Adipose tissue gene expression in obese dogs after weight loss

Effects of ACTH-Induced Long-Term Hypercortisolism on the Transcriptome of Canine Visceral Adipose Tissue

Cushing’s syndrome, or hypercortisolism (HC), a common endocrinopathy in adult dogs, is caused by chronic hypercortisolemia. Among different metabolic disorders, this syndrome is associated with enhanced subcutaneous lipolysis and visceral adiposity. However, effects of HC in adipose tissue, especially regarding visceral adipose tissue (VAT), are still poorly understood. Herein, the transcriptomic effects of chronic HC on VAT of dogs were evaluated. For this, subcutaneously implanted ACTH-releasing pumps were used, followed by deep RNA sequencing of the canine VAT. Prolonged HC seems to affect a plethora of regulatory mechanisms in VAT of treated dogs, with 1190 differentially expressed genes (DEGs, p and FDR < 0.01) being found. The 691 downregulated DEGs were mostly associated with functional terms like cell adhesion and migration, intracellular signaling, immune response, extracellular matrix and angiogenesis. Treatment also appeared to modulate local glucocorticoid and insulin signaling and hormonal sensitivity, and several factors, e.g., TIMP4, FGF1, CCR2, CXCR4 and HSD11B1/2, were identified as possible important players in the glucocorticoid-related expansion of VAT. Modulation of their function during chronic HC might present interesting targets for further clinical studies. Similarities in the effects of chronic HC on VAT of dogs and humans are highlighted.

Relationships between expression levels of genes related to adipogenesis and adipocyte function in dogs

There are three kinds of adipocytes; white adipocytes accumulate excess energy as fat, whereas brown/beige adipocytes dissipate energy through expression of uncoupling protein 1 (UCP1). Obesity, a feature of excess accumulation of white adipocytes in a body, is one of the risk factors for onset of various diseases in dogs. As the first step to explore adipose genes related to dog obesity, we examined relationships among mRNA levels of putative molecules related to adipogenesis and function of adipocytes in fat of hospitalized dogs. Gonadal adipose tissues were collected from a total of 29 dogs, and the gene expression levels were examined by quantitative RT-PCR analysis. The multicollinearity analysis revealed that body condition score (BCS), which reflects adiposity, did not correlate with expression levels of any genes but correlated with age of dog. Bone morphogenetic protein (BMP) pathway stimulates not only commitment of mesenchymal stem cells to white adipocyte-lineage cells but also brown/beige adipogenesis. Some relationships between expression levels of BMP receptors were significant; especially, expression levels of activin receptor-like kinase (Alk) 3 (a BMP type I receptor) positively related to those of Alk2 (another BMP type I receptor), activin receptor type II (ActRII) A (a type II receptor to transmit BMP signal), ActRIIB (another type II receptor to transmit BMP signal) and BMP receptor type 2 (Bmpr2). PR domain containing 16 (Prdm16) expression levels strongly correlated with expression levels of ActRIIB. Although PRDM16 is known to stimulate brown/beige adipogenesis, expression levels of Ucp1 did not correlate with those of Prdm16. On the other hand, expression levels of Ucp1 correlated with those of Alk6. The present study suggests close relationships among adipose expressions of BMP signal components, and the relationships of expression levels of BMP receptor and those of Prdm16 or Ucp1 in dogs. Further studies using more dogs with various BCS potentially lead to identification of adipose factors to relate with adiposity in dogs.

Short-term obesity results in detrimental metabolic and cardiovascular changes that may not be reversed with weight loss in an obese dog model

The time course of metabolic and cardiovascular changes with weight gain and subsequent weight loss has not been elucidated. The goal of the present study was to determine how weight gain, weight loss and altered body fat distribution affected metabolic and cardiovascular changes in an obese dog model. Testing was performed when the dogs were lean (scores 4-5 on a nine-point scale), after ad libitum feeding for 12 and 32 weeks to promote obesity (>5 score), and after weight loss. Measurements included serum glucose and insulin, plasma leptin, adiponectin and C-reactive protein, echocardiography, flow-mediated dilation and blood pressure. Body fat distribution was assessed by computed tomography. Fasting serum glucose concentrations increased significantly with obesity (P< 0·05). Heart rate increased by 22 (SE 5) bpm after 12 weeks of obesity (P= 0·003). Systolic left ventricular free wall thickness increased after 12 weeks of obesity (P= 0·002), but decreased after weight loss compared with that observed in the lean phase (P= 0·03). Ventricular free wall thickness was more strongly correlated with visceral fat (r 0·6, P= 0·001) than with total body fat (r 0·4, P= 0·03) and was not significantly correlated with subcutaneous body fat (r 0·3, P= 0·1). The present study provides evidence that metabolic and cardiovascular alterations occur within only 12 weeks of obesity in an obese dog model and are strongly predicted by visceral fat. These results emphasise the importance of obesity prevention, as weight loss did not result in the return of all metabolic indicators to their normal levels. Moreover, systolic cardiac muscle thickness was reduced after weight loss compared with the pre-obesity levels, suggesting possible acute adverse cardiovascular effects.

