What are triglycerides, chylomicrons, and VLDL?

Triglyceride is a fatty substance that is composed of three fatty acids. Like cholesterol, triglyceride in the blood either comes from the diet or the liver. Also, like cholesterol, triglyceride cannot dissolve and circulate in the blood without combining with a lipoprotein. Thus, after a meal, the triglyceride and cholesterol that are absorbed into the intestines are packaged into round particles called chylomicrons before they are released into the blood circulation.

A chylomicron is a collection of cholesterol and triglyceride that is surrounded by a lipoprotein outer coat. (Chylomicrons contain 90% triglyceride and 10% cholesterol.)

The liver removes triglyceride and chylomicrons from the blood, and it synthesizes and packages triglyceride into VLDL (very low-density lipoprotein) particles and releases them back into the blood circulation.

Do high triglyceride levels cause atherosclerosis?

Whether elevated triglyceride levels in the blood lead to atherosclerosis and heart attacks is controversial. While most doctors now believe that an abnormally high triglyceride level is a risk factor for atherosclerosis, it is difficult to conclusively prove that elevated triglyceride by itself can cause atherosclerosis. However, it is increasingly recognized that elevated triglyceride is often associated with other conditions that increase the risk of atherosclerosis, including obesity, low levels of HDL- cholesterol, insulin resistance and poorly controlled diabetes mellitus, and small, dense LDL cholesterol particles.

What are the causes of elevated triglyceride levels?

In some people, abnormally high triglyceride levels (hypertriglyceridemia) are inherited. Examples of inherited hypertriglyceridemia disorders include mixed hypertriglyceridemia, familial hypertriglyceridemia, and familial dysbetalipoproteinemia.

Hypertriglyceridemia can often be caused by non-genetic factors such as obesity, excessive alcohol intake, diabetes mellitus, kidney disease, and estrogen- containing medications such as birth control pills.

How can elevated blood triglyceride levels be treated?

The first step in treating hypertriglyceridemia is a low fat diet with a limited amount of sweets, regular aerobic exercise, loss of excess weight, reduction of alcohol consumption, and stopping cigarette smoking. In patients with diabetes mellitus, meticulous control of elevated blood glucose is also important.

When medications are necessary, fibrates (such as Lopid), nicotinic acid, and statin medications can be used. Lopid not only decreases triglyceride levels but also increases HDL cholesterol levels and LDL cholesterol particle size. Nicotinic acid lowers triglyceride levels, increases HDL cholesterol levels and the size of LDL cholesterol particles, as well as lowers the levels of Lp (a) cholesterol.

The statin drugs have been found effective in decreasing triglyceride as well as LDL cholesterol levels and, to a lesser extent, in elevating HDL cholesterol levels. A relatively new medicine, fenofibrate (Tricor), shows promise as an effective agent in lowering serum triglyceride levels as well as raising HDL levels, particularly in patients who have had suboptimal responses to Lopid. In some patients, a combination of Lopid or Tricor with adjunctive statin therapy (see below) may be prescribed. While this combination is often effective in patients with complex lipid disorders, the potential for side effects may be increased and such patients should be under strict medical supervision.

What are lipid-altering medications?

Lipid altering medications are used in lowering blood levels of undesirable lipids such as LDL cholesterol and triglycerides and increasing blood levels of desirable lipids such as HDL cholesterol. Several classes of medications are available in the United States, including HMG CoA reductase inhibitors (statins), nicotinic acid, fibric acid derivatives, and medications that decrease intestinal cholesterol absorption (bile acid sequestrants and cholesterol absorption inhibitors). Some of these medications are primarily useful in lowering LDL cholesterol, others in lowering triglycerides, and some in elevating HDL cholesterol. Medications also can be combined to more aggressively lower LDL, as well as in lowering LDL and increasing HDL at the same time.

How can levels of HDL cholesterol be raised?

The first step in increasing HDL cholesterol levels (and decreasing LDL/HDL ratios) is therapeutic life style changes. When these modifications are insufficient, medications are used. In prescribing medications or medication combinations, doctors have to take into account medication side effects as well as the presence or absence of other abnormalities in cholesterol profiles.

Regular aerobic exercise, loss of excess weight (fat), and cessation of smoking cigarettes will increase HDL cholesterol levels. Regular alcohol consumption (such as one drink a day) will also raise HDL cholesterol. Because of other adverse health consequences of excessive alcohol consumption, alcohol is not recommended as a standard treatment for low HDL cholesterol.

Medications that are effective in increasing HDL cholesterol include nicotinic acid (niacin), gemfibrozil (Lopid), estrogen, and to a much lesser extent, the statin drugs (discussed below). A newer medicine, fenofibrate (Tricor) has shown much promise in selectively increasing HDL levels and reducing serum triglycerides.

