Short-term effects of canagliflozin on glucose and insulin responses in insulin dysregulated horses: A randomized, placebo-controlled, double-blind, study.

BACKGROUND: Decreasing hyperinsulinemia is crucial in preventing laminitis in insulin dysregulated (ID) horses. Complementary pharmacological treatments that efficiently decrease postprandial hyperinsulinemia in ID horses are needed. OBJECTIVES: Compare short-term effects of canagliflozin vs placebo on glucose and insulin responses to an oral sugar test (OST) as well as the effects on body weight and triglyceride concentrations in horses with ID. ANIMALS: Sixteen privately-owned ID horses. METHODS: A single-center, randomized, double-blind, placebo-controlled, parallel design study. The horses were randomized (ratio 1:1) to either once daily PO treatment with 0.6 mg/kg canagliflozin or placebo. The study consisted of an initial 3-day period for obtaining baseline data, a 3-week double-blind treatment period at home, and a 3-day follow-up period similar to the initial baseline period but with continued double-blind treatment. Horses were subjected to an 8-sample OST in the morning of the third day on both visits. RESULTS: Maximal geometric least square (LS) mean insulin concentration (95% confidence interval [CI]) during the OST decreased after 3 weeks of canagliflozin treatment compared with placebo (83.2; 55.4-125.0 vs 215.2; 143.2-323.2 µIU/mL). The geometric LS mean insulin response (insulin AUC0-180 ) for canagliflozin-treated horses was >66% lower compared with placebo. Least square mean body weight decreased by 11.1 (4-18.1) kg and LS mean triglyceride concentrations increased by 0.99 (0.47-1.5) mmol/L with canagliflozin treatment. CONCLUSIONS AND CLINICAL IMPORTANCE: Canagliflozin is a promising drug for treatment of ID horses that requires future studies.

Serum amyloid A as a marker to detect sepsis and predict outcome in hospitalized neonatal foals.

BACKGROUND: Serum amyloid A (SAA) has been reported to hold promise as diagnostic and prognostic marker in foals. This has not been investigated thoroughly. OBJECTIVES: Evaluate admission SAA concentrations as predictor of sepsis and outcome. ANIMALS: Five hundred and ninety hospitalized foals <14 days old. METHODS: Retrospective multicenter study. Foals were scored with sepsis and survival scores, grouped according to health category (septic, sick but nonseptic, uncertain sepsis status) and outcome; septic foals were further categorized according to severity (normal sepsis, severe sepsis, and septic shock). SAA was compared between groups using Mann-Whitney test and Kruskal-Wallis test. Receiver operating characteristic curves identified optimal SAA cut off values for detecting sepsis and predicting outcome. RESULTS: Admission SAA concentrations differed significantly between sick nonseptic foals (312.1 ± 685.4 mg/L) and septic foals (1079.7 ± 1254.5 mg/L) and increased with increasing sepsis score. SAA did not differ between sepsis severity groups. The optimal cut off for sepsis detection was 1050 mg/L (sensitivity 30.2%, specificity 90.7%). Admission SAA concentrations were lower in surviving (435.0 ± 723.6 mg/L) compared to nonsurviving foals (1062.7 ± 1440.1 mg/L) and decreased with increasing survival score. The optimal cut off for nonsurvival prediction was 1250 mg/L (sensitivity 22.1%, specificity 90.8%). CONCLUSIONS AND CLINICAL IMPORTANCE: SAA concentration was higher in septic foals and nonsurviving foals. Even though optimal cut offs for SAA to detect sepsis and predict outcome had low sensitivity, they had good specificity. SAA can therefore be used as a marker to rule out sepsis and nonsurvival.

The disposition of trimethoprim and sulfadiazine in neonatal foals after intravenous administration.

