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Ramachandran K, Futtner CR, Sommars MA, Quattrocelli M, Omura Y, Fruzyna E, Wang JC, Waldeck NJ, Senagolage MD, Telles CG, Demonbreun AR, Prendergast E, Lai N, Arango D, Bederman IR, McNally EM, Barish GD. Transcriptional programming of translation by BCL6 controls skeletal muscle proteostasis. Nat Metab 2024; 6:304-322. [PMID: 38337096 PMCID: PMC10949880 DOI: 10.1038/s42255-024-00983-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2022] [Accepted: 01/09/2024] [Indexed: 02/12/2024]
Abstract
Skeletal muscle is dynamically controlled by the balance of protein synthesis and degradation. Here we discover an unexpected function for the transcriptional repressor B cell lymphoma 6 (BCL6) in muscle proteostasis and strength in mice. Skeletal muscle-specific Bcl6 ablation in utero or in adult mice results in over 30% decreased muscle mass and force production due to reduced protein synthesis and increased autophagy, while it promotes a shift to a slower myosin heavy chain fibre profile. Ribosome profiling reveals reduced overall translation efficiency in Bcl6-ablated muscles. Mechanistically, tandem chromatin immunoprecipitation, transcriptomic and translational analyses identify direct BCL6 repression of eukaryotic translation initiation factor 4E-binding protein 1 (Eif4ebp1) and activation of insulin-like growth factor 1 (Igf1) and androgen receptor (Ar). Together, these results uncover a bifunctional role for BCL6 in the transcriptional and translational control of muscle proteostasis.
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Affiliation(s)
- Krithika Ramachandran
- Division of Endocrinology, Metabolism, and Molecular Medicine, Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Christopher R Futtner
- Division of Endocrinology, Metabolism, and Molecular Medicine, Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
- Jesse Brown VA Medical Center, Chicago, IL, USA
| | - Meredith A Sommars
- Division of Endocrinology, Metabolism, and Molecular Medicine, Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Mattia Quattrocelli
- Center for Genetic Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
- Division of Molecular Cardiovascular Biology, Heart Institute, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
- Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Yasuhiro Omura
- Division of Endocrinology, Metabolism, and Molecular Medicine, Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
- Jesse Brown VA Medical Center, Chicago, IL, USA
| | - Ellen Fruzyna
- Division of Endocrinology, Metabolism, and Molecular Medicine, Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Janice C Wang
- Division of Endocrinology, Metabolism, and Molecular Medicine, Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Nathan J Waldeck
- Division of Endocrinology, Metabolism, and Molecular Medicine, Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Madhavi D Senagolage
- Division of Endocrinology, Metabolism, and Molecular Medicine, Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Carmen G Telles
- Division of Endocrinology, Metabolism, and Molecular Medicine, Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Alexis R Demonbreun
- Center for Genetic Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Erin Prendergast
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, USA
| | - Nicola Lai
- Department of Mechanical, Chemical, and Materials Engineering, University of Cagliari, Cagliari, Italy
| | - Daniel Arango
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Ilya R Bederman
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, USA
| | - Elizabeth M McNally
- Center for Genetic Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Grant D Barish
- Division of Endocrinology, Metabolism, and Molecular Medicine, Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.
- Jesse Brown VA Medical Center, Chicago, IL, USA.
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2
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Ranea-Robles P, Pavlova NN, Bender A, Pereyra AS, Ellis JM, Stauffer B, Yu C, Thompson CB, Argmann C, Puchowicz M, Houten SM. A mitochondrial long-chain fatty acid oxidation defect leads to transfer RNA uncharging and activation of the integrated stress response in the mouse heart. Cardiovasc Res 2022; 118:3198-3210. [PMID: 35388887 PMCID: PMC9799058 DOI: 10.1093/cvr/cvac050] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Revised: 03/08/2022] [Accepted: 03/23/2022] [Indexed: 01/25/2023] Open
Abstract
AIMS Cardiomyopathy and arrhythmias can be severe presentations in patients with inherited defects of mitochondrial long-chain fatty acid β-oxidation (FAO). The pathophysiological mechanisms that underlie these cardiac abnormalities remain largely unknown. We investigated the molecular adaptations to a FAO deficiency in the heart using the long-chain acyl-CoA dehydrogenase (LCAD) knockout (KO) mouse model. METHODS AND RESULTS We observed enrichment of amino acid metabolic pathways and of ATF4 target genes among the upregulated genes in the LCAD KO heart transcriptome. We also found a prominent activation of the eIF2α/ATF4 axis at the protein level that was independent of the feeding status, in addition to a reduction of cardiac protein synthesis during a short period of food withdrawal. These findings are consistent with an activation of the integrated stress response (ISR) in the LCAD KO mouse heart. Notably, charging of several transfer RNAs (tRNAs), such as tRNAGln was decreased in LCAD KO hearts, reflecting a reduced availability of cardiac amino acids, in particular, glutamine. We replicated the activation of the ISR in the hearts of mice with muscle-specific deletion of carnitine palmitoyltransferase 2. CONCLUSIONS Our results show that perturbations in amino acid metabolism caused by long-chain FAO deficiency impact cardiac metabolic signalling, in particular the ISR. These results may serve as a foundation for investigating the role of the ISR in the cardiac pathology associated with long-chain FAO defects.Translational Perspective: The heart relies mainly on mitochondrial fatty acid β-oxidation (FAO) for its high energy requirements. The heart disease observed in patients with a genetic defect in this pathway highlights the importance of FAO for cardiac health. We show that the consequences of a FAO defect extend beyond cardiac energy homeostasis and include amino acid metabolism and associated signalling pathways such as the integrated stress response.
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Affiliation(s)
- Pablo Ranea-Robles
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, 1425 Madison Avenue, Box 1498, New York, NY 10029, USA
| | - Natalya N Pavlova
- Cancer Biology & Genetics Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Aaron Bender
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, 1425 Madison Avenue, Box 1498, New York, NY 10029, USA
| | - Andrea S Pereyra
- Brody School of Medicine at East Carolina University, Department of Physiology, and East Carolina Diabetes and Obesity Institute, Greenville, NC 27858, USA
| | - Jessica M Ellis
- Brody School of Medicine at East Carolina University, Department of Physiology, and East Carolina Diabetes and Obesity Institute, Greenville, NC 27858, USA
| | - Brandon Stauffer
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, 1425 Madison Avenue, Box 1498, New York, NY 10029, USA
- Mount Sinai Genomics, Inc, Stamford, CT 06902, USA
| | - Chunli Yu
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, 1425 Madison Avenue, Box 1498, New York, NY 10029, USA
- Mount Sinai Genomics, Inc, Stamford, CT 06902, USA
| | - Craig B Thompson
- Cancer Biology & Genetics Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Carmen Argmann
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, 1425 Madison Avenue, Box 1498, New York, NY 10029, USA
| | - Michelle Puchowicz
- Department of Nutrition, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA
- Department of Pediatrics, University of Tennessee Health Science Center, Memphis, TN 38163, USA
| | - Sander M Houten
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, 1425 Madison Avenue, Box 1498, New York, NY 10029, USA
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3
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Abstract
The use of deuterium oxide (D2O) has greatly expanded the scope of what is possible for the measurement of protein synthesis. The greatest asset of D2O labeling is that it facilitates the measurement of synthesis rates over prolonged periods of time from single proteins through integrated tissue-based measurements. Because the ease of administration, the method is amenable for use in a variety of models and conditions. Although the method adheres to the same rules as other isotope methods, the flexibility can create conditions that are not the same as other approaches and thus requires careful execution to maintain validity and reliability. For this CORP article, we provide a history that gave rise to the method and discuss the advantages and disadvantages of the method, the critical assumptions, guidelines, and best practices based on instrumentation, models, and experimental design. The goal of this CORP article is to propagate additional use of D2O in a manner that produces reliable and valid data.
