1
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Alemany M. The Metabolic Syndrome, a Human Disease. Int J Mol Sci 2024; 25:2251. [PMID: 38396928 PMCID: PMC10888680 DOI: 10.3390/ijms25042251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Revised: 01/29/2024] [Accepted: 01/31/2024] [Indexed: 02/25/2024] Open
Abstract
This review focuses on the question of metabolic syndrome (MS) being a complex, but essentially monophyletic, galaxy of associated diseases/disorders, or just a syndrome of related but rather independent pathologies. The human nature of MS (its exceptionality in Nature and its close interdependence with human action and evolution) is presented and discussed. The text also describes the close interdependence of its components, with special emphasis on the description of their interrelations (including their syndromic development and recruitment), as well as their consequences upon energy handling and partition. The main theories on MS's origin and development are presented in relation to hepatic steatosis, type 2 diabetes, and obesity, but encompass most of the MS components described so far. The differential effects of sex and its biological consequences are considered under the light of human social needs and evolution, which are also directly related to MS epidemiology, severity, and relations with senescence. The triggering and maintenance factors of MS are discussed, with especial emphasis on inflammation, a complex process affecting different levels of organization and which is a critical element for MS development. Inflammation is also related to the operation of connective tissue (including the adipose organ) and the widely studied and acknowledged influence of diet. The role of diet composition, including the transcendence of the anaplerotic maintenance of the Krebs cycle from dietary amino acid supply (and its timing), is developed in the context of testosterone and β-estradiol control of the insulin-glycaemia hepatic core system of carbohydrate-triacylglycerol energy handling. The high probability of MS acting as a unique complex biological control system (essentially monophyletic) is presented, together with additional perspectives/considerations on the treatment of this 'very' human disease.
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Affiliation(s)
- Marià Alemany
- Faculty of Biology, Universitat de Barcelona, 08028 Barcelona, Catalonia, Spain
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2
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Acevedo LM, Vidal Á, Aguilera-Tejero E, Rivero JLL. Muscle plasticity is influenced by renal function and caloric intake through the FGF23-vitamin D axis. Am J Physiol Cell Physiol 2023; 324:C14-C28. [PMID: 36409180 DOI: 10.1152/ajpcell.00306.2022] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Skeletal muscle, the main metabolic engine in the body of vertebrates, is endowed with great plasticity. The association between skeletal muscle plasticity and two highly prevalent health problems: renal dysfunction and obesity, which share etiologic links as well as many comorbidities, is a subject of great relevance. It is important to know how these alterations impact on the structure and function of skeletal muscle because the changes in muscle phenotype have a major influence on the quality of life of the patients. This literature review aims to discuss the influence of a nontraditional axis involving kidney, bone, and muscle on skeletal muscle plasticity. In this axis, the kidneys play a role as the main site for vitamin D activation. Renal disease leads to a direct decrease in 1,25(OH)2-vitamin D, secondary to reduction in renal functional mass, and has an indirect effect, through phosphate retention, that contributes to stimulate fibroblast growth factor 23 (FGF23) secretion by bone cells. FGF23 downregulates the renal synthesis of 1,25(OH)2-vitamin D and upregulates its metabolism. Skeletal production of FGF23 is also regulated by caloric intake: it is increased in obesity and decreased by caloric restriction, and these changes impact on 1,25(OH)2-vitamin D concentrations, which are decreased in obesity and increased after caloric restriction. Thus, both phosphate retention, that develops secondary to renal failure, and caloric intake influence 1,25(OH)2-vitamin D that in turn plays a key role in muscle anabolism.
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Affiliation(s)
- Luz M Acevedo
- Department of Comparative Anatomy and Pathological Anatomy and Toxicology, Faculty of Veterinary Sciences, Laboratory of Muscular Biopathology, University of Cordoba, Spain.,Departamento de Ciencias Biomédicas, Facultad de Ciencias Veterinarias, Universidad Central de Venezuela, Maracay, Venezuela
| | - Ángela Vidal
- Maimonides Biomedical Research Institute of Cordoba (IMIBIC), Reina Sofia University Hospital, University of Cordoba, Spain
| | - Escolástico Aguilera-Tejero
- Maimonides Biomedical Research Institute of Cordoba (IMIBIC), Reina Sofia University Hospital, University of Cordoba, Spain
| | - José-Luis L Rivero
- Department of Comparative Anatomy and Pathological Anatomy and Toxicology, Faculty of Veterinary Sciences, Laboratory of Muscular Biopathology, University of Cordoba, Spain
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3
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Handy RM, Holloway GP. Insights into the development of insulin resistance: Unraveling the interaction of physical inactivity, lipid metabolism and mitochondrial biology. Front Physiol 2023; 14:1151389. [PMID: 37153211 PMCID: PMC10157178 DOI: 10.3389/fphys.2023.1151389] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Accepted: 04/07/2023] [Indexed: 05/09/2023] Open
Abstract
While impairments in peripheral tissue insulin signalling have a well-characterized role in the development of insulin resistance and type 2 diabetes (T2D), the specific mechanisms that contribute to these impairments remain debatable. Nonetheless, a prominent hypothesis implicates the presence of a high-lipid environment, resulting in both reactive lipid accumulation and increased mitochondrial reactive oxygen species (ROS) production in the induction of peripheral tissue insulin resistance. While the etiology of insulin resistance in a high lipid environment is rapid and well documented, physical inactivity promotes insulin resistance in the absence of redox stress/lipid-mediated mechanisms, suggesting alternative mechanisms-of-action. One possible mechanism is a reduction in protein synthesis and the resultant decrease in key metabolic proteins, including canonical insulin signaling and mitochondrial proteins. While reductions in mitochondrial content associated with physical inactivity are not required for the induction of insulin resistance, this could predispose individuals to the detrimental effects of a high-lipid environment. Conversely, exercise-training induced mitochondrial biogenesis has been implicated in the protective effects of exercise. Given mitochondrial biology may represent a point of convergence linking impaired insulin sensitivity in both scenarios of chronic overfeeding and physical inactivity, this review aims to describe the interaction between mitochondrial biology, physical (in)activity and lipid metabolism within the context of insulin signalling.
