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Rahnama S, Spence R, Vathsangam N, Baskerville CL, Bailey SR, de Laat MA, Anderson ST, Pollitt CC, Sillence MN. Effects of insulin on IGF-1 receptors in equine lamellar tissue in vitro. Domest Anim Endocrinol 2021; 74:106530. [PMID: 32818904 DOI: 10.1016/j.domaniend.2020.106530] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Revised: 07/23/2020] [Accepted: 07/23/2020] [Indexed: 11/21/2022]
Abstract
Although it is understood that equine endocrinopathic laminitis can be triggered by high concentrations of insulin, it is unclear whether this represents a direct action on lamellar tissue via insulin receptors (InsR), an interaction with IGF-1 receptors (IGF-1R), or some other, indirect action. This uncertainty is because of the reported scarcity of InsR in lamellar tissue and the low affinity of insulin for equine IGF-1R. In the present study, the effects of insulin and IGF-1 (as a positive control) were examined using lamellar explants isolated from the hooves of healthy horses and incubated in cell culture medium for between 2 min and 48 h. In this system, a low physiological concentration of IGF-1 (10 nM; 1.31 ng/mL) caused a marked increase in the appearance of phosphorylated IGF-1R after 5 min (P < 0.05), and this effect was blocked by a human anti-IGF-1R monoclonal antibody (mAb). However, a high concentration of insulin (10 nM; 1,430 μIU/mL) appeared to cause dephosphorylation of the IGF-1R after 5 min (P < 0.01), 15 min, and 30 min (P < 0.001). Using 3H-thymidine as a marker, it was also demonstrated that insulin and IGF-1-stimulated cell proliferation in lamellar explants over the same concentration range as each other (1-100 nM), implying that each peptide acts via its own receptor (P < 0.001). Conversely, the effect of both peptides could be blocked using a selective anti-IGF-1R mAb (P < 0.001), implying that insulin acts via IGF1-R (either directly or indirectly). Notwithstanding this conundrum, the results demonstrate that insulin acts directly on lamellar tissue and suggest that a therapeutic anti-IGF-1R mAb could be useful in treating or preventing endocrinopathic laminitis.
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Affiliation(s)
- S Rahnama
- School of Biology and Environmental Science, Queensland University of Technology, Brisbane, Queensland, Australia
| | - R Spence
- School of Biology and Environmental Science, Queensland University of Technology, Brisbane, Queensland, Australia
| | - N Vathsangam
- Department of Veterinary Biosciences, The University of Melbourne, Melbourne, Victoria, Australia
| | - C L Baskerville
- Department of Veterinary Biosciences, The University of Melbourne, Melbourne, Victoria, Australia
| | - S R Bailey
- Department of Veterinary Biosciences, The University of Melbourne, Melbourne, Victoria, Australia
| | - M A de Laat
- School of Biology and Environmental Science, Queensland University of Technology, Brisbane, Queensland, Australia
| | - S T Anderson
- School of Biomedical Sciences, The University of Queensland, St Lucia, Queensland, Australia
| | - C C Pollitt
- School of Veterinary Science, The University of Queensland, Gatton, Australia
| | - M N Sillence
- School of Biology and Environmental Science, Queensland University of Technology, Brisbane, Queensland, Australia.
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Stokes SM, Bertin FR, Stefanovski D, Belknap JK, Medina-Torres CE, Pollitt CC, van Eps AW. Lamellar energy metabolism and perfusion in the euglycaemic hyperinsulinaemic clamp model of equine laminitis. Equine Vet J 2020; 52:577-584. [PMID: 31845378 DOI: 10.1111/evj.13224] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Revised: 10/29/2019] [Accepted: 12/04/2019] [Indexed: 01/19/2023]
Abstract
BACKGROUND Hyperinsulinaemia is associated with the development of endocrinopathic laminitis; however, the mechanisms remain unclear. OBJECTIVES Evaluate the effects of hyperinsulinaemia on lamellar energy metabolism and perfusion during laminitis development. STUDY DESIGN In vivo experiment. METHODS Eight Standardbred horses were instrumented with a microdialysis probe in the lamellae of a forelimb. A 24 hours baseline period (BASELINE) was followed by 48 hours of a continuous euglycaemic hyperinsulinaemic clamp (EHC) from 24 to 72 hours (CLAMP). Microdialysate was collected every 6 hours and analysed for glucose, lactate and pyruvate concentrations and lactate-to-pyruvate ratio (L:P). Microdialysis urea clearance was used to estimate lamellar tissue perfusion. Archived microdialysis samples from six identically instrumented Standardbred horses served as controls (CON). Variables were compared over time and between EHC and CON horses using a mixed-effects linear regression model. RESULTS Glucose concentration decreased during the CLAMP period in CON and EHC horses (P < .001), but there was no difference between CON and EHC (P > .9). Lactate concentration increased during the CLAMP period in CON and EHC horses (P < .001), however, the rate of increase was significantly higher in EHC horses relative to CON (P = .014). There was a relative increase in pyruvate concentration in EHC horses compared with CON during the CLAMP period (P = .03). L:P increased significantly in CON horses during the CLAMP period (P < .001) but not in EHC (P = .1). Urea clearance did not change in CON (P = .9) or EHC (P = .05) during the CLAMP, but did increase in EHC relative to CON (P = .02). MAIN LIMITATIONS The effects of microdialysis probe implantation on perfusion and metabolism remain unclear. The EHC model may not mimic natural endocrinopathic laminitis. CONCLUSIONS Laminitis developed without evidence of lamellar hypoperfusion or energy stress. Therapies to improve perfusion are unlikely to affect the initial development of endocrinopathic laminitis.
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Affiliation(s)
- Simon M Stokes
- Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton, Qld, Australia
| | - Francois R Bertin
- Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton, Qld, Australia
| | - Darko Stefanovski
- New Bolton Center, Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, Pennsylvania
| | - James K Belknap
- Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio
| | - Carlos E Medina-Torres
- Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton, Qld, Australia
| | - Christopher C Pollitt
- Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton, Qld, Australia
| | - Andrew W van Eps
- Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton, Qld, Australia.,New Bolton Center, Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, Pennsylvania
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Stokes SM, Bertin FR, Stefanovski D, Poulsen L, Belknap JK, Medina-Torres CE, Pollitt CC, van Eps AW. The effect of continuous digital hypothermia on lamellar energy metabolism and perfusion during laminitis development in two experimental models. Equine Vet J 2020; 52:585-592. [PMID: 31793047 DOI: 10.1111/evj.13215] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Revised: 10/22/2019] [Accepted: 11/23/2019] [Indexed: 12/11/2022]
Abstract
BACKGROUND Continuous digital hypothermia (CDH) prevents lamellar failure in the euglycaemic hyperinsulinaemic clamp (EHC) and oligofructose (OF) laminitis models, but the mechanisms remain unclear. OBJECTIVES To evaluate the effects of CDH on lamellar energy metabolism and perfusion in healthy horses and during EHC and OF laminitis models. STUDY DESIGN In vivo experiment. METHODS Archived samples were used from Standardbred geldings that received no treatment (CON) (n = 8) or underwent EHC (n = 8) or OF (n = 6) laminitis models. Both forelimbs were instrumented with a lamellar microdialysis system, and one forelimb was cooled (CDH) with the other maintained at ambient temperature (AMB). Microdialysate was collected every 6 hours and analysed for glucose, lactate and pyruvate concentrations and lactate to pyruvate ratio (L:P). Microdialysis urea clearance was used to estimate lamellar tissue perfusion. Data were analysed using a mixed-effects linear regression model. RESULTS Glucose did not change in CDH limbs relative to AMB in CON (P = .3), EHC (P = .3) or OF (P = .6) groups. There was a decrease in lactate (P < .001) and pyruvate (P < .01) in CDH limbs relative to AMB in all groups. L:P decreased in CON CDH relative to CON AMB (P < .001) but was not different in EHC (P = .6) and OF (P = .07) groups. Urea clearance decreased in CDH limbs relative to AMB in CON (P = .002) and EHC (P < .001), but not in OF (P = .4). MAIN LIMITATIONS The EHC model may not mimic natural endocrinopathic laminitis. CONCLUSIONS CDH caused a marked decrease in lamellar glucose metabolism (CON, EHC and OF) and perfusion (CON and EHC) without affecting lamellar glucose concentration. Although cellular energy failure is not a primary pathophysiological event in EHC and OF laminitis models, CDH may act by limiting energy supply to pathologic cellular processes whilst preserving those critical to lamellar homoeostasis.
