Generalized obesity, regional adiposity, hyperinsulinemia and hypertriglyceridemia are all potential indicators of equine metabolic syndrome (EMS). This study aimed to assess the relationship between morphometric measurements of body condition and metabolic hormone concentrations in ponies, with and without a neck crest or generalised obesity. Twenty-six ponies were assigned a body condition score (BCS) and cresty neck score (CNS). Height, girth, and neck measurements were taken. An oral glucose test (OGT; 0.75g dextrose/kg BW) was performed and blood samples collected prior to and 2 hours post dosing. Basal blood samples were analysed for blood glucose, serum insulin, triglyceride and leptin, and plasma HMW adiponectin concentrations. Post-prandial samples were analysed for serum insulin concentration. The ponies were grouped as having a) a normal to fleshy body status (BCS ≤7 and CNS ≤2; n = 10); b) having a high CNS, but without generalised obesity (BCS ≤7 and CNS ≥3; n = 11), or c) being obese (BCS ≥8 and CNS ≥1; n = 5). Responses to the OGT indicated that both normal and insulin-dysregulated ponies were included in the cohort. Post-prandial serum insulin was positively associated with CNS (P<0.035) and ponies with a CNS ≥ 3 had 5 times greater odds of being insulin-dysregulated. The high CNS group had a greater insulin response to the OGT than those in the normal/fleshy group (P = 0.006), whereas obese ponies did not differ from the other two groups. Basal HMW adiponectin was negatively correlated with post-prandial insulin concentrations (r = -0.5, P = 0.009), as well as being decreased in the group with a high CNS, compared to the obese group (P = 0.05). Cresty neck score was more predictive of insulin dysregulation than BCS, and this may be relevant to the diagnosis of EMS. Adiponectin may also be a measure of insulin dysregulation that is independent of body condition.

Background: Gastrointestinal peptides, such as glucagon‐like peptide‐2 (GLP‐2), could play a direct role in the development of equine hyperinsulinaemia. Objectives: To describe the secretory pattern of endogenous GLP‐2 over 24 h in healthy ponies and determine whether oral administration of a synthetic GLP‐2 peptide increases blood glucose or insulin responses to feeding. Study Design: A cohort study followed by a randomised, controlled, cross‐over study. Methods: In the cohort study, blood samples were collected every 2 h for 24 h in seven healthy ponies and plasma [GLP‐2] was measured. In the cross‐over study, 75 μg/kg bodyweight of synthetic GLP‐2, or carrier only, was orally administered to 10 ponies twice daily for 10 days. The area under the curve (AUC _0–3h ) of post‐prandial blood glucose and insulin were determined before and after each treatment. Results: Endogenous [GLP‐2] ranged from <0.55 to 1.95 ± 0.29 [CI 0.27] ng/mL with similar peak concentrations in response to meals containing 88–180 g of non‐structural carbohydrate, that were ~4‐fold higher ( P < 0.001) than the overnight nadir. After GLP‐2 treatment peak plasma [GLP‐2] increased from 1.1 [0.63–1.37] ng/mL to 1.54 [1.1–2.31] ng/mL (28.6%; P = 0.002), and AUC _0–3h was larger ( P = 0.01) than before treatment. The peptide decreased (7%; P = 0.003) peak blood glucose responses to feeding from 5.33 ± 0.45 mmol/L to 5.0 ± 0.21 mmol/L, but not AUC _0–3h ( P = 0.07). There was no effect on insulin secretion. Main Limitations: The study only included healthy ponies and administration of a single dose of GLP‐2. Conclusions: The diurnal pattern of GLP‐2 secretion in ponies was similar to other species with no apparent effect of daylight. Although GLP‐2 treatment did not increase post‐prandial glucose or insulin responses to eating, studies using alternative dosing strategies for GLP‐2 are required.

