Cholesterol: is actually My Heart at Risk?
- June 17, 2017
- Posted by: marlenedubois
- Category: CPR Training
Cholesterol is actually a waxy steroid of fat produced in liver or intestine, used for the synthesis of hormones along with cell membranes along with transported within the blood plasma of all mammals. Cholesterol is actually a very essential structural component of plasma membrane of mammals required for maintaining proper membrane permeability along with fluidity. the item is actually also an important agent required for the manufacture of bile acids, steroid hormones along with vitamin D. the item is actually the principal steroid synthesized by animals however, smaller amounts are also produced in plants along with fungi. Cholesterol is actually entirely absent among prokaryotes. If its concentration increases in blood then the risk of cardiovascular diseases increases so its level must be kept under control. The word cholesterol has originated through a Greek word along with was first discovered by Francois Poulletier de la Salle in gallstones in solid form in 1769 yet, chemical identification was done by Eugène Chevreul in 1815 who gave the term cholesterine.
Cholesterol participates within the synthesis of male along with female steroid hormones especially testosterone along with estrogens. About 80% of the body’s cholesterol is actually synthesized by the liver while rest comes through our diet. The major sources of dietary cholesterol are meat, fish, poultry, along with dairy products. Among meat, liver is actually excessively rich in cholesterol content while foods of plant origin lack cholesterol. After consuming a meal, the dietary cholesterol is actually absorbed through the intestine along with packaged inside a protein coat. This particular cholesterol-protein coat complex is actually known as chylomicron which is actually later stored within the liver. Liver bears the potential of regulating cholesterol levels within the blood stream. Cholesterol synthesis starts through simpler elements present within the body. In blood circulation the item is actually transported within lipoproteins along with if its level increases then the risk of atherosclerosis increases. Typically for a person weighing 68 kg the total body cholesterol synthesis is actually 1 g per day. The daily additional dietary intake of cholesterol within the United States is actually 0-300 mg. The body maintains equilibrium by minimizing the total amount synthesized within the body if the dietary intake of cholesterol increases.
Cholesterol is actually also recycled, the item is actually excreted by the liver via bile into the digestive tract. About 50% of the excreted cholesterol is actually again reabsorbed within the modest intestine along with reaches blood stream. Phytosterols can compete with cholesterol reabsorption within the intestine along with so, reduce cholesterol level. Cholesterol is actually a fat required by the body in modest amounts. High blood levels of cholesterol can lead to coronary artery disease along with angina. Nitrates are used to relieve angina. Most people require regular tests for knowing blood cholesterol levels of which comprise checking of triglycerides, high density lipoproteins (HDL), low density lipoproteins (LDL) along with total cholesterol levels.
Methods for increasing the levels of not bad cholesterol or lowering blood cholesterol levels include cholesterol reducing drugs like statins, fibrates, niacin along with bile acid resins. These drugs are not able to reverse calcification along with if coronary arteries are blocked then heart attack may occur. The two chief types of cholesterols are high density lipoproteins (HDL) along with low density lipoproteins (LDL). For the sake of simplicity HDL is actually considered as not bad cholesterol while LDL is actually known as the bad cholesterol. We can conclude of which the bad cholesterol is actually responsible for forming plaques within the arteries along with so, increases the risk of heart attack. The not bad cholesterol on the different hand, reverses cholesterol transport by taking the item out of the plaque along with sending the item back to blood circulation for excretion via liver.
Three major types of lipoproteins are found within the serum of a fasting individual namely, low density lipoproteins (LDL), high density lipoproteins (HDL) along with very low density lipoproteins (VLDL).