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4
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Gilloteaux J, Nicaise C, Sprimont L, Bissler J, Finkelstein JA, Payne WR. Leptin receptor defect with diabetes causes skeletal muscle atrophy in female obese Zucker rats where peculiar depots networked with mitochondrial damages. Ultrastruct Pathol 2021; 45:346-375. [PMID: 34743665 DOI: 10.1080/01913123.2021.1983099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Tibialis anterior muscles of 45-week-old female obese Zucker rats with defective leptin receptor and non-insulin dependent diabetes mellitus (NIDDM) showed a significative atrophy compared to lean muscles, based on histochemical-stained section's measurements in the sequence: oxidative slow twitch (SO, type I) < oxidative fast twitch (FOG, type IIa) < fast glycolytic (FG, type IIb). Both oxidative fiber's outskirts resembled 'ragged' fibers and, in these zones, ultrastructure revealed small clusters of endoplasm-like reticulum filled with unidentified electron contrasted compounds, contiguous and continuous with adjacent mitochondria envelope. The linings appeared crenated stabbed by circular patterns resembling those found of ceramides. The same fibers contained scattered degraded mitochondria that tethered electron contrasted droplets favoring larger depots while mitoptosis were widespread in FG fibers. Based on other interdisciplinary investigations on the lipid depots of diabetes 2 muscles made us to propose these accumulated contrasted contents to be made of peculiar lipids, including acyl-ceramides, as those were only found while diabetes 2 progresses in aging obese rats. These could interfere in NIDDM with mitochondrial oxidative energetic demands and muscle functions.
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Affiliation(s)
- Jacques Gilloteaux
- Department of Anatomical Sciences, St George's University School of Medicine, K B Taylor Global Scholar's Program at the University of Northumbria, School of Health and Life Sciences, Newcastle upon Tyne, UK.,Unité de Recherches de Physiologie Moleculaire (URPHyM) - Narilis, Département de Médecine, Université de Namur, Namur, Belgium.,Department of Anatomy, Northeast Ohio Medical University (Neomed), Rootstown, OH, USA
| | - Charles Nicaise
- Unité de Recherches de Physiologie Moleculaire (URPHyM) - Narilis, Département de Médecine, Université de Namur, Namur, Belgium
| | - Lindsay Sprimont
- Unité de Recherches de Physiologie Moleculaire (URPHyM) - Narilis, Département de Médecine, Université de Namur, Namur, Belgium
| | - John Bissler
- Department of Anatomy, Northeast Ohio Medical University (Neomed), Rootstown, OH, USA.,Division of Nephrology at St. Jude Children's Research Hospital and Le Bonheur Children's Hospital, The University of Tennessee Health Science Center, Memphis, TN, USA
| | - Judith A Finkelstein
- Department of Anatomy, Northeast Ohio Medical University (Neomed), Rootstown, OH, USA
| | - Warren R Payne
- Institute for Sport and Health, Footscray Park Campus, Victoria University, Melbourne, VIC, Australia
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5
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Genders AJ, Holloway GP, Bishop DJ. Are Alterations in Skeletal Muscle Mitochondria a Cause or Consequence of Insulin Resistance? Int J Mol Sci 2020; 21:ijms21186948. [PMID: 32971810 PMCID: PMC7554894 DOI: 10.3390/ijms21186948] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Revised: 09/18/2020] [Accepted: 09/18/2020] [Indexed: 12/14/2022] Open
Abstract
As a major site of glucose uptake following a meal, skeletal muscle has an important role in whole-body glucose metabolism. Evidence in humans and animal models of insulin resistance and type 2 diabetes suggests that alterations in mitochondrial characteristics accompany the development of skeletal muscle insulin resistance. However, it is unclear whether changes in mitochondrial content, respiratory function, or substrate oxidation are central to the development of insulin resistance or occur in response to insulin resistance. Thus, this review will aim to evaluate the apparent conflicting information placing mitochondria as a key organelle in the development of insulin resistance in skeletal muscle.
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Affiliation(s)
- Amanda J. Genders
- Institute for Health and Sport (iHeS), Victoria University, Melbourne 8001, Australia;
- Correspondence: ; Tel.: +61-3-9919-9556
| | - Graham P. Holloway
- Dept. Human Health and Nutritional Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada;
| | - David J. Bishop
- Institute for Health and Sport (iHeS), Victoria University, Melbourne 8001, Australia;
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6
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Liu Y, Neumann D, Glatz JFC, Luiken JJFP. Molecular mechanism of lipid-induced cardiac insulin resistance and contractile dysfunction. Prostaglandins Leukot Essent Fatty Acids 2018; 136:131-141. [PMID: 27372802 DOI: 10.1016/j.plefa.2016.06.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Accepted: 06/10/2016] [Indexed: 01/04/2023]
Abstract
Long-chain fatty acids are the main cardiac substrates from which ATP is generated continually to serve the high energy demand and sustain the normal function of the heart. Under healthy conditions, fatty acid β-oxidation produces 50-70% of the energy demands with the remainder largely accounted for by glucose. Chronically increased dietary lipid supply often leads to excess lipid accumulation in the heart, which is linked to a variety of maladaptive phenomena, such as insulin resistance, cardiac hypertrophy and contractile dysfunction. CD36, the predominant cardiac fatty acid transporter, has a key role in setting the heart on a road to contractile dysfunction upon the onset of chronic lipid oversupply by translocating to the cell surface and opening the cellular 'doors' for fatty acids. The sequence of events after the CD36-mediated myocellular lipid accumulation is less understood, but in general it has been accepted that the excessively imported lipids cause insulin resistance, which in turn leads to contractile dysfunction. There are several gaps of knowledge in this proposed order of events which this review aims to discuss. First, the molecular mechanisms underlying lipid-induced insulin resistance are not yet completely disclosed. Specifically, several mediators have been proposed, such as diacylglycerols, ceramides, peroxisome proliferator-activated receptors (PPAR), inflammatory kinases and reactive oxygen species (ROS), but their relative contributions to the onset of insulin resistance and their putatively synergistic actions are topics of controversy. Second, there are also pieces of evidence that lipids can induce contractile dysfunction independently of insulin resistance. Perhaps, a more integrative view is needed, in which several lipid-induced pathways operate synergistically or in parallel to induce contractile dysfunction. Unraveling of these processes is expected to be important in designing effective therapeutic strategies to protect the lipid-overloaded heart.
