Abstract
Fibroblast growth factor (FGF) 21 is a class of hepatokines that plays a protective role against obesity, insulin resistance, and liver damage. Despite this, protective effects of FGF21 in human appear to be minimal, possibly due to its proteolytic cleavage by the fibroblast activation protein (FAP). Here, we presented a novel FAP inhibitor, BR103354, and described its pharmacological activities as a potential therapeutic agent for the treatment of metabolic disorders. BR103354 inhibited FAP with an IC50 value of 14 nM, showing high selectivity against dipeptidyl peptidase (DPP)-related enzymes and prolyl oligopeptidase (PREP). In differentiated 3T3/L1 adipocytes, the addition of FAP diminished hFGF21-induced Glut1 and phosphorylated levels of ERK, which were restored by BR103354. BR103354 exhibited good pharmacokinetic properties as evidenced by oral bioavailability of 48.4% and minimal hERG inhibition. Single co-administration of BR103354 with hFGF21 reduced nonfasting blood glucose concentrations, in association with increased intact form of hFGF21 in ob/ob mice. Additionally, chronic treatment of BR103354 for 4 weeks reduced nonfasting blood glucose concentrations with improved glucose tolerance and with reduced triglyceride (TG) content in liver of ob/ob mice. Consistently, BR103354 improved hepatic steatosis and fibrosis in a choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD)-induced non-alcoholic steatohepatitis (NASH) mouse model. FAP inhibitory effects of BR103354 were confirmed in normal cynomolgus monkeys. Together, BR103354 acts as an effective FAP inhibitor in vitro and in vivo, thereby demonstrating its potential application as an anti-diabetic and anti-NASH agent.
Highlights
Type 2 diabetes is a major cause of death worldwide, and increasing cases pose a serious threat to human health[1]
Increased circulating FGF21 levels have been observed in cases of obesity, type 2 diabetes, or nonalcoholic fatty liver disease[8,9,10,11], which suggests its protective effects against various metabolic disorders
When full-length recombinant hFGF21 was incubated with fibroblast activation protein (FAP) in an assay buffer in a cell-free system, hFGF21 cleavage occurred rapidly, but cleavage was inhibited in the presence of BR103354 starting at a concentration of 0.4 μM, as determined by sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS-PAGE) (Fig. 1c), indicating that BR103354 was capable of blocking FAP-mediated cleavage of hFGF21
Summary
Type 2 diabetes is a major cause of death worldwide, and increasing cases pose a serious threat to human health[1]. Increased circulating FGF21 levels have been observed in cases of obesity, type 2 diabetes, or nonalcoholic fatty liver disease[8,9,10,11], which suggests its protective effects against various metabolic disorders. Levels in diet-induced obese m ice[15,16] and in obese diabetic cynomolgus m onkeys[17] Based on these observations, Eli Lilly developed the FGF21 analog, LY2405319, and confirmed the improvement of metabolic disorders in rodents and nonhuman p rimates[18]. LY2405319 administration to obese human subjects with type 2 diabetes resulted in lower body weight and lipid levels, but did not reduce blood glucose levels[19]. To overcome the limitation of rapid cleavage of hFGF21 by FAP, various approaches have been investigated, such as the attachment of polyethylene glycol to F GF2133–35 and the fusion of FGF21 to an Fc fragment[28], as treatments for diabetes and metabolic diseases
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