1. Low density lipoproteins (LDL) or bad cholesterol along with its management
LDL or bad cholesterol comprises 60-70% of the total serum cholesterol. the item is actually the major atherogenic lipoprotein used within the cholesterol lowering therapy as its higher levels are dangerous. the item deposits cholesterol on the walls of arteries resulting within the formation of a hard substance known as cholesterol plaque. This particular plaque is actually responsible for the hardening of arterial walls so they become narrow along with the process is actually identified as atherosclerosis. Liver not only manufactures along with secretes LDL cholesterol within the blood stream yet also removes the item through the blood. A large number of active receptors are present on the surface of liver of which actively bind to the LDL cholesterol molecules along with remove the item through blood. A deficiency of LDL receptors is actually associated with the higher level of these molecules within the blood.
numerous advantages are known when the levels of bad cholesterol undergo reduction for example, declination within the formation of completely new plaques on the walls of the arteries, removal of existing plaques through the arterial walls, narrowed arteries attain their normal shape, avoidance of rupturing of plaques which facilitates formation of blood clots along with finally the risk of heart attack is actually reduced. numerous studies have indicated of which the risk of heart attack diminishes by 25% for every 10% drop within the LDL cholesterol level along with the item is actually the key factor ensuring of which total blood cholesterol level has reached a safer zone. A study carried out with 4,000 individuals has confirmed of which the levels of bad cholesterol along with risk of heart attack were reduced to about 25% along with 42%by using the drug statin. the item is actually profitable of which the daily calorie intake of fat must be reduced down to 30% along with consumption different kinds of foods rich in carbohydrates, proteins must be increased as the body will convert them into triglycerides which are later stored as fat.
Foods rich in saturated fats increase levels of LDL cholesterol in blood stream. Fats may be classified as saturated along with unsaturated fats. Saturated fats are easily available within the meat, dairy products along with some vegetable oils especially those derived through coconut, palm along with cocoa. Therapeutic lifestyle improvements adopted for lowering the levels of bad cholesterol include regular exercise, loss of excess body weight along with following a diet with low concentration of saturated fats along with cholesterol. When lifestyle improvements fail to give desired results then medications are taken into consideration. Statins are the most effective drugs giving best results for lowering the levels of bad cholesterol along with also reducing the risk of heart diseases. different drugs of which can be used include fibrates like gemfibrozin, resins such as cholestyramine, ezetimibe along with Zetia. The National Institute of Health, the American Heart Association along with the American College of Cardiology have published some guidelines of which can help the medical experts while dealing with cases of high cholesterol.
2. High density lipoproteins (LDL) or not bad cholesterol along with its advantages
HDL cholesterol or the not bad cholesterol as the item prevents atherosclerosis by extracting cholesterol through the arterial walls along with disposing them through liver. High levels of LDL cholesterol along with low levels of HDL cholesterol are associated with the risk of heart diseases. So the levels must be maintained in order to enjoy a happy along with healthy life. HDL cholesterol accounts for 20-30% of the total serum cholesterol. Since the item reduces the risk of atherosclerosis its level must be checked through time to time. Both heredity along with diet have a significant effect on a person’s HDL, LDL along with total cholesterol levels. Families with low HDL levels are at an elevated risk of heart attack along with vice versa. Lifestyle along with different factors also influence HDL levels. HDL levels are low in individuals who smoke, are overweight, inactive along with suffer through Type II diabetes mellitus. HDL levels are higher in individuals who are lean, exercise regularly along with do not smoke. Estrogens also increase HDL levels so women have high HDL cholesterol levels as compared to men.
Lowering of the LDL cholesterol level is actually however easier than elevating the levels of HDL cholesterol. Reducing LDL along with raising HDL levels have a beneficial effect on an individual’s health. Earlier the researchers were much focused on the ways of reducing the levels of bad cholesterol yet with advancement in research the item became clear of which the item is actually better to raise the levels of not bad cholesterol as the item will automatically reduce bad cholesterol levels. The levels may be raised by weight loss, regular exercise along with intake of niacin. Some studies have suggested of which drugs like statin when coupled with niacin give better results along with women with high levels of HDL have reduced risk of heart attack. The average HDL level for women must be in between 50-55 mg/dL along with for men 40-50 mg/dL. The total cholesterol to HDL cholesterol ratio can be of help in estimating the risk of atherosclerosis. An average ratio must be in between 4-5.
