Experimental and clinical studies on plasma leptin in obese dogs

Nutritional Factors Related to Canine Gallbladder Diseases-A Scoping Review

Gallbladder mucocele, cholelithiasis, choledocholithiasis, and cholecystitis are significant contributors to morbidity and mortality in dogs. The exact etiology of these conditions remains poorly understood, though various factors, such as endocrinopathies, dyslipidemia, and impaired gallbladder motility, have been suggested as potential contributors. Surgical intervention has been described as the first choice of treatment when biliary rupture or obstruction is suspected; however, medical management may be an important part of therapeutic or preventative strategy. Reports of medical management typically involve the use of a choleretic used to stimulate the flow of bile into the duodenum or substances that act as a "hepatoprotective" agent such as S-adenosylmethionine. In people, some nutrients appear to modify bile flow and are used as agents in the prevention and treatment of these conditions in the gallbladder. This paper provides a review of the literature about possible nutritional factors involved in the pathogenesis and treatment of canine gallbladder mucocele and cholelithiasis. Opportunities for the prevention and treatment of common biliary diseases in dogs may include the reduction of dietary fat, control of hyperlipidemia with omega-3 and fiber supplementation, ensuring an adequate supply of amino acids such as methionine and tryptophan, and the evaluation of vitamins such as vitamin D.

Feline obesity causes hematological and biochemical changes and oxidative stress - a pilot study

Obesity, an extremely important factor in feline clinical practice, is estimated to affect up to one third of the feline population. Moreover, it can trigger chronic inflammation, which could predispose to oxidative stress by increasing reactive oxygen species, thereby generating potentially irreversible cellular damage. This study analyzed hematological, biochemical and oxidative stress profiles at various degrees of feline obesity. Forty-five cats were selected and divided into three groups: control (n = 17), overweight (n = 13) and obese (n = 15), after clinical and laboratory evaluation and body condition score. Biochemical and oxidative stress analyses were performed using a photocolorimeter and hematological analyses were performed in a veterinary cell counter. Obese cats showed increased mean corpuscular volume (MCV), red cell distribution width (RDW), HDL cholesterol and triglycerides and decreased activity of gamma-glutamyl transferase (GGT) than control cats, although within the reference ranges for the species. As for oxidative stress, obese cats showed higher total antioxidant capacity (TAC), by the inhibition of 2,2'-Azino-Bis-3-Ethylbenzthiazoline-6-Sulfonic Acid (ABTS), inhibition of ABTS associated with horseradish peroxidase (ABTS + HRP), cupric ion reducing antioxidant capacity (CUPRAC) and ferric reducing antioxidant power (FRAP) methods, while overweight cats had a higher TAC-ABTS + HRP and TAC-FRAP than control cats. We conclude that the conditions of natural obesity and overweight in the feline species alter its hematological, biochemical and oxidative stress parameters.

Obesity, inflammation, and cancer in dogs: Review and perspectives

Obesity is the most common nutritional disease in dogs, and its prevalence has increased in recent decades. Several countries have demonstrated a prevalence of obesity in dogs similar to that observed in humans. Chronic low-grade inflammation is a prominent basis used to explain how obesity results in numerous negative health consequences. This is well known and understood, and recent studies have pointed to the association between obesity and predisposition to specific types of cancers and their complications. Such elucidations are important because, like obesity, the prevalence of cancer in dogs has increased in recent decades, establishing cancer as a significant cause of death for these animals. In the same way, intensive advances in technology in the field of human and veterinary medicine (which even proposes the use of animal models) have optimized existing therapeutic methods, led to the development of innovative treatments, and shortened the time to diagnosis of cancer. Despite the great challenges, this review aims to highlight the evidence obtained to date on the association between obesity, inflammation, and cancer in dogs, and the possible pathophysiological mechanisms that link obesity and carcinogenesis. The potential to control cancer in animals using existing knowledge is also presented.

Metabolic variables of obese dogs with insulin resistance supplemented with yeast beta-glucan

Background

Obesity is one of the most common nutritional disorders in dogs and cats and is related to the development metabolic comorbidities. Weight loss is the recommended treatment, but success is difficult due to the poor satiety control. Yeast beta-glucans are known as biological modifiers because of their innumerable functions reported in studies with mice and humans, but only one study with dogs was found. This study aimed to evaluate the effects of a diet supplemented with 0.1% beta-glucan on glucose, lipid homeostasis, inflammatory cytokines and satiety parameters in obese dogs. Fourteen dogs composed three experimental groups: Obese group (OG) with seven dogs with body condition score (BCS) 8 or 9; Lean group (LG) included seven non-obese dogs with a BCS of 5; and Supplemented Obese group (SOG) was the OG dogs after 90 days of consumption of the experimental diet.

Results

Compared to OG, SOG had lower plasma basal glycemic values (p = 0.05) and reduced serum cholesterol and triglyceride levels. TNF-α was lower in SOG than in OG (p = 0.05), and GLP-1 was increased in SOG compared to OG and LG (p = 0.02).

Conclusion

These results are novel and important for recognizing the possibility of using beta-glucan in obesity prevention and treatment.

Leptin Modulates the Metastasis of Canine Inflammatory Mammary Adenocarcinoma Cells Through Downregulation of Lysosomal Protective Protein Cathepsin A (CTSA)

Canine malignant mammary gland tumors present with a poor prognosis due to metastasis to other organs, such as lung and lymph node metastases. Unlike in human studies where obesity has been shown to increase the risk of breast cancer, this has not been well studied in veterinary science. In our preliminary study, we discovered that leptin downregulated cathepsin A, which is responsible for lysosomal-associated membrane protein 2a (LAMP2a) degradation. LAMP2a is a rate-limiting factor in chaperone-mediated autophagy and is highly active in malignant cancers. Therefore, in this study, alterations in metastatic capacity through cathepsin A by leptin, which are secreted at high levels in the blood of obese patients, were investigated. We used a canine inflammatory mammary gland adenocarcinoma (CHMp) cell line cultured with RPMI-1640 and 10% fetal bovine serum. The samples were then subjected to real-time polymerase chain reaction, Western blot, immunocytochemistry, and lysosome isolation to investigate and visualize the metastasis and chaperone-mediated autophagy-related proteins. Results showed that leptin downregulated cathepsin A expression at both transcript and protein levels, whereas LAMP2a, the rate-limiting factor of chaperone-mediated autophagy, was upregulated by inhibition of LAMP2a degradation. Furthermore, leptin promoted LAMP2a multimerization through the lysosomal mTORC2 (mTOR complex 2)/PH domain and leucine rich repeat protein phosphatase 1 (PHLPP1)/AKT1 (Serine/threonine-protein kinase 1) pathway. These findings suggest that targeting leptin receptors can alleviate mammary gland cancer cell metastasis in dogs.

