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Vitamin A supplementation redirects the flow of retinyl esters from peripheral to central organs of neonatal rats raised under vitamin A–marginal conditions

Hodges, Joanna K, Tan, Libo, Green, Michael H, Ross, A Catharine
TheAmerican journal of clinical nutrition 2017 v.105 no.5 pp. 1110-1121
body weight, brain, canola oil, children, computer software, diet, laboratory animals, liver, malnutrition, mortality, mothers, neonates, oral administration, pups, retinol-binding protein, retinyl palmitate, tritium, vitamin A, white adipose tissue
Background: Vitamin A (VA; retinol) supplementation is used to reduce child mortality in countries with high rates of malnutrition. Existing research suggests that neonates (<1 mo old) may have a limited capacity to store VA in organs other than the liver; however, knowledge about VA distribution and kinetics in individual, nonhepatic organs is limited. Objective: We examined retinol uptake and turnover in nonhepatic organs, including skin, brain, and adipose tissue, in neonatal rats without and after VA supplementation. Design: Sprague-Dawley neonatal rats (n = 104) were nursed by mothers fed a VA-marginal diet (0.35 mg retinol/kg diet) and treated on postnatal day 4 with an oral dose of either VA (6 μg retinyl palmitate/g body weight) or canola oil (control), both containing 1.8 μCi of [³H]retinol. Subsequently, pups (n = 4 · group⁻¹ · time⁻¹) were killed at 13 different times from 30 min to 24 d after dosing. The fractional and absolute transfer of chylomicron retinyl esters (CM-REs), retinol bound to retinol-binding protein (RBP-ROH), and total retinol were estimated in WinSAAM software. Results: VA supplementation redirected the flow of CM-REs from peripheral to central organs and accumulated mainly in the liver. The RBP-ROH released from the liver was acquired mainly by the peripheral tissues but not retained efficiently, causing repeated recycling of retinol between plasma and tissues (541 compared with 5 times in the supplemented group and control group, respectively) and its rapid turnover in all organs, except the brain and white adipose tissue. Retinol stores in the liver lasted for ∼2 wk before being gradually transferred to other organs. Conclusions: VA supplementation administered in a single high dose during the first month after birth is readily acquired but not retained efficiently in peripheral tissues of neonatal rats, suggesting that a more frequent, lower-dose supplementation may be necessary to maintain steady VA concentrations in rapidly developing neonatal tissues.