Iron Absortpion In Pregnant And Non-Pregnant Women And Mechanisms Of Placental Iron Transfer

Abstract

Iron deficiency anemia is the most common nutrient deficiency in the world , with highest rates in pregnant women and young children. Despite the magnitude and severity of iron deficiency, there remains gaps in our knowledge of iron metabolism. Hepcidin is a key regulator of iron homeostasis yet limited data is available on its role during pregnancy. Although our knowledge of non-heme iron metabolism has increased substantially in recent years, the mechanisms regulating heme iron metabolism remain elusive. The overall goal o f this research is to further understand the primary determinants of iron absorption and placental iron transfer in women of childbearing age. To address these issues stable iron isotopes (57Fe and 58Fe) were used to measure iron absorption in non-pregnant (ages 18-32 years, n = 30) and pregnant (ages 16-32 years, n = 20) subjects and placental iron transfer in pregnant women. Nonheme iron absorption was inversely associated with iron status and serum hepcidin. However, heme iron absorption was not signif icantly associated with serum hepcidin or iron stores, suggesting differential regulation. In a subset of 18 non-pregnant subjects serum prohepcidin (hepcidin precursor) was also assessed but was not significantly associated with measures of iron absorptio n or serum hepcidin. Both pregnant and non-pregnant women absorbed significantly more iron from a heme based meal compared to a non-heme iron supplement. Interestingly there also appears to be preferential fetal utilization of maternally ingested heme iron compared to nonheme iron during pregnancy. Iron status in the maternal-neonatal dyad and maternal serum hepcidin were inversely associated with heme and non-heme placental iron transfer. In a cohort of 92 pregnant adolescents (ages 14-18 years), the placental protein expression of transferrin receptor was likewise increased in response to altered iron stores in the mother and neonate. Despite increased iron absorption by women during pregnancy, placental iron transporter expression and placental iron tr ansfer, many of the mothers and the neonates had suboptimal iron status at the time of delivery. Based on study results, further research on the mechanisms of heme iron metabolism and mechanisms of placental iron transfer are warranted.