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Affiliation(s)
- Simon M Stokes
- Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia
| | - Francois-Rene Bertin
- Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia
| | - Darko Stefanovski
- New Bolton Center, Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, Pennsylvania, USA
| | - Lea Poulsen
- Institute of Veterinary Science, University of Liverpool, Liverpool, UK
| | - James K Belknap
- Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio, USA
| | - Carlos E Medina-Torres
- Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia
| | - Christopher C Pollitt
- Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia
| | - Andrew W van Eps
- Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia.,New Bolton Center, Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, Pennsylvania, USA
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de Laat MA, Spence RJ, Sillence MN, Pollitt CC. An investigation of the equine epidermal growth factor system during hyperinsulinemic laminitis. PLoS One 2019; 14:e0225843. [PMID: 31805097 PMCID: PMC6894753 DOI: 10.1371/journal.pone.0225843] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Accepted: 11/13/2019] [Indexed: 11/18/2022] Open
Abstract
Equine laminitis is a disease of the digital epidermal lamellae typified by epidermal cell proliferation and structural collapse. Most commonly the disease is caused by hyperinsulinemia, although the pathogenesis is incompletely understood. Insulin can activate the epidermal growth factor (EGF) system in other species and the present study tested the hypothesis that upregulation of EGF receptor (EGFR) signalling is a key factor in laminitis pathophysiology. First, we examined lamellar tissue from healthy Standardbred horses and those with induced hyperinsulinemia and laminitis for EGFR distribution and quantity using immunostaining and gene expression, respectively. Phosphorylation of EGFR was also quantified. Next, plasma EGF concentrations were compared in healthy and insulin-infused horses, and in healthy and insulin-dysregulated ponies before and after feeding. The EGFR were localised to the secondary epidermal lamellae, with stronger staining in parabasal, rather than basal, cells. No change in EGFR gene expression occurred with laminitis, although the receptor showed some phosphorylation. No difference was seen in EGF concentrations in horses, but in insulin-dysregulated ponies mean, post-prandial EGF concentrations were almost three times higher than in healthy ponies (274 ± 90 vs. 97.4 ± 20.9 pg/mL, P = 0.05). Although the EGFR does not appear to play a major pathogenic role in hyperinsulinemic laminitis, the significance of increased EGF in insulin-dysregulated ponies deserves further investigation.
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Affiliation(s)
- Melody A. de Laat
- Earth, Environmental and Biological Sciences, Queensland University of Technology, Brisbane, Queensland, Australia
- * E-mail:
| | - Robert J. Spence
- Earth, Environmental and Biological Sciences, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Martin N. Sillence
- Earth, Environmental and Biological Sciences, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Christopher C. Pollitt
- School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia
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Fitzgerald DM, Pollitt CC, Walsh DM, Sillence MN, de Laat MA. The effect of different grazing conditions on the insulin and incretin response to the oral glucose test in ponies. BMC Vet Res 2019; 15:345. [PMID: 31619223 PMCID: PMC6794863 DOI: 10.1186/s12917-019-2088-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Accepted: 09/12/2019] [Indexed: 01/21/2023] Open
Abstract
Background The oral glucose test (OGT) is a useful tool for diagnosing insulin dysregulation (ID) and is somewhat repeatable in ponies under consistent management. This study aimed to determine whether the insulin and incretin responses to an OGT in ponies differed after short-term access to fertilised pasture, compared to unfertilised pasture, by using a randomised, repeated measures study design. Sixteen mixed-breed ponies were classified as severely insulin-dysregulated (SD; post-prandial insulin ≥80 μIU/mL) or not severely insulin-dysregulated (NSD; post-prandial insulin < 80 μIU/mL) using an OGT prior to the study. The ponies accessed pasture that was fertilised, or unfertilised, for 5 days (4 h/day, with supplemental hay provided at 0.7% bodyweight), with a 10 day period between phases. An OGT was performed after each phase. Glucose, insulin, active glucagon-like peptide-1 (aGLP-1), and glucose-dependent insulinotropic polypeptide (GIP) were measured in post-prandial blood samples. Results The volume of fertilised pasture was five-fold greater than unfertilised pasture, with % non-structural carbohydrates (NSC) similar between all forages. Consuming fertilised pasture increased (P = 0.018) the serum insulin response to an OGT, compared to grazing unfertilised pasture. A limitation of the study was that pasture intake was unable to be quantified. Insulin responses were greater in SD, compared to NSD, ponies (P < 0.001) and remained well above the test cut-off at all times. A subset of ponies, initially screened as NSD, became (more) insulin-dysregulated after pasture access. Further, aGLP-1 was a significant predictor of insulin concentration in this cohort. Conclusions Whereas some insulin-dysregulated ponies were comparatively resistant to dietary intervention, others showed markedly different OGT responses following subtle changes in their forage-based diet. This implies that mild/early ID might be unmasked by dietary change, and that dietary management is important in these ponies. However, dietary management alone may not be adequate for all cases of ID.
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Affiliation(s)
- Danielle M Fitzgerald
- School of Earth, Environmental and Biological Sciences, Queensland University of Technology, Brisbane, QLD, Australia
| | | | | | - Martin N Sillence
- School of Earth, Environmental and Biological Sciences, Queensland University of Technology, Brisbane, QLD, Australia
| | - Melody A de Laat
- School of Earth, Environmental and Biological Sciences, Queensland University of Technology, Brisbane, QLD, Australia.
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de Laat MA, Pollitt CC. Ultrastructural examination of basement membrane pathology in horses with insulin-induced laminitis. Domest Anim Endocrinol 2019; 69:30-34. [PMID: 31280023 DOI: 10.1016/j.domaniend.2019.04.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Revised: 04/05/2019] [Accepted: 04/18/2019] [Indexed: 01/19/2023]
Abstract
The third phalanx of the equine digit is suspended within the hoof capsule by a specialized interdigitating dermoepidermal layer called the lamellae, which fails during laminitis. Pathology of the basement membrane (BM), which interfaces epidermis and dermis, is evident during acute laminitis. However, BM damage appears to be less prevalent in ponies with the insulin-associated form of laminitis. The aim of the present study was to investigate changes to the ultrastructure and morphometry of the lamellar BM in the acute phase of insulin-induced laminitis in horses. Lamellar tissue from the left forefoot of 3 horses with acute hyperinsulinemic laminitis was examined with transmission electron microscopy and compared with tissue from normal horses. Lamellar BM width and hemidesmosome (HD) density were assessed every 5 μm along ∼200 μm of secondary epidermal lamellar BM. The BM zone of treated horses was extensively disorganized with loss of uniformity of the lamina lucida and lamina densa, fragmentation and disorientation of HDs, and cytoskeletal disengagement of the HDs. The mean (±SD) lamellar BM was twice as wide in treated (0.25 ± 0.05 μm), compared with control (0.14 ± 0.02 μm), horses. The HD density (HDs/μm) was reduced by half in the treatment group (1.88 ± 0.37), compared with controls (3.6 ± 0.13). The reduced number of HDs in horses with laminitis may contribute to the weakening of the dermoepidermal junction and lamellar failure. Disassembly of HDs during excessive cellular proliferation, secondary to hyperinsulinemia, may account for HD loss. Further investigation of the underlying etiopathogenesis of BM dysfunction during hyperinsulinemic laminitis in horses may facilitate an improved understanding of the disease.
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Affiliation(s)
- M A de Laat
- School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia.
| | - C C Pollitt
- School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia
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Fitzgerald DM, Walsh DM, Sillence MN, Pollitt CC, de Laat MA. Insulin and incretin responses to grazing in insulin-dysregulated and healthy ponies. J Vet Intern Med 2018; 33:225-232. [PMID: 30506731 PMCID: PMC6335545 DOI: 10.1111/jvim.15363] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Accepted: 10/19/2018] [Indexed: 12/27/2022] Open
Abstract
Background Supraphysiological insulin and incretin responses to a cereal‐based diet have been described in horses and ponies with insulin dysregulation (ID). However, the hormonal responses to grazing have not yet been described. Objectives To determine if there is a difference in the insulin and incretin responses to grazing pasture between insulin‐dysregulated and healthy ponies. Animals A cohort of 16 ponies comprising 5 with normal insulin regulation (NIR), 6 with moderate ID (MID), and 5 with severe ID (SID). Methods In this case‐control study, an oral glucose test (OGT) was used to determine the insulin responsiveness of each pony to PO carbohydrate before grazing pasture (4 hours) for 3 consecutive days. Serial blood samples collected during grazing were analyzed for glucose, insulin, glucose‐dependent insulinotropic peptide (GIP) and active glucagon‐like peptide‐1 (aGLP‐1), and compared among pony groups and day of pasture access. Results The area under the insulin curve when grazing increased with ID severity (P < .03). The median (range) maximal insulin concentration was greater in the MID (72.5 [129] μIU/mL) and SID (255 [338.5] μIU/mL) groups, compared to the NIR (11.7 [24.9] μIU/mL) group (P < .03) and occurred within 2‐4 hours of grazing. Postprandial OGT insulin concentration was positively correlated with 2 hours post‐grazing insulin across all 3 grazing days (P ≤ .03). The aGLP‐1 and GIP concentrations increased in response to grazing but did not differ among groups. Conclusions and Clinical Importance Grazing pasture provoked an increased insulin and incretin response in insulin‐dysregulated ponies within 4 hours of grazing. The pasture and OGT insulin concentrations were correlated.
