The Difference Between Good And Bad Cholesterol
If cholesterol is so necessary, why is it sometimes described as bad and at other times as good?
Your liver packages cholesterol into so-called lipoproteins, which are combinations of lipids and proteins. Lipoproteins operate like commuter buses that carry cholesterol, other lipids like triglycerides, fat-soluble vitamins, and other substances through the bloodstream to the cells that need them.
- Low-density lipoproteins, sometimes called bad cholesterol, gets its bad reputation from the fact that high levels of it are associated with increasing your risk of heart disease. LDL contains more cholesterol than protein, making it lighter in weight. LDL travels through the bloodstream and carries cholesterol to cells that need it. When it becomes oxidized, LDL can promote inflammation and force lipids to accumulate on the walls of vessels in the heart and rest of the body, forming plaques. These plaques can thicken and may limit or completely block blood and nutrients to affected tissues or organs.
- HDLor high-density lipoproteinsis also commonly referred to as good cholesterol. HDL is heavier than LDL because it contains more protein and less cholesterol. HDL gets its good reputation from the fact that it takes cholesterol from the cells and brings it to the liver. Having higher levels of HDL may also help lower your risk of developing cardiovascular disease.
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Regulation Of Cholesterol Synthesis
Biosynthesis of cholesterol is directly regulated by the cholesterol levels present, though the homeostatic mechanisms involved are only partly understood. A higher intake from food leads to a net decrease in endogenous production, whereas lower intake from food has the opposite effect. The main regulatory mechanism is the sensing of intracellular cholesterol in the endoplasmic reticulum by the proteinSREBP . In the presence of cholesterol, SREBP is bound to two other proteins: SCAP and INSIG-1. When cholesterol levels fall, INSIG-1 dissociates from the SREBP-SCAP complex, which allows the complex to migrate to the Golgi apparatus. Here SREBP is cleaved by S1P and S2P , two enzymes that are activated by SCAP when cholesterol levels are low.
Cholesterol synthesis can also be turned off when cholesterol levels are high. HMG-CoA reductase contains both a cytosolic domain and a membrane domain. The membrane domain senses signals for its degradation. Increasing concentrations of cholesterol cause a change in this domain’s oligomerization state, which makes it more susceptible to destruction by the proteasome. This enzyme’s activity can also be reduced by phosphorylation by an AMP-activated protein kinase. Because this kinase is activated by AMP, which is produced when ATP is hydrolyzed, it follows that cholesterol synthesis is halted when ATP levels are low.
Main Functions Of The Liver:
Other than the production of cholesterol, the liver is known to possess more than 500 vital functions in the body.
These functions include but are not limited to the production of bile that is associated with the digestion of fat, production of proteins for the blood plasma.
It regulates the level of amino acid in the blood that is essential for the manufacture of protein within the body.
Liver also carries out filtering out the blood for the elimination of toxic products in the body, and the conversion of harmful ammonia into urea, which is later excreted through urine.
The liver stores iron in the body, so it also processes the hemoglobin for utilization of the iron content.
Regulating the process of blood clotting and countering infections by monitoring the immunity of the body and removing the bacteria from the system is also done by the liver.
The liver also plays a role in clearing out bilirubin from the hemoglobin. Accumulation of excess bilirubin in the bloodstream results in yellowing of skin and eyes.
As the liver breaks down the harmful substance in the body, bile is produced hat is later excreted through feces and the harmful urea is excreted through urine, thus keeping the body toxicity free.
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Medical Guidelines And Recommendations
In 2015, the United States Department of Agriculture Dietary Guidelines Advisory Committee recommended that Americans eat as little dietary cholesterol as possible, because most foods that are rich in cholesterol are also high in saturated fat and thereby may increase the risk of cardiovascular disease. For over 2 decades, the Dietary Guidelines for Americans recommended that dietary cholesterol be no more than 300 mg per day. In a 2014 draft, DGAC dropped this recommendation because evidence showed no appreciable relationship between dietary and serum cholesterol. This caught the eye of the Physicians Committee for Responsible Medicine , which sued DGAC due to concerns of conflicts of interest which prompted the final draft to recommend eating “as little dietary cholesterol as possible”. A 2013 report by the American Heart Association and the American College of Cardiology recommended to instead focus on healthy dietary patterns rather than cholesterol limits as they are hard for clinicians and consumers to implement. They recommend the DASH and Mediterranean diet, which are low in cholesterol. A 2017 review by the American Heart Association recommends switching saturated fats for polyunsaturated fats to reduce cardiovascular disease risk.
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Cholesterol In Cell Membranes
Every cell throughout your body is surrounded by a membrane, which consists of proteins, phospholipids and cholesterol. Phospholipids form most of the membranes structure. Theyre amphipathic and shaped like a matchstick, with insoluble fatty acids forming the stick and a soluble phosphate functional group at the top. Cholesterols hydroxyl group can attach to the phosphate head, while its hydrocarbons connect to the phospholipids fatty acids. Cholesterol adds rigidity to the phospholipids, which are fluid and constantly moving. It also regulates what can get through the membrane by making it less permeable and anchors proteins to the membrane.
