Which Vitamin Is Derived From Cholesterol

Initial Activation Steps In Cholesterol Synthesis

The reactions shown in this slide are catalyzed by thiolase , HMG-CoA synthase , HMG-CoA reductase , mevalonate kinase, phosphomevalonate kinase , and diphosphomevalonate decarboxylase, and diphosphomevalonate decarboxylase again .68 In the subsequent steps of the pathway, six molecules of isopentenyl-pyrophosphate are used for the synthesis of one cholesterol molecule.

11.2.3

What Causes High Cholesterol

The most common cause of high cholesterol is an unhealthy lifestyle. This can include

• Unhealthy eating habits, such as eating lots of bad fats. One type, saturated fat, is found in some meats, dairy products, chocolate, baked goods, and deep-fried and processed foods. Another type, trans fat, is in some fried and processed foods. Eating these fats can raise your LDL cholesterol.
• Lack of physical activity, with lots of sitting and little exercise. This lowers your HDL cholesterol.
• Smoking, which lowers HDL cholesterol, especially in women. It also raises your LDL cholesterol.

Genetics may also cause people to have high cholesterol. For example, familial hypercholesterolemia is an inherited form of high cholesterol. Other medical conditions and certain medicines may also cause high cholesterol.

Bile Acid Cycling Involves Multiple Transport Proteins

A variety of transport proteins enable the bile acid enterohepatic cycle. Secretion from the liver cell into the bile is driven by ABCC2, another ABC type transporter . Reuptake from the lumen of the gut is mediated by the apical sodium-coupled bile acid transporter . A similar transporter, the Na+-dependent taurocholate cotransporting polypeptide , mediates uptake from the blood back into the liver cell. At the basolateral membranes of both intestinal and liver cells, organic anion transport proteins , which have a fairly low degree of substrate specificity, participate in bile acid transport.

11.5.4

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Only About 20% Of The Cholesterol In Your Bloodstream Comes From The Food You Eat Your Body Makes The Rest

Cholesterol has a bad reputation, thanks to its well-known role in promoting heart disease. Excess cholesterol in the bloodstream is a key contributor to artery-clogging plaque, which can accumulate and set the stage for a heart attack. However, the role of cholesterol in your body is not all negative.

To fully explain cholesterol, you need to realize that it’s also vital to your health and well-being. Although we measure cholesterol production in the blood, it’s found in every cell in the body. The;Harvard Special Health Report;Managing Your Cholesterol;explains cholesterol as a waxy, whitish-yellow fat and a crucial building block in cell membranes. Cholesterol also is needed to make vitamin D, hormones , and fat-dissolving bile acids. In fact, cholesterol production is so important that your liver and intestines make about 80% of the cholesterol you need to stay healthy. Only about 20% comes from the foods you eat.;

If you eat only 200 to 300 milligrams of cholesterol a day , your liver will produce an additional 800 milligrams per day from raw materials such as fat, sugars, and proteins.

Since cholesterol is a fat, it can’t travel alone in the bloodstream. It would end up as useless globs . To get around this problem, the body packages cholesterol and other lipids into minuscule protein-covered particles that mix easily with blood. These tiny particles, called lipoproteins , move cholesterol and other fats throughout the body.

Sterols: 2 Oxysterols And Other Cholesterol Derivatives

Oxysterols as defined and discussed here are oxygenated derivatives of cholesterol and its precursors, i.e. with additional hydroxyl, epoxyl or keto groups,that are found in all animal tissues.Many of these have vital functions in animals, while others are important as short-lived intermediates or end products in the catabolism or excretion of cholesterol or in the biosynthesis of steroid hormones, bile acids and 1,25dihydroxy-vitamin D3. They are normally present in biological membranes and lipoproteins at trace levels only, though they can exert profound biological effects at these concentrations. However, they are always accompanied by a great excess of cholesterol per se.