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Affiliation(s)
- Danielle M Fitzgerald
- Department of Bioscience, Science and Engineering Faculty, Queensland University of Technology, Brisbane, Queensland, Australia
| | | | - Martin N Sillence
- Department of Bioscience, Science and Engineering Faculty, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Christopher C Pollitt
- School of Veterinary Science, University of Queensland, Gatton, Queensland, Australia
| | - Melody A de Laat
- Department of Bioscience, Science and Engineering Faculty, Queensland University of Technology, Brisbane, Queensland, Australia
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Meier AD, de Laat MA, Reiche DB, Pollitt CC, Walsh DM, McGree JM, Sillence MN. The oral glucose test predicts laminitis risk in ponies fed a diet high in nonstructural carbohydrates. Domest Anim Endocrinol 2018; 63:1-9. [PMID: 29172109 DOI: 10.1016/j.domaniend.2017.10.008] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Revised: 10/24/2017] [Accepted: 10/25/2017] [Indexed: 10/18/2022]
Abstract
The aim of this study was to investigate the relationship between laminitis development in ponies and insulin/glucose concentrations in response to the oral glucose test (OGT) and a dietary challenge high in nonstructural carbohydrates (NSCs). After undergoing an OGT (1 g dextrose/kg BW in feed), 37 ponies with 2-h serum insulin concentrations ranging from 22 to 1,133 μIU/mL were subjected to a diet challenge period (DCP), consuming 12 g NSC/kg BW/d for up to 18 d. Insulin and glucose responses were measured on day 2 of the DCP. Clinical laminitis was diagnosed by blinded experts and confirmed radiographically. Basal ACTH levels and clinical signs were assessed to investigate concurrent putative pituitary pars intermedia dysfunction (PPID). The diet induced Obel grade 1 or 2 laminitis in 14 ponies (38%). The ponies that developed laminitis had higher maximum concentrations of blood glucose (P = 0.04) and serum insulin (P = 0.02) in response to the diet. The geometric mean (95% CI) blood glucose concentration for laminitis cases was 14.9 (12.9-17.2) mM, compared to 10.7 (9.2-12.5) mM for ponies who did not develop laminitis. Similarly, the geometric mean (95% CI) for serum insulin was 396 (301-520) μIU/mL for laminitis cases, compared to 216 (148-316) μIU/mL for ponies who did not develop laminitis. Laminitis incidence was likewise associated with insulin concentrations measured during the OGT. Laminitis occurred at frequencies of 0% (0/7) if postdextrose insulin (μIU/mL) was <50; 35% (8/23) if insulin was 50 to 195; and 86% (6/7) if insulin was >195 μIU/mL. Basal ACTH concentrations were above seasonally accepted reference ranges in 16/37 ponies, and 8 of these animals (50%) developed laminitis. This included all 5 ponies in the study that had clinical signs of PPID (100%). In contrast, hyperinsulinemia and laminitis occurred in only 3/11 ponies (27%) with elevated ACTH concentrations and no clinical signs of PPID (P = 0.009). Thus, laminitis occurrence was associated with higher glucose and insulin responses to both the OGT and challenge diet, and the frequency of laminitis can be predicted based on insulin and glucose hyperresponsiveness to these oral carbohydrate challenges.
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Affiliation(s)
- A D Meier
- Earth, Environmental and Biological Sciences School, Queensland University of Technology, Queensland, Australia
| | - M A de Laat
- Earth, Environmental and Biological Sciences School, Queensland University of Technology, Queensland, Australia
| | - D B Reiche
- Boehringer Ingelheim Vetmedica, Ingelheim am Rhein, Germany
| | - C C Pollitt
- Australian Equine Laminitis Research Unit, School of Veterinary Science, University of Queensland, Queensland, Australia
| | - D M Walsh
- Animal Health Foundation, Pacific, Missouri, USA
| | - J M McGree
- School of Mathematical Sciences, Queensland University of Technology, Queensland, Australia
| | - M N Sillence
- Earth, Environmental and Biological Sciences School, Queensland University of Technology, Queensland, Australia.
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Wylie CE, Pollitt CC. In Horses With Chronic Laminitis, Do Venograms Compared to Plain Radiographs Give Greater Diagnostic or Prognostic Information? VE 2017. [DOI: 10.18849/ve.v2i3.124] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
<p>There is no conclusive evidence available to guide recommendations as to whether venograms provide any greater diagnostic or prognostic information compared to the use of plain radiographs in horses with chronic laminitis. Further evidence is needed to better answer this PICO.</p><br /> <img src="https://www.veterinaryevidence.org/rcvskmod/icons/oa-icon.jpg" alt="Open Access" /> <img src="https://www.veterinaryevidence.org/rcvskmod/icons/pr-icon.jpg" alt="Peer Reviewed" />
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de Laat MA, Hampson BA, Sillence MN, Pollitt CC. Sustained, Low-Intensity Exercise Achieved by a Dynamic Feeding System Decreases Body Fat in Ponies. J Vet Intern Med 2016; 30:1732-1738. [PMID: 27639952 PMCID: PMC5032883 DOI: 10.1111/jvim.14577] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Revised: 07/26/2016] [Accepted: 08/22/2016] [Indexed: 12/27/2022] Open
Abstract
Background Obesity 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. Hypothesis Our 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). Animals Eight, university‐owned, mixed‐breed, adult ponies with body condition scores (BCS) ≥5/9 were used. Methods Two 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. Results The 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 Importance A 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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Affiliation(s)
- M A de Laat
- Earth, Environmental and Biological Sciences, Queensland University of Technology (QUT), Brisbane, Qld, Australia.
| | - B A Hampson
- Sunshine Coast Equine Podiatry Services, Coolum, Qld, Australia
| | - M N Sillence
- Earth, Environmental and Biological Sciences, Queensland University of Technology (QUT), Brisbane, Qld, Australia
| | - C C Pollitt
- Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton, Qld Australia
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Underwood C, Pollitt CC, Metselaar JM, Laverman P, van Bloois L, van den Hoven JM, Storm G, van Eps AW. Distribution of technetium-99m PEG-liposomes during oligofructose-induced laminitis development in horses. Vet J 2015; 206:218-25. [PMID: 26403954 DOI: 10.1016/j.tvjl.2015.07.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2014] [Revised: 04/08/2015] [Accepted: 07/12/2015] [Indexed: 12/16/2022]
Abstract
Liposomes are phospholipid nanoparticles used for targeted drug delivery. This study aimed to determine whether intravenous liposomes accumulate in lamellar tissue during laminitis development in horses so as to assess their potential for targeted lamellar drug delivery. Polyethylene-glycol (PEG) coated liposomes were prepared according to the film hydration method and labelled using (99m)Tc-hexamethyl-propylene-amine-oxime. Six horses received 10 g/kg oligofructose via nasogastric tube to induce laminitis, and four control horses received water via nasogastric tube. All horses received 300 µmol (99m)Tc-PEG-liposomes (5.5 GBq) plus 5.5 µmol/kg PEG-liposomes by slow intravenous infusion. Scintigraphic imaging was performed at 0, 6 and 12 h post-infusion. Technetium-99m liposome uptake was measured in regions of interest over the hoof, fetlock and metacarpus. At the study end-point horses were euthanased, tissue samples collected and tissue liposome levels were calculated as the percentage of the injected dose of (99m)Tc-liposomes per kilogram of tissue. Data were analysed non-parametrically. All horses receiving oligofructose developed clinical and histological signs of laminitis. Technetium-99m liposome uptake in the hoof increased with time in laminitis horses (P = 0.04), but decreased with time in control horses (P = 0.01). Technetium-99m liposome levels in lamellar tissue from laminitis horses were 3.2-fold higher than controls (P = 0.02) and were also higher in laminitis vs. control skin, muscle, jejunum, colon, and kidney (P < 0.05). Liposomes accumulated in lamellar tissue during oligofructose-induced laminitis development and demonstrated potential for targeted lamellar drug delivery in acute laminitis. This study provides further evidence that lamellar inflammation occurs during laminitis development. Liposome accumulation also occurred in the skin, muscle, jejunum, colon and kidneys, suggesting systemic inflammation in this model.
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Affiliation(s)
- Claire Underwood
- Australian Equine Laminitis Research Unit, School of Veterinary Science, University of Queensland, Gatton, QLD 4343, Australia.
