Cholesterol
IUPAC name	(10R,13R)-10,13-dimethyl-17-(6-methylheptan-2-yl)- 2,3,4,7,8,9,11,12,14,15,16,17-dodecahydro-1H- cyclopenta[a]phenanthren-3-ol
Identifiers
CAS number	[57-88-5]
PubChem	5997
SMILES	CC(C)CCCC(C)C1CCC2C1 (CCC3C2CC=C4C3(CCC(C4)O)C)C
Properties
Molecular formula	C27H46O
Molar mass	386. IUPAC Nomenclature is a system of naming Chemical compounds and of describing the science of Chemistry in general CAS registry numbers are unique numerical identifiers for Chemical compounds Polymers biological sequences mixtures and Alloys They are also referred to PubChem is a Database of chemical Molecules The system is maintained by the National Center for Biotechnology Information (NCBI a component A chemical formula is a way of expressing information about the Atoms that constitute a particular Chemical compound, and how the relationship between those atoms changes Molar mass, symbol M, is the Mass of one mole of a substance ( Chemical element or Chemical compound) 654
Appearance	white crystalline powder [1]
Melting point	148–150 °C [1]
Boiling point	360 °C (decomposes)
Solubility in water	0. The melting point of a solid is the temperature range at which it changes state from solid to Liquid. The boiling point of a liquid is the temperature at which the Vapor pressure of the liquid equals the environmental pressure surrounding the liquid Solubility is the characteristic Physical property referring to the ability of a given substance the Solute, to dissolve in a Solvent. Water is a common Chemical substance that is essential for the survival of all known forms of Life. 095 mg/L (30 °C)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Cholesterol is a lipid found in the cell membranes of all animal tissues, and it is transported in the blood plasma of all animals. Lipids are broadly defined as any fat- Soluble ( lipophilic) naturally-occurring Molecule, such as fats oils waxes cholesterol sterols fat-soluble The cell membrane (also called the plasma membrane, plasmalemma, or "phospholipid bilayer" is a Selectively permeable Lipid bilayer Blood plasma is the Liquid component of Blood, in which the Blood cells are suspended Cholesterol is also a sterol (a combination steroid and alcohol). Sterols, or steroid alcohols are a subgroup of Steroids with a Hydroxyl group at the 3-position of the A-ring A steroid is a Terpenoid Lipid characterized by a Carbon skeleton with four fused rings generally arranged in a 6-6-6-5 fashion In Chemistry, an alcohol is any Organic compound in which a Hydroxyl group ( - O[[hydrogen H]]) is bound to a Carbon Because cholesterol is synthesized by all eukaryotes, trace amounts of cholesterol are also found in membranes of plants and fungi. Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex Plants are living Organisms belonging to the kingdom Plantae. A fungus (ˈfʌŋgəs is a eukaryotic Organism that is a member of the kingdom Fungi (ˈfʌndʒaɪ

The name originates from the Greek chole- (bile) and stereos (solid), and the chemical suffix -ol for an alcohol, as researchers first identified cholesterol in solid form in gallstones by François Poulletier de la Salle in 1769. Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly Bile or gall is a bitter yellow or green Alkaline fluid secreted by Hepatocytes from the Liver of most Vertebrates In many species A chemical substance is a Material with a definite chemical composition. In Grammar, a suffix (also postfix, ending) is an Affix which is placed at the end of a word In Medicine, gallstones (choleliths are Crystalline bodies formed within the body by accretion or concretion of normal or abnormal Bile component Year 1769 ( MDCCLXIX) was a Common year starting on Sunday (link will display the full calendar of the Gregorian calendar (or a However, it is only in 1815 that chemist Eugène Chevreul named the compound "cholesterine". Year 1815 ( MDCCCXV) was a Common year starting on Sunday (link will display the full calendar of the Gregorian calendar (or a Common year Michel Eugène Chevreul ( August 31, 1786 &ndash April 9, 1889) was a French Chemist whose work with Fatty acids ^[2]