- Every cell throughout your body is surrounded by a membrane, which consists of proteins, phospholipids and cholesterol.
- Cholesterol adds rigidity to the phospholipids, which are fluid and constantly moving.
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Anatomy Of The Liver:
Since the liver is the principal site of cholesterol synthesis within the body, it is crucial to understand the anatomy of the liver.
The liver is conical in shape and dark reddish-brown in color and weighing roughly 3 pounds.
The blood source of the liver is the circulation carried out by the hepatic artery and the blood carrying nutrients reaching the liver through the hepatic portal vein.
13% of the bodys blood supply is held with the liver at any given point in time.
The liver can be segmented into two main lobes, each of which is made up of 8 segments containing 1000 ducts.
These are connected to smaller ducts that, in turn, combine to form the common hepatic ducts.
This common hepatic duct is responsible for the transportation of bile produced in the liver to the gall bladder and the duodenum through the common bile duct.
What Are The 3 Cholesterol
The three cholesterol are cholesterol, triglycerides, and HDL . These are important because they are all associated with heart disease. Cholesterol is the most important type of fat in the body and is responsible for making the heart work properly. Triglycerides are another type of fat and are responsible for making the heart work too. HDL is also important and helps to reduce the risk of heart disease.
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Adrenal Microsomal Subfractions From Other Species
To eliminate the possibility that the presence of translocon-associated proteins in adrenal smooth microsomes was confined to the guinea pig, we examined similarly prepared microsomes from adrenals of several species: rat, dog, cattle, rabbit, sheep, and pig. In most, as in the guinea pig adrenal, OST and Sec61 complex subunits as well as the molecular chaperones BiP, GRP94, and calnexin, were found to be in equal or greater concentration in smooth microsomes compared with rough microsomes . The sole exceptions to the equal or greater concentration of these proteins in the smooth microsomes were in the rat adrenal. In the rat adrenal, the OST components as well as BiP and GRP94 were in greater concentration in the rough microsomes. In all of the species examined, however, the SER markers CYP17 and 3HSD were in greater concentration in the smooth microsomes than in rough microsomes. In all cases, the ribosomal protein S3 was localized to the ribosome bearing fractions . This gives increased confidence that the broader distribution of translocon-associated proteins in the ER is a property of most adrenocortical cells and perhaps of steroid-secreting cells in general.
Formation Of A C10 Intermediate
The next stage begins with the conversion of one molecule of isopentenyl-pyrophosphate to dimethylallyl-pyrophosphate, catalyzed by the isopentenyl-pyrophosphate isomerase. The product is condensed with another molecule of isopentenyl-pyrophosphate to yield geranyl-pyrophosphate. In this reaction, catalyzed by geranyl-pyrophosphate synthase, the pyrophosphate of the first substrate serves as a leaving group. The resulting carbocation reacts with the double bond of the second substrate.
With all of the bad publicity cholesterol gets, people are often surprised to learn that its actually necessary for our existence.
Whats also surprising is that our bodies produce cholesterol naturally. But cholesterol isnt all good, nor is it all bad its a complex topic and one worth knowing more about.
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Bile Acids Undergo Enterohepatic Cycling
In an enterohepatic cycle, a substance is secreted by the liver into the bile, passes into the intestine and is taken up again into the blood, either by passive diffusion across cell membranes or by active transport. Since blood drained from the intestines feeds into the portal vein, the substance will return to the liver, where it may be captured by liver cells and once again secreted into the bile.
Bile acids are taken up by active transport in the terminal ileum, that is, in the lowermost section of the small intestine. The efficiency of reuptake is normally > 90Ã %. Only the fraction that is not recovered needs to be replaced by de novo synthesis from cholesterol.
During their repeated passages through the intestine, some bile acids undergo modification by microbial enzymes an example is the formation of deoxycholate from cholate. Such modified molecules become part of the circulating bile acid pool.
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.
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Cholesterol Deficiency And Sonic Hedgehog Signaling
Cholesterol is an end product of the mevalonate pathway and is required for normal development. Ethanol has been shown to inhibit the mevalonate pathway and thus cholesterol biosynthesis . In mice, the lack of availability of cholesterol results in a drastic decline in sonic hedgehog signals transduction . Moreover, chicken and mouse embryos exposed to ethanol displayed reduced shh signaling . Therefore, alcohol-dependent inhibition of the cholesterol modification of shh produces morphologic defects which are similar to FASD phenotypes. In zebrafish embryos, ethanol treatment causes a dose-dependent reduction in cholesterol content, decreased cholesterol modification of shh, and a loss of shh signal transduction resulting in cyclopia, craniofacial hypoplasia, and holoprosencephaly . Further, supplementation of cholesterol is able to rescue the zebrafish embryos from these phenotypic defects.
