Learning Lipids

Learning Lipids

Dr. S.M.Sadikot.
Hon. Endocrinologist,
Jaslok Hospital and Research Centre,
Mumbai 400026

Your doctor must have asked you to carry out a blood test for your "Lipid Profile". After seeing your results, you may have been told that your lipid levels are abnormal and that this would require correction.

What are these "lipids" and have you wondered what these have to do with your diabetes?

People who have diabetes, have abnormal levels of "lipids" in their blood.

Commonly known as blood "fats", basically, when we talk about lipids, we are referring to the levels of cholesterol and triglycerides in the blood.

Cholesterol and triglycerides are two forms of lipid, or fat. Both cholesterol and triglycerides are necessary for life itself.

Cholesterol has received such a bad name that many people feel that all cholesterol is bad. This is far from true. Everyone has cholesterol; we all need it. In fact, without cholesterol, life may not be possible!

Cholesterol is a waxy substance that occurs naturally in all parts of the body and is needed by the body to function normally. It is present in cell walls or membranes everywhere in the body, including the brain, nerves, muscle, skin, liver, intestines, and heart. The body uses cholesterol to produce many hormones, vitamin D, and the bile acids that help to digest fat. It takes only a small amount of cholesterol in the blood to meet these needs.

However, problems arise when the levels of cholesterol exceed the amounts which are necessary. Excess cholesterol can lead to atherosclerosis, a condition in which fat and cholesterol are deposited in the walls of the arteries in many parts of the body, including the coronary arteries feeding the heart. In time, narrowing of the coronary arteries by atherosclerosis can produce the signs and symptoms of CHD, including angina and heart attack.

Triglycerides are the main type of fat in the body. Fat molecules are high-energy fuels that can be used by muscles or stored in fat cells for later use. Most of your body's fat is in the form of triglycerides stored in fat tissue. When required as a source of energy, they are carried in the blood. Only a small portion of your triglycerides is found in the bloodstream. Here again, if the blood contains too high a level of triglycerides, one is at an increased risk for atherosclerosis!

There are two sources for these lipids: dietary sources, and endogenous sources (i.e., manufactured within the body).

Dietary cholesterol and triglycerides mainly come from eating animal products and saturated fat. These dietary lipids are absorbed through the gut, assembled there into special packets called chylomicrons, and then are delivered through the bloodstream to the liver, where they are processed.

One of the main jobs of the liver is to make sure all the tissues of the body receive the cholesterol and triglycerides they need to function. Whenever possible (i.e., for about 8 hours after a meal), the liver takes up dietary cholesterol and triglycerides from the chylomicrons produced in the intestines. During times when dietary lipids are not available, the liver produces cholesterol and triglycerides itself.

The liver then packages the cholesterol and triglycerides, along with special proteins, into tiny spheres called lipoproteins. The lipoproteins are released into the circulation, and are delivered to the cells of the body. The cells remove the needed cholesterol and triglycerides from the lipoproteins, as they are needed

Cholesterol travels in the blood in packages called lipoproteins. Just like oil and water, cholesterol, which is fatty, and blood, which is watery, do not mix. However, cholesterol is able to "dissolve" in the blood when it joins up with special proteins. These proteins escort cholesterol, triglycerides and other substances throughout the blood stream. When they are all together (cholesterol, triglycerides and these special proteins) they are called lipoproteins.

One can think of lipoproteins as cholesterol luggage. Lipoproteins carry cholesterol, triglycerides and other material making it possible for these substances to be transported to areas where they are needed via the bloodstream. There are four basic types of cholesterol "carrying cases": chylomicrons, very-low-density lipoproteins (VLDL), low-density lipoproteins (LDL), and high-density lipoproteins (HDL).

Classification of Lipids

Chylomicrons are lipoproteins that transport the triglycerides we eat. VLDL's transport triglyceride and cholesterol molecules that are made in the liver. Both chylomicrons and VLDL's carry triglycerides either to our muscles to be used as fuel, or our fat stores where the triglycerides are deposited for future use.

The "BAD", the "GOOD" and………..the "UGLY"!

BadYou have probably heard of LDL as the "bad cholesterol." But LDL is not all bad; we need it to transport cholesterol and some vitamins in our bloodstream. The problem is we often have too much LDL. Our liver is important in clearing LDL. When the LDL reaches the liver it is removed from the blood. However, if the liver cannot remove the LDL fast enough, either because of a genetic defect or because our diet is too high in fat or calories, the LDL level in the blood increases. When the LDL is high there are cells in our artery walls that act as LDL sponges. The LDL tends to stick to the lining of the blood vessels, leading to the stimulation of "atherosclerosis," or hardening of the arteries. The cells fill up with LDL and cause the walls to bulge and make the center of the blood vessel smaller.

