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Journal of veterinary internal medicine2020; 35(1); 597-605; doi: 10.1111/jvim.15992

Metabolic changes induced by oral glucose tests in horses and their diagnostic use.

Abstract: Little is known about the implications of hyperinsulinemia on energy metabolism, and such knowledge might help understand the pathophysiology of insulin dysregulation. Objective: Describe differences in the metabolic response to an oral glucose test, depending on the magnitude of the insulin response. Methods: 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: 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.
© 2020 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC. on behalf of the American College of Veterinary Internal Medicine.
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Publication Date: 2020-12-05 PubMed ID: 33277752PubMed Central: PMC7848347DOI: 10.1111/jvim.15992Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research study attempts to understand the imbalance in insulin production and its effects on energy metabolism in horses. Through oral glucose tests on 12 horses, the researchers identified differences in metabolic responses depending on the insulin release magnitude. The research findings reveal that lower arginine and carnitine levels could be connected to a high insulin release, thereby revealing potential therapeutic targets.

Research Methodology

  • The research focused on 12 Icelandic horses that have different metabolic states.
  • The horses were subjected to 3 oral glucose tests where glucose of 0.5 g/kg body weight was used.
  • They analyzed samples taken before (basal), and after 120 and 180 minutes of the oral glucose intake using metabolomic assays which involved combined liquid chromatography tandem mass spectrometry and flow injection analysis tandem mass spectrometry.
  • The researchers measured insulin concentrations using an Enzyme-Linked Immunosorbent Assay (ELISA), a common method for measuring substances that the immune system can recognize and respond to, like hormones or proteins.
  • Their analysis was carried out using linear models and partial least-squares regression, statistical techniques that help understand the relationship between the input, which is glucose in this case, and the resultant insulin response.

Research Findings

  • The ratio of kynurenine to tryptophan, two key components involved in many biological processes such as protein synthesis and functional enzyme activities, increased over time during the oral glucose test.
  • A high insulin response was found to correlate with lower arginine and carnitine concentrations. Both arginine and carnitine play an essential role in metabolism. While arginine is a vital amino acid that helps build proteins and boosts immune response, carnitine is needed to convert fatty acids into usable energy.
  • The researchers were able to develop an effective predictive model using only the baseline or beginning samples. This model performed well with a sensitivity of 86% and specificity of 88%, meaning the model was very precise in distinguishing horses with insulin dysregulation from those without it by using just a small number of distinct metabolites.

Conclusions and Implications

  • The obtained results suggest the occurrence of low-grade inflammation during the oral glucose test, which could explain the increase in the kynurenine: tryptophan ratio.
  • The finding that plasma arginine and carnitine concentrations were lower in horses with a high insulin response could provide potential therapeutic targets for addressing hyperinsulinemia (excess insulin) in horses.
  • The possibility of developing screening tools to identify insulin-dysregulated horses using only baseline blood samples appears promising, which could significantly simplify and speed up the diagnosis process.

Cite This Article

APA
Delarocque J, Frers F, Feige K, Huber K, Jung K, Warnken T. (2020). Metabolic changes induced by oral glucose tests in horses and their diagnostic use. J Vet Intern Med, 35(1), 597-605. https://doi.org/10.1111/jvim.15992

Publication

Journal of veterinary internal medicine
ISSN: 1939-1676
NlmUniqueID: 8708660
Country: United States
Language: English
Volume: 35
Issue: 1
Pages: 597-605

Researcher Affiliations

Delarocque, Julien
  • Clinic for Horses, University of Veterinary Medicine Hannover, Foundation, Hanover, Germany.
Frers, Florian
  • Clinic for Horses, University of Veterinary Medicine Hannover, Foundation, Hanover, Germany.
Feige, Karsten
  • Clinic for Horses, University of Veterinary Medicine Hannover, Foundation, Hanover, Germany.
Huber, Korinna
  • Institute of Animal Science, Faculty of Agricultural Sciences, University of Hohenheim, Stuttgart, Germany.
Jung, Klaus
  • Institute for Animal Breeding and Genetics, University of Veterinary Medicine Hannover, Foundation, Hanover, Germany.
Warnken, Tobias
  • Clinic for Horses, University of Veterinary Medicine Hannover, Foundation, Hanover, Germany.

MeSH Terms

  • Animals
  • Blood Glucose
  • Carnitine
  • Glucose
  • Glucose Tolerance Test / veterinary
  • Horse Diseases / diagnosis
  • Horses
  • Hyperinsulinism / veterinary
  • Insulin

Conflict of Interest Statement

Authors declare no conflict of interest.

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