Most of the cholesterol in the body is synthesized by the body and some has dietary origin. Cholesterol is more abundant in tissues which either synthesize more or have more abundant densely-packed membranes, for example, the liver, spinal cord and brain. The liver is a vital organ in the human body and is present in Vertebrates and some other animals The spinal cord is a long thin tubular bundle of Nerves that is an extension of the Central nervous system from the brain and is enclosed in and protected The brain is the center of the Nervous system in animals All Vertebrates and the majority of Invertebrates have a brain It plays a central role in many biochemical processes, such as the composition of cell membranes and the synthesis of steroid hormones. Biochemistry is the study of the chemical processes in living Organisms It deals with the Structure and function of cellular components such as The cell membrane (also called the plasma membrane, plasmalemma, or "phospholipid bilayer" is a Selectively permeable Lipid bilayer Steroid hormones are Steroids which act as Hormones Mammalian steroid hormones can be grouped into five groups by the receptors to which they bind ^[3]

Since cholesterol is insoluble in blood, it is transported in the circulatory system within lipoproteins, complex spherical particles which have an exterior composed mainly of water-soluble proteins; fats and cholesterol are carried internally. A lipoprotein is a biochemical assembly that contains both Proteins and Lipids The lipids or their derivatives may be covalently or non-covalently bound Lipids are broadly defined as any fat- Soluble ( lipophilic) naturally-occurring Molecule, such as fats oils waxes cholesterol sterols fat-soluble There is a large range of lipoproteins within blood, generally called, from larger to smaller size: chylomicrons, very low density lipoprotein (VLDL), intermediate density lipoprotein (IDL), low density lipoprotein (LDL) and high density lipoprotein (HDL). Chylomicrons are large lipoprotein particles that transport dietary lipids from the intestines to other locations in the body Low-density lipoprotein ( LDL) is a type of Lipoprotein that transports Cholesterol and Triglycerides from the Liver to peripheral High-density lipoproteins ( HDL) is one of the 5 major groups of Lipoproteins ( Chylomicrons, VLDL, IDL, LDL, HDL The cholesterol within all the various lipoproteins is identical.

According to the lipid hypothesis, abnormally high cholesterol levels (hypercholesterolemia), or, more correctly, higher concentrations of LDL and lower concentrations of functional HDL are strongly associated with cardiovascular disease because these promote atheroma development in arteries (atherosclerosis). The lipid hypothesis was one of two hypotheses developed in the 1850s to explain the Pathogenesis of Atherosclerosis. Hypercholesterolemia (literally high blood cholesterol is the presence of high levels of Cholesterol in the blood. Cardiovascular disease or cardiovascular diseases refers to the class of diseases that involve the Heart or Blood vessels ( arteries and In Pathology, an atheroma (plural atheromata is an accumulation and swelling (-oma in Artery walls that is made up of cells (mostly Macrophage cells Atherosclerosis is a Disease affecting arterial Blood vessels It is a chronic inflammatory response in the walls of arteries in large part due to the accumulation This disease process leads to myocardial infarction (heart attack), stroke and peripheral vascular disease. Myocardial infarction ( MI or AMI for acute myocardial infarction) also known as a heart attack, occurs when the blood supply A stroke is the rapidly developing loss of brain functions due to a disturbance in the blood vessels supplying blood to the brain Peripheral vascular disease (PVD also known as peripheral artery disease (PAD or peripheral artery occlusive disease (PAOD is a collator for all Diseases Since higher blood LDL, especially higher LDL particle concentrations and smaller LDL particle size, contribute to this process more than the cholesterol content of the LDL particles ^[4], LDL particles are often termed "bad cholesterol" because they have been linked to atheroma formation. On the other hand, high concentrations of functional HDL, which can remove cholesterol from cells and atheroma, offer protection. These balances are mostly genetically determined but can be changed by body build, medications, food choices and other factors. Medication, also referred to as medicine, can be loosely defined as any substance intended for use in the diagnosis cure mitigation treatment or prevention of disease ^[5]

Contents 1 Physiology 1.1 Function 1.2 Synthesis and intake 1.2.1 Regulation 1.3 Excretion 1.4 In blood 2 Clinical significance 2.1 Hypercholesterolemia 2.2 Hypocholesterolemia 2.3 Cholesterol testing 3 Food sources 4 Cholesteric liquid crystals 5 See also 6 Additional images 7 References 8 External links

