Cholesterol – a wax steroid of the fat made in a liver or an intestines, used for synthesis of hormones both cellular membranes and transported in plasma of blood of all mammals. Cholesterol – very essential structural component of a plasma membrane of the mammals, demanded to support ought мембранную permeability and fluidity. It – also the important means demanded for manufacturing bilious acids, steroid and vitamin D hormones. It is the basic steroid synthesised by animals however, the smaller quantity also is made at factories and mushrooms. Cholesterol completely is absent among прокариотов. If its increases in concentration of blood then risk of increases in cardiovascular diseases so its level have to be kept control. Word cholesterol has occurred from the Greek word and at first François Pullete де ла Salem in bilious конкрементах in the firm form in 1769 has been found out, but, chemical identification has been made by Eugene Chevreulom in 1815 which has given the term cholesterine.
Physiology
Cholesterol participates in synthesis of man’s and female hormones of a steroid especially testosterone and an estrogen. Approximately 80 % of cholesterol of a body are synthesised by a liver while rest arrives from our diet. The basic sources of dietary cholesterol – meat, fish, poultry, and dairy products. Among meat the liver is excessively rich with the cholesterol maintenance while products of an origin of factory lack cholesterol. After meal consumption dietary cholesterol is absorbed from intestines and packed in an albuminous cover. This complex of an albuminous cover of cholesterol is known as chylomicron which is stored in a liver later. The liver has potential of regulation of levels of cholesterol in a blood-groove. Cholesterol synthesis begins with more simple elements existing in a body. In blood circulation it is transported in limits липопротеинов and if its level increases then risk of increases in an atherosclerosis. As a rule for the person weighing of 68 kg, full synthesis of cholesterol of a body makes 1 г in day. Daily additional dietary consumption of cholesterol in the United States makes 200-300 mg. The body supports balance, minimising a total sum synthesised in a body if dietary consumption of cholesterol increases.
Cholesterol also is processed, it экскретируется a liver through bile in a digestive path. Approximately 50 % экскретируемого cholesterol again are repeatedly absorbed by a small intestine and reach a blood-groove. Phytosterols can compete with реабсорбцией cholesterol in intestines and thus, to reduce cholesterol level. Cholesterol – the fat demanded by a body in small amounts. High blood levels of cholesterol can lead to disease of a coronary artery and a stenocardia. Nitrates are used to facilitate a stenocardia. The majority of people demands regular analyses on knowledge of levels of cholesterol in blood which include check триглицеридов, high липопротеины density (ЛПВП), low липопротеины density (ЛПНП) and full levels of cholesterol.
Methods to increase levels of good cholesterol or to lower cholesterol levels in blood include preparations of easing of cholesterol as статины, fibrates, nicotinic acid and pitches of bilious acid. These preparations not in a condition to reverse кальциноз and if coronary arteries are blocked then, heart attack can meet. Two main types холестеринов – high липопротеины density (ЛПВП) and low липопротеины density (ЛПНП). For the sake of simplicity ЛПВП consider as good cholesterol while ЛПНП it is known as bad cholesterol. We can come to conclusion that bad cholesterol is responsible for formation of plaques in arteries and thus, increases risk of heart attack. Good cholesterol on the other hand, transport of cholesterol of changes, taking out it from a plaque and sending it back to blood circulation for экскреции through a liver.
Types
Three main types липопротеинов are in whey of the fast person namely, low липопротеины density (ЛПНП), high липопротеины density (ЛПВП) and very low липопротеины density (VLDL).
1. Low липопротеины density (ЛПНП) or bad cholesterol and its management
ЛПНП or bad cholesterol include 60-70 % of full cholesterol of whey. It is main атерогенный липопротеин, used in therapy of fall of cholesterol as its higher levels are dangerous. It brings cholesterol on walls of the arteries which are coming to an end with formation of firm substance, known as a cholesterol plaque. This plaque is responsible for hardening of arterial walls, thus, they become narrow, and process is identified as an atherosclerosis. The liver not only makes and секретирует cholesterol ЛПНП in a blood-groove, but also and deletes it from blood. A considerable quantity of active receptors is present on surface of a liver which actively connect with molecules of cholesterol ЛПНП and delete it from blood. Deficiency of receptors ЛПНП is connected with higher level of these molecules in blood.
