Differential circulating concentrations of adipokines, glucagon and adropin in a clinical population of lean, overweight and diabetic cats

Obesity-induced changes in gene expression in feline adipose and skeletal muscle tissue

Indoor-confined cats are prone to developing obesity due to a sedentary life and an energy intake exceeding energy requirements. As in humans, feline obesity decreases insulin sensitivity and increases the risk of developing feline diabetes mellitus, but the pathophysiological mechanisms are currently poorly understood. Human obesity-related metabolic alterations seem to relate to changes in the expression of genes involved in glucose metabolism, insulin action and inflammation. The objective of the current study was to investigate changes in the expression of genes relating to obesity, glucose metabolism and inflammation in cats with non-experimentally induced obesity. Biopsies from the sartorius muscle and subcutaneous adipose tissue were obtained from 73 healthy, neutered, indoor-confined domestic shorthaired cats ranging from lean to obese. Quantification of obesity-related gene expression levels relative to glyceraldehyde-3-phosphate dehydrogenase was performed by quantitative real-time polymerase chain reaction. A negative association between obesity and adiponectin expression was observed in the adipose tissue (mean ± SD; normal weight, 27.30 × 10-3  ± 77.14 × 10-3 ; overweight, 2.89 × 10-3  ± 0.38 × 10-3 and obese, 2.93 × 10-3  ± 4.20 × 10-3 , p < 0.05). In muscle, the expression of peroxisome proliferative activated receptor-γ2 and plasminogen activator inhibitor-1 was increased in the obese compared to the normal-weight cats, and resistin was increased in the normal-weight compared to the overweight cats. There were no detectable obesity-related changes in the messenger RNA levels of inflammatory cytokines. In conclusion, a possible obesity-related low-grade inflammation caused by increased expression of key proinflammatory regulators was not observed. This could imply that the development of feline obesity and ensuing insulin resistance may not be based on tissue-derived inflammation, but caused by several determining factors, many of which still need further investigation.

Adipokines as potential biomarkers for type 2 diabetes mellitus in cats

Type 2 diabetes mellitus (T2DM) is no longer only a disease of humans, but also of domestic animals, and it particularly affects cats. It is increasingly thought that because of its unique characteristics, T2DM may belong not only to the group of metabolic diseases but also to the group of autoimmune diseases. This is due to the involvement of the immune system in the inflammation that occurs with T2DM. Various pro- and anti-inflammatory substances are secreted, especially cytokines in patients with T2DM. Cytokines secreted by adipose tissue are called adipokines, and leptin, adiponectin, resistin, omentin, TNF-α, and IL-6 have been implicated in T2DM. In cats, approximately 90% of diabetic cases are T2DM. Risk factors include older age, male sex, Burmese breed, presence of obesity, and insulin resistance. Diagnosis of a cat requires repeated testing and is complicated compared to human diagnosis. Based on similarities in the pathogenesis of T2DM between humans and cats, adipokines previously proposed as biomarkers for human T2DM may also serve in the diagnosis of this disease in cats.

Analytical performance of a canine ELISA monocyte chemoattractant protein-1 assay for use in cats and evaluation of circulating levels in normal weight and obese cats

BACKGROUND

In human and murine obesity, adipose tissue dwelling macrophages and adipocytes produce monocyte chemoattractant protein-1 (MCP-1) leading to systemic low-grade inflammation. The aim of the study was to validate a canine MCP-1 ELISA assay for use in cats and to investigate whether a difference in MCP-1 concentrations could be detected between: a) cats having normal or elevated circulating serum amyloid A (SAA) levels and b) normal weight and obese cats. Serum obtained from 36 client-owned cats of various breed, age and sex with normal (n = 20) to elevated SAA (n = 16) was used for the validation of the canine MCP-1 ELISA assay. As no golden standard exists for measurement of inflammation, circulating MCP-1 concentrations were compared to SAA measurements, as an indicator of systemic inflammation. Analytical precision, dilution recovery and detection limit were calculated. A possible correlation between MCP-1 concentrations and obesity related measures (body fat percentage (BF%), insulin sensitivity and cytokine expression) were investigated in another population of 73 healthy, lean to obese, neutered domestic short-haired cats.

RESULTS

Intra- (2.7-4.1%) and inter-assay (2.2-3.6%) coefficient of variation and dilution recovery were acceptable, and the detection limit was 27.1 pg/mL. MCP-1 did not correlate with SAA, and there was no difference between the inflammatory (SAA > 20 mg/L) and non-inflammatory group, due to a marked overlap in MCP-1 concentrations. Circulating MCP-1 concentrations were unaffected by BF% (r2 = 2.7 × 10-6, P = 0.21) and other obesity-related markers.

