Blood Lipids Overview

Lipids (fats) circulating in the bloodstream, either free or bound to other molecules. Primarily transported within a phospholipid capsule. Their type of protein determines their fate and impact on metabolism.

A waxy substance produced by the body and found in animal products. It is a crucial component of cells.

A type of cholesterol that is beneficial for the body. It helps transport cholesterol away from the arteries and back to the liver.

A type of cholesterol that is harmful for the body. It can build up in the arteries, forming plaques which can lead to heart disease.

Another type of fat produced by the body and found in food. High levels are primarily due to lifestyle choices like poor diet, smoking, and lack of exercise.

A condition characterized by elevated or abnormal levels of lipids and/or lipoproteins in the blood. It significantly increases the risk of cardiovascular disease.

The build-up of plaque on the walls of blood vessels, leading to blocked arteries, high blood pressure, stroke, heart disease, or heart attack.

A condition that elevates the risk of heart disease and other health problems. It is often linked to high triglycerides, obesity, and insulin resistance.

Cholesterol, being poorly soluble in water, is transported in the bloodstream by water-soluble lipoproteins.

The different types of apolipoproteins on the lipoprotein surface determine where cholesterol will be taken from and where it will be delivered.

Chylomicrons are the largest lipoproteins, transporting fats from the intestines to the liver, carrying mostly triglycerides.

In the liver, chylomicrons release triglycerides and some cholesterol.

The liver converts unburned food metabolites into VLDL, which are secreted into plasma and converted to IDL and then to LDL particles and non-esterified fatty acids.

Most LDL particles in healthy individuals are large and buoyant (Ib-LDL) and are cardiovascularly neutral.

Small and dense LDL (sd-LDL) particles are strongly associated with atheromatous disease (plaque buildup) in the arteries.

After being transported to the liver by HDL, cholesterol is delivered to the intestines via bile production. However, 92-97% is reabsorbed in the intestines and recycled through enterohepatic circulation.

Long-chain fatty acids are too large to be absorbed directly into the bloodstream, so they are packaged into chylomicrons, which then enter the lymphatic capillaries and eventually the bloodstream at the left subclavian vein.

After a meal, the rise in blood fatty acid levels is balanced by increased uptake of fatty acids by liver, adipose, and muscle cells. Insulin plays a role in regulating this process.

Lipoproteins, which are particles made of lipids and proteins, determine how cholesterol is transported in the blood.

Chylomicrons are formed in the small intestine during digestion. Lipids, including cholesterol and other fatty acids, are packed into these particles for transport.

Adipocytes release stored fatty acids into the blood as free fatty acids, primarily used for energy by muscle cells.

The liver converts some absorbed fatty acids into VLDL, which are then secreted back into the bloodstream. This contributes to the transport of triglycerides and cholesterol throughout the body.

Chylomicrons are taken up by liver cells through interactions with apolipoprotein E and LDL receptors on the liver cell surface.

Higher blood cholesterol levels are linked to increased age and are typically higher in winter, potentially due to lower vitamin C intake.