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Affiliation(s)
- Benjamin F Miller
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma
| | - Justin J Reid
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma
| | - John C Price
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah
| | - Hsien-Jung L Lin
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah
| | - Philip J Atherton
- MRC-ARUK Center for Musculoskeletal Ageing Research, School of Medicine, University of Nottingham, Derby, United Kingdom
| | - Kenneth Smith
- MRC-ARUK Center for Musculoskeletal Ageing Research, School of Medicine, University of Nottingham, Derby, United Kingdom
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4
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Abstract
"Omics"-based analyses are widely used in numerous areas of research, advances in instrumentation (both hardware and software) allow investigators to collect a wealth of data and therein characterize metabolic systems. Although analyses generally examine differences in absolute or relative (fold-) changes in concentrations, the ability to extract mechanistic insight would benefit from the use of isotopic tracers. Herein, we discuss important concepts that should be considered when stable isotope tracers are used to capture biochemical flux. Special attention is placed on in vivo systems, however, many of the general ideas have immediate impact on studies in cellular models or isolated-perfused tissues. While it is somewhat trivial to administer labeled precursor molecules and measure the enrichment of downstream products, the ability to make correct interpretations can be challenging. We will outline several critical factors that may influence choices when developing and/or applying a stable isotope tracer method. For example, is there a "best" tracer for a given study? How do I administer a tracer? When do I collect my sample(s)? While these questions may seem straightforward, we will present scenarios that can have dramatic effects on conclusions surrounding apparent rates of metabolic activity.
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Affiliation(s)
- Stephen F Previs
- Department of Chemistry, Merck & Co., Inc., Kenilworth, NJ, USA.
| | - Daniel P Downes
- Department of Chemistry, Merck & Co., Inc., Kenilworth, NJ, USA
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5
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Senagolage MD, Sommars MA, Ramachandran K, Futtner CR, Omura Y, Allred AL, Wang J, Yang C, Procissi D, Evans RM, Han X, Bederman IR, Barish GD. Loss of Transcriptional Repression by BCL6 Confers Insulin Sensitivity in the Setting of Obesity. Cell Rep 2018; 25:3283-3298.e6. [PMID: 30566857 DOI: 10.1016/j.celrep.2018.11.074] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Revised: 09/24/2018] [Accepted: 11/16/2018] [Indexed: 12/27/2022] Open
Abstract
Accumulation of visceral adiposity is directly linked to the morbidity of obesity, while subcutaneous body fat is considered more benign. We have identified an unexpected role for B cell lymphoma 6 (BCL6), a critical regulator of immunity, in the developmental expansion of subcutaneous adipose tissue. In adipocyte-specific knockout mice (Bcl6AKO), we found that Bcl6 deletion results in strikingly increased inguinal, but not perigonadal, adipocyte size and tissue mass in addition to marked insulin sensitivity. Genome-wide RNA expression and DNA binding analyses revealed that BCL6 controls gene networks involved in cell growth and fatty acid biosynthesis. Using deuterium label incorporation and comprehensive adipokine and lipid profiling, we discovered that ablation of adipocyte Bcl6 enhances subcutaneous adipocyte lipogenesis, increases levels of adiponectin and fatty acid esters of hydroxy fatty acids (FAHFAs), and prevents steatosis. Thus, our studies identify BCL6 as a negative regulator of subcutaneous adipose tissue expansion and metabolic health. Senagolage et al. identify BCL6 as a key regulator of body fat distribution. BCL6 directly represses fatty acid biosynthetic and growth genes in adipocytes. Mice constitutively lacking adipocyte Bcl6 exhibit expansion of their subcutaneous adipose tissue, enhanced insulin sensitivity, and protection from hepatic steatosis.
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6
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Sommars MA, Ramachandran K, Senagolage MD, Futtner CR, Germain DM, Allred AL, Omura Y, Bederman IR, Barish GD. Dynamic repression by BCL6 controls the genome-wide liver response to fasting and steatosis. eLife 2019; 8:e43922. [PMID: 30983568 PMCID: PMC6464608 DOI: 10.7554/elife.43922] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Accepted: 03/14/2019] [Indexed: 12/14/2022] Open
Abstract
Transcription is tightly regulated to maintain energy homeostasis during periods of feeding or fasting, but the molecular factors that control these alternating gene programs are incompletely understood. Here, we find that the B cell lymphoma 6 (BCL6) repressor is enriched in the fed state and converges genome-wide with PPARα to potently suppress the induction of fasting transcription. Deletion of hepatocyte Bcl6 enhances lipid catabolism and ameliorates high-fat-diet-induced steatosis. In Ppara-null mice, hepatocyte Bcl6 ablation restores enhancer activity at PPARα-dependent genes and overcomes defective fasting-induced fatty acid oxidation and lipid accumulation. Together, these findings identify BCL6 as a negative regulator of oxidative metabolism and reveal that alternating recruitment of repressive and activating transcription factors to shared cis-regulatory regions dictates hepatic lipid handling.
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Affiliation(s)
- Meredith A Sommars
- Division of Endocrinology, Metabolism, and Molecular Medicine, Department of Medicine, Feinberg School of MedicineNorthwestern UniversityChicagoUnited States
| | - Krithika Ramachandran
- Division of Endocrinology, Metabolism, and Molecular Medicine, Department of Medicine, Feinberg School of MedicineNorthwestern UniversityChicagoUnited States
| | - Madhavi D Senagolage
- Division of Endocrinology, Metabolism, and Molecular Medicine, Department of Medicine, Feinberg School of MedicineNorthwestern UniversityChicagoUnited States
| | - Christopher R Futtner
- Division of Endocrinology, Metabolism, and Molecular Medicine, Department of Medicine, Feinberg School of MedicineNorthwestern UniversityChicagoUnited States
| | - Derrik M Germain
- Division of Endocrinology, Metabolism, and Molecular Medicine, Department of Medicine, Feinberg School of MedicineNorthwestern UniversityChicagoUnited States
| | - Amanda L Allred
- Division of Endocrinology, Metabolism, and Molecular Medicine, Department of Medicine, Feinberg School of MedicineNorthwestern UniversityChicagoUnited States
| | - Yasuhiro Omura
- Division of Endocrinology, Metabolism, and Molecular Medicine, Department of Medicine, Feinberg School of MedicineNorthwestern UniversityChicagoUnited States
| | - Ilya R Bederman
- Department of PediatricsCase Western Reserve UniversityClevelandUnited States
| | - Grant D Barish
- Division of Endocrinology, Metabolism, and Molecular Medicine, Department of Medicine, Feinberg School of MedicineNorthwestern UniversityChicagoUnited States
- Robert H. Lurie Comprehensive Cancer CenterNorthwestern UniversityChicagoUnited States
- Jesse Brown VA Medical CenterChicagoUnited States
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7
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Bederman IR, Pora G, O’Reilly M, Poleman J, Spoonhower K, Puchowicz M, Perez A, Erokwu BO, Rodriguez-Palacios A, Flask CA, Drumm ML. Absence of leptin signaling allows fat accretion in cystic fibrosis mice. Am J Physiol Gastrointest Liver Physiol 2018; 315:G685-G698. [PMID: 30118352 PMCID: PMC6293256 DOI: 10.1152/ajpgi.00344.2017] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Negative energy balance is a prevalent feature of cystic fibrosis (CF). Pancreatic insufficiency, elevated energy expenditure, lung disease, and malnutrition, all characteristic of CF, contribute to the negative energy balance causing low body-growth phenotype. As low body weight and body mass index strongly correlate with poor lung health and survival of patients with CF, improving energy balance is an important clinical goal (e.g., high-fat diet). CF mouse models also exhibit negative energy balance (growth retardation and high energy expenditure), independent from exocrine pancreatic insufficiency, lung disease, and malnutrition. To improve energy balance through increased caloric intake and reduced energy expenditure, we disrupted leptin signaling by crossing the db/db leptin receptor allele with mice carrying the R117H Cftr mutation. Compared with db/db mice, absence of leptin signaling in CF mice (CF db/db) resulted in delayed and moderate hyperphagia with lower de novo lipogenesis and lipid deposition, producing only moderately obese CF mice. Greater body length was found in db/db mice but not in CF db/db, suggesting CF-dependent effect on bone growth. The db/db genotype resulted in lower energy expenditure regardless of Cftr genotype leading to obesity. Despite the db/db genotype, the CF genotype exhibited high respiratory quotient indicating elevated carbohydrate oxidation, thus limiting carbohydrates for lipogenesis. In summary, db/db-linked hyperphagia, elevated lipogenesis, and morbid obesity were partially suppressed by reduced CFTR activity. CF mice still accrued large amounts of adipose tissue in contrast to mice fed a high-fat diet, thus highlighting the importance of dietary carbohydrates and not simply fat for energy balance in CF. NEW & NOTEWORTHY We show that cystic fibrosis (CF) mice are able to accrue fat under conditions of carbohydrate overfeeding, increased lipogenesis, and decreased energy expenditure, although length was unaffected. High-fat diet feeding failed to improve growth in CF mice. Morbid db/db-like obesity was reduced in CF double-mutant mice by reduced CFTR activity.