| | - Christopher C Pollitt
- Australian Equine Laminitis Research Unit, School of Veterinary Science, University of Queensland, Gatton, QLD 4343, Australia
| | - Josbert M Metselaar
- Department of Experimental Molecular Imaging, University Clinic and Helmholtz Institute for Biomedical Engineering, RWTH-Aachen University, Aachen, Germany
| | - Peter Laverman
- Radboud University Medical Centre Nijmegen, The Netherlands
| | - Louis van Bloois
- Department of Pharmaceutics, Utrecht Institute for Pharmaceutical Sciences (UIPS), University of Utrecht, The Netherlands
| | | | - Gert Storm
- Department of Pharmaceutics, Utrecht Institute for Pharmaceutical Sciences (UIPS), University of Utrecht, The Netherlands
| | - Andrew W van Eps
- Australian Equine Laminitis Research Unit, School of Veterinary Science, University of Queensland, Gatton, QLD 4343, Australia
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12
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Abstract
REASONS FOR PERFORMING STUDY The suspensory apparatus of the distal phalanx (SADP) is functionally and clinically important. OBJECTIVES To investigate SADP form and function and the microanatomy of its insertion zone. STUDY DESIGN Descriptive gross and microanatomy. METHODS The feet of 6 normal Standardbred horses were sectioned into blocks along the traditional perpendicular transverse axis and along functional axes of the SADP, decalcified and processed for staining with haematoxylin and eosin, Jones' periodic acid silver methenamine or Masson's trichrome stains. RESULTS In traditional midline toe transverse plane sections SADP collagen bundles were irregular with an unstructured appearance. In sections made transversely along planes (70° and 30°) aligned with the long axis of the SADP, collagen bundles were arranged in linear rows. The linear bundles were continuous from their origin on parietal ridges of the distal phalanx through to the secondary epidermal lamellar basement membrane. At the parietal ridge interface the collagen bundles coalesced into smaller, strongly silver staining, linear structures that penetrated the cortical bone and merged with adjacent osteons. In proximal sagittal sections collagen bundles were also linear, angled at 70° to the ground surface. In distal sagittal sections collagen bundles were also arranged linearly but in a multi-angled, 'spokes of a wheel' arrangement, centred on the distal phalanx apex. CONCLUSIONS Sectioning along functional axes demonstrated the true suspensory nature of the SADP connecting the parietal surface to the lamellar hoof wall. SADP/distal phalanx insertions showed penetrating fibres extending through the chondral-apophyseal interface up to and between distal phalanx osteons. Lamellar measurements made from sections perpendicular to the dorsal aspect of the distal phalanx are underestimations but if made along the longer, functional midline 70° transverse plane would accurately reflect the suspensory function of the lamellae. Laminitis pathophysiology correctly viewed as SADP degradation should inform logical, future therapeutic strategies.
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Affiliation(s)
- C C Pollitt
- Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton Campus, Australia
| | - S N Collins
- Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton Campus, Australia
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Chinkangsadarn T, Wilson GJ, Greer RM, Pollitt CC, Bird PS. An abattoir survey of equine dental abnormalities in Queensland, Australia. Aust Vet J 2015; 93:189-94. [DOI: 10.1111/avj.12327] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Revised: 07/20/2014] [Accepted: 09/02/2014] [Indexed: 11/29/2022]
Affiliation(s)
- T Chinkangsadarn
- School of Veterinary Science; University of Queensland; Gatton Queensland Australia
| | - GJ Wilson
- School of Veterinary Science; University of Queensland; Gatton Queensland Australia
| | - RM Greer
- School of Veterinary Science; University of Queensland; Gatton Queensland Australia
| | - CC Pollitt
- School of Veterinary Science; University of Queensland; Gatton Queensland Australia
| | - PS Bird
- School of Veterinary Science; University of Queensland; Gatton Queensland Australia
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14
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de Laat MA, Gruntmeir KJ, Pollitt CC, McGowan CM, Sillence MN, Lacombe VA. Hyperinsulinemia Down-Regulates TLR4 Expression in the Mammalian Heart. Front Endocrinol (Lausanne) 2014; 5:120. [PMID: 25101057 PMCID: PMC4105691 DOI: 10.3389/fendo.2014.00120] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2014] [Accepted: 07/08/2014] [Indexed: 01/04/2023] Open
Abstract
Toll-like receptors (TLR) are key regulators of innate immune and inflammatory responses and their activation is linked to impaired glucose metabolism during metabolic disease. Determination of whether TLR4 signaling can be activated in the heart by insulin may shed light on the pathogenesis of diabetic cardiomyopathy, a process that is often complicated by obesity and insulin resistance. The aim of the current study was to determine if supraphysiological insulin concentrations alter the expression of TLR4, markers of TLR4 signaling and glucose transporters (GLUTs) in the heart. Firstly, the effect of insulin on TLR4 protein expression was investigated in vitro in isolated rat cardiac myocytes. Secondly, protein expression of TLR4, the pro-inflammatory cytokines interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) suppressor of cytokine signaling 3 (SOCS3) and GLUTs (1, 4, 8, 12) were examined in the equine ventricular myocardium following a prolonged, euglycemic, hyperinsulinemic clamp. Down-regulation of TLR4 protein content in rat cardiac myocytes was observed after incubation with a supraphysiologic concentration of insulin as well as in the equine myocardium after prolonged insulin infusion. Further, cardiac TLR4 expression was negatively correlated with serum insulin concentration. Markers of cardiac TLR4 signaling and GLUT expression were not affected by hyperinsulinemia and concomitant TLR4 down-regulation. Since TLRs are major determinants of the inflammatory response, our findings suggest that insulin infusion exerts an anti-inflammatory effect in the hearts of non-obese individuals. Understanding the regulation of cardiac TLR4 signaling during metabolic dysfunction will facilitate improved management of cardiac sequela to metabolic syndrome and diabetes.
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Affiliation(s)
- Melody A. de Laat
- Department of Physiological Sciences, Center for Veterinary Health Sciences, Oklahoma State University, Stillwater, OK, USA
| | - Kaylynn J. Gruntmeir
- Department of Physiological Sciences, Center for Veterinary Health Sciences, Oklahoma State University, Stillwater, OK, USA
| | - Christopher C. Pollitt
- Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton, QLD, Australia
| | - Catherine M. McGowan
- Institute of Ageing and Chronic Disease, Faculty of Health and Life Sciences, University of Liverpool, Neston, UK
| | - Martin N. Sillence
- Earth, Environmental and Biological Sciences, Queensland University of Technology, Brisbane, QLD, Australia
| | - Véronique A. Lacombe
- Department of Physiological Sciences, Center for Veterinary Health Sciences, Oklahoma State University, Stillwater, OK, USA
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Underwood C, Collins SN, van Eps AW, Allavena RE, Medina-Torres CE, Pollitt CC. Ultrafiltration of equine digital lamellar tissue. Vet J 2014; 202:314-22. [PMID: 25439438 DOI: 10.1016/j.tvjl.2014.05.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Revised: 05/02/2014] [Accepted: 05/03/2014] [Indexed: 10/25/2022]
Abstract
There are no experimentally validated pharmacological means of preventing laminitis; however, locally acting pharmaceutical agents with the potential to prevent laminitis have been identified. Demonstrating therapeutic drug concentrations in lamellar tissue is essential for evaluating the efficacy of these agents. The aim of this study was to develop an experimental technique for repeatedly sampling lamellar interstitial fluid. A technique for placing ultrafiltration probes was developed in vitro using 15 cadaver limbs. Subsequently, lamellar ultrafiltration probes were placed in one forelimb in six living horses. Interstitial fluid was collected continuously from the probes as ultrafiltrate for 4 (n = 4) or 14 days (n = 2). The rate of ultrafiltrate collection was calculated every 12 h. Biochemical analyses were performed on ultrafiltrate collected on night 1 (12-24 h post-implantation) and night 4 (84-96 h post-implantation). Sections surrounding the probe and control tissue from the contralateral limb were harvested, stained with H&E and Masson's trichrome and scored based on the tissue response to the probe. Ultrafiltration probes were placed in the lamellar tissue in all six horses. Ultrafiltrate was collected from these probes at 55 (30-63) μL/h (median [interquartile range]). Fluid production decreased significantly with time from night 3 onwards (P < 0.05). There was no significant change in the constituents of the ultrafiltrate between nights 1 and 4 (P > 0.05). The technique was well tolerated. This study demonstrates that ultrafiltration can be used to sample equine digital lamellar interstitial fluid, and has potential for measuring lamellar drug levels.
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Affiliation(s)
- Claire Underwood
- Australian Equine Laminitis Research Unit, School of Veterinary Science, University of Queensland, Gatton Campus, Gatton, Qld 4343, Australia.
| | - Simon N Collins
- Australian Equine Laminitis Research Unit, School of Veterinary Science, University of Queensland, Gatton Campus, Gatton, Qld 4343, Australia
| | - Andrew W van Eps
- Australian Equine Laminitis Research Unit, School of Veterinary Science, University of Queensland, Gatton Campus, Gatton, Qld 4343, Australia
| | - Rachel E Allavena
- Australian Equine Laminitis Research Unit, School of Veterinary Science, University of Queensland, Gatton Campus, Gatton, Qld 4343, Australia
| | - Carlos E Medina-Torres
- Australian Equine Laminitis Research Unit, School of Veterinary Science, University of Queensland, Gatton Campus, Gatton, Qld 4343, Australia
| | - Christopher C Pollitt
- Australian Equine Laminitis Research Unit, School of Veterinary Science, University of Queensland, Gatton Campus, Gatton, Qld 4343, Australia
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van Eps AW, Pollitt CC, Underwood C, Medina-Torres CE, Goodwin WA, Belknap JK. Continuous digital hypothermia initiated after the onset of lameness prevents lamellar failure in the oligofructose laminitis model. Equine Vet J 2013; 46:625-30. [PMID: 24004323 DOI: 10.1111/evj.12180] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Accepted: 08/22/2013] [Indexed: 11/25/2022]
Abstract
REASONS FOR PERFORMING STUDY Prophylactic digital hypothermia reduces the severity of acute laminitis experimentally but there is no evidence for its efficacy as a treatment once lameness has already developed. OBJECTIVES To investigate the therapeutic effects of digital hypothermia, applied after the onset of lameness, in an experimental acute laminitis model. STUDY DESIGN Randomised, controlled (within subject), blinded, experimental trial. METHODS Eight Standardbred horses underwent laminitis induction using the oligofructose model. Once lameness was detected at the walk, one forelimb was continuously cooled (CRYO), with the other forelimb maintained at ambient temperature (NON-RX). Dorsal lamellar sections (proximal, middle and distal) harvested 36 h after the onset of lameness/initiation of cryotherapy were analysed by 2 blinded observers: laminitis pathology was scored (0 [normal] to 4 [severe]) and morphometric analyses performed. RESULTS Median (interquartile range) histological scores were greater (P<0.05) in NON-RX (proximal 2.8 [2.5-4]; middle 3.5 [2-4]; distal 2.5 [2-3.8]) compared with CRYO limbs (proximal 0.5 [0.5-1.4]; middle 1 [0.6-1]; distal 0.75 [0.5-1]). There was complete physical separation of lamellar dermis from epidermis (score of 4) in 4 of the NON-RX feet at one or more section level(s), which was not observed in any CRYO sections. Histomorphometry was thus limited to sections that remained intact; there was a trend of increased total (TELL) and secondary (SELL) epidermal lamellar length and decreased secondary epidermal lamellar width (SELW) in NON-RX limbs compared with CRYO at all 3 levels; differences were significant (P<0.05) for SELL and SELW in the distal sections. CONCLUSIONS Digital hypothermia reduced the severity of lamellar injury and prevented lamellar structural failure (complete dermoepidermal separation) when initiated at the detection of lameness in an acute laminitis model. This study provides the first evidence to support the use of therapeutic digital hypothermia as a treatment for acute laminitis.
