Studies on copper metabolism. XXIX. A critical analysis of serum copper and ceruloplasmin concentrations in normal subjects, patients with Wilson's disease and relatives of patients with Wilson's disease

Wilson’s Disease—Genetic Puzzles with Diagnostic Implications

(1) Introduction: Wilson’s disease (WND) is an autosomal recessive disorder of copper metabolism. The WND gene is ATP7B, located on chromosome 13. WND is characterized by high clinical variability, which causes diagnostic difficulties. (2) Methods: The PubMed, Science Direct, and Wiley Online Library medical databases were reviewed using the following phrases: “Wilson’s disease”, “ATP7B genotype”, “genotype-phenotype”, “epigenetics”, “genetic modifiers”, and their combinations. Publications presenting the results of experimental and clinical studies, as well as review papers, were selected, which concerned: (i) the diversity of genetic strategies and tests used in WND diagnosis; (ii) the difficulties of genetic diagnosis, including uncertainty as to the pathogenicity of variants; (iii) genetic counseling; (iv) phenotypic effects of ATP7B variants in patients with WND and in heterozygous carriers (HzcWND); (v) genetic and epigenetics factors modifying the clinical picture of the disease. (3) Results and conclusions: The genetic diagnosis of WND is carried out using a variety of strategies and tests. Due to the large number of known variants in the ATP7B gene (>900), the usefulness of genetic tests in routine diagnostics is still relatively small and even analyses performed using the most advanced technologies, including next-generation sequencing, require additional tests, including biochemical evidence of abnormal copper metabolism, to confirm the diagnosis of WND. Pseudodominant inheritance, the presence of three various pathogenic variants in the same patient, genotypes indicating the possibility of segmental uniparental disomy, have been reported. Genotype–phenotype relationships in WND are complex. The ATP7B genotype, to some extent, determines the clinical picture of the disease, but other genetic and epigenetic modifiers are also relevant.

Recent views of heavy metals as possible risk factors and potential preventive and therapeutic agents in prostate cancer

Prostate cancer is the most common cancer in men in many industrialized countries. A role for androgens in prostate tumor progression is well recognized, while estrogens may cooperate with androgens in prostate carcinogenesis. The incidence of prostate cancer is highly variable in the different countries, suggesting an important role of environmental factors. Heavy metals are common environmental contaminants and some of them are confirmed or suspected human carcinogens. Some metals are endowed with estrogenic and/or androgenic activities and may play a role as cancer risk factors through this mechanism. Moreover, prostate cancer may present alterations in the intracellular balance of trace metals, such as zinc and copper, which are involved in several regulatory proteins. Herein, we review the possible role of environmental heavy metals and of metal-dyshomeostasis in prostate cancer development and promotion as well as the potential use of some metals in the prevention and therapy of prostate cancer.

Metal ions and electrolytes regulate the dissociation of heme from human hemopexin at physiological pH

The stability of the hemopexin-heme (Hx-heme) complex to dissociation of the heme prosthetic group has been examined in bicarbonate buffers in the presence and absence of various divalent metal ions. In NH(4)HCO(3) buffer (pH 7.4, 20 mm, 25 degrees C) containing Zn(2+) (100 microm), 14% of the heme dissociates from this complex (4.5 microm) within 10 min, and 50% dissociates within 2 h. In the absence of metal ions, the rate of dissociation of this complex is far lower, is decreased further in KHCO(3) solution, and is minimal in NaHCO(3). In NH(4)HCO(3) buffer, dissociation of the Hx-heme complex is accelerated by addition of divalent metals with decreasing efficiency in the order Zn(2+) > Cu(2+) >> Ni(2+) > Co(2+)>>Mn(2+). Addition of Ca(2+) prior to addition of Zn(2+) stabilizes the Hx-heme complex to dissociation of the heme group, and addition of Ca(2+) after Zn(2+)-induced dissociation of the Hx-heme complex results in re-formation of the Hx-heme complex. These effects are greatly accelerated at 37 degrees C and diminished in other buffers. Overall, the solution conditions that promote formation of the Hx-heme complex are similar to those found in blood plasma, and conditions that promote release of heme are similar to those that the Hx-heme complex should encounter in endosomes following endocytosis of the complex formed with its hepatic receptor.

Detection of caeruloplasmin in bovine milk and blood serum

The copper-binding protein, caeruloplasmin, has been detected in bovine blood serum, colostrum and normal milk using immuno-diffusion techniques by comparison with a precipitating oxidase-positive system of human caeruloplasmin and anti-caeruloplasmin. The possible importance of this copper-binding protein of milk in the oxidative deterioration of milk and dairy products is discussed.

Wilson's disease in two siblings--one with fatal outcome

The clinical and biochemical findings in two siblings with Wilson's disease are described. One of them, an 11-year-old girl, developed acute liver failure terminating in death within a few weeks. Prior to her terminal illness she had been in good health without symptoms suggestive of Wilson's disease. Copper contents of urine, liver, kidney and brain were 20-100 times above the upper normal limits. The liver showed extensive micronodular cirrhosis with nonbile pigment deposits. Her 15-year-old brother had abnormal liver function tests with urinary copper excretion 20 times above the upper normal limit. Treatment with penicillamine was started. Following a short period of deterioration his condition has steadily improved.

