Studies on the gene expression and physiological roles of cellular retinol-binding protein, type II in small intestine

1)以大鼠为实验对象，探讨膳食脂肪酸对空肠细胞视黄醇结合蛋白II型（CRBP (II)）及类视黄醇受体（RXR）和过氧化物酶体增殖物激活受体（PPAR）核因子的调节作用。所有不饱和脂肪酸（油酸、亚油酸和亚麻酸）均能提高CRBP (II) mRNA水平，但不影响RXR_< α >和PPAR_< α >水平。2)研究花生四烯酸和过氧化物酶体增殖剂（纤维酸和二十碳四烯酸（ETYA））是否能增强人肠道细胞系Caco-2细胞中CRBP （II）和RXR_< α >和PPAR_< α >基因的表达。暴露于纤维酸、花生四烯酸和ETYA的细胞增强了CRBP (II) mRNA的表达，但不增强RXR_< α >和PPAR_< α > mRNA的表达。在Caco-2细胞中观察到ETYA联合9-顺式维甲酸对CRBP （II）基因表达的加性作用。3)凝胶位移法观察到，高脂（玉米油）饲粮大鼠空肠核提取物与大鼠CRBP （II）原5'侧区核受体反应元件（RXRE & RE3）结合，RXR抗体可阻止这种结合。高脂饮食提高了核提取物与DNA反应元件的结合水平。4)凝胶移位实验显示，etya处理Caco-2细胞CRBP (II) mRNA水平升高与受体反应元件（RE3）与细胞核提取物的核相互作用增强有关。放线菌素D处理Caco-2细胞后，ETYA抑制了CRBP (II) mRNA的表达，表明ETYA处理增加了RXR/PPAR复合物与5'侧翼区域的结合，可能会提高CRBP （II）基因的水平。饲喂过量β -胡萝卜素不增加大鼠空肠CRBP （II）水平和空肠未酯化视黄醇和棕榈酸视黄醇含量。

1) Dietary fatty acids which modulate jejunal cellular retinol binding protein type II (CRBP (II)) and nuclear factors of retinoid receptor (RXR) and peroxisome proliferator-activated receptor (PPAR) were explored using rats. All unsaturated fatty acids (oleic, linoleic and linolenic) enhanced the CRBP (II) mRNA levels, but not the RXR_<alpha> and PPAR_<alpha> levels.2) We investigated whether arachidonic acids and peroxisome proliferators (clofibric acid and eicosatetraynoic acid (ETYA)) enhance gene expression of CRBP (II) and RXR_<alpha> & PPAR_<alpha> in human intestinal cell line, Caco-2 cells. The cells exposed to clofibric acid, arachidonic acid and ETYA enhanced CRBP (II) mRNA expression, but not RXR_<alpha> and PPAR_<alpha> mRNAs. Additive effect on CRBP (II) gene expression by ETYA in combination with 9-cis retinoic acid were observed in Caco-2 cells.3) It was observed by gel shift assay that jejunum nuclear extracts from rats fed high fat (corn oil) diet bound to nucler receptor response elements (RXRE & RE3) in a 5'flanking region of the rat CRBP (II) gen, and the binding was prevented with RXR antibody. The binding level of the nuclear extracts to the DNA response elements were elevated in rats fed the high fat diet.4) Gel shift assay revealed that the increased CRBP (II) mRNA level in ETYA-treatmented Caco-2 cells were related to the enhanced nuclear interaction of the receptor response elements (RE3) with nuclear extracts from the cells. Actinomycin D treatment of the Caco-2 cells brought about a inhibition of the the CRBP (II) mRNA expressio n by ETYA,suggesting a increased binding of RXR/PPAR omplex to a 5'flanking region by the ETYA reatment may enhance CRBP (II) gene level5) Effects of feeding excessbeta-carotene on CRBP (II) and vitamin A levels were investigated. Feeding excessbeta-carotene did not increase jejunum CRBP (II) levels and jejunal contents of unesterified retinol and retinyl palmitate in rats.