1
|
Hota M, Barber JL, Ruiz-Ramie JJ, Schwartz CS, Lam DTUH, Rao P, Mi MY, Katz DH, Robbins JM, Clish CB, Gerszten RE, Sarzynski MA, Ghosh S, Bouchard C. Omics-driven investigation of the biology underlying intrinsic submaximal working capacity and its trainability. Physiol Genomics 2023; 55:517-543. [PMID: 37661925 PMCID: PMC11178266 DOI: 10.1152/physiolgenomics.00163.2022] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Revised: 07/21/2023] [Accepted: 08/31/2023] [Indexed: 09/05/2023] Open
Abstract
Submaximal exercise capacity is an indicator of cardiorespiratory fitness with clinical and public health implications. Submaximal exercise capacity and its response to exercise programs are characterized by heritability levels of about 40%. Using physical working capacity (power output) at a heart rate of 150 beats/min (PWC150) as an indicator of submaximal exercise capacity in subjects of the HERITAGE Family Study, we have undertaken multi-omics and in silico explorations of the underlying biology of PWC150 and its response to 20 wk of endurance training. Our goal was to illuminate the biological processes and identify panels of genes associated with human variability in intrinsic PWC150 (iPWC150) and its trainability (dPWC150). Our bioinformatics approach was based on a combination of genome-wide association, skeletal muscle gene expression, and plasma proteomics and metabolomics experiments. Genes, proteins, and metabolites showing significant associations with iPWC150 or dPWC150 were further queried for the enrichment of biological pathways. We compared genotype-phenotype associations of emerging candidate genes with reported functional consequences of gene knockouts in mouse models. We investigated the associations between DNA variants and multiple muscle and cardiovascular phenotypes measured in HERITAGE subjects. Two panels of prioritized genes of biological relevance to iPWC150 (13 genes) and dPWC150 (6 genes) were identified, supporting the hypothesis that genes and pathways associated with iPWC150 are different from those underlying dPWC150. Finally, the functions of these genes and pathways suggested that human variation in submaximal exercise capacity is mainly driven by skeletal muscle morphology and metabolism and red blood cell oxygen-carrying capacity.NEW & NOTEWORTHY Multi-omics and in silico explorations of the genes and underlying biology of submaximal exercise capacity and its response to 20 wk of endurance training were undertaken. Prioritized genes were identified: 13 genes for variation in submaximal exercise capacity in the sedentary state and 5 genes for the response level to endurance training, with no overlap between them. Genes and pathways associated with submaximal exercise capacity in the sedentary state are different from those underlying trainability.
Collapse
Affiliation(s)
- Monalisa Hota
- Centre for Computational Biology, Duke-National University of Singapore Medical School, Singapore, Singapore
| | - Jacob L Barber
- Department of Exercise Science, Arnold School of Public Health, University of South Carolina, Columbia, South Carolina, United States
| | - Jonathan J Ruiz-Ramie
- Department of Exercise Science, Arnold School of Public Health, University of South Carolina, Columbia, South Carolina, United States
- Department of Kinesiology, Augusta University, Augusta, Georgia, United States
| | - Charles S Schwartz
- Department of Exercise Science, Arnold School of Public Health, University of South Carolina, Columbia, South Carolina, United States
| | - Do Thuy Uyen Ha Lam
- Centre for Computational Biology, Duke-National University of Singapore Medical School, Singapore, Singapore
| | - Prashant Rao
- Division of Cardiovascular Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States
| | - Michael Y Mi
- Division of Cardiovascular Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States
| | - Daniel H Katz
- Division of Cardiovascular Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States
| | - Jeremy M Robbins
- Division of Cardiovascular Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States
| | - Clary B Clish
- Metabolomics Platform, Broad Institute, Boston, Massachusetts, United States
| | - Robert E Gerszten
- Division of Cardiovascular Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States
| | - Mark A Sarzynski
- Department of Exercise Science, Arnold School of Public Health, University of South Carolina, Columbia, South Carolina, United States
| | - Sujoy Ghosh
- Centre for Computational Biology, Duke-National University of Singapore Medical School, Singapore, Singapore
- Bioinformatics Section, Human Genomics Core, Pennington Biomedical Research Center, Baton Rouge, Louisiana, United States
- Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Medical School, Singapore, Singapore
| | - Claude Bouchard
- Human Genomics Laboratory, Pennington Biomedical Research Center, Baton Rouge, Louisiana, United States
| |
Collapse
|
2
|
Wall BT, Machin D, Dunlop MV, Stephens FB. Caffeine ingestion stimulates plasma carnitine clearance in humans. Physiol Rep 2023; 11:e15615. [PMID: 36806708 PMCID: PMC9938004 DOI: 10.14814/phy2.15615] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Revised: 02/01/2023] [Accepted: 02/02/2023] [Indexed: 02/20/2023] Open
Abstract
Increasing skeletal muscle carnitine content can manipulate fuel metabolism and improve exercise performance. Intravenous insulin infusion during hypercarnitinemia increases plasma carnitine clearance and Na+ -dependent muscle carnitine accretion, likely via stimulating Na+ /K+ ATPase pump activity. We hypothesized that the ingestion of high-dose caffeine, also known to stimulate Na+ /K+ ATPase activity, would stimulate plasma carnitine clearance during hypercarnitinemia in humans. In a randomized placebo-controlled study, six healthy young adults (aged 24 ± 5 years, height 175 ± 8 cm, and weight 70 ± 13 kg) underwent three 5-h laboratory visits involving the primed continuous intravenous infusion of l-carnitine (CARN and CARN + CAFF) or saline (CAFF) in parallel with ingestion of caffeine (CARN + CAFF and CAFF) or placebo (CARN) at 0, 2, 3, and 4 h. Regular blood samples were collected to determine concentrations of blood Na+ and K+ , and plasma carnitine and caffeine, concentrations. Caffeine ingestion (i.e., CAFF and CARN + CAFF conditions) and l-carnitine infusion (i.e., CARN and CARN + CAFF) elevated steady-state plasma caffeine (to ~7 μg·mL-1 ) and carnitine (to ~400 μmol·L-1 ) concentrations, respectively, throughout the 5 h infusions. Plasma carnitine concentration was ~15% lower in CARN + CAFF compared with CARN during the final 90 min of the infusion (at 210 min, 356 ± 96 vs. 412 ± 94 μmol·L-1 ; p = 0.0080: at 240 min, 350 ± 91 vs. 406 ± 102 μmol·L-1 ; p = 0.0079: and at 300 min, 357 ± 91 vs. 413 ± 110 μmol·L-1 ; p = 0.0073, respectively). Blood Na+ concentrations were greater in CAFF and CARN + CAFF compared with CARN. Ingestion of high-dose caffeine stimulates plasma carnitine clearance during hypercarnitinemia, likely via increased Na+ /K+ ATPase activity. Carnitine co-ingestion with caffeine may represent a novel muscle carnitine loading strategy in humans, and therefore manipulate skeletal muscle fuel metabolism and improve exercise performance.
