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Millward DJ, Smith K. The application of stable-isotope tracers to study human musculoskeletal protein turnover: a tale of bag filling and bag enlargement. J Physiol 2019; 597:1235-1249. [PMID: 30097998 PMCID: PMC6395420 DOI: 10.1113/jp275430] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Accepted: 07/09/2018] [Indexed: 01/15/2023] Open
Abstract
The nutritional regulation of protein and amino acid balance in human skeletal muscle carried out by the authors with Mike Rennie is reviewed in the context of a simple physiological model for the regulation of the maintenance and growth of skeletal muscle, the "Bag Theory". Beginning in London in the late 1970s the work has involved the use of stable isotopes to probe muscle protein synthesis and breakdown with two basic experimental models, primed-dose continuous tracer infusions combined with muscle biopsies and arterio-venous (A-V) studies across a limb, most often the leg, allowing both protein synthesis and breakdown as well as net balance to be measured. In this way, over a 30 year period, the way in which amino acids and insulin mediate the anabolic effect of a meal has been elaborated in great detail confirming the original concepts of bag filling within the muscle endomysial "bag", which is limited by the "bag" size unless bag enlargement occurs requiring new collagen synthesis. Finally we briefly review some new developments involving 2 H2 O labelling of muscle proteins.
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Affiliation(s)
- D. Joe Millward
- Department of Nutritional SciencesSchool of Biosciences and MedicineFaculty of Health and Medical SciencesUniversity of SurreyGuildfordUK
- MRC/ARUK Centre of Excellence for Musculoskeletal Ageing ResearchNational Institute for Health Research Nottingham Biomedical Research CentreUniversity of NottinghamDerbyUK
| | - Ken Smith
- Department of Nutritional SciencesSchool of Biosciences and MedicineFaculty of Health and Medical SciencesUniversity of SurreyGuildfordUK
- MRC/ARUK Centre of Excellence for Musculoskeletal Ageing ResearchNational Institute for Health Research Nottingham Biomedical Research CentreUniversity of NottinghamDerbyUK
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Hines KM, Ford GC, Klaus KA, Irving BA, Ford BL, Johnson KL, Lanza IR, Nair KS. Application of high-resolution mass spectrometry to measure low abundance isotope enrichment in individual muscle proteins. Anal Bioanal Chem 2015; 407:4045-52. [PMID: 25832482 PMCID: PMC4539943 DOI: 10.1007/s00216-015-8641-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2014] [Revised: 03/11/2015] [Accepted: 03/12/2015] [Indexed: 10/23/2022]
Abstract
Stable isotope-labeled amino acids have long been used to measure the fractional synthesis rate of proteins, although the mass spectrometry platforms used for such analyses have changed throughout the years. More recently, tandem mass spectrometers such as triple quadrupoles have been accepted as the standard platform for enrichment measurement due to their sensitivity and the enhanced specificity offered by multiple reaction monitoring (MRM) experiments. The limit in the utility of such platforms for enrichment analysis occurs when measuring very low levels of enrichment from small amounts of sample, particularly proteins isolated from two-dimensional gel electrophoresis (2D-GE), where interference from contaminant ions impacts the sensitivity of the measurement. We therefore applied a high-resolution orbitrap mass spectrometer to the analysis of [ring-(13)C6]-phenylalanine enrichment in individual muscle proteins isolated with 2D-GE. Comparison of samples analyzed on both platforms revealed that the high-resolution MS has significantly improved sensitivity relative to the triple quadrupole MS at very low-level enrichments due to its ability to resolve interferences in the m/z dimension. At higher enrichment levels, enrichment measurements from the orbitrap platform showed significant correlation (R (2) > 0.5) with those of the triple quadrupole platform. Together, these results indicate that high-resolution MS platforms such as the orbitrap are not only as capable of performing isotope enrichment measurements as the more commonly preferred triple quadrupole instruments, but offer unparalleled advantages in terms of mass accuracy and sensitivity in the presence of similar-mass contaminants.
