Clinical profile and outcome of cardiomyopathies in infants and children seen at a tertiary centre

INTRODUCTION

Due to their rare prevalence and marked heterogeneity, pediatric cardiomyopathies (CMPs) are little known and scarcely reported. We report the etiology, clinical profile and outcome of a consecutive cohort of children diagnosed with CMP and followed at Meyer Children's Hospital over a decade.

PATIENTS AND METHODS

We retrospectively reviewed patients consecutively referred from May 2008 to May 2019 for pediatric onset CMP (<18 years). Heart disease caused by arrhythmic disorders, toxic agents, rheumatic conditions and maternal disease were excluded.

RESULTS

We enrolled 110 patients (65 males), diagnosed at a median age of 27 [4-134] months; 35% had an infant onset (<1 year of age). A positive family history was more often associated with childhood-onset (38.8%). Hypertrophic cardiomyopathy (HCM; 48 patients) was the most frequent phenotype, followed by dilated cardiomyopathy (DCM; 35 patients). While metabolic and idiopathic etiologies were preponderant in infants, metabolic and sarcomeric diseases were most frequent in the childhood-onset group. Major adverse cardiac events (MACE) occurred in 31.8% of patients, including hospitalization for acute heart failure in 25.5% of patients, most commonly due to DCM. Overall, the most severe outcomes were documented in patients with metabolic diseases.

CONCLUSIONS

In a consecutive cohort of pediatric patients with CMP, those with infantile onset and with a metabolic etiology had the worst prognosis. Overall, MACE occurred in 41% of the entire population, most commonly associated with DCM, inborn errors of metabolism and genetic syndromes. Systematic NGS genetic testing was critical for etiological diagnosis and management.

Autopsy and genetic characterization of juvenile sudden cardiac arrest and death: the ToRSADE experience

Funding Acknowledgements

Type of funding sources: Public Institution(s). Main funding source(s): FAS-Salute 2014, regione Toscana

Background

Sudden cardiac arrest (SCA) or death (SCD) in young people represents a dramatic event, often leading to severe neurologic outcomes or death. However, the incidence of this phenomenon remains largely unknown, since the recording of cases, and consequently the identification of the underlying causes, requires a multi-professional and disciplinary approach, including genetic counselling.

Purpose

In this study, we aimed to monitor and investigate SCA and SCD in young people (≤50 years) recorded in the ToRSADE© registry comparing clinical and molecular data.

Methods and Results

A total of 22 blood samples were analyzed; 14 were collected from dead patients during autopsy and 8 from resuscitated patients after cardiac arrest. Next Generation Sequencing (NGS) analysis revealed 38% of total cases with Likely Pathogenetic (LP) variants associated to Cardiomyopathy (CM) or Channelopathy, and 61% with Variant of Uncertain Significance (VUS). In three cases, NGS confirmed autopsy and histology findings: the p.(Leu466Phe) variant in SCN5A associated with Brugada Syndrome (1a), the p.(Glu173del) in TNNT2 for Hypertrophic CM (1b) and the p. (Asn480Lysfs*20) in PKP2 for Arrhythmogenic Cardiomyopathy (AC) (1c).

Conclusions

Creation of the ToRSADE© registry allowed implementation of a blood repository for molecular and genetic analysis. Genetic analysis combined with clinical information and post-mortem evaluation constitute a multi-disciplinary approach to juvenile SCD and SCA, while providing medical and genetic assistance to families, public awareness especially among youths and athletes, as well as up-to-date research on the underlying mechanisms of cardiomyopathies.

Hidden familial cardiomyopathies in children: Role of genetic testing

Pediatric cardiomyopathies harbour significant phenotypic and genetic heterogeneity. Genetic testing is essential for the initial evaluation and the ongoing care of child and family, although challenges remain regarding its appropriate clinical implementation in minors. We here discuss the key role of genetic diagnosis in the clinical management of two patients.

