Background: Little is known about the implications of hyperinsulinemia on energy metabolism, and such knowledge might help understand the pathophysiology of insulin dysregulation. Objectives: Describe differences in the metabolic response to an oral glucose test, depending on the magnitude of the insulin response. Animals: Twelve Icelandic horses in various metabolic states. Methods: Horses were subjected to 3 oral glucose tests (OGT; 0.5 g/kg body weight glucose). Basal, 120 and 180 minutes samples were analyzed using a combined liquid chromatography tandem mass spectrometry and flow injection analysis tandem mass spectrometry metabolomic assay. Insulin concentrations were measured using an ELISA. Analysis was performed using linear models and partial least-squares regression. Results: The kynurenine : tryptophan ratio increased over time during the OGT (adjusted P-value = .001). A high insulin response was associated with lower arginine (adjusted P-value = .02) and carnitine (adjusted P-value = .03) concentrations. A predictive model using only baseline samples performed well with as few as 7 distinct metabolites (sensitivity, 86%; 95% confidence interval [CI], 81%-90%; specificity, 88%; 95% CI, 84%-92%). Conclusions and Clinical Importance: Our results suggest induction of low-grade inflammation during the OGT. Plasma arginine and carnitine concentrations were lower in horses with high insulin response and could constitute potential therapeutic targets. Development of screening tools to identify insulin-dysregulated horses using only baseline blood sample appears promising.

Background Insulin dysregulation (ID) goes along with lasting or transient hyperinsulinemia able to trigger equine laminitis, a painful and crippling foot condition. Promoting weight loss through dietary changes and physical activity is currently the main option to prevent this disease. This study aimed at describing the relationship between weight variations and the level of ID as determined by oral glucose tests (OGT). Therefore, the insulin response of 19 Icelandic horses to repeated OGTs was retrospectively analysed considering the variations in their body weight. Results There was a strong linear relationship between variations in body weight and variations in the total insulin response to OGT as approximated by the area under the curve of insulin (p < 0.001). As indicated by a weighted least squares model, the insulin response decreased by 22% for 5% weight loss on average. However some horses did not respond to weight loss with a reduction of their insulin response to OGT. Additionally, a high correlation between 120 min serum insulin concentration and total insulin response was observed (r = 0.96, p < 0.001). Conclusions The results corroborate that weight loss is effective against ID and allow for a better quantification of the expected improvement of the insulin response after weight loss. However, it is unclear why some horses did not respond as expected. The high correlation between the 120 min insulin concentration and total insulin response suggests that insulin status can be accurately determined and monitored with only few samples in a practical setting.

Background Insulin dysregulation (ID) is an equine endocrine disorder, which is often accompanied by obesity and various metabolic perturbations. The relationship between weight variations and fluctuations of the insulin response to oral glucose tests (OGT) as well as the metabolic impact of ID have been described previously. The present study seeks to characterize the concomitant metabolic impact of variations in the insulin response and bodyweight during repeated OGTs using a metabolomics approach. Methods Nineteen Icelandic horses were subjected to five OGTs over one year and their bodyweight, insulin and metabolic response were monitored. Analysis of metabolite concentrations depending on time (during the OGT), relative bodyweight (rWeight; defined as the bodyweight at one OGT divided by the mean bodyweight across all OGTs) and relative insulin response (rAUCins; defined accordingly from the area under the insulin curve during OGT) was performed using linear models. Additionally, the pathways significantly associated with time, rWeight and rAUCins were identified by rotation set testing. Results The results suggested that weight gain and worsening of ID activate distinct metabolic pathways. The metabolic profile associated with weight gain indicated an increased activation of arginase, while the pathways associated with time and rAUCins were consistent with the expected effect of glucose and insulin, respectively. Overall, more metabolites were significantly associated with rWeight than with rAUCins.

Traumatic vertebral injuries are typically caused by incidents such as collision with immovable objects or a fall. Although injury to the vertebral column may occur at any site, in adult horses, the caudal neck and caudal thoracic (T15-18) are the most affected regions.In contrast, traumatic vertebral injury of the cranial to mid-thoracic and lumbar (L) spine is rare in equids (Feige et al., 2000;Robertson & Samii, 2012).The degree and type of the neurological abnormalities depend on location, severity of the insult and damage of the spinal cord.Cases may either be asymptomatic without any neurological signs or may exhibit severe tetraparesis or tetraplegia. Injuries to the caudal cervical (C) or thoracic spinal cord more likely lead to lateral recumbency compared with lesions of the cranial cervical or lumbosacral spine (Feige et al., 2000). Lesions of the spinal cord localised between the 2nd thoracic vertebra and the 3rd lumbar vertebra may lead to pelvic limb paralysis with concurrent extensor rigidity of the thoracic limbs. This condition is referred to as Schiff-Sherrington syndrome (Coates & O'Brien, 2004;deLahunta, 1983). To the authors' knowledge only two cases of Schiff-Sherrington syndrome in horses have been reported (Chiapetta et al., 1985;Lhamas et al., 2015).

Background Oral glycemic challenge (GC) tests are recommended for diagnosis of insulin dysregulation (ID). Various protocols are used, but all have limitations in terms of palatability, ease of use, variable composition, geographic availability, or some combination of these. Hypothesis/Objective To evaluate newly developed formulations with defined carbohydrate composition for use as oral GCs. Animals Thirty‐four horses and ponies in various metabolic states. Methods Our objectives were carried out in 2 separate cross‐over experiments. First, the palatability and acceptance of various GCs (2 syrups, 1 granulate) offered for free intake were compared to glucose mixed in a chaff‐based diet. Subsequently, syrups were administered by syringe and compared to an oral glucose test using naso‐gastric tubing (tube OGT) to investigate the glycemic and insulinemic responses. Second, these variables were compared in the best performing GC‐formulations (granulate further optimized to pelleted formulation and 1 syrup) and a tube OGT. All GCs were administered with equivalent amounts of 0.5 g glycemic carbohydrates per kg body weight. Results Only the GC pellets were consumed completely by all horses (consumption time 5 ± 2 min). When administered by syringe, the GC syrup also was well accepted. The insulin concentrations at 120 min correlated significantly between tube OGT and GC pellets (r = .717; P < .001) or GC syrup (r = .913; P < .001). The new GC syrup and GC pellets discriminate between healthy and ID horses. Conclusions and Clinical Significance The GC pellets (DysChEq)™ and GC syrup can be used as palatable and well‐accepted oral GC tests for assessment of ID in horses.