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What is a triglyceride?

What is a triglyceride?



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I'm confused on what a triglyceride is, from what my text book it says its a type of gylercide, then from a website it said

Glycerides can be subdivided into two categories. The first group, the neutral glycerides are nonionic and nonpolar. The second group, the phosphoglycerides contain a polar region, the phosphoryl group.

Which makes triglyceride not a directly under a glyceride but under one of these groups. Then it says

Esterification may occur at one, two or all three positions producing monoglycerides (monoacylglycerols), diglycerides (diacylglycerols), or triglycerides (triacylglycerols). The most prevalent and most important are the triglycerides.

So does that mean that triglyceride can be produced by either of the two groups phosphoglycerides and neutral glycerides. And if that's correct then how are monoglycerides and diglycerides produced.

Source


The following answer was giving by Michael D. Dryden from https://chemistry.stackexchange.com/questions/24797/what-is-a-triglyceride/24799#24799

There is some minor argument as far as nomenclature goes for these lipids. Most sources I can find, including IUPAC have glycerides as only including esters of glycerol with fatty acids. Monoglycerides have a single fatty acid ester with two free OH groups, diglycerides have two fatty acid esters, and triglycerides have three. Phosphoglycerides are defined separately as esterified derivatives of phosphatidic acids, so you can think of them like glycerides where for one of the substituents, instead of a fatty acid, some derivative of phosphoric acid is present. However, the way the two terms are defined, they don't encompass any common molecules, i.e. there are no molecules that are both glycerides and phosphoglicerides and neither group is a subset of the other.

So: mono-, di-, and triglycerides are subsets of glycerides while phosphoglycerides are a different group altogether, though structurally similar.


Triglyceride. It has 3 fatty acids, which are non polar (water-fearing). so they are hydrophobic. These 3 fatty acids are connected to a glycerol molecule. This molecule is polar and is hydrophilic (water-loving). The glycerol is attached to the 3 fatty acids via a dehydration reaction. When they are connected, they loose a water molecule, and form an ester.


Medical Definition of Triglycerides

Triglycerides: The major form of fat stored by the body. A triglyceride consists of three molecules of fatty acid combined with a molecule of the alcohol glycerol. Triglycerides serve as the backbone of many types of lipids (fats). Triglycerides come from the food we eat as well as from being produced by the body.

Triglyceride levels are influenced by recent fat and alcohol intake, and should be measured after fasting for at least 12 hours. A period of abstinence from alcohol is advised before testing for triglycerides.

Elevated triglyceride levels are considered to be a risk factor for atherosclerosis (hardening of the arteries) because many of the triglyceride-containing lipoproteins that transport fat in the bloodstream also transport cholesterol, a known contributor to atherosclerosis.

Markedly high triglyceride levels (greater than 500mg/dl) can cause inflammation of the pancreas (pancreatitis). Therefore, these high levels should be treated aggressively with low fat diets and medications, if needed.

The word "triglyceride" reflects the fact that a triglyceride consists of three ("tri-") molecules of fatty acid combined with a molecule of the alcohol glycerol ("-glyceride") that serves as the backbone in many types of lipids (fats).


Triglyceride Test (Lowering Your Triglycerides)

Triglycerides can be lowered without drugs. For example, they can be lowered naturally through diet changes, decreasing consumption of alcohol or sugary beverages, by increasing physical activity, by losing weight, and other ways. As little as 5% to 10% reduction in body weight may lower triglycerides. The table below summarizes how much benefit different changes can effect.

LDL and HDL: What are triglycerides?

Triglycerides are chemical compounds digested by the body to provide it with the energy for metabolism. Triglycerides are the most common form of fat in the body. They are the main ingredient in vegetable oils and animal fats.

The triglyceride molecule is a form of the chemical glycerol (tri=three molecules of fatty acid + glyceride=glycerol) that contains three fatty acids. To be absorbed, these parts are broken apart in the small intestine, and afterwards are reassembled with cholesterol to form chylomicrons. This is the source of energy for cells in the body. Fat cells and liver cells are used as storage sites and release chylomicrons when the body needs the energy.

Elevated triglyceride levels are a risk factor for atherosclerosis, the narrowing of arteries with the buildup of fatty plaques that may lead to heart attack, stroke, and peripheral artery disease. Markedly elevated triglyceride levels may also cause fatty liver disease and pancreatitis.

