Reverse cholesterol transport in mice expressing simian cholesteryl ester transfer protein

Area of Science:

• Cardiovascular Biology
• Lipid Metabolism
• Atherosclerosis Research

Background:

• The role of cholesteryl ester transfer protein (CETP) in atherosclerosis is debated, with conflicting pro- and anti-atherogenic effects reported.
• While CETP influences HDL cholesteryl ester turnover, its in vivo cholesterol mobilization capacity remains unproven.

Purpose of the Study:

• To investigate whether elevated CETP expression enhances cholesterol mobilization in vivo.
• To assess the impact of CETP on the clearance of exogenous cholesterol from muscle tissue.

Main Methods:

• Comparison of cholesterol removal rates from leg muscle in CETP transgenic and control mice using injected cationized LDL (cat-LDL).
• Utilized radiolabeled 3H-cholesterol oleate (3H-CE) and its non-hydrolyzable analog 3H-cholesteryl oleoyl ether (3H-COE) to track cholesterol and cholesteryl ester fate.
• Quantified radioactivity in muscle and liver tissue over time to determine cholesterol clearance and localization.

Main Results:

• Exogenous cholesterol mass retained in muscle was similar between CETP transgenic and control mice at all measured time points (days 4, 8, and 28).
• Clearance of 3H-cholesterol from muscle showed a half-life of 4 days, while the non-hydrolyzable 3H-COE showed minimal loss, indicating esterified cholesterol stability.
• Liver radioactivity increased in CETP transgenic mice, with 3H-COE accounting for a significant portion, suggesting CETP's interaction with extracellular cholesteryl esters.

Conclusions:

• High plasma CETP levels in mice do not accelerate the in vivo mobilization of cholesterol from tissues.
• CETP's function may be related to the processing of extracellular cholesteryl esters rather than direct cholesterol transport.
• These findings contribute to understanding CETP's complex role in lipid metabolism and cardiovascular disease.