Metabolism and pharmacokinetics of pharmaceuticals in cats (Felix sylvestris catus) and implications for the risk assessment of feed additives and contaminants

In animal health risk assessment, hazard characterisation of feed additives has been often using the default uncertainty factor (UF) of 100 to translate a no-observed-adverse-effect level in test species (rat, mouse, dog, rabbit) to a 'safe' level of chronic exposure in farm and companion animal species. Historically, both 10-fold factors have been further divided to include chemical-specific data in both dimensions when available. For cats (Felis Sylvestris catus), an extra default UF of 5 is applied due to the species' deficiency in particularly glucuronidation and glycine conjugation. This paper aims to assess the scientific basis and validity of the UF for inter-species differences in kinetics (4.0) and the extra UF applied for cats through a comparison of kinetic parameters between rats and cats for 30 substrates of phase I and phase II metabolism. When the parent compound undergoes glucuronidation the default factor of 4.0 is exceeded, with exceptions for zidovudine and S-carprofen. Compounds that were mainly renally excreted did not exceed the 4.0-fold default. Mixed results were obtained for chemicals which are metabolised by CYP3A in rats. When chemicals were administered intravenously the 4.0-fold default was not exceeded with the exception of clomipramine, lidocaine and alfentanil. The differences seen after oral administration might be due to differences in first-pass metabolism and bioavailability. Further work is needed to further characterise phase I, phase II enzymes and transporters in cats to support the development of databases and in silico models to support hazard characterisation of chemicals particularly for feed additives.

Prevalence of adverse cardiovascular events in pediatric cardiomyopathies: an analysis of 110 patients followed at a long-standing tertiary care paediatric centre

Introduction

Pediatric cardiomyopathies (CMP) are disorders of the morphology and function of the heart, with a greater heterogeneity concerning etiology and clinical presentation than adult CMP. The assessment of etiology and genetic status is of paramount importance for prognosis, family screening, and therapeutic choices.

Purpose

To report clinical presentation, etiology, and outcome of a cohort of children diagnosed with CMP followed at tertiary care pediatric referral centre.

Methods

We retrospectively reviewed clinical, laboratory and imaging data of all patients referred to our cardiomyopathy centre from May 2008 to May 2019 for pediatric CMP (&lt;18 years). CMP due to arrhythmic disorders, toxic agents' exposure, rheumatic conditions and maternal disease (i.e. maternal diabetes) were excluded. Primary endpoint was a composite of major adverse cardiovascular events (MACE: cardiovascular death, heart failure [HF] hospitalization, arrhythmic events, need for surgery or heart transplant referral).

Results

We enrolled 110 patients (65 males, age at diagnosis 67±71 months). Hypertrophic cardiomyopathy (HCM, N=48, 44%) was most frequent, followed by dilated cardiomyopathy (DCM, N=35 32%) and left ventricular non-compaction phenotype (LVNC, N=12, 11%). Mixed phenotype (N=7, 6%) and restrictive cardiomyopathy (RCM, N=3, 3%) were less common. No cases of arrhythmogenic right ventricular cardiomyopathy (ARVC) were detected. Five genotype-positive patients presented with negative clinical phenotype. A diagnosis was confirmed in all patients; the most common was sarcomere disease (30%, N=33) followed by metabolic (28%,N=31) disease, genetic syndromes (11%, N=12), neuromuscular (7,3%, N=8) diseases, and post-myocarditis cases (4,5%,N=5). Twenty-one patients (19%) were identified as idiopathic. At referral, 4,5% of children presented with NYHA class III/IV.

At 35 [14–72] months, 4 (3.7%) patients required ICD implantation, 8 (7.4%) underwent cardiac surgery, and 1 (1%) underwent heart transplant. Furthermore, 28 (26%) patients required hospitalization due to acute HF, with DCM patients being at higher risk (p&lt;0.01), 7 (6.8%) experienced arrhythmic events and 4 (3.9%) had syncope. Overall, 13 (12%) died (7 with metabolic disorders, 3 with genetic syndromes, 1 with a sarcomeric mutation, 1 post myocarditis, and 1 idiopathic).

Conclusions

In our cohort, HCM was the most common cause of pediatric CMP followed by DCM and non-compaction. MACE were present in 41% of patients. While HCM had a less severe phenotype (characterized by a higher arrhythmic burden), DCM was characterized by a higher prevalence of HF hospitalizations. DCM, inborn errors in metabolism and genetic syndromes had the worst outcome in terms mortality and heart failure long term.

Widespread availability of genetic testing provides several benefits to the clinician, confirming diagnosis in ambiguous cases and defining etiology in order to guide management and identifying relatives at risk.

Figure 1

Funding Acknowledgement

Type of funding source: None

The genetic architecture of left ventricular non-compaction reveals both substantial overlap with other cardiomyopathies and a distinct aetiology in a subset of cases

Background

Left ventricular non-compaction (LVNC) is a condition characterised by trabeculations in the myocardial wall and is the subject of considerable conjecture as to whether it represents a distinct pathology or a secondary phenotype associated with other cardiac diseases, particularly cardiomyopathies.