Background: Active glucagon‐like peptide‐1 (aGLP‐1) has been implicated in the pathogenesis of equine insulin dysregulation (ID), but its role is unclear. Cleavage of proglucagon (coded by the GCG gene) produces aGLP‐1 in enteral L cells. Objectives: The aim in vivo was to examine the sequence of the exons of GCG in horses with and without ID, where aGLP‐1 was higher in the group with ID. The aims in vitro were to identify and quantify the expression of GCG in the equine intestine (as a marker of L cells) and determine intestinal secretion of aGLP‐1. Study design: Genomic studies were case–control studies. Expression and secretion studies in vitro were cross‐sectional. Methods: The GCG gene sequence of the exons was determined using a hybridisation capture protocol. Expression and quantification of GCG in samples of stomach duodenum, jejunum, ileum, caecum and ascending and descending colon was achieved with droplet digital PCR. For secretory studies tissue explants were incubated with 12 mM glucose and aGLP‐1 secretion was measured with an ELISA. Results: Although the median [IQR] post‐prandial aGLP‐1 concentrations were higher ( p = 0.03) in animals with ID (10.2 [8.79–15.5]), compared with healthy animals (8.47 [6.12–11.7]), there was 100% pairwise identity of the exons of the GCG sequence for the cohort. The mRNA concentrations of GCG and secretion of aGLP‐1 differed ( p < 0.001) throughout the intestine. Main limitations: Only the exons of the GCG gene were sequenced and breeds were not compared. The horses used for the study in vitro were not assessed for ID and different horses were used for the small, and large, intestinal studies. Conclusions: Differences in post‐prandial aGLP‐1 concentration were not due to a variant in the exons of the GCG gene sequence in this cohort. Both the large and small intestine are sites of GLP‐1 secretion.

Ecdysterone controls moulting and reproduction in insects, crustaceans, and helminths. It is also produced by many plants, probably as an insect deterrent. The steroid is not made by vertebrates but has anabolic effects in mammals and could be useful for treating sarcopenia in aged horses. However, ecdysterone is banned in horseracing and equestrian sports, and with no limit of reporting, the risk of unintended exposure to this naturally occurring prohibited substance is a concern. To explore this risk, pasture plants and hay samples were analysed for ecdysterone content, as well as samples of blood, faeces, and intestinal mucosa from horses (euthanized for non-research purposes) with varying degrees of endo-parasite infestation. The variability in serum ecdysterone concentrations between different horses after administering a fixed dose was also examined. Ecdysterone was detected in 24 hay samples (0.09 to 3.74 µg/g) and several weeds, with particularly high concentrations in Chenopodium album (244 µg/g) and Solanum nigrum (233 µg/g). There was a positive correlation between faecal ecdysterone and faecal egg counts, but no effect of anthelmintic treatment and no relation to the number of encysted cyathostome larvae in the large intestine mucosa. Certain horses maintained an unusually high serum ecdysterone concentration over several weeks and/or displayed an abnormally large response to oral ecdysterone administration. Thus, the risk of environmental exposure to ecdysterone is apparent, and several factors must be considered when determining an appropriate dosage for clinical studies or setting a reporting threshold for equine sports.

Background: Total adiponectin concentration is associated with hyperinsulinemia and laminitis risk in ponies but the high molecular weight (HMW) multimer is a more sensitive indicator of metabolic disease in other species and could be a useful biomarker for insulin dysregulation (ID). Hypothesis/Objectives: To determine a cut-off value for using HMW adiponectin as an adjunct diagnostic tool for ID. Animals: Cohort of 127 privately and university-owned horses and ponies of various breeds with 55 classified as ID positive and 72 as ID negative. Methods: Cohort study. Baseline and postprandial blood samples from an in-feed oral glucose test (0.75 g/kg dextrose) were used to determine ID status. Insulin and HMW adiponectin concentrations were measured using validated immunoassays. High molecular weight adiponectin cut-off values were derived with receiver-operator characteristic curve analysis using a bootstrap method to maximize the sum of sensitivity and specificity. Results: Median [IQR] HMW adiponectin concentration was higher (P < .001) in ID negative animals (4.19 [2-6.5] μg/mL) compared to ID positive animals (1.79 [0.63-3.5] μg/mL), with a cut-off value (95% CI) of 2.1 (1.26, 3.15) μg/mL (area under the curve 0.71; sensitivity 0.62; and specificity 0.74). Horses had higher (P < .001) HMW adiponectin concentrations (4.38 [2.22-7.3] μg/mL) than ponies (1.84 [0.64-3.75] μg/mL). However, HMW adiponectin did not differ between horses with and without ID, and both horse subgroups had concentrations higher (P ≤ .002) than ponies with ID. Conclusions and clinical importance: Use of a single cut-off value for HMW adiponectin as an adjunct biomarker for ID for both horses and ponies is not accurate.