Repeatability of the Combined Glucose‐Insulin Tolerance Test and the Effect of a Stressor before Testing in Horses of 2 Breeds

Bröjer, Johan; Lindåse, Sanna; Hedenskog, J.; Alvarsson, K.; Nostell, Katarina

doi:10.1111/jvim.12172

Cited by 27 publications

(21 citation statements)

References 17 publications

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“…Data had to be converted from μg/L into the commonly used SI unit μIU/mL to compare the results from ELISA with results derived from RIA and CLIA. In previous studies in which insulin analysis had been performed with the equine-optimized porcine-specific ELISA, data was either presented in μg/L [9, 10, 18] or converted into mU/L [19]. In the latter case, conversion was performed without an exact statement regarding the conversion factor, which was suggested to be 10 in an earlier publication by the same author [9].…”

Section: Discussionmentioning

confidence: 99%

Comparison of three different methods for the quantification of equine insulin

2016

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BackgroundExact analysis of equine insulin in blood samples is the key element for assessing insulin resistance or insulin dysregulation in horses. However, previous studies indicated marked differences in insulin concentrations obtained from sample analyses with different immunoassays. Most assays used in veterinary medicine are originally designed for use in human diagnostics and are based on antibodies directed against human insulin, although amino acid sequences between equine and human insulin differ. Species-specific assays are being used more frequently and seem to provide advantages compared to human-specific assays. The aim of this study was to compare three immunoassays, one porcine-specific insulin enzyme-linked immunosorbent assay (ELISA), advertised to be specific for equine insulin, one porcine-specific insulin radioimmunoassay (RIA) and one human-specific insulin chemiluminescence immunoassay (CLIA), all three widely used in veterinary laboratories for the analysis of equine insulin. Furthermore, we tested their clinical applicability in assessing insulin resistance and dysregulation by analysis of basal blood and blood samples obtained during a dynamic diagnostic stimulation test (OGT) with elevated insulin concentrations.ResultsInsulin values obtained from the ELISA, RIA and CLIA, investigated for analyses of basal blood samples differed significantly between all three assays. Analyses of samples obtained during dynamic diagnostic stimulation testing with consecutively higher insulin concentrations revealed significantly (p < 0.001) lower insulin concentrations supplied by the CLIA compared to the ELISA. However, values measured by ELISA were intermediate and not different to those measured by RIA. Calculated recovery upon dilution, as a marker for assay accuracy in diluted samples, was 98 ± 4 % for ELISA, 160 ± 41 % for RIA and 101 ± 11 % for CLIA.ConclusionsOur results indicate that insulin concentrations of one sample measured by different methods vary greatly and should be interpreted carefully. Consideration of the immunoassay method and reliable assay-specific reference ranges are of particular importance especially in clinical cases where small changes in insulin levels can cause false classification in terms of insulin sensitivity of horses and ponies.

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Section: Discussionmentioning

confidence: 99%

Comparison of three different methods for the quantification of equine insulin

2016

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“…Fasting triglyceride concentration was determined by enzymatic determination (AU680) in serum samples collected at 0800 immediately before and immediately after each phase. A combined glucose‐insulin tolerance test (CGIT) also was performed immediately before and after each treatment phase at 0800 after an overnight fast according to standard protocols . Briefly, the evening before each test an indwelling catheter was placed aseptically in a jugular vein and covered, with patency maintained with heparinized saline.…”

Section: Methodsmentioning

confidence: 99%

Sustained, Low‐Intensity Exercise Achieved by a Dynamic Feeding System Decreases Body Fat in Ponies

Laat

Hampson²,

Sillence

et al. 2016

Veterinary Internal Medicne

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BackgroundObesity in horses is increasing in prevalence and can be associated with insulin insensitivity and laminitis. Current treatment strategies for obesity include dietary restriction and exercise. However, whether exercise alone is effective for decreasing body fat is uncertain.HypothesisOur hypothesis was that twice daily use of a dynamic feeding system for 3 months would induce sustained, low‐intensity exercise thereby decreasing adiposity and improving insulin sensitivity (SI).AnimalsEight, university‐owned, mixed‐breed, adult ponies with body condition scores (BCS) ≥5/9 were used.MethodsTwo treatments (“feeder on” or “feeder off”) were administered for a 3‐month period by a randomized, crossover design (n = 4/treatment). An interim equilibration period of 6 weeks at pasture separated the 2 study phases. Measurements of body mass (body weight, BCS, cresty neck score [CrNS], and morphometry), body fat (determined before and after the “feeder on” treatment only), triglycerides, and insulin sensitivity (SI; combined glucose‐insulin test) were undertaken before and after treatments.ResultsThe dynamic feeding system induced a 3.7‐fold increase in the daily distance travelled (n = 6), compared to with a stationary feeder, which significantly decreased mean BCS (6.53 ± 0.94 to 5.38 ± 1.71), CrNS (2.56 ± 1.12 to 1.63 ± 1.06) and body fat (by 4.95%). An improvement in SI did not occur in all ponies.Conclusions and Clinical ImportanceA dynamic feeding system can be used to induce sustained (daily), low‐intensity exercise that promotes weight loss in ponies. However, this exercise may not be sufficient to substantially improve SI.

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“…Gold standard diagnostic tests for insulin sensitivity in equids include the euglycaemic, hyperinsulinaemic clamp and frequently sampled intravenous (i.v.) glucose tolerance test, are easier to perform, but are subject to variability and remain reasonably impractical in a field environment [6]. However, these tests are expensive and cumbersome.…”

Section: Introductionmentioning

confidence: 99%

“…Less direct tests for insulin sensitivity, such as the combined glucose insulin tolerance test and i.v. glucose tolerance test, are easier to perform, but are subject to variability and remain reasonably impractical in a field environment [6].…”

Section: Introductionmentioning

confidence: 99%