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Affiliation(s)
- Yilin Liu
- Department of Molecular Genetics, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands
| | - Dietbert Neumann
- Department of Molecular Genetics, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands
| | - Jan F C Glatz
- Department of Molecular Genetics, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands.
| | - Joost J F P Luiken
- Department of Molecular Genetics, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands
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7
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Daemen S, van Polanen N, Hesselink MKC. The effect of diet and exercise on lipid droplet dynamics in human muscle tissue. ACTA ACUST UNITED AC 2018. [PMID: 29514886 DOI: 10.1242/jeb.167015] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The majority of fat in the human body is stored as triacylglycerols in white adipose tissue. In the obese state, adipose tissue mass expands and excess lipids are stored in non-adipose tissues, such as skeletal muscle. Lipids are stored in skeletal muscle in the form of small lipid droplets. Although originally viewed as dull organelles that simply store lipids as a consequence of lipid overflow from adipose tissue, lipid droplets are now recognized as key components in the cell that exert a variety of relevant functions in multiple tissues (including muscle). Here, we review the effect of diet and exercise interventions on myocellular lipid droplets and their putative role in insulin sensitivity from a human perspective. We also provide an overview of lipid droplet biology and identify gaps for future research.
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Affiliation(s)
- Sabine Daemen
- Department of Human Biology and Human Movement Sciences, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, 6200MD Maastricht, The Netherlands
| | - Nynke van Polanen
- Department of Human Biology and Human Movement Sciences, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, 6200MD Maastricht, The Netherlands
| | - Matthijs K C Hesselink
- Department of Human Biology and Human Movement Sciences, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, 6200MD Maastricht, The Netherlands
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8
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Nielsen J, Christensen AE, Nellemann B, Christensen B. Lipid droplet size and location in human skeletal muscle fibers are associated with insulin sensitivity. Am J Physiol Endocrinol Metab 2017; 313:E721-E730. [PMID: 28743757 DOI: 10.1152/ajpendo.00062.2017] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Revised: 06/28/2017] [Accepted: 07/18/2017] [Indexed: 11/22/2022]
Abstract
In skeletal muscle, an accumulation of lipid droplets (LDs) in the subsarcolemmal space is associated with insulin resistance, but the underlying mechanism is not clear. We aimed to investigate how the size, number, and location of LDs are associated with insulin sensitivity and muscle fiber types and are regulated by aerobic training and treatment with an erythropoiesis-stimulating agent (ESA) in healthy young untrained men. LD analyses were performed by quantitative transmission electron microscopy, and insulin sensitivity was assessed by a hyperinsulinemic-euglycemic clamp. At baseline, we found that only the diameter (and not the number) of individual subsarcolemmal LDs was negatively associated with insulin sensitivity (R2 = 0.20, P = 0.03, n = 29). Despite 34% (P = 0.004) fewer LDs, the diameter of individual subsarcolemmal LDs was 20% (P = 0.0004) larger in type 2 fibers than in type 1 fibers. Furthermore, aerobic training decreased the size of subsarcolemmal LDs in the type 2 fibers, and ESA treatment lowered the number of both intermyofibrillar and subsarcolemmal LDs in the type 1 fibers. In conclusion, the size of individual subsarcolemmal LDs may be involved in the mechanism by which LDs are associated with insulin resistance in skeletal muscle.
