Dietary management of labrador retrievers with subclinical hepatic copper accumulation

Copper hepatopathies in Australian dogs

INTRODUCTION

To evaluate hepatopathies in Australian dogs according to the World Small Animal Veterinary Association (WSAVA) guidelines. Specifically, to describe the prevalence and survival of dogs with copper-associated hepatopathy.

MATERIALS AND METHODS

Medical records from the Small Animal Specialist Hospital were reviewed to identify dogs with liver disease and liver biopsy between November 2008 and November 2021. Liver histopathology reports were reviewed with a board-certified veterinary pathologist and classified according to the WSAVA guidelines. Histopathology reports and clinical records were reviewed to ascertain the most important histological process for statistical analysis. Copper-associated hepatopathy was defined as (i) histological evidence of copper accumulation in centrilobular areas (Zone 3) associated with hepatocyte necrosis, inflammation with copper-laden macrophages and chronic hepatitis (ii) histochemical copper staining showing hepatocyte copper accumulation in the centrilobular areas and iii) hepatic copper measurement with concentrations greater than 600 μg/g dry weight of liver. Dogs with primary inflammatory parenchymal disease included dogs with copper-associated hepatopathy, idiopathic chronic hepatitis, non-specific reactive hepatitis, chronic bacterial hepatitis and immune-mediated chronic hepatitis. Descriptive statistics were performed for all dogs. Age, weight and clinicopathologic data were compared between dogs with copper-associated hepatopathy and dogs with other causes of chronic primary inflammatory parenchymal liver disease (Kruskal-Wallis test). Survival times were calculated and compared (Kaplan-Meier curves and log rank test) between dogs with copper-associated hepatopathy and dogs with other chronic primary inflammatory parenchymal liver diseases. Breed was evaluated to determine the breed most commonly affected with copper-associated hepatopathy and identify any breed in which this disease has not previously been described.

RESULTS

Sixty-seven (43 female, 24 male) dogs with a median age of 7.8 years (quartile [Q] Q1-Q3 4.5-9.6 years) were included. Thirteen dogs had copper-associated hepatopathy, eight dogs had idiopathic chronic hepatitis, eight dogs had non-specific reactive hepatitis, seven dogs had disorders associated with portal hypertension, five dogs had chronic bacterial hepatitis and four dogs had immune-mediated chronic hepatitis. Compared with dogs with other causes of chronic primary inflammatory parenchymal liver disease, dogs with copper-associated hepatopathy tended to be younger (6.73 vs. 8.01 years, P = 0.057) and heavier (19.8 vs. 9.6 kg, P = 0.052) than dogs with other causes of primary chronic inflammatory parenchymal diseases. There was no statistically significant difference when ALT (P = 0.30), ALP (P = 0.18) and total bilirubin (P = 0.13) were compared between the two groups. The median survival time for all dogs after liver biopsy was 2010 days (CI 1321 days - not reached). There was no significant difference in survival between dogs with copper-associated hepatopathy and dogs with other causes of chronic primary inflammatory parenchymal liver disease (P = 0.5).

CONCLUSIONS

Copper-associated hepatopathy was common among Australian dogs with chronic hepatopathies, occurring in younger and heavier dogs than other causes of primary inflammatory parenchymal liver disease. Clinical pathology is not useful for differentiating between copper-associated hepatopathy and other causes of chronic primary inflammatory parenchymal liver disease. When copper-associated hepatopathy is treated, the prognosis can be good. This is the first report of copper-associated hepatopathy in Australian Cavalier King Charles Spaniels.

Copper-associated chronic hepatitis in Cavalier King Charles spaniels

BACKGROUND

Copper-associated chronic hepatitis (CuCH) is poorly characterised in Cavalier King Charles spaniels (CKCS).

METHODS

Hepatic copper accumulation was qualitatively and quantitatively assessed, and blood samples were used for genetic testing to screen for known CuCH-associated genetic variants.

