HYPERLIPIDEMIA

What is hyperlipidemia?

Hyperlipidemia is an elevation of lipids (fats) in the bloodstream. These lipids include cholesterol, cholesterol esters (compounds), phospholipids and triglycerides. They're transported in the blood as part of large molecules called lipoproteins.

These are the five major families of blood (plasma) lipoproteins:

1 chylomicrons
2 very low-density lipoproteins (VLDL)
3 intermediate-density lipoproteins (IDL)
4 low-density lipoproteins (LDL)
5 high-density lipoproteins (HDL)

What are the types of hyperlipidemia?

When hyperlipidemia is defined in terms of a class or classes of elevated lipoproteins in the blood, the term hyperlipoproteinemia is used. Hypercholesterolemia is the term for high cholesterol levels in the blood. Hypertriglyceridemia refers to high triglyceride levels in the blood.

What is cholesterol?

Cholesterol is a soft, waxy substance found among the lipids (fats) in the bloodstream and in all your body's cells. It's an important part of a healthy body because it's used to form cell membranes, some hormones and is needed for other functions. But a high level of cholesterol in the blood -- hypercholesterolemia -- is a major risk factor for coronary heart disease, which leads to heart attack.

Cholesterol and other fats can't dissolve in the blood. They have to be transported to and from the cells by special carriers called lipoproteins. There are several kinds, but the ones to focus on are low-density lipoprotein (LDL) and high-density lipoprotein (HDL).

What is LDL cholesterol?

Low-density lipoprotein is the major cholesterol carrier in the blood. If too much LDL cholesterol circulates in the blood, it can slowly build up in the walls of the arteries feeding the heart and brain. Together with other substances it can form plaque, a thick, hard deposit that can clog those arteries. This condition is known as atherosclerosis. A clot (thrombus) that forms near this plaque can block the blood flow to part of the heart muscle and cause a heart attack. If a clot blocks the blood flow to part of the brain, a stroke results. A high level of LDL cholesterol (160 mg/dL and above, or 4.2 mM and above) has been shown conclusively to reflect an increased risk of heart disease. That's why LDL cholesterol is called "bad" cholesterol. Lower levels of LDL cholesterol reflect a lower risk of heart disease.

What is HDL cholesterol?

About one-third to one-fourth of blood cholesterol is carried by HDL. Medical experts think HDL tends to carry cholesterol away from the arteries and back to the liver, where it's passed from the body. Some experts believe HDL removes excess cholesterol from plaques and thus slows their growth. HDL cholesterol is known as "good" cholesterol because a high HDL level seems to protect against heart attack. The opposite is also true: a low HDL level (less than 40 mg/dL or 1.0 mM) indicates a greater risk. A low HDL cholesterol level also may raise stroke risk.

What about cholesterol and diet?

People get cholesterol in two ways. The body -- mainly the liver -- produces varying amounts, usually about 1,000 milligrams a day. Foods also can contain cholesterol. Foods from animals (especially egg yolks, meat, poultry, fish, seafood and whole-milk dairy products) contain it. Foods from plants (fruits, vegetables, grains, nuts and seeds) don't contain cholesterol.

Typically the body makes all the cholesterol it needs, so people don't need to consume it. Saturated fatty acids are the main culprit in raising blood cholesterol, which increases your risk of heart disease. Trans-fats also raise blood cholesterol. But dietary cholesterol also plays a part. The average American man consumes about 337 milligrams of cholesterol a day; the average woman, 217 milligrams.

Some of the excess dietary cholesterol is removed from the body through the liver. Still, it is recommended that you limit your average daily cholesterol intake to less than 300 milligrams. If you have heart disease, limit your daily intake to less than 200 milligrams. Still, everyone should remember that by keeping their dietary intake of saturated fats low, they can significantly lower their dietary cholesterol intake. Foods high in saturated fat generally contain substantial amounts of dietary cholesterol.

