BMC veterinary research2018; 14(1); 146; doi: 10.1186/s12917-018-1479-z

Lower plasma trans-4-hydroxyproline and methionine sulfoxide levels are associated with insulin dysregulation in horses.

Abstract: Insulin dysregulation in horses is a metabolic condition defined by high insulin concentrations in the blood and peripheral insulin resistance. This hyperinsulinemia is often associated with severe damage in the hooves, resulting in laminitis. However, we currently lack detailed information regarding the potential involvement of particular metabolic pathways in pathophysiological causes and consequences of equine insulin dysregulation. This study aimed to assess the dynamic metabolic responses given to an oral glucose test (OGT) in insulin-sensitive and insulin-dysregulated horses by a targeted metabolomics approach to identify novel metabolites associated with insulin dysregulation. Results: Oral glucose testing triggered alterations in serum insulin (26.28 ± 4.20 vs. 422.84 ± 88.86 μIU/mL, p < 0.001) and plasma glucose concentrations (5.00 ± 0.08 vs. 9.43 ± 0.44 mmol/L, p < 0.001) comparing basal and stimulated conditions after 180 min. Metabolome analyses indicated OGT-induced changes in short-chain acylcarnitines (6.00 ± 0.53 vs. 3.99 ± 0.23 μmol/L, p < 0.001), long-chain acylcarnitines (0.13 ± 0.004 vs. 0.11 ± 0.002 μmol/L, p < 0.001) and amino acids (2.18 ± 0.11 vs. 1.87 ± 0.08 μmol/L, p < 0.05). Kynurenine concentrations increased (2.88 ± 0.18 vs. 3.50 ± 0.19 μmol/L, p < 0.01), whereas spermidine concentrations decreased during OGT (0.09 ± 0.004 vs. 0.08 ± 0.002 μmol/L, p < 0.01), indicating proinflammatory conditions after oral glucose load. Insulin dysregulation was associated with lower concentrations of trans-4-hydroxyproline (4.41 ± 0.29 vs. 6.37 ± 0.71 μmol/L, p < 0.05) and methionine sulfoxide (0.40 ± 0.06 vs. 0.87 ± 0.13 μmol/L, p < 0.01; mean ± SEM in insulin-dysregulated vs. insulin-sensitive basal samples, respectively), two metabolites which are related to antioxidant defense mechanisms. Conclusions: Oral glucose application during OGT resulted in profound metabolic and proinflammatory changes in horses. Furthermore, insulin dysregulation was predicted in basal samples (without OGT) by pathways associated with trans-4-hydroxyproline and methionine sulfoxide, suggesting that oxidative stress and oxidant-antioxidant disequilibrium are contributing factors to insulin dysregulation. The present findings provide new hypotheses for future research to better understand the underlying pathophysiology of insulin dysregulation in horses.
Publication Date: 2018-05-02 PubMed ID: 29716602PubMed Central: PMC5930486DOI: 10.1186/s12917-018-1479-zGoogle Scholar: Lookup
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The research paper explores the connection between lower levels of certain metabolites, particularly trans-4-hydroxyproline and methionine sulfoxide, and insulin dysregulation in horses. The findings suggest that oxidative stress and imbalance between oxidants and antioxidants could contribute to insulin dysregulation, offering new areas to explore in future research.

Study Objective and Methodology

  • The research aimed to further understand the metabolic pathways that could be involved in causing insulin dysregulation in horses. This salient condition is characterised by high insulin concentrations in the blood and it often leads to severe hoof damage resulting in laminitis.
  • The researchers subjected insulin-sensitive and insulin-dysregulated horses to an oral glucose test (OGT) and assessed the metabolic responses, with the objective of identifying new metabolites associated with insulin dysregulation.

Results and Findings

  • The oral glucose testing led to significant alterations in serum insulin and plasma glucose concentrations compared to the basal state after 180 minutes. This highlights the sensitivity and dysregulated response of insulin in affected horses.
  • The study also pointed out changes in short-chain acylcarnitines, long-chain acylcarnitines, and amino acids resulting from the OGT.
  • Increased levels of Kynurenine and decreased levels of spermidine were noted during the OGT, suggesting that the oral glucose load induced proinflammatory conditions.
  • What stood out most notably was that insulin dysregulation appeared to be associated with lower concentrations of trans-4-hydroxyproline and methionine sulfoxide, two metabolites related to antioxidant defense mechanisms. This correlation implies that oxidative stress and imbalance in the antioxidant system might be contributory factors to insulin dysregulation in horses.

Conclusions and Implications for Future Research

  • The paper concluded that the application of oral glucose during the OGT instigated marked metabolic and proinflammatory alterations in horses.
  • The correlation between lower trans-4-hydroxyproline and methionine sulfoxide and insulin dysregulation suggests potential pathways and factors to investigate in future research.
  • The implication of oxidative stress and oxidant-antioxidant disequilibrium in insulin dysregulation in horses is a valuable insight, providing a basis for developing further hypotheses and carrying out more detailed studies.

