Validity and application of immunoturbidimetric and enzyme-linked immunosorbent assays for the measurement of adiponectin concentration in ponies

Comparison of one novel and four established diagnostic tests for insulin dysregulation in ponies

Several tests have been advocated for diagnosis of insulin dysregulation (ID). Tests using simple sugars may not reflect the response to naturally ingested carbohydrates. This study aimed to evaluate agreement between the oral glucose test (OGT), the oral sugar test (OST), a novel oral test using a proprietary cereal (WEET), the IV combined glucose-insulin tolerance test (CGIT) and fasted basal insulin (FI) for diagnosis of ID. Each of the five tests above was performed on a group of six normal and six insulin dysregulated mixed-breed ponies in a randomised crossover study. Area under the curve (AUC) and maximum concentration of insulin from OGT, OST and WEET showed strong to very strong bivariate correlations (r = 0.85-0.94, and r = 0.87-0.92, respectively; P ≤ 0.001) and were significantly different between tests (associated with dose of carbohydrate) and between CGIT-positive and -negative ponies. Dichotomous results showed substantial agreement between OST and both WEET (κ = 0.65; P = 0.02) and OGT (κ = 0.67; P = 0.01) and between CGIT and both OST (κ = 0.63; P = 0.03) and OGT (κ = 0.67; P = 0.01), and no agreement between FI, which had low sensitivity, and all other tests (κ = 0.15 - 0.31; P > 0. 05). Palatability of WEET was variable, resulting in one pony being excluded for analysis of WEET data. Further work on development of an oral test using a more palatable feedstuff and appropriate cut-offs or diagnostic thresholds for tests of ID is warranted.

Variation in insulin response to oral sugar test in a cohort of horses throughout the year and evaluation of risk factors for insulin dysregulation

BACKGROUND

The oral sugar test (OST) is commonly used to diagnose insulin dysregulation (ID) and equine metabolic syndrome; however, possible seasonal changes in OST results have not been evaluated.

OBJECTIVE

To determine the possible variation in insulin response to OST throughout the year and risk factors associated with maximum insulin concentration (InsMax) and ID.

STUDY DESIGN

Prospective, longitudinal cohort study.

METHODS

The OST was performed on 29 Finnhorses every other month six times. Serum total adiponectin concentration and phenotypic variables related to obesity were also measured. Changes in InsMax, adiponectin, scale weight, body condition score, cresty neck score (CNS), and fasting glucose concentration were assessed. Risk factor analyses were performed on InsMax and ID status, and ID groups were compared with each other.

RESULTS

Fourteen horses were categorised with non-ID each time and 15 as having ID at least once during the follow-up period. The ID status of 12 horses varied throughout the year, but neither the insulin variables measured during the OST nor adiponectin expressed significant seasonal variation. Increasing age and CNS, and decreasing adiponectin were observed as risk factors for a high InsMax after OST. The risk of ID was higher in horses with no exercise compared to horses with exercise (OR 7.6, 95% CI 1.2-49.3, P = .03). Horses with ID had lower serum adiponectin concentrations, longer neck circumference and larger height than horses in the non-ID group.

MAIN LIMITATIONS

The environmental conditions (feeding, exercise) were not constant for all horses throughout the study and only one breed was used.

CONCLUSIONS

Neither OST results nor adiponectin varies with season; however, there were a substantial number of horses with variable ID status throughout the year, in which repeated OSTs may be beneficial. Lack of exercise was a risk factor for ID.

Interobserver and intraobserver reliability for 2 grading systems for gastric ulcer syndrome in horses

Background

Grading of equine gastric ulcer syndrome (EGUS) is undertaken in clinical and research settings, but the reliability of EGUS grading systems is poorly understood.

Hypothesis/Objectives

Investigate interobserver and intraobserver reliability of an established ordinal grading system and a novel visual analog scale (VAS), and assess the influence of observer experience.