RESULTS

The study included 13 CKCS with CuCH and eight unaffected controls. Increased transaminase activities, elevated biliary enzyme concentrations and portal hypertension were documented in 100%, 73% and 38% of dogs with CuCH, respectively. Five dogs had three or more abnormalities in measures of liver function. All 11 dogs with CuCh that underwent genetic testing were homozygous negative for the COMMD1 deletion and ATP7A variant but homozygous positive (n = 7) or heterozygous (n = 4) for the ATP7B variant. Liver histology often demonstrated marked architectural distortion by severe, bridging fibrosis and regenerative nodules with lymphoplasmacytic inflammation. Centrilobular copper accumulation characterised early cases with minimal fibrosis. When fibrosis was significant, copper was often differentially concentrated within regenerative nodules. Chelation therapy resolved laboratory derangements and portal hypertension in five of seven dogs. Of the 7 non-surviving dogs with CuCH, 6 had not received chelation therapy.

LIMITATIONS

Limitations include a small cohort size and the lack of pedigree analyses to corroborate heritability.

CONCLUSIONS

CuCH should be considered in CKCS with suspected liver disease. Long-term prognosis seems favourable in dogs receiving chelation therapy, notwithstanding the presence of previously reported negative prognostic markers.

Nutritional management of a dog with hepatic enzymopathy suspected to be secondary to copper-associated hepatitis: a case report

A 4-year-old, female-spayed American Bulldog presented to the Ontario Veterinary College's Health Sciences Center's Clinical Nutrition Service for nutritional management of hepatic enzymopathy and suspected copper-associated hepatitis. Medical history revealed a 3-month history of gradually increasing serum ALT. Additional diagnostics included negative Leptospira titters, normal bile acids, and laparoscopic liver biopsy. Histopathology findings were consistent with diffuse moderate vacuole hepatocellular degeneration, mild positive copper staining, mild chronic lymphoplasmacytic hepatitis both portal and central, and mild biliary hyperplasia. Hepatic copper quantification results were above normal ranges (630 μg/g dry tissue), but below those seen in familial copper-associated hepatitis (>800-1,000 μg/g dry tissue). The patient was prescribed ursodeoxycholic acid, recommended to be fed a homemade diet (HMD), and referred for a nutrition consult. Two days before the nutrition consult, serum ALT fell within the normal range. The body condition score was 5/9, with a good muscle condition score and the dog's appetite and body weight remained stable. Energy intake was appropriate for maintenance. Key nutrient levels of all diets reported were compared to industry standards (AAFCO, NRC, and FEDIAF). Diet history included a commercially available raw meat-based diet (RMBD), of unknown copper content; a high energy commercial dry food (HEC), with copper content higher than the maximum recommended by FEDIAF and immediately prior to nutrition consult the patient had been eating an unbalanced homemade diet (HMD1) for 4 weeks. HMD1 was low in copper and deficient in the hepatoprotectant nutrients vitamin E and zinc. As per the owner's preference and to accommodate the patient's unique nutritional needs, a homemade diet addressing key nutrients for liver disease was formulated (HMD2), with copper content just above the recommended minimum. The new diet was found palatable and the patient's body weight, body, and muscle condition scores remained unchanged. Two months after starting HMD2, all bloodwork values remained within the normal range, including ALT. The reduction of dietary copper content likely reduced serum ALT. However, unbalanced diets cause a risk of nutrient deficiencies and excess. This dog was maintained with no known adverse effects on a complete and balanced HMD diet with a moderately low copper content, moderate protein, and inclusion of hepatoprotective nutrients.

Hepatic copper accumulates in ferrets with and without hepatobiliary disease

OBJECTIVE

To determine hepatic copper concentrations and zonal distribution in ferrets with and without hepatobiliary disease, validate rhodanine-based qualitative copper scoring and digital copper quantification in ferret hepatic samples, and ascertain whether clinical features predicted copper accumulation.

ANIMALS

34 ferrets, including 7 with necroinflammatory disease, 5 with hepatocellular carcinoma, 13 with non-necroinflammatory disease, and 9 with no hepatobiliary disease.

PROCEDURES

Rhodanine-based digital copper quantification was validated by use of liver dually measured by atomic absorption spectroscopy and digital scanning (R2 = 0.98). Clinical features and hepatic copper scores and concentrations (dry weight liver) were compared between groups. Zonal copper distribution was determined.

