What Is The Role Of Cholesterol

How To Check Your Cholesterol

A lipid profile blood test can measure your LDL cholesterol, HDL cholesterol, total cholesterol, and triglyceride levels. It is difficult to measure VLDL directly with a private home blood test but can be done through your GP. A lab will estimate your VLDL levels with the help of of your triglyceride level.

What Are The Functions Of Cholesterol

Although cholesterol has a bad reputation, the body actually needs it. Here are some functions of cholesterol:

• Helps in the formation and maintenance of cell membranes and structures.
• Important for the making of many critical hormones like cortisol, testosterone, progesterone, and estrogen.
• Used by the liver to make bile.
• Nerve cells use cholesterol for insulation.
• Also needed for the production of vitamin D.

Cholesterol And Membrane Rafts

Cholesterol displays a very important function as a component of cellular membranes, specially the cell plasma membrane where it is found in higher concentrations. Its positioning into the lipid bilayer and interaction with other lipids have a significant role in membrane fluidity together with other lipid components, such as the amount of sphingomyelin or the degree of saturation of the phospholipid acyl chains . Cholesterol fits most of its structure into the lipid bilayer and only the small hydroxyl group faces the external environment. As a consequence, its steroid rings are in close proximity and attracted to the hydrocarbon chains of neighboring lipids. This gives a condensing effect on the packing of lipids in cell membranes . However this effect seems to depend on the type of lipid it interacts with. As cholesterol hydrocarbon chain is rigid it tends to segregate together with fatty acids with saturated long acyl chains, especially sphingomyelin, leading to the formation of more compact liquid ordered and less fluid phases .

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Overview Of Cholesterol Synthesis

Cholesterol synthesis starts with acetyl-CoA, which is used to synthesize hydroxymethylglutaryl-CoA . The reactions in this initial stage are the same as in ketogenesis . However, while ketogenesis occurs in the mitochondria, HMG-CoA destined for sterol synthesis is formed in the cytosol. Therefore, like the synthesis of fatty acids, cholesterol biosynthesis depends on the export of acetyl-CoA from the mitochondria. Also as with fatty acids, multiple steps in the cholesterol synthesis require NADPH. How these two requirements are met has been discussed earlier .

All steps downstream of HMG-CoA occur in the smooth endoplasmic reticulum. HMG-CoA reductase reduces HMG-CoA to mevalonate this enzyme is the major target of regulation in the entire pathway. Mevalonate is converted to various isoprene intermediates. Several rounds of ââ¬Åpolymerizationââ¬ï¿½Ã¢â¬âIââ¬â¢m using the term looselyââ¬âproduce the linear hydrocarbon molecule squalene, which is cyclized to the first sterol intermediate. This molecule, lanosterol, is then converted to cholesterol by several successive modifications.

11.2.2

What Is The Role Of Cholesterol In The Cell Membrane

Cholesterol is a sterol made in animal cells. Sterols are molecules found in the cell membranes of plants. Sterols are basically steroid alcohols. Animal cells have cholesterol in the membrane and sterols in bilayers. Sterols occupy gaps left by kinks in the short-tailed hydrocarbon molecules. The short-tailed hydrocarbon molecules are essentially the HDL cholesterol or what is commonly known as good cholesterol. The chemical formula of a cholesterol molecule is C27H46O. Deposits of cholesterol appear as fatty layers and in common parlance are called lipids or fats.

Contents

• 1.5 Cholesterol functions in the cell membrane

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Only About 20% Of The Cholesterol In Your Bloodstream Comes From The Food You Eat Your Body Makes The Rest

Cholesterol has a bad reputation, thanks to its well-known role in promoting heart disease. Excess cholesterol in the bloodstream is a key contributor to artery-clogging plaque, which can accumulate and set the stage for a heart attack. However, the role of cholesterol in your body is not all negative.

To fully explain cholesterol, you need to realize that it’s also vital to your health and well-being. Although we measure cholesterol production in the blood, it’s found in every cell in the body. The Harvard Special Health Report Managing Your Cholesterol explains cholesterol as a waxy, whitish-yellow fat and a crucial building block in cell membranes. Cholesterol also is needed to make vitamin D, hormones , and fat-dissolving bile acids. In fact, cholesterol production is so important that your liver and intestines make about 80% of the cholesterol you need to stay healthy. Only about 20% comes from the foods you eat.

If you eat only 200 to 300 milligrams of cholesterol a day , your liver will produce an additional 800 milligrams per day from raw materials such as fat, sugars, and proteins.

Since cholesterol is a fat, it can’t travel alone in the bloodstream. It would end up as useless globs . To get around this problem, the body packages cholesterol and other lipids into minuscule protein-covered particles that mix easily with blood. These tiny particles, called lipoproteins , move cholesterol and other fats throughout the body.

Why Is Ldl Bad

LDL is known as the bad cholesterol because too much of it can lead to hardening of the arteries.