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Affiliation(s)
- Kelly M. Hines
- Metabolomics Resource Core, Mayo Clinic, Rochester, MN 55905, USA
- Division of Endocrinology, Diabetes, Metabolism and Nutrition, Mayo Clinic, Rochester, MN 55905, USA
| | - G. Charles Ford
- Metabolomics Resource Core, Mayo Clinic, Rochester, MN 55905, USA
| | - Katherine A. Klaus
- Division of Endocrinology, Diabetes, Metabolism and Nutrition, Mayo Clinic, Rochester, MN 55905, USA
| | - Brian A. Irving
- Division of Endocrinology, Diabetes, Metabolism and Nutrition, Mayo Clinic, Rochester, MN 55905, USA
| | - Beverly L. Ford
- Metabolomics Resource Core, Mayo Clinic, Rochester, MN 55905, USA
| | - Kenneth L. Johnson
- Medical Genome Facility Proteomics Core, Mayo Clinic, Rochester, MN 55905
| | - Ian R. Lanza
- Metabolomics Resource Core, Mayo Clinic, Rochester, MN 55905, USA
- Division of Endocrinology, Diabetes, Metabolism and Nutrition, Mayo Clinic, Rochester, MN 55905, USA
| | - K. Sreekumaran Nair
- Metabolomics Resource Core, Mayo Clinic, Rochester, MN 55905, USA
- Division of Endocrinology, Diabetes, Metabolism and Nutrition, Mayo Clinic, Rochester, MN 55905, USA
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Zabielski P, Ford GC, Persson XM, Jaleel A, Dewey JD, Nair KS. Comparison of different mass spectrometry techniques in the measurement of L-[ring-(13)C6]phenylalanine incorporation into mixed muscle proteins. JOURNAL OF MASS SPECTROMETRY : JMS 2013; 48:269-275. [PMID: 23378099 PMCID: PMC3721634 DOI: 10.1002/jms.3120] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Revised: 09/25/2012] [Accepted: 10/04/2012] [Indexed: 06/01/2023]
Abstract
Precise measurement of low enrichment of stable isotope labeled amino-acid tracers in tissue samples is a prerequisite in measuring tissue protein synthesis rates. The challenge of this analysis is augmented when small sample size is a critical factor. Muscle samples from human participants following an 8 h intravenous infusion of L-[ring-(13)C(6)]phenylalanine and a bolus dose of L-[ring-(13)C(6)]phenylalanine in a mouse were utilized. Liquid chromatography tandem mass spectrometry (LC/MS/MS), gas chromatography (GC) MS/MS and GC/MS were compared to the GC-combustion-isotope ratio MS (GC/C/IRMS), to measure mixed muscle protein enrichment of [ring-(13)C(6)]phenylalanine enrichment. The sample isotope enrichment ranged from 0.0091 to 0.1312 molar percent excess. As compared with GC/C/IRMS, LC/MS/MS, GC/MS/MS and GC/MS showed coefficients of determination of R(2)= 0.9962 and R(2) = 0.9942, and 0.9217 respectively. However, the precision of measurements (coefficients of variation) for intra-assay are 13.0%, 1.7%, 6.3% and 13.5% and for inter-assay are 9.2%, 3.2%, 10.2% and 25% for GC/C/IRMS, LC/MS/MS, GC/MS/MS and GC/MS, respectively. The muscle sample sizes required to obtain these results were 8 µg, 0.8 µg, 3 µg and 3 µg for GC/C/IRMS, LC/MS/MS, GC/MS/MS and GC/MS, respectively. We conclude that LC/MS/MS is optimally suited for precise measurements of L-[ring-(13)C(6)]phenylalanine tracer enrichment in low abundance and in small quantity samples.
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Affiliation(s)
- Piotr Zabielski
- Division of Endocrinology, Diabetes, Metabolism and Nutrition, Mayo Clinic, 200 First St. SW, 5-194 Joseph, Rochester, MN 55905, USA
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Abstract
The pathophysiology of hepatic steatosis, a prerequisite of nonalcoholic fatty liver disease, is poorly understood. Because very-low-density lipoprotein (VLDL) formation is the chief route of hepatic lipid export, we hypothesized that the synthesis of apoB-100, a rate-determining step in hepatic VLDL formation, may be altered in patients with nonalcoholic steatohepatitis (NASH). This study evaluated the relative synthesis rates of apolipoprotein B-100 (apoB-100) in patients with NASH and in lean and body mass index (BMI)-matched (obese) controls without NASH. A primed continuous infusion of L-[1-(13)C] leucine was used to measure the absolute synthesis rates (ASR) of apoB-100 and fibrinogen in 7 patients with NASH and compared them with 7 lean and 7 obese (BMI-matched) controls without NASH. The ASRs of fibrinogen and albumin also were measured. The mean ASR of apoB-100 in patients with NASH was lower (31.5 +/- 3.4 mg/kg/d) than that of obese (115.2 +/- 7.2 mg/kg/d, P <.001) and lean controls (82.4 +/- 4.1 mg/kg/d, P =.002). In contrast, the mean ASR of fibrinogen was greater in subjects with NASH than in both control groups. These data indicate that NASH is associated with markedly altered hepatic synthesis of apoB-100. The finding that albumin synthesis was not similarly decreased in patients with NASH shows that the attenuation of apoB-100 synthesis is not on the basis of globally impaired hepatic protein synthesis. In conclusion, because apoB-100 synthesis is a rate-determining step in hepatocyte lipid export, decreased synthesis of this protein may be an important factor in the development of hepatic steatosis, a prerequisite for NASH.
