Potential predictive biomarkers of obesity in Burmese cats

Pathophysiology of Prediabetes, Diabetes, and Diabetic Remission in Cats

Diabetes mellitus (DM) has a heterogenous cause, and the exact pathogenesis differs between patients. Most diabetic cats have a cause similar to human type 2 DM but, in some, DM is associated with underlying conditions, such as hypersomatotropism, hyperadrenocorticism, or administration of diabetogenic drugs. Predisposing factors for feline DM include obesity, reduced physical activity, male sex, and increasing age. Gluco(lipo)toxicity and genetic predisposition also likely play roles in pathogenesis. Prediabetes cannot be accurately diagnosed in cats at the current time. Diabetic cats can enter remission, but relapses are common, as these cats might have ongoing, abnormal glucose homeostasis.

A genome-wide association study identifies novel candidate genes for susceptibility to diabetes mellitus in non-obese cats

Diabetes mellitus (DM) is a common feline endocrinopathy, which is similar to human type 2 diabetes (T2DM) in terms of its pathophysiology. T2DM occurs due to peripheral insulin resistance and/or β-cell dysfunction. Several studies have identified genetic and environmental factors that contribute to susceptibility to human T2DM. In cats, environmental factors such as obesity and physical inactivity have been linked with DM, although to date, the only genetic association that has been demonstrated is with a polymorphism in the feline MC4R gene. The aim of this study was to perform a genome-wide association study (GWAS) to identify polymorphisms associated with feline DM. Illumina Infinium 63k iSelect DNA arrays were used to analyse genomic DNA samples from 200 diabetic domestic shorthair cats and 399 non-diabetic control cats. Data was analysed using PLINK whole genome data analysis toolset. A linear model analysis, EMMAX, was done to test for population structure and HAPLOVIEW was used to identify haplotype blocks surrounding the significant SNPs to assist with candidate gene nomination. A total of 47,497 SNPs were available for analysis. Four SNPs were identified with genome-wide significance: chrA2.4150731 (p_raw = 9.94 x10^-8); chrUn17.115508 (p_raw = 6.51 x10^-8); chrUn17.394136 (p_raw = 2.53 x10^-8); chrUn17.314128 (p_raw = 2.53 x10^-8) as being associated with DM. The first SNP is located within chromosome A2, less than 4kb upstream of the dipeptidyl-peptidase-9 (DPP9) gene, a peptidase involved in incretin inactivation. The remaining three SNPs are located within a haplotype block towards the end of chromosome A3; within this region, genes of interest include TMEM18 and ACP1, both previously associated with T2DM. This study indicates a polygenic component to susceptibility to DM in cats and has highlighted several loci and candidate genes worthy of further investigation.

Differences in metabolic profiles between the Burmese, the Maine coon and the Birman cat-Three breeds with varying risk for diabetes mellitus

Feline diabetes mellitus shares many features with type 2 diabetes in people, regarding clinical presentation, physiology, and pathology. A breed predisposition for type 2 diabetes has been identified, with the Burmese breed at a fivefold increased risk of developing the condition compared to other purebred cats. We aimed to characterize the serum metabolome in cats (n = 63) using nuclear magnetic resonance metabolomics, and to compare the metabolite pattern of Burmese cats with that of two cat breeds of medium or low risk of diabetes, the Maine coon (MCO) and Birman cat, respectively. Serum concentrations of adiponectin, insulin and insulin-like growth factor-1 were also measured (n = 94). Burmese cats had higher insulin and lower adiponectin concentrations than MCO cats. Twenty one metabolites were discriminative between breeds using a multivariate statistical approach and 15 remained significant after adjustment for body weight and body condition score. Burmese cats had higher plasma levels of 2-hydroxybutyrate relative to MCO and Birman cats and increased concentrations of 2-oxoisocaproic acid, and tyrosine, and lower concentrations of dimethylglycine relative to MCO cats. The metabolic profile of MCO cats was characterized by high concentrations of arginine, asparagine, methionine, succinic acid and low levels of acetylcarnitine while Birman cats had the highest creatinine and the lowest taurine plasma levels, compared with MCO and Burmese. The pattern of metabolites in Burmese cats is similar to that in people with insulin resistance. In conclusion, the metabolic profile differed between healthy cats of three breeds. Detection of an abnormal metabolome might identify cats at risk of developing diabetes.