Collapse
Affiliation(s)
- Benjamin T. Wall
- Department of Public Health and Sport SciencesUniversity of ExeterExeterUK
| | - David Machin
- Department of Public Health and Sport SciencesUniversity of ExeterExeterUK
| | - Mandy V. Dunlop
- Department of Public Health and Sport SciencesUniversity of ExeterExeterUK
| | | |
Collapse
|
3
|
L-Carnitine Functionalization to Increase Skeletal Muscle Tropism of PLGA Nanoparticles. Int J Mol Sci 2022; 24:ijms24010294. [PMID: 36613739 PMCID: PMC9820419 DOI: 10.3390/ijms24010294] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2022] [Revised: 12/19/2022] [Accepted: 12/21/2022] [Indexed: 12/28/2022] Open
Abstract
Muscular dystrophies are a group of rare genetic pathologies, encompassing a variety of clinical phenotypes and mechanisms of disease. Several compounds have been proposed to treat compromised muscles, but it is known that pharmacokinetics and pharmacodynamics problems could occur. To solve these issues, it has been suggested that nanocarriers could be used to allow controlled and targeted drug release. Therefore, the aim of this study was to prepare actively targeted poly(lactide-co-glycolide) (PLGA) nanoparticles (NPs) for the treatment of muscular pathologies. By taking advantage of the high affinity for carnitine of skeletal muscle cells due to the expression of Na+-coupled carnitine transporter (OCTN), NPs have been actively targeted via association to an amphiphilic derivative of L-carnitine. Furthermore, pentamidine, an old drug repurposed for its positive effects on myotonic dystrophy type I, was incorporated into NPs. We obtained monodispersed targeted NPs, with a mean diameter of about 100 nm and a negative zeta potential. To assess the targeting ability of the NPs, cell uptake studies were performed on C2C12 myoblasts and myotubes using confocal and transmission electron microscopy. The results showed an increased uptake of carnitine-functionalized NPs compared to nontargeted carriers in myotubes, which was probably due to the interaction with OCTN receptors occurring in large amounts in these differentiated muscle cells.
Collapse
|
4
|
Effect of l-carnitine and mildronate on the mitochondrial metabolism of heart and bacterial composition of the gut microbiome in ageing mice. Life Sci 2022; 293:120333. [PMID: 35051422 DOI: 10.1016/j.lfs.2022.120333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Revised: 01/13/2022] [Accepted: 01/13/2022] [Indexed: 11/20/2022]
Abstract
Ageing is the most significant risk factor for cardiovascular diseases. l-Carnitine has a potent cardioprotective effect and its synthesis decreases during ageing. At the same time, there are pharmaceuticals, such as mildronate which, on the contrary, are aimed at reducing the concentration of l-carnitine in the heart and lead to slows down the oxidation of fatty acids in mitochondria. Despite this, both l-carnitine and mildronate are positioned as cardio protectors. We showed that l-carnitine supplementation to the diet of 15-month-old mice increased expression of the PGC-1α gene, which is responsible for the regulation of fatty acid oxidation, and the Nrf2 gene, which is responsible for protecting mitochondria by regulating the expression of antioxidants and mitophagy, in the heart. Mildronate activated the expression of genes that regulate glucose metabolism. Probably, this metabolic shift may protect the mitochondria of the heart from the accumulation of acyl-carnitine, which occurs during the oxidation of fatty acids under oxygen deficiency. Both pharmaceuticals impacted the gut microbiome bacterial composition. l-Carnitine increased the level of Lachnoanaerobaculum and [Eubacterium] hallii group, mildronate increased the level of Bifidobacterium, Rikinella, Christensenellaceae. Considered, that these bacteria for protection the organism from various pathogens and chronic inflammation. Thus, we suggested that the positive effects of both drugs on the mitochondria metabolism and gut microbiome bacterial composition may contribute to the protection of the heart during ageing.
Collapse
|
5
|
Bruls YMH, op den Kamp YJM, Phielix E, Lindeboom L, Havekes B, Schaart G, Moonen-Kornips E, Wildberger JE, Hesselink MKC, Schrauwen P, Schrauwen-Hinderling VB. L-carnitine infusion does not alleviate lipid-induced insulin resistance and metabolic inflexibility. PLoS One 2020; 15:e0239506. [PMID: 32976523 PMCID: PMC7518598 DOI: 10.1371/journal.pone.0239506] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Accepted: 09/07/2020] [Indexed: 01/02/2023] Open
Abstract
BACKGROUND Low carnitine status may underlie the development of insulin resistance and metabolic inflexibility. Intravenous lipid infusion elevates plasma free fatty acid (FFA) concentration and is a model for simulating insulin resistance and metabolic inflexibility in healthy, insulin sensitive volunteers. Here, we hypothesized that co-infusion of L-carnitine may alleviate lipid-induced insulin resistance and metabolic inflexibility. METHODS In a randomized crossover trial, eight young healthy volunteers underwent hyperinsulinemic-euglycemic clamps (40mU/m2/min) with simultaneous infusion of saline (CON), Intralipid (20%, 90mL/h) (LIPID), or Intralipid (20%, 90mL/h) combined with L-carnitine infusion (28mg/kg) (LIPID+CAR). Ten volunteers were randomized for the intervention arms (CON, LIPID and LIPID+CAR), but two dropped-out during the study. Therefore, eight volunteers participated in all three intervention arms and were included for analysis. RESULTS L-carnitine infusion elevated plasma free carnitine availability and resulted in a more pronounced increase in plasma acetylcarnitine, short-, medium-, and long-chain acylcarnitines compared to lipid infusion, however no differences in skeletal muscle free carnitine or acetylcarnitine were found. Peripheral insulin sensitivity and metabolic flexibility were blunted upon lipid infusion compared to CON but L-carnitine infusion did not alleviate this. CONCLUSION Acute L-carnitine infusion could not alleviated lipid-induced insulin resistance and metabolic inflexibility and did not alter skeletal muscle carnitine availability. Possibly, lipid-induced insulin resistance may also have affected carnitine uptake and may have blunted the insulin-induced carnitine storage in muscle. Future studies are needed to investigate this.
Collapse
Affiliation(s)
- Yvonne M. H. Bruls
- Departments of Radiology and Nuclear Medicine, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Center, Maastricht, The Netherlands
- Departments of Nutrition and Movement Sciences, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Yvo J. M. op den Kamp
- Departments of Nutrition and Movement Sciences, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Esther Phielix
- Departments of Nutrition and Movement Sciences, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Lucas Lindeboom
- Departments of Radiology and Nuclear Medicine, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Center, Maastricht, The Netherlands
- Departments of Nutrition and Movement Sciences, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Bas Havekes
- Division of Endocrinology, Department of Internal Medicine, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Gert Schaart
- Departments of Nutrition and Movement Sciences, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Esther Moonen-Kornips
- Departments of Nutrition and Movement Sciences, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Joachim E. Wildberger
- Departments of Radiology and Nuclear Medicine, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Matthijs K. C. Hesselink
- Departments of Nutrition and Movement Sciences, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Patrick Schrauwen
- Departments of Nutrition and Movement Sciences, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Vera B. Schrauwen-Hinderling
- Departments of Radiology and Nuclear Medicine, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Center, Maastricht, The Netherlands
- Departments of Nutrition and Movement Sciences, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Center, Maastricht, The Netherlands
- * E-mail:
| |
Collapse
|
6
|
Gnoni A, Longo S, Gnoni GV, Giudetti AM. Carnitine in Human Muscle Bioenergetics: Can Carnitine Supplementation Improve Physical Exercise? Molecules 2020; 25:E182. [PMID: 31906370 PMCID: PMC6982879 DOI: 10.3390/molecules25010182] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Revised: 12/27/2019] [Accepted: 12/31/2019] [Indexed: 12/18/2022] Open
Abstract
l-Carnitine is an amino acid derivative widely known for its involvement in the transport of long-chain fatty acids into the mitochondrial matrix, where fatty acid oxidation occurs. Moreover, l-Carnitine protects the cell from acyl-CoA accretion through the generation of acylcarnitines. Circulating carnitine is mainly supplied by animal-based food products and to a lesser extent by endogenous biosynthesis in the liver and kidney. Human muscle contains high amounts of carnitine but it depends on the uptake of this compound from the bloodstream, due to muscle inability to synthesize carnitine. Mitochondrial fatty acid oxidation represents an important energy source for muscle metabolism particularly during physical exercise. However, especially during high-intensity exercise, this process seems to be limited by the mitochondrial availability of free l-carnitine. Hence, fatty acid oxidation rapidly declines, increasing exercise intensity from moderate to high. Considering the important role of fatty acids in muscle bioenergetics, and the limiting effect of free carnitine in fatty acid oxidation during endurance exercise, l-carnitine supplementation has been hypothesized to improve exercise performance. So far, the question of the role of l-carnitine supplementation on muscle performance has not definitively been clarified. Differences in exercise intensity, training or conditioning of the subjects, amount of l-carnitine administered, route and timing of administration relative to the exercise led to different experimental results. In this review, we will describe the role of l-carnitine in muscle energetics and the main causes that led to conflicting data on the use of l-carnitine as a supplement.
