Diet- and diabetes-induced changes of ob gene expression in rat adipose tissue

ob gene regulation is as yet unknown. We first examined whether the ob gene is under physiological control by the nutritional state. Fasting produced a sharp (95%) decrease of ob mRNA in epididymal and inguinal fat pads from 24 h onward. Refeeding rapidly (3-6 h) re-induced ob gene expression and corrected it within 24 h. Similar changes in fatty acid synthase (FAS) and GLUT4 mRNAs were observed, whereas phosphoenolpyruvate carboxykinase (PEPCK) mRNA showed an opposite evolution. We next examined the potential role of insulin. In adipose tissue of streptozotocin-diabetic rats, ob mRNA levels were decreased by 80%. Insulin treatment (4 days) only marginally increased ob mRNA, but restored euglycemia and overcorrected FAS, GLUT4 and PEPCK expression. In conclusion, we provide evidence for a physiological regulation of ob gene by variations in the nutritional state. We also show that ob expression is impaired in streptozotocin-diabetic rats and only slightly restored by insulin treatment, which suggests that ob gene is not or only minimally regulated by the hormone.