Many advantages are known, when levels of bad cholesterol transfer reduction for example, the inclination in formation of new plaques on walls of arteries, removal of existing plaques from arterial walls, was narrowed, arteries reach the normal form, prevention разрывания plaques which facilitates formation of blood clots and at last risk of heart attack decreases. Many researches have specified that the risk of heart attack decreases for 25 % for each 10 %, look to level of cholesterol ЛПНП, and it is the key factor guaranteeing that full level of cholesterol in blood has reached more safe zone. The research executed from 4 000 people, has confirmed that levels of bad cholesterol and risk of heart attack have been reduced approximately to 25 % and 42%by use статина a medical product. It is favourable that daily consumption of a calorie of fat should be reduced down to 30 % and various kinds of consumption of the products rich with carbohydrates, fibers should be increased, as the body will transform them in триглицериды which are stored as fat later.
The products rich with sated fats, increase levels of cholesterol ЛПНП in a blood-groove. Fats can be carried as sated and nonsaturated fats. The sated fats are easily accessible in meat, dairy products and a small amount of vegetable oils especially received of a coconut, palm trees and cocoa. Therapeutic changes of the way of life, accepted to lower levels of bad cholesterol, include regular realisation, loss of superfluous weight of a body and observance of a diet with low concentration of the sated fats and cholesterol. When changes of a way of life not in a condition to yield desirable results then, medicines are considered. Статины – the most effective preparations giving, is better comes to an end to lower levels of bad cholesterol and also to reduce risk of heart troubles. Other preparations which can be used, include fibrates as gemfibrozin, pitches, such as cholestyramine, ezetimibe and Zetia. The national Institute of Health, the American Warm Association and the American College of Cardiology is have published some supervising principles which can help medical experts, dealing with cases of high cholesterol.
2. High липопротеины density (ЛПНП) or good cholesterol and its advantages
Cholesterol ЛПВП or good cholesterol as it prevents an atherosclerosis, taking cholesterol from arterial walls and having them through a liver. High levels of levels of cholesterol ЛПНП and low levels of cholesterol ЛПВП are connected with risk of heart troubles. Thus, levels should be supported to enjoy happy and healthy life. Cholesterol ЛПВП makes 20-30 % of full cholesterol of whey. As it reduces risk of an atherosclerosis, its level should be checked from time to time. Both the heredity and a diet have considerable effect on ЛПВП the person, ЛПНП and full levels of cholesterol. Families with low levels ЛПВП in the raised risk of heart attack and on the contrary. The Way of life and other factors also influence levels ЛПВП. Levels ЛПВП are low in people who smoke, more norms weigh, inactive and are ill from Type a diabetes. Levels ЛПВП above in people who are thin, regularly train and do not smoke. Estrogen also increases levels ЛПВП, thus, women have high levels of cholesterol ЛПВП in comparison with men.
Fall of level of cholesterol ЛПНП however is easier than lifting of levels of cholesterol ЛПВП. At easing ЛПНП and lifting levels ЛПВП there is a favorable influence on health of the person. Earlier researchers have been very concentrated to ways to reduce levels of bad cholesterol, but with advancement in research it became clear that it is better to lift levels of good cholesterol as it will automatically reduce bad levels of cholesterol. Levels can be lifted in развес loss, regular realisation and consumption of nicotinic acid. Some researches have assumed that preparations as статин when together with nicotinic acid yield the best results and women with high levels ЛПВП, have reduced risk of heart attack. Average level ЛПВП for women should be intermediate 50-55 mg/dl and for men of 40-50 mg/dl. Full cholesterol to the relation of cholesterol ЛПВП can help with an estimation of risk of an atherosclerosis. The average relation should be intermediate 4-5.
