RESUMO
The endocannabinoid system is highly implicated in the development of insulin resistance associated with obesity. It has been shown that antagonism of the CB(1) receptor improves insulin sensitivity (S(I)). However, it is unknown whether this improvement is due to the direct effect of CB(1) blockade on peripheral tissues or secondary to decreased fat mass. Here, we examine in the canine dog model the longitudinal changes in S(I) and fat deposition when obesity was induced with a high-fat diet (HFD) and animals were treated with the CB(1) antagonist rimonabant. S(I) was assessed (n = 20) in animals fed a HFD for 6 wk to establish obesity. Thereafter, while HFD was continued for 16 additional weeks, animals were divided into two groups: rimonabant (1.25 mg·kg(-1)·day(-1) RIM; n = 11) and placebo (n = 9). Euglycemic hyperinsulinemic clamps were performed to evaluate changes in insulin resistance and glucose turnover before HFD (week -6) after HFD but before treatment (week 0) and at weeks 2, 6, 12, and 16 of treatment (or placebo) + HFD. Magnetic resonance imaging was performed to determine adiposity- related changes in S(I). Animals developed significant insulin resistance and increased visceral and subcutaneous adiposity after 6 wk of HFD. Treatment with RIM resulted in a modest decrease in total trunk fat with relatively little change in peripheral glucose uptake. However, there was significant improvement in hepatic insulin resistance after only 2 wk of RIM treatment with a concomitant increase in plasma adiponectin levels; both were maintained for the duration of the RIM treatment. CB(1) receptor antagonism appears to have a direct effect on hepatic insulin sensitivity that may be mediated by adiponectin and independent of pronounced reductions in body fat. However, the relatively modest effect on peripheral insulin sensitivity suggests that significant improvements may be secondary to reduced fat mass.
Assuntos
Resistência à Insulina/fisiologia , Fígado/metabolismo , Obesidade/tratamento farmacológico , Obesidade/metabolismo , Piperidinas/farmacologia , Pirazóis/farmacologia , Receptor CB1 de Canabinoide/antagonistas & inibidores , Gordura Abdominal/metabolismo , Gordura Abdominal/patologia , Adiponectina/sangue , Animais , Glicemia/metabolismo , Composição Corporal/efeitos dos fármacos , Composição Corporal/fisiologia , Antagonistas de Receptores de Canabinoides , Gorduras na Dieta/farmacologia , Modelos Animais de Doenças , Cães , Ingestão de Energia/fisiologia , Ácidos Graxos não Esterificados/sangue , Técnica Clamp de Glucose , Insulina/sangue , Masculino , Obesidade/patologia , Receptor CB1 de Canabinoide/metabolismo , RimonabantoRESUMO
BACKGROUND: Levels exceeding the standard reference interval (RI) for total thyroxine (TT4) concentrations are diagnostic for hyperthyroidism, however some hyperthyroid cats have TT4 values within the RI. Determining outlier TT4 concentrations should aid practitioners in identification of hyperthyroidism. The objective of this study was to determine the expected distribution of TT4 concentration using a large population of cats (531,765) of unknown health status to identify unexpected TT4 concentrations (outlier), and determine whether this concentration changes with age. METHODOLOGY/PRINCIPLE FINDINGS: This study is a population-based, retrospective study evaluating an electronic database of laboratory results to identify unique TT4 measurement between January 2014 and July 2015. An expected distribution of TT4 concentrations was determined using a large population of cats (531,765) of unknown health status, and this in turn was used to identify unexpected TT4 concentrations (outlier) and determine whether this concentration changes with age. All cats between the age of 1 and 9 years (n = 141,294) had the same expected distribution of TT4 concentration (0.5-3.5ug/dL), and cats with a TT4 value >3.5ug/dL were determined to be unexpected outliers. There was a steep and progressive rise in both the total number and percentage of statistical outliers in the feline population as a function of age. The greatest acceleration in the percentage of outliers occurred between the age of 7 and 14 years, which was up to 4.6 times the rate seen between the age of 3 and 7 years. CONCLUSIONS: TT4 concentrations >3.5ug/dL represent outliers from the expected distribution of TT4 concentration. Furthermore, age has a strong influence on the proportion of cats. These findings suggest that patients with TT4 concentrations >3.5ug/dL should be more closely evaluated for hyperthyroidism, particularly between the ages of 7 and 14 years. This finding may aid clinicians in earlier identification of hyperthyroidism in at-risk patients.