Physiology

Function

Cholesterol is required to build and maintain cell membranes; it regulates membrane fluidity over a wide range of temperatures. The cell membrane (also called the plasma membrane, plasmalemma, or "phospholipid bilayer" is a Selectively permeable Lipid bilayer Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature The hydroxyl group on cholesterol interacts with the phosphate head of the membrane, while the bulky steroid and the hydrocarbon chain is embedded in the membrane. Hydroxyl in Chemistry stands for a molecule consisting of an Oxygen atom and a Hydrogen atom connected by a Covalent bond. A phosphate, an Inorganic chemical, is a salt of Phosphoric acid. A steroid is a Terpenoid Lipid characterized by a Carbon skeleton with four fused rings generally arranged in a 6-6-6-5 fashion In Organic chemistry, a hydrocarbon is an Organic compound consisting entirely of Hydrogen and Carbon. Some research indicates that cholesterol may act as an antioxidant. An antioxidant is a Molecule capable of slowing or preventing the oxidation of other molecules ^[6] Cholesterol also aids in the manufacture of bile (which is stored in the gallbladder and helps digest fats), and is also important for the metabolism of fat soluble vitamins, including vitamins A, D, E and K. Bile or gall is a bitter yellow or green Alkaline fluid secreted by Hepatocytes from the Liver of most Vertebrates In many species Vitamin A refers to a family of similarly shaped molecules the Retinoids. Vitamin D is a group of fat-soluble Prohormones, the two major forms of which are vitamin D2 (or Ergocalciferol) and vitamin D3 (or See also Tocopherol, Tocotrienol Vitamin E is the collective name for a set of 8 related Tocopherols and Tocotrienols which are fat-soluble Vitamin K (K from "Koagulations-Vitamin" in German Danish Swedish and Norwegian denotes a group of Lipophilic, Hydrophobic Vitamins that It is the major precursor for the synthesis of vitamin D and of the various steroid hormones (which include cortisol and aldosterone in the adrenal glands, and the sex hormones progesterone, the various estrogens, testosterone, and derivatives). Vitamin D is a group of fat-soluble Prohormones, the two major forms of which are vitamin D2 (or Ergocalciferol) and vitamin D3 (or Steroid hormones are Steroids which act as Hormones Mammalian steroid hormones can be grouped into five groups by the receptors to which they bind Cortisol is a Corticosteroid Hormone produced by the Adrenal gland (in the Zona fasciculata of the Adrenal cortex) Aldosterone is a hormone that causes the tubules of the kidneys to retain sodium and water In Mammals the adrenal glands (also known as suprarenal glands) are the triangle-shaped Endocrine glands that sit on top of the Kidneys their Progesterone is a C-21 Steroid Hormone involved in the Female Menstrual cycle, Pregnancy (supports Gestation Estrogens (US otherwise oestrogens or œstrogens) are a group of Steroid compounds named for their importance in the Estrous cycle, Testosterone is a Steroid hormone from the Androgen group In mammals testosterone is primarily secreted in the testes of males and the Ovaries

Recently, cholesterol has also been implicated in cell signaling processes, where it has been suggested that it assists in the formation of lipid rafts in the plasma membrane. A lipid raft is a Cholesterol -enriched microdomain in Cell membranes Properties of lipid rafts Rietveld & Simons related lipid rafts in model The cell membrane (also called the plasma membrane, plasmalemma, or "phospholipid bilayer" is a Selectively permeable Lipid bilayer It also reduces the permeability of the plasma membrane to hydrogen ions (protons) and sodium ions. Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive Sodium (ˈsoʊdiəm is an element which has the symbol Na( Latin natrium, from Arabic natrun) atomic number 11 atomic mass 22 ^[7]

Cholesterol is essential for the structure and function of invaginated caveolae and clathrin-coated pits, including the caveolae-dependent endocytosis and clathrin-dependent endocytosis. In Biology, caveolae ( Latin for little caves) are small (50&ndash100 Nanometer) invaginations of the Plasma membrane in many vertebrate Endocytosis is a process where cells absorb material ( Molecules such as proteins from the outside by engulfing it with their Cell membrane. The role of cholesterol in caveolae-dependent and clathrin-dependent endocytosis can be investigated by using methyl beta cyclodextrin (MβCD) to remove cholesterol from the plasma membrane. Cyclodextrins (sometimes called cycloamyloses make up a family of cyclic Oligosaccharides, composed of 5 or more α-D-glucopyranoside units linked 1->4 as in Amylose

