Globally, the number of people with type 2 diabetes mellitus (T2D) is approaching 350 million [1]. With this number rapidly rising, the urgent need for effective therapeutics to treat this disease is also increasing. Research efforts have produced significant advances in treatment options, including the introduction of dipeptidyl peptidase 4 (DPP4) inhibitors, glucagon-like peptide-1 (GLP-1) mimetics and SGLT2 inhibitors to improve glucose-stimulated insulin secretion and lower blood glucose. Despite these advances, there remains a gap in the normalization of glucose and the prevention of complications among the population that current treatments have been unable to address, leaving millions of patients with insufficient and unsafe levels of glucose control. Recently, a protease enzyme called fibroblast activation protein (FAP) has emerged as a potential target for the treatment of T2D and obesity [2]. FAP is the most closely related enzyme to DPP4 [3, 4], a validated drug target. Multiple pharmacological inhibitors of DPP4 are now widely used in patients with T2D [5]. Previous interest in FAP has focused on its potential as a target for cancer therapy due to its upregulation in epithelial tumors [6]. However, recent FAP-specific activity assays have identified FAP activity in the circulation, as well as in several tissues with roles in metabolic regulation [7]. Most intriguingly, preliminary characterization of a global FAP knockout (Fap-/-) mouse demonstrated a) significant protection against diet-induced obesity and b) improved glycemia, phenotypic findings similar to those described in the global DPP4 knockout (Dpp4-/-) mouse [2]. Importantly, FAP has a unique endopeptidase activity, suggesting that its enzymatic targets are different from those of DPP4. Thus, FAP inhibition may provide a novel route to treatment of diabetes. We have independently generated mutant Fap-/- mice, enabling us to determine the metabolic phenotype ensuing from genetic FAP deficiency. Complementary experiments will utilize a potent and specific FAP inhibitor, compound 5057, to determine whether pharmacological FAP inhibition produces the same metabolic benefits observed in Fap-/- mice. Fap-/- mice and wild-type mice treated with compound 5057 will be employed to identify physiological mechanisms (and FAP substrates) underlying the metabolic benefits of FAP inactivation. We are hopeful that this research will lay the groundwork for clinical testing of a new class of drugs for the treatment of T2D.

Public Health Relevance

According the World Health Organization, there are nearly 350 million people worldwide suffering from diabetes, with the associated complications costing upwards of $250 billion annually in the United States alone. Preventative measures against obesity and type 2 diabetes by adherence to healthy diets and lifestyles are useful, but not sufficient, necessitating new therapeutic approaches to aid in the correction of underlying metabolic disorders in type 2 diabetics. Based on preliminary results suggesting that the protease known as fibroblast activation protein (FAP) regulates pathways underlying the pathophysiology of obesity-linked type 2 diabetes, the goal of this project is to validate and understand the therapeutic potential of this drug target for the eventual treatment of diabetic patients.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Postdoctoral Individual National Research Service Award (F32)
Project #
Application #
Study Section
Special Emphasis Panel (ZDK1)
Program Officer
Castle, Arthur
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Sinai Health System
Zip Code
M5 1X5
Panaro, Brandon L; Flock, Grace B; Campbell, Jonathan E et al. (2017) ?-Cell Inactivation of Gpr119 Unmasks Incretin Dependence of GPR119-Mediated Glucoregulation. Diabetes 66:1626-1635