Researches have specified, what even the small increase in level of cholesterol ЛПВП can reduce risk of heart attack. For each increase on 1 mg/dl of level of cholesterol ЛПВП the risk of an ischemic heart trouble reduces by 2-4 %. However, therapeutic changes of a way of life can help with increase in levels ЛПВП. When these changes not in a condition to yield positive results then, treatment is taken into consideration. Regular employment by aerobics, loss of excessive weight of a body and the smoking termination are useful in lifting of levels ЛПВП. Regular alcoholic consumption for example, having taken one sip in day can help also in this respect but as alcoholic consumption together with many harm, this criterion is not considered. Effective preparations include gemfibrozil, an estrogen and lower doses статина. Newer medicine, fenofibrate also has yielded the best results and is used in easing серологических триглицеридов.
3. Триглицериды or very low липопротеины density (VLDL) or ugly cholesterol and its effects
Ugly cholesterol – триглицеридный rich липопротеин which makes 10-15 % of full cholesterol of whey. This cholesterol is made by a liver, and some rests VLDL, apparently, cause an atherosclerosis similar to volume from ЛПНП. Триглицерид – the form of the fat transported to a fabric through blood. The majority of a body of a fatty fabric is made from триглицеридов. Триглицериды whey can be received from two sources. The first source – meal which we consume for example if we consume a diet rich with fats then, intestines packs some of them while rest is transported to a liver. The second source – a liver directly. When fats turn out a liver, it takes the fat acids which have been let out by fatty cages, and connects them in триглицеридных sheaves which are used as fuel later. There is a contradiction about the fact it, whether only триглицеридов high levels of one are responsible for an ischemic heart trouble or not.
Other clinical conditions it is frequent together with high триглицеридными levels – a high blood pressure, adiposity, a diabetes, a chronic kidney, a liver and illness of bodies of blood circulation and гипотиреоз. In increased триглицеридных levels of some people are inherited, and this condition is identified as hypertriglyceridemia. The general examples hypertriglyceridemia include mixed hypertriglyceridemia, family hypertriglyceridemia and family dysbetalipoproteinemia. Hypertriglyceridemia can meet also because of some not genetic factors as adiposity, excessive alcohol, a diabetes, illness of kidneys and use of the estrogen containing medicines as contraceptive tablets. Levels can be returned back to normal without treatment, taking the help of the doctor. The first step involved in treatment hypertriglyceridemia, includes diet consumption low in fats with the limited consumption of sweets, regular employment by aerobics, loss of superfluous weight of a body, reduction of alcoholic consumption and throwing to smoke. At patients with a diabetes effective control of level of glucose is necessary.
When medicines become necessary статинами, fibrates, and nicotinic acid can be used. Fibrates not only reduce триглицеридные levels, but also and lift levels ЛПВП and the size of particles of molecules ЛПНП. The Same problem becomes nicotinic acid, but it lowers long-playing record levels (a) cholesterol. Статины on the other hand, reduce and триглицерид and levels ЛПНП, but are inefficient in lifting of levels ЛПВП. Recently begun medicine, fenofibrate has shown promising results in fall триглицерида and levels ЛПНП just as lifting of levels ЛПВП especially in those people who show подоптимальные reactions with fibrates. In some people the mixed dose fibrate or fenofibrate along with статином is offered for the best results.
Function
Cholesterol is necessary for building and service of membranes as it modulates мембранную fluidity on a wide range of physiological temperatures. The gidroksilnaja group located on a molecule of cholesterol, co-operates with polar main groups мембранных фосфолипидов and sphingolipids and thus, reduces permeability of a membrane to protons. Within a cellular membrane it also functions in endocellular transport, carrying out of a nerve and cage signalling. Cholesterol also is very important for structure and function инвагинированного caveolae, and clathrin pole coverlets in эндоцитозе. Recently, it was supposed that cholesterol also plays some role in the course of cage signalling, helping with formation of rafts липида in a plasma membrane. нейронах cholesterol is present at many rich миелиновая a cover which turns out from compact layers of the help of a cellular membrane of Shvanna in effective carrying out of a nerve. This layer also provides isolation. Within cholesterol of cages also operates as a molecule of the predecessor for several biochemical processes. In a liver cholesterol is transformed to bile which then is stored in a gall bladder. Bile is rich with salts of bile which actively do soluble thick molecules in a digestive path and thus, the help in intestinal absorption of thick molecules and fat-soluble vitamins as A, D, E and K. It – also an essential molecule of the predecessor for synthesis of hormones of a steroid and vitamin D.