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How Is High Cholesterol Diagnosed

There are usually no signs or symptoms that you have high cholesterol. There is a blood test to measure your cholesterol level. When and how often you should get this test depends on your age, risk factors, and family history. The general recommendations are:

For people who are age 19 or younger:

• The first test should be between ages 9 to 11
• Children should have the test again every 5 years
• Some children may have this test starting at age 2 if there is a family history of high blood cholesterol, heart attack, or stroke

For people who are age 20 or older:

• Younger adults should have the test every 5 years
• Men ages 45 to 65 and women ages 55 to 65 should have it every 1 to 2 years

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Cholesterol Glycosides And Other Cholesterol Derivatives

Sterol glycosides are common constituents of plants , and it has become evident that cholesterol glucoside and less often cholesterol acyl-glucoside are also present in animal tissues. Both lipids were first found in the skin of snakes, reptiles and birds, but cholesterol glucoside occurs also in human plasma, fibroblasts and gastric mucosa, and some rat and mouse tissues, where it may act as a mediator of signal transduction in the early stages of heat stress.Indeed, both cholesterol glucoside and galactoside are present throughout development from embryo to adult in mouse brain. As with plant and fungal sterol glycosides, these have a -glucosidic linkage to cholesterol.In embryonic chicken brain, cholesterol -glucoside is accompanied by sitosterol glucoside, and there are suggestions that they may be involved in neurodegenerative disorders such as Gaucher disease and Parkinson’s disease.In addition, a cholesterol-conjugate with glucuronic acid has been isolated from human liver and plasma, but its origin, function and metabolic fate are unknown.

Cholesterol is found linked covalently to essential developmental proteins, known as the hedgehog signalling family, where one function of the cholesterol moiety is to anchor the protein in a membrane, but this is discussed in our web page on proteolipids.

Get In Gear With Exercise

Moving more can lower your LDL and raise your HDL, according to the Cleveland Clinic. Exactly how exercise does this is still being researched, but there are a few possibilities. Working out might increase the size of your LDL particles so they pose less of a heart disease risk, studies have shown. It might also speed the delivery of cholesterol to the liver, studies in mice have suggested. Exercise might also reduce the amount of cholesterol absorbed into the bloodstream.

Burning more calories can also, of course, help you drop pounds, which has benefits for all elements of your cholesterol profile. Aim to get in:

• At least 150 minutes a week of moderate-intensity aerobic activity or 75 minutes of vigorous aerobic activity every week

• Muscle-building, weight-training workouts at least two days a week

If this seems like a lot, dont get overwhelmedyou can start where you are and build up gradually from there. In fact, you can exercise in short nuggets throughout the day to chip away at your weekly goals. An activity as simple as a brisk daily walk or yard work is a good place to begin getting some more movement into your life. What matters is that you try to make exercise part of your everyday life.

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Link Between Cholesterol And Vitamin D Production Identified

UNSW scientists have identified a molecular switch in the body that regulates production of two substances vital to human health cholesterol and vitamin D.

UNSW scientists have identified a molecular switch in the body that regulates production of two substances vital to human health cholesterol and vitamin D.

They have shown that when levels of cholesterol are high, the switch is flicked so that less cholesterol is made and more vitamin D is produced in the skin.

The researchers say it is important to understand the processes that control production of these two vital substances and ensure a balance is maintained, to inform future medical recommendations.

Too much cholesterol can lead to heart disease, says lead author Anika Prabhu, of the UNSW School of Biotechnology and Biomolecular Sciences.

On the other hand, vitamin D deficiency has been associated with an increased risk of several conditions, including osteoporosis, autoimmune disease and diabetes.

More and more individuals are being diagnosed with vitamin D deficiency and taking supplements. So it is particularly important that we develop a better understanding of the control of vitamin D levels in the body, as well as levels of cholesterol,” she says.

The study by Professor Andrew Browns lab at UNSW is published in the;Journal of Biological Chemistry.

This substance, 7DHC, can also be turned into vitamin D by UV from sunlight.

Squalene Cyclization Yields The First Sterol Intermediate

The reactions shown here are catalyzed by squalene epoxidase and lanosterol synthase. The rearrangement indicated by the dashed arrow is not a real reactionââ¬âwe just rotate a couple of single bonds to show how the pieces fall into place for the subsequent cyclization.