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Affiliation(s)
- Michael Charlton
- Department of Gastroenterology and Hepatology, Mayo Clinic and Foundation, Rochester, MN 55905, USA.
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Abstract
BACKGROUND & AIMS Insulin deficiency was recently shown to stimulate splanchnic protein synthesis in vivo, whereas insulin enhances small intestinal mucosal cell proliferation in vitro. Because insulin is a postprandial hormone, it was hypothesized that it has an important role in regulating small intestinal protein synthesis in humans. METHODS Small intestinal mucosal protein synthesis was measured in C-peptide-negative patients with type 1 diabetes mellitus during insulin deprivation (n = 6) and during insulin treatment (n = 6) and in nondiabetic control subjects (n = 6). Mucosal protein synthesis was measured from the increment of [(13)C]leucine enrichment in endoscopically obtained duodenal mucosa samples during a primed continuous infusion of L-[1-(13)C]leucine. RESULTS During insulin treatment, the rate of mucosal protein synthesis in patients with type 1 diabetes was similar (1.32% +/- 0.05%/h) to that of nondiabetic controls (1.33% +/- 0.06%/h). However, during insulin deprivation, the mucosal protein synthesis rate in patients with type 1 diabetes was significantly lower (1.15% +/- 0.33%/h) than during either insulin treatment (P = 0.01) or in nondiabetic controls (P = 0.04). CONCLUSIONS These studies show that insulin is required for the maintenance of normal rates of protein synthesis in small intestinal mucosa. Because protein synthesis is an essential component of the remodeling process of this fast turning over tissue, the decline in the synthesis rate of small intestinal mucosa during insulin deprivation may be a contributing factor in the development of gastrointestinal complications that occur in poorly controlled type 1 diabetic patients.
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Affiliation(s)
- M Charlton
- Department of Gastroenterology and Hepatology, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA.
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Young VR, Ajami A. The Rudolf Schoenheimer Centenary Lecture. Isotopes in nutrition research. Proc Nutr Soc 1999; 58:15-32. [PMID: 10343336 DOI: 10.1079/pns19990004] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The present lecture begins with a brief overview of the professional and scientific journey taken by Rudolf Schoenheimer, before turning to a discussion of the power of isotopic tracers in nutrition research. Schoenheimer's remarkable contributions to the study of intermediary metabolism and the turnover of body constituents, based initially on compounds tagged with 2H and later with 15N, spanned a mere decade. It is difficult, however, to overestimate the enormous impact of Schoenheimer's research on the evolution of biological science. After a relative hiatus, following Schoenheimer's death in 1941, in the use of stable nuclides as tracers in metabolism and nutrition, especially in human subjects, there is now an expanded and exciting range of techniques, experimental protocols and stable-isotope tracer compounds that are helping to probe the dynamic aspects of the metabolism of the major energy-yielding substrates, amino acids and other N-containing compounds, vitamins and mineral elements in human subjects. Various aspects of the contemporary applications of these tracers in nutrition research are covered in the present lecture.
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Affiliation(s)
- V R Young
- Laboratory of Human Nutrition, School of Science, Massachusetts Institute of Technology, Cambridge 02139, USA.