What are LDL/HDL and total/HDL ratios?

The total cholesterol to HDL cholesterol ratio (total chol/HDL) is a number that is helpful in estimating the risk of developing atherosclerosis. The number is obtained by dividing total cholesterol by HDL cholesterol. (High ratios indicate a higher risk of heart attacks, whereas low ratios indicate a lower risk).

High total cholesterol and low HDL cholesterol increases the ratio and is undesirable. Conversely, high HDL cholesterol and low total cholesterol lowers the ratio and is desirable. An average ratio would be about 4.5. Ideally, one should strive for ratios of 2 or 3 (less than 4).

Why is HDL the good cholesterol?

HDL is the good cholesterol because it protects the arteries from the atherosclerosis process. HDL cholesterol extracts cholesterol particles from the artery walls and transports them to the liver to be disposed through the bile. It also interferes with the accumulation of LDL cholesterol particles in the artery walls.

The risk of atherosclerosis and heart attacks in both men and is strongly related to HDL cholesterol levels. Low levels of HDL cholesterol are linked to a higher risk, whereas high HDL cholesterol levels are associated with a lower risk.

Very low and very high HDL cholesterol levels can run in families. Families with low HDL cholesterol levels have a higher incidence of heart attacks than the general population, while families with high HDL cholesterol levels tend to live longer with a lower frequency of heart attacks.

Like LDL cholesterol, life style factors and other conditions influence HDL cholesterol levels. HDL cholesterol levels are lower in persons who smoke cigarettes, eat a lot of sweets, are overweight and inactive, and in patients with type II diabetes mellitus.

HDL cholesterol is higher in people who are lean, exercise regularly, and do not smoke cigarettes. Estrogen increases a person's HDL cholesterol, which explains why women generally have higher HDL levels than men do.

For individuals with low HDL cholesterol levels, a high total or LDL cholesterol blood level further increases the incidence of atherosclerosis and heart attacks. Therefore, the combination of high levels of total and LDL cholesterol with low levels of HDL cholesterol is undesirable whereas the combination of low levels of total and LDL cholesterol and high levels of HDL cholesterol is favorable.

What are the 2004 NCEP cholesterol treatment guidelines?

After reviewing these large randomized cholesterol-lowering trials, The National Cholesterol Education Program (NCEP) expert panel published their new recommendations. The new NCEP recommendations, presented in the June, 2004 issue of Circulation, are:

1. The report advised physicians to consider more intensive LDL cholesterol-lowering for people at very high, high, and moderately high risk for a heart attack. These options include setting lower treatment goals for LDL cholesterol and initiating cholesterol-lowering drug therapy at lower LDL thresholds, as compared to ATP III guidelines published in 2001. For example, for patients with a very high risk of heart attacks, the LDL cholesterol treatment goal remains at <100mg/dl,>
2. The report emphasized the importance of initiating therapeutic lifestyle changes (TLC) to modify lifestyle-related risk factors (obesity, physical inactivity, metabolic syndrome, high blood triglyceride levels and low HDL cholesterol levels). TLC Lifestyle changes have the potential to reduce heart attack and stroke risks through several mechanisms beyond the lowering of LDL cholesterol.
3. When LDL-lowering medication is used for very high, high or moderately high risk patients, the report advises that the intensity of LDL-lowering drug therapy be sufficient to achieve at least a 30 to 40 percent reduction in LDL cholesterol levels.
4. When a very high or high risk patient also has high blood triglyceride or low HDL cholesterol levels, doctors may consider combining nicotinic acid or a fibrate with a statin. Nicotinic acid and fibrates are more effective than statins in lowering triglycerides and increasing HDL.
5. Age should not be a consideration since older persons also benefit from lowering LDL cholesterol. Thus, it is never too late or the patient too old to begin lifestyle changes and medications to lower LDL cholesterol. A word of caution is in order. Elderly patients are more likely to have liver and kidney dysfunction, and are also more likely to be on multiple medications some of which may interfere with the breakdown of cholesterol-lowering drugs such as statins. Thus lower dosing may be necessary to avoid adverse side effects

What are the 2004 NCEP cholesterol treatment guidelines?

