Association of dietary copper and zinc levels with hepatic copper and zinc concentration in Labrador Retrievers

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.

Quantitative bioimaging of copper in frozen liver specimens from cats using laser ablation-inductively coupled plasma-mass spectrometry

OBJECTIVES

The aim of this study was to assess laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) as a tool for measuring concentrations and determining accumulation of copper in frozen liver specimens from cats.

METHODS

Six frozen liver specimens were evaluated by qualitative copper staining and quantitative flame atomic absorption spectroscopy. Tissue specimens were cryo-sectioned and quantitative bioimaging of copper was performed using LA-ICP-MS. Results were compared with those obtained using conventional methods.

RESULTS

Of the six specimens, only one showed positive staining for copper with rhodanine. Using flame atomic absorption spectroscopy (FAAS), one specimen showed a deficient copper level (<100 µg/g dry weight), two specimens had copper within the reference interval (RI; 150-180 µg/g) and three specimens had copper concentrations above the RI. Bioimaging from LA-ICP-MS showed inhomogeneous distribution of hepatic copper. The areas with dense copper accumulation were represented as hotspots in the liver specimens. Hepatic copper quantification by LA-ICP-MS correlated well with copper quantified by FAAS (r = 0.96, P = 0.002).

CONCLUSIONS AND RELEVANCE

Our findings suggest that quantitative bioimaging by LA-ICP-MS could be used to demonstrate the distribution and concentration of copper in frozen liver specimens from cats. The distribution of copper in these specimens was inhomogeneous with dense accumulation represented as hotspots on tissue sections. A positive correlation of hepatic copper concentrations determined by LA-ICP-MS and FAAS was found. Further studies to establish an RI for hepatic copper using this technique and to further determine its clinical utility are warranted.

Mineral and heavy metal content in dry dog foods with different main animal components

Dog caregivers, mainly for economic reasons and easy availability, choose dry, over the counter diets (OTC). The mineral composition of OTC foods depends primarily on the components used in the production of the pet food. Regardless of the main component of the food, it must meet the recommended minimum mineral content, established by nutritional guidelines. Therefore, the aim of this study was to determine the mineral (Ca, K, Mg, Na, Fe, Mn, Zn, Cu, Mo) and heavy metal content (Pb, Co, Cd, Cr, Ni) using the methods of colorimetry and mass spectrometry, of OTC dry dog foods and to compare with the FEDIAF and AAFCO nutritional guidelines. Dry foods pose no risk to dogs in terms of heavy metal content. The worst results in terms of mineral content were obtained in mixed foods, therefore it is worth considering feeding the dog a mono-protein food. The PCA analysis disproved our hypothesis and revealed that the main animal source did not statistically significantly affect the levels of minerals and their ratios. However, the analysis of contrasts confirms the differentiation of the content of individual minerals between the groups of foods. For the first time, we proved that pet food with a mineral composition similar to the MIN-RL may be characterized by unfavorable mineral ratios.

ATP7A, ATP7B, and RETN genotypes in Labrador Retrievers with and without copper-associated hepatopathy

OBJECTIVE

To determine the frequency of previously reported coding variants in the ATP7A, ATP7B, and RETN genes in a US population of Labrador Retrievers and to explore potential associations of these genotypes with pathologic hepatic copper accumulation.

SAMPLE

Archived hepatic specimens from 90 Labrador Retrievers collected between 2013 and 2021.

PROCEDURES

The Michigan State University Veterinary Diagnostic Laboratory database was searched to identify archived tissues from Labrador Retrievers that had undergone hepatic histopathologic assessment. Cases were classified into control, copper-associated hepatopathy (CAH), and intermediate populations on the basis of histopathologic features and hepatic copper accumulation. The DNA was extracted from archived tissues and genotyped for reported variants in the 3 genes. Allele frequencies were determined, and associations of genotypes with CAH status were evaluated.

RESULTS

29 control dogs, 45 CAH dogs, and 16 intermediate dogs were included in the study. The overall ATP7A and RETN variant allele frequencies were 30% and 13%, respectively, and were not significantly different among control, CAH, and intermediate populations. The ATP7B variant allele frequency was significantly higher in the CAH population (30%) as compared to the control population (13%). However, 21 of 45 (47%) CAH dogs did not have an ATP7B variant allele whereas 7 of 28 (25%) control dogs did have an ATP7B variant allele.

CLINICAL RELEVANCE

Study results supported a contributory role for the ATP7B variant in CAH pathogenesis in Labrador Retrievers. However, the application of genetic testing in a clinical setting is complicated by genotypic variability within healthy and diseased dogs.

Evaluation of iron, copper and zinc concentrations in commercial foods formulated for healthy cats

OBJECTIVES

The aim of this study was to analyze iron, copper and zinc concentrations in commercial foods and compare among food formats (dry, canned, raw), foods marketed by age category (adult 1+ years and senior 7+ years) and foods intended for adult maintenance vs all life stages.

METHODS

In total, 112 commercial non-therapeutic food products marketed for healthy adult and senior cats were purchased in the USA. Foods were analyzed for their proximate composition. Trace mineral concentrations were measured using inductively coupled argon plasma-optical emission spectroscopy and described on a calculated metabolizable energy basis using standard modified Atwater values.