The oxygen is introduced by squalene epoxidase, a cytochrome P450 enzyme. Such enzymes use NADPH to reduce one of the two atoms of molecular oxygen, while retaining the other one in a highly reactive state, which they then use toward their specific purposes . Squalene synthase inserts its active oxygen into a C=C double bond of the substrate to form an epoxide. The subsequent cleavage of the epoxide by lanosterol synthase starts a cascade of reactions that goes from one end of the molecule to the other, closing all four rings of the sterol skeleton in the process. Note that a methyl group also changes its place on the sterol ring; the reaction mechanism is quite intricate.

11.2.6

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Best Vitamins To Reduce Cholesterol

Now that we know the risk factors associated with high total cholesterol levels and some of the lifestyle changes we can make to improve our HDL and reduce our LDL, it’s time to move on to one of the most important sections of this article, which is the various vitamins and dietary supplements that people can take to improve their cholesterol. We live busy lives, so it is not always easy to get enough exercise or cook the perfect heart-healthy meals, so many people will take vitamin supplements to carry some of the load. Even if you are exercising enough and cooking healthy meals, these vitamins can be the cherry on top of your cholesterol-improving routine for the best results.;

1. Niacin

Niacin, also known as vitamin B3, is part of the B-complex that also includes thiamine , riboflavin , pantothenic acid , pyridoxine , biotin , folate , and cobalamin . Together, the B vitamins play important roles in energy production, weight maintenance, and maintaining overall health, but Niacin is especially well known for its benefits to cholesterol levels in addition to its role in proper metabolization, proper nervous system functioning, and antioxidant protection.;

There are a number of reasons that people with cholesterol trouble often take niacin. Firstly, niacin helps boost levels of healthy HDL cholesterol. Additionally, niacin has been shown to lower triglyceride levels and moderately lower the overall levels of LDL in the bloodstream.;

2. Psyllium;

3. Red Yeast Rice

Risks And Side Effects

Is too much vitamin K2 bad for you? While its rare to experience side effects or vitamin k2 toxicity from getting high amounts from food alone, you might develop symptoms if you take high doses of vitamin K supplements.

However, for most people even high doses of this vitamin, such as 15milligrams three times a day, have been shown to generally be safe.

Are there potential drug interactions to worry about? If youre someone who takes the drug Coumadin, a potential side effect associated with taking too much vitamin K is increasing your risk for heart-related problems.

Too much vitamin K can also also contribute to complications in people with blood clotting disorders.

Look for a supplement that specifically lists menaquinone if you plan to supplement. Because vitamin K supplements can interact with many medications, talk to your doctor if you plan to take a vitamin K supplement and are taking any daily medications.

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Electrocyclizations Without Subsequent 6 Electrocyclization

Vitamin D3 is synthesized in the skin of vertebrates through the participation of a cholesterol derivative in a pericyclic cascade involving a 6 conrotatory electrocyclic ring opening, followed by an antarafacial sigmatropic hydride shift. Vitamin D3 is then hydroxylated in the liver to yield 25-hydroxyvitamin D3 and hydroxylated further in the kidneys to yield 1,25-dihydroxyvitamin D3, a potent ligand of the vitamin D receptor. The propensity of these natural substances to partake in pericyclic reactions was used in the preparation of conformationally locked analogs of 1,25-dihydroxyvitamin D3 .88 Cyclooctatriene 371 was prepared via a thermal conrotatory 8 electrocyclization of 370, generated in situ by the partial reduction of trieneyne 369 under Lindlar conditions. The cyclization was torquoselective, where bond formation occurs via an equatorial attack on the trans-fused hexahydroindene moiety. The cyclooctatriene product does not undergo a subsequent 6 electrocyclization, presumably due to the strained nature of the resulting spiro-compound.

Scheme 64. Synthesis of vitamin D3 analogs.

Scheme 65. Electrocyclic transformation of squarate esters.

Table 16. Electrocyclic transformation of squarate esters

Entry

Martin Kohlmeier, in, 2015

Muscle Problems That Are Thought To Be Caused By Statins

Its possible that muscle aches and pains that are often thought to be caused by statins are actually caused by a lack of vitamin D. Too little vitamin D can cause muscle weakness and tenderness in the bones these muscle problems seem very similar to the ones linked to statins.

Because a lack of vitamin D is so common, its likely that many people who are taking statins dont have enough vitamin D.

Your doctor can check if you have enough vitamin D in your blood using a simple blood test.