Collapse
Affiliation(s)
- Antonio Gnoni
- Department of Basic Medical Sciences, Neuroscience and Sense Organs, University of Bari “Aldo Moro”, 70124 Bari, Italy;
| | - Serena Longo
- Department of Biological and Environmental Sciences and Technologies, University of Salento, 73100 Lecce, Italy; (S.L.); (G.V.G.)
| | - Gabriele V. Gnoni
- Department of Biological and Environmental Sciences and Technologies, University of Salento, 73100 Lecce, Italy; (S.L.); (G.V.G.)
| | - Anna M. Giudetti
- Department of Biological and Environmental Sciences and Technologies, University of Salento, 73100 Lecce, Italy; (S.L.); (G.V.G.)
| |
Collapse
|
7
|
Pan H, Li LY, Li JM, Wang WL, Limbu SM, Degrace P, Li DL, Du ZY. Inhibited fatty acid β-oxidation impairs stress resistance ability in Nile tilapia (Oreochromis niloticus). FISH & SHELLFISH IMMUNOLOGY 2017; 68:500-508. [PMID: 28774846 DOI: 10.1016/j.fsi.2017.07.058] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2017] [Revised: 07/24/2017] [Accepted: 07/29/2017] [Indexed: 05/23/2023]
Abstract
Energy metabolism plays important roles in stress resistance and immunity in mammals, however, such functions have not been established in fish. In the present study, Nile tilapia (Oreochromis niloticus) was fed with mildronate, an inhibitor of mitochondrial fatty acid (FA) β-oxidation, for six weeks subsequently challenged with Aeromonas hydrophila and ammonia nitrogen exposure. Mildronate treatment reduced significantly l-carnitine concentration and mitochondrial FA β-oxidation efficiency, while it increased lipid accumulation in liver. The fish with inhibited hepatic FA catabolism had lower survival rate when exposed to Aeromonas hydrophila and ammonia nitrogen. Moreover, fish fed mildronate supplemented diet had lower immune enzymes activities and anti-inflammatory cytokine genes expressions, but had higher pro-inflammatory cytokine genes expressions. However, the oxidative stress-related biochemical indexes were not significantly affected by mildronate treatment. Taken together, inhibited mitochondrial FA β-oxidation impaired stress resistance ability in Nile tilapia mainly through inhibiting immune functions and triggering inflammation. This is the first study showing the regulatory effects of lipid catabolism on stress resistance and immune functions in fish.
Collapse
Affiliation(s)
- Han Pan
- Laboratory of Aquaculture Nutrition and Environmental Health (LANEH), School of Life Sciences, East China Normal University, Shanghai, PR China
| | - Ling-Yu Li
- Laboratory of Aquaculture Nutrition and Environmental Health (LANEH), School of Life Sciences, East China Normal University, Shanghai, PR China
| | - Jia-Min Li
- Laboratory of Aquaculture Nutrition and Environmental Health (LANEH), School of Life Sciences, East China Normal University, Shanghai, PR China
| | - Wei-Li Wang
- Laboratory of Aquaculture Nutrition and Environmental Health (LANEH), School of Life Sciences, East China Normal University, Shanghai, PR China
| | - Samwel Mchele Limbu
- Laboratory of Aquaculture Nutrition and Environmental Health (LANEH), School of Life Sciences, East China Normal University, Shanghai, PR China; Department of Aquatic Sciences and Fisheries Technology, University of Dar Es Salaam, Dar Es Salaam, Tanzania
| | - Pascal Degrace
- Team Pathophysiology of Dyslipidemia, INSERM UMR1231, "Lipids, Nutrition, Cancer", Université de Bourgogne Franche-Comté, Dijon, France
| | - Dong-Liang Li
- Laboratory of Aquaculture Nutrition and Environmental Health (LANEH), School of Life Sciences, East China Normal University, Shanghai, PR China.
| | - Zhen-Yu Du
- Laboratory of Aquaculture Nutrition and Environmental Health (LANEH), School of Life Sciences, East China Normal University, Shanghai, PR China.
| |
Collapse
|
8
|
Porter C, Constantin-Teodosiu D, Constantin D, Leighton B, Poucher SM, Greenhaff PL. Muscle carnitine availability plays a central role in regulating fuel metabolism in the rodent. J Physiol 2017; 595:5765-5780. [PMID: 28605113 DOI: 10.1113/jp274415] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Accepted: 05/31/2017] [Indexed: 01/05/2023] Open
Abstract
KEY POINTS Meldonium inhibits endogenous carnitine synthesis and tissue uptake, and accelerates urinary carnitine excretion, although the impact of meldonium-mediated muscle carnitine depletion on whole-body fuel selection, and muscle fuel metabolism and its molecular regulation is under-investigated. Ten days of oral meldonium administration did not impact on food or fluid intake, physical activity levels or body weight gain in the rat, whereas it depleted muscle carnitine content (all moieties), increased whole-body carbohydrate oxidation and muscle and liver glycogen utilization, and reduced whole-body fat oxidation. Meldonium reduced carnitine transporter protein expression across muscles of different contractile and metabolic phenotypes. A TaqMan PCR low-density array card approach revealed the abundance of 189 mRNAs regulating fuel selection was altered in soleus muscle by meldonium, highlighting the modulation of discrete cellular functions and metabolic pathways. These novel findings strongly support the premise that muscle carnitine availability is a primary regulator of fuel selection in vivo. ABSTRACT The body carnitine pool is primarily confined to skeletal muscle, where it regulates carbohydrate (CHO) and fat usage. Meldonium (3-(2,2,2-trimethylhydrazinium)-propionate) inhibits carnitine synthesis and tissue uptake, although the impact of carnitine depletion on whole-body fuel selection, muscle fuel metabolism and its molecular regulation is under-investigated. Male lean Zucker rats received water (control, n = 8) or meldonium-supplemented water (meldonium, n = 8) for 10 days [1.6 g kg-1 body mass (BM) day-1 days 1-2, 0.8 g kg-1 BM day-1 thereafter]. From days 7-10, animals were housed in indirect calorimetry chambers after which soleus muscle and liver were harvested. Food and fluid intake, weight gain and physical activity levels were similar between groups from days 7 to 10. Compared to control, meldonium depleted muscle total carnitine (P < 0.001) and all carnitine esters. Furthermore, whole-body fat oxidation was less (P < 0.001) and CHO oxidation was greater (P < 0.05) compared to the control, whereas soleus and liver glycogen contents were less (P < 0.01 and P < 0.01, respectively). In a second study, male Wistar rats received water (n = 8) or meldonium-supplemented water (n = 8) as above, and kidney, heart and extensor digitorum longus muscle (EDL) and soleus muscles were collected. Compared to control, meldonium depleted total carnitine content (all P < 0.001), reduced carnitine transporter protein and glycogen content, and increased pyruvate dehydrogenase kinase 4 mRNA abundance in the heart, EDL and soleus. In total, 189 mRNAs regulating fuel selection were differentially expressed in soleus in meldonium vs. control, and a number of cellular functions and pathways strongly associated with carnitine depletion were identified. Collectively, these data firmly support the premise that muscle carnitine availability is a primary regulator of fuel selection in vivo.