Synthesis and intake

Cholesterol is required in the membrane of mammalian cells for normal cellular function, and is either synthesized in the endoplasmic reticulum, or derived from the diet, in which case it is delivered by the bloodstream in low-density lipoproteins. The endoplasmic reticulum (Greek endo = "within" (prefix plásma = "formed entity" Latin reticulum = "little net" or ER, is an Organelle Low-density lipoprotein ( LDL) is a type of Lipoprotein that transports Cholesterol and Triglycerides from the Liver to peripheral These are taken into the cell by LDL receptor-mediated endocytosis in clathrin-coated pits, and then hydrolysed in lysosomes. The LDL Receptor is a mosaic protein that mediates the Endocytosis of cholesterol-rich LDL. Endocytosis is a process where cells absorb material ( Molecules such as proteins from the outside by engulfing it with their Cell membrane. Clathrin is a Protein that is the major constituent of the 'coat' of the clathrin- Coated pits and coated Vesicles formed during Endocytosis In Biology, caveolae ( Latin for little caves) are small (50&ndash100 Nanometer) invaginations of the Plasma membrane in many vertebrate

Cholesterol is primarily synthesized from acetyl CoA through the HMG-CoA reductase pathway in many cells and tissues. Acetyl-CoA is an important molecule in metabolism used in many biochemical reactions The mevalonate pathway or HMG-CoA reductase pathway or mevalonate-dependent (MAD route, is an important cellular Metabolic pathway present The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called Tissue is a cellular organizational level intermediate between cells and a complete organism About 20–25% of total daily production (~1 g/day) occurs in the liver; other sites of higher synthesis rates include the intestines, adrenal glands and reproductive organs. For other uses of the words gram or gramme see Gram (disambiguation. A day (symbol d is a unit of Time equivalent to 24 Hours and the duration of a single Rotation of planet Earth with respect to the The liver is a vital organ in the human body and is present in Vertebrates and some other animals In Anatomy, the intestine is the segment of the alimentary canal extending from the Stomach to the Anus and in humans and other mammals consists In Mammals the adrenal glands (also known as suprarenal glands) are the triangle-shaped Endocrine glands that sit on top of the Kidneys their A sex organ, or primary sexual characteristic, as narrowly defined is any of the anatomical parts of the body which are involved in sexual reproduction and constitute For a person of about 150 pounds (68 kg), typical total body content is about 35 g, typical daily internal production is about 1 g and typical daily dietary intake is 200–300 mg in the United States and societies adopting its dietary patterns. Of the cholesterol input to the intestines via bile production, 92–97% is reabsorbed in the intestines and recycled via enterohepatic circulation. Enterohepatic circulation refers to the circulation of Bile from the Liver, where it is produced to the Small intestine, where it aids in Digestion

Konrad Bloch and Feodor Lynen shared the Nobel Prize in Physiology or Medicine in 1964 for their discoveries concerning the mechanism and regulation of the cholesterol and fatty acid metabolism. Konrad Emil Bloch (b January 21 1912 &ndash October 15 2000) was a German American biochemist. Feodor Felix Konrad Lynen ( 6 April 1911 &ndash 6 August 1979) was a German Biochemist. The Nobel Prize in Physiology or Medicine (Nobelpriset i fysiologi eller medicin is awarded once a year by the Swedish Karolinska Institute. In Chemistry, especially Biochemistry, a fatty acid is a Carboxylic acid often with a long unbranched Aliphatic tail ( chain) which