Assuntos
Biomarcadores/sangue , Doenças do Gato/diagnóstico , Hipertireoidismo/veterinária , Tiroxina/sangue , Animais , Doenças do Gato/sangue , Doenças do Gato/epidemiologia , Gatos , Feminino , Hipertireoidismo/sangue , Hipertireoidismo/diagnóstico , Masculino , Estudos Retrospectivos , Fatores de Tempo , Estados Unidos/epidemiologiaRESUMO
OBJECTIVE To evaluate clinical signs, endocrine test results, and pituitary tumor size for dogs with medically managed pituitary-dependent hyperadrenocorticism (PDH) and macroadenoma following 6 months of concurrent treatment with pasireotide. DESIGN Prospective case series. ANIMALS 9 client-owned dogs with PDH and macroadenoma in which PDH had been successfully managed with adrenal-directed treatment (trilostane or mitotane). PROCEDURES Dogs were given pasireotide (0.03 mg/kg [0.014 mg/lb], SC, q 12 h) for 6 months, while adrenal-directed treatment was continued. Physical examination, basic clinicopathologic testing, ACTH stimulation testing, and plasma ACTH concentration measurement were performed before (baseline) and 3 and 6 months after treatment began. Measurements of pituitary gland volume and pituitary gland-to-brain ratio were performed via MRI at baseline and 6 months after treatment began. RESULTS No dog developed neurologic abnormalities or signs of adverse effects during the study period. No differences from baseline were identified in clinicopathologic values, ACTH stimulation test results, or plasma ACTH concentration at the 3- or 6-month assessment points. After 6 months of pasireotide treatment, 6 dogs had decreases in MRI-measured values, and 3 had increases. CONCLUSIONS AND CLINICAL RELEVANCE Pasireotide as administered in this study had no noted adverse effects on dogs with PDH and macroadenoma successfully managed with standard treatment. Placebo-controlled, randomized studies are needed to determine whether pasireotide protects from the development of neurologic signs or improves outcome in dogs with pituitary macroadenomas.
Assuntos
Adenoma/veterinária , Hiperfunção Adrenocortical/veterinária , Doenças do Cão/tratamento farmacológico , Hormônios/uso terapêutico , Hipersecreção Hipofisária de ACTH/veterinária , Somatostatina/análogos & derivados , Adenoma/classificação , Adenoma/tratamento farmacológico , Hiperfunção Adrenocortical/tratamento farmacológico , Animais , Cães , Feminino , Masculino , Hipersecreção Hipofisária de ACTH/tratamento farmacológico , Neoplasias Hipofisárias/veterinária , Estudos Prospectivos , Somatostatina/uso terapêuticoRESUMO
BACKGROUND: Obesity has been associated with elevated plasma anandamide levels. In addition, anandamide has been shown to stimulate insulin secretion in vitro, suggesting that anandamide might be linked to hyperinsulinemia. OBJECTIVE: To determine whether high-fat diet-induced insulin resistance increases anandamide levels and potentiates the insulinotropic effect of anandamide in isolated pancreatic islets. DESIGN AND METHODS: Dogs were fed a high-fat diet (n = 9) for 22 weeks. Abdominal fat depot was quantified by MRI. Insulin sensitivity was assessed by the euglycemic-hyperinsulinemic clamp. Fasting plasma endocannabinoid levels were analyzed by liquid chromatography-mass spectrometry. All metabolic assessments were performed before and after fat diet regimen. At the end of the study, pancreatic islets were isolated prior to euthanasia to test the in vitro effect of anandamide on islet hormones. mRNA expression of cannabinoid receptors was determined in intact islets. The findings in vitro were compared with those from animals fed a control diet (n = 7). RESULTS: Prolonged fat feeding increased abdominal fat content by 81.3±21.6% (mean±S.E.M, P<0.01). In vivo insulin sensitivity decreased by 31.3±12.1% (P<0.05), concomitant with a decrease in plasma 2-arachidonoyl glycerol (from 39.1±5.2 to 15.7±2.0 nmol/L) but not anandamide, oleoyl ethanolamide, linoleoyl ethanolamide, or palmitoyl ethanolamide. In control-diet animals (body weight: 28.8±1.0 kg), islets incubated with anandamide had a higher basal and glucose-stimulated insulin secretion as compared with no treatment. Islets from fat-fed animals (34.5±1.3 kg; P<0.05 versus control) did not exhibit further potentiation of anandamide-induced insulin secretion as compared with control-diet animals. Glucagon but not somatostatin secretion in vitro was also increased in response to anandamide, but there was no difference between groups (P = 0.705). No differences in gene expression of CB1R or CB2R between groups were found. CONCLUSIONS: In canines, high-fat diet-induced insulin resistance does not alter plasma anandamide levels or further potentiate the insulinotropic effect of anandamide in vitro.
