Chronic vitamin A intake affects the expression of mRNA for apolipoprotein A-I, but not for nuclear retinoid receptors, in liver of young and aging Lewis rats.
We have investigated the effects of chronic retinoid status and age on the steady-state levels in rat liver of the mRNAs for the retinoid-responsive gene apolipoprotein A-I (apo A-I), and for three nuclear retinoid receptors, RAR-alpha, RAR-beta, and RXR-alpha. Weanling male Lewis rats (five per age-diet group) were fed a semi-synthetic diet with vitamin A at marginal, control, or supplemented levels until they were 2 or 8 months of age. The relative abundance of apo A-I mRNA (compared to beta-actin which did not differ among treatments) was about 50% lower in aging versus young rats, regardless of their vitamin A status. For both ages, apo A-I mRNA was approximately 40-50% higher (P < 0.05) for the vitamin A-marginal groups and 20-30% lower (P > 0.05) for the vitamin A-supplemented groups than the controls. Neither chronic diet nor age affected the levels of mRNA for RAR-alpha or RXR-alpha, two major retinoid receptors in liver, or for RAR-beta, a receptor known to be autoregulated by RA. Although vitamin A did not have a significant effect on the mRNA levels of the receptors examined in this study, they are still likely to be involved in regulating apo A-I gene expression because in vitro studies have shown that both RAR-alpha and RXR-alpha bind to the regulatory region of the apo A-I gene.
D000375:Aging; D000818:Animals; D016632:Apolipoprotein A-I / Q000235:genetics*; D001835:Body Weight; D015870:Gene Expression; D008099:Liver / Q000378:metabolism*; D008297:Male; D051381:Rats; D011917:Rats, Inbred Lew; D018168:Receptors, Retinoic Acid / Q000235:genetics*; D014801:Vitamin A / Q000008:administration & dosage* / Q000097:blood
D016632:Apolipoprotein A-I; D018168:Receptors, Retinoic Acid; D014801:Vitamin A