BACKGROUND: Septicaemia in the neonatal foal is caused by both Gram positive and Gram negative bacteria. The life-threatening nature of this condition requires treatment to be initiated with broad spectrum antimicrobial drugs pending antimicrobial susceptibility testing. Potentiated sulphonamides, for example, trimethoprim combined with sulfadiazine, could be clinically relevant options but their pharmacokinetics in the neonatal foal are unknown. OBJECTIVES: To describe the plasma disposition of trimethoprim and sulfadiazine in neonatal foals and to relate the results to patterns in the minimum inhibitory concentration (MIC) for Escherichia coli, a recognized pathogen in neonatal foal sepsis. METHOD: A total of five doses of trimethoprim (2.5 mg/kg) and sulfadiazine (12.5 mg/kg) were administered intravenously every 12 h to eight neonatal foals that were 3 days old at inclusion. A non-linear mixed effects model was fitted to the trimethoprim and sulfadiazine experimental data. The 24 h area under the free plasma trimethoprim and sulfadiazine concentration-time curves (fAUC) and the pharmacokinetic/pharmacodynamik (PK/PD)-index fAUC/MIC was calculated to evaluate the potential clinical benefits of the administered dose. RESULTS: For trimethoprim, the typical values were 1.99 L/kg, 0.33 L/h·kg and 4.2 h for the apparent volume of distribution, clearance and terminal half-life, respectively. The 24 h fAUC for trimethoprim was 11.3 µg·h/ml (7.2-15.2) and the fAUC/MIC ratio for E. coli was 23 (16.4-29.2) (population mean (range)). For sulfadiazine, the typical values were 0.61 L/kg, 0.09 L/h·kg and 5.3 h for the apparent volume of distribution, clearance and terminal half-life, respectively. The 24 h fAUC for sulfadiazine was 246.8 µg·h/ml (175.6-335.4). CONCLUSION: For trimethoprim, the plasma exposure is insufficient in some foals to successfully treat bacterial infections with an MIC-value of 0.5 µg/ml using the studied dosing regimen.

Atrial fibrillatory rate as predictor of recurrence of atrial fibrillation in horses treated medically or with electrical cardioversion.

BACKGROUND: The recurrence rate of atrial fibrillation (AF) in horses after cardioversion to sinus rhythm (SR) is relatively high. Atrial fibrillatory rate (AFR) derived from surface ECG is considered a biomarker for electrical remodelling and could potentially be used for the prediction of successful AF cardioversion and AF recurrence. OBJECTIVES: Evaluate if AFR was associated with successful treatment and could predict AF recurrence in horses. STUDY DESIGN: Retrospective multicentre study. METHODS: Electrocardiograms (ECG) from horses with persistent AF admitted for cardioversion with either medical treatment (quinidine) or transvenous electrical cardioversion (TVEC) were included. Bipolar surface ECG recordings were analysed by spatiotemporal cancellation of QRST complexes and calculation of AFR from the remaining atrial signal. Kaplan-Meier survival curve and Cox regression analyses were performed to assess the relationship between AFR and the risk of AF recurrence. RESULTS: Of the 195 horses included, 74 received quinidine treatment and 121 were treated with TVEC. Ten horses did not cardiovert to SR after quinidine treatment and AFR was higher in these, compared with the horses that successfully cardioverted to SR (median [interquartile range]), (383 [367-422] vs 351 [332-389] fibrillations per minute (fpm), P < .01). Within the first 180 days following AF cardioversion, 12% of the quinidine and 34% of TVEC horses had AF recurrence. For the horses successfully cardioverted with TVEC, AFR above 380 fpm was significantly associated with AF recurrence (hazard ratio = 2.4, 95% confidence interval 1.2-4.8, P = .01). MAIN LIMITATIONS: The treatment groups were different and not randomly allocated, therefore the two treatments cannot be compared. Medical records and the follow-up strategy varied between the centres. CONCLUSIONS: High AFR is associated with failure of quinidine cardioversion and AF recurrence after successful TVEC. As a noninvasive marker that can be retrieved from surface ECG, AFR can be clinically useful in predicting the probability of responding to quinidine treatment as well as maintaining SR after electrical cardioversion.

Evaluation of fasting plasma insulin and proxy measurements to assess insulin sensitivity in horses.