According to the American Heart Association, LDL leads to plaque accumulation on the walls of your arteries. When this plaque builds up, it can cause two separate, and equally bad, issues.

First, it can narrow the blood vessels, straining the flow of oxygen-rich blood throughout the body. Second, it can lead to blood clots, which can break loose and block the flow of blood, causing a heart attack or stroke.

When it comes to your cholesterol numbers, your LDL is the one you want to keep low ideally less than 100 milligrams per deciliter .

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What Is Cell Membrane

The cell membrane is described to be a fluid mosaic. This is because the structure of the membrane is flexible and fluid, and is also made up of a variety of molecules. There are four main molecules that make up the mosaic structure of the cell membrane.

They are phospholipids, cholesterol, proteins, as well as carbohydrates. Each of these molecules gives the cell membrane unique characteristics depending upon the way the molecules interact with each other. Large reservoirs of cholesterol reside in blood serum in the form of lipoproteins.

These are taken up by cells through endocytosis and recycled into the intracellular pool of cholesterol. Thus cholesterol cycles within as well as in and out of cells using many of these transport functions involving fission and fusion between different membranes.

Because cholesterol has profound physical effects on the membranes in which it resides, it is to be expected that membrane cholesterol also dramatically affects membrane fusion and membrane fission.

Can Stress Raise Your Cholesterol

High levels of cortisol from long-term stress may be the mechanism behind how stress can increase cholesterol. Adrenaline may also be released, and these hormones can trigger a fight or flight response to deal with the stress. This response will then trigger triglycerides, which can boost bad cholesterol.

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How Fat Moves From Food To The Bloodstream

Fat and cholesterol cant dissolve in water or blood. Instead, the body packages fat and cholesterol into tiny, protein-covered particles called lipoproteins. Lipoproteins can transport a lot of fat they mix easily with blood and flow with it. Some of these particles are big and fluffy, while others are small and dense. The most important ones are low-density lipoproteins , high-density lipoproteins , and triglycerides.

• Low Density lipoproteins

Low-density lipoproteins carry cholesterol from the liver to the rest of the body. Cells latch onto these particles and extract fat and cholesterol from them. When there is too much LDL cholesterol in the blood, these particles can form deposits in the walls of the coronary arteries and other arteries throughout the body. Such deposits, called plaque, can narrow arteries and limit blood flow. When plaque breaks apart, it can cause a heart attack or stroke. Because of this, LDL cholesterol is often referred to as bad, or harmful, cholesterol.

• High-density lipoproteins

High-density lipoproteins scavenge cholesterol from the bloodstream, from LDL, and from artery walls and ferry it back to the liver for disposal. Think of HDL as the garbage trucks of the bloodstream. HDL cholesterol is often referred to as good, or protective, cholesterol.

• Triglycerides

In general, the lower your LDL and the higher your HDL, the better your chances of preventing heart disease and other chronic conditions.

How To Lower Vldl Cholesterol

Reducing triglyceride levels will help reduce your VLDL levels.

Your body makes a type of fat called triglycerides when you eat more calories than you need. Eating in a way that is good for you can help prevent this. Following hunger cues, eating slowly, chewing thoroughly, thinking about how it makes you feel, and stopping when full are some of the things that can be done with conscious eating.

In susceptible people, small amounts of alcohol can raise triglyceride levels, so be sure to keep your alcohol intake low. It is better to spend alcohol-free days as the harmful effects of alcohol intake far outweigh its benefits.

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How Cholesterol Moves Around The Body

Cholesterol is a white, insoluble and waxy substance. It is carried around the body by two key transport systems in the blood, which include:

• Low-density lipoprotein cholesterol carries most of the cholesterol that is delivered to cells. It is called the bad cholesterol because when its level in the bloodstream is high, it can clog up your arteries.
• High-density lipoprotein cholesterol is called the good cholesterol, because it helps remove excess cholesterol out of the cells, including cells in the arteries.

How Do I Know What My Hdl Level Is

A blood test can measure your cholesterol levels, including HDL. When and how often you should get this test depends on your age, risk factors, and family history. The general recommendations are:

For people who are age 19 or younger:

• The first test should be between ages 9 to 11
• Children should have the test again every 5 years
• Some children may have this test starting at age 2 if there is a family history of high blood cholesterol, heart attack, or stroke

For people who are age 20 or older:

• Younger adults should have the test every 5 years
• Men ages 45 to 65 and women ages 55 to 65 should have it every 1 to 2 years

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Enhancing Up Immune System:

Cholesterol is crucial for our immune system to function effectively. Our immune cells base on cholesterol to fight against infections and repair themselves after the fight. Furthermore, LDL-cholesterol, also called bad cholesterol, directly binds and immobilizes dangerous bacterial toxins, halting them from doing any damage in the body. People with low-level cholesterol are prone to different infections, suffer from them longer and are more probable to die from an infection.