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Affiliation(s)
- A W van Eps
- Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton, Australia
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17
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Kampmann S, Hampson BA, Pollitt CC. Population dynamics of feral horses (Equus caballus) following above-average rainfall in a semi-arid environment of Australia. Aust Vet J 2013; 91:482-7. [DOI: 10.1111/avj.12120] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/20/2013] [Indexed: 11/28/2022]
Affiliation(s)
- S Kampmann
- Zoological Institute: Population Genetics; Department of Biology; Faculty of Mathematics and Natural Sciences; Christian-Albrechts-University of Kiel; Germany
| | - BA Hampson
- The Australian Brumby Research Unit; School of Veterinary Science; The University of Queensland; Gatton Queensland 4343 Australia
| | - CC Pollitt
- The Australian Brumby Research Unit; School of Veterinary Science; The University of Queensland; Gatton Queensland 4343 Australia
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18
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de Laat MA, Clement CK, McGowan CM, Sillence MN, Pollitt CC, Lacombe VA. Toll-like receptor and pro-inflammatory cytokine expression during prolonged hyperinsulinaemia in horses: implications for laminitis. Vet Immunol Immunopathol 2013; 157:78-86. [PMID: 24246153 DOI: 10.1016/j.vetimm.2013.10.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Revised: 10/12/2013] [Accepted: 10/18/2013] [Indexed: 12/31/2022]
Abstract
Equine laminitis, a disease of the lamellar structure of the horse's hoof, can be incited by numerous factors that include inflammatory and metabolic aetiologies. However, the role of inflammation in hyperinsulinaemic laminitis has not been adequately defined. Toll-like receptor (TLR) activation results in up-regulation of inflammatory pathways and the release of pro-inflammatory cytokines, including interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF-α), and may be a pathogenic factor in laminitis. The aim of this study was to determine whether TLR4 expression and subsequent pro-inflammatory cytokine production is increased in lamellae and skeletal muscle during equine hyperinsulinaemia. Standardbred horses were treated with either a prolonged, euglycaemic hyperinsulinaemic clamp (p-EHC) or a prolonged, glucose infusion (p-GI), which induced marked and moderate hyperinsulinaemia, respectively. Age-matched control horses were treated simultaneously with a balanced electrolyte solution. Treated horses developed clinical (p-EHC) or subclinical (p-GI) laminitis, whereas controls did not. Skeletal muscle and lamellar protein extracts were analysed by Western blotting for TLR4, IL-6, TNF-α and suppressor of cytokine signalling 3 (SOCS3) expression. Lamellar protein expression of TLR4 and TNF-α, but not IL-6, was increased by the p-EHC, compared to control horses. A significant positive correlation was found between lamellar TLR4 and SOCS3. Skeletal muscle protein expression of TLR4 signalling parameters did not differ between control and p-EHC-treated horses. Similarly, the p-GI did not result in up-regulation of lamellar protein expression of any parameter. The results suggest that insulin-sensitive tissues may not accurately reflect lamellar pathology during hyperinsulinaemia. While TLR4 is present in the lamellae, its activation appears unlikely to contribute significantly to the developmental pathogenesis of hyperinsulinaemic laminitis. However, inflammation may have a role to play in the later stages (e.g., repair or remodelling) of the disease.
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Affiliation(s)
- M A de Laat
- Department of Physiological Sciences, Center for Veterinary Health Sciences, Oklahoma State University, Stillwater, OK 74078, USA
| | - C K Clement
- Department of Physiological Sciences, Center for Veterinary Health Sciences, Oklahoma State University, Stillwater, OK 74078, USA
| | - C M McGowan
- Institute of Ageing and Chronic Disease, Faculty of Health and Life Sciences, University of Liverpool, Neston, CH64 7TE, UK
| | - M N Sillence
- Earth, Environmental and Biological Sciences, Queensland University of Technology, Brisbane, Queensland, 4001, Australia
| | - C C Pollitt
- Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton, Queensland, 4343, Australia
| | - V A Lacombe
- Department of Physiological Sciences, Center for Veterinary Health Sciences, Oklahoma State University, Stillwater, OK 74078, USA.
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19
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Galantino-Homer HL, Johnson PJ, Engiles JB, Pollitt CC, Linardi RL, Megee S, Modelski M. Loss of lamellar epidermal cytolinker and desmosomal proteins: Does it contribute to the failure of the suspensory apparatus of the distal phalanx in equine laminitis? J Equine Vet Sci 2013. [DOI: 10.1016/j.jevs.2013.08.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Hampson BA, de Laat MA, Mills PC, Walsh DM, Pollitt CC. The feral horse foot. Part B: radiographic, gross visual and histopathological parameters of foot health in 100 Australian feral horses. Aust Vet J 2013; 91:23-30. [PMID: 23356368 DOI: 10.1111/avj.12017] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/31/2012] [Indexed: 11/28/2022]
Abstract
BACKGROUND It has been proposed that the feral horse foot is a benchmark model for foot health in horses. However, the foot health of feral horses has not been formally investigated. OBJECTIVES To investigate the foot health of Australian feral horses and determine if foot health is affected by environmental factors, such as substrate properties and distance travelled. METHODS Twenty adult feral horses from five populations (n = 100) were investigated. Populations were selected on the basis of substrate hardness and the amount of travel typical for the population. Feet were radiographed and photographed, and digital images were surveyed by two experienced assessors blinded to each other's assessment and to the population origin. Lamellar samples from 15 feet from three populations were investigated histologically for evidence of laminitis. RESULTS There was a total of 377 gross foot abnormalities identified in 100 left forefeet. There were no abnormalities detected in three of the feet surveyed. Each population had a comparable prevalence of foot abnormalities, although the type and severity of abnormality varied among populations. Of the three populations surveyed by histopathology, the prevalence of chronic laminitis ranged between 40% and 93%. CONCLUSIONS Foot health appeared to be affected by the environment inhabited by the horses. The observed chronic laminitis may be attributable to either nutritional or traumatic causes. Given the overwhelming evidence of suboptimal foot health, it may not be appropriate for the feral horse foot to be the benchmark model for equine foot health.
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Affiliation(s)
- B A Hampson
- Australian Brumby Research Unit, School of Veterinary Science, The University of Queensland, St Lucia, Australia.
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Hampson BA, de Laat MA, Monot J, Bailliu D, Pollitt CC. Adaption of horses to a novel dynamic feeding system: movement and behavioural responses. Equine Vet J 2012; 45:481-4. [PMID: 23216599 DOI: 10.1111/evj.12002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Accepted: 10/03/2012] [Indexed: 11/29/2022]
Abstract
REASONS FOR PERFORMING STUDY Many domestic horses and ponies are sedentary and obese due to confinement to small paddocks and stables and a diet of infrequent, high-energy rations. Severe health consequences can be associated with this altered lifestyle. OBJECTIVES The aims of this study were to investigate the ability of horses to learn to use a dynamic feeder system and determine the movement and behavioural responses of horses to the novel system. METHODS A dynamic feed station was developed to encourage horses to exercise in order to access ad libitum hay. Five pairs of horses (n = 10) were studied using a randomised crossover design with each pair studied in a control paddock containing a standard hay feeder and an experimental paddock containing the novel hay feeder. Horse movement was monitored by a global positioning system (GPS) and horses observed and their ability to learn to use the system and the behavioural responses to its use assessed. RESULTS With initial human intervention all horses used the novel feeder within 1 h. Some aggressive behaviour was observed between horses not well matched in dominance behaviour. The median distance walked by the horses was less (P = 0.002) during a 4 h period (117 [57-185] m) in the control paddock than in the experimental paddock (630 [509-719] m). CONCLUSIONS The use of an automated feeding system promotes increased activity levels in horses housed in small paddocks, compared with a stationary feeder. POTENTIAL RELEVANCE The novel feeder system may have application in the husbandry of horses and ponies kept in small paddocks by encouraging a natural pattern of exercise without human intervention and an ad libitum diet of hay. This may improve the health and welfare of horses.