Effect of a Weight Loss Program on Biochemical and Immunological Profile, Serum Leptin Levels, and Cardiovascular Parameters in Obese Dogs

This study aimed to investigate the effects of a weight loss program (WLP) on biochemical and immunological profile, and cardiovascular parameters in a cohort of dogs with naturally occurring obesity. Eleven obese dogs [body condition scoring (BCS), ≥7/9] were enrolled into the study and underwent clinical and cardiovascular examination, and blood testing before (T0) and after 6 months (T1) of WLP. Eleven normal weight (BCS, 4/5) healthy dogs were used as a control (CTR) group. Compared to the CTR group, at T0 obese dogs expressed higher serum leptin concentrations (p < 0.0005) that significantly decreased after weight loss (p < 0.005) but remained higher than the CTR group. Furthermore, obese dogs showed considerably lower levels (p < 0.0005) of regulatory T cell (Treg) compared to the CTR group, but they did not change after weight loss at T1. In obese dogs, tumor necrosis factor (TNF)-α and interleukin (IL)-6 concentrations were substantially reduced at T1 (p < 0.0001 and p < 0.005). Regarding the cardiovascular parameters, only one obese dog was hypertensive at T0, and systolic blood pressure values showed no significant differences at the end of the WLP. The ratio of interventricular septal thickness in diastole to left ventricle internal diameter in diastole (IVSd/LVIDd) was significantly greater in obese dogs at T0 than in the CTR group (p < 0.005). It decreased after weight loss (p < 0.05). In obese dogs, troponin I level significantly reduced with weight loss (p < 0.05), while endothelin-1 level did not differ statistically. The results suggest that the immune dysregulation in the presence of high leptin levels and reduced number of Treg could affect obese dogs as well as humans. Based on our findings, we may speculate that a more complete immune-regulation restore could be obtained by a greater reduction in fat mass and a longer-term WLP. Finally, left ventricular remodeling may occur in some obese dogs. However, in canine species, further studies are needed to investigate the impact of obesity and related WLP on cardiovascular system.

Markers of inflammation and insulin resistance in dogs before and after weight loss versus lean healthy dogs

ABSTRACT: Chronic low-grade inflammation in obesity is characterized by an increased production of pro-inflammatory cytokines that contribute to insulin resistance. For this study body composition, markers of inflammation and of insulin resistance in dogs before and after weight loss were compared to those of lean dogs. Eleven client-owned obese adult dogs underwent a weight loss program with commercial dry food for weight loss and reached an ideal body condition score (BCS) six months after the beginning of the weight loss program. A Control Group of nine dogs with ideal BCS were selected for the comparison. Shapiro-Wilk test was used to test for normality, Mann Whitney were used for non-normally distributes data, and Student t-test was used for normally distributed parameters. In the Obese Group body fat decreased from 41.6% (30.7-58.6) to 29.1% (18.6-46.3) (P<0.01) and dogs maintained lean body mass throughout the weight loss program (P>0.05). Obese dogs presented higher concentration of fructosamine, triglycerides, insulin, IGF-1 and leptin than the Control Group before weight reduction (P<0.05). Serum concentrations of triglycerides, IL-2, IL-6, TNF-α, insulin, leptin and IGF-1 decreased after weight loss (P<0.01), and these concentrations were similar to the Control Group (P>0.05), except for leptin (P<0.001). No alteration on peptide YY was found. Leptin (r=0.60, P=0.01), fructosamine (r=0.44, P=0.02) and triglycerides (r=0.40, P=0.04) concentrations correlated with the reduction of body fat. Weight loss reduced the concentrations of inflammatory and insulin resistance markers and most parameters became similar to dogs that have always been lean, reinforcing the importance of weight loss in small animal practice.

Relationship of serum leptin concentration with pituitary-dependent hyperadrenocorticism and cholestatic disease in dogs

OBJECTIVES

To measure serum leptin concentration in dogs with pituitary-dependent hyperadrenocorticism and varying degrees of cholestatic disease and determine whether serum levels differed between dogs with pituitary-dependent hyperadrenocorticism and those with gall bladder mucocoele.

MATERIALS AND METHODS

Client-owned healthy dogs (n=20), dogs diagnosed with gall bladder mucocoele (n=20) and dogs diagnosed with pituitary-dependent hyperadrenocorticism (n=60) were enrolled. Only dogs of normal body condition score were included. Dogs with pituitary-dependent hyperadrenocorticism were divided into three groups according to the severity of cholestatic disease: normal gall bladder (n=20), cholestasis (n=20) and gall bladder mucocoele (n=20). Serum leptin levels were measured using sandwich enzyme-linked immunosorbent assay.

RESULTS

Serum concentrations of leptin were similar between dogs with gall bladder mucocoele and those with pituitary-dependent hyperadrenocorticism accompanied by gall bladder mucocoele; these concentrations were significantly higher than those in healthy control dogs. In dogs with pituitary-dependent hyperadrenocorticism, circulating leptin concentration significantly increased with the severity of cholestasis: higher in the cholestasis group than the normal gall bladder group and higher in the gall bladder mucocoele group than the cholestasis group.

CLINICAL SIGNIFICANCE

Elevated circulating leptin concentration was associated with canine pituitary-dependent hyperadrenocorticism and gall bladder mucocoele. Homeostatic imbalance of leptin concentration might be associated with severity of cholestatic disease in pituitary-dependent hyperadrenocorticism.