RESULTS

Measured iron (median 58.4 mg/1000 kcal [range 15.7-379.0]), copper (median 5.6 mg/1000 kcal [range 0.8-13.3]) and zinc (median 47.6 mg/1000 kcal [range 7.6-128.1]) concentrations were highly variable among cat foods. When all food products - regardless of their nutritional adequacy substantiation method - were compared with the Association of American Feed Control Officials regulatory minimums, 13/112 food products had a mineral deficiency, of which a majority (n = 11/13) were raw food products. Raw foods had significantly lower trace mineral concentrations compared with dry food products and, except for copper, canned food products. Cat foods marketed for senior cats had higher iron (P = 0.019) and zinc (P <0.0001) concentrations than foods marketed for adult cats. Foods intended for adult maintenance had higher iron (P = 0.003) and zinc concentrations than foods intended for all life stages (P <0.0001).

CONCLUSIONS AND RELEVANCE

Iron, copper and zinc concentrations in commercial non-therapeutic foods for adult and senior cats are highly variable. A minority of foods - mainly raw food products - were deficient in these minerals. It is unknown if some foods with high trace mineral concentrations could have adverse effects as studies are needed to establish safe upper limits for dietary intake of trace minerals in healthy cats.

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.

Computer-aided ration calculation (Diet Check Munich© ) versus blood profile in raw fed privately owned dogs

Many dog owners create nutritionally imbalanced raw meat-based diets (RMBD) with information from the Internet and pseudo-scientific books, some even use pre-prepared frozen raw feed from online shops, local butchers or other providers. The risk of nutritional imbalances is therefore present. Blood profiles for dogs fed RMBD are promoted by laboratories as a simple tool for the owner to check the nutritional supply situation. Veterinarian nutrition specialists seem to be consulted less frequently and, in most cases, when blood analyses show deviations from reference ranges. The aim of the present study was to evaluate whether a RMBD blood profile reflects possible malnutrition according to a computer-aided ration check and to assess its clinical relevance. Using standardized questionnaires, the average daily rations of 104 dogs, 83 of which were fed raw diets versus 21 commercially fed dogs, were analysed using Diet Check Munich©, based on the National Research Council values. Afterwards, the SYNLAB.vet GmbH 'Barfer-Profil' test including calcium, phosphate, calcium/phosphate ratio, vitamin A, vitamin D, copper, zinc and iodine with additional parameters taurine, urea, uric acid and creatinine was carried out. No significant correlation between nutrient supply and associated blood parameters could be detected. Diet calculation revealed significantly more nutritional imbalances in the RMBD group than in the control group. Low plasma taurine could be detected only in the RMBD group. After participating, 30% of the dog owners (RMBD group) decided to adjust their dogs' diets at the nutrition consultation of the Clinic for Small Animal Internal Medicine of the LMU Munich. Based on these results, for most parameters a RMBD blood profile is not an appropriate tool to monitor a dog's nutrition and computer-aided ration calculation remains the gold standard for detecting nutritional imbalances.

Hepatic lead and copper concentrations in dogs with chronic hepatitis and their relationship with hematology, serum biochemistry, and histopathology

BACKGROUND

Although the influence of copper ([Cu]) on chronic hepatitis (CH) has been widely studied in dogs, little information is available about the accumulation of other metals.

HYPOTHESIS/OBJECTIVES

We assessed the concentration of lead ([Pb]) in the livers of dogs with CH with or without abnormal hepatic [Cu] to establish if any association existed between [Pb] and either hematologic or biochemical variables, fibrosis, necrosis and inflammation of the liver on histology.

ANIMALS

Thirty-four dogs with CH that had hepatic [Cu] and [Pb] determined.

METHODS

Retrospective review of medical records of dogs with CH and hepatic [Cu] and [Pb]. Chronic hepatitis was defined using current American College of Veterinary Internal Medicine consensus statement guidelines. Hepatic [Cu] and [Pb] were determined using square wave anodic stripping voltammetry. Dogs were divided into 2 groups based on [Cu]: <400 ppm (LoCu) and ≥400 ppm (HiCu).

RESULTS

The median [Cu] and [Pb] were 357 ppm (range, 100-7743 ppm) and 58.7 (range, 6.89-224.4 ppm), respectively. Nineteen dogs had LoCu and 15 dogs had HiCu. Median [Pb] was significantly higher in HiCu compared to LoCu dogs (P < .001). Hepatic [Pb] and [Cu] were significantly correlated (rho = 0.7; P < .001). Dogs with microcytosis had higher [Pb] than did dogs with normal red cell volume (P = .02). Hepatic [Pb] was not correlated with either necroinflammatory or fibrosis scores.

CONCLUSIONS AND CLINICAL IMPORTANCE

Although additional studies are needed to better understand the clinical role of hepatic [Pb], dogs with abnormal hepatic [Cu] may also have higher hepatic [Pb]. In addition, in dogs with high hepatic [Pb], microcytosis may be present.

Assessment of copper accumulation in archived liver specimens from cats

OBJECTIVES

The aim of this study was to assess hepatic copper concentrations and zonal distribution in cat liver specimens.