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Charlton MR, Adey DB, Nair KS. Evidence for a catabolic role of glucagon during an amino acid load. J Clin Invest 1996; 98:90-9. [PMID: 8690809 PMCID: PMC507404 DOI: 10.1172/jci118782] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Despite the strong association between protein catabolic conditions and hyperglucagonemia, and enhanced glucagon secretion by amino acids (AA), glucagon's effects on protein metabolism remain less clear than on glucose metabolism. To clearly define glucagon's catabolic effect on protein metabolism during AA load, we studied the effects of glucagon on circulating AA and protein dynamics in six healthy subjects. Five protocols were performed in each subject using somatostatin to inhibit the secretion of insulin, glucagon, and growth hormone (GH) and selectively replacing these hormones in different protocols. Total AA concentration was the highest when glucagon, insulin, and GH were low. Selective increase of glucagon levels prevented this increment in AA. Addition of high levels of insulin and GH to high glucagon had no effect on total AA levels, although branched chain AA levels declined. Glucagon mostly decreased glucogenic AA and enhanced glucose production. Endogenous leucine flux, reflecting proteolysis, decreased while leucine oxidation increased in protocols where AA were infused and these changes were unaffected by the hormones. Nonoxidative leucine flux reflecting protein synthesis was stimulated by AA, but high glucagon attenuated this effect. Addition of GH and insulin partially reversed the inhibitory effect of glucagon on protein synthesis. We conclude that glucagon is the pivotal hormone in amino acid disposal during an AA load and, by reducing the availability of AA, glucagon inhibits protein synthesis stimulated by AA. These data provide further support for a catabolic role of glucagon at physiological concentrations.
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Affiliation(s)
- M R Charlton
- Endocrine Research Unit, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA
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8
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Perier C, Doumit J, Frey J. An improved scheme of leucine derivative fragmentation in mass spectrometry. Amino Acids 1996; 10:273-6. [DOI: 10.1007/bf00807329] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/1995] [Accepted: 10/20/1995] [Indexed: 11/30/2022]
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Gelding SV, Coldham N, Anyaoku V, Heslop K, Halliday D, Johnston DG. Differential metabolic actions of biosynthetic insulin analogues in normal man assessed by stable isotopic tracers. Diabet Med 1993; 10:470-6. [PMID: 8334829 DOI: 10.1111/j.1464-5491.1993.tb00101.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Insulin analogues have been produced with high affinity for the insulin receptor and with affinity lower than that of native insulin, but differences in activity when administered in vivo to man are unconvincing. We have used very low dose insulin (0.005 units kg-1 h-1) to investigate possible differences in effect of these insulin analogues on lipolysis in seven healthy subjects. Only minor effects on blood glucose concentration were observed and glucose turnover measured isotopically with 6,6 2H glucose and leucine turnover measured with 1-13C leucine did not change significantly. Fatty acid levels decreased with insulin (area under curve, median (range) -23 (-41-10) mmol l-1) and with the low affinity analogue (-28 (-42-19) mmol l-1 h,), but the high affinity analogue had no significant effect compared with controls (high affinity analogue -8 (-28-35) mmol l-1 h; control +15 (11-53) mmol l-1). Glycerol production measured isotopically decreased with insulin (-0.54 (-1.50-0.63) mumol kg-1 min-1) and with the low affinity analogue (-0.74 (-1.76-0.72) mumol kg-1 min-1), but the high affinity analogue at these doses had no significant effect on glycerol turnover (-0.19 (-0.74-1.13) mumol kg-1 min-1). Thus at these low infusion rates insulin itself and the low affinity analogue suppressed lipolysis, as assessed by glycerol turnover and by circulating fatty acid concentrations. The high affinity analogue was cleared rapidly from the circulation producing no measurable increase in immunoreactive insulin concentrations, and no effect was observed on lipolysis.
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Affiliation(s)
- S V Gelding
- Unit of Metabolic Medicine, St. Mary's Hospital Medical School, London, UK
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10
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Pacy PJ, Halliday D. Muscle protein synthesis in steroid-induced proximal myopathy: a case report. Muscle Nerve 1989; 12:378-81. [PMID: 2725564 DOI: 10.1002/mus.880120507] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
A 51-year-old man with proven adenosquamous carcinoma of the lung presented with clinically acute steroid myopathy. Postabsorptive whole body leucine kinetics and fractional mixed muscle protein synthesis rate (MPSR) were determined by a steady-state approach during continuous L-(1-13C) leucine infusion. Plasma 13C alpha-ketoisocaproic acid enrichment was taken to represent labeling of the precursor pool. Postabsorptive whole body leucine flux and protein synthesis were less than the 1 in 500 confidence intervals of control values. Fractional MPSR was significantly reduced (P less than 0.01). Simultaneous calculation of MPSR from two adjacent sites was in excellent agreement (0.0372 and 0.0395% h-1). This is the first report that steroid myopathy is associated with reduced whole body protein synthesis and fractional MPSR in man.