Studies have indicated of which even a modest increase within the level of HDL cholesterol can reduce the risk of heart attack. For every 1 mg/dL rise within the HDL cholesterol level the risk of coronary heart disease reduces by 2-4%. However, therapeutic lifestyle improvements can help in increasing the HDL levels. When these improvements fail to give positive results then medication is actually taken into account. Regular aerobic exercise, loss of excessive body weight along with cessation of smoking are helpful in raising HDL levels. Regular alcohol consumption for example, taking one drink per day can also help in This particular regard yet as alcohol consumption is actually coupled with many adverse health effects This particular criterion is actually not taken into consideration. Effective drugs include gemfibrozil, estrogen along with lower doses of statin. A newer medicine, fenofibrate has also given better results along with is actually used in reducing serum triglycerides.
3. Triglycerides or very low density lipoproteins (VLDL) or ugly cholesterol along with its effects
The ugly cholesterol is actually a triglyceride rich lipoprotein of which accounts for 10-15% of the total serum cholesterol. This particular cholesterol is actually produced by liver along with some remnants of VLDL seem to promote atherosclerosis similar to of which of LDL. Triglyceride is actually a form of fat transported to the tissue through blood. Body’s majority of fatty tissue is actually composed of triglycerides. Serum triglycerides can be derived through two sources. The first source is actually the food of which we consume for example, if we consume a diet rich in fats then intestine packs some of them while rest is actually transported to the liver. The second source is actually the liver itself. When fats are received by the liver, the item takes fatty acids released by the fat cells along with ties them in triglyceride bundles of which are later utilized as fuel. There is actually a controversy about the fact of which whether high levels of triglycerides alone are responsible for coronary heart disease or not.
different clinical conditions frequently coupled with high triglyceride levels are high blood pressure, obesity, diabetes, chronic kidney, liver along with circulatory disease along with hypothyroidism. In some individuals elevated triglyceride levels are inherited along with This particular condition is actually identified as hypertriglyceridemia. The common examples of hypertriglyceridemia include mixed hypertriglyceridemia, familial hypertriglyceridemia along with familial dysbetalipoproteinemia. Hypertriglyceridemia can also occur due to some non-genetic factors like obesity, excessive alcohol, diabetes mellitus, kidney disease along with use of estrogen containing medicines like birth control pills. The levels can be returned back to normal without medication by taking the help of a physician. The first step involved within the treatment of hypertriglyceridemia includes intake of a diet low in fats with limited consumption of sweets, regular aerobic exercise, loss of excess body weight, reduction of alcohol consumption along with quitting smoking. In patients with diabetes mellitus effective control of glucose level is actually needed.
When medications become necessary statins, fibrates along with niacin can be used. Fibrates not only reduce the triglyceride levels yet also raise the HDL levels along with particle size of LDL molecules. Same task is actually done by niacin yet the item lowers the levels of Lp (a) cholesterol. Statins on the different hand, reduce both triglyceride along with LDL levels yet are ineffective in raising HDL levels. A newly launched medicine, fenofibrate has shown promising results in lowering triglyceride along with LDL levels as well as raising HDL levels especially in those individuals who show sub-optimal responses with fibrates. In some individuals a mixed dose of fibrate or fenofibrate along with statin is actually prescribed for better results.
Cholesterol is actually needed for building along with maintenance of membranes as the item modulates membrane fluidity over a wide range of physiological temperatures. The hydroxyl group located on the cholesterol molecule interacts with the polar head groups of membrane phospholipids along with sphingolipids along with so, reduces permeability of membrane to protons. Within the cell membrane the item also functions in intracellular transport, nerve conduction along with cell signaling. Cholesterol is actually also very essential for the structure along with function of invaginated caveolae along with clathrin coated pits in endocytosis. Recently, the item has been suggested of which cholesterol also plays some role in cell signaling process by assisting in formation of lipid rafts in plasma membrane. In many neurons a cholesterol rich myelin sheath is actually present which is actually derived through the compact layers of Schwann cell membrane helping in efficient nerve conduction. This particular layer also provides insulation. Within cells cholesterol also acts as a precursor molecule for several biochemical processes. In liver, cholesterol is actually converted into bile which is actually then stored in gallbladder. Bile is actually rich in bile salts which actively solubilize fat molecules within the digestive tract along with so, aid in intestinal absorption of fat molecules along with fat soluble vitamins like A,D,E along with K. the item is actually also an essential precursor molecule for the synthesis of vitamin D along with steroid hormones.
