Aceruloplasminemia, an inherited disorder of iron metabolism

Abstract

Ceruloplasmin, a multi-copper ferroxidase that affects the distribution of tissue iron, has antioxidant effects through the oxidation of ferrous iron to ferric iron. Aceruloplasminemia is an inherited disorder of iron metabolism due to the complete lack of ceruloplasmin ferroxidase activity caused by mutations in the ceruloplasmin gene. It is characterized by iron accumulation in the brain as well as visceral organs. Clinically, the disease consists of the triad of retinal degeneration, diabetes mellitus, and neurological disease, which include ataxia, involuntary movements, and dementia. These symptoms reflect the sites of iron deposition. The unique involvement of the central nervous system distinguishes aceruloplasminemia from other inherited and acquired iron storage disorders. Twenty-one mutations in the ceruloplasmin gene have been reported in 24 families worldwide. In Japan, the incidence was estimated to be approximately one per 2,000,000 in the case of non-consanguineous marriages. Excess iron functions as a potent catalyst of biologic oxidation. Previously we showed that an increased iron concentration is associated with increased levels of lipid peroxidation in the serum, cerebrospinal fluid, and erythrocyte membranes. The levels of malondialdehyde and 4-hydroxynonenals, indicators of lipid peroxidation, were also elevated in the basal ganglia and cerebral cortex. Positron emission tomography showed diminished brain metabolism of glucose and oxygen. Enzyme activities in the mitochondrial respiratory chain of the basal ganglia were reduced to approximate 45% and 42%, respectively, for complexes I and IV. These findings suggest that iron-mediated free radicals causes neuronal cell damage through lipid peroxidation and mitochondrial dysfunction in aceruloplasminemia brains.