Assuntos
Ácidos Araquidônicos/genética , Endocanabinoides/genética , Resistência à Insulina , Insulina/metabolismo , Ilhotas Pancreáticas/metabolismo , Obesidade/sangue , Gordura Abdominal/efeitos dos fármacos , Gordura Abdominal/metabolismo , Animais , Peptídeos Catiônicos Antimicrobianos/biossíntese , Ácidos Araquidônicos/sangue , Glicemia , Peso Corporal , Dieta Hiperlipídica/efeitos adversos , Cães , Endocanabinoides/sangue , Humanos , Ilhotas Pancreáticas/patologia , Obesidade/patologia , Alcamidas Poli-Insaturadas/sangue , Receptor CB2 de Canabinoide/biossínteseRESUMO
OBJECTIVE: Insulin resistance is a powerful risk factor for Type 2 diabetes and a constellation of chronic diseases, and is most commonly associated with obesity. We examined if factors other than obesity are more substantial predictors of insulin sensitivity under baseline, nonstimulated conditions. METHODS: Metabolic assessment was performed in healthy dogs (n = 90). Whole-body sensitivity from euglycemic clamps (SICLAMP ) was the primary outcome variable, and was measured independently by IVGTT (n = 36). Adiposity was measured by MRI (n = 90), and glucose-stimulated insulin response was measured from hyperglycemic clamp or IVGTT (n = 86 and 36, respectively). RESULTS: SICLAMP was highly variable (5.9-75.9 dl/min per kg per µU/ml). Despite narrow range of body weight (mean, 28.7 ± 0.3 kg), adiposity varied approximately eight-fold and was inversely correlated with SICLAMP (P < 0.025). SICLAMP was negatively associated with fasting insulin, but most strongly associated with insulin clearance. Clearance was the dominant factor associated with sensitivity (r = 0.53, P < 0.00001), whether calculated from clamp or IVGTT. CONCLUSIONS: These data suggest that insulin clearance contributes substantially to insulin sensitivity, and may be pivotal in understanding the pathogenesis of insulin resistance. We propose the hyperinsulinemia due to reduction in insulin clearance is responsible for insulin resistance secondary to changes in body weight.
Assuntos
Resistência à Insulina/fisiologia , Insulina/sangue , Animais , Glicemia/metabolismo , Composição Corporal , Índice de Massa Corporal , Peso Corporal , Diabetes Mellitus Tipo 2/sangue , Cães , Jejum , Técnica Clamp de Glucose/métodos , Hiperinsulinismo , Fígado/metabolismo , Imageamento por Ressonância Magnética , Masculino , Obesidade/sangueRESUMO
OBJECTIVES: The canine model has been used extensively to improve the human pancreatic islet isolation technique. At the functional level, dog islets show high similarity to human islets and thus can be a helpful tool for islet research. We describe and compare 2 manual isolation methods, M1 (initial) and M2 (modified), and analyze the variables associated with the outcomes, including islet yield, purity, and glucose-stimulated insulin secretion (GSIS). METHODS: Male mongrel dogs were used in the study. M2 (n = 7) included higher collagenase concentration, shorter digestion time, faster shaking speed, colder purification temperature, and higher differential density gradient than M1 (n = 7). RESULTS: Islet yield was similar between methods (3111.0 ± 309.1 and 3155.8 ± 644.5 islets/g, M1 and M2, respectively; P = 0.951). Pancreas weight and purity together were directly associated with the yield (adjusted R(2) = 0.61; P = 0.002). Purity was considerably improved with M2 (96.7% ± 1.2% vs 75.0% ± 6.3%; P = 0.006). M2 improved GSIS (P = 0.021). Independently, digestion time was inversely associated with GSIS. CONCLUSIONS: We describe an isolation method (M2) to obtain a highly pure yield of dog islets with adequate ß-cell glucose responsiveness. The isolation variables associated with the outcomes in our canine model confirm previous reports in other species, including humans.
