroxy-acyl-CoA dehydrogenase and carnitine palmitoyl-transferase-I enzymatic activities, electron transport chain proteins, nor in their rates of LCFA oxidation either in cardiac myocytes or in isolated SS and IMF mitochondria (P > 0.05). In contrast, sarcolemmal plasma membrane fatty acid binding protein (FABPpm) and fatty acid translocase (FAT/CD36) protein and palmitate transport rates into cardiac vesicles were increased (P < 0.05; +50%) in obese animals. Collectively these data indicate that mitochondrial dysfunction in LCFA oxidation is not responsible for lipid accumulation in obese Zucker rat hearts. Rather, increased sarcolemmal LCFA transport proteins and rates of LCFA transport result in a greater number of lipid droplets within cardiac muscle.
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Affiliation(s)
- Graham P Holloway
- Human Health & Nutritional Sciences, University of Guelph, Guelph, Canada.
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20
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Holloway GP, Schwenk RW, Luiken JJFP, Glatz JFC, Bonen A. Fatty acid transport in skeletal muscle: role in energy provision and insulin resistance. ACTA ACUST UNITED AC 2010. [DOI: 10.2217/clp.10.51] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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21
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Talanian JL, Holloway GP, Snook LA, Heigenhauser GJF, Bonen A, Spriet LL. Exercise training increases sarcolemmal and mitochondrial fatty acid transport proteins in human skeletal muscle. Am J Physiol Endocrinol Metab 2010; 299:E180-8. [PMID: 20484014 DOI: 10.1152/ajpendo.00073.2010] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Fatty acid oxidation is highly regulated in skeletal muscle and involves several sites of regulation, including the transport of fatty acids across both the plasma and mitochondrial membranes. Transport across these membranes is recognized to be primarily protein mediated, limited by the abundance of fatty acid transport proteins on the respective membranes. In recent years, evidence has shown that fatty acid transport proteins move in response to acute and chronic perturbations; however, in human skeletal muscle the localization of fatty acid transport proteins in response to training has not been examined. Therefore, we determined whether high-intensity interval training (HIIT) increased total skeletal muscle, sarcolemmal, and mitochondrial membrane fatty acid transport protein contents. Ten untrained females (22 +/- 1 yr, 65 +/- 2 kg; .VO(2peak): 2.8 +/- 0.1 l/min) completed 6 wk of HIIT, and biopsies from the vastus lateralis muscle were taken before training, and following 2 and 6 wk of HIIT. Training significantly increased maximal oxygen uptake at 2 and 6 wk (3.1 +/- 0.1, 3.3 +/- 0.1 l/min). Training for 6 wk increased FAT/CD36 at the whole muscle (10%) and mitochondrial levels (51%) without alterations in sarcolemmal content. Whole muscle plasma membrane fatty acid binding protein (FABPpm) also increased (48%) after 6 wk of training, but in contrast to FAT/CD36, sarcolemmal FABPpm increased (23%), whereas mitochondrial FABPpm was unaltered. The changes on sarcolemmal and mitochondrial membranes occurred rapidly, since differences (< or =2 wk) were not observed between 2 and 6 wk. This is the first study to demonstrate that exercise training increases fatty acid transport protein content in whole muscle (FAT/CD36 and FABPpm) and sarcolemmal (FABPpm) and mitochondrial (FAT/CD36) membranes in human skeletal muscle of females. These results suggest that increases in skeletal muscle fatty acid oxidation following training are related in part to changes in fatty acid transport protein content and localization.
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Affiliation(s)
- Jason L Talanian
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada.
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22
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Glatz JFC, Luiken JJFP, Bonen A. Membrane Fatty Acid Transporters as Regulators of Lipid Metabolism: Implications for Metabolic Disease. Physiol Rev 2010; 90:367-417. [DOI: 10.1152/physrev.00003.2009] [Citation(s) in RCA: 515] [Impact Index Per Article: 36.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Long-chain fatty acids and lipids serve a wide variety of functions in mammalian homeostasis, particularly in the formation and dynamic properties of biological membranes and as fuels for energy production in tissues such as heart and skeletal muscle. On the other hand, long-chain fatty acid metabolites may exert toxic effects on cellular functions and cause cell injury. Therefore, fatty acid uptake into the cell and intracellular handling need to be carefully controlled. In the last few years, our knowledge of the regulation of cellular fatty acid uptake has dramatically increased. Notably, fatty acid uptake was found to occur by a mechanism that resembles that of cellular glucose uptake. Thus, following an acute stimulus, particularly insulin or muscle contraction, specific fatty acid transporters translocate from intracellular stores to the plasma membrane to facilitate fatty acid uptake, just as these same stimuli recruit glucose transporters to increase glucose uptake. This regulatory mechanism is important to clear lipids from the circulation postprandially and to rapidly facilitate substrate provision when the metabolic demands of heart and muscle are increased by contractile activity. Studies in both humans and animal models have implicated fatty acid transporters in the pathogenesis of diseases such as the progression of obesity to insulin resistance and type 2 diabetes. As a result, membrane fatty acid transporters are now being regarded as a promising therapeutic target to redirect lipid fluxes in the body in an organ-specific fashion.
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Affiliation(s)
- Jan F. C. Glatz
- Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, Maastricht, The Netherlands; and Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Canada
| | - Joost J. F. P. Luiken
- Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, Maastricht, The Netherlands; and Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Canada
| | - Arend Bonen
- Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, Maastricht, The Netherlands; and Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Canada
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23
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McFarlan JT, Bonen A, Guglielmo CG. Seasonal upregulation of fatty acid transporters in flight muscles of migratory white-throated sparrows (Zonotrichia albicollis). J Exp Biol 2009; 212:2934-40. [DOI: 10.1242/jeb.031682] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
SUMMARY
Endurance flights of birds, some known to last several days, can only be sustained by high rates of fatty acid uptake by flight muscles. Previous research in migratory shorebirds indicates that this is made possible in part by very high concentrations of cytosolic heart-type fatty acid binding protein(H-FABP), which is substantially upregulated during migratory seasons. We investigated if H-FABP and other components of muscle fatty acid transport also increase during these seasons in a passerine species, the white-throated sparrow (Zonotrichia albicollis). Fatty acid translocase (FAT/CD36)and plasma-membrane fatty acid binding protein (FABPpm) are well characterized mammalian proteins that facilitate transport of fatty acid through the muscle membrane, and in this study they were identified for the first time in birds. We used quantitative PCR to measure mRNA of FAT/CD36, FABPpm and H-FABP and immunoblotting to measure protein expression of FABPpm and H-FABP in the pectoralis muscles of sparrows captured in migratory (spring, fall) and non-migratory (winter) seasons. During migratory seasons, mRNA expression of these genes increased 70–1000% above wintering levels, while protein expression of H-FABP and FABPpm increased 43% and 110% above wintering levels. Activities of key metabolic enzymes, 3-hydroxyacyl-CoA-dehydrogenase (HOAD),carnitine palmitoyl transferase II (CPT II), and citrate synthase (CS) also increased (90–110%) in pectoralis muscles of migrant birds. These results support the hypothesis that enhanced protein-mediated transport of fatty acids from the circulation into muscle is a key component of the changes in muscle biochemistry required for migration in birds.
