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Ceruloplasmin, Superoxide Dismutase and Copper in Autistic Patients

2005; Wiley; Volume: 96; Issue: 2 Linguagem: Inglês

10.1111/j.1742-7843.2005.pto960210.x

1742-7843

Gudlaug Tórsdóttir, Stefán Hreiðarsson, Jakob Kristinsson, Jón Snædal, Torkell Jøhannesson,

Trace Elements in Health

Autism is a neurodevelopmental disorder, involving a wide variety of sociobehavioural, linguistic and perceptuomotor abnormalities. The prevalence in the general population is at least 5 in 10,000, with a reported male/female ratio of 3–4/1 (Lamb et al. 2000). Strong evidence from twin and family studies indicate the importance of genetic factors in the development of idiopathic autism (Lamb et al. 2000). In a study of population-based Danish registers, Lauritsen et al. (2002) noted a highly significant increased frequency of congenital malformations associated whith autism which is furthermore indicative of abnormal embryogenesis. In this context it should also be noted that the age-related changes seen in some neurones in autistic brains appear to be a prolonged process that extends from neural hyperthrophy in childhood to atrophy and cell loss in later adult life and are without concomitant gliosis or other outright signs of degeneration (Kemper & Bauman 1998). Ceruloplasmin is a copper-containing enzyme with a powerful redox activity in serum. Superoxide dismutase is another copper enzyme found in cytosol of most cells that dismutases superoxide anion radicals (·O2−) to H2O2 and O2. In our previous studies we have measured the activity of the two enzymes, ceruloplasmin in serum and superoxide dismutase in erythrocytes and copper in plasma in some neurodegenerative diseases: Alzheimer's disease, Parkinson's disease, amyothropic lateral sclerosis and also in Down's syndrome, as Down's syndrome is characterized by the development of dementia when the patients exceed 40–50 years of age. The results showed that copper dyshomeostasis prevailed in these diseases as the activity of both enzymes was either decreased or deranged although the levels of copper were the same (Snaedal et al. 1998; Tórsdóttir et al. 1999, 2000 & 2001). In this study we put to test whether or not similar changes can be found in a group of autistic patients. Autism is considered a congenital and more or less stationary condition, unlike the degenerative, progressive diseases we have studied earlier. Furthermore the role and metabolism of free radicals have not been much studied in the autistic population and the results of the studies already published up to now are to some extent inconsitent. A cohort of young adults with diagnosed autism was secured from the National Registry of Handicapped Persons in Iceland that is kept by law by the State Diagnostic and Counceling Center. All subjects had been diagnosed either at the Paediatric Psychiatry Division of the Icelandic University Hospital or the State Diagnostic and Counceling Center. All were receiving special services for autistic persons. Thirty-five persons were thus identified and their guardians asked for participation in the study. A high proportion of refusals was encountered, most frequently because of concern of the guardians that the blood sample collection would cause emotional disturbance to their clients, given their handicap. The final group thus consisted of only13 patients, 10 males and 3 females, on an average 24.6 years old and with a range of 18–35 years. Every patient had a gender- and age-matched control. The controls were healthy and living independently in their homes. The study was consented by the National Bioethics Committee of Iceland. Blood samples were taken in the morning in the fasting state and the blood sampling units used were specially prepared for metal analysis (Sarstédt). Same blood sampling procedure were used for both patients and controls. Copper in the samples was determined by atomic absorption spectrophotometry, with an internationally assessed method, at the Icelandic Fisheries Laboratories, Reykjavık. Ceruloplasmin levels in serum were determined at the Icelandic University Hospital Laboratories with rate nephelometry immunoassay (Beckman Immunochemistry Systems, ICS-2 Beckman Instruments Inc.). Ceruloplasmin oxidative activity in serum was determined at the Department of Pharmacology and Toxicology, University of Iceland, with the manual kinetic assay described by Boyett et al. (1976). The specific oxidative activity of ceruloplasmin in serum (oxidative activity related to mass) was calculated as ceruloplasmin oxidative activity, units/ml, divided by the value of ceruloplasmin concentration, mg/l, and multiplied by 1000. Superoxide dismutase activity in erythrocytes was determined at the Department of Pharmacology and Toxicology, University of Iceland, with a spectrophotometric assay (Bioxytech®, SOD-525) as described by Nebot et al. (1993). The reagents used in the analyses were obtained from Oxis International, Inc., Portland, Oregon, USA. Ceruloplasmin concentration, ceruloplasmin oxidative activity and specific oxidative activity as well as superoxide dismutase activity and the concentration of copper was statistically the same in the patients and their controls (table 1). The results closest to reach significant level were the results of ceruloplasmin oxidative activity and ceruloplasmin specific oxidative activity (P=0.069 and 0.082 respectively). When calculating the power of the study we found that to reach a power of 80% we would have needed at least 18 patients for ceruloplasmin specific oxidative activity and 25 patients for the ceruloplasmin concentration. According to these results, copper dyshomeostasis is not likely to play a part in the pathogenesis of autism. Still it is worth mentioning that two trends can be noticed, althought not reaching the level of significance: The ceruloplasmin concentration was higher in the autistic group while the specific oxidative activity (activity related to mass) was higher in the control group. This leads to the suggestion that the quality of ceruloplasmin in the autistic group was poorer, but was compensated with higher concentration, resulting in same total oxidative activity of the ceruloplasmin in both groups. Similar trend was noticed in the work of Fatemi et al. (2002) where ceruloplasmin concentration was determined in serum of 13 autistic twins, their siblings and parents (total 58 persons) and compared with a control group. Ceruloplasmin concentration was higher in the patients and their relatives than in the control group but the difference did not reach the level of significance in that study either. In our study on Down's patients (Tórsdóttir et al. 2001) we also noted signifcantly rising concentration of ceruloplasmin with age while the oxidative activity were unchanged. This was interpreted as a result of compensatory increase oriented towards lower specific activity of ceruloplasmin with age, found in Down's patients. In older litterature, Golse et al. (1978) found increased activity of superoxide dismutase but lowered function of glutathione (GSH) peroxidase in erythrocytes of children with autism. Yorbik et al. (2002) have recently found significantly lower activity of superoxide dismutase and GSH peroxidase in erythrocytes of autistic children. Neither of these findings are as far as superoxide dismutase activity is concerned supported by our study. Sögˇüt et al. (2003) on the other hand found increased GSH peroxidase activity and in agreement with our results normal superoxide dismutase activity in plasma of autistic patients compared to controls. Jackson et al. (1978) determined zink, copper and amino acid levels in the blood of a group of autistic children and found all variables to be normal. These results thus support our findings of normal copper levels in the autistic patients. Work on superoxide dismutase activity in autistic patients has hitherto obviously given controversial results. The few data available on copper and ceruloplasmin in autistic patients indicate that there is probably no difference of significance between the autistic and normal population.