Serum ceruloplasmin and ferroxidase activity are decreased in HFE C282Y homozygote male iron-overloaded patients

Novel predictive models using serum ceruloplasmin levels for hepatic steatosis in patients with chronic hepatitis B infection

AIMS

To evaluate the significance of serum ceruloplasmin (CP) to diagnosis hepatic steatosis (HS) in Chronic hepatitis B (CHB) patients.

METHODS

A total of 360 CHB patients with HS (n = 136) or without HS (n = 224) were included. Relationships between CP and HS degrees were analyzed by Spearman rank correlation. HS-predictive models including CP were constructed using multivariate logistic regression analysis and compared to other HS predicting indexes.

RESULTS

Serum CP were significantly higher in CHB patients with HS than in patients without HS (P < 0.001) and were positively correlated with HS degree (r = 0.487, P < 0.001). The area under the receiver-operating characteristic curves (AUCs) of using CP to predict HS (S ≥ 1), moderate and severe steatosis (S ≥ 2) and severe steatosis (S = 3) were 0.758, 0.794 and 0.883, respectively. Multivariate analysis showed that CP, age, high density lipoprotein (HDL) and hemoglobin were independent predictors of HS, and CP, body mass index and HDL were independent predictors of moderate and severe HS. Two novel indexes for predicting HS of CHB patients were generated. The AUC of HSCHB-1 (for S ≥ 1) and HSCHB-2 (for S ≥ 2) were 0.881 and 0.916 in the training group, and 0.865 and 0.841 in the validation group, respectively. HSCHB-1 was superior to HS index (P < 0.001), fatty liver disease index (P = 0.0043) and steatosis index of patients with hepatitis B virus infection (P = 0.0029) in predicting HS in CHB patients.

CONCLUSIONS

HS of CHB patients was positively associated with serum CP. HSCHB-1 and HSCHB-2 with inclusion of CP are two novel models for predicting HS in CHB patients.

Rat ceruloplasmin: a new labile copper binding site and zinc/copper mosaic

Ceruloplasmin (Cp) is a copper-containing multifunctional oxidase of plasma, an antioxidant, an acute-phase protein and a free radical scavenger. The structural organization of Cp causes its sensitivity to proteolysis and ROS (reactive oxygen species), which can alter some of the important Cp functions. Elucidation of the orthorhombic crystal structure of rat Cp at 2.3 Å resolution revealed the basis for stronger resistance of rat Cp to proteolysis and a new labile copper binding site. The presence of this site appears as a very rare and distinctive feature of rat Cp as was shown by sequence alignment of ceruloplasmin, hephaestin and zyklopen in the Deuterostomia taxonomic group. The trigonal crystal form of rat Cp at 3.2 Å demonstrates unexpected partial substitution of copper by zinc.

HFE gene mutations and Wilson's disease in Sardinia

BACKGROUND

Hypocaeruloplasminaemia can lead to tissue iron storage in Wilson's disease and the possibility of iron overload in long-term overtreated patients should be considered. The HFE gene encodes a protein that is intimately involved in intestinal iron absorption.

AIMS

The aim of this study was to determine the prevalence of the HFE gene mutation, its role in iron metabolism of Wilson's disease patients and the interplay of therapy in copper and iron homeostasis.

METHODS

The records of 32 patients with Wilson's disease were reviewed for iron and copper indices, HFE gene mutations and liver biopsy.

RESULTS

Twenty-six patients were negative for HFE gene mutations and did not present significant alterations of iron metabolism. The HFE mutation was significantly associated with increased hepatic iron content (P<0.02) and transferrin saturation index (P<0.03). After treatment period, iron indices were significantly decreased only in HFE gene wild-type.

CONCLUSIONS

The HFE gene mutations may be an addictional factor in iron overload in Wilson's disease. Our results showed that an adjustment of dosage of drugs could prevent further iron overload induced by overtreatment only in patients HFE wild-type.

Ceruloplasmin expression by human peripheral blood lymphocytes: a new link between immunity and iron metabolism

Ceruloplasmin (CP) is a multicopper oxidase involved in the acute phase reaction to stress. Although the physiological role of CP is uncertain, its role in iron (Fe) homeostasis and protection against free radical-initiated cell injury has been widely documented. Previous studies showed the existence of two molecular isoforms of CP: secreted CP (sCP) and a membrane glycosylphosphatidylinositol (GPI)-anchored form of CP (GPI-CP). sCP is produced mainly by the liver and is abundant in human serum whereas GPI-CP is expressed in mammalian astrocytes, rat leptomeningeal cells, and Sertolli cells. Herein, we show using RT-PCR that human peripheral blood lymphocytes (huPBL) constitutively express the transcripts for both CP molecular isoforms previously reported. Also, expression of CP in huPBL is demonstrated by immunofluorescence with confocal microscopy and flow cytometry analysis using cells isolated from healthy blood donors with normal Fe status. Importantly, the results obtained show that natural killer cells have a significantly higher CP expression compared to all other major lymphocyte subsets. In this context, the involvement of lymphocyte-derived CP on host defense processes via its anti/prooxidant properties is proposed, giving further support for a close functional interaction between the immune system and the Fe metabolism.

Cys-881 is essential for the trafficking and secretion of truncated mutant ceruloplasmin in aceruloplasminemia

BACKGROUND/AIMS

Aceruloplasminemia is an inherited iron overload disorder caused by a mutation in the ceruloplasmin gene and characterized by iron accumulation in both the liver and brain. The aim of this study was to elucidate the molecular pathogenesis of aceruloplasminemia by a functional analysis of mutant ceruloplasmin.

