Effect of vitamin E supplementation on hepatic fibrogenesis in chronic dietary iron overload

It has been suggested that lipid peroxidation plays an important role in hepatic fibrogenesis resulting from chronic iron overload. Vitamin E is an important lipid-soluble antioxidant that has been shown to be decreased in patients with hereditary hemochromatosis and in experimental iron overload. The aim of this study was to determine the effects of vitamin E supplementation on hepatic lipid peroxidation and fibrogenesis in an animal model of chronic iron overload. Rats were fed the following diets for 4, 8, or 14 mo: standard laboratory diet (control), diet with supplemental vitamin E (200 IU/kg, control + E), diet with carbonyl iron (Fe), and diet with carbonyl iron supplemented with vitamin E (200 IU/kg. Fe + E). Iron loading resulted in significant decreases in hepatic and plasma vitamin E levels at all time points, which were overcome by vitamin E supplementation. Thiobarbituric acid-reactive substances (an index of lipid peroxidation) were increased three- to fivefold in the iron-loaded livers; supplementation with vitamin E reduced these levels by at least 50% at all time points. Hepatic hydroxyproline levels were increased twofold by iron loading. Vitamin E did not affect hydroxyproline content at 4 or 8 mo but caused an 18% reduction at 14 mo in iron-loaded livers. At 8 and 14 mo, vitamin E decreased the number of alpha-smooth muscle actin-positive stellate cells in iron-loaded livers. These results demonstrate a dissociation between lipid peroxidation and collagen production and suggest that the profibrogenic action of iron in this model is mediated through effects which cannot be completely suppressed by vitamin E.