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Affiliation(s)
- Ilya R. Bederman
- 1Department of Pediatrics, Case Western Reserve University, Cleveland, Ohio
| | - Gavriella Pora
- 1Department of Pediatrics, Case Western Reserve University, Cleveland, Ohio
| | - Maureen O’Reilly
- 1Department of Pediatrics, Case Western Reserve University, Cleveland, Ohio
| | - James Poleman
- 1Department of Pediatrics, Case Western Reserve University, Cleveland, Ohio
| | | | - Michelle Puchowicz
- 2Department of Nutrition, Case Western Reserve University, Cleveland, Ohio
| | - Aura Perez
- 1Department of Pediatrics, Case Western Reserve University, Cleveland, Ohio
| | | | - Alex Rodriguez-Palacios
- 4Department of Medicine, School of Medicine, Case Western Reserve University, Cleveland, Ohio
| | - Chris A. Flask
- 1Department of Pediatrics, Case Western Reserve University, Cleveland, Ohio,3Department of Radiology, Case Western Reserve University, Cleveland, Ohio,5Department of Biomedical Engineering, School of Engineering, Case Western Reserve University, Cleveland, Ohio
| | - Mitchell L. Drumm
- 1Department of Pediatrics, Case Western Reserve University, Cleveland, Ohio
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8
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Yoshida K, Kita Y, Tokuoka SM, Hamano F, Yamazaki M, Sakimura K, Kano M, Shimizu T. Monoacylglycerol lipase deficiency affects diet-induced obesity, fat absorption, and feeding behavior in CB 1 cannabinoid receptor-deficient mice. FASEB J 2018; 33:2484-2497. [PMID: 30265576 DOI: 10.1096/fj.201801203r] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Excess energy intake causes obesity, which leads to insulin resistance and various other complications of metabolic syndrome, including diabetes, atherosclerosis, dyslipidemia, and nonalcoholic fatty liver disease. Although recent studies have depicted altered lipid metabolism as an underlying feature, the detailed mechanisms are still unclear. Here we describe a possible role in high-fat diet (HFD)-induced obesity for monoacylglycerol lipase (MGL), an enzyme that is also known to hydrolyze the endocannabinoid 2-arachidonoylglycerol in brain. MGL-deficient [MGL-knockout (KO)] mice fed a HFD gained less body weight than wild-type mice and were protected from insulin resistance and hepatic steatosis. Food intake and energy expenditure were not altered in MGL-KO mice, but blood triglyceride levels after oral olive oil gavage were suppressed, indicating a role for MGL in intestinal fat absorption. Experiments with cannabinoid receptor type 1 (CB1)/MGL double-KO mice revealed that these phenotypes may include mechanisms that are independent of CB1-receptor-mediated endocannabinoid functions. We also noted that MGL-KO mice had less preference for HFD over normal chow diet. Oral but not intraperitoneal lipid administration strongly suppressed the appetites of MGL-KO and CB1/MGL double-KO mice, but not of wild-type and CB1-KO mice. Appetite suppression was reversed by vagotomy, suggesting involvement of MGL in the gut-brain axis regulation of appetite. Our results provide mechanistic insights of MGL's role in diet-induced obesity, lipid metabolic disorder, and regulation of appetite.-Yoshida, K., Kita, Y., Tokuoka, S. M., Hamano, F., Yamazaki, M., Sakimura, K., Kano, M., Shimizu, T. Monoacylglycerol lipase deficiency affects diet-induced obesity, fat absorption, and feeding behavior in CB1 cannabinoid receptor-deficient mice.
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Affiliation(s)
- Kenji Yoshida
- Department of Lipidomics, The University of Tokyo, Tokyo, Japan
| | - Yoshihiro Kita
- Department of Lipidomics, The University of Tokyo, Tokyo, Japan.,Life Sciences Core Facility The University of Tokyo, Tokyo, Japan
| | | | - Fumie Hamano
- Department of Lipidomics, The University of Tokyo, Tokyo, Japan.,Life Sciences Core Facility The University of Tokyo, Tokyo, Japan.,Department of Lipid Signaling, National Center for Global Health and Medicine, Tokyo, Japan
| | - Maya Yamazaki
- Department of Cellular Neurobiology, Brain Research Institute, Niigata University, Niigata, Japan.,Department of Neurology, University of California, San Francisco, San Francisco, California, USA
| | - Kenji Sakimura
- Department of Cellular Neurobiology, Brain Research Institute, Niigata University, Niigata, Japan
| | - Masanobu Kano
- Department of Neurophysiology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; and.,International Research Center for Neurointelligence (WPI-IRCN), University of Tokyo Institutes for Advanced Study (UTIAS), The University of Tokyo, Tokyo, Japan
| | - Takao Shimizu
- Department of Lipidomics, The University of Tokyo, Tokyo, Japan.,Department of Lipid Signaling, National Center for Global Health and Medicine, Tokyo, Japan
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9
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Previs SF, Herath K, Nawrocki AR, Rodriguez CG, Slipetz D, Singh SB, Kang L, Bhat G, Roddy TP, Conarello S, Terebetski J, Erion MD, Kelley DE. Using [ 2H]water to quantify the contribution of de novo palmitate synthesis in plasma: enabling back-to-back studies. Am J Physiol Endocrinol Metab 2018; 315:E63-E71. [PMID: 29351479 DOI: 10.1152/ajpendo.00010.2017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
An increased contribution of de novo lipogenesis (DNL) may play a role in cases of dyslipidemia and adipose accretion; this suggests that inhibition of fatty acid synthesis may affect clinical phenotypes. Since it is not clear whether modulation of one step in the lipogenic pathway is more important than another, the use of tracer methods can provide a deeper level of insight regarding the control of metabolic activity. Although [2H]water is generally considered a reliable tracer for quantifying DNL in vivo (it yields a homogenous and quantifiable precursor labeling), the relatively long half-life of body water is thought to limit the ability of performing repeat studies in the same subjects; this can create a bottleneck in the development and evaluation of novel therapeutics for inhibiting DNL. Herein, we demonstrate the ability to perform back-to-back studies of DNL using [2H]water. However, this work uncovered special circumstances that affect the data interpretation, i.e., it is possible to obtain seemingly negative values for DNL. Using a rodent model, we have identified a physiological mechanism that explains the data. We show that one can use [2H]water to test inhibitors of DNL by performing back-to-back studies in higher species [i.e., treat nonhuman primates with platensimycin, an inhibitor of fatty acid synthase]; studies also demonstrate the unsuitability of [13C]acetate.