Mapping the genetic basis of diabetes mellitus in the Australian Burmese cat (Felis catus)

Diabetes mellitus, a common endocrinopathy affecting domestic cats, shares many clinical and pathologic features with type 2 diabetes in humans. In Australia and Europe, diabetes mellitus is almost four times more common among Burmese cats than in other breeds. As a genetically isolated population, the diabetic Australian Burmese cat provides a spontaneous genetic model for studying diabetes mellitus in humans. Studying complex diseases in pedigreed breeds facilitates tighter control of confounding factors including population stratification, allelic frequencies and environmental heterogeneity. We used the feline SNV array and whole genome sequence data to undertake a genome wide-association study and runs of homozygosity analysis, of a case–control cohort of Australian and European Burmese cats. Our results identified diabetes-associated haplotypes across chromosomes A3, B1 and E1 and selective sweeps across the Burmese breed on chromosomes B1, B3, D1 and D4. The locus on chromosome B1, common to both analyses, revealed coding and splice region variants in candidate genes, ANK1, EPHX2 and LOX2, implicated in diabetes mellitus and lipid dysregulation. Mapping this condition in Burmese cats has revealed a polygenic spectrum, implicating loci linked to pancreatic beta cell dysfunction, lipid dysregulation and insulin resistance in the pathogenesis of diabetes mellitus in the Burmese cat.

The vital role of ATP citrate lyase in chronic diseases

Chronic or non-communicable diseases are the leading cause of death worldwide; they usually result in long-term illnesses and demand long-term care. Despite advances in molecular therapeutics, specific biomarkers and targets for the treatment of these diseases are required. The dysregulation of de novo lipogenesis has been found to play an essential role in cell metabolism and is associated with the development and progression of many chronic diseases; this confirms the link between obesity and various chronic diseases. The main enzyme in this pathway-ATP-citrate lyase (ACLY), a lipogenic enzyme-catalyzes the critical reaction linking cellular glucose catabolism and lipogenesis. Increasing lines of evidence suggest that the modulation of ACLY expression correlates with the development and progressions of various chronic diseases such as neurodegenerative diseases, cardiovascular diseases, diabetes, obesity, inflammation, and cancer. Recent studies suggest that the inhibition of ACLY activity modulates the glycolysis and lipogenesis processes and stimulates normal physiological functions. This comprehensive review aimed to critically evaluate the role of ACLY in the development and progression of different diseases and the effects of its downregulation in the prevention and treatment of these diseases.

The Burmese cat as a genetic model of type 2 diabetes in humans

The recent extension of genetic tools to the domestic cat, together with the serendipitous consequences of selective breeding, have been essential to the study of the genetic diseases that affect them. Cats are increasingly presented for veterinary surveillance and share many of human's heritable diseases, allowing them to serve as natural models of these conditions. Feline diabetes mellitus is a common condition in domestic cats that bears close pathological and clinical resemblance to type 2 diabetes in humans, including pancreatic β-cell dysfunction and peripheral insulin resistance. In Australia, New Zealand and Europe, diabetes mellitus is almost four times more common in cats of the Burmese breed than in other breeds. This geographically based breed predisposition parallels familial and population clustering of type 2 diabetes in humans. As a genetically isolated population, the Australian Burmese breed provides a spontaneous, naturally occurring genetic model of type 2 diabetes. Genetically isolated populations typically exhibit extended linkage disequilibrium and increased opportunity for deleterious variants to reach high frequencies over many generations due to genetic drift. Studying complex diseases in such populations allows for tighter control of confounding factors including environmental heterogeneity, allelic frequencies and population stratification. The homogeneous genetic background of Australian Burmese cats may provide a unique opportunity to either refine genetic signals previously associated with type 2 diabetes or identify new risk factors for this disease.

An individual approach to feline diabetes care: a case report and literature review

Background

Achieving insulin independence is emerging as a realistic therapeutic goal in the management of feline diabetes mellitus.

Case presentation

The management of an 11-year-old spayed female Burmese cat presenting with diabetes mellitus after corticosteroid administration is described. Remission was achieved after the frequency of insulin administration was increased to four times a day, and supported by intensive home blood glucose monitoring and a high protein, low carbohydrate diet.

Conclusion

Owners are important collaborators in feline diabetes care and, with intensive home monitoring, more frequent insulin treatment may lead to remission without hypoglycemia. More frequent insulin injections than recommended in the literature may be necessary to achieve glycemic control and used as an alternative to a longer-acting insulin.

Epidemiology of Diabetes Mellitus among 193,435 Cats Attending Primary-Care Veterinary Practices in England

BACKGROUND

Diabetes mellitus (DM) is a common endocrine disease of cats. The prevalence of DM in cats in England is not well-defined.

HYPOTHESIS/OBJECTIVES

To estimate the prevalence and identify risk factors for DM in a large population of cats attending primary-care practices.

ANIMALS

A cohort of 193,563 cats in the VetCompass Programme attending 118 primary-care practices in England.

METHODS

Cross-sectional analysis of cohort clinical data. Data were extracted covering September 1st 2009 and August 31st 2014. Period prevalence of DM was calculated. Associations between risk factors and DM were assessed using logistic regression modelling.

