Acts as an anti-inflammatory factor in the intestine and colon. Binds to and acts on macrophages to down-regulate pro-inflammatory gene expression. Affects key macrophage functions, including phagocytosis, by down-regulating many key pathways for macrophage activation, partly via by STAT3 activation and signaling. May be required to dampen the immunological response in colitis. The N-terminus is probably cleaved to release a secreted extracellular portion of the protein. Highly expressed in adult liver and brain tissues. During embryo development, expressed in the brain. Up-regulated in the context of tissue inflammation. Therapeutic delivery of FNDC4 reduces the disease severity of chemical-induced colitis in mice. Truncated N-terminus.