N.S. Bhacca, in, 2000
What Is Cholesterol And What Is A Healthy Level
Cholesterol is a waxy, fat-like substance that occurs naturally in the body. It plays a vital role in how every cell works and every single cell needs and contains cholesterol. The body also turns it into vitamin D and a variety of hormones and it is also the raw material for bile acids which the body produces to aid digestion of fats .
However, the type and level of cholesterol in the body is important for health and too high a cholesterol level increases the risk of heart disease. Although genetic factors play an important role in determining a personâs cholesterol level it is also influenced strongly by diet and while cholesterol level is regarded as a major risk factor for coronary artery disease, it is regarded as a âmodifiableâ risk factor. It can be modified by diet and the type and quantity of foods we eat can make a big difference and this provides an opportunity to develop specific foods which can help lower cholesterol levels.
Cholesterol can enter the body in the foods we eat or can be produced in the body by the liver . Dietary cholesterol accounts for around 25â40% of the daily turnover of cholesterol whereas production in the body accounts for 60â75% .
The liver is the âcontrol centreâ for the bodyâs cholesterol transport system. Cholesterol is transported around the body in the form of lipoproteins. There are two main types of lipoproteins involved in cholesterol transport and these are called LDL cholesterol and HDL cholesterol .
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Connection Between Cholesterol And Alzheimer’s Disease
Cholesterol plays a central role in the biology of amyloid precursor protein and the toxic peptide generated by its cleavage, A. The ability of cholesterol to modulate A production, combined with the utility of statins in health care, suggests fertile avenues of research for treating AD. Cholesterol metabolism presents multiple targets for inhibiting A production. Furthermore, cholesterol is a very abundant component of the synaptic membrane, where the acetylcholine receptor is located. Cholesterol affects AChR proteins on multiple levels. Thus AD may be partly associated with an abnormal crosstalk between the receptor protein and the sterol in the synaptopathy .
ANDREAS UPHOFF, … PENTTI SOMERHARJU, in, 2008
High Cholesterol Can Often Be Treated By:
- Following a low fat, high fiber diet
- Increase exercise
- Control blond sugar levels if diabetic
- Taking medications as ordered to control low thyroid levels
- Quit Smoking
At Emed Primary Care & Walk in Clinic, We start with gradually comprehensive assessment to clarify your goals to overcome high cholesterol. We will determine your current health status, and assess your lifestyle.
As a result our physician will perform a physical exam to determine your risk for heart disease, diabetes, stroke and other weight-related conditions, as well as to assess your current Level of metabolic fitness. Finally based on the results of your evaluation, Emed Primary Care & Walk in Clinic weight management team will design a program just for you, incorporating nutrition, education, exercise, medical supervision and more.
Cholesterol is carried through your blood, attached to proteins. This combination of proteins and cholesterol is called a lipoprotein. There are different types of cholesterol, based on what the lipoprotein carries. They are:
- Low-density lipoprotein . LDL, or bad cholesterol, transports cholesterol particles throughout your body. LDL cholesterol builds up in the walls of your arteries, making them hard and narrow.
- High-density lipoprotein . HDL, or good cholesterol, picks up excess cholesterol and takes it back to your liver.
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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.
Drink At Least 4 Cups Of Tea Each Day
Tea can help to lower blood cholesterol, reduce arterial plaque, improve blood vessel function, and decrease lipid oxidation. If you drink coffee or soda, aim for the lower caffeine varieties. Caffeine can increase cholesterol levels by nearly 10%.
Finally, if you dont drink alcohol, dont start. If you do, only use it in small amounts, see All About Alcohol for more.
A note on supplements
With all supplements, dont run out to the vitamin store and fill your pockets. Chat with your doc first and consider what you really need.
A note about dietary cholesterol
Dietary cholesterol has minimal impact on blood cholesterol for most individuals. In general, eggs dont seem to have a negative effect on blood cholesterol measures. Omega-3 eggs might even have a beneficial effect since they improve key blood proteins and decrease blood glucose.
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Explain Lipids And Its Types
Lipids are a type of organic molecule, and its monomer, or “building block,” is a fatty acid. All organic molecules contain carbon, so lipids contain carbon too.
Lipids are categorized into three main types. They are triglycerides, steroids, and phospholipids.
Triglycerides are lipids you obtain from eating sources of fat, such as butter. They are made up of one glycerol molecule combined with three fatty acid molecules.
Steroids are lipids that include cholesterol, chlorophyll, and hormones. Out bodies use the cholesterol to make hormones.
Phospholipids are lipids that are one of the main structural components of all cell membranes in cells. The cell membranes are made up of a lipid bilayer.