Effect of iron overload and iron deficiency on atherosclerosis in the hypercholesterolemic rabbit

It has been suggested that iron plays an important role in the pathogenesis of atherosclerosis, primarily by acting as a catalyst for the atherogenic modification of LDL. Although some epidemiological data suggest that high stored iron levels are an independent risk factor for coronary artery disease and that iron has been detected in both early and advanced atherosclerotic lesions, the evidence is often contradictory and inconclusive. We used the New Zealand White rabbit to investigate the effects of iron overload (FeO) and iron deficiency (FeD) on atherosclerosis. Groups of 7 rabbits were either iron loaded by injections of iron dextran (FeO group), iron depleted by phlebotomy (FeD group), or given injections of saline (control group) for a total of 9 weeks. All rabbits were fed a chow diet containing 1% (wt/wt) cholesterol for the last 6 weeks of the study. Iron and antioxidant status and cholesterol levels were assayed in plasma before cholesterol feeding (week 3) and at the time that the rabbits were killed (week 9). In addition, the susceptibility of LDL to oxidation was measured and pathological examination of the aortic arch and thoracic aorta performed at the end of the study. FeD significantly decreased the levels of blood hemoglobin, serum iron, and transferrin saturation compared with controls. Conversely, FeO significantly increased transferrin Fe saturation. FeO but not FeD decreased plasma cholesterol levels compared with control animals both before (P<.05) and after (P=.055) cholesterol feeding. Neither FeO nor FeD had a significant effect on the levels of antioxidants and lipid peroxidation products in plasma and aortic tissue or on the susceptibility of LDL to ex-vivo oxidation. FeO significantly decreased aortic arch lesion formation by 56% compared with controls (P<.05), whereas FeD had no significant effect. These results indicate that in this animal model, FeO decreases rather than increases atherosclerosis, likely because iron dextran exerts a hypocholesterolemic effect. Our data do not support the hypotheses that elevation of Fe stores increases or that a reduction of Fe stores by phlebotomy decreases the risk of coronary artery disease.