Biosynthesis and Regulation
All cages of animals make cholesterol, but rate of manufacture changes depending on type of a cage and the involved body. Daily manufacture on approximately 20-25 % of cholesterol meets in a liver and rest in intestines, adrenal glands and reproductive bodies. Synthesis of cholesterol within a body begins with one molecule of acetyl – CoA and one molecule acetoacetyl-CoA which гидратируются, to generate 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA). HMG-CoA, so generated, decreases to generate mevalonate fermental редуктазой HMG-CoA. This step – restriction of level and an irreversible step to cholesterol synthesis. mevalonate, so generated, that is transformed in 3-isopentenyl пирофосфат in three reactions АТФ requirements. Mevalonate then decarboxylated to generate isopentenyl пирофосфат. Then three molecules isopentenyl пирофосфата co-operate together to generate farnesyl пирофосфат at presence geranyl трансферазы. Two molecules farnesyl пирофосфата connect to generate squalene in эндоплазматическом ретикулюме, and reaction катализируется squalene синтазой. Циклаза Oxidosqualene then transforms squalene in lanosterol, it at last forms cholesterol. The mechanism and cholesterol regulation have been solved by Konardom Blohom and Feodorom Lynenom for whom they have won the Noble Prize in Physiology or Medicine in 1964.
Cholesterol biosynthesis is under strict control over cholesterol levels, but гомеостатические the mechanisms involved in its regulation, are partially understood. Higher consumption of cholesterol from meal comes to an end with pure reduction in эндогенном manufacture and on the contrary. The main involved mechanism includes sensation of endocellular cholesterol albuminous SREBP (стерин regulating fiber connected by an element 1 and 2) located on эндоплазматическом ретикулюме. In the presence of cholesterol this fiber connects with two other fibers namely, SCAP (fiber SREBP-cleavage-activating) and Insig 1. When cholesterol level decreases, Insig 1 separates from complex SREBP-SCAP, allowing an input of this complex in Kompleks Goldzhi where SREBP it is split S1 and протеазами S2. These протеазы become more active SCAP when cholesterol levels decrease. Split SREBP then migrates to a kernel to operate as транскрипционный the factor, here again it connects with стерином regulating element (SRE) which stimulates a transcription of many genes for example, neutralisation circulating ЛПНП from a blood-groove low липопротеином density (ЛПНП) a receptor and increase эндогенного cholesterol manufactures редуктазой HMG-CoA. The Most part of this alarm way has been solved by doctor Michael S. Brown and doctor Joseph L. Goldstajnom in 1970 for which they have won the Noble Prize in 1985.
Cholesterol synthesis can be finished, when cholesterol levels are high. Редуктаза HMG-CoA has also cytocindery and мембранные areas. The membrannaja area is sensitive for the signals responsible for its degradation. The increased concentration of cholesterol causes change in oligomerized the state of area which does it more susceptible to деструкции proteosome. Activity of this enzyme can be reduced also фосфориляцией made active протеинкиназой АТФ. Cholesterol is only малорастворимым in water and can be terminated in the blood-groove based on water, but travel at extremely small concentration. As cholesterol is insoluble in blood, it is transported in blood system in limits липопротеиновых complexes, external parts which 1 made from амфифильных fibers and липидов. Триглицериды and difficult aethers of cholesterol bear internally. Липопротеины provide cholesterol a soluble nutrient medium which will be transported through blood, and for this reason липопротеины bear in various forms within blood namely, хиломикрона, very low липопротеины density (VLDL), intermediate липопротеины density (IDL), low липопротеины density (ЛПНП) and high липопротеины density (ЛПВП).
