Effect of 5'-adenosine monophosphate-activated protein kinase agonists on insulin and glucose dynamics in experimentally induced insulin dysregulation in horses.

BACKGROUND: 5'-adenosine monophosphate-activated protein kinase (AMPK) agonists, particularly resveratrol (RES), have not been extensively evaluated for their effect on insulin dysregulation (ID) in horses. OBJECTIVES: Evaluate the effects of treatment with RES (10 mg/kg PO q12h), metformin (MET; 30 mg/kg PO q12h), and aspirin (ASP; 20 mg/kg PO q24h) on experimentally induced ID. ANIMALS: Thirty-three healthy, adult, light-breed horses. METHODS: Unblinded, placebo-controlled, experimental trial evaluating effects of AMPK agonists (RES, MET, and ASP) on experimentally induced ID. Horses were randomly assigned to a treatment group (RES, MET/ASP, RES/ASP, RES/MET/ASP, or placebo [CON]) after induction of ID with dexamethasone (0.08 mg/kg PO q24h for 7 days). Frequently sampled insulin-modified IV glucose tolerance tests (FSIGTT) and oral sugar tests (OST) were performed at baseline, 7 days after ID, and ID plus 7 days of treatment. Minimal model and OST variables were compared between (1-way ANOVA) and within (1-way ANOVA for repeated measures) groups over time to determine effects of treatment on ID. RESULTS: Administration of dexamethasone for 14 days resulted in significantly altered insulin and glucose dynamics (SI, DI, basal [glucose], and [insulin]) and produced clinical signs of laminitis in 5 out of 33 (15%) of horses included in the study. Combination therapy with RES, MET, and ASP did not significantly improve insulin and glucose dynamics in horses with experimentally induced ID. CONCLUSIONS AND CLINICAL IMPORTANCE: Metabolic testing before glucocorticoid administration should be considered in horses with clinical signs of metabolic syndrome.

Evaluation of field-testing protocols to diagnose insulin dysregulation in ponies using a Bayesian approach.

Field tests and their association with laminitis have not been evaluated in large cohorts. The objectives of this study were to evaluate the performance of basal insulin (BI), the oral sugar test (OST) and the insulin tolerance test (ITT) to diagnose ID and investigate their association with laminitis. Insulin dysregulation status was determined in 146 ponies using BI (insulin concentration >20 µIU/mL), an OST (insulin concentration >65 µIU/mL at 60 or 90 min after oral administration of 0.45 mL/kg corn syrup) and an ITT (< 50% reduction in glucose concentration 30 min after intravenous administration of 0.1 IU/kg insulin). Laminitis was identified using modified-Obel scores. A Bayesian approach was used to define the characteristics of the tests and receiver operating characteristic curves were used to assess their association with laminitis. All tests were well tolerated and laminitis was diagnosed in 9% of ponies. Insulin dysregulation was diagnosed in 15% of ponies using BI, 38% using the OST and 54% using the ITT with 11% of ponies positive for all three tests. The sensitivities and specificities of BI, the OST and the ITT to diagnose ID were 0.52 (95% confidence interval [CI], 0.35-0.79) and 0.97 (95% CI, 0.91 - 1.00), 0.84 (95% CI, 0.70 - 0.94) and 0.60 (95% CI, 0.49 - 0.71), and 0.85 (95% CI, 0.68-0.96) and 0.88 (95% CI, 0.75 - 0.97), respectively. Only BI and the OST were associated with laminitis (P = 0.003 and 0.015, respectively).

Comparación de los valores de glucosa en caninos obtenidos con glucómetros portátiles y la prueba estándar de laboratorio / Comparação dos valores de glicose em caninos obtidos com glicômetros portáteis e o teste laboratorial padrão / Comparison of glucose values in dogs obtained with portable glucometers and the standard laboratory test

La medición de glucosa en caninos es un procedimiento habitual en la clínica diaria, actualmente este valor se puede obtener mediante dispositivos portátiles y pruebas laboratoriales. Se realizó esta investigación con el fin de aportar mayor conocimiento sobre la importancia de la medición de glucosa, ya que en los últimos años ha perdido valor entre las pruebas hematológicas a considerar debido a que solo se relaciona con determinadas patologías como la diabetes u otras enfermedades metabólicas. El presente trabajo tiene como objetivo comparar los valores de glucosa en caninos obtenidos mediante un glucómetro portátil de uso humano (Accu-chek® Active, Roche Diagnostic, Mannheim, Alemania); veterinario (aLcose® Vet Glu, jjPlus Corporation, New Taipei, Taiwán) y la prueba estándar de laboratorio, esto nos indicará la fiabilidad de los resultados obtenidos mediante estos métodos. Se realizó la toma de muestras de sangre de 50 caninos clínicamente sanos, de los cuales se obtuvo el resultado de glucemia mediante estos tres métodos. Los resultados de nuestra investigación evidenciaron que las tres formas de evaluación de la glucosa sanguínea en perros brindaban resultados estadísticamente diferentes (p < 0.05). Se obtuvo valores de glucosa diferentes entre los tres métodos de medición, teniendo como promedios finales 84.14 mg/dL, 101.12 mg/dL y 91.12 mg/dL correspondientes al glucómetro portátil de uso humano, veterinario y a la prueba estándar de laboratorio respectivamente. En conclusión, los glucómetros portátiles de uso humano subestiman los valores reales de glucosa, mientras que los de uso veterinario lo sobreestiman, comparados con la prueba estándar de laboratorio.