Purpose

To investigate the genetic architecture of LVNC by identifying genes and variant classes robustly associated with disease and comparing these to other genetically characterised cardiomyopathies.

Methods

We performed rare variant association analysis using six different LVNC cohorts comprising 840 cases together with 125,748 gnomAD population controls and compared results to similar analyses with dilated cardiomyopathy (DCM) and hypertrophic cardiomyopathy (HCM) cases.

Results

We observed substantial overlap in genes and variant classes enriched in LVNC and DCM/HCM, indicating that in many cases LVNC belongs to a spectrum of more established cardiomyopathies, with non-compaction representing a phenotypic variation in patients with DCM- or HCM-causing variants. In contrast, five variant classes were uniquely enriched in LVNC cases, of which truncating variants in MYH7, ACTN2 and PRDM16 may represent a distinct LVNC aetiology. MYH7 truncating variants are generally considered as non-pathogenic but were detected in 2% of LVNC cases compared to 0.1% of controls, including a cluster of variants around a single splice region. Additionally, structural variants (exon deletions) in RYR2 and missense variants in the transmembrane region of HCN4 were enriched in LVNC cases, confirming prior reports regarding the association of these variant classes with combined LVNC and arrhythmia phenotypes.

Conclusions

We demonstrated that genetic association analysis can clarify the relationship between LVNC and established cardiomyopathies, highlighted substantial overlap with DCM/HCM but also identified variant classes associated with distinct LVNC and with joint LVNC/arrhythmia phenotypes. These results underline the complex genetic landscape of LVNC and inform how genetic testing in LVNC cases should be pursued and interpreted.

Cardiomyopathy rare variant frequencies

Funding Acknowledgement

Type of funding source: None

AB0360 EFFICACY AND SAFETY OF THE PROSTAGLANDIN EP4 RECEPTOR ANTAGONIST CR6086 ADDED TO METHOTREXATE IN DMARD-NAÏVE EARLY RA PATIENTS: A PHASE 2 RANDOMIZED CONTROLLED TRIAL

Background:

MTX is the first line treatment in early RA. There is robust evidence from cohort studies, but less from RCTs, that a “window of opportunity” exists over 12-16 weeks symptom duration. CR6086 is a selective prostaglandin EP4 receptor antagonist, with an immunomodulatory profile.

Objectives:

To test efficacy and safety of CR6086 added to MTX in early RA, DMARD-naïve patients.

Methods:

Patients with RA (ACR/EULAR 2010 criteria), < 1 year from symptom onset and naïve to DMARDs were randomized to oral CR6086 30, 90, 180mg, or placebo bid and oral MTX (20mg weekly) for 13 weeks (NCT03163966). Primary endpoint was the ACR20 response rate: 240 patients were needed to detect a difference among groups, with 50% responders on placebo and 70% on the 90mg CR6086 target dose. Pairwise comparisons of proportions were performed, with nonresponder imputation for withdrawals. A subgroup of patients underwent dynamic contrast-enhanced (DCE) MRI for quantification of synovitis at MCP and wrist joints, evaluated as DEMRIQ-ME and DEMRIQ-vol.

Results:

The ITT population included all 244 randomized patients receiving at least one dose of study drugs (59 CR6086 30mg/MTX, 60 CR6086 90mg/MTX, 63 CR6086 180mg/MTX, 62 placebo/MTX). Safety was good with no increased rate of infections or other disorders; however, there were more minor upper GI adverse events (AEs) with CR6086, and increased dropouts due to AEs with the 180mg dose (9/63, 14.3% vs 1.7-3.4% in other groups). There were more ACR20 responders with MTX monotherapy than predicted (59.7%) and thus the 10.3% difference with the 90mg target dose (70.0%) was not significant. The low 30mg dose was no better than placebo (55.9%), while the high 180mg dose did not provide additional benefit compared with 90mg (74.0% net of dropouts). CR6086 90mg and 180mg induced a significant improvement in MRI, compared with placebo (Fig. 1). In a post-hoc analysis in patients < 6 months from symptom onset (ACR definition of early RA: 98/244, 40.2%), MTX monotherapy exerted a large 76% ACR20 response rate that precluded potentiation. Conversely, in patients of 6-12 months disease duration (146/244, 59.8%) ACR20 responders were 48.6% with MTX monotherapy vs 68.4% with 90mg, i.e. a 19.8% difference as postulated, with proportional differences in secondary endpoints (Tab. 1).