Хиломикрон – the least dense type of molecules of transportation of the cholesterol, which bowl are rich аполипопротеином B-48, аполипопротеин C and E. They bear fats from intestines to muscles and other fabrics which demand some fat acids for energy. Cholesterol which is not used by muscles, remains in shape chylomicron the rest which rises a liver through a blood-groove later. Molecules VLDL made by a liver, are loaded триацилглицеролом and cholesterol which are not necessary for a liver for manufacture of bilious acids. These molecules contain аполипопротеин B100 and apoplipoprotein E in their bowls. During transportation blood vessels split and absorb триацилглицерол from molecules IDL which have a high concentration of cholesterol. Molecules ЛПНП – the main carriers of cholesterol in blood, and each molecule contains approximately 1 500 difficult aethers of cholesterol. The bowl of molecule ЛПНП contains only one molecule аполипопротеина B100 which is recognised by a gift of receptors ЛПНП on peripheral fabrics. During fastening аполипопротеина B100 many receptors ЛПНП become limited in the clathrin-covered poles. And ЛПНП and its receptors are acquired эндоцитозом to generate a vial within a cage which then incorporates with лизосомой, containing лизосомальную acid липазу, which гидролизирует difficult aethers of cholesterol. At this stage cholesterol can be used for biosynthesis of a membrane and can be kept within a cage.
Synthesis of receptor ЛПНП is regulated by fiber SREBP. When the cage has cholesterol enough, synthesis of receptor ЛПНП is blocked, and it is more than cholesterol molecules cannot arrive in a cage. When the cage is insufficient in cholesterol is formed, more receptors ЛПНП. When this system is disadjusted, more molecules ЛПНП without receptors ЛПНП appears in кровотке especially about peripheral fabrics. These molecules then are oxidised and rise the macrophages forming foamy cages and promoting in formation of atherosclerotic plaques on walls of arteries, causing heart attack. Molecules ЛПВП participate in return transport of cholesterol as they return cholesterol back to a liver for экскреции. Cholesterol is susceptible to oxidation and can easily generate oxysterols which are the oxidised derivatives. Oxysterols can be made through three mechanisms especially autoxidation, secondary oxidation to перекисному to oxidation липидов and to the cholesterol acquiring fermental oxidation. Oxysterols also participate in biosynthesis of bilious acid, transport of various forms of cholesterol and regulation of a transcription of genes.
Cholesterol is oxidised a liver in set of bilious acids which are in turn conjugated with глицином, bull, glucuronic acid. A mix of both conjugated just as inconjugable bilious acids along with cholesterol экскретируется from a liver in bile. Approximately 95 % of bilious acids are repeatedly absorbed from intestines while rest is lost in excrements. Экскреция and реабсорбция bilious acids form the basis enterohepatic blood circulations, important for digestion and absorption of dietary fats. Under certain circumstances cholesterol кристаллизует also forms bilious конкременты especially in a gall bladder. Lecithin and bilious конкременты bilirubin as also it is known, meet, but their percent is low. Everyday approximately 1 г cholesterol, as it is known, enters into a thick gut which arrives from a diet, bile, it was shelled intestinal cages and can be acquired concerning to ободочной and a thick gut bacteria. Cholesterol, mainly, is transformed in coprostanol which is not soaked up стерином, экскретируемым in excrements. The bacterium of easing of cholesterol also has been isolated from human excrements. Some derivatives of cholesterol, as it is known, make liquid transparent холестерическую a phase.