A medição de glicose nos cães é um procedimento habitual realizado no atendimento clínico. Atualmente este valor pode ser obtido por meio de dispositivos portáteis e testes laboratoriais. Esta pesquisa foi realizada com a finalidade de destacar a importância da medição de glicose, visto que nos últimos anos esta avaliação não tem sido muito valorada entre os testes hematológicos, sendo considerada relevante apenas em relação a patologias como a diabetes e outras doenças metabólicas. O presente estudo teve como objetivo comparar os valores de glicose em cães obtidos com glicômetro portátil de uso humano; veterinário e o teste padrão de laboratório. Esta comparação poderá indicar a confiabilidade dos resultados obtidos mediante os métodos avaliados. Foi realizada a amostragem do sangue de 50 caninos clinicamente sadios os quais foram submetidos a avaliação de glicose mediante os três métodos. Os resultados de nossa investigação evidenciaram que as três formas de avaliação da glicose sanguínea têm resultados estatisticamente diferentes (p < 0,05). Os valores de glicose tiveram medias finais de 84,14 mg/dL, 101,12 mg/dL e 91,12 mg/dL para o glicômetro portátil de uso humano (Accu-chek® Active, Roche Diagnostic, Mannheim, Alemanha), veterinário (aLcose® Vet Glu, jjPlus Corporation, Nova Taipei, Taiwan) e o teste padrão de laboratório, respectivamente. Ao concluir, os glicômetros portáteis de uso humano subestimam os valores reais de glicose e os de uso veterinário os superestimam quando comparados com o teste padrão de laboratório.

The measurement of glucose in canines is a common procedure in daily clinical practice. Currently this value can be obtained by use of portable devices and laboratory tests. This research was carried out in order to provide more knowledge about the importance of glucose measurement, since in recent years it has lost value among the hematological tests to be considered because it is only related to certain pathologies such as diabetes or other metabolic diseases. The present study aimed to compare the glucose values in dogs obtained with a portable glucometer for human use, veterinarian use, and the standard laboratory test. This comparison may indicate the reliability of the results obtained through the evaluated methods. A blood sampling of 50 clinically healthy canines was taken and submitted to glucose evaluation using the three methods. Our investigation showed that the three ways of assessing blood glucose have statistically different results (p < 0.05). Glucose values had final averages of 84.14 mg/dL, 101.12 mg/dL, and 91.12 mg/dL for the portable glucometer for human use (Accu-chek® Active, Roche Diagnostic, Mannheim, Germany), veterinary (aLcose® Vet Glu, jjPlus Corporation, New Taipei, Taiwan) and the standard laboratory test, respectively. In conclusion, portable glucometers for human use underestimate the glucose values, and those for veterinary use overestimate them compared to the standard laboratory test.

Characterisation of the oral glucose and sugar tolerance tests and the enteroinsular axis response in healthy adult donkeys.

BACKGROUND: Insulin dysregulation (ID) is diagnosed in horses and ponies using oral glucose (OGTT) and oral sugar (OSTT) tolerance tests. The enteroinsular axis plays a major role in postprandial glucose disposal and insulin response in horses, ponies and foals. The insulin and incretin response to oral carbohydrate challenges has not been characterised in donkeys. OBJECTIVES: (a) To characterise OGTT and OSTT, and (b) to assess the plasma incretin response to OGTT and OSTT in healthy donkeys. STUDY DESIGN: In vivo experiments. METHODS: Six healthy adult female Andalusian donkeys were challenged with OGTT (1 g/kg glucose, 20% solution by nasogastric tube) and OSTT (0.45 mL/kg corn syrup orally by syringe) with a 1-week washout. Blood samples were collected for glucose (spectrophotometry), insulin (radioimmunoassay), glucose-dependent insulinotropic polypeptide (GIP, ELISA) and active glucagon-like peptide-1 (aGLP-1, ELISA) determination over 6 hours. Curves were analysed and proxies calculated. RESULTS: Glucose and insulin concentrations peaked at 180 minutes in OGTT, but at 300 and 150 minutes in OSTT, respectively. Plasma GIP concentrations increased in the OGTT and OSTT (peaked at 180 and 360 minutes, respectively), but aGLP-1 increased only in OGTT (240 minutes). MAIN LIMITATIONS: Single breed, narrow age and sample, diet, season and not having donkeys with evidence of ID to provide clinical validation. CONCLUSIONS: Donkeys have a functional enteroinsular axis that is activated by enteral carbohydrates. Donkeys have evident endocrine differences with horses, supporting the validation of the OSTT and OGTT to assess insulin sensitivity in this species to avoid extrapolation from horses.

