THYROID-HORMONE INHIBITS FATTY-ACID SYNTHASE GENE-TRANSCRIPTION IN CHICKEN LIVER

The effect of triiodothyronine (T-3) on regulation of fatty acid synthase in chicken liver was investigated. In hypothyroid animals, enzyme activity was about one half of that in euthyroid animals. T-3 treatment increased the enzyme activity in hypothyroid animals. There is little difference in both the mRNA concentration and the transcription rate between euthyroid and hypothyroid animals. T-3 treatment markedly decreased both the mRNA concentration and the transcription rate in euthyroid and hypothyroid animals. These results suggested that T-3 maintained the normal level of enzyme expression primarily by stimulating the post-transcriptional step, while the transcription of the gene was inhibited by hyperthyroidism.