Certain diseases and conditions may cause elevated triglyceride blood levels, for example:

  • Poorly-controlled diabetes
  • Kidney disease of the liver or other liver diseases
  • Some medications (for example, beta blockers, diuretics, birth control pills)

Alcohol consumption can raise triglyceride blood levels by causing the liver to produce more fatty acids. However, there are some beneficial aspects of moderate alcohol consumption, defined as one alcoholic beverage per day (a glass of wine, a bottle of beer, or an ounce of hard liquor), that may balance this triglyceride rise. Moderate alcohol consumption may mildly increase HDL (the good cholesterol) levels in the bloodstream and red wine, which contains antioxidants, may decrease the risk of heart disease. However, it is not recommended that people start to drink alcohol to obtain these effects.

SLIDESHOW

How are triglyceride levels measured?

Triglyceride levels in the blood are measured by a simple blood test. Often, triglycerides are measured as part of a lipoprotein panel (lipid panel) in which triglycerides, cholesterol, HDL (high-density lipoprotein), and LDL (low-density lipoprotein) are measured at the same time.

Fasting for 8-12 hours before the test is required. Fat levels in the blood are affected by recent eating and digestion. Falsely elevated results may occur if the blood test is done just after eating.

What are normal triglyceride levels? What do elevated triglyceride levels mean?

Elevated triglycerides place an individual at risk for atherosclerosis. Triglyceride and cholesterol levels are measured in the blood to provide a method of screening for this risk.


Triglycerides are in cahoots with HDL cholesterol (a.k.a. the “good cholesterol”).

Why? Because having higher amounts of HDL can help carry these fatty deposits of triglycerides away from blood vessels and be protective. A disease commonly associated with HDL cholesterol and triglycerides is atherosclerosis, in which plaque builds up inside your arteries. Because your arteries are blood vessels that carry oxygen-rich blood to your heart and other parts of your body, it is important to have the proper balance of triglycerides with artery-clearing HDL cholesterol.

The ideal ratio of triglycerides to HDL cholesterol is less than 2:1, while a ratio greater than 6:1 is considered very high risk. By lowering your triglycerides and this ratio, you can further protect yourself from cardiovascular diseases, such as a heart attack or stroke.


What is a triglyceride? - Biology

A blood sample drawn from a vein in your arm or from a fingerstick

Current standards recommend that testing be done when you are fasting. For 9 to 12 hours before the test, only water is permitted. In addition, alcohol should not be consumed for 24 hours just before the test. Your healthcare practitioner may decide that you may be tested without fasting. Follow any instructions you are given and tell the person drawing your blood whether or not you have fasted.

You may be able to find your test results on your laboratory's website or patient portal. However, you are currently at Lab Tests Online. You may have been directed here by your lab's website in order to provide you with background information about the test(s) you had performed. You will need to return to your lab's website or portal, or contact your healthcare practitioner in order to obtain your test results.

Lab Tests Online is an award-winning patient education website offering information on laboratory tests. The content on the site, which has been reviewed by laboratory scientists and other medical professionals, provides general explanations of what results might mean for each test listed on the site, such as what a high or low value might suggest to your healthcare practitioner about your health or medical condition.

The reference ranges for your tests can be found on your laboratory report. They are typically found to the right of your results.

If you do not have your lab report, consult your healthcare provider or the laboratory that performed the test(s) to obtain the reference range.

Laboratory test results are not meaningful by themselves. Their meaning comes from comparison to reference ranges. Reference ranges are the values expected for a healthy person. They are sometimes called "normal" values. By comparing your test results with reference values, you and your healthcare provider can see if any of your test results fall outside the range of expected values. Values that are outside expected ranges can provide clues to help identify possible conditions or diseases.

While accuracy of laboratory testing has significantly evolved over the past few decades, some lab-to-lab variability can occur due to differences in testing equipment, chemical reagents, and techniques. This is a reason why so few reference ranges are provided on this site. It is important to know that you must use the range supplied by the laboratory that performed your test to evaluate whether your results are "within normal limits."

For more information, please read the article Reference Ranges and What They Mean.

Triglycerides are a form of fat and a major source of energy for the body. This test measures the amount of triglycerides in the blood.

Most triglycerides are found in fat (adipose) tissue, but some triglycerides circulate in the blood to provide fuel for muscles to work. After a person eats, an increased level of triglycerides is found in the blood as the body converts the energy not needed right away into fat. Triglycerides move via the blood from the gut to adipose tissue for storage. In between meals, triglycerides are released from fat tissue to be used as an energy source for the body. Most triglycerides are carried in the blood by lipoproteins called very low-density lipoproteins (VLDL).