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Affiliation(s)
- Stephen F Previs
- Merck Research Laboratories, Merck & Company, Incorporated, Kenilworth, New Jersey
| | - Kithsiri Herath
- Merck Research Laboratories, Merck & Company, Incorporated, Kenilworth, New Jersey
| | - Andrea R Nawrocki
- Merck Research Laboratories, Merck & Company, Incorporated, Kenilworth, New Jersey
| | - Carlos G Rodriguez
- Merck Research Laboratories, Merck & Company, Incorporated, Kenilworth, New Jersey
| | - Deborah Slipetz
- Merck Research Laboratories, Merck & Company, Incorporated, Kenilworth, New Jersey
| | - Sheo B Singh
- Merck Research Laboratories, Merck & Company, Incorporated, Kenilworth, New Jersey
| | - Ling Kang
- Merck Research Laboratories, Merck & Company, Incorporated, Kenilworth, New Jersey
| | - Gowri Bhat
- Merck Research Laboratories, Merck & Company, Incorporated, Kenilworth, New Jersey
| | - Thomas P Roddy
- Merck Research Laboratories, Merck & Company, Incorporated, Kenilworth, New Jersey
| | - Stacey Conarello
- Merck Research Laboratories, Merck & Company, Incorporated, Kenilworth, New Jersey
| | - Jenna Terebetski
- Merck Research Laboratories, Merck & Company, Incorporated, Kenilworth, New Jersey
| | - Mark D Erion
- Merck Research Laboratories, Merck & Company, Incorporated, Kenilworth, New Jersey
| | - David E Kelley
- Merck Research Laboratories, Merck & Company, Incorporated, Kenilworth, New Jersey
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10
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Daurio NA, Wang SP, Chen Y, Zhou H, McLaren DG, Roddy TP, Johns DG, Milot D, Kasumov T, Erion MD, Kelley DE, Previs SF. Enhancing Studies of Pharmacodynamic Mechanisms via Measurements of Metabolic Flux: Fundamental Concepts and Guiding Principles for Using Stable Isotope Tracers. J Pharmacol Exp Ther 2017; 363:80-91. [DOI: 10.1124/jpet.117.241091] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2017] [Accepted: 06/14/2017] [Indexed: 11/22/2022] Open
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11
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Previs SF, Herath K, Castro-Perez J, Mahsut A, Zhou H, McLaren DG, Shah V, Rohm RJ, Stout SJ, Zhong W, Wang SP, Johns DG, Hubbard BK, Cleary MA, Roddy TP. Effect of Error Propagation in Stable Isotope Tracer Studies: An Approach for Estimating Impact on Apparent Biochemical Flux. Methods Enzymol 2015; 561:331-58. [PMID: 26358910 DOI: 10.1016/bs.mie.2015.06.021] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Stable isotope tracers are widely used to quantify metabolic rates, and yet a limited number of studies have considered the impact of analytical error on estimates of flux. For example, when estimating the contribution of de novo lipogenesis, one typically measures a minimum of four isotope ratios, i.e., the precursor and product labeling pre- and posttracer administration. This seemingly simple problem has 1 correct solution and 80 erroneous outcomes. In this report, we outline a methodology for evaluating the effect of error propagation on apparent physiological endpoints. We demonstrate examples of how to evaluate the influence of analytical error in case studies concerning lipid and protein synthesis; we have focused on (2)H2O as a tracer and contrast different mass spectrometry platforms including GC-quadrupole-MS, GC-pyrolysis-IRMS, LC-quadrupole-MS, and high-resolution FT-ICR-MS. The method outlined herein can be used to determine how to minimize variations in the apparent biology by altering the dose and/or the type of tracer. Likewise, one can facilitate biological studies by estimating the reduction in the noise of an outcome that is expected for a given increase in the number of replicate injections.
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Affiliation(s)
| | | | | | - Ablatt Mahsut
- Merck Research Laboratories, Kenilworth, New Jersey, USA
| | - Haihong Zhou
- Merck Research Laboratories, Kenilworth, New Jersey, USA
| | | | - Vinit Shah
- Merck Research Laboratories, Kenilworth, New Jersey, USA
| | - Rory J Rohm
- Merck Research Laboratories, Kenilworth, New Jersey, USA
| | - Steven J Stout
- Merck Research Laboratories, Kenilworth, New Jersey, USA
| | - Wendy Zhong
- Merck Research Laboratories, Kenilworth, New Jersey, USA
| | | | | | | | | | - Thomas P Roddy
- Merck Research Laboratories, Kenilworth, New Jersey, USA
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12
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Bederman IR, Lai N, Shuster J, Henderson L, Ewart S, Cabrera ME. Chronic hindlimb suspension unloading markedly decreases turnover rates of skeletal and cardiac muscle proteins and adipose tissue triglycerides. J Appl Physiol (1985) 2015; 119:16-26. [PMID: 25930021 DOI: 10.1152/japplphysiol.00004.2014] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2014] [Accepted: 04/25/2015] [Indexed: 11/22/2022] Open
Abstract
We previously showed that a single bolus of "doubly-labeled" water ((2)H2 (18)O) can be used to simultaneously determine energy expenditure and turnover rates (synthesis and degradation) of tissue-specific lipids and proteins by modeling labeling patterns of protein-bound alanine and triglyceride-bound glycerol (Bederman IR, Dufner DA, Alexander JC, Previs SF. Am J Physiol Endocrinol Metab 290: E1048-E1056, 2006). Using this novel method, we quantified changes in the whole body and tissue-specific energy balance in a rat model of simulated "microgravity" induced by hindlimb suspension unloading (HSU). After chronic HSU (3 wk), rats exhibited marked atrophy of skeletal and cardiac muscles and significant decrease in adipose tissue mass. For example, soleus muscle mass progressively decreased 11, 43, and 52%. We found similar energy expenditure between control (90 ± 3 kcal · kg(-1)· day(-1)) and hindlimb suspended (81 ± 6 kcal/kg day) animals. By comparing food intake (∼ 112 kcal · kg(-1) · day(-1)) and expenditure, we found that animals maintained positive calorie balance proportional to their body weight. From multicompartmental fitting of (2)H-labeling patterns, we found significantly (P < 0.005) decreased rates of synthesis (percent decrease from control: cardiac, 25.5%; soleus, 70.3%; extensor digitorum longus, 44.9%; gastrocnemius, 52.5%; and adipose tissue, 39.5%) and rates of degradation (muscles: cardiac, 9.7%; soleus, 52.0%; extensor digitorum longus, 27.8%; gastrocnemius, 37.4%; and adipose tissue, 50.2%). Overall, HSU affected growth of young rats by decreasing the turnover rates of proteins in skeletal and cardiac muscles and adipose tissue triglycerides. Specifically, we found that synthesis rates of skeletal and cardiac muscle proteins were affected to a much greater degree compared with the decrease in degradation rates, resulting in large negative balance and significant tissue loss. In contrast, we found a small decrease in adipose tissue triglyceride synthesis paired with a large decrease in degradation, resulting in smaller negative energy balance and loss of fat mass. We conclude that HSU in rats differentially affects turnover of muscle proteins vs. adipose tissue triglycerides.
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Affiliation(s)
| | - Nicola Lai
- Department of Pediatrics and Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio
| | | | | | | | - Marco E Cabrera
- Department of Pediatrics and Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio
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13
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Abstract
There has been a surge of interest in understanding the regulation of metabolic networks involved in disease in recent years. Quantitative models are increasingly being used to interrogate the metabolic pathways that are contained within this complex disease biology. At the core of this effort is the mathematical modeling of central carbon metabolism involving glycolysis and the citric acid cycle (referred to as energy metabolism). Here, we discuss several approaches used to quantitatively model metabolic pathways relating to energy metabolism and discuss their formalisms, successes, and limitations.
