Cholesterol – always too high, never too low PART 2
The best studied molecule in medicine and for who’s research were awarded 13 Nobel Prizes is cholesterol.
Isolated for the first time in 1784 from gallstones and exerting a hypnotic fascination on generations of scientists, cholesterol is a molecule with a Janus head: just the property which in the cell membrane makes it so useful, its absolute insolubility to water makes it a mortal threat.
The cholesterol is a polycyclic alcohol, which fatty acids binds to, forming esterified cholesterol, thus becoming a fat which is met in almost all foods of animal origin. Most cholesterol in the body is found in cell membranes, where is acting as a stabilizing agent. About a quarter of total cholesterol is found in the membranes of the nervous system – brain, spinal cord and peripheral nerves. In his role as precursor, the cholesterol provides the molecular skeleton for:
- bile acids formation, with an important role in the digestion of fats in the intestine;
- production of adrenal cortical hormones, sexual, male and female;
- the formation of vitamin D.
The cholesterol is a main component of each cell membrane. The importance of this substance can be deduced from the fact that the body manufactures its needed cholesterol, without needing any food intake.
Cholesterol biosynthesis occurs in every nucleus cell. While it was believed that most of the cholesterol synthesis occurs in the liver, researches showed that mass body tissues respond of the overwhelming majority of the endogenous cholesterol productions. In humans, hepatic synthesis represents 10-20% of all daily productions. And because most cholesterol synthesis occurs in extrahepatic tissues and the only excretion and catabolism of the cholesterol is the liver, about 600-800 mg of holesterol must be transported daily from peripheral tissues to liver, which in turn, can carry catabolism and bile secretion.
The total amount of cholesterol in the body is about 145 g, of which one third is found in the central nervous system. In the plasma is found between 7.5 and 9 grams. The content of cholesterol of human tissues is 2-3 mg in a gram of wet tissue.
One of the main roles of cholesterol is to help transport the absorbed fats. But fats, as well as cholesterol, are insoluble in water, and the blood consists, for the most part, of water. For the transport can still be done, fats along with cholesterol is packed in a protein wrapper, and what emerges from that is called lipoproteins. In other words, fats along with cholesterol binds to protein transport.
Normally, this transport operates smoothly. However, if foods contain too much fat, the transport system collapses. And the consequence is that fat, in particular cholesterol, are crowded into the circulatory system, storing the blood vessels.