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Affiliation(s)
- Jay T. McFarlan
- Department of Biology, University of Western Ontario, London, ON, Canada, N6A 5B7
- Department of Human Health and Nutritional Science, University of Guelph,Guelph, ON, Canada, N1G 2W1
| | - Arend Bonen
- Department of Human Health and Nutritional Science, University of Guelph,Guelph, ON, Canada, N1G 2W1
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24
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Jain SS, Chabowski A, Snook LA, Schwenk RW, Glatz JFC, Luiken JJFP, Bonen A. Additive effects of insulin and muscle contraction on fatty acid transport and fatty acid transporters, FAT/CD36, FABPpm, FATP1, 4 and 6. FEBS Lett 2009; 583:2294-300. [PMID: 19527715 DOI: 10.1016/j.febslet.2009.06.020] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2009] [Revised: 05/29/2009] [Accepted: 06/08/2009] [Indexed: 11/29/2022]
Abstract
Insulin and muscle contraction increase fatty acid transport into muscle by inducing the translocation of FAT/CD36. We examined (a) whether these effects are additive, and (b) whether other fatty acid transporters (FABPpm, FATP1, FATP4, and FATP6) are also induced to translocate. Insulin and muscle contraction increased glucose transport and plasmalemmal GLUT4 independently and additively (positive control). Palmitate transport was also stimulated independently and additively by insulin and by muscle contraction. Insulin and muscle contraction increased plasmalemmal FAT/CD36, FABPpm, FATP1, and FATP4, but not FATP6. Only FAT/CD36 and FATP1 were stimulated in an additive manner by insulin and by muscle contraction.
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Affiliation(s)
- Swati S Jain
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
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25
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Nickerson JG, Alkhateeb H, Benton CR, Lally J, Nickerson J, Han XX, Wilson MH, Jain SS, Snook LA, Glatz JFC, Chabowski A, Luiken JJFP, Bonen A. Greater transport efficiencies of the membrane fatty acid transporters FAT/CD36 and FATP4 compared with FABPpm and FATP1 and differential effects on fatty acid esterification and oxidation in rat skeletal muscle. J Biol Chem 2009; 284:16522-16530. [PMID: 19380575 DOI: 10.1074/jbc.m109.004788] [Citation(s) in RCA: 138] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In selected mammalian tissues, long chain fatty acid transporters (FABPpm, FAT/CD36, FATP1, and FATP4) are co-expressed. There is controversy as to whether they all function as membrane-bound transporters and whether they channel fatty acids to oxidation and/or esterification. Among skeletal muscles, the protein expression of FABPpm, FAT/CD36, and FATP4, but not FATP1, correlated highly with the capacities for oxidative metabolism (r>or=0.94), fatty acid oxidation (r>or=0.88), and triacylglycerol esterification (r>or=0.87). We overexpressed independently FABPpm, FAT/CD36, FATP1, and FATP4, within a normal physiologic range, in rat skeletal muscle, to determine the effects on fatty acid transport and metabolism. Independent overexpression of each fatty acid transporter occurred without altering either the expression or plasmalemmal content of other fatty acid transporters. All transporters increased fatty acid transport, but FAT/CD36 and FATP4 were 2.3- and 1.7-fold more effective than FABPpm and FATP1, respectively. Fatty acid transporters failed to alter the rates of fatty acid esterification into triacylglycerols. In contrast, all transporters increased the rates of long chain fatty acid oxidation, but the effects of FABPpm and FAT/CD36 were 3-fold greater than for FATP1 and FATP4. Thus, fatty acid transporters exhibit different capacities for fatty acid transport and metabolism. In vivo, FAT/CD36 and FATP4 are the most effective fatty acid transporters, whereas FABPpm and FAT/CD36 are key for stimulating fatty acid oxidation.
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Affiliation(s)
- James G Nickerson
- From the Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Hakam Alkhateeb
- Department of Laboratory Medical Sciences, Hashemite University, Zarqa 13115, Jordan
| | - Carley R Benton
- From the Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - James Lally
- From the Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Jennifer Nickerson
- From the Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Xiao-Xia Han
- From the Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Meredith H Wilson
- From the Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Swati S Jain
- From the Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Laelie A Snook
- From the Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Jan F C Glatz
- Department of Molecular Genetics, Maastricht University, 6200 MD Maastricht, The Netherlands
| | - Adrian Chabowski
- Department of Physiology, Medical University of Bialystok, 15-222 Bialystok, Poland
| | - Joost J F P Luiken
- Department of Molecular Genetics, Maastricht University, 6200 MD Maastricht, The Netherlands
| | - Arend Bonen
- From the Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
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26
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Bergouignan A, Trudel G, Simon C, Chopard A, Schoeller DA, Momken I, Votruba SB, Desage M, Burdge GC, Gauquelin-Koch G, Normand S, Blanc S. Physical inactivity differentially alters dietary oleate and palmitate trafficking. Diabetes 2009; 58:367-76. [PMID: 19017764 PMCID: PMC2628610 DOI: 10.2337/db08-0263] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
OBJECTIVE Obesity and diabetes are characterized by the incapacity to use fat as fuel. We hypothesized that this reduced fat oxidation is secondary to a sedentary lifestyle. RESEARCH DESIGN AND METHODS We investigated the effect of a 2-month bed rest on the dietary oleate and palmitate trafficking in lean women (control group, n = 8) and the effect of concomitant resistance/aerobic exercise training as a countermeasure (exercise group, n = 8). Trafficking of stable isotope-labeled dietary fats was combined with muscle gene expression and magnetic resonance imaging-derived muscle fat content analyses. RESULTS In the control group, bed rest increased the cumulative [1-(13)C]oleate and [d(31)]palmitate appearance in triglycerides (37%, P = 0.009, and 34%, P = 0.016, respectively) and nonesterified fatty acids (NEFAs) (37%, P = 0.038, and 38%, P = 0.002) and decreased muscle lipoprotein lipase (P = 0.043) and fatty acid translocase CD36 (P = 0.043) mRNA expressions. Plasma NEFA-to-triglyceride ratios for [1-(13)C]oleate and [d(31)]palmitate remained unchanged, suggesting that the same proportion of tracers enters the peripheral tissues after bed rest. Bed rest did not affect [1-(13)C]oleate oxidation but decreased [d(31)]palmitate oxidation by -8.2 +/- 4.9% (P < 0.0001). Despite a decreased spontaneous energy intake and a reduction of 1.9 +/- 0.3 kg (P = 0.001) in fat mass, exercise training did not mitigate these alterations but partially maintained fat-free mass, insulin sensitivity, and total lipid oxidation in fasting and fed states. In both groups, muscle fat content increased by 2.7% after bed rest and negatively correlated with the reduction in [d(31)]palmitate oxidation (r(2) = 0.48, P = 0.003). CONCLUSIONS While saturated and monounsaturated fats have similar plasma trafficking and clearance, physical inactivity affects the partitioning of saturated fats toward storage, likely leading to an accumulation of palmitate in muscle fat.
