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Green MH, Lopez-Teros V, Avila-Prado J, Green JB. Use of Theoretical Women and Model-Based Compartmental Analysis to Evaluate the Impact of Vitamin A Intake with or without a Daily Vitamin A Supplement on Vitamin A Total Body Stores and Balance During Lactation. J Nutr 2024; 154:2374-2380. [PMID: 38857673 DOI: 10.1016/j.tjnut.2024.06.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2024] [Revised: 05/29/2024] [Accepted: 06/05/2024] [Indexed: 06/12/2024] Open
Abstract
BACKGROUND Inadequate vitamin A (VA) intake is common among lactating women in many communities worldwide, but high-dose VA supplementation for postpartum women is not recommended by the World Health Organization as an effective intervention. OBJECTIVES To simulate the impact of VA intake via diet and daily VA supplements on VA total body stores (TBS) and balance in theoretical lactating women with low/moderate TBS. METHODS We studied 6 theoretical subjects with assigned values for TBS from 219-624 μmol. Using Simulation, Analysis, and Modeling software and a previously published compartmental model for whole-body VA metabolism, we simulated TBS over 6 mo of established lactation for each subject under 4 conditions: 1) prelactation VA intake was increased to maintain VA balance (LSS); 2) prelactation VA intake was maintained (NLSS); 3) VA intake was the same as 2) but a daily VA supplement (2.8 μmol/d) was added (NLSS+S); and 4) VA intake was as 1) and the daily VA supplement was included (LSS+S). RESULTS To compensate for the loss of VA via milk while VA balance was maintained (LSS) over 6 mo of lactation, VA intake had to increase by 0.8-1.87 μmol/d (n = 6) compared with NLSS. Over 6 mo of NLSS treatment, VA balance was negative (geometric mean, -0.77 μmol/d) compared with LSS, whereas balance was positive under NLSS+S and LSS+S conditions (0.75 and 1.5 μmol/d, respectively). For LSS, the proportion of total VA disposal was 37% via breastmilk, 32% from VA stores, and 32% from nonstorage tissues. CONCLUSIONS Adding a daily VA supplement (2.8 μmol/d) to the diet of lactating women with suboptimal VA intake may effectively counterbalance the negative VA balance resulting from the output of VA via breastmilk and thus benefit both mother and infant by maintaining or increasing VA stores and breastmilk VA concentration.
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Affiliation(s)
- Michael H Green
- Department of Nutritional Sciences, College of Health and Human Development, The Pennsylvania State University, University Park, PA, United States
| | - Veronica Lopez-Teros
- Department of Chemical and Biological Sciences, Universidad de Sonora, Hermosillo, Sonora, Mexico.
| | - Jessica Avila-Prado
- Department of Chemical and Biological Sciences, Universidad de Sonora, Hermosillo, Sonora, Mexico
| | - Joanne Balmer Green
- Department of Nutritional Sciences, College of Health and Human Development, The Pennsylvania State University, University Park, PA, United States
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Reboul E. Proteins involved in fat-soluble vitamin and carotenoid transport across the intestinal cells: New insights from the past decade. Prog Lipid Res 2023; 89:101208. [PMID: 36493998 DOI: 10.1016/j.plipres.2022.101208] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Revised: 11/28/2022] [Accepted: 11/29/2022] [Indexed: 12/12/2022]
Abstract
It is now well established that vitamins D, E, and K and carotenoids are not absorbed solely through passive diffusion. Broad-specificity membrane transporters such as SR-BI (scavenger receptor class B type I), CD36 (CD36 molecule), NPC1L1 (Niemann Pick C1-like 1) or ABCA1 (ATP-binding cassette A1) are involved in the uptake of these micronutrients from the lumen to the enterocyte cytosol and in their secretion into the bloodstream. Recently, the existence of efflux pathways from the enterocyte back to the lumen or from the bloodstream to the lumen, involving ABCB1 (P-glycoprotein/MDR1) or the ABCG5/ABCG8 complex, has also been evidenced for vitamins D and K. Surprisingly, no membrane proteins have been involved in dietary vitamin A uptake so far. After an overview of the metabolism of fat-soluble vitamins and carotenoids along the gastrointestinal tract (from the mouth to the colon where interactions with microbiota may occur), a focus is placed on the identified and candidate proteins participating in the apical uptake, intracellular transport, basolateral secretion and efflux back to the lumen of fat-soluble vitamins and carotenoids in enterocytes. This review also highlights the mechanisms that remain to be identified to fully unravel the pathways involved in fat-soluble vitamin and carotenoid intestinal absorption.
