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.

scholarly journals A compartmental model of zinc metabolism in healthy women using oral and intravenous stable isotope tracers

1997 ◽  
Vol 65 (6) ◽  
pp. 1810-1819 ◽  
Author(s):  
N M Lowe ◽  
D M Shames ◽  
L R Woodhouse ◽  
J S Matel ◽  
R Roehl ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Compartmental Model ◽  
Zinc Metabolism ◽  
Stable Isotope Tracers ◽  
Isotope Tracers ◽  
Healthy Women

scholarly journals Use of stable isotopes to study carbohydrate and fat metabolism at the whole-body level

1999 ◽  
Vol 58 (4) ◽  
pp. 953-961 ◽  
Author(s):  
Andrew R. Coggan
Keyword(s):  
Stable Isotope ◽  
Radioactive Isotope ◽  
Fat Metabolism ◽  
Whole Body ◽  
Selected Ion Monitoring ◽  
Stable Isotope Tracers ◽  
Isotope Tracers ◽  
Isotope Tracer ◽  
Body Level ◽  
Muscle Biopsies

The present review discusses the advantages and limitations of using stable-isotope tracers to assess carbohydrate and fat metabolism at the whole-body level. One advantage of stable-(v. radioactive-) isotope tracers is the relative ease with which the location of a label within a molecule can be determined using selected-ion-monitoring GC-mass spectrometry (SIM-GC- MS). This technique minimizes potential problems due to label recycling, allows the use of multiple-labelled compounds simultaneously (e.g. to quantify glucose cycling), and perhaps most importantly, has led to the development of unique stable-isotope methods for, for example, quantifying gluconeogenesis. However, the limited sensitivity of SIM-GC-MS sometimes requires that relatively large amounts of a stable-isotope tracer be used, thus increasing cost and potentially altering metabolism. At least theoretically, stable- (or radioactive-) isotope tracers can also be used in conjunction with indirect calorimetry to estimate utilization of muscle glycogen or triacylglycerol stores, thus potentially circumventing the need to obtain muscle biopsies. These calculations, however, require certain critical assumptions, which if incorrect could lead to major errors in the values obtained. Despite such limitations, stable-isotope tracers provide a powerful and sometimes unique tool for investigating carbohydrate and fat metabolism at the whole-body level. With continuing advances in availability, instrumentation and methods, it is likely that stable-isotope tracers will become increasingly important in the immediate future.

Time-dependent cortisol turnover in tissues using stable isotope tracers and MALDI Mass Spectrometry (MS) sampling

2018 ◽  
Author(s):  
Shazia Khan ◽  
Diego F Cobice ◽  
Dawn EW Livingstone ◽  
C Logan Mackay ◽  
Scott P Webster ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Stable Isotope ◽  
Maldi Mass Spectrometry ◽  
Time Dependent ◽  
Stable Isotope Tracers ◽  
Isotope Tracers

Compartmental model of leucine kinetics in humans

1991 ◽  
Vol 261 (4) ◽  
pp. E539-E550 ◽  
Author(s):  
C. Cobelli ◽  
M. P. Saccomani ◽  
P. Tessari ◽  
G. Biolo ◽  
L. Luzi ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Compartmental Model ◽  
Linear Time ◽  
A Priori ◽  
Normal Subjects ◽  
Whole Body ◽  
Constant Infusion ◽  
Individual Subject ◽  
Domain Of Validity

The complexity of amino acid and protein metabolism has limited the development of comprehensive, accurate whole body kinetic models. For leucine, simplified approaches are in use to measure in vivo leucine fluxes, but their domain of validity is uncertain. We propose here a comprehensive compartmental model of the kinetics of leucine and alpha-ketoisocaproate (KIC) in humans. Data from a multiple-tracer administration were generated with a two-stage (I and II) experiment. Six normal subjects were studied. In experiment I, labeled leucine and KIC were simultaneously injected into plasma. Four plasma leucine and KIC tracer concentration curves and label in the expired CO2 were measured. In experiment II, labeled bicarbonate was injected into plasma, and labeled CO2 in the expired air was measured. Radioactive (L-[1-14C]leucine, [4,5-3H]KIC, [14C]bicarbonate) and stable isotope (L-[1-13C]leucine, [5,5,5-2H3]KIC, [13C]bicarbonate) tracers were employed. The input format was a bolus (impulse) dose in the radioactive case and a constant infusion in the stable isotope case. A number of physiologically based, linear time-invariant compartmental models were proposed and tested against the data. The model finally chosen for leucine-KIC kinetics has 10 compartments: 4 for leucine, 3 for KIC, and 3 for bicarbonate. The model is a priori uniquely identifiable, and its parameters were estimated with precision from the five curves of experiment I. The separate assessment of bicarbonate kinetics (experiment II) was shown to be unnecessary. The model defines masses and fluxes of leucine in the organism, in particular its intracellular appearance from protein breakdown, its oxidation, and its incorporation into proteins. An important feature of the model is its ability to estimate leucine oxidation by resolving the bicarbonate model in each individual subject. Finally, the model allows the assessment of the domain of validity of the simpler commonly used models.

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