MOLECULAR CLONING OF ADIPONECTIN RECEPTORS IN TURBOTSCOPHTHALMUS 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 of AdipoR2 was 1940 bp, encoding 380 amino acids. The amino acid sequence of AdipoR2 was 78% identical to human and 92% to tilapia. Like invertebrates, both AdipoR1 and AdipoR2 had 7 transmembrane domains, and the N-terminal of the optimal topological structure was inside cells. Turbot adiponectin receptors were widely expressed in all detected tissues. The highest mRNA level of AdipoR1 was found in gill and kidney. The high level of AdipoR2 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鲶6, 1鲶2, 2鲶1 and 14鲶1) indicated that 1鲶2 dietary carbohydrate-to-lipid ratio but not other two diets significantly decreased the expression of AdipoR1 (P<0.05) in turbot muscle. All 3 diets had no significant effect on the AdipoR2 expression in muscle and the expressions of AdipoR1 and AdipoR2 in liver (P>0.05). These results suggest that the dietary carbohydrate-to-lipid ratios may influence the function of adiponectin through changing the adiponectin receptors expression in muscle.