People with severe high blood cholesterol levels may need an even greater reduction. Since cholesterol is in all foods from animal sources, care must be taken to eat no more than six ounces of lean meat, fish and poultry per day and to use fat-free and low-fat dairy products. High-quality proteins from vegetable sources such as beans are good substitutes for animal sources of protein.

How does exercise (physical activity) affect cholesterol?

Consistent exercise increases HDL cholesterol in some people. A higher HDL cholesterol is linked with a lower risk of heart disease. Exercise can also help control weight, diabetes and high blood pressure. Exercise that uses oxygen to provide energy to large muscles (aerobic exercise) raises your heart and breathing rates. Regular moderate to intense exercise such as brisk walking, jogging and swimming also condition your heart and lungs.

Physical inactivity is a major risk factor for heart disease. Even moderate-intensity activities, if done daily, help reduce your risk. Examples are walking for pleasure, gardening, yard work, housework, dancing and prescribed home exercise.

How does tobacco smoke affect cholesterol?

Tobacco smoke is one of the six major risk factors of heart disease that you can change or treat. Smoking lowers HDL cholesterol levels.

How does alcohol affect cholesterol?

In some studies, moderate use of alcohol is linked with higher HDL cholesterol levels. However, because of other risks, the benefit isn't great enough to recommend drinking alcohol if you don't do so already. People with diabetes should be careful about embracing this belief without consulting their doctors.

If you drink, do so in moderation. People who consume moderate amounts of alcohol (an average of one to two drinks per day for men and one drink per day for women) have a lower risk of heart disease than nondrinkers. However, increased consumption of alcohol brings other health dangers, such as alcoholism, high blood pressure, obesity, stroke, cancer, suicide, etc. Given these and other risks, we caution people against increasing their alcohol intake or starting to drink if they don't already do so.

Cholesterol-Lowering Drugs

Drug therapy can be considered for patients who, in spite of adequate dietary therapy, regular physical activity and weight loss, need further treatment for elevated blood cholesterol levels. The guidelines for those who qualify are:

If you do not have coronary heart disease and have fewer than two risk factors, drugs should be used if your LDL is 190 mg/dL (5.0 mM) or higher*. The goal is to lower LDL to less than 160 mg/dL or 4.2 mM.

If you don not have coronary heart disease but have two or more risk factors, drugs should be used if your LDL is 160 mg/dL (4.2 mM) or higher. the goal is to lower LDL to less than 130 mg/dL (3.3 mM).

If you have coronary heart disease or diabetes, drugs should be used if your LDL is 130 mg/dL (3.3 mM) or higher**. The goal is to lower LDL to 100 mg/dL (2.6 mM) or less.

* In men less than 35 years of age and premenopausal women with LDL cholesterol levels of 190 to 219 mg/dL, drug therapy should be delayed except in high-risk patients such as those with diabetes.

** In coronary heart disease patients with LDL cholesterol levels of 100 to 129 mg/dL, the physician should exercise clinical judgment in deciding whether to begin drug treatment.

In some cases, a physician may decide that using cholesterol-lowering drugs at lower LDL cholesterol levels is justified. On the other hand, drug therapy may not be appropriate for some patients who meet the above criteria. This may be true for elderly patients.

The presence of other coronary heart disease risk factors influences the use of cholesterol-lowering drugs:

1 age (for men, 45 years or older; for women, 55 years or older OR premature menopause)
2 family history of premature heart disease (a father, brother or son with a history of coronary heart disease before age 55, OR a mother, sister or daughter with CHD before age 65)
3 smoking OR living or working every day with people who smoke
4 high blood pressure (140/90 mm Hg or higher)
5 HDL cholesterol less than 40 mg/dL
6 diabetes

What drugs are most commonly used to treat high cholesterol?

