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Omega 3 Natural Fish Oil Squalene - Deep Sea Shark Liver Oil Extract
Introduction History & Discovery Sources and Properties Occurrence in Humans Cholesterol Metabolism Cancer Antioxidant Coronary Heart Diseases Skin Care Toxicity & Dosage References
 
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Cholesterol Metabolism


Cholesterol is synthesized in human body from squalene (Fig. 3). Squalene is cyclized by an enzyme called squalene cyclase to form cholesterol (Liu et al., 1975). Steps involved in the process are cyclization and carbocation. Squalene epoxide formed is converted to lanosterol by the enzyme catalase. This is followed by the removal of 3 methyl groups from lanosterol to form cholesterol (Clayton & Bloch, 1956; Popják et al., 1961)



Although cholesterol is synthesized from squalene in human body, dietary intake of squalene does not elevate serum cholesterol level.


Amounts of squalene present in human tissues vary, being rich in areas which have high sebaceous glands (face, forehead) and low in areas having poor sebaceous glands. Secretion of squalene by sebaceous glands of the skin amounts to 125-475 mg day-1 person-1 (Kelly, 1999). Although cholesterol is synthesized from squalene in human body, dietary intake of squalene does not elevate serum cholesterol level. Only microsomal bound squalene is actively involved in this process and rest of the squalene is stored in the lipid droplet (Tilvis & Miettinen, 1983). Strandberg (1990) has shown that when human volunteers were fed with squalene (90 mg day-1 person-1) for 7-30 days, serum squalene levels increased up to 17-fold, but no significant changes were noticed in serum triglycerides and cholesterol contents. But squalene feeding produced significant increase in fecal excretion of cholesterol, its non polar derivatives and bile salts suggesting that although cholesterol synthesis has increased by as much as 50%, faecal elimination was upregulated.



Oral administration of squalene also results in the reduction of low density lipoprotein cholesterol (LDL), triglycerides and increase in high density lipoprotein (HDL).


Because of high faecal elimination, no increase in serum cholesterol was noticed. Oral administration of squalene also results in the reduction of low density lipoprotein cholesterol (LDL), triglycerides and increase in high density lipoprotein (HDL).




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