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Urinary copper elevation in a mouse model of Wilson's disease is a regulated process to specifically decrease the hepatic copper load.

ABSTRACT: Body copper homeostasis is regulated by the liver, which removes excess copper via bile. In Wilson's disease (WD), this function is disrupted due to inactivation of the copper transporter ATP7B resulting in hepatic copper overload. High urinary copper is a diagnostic feature of WD linked to liver malfunction; the mechanism behind urinary copper elevation is not fully understood. Using Positron Emission Tomography-Computed Tomography (PET-CT) imaging of live Atp7b(-/-) mice at different stages of disease, a longitudinal metal analysis, and characterization of copper-binding molecules, we show that urinary copper elevation is a specific regulatory process mediated by distinct molecules. PET-CT and atomic absorption spectroscopy directly demonstrate an age-dependent decrease in the capacity of Atp7b(-/-) livers to accumulate copper, concomitant with an increase in urinary copper. This reciprocal relationship is specific for copper, indicating that cell necrosis is not the primary cause for the initial phase of metal elevation in the urine. Instead, the urinary copper increase is associated with the down-regulation of the copper-transporter Ctr1 in the liver and appearance of a 2 kDa Small Copper Carrier, SCC, in the urine. SCC is also elevated in the urine of the liver-specific Ctr1(-/-) knockouts, which have normal ATP7B function, suggesting that SCC is a normal metabolite carrying copper in the serum. In agreement with this hypothesis, partially purified SCC-Cu competes with free copper for uptake by Ctr1. Thus, hepatic down-regulation of Ctr1 allows switching to an SCC-mediated removal of copper via kidney when liver function is impaired. These results demonstrate that the body regulates copper export through more than one mechanism; better understanding of urinary copper excretion may contribute to an improved diagnosis and monitoring of WD.

SUBMITTER: Gray LW

PROVIDER: S-EPMC3390108 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Urinary copper elevation in a mouse model of Wilson's disease is a regulated process to specifically decrease the hepatic copper load.

Gray Lawrence W LW Peng Fangyu F Molloy Shannon A SA Pendyala Venkata S VS Muchenditsi Abigael A Muzik Otto O Lee Jaekwon J Kaplan Jack H JH Lutsenko Svetlana S

PloS one 20120622 6

Body copper homeostasis is regulated by the liver, which removes excess copper via bile. In Wilson's disease (WD), this function is disrupted due to inactivation of the copper transporter ATP7B resulting in hepatic copper overload. High urinary copper is a diagnostic feature of WD linked to liver malfunction; the mechanism behind urinary copper elevation is not fully understood. Using Positron Emission Tomography-Computed Tomography (PET-CT) imaging of live Atp7b(-/-) mice at different stages of ...[more]

PMID: 22802922

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Project description:HSD17B13 encodes hydroxysteroid 17-β dehydrogenase 13, a novel liver lipid-droplet associated protein that is involved in the regulation of lipid biosynthetic processes. A protein-truncating HSD17B13 variant (rs72613567) was shown to protect individuals from alcoholic and non-alcoholic liver disease. Since steatosis is a common feature in Wilson's disease (WD), we aimed to assess whether the HSD17B13 variant modulates the phenotypic presentation and progression of WD.MethodsThe HSD17B13:TA (rs72613567) variant was determined by allelic discrimination real-time PCR in 586 patients. The HSD17B13 genotype was correlated with the phenotypic presentation. The age of onset and the type of symptoms at presentation were used as markers of the WD phenotype.ResultsThe overall HSD17B13:TA allele frequency in patients with WD was 23.3% (273/1,172), not significantly different from the reported minor allele frequency. There was a significantly lower HSD17B13:TA allele frequency in patients with fulminant WD compared to all other phenotypic WD groups (11.0% vs. 24.0%, p < 0.01). Among the patients with fulminant WD there was a trend for a gender effect; none of the male patients carried the HSD17B13:TA allele. HSD17B13:TA allele frequency was more common in patients with minimal or no fibrosis (49 [31.1%] had simple steatosis and 20 minimal changes at biopsy) than in patients with cirrhosis or advanced fibrosis (22.3%, p = 0.025).ConclusionsThe HSD17B13:TA allele modulates the phenotype and outcome of WD. This allele likely ameliorates hepatic fibrosis and reduces the transition from copper induced hemolysis to fulminant disease in patients with WD.Lay summaryWilson's disease is a hereditary disease caused by accumulation of copper in the liver and other tissues. It presents with a variety of clinical symptoms. In this study we explored the role of a recently described gene mutation (HSD17B13:TA) which apparently protects the liver against toxins like alcohol. The results indicate that this mutation plays a role in the evolution of liver disease. Patients with Wilson's disease who carry this mutation are more likely to have mild disease, while the absence of the mutation is associated with the most severe form - fulminant Wilson's disease.

Dataset Information

Urinary copper elevation in a mouse model of Wilson's disease is a regulated process to specifically decrease the hepatic copper load.

Publications

Urinary copper elevation in a mouse model of Wilson's disease is a regulated process to specifically decrease the hepatic copper load.

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