Cholesterol and triglyceride levels, ..

11/02/2013 · What is the difference between cholesterol and ..

Biosynthesis (also called anabolism) is a multi-step, ..

In conditions with elevated concentrations of oxidized LDL particles, especially small LDL particles, cholesterol promotes atheroma plaque deposits in the walls of arteries, a condition known as atherosclerosis, which is a major contributor to coronary heart disease and other forms of cardiovascular disease. (In contrast, HDL particles have been the only identified mechanism by which cholesterol can be removed from atheroma. Increased concentrations of large HDL particles, not total HDL particles, correlate with lower rates of atheroma progressions, even regression.)

Cholesterol: Synthesis, Metabolism, Regulation

The average amount of blood cholesterol varies with age, typically rising gradually until one is about 60 years old. A study by Ockene et al. showed that there are seasonal variations in cholesterol levels in humans, more, on average, in winter.

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, 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). In the presence of cholesterol, SREBP is bound to two other proteins: SCAP (SREBP-cleavage activating protein) and Insig-1. 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 1/2 protease), two enzymes that are activated by SCAP when cholesterol levels are low. 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. Among the genes transcribed are the LDL receptor and HMG-CoA reductase. The former scavenges circulating LDL from the bloodstream, whereas HMG-CoA reductase leads to an increase of endogenous production of cholesterol. An excess of cholesterol can build up in the bloodstream and accumulates on the walls of arteries. This build up is what can lead to clogged ateries and eventually to heart attacks and strokes.

Cholesterol | Wiki | Everipedia

Cholesterol is required to build and maintain cell membranes; it makes the membrane's fluidity - degree of viscosity - stable over bigger temperature intervals (the hydroxyl group on cholesterol interacts with the phosphate head of the membrane, and the bulky steroid and the hydrocarbon chain is embedded in the membrane). Cholesterol also aids in the manufacture of bile (which helps digest fats), and is also important for the metabolism of fat soluble vitamins, including vitamins A, D, E and K. It is the major precursor for the synthesis of vitamin D, of the various steroid hormones, including cortisol and aldosterone in the adrenal glands, and of the sex hormones progesterone, estrogen, and testosterone. Further recent research shows that cholesterol has an important role for the brain synapses as well as in the immune system, including protecting against cancer.

other steroids such as cholesterol and ..

Cholesterol is minimally soluble in water; it cannot dissolve and travel in the water-based bloodstream. Instead, it is transported in the bloodstream by lipoproteins - protein "molecular-suitcases" that are water-soluble and carry cholesterol and fats internally. The proteins forming the surface of the given lipoprotein particle determine from what cells cholesterol will be removed and to where it will be supplied.

Cholesterol also is the precursor of steroid hormones and bile acids

Often, when most doctors talk to their patients about the health concerns of cholesterol, they are referring to "bad cholesterol", or low-density lipoprotein (LDL). "Good cholesterol" is high-density lipoprotein (HDL).

Squalene is an ancient molecule

Although relatively rare, an excessively low cholesterol level (hypocholesterolemia) (readings below 160 mg/dL) can increase the risk of depression, cancer, hemorrhagic stroke, respiratory diseases.