Chie Fujisawa

Inherited Copper Transport Disorders: Biochemical Mechanisms, Diagnosis, and Treatment

Copper is an essential trace element required by all living organisms. Excess amounts of copper, however, results in cellular damage. Disruptions to normal copper homeostasis are hallmarks of three genetic disorders: Menkes disease, occipital horn syndrome, and Wilson’s disease. Menkes disease and occipital horn syndrome are characterized by copper deficiency. Typical features of Menkes disease result from low copper-dependent enzyme activity. Standard treatment involves parenteral administration of copper-histidine. If treatment is initiated before 2 months of age, neurodegeneration can be prevented, while delayed treatment is utterly ineffective. Thus, neonatal mass screening should be implemented. Meanwhile, connective tissue disorders cannot be improved by copper-histidine treatment. Combination therapy with copper-histidine injections and oral administration of disulfiram is being investigated. Occipital horn syndrome characterized by connective tissue abnormalities is the mildest form of Menkes disease. Treatment has not been conducted for this syndrome. Wilson’s disease is characterized by copper toxicity that typically affects the hepatic and nervous systems severely. Various other symptoms are observed as well, yet its early diagnosis is sometimes difficult. Chelating agents and zinc are effective treatments, but are inefficient in most patients with fulminant hepatic failure. In addition, some patients with neurological Wilson’s disease worsen or show poor response to chelating agents. Since early treatment is critical, a screening system for Wilson’s disease should be implemented in infants. Patients with Wilson’s disease may be at risk of developing hepatocellular carcinoma. Understanding the link between Wilson’s disease and hepatocellular carcinoma will be beneficial for disease treatment and prevention.

Copper metabolism and inherited copper transport disorders: molecular mechanisms, screening, and treatment

In this review, we discuss genetic disorders involving altered copper metabolism, particularly in relation to Menkes disease (MD), occipital horn syndrome (OHS), and Wilson’s disease (WD). The responsible genes for MD and WD are ATP7A and ATP7B, respectively. Both proteins encoded by these genes are responsible for transporting copper from the cytosol to the Golgi apparatus. However, the pathology of MD is completely different from that of WD, that is, MD is characterized by a copper deficiency while WD is caused by a toxic excess of copper. The reason for this difference is related to the particular cell types in which the ATP7A and ATP7B proteins are expressed. ATP7A is expressed in almost all cell types except hepatocytes, whereas ATP7B is mainly expressed in hepatocytes. MD and OHS are X-linked recessive disorders characterized by copper deficiency. Typical features of MD, such as neurological disturbances, connective tissue disorders, and hair abnormalities, can be explained by the abnormally low activity of copper-dependent enzymes. The current standard-of-care treatment for MD is parenteral administrations of copper–histidine. When the treatment is initiated in newborn babies prior to two months of age, the neurological degeneration may be prevented, but delayed treatment is considerably less effective. Moreover, copper–histidine treatment does not improve symptoms of the connective tissue disorders. As such, systems for mass screening of neonates for MD should be implemented. At the same time, novel treatments targeting connective tissue disorders need to be developed. OHS is a milder form of MD and is characterized by connective tissue abnormalities. Although formal trials have not been conducted for OHS, OHS patients are typically treated in a similar manner to those with MD. WD is an autosomal recessive disorder characterized by the toxic effects of chronic exposure to high levels of copper. The hepatic and nervous systems are typically most severely affected. Numerous other symptoms can also be observed, however, making an early diagnosis difficult. Chelating agents and zinc are effective for the treatment of WD, but they are ineffective for the patients with fulminant hepatic failure. Some patients with neurological diseases show poor response to chelating agents; here again, early diagnosis and treatment are critical. Screening of newborn babies or infants for WD can help lead to timely diagnosis and treatment. Patients with WD may have a risk of hepatocellular carcinoma despite receiving treatment. An understanding of the relation between WD and hepatocellular carcinoma will provide clues to help prevent hepatocellular carcinoma in patients with WD.

