Effect of ileal exclusion on plant sterol metabolism in familial hypercholesterolemia

Factors regulating the metabolism of plant sterols (sitosterol and campesterol) and their serum levels were studied in sixteen patients with heterozygous familial hypercholesterolemia. Eight patients had undergone an ileal bypass operation, resulting in slight fat and severe bile acid malabsorption and in lowered serum cholesterol concentration, but normal fractional cholesterol absorption. Serum plant sterol concentrations (mg/dl) were similar in the two groups, but expressed per milligram of cholesterol were higher in the operated patients. Fecal excretion (equal with intake) and biliary secretion (reflecting absorption) of the plant sterols were similar in the two groups and were significantly correlated with the serum plant sterol content, which also correlated positively with the fractional cholesterol absorption in the control but not in the operated group. The estimated fractional absorption of the plant sterols was similar in the two groups, but that of sitosterol (3.5%) was lower than that of campesterol (9.1%). Our study shows that serum plant sterols are associated with fractional cholesterol absorption even in patients with familial hypercholesterolemia. However, after ileal exclusion dietary intake of the plant sterols is the main regulator of their serum levels.