METHODS

For this study, 121 archived, formalin-fixed, paraffin-embedded liver specimens from cats were used. Tissue sections were stained for copper with rhodanine and scored from 0 (no copper accumulation) to 5 (panlobular copper accumulation). The tissue specimens were then deparaffinized and hepatic copper concentrations were measured using flame atomic absorption spectroscopy.

RESULTS

Tissue samples were categorized into four groups based on histopathologic findings: (1) no significant histopathologic hepatic changes (n = 66); (2) hepatic steatosis (n = 18); (3) inflammatory or infectious disease (n = 24); and (4) neoplasia (n = 13). Of the 121 specimens, 13 (11%) stained positive for copper, with three having a score ⩾3. Thirty-seven specimens (31%) had copper concentrations above the reference interval ([RI] <180 µg/g dry weight liver). Copper concentrations in cats with hepatic inflammatory or infectious disease were significantly higher than cats with hepatic steatosis (P = 0.03). Copper-staining score and concentration were positively correlated (rs = 0.46, P <0.001).

CONCLUSIONS AND RELEVANCE

Despite the fact that 31% of specimens had copper concentrations above the RI, only 11% showed positive copper staining and only 2.5% had a score ⩾3. Our findings suggest that hepatic copper concentrations greater than the upper limit of the RI are relatively common in cats. Further studies to determine the factors that influence hepatic copper staining in cats and to establish contemporary RIs for hepatic copper in healthy cats are warranted.

D-Penicillamine: The State of the Art in Humans and in Dogs from a Pharmacological and Regulatory Perspective

Chelant agents are the mainstay of treatment in copper-associated hepatitis in humans, where D-penicillamine is the chelant agent of first choice. In veterinary medicine, the use of D-penicillamine has increased with the recent recognition of copper-associated hepatopathies that occur in several breeds of dogs. Although the different regulatory authorities in the world (United States Food and Drugs Administration-U.S. FDA, European Medicines Agency-EMEA, etc.) do not approve D-penicillamine for use in dogs, it has been used to treat copper-associated hepatitis in dogs since the 1970s, and is prescribed legally by veterinarians as an extra-label drug to treat this disease and alleviate suffering. The present study aims to: (a) address the pharmacological features; (b) outline the clinical scenario underlying the increased interest in D-penicillamine by overviewing the evolution of its main therapeutic goals in humans and dogs; and finally, (c) provide a discussion on its use and prescription in veterinary medicine from a regulatory perspective.

Disparities in hepatic copper concentrations determined by atomic absorption spectroscopy, inductively coupled plasma mass spectrometry, and digital image analysis of rhodanine-stained sections in dogs

OBJECTIVE

To investigate disparities in hepatic copper concentrations determined by atomic absorption spectroscopy (AAS), inductively coupled plasma mass spectrometry (ICP-MS), and digital image analysis of rhodanine-stained sections.

ANIMALS

516 dogs.

PROCEDURES

Medical records of dogs for which hepatic biopsy specimens had been submitted between January 1999 and December 2019 for evaluation of copper content were reviewed. Paired hepatic copper concentrations obtained with digital image analysis and AAS or ICP-MS were compared, and Spearman rank correlation coefficients were calculated to test for correlations between qualitative copper accumulation scores and hepatic copper concentrations. For dogs for which ≥ 4 rhodanine-stained hepatic sections were available, intraindividual variation in copper distribution across hepatic sections was evaluated.

RESULTS

Median hepatic copper concentrations obtained with digital image analysis exceeded concentrations obtained with AAS or ICP-MS. Concentrations were also higher in older dogs (≥ 9 years vs < 9 years), dogs of breeds with a typical body weight ≥ 20 kg (44 lb), and dogs with necroinflammatory changes or uneven copper distribution. Qualitative copper accumulation scores were significantly associated with hepatic copper concentrations; however, the correlation between qualitative score and concentration obtained with digital image analysis (r_s = 0.94) was higher than the correlation between qualitative score and concentration obtained with AAS (r_s = 0.75) or ICP-MS (r_s = 0.57). The coefficient of variation for hepatic copper concentrations obtained with digital image analysis was significantly higher for dogs with higher hepatic copper concentrations.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that spectroscopic-spectrometric analysis of hepatic biopsy specimens commonly underestimated the concentration obtained by digital image analysis of rhodanine-stained sections.

Zinc in Dog Nutrition, Health and Disease: A Review

Simple Summary

This work compiles the current state of knowledge regarding zinc requirements of healthy dogs and biomarkers of zinc status. To ensure an adequate zinc status, it is important to know the zinc content of foods and their bioavailability to assess the need and the ideal supplementation strategy regarding levels and sources of additives in complete dog foods. As zinc is required for enzymatic, structural, and regulatory functions in the animal body, its nutritional status has been associated with several pathologies that may be due to, or exacerbated by, a deficit of dietary zinc supply.