Pathology, clinical features and treatments of congenital copper metabolic disorders – Focus on neurologic aspects

Genetic disorders of copper metabolism, including Menkes kinky hair disease (MD), occipital horn syndrome (OHS) and Wilsons disease (WD) are reviewed with a focus on the neurological aspects. MD and OHS are X-linked recessive disorders characterized by a copper deficiency. Typical features of MD, such as neurologic disturbances, connective tissue disorders and hair abnormalities, can be explained by the abnormally low activity of copper-dependent enzymes. The current standard-of-care for treatment of MD is parenteral administration of copper-histidine. When the treatment is initiated in newborn babies, neurologic degeneration can be prevented, but delayed treatment is considerably less effective. Moreover, copper-histidine treatment does not improve connective tissue disorders. Novel treatments targeting neurologic and connective tissue disorders need to be developed. OHS is the mildest form of MD and is characterized by connective tissue abnormalities. Although formal trials have not been conducted for OHS, OHS patients are typically treated in a similar manner to MD. WD is an autosomal recessive disorder characterized by the toxic effects of chronic exposure to high levels of copper. Although the hepatic and nervous systems are typically most severely affected, initial symptoms are variable, making an early diagnosis difficult. Because early treatments are often critical, especially in patients with neurologic disorders, medical education efforts for an early diagnosis should target primary care physicians. Chelating agents and zinc are effective for the treatment of WD, but neurologic symptoms become temporarily worse just after treatment with chelating agents. Neurologic worsening in patients treated with tetrathiomolybdate has been reported to be lower than rates of neurologic worsening when treating with other chelating agents.

Effect of copper and diethyldithiocarbamate combination therapy on the macular mouse, an animal model of Menkes disease

SummaryMenkes disease (MD) is a neurodegenerative disorder characterized by a copper deficiency in the brain. It is caused by the defective intestinal absorption of copper resulting from a deficiency of a copper-transporting ATPase, ATP7A. This gives rise to an accumulation of copper in the intestine. The copper deficiency in the brain of MD patients cannot be improved by copper injections, because the administered copper accumulates at the blood–brain barrier and is not transported across to the neurons. To resolve this problem, we investigated the effect of a combination therapy of copper and sodium diethyldithiocarbamate (DEDTC), a lypophilic chelator, in an animal model of MD, the macular mouse. Four-week-old macular mice treated with 50 μg of CuCl2 on the 7th day after birth were used. Experimental mice were given a subcutaneous injection of CuCl2 (4 μg) and an intraperitoneal injection of DEDTC (0.2 mg/g body weight) twice a week for 4 weeks and then sacrificed. Copper concentrations and cytochrome-c oxidase activity in the brains of treated mice were higher than those of control macular mice, which received only copper or saline. The ratios of brain noradrenaline to dopamine and of adrenaline to dopamine were also increased by the treatment, suggesting that the activity of dopamine β-hydroxylase, a copper-dependent enzyme, was improved by the treatment. Liver and renal function tests showed no abnormalities in the treated mice, although copper concentrations in the kidneys of treated mice were higher than those of control macular mice. These results suggest that DEDTC facilitates the passage of copper across the blood–brain barrier and that the combination therapy of copper and DEDTC may be an effective treatment for the neurological disturbances suffered by patients with MD.

The first reported case of Menkes disease caused by an Alu insertion mutation

We present the first reported case of Menkes disease caused by an Alu element insertion mutation that interfered with splicing regulatory elements. A whole young AluYa5a2 element, which was 382-bp long, was identified within exon 9 of the ATP7A gene, and all of exon 9 was aberrantly skipped in the cDNA, resulting in severely truncated proteins. To confirm whether the aberrant skipping resulted in Alu insertion, an exonic splicing enhancer finder was used. The Alu element created two new high-score exonic splicing enhancer sequences in the mutation located near the site of the insertion. Exon 9, which encodes the first and second transmembrane domains, is necessary for the normal function of the ATP7A protein.

PET Imaging Analysis with 64Cu in Disulfiram Treatment for Aberrant Copper Biodistribution in Menkes Disease Mouse Model

Menkes disease (MD), an X-linked recessive disorder of copper metabolism caused by mutations in the copper-transporting ATP7A gene, results in growth failure and severe neurodegeneration in early childhood. Subcutaneous copper-histidine injection is the standard treatment for MD, but it has limited clinical efficacy. Furthermore, long-term copper injection causes excess copper accumulation in the kidneys, resulting in renal dysfunction. To attempt to resolve this issue, we used PET imaging with 64Cu to investigate the effects of disulfiram on copper biodistribution in living mice serving as an animal model for MD (MD model mice). Methods: Macular mice were used as MD model mice, and C3H/He mice were used as wild-type mice. Mice were pretreated with 2 types of chelators (disulfiram, a lipophilic chelator, and d-penicillamine, a hydrophilic chelator) 30 min before 64CuCl2 injection. After 64CuCl2 injection, emission scans covering the whole body were performed for 4 h. After the PET scans, the brain and kidneys were analyzed for radioactivity with γ counting and autoradiography. Results: After copper injection alone, marked accumulation of radioactivity (64Cu) in the liver was demonstrated in wild-type mice, whereas in MD model mice, copper was preferentially accumulated in the kidneys (25.56 ± 3.01 percentage injected dose per gram [%ID/g]) and was detected to a lesser extent in the liver (13.83 ± 0.26 %ID/g) and brain (0.96 ± 0.08 %ID/g). Copper injection with disulfiram reduced excess copper accumulation in the kidneys (14.54 ± 2.68 %ID/g) and increased copper transport into the liver (29.42 ± 0.98 %ID/g) and brain (5.12 ± 0.95 %ID/g) of MD model mice. Copper injection with d-penicillamine enhanced urinary copper excretion and reduced copper accumulation in most organs in both mouse groups. Autoradiography demonstrated that disulfiram pretreatment induced copper transport into the brain parenchyma and reduced copper accumulation in the renal medulla. Conclusion: PET studies with 64Cu revealed that disulfiram had significant effects on the copper biodistribution of MD. Disulfiram increased copper transport into the brain and reduced copper uptake in the kidneys of MD model mice. The application of 64Cu PET for the treatment of MD and other copper-related disorders may be useful in clinical settings.