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Affiliation(s)
- B A Hampson
- The Australian Brumby Research Unit, School of Veterinary Science, The University of Queensland, Queensland, Australia.
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Hampson BA, de Laat MA, Mills PC, Pollitt CC. The feral horse foot. Part A: observational study of the effect of environment on the morphometrics of the feet of 100 Australian feral horses. Aust Vet J 2012; 91:14-22. [PMID: 23356367 DOI: 10.1111/j.1751-0813.2012.00995.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/04/2012] [Indexed: 11/28/2022]
Abstract
AIM To better understand the morphology of, and the effect of different travel patterns and varying substrate environments on, the feral horse foot to better manage the feet of domestic horses. METHODS The left forefeet of 20 adult feral horses from each of five geographically separated populations in Australia (n = 100) were investigated. Populations were selected on the basis of substrate hardness under foot and the amount of travel typical for the population. Feet were radiographed and photographed and 40 morphometric measurements of each foot were obtained. RESULTS Of the 40 parameters, 37 differed significantly (P < 0.05) among the populations, which suggested that substrate hardness and travel distance have an effect on foot morphology. Harder substrates and longer travel distances were associated with short hoof walls and minimal hoof wall flaring. Softer substrates and moderate travel distances were associated with long flared walls, similar to that of typical untrimmed feet of domestic horses. CONCLUSIONS The morphology of the feral horse foot appeared to be affected by the distance travelled and by the abrasive qualities and mechanical properties of the substrate under foot. There were marked differences in some conformation parameters between the feral horses in the current study and domestic horses in previous studies. Although the conformation of the feral horse foot may have some prescriptive value, concerns regarding abnormal foot anatomy warrant further investigation.
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Affiliation(s)
- B A Hampson
- Australian Brumby Research Unit, School of Veterinary Science, The University of Queensland, St Lucia, Australia.
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de Laat MA, Patterson-Kane JC, Pollitt CC, Sillence MN, McGowan CM. Histological and morphometric lesions in the pre-clinical, developmental phase of insulin-induced laminitis in Standardbred horses. Vet J 2012; 195:305-12. [PMID: 22884985 DOI: 10.1016/j.tvjl.2012.07.003] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2011] [Revised: 06/07/2012] [Accepted: 07/04/2012] [Indexed: 01/16/2023]
Abstract
Lamellar pathology in experimentally-induced equine laminitis associated with euglycaemic hyperinsulinaemia is substantial by the acute, clinical phase (∼48h post-induction). However, lamellar pathology of the developmental, pre-clinical phase requires evaluation. The aim of this study was to analyse lamellar lesions both qualitatively and quantitatively, 6, 12 and 24h after the commencement of hyperinsulinaemia. Histological and histomorphometrical analyses of lamellar pathology at each time-point included assessment of lamellar length and width, epidermal cell proliferation and death, basement membrane (BM) pathology and leucocyte infiltration. Archived lamellar tissue from control horses and those with acute, insulin-induced laminitis (48h) was also assessed for cellular proliferative activity by counting the number of cells showing positive nuclear immuno labelling for TPX2. Decreased secondary epidermal lamellar (SEL) width and increased histomorphological evidence of SEL epidermal basal (and supra-basal) cell death occurred early in disease progression (6h). Increased cellular proliferation in SELs, infiltration of the dermis with small numbers of leucocytes and BM damage occurred later (24 and 48h). Some lesions, such as narrowing of the SELs, were progressive over this time period (6-48h). Cellular pathology preceded leucocyte infiltration and BM pathology, indicating that the latter changes may be secondary or downstream events in hyperinsulinaemic laminitis.
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Affiliation(s)
- Melody A de Laat
- Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton, Queensland 4343, Australia.
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Hampson BA, de Laat MA, Beausac C, Rovel T, Pollitt CC. Histopathological examination of chronic laminitis in Kaimanawa feral horses of New Zealand. N Z Vet J 2012; 60:285-9. [PMID: 22621688 DOI: 10.1080/00480169.2012.682271] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
AIMS To investigate the prevalence, histopathological and histomorphometric presentation of chronic laminitis in a population of Kaimanawa feral horses. METHODS Following the capture and euthanasia of feral horses from the Kaimanawa Ranges of New Zealand, the left forefoot of 28 stallions and 28 mares aged between 6 and 12 years were removed and processed for histology. Sections of lamellar samples from each horse were examined using light microscopy. The presence of laminitis was assessed and the histopathological lesions were described. Horses were grouped by histological diagnosis into laminitic and non-laminitic groups and histomorphometric analysis was conducted and compared between groups. The parameters examined were total length of primary epidermal lamellae (PEL), keratinised length of PEL, and the length of secondary epidermal lamellae (SEL) at the abaxial end and axial end of each PEL. RESULTS Of the horses examined, 25 (45%) were diagnosed with chronic laminitis. The most prevalent histopathological features were the presence of excessive cap horn, and multi-branched and attenuated SEL. Histomorphometric assessment of the lamellar architecture revealed no difference in morphometric measurements between the normal and laminitic groups for any parameter measured (p>0.05). CONCLUSIONS The current study found a high prevalence of laminitis in feral Kaimanawa horses. The reason for this in the Kaimanawa population is not known. Histomorphometric analysis may not be a good indicator of chronic laminitis in feral horses. CLINICAL RELEVANCE It is an important finding that the feral horse lifestyle in the environment of the Kaimanawa Ranges in New Zealand offers no protection against foot disease. The finding suggests that horses are vulnerable to laminitis whether in domestic care or in a feral habitat.
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Affiliation(s)
- B A Hampson
- School of Veterinary Science, The University of Queensland , Gatton Campus , Australia.
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de Laat MA, Kyaw-Tanner MT, Sillence MN, McGowan CM, Pollitt CC. Advanced glycation endproducts in horses with insulin-induced laminitis. Vet Immunol Immunopathol 2011; 145:395-401. [PMID: 22240145 DOI: 10.1016/j.vetimm.2011.12.016] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2011] [Revised: 12/19/2011] [Accepted: 12/20/2011] [Indexed: 01/07/2023]
Abstract
Advanced glycation endproducts (AGEs) have been implicated in the pathogenesis of cancer, inflammatory conditions and diabetic complications. An interaction of AGEs with their receptor (RAGE) results in increased release of pro-inflammatory cytokines and reactive oxygen species (ROS), causing damage to susceptible tissues. Laminitis, a debilitating foot condition of horses, occurs in association with endocrine dysfunction and the potential involvement of AGE and RAGE in the pathogenesis of the disease has not been previously investigated. Glucose transport in lamellar tissue is thought to be largely insulin-independent (GLUT-1), which may make the lamellae susceptible to protein glycosylation and oxidative stress during periods of increased glucose metabolism. Archived lamellar tissue from horses with insulin-induced laminitis (n=4), normal control horses (n=4) and horses in the developmental stages (6h, 12h and 24h) of the disease (n=12) was assessed for AGE accumulation and the presence of oxidative protein damage and cellular lipid peroxidation. The equine-specific RAGE gene was identified in lamellar tissue, sequenced and is now available on GenBank. Lamellar glucose transporter (GLUT-1 and GLUT-4) gene expression was assessed quantitatively with qRT-PCR in laminitic and control horses and horses in the mid-developmental time-point (24 h) of the disease. Significant AGE accumulation had occurred by the onset of insulin-induced laminitis (48 h) but not at earlier time-points, or in control horses. Evidence of oxidative stress was not found in any group. The equine-specific RAGE gene was not expressed differently in treated and control animals, nor was the insulin-dependent glucose transporter GLUT-4. However, the glucose transporter GLUT-1 was increased in lamellar tissue in the developmental stages of insulin-induced laminitis compared to control horses and the insulin-independent nature of the lamellae may facilitate AGE formation. However, due to the lack of AGE accumulation during disease development and a failure to detect an increase in ROS or upregulation of RAGE, it appears unlikely that oxidative stress and protein glycosylation play a central role in the pathogenesis of acute, insulin-induced laminitis.
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Affiliation(s)
- M A de Laat
- Australian Equine Laminitis Research Unit, School of Veterinary Science, Faculty of Science, The University of Queensland, Gatton, Queensland 4343, Australia.