Regulation

Biosynthesis of cholesterol is directly regulated by the cholesterol levels present, though the homeostatic mechanisms involved are only partly understood. Homeostasis (from Greek: ὅμος hómos, "equal" and ιστημι istēmi, "to stand" lit A higher intake from food leads to a net decrease in endogenous production, while lower intake from food has the opposite effect. The main regulatory mechanism is the sensing of intracellular cholesterol in the endoplasmic reticulum by the protein SREBP (Sterol Regulatory Element Binding Protein 1 and 2). Not to be confused with Intercellular, meaning "between cells" The endoplasmic reticulum (Greek endo = "within" (prefix plásma = "formed entity" Latin reticulum = "little net" or ER, is an Organelle Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl Sterol Regulatory Element Binding Protein s ( SREBP s are Transcription factors that bind to the Sterol regulatory element DNA sequence In the presence of cholesterol, SREBP is bound to two other proteins: SCAP (SREBP-cleavage activating protein) and Insig1. INSIG1 is short for Insulin -induced Gene 1 it is located on Chromosome 7 (7q36 When cholesterol levels fall, Insig-1 dissociates from the SREBP-SCAP complex, allowing the complex to migrate to the Golgi apparatus, where SREBP is cleaved by S1P and S2P (site-1 and -2 protease), two enzymes that are activated by SCAP when cholesterol levels are low. The Golgi apparatus (also called the The cleaved SREBP then migrates to the nucleus and acts as a transcription factor to bind to the SRE (sterol regulatory element) of a number of genes to stimulate their transcription. In the field of Molecular biology, a transcription factor (sometimes called a sequence-specific DNA binding factor is a Protein that binds to specific sequences Transcription is the synthesis of RNA under the direction of DNA Among the genes transcribed are the LDL receptor and HMG-CoA reductase. The LDL Receptor is a mosaic protein that mediates the Endocytosis of cholesterol-rich LDL. The mevalonate pathway or HMG-CoA reductase pathway or mevalonate-dependent (MAD route, is an important cellular Metabolic pathway present The former scavenges circulating LDL from the bloodstream, whereas HMG-CoA reductase leads to an increase of endogenous production of cholesterol. ^[8]

A large part of this mechanism was clarified by Dr. Michael S. Brown and Dr. Michael Stuart Brown (b April 13, 1941 in Brooklyn New York) is an American Geneticist and Nobel Laureate. Joseph L. Goldstein in the 1970s. Joseph L Goldstein (b April 18, 1940) from Kingstree South Carolina is a Nobel Prize winning Biochemist and Geneticist In 1985, they received the Nobel Prize in Physiology or Medicine for their work. The Nobel Prize in Physiology or Medicine (Nobelpriset i fysiologi eller medicin is awarded once a year by the Swedish Karolinska Institute. ^[8]

Excretion

Cholesterol is excreted from the liver in bile and reabsorbed from the intestines. The liver is a vital organ in the human body and is present in Vertebrates and some other animals Bile or gall is a bitter yellow or green Alkaline fluid secreted by Hepatocytes from the Liver of most Vertebrates In many species Under certain circumstances, when more concentrated, as in the gallbladder, it crystallises and is the major constituent of most gallstones, although lecithin and bilirubin gallstones also occur less frequently. The gallbladder (or cholecyst sometimes gall bladder is a small organ whose function in the body is to store Bile and aid in the digestive process In Medicine, gallstones (choleliths are Crystalline bodies formed within the body by accretion or concretion of normal or abnormal Bile component Lecithin is any of a group of yellow-brownish fatty substances occurring in animal and plant tissues and in egg yolk composed of Phosphoric acid, Choline, Bilirubin (formerly referred to as hematoidin) is the yellow breakdown product of normal Heme Catabolism.

In blood

See also: Blood lipids

Cholesterol is minimally soluble in water; it cannot dissolve and travel in the water-based bloodstream. Blood lipids (or blood fats are Lipids in the Blood, either free or bound to other molecules Water is a common Chemical substance that is essential for the survival of all known forms of Life. Instead, it is transported in the bloodstream by lipoproteins—protein "molecular-suitcases" that are water-soluble and carry cholesterol and triglycerides internally. A lipoprotein is a biochemical assembly that contains both Proteins and Lipids The lipids or their derivatives may be covalently or non-covalently bound (more properly known as, TAG or triacylglyceride) is Glyceride in which the Glycerol is Esterified with three Fatty acids It is the The apolipoproteins forming the surface of the given lipoprotein particle determine from what cells cholesterol will be removed and to where it will be supplied.

