Cholesterol is a waxy fat-like substance that is found in all cells of the body. The liver makes it mostly from saturated fats in foods. Very little cholesterol is found in foods except for eggs, liver, kidney, sea-foods such as prawn, all of which contain cholesterol (Olson, 2009).
Cholesterol are steroids of lipid that have a special chemical structure, this structure is made of four rings of carbon substance. Cholesterol is found especially in animal fat. Ergosterol, this is the form of cholesterol in plant but when ingested (contain in plant food) it is automatically converted to cholesterol. (Hainer, 2009) other steroid include hormone, steroid like cortisol, Oestrogen and testosterone. Cholesterol is produced and transported in the blood plasma of all mammals.
Importance of cholesterol
Cholesterol plays a vital role on how the cell work in the body. It is the material which the body uses to make other vital chemicals, such as hormones and vitamin D, it is an essential lipid constituent of cell membrane (Pearson, 2012). However, too much cholesterol in the body can increase the risk of getting heart and circulating disease. Heart and circulating disease includes coronary heart disease, stroke and diseases that affect the circulation such as peripheral arterial disease.
Functions of cholesterol
- It build and maintains cell membrane(outer layer) and prevent crystallization of hydrocarbons in the membrane
- It is involved in the production of sex hormones released by the adrenal glands(cortisol, corticosterone, aldosterone and others)
- It aid in the production of bile
- It convert sunshine to vitamin D
- It is important for metabolism of fat soluble vitamins, including vitamin A,D,E and K
- It insulates nerves fibers
- It is essential for determining which molecule can pass into the cell and which cannot (cell membrane permeability)
Sources of cholesterol
All foods containing animal fat contain cholesterol to varying extent (Christie, 2013) major sources of dietary cholesterol are egg yolk, beef, and shrimp human breast milk, also contain significant amount of cholesterol.
Types of cholesterol
There are different types of cholesterol in the body, but the important types that are of medical significant are:
- Low–density lipoprotein (LDL): These are known as bad cholesterol. They are produce by the liver and they carry cholesterol and fats to different parts of the body from the liver examples of place where they carry fat to are muscle, tissues, organs and heart. Too much low-density lipoprotein build up the walls of the arteries that feeds the heart and the brains, this clot the arteries resulting in a condition known as atherosclerosis (Durrington, 2006).
- High-density lipoprotein (HDL): This is considered good cholesterol it is produced by the liver and they carry cholesterol from the tissues and organs back to the liver for recycling high level of HDL is a good indicator of a healthy heart.
- Very low density lipoprotein (VLDL): They carry cholesterol from the liver to organs and tissues in the body. They are formed by the combination of cholesterol and triglycerides. They are associated with atherosclerosis and heart disease because it deposit cholesterol at any site of the body.
Synthesis of cholesterol
Cholesterol is a fat like material (steroid) present in blood, must tissue especially nervous tissue (Emma, 2009). It occurs in the body naturally, it is synthesized from acetate mainly in the liver. About 20-25% of daily cholesterol is produced in the liver, but other site in the body such as intestine, adrenal glands and reproductive organs can produce cholesterol. Cholesterol is transported in the body to and fro from cell and tissue by special carries known as lipoprotein. It can be synthesized in animals in form of sterol but absent in prokaryotes such as bacterial etc. although cholesterol is an important and necessary molecule in man, a high level of serum cholesterol is an indication of disease such as heart disease.
Cholesterol metabolism and recycling excretion
Cholesterol is susceptible to oxidation and easily from oxygenated derivatives known as oxsterols. Three different mechanism can form these auto-oxidation, secondary oxidation to lipid peroxidation and cholesterol metabolizing enzymes oxidation (Setarch, 2009). A great intestine oxysterols arose when they were shown to exact inhibitory action on cholesterol biosynthesis. Additional roles for oxysterol in human physiology including their participation in bile and biosynthesis function as transport forms of cholesterol and regulation of gene transcription (Hanukoglu, 2008).
Cholesterol is oxidized by the liver into a variety of bile acid, thus in turn are conjugated with glycine, glucoronic acid. A mixture of conjugated and unconjugated bile acids along with cholesterol. It is excreted from the liver into the bile duct. Approximately 95% of the bile acids are reabsorbed from the intestine and reminders are lost in the faeces (Jayanta, 2009).
The excretion and reabsorption of bile acids from the basis of the enter hepatic circulation which is essentially for the digestion and absorption of dietary fats. Every day to 1g of cholesterol enters the colon. This cholesterol originates from the diet bile and desequainated intestinal cells and can be metabolized and colonic bacteria. Cholesterol is converted mainly into coyrrostanol, a non-absorbable sterol that is excreted in faeces. A cholesterol-reducing bacterium origin has been isolated from human faeces.
Clinical significance of cholesterol
Hypercholesterolemia
According to the lipid hypothesis, abnormal cholesterol levels, actually higher concentration lower-density lipoprotein particles and lower concentration of functional high-density lipoprotein particles are strongly associated with cardiovascular disease (Lecerf, 2011).
Hypocholesterolemia
Abnormally low levels of cholesterol are termed hypocholesterolemia and some major causes are depression and cerebral haemorrhage. In general the low level of cholesterol seen to be a consequence, rather than a causes of an underlying illness.
Diagnosis
Approximately, 85% of individual with this disorder have not be diagnosed and consequently are not receiving lipid lowering treatment. Physical examination finding can help the physician make the diagnosis of a familial hypercholesterolaemia tendon xanthomas are seen in 20-40% of individual with familial hypercholesterolaemia and are pathognomonic for the condition. A xanthelasma or corneal arcus may also be seen. These common signs are supportive of the diagnosis but are non-specific findings.
Conclusion
Cholesterol is very essential in the body therefore it is needed for the proper up keep of the body cells for proper functioning. Excess cholesterol in the blood is very risky which may likely cause heart attack, heart disease, and hypertension and also result in stroke. Though cholesterol is very essential for use in the body it is also important that it should be monitored often especially adults and obsess individuals Increased level does not give specific symptom that is why it is important for individual to check their cholesterol level before it causes damages which may result in death.
References
Olson RE (2009) “Discovery of the lipoproteins, their role in fat transport and their significance as risk factors” J, Nutr. (suppl) :128. 439-443
Hainer T. (2009): high density lipoprotein cholesterol, Circulation 64 (3part): 63-64
Pearson, A (2012): phytogenetic and biochemical evidence for steroid synthesis. Prod. Natl. Acid Sci vol 2(6): 153-257
Christie W (2012): lipid analysis, isolation, separation, identification and structural analysis of lipid. Scotland Voly Press pp. 5-7
Durrighton, P. (2006): hyperlipidemia diagnosis and management (2nd edition) oxford. Butterworth Heinemann publishers. Pp. 182-183
Emma L (2009): cholesterol lipodemia. Gateway 4(1): 42-43
Setarch, A (2009). Material plasma lipid concentration and risk of severe prepsis park. J. Med.Sc 25,563-567
Hanukoglu L (2008): steroidogenic enzymes structure function and role in regulation of steroid hormone biosynthesis”. J steroid Biochem Mol Biol 43(8): 779-804
Jayanta, D, (2009) study of steroid lipid profile in induced hypertension.Ind.J. Clin Biochem 21:165-168
Lecerf JM (2011), “Dietary cholesterol: from physiology to cardiovascular risk” Br J Nutr 106(1):6-14.
