Isotopic signatures of iron in body tissues as a potential biomarker for ironmetabolism

Abstract

Previous studies using MC-ICP-MS for high precision isotope ratio analysis revealed that human blood is enriched in light iron isotopes relative to dietary iron. Moreover, distinct differences in blood iron isotopic patterns between individual subjects can be observed. Discrimination of heavy iron isotopes during uptake of dietary iron in the gastrointestinal tract may explain this observation. This hypothesis was now tested in the pig model. Samples of tissues relevant to iron metabolism were screened for iron isotopic patterns using MC-ICP-MS, revealing considerable isotope fractionation during intestinal uptake on one hand and during distribution between body tissues on the other hand. Light iron isotopes are enriched in the gastrointestinal mucosa relative to feed, with isotopic patterns reflecting major iron absorption sites in mammals along the gut. While heavy iron isotopes are enriched in the liver, spleen and bone marrow, light isotopes are enriched in red blood cells. Well-established links between iron absorption efficiency and iron distribution between functional compartments and stores point to blood iron isotope signatures as a novel type of compound biomarker of element metabolism.