scholarly journals Oxazolinone derivative of leucine for GC-MS: a sensitive and robust method for stable isotope kinetic studies of lipoproteins

2002 ◽  
Vol 43 (2) ◽  
pp. 344-349 ◽  
Author(s):  
Kevin P. Dwyer ◽  
P. Hugh R. Barrett ◽  
Dick Chan ◽  
Jock I. Foo ◽  
Gerald F. Watts ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Kinetic Studies ◽  
Robust Method

Ion Trap Mass Spectrometry for Kinetic Studies of Stable Isotope Labeled Vitamin A at Low Enrichments

1998 ◽  
Vol 70 (7) ◽  
pp. 1369-1374 ◽  
Author(s):  
Stephen R. Dueker ◽  
Roger S. Mercer ◽  
A. Daniel Jones ◽  
Andrew J. Clifford
Keyword(s):  
Mass Spectrometry ◽  
Stable Isotope ◽  
Vitamin A ◽  
Ion Trap ◽  
Kinetic Studies ◽  
Ion Trap Mass Spectrometry

Lipoprotein transport in the metabolic syndrome: methodological aspects of stable isotope kinetic studies

2004 ◽  
Vol 107 (3) ◽  
pp. 221-232 ◽  
Author(s):  
Dick C. CHAN ◽  
P. Hugh R. BARRETT ◽  
Gerald F. WATTS
Keyword(s):  
Metabolic Syndrome ◽  
Stable Isotope ◽  
Plasma Concentrations ◽  
Lipoprotein Metabolism ◽  
Visceral Obesity ◽  
Kinetic Studies ◽  
Kinetic Properties ◽  
The Metabolic Syndrome ◽  
Methodological Aspects

The metabolic syndrome encapsulates visceral obesity, insulin resistance, diabetes, hypertension and dyslipidaemia. Dyslipidaemia is a cardinal feature of the metabolic syndrome that accelerates the risk of cardiovascular disease. It is usually characterized by high plasma concentrations of triacylglycerol (triglyceride)-rich and apoB (apolipoprotein B)-containing lipoproteins, with depressed concentrations of HDL (high-density lipoprotein). However, lipoprotein metabolism is complex and abnormal plasma concentrations can result from alterations in the rates of production and/or catabolism of these lipoprotein particles. Our in vivo understanding of kinetic defects in lipoprotein metabolism in the metabolic syndrome has been achieved chiefly by ongoing developments in the use of stable isotope tracers and mathematical modelling. This review deals with the methodological aspects of stable isotope kinetic studies. The design of in vivo turnover studies requires considerations related to stable isotope tracer administration, duration of sampling protocol and interpretation of tracer data, all of which are critically dependent on the kinetic properties of the lipoproteins under investigation. Such models provide novel insight that further understanding of metabolic disorders and effects of treatments. Future investigations of the pathophysiology and therapy of the dyslipoproteinaemia of the metabolic syndrome will require the development of novel kinetic methodologies. Specifically, new stable isotope techniques are required for investigating in vivo the turnover of the HDL subpopulation of particles, as well as the cellular efflux of cholesterol into the extracellular space and its subsequent transport in plasma and metabolic fate in the liver.

scholarly journals Selenium Kinetics in Humans Change Following 2 Years of Supplementation With Selenomethionine

2021 ◽  
Vol 12 ◽  
Author(s):  
Blossom H. Patterson ◽  
Gerald F. Combs ◽  
Philip R. Taylor ◽  
Kristine Y. Patterson ◽  
James E. Moler ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Compartmental Model ◽  
Kinetic Studies ◽  
Whole Body ◽  
Essential Trace Element ◽  
Stable Isotope Tracers ◽  
Isotope Tracers ◽  
Plasma Pool ◽  
Before And After ◽  
Fractional Absorption