BACKGROUND: Proxies are mathematical calculations based on fasting glucose and/or insulin concentrations developed to allow prediction of insulin sensitivity (IS) and ß-cell response. These proxies have not been evaluated in horses with insulin dysregulation. The first objective of this study was to evaluate how fasting insulin (FI) and proxies for IS (1/Insulin, reciprocal of the square root of insulin (RISQI) and the quantitative insulin sensitivity check index (QUICKI)) and ß-cell response (the modified insulin-to-glucose ratio (MIRG) and the homeostatic model assessment of ß-cell function (HOMA-ß)) were correlated to measures of IS (M index) using the euglycemic hyperinsulinemic clamp (EHC) in horses with insulin resistance (IR) and normal IS. A second objective was to evaluate the repeatability of FI and proxies in horses based on sampling on consecutive days. The last objective was to investigate the most appropriate cut-off value for the proxies and FI. RESULTS: Thirty-four horses were categorized as IR and 26 as IS based on the M index. The proxies and FI had coefficients of variation (CVs) ≤ 25.3 % and very good reliability (intraclass correlation coefficients ≥ 0.89). All proxies and FI were good predictors of the M index (r = 0.76-0.85; P < 0.001). The proxies for IS had a positive linear relationship with the M index whereas proxies for ß-cell response and FI had an inverse relationship with the M index. Cut-off values to distinguish horses with IR from horses with normal IS based on the M index were established for all proxies and FI using receiver operating characteristic curves, with sensitivity between 79 % and 91 % and specificity between 85 % and 96 %. The cut-off values to predict IR were < 0.32 (RISQI), < 0.33 (QUICKI) and > 9.5 µIU/mL for FI. CONCLUSIONS: All proxies and FI provided repeatable estimates of horses' IS. However, there is no advantage of using proxies instead of FI to estimate IR in the horse. Due to the heteroscedasticity of the data, proxies and FI in general are more suitable for epidemiological studies and larger clinical studies than as a diagnostic tool for measurement of IR in individual horses.

The effect of diet-induced obesity and pasture on blood pressure and serum cortisol in Standardbred mares.

BACKGROUND: Obesity is associated with insulin resistance, vascular dysfunction and altered cortisol metabolism both in humans and in horses. OBJECTIVES: Evaluate the effect of weight gain induced by a haylage diet low in nonstructural carbohydrates (NSC) on insulin sensitivity, blood pressure and serum cortisol concentrations. STUDY DESIGN: In vivo experiment. METHODS: Nine adult Standardbred mares fed a fat supplemented haylage diet at 250% of the horses' daily metabolisable energy requirements for 22 weeks. Horses were then turned out on pasture for 4 weeks. Insulin sensitivity (SICLAMP ) was measured before and after weight gain and after 4 weeks of pasture using the euglycemic hyperinsulinaemic clamp (EHC) method. Body condition score (BCS), blood pressure and serum cortisol were monitored throughout the study. All data were analysed using the linear mixed model procedure. Values of P < 0.05 were considered as statistically different. RESULTS: All horses became obese during the weight gain period (BCS> 7). Mean arterial blood pressure (MAP) increased during the weight gain period and was significantly higher than initial values at the end of the weight gain period (78 ± 3 mm Hg vs 92 ± 3 mmHg). MAP remained increased on pasture (93 ± 3 mmHg). SICLAMP was unaffected by weight gain 0.9 ± 0.1 vs 1.0 ± 0.1 ([mg/kg/min × 103 ]/[µIU/mL × mmol/L])) but improved after pasture (1.6 ± 0.1 ([mg/kg/min × 103 ]/ [mU/L]). Serum cortisol concentrations increased during the weight gain period (80 ± 9 nmol/L vs 112 ± 9 nmol/L) and remained increased during pasture. MAIN LIMITATIONS: Limited number of horses and no control group. CONCLUSIONS: Obesity was associated with a linear increase in blood pressure and an increase in serum cortisol that was not associated with insulin sensitivity.

Hematologic, prostaglandin F2α -metabolite, serum amyloid A, and serum iron changes in horses with experimentally induced endotoxemia.

BACKGROUND: Endotoxemia is a common and severe disease of horses. Most previous studies have monitored changes caused by a bolus dose of endotoxin over short time periods. OBJECTIVES: We aimed to describe inflammatory responses to endotoxin with inflammatory and hematologic markers monitored over a longer time than has been performed in the past using more prolonged endotoxin exposures. METHODS: Escherichia coli O55:B5 endotoxin was administered as a 6-hour continuous intravenous infusion of lipopolysaccharide (LPS) to eight horses. Blood cell counts, and prostaglandin F2α -metabolite (PGM), serum amyloid A (SAA), and serum total iron concentrations were monitored for up to 3 or 6 days. RESULTS: An immediate and severe decrease in neutrophils and monocytes occurred in all horses, which subsequently changed to a moderate to strong neutrophilia and monocytosis that persisted for more than 78 hours postinfusion (PI) of LPS. Lymphocyte and eosinophil numbers decreased gradually and then normalized after 66- and 78-hours PI, respectively. Mild to moderate, biphasic thrombocytopenia occurred. A pronounced, transient increase in PGM occurred between 1 and 7 hours, peaking at 2 hours. Serum amyloid A began to increase after 6 hours PI and remained elevated after 72 hours PI. Serum iron was decreased between 6 and 48 hours. The clinical signs were most prominent during the first 24 hours PI and subsided within 48 hours PI. CONCLUSIONS: Neutrophilia, monocytoses, and high SAA concentrations were present in horses even after the clinical signs had subsided. Serum iron normalized before SAA. Knowledge of these findings is imperative when interpreting laboratory results in horses with possible endotoxin exposure.