Abstract

Zinc is an essential trace element, required for enzymatic, structural, and regulatory functions. As body reserves are scarce, an adequate zinc status relies on proper dietary supply and efficient homeostasis. Several biomarkers have been proposed that enable the detection of poor zinc status, but more sensitive and specific ones are needed to detect marginal deficiencies. The zinc content of commercial dry dog foods has great variability, with a more frequent non-compliance with the maximum authorized limit than with the nutritional requirement. The bioavailability of dietary zinc also plays a crucial role in ensuring an adequate zinc status. Despite controversial results, organic zinc sources have been considered more bioavailable than inorganic sources, albeit the zinc source effect is more evident after a restriction period of dietary zinc. Many disorders have been associated with inadequate zinc status, not being clear whether the occurrence of the disease is the consequence or the cause. This review presents data on zinc requirements and biomarkers for zinc status, that can be applied for the development of supplementation strategies of zinc in complete pet foods. Moreover, it provides an understanding of the role zinc plays in the health of dogs, and how altered zinc status affects diseases in dogs.

Investigation of Genetic Modifiers of Copper Toxicosis in Labrador Retrievers

Copper toxicosis is a complex genetic disorder in Labrador retrievers characterized by hepatic copper accumulation eventually leading to liver cirrhosis. The variation of hepatic copper levels in Labrador retrievers has been partly explained by mutations in ATP7A c.980C>T and ATP7B c.4358G>A. To further elucidate the genetic background of this disease, we used targeted Next Generation Sequencing (NGS) in a cohort of 95 Labrador retrievers to analyze 72 potential modifier genes for variations associated with hepatic copper levels. Variants associated with copper levels were subsequently evaluated in a replication cohort of 144 Labrador retrievers. A total of 44 variants in 25 different genes were identified, of which four showed significant association with copper levels. Of the four variants found associated with hepatic copper levels in the NGS cohort, one was validated in the replication cohort. The non-reference allele of the variant NC_006602.3.g.52434480C>T in RETN resulting in amino-acid change p.Leu7Phe was associated with decreased hepatic copper levels. In humans, resistin is associated with severity of non-alcoholic fatty liver disease, fibrosis, cirrhosis and mitochondrial dysfunction in hepatocytes. Further studies are needed to investigate the biological function of RETN p.Leu7Phe in the development of copper toxicosis in Labrador retrievers.

Reduced FXR Target Gene Expression in Copper-Laden Livers of COMMD1-Deficient Dogs

Wilson’s disease (WD), an autosomal recessive disorder, results in copper accumulation in the liver as a consequence of mutations in the gene ATPase copper transporting beta (ATP7B). The disease is characterized by chronic hepatitis, eventually resulting in liver cirrhosis. Recent studies have shown that dysregulation of nuclear receptors (NR) by high hepatic copper levels is an important event in the pathogenesis of liver disease in WD. Intracellular trafficking of ATP7B is mediated by COMMD1 and, in Bedlington terriers, a mutation in the COMMD1 gene results in high hepatic copper levels. Here, we demonstrate a reduced Farnesoid X nuclear receptor (FXR)-activity in liver biopsies of COMMD1-deficient dogs with copper toxicosis, a unique large animal model of WD. FXR-induced target genes, small heterodimer partner (SHP), and apolipoprotein E (ApoE) were down-regulated in liver samples from COMMD1-deficient dogs with hepatic copper accumulation. In contrast, the relative mRNA levels of the two CYP-enzymes (reduced by FXR activity) was similar in both groups. These data are in line with the previously observed reduced FXR activity in livers of ATP7B−/− mice and WD patients. Therefore, these data further corroborate on the importance of the COMMD1-deficient dogs as a large animal model for WD.

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.

Association of circulating microRNA-122 and microRNA-29a with stage of fibrosis and progression of chronic hepatitis in Labrador Retrievers

BACKGROUND

Chronic hepatitis (CH) in dogs is common and has the tendency to progress to liver cirrhosis (LC). Circulating microRNAs might have the potential as markers for disease progression.

OBJECTIVES

To investigate whether concentration of specific microRNAs in serum correlate with the stage and grade of CH in Labrador Retrievers.

ANIMALS

Twenty-two Labrador Retrievers with histological CH (n = 8), LC (n = 7), and normal liver (NL, n = 7).

METHODS

In this retrospective study, serum concentrations of miR-122, miR-29a, miR-133a, miR-181b, and miR-17-5p were measured by quantitative real-time PCR and evaluated using univariate linear regression in dogs. A multivariate model was fit including the grade of hepatitis and the stage of fibrosis.

RESULTS

Of the 5 microRNAs, only circulating miR-122 and miR-29a were significantly associated with the grade of hepatitis and the stage of fibrosis. A positive correlation was identified between the grade of hepatitis with miR-122 (r_s  = 0.79, P < .001) and miR-29a (r_s  = 0.78, P < .001). Both miR-122 (r_s  = 0.81, P < .001) and miR-29a (r_s  = 0.67, P < .001) showed a significant positive correlation with the stage of fibrosis. MiR-122 concentrations were significantly higher in the CH (P < .01) and LC groups (P < .001) compared to the NL group. MiR-29a concentrations were significantly higher in the CH (P < .001) and LC (P < .001) groups compared to the NL group.

CONCLUSIONS AND CLINICAL IMPORTANCE

Circulating miR-122 and miR-29a concentrations might be useful for monitoring the response to treatment and progression of canine CH.