Collapse
Affiliation(s)
- Craig Porter
- MRC/ARUK Centre for Musculoskeletal Ageing Research, School of Life Sciences, University of Nottingham Medical School, Nottingham, UK
| | - Dumitru Constantin-Teodosiu
- MRC/ARUK Centre for Musculoskeletal Ageing Research, School of Life Sciences, University of Nottingham Medical School, Nottingham, UK
| | - Despina Constantin
- MRC/ARUK Centre for Musculoskeletal Ageing Research, School of Life Sciences, University of Nottingham Medical School, Nottingham, UK
| | | | | | - Paul L Greenhaff
- MRC/ARUK Centre for Musculoskeletal Ageing Research, School of Life Sciences, University of Nottingham Medical School, Nottingham, UK
| |
Collapse
|
9
|
Shaw A, Jeromson S, Watterson KR, Pediani JD, Gallagher IJ, Whalley T, Dreczkowski G, Brooks N, Galloway SD, Hamilton DL. Multiple AMPK activators inhibit l-carnitine uptake in C2C12 skeletal muscle myotubes. Am J Physiol Cell Physiol 2017; 312:C689-C696. [PMID: 28298333 DOI: 10.1152/ajpcell.00026.2016] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Revised: 02/21/2017] [Accepted: 03/14/2017] [Indexed: 12/29/2022]
Abstract
Mutations in the gene that encodes the principal l-carnitine transporter, OCTN2, can lead to a reduced intracellular l-carnitine pool and the disease Primary Carnitine Deficiency. l-Carnitine supplementation is used therapeutically to increase intracellular l-carnitine. As AMPK and insulin regulate fat metabolism and substrate uptake, we hypothesized that AMPK-activating compounds and insulin would increase l-carnitine uptake in C2C12 myotubes. The cells express all three OCTN transporters at the mRNA level, and immunohistochemistry confirmed expression at the protein level. Contrary to our hypothesis, despite significant activation of PKB and 2DG uptake, insulin did not increase l-carnitine uptake at 100 nM. However, l-carnitine uptake was modestly increased at a dose of 150 nM insulin. A range of AMPK activators that increase intracellular calcium content [caffeine (10 mM, 5 mM, 1 mM, 0.5 mM), A23187 (10 μM)], inhibit mitochondrial function [sodium azide (75 μM), rotenone (1 μM), berberine (100 μM), DNP (500 μM)], or directly activate AMPK [AICAR (250 μM)] were assessed for their ability to regulate l-carnitine uptake. All compounds tested significantly inhibited l-carnitine uptake. Inhibition by caffeine was not dantrolene (10 μM) sensitive despite dantrolene inhibiting caffeine-mediated calcium release. Saturation curve analysis suggested that caffeine did not competitively inhibit l-carnitine transport. To assess the potential role of AMPK in this process, we assessed the ability of the AMPK inhibitor Compound C (10 μM) to rescue the effect of caffeine. Compound C offered a partial rescue of l-carnitine uptake with 0.5 mM caffeine, suggesting that AMPK may play a role in the inhibitory effects of caffeine. However, caffeine likely inhibits l-carnitine uptake by alternative mechanisms independently of calcium release. PKA activation or direct interference with transporter function may play a role.
Collapse
Affiliation(s)
- Andy Shaw
- Physiology, Exercise and Nutrition Research Group, Faculty of Health Sciences and Sport, University of Stirling, Stirling, United Kingdom
| | - Stewart Jeromson
- Physiology, Exercise and Nutrition Research Group, Faculty of Health Sciences and Sport, University of Stirling, Stirling, United Kingdom
| | - Kenneth R Watterson
- Molecular Pharmacology Group, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom; and
| | - John D Pediani
- Molecular Pharmacology Group, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom; and
| | - Iain J Gallagher
- Physiology, Exercise and Nutrition Research Group, Faculty of Health Sciences and Sport, University of Stirling, Stirling, United Kingdom
| | - Tim Whalley
- Biological and Environmental Sciences, School of Natural Sciences, University of Stirling, Stirling, United Kingdom
| | - Gillian Dreczkowski
- Physiology, Exercise and Nutrition Research Group, Faculty of Health Sciences and Sport, University of Stirling, Stirling, United Kingdom
| | - Naomi Brooks
- Physiology, Exercise and Nutrition Research Group, Faculty of Health Sciences and Sport, University of Stirling, Stirling, United Kingdom
| | - Stuart D Galloway
- Physiology, Exercise and Nutrition Research Group, Faculty of Health Sciences and Sport, University of Stirling, Stirling, United Kingdom
| | - D Lee Hamilton
- Physiology, Exercise and Nutrition Research Group, Faculty of Health Sciences and Sport, University of Stirling, Stirling, United Kingdom;
| |
Collapse
|
10
|
Pirkmajer S, Chibalin AV. Na,K-ATPase regulation in skeletal muscle. Am J Physiol Endocrinol Metab 2016; 311:E1-E31. [PMID: 27166285 DOI: 10.1152/ajpendo.00539.2015] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Accepted: 05/02/2016] [Indexed: 12/17/2022]
Abstract
Skeletal muscle contains one of the largest and the most dynamic pools of Na,K-ATPase (NKA) in the body. Under resting conditions, NKA in skeletal muscle operates at only a fraction of maximal pumping capacity, but it can be markedly activated when demands for ion transport increase, such as during exercise or following food intake. Given the size, capacity, and dynamic range of the NKA pool in skeletal muscle, its tight regulation is essential to maintain whole body homeostasis as well as muscle function. To reconcile functional needs of systemic homeostasis with those of skeletal muscle, NKA is regulated in a coordinated manner by extrinsic stimuli, such as hormones and nerve-derived factors, as well as by local stimuli arising in skeletal muscle fibers, such as contractions and muscle energy status. These stimuli regulate NKA acutely by controlling its enzymatic activity and/or its distribution between the plasma membrane and the intracellular storage compartment. They also regulate NKA chronically by controlling NKA gene expression, thus determining total NKA content in skeletal muscle and its maximal pumping capacity. This review focuses on molecular mechanisms that underlie regulation of NKA in skeletal muscle by major extrinsic and local stimuli. Special emphasis is given to stimuli and mechanisms linking regulation of NKA and energy metabolism in skeletal muscle, such as insulin and the energy-sensing AMP-activated protein kinase. Finally, the recently uncovered roles for glutathionylation, nitric oxide, and extracellular K(+) in the regulation of NKA in skeletal muscle are highlighted.
Collapse
Affiliation(s)
- Sergej Pirkmajer
- Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia; and
| | - Alexander V Chibalin
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
| |
Collapse
|
11
|
Mendes GD, Zaffalon GT, Silveira AS, Ramacciato JC, Motta RHL, Gagliano-Jucá T, Lopes AG, de Almeida Magalhães JC, De Nucci G. Assessment of pharmacokinetic interaction between piracetam and l-carnitine in healthy subjects. Biomed Chromatogr 2015; 30:536-42. [PMID: 26248695 DOI: 10.1002/bmc.3579] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Revised: 07/11/2015] [Accepted: 08/03/2015] [Indexed: 11/07/2022]
Abstract
A rapid, sensitive and specific method for quantifying piracetam in human plasma using Piracetam d-8 as the internal standard (IS) is described. The analyte and the IS were extracted from plasma by one-step precipitation of protein using an acetonitrile (100%). The extracts were analyzed by high-performance liquid chromatography coupled with electrospray tandem mass spectrometry (HPLC-MS/MS). The method had a chromatographic run time of 3.8 min and a linear calibration curve over the range 0.5-50 µg/mL (r > 0.99). This LC-MS-MS procedure was used to assess the bioavailability of two piracetam formulations: piracetam + l-carnitine (Piracar®; 270/330 mg tablet) and piracetam (Nootropil®; 800 mg tablet) in healthy volunteers of both sexes. The geometric means with corresponding 90% confidence interval (CI) for test/reference percentage ratios were 88.49% (90% CI = 81.19 - 96.46) for peak concentration/dose and 102.55% (90% CI = 100.62 - 104.51) for AUCinf /dose. The limit of quantitation of 0.5 µg/mL is well suited for pharmacokinetic studies in healthy volunteers. It was concluded that piracetam (Piracar®; 270/330 mg tablet) has a bioavailability equivalent to the piracetam (Nootropil®; 800 mg tablet) formulation with regard to both the rate and the extent of absorption.
