#2/n: What is HDL and LDL? There is no 'good' and 'bad'.

So, in my previous post I talked about what cholesterol is, and let me re-iterate that cholesterol = life. I love and appreciate cholesterol, and I thank it for allowing me to have a functioning brain, or allowing me to deal with the stresses of life via cortisol, or even allowing me to feel love via progesterone, and having regular bowel movements via bile acids. Shout out to all my homies (cells) in my body right now who are working hard to produce cholesterol in order to keep things going. 

#1: There is no such thing as blood cholesterol ...

Yes, you read that right. Cholesterol cannot dissolve in our blood! If it did, then our blood would be like a mix of oil and water- how would that work? 

Instead cholesterol is found in the blood in the cell membranes (all cell membranes are made from cholesterol).  Or, it is stored in the form of an ester within something called a lipoprotein.

EVERY CELL IN YOUR BODY IS MADE OF CHOLESTEROL. EVERY SINGLE CELL.

#2: What is this 'good' cholesterol and 'bad' cholesterol? Such a thing does not exist..

There cannot be a good cholesterol or a bad cholesterol, because cholesterol is cholesterol - it is the same exact molecular thing whether it is in HDL or LDL.
Cholesterol is found as esters (see previous article), within proteins such as LDL and HDL.

LDL and HDL are proteins, they are NOT cholesterol. These proteins are part of ONE SYSTEM that interacts with one another, and need each other to function. 

They are proteins that carry many things within them such as:

• cholesterol in the form of esters
• phospholipids 
• triglycerides (3 chains of fats)
• fat soluble vitamins and anti-oxidants such as Vitamin A, Vitamin E, CoQ10

There are various types of lipoproteins such as:

• Chylomicrons
• VLDL
• IDL
• LDL
• Lp(a)
• HDL 

And perhaps there are more which we do not know of! These proteins all have different tags or markers on them for identification.

What are these proteins and why do they exist?

Our liver produces a lipoprotein called VLDL (very low density lipoprotein), which then converts into IDL (intermediate density lipoprotein) and then LDL (low density lipoprotein). All of these particles have a little “identification” marker called Apo-B on them. 

These proteins play numerous roles in the body such as:

• Transporting fatty acids to various tissues to be used as energy. The heart primarily gets energy by oxidizing fatty acids.

• 💁🏽‍♀️ if you are a woman, your ovaries have LDL receptors. LDL will supply cholesterol to your ovaries to produce hormones such as oestrogen and progesterone.

• 🙋‍♂️if you are a man, your testicles will have LDL receptors. LDL will supply cholesterol to your testicles, because testosterone is made from cholesterol.

• 🧠 our brain is made of fat and cholesterol. But because LDL cannot cross its way into the blood brain barrier, the brain produces all of the cholesterol it needs. And it needs LOTS of it. We still do not understand all of the roles that cholesterol plays in the brain. But let me tell you something - your brain loves cholesterol!

• 👉🏽every nerve cell in the body and brain is lined by a sheath called “myelin” which is made from cholesterol. And who gives cholesterol to our nerve cells? LDL. HIGH CHOLESTEROL IS ESSENTIAL FOR ALL YOUR NERVES INCLUDING THE BRAIN! [Fig 1D] This is why statins can cause nerve damage problems. More on that later 👋 [1,2]

• 🚌 transport of vitamins: LDL, our truck driver transports fat soluble vitamins such as vitamin A, D, E, K to different parts of the body. Did you know that vitamin A is a saturated fat? How dangerous! And vitamin D, is made from cholesterol? Lethal, indeed.

• 🍵 antioxidant properties and modulation of inflammation: yes! you read that right - green tea and red wine don’t stand a chance compared to our body's natural antioxidants. Cholesterol is an antioxidant! Our cell membranes are quite fragile, and cholesterol fights the bad guys in order to protect our cell membranes! And when they get damaged, LDL, with its tool box of anti-oxidant vitamins and chemicals, comes and helps out. LDL has antioxidants within it which clears out the bad guys (free radicals) that can be very very dangerous! vitamin E, for example is a potent anti-oxidant that protects our cell membranes from damage. cholesterol helps regenerate the vitamin E in our cells membranes as well. Also, CoQ10 is an essential antioxidant that has a multitude of functions - it is made FROM cholesterol. 

• 🧑‍🔧 fixing of damaged cells: When a cell membrane is damaged, whether it is a cut from a knife, or an injury in your blood vessels from high blood sugar, smoking or stress, cholesterol will be needed for repairing the cell membrane. And guess who transports cholesterol to these damaged cells? You guessed it. LDL, and Lp(a) a special type of LDL that stabilizes clots.

• 🦀 killing cancer cells through a process of ‘immune surveillance’: Cancer cells pop up in our body at random times, from time to time, but if we have a good immune system, they get killed off very quickly. LDL protein has a key function in recognizing, and helping to fight cancer cells. This is why those with high cholesterol live longer and have lower rates of cancer, infection and death.

