Fibroblast activation protein is an extracellular membrane bound and soluble protease that is commonly used as a marker of activated fibroblasts. Expression of FAP in healthy adult tissues is limited, but up-regulation is observed in a number of inflammatory and tissue remodeling processes, including wound healing, liver fibrosis and epithelial cancer, where it is thought to participate in remodeling of the extracellular matrix via its protease activity.

We hypothesized that FAP would also be up-regulated in the pancreatic remodeling and inflammatory process associated with type I diabetes. FAP has the potential to participate in this disease process in a number of ways. First, it has been suggested that immune cells cannot infiltrate pancreatic islets unless the membranous capsule is destabilized in some way. As a protease with collagenase activity, FAP may participate in degradation of the basement membrane allowing immune cell infiltration into the islets. Second, FAP may cleave hormones involved in glucose metabolism. The FAP KO mouse has been reported to have improved glucose tolerance, particularly after high fat feeding, suggesting as yet undiscovered substrates may exist for FAP. Preliminary work in our lab has identified FAP cleavage of a number of metabolically active hormones in vitro and FAP consensus sequences exist in many soluble factors including the hormone betatrophin. Thus FAP may have substrates of consequence related to beta cell regeneration or glucose control.

The goal of this project is to quantify FAP activity in the pancreas and serum of type 1 and type 2 diabetics compared to controls. This study will also be, to our knowledge, the first to examine FAP activity in the human pancreas.