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Green MH, Green JB. The Use of Datasets for Theoretical Subjects to Validate Vitamin A-Related Methods and Experimental Designs. J Nutr 2022; 152:707-713. [PMID: 34967904 DOI: 10.1093/jn/nxab441] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2021] [Revised: 11/22/2021] [Accepted: 12/23/2021] [Indexed: 11/12/2022] Open
Abstract
We review recent work in which model-based compartmental analysis has been applied to data for theoretical human subjects in order to study questions related to vitamin A kinetics and metabolism. Using model simulations in this way, one can validate experimental designs, evaluate or improve vitamin A assessment methods, study the influence of perturbations on assessment methods, and/or advance information related to retinol kinetics. We also provide some information on the rationale for assigning physiologically appropriate values for specified characteristics [e.g., plasma retinol concentration, vitamin A total body stores (TBS), vitamin A intake] to hypothetical individuals, and in addition, we outline how one might first select an appropriate compartmental model for whole-body vitamin A metabolism and then specify physiologically reasonable values for the associated retinol kinetic parameters. In the studies discussed here, the Simulation, Analysis, and Modeling software was used to simulate responses in key model compartments for hypothetical subjects so that model predictions could be compared to assigned values or projected outcomes. For example, in the case of the retinol isotope dilution (RID) method that is used to assess vitamin A status, application of this approach has provided a way to evaluate the accuracy of TBS predictions under different steady state and non-steady state conditions, thus increasing confidence about the validity of RID results obtained in the field. Although datasets for theoretical subjects have been used to evaluate protocols in pharmacokinetics, to our knowledge, other nutrition researchers have not previously used approaches such as those described here. Our results to date indicate that this strategy has the potential to provide useful information related not only to vitamin A but perhaps to other nutrients as well.
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Affiliation(s)
- Michael H Green
- Department of Nutritional Sciences, College of Health and Human Development, The Pennsylvania State University, University Park, PA, USA
| | - Joanne Balmer Green
- Department of Nutritional Sciences, College of Health and Human Development, The Pennsylvania State University, University Park, PA, USA
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Hooper L, Esio-Bassey C, Brainard J, Fynn J, Jennings A, Jones N, Tailor BV, Abdelhamid A, Coe C, Esgunoglu L, Fallon C, Gyamfi E, Hill C, Howard Wilsher S, Narayanan N, Oladosu T, Parkinson E, Prentice E, Qurashi M, Read L, Getley H, Song F, Welch AA, Aggett P, Lietz G. Evidence to Underpin Vitamin A Requirements and Upper Limits in Children Aged 0 to 48 Months: A Scoping Review. Nutrients 2022; 14:nu14030407. [PMID: 35276767 PMCID: PMC8840537 DOI: 10.3390/nu14030407] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Revised: 12/31/2021] [Accepted: 01/10/2022] [Indexed: 02/04/2023] Open
Abstract
Vitamin A deficiency is a major health risk for infants and children in low- and middle-income countries. This scoping review identified, quantified, and mapped research for use in updating nutrient requirements and upper limits for vitamin A in children aged 0 to 48 months, using health-based or modelling-based approaches. Structured searches were run on Medline, EMBASE, and Cochrane Central, from inception to 19 March 2021. Titles and abstracts were assessed independently in duplicate, as were 20% of full texts. Included studies were tabulated by question, methodology and date, with the most relevant data extracted and assessed for risk of bias. We found that the most recent health-based systematic reviews and trials assessed the effects of supplementation, though some addressed the effects of staple food fortification, complementary foods, biofortified maize or cassava, and fortified drinks, on health outcomes. Recent isotopic tracer studies and modelling approaches may help quantify the effects of bio-fortification, fortification, and food-based approaches for increasing vitamin A depots. A systematic review and several trials identified adverse events associated with higher vitamin A intakes, which should be useful for setting upper limits. We have generated and provide a database of relevant research. Full systematic reviews, based on this scoping review, are needed to answer specific questions to set vitamin A requirements and upper limits.
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Affiliation(s)
- Lee Hooper
- Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK; (C.E.-B.); (J.B.); (J.F.); (A.J.); (B.V.T.); (A.A.); (C.C.); (L.E.); (C.F.); (E.G.); (C.H.); (S.H.W.); (N.N.); (T.O.); or (E.P.); (L.R.); (H.G.); (F.S.); (A.A.W.)