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Affiliation(s)
- P J Pacy
- Nutrition Research Group, Clinical Research Centre, Harrow, UK
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11
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Morrison WL, Gibson JN, Rennie MJ. Skeletal muscle and whole body protein turnover in cardiac cachexia: influence of branched-chain amino acid administration. Eur J Clin Invest 1988; 18:648-54. [PMID: 3147192 DOI: 10.1111/j.1365-2362.1988.tb01282.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Muscle protein wasting commonly accompanies severe heart failure. The mechanism of this so-called cardiac cachexia has been investigated in eight patients with an average body weight decrement of 19%, whose results have been compared with those from 11 healthy control subjects. Exchanges of tyrosine and 3-methylhistidine across leg tissue were used as specific indicators of net protein balance and myofibrillar protein breakdown, respectively. Whole body protein turnover was measured using a stable isotope labelling technique with L-[1-13C]leucine as tracer. In patients with cardiac cachexia there were greater values, relative to those values in normal control subjects, of leg efflux of tyrosine (-8.1 +/- 0.6 nmol 100 ml leg tissue-1 min-1 vs. -4.2 +/- 0.3 nmol 100 ml-1 min-1 (P less than 0.01) and of 3-methylhistidine (-0.8 +/- 0.1 nmol 100 ml leg tissue-1 min-1 vs. -0.1 +/- 0.02 nmol 100 ml-1 min-1 (P less than 0.005), mean +/- SEM). The results suggest that in patients with cardiac cachexia the state of net negative protein balance across leg tissue is associated with an increased rate of myofibrillar protein breakdown. In cardiac cachexia, neither efflux of tyrosine (-8.4 +/- 0.7 nmol 100 ml leg tissue-1 min-1) nor of 3-methylhistidine (-1.0 +/- 0.2 nmol 100 ml leg tissue-1 min-1) were significantly altered by branched-chain amino acid (BCAA) infusion to plasma concentrations of 1300 +/- 14 mumol ml-1, i.e., four times normal plasma values (282 +/- 11 mumol ml-1).(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- W L Morrison
- Department of Physiology, University of Dundee, U.K
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Affiliation(s)
- W T Buckley
- Agriculture Canada, Agassiz, British Columbia
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13
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Nair KS, Welle SL, Halliday D, Campbell RG. Effect of beta-hydroxybutyrate on whole-body leucine kinetics and fractional mixed skeletal muscle protein synthesis in humans. J Clin Invest 1988; 82:198-205. [PMID: 3392207 PMCID: PMC303494 DOI: 10.1172/jci113570] [Citation(s) in RCA: 144] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Because intravenous infusion of beta-hydroxybutyrate (beta-OHB) has been reported to decrease urinary nitrogen excretion, we investigated in vivo metabolism of leucine, an essential amino acid, using L-[1-13C]leucine as a tracer during beta-OHB infusion. Leucine flux during beta-OHB infusion did not differ from leucine flux during normal saline infusion in nine normal subjects, whereas leucine oxidation decreased 18-41% (mean = 30%) from 18.1 +/- 1.1 mumol.kg-1.h-1 (P less than 0.01), and incorporation of leucine into skeletal muscle protein increased 5-17% (mean = 10%) from 0.048 + 0.003%/h (P less than 0.02). Since blood pH during beta-OHB infusion was higher than the pH during saline infusion, we performed separate experiments to study the effect of increased blood pH on leucine kinetics by infusing sodium bicarbonate intravenously. Blood pH during sodium bicarbonate infusion was similar to that observed during the beta-OHB infusion, but bicarbonate infusion had no effect on leucine flux or leucine oxidation. We conclude that beta-OHB decreases leucine oxidation and promotes protein synthesis in human beings.