Effects of dietary antioxidants on glucose and insulin responses to glucose tolerance test in transition dairy cows.

Oxidative stress occurs during the transition period and causes insulin resistance, which may be reduced by the use of antioxidants in this period. Twenty-four multiparous Holstein dairy cows, at 8 wk before parturition, were divided into 4 equal groups, namely control (Ctrl), vitamin E (VE), selenium (Se), and vitamin E plus selenium (VE + Se) groups. On a daily basis, VE and Se cows received dietary 1.5 IU vitamin E/kg BW and 0.3 mg/kg DM selenium, respectively, from 8 wk before to 3 wk after parturition. Vitamin E plus selenium group received doses similar to VE and Se groups. Insulin sensitivity was evaluated through intravenous glucose tolerance test (ivGTT) at weekly intervals from 3 wk before to 3 wk after parturition. Serum concentrations of total antioxidant status (TAS), malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GPx), nonesterified fatty acid (NEFA), and beta-hydroxybutyric acid (BHBA) were assayed weekly before the commencement of ivGTT. Based on the results of ivGTT, the lowest and the highest degrees of insulin sensitivity were detected in Ctrl and VE + Se groups, respectively. The highest and the lowest concentrations of NEFA and BHBA were observed in Ctrl and VE + Se groups, respectively. Total antioxidant status, SOD, and GPx values were significantly lower in Ctrl cows and significantly higher in VE + Se-received cows compared with other groups. However, MDA values in Ctrl and VE + Se cows were significantly higher and lower than the other groups, respectively. Collectively, our results show that dietary administration of vitamin E and selenium ameliorates oxidative stress and lipid mobilization and increases insulin sensitivity in transition cows.

The effect of different grazing conditions on the insulin and incretin response to the oral glucose test in ponies.

BACKGROUND: The oral glucose test (OGT) is a useful tool for diagnosing insulin dysregulation (ID) and is somewhat repeatable in ponies under consistent management. This study aimed to determine whether the insulin and incretin responses to an OGT in ponies differed after short-term access to fertilised pasture, compared to unfertilised pasture, by using a randomised, repeated measures study design. Sixteen mixed-breed ponies were classified as severely insulin-dysregulated (SD; post-prandial insulin ≥80 µIU/mL) or not severely insulin-dysregulated (NSD; post-prandial insulin < 80 µIU/mL) using an OGT prior to the study. The ponies accessed pasture that was fertilised, or unfertilised, for 5 days (4 h/day, with supplemental hay provided at 0.7% bodyweight), with a 10 day period between phases. An OGT was performed after each phase. Glucose, insulin, active glucagon-like peptide-1 (aGLP-1), and glucose-dependent insulinotropic polypeptide (GIP) were measured in post-prandial blood samples. RESULTS: The volume of fertilised pasture was five-fold greater than unfertilised pasture, with % non-structural carbohydrates (NSC) similar between all forages. Consuming fertilised pasture increased (P = 0.018) the serum insulin response to an OGT, compared to grazing unfertilised pasture. A limitation of the study was that pasture intake was unable to be quantified. Insulin responses were greater in SD, compared to NSD, ponies (P < 0.001) and remained well above the test cut-off at all times. A subset of ponies, initially screened as NSD, became (more) insulin-dysregulated after pasture access. Further, aGLP-1 was a significant predictor of insulin concentration in this cohort. CONCLUSIONS: Whereas some insulin-dysregulated ponies were comparatively resistant to dietary intervention, others showed markedly different OGT responses following subtle changes in their forage-based diet. This implies that mild/early ID might be unmasked by dietary change, and that dietary management is important in these ponies. However, dietary management alone may not be adequate for all cases of ID.

Enteroinsular axis response to carbohydrates and fasting in healthy newborn foals.

