As posted by Androgenic:

What is hdl ,ldl ,triglycerides ?
We generally think of HDL as the "good" cholesterol and the LDL as the "bad" cholesterol without having a clue as to what HDL and LDL cholesterol is.We could peacefully live our lives without knowing anything about what they are. However, that doesn't erase its importance and we shouldn't believe something just because it is something that is engrained. We should understand how cholesterol fits into theinsulin,glucagon and insulin control equation--- notably if heart disease or elevated cholesterol runs in the family.

Lipoproteins can be invisioned as envelopes that enclose cholesterol and triglycerides that makes them soluble in blood which allows them to be trasported to the body's tissues. Neither cholesterol ( a waxy/ fatty solid ) nor triglycerides ( how fat is stored in the body ) are blood soluble and need to be wrapped and carried through the bloodstream by a substance that is soluble. Enter the lipoprotein.

Low Density Lipoprotein ( LDL ) while High Density Lipoprotein ( HDL ). The names tell us nothing about what they do. The names just reveal their degree of density. The lightest of the blood fats,triglycerides, are a grouping of blood fats that would float to the top, like cream ( yummy ). Very-low-density lipoprotein VLDL ) carry some triglycerides and some cholesterol. LDL molecules carry primarily cholesterol. The densest of them all is the HDL or high density lipoprotein.

As you are aware, liver cells make and release VLDL into the bloodstream as a molecule composed mainly of triglycerides but with a very little amount of cholesterol. As this molecule matures, it increases its girth in cholesterol. Once mature the VLDL particle ships triglycerides to the tissues to be burned for energy or stored as fat. The remnants of this distribution are rich in cholesterol with a scant level of triglycerides and become low-density lipoprotein. This so-called "bad" cholesterol is now circulating throughout the bloodstream and is the number 1 mode of transportation for maneuvering cholesterol to the tissues at the body's perimeter . This cholesterol will undergo a possibility of 3 fates: They can be removed from circulation by the liver which is the true manner in which healthy cholesterol levels are maintained; other tissues may need theis "excess' cholesterol and can absorb the needed molecules; or , the least desireable, the can be depositied in the arteries.

LDL receptors is how our cells remove LDL from circulation. It is these receptors, manufacture in cells then sent to the cell's surface, that catches the LDL.Obviously the more LDL receptors we have the more capable our cells become at harvesting these molecules.

There are 2 hormones capable of affecting the rate limiting enzyme HMG-CoA reductase.These hormones are known as insulin and glucagon. Insulin stimulates this enzyme while glucagon inhibits it. People with elevated insulin levels tend to also have elevated cholesterol levels.

Glucagon, which does the opposite by inhibiting HMG-CoA activity comparable to lovastatin's ability and brings about similar results. Glucagon will slow down the production of cholesterol within the cell and as the supply runs low, the cell will send the trusty LDL receptors to the surface to harvest LDL cholesterol from the bloodstream. Interesting, if you want to control your cholesterol levels, ideally, you have to control your insulin/glucagon levels.

Remembering that LDL delivers cholesterol to the tissues. HDL gathers cholesterol from the tissues and returns it to the liver to be disposed of. Since both processes occur in synch with each other the amount of cholesterol depends on the balance of LDL and HDL in the blood. If you have a rich supply of LDL and not much HDL then the bulk of cholesterol traffic will be in the tissues,however, if HDL is in greater supply, more cholesterol wll be carried away to be discarded by the liver.

How do you balance LDL and HDL? By balancing insulin and glucagon. How do you balance these hormones? by reducing sugar/carbohydrates from the diet. Imagine, Cholesterol and insulin/glucagon don't seem to be related but it is plain to see that they are the yin and yan of healthy cholesterol / triglyceride levels. It also seems that a diet high in fats and cholesterol are not responsible for high cholesterol levels.
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