Collapse
Affiliation(s)
- Gustavo D Mendes
- Department of Pharmacology, University Camilo Castelo Branco, SP, Brazil.,Galeno Research Unit, Latino Coelho St, 1301, Parque Taquaral, 13087-010, Campinas, SP, Brazil
| | - Gabriela Traldi Zaffalon
- Department of Pharmacology, University Camilo Castelo Branco, SP, Brazil.,Faculty of Odontology, Dental Research Center São Leopoldo Mandic, Campinas, SP, Brazil
| | - Antonio Sérgio Silveira
- Galeno Research Unit, Latino Coelho St, 1301, Parque Taquaral, 13087-010, Campinas, SP, Brazil
| | | | | | - Thiago Gagliano-Jucá
- Galeno Research Unit, Latino Coelho St, 1301, Parque Taquaral, 13087-010, Campinas, SP, Brazil
| | - Anibal Gil Lopes
- Department of Physiology, Faculty of Medicine, University Camilo Castelo Branco, SP, Brazil
| | | | - Gilberto De Nucci
- Department of Pharmacology, University Camilo Castelo Branco, SP, Brazil.,Department of Pharmacology, University of Sao Paulo, São Paulo, SP, Brazil
| |
Collapse
|
12
|
Vaz FM, van Vlies N. Dioxygenases of Carnitine Biosynthesis: 6- N-Trimethyllysine and γ-Butyrobetaine Hydroxylases. 2-OXOGLUTARATE-DEPENDENT OXYGENASES 2015. [DOI: 10.1039/9781782621959-00324] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
This chapter describes the state of knowledge of the two 2-oxoglutarate-dependent dioxygenases of carnitine biosynthesis: 6-N-trimethyllysine hydroxylase and γ-butyrobetaine hydroxylase. Both enzymes have been extensively investigated as carnitine plays an important role in fatty acid metabolism in animals and some other life forms. Carnitine metabolism is introduced followed by a comprehensive review of the properties of the two carnitine biosynthesis dioxygenases including their purification, kinetic and biophysical characterization, regulation and roles in metabolism.
Collapse
Affiliation(s)
- Frédéric M. Vaz
- Laboratory Genetic Metabolic Diseases, Departments of Paediatrics and Clinical Chemistry, Emma Children’s Hospital, Academic Medical Center 1105 AZ Amsterdam The Netherlands
| | - Naomi van Vlies
- Laboratory Genetic Metabolic Diseases, Departments of Paediatrics and Clinical Chemistry, Emma Children’s Hospital, Academic Medical Center 1105 AZ Amsterdam The Netherlands
| |
Collapse
|
13
|
Aguer C, McCoin CS, Knotts TA, Thrush AB, Ono-Moore K, McPherson R, Dent R, Hwang DH, Adams SH, Harper ME. Acylcarnitines: potential implications for skeletal muscle insulin resistance. FASEB J 2014; 29:336-45. [PMID: 25342132 DOI: 10.1096/fj.14-255901] [Citation(s) in RCA: 176] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Insulin resistance may be linked to incomplete fatty acid β-oxidation and the subsequent increase in acylcarnitine species in different tissues including skeletal muscle. It is not known if acylcarnitines participate in muscle insulin resistance or simply reflect dysregulated metabolism. The aims of this study were to determine whether acylcarnitines can elicit muscle insulin resistance and to better understand the link between incomplete muscle fatty acid β-oxidation, oxidative stress, inflammation, and insulin-resistance development. Differentiated C2C12, primary mouse, and human myotubes were treated with acylcarnitines (C4:0, C14:0, C16:0) or with palmitate with or without carnitine acyltransferase inhibition by mildronate. Treatment with C4:0, C14:0, and C16:0 acylcarnitines resulted in 20-30% decrease in insulin response at the level of Akt phosphorylation and/or glucose uptake. Mildronate reversed palmitate-induced insulin resistance concomitant with an ∼25% decrease in short-chain acylcarnitine and acetylcarnitine secretion. Although proinflammatory cytokines were not affected under these conditions, oxidative stress was increased by 2-3 times by short- or long-chain acylcarnitines. Acylcarnitine-induced oxidative stress and insulin resistance were reversed by treatment with antioxidants. Results are consistent with the conclusion that incomplete muscle fatty acid β-oxidation causes acylcarnitine accumulation and associated oxidative stress, raising the possibility that these metabolites play a role in muscle insulin resistance.
Collapse
Affiliation(s)
- Céline Aguer
- Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Colin S McCoin
- Molecular, Cellular, & Integrative Physiology Graduate Program, University of California, Davis, California, USA; Obesity & Metabolism Research Unit, United States Department of Agriculture-Agricultural Research Service Western Human Nutrition Research Center, Davis, California, USA
| | - Trina A Knotts
- Obesity & Metabolism Research Unit, United States Department of Agriculture-Agricultural Research Service Western Human Nutrition Research Center, Davis, California, USA; Department of Nutrition, University of California, Davis, California, USA
| | - A Brianne Thrush
- Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Kikumi Ono-Moore
- Obesity & Metabolism Research Unit, United States Department of Agriculture-Agricultural Research Service Western Human Nutrition Research Center, Davis, California, USA; Department of Nutrition, University of California, Davis, California, USA
| | - Ruth McPherson
- Division of Cardiology, University of Ottawa Heart Institute, Ottawa, Ontario, Canada
| | - Robert Dent
- Ottawa Hospital Weight Management Clinic, Ottawa, Ontario, Canada
| | - Daniel H Hwang
- Immunity & Disease Prevention Research Unit, U.S. Department of Agriculture-Agricultural Research Service Western Human Nutrition Research Center, Davis, California, USA Department of Nutrition, University of California, Davis, California, USA
| | - Sean H Adams
- Molecular, Cellular, & Integrative Physiology Graduate Program, University of California, Davis, California, USA; Obesity & Metabolism Research Unit, United States Department of Agriculture-Agricultural Research Service Western Human Nutrition Research Center, Davis, California, USA; Department of Nutrition, University of California, Davis, California, USA;
| | - Mary-Ellen Harper
- Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada;
| |
Collapse
|
14
|
Le Borgne F, Guyot S, Logerot M, Beney L, Gervais P, Demarquoy J. Exploration of lipid metabolism in relation with plasma membrane properties of Duchenne muscular dystrophy cells: influence of L-carnitine. PLoS One 2012; 7:e49346. [PMID: 23209572 PMCID: PMC3507830 DOI: 10.1371/journal.pone.0049346] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Accepted: 10/10/2012] [Indexed: 01/04/2023] Open
Abstract
Duchenne muscular dystrophy (DMD) arises as a consequence of mutations in the dystrophin gene. Dystrophin is a membrane-spanning protein that connects the cytoskeleton and the basal lamina. The most distinctive features of DMD are a progressive muscular dystrophy, a myofiber degeneration with fibrosis and metabolic alterations such as fatty infiltration, however, little is known on lipid metabolism changes arising in Duchenne patient cells. Our goal was to identify metabolic changes occurring in Duchenne patient cells especially in terms of L-carnitine homeostasis, fatty acid metabolism both at the mitochondrial and peroxisomal level and the consequences on the membrane structure and function. In this paper, we compared the structural and functional characteristics of DMD patient and control cells. Using radiolabeled L-carnitine, we found, in patient muscle cells, a marked decrease in the uptake and the intracellular level of L-carnitine. Associated with this change, a decrease in the mitochondrial metabolism can be seen from the analysis of mRNA encoding for mitochondrial proteins. Probably, associated with these changes in fatty acid metabolism, alterations in the lipid composition of the cells were identified: with an increase in poly unsaturated fatty acids and a decrease in medium chain fatty acids, mono unsaturated fatty acids and in cholesterol contents. Functionally, the membrane of cells lacking dystrophin appeared to be less fluid, as determined at 37°C by fluorescence anisotropy. These changes may, at least in part, be responsible for changes in the phospholipids and cholesterol profile in cell membranes and ultimately may reduce the fluidity of the membrane. A supplementation with L-carnitine partly restored the fatty acid profile by increasing saturated fatty acid content and decreasing the amounts of MUFA, PUFA, VLCFA. L-carnitine supplementation also restored muscle membrane fluidity. This suggests that regulating lipid metabolism in DMD cells may improve the function of cells lacking dystrophin.
