Phytosterol metabolism inhibition

Phytosterols are found in most common vegetable oils. For example, soybean oil, one of the most commonly consumed oils, is reported to contain approximately 0.36% sterols and 0.124% tocopherols (15). The effect of phytosterols on the reduction of serum cholesterol has been attributed to the possible inhibition of intestinal reabsorption of circulating cholesterol. The saturated version of sterols, stands, is reported to be more readily metabolized, and this has led to the development of nutritional supplements and it is used commercially in food products such as margarines. The main stanol reported for this application is sitostanol, a saturated derivative of sitosterol. Sterol and cholesterol are used by the human body to synthesize important hormones, e.g., testosterone and progesterone, which are used also in many pharmaceutical applications. 

The firebrat, Thermobia domestica of the order Thysanura, is the most primitive insect found to be capable of dealkylating phytosterols to cholesterol (6). In this study, dietary sitosterol was shown to be converted to cholesterol, and with the inclusion in the diet of an azasteroid that inhibits A -reductase and causes an accumulation of desmosterol, it was also determined that desmosterol was an intermediate in the conversion of sitosterol to cholesterol. To date, this is the most primitive insect that has been examined with respect to sterol metabolism. 

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