• 🦠 if there’s a virus or bacteria trying to kill you, the LDL, with its toolbox of antioxidants plays a role in preventing the virus or bacteria from hijacking your cells. This is called ‘Quorum sensing’. See chapter 3.

• 💚 bile acids, used for digestion are made from cholesterol, and these are designed to digest fats and fat-soluble vitamins such as vitamin A, D, E, K. if you eat a very low fat diet, then the bile acids don’t get released into the digestive tract, they just stay there in the gall bladder. This is called ‘gall bladder stasis’ which can cause gall stones! YES A LOW-FAT DIET CAN CAUSE GALL STONES!

• ☀️our skin cells have LDL receptors, because when we are in the sunshine, our skin cells produce vitamin D from cholesterol.

• 😖 if you are stressed out, need to exercise, run from a tiger, study for an exam, your body needs a hormone called cortisol (the stress hormone). Your adrenal glands have an LDL receptor so that it can produce cortisol from cholesterol in times of need. If didn’t have enough cholesterol in my body, I would have struggled to deal with the stress of reading so much research!

• REVERSE CHOLESTEROL TRANSPORT: When there is inflammation in the body, it can activate the innate immune system (as explained above LDL and Lp(a) are a part of the immune system).. When LDL fights an infection or a noxious stimulus, it can get oxidised to become a foam cell. If there is continuous inflammation in the body, that can be bad news and increase your risk of getting a plaque or heart attack. HDL and LDL plays a role in clearing out these foam cells, this is called RCT or reverse cholesterol transport. Once HDL clears cholesterol from foam cells, it gives it to LDL, which then returns to the liver. [2]

Why is HDL considered good?

• This is simply because those with high HDL cholesterol have low risk of heart disease. The reason for this is that HDL cholesterol, when high is a sign of insulin sensitivity. That is it.
• HDL has a role in something called reverse cholesterol transport, but so does LDL. HDL actually gives cholesterol to LDL in order to return back to the liver. 
• HDL cannot complete it's function without LDL, therefore it does not make sense that LDL is bad.

What is LDL cholesterol and HDL cholesterol on a blood test?

• The amount of cholesterol (as esters) carried within each of these proteins is what your blood test tells you.
• This is not an exact science, but an estimation.
• TC = HDL + VLDL + IDL + LDL + Lp(a)
• SO, on a standard blood test, LDL-C Or so called 'bad' cholesterol (which is not really bad, but it's good for you), is estimated based on a random equation. It's not even proper mathematics.
• The LDL-C blood test does not accurately measure the amount of cholesterol within your LDL particles.

The entire lipoprotein system is a marvellous, complex work of evolution that has evolved in vertebrate animals. It does not make sense that HDL is good and LDL is bad, because they work together. If LDL is so bad, then all animals with high LDL should get heart attacks - but only civilized people and zoo animals get heart disease.

What is a plaque? A blood clot in your arteries!

Heart attack happens when your arteries get 'clogged' up, essentially. Plaque is not just made up of cholesterol, but of various components such as:

• white blood cells and macrophages
• foam' cells which are white blood cells that contain oxidized LDL and Lp(a) within it. 
• red blood cells that have been engulfed by WBCs
• smooth muscle cells that migrate and make the plaque bigger.

A plaque is nothing but a blood clot that has built up in the wall of the artery. I repeat - a plaque is a blood clot that builds up in the wall of the artery, over many years, due to damage to the arterial wall. [1] This can happen only when the inner lining of the blood vessel (endothelium) is damaged - as in high blood sugar, smoking, emotional stress, blood pressure, pollution.

This is why doctors prescribe anti-coagulants such as aspirin to prevent and treat heart attacks.

Why do plaques contain cholesterol! Surely this must come from LDL!

It is physiologically impossible for the cholesterol within the plaque to come from LDL. But before I explain why, let’s look at what is LDL?

• LDL cannot penetrate the endothelium (inner lining of the blood vessel), because the endothelium is a one-layered thin wall with 'tight' junctions that do not allow ANYTHING to pass through. If LDL could pass through, so could water. And then you would start getting puffy and leaky everywhere. This happens in dangerous conditions such as dengue fever. [link to paper on LDL functions]
• LDL cannot form a foam cell UNLESS it is oxidized, because the plaque is made of mostly foam cells! 
• The cholesterol within the plaque cannot be from LDL, because:
• The cholesterol within LDL is stored as an ester, and the cholesterol found within the plaque is free cholesterol crystals. Normally, the enzymatic reaction needs to occur to convert the ester into crystals. 
• SOME of the LDL within the plaques may break down, liberating esters and perhaps becoming crystals. There is evidence for this. But given how small LDL is, it is unlikely to be solely from LDL.

The only place from which free cholesterol comes is from the RED BLOOD CELL, whose membrane is rich in free cholesterol (remember cholesterol is a part of the cell membrane). It is also likely that when there is chronic inflammation, foam cells will spit out cholesterol continuously.

[1] The Clot Thickens, Malcolm Kendrick

[2] Reverse cholesterol transport - Wikipedia; LDL Contributes to Reverse Cholesterol Transport | Circulation Research