Leptin and Immunological Profile in Obesity and Its Associated Diseases in Dogs

Growing scientific evidence has unveiled increased incidences of obesity in domestic animals and its influence on a plethora of associated disorders. Leptin, an adipokine regulating body fat mass, represents a key molecule in obesity, able to modulate immune responses and foster chronic inflammatory response in peripheral tissues. High levels of cytokines and inflammatory markers suggest an association between inflammatory state and obesity in dogs, highlighting the parallelism with humans. Canine obesity is a relevant disease always accompanied with several health conditions such as inflammation, immune-dysregulation, insulin resistance, pancreatitis, orthopaedic disorders, cardiovascular disease, and neoplasia. However, leptin involvement in many disease processes in veterinary medicine is poorly understood. Moreover, hyperleptinemia as well as leptin resistance occur with cardiac dysfunction as a consequence of altered cardiac mitochondrial metabolism in obese dogs. Similarly, leptin dysregulation seems to be involved in the pancreatitis pathophysiology. This review aims to examine literature concerning leptin and immunological status in obese dogs, in particular for the aspects related to obesity-associated diseases.

Preactivation of neutrophils and systemic oxidative stress in dogs with hyperleptinemia

High occurrence of obesity currently constitutes the main nutritional disease of the canine species. There is evidence that leptin increases during obesity in dogs. Hyperleptinemia is associated with increased neutrophil oxidative metabolism in obese humans and contributes to oxidative stress. However, in obese dogs, the probable relationship between this condition and the activation of the oxidative metabolism of neutrophils has yet to be established. Thus, we investigated the hypothesis that neutrophil activation and systemic oxidative stress occur in dogs with hyperleptinemia. A control group of 24 healthy dogs with a body condition score (BCS) of 4-5, an overweight group of 25 dogs with a BCS of 6-7, and 27 obese dogs with a BCS of 8-9, were composed. Two subgroups were formed composed of dogs with and without hyperleptinemia, grouped according to the 95% confidence interval obtained for plasma leptin values of the control group. Changes in obesity markers (body condition score, adiponectin and plasma leptin) and plasma oxidative stress (lipid peroxidation, total antioxidant and oxidant capacities and oxidative stress index) were measured in all the dogs selected. Neutrophil oxidative metabolism was evaluated in flow cytometry by superoxide production with the probe hydroethidine and by hydrogen peroxide production with the probe 2',7'-dichlorofluorescein diacetate, with or without phorbol myristate acetate (PMA) stimulation. Apoptosis and neutrophil viability were quantified in a capillary flow cytometer using Annexin VPE, with or without camptothecin apoptosis inducing effect. Obese dogs presented higher systemic oxidative stress, hyperleptinemia and preactivated neutrophils with accelerated apoptosis. Dogs with hyperleptinemia and obese dogs presented higher neutrophil superoxide production under PMA stimulation and the presence of systemic oxidative stress compared with control. To our knowledge, this is probably the first evidence that preactivation of the oxidative metabolism of circulating neutrophils occurs in dogs with hyperleptinemia, a condition that can induce systemic oxidative stress in the canine species.

Macronutrient intake of dogs, self-selecting diets varying in composition offered ad libitum

The diet of the domestic dog has changed significantly from that of its wolf ancestor, with to date only two studies having examined macronutrient self-selection in dogs. Whilst the first focused solely on protein intake, determining an intake of 30% metabolisable energy (ME), the second investigated dietary protein, fat and carbohydrate (PFC), indicating an intake ratio of 30:63:7% by energy. This study's aim was to further elucidate macronutrient intake by providing greater macronutrient range, energy content, and to investigate over a longer duration than previous studies. Fifteen adult dogs were given access to three wet diets providing 500% of daily ME, twice daily over 10 days. The diets were nutritionally complete and formulated using the same four ingredients in different proportions to supply high levels of protein (58% ME), fat (86% ME) or carbohydrate (54% ME). Overall fat and carbohydrate consumption significantly declined from 6,382 to 917 kcals per day (p < 0.001) and 553 to 214 kcals day^-1 (p < .01) respectively. Protein intake, however, remained constant over the study and ranged from 4,786 to 4,156 kcals day^-1 . Such results impacted on percentage total energy intake, with fat decreasing from 68% to 52% (p < .001) and protein increasing from 29% to 44% (p < .01). Our findings suggest that dogs still possess a "feast or famine" mentality, wherein energy dense fat is prioritised over protein initially. With continued feeding over 10 days, a transition to a more balanced energy contribution from both macronutrients is evident. The study also shows that given the option, dogs do not select carbohydrate to be a significant portion of the diet. The health implications of such dietary selection are of interest.

Other Risks/Possible Benefits of Obesity

Obesity is not a cosmetic or social issue; it is an animal health issue. The metabolic effects of obesity on insulin resistance and development of hyperlipidemia and the mechanical stress excess weight places on the musculoskeletal system are well established in the literature. Additional health risks from obesity, such as fatty accumulation in the liver, intestinal bacterial dysbiosis, and changes to renal architecture, are less well understood, but have been demonstrated to occur clinically in obese animals and may lead to deleterious long-term health effects. Keeping dogs and cats lean lowers their risk for development of certain diseases and leads to a longer and better quality of life.

Pervasive Effects of Aging on Gene Expression in Wild Wolves

Gene expression levels change as an individual ages and responds to environmental conditions. With the exception of humans, such patterns have principally been studied under controlled conditions, overlooking the array of developmental and environmental influences that organisms encounter under conditions in which natural selection operates. We used high-throughput RNA sequencing (RNA-Seq) of whole blood to assess the relative impacts of social status, age, disease, and sex on gene expression levels in a natural population of gray wolves (Canis lupus). Our findings suggest that age is broadly associated with gene expression levels, whereas other examined factors have minimal effects on gene expression patterns. Further, our results reveal evolutionarily conserved signatures of senescence, such as immunosenescence and metabolic aging, between wolves and humans despite major differences in life history and environment. The effects of aging on gene expression levels in wolves exhibit conservation with humans, but the more rapid expression differences observed in aging wolves is evolutionarily appropriate given the species' high level of extrinsic mortality due to intraspecific aggression. Some expression changes that occur with age can facilitate physical age-related changes that may enhance fitness in older wolves. However, the expression of these ancestral patterns of aging in descendant modern dogs living in highly modified domestic environments may be maladaptive and cause disease. This work provides evolutionary insight into aging patterns observed in domestic dogs and demonstrates the applicability of studying natural populations to investigate the mechanisms of aging.

