Primary hypercholesterolemia: effect of treatment on serum lipids, lipoprotein fractions, cholesterol absorption, sterol balance, and platelet aggregation

Abstract

The nonabsorbable bile acid sequestrant resin, colestipol, was administered to 16 patients with primary hypercholesterolemia, and its effect on serum lipids, lipoprotein fractions, and circulating platelet aggregate ratio and platelet aggregation in response to adenosine diphosphate (ADP) was compared with that of sitosterol. Cholesterol absorption and sterol balance studies were done in four of the subjects during the following treatment periods: diet alone, colestipol, and sitosterol. Total serum cholesterol was significantly reduced by colestipol but only slightly decreased by sitosterol. Combination treatment with colestipol and sitosterol was associated with a smaller decrease in serum cholesterol than was demonstrated with colestipol alone. Serum triglycerides tended to increase during colestipol therapy (this increase was not clinically significant) but showed a minimal nonsignificant decrease with sitosterol treatment. Colestipol decreased cholesterol absorption, whereas sitosterol slightly increased it. Fecal sterol excretion was increased with colestipol treatment but was minimally affected by administration of sitosterol. Low-density lipoprotein and high-density lipoprotein cholesterol significantly decreased with colestipol treatment. The circulating platelet aggregate ratio was significantly lower in the group of patients with hypercholesterolemia who received colestipol initially than in control subjects, but platelet aggregation in response to ADP was not significantly different between these two groups. No significant change in platelet aggregation was noted during colestipol or sitosterol treatment despite a significant decrease in total serum cholesterol with colestipol therapy, a suggestion that the platelet and lipid abnormalities are not interrelated.