BACKGROUND: The enteroinsular axis (EIA) comprises intestinal factors (incretins) that stimulate insulin release after PO ingestion of nutrients. Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are the main incretins. The EIA has not been investigated in healthy neonatal foals but should be important because energy demands are high in healthy foals and dysregulation is frequent in sick foals. OBJECTIVES AND HYPOTHESIS: To evaluate the EIA response to carbohydrates or fasting in newborn foals. We hypothesized that incretin secretion would be higher after PO versus IV carbohydrate administration or fasting. ANIMALS: Thirty-six healthy Standardbred foals ≤4 days of age. METHODS: Prospective study. Blood was collected before and after a PO glucose test (OGT; 300, 500, 1000 mg/kg), an IV glucose test (IVGT; 300, 500, 1000 mg/kg), a PO lactose test (OLT; 1000 mg/kg), and fasting. Foals were muzzled for 240 minutes. Blood was collected over 210 minutes glucose, insulin, GIP, and GLP-1 concentrations were measured. RESULTS: Only PO lactose caused a significant increase in blood glucose concentration (P < .05). All IV glucose doses induced hyperglycemia and hyperinsulinemia. Concentrations of GIP and GLP-1 decreased until foals nursed (P < .05), at which time rapid increases in glucose, insulin, GIP, and GLP-1 concentrations occurred (P < .05). CONCLUSIONS AND CLINICAL IMPORTANCE: Healthy newborn foals have a functional EIA that is more responsive to milk and lactose than glucose. Non-carbohydrate factors in mare's milk may be important for EIA activity. Constant exposure of intestinal cells to nutrients to maintain EIA activity could be relevant to management of sick foals. Foals can be fasted for 4 hours without experiencing hypoglycemia.

Effect of thyrotropin-releasing hormone stimulation testing on the oral sugar test in horses when performed as a combined protocol.

BACKGROUND: The use of parallel dynamic tests to identify insulin dysregulation (ID) and pituitary pars intermedia dysfunction (PPID) in horses could have better diagnostic utility than measuring baseline hormone concentrations, if the tests do not alter diagnostic interpretation of one another. HYPOTHESIS: Performing a thyrotropin-releasing hormone (TRH) stimulation test before an oral sugar test (OST) would not affect results of OST. ANIMALS: Twenty-six healthy university-owned horses. METHODS: A prospective randomized placebo-controlled, crossover design was used to evaluate 3 OST protocols: OST alone, TRH followed by OST (TRH + OST), and placebo followed by OST (placebo + OST). Agreement for plasma insulin concentrations and diagnostic interpretation were assessed with Bland-Altman and logistic regression analyses, respectively. RESULTS: Bland-Altman analysis of TRH + OST versus OST alone showed good agreement between testing protocols, with bias ± SD for insulin concentrations at baseline 0.4 ± 4.7 µIU/mL (95% limits of agreement [LOA], -8.8 to 9.7), 60 minute -0.5 ± 22.6 µIU/mL (95% LOA, -44.7 to 43.8), and 90 minute 1.9 ± 20.6 µIU/mL (95% LOA, -38.5 to 42.4) after OST, similar to placebo + OST versus OST alone. Diagnostic interpretation (positive/negative) was not different between protocols (TRH + OST versus OST alone [P = .78], placebo + OST versus OST alone [P = .77], or TRH + OST versus placebo + OST [P = .57]). CONCLUSIONS AND CLINICAL IMPORTANCE: Concurrent testing for PPID and ID with a TRH stimulation test before an OST is an acceptable diagnostic tool for investigation of endocrinopathies in horses and allows accurate testing to be performed efficiently in 1 visit.

Effects of body condition score on direct and indirect measurements of insulin sensitivity in periparturient dairy cows.

Reductions in insulin sensitivity in periparturient dairy cows develop as a means to support lactation; however, excessive mobilization of fatty acids (FA) increases the risk for peripartal metabolic disorders. Our objectives were to investigate the effect of prepartum body condition score (BCS) on systemic glucose and insulin tolerance, and to compare direct and indirect measurements of insulin sensitivity in peripartal lean and overweight dairy cows. Fourteen multiparous Holstein cows were allocated into two groups according to their BCS at day -28 prepartum: lean (n = 7; BCS ≤ 3.0) or overweight; (n = 7; BCS ≥ 4.0). Liver biopsies were performed on day -27, -14 and 4, relative to expected parturition. Intravenous insulin or glucose tolerances tests were performed following each liver biopsy. Relative to lean cows, overweight cows exhibited lower dry matter intake, lost more BCS and displayed increased plasma FA and ß-hydroxybutyrate concentrations and elevated liver lipid content during peripartum. Glucose clearance rate was lower for all cows postpartum. Prepartum BCS had minimal effects on insulin and glucose tolerance; however, the ability of the cow to restore blood glucose levels following an insulin challenge was suppressed by increased BCS. Glucose-dependent parameters of insulin and glucose tolerance were not correlated with surrogate indices of insulin sensitivity. We conclude that prepartum BCS had minimal effect on systemic insulin sensitivity following parturition. The observed inconsistency between surrogate indices of insulin sensitivity and direct measurements of insulin and glucose tolerance adds support to growing concerns regarding their usefulness as tools to estimate systemic insulin action in periparturient cows.

Insulin and incretin responses to grazing in insulin-dysregulated and healthy ponies.