Clinicopathological Correlation and Prevalence of Increased Copper in Canine Hepatic Cytology

Special staining and grading of canine liver cytology samples aids in detection of increased copper content. The prevalence of copper in routine diagnostic liver cytology samples, clinical findings associated with high cytologic copper (cCu) grade, and the correlation between cCu grade and histologic findings, including histologic copper (hCu) grade, are unknown. This data may be helpful in ascertaining when to determine a cCu grade and when interpreting cCu grade. Clinical data and available archived hepatic histologic and cytologic samples from 198 dogs were collected, evaluated, rhodanine stained, and graded for copper. Prevalence of increased cCu >5 in a randomly collected group of 163 individuals, and the correlation between cCu and clinical data (n = 198), hCu grade (n = 37), or findings on hematoxylin and eosin-stained hepatic sections (n = 32) were evaluated. The observed prevalence was 1.23%. Dogs with elevated alanine transaminase >180 IU/L or aspartate transaminase >90 IU/L and patients who subsequently had hepatic copper quantification were statistically more likely to have pathologic levels of copper detected by cytology. There was significant and modest correlation between cCu and hCu, interface hepatitis, portal inflammation, and fibrosis. Evidence of hepatocellular leakage may be indications for determination of cCu.

Hepatic copper concentrations in 546 dogs (1982-2015)

BACKGROUND

Copper associated hepatitis (CAH) has been increasingly recognized in dogs, and speculation exists that hereditary defects in copper metabolism have been exacerbated by increased environmental copper exposure. However, no broad epidemiological investigations have been performed to investigate quantitative hepatic copper concentrations ([Cu]H ) over time in both dogs that are (predisposed breed [PB]), and are not (non-predisposed breed [NPB]), considered at-risk for CAH.

OBJECTIVES

To investigate [Cu]H in dogs and explore temporal, demographic, and histologic associations spanning 34 years.

ANIMALS

546 archived liver specimens.

METHODS

Retrospective study. Searches of the Michigan State University Veterinary Diagnostic Laboratory database identified dogs that had undergone hepatic histopathologic assessment. Cases with archived tissue were reviewed and classified by breed, time period, and presence or absence of hepatitis. Inductively coupled plasma mass spectrometry was used to determine [Cu]H .

RESULTS

In time period 2009-2015, median [Cu]H were 101 μg/g and 313 μg/g greater than median [Cu]H in time period 1982-1988 for NPB and PB dogs, respectively (P < .001 for both comparisons). The proportion of dogs with [CU]H > 300 μg/g increased in NPB (28% to 49%) and PB dogs (48% to 71%) during these periods (P = .002 for both comparisons). Median [Cu]H in dogs with hepatitis increased 3-fold over time in both NPB (P = .004) and PB populations (P < .001).

CONCLUSIONS AND CLINICAL IMPORTANCE

The frequent recognition of CAH in recent years is likely due to the observed increases in [Cu]H over time. Importantly, effects are not limited to PB dogs.

Animal models of Wilson disease

Wilson disease (WD) is an autosomal recessive disorder of copper metabolism manifesting with hepatic, neurological and psychiatric symptoms. The limitations of the currently available therapy for WD (particularly in the management of neuropsychiatric disease), together with our limited understanding of key aspects of this illness (e.g. neurological vs. hepatic presentation) justify the ongoing need to study WD in suitable animal models. Four animal models of WD have been established: the Long-Evans Cinnamon rat, the toxic-milk mouse, the Atp7b knockout mouse and the Labrador retriever. The existing models of WD all show good similarity to human hepatic WD and have been helpful in developing an improved understanding of the human disease. As mammals, the mouse, rat and canine models also benefit from high homology to the human genome. However, important differences exist between these mammalian models and human disease, particularly the absence of a convincing neurological phenotype. This review will first provide an overview of our current knowledge of the orthologous genes encoding ATP7B and the closely related ATP7A protein in C. elegans, Drosophila and zebrafish (Danio rerio) and then summarise key characteristics of rodent and larger mammalian models of ATP7B-deficiency.

Mineral Composition of Dry Dog Foods: Impact on Nutrition and Potential Toxicity

Detailed mineral profile of a selection of commercially available complete dry dog foods was determined using ICP-MS (Se, Cu, Mn, Zn, and nonessential trace elements), flame photometry (Na and K) and atomic and molecular spectrophotometry (Ca, P, Mg, and Fe). The contribution of ingredients to the mineral composition was correlated to the food market segment. Results showed an oversupply of essential elements due to the energy density effect on feed intake. Additives contributed from 40.8 to 55.1% to the total trace elements contents. With the exception of Se, all trace elements were supplied above the nutritional requirements of adult dogs. Legal limits of Cu, Se, and Zn were surpassed. The content of nonessential trace elements included values in the range of nanograms to micrograms per kg, without surpassing safe upper limits. This work brings awareness to the need to find supplementation strategies that ensure nutritional adequacy and avoid waste.

Sensitivity and Specificity of Plasma ALT, ALP, and Bile Acids for Hepatitis in Labrador Retrievers

Background

Biochemical indicators for diagnosing liver disease are plasma alanine aminotransferase activity (ALT), alkaline phosphatase activity (ALP), and bile acid concentration (BA).

Objectives

To determine the sensitivity and specificity of ALT, ALP, and BA for detecting primary hepatitis (PH) in clinically healthy Labrador retrievers and investigate whether ALT and ALP can discriminate between dogs with PH and nonspecific reactive hepatitis (RH).

Animals

191 clinically healthy and 51 clinically ill Labrador retrievers with hepatic histopathology.