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Affiliation(s)
- Joachim Nielsen
- Department of Sports Science and Clinical Biomechanics, SDU Muscle Research Cluster (SMRC), University of Southern Denmark, Odense M, Denmark;
- Department of Pathology, SDU Muscle Research Cluster (SMRC), Odense University Hospital, Odense C, Denmark; and
| | - Anders E Christensen
- Department of Sports Science and Clinical Biomechanics, SDU Muscle Research Cluster (SMRC), University of Southern Denmark, Odense M, Denmark
| | - Birgitte Nellemann
- Department of Endocrinology and Internal Medicine, NBG/THG, Aarhus University Hospital, Aarhus, Denmark
| | - Britt Christensen
- Department of Endocrinology and Internal Medicine, NBG/THG, Aarhus University Hospital, Aarhus, Denmark
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9
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Acevedo LM, Raya AI, Ríos R, Aguilera-Tejero E, Rivero JLL. Obesity-induced discrepancy between contractile and metabolic phenotypes in slow- and fast-twitch skeletal muscles of female obese Zucker rats. J Appl Physiol (1985) 2017; 123:249-259. [PMID: 28522764 DOI: 10.1152/japplphysiol.00282.2017] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 05/10/2017] [Accepted: 05/10/2017] [Indexed: 01/02/2023] Open
Abstract
A clear picture of skeletal muscle adaptations to obesity and related comorbidities remains elusive. This study describes fiber-type characteristics (size, proportions, and oxidative enzyme activity) in two typical hindlimb muscles with opposite structure and function in an animal model of genetic obesity. Lesser fiber diameter, fiber-type composition, and histochemical succinic dehydrogenase activity (an oxidative marker) of muscle fiber types were assessed in slow (soleus)- and fast (tibialis cranialis)-twitch muscles of obese Zucker rats and compared with age (16 wk)- and sex (females)-matched lean Zucker rats (n = 16/group). Muscle mass and lesser fiber diameter were lower in both muscle types of obese compared with lean animals even though body weights were increased in the obese cohort. A faster fiber-type phenotype also occurred in slow- and fast-twitch muscles of obese rats compared with lean rats. These adaptations were accompanied by a significant increment in histochemical succinic dehydrogenase activity of slow-twitch fibers in the soleus muscle and fast-twitch fiber types in the tibialis cranialis muscle. Obesity significantly increased plasma levels of proinflammatory cytokines but did not significantly affect protein levels of peroxisome proliferator-activated receptors PPARγ or PGC1α in either muscle. These data demonstrate that, in female Zucker rats, obesity induces a reduction of muscle mass in which skeletal muscles show a diminished fiber size and a faster and more oxidative phenotype. It was noteworthy that this discrepancy in muscle's contractile and metabolic features was of comparable nature and extent in muscles with different fiber-type composition and antagonist functions.NEW & NOTEWORTHY This study demonstrates a discrepancy between morphological (reduced muscle mass), contractile (shift toward a faster phenotype), and metabolic (increased mitochondrial oxidative enzyme activity) characteristics in skeletal muscles of female Zucker fatty rats. It is noteworthy that this inconsistency was comparable (in nature and extent) in muscles with different structure and function.
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Affiliation(s)
- Luz M Acevedo
- Laboratorio de Biopatología Muscular, Departamento de Anatomía y Anatomía Patológica Comparadas, Universidad de Córdoba, Córdoba, Spain.,Departamento de Ciencias Biomédicas, Universidad Central de Venezuela, Maracay, Venezuela
| | - Ana I Raya
- Departamento de Medicina y Cirugía Animal, Universidad de Córdoba, Córdoba, Spain.,Instituto Maimónides de Investigación Biomédica de Córdoba, Hospital Universitario Reina Sofia, Universidad de Córdoba, Córdoba, Spain; and
| | - Rafael Ríos
- Departamento de Medicina y Cirugía Animal, Universidad de Córdoba, Córdoba, Spain.,Instituto Maimónides de Investigación Biomédica de Córdoba, Hospital Universitario Reina Sofia, Universidad de Córdoba, Córdoba, Spain; and
| | - Escolástico Aguilera-Tejero
- Departamento de Medicina y Cirugía Animal, Universidad de Córdoba, Córdoba, Spain.,Instituto Maimónides de Investigación Biomédica de Córdoba, Hospital Universitario Reina Sofia, Universidad de Córdoba, Córdoba, Spain; and
| | - José-Luis L Rivero
- Laboratorio de Biopatología Muscular, Departamento de Anatomía y Anatomía Patológica Comparadas, Universidad de Córdoba, Córdoba, Spain;
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10
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Colin IM, Colin H, Dufour I, Gielen CE, Many MC, Saey J, Knoops B, Gérard AC. Extrapancreatic effects of incretin hormones: evidence for weight-independent changes in morphological aspects and oxidative status in insulin-sensitive organs of the obese nondiabetic Zucker rat (ZFR). Physiol Rep 2017; 4:4/15/e12886. [PMID: 27511983 PMCID: PMC4985551 DOI: 10.14814/phy2.12886] [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: 04/10/2016] [Accepted: 07/18/2016] [Indexed: 12/16/2022] Open
Abstract
Incretin‐based therapies are widely used to treat type 2 diabetes. Although hypoglycemic actions of incretins are mostly due to their insulinotropic/glucagonostatic effects, they may also influence extrapancreatic metabolism. We administered exendin‐4 (Ex‐4), a long‐acting glucagon‐like peptide receptor agonist, at low dose (0.1 nmol/kg/day) for a short period (10 days), in obese nondiabetic fa/fa Zucker rats (ZFRs). Ex‐4‐treated ZFRs were compared to vehicle (saline)‐treated ZFRs and vehicle‐ and Ex‐4‐treated lean rats (LRs). Blood glucose levels were measured at days 0, 9, and 10. Ingested food and animal weight were recorded daily. On the day of sacrifice (d10), blood was sampled along with liver, epididymal, subcutaneous, brown adipose, and skeletal muscle tissues from animals fasted for 24 h. Plasma insulin and blood glucose levels, food intake, and body and epididymal fat weight were unchanged, but gross morphological changes were observed in insulin‐sensitive tissues. The average size of hepatocytes was significantly lower in Ex‐4‐treated ZFRs, associated with decreased number and size of lipid droplets and 4‐hydroxy‐2‐nonenal (HNE) staining, a marker of oxidative stress (OS). Myocytes, which were smaller in ZFRs than in LRs, were significantly enlarged and depleted of lipid droplets in Ex‐4‐treated ZFRs. Weak HNE staining was increased by Ex‐4. A similar observation was made in brown adipose tissue, whereas the elevated HNE staining observed in epididymal adipocytes of ZFRs, suggestive of strong OS, was decreased by Ex‐4. These results suggest that incretins by acting on OS in insulin‐sensitive tissues may contribute to weight‐independent improvement in insulin sensitivity.
