Differential regulation of the stearoyl-CoA desaturase genes by thiazolidinediones in 3T3-L1 adipocytes

Two stearoyl-CoA desaturase (SCD) isoforms can be expressed during the diff erentiation of 3T3-L1 preadipocytes into adipocytes, Here we report on the effects of the peroxisome proliferator-activated receptor gamma ligand trog litazone (TRO) on scd1 and scd2 mRNA levels as determined by Northern blott ing, on SCD protein expression as determined by Western blotting, and on to tal lipid composition as determined by GC during differentiation. In preadi pocytes, scd1 mRNA and SCD protein were not detected, whereas scd2 mRNA was detected. These cells have high levels of palmitate (16:0), stearate (18:0 ), and monounsaturated oleate (Delta(9)-18:1) and low levels of monounsatur ated palmitoleate (Delta(9)-16:1). In MDI (methylisobutylxanthine, dexameth asone, and insulin)-treated cells, scd1 mRNA and SCD protein were increased similar to 100-fold relative to preadipocyte levels, the scd2 mRNA level w as increased 2-fold, Delta(9)-16:1 was increased similar to 20-fold, and 18 :0 was decreased similar to 3-fold, In TRO-treated cells, the scd1 mRNA lev el was lower than that observed in preadipocytes, while the scd2 mRNA level was similar. TRO also decreased scd1 mRNA in primary adipocytes, The TRO-t reated cells contained a Delta(9)-18:1 level typical of MDI-treated cells w hereas, conversely, these cells also contained a low Delta(9)-16:1 level ty pical of preadipocytes. The implications of these correlations for the regu latory and enzymatic mechanism(s) used to establish and maintain lipid comp osition are discussed.