Dietary sources of cholesterol
Animal fats – difficult mixes триглицеридов, having lower proportions фосфолипидов and cholesterol. The main dietary sources of cholesterol include cheese, egg yolks, beef, pork, shrimps and poultry. Human chest milk also contains cholesterol enough. The cholesterol of quantity existing in vegetative sources, is less at comparison with sources of animals. Factory products as have peanuts and flax seeds phytosterols which are cholesterol as the structures, helping to lower levels of cholesterol of whey. Full consumption of fats especially in the form of the sated fats and trans-fats plays large role in cholesterol in blood, instead of cholesterol consumption directly. The sated fats are present at full fat dairy products, animal fats, chocolate and several types of oils much.
Trans-fats turn out partial гидрогенизацией nonsaturated fats and do not meet in essential quantity in the nature. They are present at good quantity in margarine, гидрогенизируемых vegetative fats and in many fast foods as the snack fried or выпечные of a product. Avoiding cholesterol consumption rich products of an animal origin not only reduce quantity of the cholesterol, passed a diet, but also and reduce cholesterol synthesis. The people interesting to reduce their levels of cholesterol through a diet, should consume less than 7 % of the daily energy needs from animal fats and less than 200 mg of cholesterol a day. It is disputable, which has reduced consumption of dietary fat, and cholesterol can lower cholesterol levels in blood because any inclination in dietary absorption of cholesterol is given indemnification by the bodies involved in its synthesis so that levels could be kept constants.
Products which could cholesterol
Dietary fibres star in maintenance of our health just as also protect us from many illnesses as a diabetes and heart troubles. Oats, bran овсяного grains and meal овсяного grains contain special type of the soluble fibre known so beta-glucan which helps with easing of levels of cholesterol ЛПНП. Fibres овсяного grains differ from other fibres in such a manner that they reduce levels of bad cholesterol while levels of good cholesterol remain invariable. Thus, we can tell that fibres овсяного grains help with easing of risk of an ischemic heart trouble. Researches also have specified that if people with high levels ЛПВП consume 3 г a soluble fibre овсяного grains in the day, full levels of cholesterol can be reduced. Fiber of a soya also protects from heart troubles and гиперхолестеринемии as it reduces bad cholesterol and lifts good cholesterol. It also prevents oxidation of bad cholesterol so that it, probably, not коагулировало on arterial walls.
Some researches have specified that drink of green or black teas also reduces concentration of cholesterol in blood, a blood pressure and ингибирует a fibrillation and also provides some protection against cardiovascular diseases. Green tea is rich catechins while black tea contains рибофлавины, which ингибируют oxidation of bad cholesterol. Tea also contains folic acid which helps with easing of risk of heart attack and a cancer. The person can receive 25 % RDA for folic acid at drink of five cups of tea every other day. Some researches have specified that only has some unique medical stimulating actions specially for heart. Fighting capacity of cholesterol of barley is more obvious than that from oats. Researches have specified that it can reduce to 15 % of full levels of cholesterol in people with the raised levels of cholesterol. Barley – also a rich source beta-glucan which detains fat and absorption of cholesterol by intestines. The fibre, as it is known, connects salts of bile and thus, deletes cholesterol from a body. Peel Psyllium – also a rich source of soluble and insoluble fibres which, as it is known, have reduced risk of cardiovascular diseases, cholesterol of whey, levels ЛПНП, триглицеридов and аполипопротеина, B.Psilliuma’s peel is rich with a fibre known as beta-sitosterol.
Testing of cholesterol and easing of high cholesterol
The American Warm Association recommends, that levels of cholesterol of people above 20 years of age have been checked up every five years. The sample of blood after the 12-sentry of restriction of food undertakes the medical expert for definition липопротеинового a profile. It defines ЛПНП, ЛПВП, full cholesterol and триглицеридные levels. The reasons of high cholesterol can change from the person to the person and under the influence of a way of life and a sex of person. Many steps can be made to reduce high levels of cholesterol for example loss of excessive weight of a body. Prevention of consumption of the products received from animal fats, regular physical activity and realisation, can help with maintenance of low levels of cholesterol also. Levels of cholesterol both in men and in women increase after the certain age and levels in women tend to increase after менопаузы. Genes also play an important role in health of the person.