Effect of copper and disulfiram combination therapy on the macular mouse, a model of Menkes disease.

Menkes disease (MD) is a genetic neurodegenerative disorder characterized by copper deficiency due to a defect in ATP7A. Standard treatment involves parenteral copper-histidine administration. However, the treatment is ineffective if initiated after two months of age, because the administered copper accumulates in the blood-brain barrier and is not transported to neurons. To resolve this issue, we investigated the effects of a combination therapy comprising copper and disulfiram, a lipophilic chelator, in the macular mouse, an animal model of MD. Seven-day-old macular mice treated subcutaneously with 50 μg of CuCl(2) on postnatal day 4 were used. The mice were given a subcutaneous injection of CuCl(2) (10 μg) with oral administration of disulfiram (0.3mg/g body weight) twice a week until eight weeks of age, and then sacrificed. Copper concentrations in the cerebellum, liver, and serum of treated macular mice were significantly higher than those of control macular mice, which received only copper. Mice treated with the combination therapy exhibited higher cytochrome c oxidase activity in the brain. The ratios of noradrenaline and adrenaline to dopamine in the brain were also increased by the treatment, suggesting that dopamine β-hydroxylase activity was improved by the combination therapy. Liver and renal functions were almost normal, although renal copper concentration was higher in treated macular mice than in controls. These results suggest that disulfiram facilitates the passage of copper across the blood-brain barrier and that copper-disulfiram combination therapy may be an effective treatment for MD patients.

Copper-trafficking efficacy of copper-pyruvaldehyde bis(N4-methylthiosemicarbazone) on the macular mouse, an animal model of Menkes disease

Background:Menkes disease (MD) is a disorder of copper transport caused by ATP7A mutations. Although parenteral copper supplements are partly effective in treating MD, the copper level in the brain remains insufficient, whereas copper accumulates in the kidney. We investigated the copper-trafficking efficacy of copper-pyruvaldehyde bis(N4-methylthiosemicarbazone) (Cu-PTSM), a lipophilic copper complex, in macular mice, an animal model of MD.Methods:Macular mice were treated with cupric chloride (CuCl2) or Cu-PTSM on postnatal days 4, 10, and 17. At 4 wk of age, the copper levels in major organs and cytochrome oxidase (CO) activity in brain tissue were measured. Hematology, blood biochemistry, and urinary β2-microglobulin (β2-M) secretion were also assessed.Results:The copper levels in the brains of the Cu-PTSM-treated group remained low, but CO activity in the cerebral and cerebellar cortices in the Cu-PTSM-treated group were higher than those in the CuCl2-treated group. There were no significant differences in hematological or biochemical findings or in urinary β2-M secretion among the groups.Conclusion:Although the copper-trafficking efficacy of Cu-PTSM was limited, the improved CO activity in the brain suggests that Cu-PTSM delivered copper more effectively to neuronal CO than did CuCl2. Reduced renal copper accumulation may be beneficial in prolonged copper supplementation.

Hypothyroidism caused by iodine deficiency and iodine levels in enteral formulas

Background:  A 4‐year‐old female patient was diagnosed with hypothyroidism caused by iodine deficiency. The patients iodine levels in serum and urine were significantly low. The iodine concentration in the enteral formula was 1.6 µg/100 kcal as measured by inductively coupled plasma mass spectrometry. The patients iodine intake while receiving the enteral formula was calculated to be 16 µg/day, which is much lower than the recommended dietary reference intake of 80 µg for children aged 3–5 years. The purpose of this study was to assess iodine concentrations in 20 enteral nutritional formulas available in Japan in order to assess whether low iodine concentration is a characteristic of one specific formula or whether it is a more prevalent problem.