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Affiliation(s)
- Ides M Colin
- Endocrino-Diabetology Research Unit, Centre Hospitalier Régional (CHR) Mons-Hainaut, Mons, Belgium
| | - Henri Colin
- Faculté de Médecine, Pôle de Morphologie, Institut de Recherche Expérimentale et Clinique (IREC) Secteur des Sciences de la Santé (SSS) Université catholique de Louvain (UCL), Brussels, Belgium
| | - Ines Dufour
- Faculté de Médecine, Pôle de Morphologie, Institut de Recherche Expérimentale et Clinique (IREC) Secteur des Sciences de la Santé (SSS) Université catholique de Louvain (UCL), Brussels, Belgium
| | - Charles-Edouard Gielen
- Faculté de Médecine, Pôle de Morphologie, Institut de Recherche Expérimentale et Clinique (IREC) Secteur des Sciences de la Santé (SSS) Université catholique de Louvain (UCL), Brussels, Belgium
| | - Marie-Christine Many
- Faculté de Médecine, Pôle de Morphologie, Institut de Recherche Expérimentale et Clinique (IREC) Secteur des Sciences de la Santé (SSS) Université catholique de Louvain (UCL), Brussels, Belgium
| | - Jean Saey
- Endocrino-Diabetology Research Unit, Centre Hospitalier Régional (CHR) Mons-Hainaut, Mons, Belgium
| | - Bernard Knoops
- Group of Animal and Molecular Cell Biology, Institut des Sciences de la Vie, Université catholique de Louvain (UCL), Louvain-La-Neuve, Belgium
| | - Anne-Catherine Gérard
- Endocrino-Diabetology Research Unit, Centre Hospitalier Régional (CHR) Mons-Hainaut, Mons, Belgium Group of Animal and Molecular Cell Biology, Institut des Sciences de la Vie, Université catholique de Louvain (UCL), Louvain-La-Neuve, Belgium
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11
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Acevedo LM, Raya AI, Martínez-Moreno JM, Aguilera–Tejero E, Rivero JLL. Mangiferin protects against adverse skeletal muscle changes and enhances muscle oxidative capacity in obese rats. PLoS One 2017; 12:e0173028. [PMID: 28253314 PMCID: PMC5333851 DOI: 10.1371/journal.pone.0173028] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Accepted: 02/13/2017] [Indexed: 12/12/2022] Open
Abstract
Obesity-related skeletal muscle changes include muscle atrophy, slow-to-fast fiber-type transformation, and impaired mitochondrial oxidative capacity. These changes relate with increased risk of insulin resistance. Mangiferin, the major component of the plant Mangifera indica, is a well-known anti-inflammatory, anti-diabetic, and antihyperlipidemic agent. This study tested the hypothesis that mangiferin treatment counteracts obesity-induced fiber atrophy and slow-to-fast fiber transition, and favors an oxidative phenotype in skeletal muscle of obese rats. Obese Zucker rats were fed gelatin pellets with (15 mg/kg BW/day) or without (placebo group) mangiferin for 8 weeks. Lean Zucker rats received the same gelatin pellets without mangiferin and served as non-obese and non-diabetic controls. Lesser diameter, fiber composition, and histochemical succinic dehydrogenase activity (an oxidative marker) of myosin-based fiber-types were assessed in soleus and tibialis cranialis muscles. A multivariate discriminant analysis encompassing all fiber-type features indicated that obese rats treated with mangiferin displayed skeletal muscle phenotypes significantly different compared with both lean and obese control rats. Mangiferin significantly decreased inflammatory cytokines, preserved skeletal muscle mass, fiber cross-sectional size, and fiber-type composition, and enhanced muscle fiber oxidative capacity. These data demonstrate that mangiferin attenuated adverse skeletal muscle changes in obese rats.
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Affiliation(s)
- Luz M. Acevedo
- Laboratory of Muscular Biopathology, Department of Comparative Anatomy and Pathological Anatomy, University of Cordoba, Cordoba, Spain
| | - Ana I. Raya
- Department of Animal Medicine and Surgery, University of Cordoba, Cordoba, Spain
- Instituto Maimonides de Investigacion Biomedica de Cordoba (IMIBIC), Hospital Universitario Reina Sofia, University of Cordoba, Cordoba, Spain
| | - Julio M. Martínez-Moreno
- Instituto Maimonides de Investigacion Biomedica de Cordoba (IMIBIC), Hospital Universitario Reina Sofia, University of Cordoba, Cordoba, Spain
| | - Escolástico Aguilera–Tejero
- Department of Animal Medicine and Surgery, University of Cordoba, Cordoba, Spain
- Instituto Maimonides de Investigacion Biomedica de Cordoba (IMIBIC), Hospital Universitario Reina Sofia, University of Cordoba, Cordoba, Spain
| | - José-Luis L. Rivero
- Laboratory of Muscular Biopathology, Department of Comparative Anatomy and Pathological Anatomy, University of Cordoba, Cordoba, Spain
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12
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Gemmink A, Bosma M, Kuijpers HJH, Hoeks J, Schaart G, van Zandvoort MAMJ, Schrauwen P, Hesselink MKC. Decoration of intramyocellular lipid droplets with PLIN5 modulates fasting-induced insulin resistance and lipotoxicity in humans. Diabetologia 2016; 59:1040-8. [PMID: 26864436 PMCID: PMC4826431 DOI: 10.1007/s00125-016-3865-z] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Accepted: 12/14/2015] [Indexed: 12/24/2022]
Abstract
AIMS/HYPOTHESIS In contrast to insulin-resistant individuals, insulin-sensitive athletes possess high intramyocellular lipid content (IMCL), good mitochondrial function and high perilipin 5 (PLIN5) levels, suggesting a role for PLIN5 in benign IMCL storage. We hypothesised a role for PLIN5 in modulating fasting-mediated insulin resistance. METHODS Twelve men were fasted for 60 h, before and after which muscle biopsies were taken and stained for lipid droplets (LDs), PLIN5 and laminin. Confocal microscopy images were analysed for LD size, number, PLIN5 association and subcellular distribution. RESULTS Fasting elevated IMCL content 2.8-fold and reduced insulin sensitivity (by 55%). Individuals with the most prominent increase in IMCL showed the least reduction in insulin sensitivity (r = 0.657; p = 0.028) and mitochondrial function (r = 0.896; p = 0.006). During fasting, PLIN5 gene expression or PLIN5 protein content in muscle homogenates was unaffected, microscopy analyses revealed that the fraction of PLIN5 associated with LDs (PLIN5+) increased significantly (+26%) upon fasting, suggesting PLIN5 redistribution. The significant increase in LD number (+23%) and size (+23%) upon fasting was entirely accounted for by PLIN5+ LDs, not by LDs devoid of PLIN5. Also the association between IMCL storage capacity and insulin resistance and mitochondrial dysfunction was only apparent for PLIN5+ LDs. CONCLUSIONS/INTERPRETATION Fasting results in subcellular redistribution of PLIN5 and promotes the capacity to store excess fat in larger and more numerous PLIN5-decorated LDs. This associates with blunting of fasting-induced insulin resistance and mitochondrial dysfunction, suggesting a role for PLIN5 in the modulation of fasting-mediated lipotoxicity. TRIAL REGISTRATION trialregister.nl NTR 2042.
