4-Phenyl butyric acid does not generally reduce glucose levels in rodent models of diabetes.

1. Endoplasmic reticulum (ER) stress plays a role in the pathogenesis of diabetes. The aim of the present study was to investigate the effect of 4-phenyl butyric acid (PBA), a novel chemical chaperone reducing ER stress, on serum glucose level in different strains of normal and diabetic rodents. 2. 4-Phenyl butyric acid (1 g/kg per day, i.g.) was administered to ob/ob Type 2 diabetic mice, alloxan-induced Type 1 diabetic mice and hydrocortisone (HC)-induced Type 2 diabetic mice as well as normal C57BL/6J mice and Kumming mice for 14 days to evaluate its effect on serum glucose levels. In addition, mice were treated simultaneously with PBA (1 g/kg per day) and HC for 9 days to determine its preventive effect against the development of insulin resistance. PBA (0.7 and 1.4 g/kg per day) was administered to non-obese Type 2 diabetic Goto-Kakizaki (GK) and normal Wistar-Kyoto (WKY) rats for 14 and 7 days, respectively, to determine its effects on serum glucose levels. 3. 4-Phenyl butyric acid significantly reduced serum glucose levels in obese Type 2 diabetic ob/ob mice. Normoglycaemia was obtained in ob/ob mice after 4 days of PBA treatment and was maintained for up to 14 days treatment. 4. 4-Phenyl butyric acid had no glucose-lowering effect in alloxan-induced Type 1 diabetic mice, HC-induced Type 2 diabetic mice and non-obese Type 2 diabetic GK rats. In addition, it had no beneficial effects on insulin resistance in HC-treated mice. 5. 4-Phenyl butyric acid did not affect normal serum glucose levels in C57BL/6 J mice, Kunming mice or WKY rats. 6. In conclusion, PBA does not generally reduce glucose levels in rodent models of diabetes, although it can normalize glucose levels in ob/ob diabetic mice, indicating that restoration of ER function as diabetes therapy is limited to conditions under which ER stress is involved in the high glucose levels.