- Correspondence: ; Tel.: +44-1603-591268
| | - Chizoba Esio-Bassey
- Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK; (C.E.-B.); (J.B.); (J.F.); (A.J.); (B.V.T.); (A.A.); (C.C.); (L.E.); (C.F.); (E.G.); (C.H.); (S.H.W.); (N.N.); (T.O.); or (E.P.); (L.R.); (H.G.); (F.S.); (A.A.W.)
| | - Julii Brainard
- Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK; (C.E.-B.); (J.B.); (J.F.); (A.J.); (B.V.T.); (A.A.); (C.C.); (L.E.); (C.F.); (E.G.); (C.H.); (S.H.W.); (N.N.); (T.O.); or (E.P.); (L.R.); (H.G.); (F.S.); (A.A.W.)
| | - Judith Fynn
- Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK; (C.E.-B.); (J.B.); (J.F.); (A.J.); (B.V.T.); (A.A.); (C.C.); (L.E.); (C.F.); (E.G.); (C.H.); (S.H.W.); (N.N.); (T.O.); or (E.P.); (L.R.); (H.G.); (F.S.); (A.A.W.)
| | - Amy Jennings
- Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK; (C.E.-B.); (J.B.); (J.F.); (A.J.); (B.V.T.); (A.A.); (C.C.); (L.E.); (C.F.); (E.G.); (C.H.); (S.H.W.); (N.N.); (T.O.); or (E.P.); (L.R.); (H.G.); (F.S.); (A.A.W.)
| | - Natalia Jones
- School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK;
| | - Bhavesh V. Tailor
- Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK; (C.E.-B.); (J.B.); (J.F.); (A.J.); (B.V.T.); (A.A.); (C.C.); (L.E.); (C.F.); (E.G.); (C.H.); (S.H.W.); (N.N.); (T.O.); or (E.P.); (L.R.); (H.G.); (F.S.); (A.A.W.)
| | - Asmaa Abdelhamid
- Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK; (C.E.-B.); (J.B.); (J.F.); (A.J.); (B.V.T.); (A.A.); (C.C.); (L.E.); (C.F.); (E.G.); (C.H.); (S.H.W.); (N.N.); (T.O.); or (E.P.); (L.R.); (H.G.); (F.S.); (A.A.W.)
| | - Calvin Coe
- Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK; (C.E.-B.); (J.B.); (J.F.); (A.J.); (B.V.T.); (A.A.); (C.C.); (L.E.); (C.F.); (E.G.); (C.H.); (S.H.W.); (N.N.); (T.O.); or (E.P.); (L.R.); (H.G.); (F.S.); (A.A.W.)
| | - Latife Esgunoglu
- Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK; (C.E.-B.); (J.B.); (J.F.); (A.J.); (B.V.T.); (A.A.); (C.C.); (L.E.); (C.F.); (E.G.); (C.H.); (S.H.W.); (N.N.); (T.O.); or (E.P.); (L.R.); (H.G.); (F.S.); (A.A.W.)
| | - Ciara Fallon
- Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK; (C.E.-B.); (J.B.); (J.F.); (A.J.); (B.V.T.); (A.A.); (C.C.); (L.E.); (C.F.); (E.G.); (C.H.); (S.H.W.); (N.N.); (T.O.); or (E.P.); (L.R.); (H.G.); (F.S.); (A.A.W.)
| | - Ernestina Gyamfi
- Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK; (C.E.-B.); (J.B.); (J.F.); (A.J.); (B.V.T.); (A.A.); (C.C.); (L.E.); (C.F.); (E.G.); (C.H.); (S.H.W.); (N.N.); (T.O.); or (E.P.); (L.R.); (H.G.); (F.S.); (A.A.W.)
| | - Claire Hill
- Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK; (C.E.-B.); (J.B.); (J.F.); (A.J.); (B.V.T.); (A.A.); (C.C.); (L.E.); (C.F.); (E.G.); (C.H.); (S.H.W.); (N.N.); (T.O.); or (E.P.); (L.R.); (H.G.); (F.S.); (A.A.W.)
| | - Stephanie Howard Wilsher
- Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK; (C.E.-B.); (J.B.); (J.F.); (A.J.); (B.V.T.); (A.A.); (C.C.); (L.E.); (C.F.); (E.G.); (C.H.); (S.H.W.); (N.N.); (T.O.); or (E.P.); (L.R.); (H.G.); (F.S.); (A.A.W.)
