Maintaining healthy circulating cholesterol levels is essential for optimal health. Low cholesterol levels are indicative of impaired liver or peripheral cell health and is associated with increased mortality.
To access the FREE seminars with full presentations and videos please visit Dr. Goodenowe’s resource site here. This is the article for seminar B110, Blood Tests and Biomarkers (Series B).
Cholesterol is one of most important lipids in the body. Its primary role is to regulate the phospholipid bilayer structure of all the membranes in the body. If plasmalogens are the yin, then cholesterol is the yang. Most of the body’s cholesterol is in the outer plasma membrane of all the cells in the body. It is also a component of intracellular membranes as well. 80-85% of all the cholesterol in the body is in membranes and is in its non-esterified form. The rest of the cholesterol is in the circulatory system, but there it is in a different form – it is esterified (with a fatty acid) and attached to transport proteins. Due to its critical importance, the body has sophisticated transport and regulation systems for cholesterol; however, the overall purpose of these systems is to ensure that every cell in the body can efficiently adjust its cholesterol needs on demand.
The bulk of the circulating cholesterol in the body is derived from liver synthesis (75%). Dietary consumption accounts for approximately 25%. Cholesterol is then esterified. The sn-2 fatty acid of phosphatidylcholine is transferred to cholesterol and then this esterified cholesterol is packaged along with triglycerides on very low-density lipoproteins (VLDL) which are then converted to LDL. LDL is the main circulatory source of cholesterol which ensures that all cells of the body have access to cholesterol.
All cells of the body have LDL receptors which enable them to capture and absorb LDL from the blood. This absorbed LDL is then transported to the lysosome where the cholesterol esters and triglycerides are metabolized into free cholesterol and free fatty acids. The free cholesterol is then transported to the plasma membrane and the fatty acids are converted to either carnitine or CoA esters for metabolism in the mitochondria or peroxisome/endoplasmic reticulum, respectively. LDL uptake is stimulated under conditions of intracellular cholesterol starvation, such as statin treatment or cancer. High intracellular demand will also reduce circulating LDL levels.
Circulating LDL levels is an indicator of cellular cholesterol demand. High means low demand, low means high demand.
Intracellular synthesis regulation is performed as part of the cell’s membrane esterification and export system. The whole purpose of cholesterol regulation systems is to maintain optimal membrane cholesterol levels. Membrane DHA-plasmalogen levels are the key regulator of membrane cholesterol esterification. If the cell has healthy functioning peroxisomes, it is making healthy levels of both cholesterol and DHA-plasmalogens. Excess cholesterol is esterified and exported on the outside of the membrane by HDL proteins and on the inside of the membrane by intracellular LDL proteins. Increased intracellular cholesterol naturally shuts down intracellular cholesterol synthesis and reduces LDL absorption from the blood supply.
Circulating HDL levels is a direct indicator of cellular cholesterol export and an indirect measure of membrane cholesterol. Low HDL levels indicate impaired cholesterol export and high membrane cholesterol levels. High HDL is associated with healthy export and low membrane cholesterol.
ProdromeScan measures total cholesterol and HDL-cholesterol levels and calculates the LDL-cholesterol levels in serum.
Dr. Goodenowe explains the relevant research and literature regarding blood cholesterol levels in seminar B110 – Total, HDL, and LDL Cholesterol.