High levels of triglycerides in the blood are associated with an increased risk of developing cardiovascular disease (CVD), although the reason for this is not well understood. Certain factors can contribute to high triglyceride levels and to risk of CVD, including lack of exercise, being overweight, smoking cigarettes, consuming excess alcohol, and having medical conditions such as diabetes and kidney disease.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm. Sometimes, a drop of blood is collected by puncturing the skin on a fingertip. This fingerstick sample is typically used when a lipid profile (total cholesterol, HDL-C, LDL-C and TG) is being measured on a portable testing device, for example, at a health fair.

Is any test preparation needed to ensure the quality of the sample?

Current standards recommend that testing be done when you are fasting. For 9 to 12 hours before the test, only water is permitted. Your healthcare practitioner may decide that you may be tested without fasting. Follow any instructions you are given and tell the person drawing your blood whether or not you have fasted. In addition, alcohol should not be consumed for 24 hours just before the test.

Blood tests for triglycerides are usually part of a lipid profile that is used to help identify an individual's risk of developing heart disease and to help make decisions about what treatment may be needed if there is borderline or high risk. As part of a lipid profile, it may be used to monitor people who have risk factors for heart disease, those who have had a heart attack, or those who are being treated for high lipid and/or high triglyceride levels.

Results of the cholesterol test and other components of the lipid profile are used along with other known risk factors of heart disease to develop a plan of treatment and follow-up. Treatment options may include lifestyle changes, such as diet or exercise programs, or lipid-lowering drugs, such as statins.

A lipid profile, which includes triglycerides, is recommended every 4 to 6 years to evaluate risk of heart disease in healthy adults. Children should have a lipid profile screening at least once between the ages of 9 and 11 and once again between the ages of 17 and 21.

Testing may be ordered more frequently when people have identified risk factors for heart disease. Some risk factors for heart disease include:

  • Cigarette smoking
  • Being overweight or obese
  • Unhealthy diet
  • Being physically inactive—not getting enough exercise
  • Age (men 45 years or older or women 55 years or older)
  • High blood pressure (hypertension—blood pressure of 140/90 or higher or taking high blood pressure medication)
  • Family history of premature heart disease (heart disease in an immediate family member—male relative under age 55 or female relative under age 65)
  • Pre-existing heart disease or already having had a heart attack or prediabetes

For diabetics, it is especially important to have triglycerides measured as part of any lipid testing since triglycerides increase significantly when blood glucose levels are not well-controlled.

Screening for high cholesterol as part of a lipid profile is recommended for children and young adults. They should be tested once between the ages of 9 and 11 and then again between the ages of 17 and 21. Earlier and more frequent screening with a lipid profile is recommended for children and youths who are at an increased risk of developing heart disease as adults. Some of the risk factors are similar to those in adults and include a family history of heart disease or health problems such as diabetes, high blood pressure, or being overweight.

High-risk children should have their first cholesterol test between 2 and 8 years old, according to the American Academy of Pediatrics. Children younger than 2 years old are too young to be tested.

As part of a lipid profile, triglycerides tests may be ordered at regular intervals to evaluate the success of lipid-lowering lifestyle changes, such as diet and exercise, or to determine the effectiveness of drug therapy such as statins. Guidelines from the American College of Cardiology and the American Heart Association recommend that adults taking statins have a fasting lipid profile done 4 to 12 weeks after starting therapy and then every 3 to 12 months thereafter to assure that the drug is working.

In general, healthy lipid levels help to maintain a healthy heart and lower the risk of heart attack or stroke. A healthcare practitioner will take into consideration the results of each component of the lipid profile as well as other risk factors to help determine a person's overall risk of heart disease, whether treatment is necessary and, if so, which treatment will best help to lower the person's risk.

In 2002, the National Cholesterol Education Program (NCEP) Adult Treatment Panel III (ATPIII) provided the guidelines for evaluating lipid levels and determining treatment. In 2013, the American College of Cardiology and the American Heart Association issued guidelines for adults that made recommendations on who should receive cholesterol-lowing therapy. (For more details, see the Lipid Profile article).