BACKGROUND: Supraphysiological insulin and incretin responses to a cereal-based diet have been described in horses and ponies with insulin dysregulation (ID). However, the hormonal responses to grazing have not yet been described. OBJECTIVES: To determine if there is a difference in the insulin and incretin responses to grazing pasture between insulin-dysregulated and healthy ponies. ANIMALS: A cohort of 16 ponies comprising 5 with normal insulin regulation (NIR), 6 with moderate ID (MID), and 5 with severe ID (SID). METHODS: In this case-control study, an oral glucose test (OGT) was used to determine the insulin responsiveness of each pony to PO carbohydrate before grazing pasture (4 hours) for 3 consecutive days. Serial blood samples collected during grazing were analyzed for glucose, insulin, glucose-dependent insulinotropic peptide (GIP) and active glucagon-like peptide-1 (aGLP-1), and compared among pony groups and day of pasture access. RESULTS: The area under the insulin curve when grazing increased with ID severity (P < .03). The median (range) maximal insulin concentration was greater in the MID (72.5 [129] µIU/mL) and SID (255 [338.5] µIU/mL) groups, compared to the NIR (11.7 [24.9] µIU/mL) group (P < .03) and occurred within 2-4 hours of grazing. Postprandial OGT insulin concentration was positively correlated with 2 hours post-grazing insulin across all 3 grazing days (P ≤ .03). The aGLP-1 and GIP concentrations increased in response to grazing but did not differ among groups. CONCLUSIONS AND CLINICAL IMPORTANCE: Grazing pasture provoked an increased insulin and incretin response in insulin-dysregulated ponies within 4 hours of grazing. The pasture and OGT insulin concentrations were correlated.

Inflammatory bowel disease (IBD) in horses: a retrospective study exploring the value of different diagnostic approaches.

BACKGROUND: Diagnosing IBD in horses is challenging and requires a multimodal approach, since no conclusive diagnostic test is available. The objectives of this study were to provide an overview of population characteristics, results of applied diagnostic tests, treatment modalities and outcome in a large group of horses thought to have IBD and that were presented to four large equine referral hospitals, and to provide an exploratory investigation of possible associations between results of applied diagnostic tests, applied treatment modalities and outcome. A retrospective case series was performed across four large equine referral hospitals. Seventy-eight horses, thought to have IBD were included. Case history, clinical findings, diagnostic test results including oral glucose tolerance test (OGTT) and enteral biopsies (both duodenal and rectal), applied therapy and outcome were studied. A Chi-Square test was used to identify associations between results of diagnostic tests, treatment and outcome. P-values < 0.05 were considered significant. RESULTS: Lethargy, diarrhoea, recurrent colic and weight loss were recorded in respectively 21,8%; 14,1%; 28,2% and 78,2% of cases. Over 70% of horses thought to have IBD had an abnormal OGTT. Only weight loss was significantly associated with aberrant enteral biopsy results, but not with abnormal OGTT results or low blood total protein. There was no association between an aberrant biopsy result and a disturbed OGTT. There was no association between either OGTT results or enteral biopsy results and a low blood total protein content, presence of gastric ulcer disease or an aberrant endoscopic aspect of the duodenal entrance. CONCLUSIONS: Weight loss is a highly prevalent symptom in IBD suspected horses. Enteral biopsies may be a useful diagnostic aid in the work-up of horses thought to suffer from IBD, however further research is required to demonstrate their true diagnostic value. Until more standardized scientific research is available, one should be careful with the interpretation of enteral biopsy results There is a need for better standardization of enteral biopsy procedures and the histopathological scoring of biopsies.

Effect of transmucosal corn syrup application on postoperative blood glucose concentrations in kittens.

Objectives The aim of the study was to determine the effect of a common clinical practice, the transmucosal (TM) application of corn syrup, on postoperative blood glucose concentrations in kittens. Methods This study was designed as a randomized controlled trial. Seventy-five kittens between the age of 8 and 16 weeks scheduled for surgical sterilization by gonadectomy at an animal shelter were enrolled. Kittens were randomly assigned to either a routine treatment group that received the shelter's typical postoperative application of corn syrup immediately following gonadectomy or to a control group that did not receive typical treatment. Three blood glucose measurements were obtained per kitten: baseline reading prior to preoperative examination, immediately postoperatively and 20 mins postoperatively. The median values of the 20 min postoperative blood glucose reading for the control and treatment groups were compared using the Wilcoxon rank-sum test. Results Postoperative application of corn syrup to the oral mucosa of kittens did not result in significant elevations in blood glucose compared with controls. No kitten was hypoglycemic (⩽60 mg/dl) at any point during the study. Conclusions and relevance TM application of corn syrup did not affect postoperative blood glucose concentrations in kittens. Protocols that use routine TM administration of corn syrup in kittens should be re-evaluated.

Cutpoints for screening blood glucose concentrations in healthy senior cats.