Evaluation of the foal survival score in a Danish-Swedish population of neonatal foals upon hospital admission.

BACKGROUND: It is highly desirable to assess the probability of survival in sick neonatal foals upon admission. The foal survival score (FSS) is a published scoring system used to estimate the probability of survival in hospitalized neonatal foals <4 days old. HYPOTHESIS/OBJECTIVES: To evaluate the ability of the FSS to predict survival in older foals from a geographically different area compared to the original study. ANIMALS: Five-hundred ninety hospitalized neonatal foals ≤14 days of age. METHODS: Retrospective Danish-Swedish multicenter study that included details of signalment, history, clinical examination, laboratory results, necropsy findings, and outcome. Scores and score variables were compared between survivors and nonsurvivors using logistic regression. The optimal cutoff and its test parameters were calculated using a receiver operator characteristic curve. RESULTS: Prematurity, cold extremities, ≥2 infectious or inflammatory sites, blood glucose concentration, and total white blood cell counts were significantly associated with nonsurvival (P ≤ .02). The optimal cutoff to predict survival was ≥6, resulting in sensitivity 78%, specificity 58%, 92% positive predictive value, and 31% negative predictive value. The test performed equally well in foals <4 days old compared to those 4-14 days old. CONCLUSIONS AND CLINICAL IMPORTANCE: Using the suggested optimal cutoff of ≥6, the FSS performed moderately well and may aid in early determination of prognosis for survival. However, the FSS did perform differently in another population and therefore should be assessed under local conditions so that its diagnostic potential is not overestimated.

A modified oral sugar test for evaluation of insulin and glucose dynamics in horses.

BACKGROUND: An oral sugar test (OST) using Karo® Light Corn Syrup has been developed in the USA as a field test for the assessment of insulin dysregulation in horses but the syrup is not available in Scandinavian grocery stores. The aim of the study was to compare the results of a modified OST between horses with equine metabolic syndrome (EMS) and healthy horses using a Scandinavian commercially available glucose syrup (Dansukker glykossirap). In addition, the effect of breed and the repeatability of the test were evaluated. In the present study, clinically healthy horses (7 Shetland ponies, 8 Icelandic horses, 8 Standardbred horses) and 20 horses of various breeds with EMS underwent the modified OST test. The Icelandic horses and Shetland ponies underwent the OST twice. Insulin and glucose data from the OST were used to calculate peak insulin concentration (PeakINS), time to peak insulin concentration (T-peakINS), area under the curve for insulin (AUCINS) and glucose (AUCGLU) as well as whole body insulin sensitivity index (ISICOMP). RESULTS: Compared to the healthy group, the EMS group had 6-7 times higher geometric mean for PeakINS and AUCINS and 8 times lower geometric mean for ISICOMP. The EMS group had a delayed T-peakINS compared to the healthy group. There was no effect of breed in the group of healthy horses on PeakINS, T-peakINS, AUCINS, AUCGLU and ISICOMP. Coefficient of variation for repeated tests was 19.8, 19.0 and 17.6 % for PeakINS, AUCINS and ISICOMP respectively. CONCLUSIONS: The results of the present study demonstrate that the modified OST appears to be a practical and useful diagnostic tool for assessment of insulin dysregulation in the horse. However, to make it possible to establish the most appropriate sampling interval and to evaluate the accuracy of the modified OST, further studies in horses with a variable degree of insulin resistance are needed, where results from the modified OST are compared with quantitative measurements for IS.

Blood pressure in Warmblood horses before and during a euglycemic-hyperinsulinemic clamp.