Collapse
Affiliation(s)
- Françoise Le Borgne
- Laboratoire Bio-PeroxIL, Biochimie du Peroxysome, Inflammation et Métabolisme Lipidique, Université de Bourgogne - Faculté des Sciences Gabriel, Dijon, France
| | - Stéphane Guyot
- UMR A 02.102 Procédés Alimentaires et Microbiologiques, Equipe Procédés Microbiologiques et Biotechnologiques, AgroSup Dijon/Université de Bourgogne, bât Erasme, Dijon, France
| | - Morgan Logerot
- Laboratoire Bio-PeroxIL, Biochimie du Peroxysome, Inflammation et Métabolisme Lipidique, Université de Bourgogne - Faculté des Sciences Gabriel, Dijon, France
| | - Laurent Beney
- UMR A 02.102 Procédés Alimentaires et Microbiologiques, Equipe Procédés Microbiologiques et Biotechnologiques, AgroSup Dijon/Université de Bourgogne, bât Erasme, Dijon, France
| | - Patrick Gervais
- UMR A 02.102 Procédés Alimentaires et Microbiologiques, Equipe Procédés Microbiologiques et Biotechnologiques, AgroSup Dijon/Université de Bourgogne, bât Erasme, Dijon, France
| | - Jean Demarquoy
- Laboratoire Bio-PeroxIL, Biochimie du Peroxysome, Inflammation et Métabolisme Lipidique, Université de Bourgogne - Faculté des Sciences Gabriel, Dijon, France
- * E-mail:
| |
Collapse
|
15
|
Vardar SA, Gunduz O, Altun GD, Aydogdu N, Karadag H, Torun N, Kaya O. The alteration of asymmetric dimetilarginine (ADMA) levels in cardiac and gastrocnemius muscles following radioactive iodine application in guinea pigs and the effect of L-carnitine on this alteration. Int J Radiat Biol 2010. [DOI: 10.3109/09553002.2011.518209] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
|
16
|
Vardar SA, Gunduz O, Altun GD, Aydogdu N, Karadag H, Torun N, Kaya O. The alteration of asymmetric dimetilarginine (ADMA) levels in cardiac and gastrocnemius muscles following radioactive iodine application in guinea pigs and the effect of L-carnitine on this alteration. Int J Radiat Biol 2010; 87:2-7. [DOI: 10.3109/09553002.2010.518209] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
|
17
|
Furuichi Y, Sugiura T, Kato Y, Shimada Y, Masuda K. OCTN2 is associated with carnitine transport capacity of rat skeletal muscles. Acta Physiol (Oxf) 2010; 200:57-64. [PMID: 20219053 DOI: 10.1111/j.1748-1716.2010.02101.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIM Carnitine plays an essential role in fat oxidation in skeletal muscles; therefore carnitine influx could be crucial for muscle metabolism. OCTN2, a sodium-dependent solute carrier, is assumed to transport carnitine into various organs. However, OCTN2 protein expression and the functional importance of carnitine transport for muscle metabolism have not been studied. We tested the hypothesis that OCTN2 is expressed at higher levels in oxidative muscles than in other muscles, and that the carnitine uptake capacity of skeletal muscles depends on the amount of OCTN2. METHODS Rat hindlimb muscles (soleus, plantaris, and the surface and deep portions of gastrocnemius) were used for Western blotting to detect OCTN2. Tissue carnitine uptake was examined by an integration plot analysis using l-[(3)H]carnitine as a tracer. Tissue carnitine content was determined by enzymatic cycling methods. The percentage of type I fibres was determined by histochemical analysis. RESULTS OCTN2 was detected in all skeletal muscles although the amount was lower than that in the kidney. OCTN2 expression was significantly higher in soleus than in the other skeletal muscles. The amount of OCTN2 was positively correlated with the percentage of type I fibres in hindlimb muscles. The integration plot analysis revealed a positive correlation between the uptake clearance of l-[(3)H]carnitine and the amount of OCTN2 in skeletal muscles. However, the carnitine content in soleus was lower than that in other skeletal muscles. CONCLUSION OCTN2 is functionally expressed in skeletal muscles and is involved in the import of carnitine for fatty acid oxidation, especially in highly oxidative muscles.
Collapse
Affiliation(s)
- Y Furuichi
- Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa-city, Ishikawa, Japan
| | | | | | | | | |
Collapse
|
18
|
Grigat S, Fork C, Bach M, Golz S, Geerts A, Schömig E, Gründemann D. The Carnitine Transporter SLC22A5 Is Not a General Drug Transporter, but It Efficiently Translocates Mildronate. Drug Metab Dispos 2008; 37:330-7. [DOI: 10.1124/dmd.108.023929] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
|
19
|
Oppedisano F, Fanello D, Calvani M, Indiveri C. Interaction of mildronate with the mitochondrial carnitine/acylcarnitine transport protein. J Biochem Mol Toxicol 2008; 22:8-14. [PMID: 18273902 DOI: 10.1002/jbt.20208] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The interaction of mildronate [3-(2,2,2-trimethylhydrazine) propionate] with the purified mitochondrial carnitine/acylcarnitine transporter reconstituted in liposomes has been studied. Mildronate, externally added to the proteoliposomes, strongly inhibited the carnitine/carnitine antiport catalyzed by the reconstituted transporter with an IC(50) of 560 muM. A kinetic analysis revealed that the inhibition is completely competitive, that is, mildronate interacts with the substrate-binding site. The half-saturation constant of the transporter for external mildronate (K(i)) is 530 muM. Carnitine/mildronate antiport has been measured as [(3)H]carnitine uptake into proteoliposomes containing internal mildronate or as [(3)H]carnitine efflux from proteoliposomes in the presence of external mildronate, indicating that mildronate is transported by the carnitine/acylcarnitine transporter and that the inhibition observed was due to the transport of mildronate in the place of carnitine. The intraliposomal half-saturation constant for mildronate transport (K(m)) has been determined. Its value, 18 mM, is much higher than the external half-saturation constant (K(i)) in agreement with the asymmetric properties of the transporter. In vivo, the antiport reaction between cytosolic (administered) mildronate and matrix carnitine may cause intramitochondrial carnitine depletion. This effect, together with the inhibition of the physiological transport, will lead to impairment of fatty acid utilization.
