The Molecular Basis for Zinc Bioavailability

Abstract

Zinc is an essential micronutrient, and its deficiency is perhaps the most prevalent and least understood worldwide. Recent advances have expanded the understanding of zinc’s unique chemistry and molecular roles in a vast array of critical functions. However, beyond the concept of zinc absorption, few studies have explored the molecular basis of zinc bioavailability that determines the proportion of dietary zinc utilized in zinc-dependent processes in the body. The purpose of this review is to merge the concepts of zinc molecular biology and bioavailability with a focus on the molecular determinants of zinc luminal availability, absorption, transport, and utilization.

Caseinophosphopeptides Overcome Calcium Phytate Inhibition on Zinc Bioavailability by Retaining Zinc from Coprecipitation as Zinc/Calcium Phytate Nanocomplexes

“…39 In addition, apical peptide transporter 1 has been frequently expected to transport di/tripeptides-bound Zn 2+ into the enterocytes. 25 Considering the much higher zinc dissociation constant (pK d ) of phytate than that of Zip4, 36 intestinal epithelial cells were unlikely to capture Zn 2+ from Zn/CaPA-NCs by using the zinc transporter Zip4. As shown in Figure 5c, glycylsarcosine and 2-aminoethyl diphenyl borinate, the typical inhibitors of peptide transporter 1 and the ion channel TRPM7, respectively, 40 exerted no significant effect on casein hydrolysate's effectiveness to increase ex vivo zinc transport from the zinc−calcium−phytate ternary system, suggesting the peptide transporter 1-and TRPM7-independent intestinal absorption of zinc from Zn/CaPA-NCs.…”

“…We hypothesize that CaPA precipitates and CPP-stabilized CaPA nanoparticles compete for the surface sequestration of Zn 2+ ions. The zinc dissociation constants (p K d ) of phytate and O -phosphoserine have been reported to be 10.4 and 4.46, respectively, , so phytate phosphate groups should have a greater binding affinity for zinc than CPPs, implicating a dominant role of phytate phosphate groups in surface retention of zinc by CPP-stabilized CaPA nanoparticles. Considering their rather small size, CPP-stabilized CaPA nanoparticles should have much larger specific surface area than CaPA precipitates and so appear to be highly competitive for surface sequestration of zinc compared to CaPA precipitates, which may account for the effective retention of zinc in solution by casein hydrolysate in spite of the heavy precipitation of CaPA (Figure b).…”

Preventing and Controlling Zinc Deficiency Across the Life Course: A Call to Action

“…The chemical form has an impact on the solubility and, thus, absorption of zinc from the gastrointestinal tract [ 85 ]. Whether the supplement is taken in the fasting state or with a meal also has an impact on how it is absorbed and metabolized [ 86 , 87 ]. A disadvantage of supplementation is that it requires behavior change; thus, the level of compliance has a major impact on its success [ 88 ].…”

Zinc-Fortified Rice: Approach to Improve Dietary Zinc Consumption and Effect on Human Health

“…Bioavailability is usually divided into three phases: (1) luminal availability; (2) absorption, retention, and distribution in the body; and (3) cellular and tissue utilization. 126 Absorbed Zn may be retained for utilization or secreted as a part of pancreatic juice that may be reabsorbed or excreted in the feces. Amino acids and peptide, the soluble zinc-binding ligands assist in maintaining the solubility of Zn and hence promote its access to Zn transporters.…”

“…It is usually expressed as a percent or fraction of the total dietary zinc. Bioavailability is usually divided into three phases: (1) luminal availability; (2) absorption, retention, and distribution in the body; and (3) cellular and tissue utilization . Absorbed Zn may be retained for utilization or secreted as a part of pancreatic juice that may be reabsorbed or excreted in the feces.…”