Leptin is an adipocytokine that links nutrition to immunity. Previous observation that a genetic polymorphism in the leptin receptor affected susceptibility to Entamoeba histolytica infection led to the hypothesis that leptin signaling has a protective role during intestinal amebic infection. In this study we show that mice lacking the functional leptin receptor developed devastating mucosal destruction after E. histolytica infection. Bone marrow chimera experiments demonstrated that leptin receptor expressed on hematopoietic cells was not sufficient to confer resistance. Similarly, peripheral knockout of the leptin receptor rendered animals susceptible, indicating that central expression of the leptin receptor was not sufficient to confer protection. The site of leptin action was localized to the gut via an intestinal epithelium-specific deletion of the leptin receptor, which rendered mice susceptible to infection and mucosal destruction by the parasite. Mutation of tyrosine 985 or 1138 in the intracellular domain of the leptin receptor, which mediates signaling through the SH2-containing tyrosine phosphatase/extracellular signal-regulated kinase (SHP2/ERK) and signal transducer and activator of transcription 3 (STAT3) pathways, respectively, demonstrated that both were important for mucosal protection. We conclude that leptin-mediated resistance to amebiasis is via its actions on intestinal epithelium rather than hematopoietic cells or the brain, and requires leptin receptor signaling through both the STAT3 and SHP2/ERK pathways.