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Affiliation(s)
- Audrey Bergouignan
- Department of Ecology, Physiology, and Ethology, Hubert Curien Pluridisciplinary Institute, Louis Pasteur University, UMR7178 Centre National de Recherche Scientifique (CNRS), Strasbourg, France
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27
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Contractions but not AICAR increase FABPpm content in rat muscle sarcolemma. Mol Cell Biochem 2009; 326:45-53. [PMID: 19142713 DOI: 10.1007/s11010-008-0006-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2007] [Accepted: 06/17/2008] [Indexed: 12/30/2022]
Abstract
UNLABELLED In the present study, it was investigated whether acute muscle contractions in rat skeletal muscle increased the protein content of FABPpm in the plasma membrane. Furthermore, the effect of AICAR stimulation on FAT/CD36 and FABPpm protein content in sarcolemma of rat skeletal muscle was evaluated. METHODS Male wistar rats (150 g) were anesthetized and either subjected to in situ electrically induced contractions (hindlimb muscles: 20 min, 10-20 V, 200 ms trains, 100 Hz) or stimulated with the pharmacological activator of AMPK, AICAR. To investigate changes in the content of FABPpm and FAT/CD36 in the plasma membrane by these stimuli, the giant sarcolemma vesicle (GSV) technique was applied. The hindlimb muscles were removed and used for the production of GSV and lysates. All samples were analyzed using the western blotting technique. RESULTS Electrical stimulation of rat hindlimb muscle resulted in an increase in FABPpm protein content in the GSV of 61% (P < 0.05) and in FAT/CD36 protein content in the GSV of 33% (P < 0.05). AICAR stimulation increased FAT/CD36 protein content in GSV by 22% (P < 0.05), whereas FABPpm protein content in GSV was unaffected by AICAR treatment. There was no change in total FAT/CD36 and FABPpm protein expression, measured in lysates with western blotting, by either stimulus. AMPK thr172 and ERK1/2 thr202/204 phosphorylation were significantly increased with muscle contractions (P < 0.05), whereas only AMPK thr172 phosphorylation was increased with AICAR stimulation (P < 0.05). CONCLUSION These data show that contractions increase both FAT/CD36 and FABPpm protein content in skeletal muscle plasma membrane, whereas only FAT/CD36 protein content is increased when muscle are stimulated with AICAR. This suggests that AMPK is involved in regulation of FAT/CD36, but not FABPpm in skeletal muscle. However, since both ERK1/2 thr202/204 and AMPK thr172 phosphorylation are increased during muscle contractions, the present study cannot rule out that both could play a significant role in regulation of FAT/CD36 and FABPpm during muscle contractions.
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Bonen A, Han XX, Tandon NN, Glatz JFC, Lally J, Snook LA, Luiken JJFP. FAT/CD36 expression is not ablated in spontaneously hypertensive rats. J Lipid Res 2008; 50:740-8. [PMID: 19066404 DOI: 10.1194/jlr.m800237-jlr200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
There is doubt whether spontaneously hypertensive rats (SHR; North American strain) are null for fatty acid translocase (FAT/CD36). Therefore, we examined whether FAT/CD36 is expressed in heart, muscle, liver and adipose tissue in SHR. Insulin resistance was present in SHR skeletal muscle. We confirmed that SHR expressed aberrant FAT mRNAs in key metabolic tissues; namely, the major 2.9 kb transcript was not expressed, but 3.8 and 5.4 kb transcripts were present. Despite this, FAT/CD36 protein was expressed in all tissues, although there were tissue-specific reductions in FAT/CD36 protein expression and plasmalemmal content, ranging from 26-85%. Fatty acid transport was reduced in adipose tissue (-50%) and was increased in liver (+47%). Normal rates of fatty acid transport occurred in heart and muscle, possibly due to compensatory upregulation of plasmalemmal fatty acid binding protein (FABPpm) in red (+123%) and white muscle (+110%). In conclusion, SHRs (North American strain) are not a natural FAT/CD36 null model, the North American strain of SHR express FAT/CD36, albeit at reduced levels.
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Affiliation(s)
- Arend Bonen
- Department of Human Health and Nutritional Sciences University of -Guelph, Guelph, Ontario, N1G 2W1, Canada.