Maintenance energy requirements in miniature colony dogs

There are numerous reports of maintenance energy requirements (MER) in dogs, but little information is available about energy requirements of miniature dog breeds. In this prospective, observational, cohort study, we aimed to determine MER in dogs from a number of miniature breeds and to determine which factors were associated with it. Forty-two dogs participated in the study. MER was calculated by determining daily energy intake (EI) during a period of 196 days (28-359 days) when body weight did not change significantly (e.g. ±2% in 12 weeks). Estimated median MER was 473 kJ/kg(0.75) /day (285-766 kJ/kg(0.75) /day), that is, median 113 kcal/kg(0.75) /day (68-183 kcal/kg(0.75) /day). In the obese dogs that lost weight, median MER after weight loss was completed was 360 kJ/kg(0.75) /day (285-515 kJ/kg(0.75) /day), that is, 86 kcal/kg(0.75) /day, (68-123 kcal/kg(0.75) /day). Simple linear regression analysis suggested that three breeds (e.g. Chihuahua, p = 0.002; Yorkshire terrier, p = 0.039; dachshund, p = 0.035) had an effect on MER. In addition to breed, simple linear regression revealed that neuter status (p = 0.079) and having previously been overweight (p = 0.002) were also of significance. However, with multiple linear regression analysis, only previous overweight status (MER less in dogs previously overweight p = 0.008) and breed (MER greater in Yorkshire terriers [p = 0.029] and less in Chihuahuas [p = 0.089]) remained in the final model. This study is the first to estimate MER in dogs of miniature breeds. Although further information from pet dogs is now needed, the current work will be useful for setting energy and nutrient requirement in such dogs for the future.

Dog obesity--the need for identifying predisposing genetic markers

Incidence of overweight and obesity in dogs exceeds 30%, and several breeds are predisposed to this heritable phenotype. Rapid progress of canine genomics and advanced knowledge on the genetic background of human obesity bring a unique opportunity to perform such studies in dogs. Natural candidate genes for obesity are these encoding adipokines. Extended studies in humans indicated that polymorphisms of three of them, i.e. ADIPOQ, IL1 and TNF, are associated with predisposition to obesity. On the other hand, the use of genome-wide association studies revealed an association between human obesity and polymorphism of more than 50 other genes. Until now only few preliminary reports on polymorphism of canine FTO, MC4R, MC3R and PPARG genes have been published. Since the dog is a valuable model organism for human diseases one can foresee that such studies may also contribute to an in-depth understanding of human obesity pathogenesis.

Effect of mitratapide on body composition, body measurements and glucose tolerance in obese Beagles

The objective of this study was to confirm that weight loss after treatment with mitratapide (Yarvitan®) is loss of adipose tissue. Obese dogs were treated with the recommended treatment schedule of mitratapide. Dual-energy X-ray absorptiometry (DEXA) was done before and after the treatment schedule. Body weight, feed consumption and pelvic circumference were recorded and a glucose tolerance test was performed. Dualenergy X-ray absorptiometry measurements showed an impressive loss of fat tissue, corresponding to a mean loss of approximately 41.6% of the body fat mass recorded before treatment. After treatment with mitratapide, the mean body fat percentage had returned within the normal range. At the end of the study, the dogs had lost on average 14.2% of their body weight and 15.2% of their pelvic circumference compared to baseline. The results also suggest that losing weight with mitratapide might help to reverse insulin resistance.

Obesity in dogs and cats: a metabolic and endocrine disorder

Obesity is defined as an accumulation of excessive amounts of adipose tissue in the body, and has been called the most common nutritional disease of dogs in Western countries. Most investigators agree that at least 33% of the dogs presented to veterinary clinics are obese, and that the incidence is increasing as human obesity increases in the overall population. Obesity is not just the accumulation of large amounts of adipose tissue, but is associated with important metabolic and hormonal changes in the body, which are the focus of this review. Obesity is associated with a variety of conditions, including osteoarthritis, respiratory distress, glucose intolerance and diabetes mellitus, hypertension, dystocia, decreased heat tolerance, some forms of cancer, and increased risk of anesthetic and surgical complications. Prevention and early recognition of obesity, as well as correcting obesity when it is present, are essential to appropriate health care, and increases both the quality and quantity of life for pets.