Biosynthesis along with Regulation
All animal cells manufacture cholesterol yet the rate of production varies depending upon the cell type along with the organ involved. About 20-25% daily production of cholesterol occurs within the liver along with rest in intestines, adrenal glands along with reproductive organs. Synthesis of cholesterol within the body starts with one molecule of acetyl- CoA along with one molecule of acetoacetyl-CoA of which are hydrated to form 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA). The HMG-CoA so formed is actually reduced to form mevalonate by the enzyme HMG-CoA reductase. This particular step is actually the rate limiting along with irreversible step within the cholesterol synthesis. The mevalonate so formed is actually converted into 3-isopentenyl pyrophosphate in three reactions of which need ATP. Mevalonate is actually then decarboxylated to form isopentenyl pyrophosphate. Then three molecules of isopentenyl pyrophosphate collaborate together to form farnesyl pyrophosphate within the presence of geranyl transferase. Two molecules of farnesyl pyrophosphate join to form squalene within the endoplasmic reticulum along with the reaction is actually catalyzed by squalene synthase. Oxidosqualene cyclase then converts squalene to lanosterol of which finally forms cholesterol. The mechanism along with regulation of cholesterol was worked out by Konard Bloch along with Feodor Lynen for which they received Noble Prize in Physiology or Medicine in 1964.
The biosynthesis of cholesterol is actually under the strict control of the cholesterol levels yet homeostatic mechanisms involved in its regulation are partly understood. A higher intake of cholesterol through food results in a net decrease in endogenous production along with vice versa. The main mechanism involved comprises sensing of intracellular cholesterol by the protein SREBP (sterol regulatory element-binding protein 1 along with 2) located on the endoplasmic reticulum. within the presence of cholesterol This particular protein binds with two different proteins namely, SCAP (SREBP-cleavage-activating protein) along with Insig 1. When the cholesterol level declines Insig 1 dissociates through the SREBP-SCAP complex, allowing entry of This particular complex into the Golgi apparatus, where SREBP is actually cleaved by S1 along with S2 proteases. These proteases are activated by SCAP when cholesterol levels decline. The cleaved SREBP then migrates towards the nucleus to act as a transcription factor along with here the item binds to the sterol regulatory element (SRE) which stimulates transcription of many genes for example, scavenging of circulating LDL through the blood stream by low density lipoprotein (LDL) receptor along with increase within the endogenous production of cholesterol by HMG-CoA reductase. A larger part of This particular signaling pathway was worked out by Dr. Michael S. Brown along with Dr. Joseph L. Goldstein in 1970s for which they received Noble Prize in 1985.
Cholesterol synthesis can be terminated when cholesterol levels are high. HMG-CoA reductase bears both cytosolic along with membrane domains. The membrane domain is actually sensitive for the signals responsible for its degradation. Increased concentration of cholesterol causes a change within the oligomerized state of domain of which makes the item more susceptible to destruction by proteosome. The activity of This particular enzyme can also be reduced by phosphorylation by an AMP activated protein kinase. Cholesterol is actually only slightly soluble in water along with can be dissolved in water-based blood stream yet travels at exceedingly modest concentrations. As cholesterol is actually insoluble in blood the item is actually transported within the circulatory system within the lipoprotein complexes whose outer part is actually made up of amphiphilic proteins along with lipids. Triglycerides along with cholesterol esters are carried internally. Lipoproteins provide cholesterol a soluble medium to be transported through blood along with just for This particular reason lipoproteins are carried in different forms within blood namely, chylomicrons, very low density lipoproteins (VLDL), intermediate density lipoproteins (IDL), low density lipoproteins (LDL) along with high density lipoproteins (HDL).