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Holloway GP, Luiken JJFP, Glatz JFC, Spriet LL, Bonen A. Contribution of FAT/CD36 to the regulation of skeletal muscle fatty acid oxidation: an overview. Acta Physiol (Oxf) 2008; 194:293-309. [PMID: 18510711 DOI: 10.1111/j.1748-1716.2008.01878.x] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Long chain fatty acids (LCFAs) are an important substrate for ATP production within the skeletal muscle. The process of LCFA delivery from adipose tissue to muscle mitochondria involves many regulatory steps. Recently, it has been recognized that LCFA oxidation is not only dependent on LCFA delivery to the muscle, but also on regulatory steps within the muscle. Increasing selected fatty acid binding proteins/transporters on the plasma membrane facilitates a very rapid LCFA increase into the muscle, independent of any changes in LCFA delivery to the muscle. Such a mechanism of LCFA transporter translocation is activated by muscle contraction. Intramuscular triacylglycerols may also be hydrolysed to provide fatty acids for mitochondrial oxidation, particularly during exercise, when hormone-sensitive lipase and other enzymes are activated. Mitochondrial LCFA entry is also highly regulated. This however does not involve only the malonyl CoA carnitine palmitoyltransferase-I (CPTI) axis. Exercise-induced fatty acid entry into mitochondria is also regulated by at least one of the proteins (FAT/CD36) that also regulates plasma membrane fatty acid transport. Among individuals, differences in mitochondrial fatty acid oxidation appear to be correlated with the content of mitochondrial CPTI and FAT/CD36. This paper provides a brief overview of mechanisms that regulate LCFA uptake and oxidation in skeletal muscle during exercise and in obesity. We focus largely on our own work on FAT/CD36, which contributes to regulating, in a coordinated fashion, LCFA uptake across the plasma membrane and the mitochondrial membrane. Very little is known about the roles of FATP1-6 on fatty acid transport in skeletal muscle.
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Affiliation(s)
- G P Holloway
- Department of Human Health and Nutritional Sciences University of Guelph, Guelph, ON, Canada
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30
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Nickerson JG, Momken I, Benton CR, Lally J, Holloway GP, Han XX, Glatz JFC, Chabowski A, Luiken JJFP, Bonen A. Protein-mediated fatty acid uptake: regulation by contraction, AMP-activated protein kinase, and endocrine signals. Appl Physiol Nutr Metab 2008; 32:865-73. [PMID: 18059611 DOI: 10.1139/h07-084] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Fatty acid transport into heart and skeletal muscle occurs largely through a highly regulated protein-mediated mechanism involving a number of fatty acid transporters. Chronically altered muscle activity (chronic muscle stimulation, denervation) alters fatty acid transport by altering the expression of fatty acid transporters and (or) their subcellular location. Chronic exposure to leptin downregulates while insulin upregulates fatty acid transport by altering concomitantly the expression of fatty acid transporters. Fatty acid transport can also be regulated within minutes, by muscle contraction, AMP-activated protein kinase activation, leptin, and insulin, through induction of the translocation of fatty acid translocase (FAT)/CD36 from its intracellular depot to the plasma membrane. In insulin-resistant muscle, a permanent relocation of FAT/CD36 to the sarcolemma appears to account for the excess accretion of intracellular lipids that interfere with insulin signaling. Recent work has also shown that FAT/ CD36, but not plasma membrane associated fatty acid binding protein, is involved, along with carnitine palmitoyltransferase, in regulating mitochondrial fatty acid oxidation. Finally, studies in FAT/CD36 null mice indicate that this transporter has a key role in regulating fatty acid metabolism in muscle.
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Affiliation(s)
- James G Nickerson
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
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31
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Chabowski A, Górski J, Luiken JJFP, Glatz JFC, Bonen A. Evidence for concerted action of FAT/CD36 and FABPpm to increase fatty acid transport across the plasma membrane. Prostaglandins Leukot Essent Fatty Acids 2007; 77:345-53. [PMID: 18240411 DOI: 10.1016/j.plefa.2007.10.017] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
There is substantial molecular, biochemical and physiologic evidence that long-chain fatty acid transport involves a protein-mediated process. A number of fatty acid transport proteins have been identified, and for unknown reasons, some of these are coexpressed in the same tissues. In muscle and heart FAT/CD36 and FABPpm appear to be key transporters. Both proteins are regulated acutely (within minutes) and chronically (hours to days) by selected physiologic stimuli (insulin, AMP kinase activation). Acute regulation involves the translocation of FAT/CD36 by insulin, muscle contraction and AMP kinase activation, while FABPpm is induced to translocate by muscle contraction and AMP kinase activation, but not by insulin. Protein expression ofFAT/CD36 and FABPpm is regulated by prolonged AMP kinase activation (heart) or increased muscle contraction. Prolonged insulin exposure increases the expression of FAT/CD36 but not FABPpm. Trafficking of fatty acid transporters between an intracellular compartment(s) and the plasma membrane is altered in insulin-resistant skeletal muscle, as some FAT/CD36 is permanently relocated to plasma membrane, thereby contributing to insulin resistance due to the increased influx of fatty acids into muscle cells. Studies in FAT/CD36 null mice have revealed that this transporter is key to regulating the increase in the rate of fatty acid metabolism in heart and skeletal muscle. It appears based on a number of experiments that FAT/CD36 and FABPpm may collaborate to increase the rates of fatty acid transport, as these proteins co-immunoprecipitate.
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Affiliation(s)
- Adrian Chabowski
- Department of Physiology, Medical University of Bialystok, 15-089 Bialystok, Poland
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32
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Holloway GP, Thrush AB, Heigenhauser GJF, Tandon NN, Dyck DJ, Bonen A, Spriet LL. Skeletal muscle mitochondrial FAT/CD36 content and palmitate oxidation are not decreased in obese women. Am J Physiol Endocrinol Metab 2007; 292:E1782-9. [PMID: 17311893 DOI: 10.1152/ajpendo.00639.2006] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A reduction in fatty acid oxidation has been associated with lipid accumulation and insulin resistance in the skeletal muscle of obese individuals. We examined whether this decrease in fatty acid oxidation was attributable to a reduction in muscle mitochondrial content and/or a dysfunction in fatty acid oxidation within mitochondria obtained from skeletal muscle of age-matched, lean [body mass index (BMI) = 23.3 +/- 0.7 kg/m2] and obese women (BMI = 37.6 +/- 2.2 kg/m2). The mitochondrial marker enzymes citrate synthase (-34%), beta-hydroxyacyl-CoA dehydrogenase (-17%), and cytochrome c oxidase (-32%) were reduced (P < 0.05) in obese participants, indicating that mitochondrial content was diminished. Obesity did not alter the ability of isolated mitochondria to oxidize palmitate; however, fatty acid oxidation was reduced at the whole muscle level by 28% (P < 0.05) in the obese. Mitochondrial fatty acid translocase (FAT/CD36) did not differ in lean and obese individuals, but mitochondrial FAT/CD36 was correlated with mitochondrial fatty acid oxidation (r = 0.67, P < 0.05). We conclude that the reduction in fatty acid oxidation in obese individuals is attributable to a decrease in mitochondrial content, not to an intrinsic defect in the mitochondria obtained from skeletal muscle of obese individuals. In addition, it appears that mitochondrial FAT/CD36 may be involved in regulating fatty acid oxidation in human skeletal muscle.