Cite This Article

Kenu00e9z u00c1, Warnken T, Feige K, Huber K. (2018). Lower plasma trans-4-hydroxyproline and methionine sulfoxide levels are associated with insulin dysregulation in horses. BMC Vet Res, 14(1), 146.


ISSN: 1746-6148
NlmUniqueID: 101249759
Country: England
Language: English
Volume: 14
Issue: 1
Pages: 146
PII: 146

Researcher Affiliations

Kenu00e9z, u00c1kos
  • Institute of Animal Science, Faculty of Agricultural Sciences, University of Hohenheim, Fruwirthstrau00dfe 35, 70593, Stuttgart, Germany.
  • Present address: College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Kowloon Tong, Hong Kong SAR.
Warnken, Tobias
  • Clinic for Horses, University of Veterinary Medicine Hannover, Foundation, Bu00fcnteweg 9, 30559, Hannover, Germany.
Feige, Karsten
  • Clinic for Horses, University of Veterinary Medicine Hannover, Foundation, Bu00fcnteweg 9, 30559, Hannover, Germany.
Huber, Korinna
  • Institute of Animal Science, Faculty of Agricultural Sciences, University of Hohenheim, Fruwirthstrau00dfe 35, 70593, Stuttgart, Germany.

MeSH Terms

  • Animals
  • Blood Glucose / analysis
  • Glucose Tolerance Test / veterinary
  • Horses / blood
  • Horses / metabolism
  • Hydroxyproline / blood
  • Insulin / blood
  • Insulin Resistance
  • Metabolomics
  • Methionine / analogs & derivatives
  • Methionine / blood

Conflict of Interest Statement

ETHICS APPROVAL AND CONSENT TO PARTICIPATE: Samples from ID horses and ponies were collected during routine diagnostic procedures in the Clinic for Horses, Hannover, and owners gave written informed consent for the study. CONSENT FOR PUBLICATION: Owners gave written informed consent for publication by means of signing our official client acceptance form. COMPETING INTERESTS: The authors declare that they have no competing interests. PUBLISHER’S NOTE: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.


This article includes 21 references
  1. Frank N, Geor RJ, Bailey SR, Durham AE, Johnson PJ. Equine metabolic syndrome.. J Vet Intern Med 2010 May-Jun;24(3):467-75.
  2. Frank N, Tadros EM. Insulin dysregulation.. Equine Vet J 2014 Jan;46(1):103-12.
    doi: 10.1111/evj.12169pubmed: 24033478google scholar: lookup
  3. Johnson PJ, Messer NT, Slight SH, Wiedmeyer C, Buff P, Ganjam VK. Endocrinopathic laminitis in the horse. Clin Tech Equine Prac. 2004;3(1):45u201356. doi: 10.1053/j.ctep.2004.07.004.
  4. Patti GJ, Yanes O, Siuzdak G. Innovation: Metabolomics: the apogee of the omics trilogy.. Nat Rev Mol Cell Biol 2012 Mar 22;13(4):263-9.
    doi: 10.1038/nrm3314pmc: PMC3682684pubmed: 22436749google scholar: lookup
  5. Henneke DR, Potter GD, Kreider JL, Yeates BF. Relationship between condition score, physical measurements and body fat percentage in mares.. Equine Vet J 1983 Oct;15(4):371-2.
  6. Ralston SL. Insulin and glucose regulation.. Vet Clin North Am Equine Pract 2002 Aug;18(2):295-304, vii.
    pubmed: 15635909doi: 10.1016/s0749-0739(02)00014-7google scholar: lookup
  7. Warnken T, Huber K, Feige K. Comparison of three different methods for the quantification of equine insulin.. BMC Vet Res 2016 Sep 9;12(1):196.
    doi: 10.1186/s12917-016-0828-zpmc: PMC5016943pubmed: 27613127google scholar: lookup
  8. Ramsay SL, Stoeggl WM, Weinberger KM, Graber A, Guggenbichler W. Apparatus and method for analyzing a metabolite profile. 2007.
  9. Xia J, Sinelnikov IV, Han B, Wishart DS. MetaboAnalyst 3.0--making metabolomics more meaningful.. Nucleic Acids Res 2015 Jul 1;43(W1):W251-7.
    doi: 10.1093/nar/gkv380pmc: PMC4489235pubmed: 25897128google scholar: lookup
  10. Oxenkrug G. Insulin resistance and dysregulation of tryptophan-kynurenine and kynurenine-nicotinamide adenine dinucleotide metabolic pathways.. Mol Neurobiol 2013 Oct;48(2):294-301.
    doi: 10.1007/s12035-013-8497-4pmc: PMC3779535pubmed: 23813101google scholar: lookup
  11. Stadtman ER, Levine RL. Free radical-mediated oxidation of free amino acids and amino acid residues in proteins.. Amino Acids 2003 Dec;25(3-4):207-18.
    doi: 10.1007/s00726-003-0011-2pubmed: 14661084google scholar: lookup
  12. Sesti G, Fiorentino TV, Succurro E, Perticone M, Arturi F, Sciacqua A, Perticone F. Elevated 1-h post-load plasma glucose levels in subjects with normal glucose tolerance are associated with unfavorable inflammatory profile.. Acta Diabetol 2014 Dec;51(6):927-32.
    doi: 10.1007/s00592-013-0539-xpubmed: 24619654google scholar: lookup
  13. Gugliucci A, Menini T. The polyamines spermine and spermidine protect proteins from structural and functional damage by AGE precursors: a new role for old molecules?. Life Sci 2003 Apr 25;72(23):2603-16.
    doi: 10.1016/S0024-3205(03)00166-8pubmed: 12672506google scholar: lookup
  14. Argenzio RA, Southworth M, Stevens CE. Sites of organic acid production and absorption in the equine gastrointestinal tract.. Am J Physiol 1974 May;226(5):1043-50.
  15. Randle PJ, Garland PB, Newsholme EA, Hales CN. The glucose fatty acid cycle in obesity and maturity onset diabetes mellitus.. Ann N Y Acad Sci 1965 Oct 8;131(1):324-33.
  16. Levine RL, Mosoni L, Berlett BS, Stadtman ER. Methionine residues as endogenous antioxidants in proteins.. Proc Natl Acad Sci U S A 1996 Dec 24;93(26):15036-40.
    doi: 10.1073/pnas.93.26.15036pmc: PMC26351pubmed: 8986759google scholar: lookup
  17. Padh H. Vitamin C: newer insights into its biochemical functions.. Nutr Rev 1991 Mar;49(3):65-70.
  18. Vinayagamoorthi R, Bobby Z, Sridhar MG. Antioxidants preserve redox balance and inhibit c-Jun-N-terminal kinase pathway while improving insulin signaling in fat-fed rats: evidence for the role of oxidative stress on IRS-1 serine phosphorylation and insulin resistance.. J Endocrinol 2008 May;197(2):287-96.
    doi: 10.1677/JOE-08-0061pubmed: 18434358google scholar: lookup
  19. Kusano K, Yamazaki M, Kiuchi M, Kaneko K, Koyama K. Reference range of blood biomarkers for oxidative stress in Thoroughbred racehorses (2-5 years old).. J Equine Sci 2016;27(3):125-129.
    doi: 10.1294/jes.27.125pmc: PMC5048360pubmed: 27703408google scholar: lookup
  20. El-Bahr SM, El-Deeb WM. Acute-phase proteins, oxidative stress biomarkers, proinflammatory cytokines, and cardiac troponin in Arabian mares affected with pyometra.. Theriogenology 2016 Sep 1;86(4):1132-1136.
  21. Banse HE, Frank N, Kwong GP, McFarlane D. Relationship of oxidative stress in skeletal muscle with obesity and obesity-associated hyperinsulinemia in horses.. Can J Vet Res 2015 Oct;79(4):329-38.
    pmc: PMC4581679pubmed: 26424915


