Lack of Intestinal Divalent Metal‐ion Transporter 1 (DMT1) Impairs Copper Absorption in Female Mice
Authors: Wang Xiaoyu , Flores Shireen RL , Ha Jung‐Heun , Doguer Caglar , Wang Tao , Collins James 
Published: November 2023

Introduction

Iron and copper homeostasis is intimately intertwined. This is not surprising given the similar physiochemical and toxicological properties of the two redox‐active metals. Previous studies showed that copper accumulates in tissues important for iron homeostasis during iron deprivation (e.g. the intestinal mucosa, liver, blood). Also, the main intestinal iron importer, DMT1, can transport copper during iron deprivation in rats and in DMT1‐expressing HEK293 cells. Copper transport by intestinal DMT1 could provide a mechanistic explanation for tissue copper accumulation during iron deficiency. The current study was thus designed to test the hypothesis that intestinal DMT1 can transport copper, under certain physiologic conditions.

Methods

We utilized mice lacking DMT1 only in the intestine (DMT1int/int) and WT littermates (DMT1flox/flox). For the in vivo 64Cu absorption study, weanling mice of both sexes (n = 3–7 mice/group) were fed the following AIN‐93G‐based diets: Dietary Group A = WT mice fed a control diet (50 ppm Fe) for 4 weeks or KO mice fed a high‐iron diet (1% carbonyl Fe) for 1 week followed by the control diet for 3 weeks (this was intended to normalize Hb levels in the KOs to WT levels); and Dietary Group B = WT mice fed a low Fe diet (~3 ppm Fe) and KO mice fed the control diet (both groups were anticipated to be anemic). Subsequent to the dietary treatments and after an overnight fast (but with access to water), copper absorption was quantified by providing a 64Cu containing solution to mice by oral gavage. After the gavage, mice were given free access to food. Mice were sacrificed 9 hours later and copper absorption was calculated by quantifying 64Cu accumulation in the carcass, after subtracting counts from within the GI tract (representing unabsorbed copper). All data mentioned below reached statistical significance (two‐way ANOVA); n = 3–7 mice/group.

Results

Copper absorption was impaired in female KOs with normal Hb levels, while no change was noted in males. Copper absorption trended higher in the iron‐deficient KOs compared to the iron‐deprived WT mice (but data did not reach statistical significance). 64Cu content of duodenum, liver, kidney, heart and bone were significantly lower in female KOs with normal Hb levels. Under anemic conditions, 64Cu content in blood, duodenum, kidney, spleen, heart and bone were significantly higher in female KOs compared to WT.

Conclusions

In female mice, when hemoglobin levels were normalized by high‐iron feeding, 64Cu absorption was impaired in the KOs. Under anemic conditions, copper absorption was not statistically different between WT and KOs, but tissue 64Cu accumulation was higher in the KOs lacking intestinal DMT1. It is thus conceivable that there is an upregulation in the expression of an intestinal copper transporter in the iron‐deficient KOs. Overall, this investigation provides additional evidence that intestinal DMT1 can transport copper under some physiologic conditions and further that DMT1 may secondarily influence copper homeostasis by unknown mechanisms.

Support or Funding Information

Supported by NIH grant 1R01 DK074867 (to J.F.C.).