Conclusion:

There was no benefit demonstrated for CR6086 added to MTX in the study cohort as a whole. However, in a post-hoc analysis, enhanced responses were observed with CR6086 90mg bid added to MTX in patients >6 months disease duration. This generated the hypothesis that addition of CR6086 90mg bid may benefit in RA patients initiating MTX after the window of opportunity, to be tested in further studies.

Table 1.

Patient characteristics & pregnancy outcomes

Symptom onset <12 months(principal analysis)Symptom onset 6-12 months(post-hoc analysis)*Placebo+MTX(N=62)CR6086 90mg+MTX(N=60)Placebo+MTX(N=37)CR6086 90mg+MTX(N=38)ACR20, %59.7%70.0%48.6%68.4%ACR50, %33.9%38.3%29.7%39.5%ACR70, %17.7%23.3%10.8%28.9%DAS28 (CRP) <2.6, %12.9%20.0%8.1%18.4%CDAI ≤2.8, %8.1%11.7%5.4%15.8%SDAI ≤3.3, %6.5%10.0%2.7%15.8%Boolean-based remission, %6.5%6.7%2.7%10.5%

*In patients with symptom onset <6 months, MTX monotherapy exerted a large 76% ACR20 response, and correspondingly high secondary efficacy parameters, precluding potentiation in this subset

Figure 1.

Change in MRI (DEMRIQ-ME#) after 13 weeks

Disclosure of Interests:

Karel Pavelka Consultant of: Abbvie, MSD, BMS, Egis, Roche, UCB, Medac, Pfizer, Biogen, Speakers bureau: Abbvie, MSD, BMS, Egis, Roche, UCB, Medac, Pfizer, Biogen, Ivanova Delina2 Delina: None declared, Minodora Mazur: None declared, Massimo D’Amato Employee of: Rottapharm Biotech, GIAMPAOLO GIACOVELLI Employee of: Rottapharm Biotech, Federica Girolami Employee of: Rottapharm Biotech, Marek Krogulec: None declared, René Østgård: None declared, Asger Reinstrup Bihlet Shareholder of: Nordic Bioscience A/S., Olga Kubassova Shareholder of: IAG, Image Analysis Group, Consultant of: Novartis, Takeda, Lilly, Employee of: IAG, Image Analysis Group, Lucio Rovati Shareholder of: Rottapharm Biotech, Employee of: Rottapharm Biotech, Peter C. Taylor Grant/research support from: Celgene, Eli Lilly and Company, Galapagos, and Gilead, Consultant of: AbbVie, Biogen, Eli Lilly and Company, Fresenius, Galapagos, Gilead, GlaxoSmithKline, Janssen, Nordic Pharma, Pfizer Roche, and UCB

Efficacy and safety of the first-in-class imidazoline-2 receptor ligand CR4056 in pain from knee osteoarthritis and disease phenotypes: a randomized, double-blind, placebo-controlled phase 2 trial

OBJECTIVE

CR4056 is a selective imidazoline-2 (I2) receptor ligand with potent analgesic activity in animal pain models. This proof-of-concept study tested CR4056 efficacy and safety in patients with knee osteoarthritis (OA) and different phenotypes.

DESIGN

This is a multicenter, randomized, double-blind, placebo-controlled trial. Knee OA patients with moderate to severe pain received CR4056 (women 100 mg bid; men 200 mg bid) or placebo (both genders) for 14 days. The primary outcome was the change in WOMAC pain score (0-100 scale) compared to placebo, analyzed in the intention-to-treat population and pre-defined OA phenotypes.

RESULTS

213 patients were treated with CR4056 (92 women; 52 men) or placebo (69 overall). After 14 days, median WOMAC pain improvements were 10 points on placebo and 14, 20 and 16 in women, men, and pooled CR4056 groups (P = 0.184, 0.030 and 0.070 vs placebo, respectively). Pre-specified subgroup analysis in the metabolic OA phenotype (BMI ≥ 27.5 kg/m², N = 156) showed statistically significant differences in all CR4056-treated groups vs placebo of 12-18 points. Conversely, there were too few patients with a neuropathic or inflammatory phenotype for a meaningful analysis. CR4056 was well tolerated; the most common adverse event was mild headache.

CONCLUSIONS

Although the primary endpoint was met in males only, this exploratory phase 2 trial shows that CR4056 might be an effective analgesic against knee OA pain, especially in overweight patients representing the metabolic OA phenotype. These findings, along with the broad-spectrum analgesic activity of CR4056 in animal models, warrant further clinical investigation in OA and other pain conditions.