Preliminary X-ray crystallographic and physico-chemical investigations of human ceruloplasmin

Single crystals of the plasma protein ceruloplasmin (CP) and its two modified forms: neuraminidase-treated CP (asialoCP) and NaN3-inhibited CP (NaN3-CP) suitable for X-ray studies have been grown. The native CP crystallizes as described previously by Magdoff-Fairchield et al. (1969) in the tetragonal space group 14 (a = b = 268.2 A, c = 129.1 A) with two protein molecules in the asymmetric part of a unit cell. AsialoCP crystals belong to the trigonal space group P 3(1)21 or P321 (a = b = 215.0 A, c = 84.5 A) and have one protein molecule in the asymmetric part of a unit cell. NaN3-CP crystals are isomorphous to crystals of native CP. Despite some differences in electrophoretic mobility and optical properties, the conformations of the native CP molecule and its modified forms are similar, as can be concluded from a study of ORD and CD spectra.

Ceruloplasmin metabolism and function

Ceruloplasmin is a serum ferroxidase that contains greater than 95% of the copper found in plasma. This protein is a member of the multicopper oxidase family, an evolutionarily conserved group of proteins that utilize copper to couple substrate oxidation with the four-electron reduction of oxygen to water. Despite the need for copper in ceruloplasmin function, this protein plays no essential role in the transport or metabolism of this metal. Aceruloplasminemia is a neurodegenerative disease resulting from inherited loss-of-function mutations in the ceruloplasmin gene. Characterization of this disorder revealed a critical physiological role for ceruloplasmin in determining the rate of iron efflux from cells with mobilizable iron stores and has provided new insights into human iron metabolism and nutrition.

The copper-iron connection: hereditary aceruloplasminemia

Hereditary aceruloplasminemia is an autosomal recessive disorder of iron homeostasis due to loss-of-function mutations in the ceruloplasmin gene. Affected individuals may present in adulthood with evidence of hepatic iron overload, diabetes, peripheral retinal degeneration, dystonia, dementia, or dysarthria. Laboratory studies demonstrate microcytic anemia, elevated serum ferritin, and a complete absence of serum ceruloplasmin ferroxidase activity. Consistent with the observed neurologic findings, magnetic resonance imaging reveals iron accumulation within the basal ganglia. Histologic studies detect abundant iron in hepatocytes, reticuloendothelial cells of the liver and spleen, beta cells of the pancreas, and astrocytes and neurons throughout the central nervous system. Characterization of this disorder reveals an essential role for ceruloplasmin in determining the rate of iron efflux from cells with mobilizable iron stores and provides new insights into the mechanisms of human iron metabolism.

Aceruloplasminemia

Aceruloplasminemia is an autosomal recessive disorder of iron metabolism characterized by diabetes, retinal degeneration, and neurologic symptoms. Affected patients evidence marked parenchymal iron accumulation in conjunction with an absence of circulating serum ceruloplasmin and molecular genetic analysis reveals inherited mutations in the ceruloplasmin gene. Taken together with earlier studies that characterized ceruloplasmin as a ferroxidase and recent work indicating an essential role for a homologous multicopper oxidase in iron metabolism in Saccharomyces cerevisiae, these findings reveal an essential role for ceruloplasmin in human iron metabolism. The presence of neurologic symptoms in patients with aceruloplasminemia is unique among the characterized disorders of iron metabolism, and recent findings indicate that astrocyte-specific ceruloplasmin gene expression is critical for iron metabolism and neuronal survival in the retina and basal ganglia. The discovery of this disease provides new insights into the pathways of CNS iron metabolism of direct relevance to a variety of nutritional and genetic disorders of childhood.

Aceruloplasminemia: molecular characterization of this disorder of iron metabolism

Ceruloplasmin is an abundant alpha 2-serum glycoprotein that contains 95% of the copper found in the plasma of vertebrate species. We report here on the identification of a genetic defect in the ceruloplasmin gene in a patient previously noted to have a total absence of circulating serum ceruloplasmin in association with late-onset retinal and basal ganglia degeneration. In this patient T2 (transverse relaxation time)-weighted magnetic resonance imaging of the brain revealed basal ganglia densities consistent with iron deposition, and liver biopsy confirmed the presence of excess iron. Although Southern blot analysis of the patient's DNA was normal, PCR amplification of 18 of the 19 exons composing the human ceruloplasmin gene revealed a distinct size difference in exon 7. DNA sequence analysis of this exon revealed a 5-bp insertion at amino acid 410, resulting in a frame-shift mutation and a truncated open reading frame. The validity of this mutation was confirmed by analysis of DNA from the patient's daughter, which revealed heterozygosity for this same 5-bp insertion. The presence of this mutation in conjunction with the clinical and pathologic findings demonstrates an essential role for ceruloplasmin in human biology and identifies aceruloplasminemia as an autosomal recessive disorder of iron metabolism. These findings support previous studies that identified ceruloplasmin as a ferroxidase and are remarkably consistent with recent studies on the essential role of a homologous copper oxidase in iron metabolism in yeast. The clinical and laboratory findings suggest that additional patients with movement disorders and nonclassical Wilson disease should be examined for ceruloplasmin gene mutations.