RESULTS

Of 1,128 DM cases were identified among 194,563 cats (period prevalence 0.58%; 95% confidence interval [CI] 0.54-0.61). Multivariable modelling indicated that Tonkinese (OR 4.1; 95% CI 1.8-9.6; P = .001), Norwegian Forest (odds ratio [OR] 3.5; 95% CI 1.3-9.6; P = .001) and Burmese (OR 3.0; 95% CI 2.0-4.4; P < .001) cats had increased odds of DM compared with crossbred cats. DM odds increased as bodyweight categories increased above 4 kg (P < .001), as cats aged beyond 6 years old (P < .001) and in insured cats (OR 2.0; 95% CI 1.6-2.4; P < .001) but sex was not significantly associated with DM.

CONCLUSIONS AND CLINICAL IMPORTANCE

Diabetes mellitus is an important component of the primary-care practice caseload with 1-in-200 cats affected. An increased risk of DM in certain cat breeds supports a genetic predisposition. These results can guide future research and preventative healthcare.

Incidence of Diabetes Mellitus in Insured Swedish Cats in Relation to Age, Breed and Sex

BACKGROUND

Diabetes mellitus (DM) is a common endocrinopathy in cats. Most affected cats suffer from a type of diabetes similar to type 2 diabetes in humans. An increasing prevalence has been described in cats, as in humans, related to obesity and other lifestyle factors.

OBJECTIVES

To describe the incidence of DM in insured Swedish cats and the association of DM with demographic risk factors, such as age, breed and sex.

ANIMALS

A cohort of 504,688 individual cats accounting for 1,229,699 cat-years at risk (CYAR) insured by a Swedish insurance company from 2009 to 2013.

METHODS

We used reimbursed insurance claims for the diagnosis of DM. Overall incidence rates and incidence rates stratified on year, age, breed, and sex were estimated.

RESULTS

The overall incidence rate of DM in the cohort was 11.6 cases (95% confidence interval [CI], 11.0-12.2) per 10,000 CYAR. Male cats had twice as high incidence rate (15.4; 95% CI, 14.4-16.4) as females (7.6; 95% CI, 6.9-8.3). Domestic cats were at higher risk compared to purebred cats. A significant association with breed was seen, with the Burmese, Russian Blue, Norwegian Forest cat, and Abyssinian breeds at a higher risk compared to other cats. No sex predisposition was found among Burmese cats. Several breeds with a lower risk of DM were identified.

CONCLUSIONS AND CLINICAL IMPORTANCE

Our results verify that the Burmese breed is at increased risk of developing DM. We also identified several previously unreported breeds with increased or decreased risk of DM.

Feline diabetes mellitus: clinical use of long-acting glargine and detemir

PRACTICAL RELEVANCE

Diabetes mellitus is a common endocrine disorder in feline practice, affecting approximately 1 in 200 cats. The majority of diabetic cats have type 2 diabetes mellitus, which results from a combination of peripheral insulin resistance and a progressive reduction in insulin production.

CLINICAL CHALLENGES

While usually easy to diagnose, management of diabetes mellitus presents a number of challenges for practitioners and clients alike. Practitioners must decide on diet, insulin type and dose, monitoring method and intensity, and concomitant therapy, which will vary based on individual patient and client needs, and geographic location. Practitioners may also encounter patients with diabetic ketoacidosis or other diabetic complications, and patients with multiple concurrent diseases. Clients may be challenged by the substantial time and financial commitment involved in owning a diabetic cat.

AUDIENCE

Understanding the pathophysiology, optimal treatment protocols and current goals of diabetes management will benefit practitioners managing diabetic cats. This article reviews the most current management plans for feline diabetics. It places particular emphasis on best practice for achieving diabetic remission, which is an attainable goal in the majority of newly diagnosed diabetic cats.

EVIDENCE BASE

The information in this article is drawn from the recent human and veterinary literature, including prospective and retrospective studies. The body of prospective clinical data on the use of newer, long-acting insulins (glargine and especially detemir) in cats is limited, but growing.

Decreased gene expressions of insulin signal molecules in canine hyperadrenocorticism

Hyperadrenocorticism (HAC) is a common endocrine disorder in dogs, in which excess glucocorticoid causes insulin resistance. Disturbance of insulin action may be caused by multiple factors, including transcriptional modulation of insulin signal molecules which lie downstream of insulin binding to insulin receptors. In this study, gene expressions of insulin signal molecules were examined using neutrophils of the HAC dogs (the untreated dogs and the dogs which had been treated with trilostane). Insulin receptor substrate (IRS)-1, IRS-2, phosphatidylinositol 3-kinase (PI3-K), protein kinase B/Akt kinase (Akt)-2 and protein kinase C (PKC)-lambda were analyzed in the HAC dogs and compared with those from normal dogs. The IRS-1 gene expressions decreased by 37% and 35% of the control dogs in the untreated and treated groups, respectively. The IRS-2 gene expressions decreased by 61% and 72%, the PI3-K gene expressions decreased by 47% and 55%, and the Akt-2 gene expressions decreased by 45% and 56% of the control dogs, similarly. Collectively, gene expressions of insulin signal molecules are suppressed in the HAC dogs, which may partially contribute to the induction of insulin resistance.