After reviewing these large randomized cholesterol-lowering trials, The National Cholesterol Education Program (NCEP) expert panel published their new recommendations. The new NCEP recommendations, presented in the June, 2004 issue of Circulation, are:

1. The report advised physicians to consider more intensive LDL cholesterol-lowering for people at very high, high, and moderately high risk for a heart attack. These options include setting lower treatment goals for LDL cholesterol and initiating cholesterol-lowering drug therapy at lower LDL thresholds, as compared to ATP III guidelines published in 2001. For example, for patients with a very high risk of heart attacks, the LDL cholesterol treatment goal remains at <100mg/dl,>
2. The report emphasized the importance of initiating therapeutic lifestyle changes (TLC) to modify lifestyle-related risk factors (obesity, physical inactivity, metabolic syndrome, high blood triglyceride levels and low HDL cholesterol levels). TLC Lifestyle changes have the potential to reduce heart attack and stroke risks through several mechanisms beyond the lowering of LDL cholesterol.
3. When LDL-lowering medication is used for very high, high or moderately high risk patients, the report advises that the intensity of LDL-lowering drug therapy be sufficient to achieve at least a 30 to 40 percent reduction in LDL cholesterol levels.
4. When a very high or high risk patient also has high blood triglyceride or low HDL cholesterol levels, doctors may consider combining nicotinic acid or a fibrate with a statin. Nicotinic acid and fibrates are more effective than statins in lowering triglycerides and increasing HDL.
5. Age should not be a consideration since older persons also benefit from lowering LDL cholesterol. Thus, it is never too late or the patient too old to begin lifestyle changes and medications to lower LDL cholesterol. A word of caution is in order. Elderly patients are more likely to have liver and kidney dysfunction, and are also more likely to be on multiple medications some of which may interfere with the breakdown of cholesterol-lowering drugs such as statins. Thus lower dosing may be necessary to avoid adverse side effects

How can LDL cholesterol levels be lowered?

Therapeutic lifestyle changes to lower cholesterol

Lowering LDL cholesterol involves losing excess weight, exercising regularly, and following a diet that is low in saturated fat and cholesterol. For more, please read the TLC, Therapeutic Lifestyle Changes article.

Medications to lower cholesterol

Medications are prescribed when lifestyle changes cannot reduce the LDL cholesterol to desired levels. The most effective and widely used medications to lower LDL cholesterol are called statins. Most of the large controlled trials that demonstrated the heart attack and stroke prevention benefits of lowering LDL cholesterol used one of the statins. Other medications used in lowering LDL cholesterol and in altering cholesterol profiles include nicotinic acid (niacin), fibrates such as gemfibrozil (Lopid), resins such as cholestyramine (Questran), and ezetimibe, Zetia. (An in-depth discussion of these drugs is presented in this article starting at the heading: What are the statin drugs?)

What are "normal" cholesterol blood levels?

There are no established "normal" blood levels for total and LDL cholesterol. In most other blood tests in medicine, normal ranges can be set by taking measurements from large number of healthy subjects. For example, normal fasting blood sugar levels can be established by performing blood tests among healthy subjects without diabetes mellitus. If a patient's fasting blood glucose falls within this normal range, he/she most likely does not have diabetes mellitus, whereas if the patient's fasting blood sugar tests higher than the normal range, he/she probably has diabetes mellitus and further tests can be performed to confirm the diagnosis. Medications, such as insulin or oral diabetes medications can be prescribed to lower abnormally high blood sugar levels.

Unfortunately, the normal range of LDL cholesterol among "healthy" adults (adults with no known coronary heart disease) in the United States may be too high. The atherosclerosis process may be quietly progressing in many healthy adults with average LDL cholesterol blood levels, putting them at risk of developing coronary heart diseases in the future

Does lowering LDL cholesterol prevent heart attacks and strokes?

• Reducing or stopping the formation of new cholesterol plaques on the artery walls;
• Reducing existing cholesterol plaques on the artery walls;
• Widening narrowed arteries;
• Preventing the rupture of cholesterol plaques, which initiates blood clot formation;
• Decreasing the risk of heart attacks; and
• Decreasing the risk of strokes. The same measures that retard atherosclerosis in coronary arteries also benefit the carotid and cerebral arteries (arteries that deliver blood to the brain).

What determines the level of LDL cholesterol in the blood?

The liver not only manufactures and secretes LDL cholesterol into the blood; it also removes LDL cholesterol from the blood. A high number of active LDL receptors on the liver surfaces is associated with the rapid removal of LDL cholesterol from the blood and low blood LDL cholesterol levels. A deficiency of LDL receptors is associated with high LDL cholesterol blood levels.

Both heredity and diet have a significant influence on a person's LDL, HDL and total cholesterol levels. For example, familial hypercholesterolemia (FH) is a common inherited disorder whose victims have a diminished number or nonexistent LDL receptors on the surface of liver cells. People with this disorder also tend to develop atherosclerosis and heart attacks during early adulthood.

Diets that are high in saturated fats and cholesterol raise the levels of LDL cholesterol in the blood. Fats are classified as saturated or unsaturated (according to their chemical structure). Saturated fats are derived primarily from meat and dairy products and can raise blood cholesterol levels. Some vegetable oils made from coconut, palm, and cocoa are also high in saturated fats.

What are LDL and HDL cholesterol?

