Inulin Modulates Iron Metabolism in Piglets Fed a High‐Iron Milk Formula

Abstract

ObjectiveIron‐fortified formula provides excessive amount of iron compared to breast milk, and there is a rising concern over the adverse effects of dietary iron overexposure at infancy. The study aimed to evaluate the effect of dietary prebiotics and synbiotics supplement on iron absorption and metabolism in a milk‐fed neonatal piglet model.MethodsOn postnatal day (PD) 2, piglets (n = 6/treatment) were blocked by sex and body weight (BW) and randomized to the following dietary treatments: 1) an iron‐adequate milk formula with 60 mg Fe/kg milk solid (AI), 2) a high‐iron milk formula with 480 mg Fe/kg milk solid (HI), 3) the HI formula supplemented with inulin (Orafti®IPS, Beneo) at 6% of milk solid (HIP), 4) the HIP formula with an oral supplement of 5 ml of Lactobacilus agilis YZ050 (L. agilis) at 1x109 CFU/ml once in every 3 days (HIS). Pigs were fed at 270 mL of milk/kg BW in 14 meals daily through an automatic programmable milk delivery system. Blood and fecal samples were collected on PD 1, 7, 14, 21, 28. On PD 28, piglets were euthanized, and tissue samples were collected. Tissue and fecal samples were analyzed for iron concentrations using flame atomic absorption spectrophotometry analysis. Blood samples were analyzed for hemoglobin (Hb) using Drabkin’s reagent and hematocrit (Hct) using Unico Micro‐hematocrit centrifuge. The mRNA expression of iron transporters and regulatory proteins in the intestinal tissues were determined by RT‐qPCR. Data were analyzed for one‐ or two‐way ANOVA with repeated measure for variables measured over time. Statistical significance was declared at P ≤0.05.ResultsOverall growth performance of piglets across the groups showed no statistical significance during the study. Both Hct and Hb were higher in HI, HIP, HIS than in AI during the study (P≤ 0.05). In comparison with AI, high‐iron formula markedly increased fecal iron concentration on PD7, 14, 21, 28 (P≤ 0.05) with exception of the comparison between AI and HIP on PD7. Use of inulin in HIP reduced fecal iron on PD21 and 28 in comparison with HI (P≤ 0.05). High‐iron formula significantly increased hepatic iron compared to AI (P≤ 0.05), while use of inulin alone or in combination with probiotics attenuated hepatic iron accumulation in comparison with HI (P≤ 0.05). The same response was also observed in analysis of iron concentration in colon content. Duodenal iron concentration was higher in HIP and HIS than in AI (P≤ 0.05), whereas ileal iron concentration was higher in HI than in AI (P≤ 0.05). The mRNA expression of divalent metal transporter 1 (DMT1) in colon was lower in HIP compared to AI (P ≤ 0.05); duodenal cytochrome b (DYCTB) in colon was lower in HI and HIP compared to AI (P ≤ 0.05).ConclusionHigh‐iron formula resulted in hepatic iron overload and increased iron flux in the large intestine and feces. Use of inulin alone or in combination with L. agilis diminished iron deposition in liver, colon, and feces caused by consumption of high‐iron formula in piglets.