Inhibition of cholesteryl ester transfer protein increases serum apolipoprotein (apo) A-I levels by increasing the synthesis of apo A-I in rabbits

Background: Inhibition of cholesteryl ester transfer protein (CETP) is an effective way to increase HDL levels in animals and humans. The effects of a CETP inhibitor, JTT-705, on the in vivo kinetics of apolipoprotein (apo) A-I and apo A-I gene expression in the liver and intestine were investigated. Methods: Japanese White rabbits were randomly fed normal rabbit chow LRC-4 (n=10, control) or a food admixture of LRC-4 and 0.75% JTT-705 (n=10, treated) for 7 months. An in vivo kinetics study of apo A-I was performed by injecting rabbit 125I-apo A-I, and apo A-I mRNA levels were quantified by RT-PCR. Results: JTT-705 significantly inhibited CETP activities, increased serum levels of HDL-cholesterol (C), HDL2-C, HDL-phospholipid, and apo A-I, and decreased HDL-triglyceride levels. The synthetic rate of apo A-I was higher in the treated rabbits than in control rabbits (13.7±2.6 versus 9.5±1.3 mg/kg per day, P<0.05), while the fractional catabolic rate was similar in the two groups. JTT-705 increased apo A-I mRNA levels in the liver without affecting those in the intestine. Conclusion: Inhibition of CETP activity by JTT-705 increases HDL levels by increasing the synthesis of apo A-I, suggesting that it could be a promising therapeutic approach for atherosclerosis.