Animals

Sixty deidentified gastroscopy videos.

Methods

Six observers (3 specialists and 3 residents) graded videos using the EGUS Council (EGUC) system and VAS. Observers graded the videos three 3 for each system, using a cross‐over design with at least 1 week between each phase. The order of videos was randomized for each phase.

Methods

Interobserver and intraobserver reliability were estimated using Gwet's agreement coefficient with ordinal weights applied (AC2) for the EGUC system and the intraclass correlation coefficient (ICC) for the VAS.

Results

Using the EGUC system, interobserver reliability was substantial for squamous (AC2 = 0.69; 95% confidence interval [CI], 0.57‐0.80) and glandular mucosa (AC2 = 0.72; 95% CI, 0.70‐0.75), and intraobserver reliability was substantial for squamous (AC2 = 0.80; 95% CI, 0.71‐0.90) and glandular mucosa (AC2 = 0.80; 95% CI, 0.74‐0.86). Interobserver reliability using the VAS was moderate for squamous (ICC = 0.64; 95% CI, 0.31‐0.96) and poor for glandular mucosa (ICC = 0.35; 95% CI, 0.06‐0.64), and intraobserver reliability was moderate for squamous (ICC = 0.74; 95% CI, 0.62‐0.86) and glandular mucosa (ICC = 0.56; 95% CI, 0.39‐0.72).

Conclusions and Clinical Importance

The EGUC system had acceptable intraobserver and interobserver reliability and performed well regardless of observer experience. Familiarity and observer experience improved reliability of the VAS.

Glucagon-like peptide-1, insulin-like growth factor-1, and adiponectin in insulin-dysregulated ponies: effects of feeding a high nonstructural carbohydrate diet and association with prospective laminitis

Endocrinopathic laminitis, related to equine metabolic syndrome and insulin dysregulation, causes marked pain and suffering in horses and represents a substantial cost to the horse industry. This study investigated the effect of feeding a diet high in nonstructural carbohydrates on concentrations of active glucagon-like peptide-1 (aGLP-1), total insulin-like growth factor-1 (IGF-1), and high-molecular-weight (HMW) adiponectin, in insulin-dysregulated ponies. Thirty-seven ponies were challenged with this diet for up to 18 d to induce hyperinsulinemia. Hormone concentrations were measured in selected samples on day 2 of the diet challenge period, over 4 h after feeding. Fourteen of the ponies developed mild laminitis induced by the diet challenge. Insulin and glucose responses to the diet have been reported previously. Feeding increased the concentrations of aGLP-1 (P < 0.05) and HMW adiponectin (P < 0.001), but there was no difference between the laminitic and nonlaminitic groups for either hormone. Concentrations of IGF-1 and insulin were inversely related, with IGF-1 being 32% lower in hyperinsulinemic/laminitic ponies compared with nonlaminitic ponies (P = < 0.05). These results indicate that unlike insulin and possibly IGF-1, concentrations of aGLP-1 and HMW adiponectin do not have a strong association with, or play a major role in, the pathogenesis of equine laminitis.

The cresty neck score is an independent predictor of insulin dysregulation in ponies

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.

ECEIM consensus statement on equine metabolic syndrome

Equine metabolic syndrome (EMS) is a widely recognized collection of risk factors for endocrinopathic laminitis. The most important of these risk factors is insulin dysregulation (ID). Clinicians and horse owners must recognize the presence of these risk factors so that they can be targeted and controlled to reduce the risk of laminitis attacks. Diagnosis of EMS is based partly on the horse's history and clinical examination findings, and partly on laboratory testing. Several choices of test exist which examine different facets of ID and other related metabolic disturbances. EMS is controlled mainly by dietary strategies and exercise programs that aim to improve insulin regulation and decrease obesity where present. In some cases, pharmacologic aids might be useful. Management of an EMS case is a long‐term strategy requiring diligence and discipline by the horse's carer and support and guidance from their veterinarians.