RESULTS

Hepatic copper concentration was strongly correlated with copper scores (ρ = 0.88). Ferrets with hepatobiliary disease were significantly older and had significantly higher serum alkaline phosphatase and γ-glutamyltransferase activities and creatinine concentrations. Centrilobular copper accumulated in 23 of 34 (64%) ferrets with (n = 15) and without (8) hepatobiliary disease. Median copper concentrations were not significantly different between ferrets with and without hepatobiliary disease but were significantly higher within neoplastic hepatic tissue in ferrets with hepatocellular carcinoma. Hepatic copper concentrations exceeded feline (> 180 µg/g) and canine (> 400 µg/g) reference limits in 19 and 9 ferrets, respectively. Hepatic copper > 1,000 µg/g occurred in 5 ferrets with and 2 without hepatobiliary disease. Clinical features did not predict copper accumulation.

CLINICAL RELEVANCE

Rhodanine-based digital copper quantification and qualitative copper scoring discerned liver copper accumulation in ferrets. Ferrets with and without hepatobiliary disease displayed a propensity for centrilobular hepatic copper accumulation of uncertain clinical importance. Clinical and clinicopathologic features could not exclusively implicate pathologic copper accumulation.

Genotype frequency of ATP7A and ATP7B mutation-related copper-associated hepatitis in a Japanese guide dog Labrador retriever population

The incidence of copper-associated hepatitis in Labrador retriever in Japan has not been examined. This study examined the genotype frequencies of ATP7B:c.4358G>A, a mutation responsible for copper-associated hepatitis, and ATP7A:c.980C>T, a modifier of this disease, in Labrador retrievers of guide dog associations in Japan. Genetic material was collected by buccal swabs from 253 Labrador retrievers and genotyping was performed for the ATP7B and ATP7A mutations. The gene frequency was 0.107 for ATP7B:c.4358A. For ATP7A:c.980C, the gene frequencies were 0.703 in females and 0.368 in males. In this study, we established genotyping methods for the ATP7B:c.4358G>A and ATP7A:c.980C>T mutations. Based on the genotyping results, the risk of copper-associated hepatitis in the study population was 0.80% in males and 1.05% in females.

COMMD1 Exemplifies the Power of Inbred Dogs to Dissect Genetic Causes of Rare Copper-Related Disorders

Wilson's Disease is a rare autosomal recessive disorder in humans, often presenting with hepatic copper overload. Finding the genetic cause of a rare disease, especially if it is related to food constituents like the trace element copper, is a Herculean task. This review describes examples of how the unique population structure of in-bred dog strains led to the discovery of a novel gene and two modifier genes involved in inherited copper toxicosis. COMMD1, after the discovery in 2002, was shown to be a highly promiscuous protein involved in copper transport, protein trafficking/degradation, regulation of virus replication, and inflammation. Mutations in the ATP7A and ATP7B proteins in Labrador retrievers and Dobermann dogs resulted in a wide variation in hepatic copper levels in these breeds. To our knowledge, numerous dog breeds with inherited copper toxicosis of unknown genetic origin exist. Therefore, the possibility that men's best friend will provide new leads in rare copper storage diseases seems realistic.

Towards Bioengineered Liver Stem Cell Transplantation Studies in a Preclinical Dog Model for Inherited Copper Toxicosis

Wilson Disease is a rare autosomal recessive liver disorder in humans. Although its clinical presentation and age of onset are highly variable, hallmarks include signs of liver disease, neurological features and so-called Kayser-Fleischer rings in the eyes of the patient. Hepatic copper accumulation leads to liver disease and eventually to liver cirrhosis. Treatment options include life-long copper chelation therapy and/or decrease in copper intake. Eventually liver transplantations are indicated. Although clinical outcome of liver transplantations is favorable, the lack of suitable donor livers hampers large numbers of transplantations. As an alternative, cell therapies with hepatocytes or liver stem cells are currently under investigation. Stem cell biology in relation to pets is in its infancy. Due to the specific population structure of dogs, canine copper toxicosis is frequently encountered in various dog breeds. Since the histology and clinical presentation resemble Wilson Disease, we combined genetics, gene-editing, and matrices-based stem cell cultures to develop a translational preclinical transplantation model for inherited copper toxicosis in dogs. Here we describe the roadmap followed, starting from the discovery of a causative copper toxicosis mutation in a specific dog breed and culminating in transplantation of genetically-engineered autologous liver stem cells.