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Affiliation(s)
- Anne Gemmink
- Department of Human Movement Sciences, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, 6200MD, Maastricht, the Netherlands
| | - Madeleen Bosma
- Department of Human Biology, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Maastricht, the Netherlands
- Department of Cell and Molecular Biology, Karolinska Institutet, Stockholm, Sweden
| | - Helma J H Kuijpers
- Department of Genetics and Cell Biology-Molecular Cell Biology, Cardiovascular Research Institute Maastricht, Maastricht University Medical Centre+, Maastricht, the Netherlands
| | - Joris Hoeks
- Department of Human Biology, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Maastricht, the Netherlands
| | - Gert Schaart
- Department of Human Movement Sciences, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, 6200MD, Maastricht, the Netherlands
| | - Marc A M J van Zandvoort
- Department of Genetics and Cell Biology-Molecular Cell Biology, Cardiovascular Research Institute Maastricht, Maastricht University Medical Centre+, Maastricht, the Netherlands
- Institute for Molecular Cardiovascular Research IMCAR, Universitätsklinikum Aachen, Aachen, Germany
| | - Patrick Schrauwen
- Department of Human Biology, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Maastricht, the Netherlands
| | - Matthijs K C Hesselink
- Department of Human Movement Sciences, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, 6200MD, Maastricht, the Netherlands.
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13
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Bonen A, Jain SS, Snook LA, Han XX, Yoshida Y, Buddo KH, Lally JS, Pask ED, Paglialunga S, Beaudoin MS, Glatz JFC, Luiken JJFP, Harasim E, Wright DC, Chabowski A, Holloway GP. Extremely rapid increase in fatty acid transport and intramyocellular lipid accumulation but markedly delayed insulin resistance after high fat feeding in rats. Diabetologia 2015. [PMID: 26197708 DOI: 10.1007/s00125-015-3691-8] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
AIMS/HYPOTHESIS The mechanisms for diet-induced intramyocellular lipid accumulation and its association with insulin resistance remain contentious. In a detailed time-course study in rats, we examined whether a high-fat diet increased intramyocellular lipid accumulation via alterations in fatty acid translocase (FAT/CD36)-mediated fatty acid transport, selected enzymes and/or fatty acid oxidation, and whether intramyocellular lipid accretion coincided with the onset of insulin resistance. METHODS We measured, daily (on days 1-7) and/or weekly (for 6 weeks), the diet-induced changes in circulating substrates, insulin, sarcolemmal substrate transporters and transport, selected enzymes, intramyocellular lipids, mitochondrial fatty acid oxidation and basal and insulin-stimulated sarcolemmal GLUT4 and glucose transport. We also examined whether upregulating fatty acid oxidation improved glucose transport in insulin-resistant muscles. Finally, in Cd36-knockout mice, we examined the role of FAT/CD36 in intramyocellular lipid accumulation, insulin sensitivity and diet-induced glucose intolerance. RESULTS Within 2-3 days, diet-induced increases occurred in insulin, sarcolemmal FAT/CD36 (but not fatty acid binding protein [FABPpm] or fatty acid transporter [FATP]1 or 4), fatty acid transport and intramyocellular triacylglycerol, diacylglycerol and ceramide, independent of enzymatic changes or muscle fatty acid oxidation. Diet-induced increases in mitochondria and mitochondrial fatty acid oxidation and impairments in insulin-stimulated glucose transport and GLUT4 translocation occurred much later (≥21 days). FAT/CD36 ablation impaired insulin-stimulated fatty acid transport and lipid accumulation, improved insulin sensitivity and prevented diet-induced glucose intolerance. Increasing fatty acid oxidation in insulin-resistant muscles improved glucose transport. CONCLUSIONS/INTERPRETATIONS High-fat feeding rapidly increases intramyocellular lipids (in 2-3 days) via insulin-mediated upregulation of sarcolemmal FAT/CD36 and fatty acid transport. The 16-19 day delay in the onset of insulin resistance suggests that additional mechanisms besides intramyocellular lipids contribute to this pathology.