Chylomicrons are the least dense type of cholesterol transporting molecules whose shells are rich in apolipoprotein B-48, apolipoprotein C along with E. They carry fats through intestine to muscles along with different tissues of which require fatty acids for energy. Cholesterol of which is actually not used by the muscles remains within the form of chylomicron remnant which is actually later taken up by the liver through blood stream. VLDL molecules produced by the liver are loaded with triacylglycerol along with cholesterol of which are not needed by the liver for the production of bile acids. These molecules contain apolipoprotein B100 along with apoplipoprotein E in their shells. During transport the blood vessels cleave along with absorb triacylglycerol through IDL molecules of which have high concentration of cholesterol. LDL molecules are the major carriers of cholesterol within the blood along with each molecule contains about 1,500 cholesterol esters. The shell of LDL molecule contains only one molecule of apolipoprotein B100 of which is actually recognized by the LDL receptors present on the peripheral tissues. During binding of apolipoprotein B100 many LDL receptors become localized within the clathrin-coated pits. Both LDL along with its receptors are internalized by endocytosis to form a vesicle within the cell which then fuses with the lysosome containing lysosomal acid lipase of which hydrolyzes cholesterol esters. At This particular stage cholesterol can be used for the biosynthesis of membrane along with can be stored within the cell.
Synthesis of LDL receptor is actually regulated by SREBP protein. When the cell has sufficient amount of cholesterol, LDL receptor synthesis is actually blocked along with no more molecules of cholesterol can enter inside the cell. When the cell is actually deficient in cholesterol more LDL receptors are formed. When This particular system is actually deregulated more LDL molecules without LDL receptors appear within the bloodstream especially near the peripheral tissues. These molecules are then oxidized along with taken up by the macrophages forming foam cells along with contributing within the formation of atherosclerotic plaques on the walls of the arteries causing heart attack. HDL molecules participate in reverse cholesterol transport as they return cholesterol back to the liver for excretion. Cholesterol is actually susceptible to oxidation along with can easily form oxysterols of which are the oxygenated derivatives. Oxysterols can be generated through three mechanisms especially by autoxidation, secondary oxidation to lipid peroxidation along with cholesterol metabolizing enzyme oxidation. Oxysterols also participate in bile acid biosynthesis, transport of different forms of cholesterol along with regulation of gene transcription.
Cholesterol is actually oxidized by the liver into a variety of bile acids which are in turn conjugated with glycine, taurine, glucuronic acid. A mixture of both conjugated as well as non-conjugated bile acids along with cholesterol is actually excreted through the liver into bile. About 95% of the bile acids are reabsorbed through the intestines while rest is actually lost in faeces. The excretion along with reabsorption of bile acids form the basis of enterohepatic circulation essential for digestion along with absorption of the dietary fats. In certain circumstances, cholesterol crystallizes along with forms gallstones especially within the gallbladder. Lecithin along with bilirubin gallstones are also known to occur yet their percentage is actually low. Everyday about 1 g of cholesterol is actually known to enter the colon which comes through diet, bile, desquamated intestinal cells along with can be metabolized by the colonic bacteria. Cholesterol is actually mainly converted into coprostanol which is actually a nonabsorbable sterol excreted in faeces. A cholesterol reducing bacterium has also been isolated through human faeces. Some cholesterol derivatives are known to generate liquid crystalline cholesteric phase.
