ABSTRACT
Sitosterolemia is a rare lipid storage disease that results in atherosclerosis and xanthomatosis (52,53). The condition is precipitated by mutations in the ATP-binding cassette proteins ABCG5 and ABCG8, which are found in the liver and intestines (54). Sitosterolemia is a rare disease; in 1998, Berger et al. (55) estimated that there were 34 cases worldwide. The genetics of sitosterolemia has been reviewed by Lee et al. (56). The possibility that excess dietary phytosterol may lead to this condition, though slight, nevertheless exists. Glueck et al. (57,58) found that subjects with premature coronary disease and their first-degree relatives exhibited elevated plasma levels of both cholesterol and phytosterol. The authors implied that phytosterolemia may have contributed to premature coronary disease. Salen et al. (59) found that in homzygotes cholesterol accounted for over 80% of plasma, tissue, and atheroma sterol. In seven subjects in the Glueck study (58), serum cholesterol levels were 7.09mmol/L whereas the concentration of campesterol, stigmasterol, and sitosterol combined was only 43.86µmol/L. The implication is that a slight excess of serum phytosterols may increase sterol deposition in the aorta. Sudhop et al. (60) reported on serum sterol levels in subjects with or without a family history of coronary heart disease. There were no differences in levels of serum lipids, lipoproteins, or cholesterol precursors. The average serum cholesterol levels of the two groups were identical: 242±46mg/dl in 27 controls and 242±31mg/dl in 26 test subjects. The serum campesterol level in the control group was 0.38mg/dl compared to 0.50mg/dl in the group with a family history of heart disease; sitosterol levels in the two groups were 0.31mg/dl and 0.40mg/dl, respectively. Levels of phytosterol in the sera of the test groups were small, representing 0.21% (campesterol) or 0.17% (sitosterol) of total serum sterol. In the control group, the percentage of serum sterol represented by campesterol is 0.16% and by sitosterol is 0.13%. If the effect is real, it is very potent indeed.