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Affiliation(s)
- Graham P Holloway
- Department of Human Health & Nutritional Sciences, University of Guelph, 50 Stone Rd., Guelph, Ontario, Canada N1G2W1.
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33
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Bonen A, Han XX, Habets DDJ, Febbraio M, Glatz JFC, Luiken JJFP. A null mutation in skeletal muscle FAT/CD36 reveals its essential role in insulin- and AICAR-stimulated fatty acid metabolism. Am J Physiol Endocrinol Metab 2007; 292:E1740-9. [PMID: 17264223 DOI: 10.1152/ajpendo.00579.2006] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Fatty acid translocase (FAT)/CD36 is involved in regulating the uptake of long-chain fatty acids into muscle cells. However, the contribution of FAT/CD36 to fatty acid metabolism remains unknown. We examined the role of FAT/CD36 on fatty acid metabolism in perfused muscles (soleus and red and white gastrocnemius) of wild-type (WT) and FAT/CD36 null (KO) mice. In general, in muscles of KO mice, 1) insulin sensitivity and 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR) sensitivity were normal, 2) key enzymes involved in fatty acid oxidation were altered minimally or not at all, and 3) except for an increase in soleus muscle FATP1 and FATP4, these fatty acid transporters were not altered in red and white gastrocnemius muscles, whereas plasma membrane-bound fatty acid binding protein was not altered in any muscle. In KO muscles perfused under basal conditions (i.e., no insulin, no AICAR), rates of hindquarter fatty acid oxidation were reduced by 26%. Similarly, in oxidative but not glycolytic muscles, the basal rates of triacylglycerol esterification were reduced by 40%. When muscles were perfused with insulin, the net increase in fatty acid esterification was threefold greater in the oxidative muscles of WT mice compared with the oxidative muscles in KO mice. With AICAR-stimulation, the net increase in fatty acid oxidation by hindquarter muscles was 3.7-fold greater in WT compared with KO mice. In conclusion, the present studies demonstrate that FAT/CD36 has a critical role in regulating fatty acid esterification and oxidation, particularly during stimulation with insulin or AICAR.
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Affiliation(s)
- Arend Bonen
- Department of Human Health and Nutritional Science, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
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Holloway GP, Lally J, Nickerson JG, Alkhateeb H, Snook LA, Heigenhauser GJF, Calles-Escandon J, Glatz JFC, Luiken JJFP, Spriet LL, Bonen A. Fatty acid binding protein facilitates sarcolemmal fatty acid transport but not mitochondrial oxidation in rat and human skeletal muscle. J Physiol 2007; 582:393-405. [PMID: 17478525 PMCID: PMC2075306 DOI: 10.1113/jphysiol.2007.135301] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The transport of long-chain fatty acids (LCFAs) across mitochondrial membranes is regulated by carnitine palmitoyltransferase I (CPTI) activity. However, it appears that additional fatty acid transport proteins, such as fatty acid translocase (FAT)/CD36, influence not only LCFA transport across the plasma membrane, but also LCFA transport into mitochondria. Plasma membrane-associated fatty acid binding protein (FABPpm) is also known to be involved in sacrolemmal LCFA transport, and it is also present on the mitochondria. At this location, it has been identified as mitochondrial aspartate amino transferase (mAspAT), despite being structurally identical to FABPpm. Whether this protein is also involved in mitochondrial LCFA transport and oxidation remains unknown. Therefore, we have examined the ability of FABPpm/mAspAT to alter mitochondrial fatty acid oxidation. Muscle contraction increased (P < 0.05) the mitochondrial FAT/CD36 content in rat (+22%) and human skeletal muscle (+33%). By contrast, muscle contraction did not alter the content of mitochondrial FABPpm/mAspAT protein in either rat or human muscles. Electrotransfecting rat soleus muscles, in vivo, with FABPpm cDNA increased FABPpm protein in whole muscle (+150%; P < 0.05), at the plasma membrane (+117%; P < 0.05) and in mitochondria (+80%; P < 0.05). In these FABPpm-transfected muscles, palmitate transport into giant vesicles was increased by +73% (P < 0.05), and fatty acid oxidation in intact muscle was increased by +18% (P < 0.05). By contrast, despite the marked increase in mitochondrial FABPpm/mAspAT protein content (+80%), the rate of mitochondrial palmitate oxidation was not altered (P > 0.05). However, electrotransfection increased mAspAT activity by +70% (P < 0.05), and the mitochondrial FABPpm/mAspAT protein content was significantly correlated with mAspAT activity (r = 0.75). It is concluded that FABPpm has two distinct functions depending on its subcellular location: (a) it contributes to increasing sarcolemmal LCFA transport while not contributing directly to LCFA transport into mitochondria; and (b) its primary role at the mitochondria level is to transport reducing equivalents into the matrix.
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Affiliation(s)
- Graham P Holloway
- Department of Human Health & Nutritional Sciences, University of Guelph, Guelph, Canada, N1G 2W1.
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35
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Bonen A, Chabowski A, Luiken JJFP, Glatz JFC. Is membrane transport of FFA mediated by lipid, protein, or both? Mechanisms and regulation of protein-mediated cellular fatty acid uptake: molecular, biochemical, and physiological evidence. Physiology (Bethesda) 2007; 22:15-29. [PMID: 17342856 DOI: 10.1152/physiologyonline.2007.22.1.15] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
- Arend Bonen
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada.
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36
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Febbraio M, Silverstein RL. CD36: implications in cardiovascular disease. Int J Biochem Cell Biol 2007; 39:2012-30. [PMID: 17466567 PMCID: PMC2034445 DOI: 10.1016/j.biocel.2007.03.012] [Citation(s) in RCA: 181] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2006] [Revised: 03/15/2007] [Accepted: 03/16/2007] [Indexed: 12/20/2022]
Abstract
CD36 is a broadly expressed membrane glycoprotein that acts as a facilitator of fatty acid uptake, a signaling molecule, and a receptor for a wide range of ligands, including apoptotic cells, modified forms of low density lipoprotein, thrombospondins, fibrillar beta-amyloid, components of Gram positive bacterial walls and malaria infected erythrocytes. CD36 expression on macrophages, dendritic and endothelial cells, and in tissues including muscle, heart, and fat, suggest diverse roles, and indeed, this is truly a multi-functional receptor involved in both homeostatic and pathological conditions. Despite an impressive increase in our knowledge of CD36 functions, in depth understanding of the mechanistic aspects of this protein remains elusive. This review focuses on CD36 in cardiovascular disease-what we know, and what we have yet to learn.