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Affiliation(s)
| | - Brandon Barker
- Division of Nutritional Sciences, Cornell University, Ithaca NY 14850
- Tri-Institutional Field of Computational Biology and Medicine, Cornell University, Ithaca NY 14850
| | - Zhenglong Gu
- Division of Nutritional Sciences, Cornell University, Ithaca NY 14850
- Tri-Institutional Field of Computational Biology and Medicine, Cornell University, Ithaca NY 14850
| | - Jason W Locasale
- Division of Nutritional Sciences, Cornell University, Ithaca NY 14850
- Tri-Institutional Field of Computational Biology and Medicine, Cornell University, Ithaca NY 14850
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14
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Lang CH, Pruznak A, Navaratnarajah M, Rankine KA, Deiter G, Magne H, Offord EA, Breuillé D. Chronic α-hydroxyisocaproic acid treatment improves muscle recovery after immobilization-induced atrophy. Am J Physiol Endocrinol Metab 2013; 305:E416-28. [PMID: 23757407 DOI: 10.1152/ajpendo.00618.2012] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Muscle disuse atrophy is observed routinely in patients recovering from traumatic injury and can be either generalized resulting from extended bed rest or localized resulting from single-limb immobilization. The present study addressed the hypothesis that a diet containing 5% α-hydroxyisocaproic acid (α-HICA), a leucine (Leu) metabolite, will slow the loss and/or improve recovery of muscle mass in response to disuse. Adult 14-wk-old male Wistar rats were provided a control diet or an isonitrogenous isocaloric diet containing either 5% α-HICA or Leu. Disuse atrophy was produced by unilateral hindlimb immobilization ("casting") for 7 days and the contralateral muscle used as control. Rats were also casted for 7 days and permitted to recover for 7 or 14 days. Casting decreased gastrocnemius mass, which was associated with both a reduction in protein synthesis and S6K1 phosphorylation as well as enhanced proteasome activity and increased atrogin-1 and MuRF1 mRNA. Although neither α-HICA nor Leu prevented the casting-induced muscle atrophy, the decreased muscle protein synthesis was not observed in α-HICA-treated rats. Neither α-HICA nor Leu altered the increased proteasome activity and atrogene expression observed with immobilization. After 14 days of recovery, muscle mass had returned to control values only in the rats fed α-HICA, and this was associated with a sustained increase in protein synthesis and phosphorylation of S6K1 and 4E-BP1 of previously immobilized muscle. Proteasome activity and atrogene mRNA content were at control levels after 14 days and not affected by either treatment. These data suggest that whereas α-HICA does not slow the loss of muscle produced by disuse, it does speed recovery at least in part by maintaining an increased rate of protein synthesis.
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Affiliation(s)
- Charles H Lang
- Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA.
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15
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Previs SF, McLaren DG, Wang SP, Stout SJ, Zhou H, Herath K, Shah V, Miller PL, Wilsie L, Castro-Perez J, Johns DG, Cleary MA, Roddy TP. New methodologies for studying lipid synthesis and turnover: looking backwards to enable moving forwards. Biochim Biophys Acta Mol Basis Dis 2013; 1842:402-13. [PMID: 23707557 DOI: 10.1016/j.bbadis.2013.05.019] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2013] [Revised: 05/11/2013] [Accepted: 05/13/2013] [Indexed: 12/26/2022]
Abstract
Our ability to understand the pathogenesis of problems surrounding lipid accretion requires attention towards quantifying lipid kinetics. In addition, studies of metabolic flux should also help unravel mechanisms that lead to imbalances in inter-organ lipid trafficking which contribute to dyslipidemia and/or peripheral lipid accumulation (e.g. hepatic fat deposits). This review aims to outline the development and use of novel methods for studying lipid kinetics in vivo. Although our focus is directed towards some of the approaches that are currently reported in the literature, we include a discussion of the older literature in order to put "new" methods in better perspective and inform readers of valuable historical research. Presumably, future advances in understanding lipid dynamics will benefit from a careful consideration of the past efforts, where possible we have tried to identify seminal papers or those that provide clear data to emphasize essential points. This article is part of a Special Issue entitled: Modulation of Adipose Tissue in Health and Disease.
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Affiliation(s)
- Stephen F Previs
- Molecular Biomarkers, Merck, 2015 Galloping Hill Road, Kenilworth, NJ 07033, USA.
| | - David G McLaren
- Molecular Biomarkers, Merck, 2015 Galloping Hill Road, Kenilworth, NJ 07033, USA
| | - Sheng-Ping Wang
- Molecular Biomarkers, Merck, 2015 Galloping Hill Road, Kenilworth, NJ 07033, USA
| | - Steven J Stout
- Molecular Biomarkers, Merck, 2015 Galloping Hill Road, Kenilworth, NJ 07033, USA
| | - Haihong Zhou
- Molecular Biomarkers, Merck, 2015 Galloping Hill Road, Kenilworth, NJ 07033, USA
| | - Kithsiri Herath
- Molecular Biomarkers, Merck, 2015 Galloping Hill Road, Kenilworth, NJ 07033, USA
| | - Vinit Shah
- Molecular Biomarkers, Merck, 2015 Galloping Hill Road, Kenilworth, NJ 07033, USA
| | - Paul L Miller
- Molecular Biomarkers, Merck, 2015 Galloping Hill Road, Kenilworth, NJ 07033, USA
| | - Larissa Wilsie
- Molecular Biomarkers, Merck, 2015 Galloping Hill Road, Kenilworth, NJ 07033, USA
| | - Jose Castro-Perez
- Molecular Biomarkers, Merck, 2015 Galloping Hill Road, Kenilworth, NJ 07033, USA
| | - Douglas G Johns
- Molecular Biomarkers, Merck, 2015 Galloping Hill Road, Kenilworth, NJ 07033, USA
| | - Michele A Cleary
- Molecular Biomarkers, Merck, 2015 Galloping Hill Road, Kenilworth, NJ 07033, USA
| | - Thomas P Roddy
- Molecular Biomarkers, Merck, 2015 Galloping Hill Road, Kenilworth, NJ 07033, USA
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Holm L, O'Rourke B, Ebenstein D, Toth MJ, Bechshoeft R, Holstein-Rathlou NH, Kjaer M, Matthews DE. Determination of steady-state protein breakdown rate in vivo by the disappearance of protein-bound tracer-labeled amino acids: a method applicable in humans. Am J Physiol Endocrinol Metab 2013; 304:E895-907. [PMID: 23423170 PMCID: PMC3625778 DOI: 10.1152/ajpendo.00579.2012] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A method to determine the rate of protein breakdown in individual proteins was developed and tested in rats and confirmed in humans, using administration of deuterium oxide and incorporation of the deuterium into alanine that was subsequently incorporated into body proteins. Measurement of the fractional breakdown rate of proteins was determined from the rate of disappearance of deuterated alanine from the proteins. The rate of disappearance of deuterated alanine from the proteins was calculated using an exponential decay, giving the fractional breakdown rate (FBR) of the proteins. The applicability of this protein-specific FBR approach is suitable for human in vivo experimentation. The labeling period of deuterium oxide administration is dependent on the turnover rate of the protein of interest.
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Affiliation(s)
- Lars Holm
- Institute of Sports Medicine, Department of Orthopedic Surgery M81, Bispebjerg Hospital, and Center for Healthy Aging, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
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17
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Crown SB, Antoniewicz MR. Parallel labeling experiments and metabolic flux analysis: Past, present and future methodologies. Metab Eng 2013; 16:21-32. [PMID: 23246523 DOI: 10.1016/j.ymben.2012.11.010] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2012] [Revised: 11/09/2012] [Accepted: 11/21/2012] [Indexed: 01/22/2023]
Abstract
Radioactive and stable isotopes have been applied for decades to elucidate metabolic pathways and quantify carbon flow in cellular systems using mass and isotope balancing approaches. Isotope-labeling experiments can be conducted as a single tracer experiment, or as parallel labeling experiments. In the latter case, several experiments are performed under identical conditions except for the choice of substrate labeling. In this review, we highlight robust approaches for probing metabolism and addressing metabolically related questions though parallel labeling experiments. In the first part, we provide a brief historical perspective on parallel labeling experiments, from the early metabolic studies when radioisotopes were predominant to present-day applications based on stable-isotopes. We also elaborate on important technical and theoretical advances that have facilitated the transition from radioisotopes to stable-isotopes. In the second part of the review, we focus on parallel labeling experiments for (13)C-metabolic flux analysis ((13)C-MFA). Parallel experiments offer several advantages that include: tailoring experiments to resolve specific fluxes with high precision; reducing the length of labeling experiments by introducing multiple entry-points of isotopes; validating biochemical network models; and improving the performance of (13)C-MFA in systems where the number of measurements is limited. We conclude by discussing some challenges facing the use of parallel labeling experiments for (13)C-MFA and highlight the need to address issues related to biological variability, data integration, and rational tracer selection.