The drugs of first choice for elevated LDL cholesterol are the HMG CoA reductase inhibitors, e.g., lovastatin, pravastatin and simvastatin and atorvastatin. Statin drugs are very effective for lowering LDL cholesterol levels and have few immediate short-term side effects. They are easy to administer, have high patient acceptance and have few drug-drug interactions. Patients who are pregnant, have active or chronic liver disease, or who are allergic to statins shouldn't use statin drugs. The most common side effects are gastrointestinal, including constipation and abdominal pain and cramps. These symptoms are usually mild to severe and generally subside as therapy continues.

Another class of drugs for lowering LDL is the bile acid sequestrants -- cholestyramine and colestipol -- and nicotinic acid (niacin). These have been shown to reduce the risk for coronary heart disease in controlled clinical trials. Both classes of drugs appear to be free of serious side effects. But both can have troublesome side effects and require considerable patient education to achieve adherence. Nicotinic acid is preferred in patients with triglyceride levels that exceed 250 mg/dL because bile acid sequestrants tend to raise triglyceride levels.

What other drugs are available to treat high cholesterol?

Other available drugs are gemfibrozil, probucol and clofibrate. Gemfibrozil and clofibrate are most effective for lowering high triglyceride levels.

If a patient doesn't respond adequately to single drug therapy, combined drug therapy should be considered to further lower LDL cholesterol levels. For patients with severe hypercholesterolemia, combining a bile acid sequestrant with either nicotinic acid or lovastatin has the potential to markedly lower LDL cholesterol. For hypercholesterolemic patients with elevated triglycerides, nicotinic acid or gemfibrozil should be considered as one agent for combined therapy.


What are triglycerides?

Triglycerides are the chemical form in which most fat exists in food as well as in the body. They're also present in blood plasma and, in association with cholesterol, form the plasma lipids.

Triglycerides in plasma are derived from fats eaten in foods or made in the body from other energy sources like carbohydrates. Calories ingested in a meal and not used immediately by tissues are converted to triglycerides and transported to fat cells to be stored. Hormones regulate the release of triglycerides from fat tissue so they meet the body's needs for energy between meals.

How is an excess of triglycerides harmful?

Excess triglycerides in plasma is called hypertriglyceridemia. It's linked to the occurrence of coronary artery disease in some people. Elevated triglycerides may be a consequence of other disease, such as untreated diabetes mellitus. Like cholesterol, increases in triglyceride levels can be detected by plasma measurements. These measurements should be made after an overnight food and alcohol fast.

The National Cholesterol Education Program guidelines for triglycerides are:

Normal Less than 150 mg/dL
Borderline-high 150 to 199 mg/dL
High 200 to 499 mg/dL
Very high 500 mg/dL or higher

These are based on fasting plasma triglyceride levels.


Dietary treatment goals

Changes in lifestyle habits are the main therapy for hypertriglyceridemia. These are the changes you need to make:

1 If you're overweight, cut down on calories to reach your ideal body weight. This includes all sources of calories, from fats, proteins, carbohydrates and alcohol.
2 Reduce the saturated fat and cholesterol content of your diet.
3 Reduce your intake of alcohol considerably. Even small amounts of alcohol can lead to large changes in plasma triglyceride levels.
4 Be physically active for at least 30 minutes on most days each week.
5 People with high triglycerides may need to substitute monounsaturated and polyunsaturated fats -- such as those found in canola oil, olive oil or liquid margarine -- for saturated fats. Substituting carbohydrates for fats may raise triglyceride levels and may decrease HDL ("good") cholesterol in some people.
6 Substitute fish high in omega-3 fatty acids instead of meats that are high in saturated fat like hamburger. Fatty fish like mackerel, lake trout, herring, sardines, albacore tuna and salmon are high in omega-3 fatty acids.
7 Because other risk factors for coronary artery disease multiply the hazard from hyperlipidemia, control high blood pressure and avoid cigarette smoking. If drugs are used to treat hypertriglyceridemia, dietary management is still important. Patients should follow the specific plans laid out by their physicians and nutritionists. Drugs that lower triglycerides belong to the fibrate class.