BACKGROUND: Insulin resistance (IR) in humans is related to hypertension and impaired vasodilation. Insulin administration has been shown to lower blood pressure both in insulin resistant as well as in insulin sensitive individuals. The aim of the study was to investigate the association between insulin sensitivity and alterations in blood pressure in healthy horses before and after a euglycemic-hyperinsulinemic clamp (EHC). A 3-h EHC was performed in 13 healthy horses (11 mares, 2 geldings). Blood samples for measurement of plasma glucose and insulin were collected before the start of the EHC, every 10 min during the EHC and immediately after the EHC. Mean, systolic- and diastolic blood pressure was measured before and during the final 10 min of the EHC using an indirect high-definition oscillometric monitor (HDO, horse model) applied to the middle of the coccygeal artery. Five consecutive measurements were made in each horse and on each occasion. Insulin and glucose data from the EHC were used to calculate the mean rate of glucose disposal per unit of insulin during steady state (M/I ratio). Insulin resistance was defined as a M/I ratio <5 mg/kg/min/mUL (Lindåse et al. in Am J Vet Res 77:300-309, 2016). RESULTS: Insulin administration decreased systolic, diastolic and mean arterial pressure in all horses. The M/I ratio for all horses was negatively correlated with the decrease in systolic blood pressure (r2 = 0.55, P = 0.004) and mean arterial pressure (r2 = 0.31, P = 0.048) but not diastolic blood pressure (r2 = 0.12, P = 0.26). Eight horses were defined as insulin resistant (IR) and five horses had normal insulin sensitivity. The five horses with normal insulin sensitivity showed a greater decrease in systolic blood pressure (-17.0 ± 7.4 vs. -3.4 ± 4.6 mmHg, P = 0.001) and MAP (19.2 ± 14.7 vs. 6.9 ± 8.7 mmHg, P = 0.04) than IR horses. There was no difference in the decrease in diastolic blood pressure between groups (16 ± 12.8 vs. 8.9 ± 12.1 mmHg, P = 0.17). CONCLUSIONS: This study indicates that there is a relationship between insulin sensitivity and systolic and MAP in horses. However, studies on a larger number of horses are needed to confirm this association.

Time-related changes in equine neutrophils after experimental endotoxemia: myeloperoxidase staining, size, and numbers.

BACKGROUND: Neutrophil myeloperoxidase content is determined by the Advia 2120 hematology system by staining characteristics. Changes in myeloperoxidase staining are shown by location of neutrophils on Advia peroxidase dot plots and as myeloperoxidase index (MPXI). Significant changes in MPXI have been reported during severe inflammation in horses, dogs, and people but conclusions were inconsistent. OBJECTIVES: Infusion of endotoxin was used to initiate an inflammatory stimulus under controlled conditions and over a longer time period than in previous studies to document kinetics of changes in neutrophil numbers, morphology, and myeloperoxidase staining. Identification of consistent time-related changes may allow better interpretation of changes in neutrophil characteristics during inflammation. MATERIALS: Five Standardbred trotting horses received an intravenous infusion over a 6-hour period with Escherichia coli endotoxin. Neutrophil count, MPXI, neutrophil characteristics in Advia 2120 Perox dot plots and neutrophil morphology in blood smears were monitored with repeated sampling for up to 10 days. RESULTS: Endotoxin infusion immediately caused severe neutropenia which converted to neutrophilia 14 hours after start of endotoxin infusion. Neutrophilia was still present 78 hours after start of infusion. Large "giant" neutrophils first appeared in blood smears and Advia Perox dot plots after 36-48 hours. A marked and consistent decrease in MPXI was seen in all horses 6 days (150 hours) after endotoxin exposure. CONCLUSIONS: Endotoxemia caused prominent, time-related changes in equine neutrophil characteristics including emergence of giant neutrophils and markedly decreased MPXI several days after endotoxin infusion.

Effects of diet-induced weight gain and turnout to pasture on insulin sensitivity in moderately insulin resistant horses.

OBJECTIVE: To quantify insulin sensitivity and monitor glucose, insulin, and lipid concentrations in a group of moderately insulin-resistant horses during induction of obesity by use of a forage diet supplemented with fat and during subsequent turnout to pasture. ANIMALS 9 adult Standardbred mares (11 to 20 years old). PROCEDURES: Weight gain of horses was induced during 22 weeks by use of a forage diet supplemented with fat fed in gradually increasing amounts, followed by feeding of that fat-supplemented diet at 2.5 times the daily maintenance requirements. Horses were then turned out to pasture. Insulin sensitivity was measured with the euglycemic hyperinsulinemic clamp method before and after weight gain and after 4 weeks at pasture. Body weight, body condition score, and cresty neck score as well as fasting and postprandial concentrations of plasma insulin, plasma glucose, serum triglyceride, and serum nonesterified fatty acids were measured during the study. RESULTS: Body weight typically increased by 10%, and body condition score (scale, 1 to 9) increased by > 1.5 from the start to the end of the weight-gain period. There was no difference in insulin sensitivity or metabolic clearance rate of insulin during the weight-gain period. Four weeks at pasture generally improved insulin sensitivity and metabolic clearance rate of insulin by 54% and 32%, respectively, but there was no change in body weight or body condition score. CONCLUSIONS AND CLINICAL RELEVANCE: Findings indicated that dietary composition played a more important role than did short-term weight gain on alterations in insulin sensitivity of horses.