Assuntos
Insulina/metabolismo , Ilhotas Pancreáticas/citologia , Ilhotas Pancreáticas/metabolismo , Animais , Sobrevivência Celular , Cães , Fluoresceínas/metabolismo , Glucose/farmacologia , Humanos , Secreção de Insulina , Ilhotas Pancreáticas/efeitos dos fármacos , Masculino , Microscopia de Fluorescência , Reprodutibilidade dos Testes , Técnicas de Cultura de Tecidos/métodosRESUMO
OBJECTIVE: Insulin resistance induces hyperinsulinemic compensation, which in turn maintains almost a constant disposition index. However, the signal that gives rise to the hyperinsulinemic compensation for insulin resistance remains unknown. METHODS: In a dog model of obesity we examined the possibility that potential early-week changes in plasma FFA, glucose, or both could be part of a cascade of signals that lead to compensatory hyperinsulinemia induced by insulin resistance. RESULTS: Hypercaloric high fat feeding in dogs resulted in modest weight gain, and an increase in adipose tissue with no change in the non-adipose tissue size. To compensate for the drop in insulin sensitivity, there was a significant rise in plasma insulin, which can be attributed in part to a decrease in the metabolic clearance rate of insulin and increased insulin secretion. In this study we observed complete compensation for high fat diet induced insulin resistance as measured by the disposition index. The compensatory hyperinsulinemia was coupled with significant changes in plasma FFAs and no change in plasma glucose. CONCLUSIONS: We postulate that early in the development of diet induced insulin resistance, a change in plasma FFAs may directly, through signaling at the level of ß-cell, or indirectly, by decreasing hepatic insulin clearance, result in the observed hyperinsulinemic compensation.
Assuntos
Dieta , Ácidos Graxos não Esterificados/sangue , Resistência à Insulina , Animais , Glicemia/metabolismo , Composição Corporal , Peso Corporal , Escuridão , Cães , Jejum/sangue , Comportamento Alimentar , Teste de Tolerância a Glucose , Insulina/sangue , Insulina/metabolismo , Secreção de Insulina , Estatísticas não Paramétricas , Fatores de TempoRESUMO
Adipocyte size plays a key role in the development of insulin resistance. We examined longitudinal changes in adipocyte size and distribution in visceral (VIS) and subcutaneous (SQ) fat during obesity-induced insulin resistance and after treatment with CB-1 receptor antagonist, rimonabant (RIM) in canines. We also examined whether adipocyte size and/or distribution is predictive of insulin resistance. Adipocyte morphology was assessed by direct microscopy and analysis of digital images in previously studied animals 6 weeks after high-fat diet (HFD) and 16 weeks of HFD + placebo (PL; n = 8) or HFD + RIM (1.25 mg/kg/day; n = 11). At 6 weeks, mean adipocyte diameter increased in both depots with a bimodal pattern only in VIS. Sixteen weeks of HFD+PL resulted in four normally distributed cell populations in VIS and a bimodal pattern in SQ. Multilevel mixed-effects linear regression with random-effects model of repeated measures showed that size combined with share of adipocytes >75 µm in VIS only was related to hepatic insulin resistance. VIS adipocytes >75 µm were predictive of whole body and hepatic insulin resistance. In contrast, there was no predictive power of SQ adipocytes >75 µm regarding insulin resistance. RIM prevented the formation of large cells, normalizing to pre-fat status in both depots. The appearance of hypertrophic adipocytes in VIS is a critical predictor of insulin resistance, supporting the deleterious effects of increased VIS adiposity in the pathogenesis of insulin resistance.