Analyses of a satiety factor NUCB2/nesfatin-1; gene expressions and modulation by different dietary components in dogs

Nesfatin-1 is an anorexic peptide derived from a precursor, nucleobindin-2 (NUCB2), which is distributed in various organs, coexists with ghrelin in the gastric X/A-like cells and closely relates to an appetite control in rodents and humans. Nesfatin-1 may be a significant factor addressing the satiety also in veterinary medicine, however, there are few reports about nesfatin-1 in dogs. In the present study, we detected canine NUCB2/nesfatin-1 mRNA in various tissues, especially abundant in pancreas, gastrointestinal tracts, testis and cerebellum. We examined circulating nesfatin-1 concentrations and NUCB2/nesfatin-1 mRNA expressions in upper gastrointestinal tracts (gastric corpus, pyloric antrum and duodenum) in dogs fed on different types of diets. Plasma nesfatin-1 concentrations in the dogs were approximately 4 ng/ml and they did not change after feeding through the study, however, NUCB2/nesfatin-1 mRNA expressions in pyloric antrum were 1.84-fold higher in the dogs fed on a High fiber/High protein diet (P<0.001), 1.48-fold higher in the dogs fed on a High fat/Low protein diet (P<0.05) and 1.02-fold higher in the dogs fed on a Low fat/High carbohydrate diet (not significant) comparing to those on a control diet. It was concluded that High fiber/High protein and High fat/Low protein diets increased NUCB2/nesfatin-1 production in canine gastrointestinal tracts. These results may set the stage for further investigations of canine NUCB2/nesfatin-1, which may relate to satiety effects in dogs.

The associations between serum adiponectin, leptin, C-reactive protein, insulin, and serum long-chain omega-3 fatty acids in Labrador Retrievers

Obesity has been associated with an increased inflammatory response and insulin resistance due to adipose tissue–derived adipokines and increases in C-reactive protein (CRP). Dogs appear to be similar to other species with the exception of adiponectin, which might not be affected by obesity status. Serum long-chain polyunsaturated fatty acid concentrations have been positively and negatively associated with serum adipokines. The aim of the study was to examine the relationship between leptin, CRP, adiponectin, and insulin to body condition score (BCS) and to the long-chain omega-3 fatty acids in serum lipoproteins, including alpha-linolenic acid, eicosapentaenoic acid (EPA), docosapentanenoic acid (DPA), and docosahexaenoic acid (DHA) as a reflection of dietary omega-3 status in the Labrador Retriever. Seventy-seven Labrador Retrievers were evaluated for BCS, percent fasting serum lipoprotein fatty acid concentrations, as well as serum leptin, adiponectin, insulin, and CRP. A multivariable general linear regression model was constructed to examine the association between the dependent variables leptin, CRP, adiponectin, and insulin and the predictor variables of BCS, age, and sex, as well as concentrations of alpha-linolenic acid, EPA, DHA, and DPA. Adiponectin concentration was positively associated with age (P<0.0008), EPA (P=0.027) and negatively associated with DHA (P=0.008). Leptin concentration was positively associated with an increased DHA (P=0.009), BCS (P<0.0001), age (P=0.02), and decreased DPA (P=0.06). Insulin concentration was only associated with BCS (P<0.0001), and no meaningful associations were found for CRP. Longer chain omega-3 fatty acids may play a role in regulating adiponectin concentrations in dogs. However, because insulin concentrations were associated only with BCSs, further examination of the role of adiponectin in canine obesity is warranted. EPA and DPA may reduce the overall inflammatory state in dogs as these omega-3 fatty acids reflect increased adiponectin (increased EPA and decreased DHA) and decreased leptin (decreased DHA and increased DPA).

Serum adipokine concentrations in dogs with acute pancreatitis

Background

Limited information is available about the role of adipokines in the development and progression of acute pancreatitis (AP) in dogs.

Objectives

To determine whether the circulating concentrations of adipokines differed between healthy dogs and dogs with AP, and whether the circulating concentrations differed between AP survivors and AP nonsurvivors.

Animals

Twenty‐eight healthy dogs and 25 client‐owned dogs with AP.

Methods

Prospective observational cohort study of 25 client‐owned dogs with newly diagnosed AP and 28 otherwise healthy dogs with similar body condition scores. The serum concentrations of leptin, adiponectin, resistin, visfatin, interleukin (IL)‐1β, IL‐6, IL‐10, IL‐18, and tumor necrosis factor (TNF)‐α were measured.

Results

The serum concentrations of leptin (P = .0021), resistin (P = .0010), visfatin (P < .0001), IL‐1β (P < .0001), IL‐6 (P = .0002), IL‐10 (P < .0001), and IL‐18 (P < .0001) were significantly higher in dogs with AP than healthy dogs, whereas the adiponectin concentration (P = .0011) was significantly lower. There were significant differences in the serum concentrations of leptin (P = .028) and adiponectin (P = .046) in survivors and nonsurvivors. After the disappearance of clinical signs, the concentrations of resistin (P = .037) and IL‐1β (P = .027) decreased significantly, whereas the serum concentrations of leptin (P > .999), adiponectin (P = .11), visfatin (P = .83), IL‐6 (P = .82), IL‐10 (P = .82), IL‐18 (P = .56), and TNF‐α (P = .94) did not differ significantly.

Conclusion and Clinical Importance

This study showed that dysregulation of adipokines might be involved in the pathogenesis of AP. In addition, leptin and adiponectin are likely to be associated with mortality rate in AP.