Dietary sources of cholesterol
Animal fats are complex mixtures of triglycerides having lower proportions of phospholipids along with cholesterol. Major dietary sources of cholesterol include cheese, egg yolks, beef, pork, shrimp along with poultry. Human breast milk also contains sufficient amounts of cholesterol. The amount cholesterol present within the plant sources is actually lesser when compared with the animal sources. Plant products like peanuts along with flax seeds bear phytosterols which are cholesterol like compounds helping to lower serum cholesterol levels. The total fat intake especially within the form of saturated along with trans fats play greater role in blood cholesterol rather than the intake of cholesterol itself. Saturated fats are abundantly present within the full fat dairy products, animal fats, chocolate along with several types of oils.
Trans fats are obtained by the partial hydrogenation of unsaturated fats along with do not occur in significant amounts in nature. They are present in not bad amounts within the margarine, hydrogenated vegetable fats along with in many fast foods like snacks, fried or baked goods. Avoiding consumption of cholesterol rich animal products not only reduces the amount of cholesterol taken through the diet yet also reduces the synthesis of cholesterol. Individuals interested to reduce their cholesterol levels through diet must consume less than 7% of their daily energy needs through the animal fats along with fewer than 0 mg of cholesterol per day. the item is actually debatable of which reduced consumption of dietary fat along with cholesterol can lower blood cholesterol levels because any declination within the dietary uptake of cholesterol is actually compensated by the organs involved in its synthesis to ensure of which the levels can be kept constant.
Foods of which might cholesterol
Dietary fibers play a major role in maintaining our health as well as also protect us through numerous diseases like diabetes along with heart diseases. Oats, oat bran along with oat meal contain a special type of soluble fiber known as beta-glucan of which helps in reducing the levels of LDL cholesterol. Oat fibers are different through different fibers within the manner of which they reduce the levels of bad cholesterol while the levels of not bad cholesterol remain unchanged. So we can say of which oat fibers help in reducing the risk of coronary heart disease. Studies have also indicated of which if individuals with high levels of HDL consume 3 g of soluble oat fiber per day the total cholesterol levels may be declined. Soy protein also protects against heart diseases along with hypercholesterolemia as the item reduces the bad cholesterol along with raises the not bad cholesterol. the item also prevents the oxidation of bad cholesterol to ensure of which the item may not coagulate on the arterial walls.
Several studies have indicated of which drinking of green or black teas also reduce the blood cholesterol concentration, blood pressure along with inhibit blood clotting along with also provide some protection against cardiovascular diseases. Green tea is actually rich in catechins while black tea contains flavins of which inhibit oxidation of bad cholesterol. Tea also contains folic acid of which helps in reducing the risk of heart attack along with cancer. A person can get 25% of RDA for folic acid by drinking 5 cups of tea in a day. Several studies have indicated of which barely has some unique health promoting effects especially for the heart. The cholesterol fighting efficiency of barley is actually more pronounced than of which of oats. Studies have indicated of which the item can reduce up to 15% of total cholesterol levels in individuals with elevated cholesterol levels. Barley is actually also a rich source of beta-glucan which retards fat along with cholesterol absorption by the intestines. The fiber is actually known to bind bile salts along with so, removes cholesterol through the body. Psyllium husk is actually also a rich source of soluble along with insoluble fibers known to reduce the risk of cardiovascular diseases, serum cholesterol, LDL levels, triglycerides along with apolipoprotein B. Psyllium husk is actually rich in a fiber known as beta-sitosterol.
Cholesterol testing along with reducing high cholesterol
The American Heart Association recommends of which the cholesterol levels of individuals above 20 years of age must be checked in every 5 years. A blood sample after 12-hour fasting is actually taken by the medical expert for the determination of the lipoprotein profile. This particular determines LDL, HDL, total cholesterol along with triglyceride levels. Causes of high cholesterol may vary through person to person along with are influenced by the lifestyle along with gender of an individual. numerous steps can be taken in order to reduce high cholesterol levels for example loss of excessive body weight. Avoidance of consumption of foods derived through animal fats, regular physical activity along with exercise can also help in maintaining low cholesterol levels. Levels of cholesterol in both males along with females increase after a certain age along with the levels in women tend to improve after menopause. Genes also play an important role in a person’s health.