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Cholesterol And Its Derivatives

Cholesterol may be the most intensely studied small molecule of biological origin. Not only are its complex biosynthetic pathway and the physiologically important products derived from it of scientific interest, but also the strong correlation in humans between high blood cholesterol levels and the incidence of heart attack and stroke is of paramount medical importance. The study of this molecule and its biological origin have resulted in more than a dozen Nobel Prizes.

Cholesterol is a prominent member of a large class of lipids called isoprenoids that are widely distributed in nature. The class name derives from the fact that these molecules are formed by chemical condensation of a simple five-carbon molecule, isoprene. Isoprenoids encompassdiverse biological molecules such as steroid hormones, sterols , bile acids, the lipid-soluble vitamins , phytol , the insect juvenile hormones, plant hormones , and polyisoprene . Many other biologically important isoprenoids play more-subtle roles in biology.

The Synthesis Of Progesterone And Corticosteroids From Pregnenolone

Progesterone is synthesized from pregnenolone in two steps. The 3-hydroxyl group of pregnenolone is oxidized to a 3-keto group, and the 5 double bond is isomerized to a 4 double bond . Cortisol, the major glucocorticoid, is synthesized from progesterone by hydroxylations at -17, C-21, and C-11; C-17 must be hydroxylated before C-21 is, whereas C-11 can be hydroxylated at any stage. The enzymes catalyzing these hydroxylations are highly specific, as shown by some inherited disorders. The initial step in the synthesis of aldosterone, the major mineralocorticoid, is the hydroxylation of progesterone at C-21. The resulting deoxycorticosterone is hydroxylated at C-11. The oxidation of the C-18 angular methyl group to an aldehyde then yields aldosterone.

Pathways for the Formation of Progesterone, Cortisol, and Aldosterone.

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The Synthesis Of Androgens And Estrogens From Pregnenolone

Androgens and estrogens also are synthesized from pregnenolone through the intermediate progesterone. Androgens contain 19 carbon atoms. The synthesis of androgens starts with the hydroxylation of progesterone at -17. The side chain consisting of C-20 and C-21 is then cleaved to yield androstenedione, an androgen. Testosterone, another androgen, is formed by the reduction of the 17-keto group of androstenedione. Testosterone, through its actions in the brain, is paramount in the development of male sexual behavior. It is also important for maintenance of the testes and development of muscle mass. Owing to the latter activity, testosterone is referred to as an anabolic steroid. Testosterone is reduced by 5a-reductase to yield dihydrotestosterone , a powerful embryonic androgen that instigates the development and differentiation of the male phenotype. Estrogens are synthesized from androgens by the loss of the C-19 angular methyl group and the formation of an aromatic ring. Estrone, an estrogen, is derived from androstenedione, whereas estradiol, another estrogen, is formed from testosterone.

Pathways for the Formation for Androgens and Estrogens.

How Fat Moves From Food To The Bloodstream

Fat and cholesterol cant dissolve in water or blood. Instead, the body packages fat and cholesterol into tiny, protein-covered particles called lipoproteins. Lipoproteins can transport a lot of fat; they mix easily with blood and flow with it. Some of these particles are big and fluffy, while others are small and dense. The most important ones are low-density lipoproteins , high-density lipoproteins , and triglycerides.

• Low Density lipoproteins

Low-density lipoproteins carry cholesterol from the liver to the rest of the body. Cells latch onto these particles and extract fat and cholesterol from them. When there is too much LDL cholesterol in the blood, these particles can form deposits in the walls of the coronary arteries and other arteries throughout the body. Such deposits, called plaque, can narrow arteries and limit blood flow. When plaque breaks apart, it can cause a heart attack or stroke. Because of this, LDL cholesterol is often referred to as bad, or harmful, cholesterol.

• High-density lipoproteins

High-density lipoproteins scavenge cholesterol from the bloodstream, from LDL, and from artery walls and ferry it back to the liver for disposal. Think of HDL as the garbage trucks of the bloodstream. HDL cholesterol is often referred to as good, or protective, cholesterol.

• Triglycerides

In general, the lower your LDL and the higher your HDL, the better your chances of preventing heart disease and other chronic conditions.

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