Cholesterol is transported towards peripheral tissues by the lipoproteins chylomicrons, very low density lipoproteins (VLDL) and low-density lipoproteins (LDL). Chylomicrons are large lipoprotein particles that transport dietary lipids from the intestines to other locations in the body Low-density lipoprotein ( LDL) is a type of Lipoprotein that transports Cholesterol and Triglycerides from the Liver to peripheral Large numbers of small dense LDL (sdLDL) particles are strongly associated with the presence of atheromatous disease within the arteries. In Pathology, an atheroma (plural atheromata is an accumulation and swelling (-oma in Artery walls that is made up of cells (mostly Macrophage cells For this reason, LDL is referred to as "bad cholesterol".

On the other hand, high-density lipoprotein (HDL) particles transport cholesterol back to the liver for excretion. High-density lipoproteins ( HDL) is one of the 5 major groups of Lipoproteins ( Chylomicrons, VLDL, IDL, LDL, HDL Having large numbers of large HDL particles correlates with better health outcomes, and hence it is commonly called "good cholesterol". In contrast, having small amounts of large HDL particles is independently associated with atheromatous disease progression within the arteries. In Pathology, an atheroma (plural atheromata is an accumulation and swelling (-oma in Artery walls that is made up of cells (mostly Macrophage cells

Clinical significance

Hypercholesterolemia

Main articles: hypercholesterolemia and lipid hypothesis

Conditions with elevated concentrations of oxidized LDL particles, especially "small dense LDL" (sdLDL) particles, are associated with atheroma formation in the walls of arteries, a condition known as atherosclerosis, which is the principal cause of coronary heart disease and other forms of cardiovascular disease. Hypercholesterolemia (literally high blood cholesterol is the presence of high levels of Cholesterol in the blood. The lipid hypothesis was one of two hypotheses developed in the 1850s to explain the Pathogenesis of Atherosclerosis. In Pathology, an atheroma (plural atheromata is an accumulation and swelling (-oma in Artery walls that is made up of cells (mostly Macrophage cells Arteries are Blood vessels that carry blood away from the Heart. Atherosclerosis is a Disease affecting arterial Blood vessels It is a chronic inflammatory response in the walls of arteries in large part due to the accumulation Coronary disease (or coronary heart disease) refers to the failure of Coronary circulation to supply adequate circulation to Cardiac muscle and surrounding Cardiovascular disease or cardiovascular diseases refers to the class of diseases that involve the Heart or Blood vessels ( arteries and In contrast, HDL particles (especially large HDL) have been identified as a mechanism by which cholesterol and inflammatory mediators can be removed from atheroma. Increased concentrations of HDL correlate with lower rates of atheroma progressions and even regression. A 2007 study pooling data on almost 900,000 subjects in 61 cohorts demonstrated that blood total cholesterol levels have an exponential effect on cardiovascular and total mortality, with the association more pronounced in younger subjects. Still, because cardiovascular disease is relatively rare in the younger population, the impact of high cholesterol on health is still larger in older people. ^[9] There remains some opposition to the link between cholesterol and coronary heart disease, termed the "lipid hypothesis". Coronary disease (or coronary heart disease) refers to the failure of Coronary circulation to supply adequate circulation to Cardiac muscle and surrounding The lipid hypothesis was one of two hypotheses developed in the 1850s to explain the Pathogenesis of Atherosclerosis.

Elevated levels of the lipoprotein fractions, LDL, IDL and VLDL are regarded as atherogenic (prone to cause atherosclerosis). Levels of these fractions, rather than the total cholesterol level, correlate with the extent and progress of atherosclerosis. Conversely, the total cholesterol can be within normal limits, yet be made up primarily of small LDL and small HDL particles, under which conditions atheroma growth rates would still be high. In contrast, however, if LDL particle number is low (mostly large particles) and a large percentage of the HDL particles are large, then atheroma growth rates are usually low, even negative, for any given total cholesterol concentration. Recently, a post-hoc analysis of the IDEAL and the EPIC prospective studies found an association between high levels of HDL cholesterol (adjusted for apolipoprotein A-I and apolipoprotein B) and increased risk of cardiovascular disease, casting doubt on the cardioprotective role of "good cholesterol". ^[10]

