Copper-associated chronic hepatitis in the Labrador retriever

This thesis describes copper-associated chronic hepatitis as a new disease in the Labrador. A study of 143 dogs that were prospectively assessed for clinical parameters, laboratory results, and liver copper concentrations, as well as histologic signs of inflammation revealed that more than two thirds of family members from dogs with CACH have liver copper concentrations above the normal reference range. In addition almost half of these clinically normal dogs with elevated hepatic copper concentrations had chronic hepatitis. Male gender appeared to protect dogs from copper-associated hepatitis. Molecular biologic approaches to investigate the disease included genotyping of microsatellite markers in a candidate gene approach, as well as genome wide genotyping of 340 microsatellite markers, and 22.000 single nucleotide polymorphisms (SNPs) per dog. Furthermore sequencing analysis was performed, and the expression of genes was assessed by microarray analysis and quantitative PCR. Our study excluded all investigated candidate genes from involvement in hepatic copper accumulation, under the condition that a single disease gene exists. From a genome wide genotyping approach 3 regions of possible linkage were identified within the canine genome. Based on these results further search for underlying genetic defects was narrowed down from 24.000 Mb of the whole canine genome to 3 regions of 2 Mb each. Furthermore 5 novel genes were identified that may represent an acute response to copper overload. Our randomized, double-blinded, and placebo-controlled treatment trial showed that D-penicillamine is an effective drug to decrease hepatic copper concentrations in affected Labradors., but due to the fact that the disease is most likely caused by an inherited genetic defect lifelong cure cannot be achieved with a single treatment regimen, and re-accumulation of copper is likely. Therefore a more balanced long term control of hepatic copper concentrations was the aim of our diet trial that investigated a low-copper diet as well as the usefulness of additional management with zinc. This study revealed an excellent treatment response of dogs with hepatic copper accumulation to feeding of a copper-restricted diet. Therefore it is possible that nutritional contents of copper may have an impact on the development of the disease. Stern and his colleagues from the R. Samuel McLaughlin Center for Population Health Risk assessment, in collaboration with the International Copper association recently described the difficulty of an exact definition of a safe range of copper in food and water, because studies investigating both endpoints are pending. Similar difficulties have been encountered by the European Commissions for Health and Consumer Protection directorate in a recent report, as well as the Committee on Copper in Drinking Water of the National Research Council. Our results are likely to provide some additional insight into copper metabolism. Our ongoing genetic work will likely discover new genes of copper metabolism. Thus we will probably soon be able to answer the important question “Are there additional copper homeostatic genes ?” that was recently posed by the International Copper association with a clear “Yes, there are !”.