Collapse
Affiliation(s)
- Francesca Oppedisano
- Department of Cell Biology, University of Calabria, Via P.Bucci 4c, 87036 Arcavacata di Rende, Italy
| | | | | | | |
Collapse
|
20
|
Rigault C, Bernard A, Georges B, Kandel A, Pfützner E, Le Borgne F, Demarquoy J. Extracellular ATP increases L-carnitine transport and content in C2C12 cells. Pharmacology 2008; 81:246-50. [PMID: 18230920 DOI: 10.1159/000114449] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2007] [Accepted: 10/30/2007] [Indexed: 11/19/2022]
Abstract
Extracellular ATP regulates cell proliferation, muscle contraction and myoblast differentiation. ATP present in the muscle interstitium can be released from contracting skeletal muscle cells. L-Carnitine is a key element in muscle cell metabolism, as it serves as a carrier for fatty acid through mitochondrial membranes, controlling oxidation and energy production. Treatment of C2C12 cells with 1 mmol/l of ATP induced a marked increase in L-carnitine uptake that was associated with an increase in L-carnitine content in these cells. These effects were found to be dependent on the density of the cultured cells and on the dose of ATP. The use of specific inhibitors of P2X and P2Y receptors abolished the effect of ATP on L-carnitine metabolism. As ATP can be released from stressed or exercising cells, it can be hypothesized that ATP acts as a messenger in the muscle. ATP will be released to recruit the next cells and increase their metabolism.
Collapse
Affiliation(s)
- Caroline Rigault
- INSERM U866, Laboratoire de Biochimie Métabolique et Nutritionnelle, Faculté Gabriel, Université de Bourgogne, Dijon, France
| | | | | | | | | | | | | |
Collapse
|
21
|
Rigault C, Dias JV, Demarquoy J, Le Borgne F. Characteristics of L-carnitine import into heart cells. Biochimie 2007; 90:542-6. [PMID: 17967426 DOI: 10.1016/j.biochi.2007.10.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2007] [Accepted: 10/04/2007] [Indexed: 11/17/2022]
Abstract
L-carnitine is an essential cofactor for the transport of fatty acids across the mitochondrial membranes. L-carnitine can be provided by food products or biosynthesized in the liver. After intestinal absorption or hepatic biosynthesis, L-carnitine is transferred to organs whose metabolism is dependent upon fatty acid oxidation, such as the skeletal muscle and the heart. The intracellular transport of L-carnitine into the cell requires specific transporters and today, several of these have been characterized. Most of them belong to the solute carrier family. Heart is one of the major target for carnitine transport and use, however basic properties of carnitine uptake by heart cells have never been studied. In this paper, the transport of L-carnitine by rat heart explants has been examined and the kinetic properties of this transport determined and compared to data obtained in skeletal muscle explants. As in muscle, L-carnitine uptake by heart cells was shown to be dependent on sodium and was inhibited by L-carnitine analogues. Molecules known to interact with the skeletal muscle L-carnitine transport were studied in the heart. While trimethyl hydrazinium propionate (THP) was shown to fully inhibit the L-carnitine uptake by muscle cells, it remained inefficient in inhibiting the L-carnitine uptake by heart cells. On the other hand, compounds such as verapamil and AZT were both able to inhibit both the skeletal muscle and the cardiac uptake of L-carnitine. These data suggested that the muscle and heart systems for L-carnitine uptake exhibited different systems of regulation and these results have to be taken in consideration while administrating those compounds that can alter l-carnitine uptake in the muscle and the heart and can lead to damage to these tissues.
Collapse
Affiliation(s)
- Caroline Rigault
- Inserm U 866, LBMN, Dijon, Université de Bourgogne, Faculté Gabriel, Dijon, France
| | | | | | | |
Collapse
|
22
|
Degrace P, Demizieux L, Du ZY, Gresti J, Caverot L, Djaouti L, Jourdan T, Moindrot B, Guilland JC, Hocquette JF, Clouet P. Regulation of Lipid Flux between Liver and Adipose Tissue during Transient Hepatic Steatosis in Carnitine-depleted Rats. J Biol Chem 2007; 282:20816-26. [PMID: 17496329 DOI: 10.1074/jbc.m611391200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Rats with carnitine deficiency due to trimethylhydrazinium propionate (mildronate) administered at 80 mg/100 g body weight per day for 10 days developed liver steatosis only upon fasting. This study aimed to determine whether the transient steatosis resulted from triglyceride accumulation due to the amount of fatty acids preserved through impaired fatty acid oxidation and/or from up-regulation of lipid exchange between liver and adipose tissue. In liver, mildronate decreased the carnitine content by approximately 13-fold and, in fasted rats, lowered the palmitate oxidation rate by 50% in the perfused organ, increased 9-fold the triglyceride content, and doubled the hepatic very low density lipoprotein secretion rate. Concomitantly, triglyceridemia was 13-fold greater than in controls. Hepatic carnitine palmitoyltransferase I activity and palmitate oxidation capacities measured in vitro were increased after treatment. Gene expression of hepatic proteins involved in fatty acid oxidation, triglyceride formation, and lipid uptake were all increased and were associated with increased hepatic free fatty acid content in treated rats. In periepididymal adipose tissue, mildronate markedly increased lipoprotein lipase and hormone-sensitive lipase activities in fed and fasted rats, respectively. On refeeding, carnitine-depleted rats exhibited a rapid decrease in blood triglycerides and free fatty acids, then after approximately 2 h, a marked drop of liver triglycerides and a progressive decrease in liver free fatty acids. Data show that up-regulation of liver activities, peripheral lipolysis, and lipoprotein lipase activity were likely essential factors for excess fat deposit and release alternately occurring in liver and adipose tissue of carnitine-depleted rats during the fed/fasted transition.
Collapse
Affiliation(s)
- Pascal Degrace
- UMR 866 INSERM-UB, Equipe Physiopathologie des dyslipidémies, Faculté des Sciences, 21000 Dijon, France
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
23
|
Dietary mildronate supplementation has no effect on carnitine biosynthetic enzyme mRNA expression in rat. Nutr Res 2007. [DOI: 10.1016/j.nutres.2007.01.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
24
|
Stephens FB, Constantin-Teodosiu D, Greenhaff PL. New insights concerning the role of carnitine in the regulation of fuel metabolism in skeletal muscle. J Physiol 2007; 581:431-44. [PMID: 17331998 PMCID: PMC2075186 DOI: 10.1113/jphysiol.2006.125799] [Citation(s) in RCA: 265] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
In skeletal muscle, carnitine plays an essential role in the translocation of long-chain fatty-acids into the mitochondrial matrix for subsequent beta-oxidation, and in the regulation of the mitochondrial acetyl-CoA/CoASH ratio. Interest in these vital metabolic roles of carnitine in skeletal muscle appears to have waned over the past 25 years. However, recent research has shed new light on the importance of carnitine as a regulator of muscle fuel selection. It has been established that muscle free carnitine availability may be limiting to fat oxidation during high intensity submaximal exercise. Furthermore, increasing muscle total carnitine content in resting healthy humans (via insulin-mediated stimulation of muscle carnitine transport) reduces muscle glycolysis, increases glycogen storage and is accompanied by an apparent increase in fat oxidation. By increasing muscle pyruvate dehydrogenase complex (PDC) activity and acetylcarnitine content at rest, it has also been established that PDC flux and acetyl group availability limits aerobic ATP re-synthesis at the onset of exercise (the acetyl group deficit). Thus, carnitine plays a vital role in the regulation of muscle fuel metabolism. The demonstration that its availability can be readily manipulated in humans, and impacts on physiological function, will result in renewed business and scientific interest in this compound.