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Affiliation(s)
- Maria Febbraio
- Cleveland Clinic, Lerner Research Institute, Department of Cell Biology, NC-10, 9500 Euclid Avenue, Cleveland, OH 44195, United States.
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37
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Alkhateeb H, Chabowski A, Bonen A. Viability of the isolated soleus muscle during long-term incubation. Appl Physiol Nutr Metab 2006; 31:467-76. [PMID: 16900237 DOI: 10.1139/h06-022] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Skeletal muscle metabolism has been examined in perfused hindlimb muscles and in isolated muscle preparations. While long-term viability of the fast-twitch epitrochlearis has been documented with respect to glucose transport, it appears that long-term incubated soleus muscles are less stable when incubated ex vivo for many hours. Therefore, in the present study, we have examined whether the isolated soleus muscle remains metabolically viable for up to 18 h with respect to maintaining ATP and phosphocreatine (PCr) concentrations, carbohydrate and fatty-acid metabolism, insulin signalling, and protein expression. Soleus muscles were incubated in well-oxygenated Medium 199 (M199) supplemented with low concentrations of insulin (14.3 microU/mL) for 0, 6, 12, and 18 h. During this incubating period the concentrations of ATP and PCr were stable, indicating that oxygenation and substrate supply were being maintained. In addition, the concentrations of proglycogen and macroglycogen were not altered, whereas an increase (+30%) in intramuscular triacylglycerol concentration was observed at the end of 18 h of incubation (p < 0.05). Complex molecular processes in the long-term incubated muscles were also stable. This was shown by maintenance of basal as well as insulin-stimulated rates of 3-O-methyl glucose transport, and by the maintenance of protein expression of the glucose transporter GLUT4 and the fatty acid transporters FAT/CD36 and FABPpm. In addition, the insulin-stimulated translocation of GLUT4 to the plasma membrane, which involves a complex signalling cascade, was fully preserved. In conclusion, in well-oxygenated soleus muscles maintained in M199 supplemented with extremely low concentrations of insulin, ATP and PCr concentrations, carbohydrate and fatty acid metabolism, insulin signalling, and protein expression were stably maintained for up to 18 h. This provides for opportunities to examine muscle metabolic function under very highly controlled conditions.
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Affiliation(s)
- Hakam Alkhateeb
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
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Chabowski A, Górski J, Bonen A. Regulation of fatty acid transport: from transcriptional to posttranscriptional effects. Naunyn Schmiedebergs Arch Pharmacol 2006; 373:259-63. [PMID: 16724206 DOI: 10.1007/s00210-006-0075-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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Bonen A, Nickerson JG, Momken I, Chabowski A, Calles-Escandon J, Tandon NN, Glatz JFC, Luiken JJFP. Tissue-Specific and Fatty Acid Transporter-Specific Changes in Heart and Soleus Muscle Over a 1-yr Period. Mol Cell Biochem 2006; 291:145-54. [PMID: 16718359 DOI: 10.1007/s11010-006-9208-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2006] [Accepted: 03/30/2006] [Indexed: 11/25/2022]
Abstract
Rates of fatty acid oxidation increase rapidly in both rat heart and skeletal muscle in the early postnatal period. Therefore, we examined in heart and soleus muscle, (a) whether there were rapid changes in fatty acid transporter (FAT/CD36, FABPpm) mRNA and protein expression early in life (days 10 -36) and thereafter (days 84, 160, 365), and (b) whether the rates of fatty acid transport and the plasmalemmal content of FAT/CD36 and FABPpm were altered. Protein expression was altered rapidly from day 10-36 in both heart (FAT/CD36 only, +21%, P < 0.05)) and soleus muscle (FAT/CD36 + 100%, P < 0.05; FABPpm -20%, P < 0.05), with no further changes thereafter (P < 0.05). Rates of fatty acid transport (day 10 vs day 160) were increased in heart (+33%, P < 0.05) and muscle (+85%, P < 0.05), and were associated with concomitant increases in plasmalemmal FABPpm (+44%, P < 0.05) and FAT/CD36 (+16%, P < 0.05) in the heart, and only plasmalemmal FAT/CD36 in muscle (+90%, P < 0.05). Therefore, known changes in the rates of fatty acid oxidation in heart and muscle early in life appear to be accompanied by a concurrent upregulation in the rates of fatty acid transport and the expression of FAT/CD36 in heart and muscle, as well as an increase in plasmalemmal FAT/CD36 and FABPpm in the heart, and only plasmalemmal FAT/CD36 in soleus muscle. We speculate that the rapid upregulation of fatty acid transport rates in heart and muscle are needed to support the increased rates of fatty oxidation that have been previously observed in these tissues.
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Affiliation(s)
- Arend Bonen
- Department of Human Health and Nutritional Sciences University of Guelph, Guelph, Ontario, N1G 2W1, Canada.