| | - Nithin Narayanan
- Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK; (C.E.-B.); (J.B.); (J.F.); (A.J.); (B.V.T.); (A.A.); (C.C.); (L.E.); (C.F.); (E.G.); (C.H.); (S.H.W.); (N.N.); (T.O.); or (E.P.); (L.R.); (H.G.); (F.S.); (A.A.W.)
| | - Titilopemi Oladosu
- Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK; (C.E.-B.); (J.B.); (J.F.); (A.J.); (B.V.T.); (A.A.); (C.C.); (L.E.); (C.F.); (E.G.); (C.H.); (S.H.W.); (N.N.); (T.O.); or (E.P.); (L.R.); (H.G.); (F.S.); (A.A.W.)
| | - Ellice Parkinson
- School of Health Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK;
| | - Emma Prentice
- Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK; (C.E.-B.); (J.B.); (J.F.); (A.J.); (B.V.T.); (A.A.); (C.C.); (L.E.); (C.F.); (E.G.); (C.H.); (S.H.W.); (N.N.); (T.O.); or (E.P.); (L.R.); (H.G.); (F.S.); (A.A.W.)
| | - Meysoon Qurashi
- Department of Medicine, Luton and Dunstable Hospital NHS Foundation Trust, Lewsey Road, Luton LU4 0DZ, UK;
| | - Luke Read
- Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK; (C.E.-B.); (J.B.); (J.F.); (A.J.); (B.V.T.); (A.A.); (C.C.); (L.E.); (C.F.); (E.G.); (C.H.); (S.H.W.); (N.N.); (T.O.); or (E.P.); (L.R.); (H.G.); (F.S.); (A.A.W.)
| | - Harriet Getley
- Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK; (C.E.-B.); (J.B.); (J.F.); (A.J.); (B.V.T.); (A.A.); (C.C.); (L.E.); (C.F.); (E.G.); (C.H.); (S.H.W.); (N.N.); (T.O.); or (E.P.); (L.R.); (H.G.); (F.S.); (A.A.W.)
| | - Fujian Song
- Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK; (C.E.-B.); (J.B.); (J.F.); (A.J.); (B.V.T.); (A.A.); (C.C.); (L.E.); (C.F.); (E.G.); (C.H.); (S.H.W.); (N.N.); (T.O.); or (E.P.); (L.R.); (H.G.); (F.S.); (A.A.W.)
| | - Ailsa A. Welch
- Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK; (C.E.-B.); (J.B.); (J.F.); (A.J.); (B.V.T.); (A.A.); (C.C.); (L.E.); (C.F.); (E.G.); (C.H.); (S.H.W.); (N.N.); (T.O.); or (E.P.); (L.R.); (H.G.); (F.S.); (A.A.W.)
| | - Peter Aggett
- Lancashire School of Postgraduate Medicine and Health, University of Central Lancashire, Preston PR1 2HE, UK;
| | - Georg Lietz
- Human Nutrition Research Centre, Newcastle University, Newcastle upon Tyne NE2 4HH, UK;
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Lopez-Teros V, Green MH, Haskell MJ, Green JB. Influence of Vitamin A Status on the Choice of Sampling Time for Application of the Retinol Isotope Dilution Method in Theoretical Children. J Nutr 2021; 151:3874-3881. [PMID: 34587254 DOI: 10.1093/jn/nxab310] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Revised: 06/21/2021] [Accepted: 08/19/2021] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Vitamin A status may influence the choice of a blood sampling time for applying the retinol isotope dilution (RID) equation to predict vitamin A total body stores (TBS) in children. OBJECTIVES We aimed to identify time(s) after administration of labeled vitamin A that provide accurate estimates of TBS in theoretical children with low or high TBS. METHODS We postulated 2- to 5-y-old children (12/group) with low (<200 μmol) or high TBS (≥700 μmol) and used compartmental analysis to simulate individual subject values for the RID equation TBS = FaS/SAp (Fa, fraction of dose in stores; S, retinol specific activity in plasma/in stores; SAp, retinol specific activity in plasma). Using individual SAp and group geometric mean FaS values from 1-28 d, we calculated individual and group mean TBS and compared them to assigned values. RESULTS Mean TBS was accurately predicted for both groups at all times. For individuals, predicted and assigned TBS were closest when the CV% for FaS was low [12-14%; 4-13 d (low), 12-28 d (high)]. The mean percentage error for TBS was <10% from 2-19 d (low) and 7-28 d (high). Predicted TBS was within 25% of assigned TBS for ≥80% of children from 3-23 d (low) and 9-28 d (high). Within groups, RID tended to overestimate lower TBS and underestimate higher TBS. CONCLUSIONS Using a good estimate for FaS, accurate RID predictions of TBS for individuals will be obtained at many times. If vitamin A status is low, results indicate that early sampling (e.g., 4-13 d) is optimal; if vitamin A status is high, sampling at 12-28 d is indicated. When vitamin A status is unknown, sampling at 14 d is recommended, or a super-subject design can be used to obtain the group mean FaS at various times for RID prediction of TBS in individuals.