Association of the canine ATP7A and ATP7B with hepatic copper accumulation in Dobermann dogs

BACKGROUND

Hepatic copper accumulation causes chronic hepatitis in dogs. Mutations in the copper transporters ATP7A and ATP7B were, respectively, associated with attenuation and enhancement of hepatic copper concentrations in Labrador Retrievers. There is a predisposition of Dobermanns to hepatitis with increased hepatic copper concentrations.

OBJECTIVES

To investigate whether the ATP7A:c.980C>T and ATP7B:c.4358G>A mutations identified in Labrador Retrievers were associated with hepatic copper concentrations in Dobermanns.

ANIMALS

Dobermanns from the Netherlands (n = 122) and the United States (n = 78).

METHODS

In this retrospective study, mutations in ATP7A and ATP7B were investigated as risk factors for hepatic copper accumulation in Dobermanns. Liver biopsies of 200 Dobermanns were evaluated by histochemical copper staining, quantitative copper measurement, or both modalities. ATP7A and ATP7B genotypes were obtained by Kompetitive Allele Specific PCR. A linear regression model was used to investigate an association between genotype and hepatic copper concentrations.

RESULTS

The ATP7A:c.980C>T was identified in both Dutch (2 heterozygous individuals) and American Dobermanns. In the American cohort, the minor allele frequency of the mutation was low (.081) and a possible effect on hepatic copper concentrations could not be established from this data set. A significant association of the ATP7B:c.4358G>A variant with increased hepatic copper concentrations in Dobermanns was observed.

CONCLUSIONS AND CLINICAL IMPORTANCE

The ATP7B:c.4358G>A variant could be a contributor to hepatic copper accumulation underlying the risk of development of copper-associated hepatitis in breeds other than the Labrador Retriever.

Predicting copper toxicosis: relationship between the ATP7A and ATP7B gene mutations and hepatic copper quantification in dogs

This preliminary study summarizes the genotypes of 42 Labrador Retrievers and Labrador Retriever-Golden Retriever crosses and phenotypes a subset of ten of these dogs that are homozygous mutant, heterozygous, or homozygous normal for mutations in the ATP7A and ATP7B genes that have been associated with the development of copper toxicosis in Labrador Retrievers. The purpose of this study is to evaluate whether there is a correlation between ATP7A and ATP7B genotypes and clinical evidence of hepatic pathology in young, asymptomatic Labrador Retrievers. We evaluated serum ALT levels, hepatic copper concentrations, and hepatic histopathology from ten offspring where both parents had a least one copy of the ATP7B mutation. Five were homozygous mutant, four were heterozygous, and one was homozygous normal for comparison. None had increased serum ALT activity. All dogs homozygous for the ATP7B mutation had elevated hepatic copper concentrations compared to dogs heterozygous for the ATP7B mutation regardless of sex or presence of an ATP7A mutation with the mean hepatic copper concentration being 1464 ppm (reference range 100-330 ppm). Mean hepatic copper concentration in homozygous normal and heterozygous dogs was 328 ppm. In this preliminary analysis, we found that dogs that carry two copies of the ATP7B mutation have abnormally elevated hepatic copper levels despite having normal serum ALT activity. Our findings support the hypothesis that the ATP7B DNA test can predict defects in hepatic copper metabolism. Veterinarians can test for the ATP7B gene mutation to identify Labrador Retrievers at risk for copper toxicosis so that they can take steps to prevent development of copper-associated chronic hepatitis in their patients.