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40
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Chabowski A, Momken I, Coort SLM, Calles-Escandon J, Tandon NN, Glatz JFC, Luiken JJFP, Bonen A. Prolonged AMPK activation increases the expression of fatty acid transporters in cardiac myocytes and perfused hearts. Mol Cell Biochem 2006; 288:201-12. [PMID: 16710744 DOI: 10.1007/s11010-006-9140-8] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2005] [Accepted: 01/18/2006] [Indexed: 10/24/2022]
Abstract
Recently, fatty acid transport across the plasma membrane has been shown to be a key process that contributes to the regulation of fatty acid metabolism in the heart. Since AMP kinase activation by 5-aminoimidazole-4-carboxamide-1-beta-D: -ribofuranoside (AICAR) stimulates fatty acid oxidation, as well as the expression of selected proteins involved with energy provision, we examined (a) whether AICAR induced the expression of the fatty acid transporters FABPpm and FAT/CD36 in cardiac myocytes and in perfused hearts and (b) the signaling pathway involved. Incubation of cardiac myocytes with AICAR increased the protein expression of the fatty acid transporter FABPpm after 90 min (+27%, P < 0.05) and this protein remained stably overexpressed until 180 min. Similarly, FAT/CD36 protein expression was increased after 60 min (+38%, P < 0.05) and remained overexpressed thereafter. Protein overexpression, which occurred via transcriptional mechanisms, was dependent on the AICAR concentration, with optimal induction occurring at AICAR concentrations 1-5 mM for FABPpm and at 2-8 mM for FAT/CD36. The AICAR (2 h, 2 mM AICAR) effects on FABPpm and FAT/CD36 protein expression were similar in perfused hearts and in cardiac myocytes. AICAR also induced the plasmalemmal content of FAT/CD36 (+49%) and FABPpm (+42%) (P < 0.05). This was accompanied by a marked increase in the rate of palmitate transport (2.5 fold) into giant sarcolemmal vesicles, as well as by increased rates of palmitate oxidation in cardiac myocytes. When the AICAR-induced AMPK phosphorylation was blocked, neither FAT/CD36 nor FABPpm were overexpressed, nor were palmitate uptake and oxidation increased. This study has revealed that AMPK activation stimulates the protein expression of both fatty acid transporters, FAT/CD36 and FABPpm in (a) time- and (b) dose-dependent manner via (c) the AMPK signaling pathway. AICAR also (d) increased the plasmalemmal content of FAT/CD36 and FABPm, thereby (e) increasing the rates of fatty acid transport. Thus, activation of AMPK is a key mechanism regulating the expression as well as the plasmalemmal localization of fatty acid transporters.
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Affiliation(s)
- Adrian Chabowski
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
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41
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Benton CR, Koonen DPY, Calles-Escandon J, Tandon NN, Glatz JFC, Luiken JJFP, Heikkila JJ, Bonen A. Differential effects of contraction and PPAR agonists on the expression of fatty acid transporters in rat skeletal muscle. J Physiol 2006; 573:199-210. [PMID: 16484294 PMCID: PMC1779691 DOI: 10.1113/jphysiol.2006.106013] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
We have examined over the course of a 1-week period the independent and combined effects of chronically increased muscle contraction and the peroxisome proliferator-activated receptor (PPAR)alpha and PPARgamma activators, Wy 14,643 and rosiglitazone, on the expression and plasmalemmal content of the fatty acid transporters, FAT/CD36 and FABPpm, as well as on the rate of fatty acid transport. In resting muscle, the activation of either PPARalpha or PPARgamma failed to induce the protein expression of FAT/CD36. PPARalpha activation also failed to induce the protein expression of FABPpm. In contrast, PPARgamma activation induced the expression of FABPpm protein (40%; P < 0.05). Chronic muscle contraction increased the protein expression of FAT/CD36 (approximately 50%; P < 0.05), whereas FABPpm was slightly increased (12%; P < 0.05). Neither PPARalpha nor PPARgamma activation altered the contraction-induced expression of FAT/CD36 or FABPpm. Changes in protein expression of FAT/CD36 or FABPpm, induced by either contractions or by administration of rosiglitazone, were largely attributable to increased transcription. The contraction-induced increments in FAT/CD36 were accompanied by parallel increments in plasmalemmal FAT/CD36 and in rates of fatty acid transport (P < 0.05). Up-regulation of FABPpm expression was, however, accompanied by a reduction in plasmalemmal FABPpm, which did not affect the rates of long chain fatty acid (LCFA) transport. These studies have shown that in skeletal muscle (i) neither PPARalpha nor PPARgamma activation alters FAT/CD36 expression, (ii) PPARgamma activation selectively up-regulates FABPpm expression and (iii) contraction-induced up-regulation of LCFA transport does not appear to occur via activation of either PPARalpha or PPARgamma.
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Affiliation(s)
- Carley R Benton
- Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada N2L 2W1
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Bonen A, Tandon NN, Glatz JFC, Luiken JJFP, Heigenhauser GJF. The fatty acid transporter FAT/CD36 is upregulated in subcutaneous and visceral adipose tissues in human obesity and type 2 diabetes. Int J Obes (Lond) 2006; 30:877-83. [PMID: 16418758 DOI: 10.1038/sj.ijo.0803212] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
BACKGROUND Long-chain fatty acids (LCFAs) cross the plasma membrane via a protein-mediated mechanism involving one or more LCFA-binding proteins. Among these, FAT/CD36 has been identified as key LCFA transporter in the heart and skeletal muscle, where it is regulated acutely and chronically by insulin. In skeletal muscle, FAT/CD36 expression and/or subcellular distribution is altered in obesity and type 2 diabetes. There is limited information as to whether the expression of this protein is also altered in subcutaneous and/or visceral adipose tissue depots in human obesity or type 2 diabetes. OBJECTIVES To compare (a) the expression of FAT/CD36 in subcutaneous and visceral adipose tissue depots in lean, overweight, and obese individuals and in type 2 diabetics, (b) to determine whether the protein expression of FAT/CD36 in these depots is associated with the severity of insulin resistance (type 2 diabetes>obese>overweight/lean) and (c) whether FAT/CD36 protein expression in these adipose tissue depots is associated with alterations in circulating substrates and hormones. SUBJECTS Subjects who were undergoing abdominal surgery and who were lean (n=10; three men, seven women), overweight (n=10; three men, seven women) or obese (n=7; one man, six women), or who had been diagnosed with type 2 diabetes (n=5; one man, four women) participated in this study. MEASUREMENTS Subcutaneous and visceral adipose tissue samples, as well as blood samples, were obtained from the subjects while under general anesthesia. Adipose tissue samples were analyzed for FAT/CD36 using Western blotting. Serum samples were analyzed for glucose, insulin, FFA and leptin. BMI was also calculated. RESULTS Subcutaneous adipose tissue FAT/CD36 expression was upregulated by +58, +76 and +150% in overweight, obese and type 2 diabetics, respectively. Relative to subcutaneous adipose tissue, visceral adipose tissue FAT/CD36 expression was upregulated in lean (+52%) and overweight subjects (+30%). In contrast, in obese subjects and type 2 diabetics, no difference in FAT/CD36 protein expression was observed between their subcutaneous and visceral adipose tissue depots (P>0.05). The subcutaneous adipose tissue FAT/CD36 expression (R=0.85) and the visceral adipose tissue FAT/CD36 expression (R=0.77) were associated with alteration in BMI and circulating glucose and insulin. CONCLUSIONS Subcutaneous adipose tissue FAT/CD36 expression is upregulated in obesity and type 2 diabetes. As FAT/CD36 expression is not different in lean, overweight and obese subjects, and was only increased in type 2 diabetics, it appears that visceral adipose tissue FAT/CD36 may respond in a less dynamic manner to metabolic disturbances than subcutaneous adipose tissue FAT/CD36.