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Affiliation(s)
- Veronica Lopez-Teros
- Department of Chemical and Biological Sciences, Universidad de Sonora, Hermosillo, Sonora, Mexico
| | - Michael H Green
- Department of Nutritional Sciences, College of Health and Human Development, The Pennsylvania State University, University Park, PA, USA
| | - Marjorie J Haskell
- Institute for Global Nutrition, Department of Nutrition, University of California-Davis, Davis, CA, USA
| | - Joanne Balmer Green
- Department of Nutritional Sciences, College of Health and Human Development, The Pennsylvania State University, University Park, PA, USA
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Green MH, Green JB. Use of Model-Based Compartmental Analysis and Theoretical Data to Further Explore Choice of Sampling Time for Assessing Vitamin A Status in Groups and Individual Human Subjects by the Retinol Isotope Dilution Method. J Nutr 2021; 151:2068-2074. [PMID: 33834213 PMCID: PMC8245873 DOI: 10.1093/jn/nxab061] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 01/19/2021] [Accepted: 02/17/2021] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND An optimal blood sampling time for application of the retinol isotope dilution (RID) method for predicting vitamin A total body stores (TBS) (i.e., vitamin A status) has not been established. OBJECTIVES Objectives were to identify sampling times that provide accurate estimates of TBS by RID in groups and individuals by applying compartmental modeling to data for theoretical adults and children. METHODS We selected previously generated hypothetical adults and children (20 per group) that had a wide range of assigned values for TBS and vitamin A kinetic parameters. We used the Simulation, Analysis and Modeling software to simulate individual kinetic responses; then we calculated geometric mean values for the RID equation coefficients and each individual's plasma retinol specific activity at various times, using those values to predict group mean and individual subject TBS. Predicted values for TBS were compared with assigned values. RESULTS Accurate estimates of group mean TBS were obtained at all sampling times from 1 to 30 d in both adults and children. For individuals, correlations between RID-predicted TBS and assigned values increased with time in the adults (R2 = 0.80 at day 14, 0.96 at day 21, and 0.99 at day 28); a similar trend was observed for the children, with R2 = 0.82 at day 7 and increasing to 0.97 at days 21 and 28 (P < 0.001 for all comparisons). CONCLUSIONS Although no single, unique time provided the most accurate prediction of TBS for all individuals within these groups, applying the RID method at 21 or 28 d yielded predictions that were within 25% of assigned values for 90% or 95% of adults, respectively; corresponding values for children were 80% from 10 to 20 d, and 85% at 21 and 28 d. For most subjects, early times (<14 d for adults and <10 d for children) provided less accurate predictions.
