From the Research
No, not all plasma cholesterol is esterified, with approximately 70% existing in the esterified form and 30% as free or unesterified cholesterol. This balance is crucial for normal cholesterol transport, metabolism, and homeostasis in the body 1. The esterification process is primarily catalyzed by the enzyme lecithin-cholesterol acyltransferase (LCAT) in the bloodstream.
Key Points
- Esterified cholesterol is more hydrophobic than free cholesterol, making it better suited for transport within the lipid core of lipoproteins like LDL and HDL.
- Free cholesterol tends to reside in the outer phospholipid layer of lipoproteins and can be readily exchanged between lipoproteins and cell membranes.
- The removal of cholesterol esters and free cholesterol can be delayed in certain conditions, such as familial hypercholesterolemia, but can be improved with treatment, such as high-dose simvastatin 2.
Evidence
The study by 1 found that free cholesterol was equilibrated completely between lipoprotein classes within 30-45 min, but esterified cholesterol was not completely equilibrated within 2 h. Another study by 2 found that the removal of LDE cholesteryl esters and free cholesterol was delayed in FH patients, but treatment with a high dose of simvastatin normalized the removal of cholesterol esters but not the removal of free cholesterol.
Clinical Implications
Understanding the balance between esterified and free cholesterol is important for the management of hyperlipidemia and the prevention of cardiovascular disease. Treatment options, such as statins and bile acid sequestrants, can help improve lipid profiles and reduce the risk of cardiovascular events 3, 4, 5.