Rat Adipose ob mRNA Levels in States of Altered Circulating Glucose and Insulin

We measured levels of ob mRNA in epididymal fat pads of rats exposed to manipulations designed to alter circulating insulin and glycemia. Changes in ob mRNA were compared to alterations in GLUT-4 glucose transporter mRNA, which is known to be regulated under these conditions. 48 h fasting decreased GLUT-4 mRNA to 23% of control with restoration beginning by 6 h refeeding and full restoration at 24 h. In contrast, ob mRNA decreased less markedly to 47% of control with only partial restoration by 24 h. Two days of streptozocin (STZ)-diabetes (glucose > 400 mg/100 ml) decreased GLUT-4 mRNA to 8% of control with restoration by two days of S.C. insulin. In contrast, ob mRNA decreased to 42% of control and was not restored by insulin. Six days of insulin administration to normal rats under conditions of ad lib. feeding, but without otherwise preventing the blood glucose from decreasing, resulted in no significant change in levels of either ob or GLUT-4 mRNA.