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Affiliation(s)
| | - Joanne Balmer Green
- Department of Nutritional Sciences, College of Health and Human Development, The Pennsylvania State University, University Park, PA, USA
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Green MH, Ford JL, Green JB. A Compartmental Model Describing the Kinetics of β-Carotene and β-Carotene-Derived Retinol in Healthy Older Adults. J Nutr 2021; 151:434-444. [PMID: 33188397 DOI: 10.1093/jn/nxaa306] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Revised: 07/06/2020] [Accepted: 09/15/2020] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Descriptive and quantitative information on β-carotene whole-body kinetics in humans is limited. OBJECTIVES Our objective was to advance the development of a physiologically based, working hypothesis compartmental model describing the metabolism of β-carotene and β-carotene-derived retinol. METHODS We used model-based compartmental analysis (Simulation, Analysis and Modeling software) to analyze previously published data on plasma kinetics of [2H8]β-carotene, [2H4]β-carotene-derived retinol, and [2H8]retinyl acetate-derived retinol in healthy, older US adults (3 female, 2 male; 50-68 y); subjects were studied for 56 d after consuming doses of 11 μmol [2H8]β-carotene and, 3 d later, 9 μmol [2H8]retinyl acetate in oil. RESULTS We developed a complex model for labeled β-carotene and β-carotene-derived retinol, as well as preformed vitamin A, using simulations to augment observed data during model calibration. The model predicts that mean (range) β-carotene absorption (bioavailability) was 9.5% (5.2-14%) and bioefficacy was 7.3% (3.6-14%). Of the absorbed β-carotene, 41% (25-58%) was packaged intact in chylomicrons and the balance was converted to retinol, with 58% (42-75%) transported as retinyl esters in chylomicrons and 0-2% by retinol-binding protein. Most (95%) chylomicron β-carotene was cleared by the liver. Later data revealed differences in the metabolism of retinyl acetate- versus β-carotene-derived retinol; data required that both β-carotene and derived retinol be recycled from extrahepatic tissues (e.g. adipose) in HDL. Of total bioconversion [73% (47-99%)], 82% occurred in the intestine, 17% in the liver, and 0.83% in other tissues. CONCLUSIONS Our model advances knowledge about whole-body β-carotene metabolism in healthy adults, including the kinetics of transport in all lipoprotein species, and suggests hypotheses to be tested in future studies, such as the possibility that retinol derived from hepatic conversion over a long period of time might contribute to plasma retinol homeostasis and total body vitamin A stores.
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Affiliation(s)
- Michael H Green
- Department of Nutritional Sciences, College of Health and Human Development, The Pennsylvania State University, University Park, PA, USA
| | - Jennifer Lynn Ford
- Department of Nutritional Sciences, College of Health and Human Development, The Pennsylvania State University, University Park, PA, USA
| | - Joanne Balmer Green
- Department of Nutritional Sciences, College of Health and Human Development, The Pennsylvania State University, University Park, PA, USA
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Green MH, Ford JL, Green JB. Development of a Compartmental Model to Investigate the Influence of Inflammation on Predictions of Vitamin A Total Body Stores by Retinol Isotope Dilution in Theoretical Humans. J Nutr 2021; 151:731-741. [PMID: 33484140 PMCID: PMC7948205 DOI: 10.1093/jn/nxaa407] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2020] [Revised: 10/13/2020] [Accepted: 11/23/2020] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Inflammation, both acute and chronic, is associated with reductions in the synthesis of retinol-binding protein (RBP) and the concentration of retinol in plasma. Consequently, it is currently recommended that the retinol isotope dilution (RID) method not be used to estimate vitamin A total body stores (TBS) in subjects with inflammation. OBJECTIVES To apply compartmental analysis to study the effects of inflammation on hepatic apo-RBP input, plasma retinol pool size, and RID-predicted TBS in theoretical subjects with known steady state values for these parameters. METHODS We selected 6 previously generated hypothetical subjects who ingested a dose of stable isotope-labeled vitamin A (day 0). Starting with each subject's published steady state model for retinol tracer kinetics, we developed a parallel model for unlabeled retinol and RBP that incorporated links between these entities and tied liver retinol secretion to RBP availability. Then we perturbed the steady state model by initiating chronic or acute inflammation on day 0 or acute inflammation on day 3 or 9 and simulating results for RBP, plasma retinol, and TBS. RESULTS Chronic inflammation led to substantial reductions in RID-predicted TBS for at least 2 weeks after tracer administration. In contrast, acute inflammation induced on day 0 or 3 resulted in less dramatic impacts on TBS (37% or 20% reduction, respectively, from steady state levels, with levels rebounding by 14 days). When inflammation was induced 9 days after administration of the tracer, the effects on predicted TBS were minimal. Overall, for acute inflammation initiated at 0, 3, or 9 days, accurate predictions of TBS were obtained by 2 weeks. CONCLUSIONS Compartmental analysis can be applied in the novel way described here to study the influence of perturbations such as inflammation on predictions of vitamin A status using RID. Such an approach has potential value for studying other perturbations and different nutrients.
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Affiliation(s)
| | - Jennifer Lynn Ford
- Department of Nutritional Sciences, College of Health and Human Development, The Pennsylvania State University, University Park, PA, USA
| | - Joanne Balmer Green
- Department of Nutritional Sciences, College of Health and Human Development, The Pennsylvania State University, University Park, PA, USA
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