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de Laat MA, Pollitt CC, Walsh DM, McGowan CM, Sillence MN. Persistent digital hyperthermia over a 48 h period does not induce laminitis in horses. Vet J 2011; 192:435-40. [PMID: 22023851 DOI: 10.1016/j.tvjl.2011.09.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2010] [Revised: 09/05/2011] [Accepted: 09/22/2011] [Indexed: 10/16/2022]
Abstract
Persistent digital hyperthermia, presumably due to vasodilation, occurs during the developmental and acute stages of insulin-induced laminitis. The objectives of this study were to determine if persistent digital hyperthermia is the principal pathogenic mechanism responsible for the development of laminitis. The potent vasodilator, ATP-MgCl(2) was infused continuously into the distal phalanx of the left forefoot of six Standardbred racehorses for 48 h via intra-osseous infusion to promote persistent digital hyperthermia. The right forefoot was infused with saline solution and acted as an internal control. Clinical signs of lameness at the walk were not detected at 0 h, 24h or 48 h post-infusion. Mean ± SE hoof wall temperatures of the left forefoot (29.4 ± 0.25°C) were higher (P<0.05) than those on the right (27.5 ± 0.38°C). Serum insulin (15.0 ± 2.89 μIU/mL) and blood glucose (5.4 ± 0.22 mM) concentrations remained unchanged during the experiment. Histopathological evidence of laminitis was not detected in any horse. The results demonstrated that digital vasodilation up to 30°C for a period of 48 h does not trigger laminitis in the absence of hyperinsulinaemia. Thus, although digital hyperthermia may play a role in the pathogenesis of laminitis, it is not the sole mechanism involved.
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Affiliation(s)
- Melody A de Laat
- Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton, Queensland 4343, Australia.
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Pollitt CC, Collins SN. 3D and 4D anatomy of the horse's foot: New dimensions in understanding. J Equine Vet Sci 2011. [DOI: 10.1016/j.jevs.2011.09.063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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Hampson BA, Owens E, Watts KA, Mills PC, Pollitt CC, de Laat MA. Nutritional analysis of gastric contents and body condition score at a single time point in feral horses in Australia. Am J Vet Res 2011; 72:1226-33. [PMID: 21879981 DOI: 10.2460/ajvr.72.9.1226] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To determine the impact of a free-choice diet on nutritional intake and body condition of feral horses. ANIMALS Cadavers of 41 feral horses from 5 Australian locations. PROCEDURES Body condition score (BCS) was determined (scale of 1 to 9), and the stomach was removed from horses during postmortem examination. Stomach contents were analyzed for nutritional variables and macroelement and microelement concentrations. Data were compared among the locations and also compared with recommended daily intakes for horses. RESULTS Mean BCS varied by location; all horses were judged to be moderately thin. The BCS for males was 1 to 3 points higher than that of females. Amount of protein in the stomach contents varied from 4.3% to 14.9% and was significantly associated with BCS. Amounts of water-soluble carbohydrate and ethanol-soluble carbohydrate in stomach contents of feral horses from all 5 locations were higher than those expected for horses eating high-quality forage. Some macroelement and microelement concentrations were grossly excessive, whereas others were grossly deficient. There was no evidence of ill health among the horses. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that the diet for several populations of feral horses in Australia appeared less than optimal. However, neither low BCS nor trace mineral deficiency appeared to affect survival of the horses. Additional studies on food sources in these regions, including analysis of water-soluble carbohydrate, ethanol-soluble carbohydrate, and mineral concentrations, are warranted to determine the provenance of such rich sources of nutrients. Determination of the optimal diet for horses may need revision.
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Affiliation(s)
- Brian A Hampson
- Australian Brumby Research Unit, School of Veterinary Science, University of Queensland, Gatton Campus, QLD 4343, Australia.
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Hampson BA, Studies MA, de Laat MA, Mills PC, Pollitt CC. Evaluation of primary epidermal lamellar density in the forefeet of near-term fetal Australian feral and domesticated horses. Am J Vet Res 2011; 72:871-6. [DOI: 10.2460/ajvr.72.7.871] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Abstract
REASONS FOR PERFORMING STUDY The timing of lamellar basement membrane (BM) changes occurring during laminitis development is incompletely understood. OBJECTIVES To determine the temporal progression of lamellar BM changes and whether laminin-332 (Ln-332) γ2 cleavage products are generated during laminitis development. METHODS Eight clinically normal Standardbred horses were allocated into treatment (n = 5) or sham (n = 3) groups. The treatment group received, via nasogastric intubation, an oligofructose (OF) bolus (10 g/kg bwt) while the sham group was given water. Laminitis induction proceeded for 48 h followed by euthanasia. Lamellar biopsies were obtained prior to dosing and at intervals during the treatment period for analysis (at 12, 18, 24, 30 and 36 h and at 48 h following euthanasia). RESULTS Changes in lamellar collagen type IV and Ln-332 were first observed at 12 h post dosing. A unique pattern of reactivity for the Ln-332 γ2 antibody D4B5 occurred, in which reactivity was observed only in lamellar tissue affected by laminitis. No bioactive Ln-332 γ2 proteolytic fragments were detected in lamellar samples. CONCLUSIONS Basement membrane changes occurred early during the laminitis process. Direct Ln-332 γ2 cleavage to release biologically active products did not appear to occur. Thus loss of stability or protein interaction of the BM is probably responsible for the γ2 specific reactivity observed. POTENTIAL RELEVANCE Basement membrane changes may a first step in lamellar failure occurring prior to detection with conventional methods. Thus, more sensitive detection methods of BM changes are required to study laminitis development.
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Affiliation(s)
- M B Visser
- The Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, St Lucia, Australia
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Visser MB, Pollitt CC. Immunohistochemical distribution of laminin-332 and collagen type IV in the basement membrane of normal horses and horses with induced laminitis. J Comp Pathol 2011; 145:80-7. [PMID: 21247586 DOI: 10.1016/j.jcpa.2010.11.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2010] [Revised: 08/29/2010] [Accepted: 11/15/2010] [Indexed: 10/18/2022]
Abstract
The basement membrane (BM) is a thin layer of extracellular matrix that regulates cell functions as well as providing support to tissues of the body. Primary components of the BM of epithelial tissues are laminin-332 (Ln-332) and collagen type IV. Equine laminitis is a disease characterized by destruction and dislocation of the hoof lamellar BM. Immunohistochemistry was used to characterize the distribution of Ln-332 and collagen type IV in the organs of normal horses and these proteins were found to be widespread. Analysis of a panel of tissue samples from horses with experimentally-induced laminitis revealed that Ln-332 and collagen type IV degradation occurs in the skin and stomach in addition to the hoof lamellae. These findings suggest that BM degradation is common to many epithelial tissues during equine laminitis and suggests a role for systemic trigger factors in this disease.
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Affiliation(s)
- M B Visser
- School of Veterinary Science, University of Queensland, Gatton, QLD 4343, Australia.
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Abstract
REASONS FOR PERFORMING STUDY Several conditions associated with laminitis in horses are also associated with insulin resistance, which represents the failure of glucose uptake via the insulin-responsive glucose transport proteins in certain tissues. Glucose starvation is a possible mechanism of laminitis, but glucose uptake mechanisms in the hoof are not well understood. OBJECTIVES To determine whether glucose uptake in equine lamellae is dependent on insulin, to characterise the glucose transport mechanism in lamellae from healthy horses and ponies, and to compare this with ponies with laminitis. METHODS Study 1 investigated the effects of insulin (300 µU/ml; acute and 24 h) and various concentrations of glucose up to 24 mmol/l, on 2-deoxy-D-[2,6-(3)H] glucose uptake in hoof lamellar explants in vitro. Study 2 measured the mRNA expression of GLUT1 and GLUT4 transport proteins by PCR analysis in coronary band and lamellar tissue from healthy horses and ponies, ponies with insulin-induced laminitis, and ponies suffering from chronic laminitis as a result of equine Cushing's syndrome. RESULTS Glucose uptake was not affected by insulin. Furthermore, the relationship between glucose concentration and glucose uptake was consistent with an insulin-independent glucose transport system. GLUT1 mRNA expression was strong in brain, coronary band and lamellar tissue, but was weak in skeletal muscle. Expression of GLUT4 mRNA was strong in skeletal muscle, but was either absent or barely detectable in coronary band and lamellar tissue. CONCLUSIONS The results do not support a glucose deprivation model for laminitis, in which glucose uptake in the hoof is impaired by reduced insulin sensitivity. Hoof lamellae rely on a GLUT1-mediated glucose transport system, and it is unlikely that GLUT4 proteins play a substantial role in this tissue. POTENTIAL RELEVANCE Laminitis associated with insulin resistance is unlikely to be due to impaired glucose uptake and subsequent glucose deprivation in lamellae.
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Affiliation(s)
- K E Asplin
- School of Veterinary Science, The University of Queensland, Australia.
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Abstract
REASON FOR PERFORMING STUDY The role of matrix metalloproteases (MMPs) and the timeline of proteolysis during laminitis development are incompletely understood. OBJECTIVES To determine the temporal progression of selected MMPs and protease regulators during laminitis development. METHODS Five clinically normal Standardbred horses received, via nasogastric intubation, an oligofructose (OF) bolus (10 g/kg bwt). Laminitis induction proceeded for 48 h followed by euthanasia. Lamellar biopsies were obtained prior to dosing and at intervals during the treatment period for analysis (12, 18, 24, 30 and 36 h and at 48 h following euthanasia). Tissue samples were analysed by real-time PCR, zymography and western blotting. RESULTS Activation of proMMP-2 occurs either simultaneously or at least 12 h following lamellar basement membrane (BM) damage, while no activation of proMMP-9 is seen during OF laminitis induction. Aggrecanase gene expression increased initially at 12-18 h post OF dosing, similar to BM changes. Gene expression of TIMP-2, a MMP regulator, decreases during laminitis development. CONCLUSIONS The MMP-2/MT1-MMP complex may not play a major role in initiating lamellar BM damage. Aggrecanase and TIMP-2 gene expression appear related to BM lamellar changes. POTENTIAL RELEVANCE MMPs, historically thought to cause laminitis, do not appear to play an initiating role in the lamellar lesion. Other host derived proteases and degradation of alternative lamellar matrix components need to be considered.