Methods

Retrospective study. Medical records were reviewed for ALT, ALP, preprandial BA, liver histopathology, and hepatic copper concentrations.

Results

In 64% (122/191) of the clinically healthy Labrador retrievers, hepatic histology revealed inflammatory infiltrates. This frequency might be biased because part of them was included as first‐line relatives of dogs with copper‐associated hepatitis. Sensitivity of ALT, ALP, and BA in this population for detecting acute hepatitis was 45, 15, and 15%, respectively. For chronic hepatitis, sensitivity was 71, 35, and 13%, respectively. Specificity of ALT, ALP, and BA was >90% for AH, CH, and RH. When increased liver enzymes were present, median ALT was significantly higher in PH cases (312 U/L, range 38–1,369) compared to RH cases (91 U/L, range 39–139) (P < .001). There was no difference in ALP between dogs with a PH and a RH (P = .361).

Conclusions and Clinical Importance

Histopathologic abnormalities in the liver were present in the majority of apparent clinically healthy Labrador retrievers. The sensitivity of ALT, ALP, and BA for detecting acute and chronic hepatitis in this population was low. More sensitive biomarkers are needed for early detection of liver disease in apparent clinically healthy dogs.

Gene expression patterns in the progression of canine copper-associated chronic hepatitis

Copper is an essential trace element, but can become toxic when present in abundance. The severe effects of copper-metabolism imbalance are illustrated by the inherited disorders Wilson disease and Menkes disease. The Labrador retriever dog breed is a novel non-rodent model for copper-storage disorders carrying mutations in genes known to be involved in copper transport. Besides disease initiation and progression of copper accumulation, the molecular mechanisms and pathways involved in progression towards copper-associated chronic hepatitis still remain unclear. Using expression levels of targeted candidate genes as well as transcriptome micro-arrays in liver tissue of Labrador retrievers in different stages of copper-associated hepatitis, pathways involved in progression of the disease were studied. At the initial phase of increased hepatic copper levels, transcriptomic alterations in livers mainly revealed enrichment for cell adhesion, developmental, inflammatory, and cytoskeleton pathways. Upregulation of targeted MT1A and COMMD1 mRNA shows the liver's first response to rising intrahepatic copper concentrations. In livers with copper-associated hepatitis mainly an activation of inflammatory pathways is detected. Once the hepatitis is in the chronic stage, transcriptional differences are found in cell adhesion adaptations and cytoskeleton remodelling. In view of the high similarities in copper-associated hepatopathies between men and dog extrapolation of these dog data into human biomedicine seems feasible.

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.

Use of Serum MicroRNAs as Biomarker for Hepatobiliary Diseases in Dogs

Background

Current biochemical indicators cannot discriminate between parenchymal, biliary, vascular, and neoplastic hepatobiliary diseases. MicroRNAs are promising new biomarkers for hepatobiliary disease in humans and dogs.

Objective

To measure serum concentrations of an established group of microRNAs in dogs and to investigate their concentrations in various types of hepatobiliary diseases.

Animals

Forty‐six client‐owned dogs with an established diagnosis of hepatobiliary disease and stored serum samples and eleven client‐owned healthy control Labrador Retrievers.

Methods

Retrospective study. Medical records of dogs with parenchymal, biliary, vascular, or neoplastic hepatobiliary diseases and control dogs were reviewed. Concentrations of miR‐21, miR‐122, miR‐126, miR‐148a, miR‐200c, and miR‐222 were quantified in serum by real‐time polymerase chain reaction.

Results

No different microRNA concentrations were found in the adenoma and congenital portosystemic shunt groups. In all other diseases, miR‐122 concentrations were elevated with the highest concentration in the mucocele group (267‐fold, CI: 40–1,768, P < .001). In dogs with biliary diseases, miR‐21 and miR‐222 were only increased in dogs with mucoceles (26‐fold, CI: 5–141, P = .005 and 13‐fold, CI: 2–70, P = .025, respectively). Uniquely increased microRNAs were found in the hepatocellular carcinoma group (miR‐200c, 35‐fold increase, CI: 3–382, P = .035) and the chronic hepatitis group (miR‐126, 22‐fold increase, CI: 5–91, P = .002).

Conclusions and Clinical Importance

A microRNA panel consisting of miR‐21, miR‐122, miR‐126, miR‐200c, and miR‐222 can distinguish between parenchymal, biliary, and neoplastic hepatobiliary diseases. Serum microRNA profiling is a promising new tool that might be a valuable addition to conventional diagnostics to help diagnose various hepatobiliary diseases in dogs.

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.