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Affiliation(s)
- Arend Bonen
- Department of Human Health & Nutritional Sciences, University of Guelph, Guelph, ON, Canada, N1G 2W1.
| | - Swati S Jain
- Department of Human Health & Nutritional Sciences, University of Guelph, Guelph, ON, Canada, N1G 2W1
| | - Laelie A Snook
- Department of Human Health & Nutritional Sciences, University of Guelph, Guelph, ON, Canada, N1G 2W1
| | - Xiao-Xia Han
- Department of Human Health & Nutritional Sciences, University of Guelph, Guelph, ON, Canada, N1G 2W1
| | - Yuko Yoshida
- Department of Human Health & Nutritional Sciences, University of Guelph, Guelph, ON, Canada, N1G 2W1
| | - Kathryn H Buddo
- Department of Human Health & Nutritional Sciences, University of Guelph, Guelph, ON, Canada, N1G 2W1
| | - James S Lally
- Department of Human Health & Nutritional Sciences, University of Guelph, Guelph, ON, Canada, N1G 2W1
| | - Elizabeth D Pask
- Department of Human Health & Nutritional Sciences, University of Guelph, Guelph, ON, Canada, N1G 2W1
| | - Sabina Paglialunga
- Department of Human Health & Nutritional Sciences, University of Guelph, Guelph, ON, Canada, N1G 2W1
| | - Marie-Soleil Beaudoin
- Department of Human Health & Nutritional Sciences, University of Guelph, Guelph, ON, Canada, N1G 2W1
| | - Jan F C Glatz
- Department of Molecular Genetics, Maastricht University, Maastricht, the Netherlands
| | - Joost J F P Luiken
- Department of Molecular Genetics, Maastricht University, Maastricht, the Netherlands
| | - Ewa Harasim
- Department of Physiology, Medical University of Bialystok, Bialystok, Poland
| | - David C Wright
- Department of Human Health & Nutritional Sciences, University of Guelph, Guelph, ON, Canada, N1G 2W1
| | - Adrian Chabowski
- Department of Physiology, Medical University of Bialystok, Bialystok, Poland
| | - Graham P Holloway
- Department of Human Health & Nutritional Sciences, University of Guelph, Guelph, ON, Canada, N1G 2W1
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14
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Holloway GP, Han XX, Jain SS, Bonen A, Chabowski A. Chronic muscle stimulation improves insulin sensitivity while increasing subcellular lipid droplets and reducing selected diacylglycerol and ceramide species in obese Zucker rats. Diabetologia 2014; 57:832-40. [PMID: 24458200 DOI: 10.1007/s00125-014-3169-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Accepted: 01/02/2014] [Indexed: 01/09/2023]
Abstract
AIMS/HYPOTHESIS Although insulin resistance has been associated with accumulations of specific intramuscular fatty acids and altered subcellular localisation of lipid droplets, these concepts remain controversial. Therefore, we aimed to identify specific intramuscular fatty acids and subcellular lipid localisations associated with improved insulin sensitivity following chronic muscle contraction. METHODS In lean and insulin-resistant obese Zucker rats the tibialis anterior muscle was stimulated (6 h/day for 6 days). Thereafter, muscles were examined for insulin sensitivity, intramuscular lipid droplet localisation and triacylglycerol (TAG), diacylglycerol (DAG) and ceramide fatty acid composition. RESULTS In lean and obese animals, regardless of muscle type, chronic muscle contraction improved muscle insulin sensitivity and increased intramuscular levels of total and most C14-C22 TAG fatty acids (p < 0.05). Therefore, accumulation in subcellular lipid droplet compartments reflected the oversupply of lipids within muscle. In contrast, improvements in insulin sensitivity induced by muscle contraction were associated with reductions in specific DAG and ceramide species that were not uniform in red and white muscle of obese rats. However, these reductions were insufficient to fully normalise insulin sensitivity, indicating that other mechanisms are involved. CONCLUSIONS/INTERPRETATION Reductions in 18 C length DAG and ceramide species were the most consistent in red and white muscle and therefore may represent therapeutic targets for improving insulin sensitivity.
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Affiliation(s)
- Graham P Holloway
- Department of Human Health & Nutritional Sciences, University of Guelph, Guelph, ON, Canada, NIG, 2W1,
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15
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Cao P, Fan SJ, Wang AM, Xie VB, Qiao Z, Brittenham GM, Wu EX. Diffusion magnetic resonance monitors intramyocellular lipid droplet size in vivo. Magn Reson Med 2014; 73:59-69. [PMID: 24469956 DOI: 10.1002/mrm.25116] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Revised: 11/23/2013] [Accepted: 12/13/2013] [Indexed: 01/09/2023]
Abstract
PURPOSE Intramyocellular lipid (IMCL) droplets are dynamic organelles whose morphology reflects their vital roles in lipid synthesis, usage, and storage in muscle energy metabolism. To develop noninvasive means to measure droplet microstructure in vivo, we investigated the molecular diffusion behavior of IMCL with diffusion magnetic resonance spectroscopy. METHODS Using extremely large diffusion weighting, we measured the IMCL apparent diffusion coefficients (ADCs) in hindlimb muscle of rodents from normal feeding, 60-h fasting, streptozotocin-induced diabetic, and high-fat-diet-induced obese groups. RESULTS IMCL ADCs decreased markedly with diffusion time, confirming the restricted diffusion of lipid molecules within IMCL droplets. IMCL droplet size, determined by transmission electron microscopy, was closely correlated with ADC. IMCL ADC was sensitive to metabolic alterations, decreasing in the 60-h fasting and diabetic groups while increasing in the obese group. These findings indicated that the IMCL droplet size decreased following 60-h fasting and in STZ-induced diabetes but increased in high-fat-diet-induced obesity. CONCLUSION MR diffusion characterization of IMCL droplet size provides a unique means to examine the intracellular lipid dynamics and metabolic abnormalities in vivo.
