Increased plasma cholestanol and 5α-saturated plant sterol derivatives in subjects with sitosterolemia and xanthomatosis

We have measured plasma sterol, composition in 14 subjects with sitosterolemia and xanthomatosis. In addition to elevated plasma phytosterol (campesterol 16 ± 7 mg/dl and sitosterol 35 ± 16 mg/dl) and normal to moderately high cholesterol levels (258 ± 96 mg/dl), concentrations of 5α-saturated stanols, cholestanol, 5α-campestanol, and 5α-sitostanol were at least 10 times greater than controls. Diets contained plentiful quantities of cholesterol and plant sterols, but only trace amounts of cholestanol (<2 mg/day) and no detectable 5α-campestanol and 5α-sitostanol, which indicated that the 5α-saturated stanols were formed endogenously. Treatment with cholestyramine reduced plasma cholesterol and phytosterol levels by 45% and 5α-saturated stanols by 55%. These results indicate that abnormally high plasma concentrations of cholestanol, 5α-campestanol, and 5α-sitostanol are found in subjects with sitosterolemia and xanthomatosis, and that treatment with cholestyramine effectively reduced elevated plasma sterol levels.