Differences in human serum copper and zinc levels in healthy and patient populations

This report is designed to re-examine the use of our presently accepted normal laboratory levels for human serum zinc and copper and to suggest a technique, previously unreported in the literature, to more precisely understand the relationship of serum zinc and copper in health and disease. Data from a patient population of 95 and a healthy population of 115 who met certain criteria are compared.

Copper and zinc in human serum in Norway. Relationship to geography, sex and age

Serum samples were collected from the adult population, age groups from 20 to 54 years, in 11 different Norwegian municipalities and analysed for zinc and copper by atomic absorption spectroscopy. Significant differences were found between several of the municipalities when the mean concentration of zinc in serum in 200 randomized samples were compared, with only two municipalities being different for copper. The values for zinc ranged from 13.8 to 18.3 mumol/l and copper varied between 16.3 and 19.2 mumol/l. An age related increase in the copper concentration was evident in the male population, and age-adjusted means showed a slight, but significantly higher serum copper concentration in females (18.4 mumol/l) than in males (16.5 mumol/l). For zinc the opposite sex-relationship was indicated with the highest values in males, 15.8 compared to 15.1 mumol/l in serum from females. No significant correlations were found between the concentrations of zinc and copper in serum. In all age groups of women, however, a small negative correlation was found giving a significant tendency.

Trace elements in human nutrition

Clinical recognition of the role of trace elements in human nutrition is increasing. Heretofore, many clinicians felt that the development of deficiency states was not likely except in very extreme conditions because the presence of trace elements in nature was so ubiquitous. The increased use of total parenteral nutrition seems to have made this viewpoint untenable. The recognition of additional genetic diseases of trace element metabolism such as Menkes' kinky hair syndrome and acrodermatitis enteropathica has also served to focus clinical attention on trace elements. As time passes, no doubt, additional diseases of trace element metabolism will be recognized.

Hereditary hypoceruloplasminemia

Serum ceruloplasmin values of less than 21.0 mg/100 ml in males or less than 23.0 mg/100 ml in females were observed in 14 out of 156 otherwise healthy members of a pedigree. The hypoceruloplasminemia segregated in a fashion suggesting that the affected individuals are heterozygous for a mutant gene that results in hypoceruloplasminemia. This mutant gene could be a Wilson's disease gene, but excessive copper loading was absent. It is suggested that hereditary hypoceruloplasminemia may be a benign entity distinct from Wilson's disease.

The role of ceruloplasmin in iron metabolism

The importance of ceruloplasmin in iron metabolism was studied in swine made hypoceruloplasminemic by copper deprivation. When the plasma ceruloplasmin level fell below 1% of normal, cell-to-plasma iron flow became sufficiently impaired to cause hypoferremia, even though total body iron stores were normal. When ceruloplasmin was administered to such animals, plasma iron increased immediately and continued to rise at a rate proportional to the logarithm of the ceruloplasmin dose. The administration of inorganic copper induced increases in plasma iron only after ceruloplasmin appeared in the circulation. Thus, ceruloplasmin appeared to be essential to the normal movement of iron from cells to plasma. Studies designed to define the mechanism of action of ceruloplasmin were based on the in vitro observation that ceruloplasmin behaves as an enzyme (ferroxidase) that catalyzes oxidation of ferrous iron. Retention of injected ferrous iron in the plasma of ceruloplasmin-deficient swine was significantly less than that of ferric iron, reflecting impaired transferrin iron binding. Rat ceruloplasmin, which has little ferroxidase activity, was much less effective than porcine or human ceruloplasmin in inducing increases in plasma iron. These observations suggest that ceruloplasmin acts by virtue of its ferroxidase activity. Eight patients with Wilson's disease were evaluated in order to investigate iron metabolism in a disorder characterized by reduced ceruloplasmin levels. Evidence of iron deficiency was found in six of these, and in five of the six, plasma ceruloplasmin was less than 5% of normal. In comparison, the two patients without evidence of iron deficiency had ceruloplasmin levels of 11 and 18% of normal. It is suggested that iron deficiency tends to occur in those patients with Wilson's disease who have the severest degrees of hypoceruloplasminemia, possibly because of defective transfer of iron from intestinal mucosal cells to plasma.

Ceruloplasmin in Wilson's disease

Ceruloplasmin was highly purified from one patient with Wilson's disease and partially purified from a second unrelated patient. The highly purified ceruloplasmin was indistinguishable from normal ceruloplasmin by electrophoresis, tryptic peptide map, oxidase activity, and copper, amino acid, and sugar composition. The partially purified ceruloplasmin was indistinguishable electrophoretically from normal ceruloplasmin. With penicillamine therapy, ceruloplasmin disappeared from the serum of the first patient; it reappeared after the drug was discontinued. The significance of this observation in regard to the basic defect in Wilson's disease is discussed.

Wilson's disease

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