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Bederman I, Perez A, Henderson L, Freedman JA, Poleman J, Guentert D, Ruhrkraut N, Drumm ML. Altered de novo lipogenesis contributes to low adipose stores in cystic fibrosis mice. Am J Physiol Gastrointest Liver Physiol 2012; 303:G507-18. [PMID: 22679004 PMCID: PMC3774510 DOI: 10.1152/ajpgi.00451.2011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Cystic fibrosis (CF) mouse models exhibit exocrine pancreatic function, yet they do not develop adipose stores to the levels of non-CF mice. CF mice homozygous for the Cftr mutation (F508del) at 3 wk (postweaning) and 6 wk (young adult) of age had markedly less adipose tissue than non-CF mice. Food intake was markedly lower in 3-wk-old CF mice but normalized by 6 wk of age. Both 3- and 6-wk-old mice had dietary lipid absorption and fecal lipid excretion comparable to non-CF mice. Hepatic de novo lipogenesis (DNL), determined by (2)H incorporation, was reduced in CF mice. At 3 wk, F508del mice had significantly decreased DNL of palmitate and stearate, by 83% and 80%, respectively. By 6 wk, DNL rates in non-CF mice remained unchanged compared with 3-wk-old mice, while DNL rates of F508del mice were still reduced, by 33% and 40%, respectively. Adipose tissue fatty acid (FA) profiles were comparable in CF and non-CF mice, indicating that adipose differences are quantitative, not qualitative. A correspondingly lower content of (2)H-labeled FA was found in CF adipose tissue, consistent with reduced deposition of newly made hepatic triglycerides and/or decreased adipose tissue lipogenesis. Hepatic transcriptome analysis revealed lower mRNA expression from several genes involved in FA biosynthesis, suggesting downregulation of this pathway as a mechanism for the reduced lipogenesis. These novel data provide a model for altered lipid metabolism in CF, independent of malabsorption, and may partly explain the inability of pancreatic enzyme replacement therapy to completely restore normal body mass to CF patients.
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Affiliation(s)
- Ilya Bederman
- Department of Pediatrics, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA.
| | - Aura Perez
- 1Department of Pediatrics, Case Western Reserve University School of Medicine, Cleveland, Ohio; and
| | - Leigh Henderson
- 1Department of Pediatrics, Case Western Reserve University School of Medicine, Cleveland, Ohio; and ,2Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, Ohio
| | - Joshua A. Freedman
- 1Department of Pediatrics, Case Western Reserve University School of Medicine, Cleveland, Ohio; and
| | - James Poleman
- 1Department of Pediatrics, Case Western Reserve University School of Medicine, Cleveland, Ohio; and
| | - Dana Guentert
- 1Department of Pediatrics, Case Western Reserve University School of Medicine, Cleveland, Ohio; and
| | - Nicholas Ruhrkraut
- 1Department of Pediatrics, Case Western Reserve University School of Medicine, Cleveland, Ohio; and
| | - Mitchell L. Drumm
- 1Department of Pediatrics, Case Western Reserve University School of Medicine, Cleveland, Ohio; and ,2Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, Ohio
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19
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Bederman IR, Chandramouli V, Sandlers Y, Henderson L, Cabrera ME. Time course of hepatic gluconeogenesis during hindlimb suspension unloading. Exp Physiol 2012; 98:278-89. [DOI: 10.1113/expphysiol.2012.067074] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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20
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Zhou H, Li W, Wang SP, Mendoza V, Rosa R, Hubert J, Herath K, McLaughlin T, Rohm RJ, Lassman ME, Wong KK, Johns DG, Previs SF, Hubbard BK, Roddy TP. Quantifying apoprotein synthesis in rodents: coupling LC-MS/MS analyses with the administration of labeled water. J Lipid Res 2012; 53:1223-31. [PMID: 22389331 DOI: 10.1194/jlr.d021295] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Stable isotope tracer studies of apoprotein flux in rodent models present difficulties as they require working with small volumes of plasma. We demonstrate the ability to measure apoprotein flux by administering either (2)H- or (18)O-labeled water to mice and then subjecting samples to LC-MS/MS analyses; we were able to simultaneously determine the labeling of several proteolytic peptides representing multiple apoproteins. Consistent with relative differences reported in the literature regarding apoprotein flux in humans, we found that the fractional synthetic rate of apoB is greater than apoA1 in mice. In addition, the method is suitable for quantifying acute changes in protein flux: we observed a stimulation of apoB production in mice following an intravenous injection of Intralipid and a decrease in apoB production in mice treated with an inhibitor of microsomal triglyceride transfer protein. In summary, we demonstrate a high-throughput method for studying apoprotein kinetics in rodent models. Although notable differences exist between lipoprotein profiles that are observed in rodents and humans, we expect that the method reported here has merit in studies of dyslipidemia as i) rodent models can be used to probe target engagement in cases where one aims to modulate apoprotein production and ii) the approach should be adaptable to studies in humans.
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Affiliation(s)
- Haihong Zhou
- Atherosclerosis, Merck Research Laboratories, Rahway, NJ 07065, USA
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21
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Shah V, Herath K, Previs SF, Hubbard BK, Roddy TP. Headspace analyses of acetone: a rapid method for measuring the 2H-labeling of water. Anal Biochem 2010; 404:235-7. [PMID: 20488158 DOI: 10.1016/j.ab.2010.05.010] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2010] [Revised: 04/27/2010] [Accepted: 05/12/2010] [Indexed: 10/19/2022]
Abstract
Measurements of a 2H-labeling of water in biological fluids are required for determining the rates of biochemical flux and for estimating body composition. We have been using the method which relies on the base-catalyzed exchange of hydrogen (deuterium) between water and acetone. 2H-labeling of acetone is then determined using GCMS. Although not noted in the original paper, when chloroform is used to extract the acetone there is slow but substantial back exchange between [2H]acetone and solvent (unpublished observations). We report herein on a refinement of the assay that utilizes headspace analysis, which minimizes the number of transfers and decreases sample preparation time and instrument run time.
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Affiliation(s)
- Vinit Shah
- Exploratory Biomarkers, Atherosclerosis, Merck Research Laboratories, 126 E. Lincoln Avenue, Rahway, NJ 07065, USA
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22
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Gasier HG, Fluckey JD, Previs SF. The application of 2H2O to measure skeletal muscle protein synthesis. Nutr Metab (Lond) 2010; 7:31. [PMID: 20409307 PMCID: PMC2873296 DOI: 10.1186/1743-7075-7-31] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2010] [Accepted: 04/21/2010] [Indexed: 12/21/2022] Open
Abstract
Skeletal muscle protein synthesis has generally been determined by the precursor:product labeling approach using labeled amino acids (e.g., [13C]leucine or [13C]-, [15N]-, or [2H]phenylalanine) as the tracers. Although reliable for determining rates of protein synthesis, this methodological approach requires experiments to be conducted in a controlled environment, and as a result, has limited our understanding of muscle protein renewal under free-living conditions over extended periods of time (i.e., integrative/cumulative assessments). An alternative tracer, 2H2O, has been successfully used to measure rates of muscle protein synthesis in mice, rats, fish and humans. Moreover, perturbations such as feeding and exercise have been included in these measurements without exclusion of common environmental and biological factors. In this review, we discuss the principle behind using 2H2O to measure muscle protein synthesis and highlight recent investigations that have examined the effects of feeding and exercise. The framework provided in this review should assist muscle biologists in designing experiments that advance our understanding of conditions in which anabolism is altered (e.g., exercise, feeding, growth, debilitating and metabolic pathologies).
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Affiliation(s)
- Heath G Gasier
- Naval Submarine Medical Research Laboratory, Groton, CT, USA.