Objectives The objectives of this study were to determine the reference interval for screening blood glucose in senior cats, to apply this to a population of obese senior cats, to compare screening and fasting blood glucose, to assess whether screening blood glucose is predicted by breed, body weight, body condition score (BCS), behaviour score, fasting blood glucose and/or recent carbohydrate intake and to assess its robustness to changes in methodology. Methods The study included a total of 120 clinically healthy client-owned cats aged 8 years and older of varying breeds and BCSs. Blood glucose was measured at the beginning of the consultation from an ear/paw sample using a portable glucose meter calibrated for cats, and again after physical examination from a jugular sample. Fasting blood glucose was measured after overnight hospitalisation and fasting for 18-24 h. Results The reference interval upper limit for screening blood glucose was 189 mg/dl (10.5 mmol/l). Mean screening blood glucose was greater than mean fasting glucose. Breed, body weight, BCS, behaviour score, fasting blood glucose concentration and amount of carbohydrate consumed 2-24 h before sampling collectively explained only a small proportion of the variability in screening blood glucose. Conclusions and relevance Screening blood glucose measurement represents a simple test, and cats with values from 117-189 mg/dl (6.5-10.5 mmol/l) should be retested several hours later. Cats with initial screening blood glucose >189 mg/dl (10.5 mmol/l), or a second screening blood glucose >116 mg/dl (6.4 mmol/l) several hours after the first, should have fasting glucose and glucose tolerance measured after overnight hospitalisation.

Experimental hyperlipidemia induces insulin resistance in sheep.

This study aimed to evaluate the effects of intravenous infusion of a soybean-based lipid emulsion on some blood energy-related metabolites and insulin sensitivity indexes in sheep. Four clinically healthy ewes were assigned into a 2-treatment, 2-period cross-over design. Either normal saline (NS) or lipid emulsion (LE) was intravenously introduced at a rate of 0.025 mL·kg(-1) min(-1) for 6 h. The concentrations of blood nonesterified fatty acid (NEFA), beta-hydroxybutyrate, triglyceride, cholesterol, urea, creatinine, cortisol, glucose, and insulin were measured at different time points. After 6 h, intravenous glucose tolerance test was performed. Lipid infusion elicited an increase (P < 0.05) in the NEFA, beta-hydroxybutyrate, and triglyceride concentrations compared with the baseline value and NS infusion. Infusion of NS did not influence blood glucose concentration; however, LE infusion increased plasma glucose concentration (P < 0.05). At time point 12 h, serum insulin concentrations were increased (P < 0.05) in NS treatment; however, such an increase was not observed in the LE treatment. Insulin sensitivity index for the LE infusion was lower (P < 0.05) than that for the NS treatment. The glucose effectiveness was not (P > 0.05) different among treatments. In the LE treatment, acute-phase insulin responses increased (P < 0.05) and disposition index decreased (P < 0.001) compared with NS treatment. The results showed that experimentally induced NEFA in blood could cause insulin resistance in sheep. The current model could be used to evaluate the pathogenesis of conditions associated with increased lipid mobilization and insulin resistance.

Correlação entre cálcio e insulina durante o teste de tolerância à glicose em ovelhas gestantes e não gestantes / Calcium and insulin correlation during the glucose tolerance test in pregnant non-pregnant ewes

Compararam-se as concentrações de cálcio, glicose e insulina em ovelhas gestantes e não gestantes submetidas ao teste de tolerância à glicose (TTG). Oito ovelhas gestantes (GG) e oito não gestantes (NG) foram submetidas ao TTG por meio da administração endovenosa de uma solução de glicose, na dose de 500mg/kg de peso vivo. Amostras de sangue foram coletadas nos tempos de -15, zero, 15, 30, 45, 60, 90, 120, 150 e 180 minutos, sendo zero min o momento da infusão, para avaliação da concentração sanguínea de glicose, cálcio e insulina. Foi avaliada a taxa de metabolização de glicose e insulina, por meio do cálculo da área sob a curva (ASC). As concentrações de glicose, cálcio, insulina e a ASC da insulina não diferiram entre os grupos (P>0,05), entretanto as três últimas ASCs da glicose foram mais elevados nas gestantes (P<0,05), que correspondem ao período entre 90 e 180min. O teste de correlação de Pearson revelou correlação negativa entre concentração de cálcio e insulina nas gestantes (P<0,05). Estes resultados indicam menor taxa de metabolização de glicose em ovelhas gestantes e uma possível relação de cálcio e insulina no terço final de gestação.