Multiple human trials utilizing HMG-CoA reductase inhibitors, known as statins, have repeatedly confirmed that changing lipoprotein transport patterns from unhealthy to healthier patterns significantly lowers cardiovascular disease event rates, even for people with cholesterol values currently considered low for adults. The statins (or HMG-CoA reductase inhibitors) form a class of hypolipidemic drugs used to lower Cholesterol levels in people with or at risk of Cardiovascular As a result, people with a history of cardiovascular disease may derive benefit from statins irrespective of their cholesterol levels,^[11] and in men without cardiovascular disease there is benefit from lowering abnormally high cholesterol levels ("primary prevention"). ^[12] Primary prevention in women is practiced only by extension of the findings in studies on men,^[13] since in women, none of the large statin trials has shown a reduction in overall mortality or in cardiovascular end points. ^[14]

The 1987 report of National Cholesterol Education Program, Adult Treatment Panels suggest the total blood cholesterol level should be: < 200 mg/dL normal blood cholesterol, 200–239 mg/dL borderline-high, > 240 mg/dL high cholesterol. The National Cholesterol Education Program is a program managed by the National Heart Lung and Blood Institute, a division of the National Institutes of Health ^[15]. The American Heart Association provides a similar set of guidelines for total (fasting) blood cholesterol levels and risk for heart disease:^[16]

Level mg/dL	Level mmol/L	Interpretation
< 200	< 5. The American Heart Association (AHA is a Non-profit organization in the United States that fosters appropriate For other uses of the words gram or gramme see Gram (disambiguation. The litre or liter (see spelling differences) is a unit of Volume. The mole (symbol mol) is a unit of Amount of substance: it is an SI base unit, and almost the only unit to be used to measure this The litre or liter (see spelling differences) is a unit of Volume. 2	Desirable level corresponding to lower risk for heart disease
200–240	5. 2–6. 2	Borderline high risk
> 240	> 6. 2	High risk

However, as today's testing methods determine LDL ("bad") and HDL ("good") cholesterol separately, this simplistic view has become somewhat outdated. The desirable LDL level is considered to be less than 100 mg/dL (2. 6 mmol/L)^[16], although a newer target of < 70 mg/dL can be considered in higher risk individuals based on some of the above-mentioned trials. The mole (symbol mol) is a unit of Amount of substance: it is an SI base unit, and almost the only unit to be used to measure this A ratio of total cholesterol to HDL—another useful measure—of far less than 5:1 is thought to be healthier. Of note, typical LDL values for children before fatty streaks begin to develop is 35 mg/dL. Fatty streak, though composed of macrophage white blood cells not fat is the term generally given to the earliest stages of Atheroma, as viewed at autopsy looking at

Most testing methods for LDL do not actually measure LDL in their blood, much less particle size. For cost reasons, LDL values have long been estimated using the Friedewald formula: [total cholesterol] − [total HDL] − 20% of the triglyceride value = estimated LDL. (more properly known as, TAG or triacylglyceride) is Glyceride in which the Glycerol is Esterified with three Fatty acids It is the The basis of this is that Total cholesterol is defined as the sum of HDL, LDL, and VLDL. Ordinarily just the total, HDL, and triglycerides are actually measured. The VLDL is estimated as one-fifth of the triglycerides. It is important to fast for at least eight hours before the blood test because the triglyceride level varies significantly with food intake.

Given the well-recognized role of cholesterol in cardiovascular disease, it is surprising that some studies have shown an inverse correlation between cholesterol levels and mortality in subjects over 50 years of age—an 11% increase overall and 14% increase in CVD mortality per 1 mg/dL per year drop in cholesterol levels. In the Framingham Heart Study, the researchers attributed this phenomenon to the fact that people with severe chronic diseases or cancer tend to have below-normal cholesterol levels. The Framingham Heart Study is a cardiovascular study based in Framingham Massachusetts. ^[17] This explanation is not supported by the Vorarlberg Health Monitoring and Promotion Programme, in which men of all ages and women over 50 lower cholesterol levels with very low cholesterol were increasingly likely to die of cancer, liver diseases, and mental diseases. This result indicates that the low cholesterol effect occurs even among younger respondents, contradicting the previous assessment among cohorts of older people that this is a proxy or marker for frailty occurring with age. ^[18]

