Hyperinsulinemia increases the amount of GLUT4 mRNA in white adipose tissue and decreases that of muscles: a clue for increased fat depot and insulin resistance.

To mimick a state of hyperinsulinemia, normal rats were infused with insulin for 4 days via minipumps, and compared to saline infused rats. At the end of the experimental period, the abundance of mRNA was increased in white adipose tissue (WAT) and decreased in muscles of "insulinized" rats compared to controls. These findings were accompanied, in all tissues considered, except the diaphragm, by parallel changes in the amount of the glucose transporter protein and by parallel changes in the in vivo glucose utilization index. Hyperinsulinemia is thus a driving force in stimulating adipose tissue metabolic activity, while bringing about incipient muscle insulin resistance.