Fibroblast growth factor 21: a novel long-acting hypoglycemic drug for canine diabetes

Currently, insulin is commonly used in the clinical management of canine diabetes. However, it must be injected preprandially causing much inconvenience to the owners. Therefore, the development of long-acting hypoglycemic agents has attracted much attention in the scientific community. This study aimed to investigate the long-acting hypoglycemic effect of canine fibroblast growth factor 21 (cFGF-21) in diabetic dogs. Diabetic dogs were administered with cFGF-21, polyethylene glycol-modified cFGF-21 (PEG-cFGF-21), or insulin once a day, once every 2, 3, or 4 days subcutaneously. The results showed that cFGF-21 and PEG-cFGF-21 maintained blood glucose comparable to normal levels for 2 and 3 days respectively while insulin maintained the blood glucose for only 2 h after a single injection. After treatment with cFGF-21, oral glucose tolerance test (OGTT) was significantly improved with glycosylated hemoglobin (HbA1c) close to the normal levels. In addition, cFGF-21 significantly repaired islet β cells, increased insulin content, and protected the pancreas from streptozotocin-induced injury. Furthermore, cFGF-21 exhibited both antioxidant and anti-inflammatory properties in the pancreas. We conclude, therefore, that cFGF-21 and PEG-cFGF-21 can maintain blood glucose comparable to normal levels for 2 and 3 days respectively after a single dose. The long-acting efficacy of cFGF-21 can be attributed to improvement in oxidative stress and the reduction of inflammation in the pancreas.