Assuntos
Adipócitos/citologia , Resistência à Insulina , Gordura Intra-Abdominal/metabolismo , Adipócitos/metabolismo , Adiposidade , Animais , Tamanho Celular , Dieta Hiperlipídica , Cães , Gordura Intra-Abdominal/citologia , Modelos Lineares , Masculino , Modelos Animais , Obesidade/fisiopatologia , Piperidinas/administração & dosagem , Piperidinas/metabolismo , Pirazóis/administração & dosagem , Pirazóis/metabolismo , Receptor CB1 de Canabinoide/antagonistas & inibidores , Receptor CB1 de Canabinoide/metabolismo , RimonabantoRESUMO
OBJECTIVE: Obesity causes insulin resistance, which has been interpreted as reduced downstream insulin signaling. However, changes in access of insulin to sensitive tissues such as skeletal muscle may also play a role. Insulin injected directly into skeletal muscle diffuses rapidly through the interstitial space to cause glucose uptake. When insulin resistance is induced by exogenous lipid infusion, this interstitial diffusion process is curtailed. Thus, the possibility exists that hyperlipidemia, such as that seen during obesity, may inhibit insulin action to muscle cells and exacerbate insulin resistance. Here we asked whether interstitial insulin diffusion is reduced in physiological obesity induced by a high-fat diet (HFD). RESEARCH DESIGN AND METHODS: Dogs were fed a regular diet (lean) or one supplemented with bacon grease for 9-12 weeks (HFD). Basal insulin (0.2 mU x min(-1) x kg(-1)) euglycemic clamps were performed on fat-fed animals (n = 6). During clamps performed under anesthesia, five sequential doses of insulin were injected into the vastus medialis of one hind limb (INJ); the contralateral limb (NINJ) served as a control. RESULTS: INJ lymph insulin showed an increase above NINJ in lean animals, but no change in HFD-fed animals. Muscle glucose uptake observed in lean animals did not occur in HFD-fed animals. CONCLUSIONS: Insulin resistance induced by HFD caused a failure of intramuscularly injected insulin to diffuse through the interstitial space and failure to cause glucose uptake, compared with normal animals. High-fat feeding prevents the appearance of injected insulin in the interstitial space, thus reducing binding to skeletal muscle cells and glucose uptake.
Assuntos
Hiperlipidemias/metabolismo , Hipoglicemiantes/farmacocinética , Resistência à Insulina/fisiologia , Insulina/farmacocinética , Músculo Esquelético/metabolismo , Obesidade/metabolismo , Gordura Abdominal/metabolismo , Ração Animal , Animais , Glicemia/metabolismo , Peso Corporal/fisiologia , Gorduras na Dieta/farmacologia , Cães , Técnica Clamp de Glucose , Hiperlipidemias/tratamento farmacológico , Injeções Intramusculares , Masculino , Obesidade/tratamento farmacológico , Transdução de Sinais/fisiologia , Gordura Subcutânea/metabolismoRESUMO
Visceral adiposity is strongly associated with insulin resistance; however, little evidence directly demonstrates that visceral fat per se impairs insulin action. Here, we examine the effects of the surgical removal of the greater omentum and its occupying visceral fat, an omentectomy (OM), on insulin sensitivity (S(I)) and beta-cell function in nonobese dogs. Thirteen male mongrel dogs were used in this research study; animals were randomly assigned to surgical treatment with either OM (n = 7), or sham-surgery (SHAM) (n = 6). OM failed to generate measurable changes in body weight (+2%; P = 0.1), or subcutaneous adiposity (+3%; P = 0.83) as assessed by magnetic resonance imaging (MRI). The removal of the greater omentum did not significantly reduce total visceral adipose volume (-7.3 +/- 6.4%; P = 0.29); although primary analysis showed a trend for OM to increase S(I) when compared to sham operated animals (P = 0.078), further statistical analysis revealed that this minor reduction in visceral fat alleviated insulin resistance by augmenting S(I) of the periphery (+67.7 +/- 35.2%; P = 0.03), as determined by the euglycemic-hyperinsulinemic clamp. Insulin secretory response during the hyperglycemic step clamp was not directly influenced by omental fat removal (presurgery 6.82 +/- 1.4 vs. postsurgery: 6.7 +/- 1.2 pmol/l/mg/dl, P = 0.9). These findings provide new evidence for the deleterious role of visceral fat in insulin resistance, and suggest that a greater OM procedure may effectively improve insulin sensitivity.
