19/05/2025
CLARIFYING LIPID PROFILE
🧠 Let's break it down with the functions and design of LDL, HDL, and TRIGs.
A lipoprotein is a molecular complex made of lipids (fats) and proteins. Lipids are not water-soluble, so to be transported in the blood (which is water-based), they bind to proteins, forming lipoproteins.
🟡 LDL (Low-Density Lipoprotein)—“The Delivery Truck”
✅ The primary role is to deliver cholesterol from the liver to peripheral cells and tissues that need it. Cholesterol is essential for cell membrane structure, synthesis of steroid hormones, vitamin D production, and even bile acid formation.
🧬 Why this happens:
The liver packages cholesterol into VLDL (very low-density lipoproteins), which circulates in the blood.
As VLDL loses triglycerides, it becomes LDL, now rich in cholesterol.
LDL binds to LDL receptors on cell surfaces → gets internalized → cholesterol is used or stored by the cell.
⚠️ Problem:
If there’s too much LDL or it’s not cleared properly, it can:
Deposit cholesterol in blood vessel walls
Promote plaque formation → atherosclerosis → heart disease
🔵 HDL (High-Density Lipoprotein)—“The Cleanup Crew”
✅ Primary Role is to remove excess cholesterol from tissues (including blood vessel walls) and return it to the liver for Recycling, Conversion into bile acids and excretion, which protects against cholesterol buildup in arteries.
🧬 Why this happens:
Cells do not have a good way to get rid of extra cholesterol on their own.
HDL acts like a scavenger since it accepts free cholesterol from cells and tissues in a process called reverse cholesterol transport.
HDL carries this cholesterol back to the liver → the liver removes it from the body via bile.
🟠 Triglycerides (TRIGs)—“The Energy Cargo”
Triglycerides are the main form of fat in the body and blood. They act as a concentrated energy source, especially during fasting or between meals.
🧬 Where TRIGs Come from and Where They Go:
After eating, excess calories, especially from carbohydrates and fats, are converted into triglycerides in the liver and intestines.
These triglycerides are packaged into chylomicrons (from intestines) and VLDL (very low-density lipoproteins) by the liver
VLDL travels through the bloodstream delivering triglycerides to the muscle cells (for energy) and fat (adipose) tissue (for storage)
As VLDL loses triglycerides, it becomes IDL and eventually LDL (now more cholesterol-rich).
Excess triglycerides in the blood are associated with insulin resistance, Obesity, Metabolic syndrome, Pancreatitis (if very high) and increased cardiovascular risk, especially when combined with low HDL and small, dense LDL
🔁 How TRIGs Interact with LDL & HDL
VLDL (trig-rich) becomes LDL (cholesterol-rich) → LDL delivers cholesterol to tissues.
HDL can also take up some triglycerides, but its main role is in cholesterol cleanup.
Enzymes like lipoprotein lipase (LPL) help break down TRIGs from VLDL and chylomicrons for tissue use.