CONCLUSIONS

The present canine ELISA assay seems to be able to measure circulating feline MCP-1. However, further studies are needed to determine its possible use for detecting inflammation in relation to disease processes or obesity-related low-grade inflammation in cats.

Influence of high-protein and high-carbohydrate diets on serum lipid and fructosamine concentrations in healthy cats

OBJECTIVES

The aim of this study was to determine whether high-protein and high-carbohydrate diets exert differential effects on serum cholesterol, triglyceride and fructosamine concentrations in healthy cats.

METHODS

A randomised, crossover diet trial was performed in 35 healthy shelter cats. Following baseline health assessments, cats were randomised into groups receiving either a high-protein or high-carbohydrate diet for 4 weeks. The cats were then fed a washout diet for 4 weeks before being transitioned to whichever of the two studied diets they had not yet received. Fasting serum cholesterol, triglyceride and fructosamine concentrations were determined at the end of each 4-week diet period.

RESULTS

Cats on the high-carbohydrate diet had significantly lower serum cholesterol (P <0.001) concentrations compared with baseline measurements. Cats on the high-protein diet had significantly higher serum cholesterol (P <0.001) and triglyceride (P <0.001) concentrations, yet lower fructosamine (P <0.001) concentrations compared with baseline measurements. In contrast, overweight cats (body condition score [BCS] >5) had lower cholesterol (P = 0.007) and triglyceride (P = 0.032) concentrations on the high-protein diet than cats within other BCS groups.

CONCLUSIONS AND RELEVANCE

Diets higher in protein and lower in carbohydrates appear beneficial for short-term glucose control in healthy cats. A high-protein diet was associated with significantly elevated cholesterol and triglyceride concentrations in healthy cats, even though the increase was significantly less pronounced in cats with a BCS >5. This finding suggests that overweight cats process high-protein diets, cholesterol and triglycerides differently than leaner cats.

Measures of insulin sensitivity, leptin, and adiponectin concentrations in cats in diabetic remission compared to healthy control cats

Objectives

Firstly, to compare differences in insulin, adiponectin, leptin, and measures of insulin sensitivity between diabetic cats in remission and healthy control cats, and determine whether these are predictors of diabetic relapse. Secondly, to determine if these hormones are associated with serum metabolites known to differ between groups. Thirdly, if any of the hormonal or identified metabolites are associated with measures of insulin sensitivity.

Animals

Twenty cats in diabetic remission for a median of 101 days, and 21 healthy matched control cats.

Methods

A casual blood glucose measured on admission to the clinic. Following a 24 h fast, a fasted blood glucose was measured, and blood sample taken for hormone (i.e., insulin, leptin, and adiponectin) and untargeted metabolomic (GC-MS and LC-MS) analysis. A simplified IVGGT (1 g glucose/kg) was performed 3 h later. Cats were monitored for diabetes relapse for at least 9 months (270 days).

Results

Cats in diabetic remission had significantly higher serum glucose and insulin concentrations, and decreased insulin sensitivity as indicated by an increase in HOMA and decrease in QUICKI and Bennett indices. Leptin was significantly increased, but there was no difference in adiponectin (or body condition score). Several significant correlations were found between insulin sensitivity indices, leptin, and serum metabolites identified as significantly different between remission and control cats. No metabolites were significantly correlated with adiponectin. No predictors of relapse were identified in this study.

Conclusion and clinical importance

Insulin resistance, an underlying factor in diabetic cats, persists in diabetic remission. Cats in remission should be managed to avoid further exacerbating insulin resistance.

Changes in glucose tolerance and insulin secretion in a cohort of cats with chronic obesity

Obesity, which is the most common spontaneous nutritional disorder in cats, is a known risk factor for the development of diabetes mellitus and has been linked to insulin resistance, hyperinsulinemia, and altered adipose-derived hormone secretion in cats. The objective of this study was to monitor and report changes in the results of serial intravenous glucose tolerance testing (IVGTT) and other metabolic parameters in 4 obese cats over a 4-year period. Serial IVGTT, insulin sensitivity indices, adipokine concentrations, and lipid profiles were evaluated. All cats had IVGTT changes consistent with impaired glucose tolerance and altered insulin secretory patterns during the 4-year study period. There was no significant increase in the fasting blood glucose or insulin concentrations and no changes in the insulin sensitivity indices evaluated. The mean adiponectin concentration decreased significantly over time, but there was no significant increase in the leptin concentration and no changes were observed in lipid profiles. Although IVGTT can be used to document early and/or mild impairment of glucose tolerance and changes in insulin secretory pattern, this test cannot be easily or readily carried out on client-owned cats in most clinical settings. More work needs to be done to establish reliable, convenient methods for earlier identification of cats at risk of developing clinical diabetes mellitus.