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Affiliation(s)
- K S Nair
- Department of Medicine, University of Rochester School of Medicine and Dentistry, NY 14603
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14
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Abstract
The effects of disturbances of thyroid hormone secretion on leg and whole body amino acid and protein metabolism have been investigated in seven patients with untreated thyrotoxicosis and eight patients with untreated hypothyroidism; the results were compared to those obtained in 11 normal control subjects. After treatment, the patients were restudied. Arterio-venous exchanges of tyrosine and 3-methylhistidine across leg tissue in the post-absorptive state were used as indices of net protein balance and myofibrillar protein breakdown, respectively. Whole body protein turnover was measured using stable isotope labelling techniques with 1-[1-13C] leucine. Efflux of tyrosine from leg tissues was six-fold greater in patients with untreated thyrotoxicosis than in normal control subjects (-19.39 +/- 2.21 vs. -4.20 +/- 0.31 nmol 100 g-1 leg tissue min-1, P less than 0.005, mean +/- SEM), but 3-methyl-histidine efflux was not significantly different (-0.11 +/- 0.03 nmol 100 g-1 leg tissue min-1 vs. 0.14 +/- 0.02 nmol 100 g-1 leg tissue min-1). After treatment, when the thyrotoxic patients became euthyroid, tyrosine efflux was normalized (at -4.94 +/- 0.84 nmol 100 g-1 leg tissue min-1) and 3-methylhistidine efflux was unchanged. In hypothyroid patients, neither tyrosine nor 3-methylhistidine effluxes were significantly different from those in normal subjects.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- W L Morrison
- Department of Physiology, University of Dundee, U.K
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Krawielitzki K, Schadereit R, Wünsche J. [Kinetic parameters of protein metabolism in rats on protein-free diets]. ARCHIV FUR TIERERNAHRUNG 1987; 37:1041-53. [PMID: 3442484 DOI: 10.1080/17450398709428271] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
16 male rats of 100 g live weight were given 50 mg of a mixture containing 15N labelled amino acids as a single dose within a protein-free feeding period. Following this the 15N excretion in faeces and urine as well as the development of the 15N excess in different organs and tissues were estimated over 3 days by slaughtering the animals within given 7 time intervals. Using a 3 pool model and the computer program for the interpretation of 15N tracer experiments by Töwe et al. (1984), kinetic parameters such as the rate of protein synthesis, protein breakdown and the rate of reutilization were calculated. Despite a negative N balance (-41.8 mg N/d) under protein-free conditions the protein metabolism of the rat shows high dynamics characterized by a high flux rate (225 mg N/d) and a high rate of body protein synthesis (181 mg/d). The reutilization was 85%. Depending on time the 15N excess in the tested organs and tissues showed significant differences and seems to demonstrate that under these conditions protein synthesis mainly takes place in the most important organs (e.g. intestinal tract, liver). Under protein-free feeding conditions protein synthesis and protein breakdown of the whole body seems to be slightly increased in comparison to N balanced feeding conditions.
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Affiliation(s)
- K Krawielitzki
- Akademie der Landwirtschaftswissenschaften des DDR, Forschungszentrum für Tierproduktion Dummerstorf-Rostock Bereich Tierernährung Oskar Kellner
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16
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Griggs RC, Halliday D, Kingston W, Moxley RT. Effect of testosterone on muscle protein synthesis in myotonic dystrophy. Ann Neurol 1986; 20:590-6. [PMID: 2431651 DOI: 10.1002/ana.410200506] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Muscle wasting in myotonic dystrophy may result from decreased muscle anabolic processes rather than from increased catabolism. Male patients with myotonic dystrophy often have low levels of circulating androgens, and androgen administration has been shown to increase their muscle mass. We have studied the effect of testosterone enanthate administration (3 mg/kg weekly for 3 months) on muscle and whole body protein synthesis in 6 male patients with myotonic dystrophy. Muscle protein synthesis was estimated from the rate of isotope incorporation into muscle protein obtained by quadriceps muscle biopsy during a primed continuous infusion of L-[1-13C]leucine. Testosterone administration resulted in a significant increase in muscle protein synthesis in all patients. Whole body protein synthesis did not increase, indicating that protein synthesis in other tissues may have declined. Muscle ribonucleic acid content rose significantly in response to testosterone administration, suggesting that testosterone initiated its effect by hormone receptor interaction with muscle nuclei.
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17
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Halliday D, Ford GC, Edwards RH, Rennie MJ, Griggs RC. In vivo estimation of muscle protein synthesis in myotonic dystrophy. Ann Neurol 1985; 17:65-9. [PMID: 3985589 DOI: 10.1002/ana.410170115] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The rate of muscle protein synthesis in patients with myotonic dystrophy has been studied, and results correlated with total muscle mass. Whole body and skeletal muscle protein synthesis were estimated by stable isotope methodology with a primed, continuous infusion of 1-[13C]leucine with measurement of incorporation of [13C]leucine into muscle protein in biopsy samples. Whole body leucine flux, protein synthesis, and protein breakdown were only slightly depressed, but muscle protein synthesis was markedly decreased, in myotonic dystrophy. This depression of muscle protein synthesis in myotonic dystrophy correlates with previous observations of impaired insulin-induced muscle uptake of amino acids and supports the suggestion that muscle wasting in this disease is the consequence of defective anabolism in muscle.
