What are Lipoproteins

Many people have heard of some lipoproteins groups, but are unaware of what lipoproteins are, what their function is, and how they affect the body. This article will try to give some light on what lipoproteins are, what they do, and how they affect our body.

Trying to keep it simple, lipoproteins are a biochemical assembly of lipids and proteins. The function of lipoproteins is to carry fats and cholesterol throughout the through the blood stream. There are five major groups of lipoproteins. The major groups are chylomicrons, very high density lipoproteins (VLDL), intermediate density lipoproteins (IDL), low density lipoproteins (LDL), and high density lipoproteins (HDL). The ones that we have probably heard of are low density lipoproteins (LDL) and high density lipoproteins (HDL).When talking to non-medical persons, doctors sometimes refer to these as bad cholesterol (LDL) and good cholesterol (HDL). This is more of a reference to the transporter of cholesterol (LDL/HDL) than the cholesterol itself, but more on that shortly.

A description of the five major groups of lipoproteins is as follows:

Chylomicrons: are the largest of the lipoprotein groups. They consists of triglycerides, phospholipids, cholesterol and protein. There are three stages of the chylomicrons life-cycle. From origin it is nascent, interacting with high density lipoproteins it becomes mature and after unloading the triglycerides becomes remnant. Nascent chylomicrons are created in the small intestine, become mature chylomicrons while interacting with high density lipoproteins (HDL) while circulating through the blood stream and after becoming remnant chylomicrons is taken up by the liver.

Very Low Density Lipoproteins (VLDL): is a lipoprotein which is made in the liver and consist of triglycerides, cholesterol, proteins. It functions a transport system through the blood stream. As it travels through the body and loses the triglycerides it transports it becomes intermediate density lipoproteins (IDL).

Intermediate Density Lipoproteins (IDL): are lipoproteins that transport fats and cholesterol through the body through the blood stream. Intermediate density lipoproteins (IDL) formed from the degradation is VLDL and further degradation result in low density lipoproteins (LDL). Intermediate lipoproteins (IDL) transport a variety of triglyceride fats and cholesterol and like LDL is associated with the atheroma.

Low Density Lipoproteins (LDL): sometimes called bad cholesterol, is lipoproteins that transport cholesterol throughout the body through the blood stream to be used by the body. Low density lipoproteins is created through the degradation of the IDL, which in itself is a degradation of the VLDL. A certain pattern type of the low density lipoprotein, Pattern B, has been linked to the development of certain heart diseases. Many health professionals are concerned with the reduction of low density lipoproteins in the blood stream. Through the natural degradation of VLDL into IDL and then further degradation from IDL to low density lipoproteins, the appearance of low density lipoproteins is a natural occurrence and has a useful function as a transporter of cholesterol throughout the body as it is needed. It has though been given a bad name because of this Pattern B type.

High Density Lipoproteins (HDL): is also known as good cholesterol because high density lipoproteins are capable of picking up free cholesterol and returning them to the liver or steroidogenic organs (adrenals/ovary/testes) to be reused or excreted. The cholesterol delivered to the liver is excreted after being converted to bile acid and the cholesterol delivered to the steroidogenic organs are used to make steroid hormones.

I have tried to explain what lipoproteins are and described the five major groups of lipoproteins and the function of they perform. I do apologize if some of the terms are still complicated. It was my intent to make it simple to understand without over-simplifying it. In future articles, I will attempt to explain the specific functions of different lipoproteins, especially the LDL and HDL. For now it was my intent to give meaning to some of the initials (VLDL, IDL, LDL, HDL) which often appear without definition.