CLINICAL TRIAL REGISTRATION NUMBER

EudraCT 2015-001136-37.

1177Insights on mitochondrial energetics in obstructive hypertrophic cardiomyopathy

Background

Hypertrophic cardiomyopathy (HCM) is the most common genetic cardiomyopathy, heterogeneous in phenotype and clinical course. The genotype-phenotype relationship and associated molecular mechanisms are still incompletely understood. In the HCM milieu, increased energy cost of force production, impairing performance and mitochondrial function, may be associated to patients' genotype and/or phenotype.

Purpose

To determine abnormalities in mitochondrial energetics in HCM and their possible relationship with genotype and clinical phenotype of patients.

Methods

Septal myectomies from characterized patients with obstructive HCM (HOCM, n=18) and donor hearts discarded from transplantation (CTRL, n=8) have been compared. HOCM patients were screened and demographic, clinical and instrumental data (routine ECG, echocardiography and cardiac magnetic resonance-CMR) were collected.

Genetic analysis was performed on total DNA extracted from myectomies by NGS on MiSeq platform using the TruSight Cardio Sequencing kit and testing a panel of 26 genes.

Activity and amount of mitochondrial enzymes generating/scavenging reactive oxygen species were investigated.

Results

Within the HOCM cohort 30% of patients was bearing mutations in sarcomeric genes associated with HCM.

The amount and/or activity of mitochondrial Complex I NADH dehydrogenase, of SOD2 and (m)-aconitase were upregulated in HOCM vs. CTRL. NADH dehydrogenase level was inversely correlated with the degree of mitral valve regurgitation and mitral valve backward volume by CMR (Spearman R=−0.5 and −0.8, respectively).

The Complex V enzyme ATP synthase activity decreased, whilst its amount was comparable in HOCM vs. CTRL. Analogously the SOD1 activity was similar in HOCM and CTRL.

No difference in mitochondrial DNA (mtDNA) copy number was found.

Results were unrelated to HCM-associated mutations.

Conclusions

HOCM hearts are characterized by mitochondrial hyperactivity aimed at quenching reactive oxygen species, but decreased ATP synthase activity. Overall, these data suggest an abnormal mitochondrial activity in the myocardium of HOCM patients independent of the presence of HCM-associated mutations. Moreover, our results underpin the markedly abnormal cellular energetics of HOCM, identifying potential therapeutic targets.

Acknowledgement/Funding

NET-2011-02347173, Italian Minister of Health

Identification of candidate biomarkers of the exposure to PCBs in contaminated cattle: A gene expression- and proteomic-based approach

Dioxins and polychlorinated biphenyls (PCBs) are widespread and persistent contaminants. Through a combined gene expression/proteomic-based approach, candidate biomarkers of the exposure to such environmental pollutants in cattle subjected to a real eco-contamination event were identified. Animals were removed from the polluted area and fed a standard ration for 6 months. The decontamination was monitored by evaluating dioxin and PCB levels in pericaudal fat two weeks after the removal from the contaminated area (day 0) and then bimonthly for six months (days 59, 125 and 188). Gene expression measurements demonstrated that CYP1B1 expression was significantly higher in blood lymphocytes collected in contaminated animals (day 0), and decreased over time during decontamination. mRNA levels of interleukin 2 showed an opposite quantitative trend. MALDI-TOF-MS polypeptide profiling of serum samples ascertained a progressive decrease (from day 0 to 188) of serum levels of fibrinogen β-chain and serpin A3-7-like fragments, apolipoprotein (APO) C-II and serum amyloid A-4 protein, along with an augmented representation of transthyretin isoforms, as well as APOC-III and APOA-II proteins during decontamination. When differentially represented species were combined with serum antioxidant, acute phase and proinflammatory protein levels already ascertained in the same animals (Cigliano et al., 2016), bioinformatics unveiled an interaction network linking together almost all components. This suggests the occurrence of a complex PCB-responsive mechanism associated with animal contamination/decontamination, including a cohort of protein/polypeptide species involved in blood redox homeostasis, inflammation and lipid transport. All together, these results suggest the use in combination of such biomarkers for identifying PCB-contaminated animals, and for monitoring the restoring of their healthy condition following a decontamination process.

