Determination of Pre-Absorptive Dissociation of Zinc From a Zinc Amino Acid Complex in Healthy Men
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|ClinicalTrials.gov Identifier: NCT03934346|
Recruitment Status : Completed
First Posted : May 1, 2019
Last Update Posted : January 22, 2020
|Condition or disease||Intervention/treatment||Phase|
|Fractional Zinc Absorption||Other: Zinc amino acid complex||Not Applicable|
An experimentally-determined value for any pre-absorptive dissociation of zinc from ZnAA is necessary for the accurate compartmental modeling of zinc metabolism when provided as ZnAA compared with zinc chloride, which the investigators will perform in a future study.
The current study will allow us to determine the pre-absorptive dissociation of zinc from ZnAA, while serving as a pilot test of a novel technique to determine for the first time an individual's zinc transport kinetics. Since zinc absorption kinetics follow a saturable process, the zinc transport maximum (Tr_max) and transport rate (K_Tr) can be determined by fitting Hill transport equation to measurements of absorbed zinc at 3 or more levels of zinc intake (mg zinc/d):
Total Absorbed Zinc (TAZ) = (Zinc Intake * Tr_max) / (Zinc Intake + K_Tr)
Although population data have been used to estimate zinc transport kinetics (Tran, et al. AJCN 2004), Tr_max and K_tr have never been determined in individual subjects. The investigators plan to determine the fractional zinc absorption (FZA) from multiple levels of dietary zinc in rapid succession (Chung, et al. AJCN 2004) and, therefore, estimate an individual's transport maximum and rate, Tr_max and K_Tr. Once Tr_max and K_Tr are known, the FZA can be used to determine an unknown zinc intake from zinc chloride and any zinc dissociated from the ZnAA complex using the following equation:
Zinc Intake = (Tr_max / FZA) - K_Tr
Since zinc that dissociates from the ZnAA complex will compete for absorption with the inorganic zinc stable isotopic oral tracer (70-zinc chloride), reducing the amount of that tracer absorbed, the investigators can therefore determine the total zinc intake (the sum of the known zinc in the controlled study diet and the unknown quantity of zinc dissociated from ZnAA pre-absorption) based on the transport kinetics (FZA, Tr_max and KTr).
In other words, for the meal with added ZnAA, the zinc intake is the sum of the zinc in the test meal (3.6 mg zinc and 0.4 mg 70-Zn tracer) and the zinc that dissociates from the ZnAA complex pre-absorption. Since the intact ZnAA (i.e. that zinc that does not dissociate pre-absorption from the ZnAA complex) is absorbed by a different transport mechanism (Sauer, et al. Biometals 2017), it does not compete with the stable isotope tracer for absorption via zinc cation transporters and is, therefore, not part of the "zinc intake" for the purpose of these calculations.
If the hypothesized 20% dissociation is correct (i.e. 3 mg zinc dissociated from an initial 15 mg ZnAA), the total amount of ionic zinc will be 7 mg (the 3.6 mg base diet, 0.4 mg zinc stable isotope tracer, and 3 mg dissociated zinc), and the FZA will therefore be the same as that from a 7 mg test diet (the 3.6 mg base diet, 0.4 mg zinc tracer, and 3 mg zinc as zinc chloride).
|Study Type :||Interventional (Clinical Trial)|
|Actual Enrollment :||13 participants|
|Intervention Model:||Single Group Assignment|
|Intervention Model Description:||Nonlinear regression of fractional zinc absorption from 3 test diets using the Hill transport equation, and determination of an unknown amount of zinc based on fractional absorption from a single test diet. Order of the four test diets is randomized, with the constraint that the same oral zinc stable isotope tracer is not given on consecutive days.|
|Masking:||None (Open Label)|
|Masking Description:||Subjects are not informed of the amount of zinc in each test diet, or the order of the diets. The basic foods making up the test diets are identical in appearance and amount on each of the oral zinc stable isotope tracer days, so there is no way for the subject to distinguish any differences in the amount or form of zinc given.|
|Primary Purpose:||Basic Science|
|Official Title:||Determination of Pre-Absorptive Dissociation of Zinc From a Zinc Amino Acid Complex in Healthy Men|
|Actual Study Start Date :||June 10, 2019|
|Actual Primary Completion Date :||December 16, 2019|
|Actual Study Completion Date :||December 16, 2019|
Zinc transport kinetics
Three different amounts of dietary zinc are used in the creation of a standard curve for determining zinc absorption kinetics: 4 mg, 7 mg, and 15 mg of zinc.
Other: Zinc amino acid complex
Zinc in the form of a Zinc Amino Acid Complex (ZnAA) is provided with a test diet, and the amount of zinc that dissociates from the ZnAA and is thus absorbed via an ionic zinc transport pathway is determined based on the Hill transport kinetics for the respective subject.
- Zinc Transport Curve [ Time Frame: 2 weeks ]The saturable zinc transport curve determined by fitting the zinc absorption data to the Hill transport equation
- Dissociated Amino Acid Zinc [ Time Frame: 2 weeks ]Amount of zinc dissociated from the ZnAA prior to absorption
To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.
Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT03934346
|United States, California|
|Children's Hospital and Research Center Oakland|
|Oakland, California, United States, 94609|
|Principal Investigator:||Andrew G Hall, Ph.D.||UCSF Benioff Children's Hospital Oakland|