REGULATION OF STEAROYL-COA DESATURASE-1 MESSENGER-RNA STABILITY BY POLYUNSATURATED FATTY-ACIDS IN 3T3-L1 ADIPOCYTES

The effects of arachidonic acid (20:4, n-6) and other fatty acids on t he expression of stearoyl-CoA desaturase gene 1 were investigated in f ully differentiated 3T3-L1 adipocytes. Treatment of 3T3-L1 adipocytes with arachidonic acid resulted in a decrease in stearoyl-CoA desaturas e (Scd) enzyme activity and scd1 mRNA, Arachidonic acid did not alter the transcription of the scd1 gene, whereas the half-life of the scd1 mRNA was reduced from 25.1 to 8.5 h, Blocking the conversion of arachi donic acid to eicosanoids by pretreatment of the cells with cyclooxyge nase, lipoxygenase, or cytochrome P-450 epoxygenase inhibitors did not reverse the inhibition caused by arachidonic acid, indicating that ei cosanoid synthesis is not necessary for the repression of scd1 mRNA ex pression. Treatment of adipocytes with linoleic (18:2, n-6) and linole nic (18:3, n-3) acids also resulted in inhibition of scd1 mRNA accumul ation. By contrast, oleic acid (18:1, n-9) and stearic acid (18:0) had no effect on scd1 mRNA levels. Taken together, these results suggest that polyunsaturated fatty acids repress the expression of the scd1 ge ne in mature adipocytes by reducing the stability of scd1 mRNA.