Getting to know Cholesterol and LDL

Cholesterol plays a significant role in humans and animals body processes in order for them to survive. Cholesterol is known as fats or lipids. It looks like light yellow waxy fines particles that looks like candle wax shavings. Lipids provide chemical energy as fuel for the cells that make up our body. And it is accountable for the defensive shell or membrane for cells. It is also important for digestion and absorption of nutrients from food.  It is also necessary for our sex hormones, testosterone and estrogen, and for vitamin D.

What are the Different types of Lipoproteins?

The bloodstream is the vehicle which brings cholesterol and other lipids to each cell in the body. Since lipids and blood don’t easily mix well, the body knows to wrap protein around cholesterol particles making it easy to flow within the bloodstream and this is where the term lipoprotein gets its name.

The bloodstream carries many different sizes of lipoproteins which are categorized based on the density or fat composition. Less fat and more protein mean higher density. More fat equals lower density.  There are 4 different fat containing particles in the blood. HDL or high density lipoproteins have the least amount of fat (and triglycerides) and the most protein. The largest and least dense is something called chylomicrons which contain the most fat; specifically triglycerides. The other 2 are LDL or low density lipoproteins and VLDL or very low density lipoproteins.

Most of the fat from our diet and the non-cholesterol fat in our bloodstream are called triglycerides.   Triglycerides are made up of three fatty acids and glycerol, an alcohol. Triglycerides are essential for our health and provide much of the energy our tissues need, but too much of a good thing, like cholesterol, can be dangerous to your circulatory health.

Chylomicrons , VLDL  and Triglycerides

As the digestive system process goes, after the food passes from the stomach to the intestines fat is absorbed from the food.  The intestinal enzymes take to pieces the long fat molecules into fatty acids and merge them with cholesterol into chylomicrons. Intestines discharge a large amount of chylomicrons filled with triglycerides into the blood. The triglyceride levels remain extremely high hours after eating which is the reason why Doctors order fasting before cholesterol tests or else triglyceride levels would show up in the lipid panel as being abnormally high. While this process is occurring, dietary carbohydrates and proteins pass from the intestines to the liver. They are transformed to triglycerides and joint with cholesterol and protein producing VLDL particles which are freed into the blood. As VLDL and chylomicrons travel through the bloodstream, they temporarily stick to the artery walls providing energy. Enzymes remove most of the triglycerides and what remains is rearranged and relabeled to be used again by the liver.

When and How LDL is created?

Triglycerides become smaller and denser when they are removed from VLDL and chylomicrons.  In the end what remains is the protein and cholesterol and a miniature amount of triglyceride. The liver filters out the chylomicron and recycles any remnants unlike VLDL which even after it has lost its triglyceride components, continues to circulate. VLDL continues to change and ultimately ends up as LDL particles. LDL carries the majority of our cholesterol.

Just about all cells in the body can utilize LDL for their energy needs. But there is characteristically more LDL in the bloodstream than is needed and the liver must clear the excess from the blood. It may use it for more bile acids for digestion or as new lipoproteins. If the liver cannot keep up with the excess LDL, it ends up being deposited in places it does not belong. Often this excess LDL ends up being deposited in the blood vessel linings. Occasionally these deposits end up in the skin or tendons where they may form xanthomas or xanthelasmas if they are formed on the eyelids.

HDL, the “Good Cholesterol”

HDL or High density lipoproteins are known popularly as the “good” cholesterol. High density lipoprotein is also made in the intestines and liver, but is very different than LDL.  There is a high concentration of protein and not much fat in HDL. The two main roles of HDL are to provide chylomicrons and VLD the protein component that allows the liver to recognize they need to have their fat extracted. HDLs also act as scavengers and collect excess cholesterol from blood vessel linings and other locations to be transported to the liver to be disposed of. Recently there have been studies suggesting that HDL may even counteract inflammatory molecules in LDLs which is known to cause scarring to blood vessel walls. This scarring encourages plaque and calcium to build up in the damaged areas leading to atherosclerosis. High density lipoproteins (HDL) obviously play a vital role in regulating a healthy cholesterol balance.