LEP and gastroenteritis: in vitroLeptin has been shown to induce an increased intestinal epithelial cell proliferation. In addition, intestinal epithelial cells produce leptin and luminal leptin vice versa activates the NF- κB pathway in intestinal epithelial cells. In line, rectal application in vivo results in intestinal inflammation. Leptin signaling is required for in vitro polarization of Th17 cells as leptin receptor (Lepr) deficient T cells display decreased STAT3 signaling and consecutively less RORγt expression and impaired IL-17 and IFNγ production.