Body fat distribution and metabolic consequences - Examination opportunities in dogs

The relationship between metabolic disorders and the distribution of fat in different body regions is not clearly understood in humans. The aim of this study was to develop a suitable method for assessing the regional distribution of fat deposits and their metabolic effects in dogs. Twenty-five dogs were subjected to computed tomographic (CT) imaging and blood sampling in order to characterise their metabolic status. The different fat areas were measured on a cross-sectional scan, and the animals' metabolic status was evaluated by measuring fasting glucose, insulin and leptin levels. The volume of visceral adipose tissue is the main determinant of leptin levels. The correlation of visceral fat volume and leptin concentration was found to be independent of insulin levels or the degree of insulin resistance. There was a positive correlation between the visceral to subcutaneous fat volume ratio and serum insulin concentration, and a similar trend was observed in the relationship of fat ratio and insulin resistance. The distribution of body fat essentially influences the metabolic parameters in dogs, but the effects of adiposity differ between humans and dogs. The findings can facilitate a possible extrapolation of results from animal studies to humans with regard to the metabolic consequences of different obesity types.

Serum adipokine concentrations in dogs with naturally occurring pituitary-dependent hyperadrenocorticism

BACKGROUND

An excess of intra-abdominal fat is observed frequently in dogs with hyperadrenocorticism (HAC). Adipokine dysregulation is a possible cause of complications related to visceral obesity, but little information is available on adipokine in dogs with naturally occurring HAC.

OBJECTIVES

To examine the differences in the circulating adipokines concentrations in overweight dogs with and without pituitary-dependent HAC (PDH).

ANIMALS

Thirty healthy dogs and 15 client-owned dogs with PDH.

METHODS

Case-controlled observational study, which enrolled 15 overweight dogs diagnosed with PDH and 30 otherwise healthy dogs of similar body condition score. Nine of 15 dogs with PDH were treated with low-dose trilostane twice daily and reassessed after treatment.

RESULTS

The serum leptin (P < .0001) and insulin (P < .0001) concentrations were significantly higher in the PDH group (leptin, 22.8 ± 8.8 [mean ± SD]; insulin, 9.1 ± 6.1) than the healthy group (leptin, 4.9 ± 3.7; insulin, 1.9 ± 0.9). However, there were no significant differences in the adiponectin, resistin, tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, IL-10, and IL-18 levels between the 2 groups. In the PDH group, the serum cortisol concentrations had a linear association with the leptin concentrations, and there were significant decreases in the leptin (P = .0039) and insulin (P = .0039) levels after trilostane treatment. However, the leptin and insulin levels remained higher after trilostane treatment than in healthy control dogs with similar body condition score.

CONCLUSIONS AND CLINICAL IMPORTANCE

Hypercortisolemia in dogs with PDH might upregulate the circulating leptin levels. However, a large population-based study will be necessary to determine whether the upregulation of leptin is involved directly with the complications caused by HAC.

Serum adiponectin concentration in dogs - absence of diurnal variation and lack of effect of feeding and methylprednisolone administration

The aim of the study was to determine the magnitude of diurnal variability of serum adiponectin in healthy beagle dogs, and the possible roles of feeding and glucocorticoids on adiponectin concentrations. For this, adiponectin was measured at 8:00, 10:00, 12:00, 16:00, 20:00, 24:00 and at 4:00 h in 4 beagle dogs that were fasted on the day of the experiment and in 4 dogs that were fed as usual at 9:00 h. Diurnal variability in serum adiponectin concentrations was negligible in both the fed and the fasted dogs. To study the possible effect of glucocorticoids on adiponectin, beagle dogs (n = 14) were assigned to one of three experimental groups. Dogs of the control group were injected with 0.1 ml/kg 0.9% NaCl subcutaneously, while dogs of Groups 1 and 2 were injected with 1 mg/kg and 5 mg/kg of methylprednisolone, respectively, and adiponectin was measured at 8:00, 10:00, 12:00, 16:00 and 20:00 h. Average serum adiponectin levels were not significantly different before and after methylprednisolone exposure at different time-points in the two treated groups. In conclusion, no evidence of postprandial changes in adiponectin level or effects of single-dose glucocorticoid administration on adiponectin were observed in the present study.

Effects of thyroxin therapy on different analytes related to obesity and inflammation in dogs with hypothyroidism

Hypothyroidism in dogs is accompanied by changes in intermediary metabolism including alterations in bodyweight (BW), insulin resistance, and lipid profile. In this study, changes in selected adipokines (adiponectin, leptin), butyrylcholinesterase (BChE), and acute phase proteins, including C-reactive protein, haptoglobin (Hp) and serum amyloid A (SAA), were studied in dogs with hypothyroidism under thyroxin therapy. Blood samples were collected when hypothyroidism was diagnosed (before treatment) and after treatment with thyroxin. Twenty-eight of 39 dogs exhibited a good therapeutic response (group A), whereas the remainder were considered to have been insufficiently treated (group B). Following treatment, group A dogs demonstrated a statistically significant decrease in canine thyroid stimulating hormone (c-TSH) (P<0.001) and an increase in free thyroxine (fT4) (P<0.001) concentrations, associated with a significant decrease in BW (P<0.05), leptin (P<0.01), and adiponectin, (P<0.001) and an increase in BChE (P<0.01) and Hp (P<0.05). Group B dogs showed no statistically significant changes in c-TSH, but had a significant increase in fT4 (P<0.001) accompanied by a significant decrease in adiponectin (P<0.05) of lower magnitude than group A. No significant changes in the mean circulating levels of APPs were observed in both groups, with the exception of an increase in Hp (P<0.05) in group A. In summary, the successful treatment of hypothyroidism reduces circulating levels of adiponectin and leptin, while increasing BChE activity in dogs. The mean increase in Hp values and decrease in SAA for some of the dogs after treatment warrants further investigation.

Short-term increase of body weight triggers immunological variables in dogs

Overweight in dogs is, as in other companion animals, a major risk factor for several metabolic disorders. However, it is not yet known whether immunity is challenged by increased body weight in dogs. The aim of this study was to investigate the effect of a short-term increase in body weight on immunological variables in adult healthy beagle dogs. Sixteen dogs, divided into a control group (CG) and weight gain group (WGG), were included. During a period of 13 weeks, the CG was fed at maintenance energy requirement (MER), whereas the WGG received a double amount of food. After 13 weeks, blood samples were taken for immunological and biochemical analyses. Weight gain and increased body condition score in the WGG were accompanied by a significant higher leptin concentration. Weight gain increased the number of lymphocytes and immunoglobulins A and M and was responsible for a higher proliferation of peripheral blood mononuclear cells (PBMC). Short-term increase of body weight thus seems to trigger immunological variables in dogs.

