Receptors in the Regulation of Lipoprotein Metabolism
Steroids play a number of important roles in human physiology. They are essential structural components of cell membranes, they act as humoral messengers, and they facilitate the digestion and absorption of dietary fat. The steroid nucleus itself comes from two sources. Approximately one half of the daily body burden of about 1.0 gm is produced endogenously while the rest is assimilated in the diet. Despite its biological indispensability, it is potentially toxic to cells if allowed to accumulate within them. Consequently, a number of mechanisms operate to regulate its intracellular concentration. This occurs at the expense of the extracellular (or plasma) pool whose mass is permitted to vary over a wide range. It is a popular misconception that the prevailing concentration of a plasma analyte is necessarily a reflection of the physiological requirement of the individual. While that may be the case for glucose or sodium, it is certainly not so for cholesterol. Animal studies have established that levels of as low as 1.0 mmol/l are adequate for the needs of the organism and many humans survive at values of 2–4 mmol/l.
KeywordsFamilial Hypercholesterolemia Cholesterol Homeostasis Cholesterol Acyl Transferase Chylomicron Remnant Sterol Level
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