Plaques

This is how atherosclerotic plaques are formed and ultimately results in hardening of the arteries. Atherosclerotic "plaques" cause narrowing of the arteries. Thus, the more LDL-cholesterol you have in your blood, the greater your risk of atherosclerosis and all its consequences such as heart disease (CHD), paralytic strokes, etc.

LDL's carry most of the cholesterol in the blood, and the cholesterol from LDL's is the main source of damaging buildup and blockage in the arteries, which is for this reason that LDL-Cholesterol and its close relation the IDL are popularly known as the "Bad" cholesterols.

Cholesterol

You have probably heard of HDL as the "good cholesterol."

HDL is made in the liver and the intestines and sent out into the blood to gather up excess cholesterol. HDL's carry cholesterol in the blood from other parts of the body back to the liver, which leads to its removal from the body. There is some evidence that the HDL molecule "scours" the walls of blood vessels, and cleans out excess cholesterol. So HDL's help keep cholesterol from building up in the walls of the arteries. High levels of HDL will remove cholesterol from arteries and carry it back to the liver.

Much evidence has now accumulated that increased HDL cholesterol levels are associated with a lower risk of heart disease, and that low HDL cholesterol levels are associated with an increased risk of heart disease. Thus, HDL cholesterol appears to be "good."

Good

Till recently, little attention was paid to the levels of serum triglycerides. It was well known that the levels of serum triglycerides were raised in some people and especially so in people with diabetes. While high triglyceride levels were thought to have an "association" with heart disease, it was felt that they were not directly involved.

The problem is, patients with elevated triglyceride levels almost invariably have other major risk factors for heart disease, mainly obesity, diabetes, and/or high blood pressure and low HDL levels. All efforts were spent on trying to treat these associated risk factors.

However, recent evidence strongly suggests that an elevated triglyceride level is a significant risk factor for cardiac disease, and especially so in people with diabetes.

Ugly

In the bloodstream, "bad" cholesterol is carried in LDL, "good" cholesterol is carried in HDL, and triglycerides are carried in VLDL. Most cholesterol in the blood comes from LDL. Only a small proportion is from HDL cholesterol. Thus, the total cholesterol level in the blood is usually a reflection of the amount of LDL cholesterol.

There are a number of factors that influence a person's cholesterol levels. They include diet, age, weight, gender, genetics, diseases and lifestyle.

Diet

Foods rich in fats and cholesterol can increase the cholesterol levels;

Age

The blood levels of cholesterol tend to increase as we age--a factor doctors consider when when deciding treatment options for patients with certain cholesterol levels.

Weight

People who are overweight are more likely to have high blood cholesterol levels. They also tend to have lower HDL levels. The location of the excess weight also seems to play a role in cholesterol levels. A greater risk of increased cholesterol levels occurs when that extra weight is centered in the abdominal region, as opposed to the legs or buttocks.

Gender

Men tend to have higher LDL levels and lower HDL levels than do women, especially before age 50. After age 50, when women are in their post-menopausal years, decreasing amounts of estrogen are thought to cause the LDL level to rise.

Genetics

Some people are genetically predisposed to having high levels of cholesterol. A variety of minor genetic defects can lead to excessive production of LDLs or a decreased capacity for their removal. This tendency towards high cholesterol levels is often passed on from parents to their children. If your parents have high cholesterol, you need to be tested to see if your cholesterol levels are also elevated.

Diseases

Diseases such as diabetes can lower HDL levels, increase triglycerides and accelerate the development of atherosclerosis. High blood pressure, or hypertension, can also hasten the development of atherosclerosis, and some medications used to treat it can increase LDL and triglycerides and decrease HDL levels.

Lifestyle

Factors that negatively affect cholesterol levels also include high levels of stress, which can raise total cholesterol levels, and cigarette smoking, which can lower a person's HDL level as much as 15 percent. On the other hand, strenuous exercise can increase HDL levels and decrease LDL levels. Exercise also can help reduce body weight, which, in turn, can also help reduce cholesterol. Recent research has shown that moderate alcohol use (one drink per day for women, two drinks a day for men) can raise HDL cholesterol and therefore reduce the risk of heart attack. Despite such research, it is difficult to recommend the habitual use of alcohol, because there are also negative health consequences associated with alcohol use and a high potential for abuse.

Always remember that risk factors for high cholesterol and cardiovascular disease don't exist in a vacuum--they tend to amplify each other. Reducing the risk of a cardiovascular disease involves eliminating all of the risk factors that we can control and seeking.

It is worthwhile to remember that it is only your age, sex and genes, which are beyond your control.