BackgroundSelenium (Se) is a nutritionally essential trace element and health may be improved by increased Se intake. Previous kinetic studies have shown differences in metabolism of organic vs. inorganic forms of Se [e.g., higher absorption of selenomethionine (SeMet) than selenite (Sel), and more recycling of Se from SeMet than Sel]. However, the effects on Se metabolism after prolonged Se supplementation are not known.ObjectiveTo determine how the metabolism and transport of Se changes in the whole-body in response to Se-supplementation by measuring Se kinetics before and after 2 years of Se supplementation with SeMet.MethodsWe compared Se kinetics in humans [n = 31, aged 40 ± 3 y (mean ± SEM)] studied twice after oral tracer administration; initially (PK1), then after supplementation for 2 y with 200 µg/d of Se as selenomethionine (SeMet) (PK2). On each occasion, we administered two stable isotope tracers of Se orally: SeMet, the predominant food form, and selenite (Na276SeO3, or Sel), an inorganic form. Plasma and RBC were sampled for 4 mo; urine and feces were collected for the initial 12 d of each period. Samples were analyzed for tracers and total Se by isotope dilution GC-MS. Data were analyzed using a compartmental model, we published previously, to estimate fractional transfer between pools and pool masses in PK2.ResultsWe report that fractional absorption of SeMet or Sel do not change with SeMet supplementation and the amount of Se absorbed increased. The amount of Se excreted in urine increases but does not account for all the Se absorbed. As a result, there is a net incorporation of SeMet into various body pools. Nine of the 11 plasma pools doubled in PK2; two did not change. Differences in metabolism were observed for SeMet and Sel; RBC uptake increased 247% for SeMet, urinary excretion increased from two plasma pools for Sel and from two different pools for SeMet, and recycling to liver/tissues increased from one plasma pool for Sel and from two others for SeMet. One plasma pool increased more in males than females in PK2.ConclusionsOf 11 Se pools identified kinetically in human plasma, two did not increase in size after SeMet supplementation. These pools may be regulated and important during low Se intake.

Stable Isotope Methodology for Kinetic Studies of Interconversion of Cortisol and Cortisone in a Human Subject

Steroids ◽  
1998 ◽  
Vol 63 (3) ◽  
pp. 122-129 ◽  
Author(s):  
Yasuji Kasuya ◽  
Hiromasa Ishimaru ◽  
Hiromi Shibasaki ◽  
Takashi Furuta
Keyword(s):  
Stable Isotope ◽  
Human Subject ◽  
Kinetic Studies

Flavin radicals, conformational sampling and robust design principles in interprotein electron transfer: the trimethylamine dehydrogenase-electron-transferring flavoprotein complex

2004 ◽  
Vol 71 ◽  
pp. 1-14
Author(s):  
David Leys ◽  
Jaswir Basran ◽  
François Talfournier ◽  
Kamaldeep K. Chohan ◽  
Andrew W. Munro ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Kinetic Studies ◽  
Molecular Assembly ◽  
Conformational Sampling ◽  
Trimethylamine Dehydrogenase ◽  
Key Residues ◽  
Electron Transferring Flavoprotein ◽  
Electron Transfer Complex

TMADH (trimethylamine dehydrogenase) is a complex iron-sulphur flavoprotein that forms a soluble electron-transfer complex with ETF (electron-transferring flavoprotein). The mechanism of electron transfer between TMADH and ETF has been studied using stopped-flow kinetic and mutagenesis methods, and more recently by X-ray crystallography. Potentiometric methods have also been used to identify key residues involved in the stabilization of the flavin radical semiquinone species in ETF. These studies have demonstrated a key role for 'conformational sampling' in the electron-transfer complex, facilitated by two-site contact of ETF with TMADH. Exploration of three-dimensional space in the complex allows the FAD of ETF to find conformations compatible with enhanced electronic coupling with the 4Fe-4S centre of TMADH. This mechanism of electron transfer provides for a more robust and accessible design principle for interprotein electron transfer compared with simpler models that invoke the collision of redox partners followed by electron transfer. The structure of the TMADH-ETF complex confirms the role of key residues in electron transfer and molecular assembly, originally suggested from detailed kinetic studies in wild-type and mutant complexes, and from molecular modelling.

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