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Affiliation(s)
- A Bonen
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada.
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Ljubicic V, Adhihetty PJ, Hood DA. Application of Animal Models: Chronic Electrical Stimulation-Induced Contractile Activity. ACTA ACUST UNITED AC 2005; 30:625-43. [PMID: 16293907 DOI: 10.1139/h05-144] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Unilateral, chronic low-frequency electrical stimulation (CLFS) is an experimental model that evokes numerous biochemical and physiological adaptations in skeletal muscle. These occur within a short time frame and are restricted to the stimulated muscle. The humoral effects of whole body exercise are eliminated and the nonstimulated contralaterai limb can often be used as a control muscle, if possible effects on the contralateral side are considered. CLFS induces a fast-to-slow transformation of muscle because of alterations in calcium dynamics and myofibrillar proteins, and a white-to-red transformation because of changes in mitochondrial enzymes, myoglobin, and the induction of angiogenesis. These adaptations occur in a coordinated time-dependent manner and result from altered gene expression, including transcriptional and posttranscriptional processes. CLFS techniques have also been applied to myocytes in cell culture, which provide a greater opportunity for the delivery of pharmacological agents or for the application of gene transfer methodologies. Clinical applications of the CLFS technique have been limited, but they have shown potential therapeutic value in patients in whom voluntary muscle contraction is not possible due to debilitating disease and/or injury. Thus the CLFS technique has great value for studying various aspects of muscle adaptation, and its wider scientific application to a variety of neuromuscular-based disorders in humans appears to be warranted. Key words: skeletal muscle, muscle plasticity, endurance training, mitochondrial biogenesis, fiber types
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Affiliation(s)
- Vladimir Ljubicic
- School of Kinesiology and Health Science and Department of Biology, York University, Toronto, Ontario M3J 1P3, Canada
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Roepstorff C, Vistisen B, Roepstorff K, Kiens B. Regulation of plasma long-chain fatty acid oxidation in relation to uptake in human skeletal muscle during exercise. Am J Physiol Endocrinol Metab 2004; 287:E696-705. [PMID: 15186996 DOI: 10.1152/ajpendo.00001.2004] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In the present study, we investigated possible sites of regulation of long-chain fatty acid (LCFA) oxidation in contracting human skeletal muscle. Leg plasma LCFA kinetics were determined in eight healthy men during bicycling (60 min, 65% peak oxygen uptake) with either high (H-FOX) or low (L-FOX) leg fat oxidation (H-FOX: 1,098 +/- 140; L-FOX: 494 +/- 84 micromol FA/min, P < 0.001), which was achieved by manipulating preexercise muscle glycogen (H-FOX: 197 +/- 21; L-FOX: 504 +/- 25 mmol/kg dry wt, P < 0.001). Several blood metabolites and hormones were kept nearly similar between trials by allocating a preexercise meal and infusing glucose intravenously during exercise. During exercise, leg plasma LCFA fractional extraction was identical between trials (H-FOX: 17.8 +/- 1.6; L-FOX: 18.2 +/- 1.8%, not significant), suggesting similar LCFA transport capacity in muscle. On the contrary, leg plasma LCFA oxidation was 99% higher in H-FOX than in L-FOX (421 +/- 47 vs. 212 +/- 37 micromol/min, P < 0.001). Probably due to the slightly higher (P < 0.01) plasma LCFA concentration in H-FOX than in L-FOX, leg plasma LCFA uptake was nonsignificantly (P = 0.17) higher (25%) in H-FOX than in L-FOX, yet the fraction of plasma LCFA uptake oxidized was 61% higher (P < 0.05) in H-FOX than in L-FOX. Accordingly, the muscle content of several lipid-binding proteins did not differ significantly between trials, although fatty acid translocase/CD36 and caveolin-1 were elevated (P < 0.05) by the high-intensity exercise and dietary manipulation allocated on the day before the experimental trial. The present data suggest that, in contracting human skeletal muscle with different fat oxidation rates achieved by manipulating preexercise glycogen content, transsarcolemmal transport is not limiting plasma LCFA oxidation. Rather, the latter seems to be limited by intracellular regulatory mechanisms.
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Affiliation(s)
- Carsten Roepstorff
- The Copenhagen Muscle Research Centre, Institute of Exercise and Sport Sciences, Department of Human Physiology, Universitetsparken 13, DK-2100 Ø, Denmark.
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Benton CR, Campbell SE, Tonouchi M, Hatta H, Bonen A. Monocarboxylate transporters in subsarcolemmal and intermyofibrillar mitochondria. Biochem Biophys Res Commun 2004; 323:249-53. [PMID: 15351729 DOI: 10.1016/j.bbrc.2004.08.084] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2004] [Indexed: 11/17/2022]
Abstract
Whether subsarcolemmal (SS) and intermyofibrillar (IMF) mitochondria contain monocarboxylate transporters (MCTs) is controversial. We have examined the presence of MCT1, 2, and 4 in highly purified SS and IMF mitochondria. These mitochondria were not contaminated with plasma membrane, sarcoplasmic reticulum or endosomal compartments, as the marker proteins for these sub-cellular compartments (Na+-K+-ATPase, Ca2+-ATPase, and the transferrin receptor) were not present in SS or IMF mitochondria. MCT1, MCT2, and MCT4 were all present at the plasma membrane. However, MCT1 and MCT4 were associated with SS mitochondria. In contrast, the IMF mitochondria were completely devoid of MCT1 and MCT4. However, MCT2 was associated with both SS and IMF mitochondria. These observations suggest that SS and IMF mitochondria have different capacities for metabolizing monocarboxylates. Thus, the controversy as to whether mitochondria can take up and oxidize lactate will need to take account of the different distribution of MCTs between SS and IMF mitochondria.
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Affiliation(s)
- Carley R Benton
- Department of Kinesiology, University of Waterloo, Waterloo, Ont., Canada N2L 3G1
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