However, use of the updated guidelines remains controversial. Many still use the older guidelines from the NCEP ATP III to evaluate lipid levels and cardiovascular disease risk:

For adults, triglyceride test results are categorized as follows:

  • Desirable: Less than 150 mg/dL (1.7 mmol/L)
  • Borderline high: 150 to 199 mg/dL (1.7-2.2 mmol/L)
  • High: 200 to 499 mg/dL (2.3-5.6 mmol/L)
  • Very high: Greater than 500 mg/dL (5.6 mmol/L)

For children, teens and young adults:

  • Acceptable: Less than 75 mg/dL (0.85 mmol/L)
  • Borderline high: 75-99 mg/dL (0.85-1.12 mmol/L)
  • High: Greater than 100 mg/dL (1.13 mmol/L)
  • Acceptable: Less than 90 mg/dL (1.02 mmol/L)
  • Borderline high: 90-129 mg/dL (1.02-1.46 mmol/L)
  • High: Greater than 130 mg/dL (1.47 mmol/L)

For young adults older than 19

  • Acceptable: Less than 115 mg/dL (1.30 mmol/L)
  • Borderline high: 115-149 mg/dL (1.30-1.68 mmol/L)
  • High: Greater than 150 mg/dL (1.7 mmol/L)

Note: These values are based on fasting triglyceride levels.

When triglycerides are very high (greater than 1000 mg/dL (11.30 mmol/L)), there is a risk of developing pancreatitis in children and adults. Treatment to lower triglycerides should be started as soon as possible.

If you are diabetic and your blood sugar (glucose) is out of control, triglycerides may be very high.

Triglycerides change dramatically in response to meals, increasing as much as 5 to 10 times higher than fasting levels just a few hours after eating. Even fasting levels vary considerably day to day. Therefore, modest changes in fasting triglycerides measured on different days are not considered to be abnormal.

Certain drugs such as corticosteroids, protease inhibitors for HIV, beta blockers, and estrogens can increase blood triglyceride levels.

There is increasing interest in measuring triglycerides in people who have not fasted. The reason is that a non-fasting sample may be more representative of the "usual" circulating level of triglyceride since most of the day blood lipid levels reflect post-meal (post-prandial) levels rather than fasting levels. However, it is not yet certain how to interpret non-fasting levels for evaluating risk so, at present, there is no change in the current recommendations for fasting prior to tests for lipid levels.

For many people, high triglycerides are caused by another disorder, such as diabetes, obesity, renal failure, or alcoholism. With these conditions, the strategy is to treat the primary cause. When high triglycerides are not caused by another disorder, they are often seen together with high cholesterol and treatment is directed toward lowering both cholesterol and triglycerides. Lifestyle changes, such as a healthy diet and increased exercise, are usually the primary strategy for lowering levels. If these fail, lipid-lowering medications such as statins are generally recommended. For more on this, visit the American Heart Association's webpage on Healthy Living.

A few products are available to test lipid levels, including triglycerides, at home. There are two types of home testing: those where you collect the sample at home and then mail it away to a laboratory for testing and those where you conduct the test yourself at home (self-monitoring). The American Heart Association hasn't taken a position on the use of home testing devices for measuring lipid levels. Before making the decision to use one of these products, you may want to review the article about home testing on this site: With Home Testing, Consumers Take Charge of Their Health.

Very low-density lipoprotein (VLDL) is one of the major lipoprotein particles. Others include high-density lipoprotein (HDL) and low-density lipoprotein (LDL). Each one of these particles contains a mixture of cholesterol, protein, and triglyceride but in varying amounts unique to each type of particle. LDL contains the highest amount of cholesterol. HDL contains the highest amount of protein. VLDL contains the highest amount of triglyceride. Since VLDL contains most of the circulating triglyceride and since the compositions of the different particles are relatively constant, it is possible to estimate the amount of VLDL-cholesterol by dividing the triglyceride value (in mg/dL) by 5. At present, there is no simple, direct way of measuring VLDL-cholesterol, so the estimate calculated from triglyceride is used in most settings. This calculation is not valid when the triglyceride is greater than 400 mg/dL. Increased levels of VLDL-cholesterol have been found to be associated with increased risk of heart disease and stroke.

Usually, most people with high triglyceride levels have no symptoms and the only means of discovering a high level is with blood tests. However, in rare cases, a person may have an extremely high level of triglycerides (well above 1000 mg/dL) sustained over time and the individual may experience repeated bouts of acute pancreatitis. Some of the signs and symptoms include pain in the upper half of the stomach area that develops suddenly and then gradually gets worse, fever, nausea, vomiting, and sometimes jaundice. A person with severely high levels may also develop lesions on the skin called xanthomas. These typically appear as several small, round, solid, yellow bumps mostly on the back, chest, buttocks, shoulders and thighs.

