Eleanor Raffan

A Deletion in the Canine POMC Gene Is Associated with Weight and Appetite in Obesity-Prone Labrador Retriever Dogs

Summary Sequencing of candidate genes for obesity in Labrador retriever dogs identified a 14 bp deletion in pro-opiomelanocortin (POMC) with an allele frequency of 12%. The deletion disrupts the β-MSH and β-endorphin coding sequences and is associated with body weight (per allele effect of 0.33 SD), adiposity, and greater food motivation. Among other dog breeds, the deletion was only found in the closely related flat-coat retriever (FCR), where it is similarly associated with body weight and food motivation. The mutation is significantly more common in Labrador retrievers selected to become assistance dogs than pets. In conclusion, the deletion in POMC is a significant modifier of weight and appetite in Labrador retrievers and FCRs and may influence other behavioral traits.

Development, factor structure and application of the Dog Obesity Risk and Appetite (DORA) questionnaire

Background. Dogs are compelling models in which to study obesity since the condition shares many characteristics between humans and dogs. Differences in eating behaviour are recognised to contribute to obesity susceptibility in other species but this has not been systematically studied in dogs. Aim. To develop and validate an owner-reported measure of canine eating behaviour and owner or dog related factors which can alter the development of obesity. Further, to then test variation in food-motivation in dogs and its association with obesity and owner management. Methods. Owner interviews, a literature review and existing human appetite scales were used to identify relevant topics and generate items for the questionnaire. Following a pilot phase, a 75 item online questionnaire was distributed via social media. Responses from 302 dog/owner dyads were analysed and factor structure and descriptive statistics calculated. Results were compared with descriptions of dog behaviour and management from a subset of respondents during semi-structured interviews. The optimum questions were disseminated as a 34 item final questionnaire completed by 213 owners, with a subset of respondents repeating the questionnaire 3 weeks later to assess test–retest reliability. Results. Analysis of responses to the final questionnaire relating to 213 dog/owner dyads showed a coherent factor structure and good test–retest reliability. There were three dog factors (food responsiveness and satiety, lack of selectivity, Interest in food), four owner factors (owner motivation to control dog weight, owner intervention to control dog weight, restriction of human food, exercise taken) and two dog health factors (signs of gastrointestinal disease, current poor health). Eating behaviour differed between individuals and between breed groups. High scores on dog factors (high food-motivation) and low scores on owner factors (less rigorous control of diet/exercise) were associated with obesity. Owners of more highly food-motivated dogs exerted more control over their dogs’ food intake than those of less food-motivated dogs. Conclusions. The DORA questionnaire is a reliable and informative owner-reported measure of canine eating behaviour and health and management factors which can be associated with obesity development. The tool will be applicable to study of the canine obesity model and to clinical veterinarians. Results revealed eating behaviour to be similarly associated with obesity as exercise and owners giving titbits.

The big problem: battling companion animal obesity

Obesity in companion animals is not a new problem and research is suggesting that it is a complex physiological issue, with genetic and endocrine causes. Eleanor Raffan discusses why some individuals appear to be predisposed to becoming obese, the far-reaching consequences of obesity and how veterinary clinicians can help owners to help their pets

Early Diagnosis of Werner's Syndrome Using Exome-Wide Sequencing in a Single, Atypical Patient

Genetic diagnosis of inherited metabolic disease is conventionally achieved through syndrome recognition and targeted gene sequencing, but many patients receive no specific diagnosis. Next-generation sequencing allied to capture of expressed sequences from genomic DNA now offers a powerful new diagnostic approach. Barriers to routine diagnostic use include cost, and the complexity of interpreting results arising from simultaneous identification of large numbers of variants. We applied exome-wide sequencing to an individual, 16-year-old daughter of consanguineous parents with a novel syndrome of short stature, severe insulin resistance, ptosis, and microcephaly. Pulldown of expressed sequences from genomic DNA followed by massively parallel sequencing was undertaken. Single nucleotide variants were called using SAMtools prior to filtering based on sequence quality and existence in control genomes and exomes. Of 485 genetic variants predicted to alter protein sequence and absent from control data, 24 were homozygous in the patient. One mutation – the p.Arg732X mutation in the WRN gene – has previously been reported in Werners syndrome (WS). On re-evaluation of the patient several early features of WS were detected including loss of fat from the extremities and frontal hair thinning. Lymphoblastoid cells from the proband exhibited a defective decatenation checkpoint, consistent with loss of WRN activity. We have thus diagnosed WS some 15 years earlier than average, permitting aggressive prophylactic therapy and screening for WS complications, illustrating the potential of exome-wide sequencing to achieve early diagnosis and change management of rare autosomal recessive disease, even in individual patients of consanguineous parentage with apparently novel syndromes.

