大菱鲆脂联素受体基因的克隆及饲料糖脂比对其表达的影响

脂联素作为一种重要的细胞因子在哺乳动物中起到调节糖脂代谢的重要作用, 为探究脂联素在大菱鲆糖脂代谢中是否具有同样的调节作用, 研究利用分子克隆和RACE技术克隆到了大菱鲆脂联素AdipoR1受体和AdipoR2受体的基因全长序列。其中AdipoR1受体的核苷酸序列全长为1125 bp, 共编码375个氨基酸, 氨基酸序列与其他脊椎的同源性都很高。AdipoR2受体的核苷酸序列全长为1940 bp, 共编码380个氨基酸, 氨基酸序列与其他脊椎动物同源性也都很高。蛋白跨膜结构域预测得出大菱鲆AdipoR1和AdipoR2都具有7个明显的跨膜区, 最优拓扑模型为N端在细胞内侧模型, 与其他脊椎动物相同。配制不同糖脂比(1鲶6, 1鲶2, 2鲶1和14鲶1)的饲料养殖大菱鲆9周, 利用实时荧光定量PCR技术检测大菱鲆肌肉和肝脏中脂联素受体基因的表达量。结果显示, 在饲料糖脂比为1鲶2的处理组中, 大菱鲆肌肉中AdipoR1的表达量显著低于糖脂比为1鲶6的处理组(P<0.05), 但与其他2组无显著差异。饲料糖脂比的变化对肌肉中AdipoR2和肝脏中这2种受体的表达量均没有产生显著影响(P>0.05)。由此可见, 饲料糖脂比的变化可能通过改变脂联素受体的表达量, 从而间接影响大菱鲆体内脂联素的作用。AdipoR1和AdipoR2对饲料糖脂比变化的反应不同步, 而且肌肉和肝脏中脂联素受体对饲料糖脂比变化的反应也存在不同。适量提高饲料糖脂比可以显著下调肌肉中AdipoR1的表达。

MOLECULAR CLONING OF ADIPONECTIN RECEPTORS IN TURBOT SCOPHTHALMUS MAXIMUS AND ITS EXPRESSION RESPONSE TO DIETARY RATIOS OF CARBOHYDRATE TO LIPID

The present study cloned the full-length cDNA sequences of adiponectin receptors (AdipoR1, AdipoR2) in turbot. The cDNA sequence of AdipoR1 was 1125 bp, encoding 375 amino acids. The deduced amino acid sequence of AdipoR1 was conserved with the vertebrate's AdipoR1, such as human (80%) and tilapia (97%). The cDNA sequence ofAdipoR2 was 1940 bp, encoding 380 amino acids. The amino acid sequence of AdipoR2 was 78% identical to hu-man and 92% to tilapia. Like invertebrates, both AdipoR1 and AdipoR2 had 7 transmembrane domains, and the N-ter-minal of the optimal topological structure was inside cells. Turbot adiponectin receptors were widely expressed in all detected tissues. The highest mRNA level ofAdipoR1 was found in gill and kidney. The high level ofAdipoR2 was found in gill, stomach, intestine, kidney and pyloric caeca. A 9-week feeding trial using diets with different ratios of carbohydrate to lipid (1:6, 1:2, 2:1 and 14:1) indicated that 1:2 dietary carbohydrate-to-lipid ratio but not other two di-ets significantly decreased the expression of AdipoR1 (P<0.05) in turbot muscle. All 3 diets had no significant effect on theAdipoR2 expression in muscle and the expressions ofAdipoR1 andAdipoR2 in liver (P>0.05). These results sug-gest that the dietary carbohydrate-to-lipid ratios may influence the function of adiponectin through changing the adipon-ectin receptors expression in muscle.