Acute exercise does not induce an acute phase response (APR) in Standardbred trotters.

The purpose of the study was to investigate whether acute strenuous exercise (1600- to 2500-m race) would elicit an acute phase response (APR) in Standardbred trotters. Blood levels of several inflammatory markers [serum amyloid A (SAA), haptoglobin, fibrinogen, white blood cell count (WBC), and iron], muscle enzymes [creatinine kinase (CK) and aspartate transaminase (AST)], and hemoglobin were assessed in 58 Standardbred trotters before and after racing. Hemoglobin levels increased and iron levels decreased 12 to 14 h after racing and haptoglobin concentrations, white blood cell counts, and iron levels were decreased 2 and/or 7 d after racing. Concentrations of CK, AST, SAA, and fibrinogen were unaltered in response to racing. Acute strenuous exercise did not elicit an acute phase reaction. The observed acute increase in hemoglobin levels and decreases in haptoglobin and iron levels may have been caused by exercise-induced hemolysis, which indicates that horses might experience a condition similar to athlete's anemia in humans. The pathogenesis and clinical implications of the hematological and blood-biochemical changes elicited by acute exercise in Standardbred trotters in the present study warrant further investigation.

L'objectif de la présente étude est d'investiguer l'effet de l'exercice intensif (1600­2500 m) sur l'apparition d'une phase inflammatoire aigué chez des trotteurs. Les taux sanguins de différents marqueurs inflammatoires [serum amyloid A (SAA), haptoglobine, fibrinogène, globules blanc (WBC) et fer], d'enzymes musculaires [creatinine kinase (CK) et aspartate transaminase (AST)] et d'hémoglobine ont été évalué dans 58 trotteurs avant et après la course. Respectivement une augmentation et diminution des taux d'hémoglobine et de fer furent présente 12­14 heures suivant la course. Une réduction des taux d'haptoglobine, de globules blanc et de fer était présente 2 et/ou 7 jours après la course. Aucun changement dans les concentrations de CK, AST, SAA et fibrinogène n'a pu être démontre en relation avec la course.L'exercice intense réalise lors de cette étude n'a pu induire de phase inflammatoire aigué. L'augmentation d'hémoglobine et la diminution d'haptoglobine et de fer peuvent être causées par une hémolyse induite par l'exercice, indiquant qu'une condition similaire à l'anémie de l'athlète chez l'homme existe chez le cheval. La pathogénèse et l'implication clinique des modifications hématologiques et biochimiques lié à un exercice intense chez les trotteurs dans la présente étude justifié de plus amples investigations.(Traduit par Docteur Denis Verwilghen).

Lipopolysaccharide-induced inhibition of transcription of tlr4 in vitro is reversed by dexamethasone and correlates with presence of conserved NFκB binding sites.

Engagement of Toll-like receptor 4 (TLR4) by lipopolysaccharide (LPS) is a master trigger of the deleterious effects of septic shock. Horses and humans are considered the most sensitive species to septic shock, but the mechanisms explaining these phenomena remain elusive. Analysis of tlr4 promoters revealed high similarity among LPS-sensitive species (human, chimpanzee, and horse) and low similarity with LPS-resistant species (mouse and rat). Four conserved nuclear factor kappa B (NFκB) binding sites were found in the tlr4 promoter and two in the md2 promoter sequences that are likely to be targets for dexamethasone regulation. In vitro treatment of equine peripheral blood mononuclear cells (eqPBMC) with LPS decreased transcripts of tlr4 and increased transcription of md2 (myeloid differentiation factor 2) and cd14 (cluster of differentiation 14). Treatment with dexamethasone rescued transcription of tlr4 after LPS inhibition. LPS-induced transcription of md2 was inhibited in the presence of dexamethasone. Dexamethasone alone did not affect transcription of tlr4 and md2.

Intramuscular administration of sodium benzylpenicillin in horses as an alternative to procaine benzylpenicillin.