High blood cholesterol and triglycerides themselves may not cause symptoms, so many people are unaware that their lipids are high and that they are at an increased risk. It is extremely important to find out what your lipid numbers are because lowering cholesterol and triglyceride levels and increasing HDL levels lessens the risk for developing heart disease and reduces the chance of a heart attack or dying of heart disease, even if you already have it.

Lowering your blood cholesterol level can slow, stop, or even reverse the buildup of plaque. Cholesterol lowering can reduce your risk of a heart attack by lowering the cholesterol content in unstable plaques to make them more stable and less prone to rupture. This is why lowering your LDL-cholesterol is such an important way to reduce your risk for having a heart attack. Even in people who have had one heart attack, the chances of having future attacks can be substantially reduced by cholesterol lowering.

This is important for everyone--younger, middle age, and older adults; women and men; and people with or without heart disease.

When you get a blood test for cholesterol levels, your doctor may also check your levels of total, HDL and LDL cholesterol and triglycerides.

LDL Cholesterol

Less than 100 Optimal
100 to 129 Near Optimal
130 to 159 Borderline High
160 to 189 High
190 or Greater Very High

Total Cholesterol

Less than 200 Desirable
200 to 239 Borderline High
240 or Greater High

HDL Cholesterol

Less than 40 (male) Low
Less than 45 (females) Low
60 or Greater High

Triglycerides

Less than 150 Optimal

As with many other health problems, prevention is the best medicine. You can help prevent high cholesterol and reduce your risk of cardiovascular disease by:

  • Keeping your weight in check.
  • Eating no more than 300 mg of cholesterol each day.
  • Getting no more than 30% of your daily calories from fat.
  • Exercising three to four times a week (vigorously if you can, but moderate exercise is better than none at all).
  • Quit Smoking and the use of tobacco in any form.

We have seen above that the major part of the blood cholesterol consists of LDL, the "bad" cholesterol. The "good" HDL is just a small portion of the total cholesterol. The main aim is therefore to lower the cholesterol which would decrease the LDL levels, increase the HDL levels, and to normalize the blood levels of the "ugly" triglycerides.

What are the factors which affect the LDL and the HDL levels?

HDL, LDL

a) Diagnose and treat the associated factors

You must keep the diabetes and the blood pressure under good control. Often a good control of the blood glucose levels will lead to a rise in the HDL levels and a drop in the raised triglyceride levels. Moreover, this will definitely help in decreasing the complications such as atherosclerosis.

b) Lifestyle Modifications

Diet Your diet should be low on fats and cholesterol rich foods. Your doctor will guide you on the foods which you should cut down on or avoid, if possible.

Exercise Regular exercise helps in lowering the LDL levels. It increases the HDL levels and also causes the triglyceride levels to fall. We have shown above the most important lipid abnormality in a person with diabetes is low HDL and high triglyceride levels. So exercise would be an excellent option for you, especially if you also are overweight with a large waist measurement (raised Waist to Hip ratio).

Weight If you are overweight and especially if this is "central", i.e. you have a large waist size, it is very important that you use diet and exercise to normalize the weight.

Lifestyle Modifications

c) Medications

There are four major groups of medications which are currently available for use in correcting the lipid abnormalities. These are the bile acid-binding resins, niacin, fibrates, and the HMG-CoA reductase inhibitors ( statins).

Your doctor will decide which is appropriate for you.

Is there some way I can increase the levels of the "good" HDL Cholesterol?

As opposed to lowering your bad cholesterol, it is sometimes more difficult to raise your good cholesterol levels. Most efforts that will lower the bad cholesterol 30% will only increase the good HDL cholesterol 5%. However, remember that even this modest improvement is magnified by the improved ratio of bad to good cholesterol.

Some steps which you can take in addition to whatever your doctor prescribes are

  • Regular exercise.
  • Stopping smoking not only lowers the risk of heart disease directly, but also will generally result in an increase in the HDL.
  • It is true that an ounce or so of alcohol, particularly red wine will raise HDL, but please don't start drinking alcohol for this reason!

My triglycerides are high. How can that be treated?

If treatment is needed for high triglycerides (hypertriglyceridemia), the principles are similar to that for high cholesterol. That is:

  • Reverse any medical conditions or change medication which may be worsening the problem.
  • Low fat diet (this is even more important than with high cholesterol)
  • Maintain ideal body weight (this is particularly important)
  • Exercise regularly (this is particularly important, too)
  • Avoid alcohol
  • Avoid simple sugars
  • Obtain good control of diabetes if present
  • Your doctor may prescribe drugs which are more specific in lowering triglyceride levels.

Finally,

You must realize that:

Every 1% reduction in your cholesterol reduces your risk of getting a heart attack by 2%.

Every 1 mg/100ml (not percent!) increase in your good cholesterol lowers your risk 2-5%.

So what's stopping you?