ACVIM consensus statement on the diagnosis and treatment of chronic hepatitis in dogs

This consensus statement on chronic hepatitis (CH) in dogs is based on the expert opinion of 7 specialists with extensive experience in diagnosing, treating, and conducting clinical research in hepatology in dogs. It was generated from expert opinion and information gathered from searching of PubMed for manuscripts on CH, the Veterinary Information Network for abstracts and conference proceeding from annual meetings of the American College of Veterinary Medicine and the European College of Veterinary Medicine, and selected manuscripts from the human literature on CH. The panel recognizes that the diagnosis and treatment of CH in the dog is a complex process that requires integration of clinical presentation with clinical pathology, diagnostic imaging, and hepatic biopsy. Essential to this process is an index of suspicion for CH, knowledge of how to best collect tissue samples, access to a pathologist with experience in assessing hepatic histopathology, knowledge of reasonable medical interventions, and a strategy for monitoring treatment response and complications.

Ammonium tetrathiomolybdate treatment of copper-associated hepatopathy in dogs

Background

Copper‐associated hepatopathy (CAH) is a common cause of liver disease in dogs. Although d‐penicillamine can be an effective treatment, some dogs fail treatment or develop adverse effects. Ammonium tetrathiomolybdate (TTM) has been used to treat pathologic copper accumulation in other species, but its therapeutic potential for CAH is unknown.

Objectives

To investigate short‐term safety and efficacy of TTM for treatment of CAH.

Animals

Ten dogs with CAH.

Methods

Prospective study. All dogs were treated with TTM PO for 6 weeks, and hepatic biopsies were performed after the treatment course. Dog experiencing initial decreases in hepatic copper concentrations ([Cu]_H) received 6 additional weeks of TTM treatment and underwent 1 additional biopsy. Physical and laboratory examinations were performed every 2 weeks for study duration.

Results

Eight of 10 dogs had decreases in [Cu]_H. Compared to baseline (median, 1606 μg/g; range, 572‐5158 μg/g), [Cu]_H were decreased at 6 weeks (1033 μg/g, 450‐2975 μg/g; P = .04) and 12 weeks (931 μg/g, 218‐1677 μg/g; P = .02). Hepatic molybdenum concentrations increased >50‐fold (P < 0.001). Changes in histologic scores and hematologic and biochemical test results were variable and not significantly different from baseline. One dog developed presumed immune‐mediated anemia and thrombocytopenia, but it was unclear if this was related to TTM administration.

Conclusions and Clinical Importance

Results suggest that TTM can effectively decrease [Cu]_H in some dogs with CAH. Larger studies are needed to determine the overall safety and efficacy of TTM for treating CAH and how it compares with current treatments.

Canine Breed-Specific Hepatopathies

Canine hepatopathies, both congenital and acquired, arise from an interaction between genes and environment. Many show increased breed prevalences. This article reviews the current understanding on breed predispositions for congenital portosystemic shunts; microvascular dysplasia and portal vein hypoplasia; ductal plate abnormalities (congenital hepatic fibrosis and Caroli disease); chronic hepatitis (both copper associated and idiopathic); vacuolar hepatopathies; and gallbladder mucocele. Although all these diseases can occur in many breeds and crossbreeds, understanding breed predispositions helps recognition and will guide future research to improve understanding of causes and treatments.

Canine Copper-Associated Hepatitis

Copper-associated hepatitis is recognized with increasing frequency in dogs. The disease is characterized by centrolobular hepatic copper accumulation, leading to hepatitis and eventually cirrhosis. The only way to establish the diagnosis is by histologic assessment of copper distribution and copper quantification in a liver biopsy. Treatment with the copper chelator d-penicillamine is the most commonly used treatment. In addition, a low-copper/high-zinc diet can help prevent accumulation or reaccumulation of hepatic copper. Mutations in the copper metabolism genes COMMD1 or ATP7A and ATP7B have been associated with hepatic copper concentrations in Bedlington terriers and Labrador retrievers respectively. In the Labrador retriever, dietary copper intake contributes strongly to the disease phenotype.

