Absorption of Manganese and Iron in a Mouse Model of Hemochromatosis

Hereditary hemochromatosis, an iron overload disease associated with excessive intestinal iron absorption, is commonly caused by loss of HFE gene function. Both iron and manganese absorption are regulated by iron status, but the relationships between the transport pathways of these metals and how they are affected by HFE-associated hemochromatosis remain poorly understood. Loss of HFE function is known to alter the intestinal expression of DMT1 (divalent metal transporter-1) and Fpn (ferroportin), transporters that have been implicated in absorption of both iron and manganese. Although the influence of HFE deficiency on dietary iron absorption has been characterized, potential effects on manganese metabolism have yet to be explored. To investigate the role of HFE in manganese absorption, we characterized the uptake and distribution of the metal in Hfe (-/-) knockout mice after intravenous, intragastric, and intranasal administration of (54)Mn. These values were compared to intravenous and intragastric administration of (59)Fe. Intestinal absorption of (59)Fe was increased and clearance of injected (59)Fe was also increased in Hfe(-/-) mice compared to controls. Hfe (-/-) mice displayed greater intestinal absorption of (54)Mn compared to wild-type Hfe(+/+) control mice. After intravenous injection, the distribution of (59)Fe to heart and liver was greater in Hfe (-/-) mice but no remarkable differences were observed for (54)Mn. Although olfactory absorption of (54)Mn into blood was unchanged in Hfe (-/-) mice, higher levels of intranasally-instilled (54)Mn were associated with Hfe(-/-) brain compared to controls. These results show that manganese transport and metabolism can be modified by HFE deficiency.