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Rachdaoui N, Austin L, Kramer E, Previs MJ, Anderson VE, Kasumov T, Previs SF. Measuring proteome dynamics in vivo: as easy as adding water? Mol Cell Proteomics 2009; 8:2653-63. [PMID: 19724074 DOI: 10.1074/mcp.m900026-mcp200] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Proteomics investigations typically yield information regarding static gene expression profiles. The central issues that limit the study of proteome dynamics include how to (i) administer a labeled amino acid in vivo, (ii) measure the isotopic labeling of a protein(s) (which may be low), and (iii) reliably interpret the precursor/product labeling relationships. In this study, we demonstrate the potential of quantifying proteome dynamics by coupling the administration of stable isotopes with mass spectrometric assays. Although the direct administration of a labeled amino acid(s) is typically used to measure protein synthesis, we explain the application of labeled water, comparing (2)H(2)O versus H(2)(18)O for measuring albumin biosynthesis in vivo. This application emphasizes two distinct advantages of using labeled water over a labeled amino acid(s). First, in long term studies (e.g. days or weeks), it is not practical to continuously administer a labeled amino acid(s); however, in the presence of labeled water, organisms will generate labeled amino acids. Second, to calculate rates of protein synthesis in short term studies (e.g. hours), one must utilize a precursor/product labeling ratio; when using labeled water it is possible to reliably identify and easily measure the precursor labeling (i.e. water). We demonstrate that labeled water permits studies of protein synthesis (e.g. albumin synthesis in mice) during metabolic "steady-state" or "non-steady-state" conditions, i.e. integrating transitions between the fed and fasted state or during an acute perturbation (e.g. following a meal), respectively. We expect that the use of labeled water is applicable to wide scale investigations of proteome dynamics and can therein be used to obtain a functional image of gene expression in vivo.
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Affiliation(s)
- Nadia Rachdaoui
- Department Medicine, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA
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Gasier HG, Riechman SE, Wiggs MP, Previs SF, Fluckey JD. A comparison of 2H2O and phenylalanine flooding dose to investigate muscle protein synthesis with acute exercise in rats. Am J Physiol Endocrinol Metab 2009; 297:E252-9. [PMID: 19366878 PMCID: PMC4043319 DOI: 10.1152/ajpendo.90872.2008] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The primary objective of this investigation was to determine whether (2)H(2)O and phenylalanine (Phe) flooding dose methods yield comparable fractional rates of protein synthesis (FSR) in skeletal muscle following a single bout of high-intensity resistance exercise (RE). Sprague-Dawley rats were assigned by body mass to either 4-h control (CON 4 h; n = 6), 4-h resistance exercise (RE 4 h; n = 6), 24-h control (CON 24 h; n = 6), or 24-h resistance exercise (RE 24 h; n = 6). The RE groups were operantly conditioned to engage in a single bout of high-intensity, "squat-like" RE. All rats were given an intraperitoneal injection of 99.9% (2)H(2)O and provided 4.0% (2)H(2)O drinking water for either 24 (n = 12) or 4 h (n = 12) prior to receiving a flooding dose of l-[2,3,4,5,6-(3)H]Phe 16 h post-RE. Neither method detected an effect of RE on FSR in the mixed gastrocnemius, plantaris, or soleus muscle. Aside from the qualitative similarities between methods, the 4-h (2)H(2)O FSR measurements, when expressed in percent per hour, were quantitatively greater than the 24-h (2)H(2)O and Phe flooding in all muscles (P < 0.001), and the 24-h (2)H(2)O was greater than the Phe flooding dose in the mixed gastrocnemius and plantaris (P < 0.05). In contrast, the actual percentage of newly synthesized protein was significantly higher in the 24- vs. 4-h (2)H(2)O and Phe flooding dose groups (P < 0.001). These results suggest that the methodologies provide "qualitatively" similar results when a perturbation such as RE is studied. However, due to potential quantitative differences between methods, the experimental question should determine what approach should be used.
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Affiliation(s)
- Heath G Gasier
- Department of Health and Kinesiology, Texas A & M University, College Station, TX 77843-4243, USA
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Gasier HG, Previs SF, Pohlenz C, Fluckey JD, Gatlin DM 3rd, Buentello JA. A novel approach for assessing protein synthesis in channel catfish, Ictalurus punctatus. Comp Biochem Physiol B Biochem Mol Biol 2009; 154:235-8. [PMID: 19563906 DOI: 10.1016/j.cbpb.2009.06.012] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2009] [Revised: 06/12/2009] [Accepted: 06/18/2009] [Indexed: 11/20/2022]
Abstract
A comprehensive understanding of animal growth requires adequate knowledge of protein synthesis (PS), which in fish, has traditionally been determined by the flooding dose method. However, this procedure is limited to short-term assessments and may not accurately describe fish growth over extended periods of time. Since deuterium oxide ((2)H(2)O) has been used to non-invasively quantify PS in mammals over short- and long-term periods, we aimed at determining if (2)H(2)O could also be used to measure PS in channel catfish. Fish were stocked in a 40-L aquarium with approximately 4% (2)H(2)O and sampled at 4, 8 and 24h (n=6 at each time period) to determine (2)H-labeling of body water (plasma), as well as protein-free and protein-bound (2)H-labeled alanine. The labeling of body water reflected that of aquarium water and the labeling of protein-free alanine remained constant over 24h and was approximately 3.8 times greater than that of body water. By measuring (2)H-labeled alanine incorporation after 24h of (2)H(2)O exposure we were able to calculate a rate of PS: 0.04+/-0.01% h(-1). These results demonstrate that PS in fish can be effectively measured using (2)H(2)O and, because this method yields integrative measures of PS, is relatively inexpensive and accounts for perturbations such as feeding, it is a novel and practical assessment option.
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Bederman IR, Foy S, Chandramouli V, Alexander JC, Previs SF. Triglyceride synthesis in epididymal adipose tissue: contribution of glucose and non-glucose carbon sources. J Biol Chem 2008; 284:6101-8. [PMID: 19114707 DOI: 10.1074/jbc.m808668200] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The obesity epidemic has generated interest in determining the contribution of various pathways to triglyceride synthesis, including an elucidation of the origin of triglyceride fatty acids and triglyceride glycerol. We hypothesized that a dietary intervention would demonstrate the importance of using glucose versus non-glucose carbon sources to synthesize triglycerides in white adipose tissue. C57BL/6J mice were fed either a low fat, high carbohydrate (HC) diet or a high fat, carbohydrate-free (CF) diet and maintained on 2H2O (to determine total triglyceride dynamics) or infused with [6,6-(2)H]glucose (to quantify the contribution of glucose to triglyceride glycerol). The 2H2O labeling data demonstrate that although de novo lipogenesis contributed approximately 80% versus approximately 5% to the pool of triglyceride palmitate in HC- versus CF-fed mice, the epididymal adipose tissue synthesized approximately 1.5-fold more triglyceride in CF- versus HC-fed mice, i.e. 37+/-5 versus 25+/-3 micromolxday(-1). The [6,6-(2)H]glucose labeling data demonstrate that approximately 69 and approximately 28% of triglyceride glycerol is synthesized from glucose in HC- versus CF-fed mice, respectively. Although these data are consistent with the notion that non-glucose carbon sources (e.g. glyceroneogenesis) can make substantial contributions to the synthesis of triglyceride glycerol (i.e. the absolute synthesis of triglyceride glycerol from non-glucose substrates increased from approximately 8 to approximately 26 micromolxday(-1) in HC- versus CF-fed mice), these observations suggest (i) the importance of nutritional status in affecting flux rates and (ii) the operation of a glycerol-glucose cycle.