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.

Association of circulating adipokine concentrations with indices of adiposity and sex in healthy, adult client owned cats

Background

Both diabetes mellitus (DM) and obesity are common in cats. The adipokines leptin, adiponectin, resistin and omentin are thought to have important roles in human obesity and glucose homeostasis; however, their functions in the pathophysiology of feline diabetes mellitus and obesity are poorly understood. We determined whether sexual dimorphism exists for circulating concentrations of these adipokines, whether they are associated with adiposity, and whether they correlate with basic indices of insulin sensitivity in cats. Healthy, client-owned male and female cats that were either ideal weight or obese were recruited into the study. Fasting blood glucose, fructosamine, cholesterol, triglycerides, insulin and plasma concentrations of adipokines were evaluated.

Results

Obese cats had greater serum concentrations of glucose and triglycerides than ideal weight cats, but fructosamine and cholesterol concentrations did not differ between groups. Body weight and body mass index were greater in male than female cats, but circulating metabolite cocentrations were similar between sexes of both the ideal weight and obese groups. Plasma concentrations of insulin and leptin were greater in obese than ideal weight cats, with reciprocal reduction in adiponectin concentrations in obese cats; there were no sex differences in these hormones. Interestingly, plasma omentin concentrations were greater in male than female cats but with no differences between obese and ideal weight states.

Conclusion

Together our findings suggest that rather than gender, body weight and adiposity are more important determinants of circulating concentrations of the adipokines leptin and adiponectin. On the contrary, the adipokine omentin is not affected by body weight or adiposity but instead exhibits sexual dimorphism in cats.

Adipokines secretion in feline primary adipose tissue culture in response to dietary fatty acids

Background

Obesity in cats has been associated with alterations in adipokines including: adiponectin, interleukin-6 (IL6), and tumor necrosis factor-α (TNFα). Omega-3 polyunsaturated fatty acids have multiple beneficial effects on obesity-associated disorders, and therefore may alleviate these alterations. This study aimed to determine the effects of body condition, fat depot, troglitazone, and different fatty acids on secretion of adiponectin, IL6 and TNFα from adipose tissue of healthy cats. Subcutaneous and visceral adipose tissue samples were collected from 18 healthy intact female cats, and body condition score (Range 3–7/9) was determined. Concentrations of adiponectin were measured in mature adipocytes cultures and concentrations of IL6 and TNFα were measured in stromovascular cells cultures following treatment with control medium, troglitazone at 10 μM, eicosapentaenoic acid, arachidonic acid, or palmitic acid, at 25, 50, or 100 μM.

Results

Stromovascular cells of visceral origin secreted higher concentrations of IL6 than corresponding cells of subcutaneous origin (P = 0.003). Arachidonic acid treatment at 25, 50, and 100 μM increased IL6 secretion in subcutaneous (P = 0.045, P = 0.002, and P < 0.001, respectively) and visceral (P = 0.034, P = 0.001, and P < 0.001, respectively) stromovascular cells. Eicosapentaenoic acid treatment increased TNFα secretion in subcutaneous stromovascular cells at 25, 50, and 100 μM (P = 0.002, P = 0.001, and P = 0.015, respectively) and in visceral stromovascular cells at 50 μM (P < 0.001). No significant effect on medium adiponectin concentration was observed following troglitazone treatment (P = 0.4) or fatty acids treatments at 25 (P = 0.2), 50 (P = 0.8), or 100 (P = 0.7) μM. Body condition score did not have significant effects on medium concentrations of adiponectin (P = 0.4), IL6 (P = 0.1), or TNFα (P = 0.8).

Conclusions

This study demonstrated higher basal secretion of IL6 from visceral compared to subcutaneous adipose tissue, a stimulatory effect of arachidonic acid on secretion of IL6 and a stimulatory effect of eicosapentaenoic acid on TNFα from feline adipose tissue.