On This Site

Elsewhere On The Web

Sources Used in Current Review

(© 2015). What Are High Blood Cholesterol and Triglycerides? American Heart Association. Available online at http://www.heart.org/idc/groups/heart-public/@wcm/@hcm/documents/downloadable/ucm_300308.pdf. Accessed on 5/01/16.

Wendlig, P. (2016 March 18). How High Is Too High for Triglycerides and Cardiovascular Risk? Heartwire from Medscape. Available online at http://www.medscape.com/viewarticle/860598. Accessed on 5/01/16.

(2016 April 13 Updated). Triglycerides. MedlinePlus Medical Encyclopedia. Available online at https://www.nlm.nih.gov/medlineplus/triglycerides.html. Accessed on 5/01/16.

Mayo Clinic Staff (2015 August 15 Updated). Triglycerides: Why do they matter? Mayo Clinic. Available online at http://www.mayoclinic.org/diseases-conditions/high-blood-cholesterol/in-depth/triglycerides/ART-20048186?p=1. Accessed on 5/01/16.

Sweeney, M. (2015 April 14 Updated). Hypertriglyceridemia. Medscape Drugs & Diseases. Available online at http://emedicine.medscape.com/article/126568-overview. Accessed on 5/01/16.

Driver, S. et al. (2016). Fasting or Nonfasting Lipid Measurements It Depends on the Question. J Am Coll Cardiol. 201667(10):1227-1234. Available online at http://www.medscape.com/viewarticle/860269. Accessed on 5/01/16.

Sources Used in Previous Reviews

Thomas, Clayton L., Editor (1997). Taber's Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].

Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby's Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO.

American Heart Association. What are healthy levels of cholesterol? Available online at http://216.185.112.5/presenter.jhtml?identifier=183.

American Heart Association. Cholesterol, Home testing devices. Available online at http://www.americanheart.org/presenter.jhtml?identifier=4501. Accessed August 2007.

American Heart Association. Triglycerides. Available online at http://www.americanheart.org/presenter.jhtml?identifier=4778. Accessed September 2008.

Pagana K, Pagana T. Mosby's Manual of Diagnostic and Laboratory Tests. 3rd Edition, St. Louis: Mosby Elsevier 2006. Pp 513-515.


Structure

The main molecule that starts the structure of a triglyceride is glycerol. Glycerol is a three-carbon molecule with three hydroxyl groups on them. These hydroxyl groups are the site of an ester reaction with three fatty acid molecules. The fatty acids can be different types, and the fatty acid structure defines the type of triglyceride. The fatty acids are long chains of carbons with bonded hydrogens. These are the parts of the triglycerides that are used for energy production.


Does Diet Matter?

Yes, a lot. But not in the way you might think. Even though they consist of fat, most triglycerides are made by your body from extra carbohydrates. Sugary and starchy carbs are the worst type. Seek out “complex” carbs like vegetables and whole grains instead. Cut saturated fats (found mainly in animal products) in favor of “good” fats found in olive oil, nuts, seeds, and fish.


What is Cholesterol?

Cholesterol is a type of lipid molecule containing four fused hydrocarbon rings. It is a steroid that produces several important steroid hormones in our body. There are two main types of cholesterols as good cholesterol and bad cholesterol. Good cholesterols are high-density lipoproteins that help to remove other forms of cholesterols from arteries. Bad cholesterols are mainly low-density lipoproteins, and they build up within the walls of blood vessels and cause cardiovascular diseases.

Figure 01: Cholesterol Structure

It is important to maintain the cholesterol level in the blood at an optimum level (less than 200mg/dl). Cholesterol deposition in blood vessels (mainly coronary arteries supplying the heart) will cause angina and heart attack. If it blocks the vessel in the brain, it may result in a stroke. The treatment for high cholesterol is both diet control and statins. However, statins may damage the liver. Therefore, diet control is the best option for controlling bad cholesterols. Avoiding oily fast foods, regular exercise and statins will help to prevent heart attacks and help to live a prolonged good quality life.


Phospholipids

  • Phospholipids are similar to triglycerides in they consist of a glycerol ‘backbone’ and fatty acid ‘tails’, however, the third fatty acid has been replaced by a phosphate group ‘head’.

While the fatty acid ‘tails’ are hydrophobic, the phosphate ‘head’ is hydrophilic. This means the phosphate group will orientate itself towards water and away from the rest of the molecule, and also gives rise to the special properties that allow phospholipids to be used to form membranes.

Phospholipids can contain saturated and unsaturated fatty acids. This allows for the control of the fluidity of membranes, which is useful, for example, in maintaining membrane fluidity at low temperatures.