Leptin expression in dogs with cardiac disease and congestive heart failure

BACKGROUND

Leptin belongs to the group of adipokines and has recently attracted attention because of its effects on the cardiovascular system. Increased leptin concentrations are reported in obese dogs but its role in cardiac disease (CD) is not known. Therefore, we investigated leptin expression in blood samples from dogs with congestive heart failure (CHF), and from myocardial samples of dogs with CDs.

METHODS

Leptin mRNA was analyzed from blood samples of 8 dogs presented for cardiac screening in which no abnormalities were detected and 8 dogs in CHF. In addition, myocardial samples (interventricular septum, right and left atria, and ventricles) of 10 dogs with no cardiac abnormalities (controls), 7 dogs with acquired and 3 dogs with congenital CDs were investigated using real-time polymerase chain reaction (PCR).

RESULTS

Dogs with CHF had significantly higher blood concentrations of leptin mRNA than dogs without CD (P = .013). Myocardial leptin expression was significantly increased in acquired (P = .035) and decreased in congenital CD (P = .016) in comparison to controls. Dogs in heart failure stage D showed higher myocardial leptin concentrations than dogs in stage C3 and B (P = .031). Differences according to myocardial region (P < .05) were detected and higher leptin concentrations were present in the atria in comparison to the ventricles in dogs with CD (P = .005). Comparing male and female dogs with CD revealed higher leptin concentrations in female dogs (P = .001).

CONCLUSIONS

These results indicate leptin mRNA concentrations vary with CD, severity of CD, myocardial region, and possibly sex. Therefore, leptin might play a role in canine CD.

Compensation for obesity-induced insulin resistance in dogs: assessment of the effects of leptin, adiponectin, and glucagon-like peptide-1 using path analysis

The hormonal mediators of obesity-induced insulin resistance and compensatory hyperinsulinemia in dogs have not been identified. Plasma samples were obtained after a 24-h fast from 104 client-owned lean, overweight, and obese dogs. Plasma glucose and insulin concentrations were used to calculate insulin sensitivity and β-cell function with the use of the homeostasis model assessment (HOMA(insulin sensitivity) and HOMA(β-cell function), respectively). Path analysis with multivariable linear regression was used to identify whether fasting plasma leptin, adiponectin, or glucagon-like peptide-1 concentrations were associated with adiposity, insulin sensitivity, and basal insulin secretion. None of the dogs were hyperglycemic. In the final path model, adiposity was positively associated with leptin (P < 0.01) and glucagon-like peptide-1 (P = 0.04) concentrations. No significant total effect of adiposity on adiponectin in dogs (P = 0.24) was observed. If there is a direct effect of leptin on adiponectin, then our results indicate that this is a positive relationship, which at least partly counters a negative direct relationship between adiposity and adiponectin. Fasting plasma leptin concentration was directly negatively associated with fasting insulin sensitivity (P = 0.01) and positively associated with β-cell function (P < 0.01), but no direct association was observed between adiponectin concentration and either insulin sensitivity or β-cell function (P = 0.42 and 0.11, respectively). We conclude that dogs compensate effectively for obesity-induced insulin resistance. Fasting plasma leptin concentrations appear to be associated with obesity-associated changes in insulin sensitivity and compensatory hyperinsulinemia in naturally occurring obese dogs. Adiponectin does not appear to be involved in the pathophysiology of obesity-associated changes in insulin sensitivity.

The potential role of leptin and adiponectin in obesity: a comparative review

Leptin and adiponectin are adipokines produced by the white adipose tissue. The adipokines have been shown to be valuable quantitative markers of adiposity in dogs. Leptin positively correlates with body condition score (BCS) in dogs, regardless of age, sex and breed, and is influenced by feeding state, pharmacological treatment and thyroid gland activity. Conversely, adiponectin negatively correlates with body fat mass and is therefore more abundant in lean animals. The implication of leptin and adiponectin in the pathogenesis of metabolic syndrome is well established in humans, but currently lacking in dogs. Additional studies are necessary to demonstrate their potential usefulness for monitoring the progression of obesity-related diseases and response to treatment. To date, measurement of canine leptin and adiponectin has been used in experimental studies only, whereas bodyweight and BCS are considered the first-approach parameters for the routine assessment of body fat content in obese dogs.

Assessment of five ELISAs for measurement of leptin concentrations in dogs

OBJECTIVE

To evaluate 5 commercially available ELISAs for determination of leptin concentrations in serum samples from dogs.

SAMPLE POPULATION

Serum samples from overweight-obese and thin-ideal weight clientowned dogs.

PROCEDURES

Serum samples with high and low leptin concentrations (n = 7 samples each) were used for validation of the assays. Intra- and interassay precision, linearity under dilution, spiking recovery, and limit of quantification were determined. In addition, leptin concentrations in thin-ideal weight (n = 8) and overweight-obese (37) dogs were quantified.

RESULTS

Use of 2 of the 5 ELISAs (A and B) revealed reactivity with canine leptin. Intra-and interassay coefficients of variation were < 6.1% and 76%, respectively, for assay A and 14.0% and 13.7%, respectively, for assay B. In assays A and B, dilutions of canine serum pools were used to determine linear regression equations. Recoveries were 77% to 101% for assay A and 67% to 125% for assay B. Significant differences in leptin concentrations between thin-ideal weight and overweight-obese dogs were detected only when analyzed with assay A.

CONCLUSIONS AND CLINICAL RELEVANCE

Among 5 leptin ELISAs evaluated, a canine-specific leptin ELISA had adequate precision, linearity, and ability to discriminate between high and low leptin concentrations corresponding to overweight-obese and thin-ideal weight dogs, respectively.