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Affiliation(s)
- Ilya R Bederman
- Department of Nutrition, Case Western Reserve University, Cleveland, Ohio 44106, USA
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Nye CK, Hanson RW, Kalhan SC. Glyceroneogenesis is the dominant pathway for triglyceride glycerol synthesis in vivo in the rat. J Biol Chem 2008; 283:27565-27574. [PMID: 18662986 PMCID: PMC2562054 DOI: 10.1074/jbc.m804393200] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2008] [Revised: 07/22/2008] [Indexed: 12/13/2022] Open
Abstract
Triglyceride synthesis in mammalian tissues requires glycerol 3-phosphate as the source of triglyceride glycerol. In this study the relative contribution of glyceroneogenesis and glycolysis to triglyceride glycerol synthesis was quantified in vivo in adipose tissue, skeletal muscle, and liver of the rat in response to a chow diet (controls), 48-h fast, and lipogenic (high sucrose) diet. The rate of glyceroneogenesis was quantified using the tritium ([(3)H(2)]O) labeling of body water, and the contribution of glucose, via glycolysis, was determined using a [U-(14)C]glucose tracer. In epididymal and mesenteric adipose tissue of control rats, glyceroneogenesis accounted for approximately 90% of triglyceride glycerol synthesis. Fasting for 48 h did not alter glyceroneogenesis in adipose tissue, whereas the contribution of glucose was negligible. In response to sucrose feeding, the synthesis of triglyceride glycerol via both glyceroneogenesis and glycolysis nearly doubled (versus controls); however, glyceroneogenesis remained quantitatively higher as compared with the contribution of glucose. Enhancement of triglyceride-fatty acid cycling by epinephrine infusion resulted in a higher rate of glyceroneogenesis in adipose tissue, as compared with controls, whereas the contribution of glucose via glycolysis was not measurable. Glyceroneogenesis provided the majority of triglyceride glycerol in the gastrocnemius and soleus. In the liver the fractional contribution of glyceroneogenesis remained constant (approximately 60%) under all conditions and was higher than that of glucose. Thus, glyceroneogenesis, in contrast to glucose, via glycolysis, is quantitatively the predominant source of triglyceride glycerol in adipose tissue, skeletal muscle, and liver of the rat during fasting and high sucrose feeding.
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Affiliation(s)
- Colleen K Nye
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106; Departments of Gastroenterology and Pathobiology, Cleveland Clinic, Cleveland, Ohio 44195
| | - Richard W Hanson
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106; Departments of Gastroenterology and Pathobiology, Cleveland Clinic, Cleveland, Ohio 44195
| | - Satish C Kalhan
- Departments of Gastroenterology and Pathobiology, Cleveland Clinic, Cleveland, Ohio 44195; Department of Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland Clinic, Cleveland, Ohio 44195.
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Yuan CL, Sharma N, Gilge DA, Stanley WC, Li Y, Hatzoglou M, Previs SF. Preserved protein synthesis in the heart in response to acute fasting and chronic food restriction despite reductions in liver and skeletal muscle. Am J Physiol Endocrinol Metab 2008; 295:E216-22. [PMID: 18445754 PMCID: PMC2493593 DOI: 10.1152/ajpendo.00545.2007] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Whole body protein synthesis is reduced during the fed-to-fasted transition and in cases of chronic dietary restriction; however, less is known about tissue-specific alterations. We have assessed the extent to which protein synthesis in cardiac muscle responds to dietary perturbations compared with liver and skeletal muscle by applying a novel (2)H(2)O tracer method to quantify tissue-specific responses of protein synthesis in vivo. We hypothesized that protein synthesis in cardiac muscle would be unaffected by acute fasting or food restriction, whereas protein synthesis in the liver and gastrocnemius muscle would be reduced when there is a protein-energy deficit. We found that, although protein synthesis in liver and gastrocnemius muscle was significantly reduced by acute fasting, there were no changes in protein synthesis in the left ventricle of the heart for either the total protein pool or in isolated mitochondrial or cytosolic compartments. Likewise, a chronic reduction in calorie intake, induced by food restriction, did not affect protein synthesis in the heart, whereas protein synthesis in skeletal muscle and liver was decreased. The later observations are supported by changes in the phosphorylation state of two critical mediators of protein synthesis (4E-BP1 and eIF2alpha) in the respective tissues. We conclude that cardiac protein synthesis is maintained in cases of nutritional perturbations, in strong contrast to liver and gastrocnemius muscle, where protein synthesis is decreased by acute fasting or chronic food restriction.
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Affiliation(s)
- Celvie L Yuan
- Department of Nutrition, Case Western Reserve University School of Medicine, 10900 Euclid Ave., Cleveland, OH 44106, USA
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Anderson SR, Gilge DA, Steiber AL, Previs SF. Diet-induced obesity alters protein synthesis: tissue-specific effects in fasted versus fed mice. Metabolism 2008; 57:347-54. [PMID: 18249206 PMCID: PMC2323208 DOI: 10.1016/j.metabol.2007.10.009] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2007] [Accepted: 10/29/2007] [Indexed: 11/28/2022]
Abstract
The influence of obesity on protein dynamics is not clearly understood. We have designed experiments to test the hypothesis that obesity impairs the stimulation of tissue-specific protein synthesis after nutrient ingestion. C57BL/6J mice were randomized into 2 groups: group 1 (control, n = 16) was fed a low-fat, high-carbohydrate diet, whereas group 2 (experimental, n = 16) was fed a high-fat, low-carbohydrate diet ad libitum for 9 weeks. On the experiment day, all mice were fasted for 6 hours and given an intraperitoneal injection of (2)H(2)O. They were then randomized into 2 subgroups and either given a sham saline gavage or a liquid-meal challenge. Rates of protein synthesis were determined via the incorporation of [(2)H]alanine (5 hours postchallenge) into total gastrocnemius muscle protein, total liver protein, and plasma albumin. High-fat feeding led to an increase in total body fat (P < .001) and epididymal fat pad weights (P < .001) and elevated fasting plasma glucose levels (P < .01). Diet-induced obesity (a) did not affect basal rates of skeletal muscle protein synthesis, but did impair the activation of skeletal muscle protein synthesis in response to nutrient ingestion (P < .05), and (b) slightly reduced basal rates of synthesis of total hepatic proteins and plasma albumin (P = .10), but did not affect the synthesis of either in response to the meal challenge. In conclusion, there are alterations in tissue-specific protein metabolism in the C57BL/6J mouse model of diet-induced obesity. This model may prove to be helpful in future studies that explore the mechanisms that account for altered protein dynamics in obesity.
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Affiliation(s)
- Stephanie R. Anderson
- Department of Nutrition, Case Western Reserve University School of Medicine, Cleveland, OH 44106
| | - Danielle A. Gilge
- Department of Nutrition, Case Western Reserve University School of Medicine, Cleveland, OH 44106
| | - Alison L. Steiber
- Department of Nutrition, Case Western Reserve University School of Medicine, Cleveland, OH 44106
| | - Stephen F. Previs
- Department of Nutrition, Case Western Reserve University School of Medicine, Cleveland, OH 44106
- Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH 44106
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Belloto E, Diraison F, Basset A, Allain G, Abdallah P, Beylot M. Determination of protein replacement rates by deuterated water: validation of underlying assumptions. Am J Physiol Endocrinol Metab 2007; 292:E1340-7. [PMID: 17227960 DOI: 10.1152/ajpendo.00488.2006] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
H(2)O administration has recently been proposed as a simple and convenient method to measure protein synthesis rates. (2)H(2)O administration results in deuterium labeling of free amino acids such as alanine, and incorporation into proteins of labeled alanine can then be used to measure protein synthesis rates. We examined first whether during (2)H(2)O administration plasma free alanine enrichment is a correct estimate of the enrichment in the tissue amino acid pools used for protein synthesis. We found that, after (2)H(2)O administration, deuterium labeling in plasma free alanine equilibrated rapidly with body water, and stable enrichment values were obtained within 20 min. Importantly, oral administration of (2)H(2)O induced no difference of labeling between portal and peripheral circulation except for the initial 10 min after a loading dose. The kinetics of free alanine labeling were comparable in various tissues (liver, skeletal muscle, heart) and in plasma with identical plateau values. We show next that increased glycolytic rate or absorption of unlabeled amino acids from ingested meals do not modify alanine labeling. Calculated synthesis rates of mixed proteins were much higher (20- to 70-fold) in plasma and liver than in muscle and heart. Last, comparable replacement rates of apoB100-VLDL were obtained in humans by using the kinetics of incorporation into apoB100 of infused labeled leucine or of alanine labeled by (2)H(2)O administration. All of these results support (2)H(2)O as a safe, reliable, useful, and convenient tracer for studies of protein synthesis, including proteins with slow turnover rate.
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Affiliation(s)
- Emmanuelle Belloto
- 1Institut National de la Santé et de la Recherche Médicale U499, Faculté Réne Theodore Hyacinthe, Laennec, France
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