Assuntos
Resistência à Insulina/fisiologia , Omento/fisiologia , Omento/cirurgia , Animais , Composição Corporal/fisiologia , Modelos Animais de Doenças , Cães , Jejum/fisiologia , Insulina/fisiologia , Células Secretoras de Insulina/fisiologia , Gordura Intra-Abdominal/fisiologia , MasculinoRESUMO
We investigated whether rimonabant, a type 1 cannabinoid receptor antagonist, reduces visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) in dogs maintained on a hypercaloric high-fat diet (HHFD). To determine whether energy expenditure contributed to body weight changes, we also calculated resting metabolic rate. Twenty male dogs received either rimonabant (1.25 mg.kg(-1).day(-1), orally; n = 11) or placebo (n = 9) for 16 wk, concomitant with a HHFD. VAT, SAT, and nonfat tissue were measured by magnetic resonance imaging. Resting metabolic rate was assessed by indirect calorimetry. By week 16 of treatment, rimonabant dogs lost 2.5% of their body weight (P = 0.029), whereas in placebo dogs body weight increased by 6.2% (P < 0.001). Rimonabant reduced food intake (P = 0.027), concomitant with a reduction of SAT by 19.5% (P < 0.001). In contrast with the VAT increase with placebo (P < 0.01), VAT did not change with rimonabant. Nonfat tissue remained unchanged in both groups. Body weight loss was not associated with either resting metabolic rate (r(2) = 0.24; P = 0.154) or food intake (r(2) = 0.24; P = 0.166). In conclusion, rimonabant reduced body weight together with a reduction in abdominal fat, mainly because of SAT loss. Body weight changes were not associated with either resting metabolic rate or food intake. The findings provide evidence of a peripheral effect of rimonabant to reduce adiposity and body weight, possibly through a direct effect on adipose tissue.
Assuntos
Gorduras na Dieta/farmacologia , Gordura Intra-Abdominal/efeitos dos fármacos , Obesidade/tratamento farmacológico , Piperidinas/farmacologia , Pirazóis/farmacologia , Gordura Subcutânea Abdominal/efeitos dos fármacos , Animais , Peso Corporal/efeitos dos fármacos , Cães , Ingestão de Alimentos/fisiologia , Metabolismo Energético/efeitos dos fármacos , Gordura Intra-Abdominal/patologia , Imageamento por Ressonância Magnética , Masculino , Obesidade/patologia , Receptor CB1 de Canabinoide/antagonistas & inibidores , Rimonabanto , Gordura Subcutânea Abdominal/patologiaRESUMO
The insulinotropic intestinal hormone GLP-1 is thought to exert one of its effects by direct action on the pancreatic beta-cell receptors. GLP-1 is rapidly degraded in plasma, such that only a small amount of the active form reaches the pancreas, making it questionable whether this amount is sufficient to produce a direct incretin effect. The aim of our study was to assess, in a dog model, the putative incretin action of GLP-1 acting directly on the beta-cell in the context of postprandial rises in GLP-1 and glucose. Conscious dogs were fed a high-fat, high-carbohydrate meal, and insulin response was measured. We also infused systemic glucose plus GLP-1, or glucose alone, to simulate the meal test values of these variables and measured insulin response. The results were as follows: during the meal, we measured a robust insulin response (52 +/- 9 to 136 +/- 14 pmol/l, P < 0.05 vs. basal) with increases in portal glucose and GLP-1 but only limited increases in systemic glucose (5.3 +/- 0.1 to 5.7 +/- 0.1 mmol/l, P = 0.1 vs. basal) and GLP-1 (6 +/- 0 to 9 +/- 1 pmol/l, P = 0.5 vs. basal). Exogenous infusion of systemic glucose and GLP-1 produced a moderate increase in insulin (43 +/- 5 to 84 +/- 15 pmol/l, 43% of the meal insulin). However, infusion of glucose alone, without GLP-1, produced a similar insulin response (37 +/- 6 to 82 +/- 14 pmol, 53% of the meal insulin, P = 0.7 vs. glucose and GLP-1 infusion). In conclusion, in dogs with postprandial rises in systemic glucose and GLP-1, the hormone might not have a direct insulinotropic effect and could regulate glycemia via indirect, portohepatic-initiated neural mechanisms.