The aim of this study was to investigate glucose, insulin and calcium metabolism during the Glucose Tolerance Test (GTT) in pregnant or nonpregnant ewes. Eight pregnant (PG) and nonpregnant (NPG) ewes per group received a glucose endovenosus bolus containning 500mg/kg in one minute. Blood samples were collected on -15, 0, 15, 30, 45, 60, 90, 120, 150 and 180 minutes interval (0 min - injection). These samples were used to evaluate glucose, calcium, insulin concentration, as well as insulin and glucose metabolization rate, which were determined by calculating the Area Under the Curve (AUC). The calcium, glucose and insulin concentrations were not different between groups. However, the three last glucose ASCs were higher in the pregnant group and in this group calcium and insulin blood concentrations were negatively correlated .These results showed lower glucose tolerance in pregnant ewes and suggest a link between insulin and calcium in the late pregnancy.

Effects of continuous or intermittent lipopolysaccharide administration for 48 hours on the systemic inflammatory response in horses.

OBJECTIVE: To determine whether the method of lipopolysaccharide (LPS) administration (intermittent vs continuous) affects the magnitude and duration of the systemic inflammatory response in horses and whether prolonged (48 hours) endotoxemia induces laminitis. ANIMALS: 12 healthy adult horses (10 mares and 2 geldings). PROCEDURES: Horses were randomly assigned to receive LPS (total dose, 80 µg; n = 4) or saline (0.9% NaCl) solution (80 mL/h; 4) via constant rate infusion or 8 bolus IV injections of LPS (10 µg, q 6 h;4) during a 48-hour period. Physical examinations were performed every 4 hours, inflammatory cytokine gene expression was determined for blood samples obtained every 8 hours, and IV glucose tolerance tests were performed. RESULTS: All LPS-treated horses had signs of depression and mild colic; those signs abated as the study progressed. Administration of LPS increased expression of interleukin-1ß, interleukin-6, and interleukin-8, but results were not significantly different between LPS treatment groups. Cytokine expression was significantly higher on the first day versus the second day of LPS treatment. Interleukin-1ß expression was positively correlated with rectal temperature and expression of other cytokines. Glucose and insulin dynamics for both LPS groups combined did not differ significantly from those of the saline solution group. Signs of laminitis were not detected in any of the horses. CONCLUSIONS AND CLINICAL RELEVANCE: Horses developed LPS tolerance within approximately 24 hours after administration was started, and the method of LPS administration did not affect the magnitude or duration of systemic inflammation. Laminitis was not induced in horses.

Novel link between inflammation and impaired glucose transport during equine insulin resistance.

Although insulin resistance (IR) has been increasingly recognized in horses, a clear understanding of its pathophysiology is lacking. The purpose of the present study was to determine the early pathologic changes in IR horses by characterizing alterations in proteins that play key roles in innate immunological responses and inflammatory pathways, and by identifying potential links with glucose transport and insulin signaling. Visceral (VIS) and subcutaneous (SC) adipose tissue and skeletal muscle (SM) biopsies were collected from horses, which were classified as insulin-sensitive (IS) or IR based on the results of an insulin-modified frequently sampled intravenous glucose tolerance test. Protein expression of Toll-like receptor 4 (TLR-4), suppressor of cytokine signaling 3 (SOCS-3) and tumor necrosis factor alpha (TNF-α) were quantified by Western blotting in VIS and SC adipose depots and SM, as well as insulin receptor substrate 1 (IRS-1). To better characterize the potential relationship between inflammation, IR and impaired glucose transport, we correlated active cell surface glucose transporter 4 (GLUT-4) content (measured by a cell surface biotinylated assay) with individual- and tissue-specific data related to inflammation. IR was associated with a significantly increased expression of TLR-4 and SOCS-3 in SM and VIS tissue, without a significant change in SC site. We also observed a significant increase in TNF-α in VIS, but not in SC, tissue of IR vs. IS horses. There was no difference in total content or serine phosphorylation of IRS-1 for any sampling site in IR compared to IS horses. We further observed a significant positive correlation between TLR-4 content and SOCS-3, as well as a significant negative correlation between SOCS-3 content and GLUT-4 trafficking. Taken together, the data suggested a pro-inflammatory state in SM and VIS, but not SC, adipose depot during compensated IR. In addition, SOCS-3 appears to be a novel link between inflammation and dysregulated glucose metabolism and insulin sensitivity during the early pathogenesis of insulin resistance.

Validation studies on blood collection from the jugular vein of conscious mice.

A method for blood collection from the jugular vein of mice without anesthesia was compared with a tail-incision technique. Jugular vein blood collection allowed withdrawal of almost 15% of the circulating blood volume at a time in less than 1 min. Hemolysis, hematocrit, and plasma thrombin-antithrombin complexes (a marker of blood coagulation) were higher in samples collected from the tail vein than the jugular vein. Mice produced similar plasma corticosterone levels after serial blood collection by either method. Tail incision led to a slight but significant increase in C-reactive protein levels. Using the jugular venipuncture technique, we then performed a pharmacokinetic study and an oral glucose tolerance test. Plasma concentrations of levofloxacin, an antimicrobial agent, were dose-dependently elevated after oral administration, and linear increases in C(max) and AUC were observed. We also confirmed that overall glucose excursion is significantly decreased in mice treated with exendin 4, a glucagon-like peptide 1 agonist. These results indicate that the jugular venipuncture is a useful technique from the point of view of no requirement for anesthetics, serial blood collection at short intervals, large volume of blood collection, quality of sample and animal welfare. This technique is of particular interest for studies that examine time-dependent changes in blood variables.