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  6. Leung YH, Kenu00e9z u00c1, Grob AJ, Feige K, Warnken T. Associations of plasma sphingolipid profiles with insulin response during oral glucose testing in Icelandic horses.. J Vet Intern Med 2021 Jul;35(4):2009-2018.
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  7. Delarocque J, Frers F, Huber K, Jung K, Feige K, Warnken T. Metabolic impact of weight variations in Icelandic horses.. PeerJ 2021;9:e10764.
    doi: 10.7717/peerj.10764pubmed: 33575132google scholar: lookup
  8. Delarocque J, Reiche DB, Meier AD, Warnken T, Feige K, Sillence MN. Metabolic profile distinguishes laminitis-susceptible and -resistant ponies before and after feeding a high sugar diet.. BMC Vet Res 2021 Jan 28;17(1):56.
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  9. Delarocque J, Frers F, Feige K, Huber K, Jung K, Warnken T. Metabolic changes induced by oral glucose tests in horses and their diagnostic use.. J Vet Intern Med 2021 Jan;35(1):597-605.
    doi: 10.1111/jvim.15992pubmed: 33277752google scholar: lookup
  10. Wang J, Yan W, Zhou X, Liu Y, Tang C, Peng Y, Liu H, Sun L, Xiao L, He L. Metabolomics window into the role of acute kidney injury after coronary artery bypass grafting in diabetic nephropathy progression.. PeerJ 2020;8:e9111.
    doi: 10.7717/peerj.9111pubmed: 32461830google scholar: lookup
  11. u017bak A, Siwiu0144ska N, Cheu0142mecka E, Bau017canu00f3w B, Romuk E, Adams A, Niedu017awiedu017a A, Stygar D. Effects of Advanced Age, Pituitary Pars Intermedia Dysfunction and Insulin Dysregulation on Serum Antioxidant Markers in Horses.. Antioxidants (Basel) 2020 May 21;9(5).
    doi: 10.3390/antiox9050444pubmed: 32455574google scholar: lookup
  12. Wu G. Important roles of dietary taurine, creatine, carnosine, anserine and 4-hydroxyproline in human nutrition and health.. Amino Acids 2020 Mar;52(3):329-360.
    doi: 10.1007/s00726-020-02823-6pubmed: 32072297google scholar: lookup