EFFECT OF RETINOIDS ON NUCLEAR RETINOIC ACID RECEPTORS MESSENGER-RNA IN ADIPOSE-TISSUE OF RETINOL-DEFICIENT RATS

In this study, we examined effects of retinol deficiency and three retinoids, all-trans-retinoic acid, 13-cis-retinoic acid, and etretin, the aromatic derivative of retinoic acid, on nuclear retinoic acid receptor isoforms alpha, beta, and gamma-mRNA in rat adipose tissue. Retinol deficiency caused an almost 50% decrease in isoform beta-mRNA levels of adipose tissue, whereas little change occurred in the abundance of alpha and gamma isoforms transcripts in this tissue. Intragastric administration of all-trans-retinoic acid to retinol-deficient rats increased the adipose tissue retinoic acid receptor isoforms beta and gamma-mRNA levels sixfold and twofold, respectively, in 4 h as compared to adipose tissue of retinol-deficient rats that were administered cottonseed oil. In contrast to this, 13-cis-retinoic acid and etretin at equimolar doses were not effective in inducing beta or gamma-isoforms mRNA in retinol-deficient rats. These results show that adipose tissue isoform-beta responds to retinol deficiency, and all-trans-retinoic acid rapidly induces beta and gamma-mRNA isoforms in this tissue. Thus, retinoic acid may regulate expression of specific genes through its interaction with retinoic acid receptors in adipocytes.