When the body has some healing jobs to do, it produces some cholesterol and supplies it to the site of the damage that is why regarded it as a chief healing agent. When we have a brutal infection, LDL-cholesterol goes up to against with the bacterial or viral disease.

Confirming Unhealthy Cholesterol Levels

A lipid panel usually measures total cholesterol, LDL cholesterol, and HDL cholesterol. Your test may also show the level of non-HDL cholesterol, which includes LDL and all other types of bad cholesterol that raise your risk of atherosclerosisand complications.

Your doctor may diagnose you with high blood cholesterol if your total or non-HDL cholesterol level is higher than what is healthy for you. Your doctor might also find that your level of good HDL cholesterol is too low.

Your doctor may ask that you fast before a lipid panel. This means you do not eat or drink anything except water for 9 to 12 hours before your blood is drawn. Ask you whether you should take your usual medicines before the test and if there are any other special instructions.

Your doctor may order other tests to help decide whether medicines are needed to lower your risk of heart and blood vessel diseases. These may include a coronary calcium scan, and blood tests for levels of C-reactive protein and lipoprotein-a.

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Transcriptional Regulation Of Cholesterol Synthesis Starts In The Endoplasmic Reticulum

The sterol response element is a DNA consensus sequence that controls the transcription of HMG-CoA reductase. The corresponding SRE-binding protein is initially embedded in the ER membrane, and thus evidently unable to get in touch with its DNA target. SREBP is bound to a second protein, namely, SREBP cleavage activating protein . This protein is the actual cholesterol sensor it can adopt two different conformations, depending on the content of cholesterol in the surrounding membrane. The conformation that predominates at high cholesterol content lets SCAP bind to a third protein, INSIG.69 When this ternary complex forms, it is rapidly targeted toward proteolytic degradation, and that is the end of it.

At low cholesterol concentrations, however, SCAP does not bind to INSIG, and this is when things get interesting, as shown in the next slide.

11.3.2

What Does Ldl Cholesterol Do

Bad cholesterol is the term that refers to low-density lipoprotein cholesterol. Its a bit oversimplified, as LDL helps you deliver cholesterol to your cells which is important for your health. Its strongly associated with a higher risk of heart disease if the amount of LDL circulating in your blood is too high.

High levels of LDL circulating in your blood can lead to a build-up of cholesterol plaque in your arteries. This process can sometimes block your blood vessels. This can affect the blood flow.

• Increased blood pressure
• Heart Dysfunction
• Renal Pathologies

It is important to know that this process takes a long time. There are a lot of things you can do to help lower your LDL levels if they are raised. There are a lot of things you can do to change the process.

Research shows that the role of low-density lipoprotein cholesterol in the development of heart disease is supported by decades of research. Although, only one of many factors that contribute to heart disease.

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What Is The Function Of Cholesterol

Cholesterol has many functions, one being that it helps construct and maintain cell membranes this gives cells their form and protects them from damage caused by outside forces. The body needs certain amounts of good or HDL cholesterols to help with these roles, but if they get too high then there are possible side effects such as cardiovascular disease. Its also important for bodily tissue to have some fat content so without any dietary fats present your tissues would eventually become brittle. Processed oils like vegetable oil contain trans-fats which arent healthy for humans and if you take in too much of them it can lead to the aforementioned problems.

One function of good cholesterol is its role which helps construct and maintain cell membranes this gives cells their form and protects them from damage caused by outside forces. The body needs certain amounts for healthy HDL cholesterol, but if they get too high then there are possible side effects such as cardiovascular disease. Its also important for bodily tissue to have some fat content so without any dietary fats present your tissues would eventually become brittle. Processed oils like vegetable oil contain trans-fats which arent healthy for humans and if you take in too much of them it can lead to the aforementioned problems.

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Lifestyle Tips To Cut Cholesterol

Changing some of your lifestyle habits may also help to reduce your cholesterol and triglyceride levels. Suggestions include:

• Cease alcohol consumption or reduce your alcohol intake to no more than one or two drinks a day. Avoid binge drinking. This may help lower your triglyceride levels.
• Dont smoke. Smoking increases the ability of LDL cholesterol to get into artery cells and cause damage.
• Exercise regularly . Exercise increases HDL levels while reducing LDL and triglyceride levels in the body.
• Lose any excess body fat. Being overweight may contribute to raised blood triglyceride and LDL levels.
• Control your blood sugar levels if you have diabetes. High blood sugars are linked to an increased risk of atherosclerosis , heart attacks and strokes.

Cholesterol Esters Can Be Stored Inside Lipoprotein Particles

Cholesterol is amphiphilic and tends to accumulate at lipid/water interfaces, with the OH group exposed to the aqueous phase. Free cholesterol can therefore be transported only within the outermost layer of lipid molecules of a lipoprotein particle. In contrast, cholesterol esters are entirely hydrophobic and readily partition into the interior of lipoprotein particles. The LCAT reaction therefore greatly increases the transport capacity of HDL particles for cholesterol.

11.5

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