Erythrocyte copper chaperone for superoxide dismutase and superoxide dismutase as biomarkers for hepatic copper concentrations in Labrador retrievers

Hereditary hepatic copper accumulation in Labrador retrievers leads to hepatitis with fibrosis and eventually cirrhosis. The development of a non-invasive blood-based biomarker for copper status in dogs could be helpful in identifying dogs at risk and to monitor copper concentrations during treatment. In this study, two cellular copper metabolism proteins, Cu/Zn superoxide dismutase (SOD1) and its chaperone (copper chaperone for SOD1, CCS) were measured in erythrocytes and tested for association with hepatic copper concentrations in 15 Labrador retrievers with normal or increased hepatic copper concentrations. Antibodies against CCS and SOD1 were applicable for use in canine specimens. This was demonstrated by the loss of immune-reactive bands for CCS and SOD1 in siRNA treated canine bile duct epithelial cells. Erythrocyte CCS and CCS/SOD1 ratios were decreased 2.37 (P <0.001) and 3.29 (P <0.001) fold in the high copper group compared to the normal copper group. Erythrocyte CCS and CCS/SOD1 ratio are potential new biomarkers for hepatic copper concentrations in Labrador retrievers and could facilitate early diagnosis and treatment monitoring for copper-associated hepatitis in dogs.

Canine Models for Copper Homeostasis Disorders

Copper is an essential trace nutrient metal involved in a multitude of cellular processes. Hereditary defects in copper metabolism result in disorders with a severe clinical course such as Wilson disease and Menkes disease. In Wilson disease, copper accumulation leads to liver cirrhosis and neurological impairments. A lack in genotype-phenotype correlation in Wilson disease points toward the influence of environmental factors or modifying genes. In a number of Non-Wilsonian forms of copper metabolism, the underlying genetic defects remain elusive. Several pure bred dog populations are affected with copper-associated hepatitis showing similarities to human copper metabolism disorders. Gene-mapping studies in these populations offer the opportunity to discover new genes involved in copper metabolism. Furthermore, due to the relatively large body size and long life-span of dogs they are excellent models for development of new treatment strategies. One example is the recent use of canine organoids for disease modeling and gene therapy of copper storage disease. This review addresses the opportunities offered by canine genetics for discovery of genes involved in copper metabolism disorders. Further, possibilities for the use of dogs in development of new treatment modalities for copper storage disorders, including gene repair in patient-derived hepatic organoids, are highlighted.

Hepatocyte-derived microRNAs as sensitive serum biomarkers of hepatocellular injury in Labrador retrievers

Common parenchymal liver diseases in dogs include reactive hepatopathies and primary hepatitis (acute or chronic). In chronic hepatitis, there is usually a long subclinical phase. Specific clinical signs become overt only when liver damage is severe and in this phase, treatment is usually less effective. Limited data are available regarding the sensitivity of liver enzyme activity or biomarkers for early detection of subclinical hepatitis. Hepatocyte-derived microRNAs (HDmiRs) were recently identified as promising biomarkers for hepatocellular injury in multiple species. Here, the potential of the HDmiRs miR-122 and miR-148a as sensitive diagnostic biomarkers for hepatocellular injury in Labrador retrievers was investigated. Samples from 66 Labrador retrievers with histologically normal livers, high hepatic copper, and with various forms of liver injury were evaluated for serum alanine aminotransferase (ALT) activity and microRNA values. Median values of HDmiR-122 were 34.6 times higher in dogs with liver injury and high ALT than in normal dogs (95% confidence intervals [CI], 13-95; P <0.001). HDmiR-122 values were significantly increased in dogs with liver injury and normal ALT (4.2 times; 95% CI, 2-12; P <0.01) and in dogs with high hepatic copper concentrations and unremarkable histopathology (2.9 times; 95% CI, 1.1-8.0; P <0.05). Logistic regression analyses demonstrated that miR-122 and miR-148a were both predictors of hepatocellular injury. The sensitivity of miR-122 was 84% (95% CI, 73-93%), making it superior to ALT (55%; 95% CI, 41-68%) for the detection of hepatocellular injury in Labrador retrievers (P <0.001). This study demonstrated that serum HDmiR, particularly miR-122, is a highly sensitive marker for the detection of hepatocellular injury in Labrador retrievers and is a promising new biomarker that may be used for early detection of subclinical hepatitis in dogs.