The aim was to supply information about the possibility of replacing the procaine salt with the sodium salt for benzylpenicillin IM treatment in horse in order to diminish the risk for procaine adverse effects. In a crossover study eight horses were given 15 mg/kg sodium benzylpenicillin (Na-pc) twice daily or procaine benzylpenicillin (control) once daily IM for four days. The half-life of Na-pc was 1.9h, peak concentration was 14,600 ng/mL reached after about 23 min. Trough plasma concentration was 281 ng/mL and protein binding 62.8%. The fT>MIC for Staphylococcus aureus was 63% and 100% for Streptococcus equi subsp. equi and Streptococcus zooepidemicus, indicating an adequate antimicrobial therapy. However, Na-pc cannot be recommended from a welfare point of view since the horses showed more pain related behaviour and more pain and swelling compared to the control treatment.

Interday variation and effect of transportation on indirect blood pressure measurements, plasma endothelin-1 and serum cortisol in Standardbred and Icelandic horses.

BACKGROUND: Systemic hypertension is a prominent feature in humans with metabolic syndrome (MS) and this is partly caused by an enhanced endothelin-1 (ET-1) mediated vasoconstriction. There are indications that systemic hypertension might be a feature in equine metabolic syndrome (EMS) but if ET-1 is involved in the development of hypertension in horses is not known. Increased levels of cortisol have also been found in humans with MS but there are no reports of this in horses. Before blood pressure, plasma ET-1 and serum cortisol can be evaluated in horses with EMS, it is necessary to investigate the interday variation of these parameters on clinically healthy horses. The aims of the present study were therefore to evaluate the interday variation and influence of transportation on systemic blood pressure, plasma ET-1 and serum cortisol in healthy Standardbred and Icelandic horses, and to detect potential breed differences. METHODS: Nine horses of each breed were included in the study. Blood pressure was measured and blood samples were collected between 6 and 9 am on two separate days. Eight of the horses (four of each breed) were transported to a new stable were they stayed overnight. The next morning, the sampling procedure was repeated. RESULTS: The interday variation was higher for plasma ET-1 (37%) than for indirect pressure measurements (8-21%) and serum cortisol (18%). There were no differences in systemic blood pressure between the two breeds. The Icelandic horses had significantly lower serum cortisol and significantly higher plasma ET-1 concentrations compared to the Standardbred horses. Plasma ET-1 was significantly elevated after transportation, but systemic blood pressure and serum cortisol did not differ from the values obtained in the home environment. CONCLUSIONS: Indirect blood pressure, plasma ET-1 and serum cortisol are of interest as markers for cardiovascular dysfunction in horses with EMS. The elevated plasma ET-1 concentrations recorded after transportation was likely caused by a stress response. This needs to be considered when evaluating plasma ET-1 in horses after transportation. The differences detected in plasma ET-1 and serum cortisol between the two breeds might be related to differences in genetic setup, training status as well as management conditions.

Effect of repeated oral administration of glucose and leucine immediately after exercise on plasma insulin concentration and glycogen synthesis in horses.

OBJECTIVE: To determine whether repeated oral administration of glucose and leucine during the period immediately after intense exercise would increase the release of insulin and thereby enhance glycogen synthesis in horses. ANIMALS: 12 Standardbred horses. PROCEDURES: In a crossover study design, after glycogen-depleting exercise, horses received oral boluses of glucose (1 g/kg at 0, 2, and 4 hours) and leucine (0.1 g/kg at 0 and 4 hours) or boluses of water (10 mL/kg at 0, 2, and 4 hours; control treatment). Blood samples for determination of glucose, insulin, and leucine concentrations were collected prior to and during a 6-hour period immediately after exercise. Biopsy specimens of a gluteus muscle were obtained before and immediately after exercise and at 3, 6, and 24 hours after exercise for measurement of glycogen concentration. RESULTS: When glucose and leucine were administered to the horses, plasma insulin concentration was significantly higher during the 6 hours immediately after exercise than it was when water was administered to the horses. Serum glucose concentration during the 4 hours immediately after exercise was significantly higher when glucose and leucine were administered than the serum glucose concentration when water was administered. Muscle glycogen concentrations did not differ between the 2 treatments during the 24 hours after exercise. CONCLUSIONS AND CLINICAL RELEVANCE: Synthesis of muscle glycogen after intense intermittent exercise was not enhanced by oral boluses of glucose and leucine after exercise despite pronounced increases in plasma insulin and serum glucose concentrations.

Repeated post-exercise administration with a mixture of leucine and glucose alters the plasma amino acid profile in Standardbred trotters.