Postprandial lipid-related metabolites are altered in dogs fed dietary diacylglycerol and low glycemic index starch during weight loss

In this study, we investigated a combination of a low glycemic index starch (LGIS) and diacylglycerol (DAG) on lipid, lipoprotein (LP) metabolism, and weight management. Obese, intact female adult Beagle dogs were assigned to 1 of 4 starch/oil combination diets [LGIS/DAG (LD); LGIS/triacylglycerol (TAG); high glycemic index starch (HGIS)/DAG; and HGIS/TAG (HT)] and fed for 9 wk (n = 6/group) using an incomplete 4 × 4 Latin square design. Each dog was fed 1 of 2 opposite starch/oil combination diets (e.g. LD and HT). At wk 1 and 8, postprandial blood was collected for plasma triacylglycerol (TG), β-hydroxybutyrate (BHB), total cholesterol (TC), and LP analyses. During the same week, dogs were overnight feed-deprived and post-heparin blood was collected for LP lipase and hepatic lipase activity determinations. At wk 1, 4, and 8, blood was drawn from overnight feed-deprived dogs for plasma TG, BHB, TC, LP, leptin, and adiponectin measurements. Feces were collected at wk 3 for digestibility calculations. The LGIS diets resulted in lower carbohydrate, protein, total tract dry matter digestibilities, and metabolizable energy compared with the HGIS diet groups (P < 0.05). Thus, the LGIS groups lost more body weight (P = 0.001), which was positively correlated with plasma leptin concentrations (r(2) = 0.427; P < 0.001). Moreover, the LGIS diet lowered TC concentrations in combination with DAG. The DAG diet groups decreased postprandial TG and increased BHB concentrations (P < 0.05). Starch/oil types did not alter lipase activities or adiponectin concentrations. In conclusion, the LGIS diet demonstrated potential as a weight management tool in dogs by decreasing postprandial TG and increasing BHB in combination with DAG.

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.

Endocrinology of obesity

Obesity is a growing health concern in humans and companion animals. Obesity is highly associated with various endocrine abnormalities that are characterized by hormonal imbalance and/or resistance. Weight reduction generally normalizes these endocrine alterations, implicating obesity as a direct cause. Most data in this area have been derived from obese humans, with little data pertaining to hormonal changes in obese dogs and cats. Because the literature contains inconsistent results and because considerable hormone-hormone interactions occur, we have a limited understanding of the obesity-induced changes on the endocrine system in dogs and cats.

Plasma leptin concentration in dogs with diabetes mellitus

The plasma leptin concentration was evaluated in dogs with diabetes mellitus. Twenty normal and sixteen diabetic dogs were divided into nonobese and obese groups based on body condition score, respectively. The obese normal dogs had significantly higher plasma leptin concentrations than the nonobese normal dogs, whereas there was no significant difference between the nonobese and obese diabetic dogs. In addition, the plasma leptin concentration in the obese diabetic dogs was significantly lower than that in the obese normal dogs. In conclusion, the plasma leptin concentrations in the diabetic dogs were affected by factors other than adiposity.

Unusually rapid growth and adult stature in an American hairless terrier puppy

A puppy was evaluated for rapid growth and large stature. Extensive diagnostic evaluation suggested a growth hormone independent disorder. As the sole detected abnormality was elevated leptin concentration, an obesity syndrome causing leptin resistance was speculated to explain the puppy's condition but was not confirmed. Except for large body size, the puppy remained clinically normal.

The effect of dietary supplementation with 9-cis:12-trans and 10-trans:12-cis conjugated linoleic acid (CLA) for nine months on serum cholesterol, lymphocyte proliferation and polymorphonuclear cells function in Beagle dogs

Conjugated linoleic acids (CLA), 9-cis:11-trans and 10-trans:12-cis, have been shown to be able to modify some immune cells parameters and plasma lipids in a variety of experiment models. Since lymphocytes and polymorphonuclear cells (PMNC) have a large spectrum functions in the immune response, the knowledge in this field has to be expanded. Beagle dogs were fed a control diet or a CLA supplemented diet for nine months. Blood was collected for biochemical analysis and lymphocyte and PMNC isolation. PMNC were assayed for lysosome content, phagocytic activity and superoxide anion production. A lymphocyte proliferation capacity assay was done. The CLA fed dogs had a 34% reduction in total cholesterol (P < 0.05), 28% in LDL (P < 0.05) and 28% non-HDL-cholesterol (P < 0.05). Neither of the PMNC parameters evaluated demonstrated significant alteration. Lymphocytes from CLA group increased by 45% their mitotic capacity (P < 0.05). Our study demonstrates that CLA can successfully modify the lipid profile of dogs (monogastrics) when fed at reasonable levels, but did not significantly alter inflammatory function as would generally predicted. Further, we had some indication that CLA modulated T cell responsiveness.

Inverse regulation of leptin mRNA expression by short- and long-chain fatty acids in cultured bovine adipocytes

Leptin is an adipose tissue-derived cytokine plays key roles in the regulation of food intake and energy expenditure. However, regulatory mechanisms of leptin gene expression are not fully elucidated in ruminants that utilize short-chain fatty acids (SCFA), known as volatile fatty acids, as principal energy sources. In this study, we determined effects of SCFA and long-chain fatty acids (LCFA) on leptin expression in bovine adipocytes. Bovine stromal vascular cells isolated from subcutaneous adipose tissue of Holstein cows were cultured to confluence and treated sequentially with dexamethasone and isobutylmethylxanthine for 2 days and insulin and troglitazone for 12 days to achieve full differentiation to adipocytes. The cells started to accumulate lipids 4 days after the onset of treatment, with increased mRNA expression of leptin, as well as aP2, adiponectin, and PPAR-gamma. Removal of fetal calf serum and reduction of glucose in the culture medium of differentiated adipocytes decreased leptin mRNA expression. Subsequent addition of acetate, butyrate, or propionate dose-dependently restored and rather increased leptin expression, while addition of LCFA suppressed it. The stimulatory effect of acetate was abolished by prior treatment of the cells with pertussis toxin and by addition of LCFA. Furthermore, cows fasted for 48h and fed thereafter, elaborate reduced and increased plasma leptin levels, respectively. Thus, these results suggest that plasma leptin levels in cows are inversely controlled at the transcription level by VFA and LCFA, and that the effects of SCFA possibly act through a G protein-coupled receptor for SCFA.