Interaction of mammary bovine ABCG2 with AFB1 and its metabolites and regulation by PCB 126 in a MDCKII in vitro model

The ATP-binding cassette efflux transporter ABCG2 plays a key role in the mammary excretion of drugs and toxins in humans and animals. Aflatoxins (AF) are worldwide contaminants of food and feed commodities, while PCB 126 is a dioxin-like PCB which may contaminate milk and dairy products. Both compounds are known human carcinogens. The interactions between AF and bovine ABCG2 (bABCG2) as well as the effects of PCB 126 on its efflux activity have been investigated by means of the Hoechst H33342 transport assay in MDCKII cells stably expressing mammary bABCG2. Both AFB1 and its main milk metabolite AFM1 showed interaction with bABCG2 even at concentrations approaching the legal limits in feed and food commodities. Moreover, PCB 126 significantly enhanced bABCG2 functional activity. Specific inhibitors of either AhR (CH233191) or ABCG2 (Ko143) were able to reverse the PCB 126-induced increase in bABCG2 transport activity, showing the specific upregulation of the efflux protein by the AhR pathway. The incubation of PCB 126-pretreated cells with AFM1 was able to substantially reverse such effect, with still unknown mechanism(s). Overall, results from this study point to AFB1 and AFM1 as likely bABCG2 substrates. The PCB 126-dependent increased activity of the transporter could enhance the ABCG2-mediated excretion into dairy milk of chemicals (i.e., drugs and toxins) potentially harmful to neonates and consumers.

Comparative liver accumulation of dioxin-like compounds in sheep and cattle: Possible role of AhR-mediated xenobiotic metabolizing enzymes

PCDDs, PCDFs, and PCBs are persistent organic pollutants (POPs) that accumulate in animal products and may pose serious health problems. Those able to bind the aryl hydrocarbon receptor (AhR), eliciting a plethora of toxic responses, are defined dioxin-like (DL) compounds, while the remainders are called non-DL (NDL). An EFSA opinion has highlighted the tendency of ovine liver to specifically accumulate DL-compounds to a greater extent than any other farmed ruminant species. To examine the possible role in such an accumulation of xenobiotic metabolizing enzymes (XME) involved in DL-compound biotransformation, liver samples were collected from ewes and cows reared in an area known for low dioxin contamination. A related paper reported that sheep livers had about 5-fold higher DL-compound concentrations than cattle livers, while the content of the six marker NDL-PCBs did not differ between species. Specimens from the same animals were subjected to gene expression analysis for AhR, AhR nuclear translocator (ARNT) and AhR-dependent oxidative and conjugative pathways; XME protein expression and activities were also investigated. Both AhR and ARNT mRNA levels were about 2-fold lower in ovine samples and the same occurred for CYP1A1 and CYP1A2, being approximately 3- and 9-fold less expressed in sheep compared to cattle, while CYP1B1 could be detectable in cattle only. The results of the immunoblotting and catalytic activity (most notably EROD) measurements of the CYP1A family enzymes were in line with the gene expression data. By contrast, phase II enzyme expression and activities in sheep were higher (UGT1A) or similar (GSTA1, NQO1) to those recorded in cattle. The overall low expression of CYP1 family enzymes in the sheep is in line with the observed liver accumulation of DL-compounds and is expected to affect the kinetics and the dynamics of other POPs such as many polycyclic aromatic hydrocarbons, as well as of toxins (e.g. aflatoxins) or drugs (e.g. benzimidazole anthelmintics) known to be metabolized by those enzymes.

Hepatic tyrosine aminotransferase and glucocorticoid abuse in meat cattle

Besides being extensively applied as therapeutical remedies, glucocorticoids (GCs) - most notably dexamethasone or prednisolone - are also illegally used in livestock for growth-promoting purposes. This study was designed to assess the suitability of liver tyrosine aminotransferase (TAT), a gluconeogenic enzyme known to be induced by GCs, to act as a reliable candidate biomarker to screen for GC abuse in cattle. Enzyme activity was measured spectrophotometrically in liver cytosols or in cell extracts, and TAT gene expression was determined by real-time PCR. Compared with untreated veal calves, a notable scatter (20-fold) and much higher median values (3-fold) characterized TAT specific activity in liver samples from commercially farmed veal calves. A time-related increase in both enzyme activity and gene expression was detected in rat hepatoma cell lines treated with dexamethasone concentrations (10(-8) or 10(-9) m) in the range of those recorded in noncompliant samples from EU official controls. In experimental studies in which finishing bulls were administered GCs at growth-promoting dosages, however, no such changes were recorded in dexamethasone-treated animals; a statistically significant rise in liver TAT activity (+95%) only occurred in prednisolone-treated bulls. Although further research is needed to characterize the GC-mediated response in cattle liver, TAT does not appear to be a specific and sensitive biomarker of GC abuse in the bovine species.