Collapse
Affiliation(s)
- Francis B Stephens
- Centre for Integrated Systems Biology and Medicine, School of Biomedical Sciences, Queen's Medical Centre, University of Nottingham, Nottingham NG7 2UH, UK.
| | | | | |
Collapse
|
25
|
Stephens FB, Constantin-Teodosiu D, Laithwaite D, Simpson EJ, Greenhaff PL. Insulin stimulates L-carnitine accumulation in human skeletal muscle. FASEB J 2005; 20:377-9. [PMID: 16368715 DOI: 10.1096/fj.05-4985fje] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Increasing skeletal muscle carnitine content may alleviate the decline in muscle fat oxidation seen during intense exercise. Studies to date, however, have failed to increase muscle carnitine content, in healthy humans, by dietary or intravenous L-carnitine administration. We hypothesized that insulin could augment Na+-dependent skeletal muscle carnitine transport. On two randomized visits, eight healthy men underwent 5 h of intravenous L-carnitine infusion with serum insulin maintained at fasting (7.4+/-0.4 mIU*l(-1)) or physiologically high (149.2+/-6.9 mIU*l(-1)) concentrations. The combination of hypercarnitinemia (approximately 500 micromol*l(-1)) and hyperinsulinemia increased muscle total carnitine (TC) content from 22.0 +/- 0.9 to 24.7 +/- 1.4 mmol*(kg dm)(-1) (P<0.05) and was associated with a 2.3 +/- 0.3-fold increase in carnitine transporter protein (OCTN2) mRNA expression (P<0.05). Hypercarnitinemia in the presence of a fasting insulin concentration had no effect on either of these parameters. This study demonstrates that insulin can acutely increase muscle TC content in humans during hypercarnitinemia, which is associated with an increase in OCTN2 transcription. These novel findings may be of importance to the regulation of muscle fat oxidation during exercise, particularly in obesity and type 2 diabetes where it is known to be impaired.
Collapse
Affiliation(s)
- Francis B Stephens
- Centre for Integrated Systems Biology and Medicine, School of Biomedical Sciences, Queen's Medical Centre, University of Nottingham, NG7 2UH, UK
| | | | | | | | | |
Collapse
|
26
|
Sjakste N, Gutcaits A, Kalvinsh I. Mildronate: an antiischemic drug for neurological indications. CNS DRUG REVIEWS 2005; 11:151-68. [PMID: 16007237 PMCID: PMC6741751 DOI: 10.1111/j.1527-3458.2005.tb00267.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Mildronate (3-(2,2,2-trimethylhydrazinium)propionate; MET-88; meldonium, quaterine) is an antiischemic drug developed at the Latvian Institute of Organic Synthesis. Mildronate was designed to inhibit carnitine biosynthesis in order to prevent accumulation of cytotoxic intermediate products of fatty acid beta-oxidation in ischemic tissues and to block this highly oxygen-consuming process. Mildronate is efficient in the treatment of heart ischemia and its consequences. Extensive evaluation of pharmacological activities of mildronate revealed its beneficial effect on cerebral circulation disorders and central nervous system (CNS) functions. The drug is used in neurological clinics for the treatment of brain circulation disorders. It appears to improve patients' mood; they become more active, their motor dysfunction decreases, and asthenia, dizziness and nausea become less pronounced. Since the brain does not utilize fatty acids as fuel other mechanisms of action of mildronate in CNS should be considered. Several reports indicate the possible existence of an alternative, non-carnitine dependent mechanism of action of mildronate. Our recent findings suggest that CNS effects of mildronate could be mediated by stimulation of the nitric oxide production in the vascular endothelium by modification of the gamma-butyrobetaine and its esters pools. It is hypothesized that mildronate may increase the formation of the gamma-butyrobetaine esters. The latter are potent cholinomimetics and may activate eNOS via acetylcholine receptors or specific gamma-butyrobetaine ester receptors. This article summarizes known pharmacological effects of mildronate, its pharmacokinetics, toxicology, as well as the proposed mechanisms of action.
Collapse
|
27
|
Georges B, Galland S, Rigault C, Le Borgne F, Demarquoy J. Beneficial effects of L-carnitine in myoblastic C2C12 cells. Interaction with zidovudine. Biochem Pharmacol 2003; 65:1483-8. [PMID: 12732360 DOI: 10.1016/s0006-2952(03)00110-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
L-Carnitine is a key molecule in the transfer of fatty acid across mitochondrial membranes. Bioavailable L-carnitine is either provided by an endogeneous biosynthesis or after intestinal absorption of dietary items containing L-carnitine. After intestinal absorption or hepatic biosynthesis, L-carnitine is transferred to organs whose metabolism is dependent upon fatty acid oxidation, such as skeletal muscle. To cross the muscle plasma membrane, there are several transporters involved. Among those transporters, OCTN2 is actually the only one to have been clearly characterized. Zidovudine is a commonly used inhibitor of human immunodeficiency virus (HIV) replication. Zidovudine has many side effects, including induction of myopathy characterized by a metabolic mitochondria dysfunction and a diminution of the muscle L-carnitine content. In this study, we described the characteristics of L-carnitine transport in C2C12 cells. We also demonstrated that zidovudine inhibited the L-carnitine transporter. This inhibition led to a significant reduction of the muscle cell growth. In C2C12 cells, the supplementation of L-carnitine prevented the effects of zidovudine and restored the normal cell growth.
Collapse
Affiliation(s)
- Béatrice Georges
- UPRES Lipides et Nutrition, Faculté Gabriel, Université de Bourgogne, 6 boulevard Gabriel, 21000, Dijon, France
| | | | | | | | | |
Collapse
|
28
|
Abstract
Carnitine is indispensable for energy metabolism, since it enables activated fatty acids to enter the mitochondria, where they are broken down via beta-oxidation. Carnitine is probably present in all animal species, and in numerous micro-organisms and plants. In mammals, carnitine homoeostasis is maintained by endogenous synthesis, absorption from dietary sources and efficient tubular reabsorption by the kidney. This review aims to cover the current knowledge of the enzymological, molecular, metabolic and regulatory aspects of mammalian carnitine biosynthesis, with an emphasis on the human and rat.
Collapse
|
29
|
Abstract
Carnitine is indispensable for energy metabolism, since it enables activated fatty acids to enter the mitochondria, where they are broken down via beta-oxidation. Carnitine is probably present in all animal species, and in numerous micro-organisms and plants. In mammals, carnitine homoeostasis is maintained by endogenous synthesis, absorption from dietary sources and efficient tubular reabsorption by the kidney. This review aims to cover the current knowledge of the enzymological, molecular, metabolic and regulatory aspects of mammalian carnitine biosynthesis, with an emphasis on the human and rat.
Collapse
Affiliation(s)
- Frédéric M Vaz
- Laboratory for Genetic Metabolic Diseases, Departments of Clinical Chemistry and Paediatrics, Emma Children's Hospital, Academic Medical Centre, University of Amsterdam, P.O. Box 22700, 1100 DE Amsterdam, The Netherlands.
| | | |
Collapse
|
30
|
Brooks H, Krähenbühl S. Identification and tissue distribution of two differentially spliced variants of the rat carnitine transporter OCTN2. FEBS Lett 2001; 508:175-80. [PMID: 11718711 DOI: 10.1016/s0014-5793(01)03029-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
In this paper we show that the only known Na(+) dependent transporter of carnitine in mammals, organic cation transporter number 2 (OCTN2), is subject to differential splicing. Cloning of OCTN2 in different rat tissues identified two splicing variants. We have developed a real time quantitative polymerase chain reaction method for quantification of these splice variants. Both splice variants could be detected in all tissues examined with a relative abundance of 0.1-1% of the full length transcript. We also draw attention to the previously described mutations in clinical examples of primary carnitine deficiency in humans where the described mutations appear to be those of a splicing or mis-splicing event.
Collapse
Affiliation(s)
- H Brooks
- Division of Clinical Pharmacology and Toxicology, University Hospital, Petersgraben 4, CH-4031 Basel, Switzerland
| | | |
Collapse
|