3 The use of stable isotopes in metabolic investigation

Bier, Dennis M.

doi:10.1016/s0950-351x(87)80007-1

Cited by 44 publications

(19 citation statements)

References 78 publications

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“…The increased use of stable isotopes has been prompted by advances in analytical instrumentation, increased availability of stable isotope-labeled fats, and the proliferation of misguided regulations and concerns about the safety of radioisotope tracers. A number of good reviews detail the history, theory, methodology, and applications of stable isotopes in biological studies (2)(3)(4)(5)(6)(7)(8). The focus of this review is to discuss briefly study design options, associated analytical methods, and recent studies that illustrate use of deuterium and carbon-13 isotope approaches for addressing questions relevant to fatty acid metabolism in infants and mothers.…”

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confidence: 99%

Stable isotope approaches, applications, and issues related to polyunsaturated fatty acid metabolism studies

Emken

2001

Lipids

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The use of stable isotope tracers for investigating fatty acid metabolism in human subjects has increased substantially over the last decade. Advances in analytical instrumentation, commercial availability of labeled substrates, and safety considerations are major reasons for this increased use of stable isotope tracers. Several experimental design options are available for using either deuterium or carbon-13 as tracers for fatty acid and lipid studies. Options include feeding a pulse dose of labeled fat or a mixture containing two or more labeled fats. Multiple doses of the labeled fat can be fed at timed intervals to increase enrichments. Administration by injection or continuous intravenous infusion is an alternative. Another option is to use diets containing foods from plants that have slightly higher natural carbon-13 enrichment. Each basic experimental design has its specific strengths, and the best choice of experimental design depends on the study objectives. Stable isotope studies have been used to address a variety of questions related to unsaturated fatty acid metabolism in humans. Examples are provided that illustrate the use of stable isotopes to investigate oxidation of docosahexaenoic acid, desaturation of linoleic and linolenic acids in infants and adults, incorporation of long-chain n-6 and n-3 fatty acids, bioequivalency of linolenic acid in primates, 13C nuclear magnetic resonance spectra of arachidonic acid in living rat brain, and effect of triacylglycerol structure on absorption. Radioisotope and stable isotope tracer studies in animals and humans are responsible for much of our understanding of fatty acid and lipid metabolism. However, tracer studies have limitations, and there are some unresolved issues associated with isotope studies. Examples of unresolved issues are quantification of isotope data, validity of in vivo fatty acid metabolite results, kinetic modeling, subject variability, and use of blood lipid data as a reflection of tissue lipid metabolism. Resolving these issues, developing novel methodology, and applying stable isotope tracer methods to questions related to PUFA metabolism are broad areas of interesting and challenging research opportunities.

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Stable isotope approaches, applications, and issues related to polyunsaturated fatty acid metabolism studies

Emken

2001

Lipids

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“…The isotopic abundance of ~3C labelled glucose is measurable either by selected ion monitoring gas chromatography-mass spectrometry [8] or by isotope ratio mass spectrometry (IRMS) after conversion of the glucose molecule to pure CO2 [9]. The first method is limited by the low sensitivity (0.5-1%) in the measurement of the enrichment [10].…”

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Use of a new gas chromatograph isotope ratio mass spectrometer to trace exogenous 13C labelled glucose at a very low level of enrichment in man

et al. 1990

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The use of 13C labelled glucose in human metabolic studies has been limited by the high cost of the tracer and the problems of measuring low 13C isotopic abundance in plasma glucose. In the present work we describe a new gas chromatograph-isotope ratio mass spectrometer allowing the measurement of a 0.001 atom % increase in 13C abundance over baseline, on a nanomole glucose sample. Studies were performed in rats and in human subjects. The rate of glucose appearance in 24 h fasted rats using D-[1-13C] glucose as tracer and analysed by this new method was found to be 10.4 +/- 0.7 mg.kg-1.min-1, a value 21% lower than that found using D-[6,6-2H2] glucose as tracer (13.1 +/- 1.1 mg.kg-1.min-1) analysed by classic gas chromatography-mass spectrometry. The new method was also used to trace, in combination with D-[6,6 2H2] glucose, the metabolic fate in human subjects of two oral glucose loads (0.5 g.kg.-1,1 g.kg.-1) labelled with 0.1% D-[U-13C] glucose. During the six hours following the glucose load, it was found that total glucose appearance was 0.97 +/- 0.04 g.kg.-1 and 1.2 +/- 0.04 g.kg.-1, exogenous glucose appearance was 0.51 +/- 0.02 g.kg.-1 and 0.84 +/- 0.04 g.kg.-1, endogenous glucose production was 0.44 +/- 0.04 g.kg.-1 and 0.35 +/- 0.06 g.kg.-1 after the 0.5 and 1 g.kg.-1 load respectively. These values are similar to those reported using glucose labelled with radioactive isotopes.(ABSTRACT TRUNCATED AT 250 WORDS)

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“…Under near steady-state conditions, glucose production is equivalent to total glucose turnover minus the exogenously infused natural and tracer glucose. To measure glucose turnover, a variety of recyclable and nonrecyclable tracers have been used ( 18 ). From our perspective, using the nonrecyclable tracer [6,6- 2 H 2 ]glucose is ideal because there is no real potential for this tracer to be released into the circulation via gluconeogenesis (indirect pathway) and very little, if any, for it to be incorporated and subsequently released from glycogen into the systemic circulation except by the potential of glycogen cycling ( 12 , 19 – 21 ).…”

Section: Considerations Of Measuring Gluconeogenesis In Vivomentioning

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Measurements of Gluconeogenesis and Glycogenolysis: A Methodological Review

et al. 2015

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Gluconeogenesis is a complex metabolic process that involves multiple enzymatic steps regulated by myriad factors, including substrate concentrations, the redox state, activation and inhibition of specific enzyme steps, and hormonal modulation. At present, the most widely accepted technique to determine gluconeogenesis is by measuring the incorporation of deuterium from the body water pool into newly formed glucose. However, several techniques using radioactive and stable-labeled isotopes have been used to quantitate the contribution and regulation of gluconeogenesis in humans. Each method has its advantages, methodological assumptions, and set of propagated errors. In this review, we examine the strengths and weaknesses of the most commonly used stable isotopes methods to measure gluconeogenesis in vivo. We discuss the advantages and limitations of each method and summarize the applicability of these measurements in understanding normal and pathophysiological conditions.

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3 The use of stable isotopes in metabolic investigation

Cited by 44 publications

References 78 publications

Stable isotope approaches, applications, and issues related to polyunsaturated fatty acid metabolism studies

Stable isotope approaches, applications, and issues related to polyunsaturated fatty acid metabolism studies

Use of a new gas chromatograph isotope ratio mass spectrometer to trace exogenous 13C labelled glucose at a very low level of enrichment in man

Measurements of Gluconeogenesis and Glycogenolysis: A Methodological Review

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