Chevalier S, Blaner W S, Azais-Braesco V, Tuchweber B
Department of Nutrition, University of Montreal, Québec, Canada.
J Gerontol A Biol Sci Med Sci. 1999 Sep;54(9):B384-92. doi: 10.1093/gerona/54.9.b384.
Recent studies reported that retinoid metabolism was influenced by long-term dietary restriction (DR) in rats. Because plasma retinol was decreased in rats subjected to DR, it was thought that this dietary manipulation may have an effect on retinol-binding protein (RBP) metabolism. Thus, the aim of this study was to assess retinoids, RBP, and transthyretin (TTR) levels in plasma and liver of young (3 months), adult (12 months), and old (22 months) female Sprague-Dawley rats fed ad libitum (AL) or subjected to a 40% DR, enriched (DR+), or not (DR), with vitamins and minerals. Results indicate that hepatic total retinoid concentrations and content increased with age in all the groups. DR+ rats showed higher hepatic retinoid concentrations than age-matched AL and DR rats. Adult and old DR and DR+ rats exhibited significantly lower plasma RBP-retinol and higher total retinoic acid levels than corresponding controls, although these parameters were not influenced by aging. Liver RBP levels were also decreased in DR and DR+ rats when compared to respective AL controls. There was a slight age-related decline in plasma TTR levels in DR and DR+ rats which was not associated with modifications in liver TTR levels. Hepatic gene expression of RBP and TTR, as evaluated by Northern blot hybridization, did not change with age or diet, suggesting that the lower levels of plasma RBP-retinol and liver RBP in vitamin A-sufficient rats subjected to DR may reflect post-transcriptional alterations and/or accelerated degradation of hepatic RBP. The elevated plasma levels of retinoic acid may represent an adaptive mechanism developed by DR rats to maintain retinoid-dependent functions.
近期研究报道，长期饮食限制（DR）会影响大鼠体内的类视黄醇代谢。由于饮食限制的大鼠血浆视黄醇水平降低，因此认为这种饮食干预可能对视黄醇结合蛋白（RBP）代谢有影响。因此，本研究的目的是评估自由采食（AL）或接受40%饮食限制、补充（DR+）或未补充（DR）维生素和矿物质的3月龄（幼年）、12月龄（成年）和22月龄（老年）雌性斯普拉格-道利大鼠血浆和肝脏中的类视黄醇、RBP和甲状腺素转运蛋白（TTR）水平。结果表明，所有组的肝脏总类视黄醇浓度和含量均随年龄增长而增加。DR+组大鼠的肝脏类视黄醇浓度高于年龄匹配的AL组和DR组大鼠。成年和老年DR组及DR+组大鼠的血浆RBP-视黄醇水平显著低于相应对照组，总视黄酸水平则高于对照组，尽管这些参数不受衰老影响。与各自的AL对照组相比，DR组和DR+组大鼠的肝脏RBP水平也降低。DR组和DR+组大鼠的血浆TTR水平随年龄略有下降，这与肝脏TTR水平的变化无关。通过Northern印迹杂交评估，RBP和TTR的肝脏基因表达不随年龄或饮食而变化，这表明饮食限制的维生素A充足大鼠血浆RBP-视黄醇和肝脏RBP水平较低可能反映了转录后改变和/或肝脏RBP的加速降解。视黄酸血浆水平升高可能代表饮食限制大鼠为维持类视黄醇依赖性功能而形成的一种适应性机制。