β3-Adrenoceptor agonist AJ-9677 reduces body fat in obese beagles

A selective beta3-adrenoceptor agonist, AJ-9677, was reported to ameliorate obesity and insulin resistance in KK-Ay mice. We examined the acute and chronic effects of AJ-9677 on obese dogs. Oral administration of AJ-9677 (0.01 or 0.1 mg/kg) to overnight fasted obese beagles produced a dose-dependent rise in the plasma levels of non-esterified fatty acids and insulin in 1h, followed by a gradual drop of the plasma glucose level. It produced no apparent abnormal behaviors, but easily detectable cutaneous flushing. Daily treatment of AJ-9677 at a lower dose (0.01 mg/kg) for three weeks produced no notable change in body weight, but at a higher dose (0.1 mg/kg) it reduced the body weight compared to a placebo treatment after seven weeks. Computed tomographic examinations revealed a remarkable reduction of body fat after the AJ treatment, being consistent with the histological observations that the adipose tissue of AJ-9677-treated dogs consisted of smaller and some multilocular adipocytes. The plasma levels of leptin and adiponectin were decreased and increased, respectively, after the AJ treatment, reflecting the reduction of adiposity. It was concluded that AJ-9677 is useful for the treatment of obesity in the dog.

Prevalence of obese dogs in a population of dogs with cancer

OBJECTIVE

To determine the body condition score (BCS) distribution for dogs examined at a teaching hospital and examine whether the BCS distribution for dogs with cancer differed significantly from the distribution for dogs without cancer.

SAMPLE POPULATION

1,777 dogs with cancer and 12,893 dogs without cancer.

PROCEDURES

A retrospective prevalence case-control study was conducted that used medical records from 1999 to 2004. Information was collected on BCS (9-point system), age, breed, sex, neuter status, diagnosis, and corticosteroid administration. Body condition score at the time of examination for cancer (dogs with cancer) or first chronologic visit (dogs without cancer) was recorded. Logistic regression was used to compare BCS prevalence distributions between groups.

RESULTS

The overall prevalence of obese dogs (BCS >or= 7/9) was 14.8% (2,169/14,670), and the overall prevalence of overweight dogs (BCS >or= 6/9 to < 7/9) was 21.6% (3,174/14,670). There was a significant difference in the BCS distribution between dogs with and without cancer, with a slightly lower prevalence of being overweight and obese in dogs with cancer. The prevalence of obese and overweight dogs varied with specific cancer types when compared with the prevalence for dogs without cancer.

CONCLUSIONS AND CLINICAL RELEVANCE

Differences in obesity prevalence among cancer types is suggestive of an incongruous effect of this variable on cancer expression or a differential effect of specific cancer types on weight status. Systematic use of BCSs will help elucidate the association between obesity and cancer development.

Serum concentrations of adiponectin and characterization of adiponectin protein complexes in dogs

OBJECTIVE

To assess serum concentrations of adiponectin and characterize adiponectin protein complexes in healthy dogs.

ANIMALS

11 healthy dogs.

PROCEDURES

Sera collected from 10 dogs were evaluated via velocity sedimentation and ultracentrifugation, SDS-PAGE, western immunoblotting, and radioimmunoassay. Visceral adipose tissue (approx 90 g) was collected from the falciform ligament of a healthy dog undergoing elective ovariohysterectomy, and adiponectin gene expression was assessed via a real-time PCR procedure.

RESULTS

Adiponectin gene expression was detected in visceral adipose tissue. Serum adiponectin concentrations ranged from 0.85 to 1.5 microg/mL (mean concentration, 1.22 microg/mL). In canine serum, adiponectin was present as a multimer, consisting of a low-molecular-weight complex (180 kd); as 3 (180-, 90-, and 60-kd) complexes under denaturing conditions; as 2 (90- and 60-kd) complexes under reducing conditions; and as a dimer, a monomer, and globular head region (60, 30, and 28 kd, respectively) under reducing-denaturing conditions. It is likely that adiponectin also circulates as a high-molecular-weight (360- to 540-kd) complex in canine serum, but resolution of this complex was not possible via SDS-PAGE.

CONCLUSIONS AND CLINICAL RELEVANCE

After exposure to identical experimental conditions, adiponectin protein complexes in canine serum were similar to those detected in human and rodent sera. Circulating adiponectin concentrations in canine serum were slightly lower than concentrations in human serum. Adiponectin gene expression was identified in canine visceral adipose tissue. Results suggest that adiponectin could be used as an early clinical marker for metabolic derangements, including obesity, insulin resistance, and diabetes mellitus in dogs.

Postprandial changes in leptin concentrations of cerebrospinal fluid in dogs during development of obesity

OBJECTIVE

To evaluate postprandial changes in the leptin concentration of CSF in dogs during development of obesity.

ANIMALS

4 male Beagles.

PROCEDURES

Weight gain was induced and assessments were made when the dogs were in thin, optimal, and obese body conditions (BCs). The fat area at the level of the L3 vertebra was measured via computed tomography to assess the degree of obesity. Dogs were evaluated in fed and unfed states. Dogs in the fed state received food at 9 AM. Blood and CSF samples were collected at 8 AM, 4 PM, and 10 PM.

RESULTS

Baseline CSF leptin concentrations in the thin, optimal, and obese dogs were 24.3 +/- 2.7 pg/mL, 86.1 +/- 14.7 pg/mL, and 116.2 +/- 47.3 pg/mL, respectively. In the thin BC, CSF leptin concentration transiently increased at 4 PM. In the optimal BC, baseline CSF leptin concentration was maintained until 10 PM. In the obese BC, CSF leptin concentration increased from baseline value at 4 PM and 10 PM. Correlation between CSF leptin concentration and fat area was good at all time points. There was a significant negative correlation between the CSF leptin concentration-to-serum leptin concentration ratio and fat area at 4 PM; this correlation was not significant at 8 AM and 10 PM.

CONCLUSIONS AND CLINICAL RELEVANCE

Decreased transport of leptin at the blood-brain barrier may be 1 mechanism of leptin resistance in dogs. However, leptin resistance at the blood-brain barrier may not be important in development of obesity in dogs.