(P27-011-23) Isotopic Analysis of Zinc Content in Whole Blood of Preterm Infants

Objectives: Dietary zinc is essential for infant growth and brain development. Zinc isotopes may be differentially absorbed, transported, and accumulated in humans. We hypothesized that zinc isotope distributions: 1) change over time in very preterm infants (VPIs), possibly reflecting dietary, developmental and/or pathological factors during the hospitalization; and 2) differ in VPIs versus full-term infants (FTIs).

Methods: We studied 43 VPIs [gestational age (GA) range, 24-30 weeks] and 15 FTIs (GA range, 37-39 weeks) using inductively coupled plasma-mass spectrometry (ICP-MS) to measure zinc isotope content (⁶⁴Zn, ⁶⁶Zn, ⁶⁸Zn, ⁷⁰Zn) in peripheral whole blood samples collected from VPIs at 4 time points [day of life (DOL) 1, DOL14, DOL30, hospital discharge] and in cord blood from FTIs. Zinc isotope ratios (⁶⁶Zn/⁶⁴Zn, ⁶⁸Zn/⁶⁴Zn, and ⁷⁰Zn/⁶⁴Zn) were determined and compared to published natural abundance ratios.< Differences were tested using Kruskal-Wallis and the Wilcoxon signed-rank statistical tests.

Results: Among VPIs, median zinc isotope concentrations decreased from DOL1 to DOL30 by 19-25% (p < 0.05) followed by an increase from DOL30 to discharge by 38-50% (p < 0.05). Median age at discharge was 89.5 days and zinc values at discharge were higher with longer length of stay. At discharge, median zinc values among VPIs were higher by 30% (p < 0.05) compared to median cord blood zinc values of FTIs. Median ⁷⁰Zn alone was significantly higher at DOL1 in the VPIs compared to FTIs (20%). Median isotopic ratios (⁶⁶Zn/⁶⁴Zn, ⁶⁸Zn/⁶⁴Zn) were significantly lower at DOL1, DOL14 and DOL30 compared to isotopic ratios in FTIs. Median FTI and VPI isotopic ratios were all significantly greater than natural abundance ratios.

Conclusions: ⁶⁴Zn is preferentially accumulated relative to other isotopes in VPIs in the first month of hospitalization, as indicated by the lower ⁶⁶Zn/⁶⁴Zn and ⁶⁸Zn/⁶⁴Zn ratios. This difference in isotopic accumulation becomes less pronounced by discharge. All zinc isotopes were higher at discharge in VPIs compared to FTIs. These findings may reflect VPI specific variables such as stage of development, infection, inflammation, diet, and other factors impacting zinc absorption from the gastrointestinal tract, transport across cell membranes, and interaction with cellular constituents.

Funding Sources: Gerber Foundation, NINDS, NICHD