The Menkes and Wilson disease genes counteract in copper toxicosis in Labrador retrievers: a new canine model for copper-metabolism disorders

The deleterious effects of a disrupted copper metabolism are illustrated by hereditary diseases caused by mutations in the genes coding for the copper transporters ATP7A and ATP7B. Menkes disease, involving ATP7A, is a fatal neurodegenerative disorder of copper deficiency. Mutations in ATP7B lead to Wilson disease, which is characterized by a predominantly hepatic copper accumulation. The low incidence and the phenotypic variability of human copper toxicosis hamper identification of causal genes or modifier genes involved in the disease pathogenesis. The Labrador retriever was recently characterized as a new canine model for copper toxicosis. Purebred dogs have reduced genetic variability, which facilitates identification of genes involved in complex heritable traits that might influence phenotype in both humans and dogs. We performed a genome-wide association study in 235 Labrador retrievers and identified two chromosome regions containing ATP7A and ATP7B that were associated with variation in hepatic copper levels. DNA sequence analysis identified missense mutations in each gene. The amino acid substitution ATP7B:p.Arg1453Gln was associated with copper accumulation, whereas the amino acid substitution ATP7A:p.Thr327Ile partly protected against copper accumulation. Confocal microscopy indicated that aberrant copper metabolism upon expression of the ATP7B variant occurred because of mis-localization of the protein in the endoplasmic reticulum. Dermal fibroblasts derived from ATP7A:p.Thr327Ile dogs showed copper accumulation and delayed excretion. We identified the Labrador retriever as the first natural, non-rodent model for ATP7B-associated copper toxicosis. Attenuation of copper accumulation by the ATP7A mutation sheds an interesting light on the interplay of copper transporters in body copper homeostasis and warrants a thorough investigation of ATP7A as a modifier gene in copper-metabolism disorders. The identification of two new functional variants in ATP7A and ATP7B contributes to the biological understanding of protein function, with relevance for future development of therapy.

Summary: Labrador retrievers with hereditary copper toxicosis are a useful new model for copper-metabolism disorders.

Diagnostic accuracy of Wright-Giemsa and rhodanine stain protocols for detection and semi-quantitative grading of copper in canine liver aspirates

BACKGROUND

Canine hepatic copper content has been increasing. Recognition of canine copper-associated hepatopathies is becoming more common.

OBJECTIVES

The purpose of the study was to assess the diagnostic performance of Wright-Giemsa (WG) and rhodanine staining for detection of increased canine hepatic copper following a proposed cytologic protocol for semi-quantitative evaluation of liver aspirates and the effect of previous WG staining.

METHODS

Retrospectively, 40 canine hepatic WG-stained cytology cases were rhodanine stained. Diagnostic performance of WG staining for increased hepatic copper was evaluated. A rhodanine-stained cytologic copper grading system was developed. Prospectively, 67 canine liver samples with quantitative copper measurement, a WG-then rhodanine-stained slide, and a non-WG rhodanine-stained slide were used to assess the performance of the grading system and the effect of previous WG staining.

RESULTS

Copper was not described in 40 retrospective cases on initial cytologic evaluation; 8/40 cases had increased copper content after rhodanine staining or quantitative copper assessment. Prior WG staining and destaining significantly affected the cytologic copper grade but not the diagnostic performance as measured by receiver-operating characteristic curve analysis. Quantitative copper concentration and previously WG-stained copper grade were moderately correlated (n = 67, ρ = .79 [.68-.87]). For detection of ≥ 600 ppm, dry weight (dw) copper, sensitivity was .75 and specificity was .97. For detection of ≥ 1500 ppm, dw copper, sensitivity was 1.0 and specificity was .97.

CONCLUSIONS

Wright-Giemsa staining alone does not reliably detect hepatic copper. Grading of rhodanine-stained canine hepatic cytologic samples demonstrates acceptable diagnostic performance for detection of copper content.

CCC- and WASH-mediated endosomal sorting of LDLR is required for normal clearance of circulating LDL

The low-density lipoprotein receptor (LDLR) plays a pivotal role in clearing atherogenic circulating low-density lipoprotein (LDL) cholesterol. Here we show that the COMMD/CCDC22/CCDC93 (CCC) and the Wiskott–Aldrich syndrome protein and SCAR homologue (WASH) complexes are both crucial for endosomal sorting of LDLR and for its function. We find that patients with X-linked intellectual disability caused by mutations in CCDC22 are hypercholesterolaemic, and that COMMD1-deficient dogs and liver-specific Commd1 knockout mice have elevated plasma LDL cholesterol levels. Furthermore, Commd1 depletion results in mislocalization of LDLR, accompanied by decreased LDL uptake. Increased total plasma cholesterol levels are also seen in hepatic COMMD9-deficient mice. Inactivation of the CCC-associated WASH complex causes LDLR mislocalization, increased lysosomal degradation of LDLR and impaired LDL uptake. Furthermore, a mutation in the WASH component KIAA0196 (strumpellin) is associated with hypercholesterolaemia in humans. Altogether, this study provides valuable insights into the mechanisms regulating cholesterol homeostasis and LDLR trafficking.

Low density lipoprotein receptor (LDLR) is crucial for cholesterol homeostasis. Here, the authors show that components of the CCC-protein complex, CCDC22 and COMMD1, facilitate the endosomal sorting of LDLR and that mutations in these genes cause hypercholesterolemia in dogs and mice, providing new insights into regulation of cholesterol homeostasis.

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.

Dietary management of labrador retrievers with subclinical hepatic copper accumulation

Background

Genetic and environmental factors, including dietary copper intake, contribute to the pathogenesis of copper‐associated hepatitis in Labrador retrievers. Clinical disease is preceded by a subclinical phase in which copper accumulates in the liver.

Objective

To investigate the effect of a low‐copper, high‐zinc diet on hepatic copper concentration in Labrador retrievers with increased hepatic copper concentrations.