METHODS

The effects of nonsense mutations including Y694ter, W858ter and R882ter were studied by the expression in cultured cells.

RESULTS

A biogenesis study demonstrated that the Y694ter and W858ter mutants showed protein synthesis identical to that of wild type protein, however, the mutants were retained in the endoplasmic reticulum (ER), while R882ter mutant was secreted out. Site-directed mutagenesis analyses suggested that Cys-881 was necessary for the secretion of the truncated ceruloplasmin. The W858ter mutant decreased viability in the transfected cells. The expression and the promoter activity of glucose-regulated protein 78 that is an ER stress sensor protein, were up-regulated in the transfected cells.

CONCLUSIONS

The truncated mutant containing Cys-881 was able to pass through the ER and was secreted, while the truncated mutant protein without Cys-881 appeared to accumulate in the ER thus leading to ER stress and eventually resulting in cell death.

Hepatic iron overload associated with a decreased serum ceruloplasmin level in a novel clinical type of aceruloplasminemia

BACKGROUND & AIMS

Aceruloplasminemia is a novel hereditary iron overload disease caused by a mutation in the ceruloplasmin gene and characterized by a complete deficiency of serum ceruloplasmin and iron accumulation in the liver and brain.

METHODS

We herein studied a novel clinical type of aceruloplasminemia in which a low amount of ceruloplasmin was detected in the serum of a patient. The patient presented with an asymptomatic hepatic iron overload, retinal degeneration, and diabetes mellitus. Magnetic resonance imaging of the liver and basal ganglia showed T2-hypointensity signals associated with parenchymal iron accumulation because of an absence of the ferroxidase activity in ceruloplasmin.

RESULTS

A gene analysis showed a novel G969S mutation in the ceruloplasmin gene. A biochemical analysis of the patients' serum and a biogenesis study of G969S mutant ceruloplasmin using mammalian cell culture system resulted in the synthesis and secretion of only apoceruloplasmin without any ferroxidase activity.

CONCLUSIONS

This novel clinical type of aceruloplasminemia should therefore be considered in the differential diagnosis of unexplained hemochromatosis, which is associated with a decrease in the serum ceruloplasmin level.

Serum ceruloplasmin and ferroxidase activity are not decreased in hepatic failure related to alcoholic cirrhosis: clinical and pathophysiological implications

BACKGROUND

A decrease in serum ceruloplasmin (Cp), a protein involved in iron metabolism through its ferroxidase activity, is classically claimed to be observed in severe hepatic failure of non-wilsonian chronic liver disease and therefore to be a confounding factor for the diagnosis of Wilson's disease. Moreover, a simultaneous decrease in ferroxidase activity could be hypothesized as playing a role in the development of the hepatic siderosis frequently observed in advanced chronic liver diseases. The aim of this study was to test the validity of these two statements.

METHODS

This study investigated Cp, determined by immunonephelometry, and its ferroxidase 1 activity determined by Erel's method in 33 male patients with severe alcoholic cirrhosis compared with 66 healthy male volunteers, selected on strict criteria. Each patient was age-matched with two controls. Nonparametric tests were used for statistical analysis.

RESULTS

The mean values of Cp were significantly higher in cirrhotic patients as compared with control subjects. A significant elevation of Cp was also observed in the subgroup of 11 cirrhotic patients who had normal serum C-reactive protein levels. The mean values of ferroxidase 1 activity were similar to those obtained in control subjects.

CONCLUSIONS

Low serum Cp should not be expected in severe hepatic cirrhosis of non-wilsonian origin. Hepatic siderosis in advanced chronic liver disease is likely to be unrelated to decreased ferroxidase activity.

Population screening for hemochromatosis: a study in 5370 Spanish blood donors

BACKGROUND/AIMS

Hereditary hemochromatosis is associated with homozygosity for C282Y mutation in the HFE gene, elevated serum transferrin saturation and excess iron deposits throughout the body. We conducted a population-based study in Spain to asses the prevalence of the HFE mutations and their effect on iron parameters.

METHODS

We screened 5370 blood donors for the C282Y and H63D HFE mutations by allele-specific polymerase chain reaction. Serum iron, serum ferritin and transferrin saturation were also measured.

RESULTS

We have found eight (five men and three women) blood donors who are C282Y homozygotes (0.15%) and 74 C282Y/H63D compound heterozygotes (1.38%). Four out of the eight C282Y homozygotes, all men, had high serum ferritin and transferrin saturation values. No woman was detected with both iron parameters increased. Only one of the 74 C282Y/H63D compound heterozygotes showed elevated serum ferritin and transferrin saturation values (penetrance 1.35%). Serum ferritin and transferrin saturation were significantly higher in C282Y homozygous men as compared with the rest of the genotypes.

CONCLUSIONS

The C282Y/C282Y genotype frequency in Spain is 1 in 1004. The C282Y/C282Y genotype is clearly associated with an increase in iron parameters. Biochemical expression of the disease was found in 80% of the C282Y/C282Y men.

A genetic view of iron homeostasis

Inherited disorders of iron metabolism are invariably disorders of iron balance or distribution. This review describes the proteins known to be involved in establishing and maintaining iron balance, and discusses regulation of iron homeostasis in the context of three cell types: intestinal enterocytes, reticuloendothelial macrophages, and hepatocytes. It emphasizes information gleaned from the use of genetic analyses, particularly in mice, and poses new questions to help advance our understanding of iron balance.