A small group of scientists, united in The International Network of Cholesterol Skeptics, continues to question the link between cholesterol and atherosclerosis. The International Network of Cholesterol Skeptics (or THINCS) is a group of scientists physicians and other academicians from around the world who dispute the widely accepted ^[19] However, the vast majority of doctors and medical scientists accepts the link as fact. ^[20]

Hypocholesterolemia

Abnormally low levels of cholesterol are termed hypocholesterolemia. Hypocholesterolemia is the presence of abnormally low ( hypo-) levels of Cholesterol in the Blood ( -emia) Research into the causes of this state is relatively limited, but some studies suggest a link with depression, cancer and cerebral hemorrhage. In the fields of Psychology and Psychiatry, the terms depression or depressed refer to both expected and pathologically chronic or severe Cancer (medical term Malignant Neoplasm) is a class of Diseases in which a group of cells display uncontrolled A cerebral hemorrhage (or intracerebral hemorrhage, ICH) is a subtype of Intracranial hemorrhage that occurs within the Brain tissue itself Generally, the low cholesterol levels seem to be a consequence of an underlying illness, rather than a cause. ^[9]

Cholesterol testing

It is recommended by the American Heart Association to test cholesterol every 5 years for people aged 20 years or older. The American Heart Association (AHA is a Non-profit organization in the United States that fosters appropriate ^[21] A blood sample taken after fasting is taken by a doctor or a home cholesterol monitoring device to determine a lipoprotein profile. This measures total cholesterol, LDL (bad) cholesterol, HDL (good) cholesterol and triglycerides. It is recommended to have cholesterol tested more frequently than 5 years if a person: has total cholesterol of 200 mg/dL or more, is a man over age 45 or a woman over age 50, has HDL (good) cholesterol less than 40 mg/dL, or other risk factors for heart disease and stroke.

Food sources

Cholesterol is found in animal fats: all food containing animal fats contains cholesterol; food not containing animal fats either contains no cholesterol or negligible amounts. Major dietary sources of cholesterol include egg yolks, beef, poultry, and shrimp. ^[22]

Plants have trace amounts of cholesterol, so even a vegan diet, which includes no animal foods, has traces of cholesterol. However, the amounts are very small. For example, to ingest the amount of cholesterol in one egg yolk, one would need to drink about 9. 6 litres (2. 1 imp gal/2. 5 US gal) of pure peanut oil. ^{[16] [23]}

Plant products (e. g. flax seed, peanut), also contain cholesterol-like compounds, phytosterols, which are suggested to help lower serum cholesterol. Flax (also known as common flax or linseed) (binomial name Linum usitatissimum) is a member of the genus Linum The peanut, or Groundnut ( Arachis hypogaea) is a species in the Legume family Fabaceae native to South America, Mexico Phytosterols (also called plant sterols) are a group of steroid alcohols, Phytochemicals naturally occurring in Plants. ^[24]

Cholesteric liquid crystals

Some cholesterol derivatives, (among other simple cholesteric lipids) are known to generate the liquid crystalline cholesteric phase. Liquid crystals are substances that exhibit a phase of matter that has properties between those of a conventional Liquid, and those of a Solid The cholesteric phase is in fact a chiral nematic phase, and changes colour when its temperature changes. The term chiral (pronounced /ˈkaɪɹ(əl̩/ is used to describe an object that is non- superimposable on its mirror image Liquid crystals are substances that exhibit a phase of matter that has properties between those of a conventional Liquid, and those of a Solid Therefore, cholesterol derivatives are commonly used in liquid crystal thermometers and temperature-sensitive paints. The thermometer is a device that measures Temperature or Temperature gradient using a variety of different principles it comes from the Greek roots

See also

• Triglycerides
• Diet and heart disease
• Bile salts
• Lieberman-Burchard test

Additional images

Steroidogenesis

Space-filling model of the Cholesterol molecule

References

External links

• Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults US National Institutes of Health Adult Treatment Panel III
• Aspects of fat digestion and metabolism – UN/WHO Report 1994
• American Heart Association – "About Cholesterol"

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