Identification and Characterisation of a Novel Pathogenic Mutation in the Human Lipodystrophy Gene AGPAT2

Loss-of-function mutations in AGPAT2, encoding 1-acylglycerol-3-phosphate-O-acyltransferase 2 (AGPAT2), produce congenital generalised lipodystrophy (CGL). We screened the AGPAT2 gene in two siblings who presented with pseudoacromegaly, diabetes and severe dyslipidaemia and identified a novel mutation in AGPAT2 causing a single amino acid substitution, p.Cys48Arg. We subsequently investigated the molecular pathogenic mechanism linking both this mutation and the previously reported p.Leu228Pro mutation to clinical disease. Wild-type and mutant AGPAT2 were expressed in control and AGPAT2-deficient preadipocyte cell lines. mRNA and protein expression was determined, and the ability of each AGPAT2 species to rescue adipocyte differentiation in AGPAT2-deficient cells was assessed. Protein levels of both p.Cys48Arg and p.Leu228Pro AGPAT2 were significantly reduced compared with that of wild-type AGPAT2 despite equivalent mRNA levels. Stable expression of wild-type AGPAT2 partially rescued adipogenesis in AGPAT2 deficient preadipocytes, whereas stable expression of p.Cys48Arg or p.Leu228Pro AGPAT2 did not. In conclusion, unusually severe dyslipidaemia and pseudoacromegaloid overgrowth in patients with diabetes should alert physicians to the possibility of lipodystrophy. Both the previously unreported pathogenic p.Cys48Arg mutation in AGPAT2, and the known p.Leu228Pro mutation result in decreased AGPAT2 protein expression in developing adipocytes. It is most likely that the CGL seen in homozygous carriers of these mutations is largely accounted for by loss of protein expression.

The coding sequence of POMC and obesity and appetite in Labrador retriever dogs

Abstract Background In human beings, the heritability of obesity is estimated at 40–70%, but only a small proportion ( Methods Pet dogs were prospectively selected for study. Body condition score was used to initially group them as lean or obese. They were further divided into two groups—obese, highly food-motivated dogs; and lean, non-food-motivated dogs—by a combination of a standardised questionnaire to owners and a veterinary surgeon taking a clinical and behavioural history. The coding sequence of AGRP, POMC , and MC4R were sequenced in several dogs from each group. Findings 35 dogs (15 obese, 20 lean) were studied. The coding sequence of AGRP was normal in all dogs. Six single nucleotide polymorphisms (SNPs) were identified in MC4R , and eight SNPs and two deletions (one coding, one intronic) were found in POMC . There was no significant difference in the distribution of these variants between lean and obese groups for any of the variants except the coding deletion in POMC . Of 15 obese, food-motivated dogs, that deletion was heterozygous in eight and homozygous in two; the deletion was heterozygous in two of the 20 lean, non-food-motivated dogs. The association with obesity and high food motivation was significant (p=0·001). Interpretation Melanocortin signalling has a key role in normal energy homoeostasis; POMC is a precursor protein whose cleavage products act on MC4 and MC3 receptors to suppress appetite and increase energy expenditure. The deletion of 14 base pairs in exon 3 of POMC is predicted to disrupt the POMC protein, stopping production of its cleavage products β-melanocyte-stimulating hormone and β-endorphin and is therefore a strong candidate for causing much or all of the obesity susceptibility in Labrador retriever dogs. Further genetic studies are in progress to assess the prevalence of the deletion in larger cohorts of dogs from the same and different breeds, with functional studies also planned. Funding Wellcome Trust, UK Medical Research Council, NIHR Cambridge Biomedical Research Centre.

Hepatic lipodystrophy of Galloway calves

HEPATIC lipodystrophy of Galloway calves is a rarely reported disease in the UK (Duff and others 1997, Macleod and Allison 1999), having first been diagnosed in 1965 in south-west Scotland (Stewart and others 1982). The condition has also been reported in North America since 2000 (Hazlett and Rumney 2000, Wyoming State Veterinary Laboratory 2007). The aetiology and pathogenesis of the disease has not been established; it is thought to have a genetic origin, although this has not been proven. Over the past 12 months, as part of an EBLEX-sponsored postmortem examination project at a fallen stock collection centre in County Durham, we have identified three calves fitting the case description for this condition. In summer 2014, we identified two, two-month-old male blue-grey calves from farm A, which had a 50-cow Galloway herd. The sire of both calves was an 11-year-old unregistered whitebred shorthorn bull, which had sired 200 calves in its lifetime. The first calf was recumbent with tenesmus, halitosis …

Obesity in labradors and golden retrievers

BREED predispositions suggest that genetics are important in the development of obesity in dogs, mirroring the case in people where up to 70 per cent of an individuals tendency to become obese is due to heritable factors. The GOdogs Project …

Primary hyperparathyroidism associated with hyperplasia of multiple parathyroid glands in a dog

A nine-year-old Italian Spinone dog presented with a history of urinary incontinence associated with polyuria/polydipsia (PUPD). Haematology and serum biochemistry identified hypercalcaemia. Subsequently, thoracic radiographs, abdominal ultrasound, urinalysis, serum assay of parathyroid hormone (PTH) and PTH-related protein concentrations and ultrasound of the parathyroid glands were consistent with a diagnosis of primary hyperparathyroidism. Unusually, however, all four parathyroid glands were noted to be enlarged on ultrasound, as opposed to a single parathyroid nodule (commonly an adenoma) as is normal in primary hyperparathyroidism. This presented a dilemma as to how best treat the dog; ultimately, two out of four parathyroid glands were removed. Postoperatively, normocalcaemia returned, and PUPD and incontinence resolved. Histopathological examination of the two removed glands was consistent with nodular hyperplasia of chief cells for one gland and nodular hyperplasia of chief cells and oxyphilic cells for the other gland, confirming a diagnosis of parathyroid hyperplasia.

Development and validation of the Dog Obesity Risk and Appetite (DORA) questionnaire.

Owner mismanagement is often cited as the cause of canine obesity but it is possible some dogs have higher drives to seek out and eat food than others.