BACKGROUND: The branched chain amino acid leucine is a potent stimulator of insulin secretion. Used in combination with glucose it can increase the insulin response and the post exercise re-synthesis of glycogen in man. Decreased plasma amino acid concentrations have been reported after intravenous or per oral administration of leucine in man as well as after a single per oral dose in horses. In man, a negative correlation between the insulin response and the concentrations of isoleucine, valine and methionine have been shown but results from horses are lacking. This study aims to determine the effect of repeated per oral administration with a mixture of glucose and leucine on the free amino acid profile and the insulin response in horses after glycogen-depleting exercise. METHODS: In a crossover design, after a glycogen depleting exercise, twelve Standardbred trotters received either repeated oral boluses of glucose, 1 g/kg body weight (BW) at 0, 2 and 4 h with addition of leucine 0.1 g/kg BW at 0 and 4 h (GLU+LEU), or repeated boluses of water at 0, 2 and 4 h (CON). Blood samples for analysis of glucose, insulin and amino acid concentrations were collected prior to exercise and over a 6 h post-exercise period. A mixed model approach was used for the statistical analyses. RESULTS: Plasma leucine, isoleucine, valine, tyrosine and phenylalanine concentrations increased after exercise. Post-exercise serum glucose and plasma insulin response were significantly higher in the GLU+LEU treatment compared to the CON treatment. Plasma leucine concentrations increased after supplementation. During the post-exercise period isoleucine, valine and methionine concentrations decreased in both treatments but were significantly lower in the GLU+LEU treatment. There was no correlation between the insulin response and the response in plasma leucine, isoleucine, valine and methionine. CONCLUSIONS: Repeated post-exercise administration with a mixture of leucine and glucose caused a marked insulin response and altered the plasma amino acid profile in horses in a similar manner as described in man. However, the decreases seen in plasma amino acids in horses seem to be related more to an effect of leucine and not to the insulin response as seen in man.

Cardiac troponin I and the occurrence of cardiac arrhythmias in horses with experimentally induced endotoxaemia.

The aim of this study was to determine whether experimentally-induced endotoxaemia induced elevations in plasma cardiac troponin I (cTnI) concentrations in horses and how this might affect the incidence of cardiac arrhythmias. Eight Standardbred horses received an intravenous continuous rate infusion of endotoxin (total dose 500 ng/kg) for 6 h while being monitored using electrocardiography (ECG). Blood samples were collected before the start of the endotoxin infusion, every 60 min during the infusion, then 1, 2, 3, 8, 10 and 24 h post-infusion, and analysed for cTnI concentrations. One horse was excluded from the study owing to a high initial cTnI concentration. Endotoxin infusion induced an increase in cTnI concentrations in all horses, reaching mean peak concentration of 0.135±0.094 µg/L by 1 h post-infusion. The cTnI concentrations then decreased and were no longer significantly different from pre-infusion concentrations at 6, 10 and 24 h post-infusion. The number of ventricular events was generally low during the infusion period, but increased during the first 3 h post-infusion in 6/7 horses. In conclusion, elevated cTnI concentrations could be detected early after an endotoxaemic insult using an ultrasensitive cTnI assay, with peak cTnI concentrations preceding the occurrence of ventricular events on ECG.

Resting concentrations of cardiac troponin I in fit horses and effect of racing.

OBJECTIVES: To determine normal resting values for cardiac troponin I (cTnI) in healthy Standardbred, Thoroughbred and Warmblood horses and investigate if racing has an influence on cTnI concentrations. BACKGROUND: Measuring cTnI concentrations in plasma is the gold standard for detecting myocardial injury in humans. Cardiac troponin I is highly conserved between species and has gained interest as a marker for cardiac injury in horses. Increased levels of cTnI have been reported in association with endurance and short-term strenuous exercise on a treadmill in horses. However, the effect of true racing conditions has not yet been reported. ANIMALS, MATERIALS AND METHODS: Blood samples for analysis of cTnI concentrations in plasma were collected from 67 Standardbred racehorses, 34 Thoroughbred racehorses and 35 Warmblood dressage horses at rest. Blood samples were also collected prior to and after racing in 22 Standardbred racehorses and 6 Thoroughbred racehorses. RESULTS: All horses except one had resting plasma cTnI concentrations <0.022 microg/L. Mild increases in cTnI concentrations were seen in some horses 1-2h after the race (1/17 Standardbreds and 2/6 Thoroughbreds) as well as 10-14 h after the race (4/21 Standardbreds and 1/6 Thoroughbreds). CONCLUSIONS: Resting cTnI concentrations in horses are low but mildly elevated cTnI concentrations may be detected in some horses 1-14 h after racing. These findings could be of importance when evaluating horses with suspected cardiac disease that recently have performed hard exercise.