Showing posts with label Fat. Show all posts
Showing posts with label Fat. Show all posts
November 4, 2012
Moving through the fat factory
As anyone who has ever read a nutrient chart knows, liver (as a food) is very high in fat and cholesterol. In fact, your liver is a veritable fat and cholesterol factory that collects fat fragments from your blood and uses them to make cholesterol and new fats that your body can use to build tissue and perform other physiological functions.
The next few sections explain exactly how lipoproteins are made.
Putting the fats in lipoproteins (and taking them out again)
When the chylomicron hits the liver, it picks up fat particles and mutates into the largest kind of lipoprotein, a fluffy particle called a very low density lipoprotein (VLDL).
Then your liver sends the VLDL out into the wide world — your body. As the VLDL travels far and wide, it drops globs of fat, picks up globs of cholesterol, and changes into a slightly smaller, heavier particle called an intermediate low-density lipoprotein (IDL), and then a slightly smaller, heavier low density lipoprotein (LDL).
The last step in the transformation of the baby lipoprotein (the chylomicron) occurs when an LDL has dropped so much fat and cholesterol into body tissue that it’s mostly protein. Now, you’re looking at a high density lipoprotein (HDL).
Naming the proteins in lipoproteins
The primary proteins in VLDLs, IDLs, and LDLs belong to a class of apolipoproteins called apoB. The primary proteins in HDLs belong to a class of apolipoproteins called apoA. Other less prominent apolipoproteins found in lipoproteins are apoC and apoE.
You may have heard about a blood test for apoA; this test is interesting because a high level of apoA indicates a high level of protective HDLs (the “good” particles that haul cholesterol out of your body).
November 3, 2012
Bringing up baby lipoproteins
A lipoprotein is born as a chylomicron, a particle that your intestinal cells assemble from the proteins and fats you eat. Chylomicrons are very, very low density particles.
Why are some lipoproteins called low density and others high density?
- The term density refers to a lipoprotein’s weight.
- Protein weighs more than fat.
- Lipoproteins containing proportionately less protein than fat are low density lipoproteins, also known as LDLs. LDLs are the “bad” particles that carry cholesterol into your arteries.
- Lipoproteins containing proportionately more protein than fat are high density lipoproteins, also known as HDLs. HDLs are the “good” particles that ferry cholesterol out of your body.
Now, back to chylomicrons. These lipoproteins start out with very little protein and a lot of light and fluffy fat and cholesterol. But as they flow through your bloodstream from your intestines on their way to your liver (your body’s lipoprotein factory), the chylomicrons release their fats, known as triglycerides, into your blood.
The stripped down chylomicron, also known as a chylomicron remnant, still has its cholesterol and protein. Now, the remnant slides into your liver, and fat comes back into the picture.