Animals

Twenty‐eight clinically healthy, client‐owned Labrador retrievers with a mean hepatic copper concentration of 919 ± 477 mg/kg dry weight liver (dwl) that were related to dogs previously diagnosed with clinical copper‐associated hepatitis.

Methods

Clinical trial in which dogs were fed a diet containing 1.3 ± 0.3 mg copper/Mcal and 64.3 ± 5.9 mg zinc/Mcal. Hepatic copper concentrations were determined in liver biopsy samples approximately every 6 months. Logistic regression was performed to investigate effects of sex, age, initial hepatic copper concentration and pedigree on the ability to normalize hepatic copper concentrations.

Results

In responders (15/28 dogs), hepatic copper concentrations decreased from a mean of 710 ± 216 mg/kg dwl copper to 343 ± 70 mg/kg dwl hepatic copper after a median of 7.1 months (range, 5.5–21.4 months). Dogs from a severely affected pedigree were at increased risk for inability to have their hepatic copper concentrations normalized with dietary treatment.

Conclusions and Clinical Importance

Feeding a low‐copper, high‐zinc diet resulted in a decrease in hepatic copper concentrations in a subset of clinically normal Labrador retrievers with previous hepatic copper accumulation. A positive response to diet may be influenced by genetic background. Determination of clinical benefit requires further study.

New canine models of copper toxicosis: diagnosis, treatment, and genetics

The One Health principle recognizes that human health, animal health, and environmental health are inextricably linked. An excellent example is the study of naturally occurring copper toxicosis in dogs to help understand human disorders of copper metabolism. Besides the Bedlington terrier, where copper toxicosis is caused by a mutation in the COMMD1 gene, more complex hereditary forms of copper-associated hepatitis were recognized recently in other dog breeds. The Labrador retriever is one such breed, where an interplay between genetic susceptibility and exposure to copper lead to clinical copper toxicosis. Purebred dog populations are ideal for gene mapping studies, and because genes involved in copper metabolism are highly conserved across species, newly identified gene mutations in the dog may help unravel the genetic complexity of different human forms of copper toxicosis. Furthermore, increasing knowledge with respect to diagnosis and treatment strategies will benefit both species.

Nutritional management of inherited copper-associated hepatitis in the Labrador retriever

Canine hereditary copper-associated hepatitis is characterized by gradual hepatic copper accumulation eventually leading to liver cirrhosis. Therapy is aimed at creating a negative copper balance with metal chelators, of which D-penicillamine is the most commonly used. D-penicillamine often causes gastro-intestinal side effects and life-long continuous therapy may lead to a deficiency of copper and zinc. The aim of the current study was to investigate the effect of a low-copper, high-zinc diet as an alternative to continuous D-penicillamine treatment for the long-term management of canine copper-associated hepatitis. Sixteen affected Labrador retrievers were followed for a median time period of 19.1 months (range, 5.9-39 months) after being effectively treated with D-penicillamine. The dogs were maintained on a diet containing 1.3±0.3 mg copper/1000 kcal and 64.3±5.9 mg zinc/1000 kcal. Liver biopsies were taken every 6 months for histological evaluation and copper determination. Plasma alanine aminotransferase (ALT) and alkaline phosphatase, as well as serum albumin were determined. Dietary treatment alone was sufficient to maintain hepatic copper concentration below 800 mg/kg dry weight liver in 12 dogs during the study period. Four dogs needed re-treatment with D-penicillamine. ALT activity and albumin concentration were not associated with hepatic copper concentration, but showed a significant association with the stage and grade of hepatitis respectively. In conclusion, a low-copper, high-zinc diet can be a valuable alternative to continuous d-penicillamine administration for long-term management of dogs with copper-associated hepatitis. The copper re-accumulation rate of an individual dog should be considered in the design of a long-term management protocol and in determining re-biopsy intervals.

D-penicillamine treatment of copper-associated hepatitis in Labrador retrievers

d-penicillamine is effectively used in the lifelong treatment of copper toxicosis in Bedlington terriers and Wilson's disease in humans. A complex form of copper-associated hepatitis has recently been characterized in the Labrador retriever. The aims of this study were to evaluate the effectiveness of d-penicillamine treatment for copper-associated hepatitis in this breed, to study the effects on hepatic copper, iron and zinc concentrations, and to evaluate parameters to predict optimal duration of treatment. Forty-three client owned Labrador retrievers that were diagnosed with increased hepatic copper were treated with d-penicillamine and underwent at least one follow-up examination including a liver biopsy for histopathological scoring of inflammatory lesions. Hepatic copper, iron and zinc concentrations were determined in the initial and follow-up biopsies by instrumental neutron activation analysis. The influence of initial hepatic copper concentration, sex, age, d-penicillamine formulation and the occurrence of side effects were investigated for their influence on hepatic copper concentration after a certain period of treatment by generalized mixed modelling. d-penicillamine proved to be effective in reducing hepatic copper concentration and associated inflammatory lesions. Parameters derived from the model can be used to estimate the necessary duration of d-penicillamine treatment for Labrador retrievers with increased hepatic copper concentration. Continuous, lifelong d-penicillamine treatment is not recommended in this breed, as there may be a risk for hepatic copper and zinc deficiency.