Effects of abomasal infusion of tallow or camelina oil on responses to glucose and insulin in dairy cows during late pregnancy.

Late pregnancy is associated with moderate insulin resistance in ruminants. Reduced suppression of lipolysis by insulin facilitates mobilization of nonesterified fatty acids (NEFA) from adipose tissue, resulting in elevated plasma NEFA concentrations. Decrease in dry matter intake (DMI) before parturition leads to accelerated lipomobilization and increases plasma NEFA, which may further impair insulin sensitivity. The aim of the study was to evaluate the effects of elevation of plasma NEFA concentration by abomasal infusions tallow (TAL) or camelina oil (CAM) on whole-body responses to exogenous glucose and insulin. We further assessed whether CAM, rich in C18:3n-3, enhances whole-body insulin sensitivity compared with TAL. Six late-pregnant, second-parity, rumen-cannulated dry Ayrshire dairy cows fed grass silage to meet 95% of metabolizable energy requirements were used in a replicated 3 × 3 Latin square with 5-d periods and 5 recovery days between each period. Treatments consisted of abomasal infusion of 500 mL/d (430 g of lipids/d) of water (control), TAL, or CAM administered in 10 equal doses daily. Intravenous glucose tolerance test (IVGTT) and i.v. insulin challenge (IC) were performed on d 5 after 98 and 108 h of treatment infusions, respectively. Infusion of lipids increased basal plasma NEFA concentrations on d 5 (CAM: 0.25; TAL: 0.28; control: 0.17 mmol/L). Following glucose injection, the rate of glucose clearance (CR) was lower in lipid-treated cows (CAM: 1.34; TAL: 1.48; control: 1.74%/min) and time to reach half-maximal glucose concentration (T(1/2)) was longer (CAM: 54; TAL: 47; control: 42 min). Similar responses were observed after insulin injection. Increased plasma NEFA concentration tended to decrease insulin secretion in IVGTT. Infusion of CAM increased plasma C18:3n-3 content (CAM: 26.4; TAL: 16.1; control: 20.9 g/100g of fatty acids). Data suggest that CAM had an insulin-sensitizing effect, because the disposition index and insulin sensitivity index, derived from minimal model analysis, were higher in CAM than in TAL during IVGTT, and lower insulin concentrations during IC led to similar glucose clearance in CAM as in TAL. These results indicate that elevated plasma NEFA concentration per se induces whole-body insulin resistance in late-pregnant dry cows.

The GLP-1 mimetic exenatide potentiates insulin secretion in healthy cats.

The glucagon-like peptide-1 mimetic exenatide has a glucose-dependent insulinotropic effect, and it is effective in controlling blood glucose (BG) with minimal side effects in people with type 2 diabetes. Exenatide also delays gastric emptying, increases satiety, and improves ß-cell function. We studied the effect of exenatide on insulin secretion during euglycemia and hyperglycemia in cats. Nine young, healthy, neutered, purpose-bred cats were used in a randomized, cross-over design. BG concentrations during an oral glucose tolerance test were determined in these cats previously. Two isoglycemic glucose clamps (mimicking the BG concentration during the oral glucose tolerance test) were performed in each cat on separate days, one without prior treatment (IGC) and the second with exenatide (1 µg/kg) injected subcutaneously 2 h before (ExIGC). BG, insulin, and exenatide concentrations were measured, and glucose infusion rates were recorded and compared in paired tests between the two experiments. After exenatide injection, insulin serum concentrations increased significantly (2.4-fold; range 1.0- to 9.2-fold; P = 0.004) within 15 min. This was followed by a mild decrease in BG concentration and a return of insulin concentration to baseline despite a continuous increase in serum exenatide concentrations. Insulin area under the curve (AUC) during ExIGC was significantly higher than insulin AUC during IGC (AUC ratio, 2.0 ± 0.4; P = 0.03). Total glucose infused was not significantly different between IGC and ExIGC. Exenatide was detectable in plasma at 15 min after injection. The mean exenatide concentration peaked at 45 min and then returned to baseline by 75 min. Exenatide was still detectable in the serum of three of five cats 8 h after injection. No adverse reactions to exenatide were observed. In conclusion, exenatide affects insulin secretion in cats in a glucose-dependent manner, similar to its effect in other species. Although this effect was not accompanied by a greater ability to dispose of an intravenous glucose infusion, other potentially beneficial effects of exenatide on pancreatic ß cells, mainly increasing their proliferation and survival, should be investigated in cats.