High provitamin A carotenoid serum concentrations, elevated retinyl esters, and saturated retinol-binding protein in Zambian preschool children are consistent with the presence of high liver vitamin A stores.

Abstract

BACKGROUND:

Biomarkers of micronutrient status are needed to best define deficiencies and excesses of essential nutrients.

OBJECTIVE:

We evaluated several supporting biomarkers of vitamin A status in Zambian children to determine whether any of the biomarkers were consistent with high liver retinol stores determined by using retinol isotope dilution (RID).

DESIGN:

A randomized, placebo-controlled, biofortified maize efficacy trial was conducted in 140 rural Zambian children from 4 villages. A series of biomarkers were investigated to better define the vitamin A status of these children. In addition to the assessment of total-body retinol stores (TBSs) by using RID, tests included analyses of serum carotenoids, retinyl esters, and pyridoxal-5'-phosphate (PLP) by using high-pressure liquid chromatography, retinol-binding protein by using ELISA, and alanine aminotransferase (ALT) activity by using a colorimetric assay.

RESULTS:

Children (n = 133) were analyzed quantitatively for TBSs by using RID. TBSs, retinyl esters, some carotenoids, and PLP differed by village site. Serum carotenoids were elevated above most nonintervened reference values for children. α-Carotene, β-carotene, and lutein values were >95th percentile from children in the US NHANES III, and 13% of children had hypercarotenemia (defined as total carotenoid concentration >3.7 μmol/L). Although only 2% of children had serum retinyl esters >10% of total retinol plus retinyl esters, 16% of children had >5% as esters, which was consistent with high liver retinol stores. Ratios of serum retinol to retinol-binding protein did not deviate from 1.0, which indicated full saturation. ALT activity was low, which was likely due to underlying vitamin B-6 deficiency, which was confirmed by very low serum PLP concentrations.

CONCLUSIONS:

The finding of hypervitaminosis A in Zambian children was supported by high circulating concentrations of carotenoids and mildly elevated serum retinyl esters. ALT-activity assays may be compromised with co-existing vitamin B-6 deficiency. Nutrition education to improve intakes of whole grains and animal-source foods may enhance vitamin B-6 status in Zambians.

• Authors: Stephanie Mondloch, Bryan M Gannon, Christopher R Davis, Justin Chileshe, Chisela Kaliwile, Cassim Masi, Luisa Rios-Avila, Jesse F Gregory 3rd, Sherry A Tanumihardjo
• Journal: The American journal of clinical nutrition (Am J Clin Nutr) Vol. 102 Issue 2 Pg. 497-504 (Aug 2015) ISSN: 1938-3207 [Electronic] United States
• PMID: 26178727 (Publication Type: Journal Article, Multicenter Study, Randomized Controlled Trial, Research Support, Non-U.S. Gov't)
• Copyright: © 2015 American Society for Nutrition.

Chemical References

• Biomarkers
• Carbon Isotopes
• RBP4 protein, human
• Retinol-Binding Proteins, Plasma
• Vitamin A
• Carotenoids

Topics

• Biomarkers (blood, metabolism)
• Carbon Isotopes
• Carotenoids (adverse effects, blood)
• Child
• Child Nutritional Physiological Phenomena
• Child, Preschool
• Cohort Studies
• Diet (adverse effects, ethnology)
• Female
• Humans
• Hypervitaminosis A (diagnosis, ethnology, etiology, metabolism)
• Indicator Dilution Techniques
• Liver (metabolism)
• Male
• Retinol-Binding Proteins, Plasma (analysis)
• Rural Health
• Up-Regulation
• Vitamin A (analogs & derivatives, blood, metabolism)
• Vitamin A Deficiency (diagnosis, ethnology, metabolism, prevention & control)
• Zambia