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Amino Acids Influence DMT1 Trafficking in Duodenal Enterocytes and Modulate Iron Absorption

Iron deficiency (ID), usually due to excessive menstrual bleeding, rapid neonatal and adolescent growth, pregnancy or gastric bypass, is quite common in the U.S. Iron overload (IO) also afflicts thousands of individuals in America, being most frequently associated with Hereditary Hemochromatosis (HH) and β‐thalassemia. Treatment of ID with iron supplements is not always effective, and current treatments for HH, including phlebotomy and iron chelation, are either non‐specific or have negative side effects. Development of improved treatments for these common conditions is thus a priority. We previously demonstrated that select amino acids (AA) can influence trafficking of membrane transport proteins in enterocytes and thus influence electrolyte absorption in the gut. We thus hypothesized that AAs could also influence trafficking of the predominant intestinal iron importer, divalent metal‐ion transporter 1 (DMT1), thus modulating iron absorption. To screen for effects of individual AAs on DMT1 trafficking, ex vivo duodenal loops excised from mice were incubated individually with all 20 AAs. Western blots were performed to quantify DMT1 amounts on the brush‐border membrane (BBM). Two AA formulations were subsequently made that contained mixes of AAs that either increased or decreased DMT1 BBM protein expression. 59Fe flux studies were then performed with mouse duodenal epithelial organ cultures using Ussing chambers after exposure to the AA mixtures. These experiments demonstrated that one AA formulation increased 59Fe flux by ≈4‐fold (p<0.05). In Fe‐deficient mice, short‐term 59Fe gavage studies with these AA demonstrated a significant increase in 59Fe absorption (p<0.05), and 59Fe accumulation in the liver and blood (p<0.05). To test the other AA formulation (which decreased DMT1 BBM protein expression), we utilized a mouse model of HH, hepcidin (Hamp) KO mice, in which intestinal iron absorption is inappropriately elevated. Importantly, 59Fe flux studies with Hamp−/− mice showed ≈10‐fold reduction in iron transport (p<0.05) when exposed to the AA mixture. A 3‐week daily gavage of these AA in weanling Hamp−/− mice demonstrated a significant decrease in serum ferritin (p<0.05). We thus conclude that select AAs can influence DMT1 trafficking to and from the BBM and thus alter iron flux. Although additional in vivo testing is ongoing, these findings could lead to the development of AA formulations that could be used to mitigate pathological changes in intestinal iron transport associated with both ID and IO.