Abstract
Objectives
The study assessed effect of dietary iron on iron homeostasis and dendritic architecture of hippocampal neurons in young piglets.
Methods
On postnatal day (PD) 1, 30 piglets (15 male/female) were blocked by sex and randomized to treatments by receiving no (N), low (L) or high (H) dose of iron supplement during pre- (PD1–21) and post-weaning period (PD22–35). Pigs in N, L, and H group orally received 0, 1, and 30 mg iron/(kg BW· d) as ferrous sulfate solution pre-weaning and were fed a solid diet containing 30, 125, and 1000 mg iron/kg post-weaning, respectively. Blood samples were collected on PD1 and weekly thereafter to analyze iron biomarkers. Iron homeostasis in hippocampus was assessed by measuring gene and protein expression of iron transporters. Hippocampal neurons stained with Golgi-Cox method were traced and 3D reconstructed using Neurolucida. Dendritic arborization were quantified through Sholl analysis and Neurolucida Explorer.
Results
Pigs in H group had the highest growth rate, whereas N pigs displayed growth retardation from PD27 to PD35, resulting in significant difference in body weight compared to H group (P < 0.05). Iron dose-dependently increased hemoglobin (Hb), hematocrit, plasma iron and transferrin saturation since PD7 or PD14 (P < 0.05). Pigs in N group became iron deficient since PD14 (Hb < 11 g/dL). Similarly, hippocampal ferritin expression was upregulated with the increase of iron (P < 0.05). The mRNA expression of TFRC and DMT1 in hippocampus was highest in N and lowest in H group (P < 0.05). Despite relatively low abundance, HAMP expression tended to be higher in H than that in N (P < 0.10). Sholl analysis uncovered significant main effect of treatment on basilar dendritic arborization of CA1 and CA3 pyramidal neurons (P ≤ 0.04). There were less branching nodes and dendrites in N than in H group (P < 0.05). However, the difference in dendritic arborization was primarily derived from the higher order (> 3) of branches in both regions. Iron supplementation did not affect architecture of apical dendrites of granule cells in dentate gyrus.
Conclusions
Early-life iron status affects hippocampal iron homeostasis and alters development of pyramidal neurons in a piglet model.
Funding Sources
NIFA Hatch/Multistate Research Fund.