Objective: To measure endothelium-dependent vascular relaxation in children with two genetic hyperlipidemias and to assess the effect of antioxidant vitamins on endothelial dysfunction.
Study design: Vascular reactivity in the brachial artery was measured in 45 individuals between 6 and 21 years of age (18 with familial hypercholesterolemia [FH], 15 with familial combined hyperlipoproteinemia [FCH], 12 control subjects) with the use of high-resolution two-dimensional ultrasonography. Follow-up studies were done for 11 children after 6 weeks of treatment with tocopherol (400 IU twice a day) and ascorbic acid (500 mg twice a day).
Results: The mean percent change in diameter during reactive hyperemia was 2.1 +/- 2.2 (SD) and 2.7 +/- 4.4, in FH and FCH, respectively, compared with 12. +/- 4.9 among control subjects (p < 0.001 in each case). The mean percent dilation was significantly increased (2.8 +/- 1.6 to 9.1 +/- 2.3) (p < 0.001) after antioxidant therapy.
Conclusions: Impaired endothelium-dependent vasoregulation occurs in children with FCH as well as in those with FH. The improvement in vascular reactivity observed during supplementation with antioxidant vitamins suggests that reactive oxygen species derived from oxidized lipoproteins may be responsible for the impairment of vasoregulation in subjects with hyperlipidemia.