High Glucose Represses b-Klotho Expression and Impairs Fibroblast Growth Factor 21 Action in Mouse Pancreatic Islets Involvement of Peroxisome Proliferator–Activated Receptor g Signaling

Circulating fibroblast growth factor 21 (FGF21) levels are elevated in diabetic subjects and correlate directly with abnormal glucose metabolism, while pharmacologically administered FGF21 can ameliorate hyperglycemia. The pancreatic islet is an FGF21 target, yet the actions of FGF21 in the islet under normal and diabetic conditions are not fully understood. This study investigated the effects of high glucose on islet FGF21 actions in a diabetic mouse model by investigating db/db mouse islet responses to exogenous FGF21, the direct effects of glucose on FGF21 signal-ing, and the involvement of peroxisome proliferator–activated re-ceptor g (PPARg) in FGF21 pathway activation. Results showed that both adult db/db mouse islets and normal islets treated with high glucose ex vivo displayed reduced b-klotho expression, re-sistance to FGF21, and decreased PPARg expression. Rosiglitazone, an antidiabetic PPARg ligand, ameliorated these effects. Our dat