Effect of Ezetimibe on Low‐and High‐Density Lipoprotein Subclasses in Sitosterolemia

Abstract

Sitosterolemia (STSL) is a rare sterol disease manifested by very high plasma phytosterols (PS) with normal to high total cholesterol (TC) levels and increased atherosclerosis risk. Low density lipoprotein (LDL), intermediate density lipoprotein (IDL) and very lowdensity lipoprotein (VLDL) cholesterols are proatherogenic while high density lipoprotein (HDL) cholesterol is antiatherogenic. Ezetimibe (EZ), a sterol absorption inhibitor, can reduce plasma PS and TC levels in STSL but its effect on lipoprotein subclasses has not been studied. We evaluated the effect of EZ on lipoprotein subclasses in STSL patients (pts, n=8) taken off EZ for 14 wks then placed on EZ (10 mg/d) for 14 wks. Serum total lipids and subfractions were measured enzymatically or with the Lipoprint system. Data (mean±SEM) were analyzed by paired t‐test. EZ reduced serum TC (‐13±4%, p=0.02), VLDL (‐24±4%, p=0.002) and total LDL (‐17±6%, p=0.03) levels vs off EZ. Reduced LDL values were due to decreased IDLB and C (‐22±7 and ‐21±8%, p<0.05), not to large, buoyant LDL subclasses (LDL1: ‐8±8%, p=0.23 and LDL2: +35±55%, p=0.17). LDL size did not change with EZ (275±0 vs 274±1 Å, p=0.18). EZ increased HDL levels (26±8%, p=0.008) due to increased intermediate (34±14%, p=0.02) and large (33±16%, p=0.06) HDL subclasses. These data suggest EZ can favorably affect LDL and HDL subfractions distribution, thus providing potential clinical benefit in STSL beyond reducing TC and PS accrual.Funded by NIH and CIHR