Safety and efficacy assessment of a GLP-1 mimetic: insulin glargine combination for treatment of feline diabetes mellitus

A commonly used therapeutic strategy for type 2 diabetes mellitus (DM) in humans involves the use of synthetic incretin hormone-based therapies including exenatide, a glucagon-like pepetide-1 hormone agonist. Glucagon-like pepetide-1 agonists can be used alone or as an ancillary therapy with other agents, including insulin and oral antihyperglycemics. Little is known about the role of these therapies for DM in cats. Therefore, the primary objective of this study was to evaluate the safety and efficacy of short-acting exenatide combined with insulin, as compared to placebo and insulin for the treatment of DM in cats. Treatment with exenatide was well tolerated; only 2 cats developed side effects requiring dose reduction. Two cats (25%) went into diabetic remission while receiving exenatide and insulin, whereas remission was not reported during placebo treatment. The average change in the daily exogenous insulin dose was significant (β = -0.56 U/kg, 95% confidence interval, -0.96 to -0.15, P = 0.007), and the dose of insulin administered was lower during exenatide treatment. The average weight loss experienced on exenatide was significantly higher than on placebo (β = 0.65 kg, 95% confidence interval, 0.09-1.21, P = 0.02). There was no significant difference in any of the hormone concentrations evaluated for cats on exenatide vs placebo treatments. Overall, the treatment of diabetic cats with insulin and a fixed dose of exenatide was found to be safe. The weight loss and decreased exogenous insulin requirement experienced with exenatide treatment could be a significant benefit for overweight diabetic cats and warrants further evaluation.

Adiponectin is valuable in the diagnosis of acute heart failure with renal insufficiency

Acute heart failure (AHF) is a major public health issue due to its high incidence and poor prognosis; thus, efficient and timely diagnosis is critical for improving the prognosis and lowering the mortality rate. Amino-terminal pro-brain natriuretic peptide (NT-proBNP) is widely used in the diagnosis of AHF; however, its efficacy is controversial in diagnosing AHF with renal insufficiency. There were numerous studies reporting the association of adiponectin (ADPN) and heart diseases. Therefore, the present study aimed to investigate whether ADPN is helpful in identifying AHF with renal insufficiency. A total of 407 participants (218 AHF patients and 189 controls) were enrolled into the current study. The plasma levels of ADPN and NT-proBNP were measured using a sandwich enzyme-linked immunosorbent assay and an electrochemiluminescence immunoassay, respectively. In addition, these levels were compared among the various New York Health Association classes, as well as the ischemic and non-ischemic AHF cases. The correlation between the two biomarkers and the renal function was analyzed by Spearman's correlation, while the diagnostic efficiency of ADPN and NT-proBNP was evaluated in AHF patients with and without renal insufficiency. The results revealed that NT-proBNP exhibited a higher diagnostic efficiency as compared with ADPN in patients without renal insufficiency [area under the receiver operating characteristic curve (AUC), 0.905 vs. 0.775]. By contrast, the ADPN presented a better diagnostic value in comparison with NT-proBNP in AHF with renal insufficiency (AUC, 0.872 vs. 0.828). Therefore, a combination of these two biomarkers may provide an excellent efficacy in the diagnosis of AHF with renal insufficiency (AUC, 0.904; sensitivity, 71.2%; specificity, 98.3%). In conclusion, ADPN is a valuable biomarker for diagnosing AHF, particularly in patients with impaired renal function.

Associations of body condition score with health conditions related to overweight and obesity in cats

OBJECTIVES

To explore the associations of cat body condition score with various health conditions, such as diabetes mellitus, dermatological conditions and hypertension, that have been shown to relate to overweight and/or obesity in cats, dogs or humans.

MATERIALS AND METHODS

Electronic patient records between January 3, 2005 and June 21, 2015 were obtained from a cat-focused primary accession clinic in metropolitan Sydney where the body condition score of cats was routinely evaluated. Binomial logistic regression modelling was conducted to investigate the associations, after adjusting for age, sex and breed, between 21 health conditions and body condition score recorded on a 9-point scale.

RESULTS

Fourteen of the 21 health conditions examined showed significant associations with an increased body condition score, particularly those of 7 and above. These were dermatological conditions, atopic dermatitis, musculoskeletal conditions, arthritis, hypertension, respiratory conditions, asthma, oral conditions, diarrhoea, general and lower urinary tract conditions, ophthalmic conditions, diabetes mellitus and allergic conditions. Additionally, cats with body condition score of 8 or 9 had significantly higher odds for gastrointestinal conditions and upper urinary tract conditions when compared with cats with body condition score of 5.

CLINICAL SIGNIFICANCE

As far as we know, this is the first study reporting positive associations of high body condition score with atopic dermatitis, hypertension, asthma, diarrhoea, ophthalmic conditions and allergic conditions in cats. A large number of positive associations between health conditions and high body condition score indicates that excess fat mass should be given a greater emphasis in preventive health care for cats.