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Affiliation(s)
- Peng Cao
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong, China.,Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong, China
| | - Shu-Juan Fan
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong, China.,Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong, China
| | - Anna M Wang
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong, China.,Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong, China
| | - Victor B Xie
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong, China.,Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong, China
| | - Zhongwei Qiao
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong, China.,Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong, China
| | - Gary M Brittenham
- Departments of Pediatrics and Medicine, Columbia University College of Physicians and Surgeons, New York, New York, USA
| | - Ed X Wu
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong, China.,Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong, China
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16
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Roles of Fatty Acid oversupply and impaired oxidation in lipid accumulation in tissues of obese rats. J Lipids 2013; 2013:420754. [PMID: 23762564 PMCID: PMC3666279 DOI: 10.1155/2013/420754] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Accepted: 04/19/2013] [Indexed: 12/30/2022] Open
Abstract
To test the roles of lipid oversupply versus oxidation in causing tissue lipid accumulation associated with insulin resistance/obesity, we studied in vivo fatty acid (FA) metabolism in obese (Obese) and lean (Lean) Zucker rats. Indices of local FA utilization and storage were calculated using the partially metabolizable [9,10-3H]-(R)-2-bromopalmitate (3H-R-BrP) and [U-14C]-palmitate (14C-P) FA tracers, respectively. Whole-body FA appearance (Ra) was estimated from plasma 14C-P kinetics. Whole-body FA oxidation rate (Rox) was assessed using 3H2O production from 3H-palmitate infusion, and tissue FA oxidative capacity was evaluated ex vivo. In the basal fasting state Obese had markedly elevated FA levels and Ra, associated with elevated FA utilization and storage in most tissues. Estimated rates of muscle FA oxidation were not lower in obese rats and were similarly enhanced by contraction in both lean and obese groups. At comparable levels of FA availability, achieved by nicotinic acid, Rox was lower in Obese than Lean. In Obese rats, FA oxidative capacity was 35% higher than that in Lean in skeletal muscle, 67% lower in brown fat and comparable in other organs. In conclusion, lipid accumulation in non-adipose tissues of obese Zucker rats appears to result largely from systemic FA oversupply.
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Identification of a novel malonyl-CoA IC(50) for CPT-I: implications for predicting in vivo fatty acid oxidation rates. Biochem J 2013; 448:13-20. [PMID: 22928974 DOI: 10.1042/bj20121110] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Published values regarding the sensitivity (IC(50)) of CPT-I (carnitine palmitoyltransferase I) to M-CoA (malonyl-CoA) inhibition in isolated mitochondria are inconsistent with predicted in vivo rates of fatty acid oxidation. Therefore we have re-examined M-CoA inhibition kinetics under various P-CoA (palmitoyl-CoA) concentrations in both isolated mitochondria and PMFs (permeabilized muscle fibres). PMFs have an 18-fold higher IC(50) (0.61 compared with 0.034 μM) in the presence of 25 μM P-CoA and a 13-fold higher IC(50) (6.3 compared with 0.49 μM) in the presence of 150 μM P-CoA compared with isolated mitochondria. M-CoA inhibition kinetics determined in PMFs predicts that CPT-I activity is inhibited by 33% in resting muscle compared with >95% in isolated mitochondria. Additionally, the ability of M-CoA to inhibit CPT-I appears to be dependent on P-CoA concentration, as the relative inhibitory capacity of M-CoA is decreased with increasing P-CoA concentrations. Altogether, the use of PMFs appears to provide an M-CoA IC(50) that better reflects the predicted in vivo rates of fatty acid oxidation. These findings also demonstrate that the ratio of [P-CoA]/[M-CoA] is critical for regulating CPT-I activity and may partially rectify the in vivo disconnect between M-CoA content and CPT-I flux within the context of exercise and Type 2 diabetes.
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18
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Smith BK, Mukai K, Lally JS, Maher AC, Gurd BJ, Heigenhauser GJF, Spriet LL, Holloway GP. AMP-activated protein kinase is required for exercise-induced peroxisome proliferator-activated receptor co-activator 1 translocation to subsarcolemmal mitochondria in skeletal muscle. J Physiol 2013; 591:1551-61. [PMID: 23297307 DOI: 10.1113/jphysiol.2012.245944] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
In skeletal muscle, mitochondria exist as two subcellular populations known as subsarcolemmal (SS) and intermyofibrillar (IMF) mitochondria. SS mitochondria preferentially respond to exercise training, suggesting divergent transcriptional control of the mitochondrial genomes. The transcriptional co-activator peroxisome proliferator-activated receptor γ co-activator 1α (PGC-1α) and mitochondrial transcription factor A (Tfam) have been implicated in the direct regulation of the mitochondrial genome in mice, although SS and IMF differences may exist, and the potential signalling events regulating the mitochondrial content of these proteins have not been elucidated. Therefore, we examined the potential for PGC-1α and Tfam to translocate to SS and IMF mitochondria in human subjects, and performed experiments in rodents to identify signalling mechanisms regulating these translocation events. Acute exercise in humans and rats increased PGC-1α content in SS but not IMF mitochondria. Acute exposure to 5-aminoimidazole-4-carboxamide-1-β-ribofuranoside in rats recapitulated the exercise effect of increased PGC-1α protein within SS mitochondria only, suggesting that AMP-activated protein kinase (AMPK) signalling is involved. In addition, rendering AMPK inactive (AMPK kinase dead mice) prevented exercise-induced PGC-1α translocation to SS mitochondria, further suggesting that AMPK plays an integral role in these translocation events. In contrast to the conserved PGC-1α translocation to SS mitochondria across species (humans, rats and mice), acute exercise only increased mitochondrial Tfam in rats. Nevertheless, in rat resting muscle PGC-1α and Tfam co-immunoprecipate with α-tubulin, suggesting a common cytosolic localization. These data suggest that exercise causes translocation of PGC-1α preferentially to SS mitochondria in an AMPK-dependent manner.
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Affiliation(s)
- Brennan K Smith
- Human Health and Nutritional Sciences, University of Guelph, 491 Gordon St., Guelph, ON, N1G 2W1, Canada.
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