LDL cholesterol is called "bad" cholesterol, because elevated levels of LDL cholesterol are associated with an increased risk of coronary heart disease. LDL lipoprotein deposits cholesterol on the artery walls, causing the formation of a hard, thick substance called cholesterol plaque. Over time, cholesterol plaque causes thickening of the artery walls and narrowing of the arteries, a process called atherosclerosis.

HDL cholesterol is called the "good cholesterol" because HDL cholesterol particles prevent atherosclerosis by extracting cholesterol from the artery walls and disposing of them through the liver. Thus, high levels of LDL cholesterol and low levels of HDL cholesterol (high LDL/HDL ratios) are risk factors for atherosclerosis, while low levels of LDL cholesterol and high level of HDL cholesterol (low LDL/HDL ratios) are desirable.

Total cholesterol is the sum of LDL (low density) cholesterol, HDL (high density) cholesterol, VLDL (very low density) cholesterol, and IDL (intermediate density) cholesterol.

What is cholesterol?

Cholesterol is a fatty substance (a lipid) that is an important part of the outer lining (membrane) of cells in the body of animals. Cholesterol is also found in the blood circulation of humans. The cholesterol in a person's blood originates from two major sources; dietary intake and liver production. Dietary cholesterol comes mainly from meat, poultry, fish, and dairy products. Organ meats, such as liver, are especially high in cholesterol content, while foods of plant origin contain no cholesterol. After a meal, cholesterol is absorbed by the intestines into the blood circulation and is then packaged inside a protein coat. This cholesterol-protein coat complex is called a chylomicron.

The liver is capable of removing cholesterol from the blood circulation as well as manufacturing cholesterol and secreting cholesterol into the blood circulation. After a meal, the liver removes chylomicrons from the blood circulation. In between meals, the liver manufactures and secretes cholesterol back into the blood circulation.

High and Low Cholesterol Foods

HDL (kolesterol baik) vs LDL (kolesterol jahat)

Kadar kolesterol yang tinggi di dalam darah dapat menimbulkan berbagai penyakit seperti hipertensi dan stroke (baca laporan utama). Oleh karena itu, kita perlu mengetahui jenis makanan apa saja yang perlu dihindari agar tidak terjadi peningkatan jumlah kolesterol, terutama LDL (”kolesterol jahat”), dalam tubuh, yakni:

• Makanan yang mengandung kolesterol tinggi

Biasanya ditemukan pada produk-produk dari hewan, terutama dalam kuning telur, daging sapi, unggas (terutama pada bagian kulit), dan udang. Termasuk di dalamnya hasil olahan dari produk hewani tersebut.

• Makanan yang mengandung lemak jenuh

Lemak jenuh akan meningkatkan kadar LDL dalam darah. Kebanyakan berasal dari daging, susu beserta semua hasil olahannya. Selain itu, juga terdapat pada hasil panggangan, seperti roti dan kue, serta pada minyak tumbuhan (dalam jumlah kecil).

• Makanan yang mengandung “lemak trans”

Ternyata selain mengandung lemak jenuh, di dalam makanan yang dipanggang juga terdapat lemak trans. Kadar “lemak trans” yang tinggi juga dapat ditemukan pada margarin dan pada makanan yang digoreng. Padahal lemak trans yang masuk dalam tubuh dapat meningkatkan kadar LDL (kolesterol ‘jahat’) dan menurunkan kadar HDL (kolesterol ‘baik’).

Untuk menjaga kadar kolesterol tubuh, dapat juga dilakukan dengan mengonsumsi makanan yang berpotensi menurunkan “kolesterol jahat”, antara lain:

• Makanan yang mengandung lemak tak jenuh

Di dalam tubuh, lemak tak jenuh akan menggantikan lemak jenuh yang akan berefek pada penurunan kadar kolesterol. Lemak jenis ini dapat ditemukan pada minyak zaitun yang akan menekan kadar kolesterol tanpa mengganggu kadar HDL dalam tubuh. Ikan yang kaya dengan omega-3 (jenis lemak tak jenuh ganda) seperti salmon, sarden, herring, dan tuna, akan menurunkan resiko terjadinya serangan jantung di samping dapat menurunkan kadar kolesterol. Selain itu, sumber lemak tak jenuh dapat diperoleh dari jenis kacang-kacangan, terutama kacang almond dan walnut.

• Makanan dengan kandungan serat yang larut (soluble fiber)

Bekerja dengan menurunkan penyerapan kolesterol dalam pencernaan. Soluble fiber dapat ditemukan pada oatmeal, makanan yang terbuat dari gandum, roti, nasi, sereal, dan kacang merah.

Dengan berhati-hati memilih makanan yang hendak dimakan, kita telah berusaha untuk menghormati tubuh kita sendiri, terutama jantung kita.