Fasting increases iron export by modulating ferroportin 1 expression through the Ghrelin/GHSR1α/MAPK pathway in the liver
Abstract Background: The liver is the metabolic organ considered to contribute the most to maintaining body iron homeostasis and is a regulator of body adaptation to fasting. Our previous studies implied a negative relationship between iron and ghrelin in both mice and humans and indicated that ghrelin was able to increase ferroportin 1 (Fpn1) expression in the spleen and macrophages through the GHSR/MAPK pathway. However, it remains to be explored whether fasting or ghrelin has a functional effect on iron homeostasis in the liver.Methods: In this study, we examined the roles of fasting and ghrelin in modulating the protein expression of Fpn1, transferrin receptor 1 (TfR1), and ferritin light chain (Ft-L), as well as the mRNA expression of ghrelin, hepcidin, ghrelin O-acyltransferase (GOAT) and growth hormone secretagogue receptor 1 alpha (GHSR1α) in mouse liver and cultured hepatocytes.Results: Our in vivo results suggested that fasting significantly upregulated the mRNA expression of ghrelin, GOAT and GHSR1α as well as the protein levels of ghrelin, Fpn1 and Ft-L, but not TfR1, in mouse liver. Meanwhile, in cultured hepatocytes, ghrelin significantly increased the protein expression of Fpn1 but not Ft-L and TfR1 and significantly enhanced ERK phosphorylation. Furthermore, the pretreatment of cultured hepatocytes with either a pERK inhibitor or a GHSR1α antagonist abolished the effects of ghrelin on Fpn1 expression and ERK phosphorylation.Conclusions: Our findings confirmed that fasting increases iron export in the liver by upregulating Fpn1 expression through the ghrelin/GHSR1α/MAPK signaling pathway.