REGULATION OF C-FOS EXPRESSION IN ADIPOSE AND MUSCLE-TISSUE OF DIABETIC RATS

Insulin treatment of control rats demonstrated a marked 8-fold transie nt increase (15 min) in c-fos mRNA in white adipose tissue, which retu rns to basal levels by 5 h. Similarly, insulin treatment resulted in a rapid 9-fold increase in cardiac muscle c-fos mRNA, which also return ed to control values by 1 h. By contrast, insulin treatment resulted i n only a small increase in c-jun mRNA levels in both adipose tissue an d cardiac muscle. Similarly, the expression of c-jun mRNA was only sli ghtly responsive to insulin in these tissues from streptozotocin-induc ed insulin-deficient diabetic rats. However, insulin treatment of insu lin-deficient diabetic rats resulted in a prolonged increase in c-fos message levels in adipose tissue without any significant change in the time course of c-fos mRNA induction/repression in cardiac muscle. The se data demonstrate that in contrast to c-jun, c-fos is transiently in creased in both cardiac muscle and adipose tissue by insulin treatment . Furthermore, transrepression of the c-fos gene is specifically atten uated in adipose tissue of insulin-deficient diabetic rats, but not in cardiac muscle.