Reduced susceptibility of low density lipoprotein to lipid peroxidation after cholestyramine treatment in heterozygous familial hypercholesterolemic children

Abstract

Cholestyramine treatment in children with heterozygous familial hypercholesterolemia (FHHe) can interfere with fat absorption from the intestinal tract, and has the potential to decrease the absorption of fat-soluble vitamins. The aim of this study was to examine the effect of cholestyramine treatment on the levels of the fat soluble vitamins (vitamin E, beta-carotene and lycopene) in LDL, on the glutathione system and on the susceptibility of LDL to oxidation in FHHe children. Patients were 16 children (seven girls, nine boys), age 14+/-4 years, non-smokers. Plasma LDL level before cholestyramine treatment but after dietary treatment was 239+/-50 mg% with no secondary cause for hypercholesterolemia. A control group was comprised of ten children (seven girls, three boys), age 14+/-4 years with plasma LDL level of 100+/-14 mg%. Blood was drawn from 16 FHHe children and five control children after fasting for 14 h. Thereafter cholestyramine treatment was begun in the patient group, at a dose of 8 g/day for 2 months. At the end of this period the dose was increased to 12-16 g/day for an additional 2 months. After 4 months from the beginning of the treatment, blood was drawn again. Plasma LDL cholesterol decreased after treatment by 14% (from 239+/-67 mg% before treatment to 205+/-55 mg% after treatment, P=0.07). Malondialdehyde (MDA) levels measured by thiobarbituric reactive substances (TBARS) assay in LDL at the end of oxidation were 30% higher in FHHe children in comparison to controls (P=0.02). After treatment TBARS levels in LDL (after in vitro oxidation) from FHHe children were decreased by 23% (P=0.02). Vitamin E levels in LDL from FHHe children after treatment were decreased by 65%, while beta-carotene and lycopene contents in LDL, paradoxically increased by 90 and 102%, respectively. In red blood cells (RBC), glutathione peroxidase (GPx) and glutathione transferase (GTf) activities were decreased by 29 and 24%, respectively, while glutathione reductase activity, total and oxidized glutathione contents from FHHe children did not change after cholestyramine treatment. LDL was more prone to oxidation in FHHe children than in controls, when measured by TBARS levels after LDL oxidation (with 10 &mgr;M CuSO(4)). Cholestyramine treatment for 4 months normalized LDL susceptibility to oxidation measured by TBARS levels, despite the decrease in vitamin E content in LDL from treated FHHe children. This is presumably due to the increased LDL content of beta-carotene and lycopene after treatment. GPx and GTf activities decreased after treatment, presumably due to the drop in oxidative stress within the RBCs, in parallel to the decreased LDL tendency to oxidation. Cholestyramine treatment in FHHe children has an overall antioxidant effect on LDL.