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Buckley WT, Huckin SN, Eigendorf GK. Calculation of stable isotope enrichment tracer kinetic procedures. BIOMEDICAL MASS SPECTROMETRY 1985; 12:1-5. [PMID: 3157407 DOI: 10.1002/bms.1200120102] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The choice of method of expressing isotopic enrichment in tracer kinetic experiments utilizing stable isotopes was found to affect the calculation of tracee pool size and half-life. The most commonly used definition, the difference between enriched and natural abundance, i.e. atom percent excess, was found to result in significant error in model systems when the dose of tracer was 10% of the pool size. Errors in determining first-order rate constants of efflux and in pool sizes decreased with decreasing ratio of tracer to tracee. Error in determining pool size increased with longer 'sampling' periods, while error in determining the rate constant increased with shorter sampling periods. Of three less frequently used expressions of isotopic enrichment two were found to yield the exact answers in model systems. The correct expressions of isotopic enrichment were linear functions of the quantity of tracer in the system. A practical example demonstrated the effect of choice of expression of enrichment on estimates of whole body copper pool size and turnover in dairy cattle.
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Emery PW, Edwards RH, Rennie MJ, Souhami RL, Halliday D. Protein synthesis in muscle measured in vivo in cachectic patients with cancer. BMJ 1984; 289:584-6. [PMID: 6087973 PMCID: PMC1442890 DOI: 10.1136/bmj.289.6445.584] [Citation(s) in RCA: 128] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Rates of synthesis of protein were measured in vivo in skeletal muscle and in the whole body of cachectic patients with cancer and in normal healthy men, using a tracer infusion of leucine labelled with a stable isotope. Synthesis of protein in muscle was significantly reduced in the patients with cancer (0.030 v 0.198%/hour; p less than 0.01), whereas whole body rates of protein synthesis and degradation did not differ significantly between the two groups. Thus depression of synthesis of protein in muscle appeared to be the immediate cause of muscle wasting in cancerous cachexia. Any therapeutic intervention that aims at preventing the onset of cachexia should be designed to stimulate the synthesis of protein in muscle, and measurement of turnover of protein may be used to evaluate such treatment provided that rates of protein synthesis are measured directly in specific tissues.
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Rennie MJ, Halliday D. The use of stable isotope tracers as metabolic probes of whole-body and limb metabolism. Proc Nutr Soc 1984; 43:189-96. [PMID: 6473334 DOI: 10.1079/pns19840041] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Nair KS, Garrow JS, Ford C, Mahler RF, Halliday D. Effect of poor diabetic control and obesity on whole body protein metabolism in man. Diabetologia 1983; 25:400-3. [PMID: 6317503 DOI: 10.1007/bf00282518] [Citation(s) in RCA: 135] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
We have investigated whole body protein turnover in the fasted state in five normal men, five male Type 1 diabetic patients off insulin therapy, and five obese women, using IV 13C-leucine as a tracer. In diabetic patients, there was, as expected, a greater net loss of protein in the fasted state than in normal subjects. However, contrary to animal and studies in vitro, our diabetic patients in the fasted state showed a greater rate of protein synthesis than normal subjects (p less than 0.01). The increased net loss of protein in diabetic patients compared with normal subjects arose because, in the diabetic patients, protein breakdown was increased even more than protein synthesis under the conditions of this study. Plasma leucine concentration was higher in diabetic and in insulin-insensitive obese patients than in normal subjects (p less than 0.01), and higher in diabetic than in obese patients (p less than 0.05). The rate of protein synthesis per kg lean body mass was also higher in diabetic patients than in obese or normal subjects (p less than 0.01), and higher in obese than normal subjects (p less than 0.05). We conclude that, in human subjects, whole body leucine and protein metabolism are very sensitive to the action of insulin.
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Rennie MJ, Edwards RH, Millward DJ, Wolman SL, Halliday D, Matthews DE. Effects of Duchenne muscular dystrophy on muscle protein synthesis. Nature 1982; 296:165-7. [PMID: 7063020 DOI: 10.1038/296165a0] [Citation(s) in RCA: 104] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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