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Affiliation(s)
- M B Visser
- The Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Australia.
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de Laat MA, Kyaw-Tanner MT, Nourian AR, McGowan CM, Sillence MN, Pollitt CC. The developmental and acute phases of insulin-induced laminitis involve minimal metalloproteinase activity. Vet Immunol Immunopathol 2011; 140:275-81. [PMID: 21333362 DOI: 10.1016/j.vetimm.2011.01.013] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2010] [Revised: 01/20/2011] [Accepted: 01/26/2011] [Indexed: 11/16/2022]
Abstract
Metalloproteinases have been implicated in the pathogenesis of equine laminitis and other inflammatory conditions, through their role in the degradation and remodelling of the extracellular matrix environment. Matrix metalloproteinases (MMPs) and their inhibitors are present in normal equine lamellae, with increased secretion and activation of some metalloproteinases reported in horses with laminitis associated with systemic inflammation. It is unknown whether these enzymes are involved in insulin-induced laminitis, which occurs without overt systemic inflammation. In this study, gene expression of MMP-2, MMP-9, MT1-MMP, ADAMTS-4 and TIMP-3 was determined in the lamellar tissue of normal control horses (n=4) and horses that developed laminitis after 48 h of induced hyperinsulinaemia (n=4), using quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). Protein concentrations of MMP-2 and MMP-9 were also examined using gelatin zymography in horses subject to prolonged hyperinsulinaemia for 6h (n=4), 12h (n=4), 24h (n=4) and 48 h (n=4), and in normal control horses (n=4). The only change in gene expression observed was an upregulation of MMP-9 (p<0.05) in horses that developed insulin-induced laminitis (48 h). Zymographical analysis showed an increase (p<0.05) in pro MMP-9 during the acute phase of laminitis (48 h), whereas pro MMP-2 was present in similar concentration in the tissue of all horses. Thus, MMP-2, MT1-MMP, TIMP-3 and ADAMTS-4 do not appear to play a significant role in the pathogenesis of insulin-induced laminitis. The increased expression of MMP-9 may be associated with the infiltration of inflammatory leukocytes, or may be a direct result of hyperinsulinaemia. The exact role of MMP-9 in basement membrane degradation in laminitis is uncertain as it appears to be present largely in the inactive form.
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Affiliation(s)
- M A de Laat
- Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton, Queensland 4343, Australia.
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Abstract
REASONS FOR PERFORMING STUDY Ponies with laminitis associated with insulin resistance and hyperinsulinaemia lack systemic and/or intestinal inflammatory signs, suggesting a different pathogenesis potentially reflected in differing histopathology. OBJECTIVES To describe the histological appearance and quantify morphological changes in primary and secondary epidermal lamellae (PEL and SEL) of laminitis lesions from ponies with insulin-induced laminitis. METHODS Equine hoof lamellar tissue was obtained from 4 control ponies and 5 ponies with laminitis induced following infusion of insulin (1036 ± 55 µU/ml) while maintaining euglycaemia for 55.4 ± 5.5 h. Sections from all 4 hooves were stained and examined by a veterinary pathologist. Measurements of lamellar length (PEL and SEL) were made in mid-dorsal sections of the right forefeet by 2 blinded observers. Immunolabelling for calprotectin was performed using a monoclonal antibody. RESULTS No lesions were detected in normal ponies. Lesions detected in ponies with laminitis were variable in severity between ponies. Within ponies, SEL lesions were more severe along the axial region of PEL. Lesions included swelling, disorganisation and abnormal keratinisation of epidermal cells, increased mitotic activity and apoptosis. Separation of basement membranes was minimal. Immunostaining revealed inflammatory cells within the lamellar dermis. SEL were significantly elongated in laminitic hooves relative to controls, with the greatest elongation in those attached to abaxial and middle regions of PEL. CONCLUSIONS Laminitis induced by prolonged infusion of insulin lacked widespread basement membrane disintegration, and increases in epidermal cellular proliferation at axial aspects were marked for this acute stage of disease. POTENTIAL RELEVANCE Defining equine laminitis entirely in terms of separation of the basement membrane may not be appropriate for laminitis associated with hyperinsulinaemia.
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Affiliation(s)
- K E Asplin
- School of Veterinary Science, The University of Queensland, Australia
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Pollitt CC. Preface. Metabolic and endocrinopathic laminitis. Vet Clin North Am Equine Pract 2010; 26:xiii-xv. [PMID: 20699170 DOI: 10.1016/j.cveq.2010.06.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Affiliation(s)
- Christopher C Pollitt
- Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland Gatton Campus, Gatton, QLD 4343, Australia.
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Budak MT, Orsini JA, Pollitt CC, Rubinstein NA. Corrigendum to “Gene expression in the lamellar dermis–epidermis during the developmental phase of carbohydrate overload-induced laminitis in the horse” [Vet. Immunol. Immunopathol. 131 (2009) 86–96]. Vet Immunol Immunopathol 2010. [DOI: 10.1016/j.vetimm.2010.04.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Carter RA, Shekk V, de Laat MA, Pollitt CC, Galantino-Homer HL. Novel keratins identified by quantitative proteomic analysis as the major cytoskeletal proteins of equine (Equus caballus) hoof lamellar tissue. J Anim Sci 2010; 88:3843-55. [PMID: 20622188 DOI: 10.2527/jas.2010-2964] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The dermo-epidermal interface that connects the equine distal phalanx to the cornified hoof wall withstands great biomechanical demands, but is also a region where structural failure often ensues as a result of laminitis. The cytoskeleton in this region maintains cell structure and facilitates intercellular adhesion, making it likely to be involved in laminitis pathogenesis, although it is poorly characterized in the equine hoof lamellae. The objective of the present study was to identify and quantify the cytoskeletal proteins present in the epidermal and dermal lamellae of the equine hoof by proteomic techniques. Protein was extracted from the mid-dorsal epidermal and dermal lamellae from the front feet of 5 Standardbred geldings and 1 Thoroughbred stallion. Mass spectrometry-based spectral counting techniques, PAGE, and immunoblotting were used to identify and quantify cytoskeletal proteins, and indirect immunofluorescence was used for cellular localization of K14 and K124 (where K refers to keratin). Proteins identified by spectral counting analysis included 3 actin microfilament proteins; 30 keratin proteins along with vimentin, desmin, peripherin, internexin, and 2 lamin intermediate filament proteins; and 6 tubulin microtubule proteins. Two novel keratins, K42 and K124, were identified as the most abundant cytoskeletal proteins (22.0 ± 3.2% and 23.3 ± 4.2% of cytoskeletal proteins, respectively) in equine hoof lamellae. Immunoreactivity to K14 was localized to the basal cell layer, and that to K124 was localized to basal and suprabasal cells in the secondary epidermal lamellae. Abundant proteins K124, K42, K14, K5, and α(1)-actin were identified on 1- and 2-dimensional polyacrylamide gels and aligned with the results of previous studies. Results of the present study provide the first comprehensive analysis of cytoskeletal proteins present in the equine lamellae by using mass spectrometry-based techniques for protein quantification and identification.
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Affiliation(s)
- R A Carter
- The Laminitis Institute, Department of Clinical Studies/New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square 19348, USA
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Hampson BA, Ramsey G, Macintosh AMH, Mills PC, de Laat MA, Pollitt CC. Morphometry and abnormalities of the feet of Kaimanawa feral horses in New Zealand. Aust Vet J 2010; 88:124-31. [PMID: 20402699 DOI: 10.1111/j.1751-0813.2010.00554.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVE The present study investigated the foot health of the Kaimanawa feral horse population and tested the hypotheses that horses would have a large range of foot morphology and that the incidence of foot abnormality would be significantly high. PROCEDURES Abnormality was defined as a variation from what the two veterinarian assessors considered as optimal morphology and which was considered to impact negatively on the structure and/or function of the foot. Fifteen morphometric variables were measured on four calibrated photographic views of all four feet of 20 adult Kaimanawa feral horses. Four morphometric variables were measured from the lateromedial radiographs of the left forefoot of each horse. In addition, the study identified the incidence of gross abnormality observed on the photographs and radiographs of all 80 feet. RESULTS There was a large variation between horses in the morphometric dimensions, indicating an inconsistent foot type. Mean hoof variables were outside the normal range recommended by veterinarians and hoof care providers; 35% of all feet had a long toe conformation and 15% had a mediolateral imbalance. Abnormalities included lateral (85% of horses) and dorsal (90% of horses) wall flares, presence of laminar rings (80% of horses) and bull-nose tip of the distal phalanx (75% of horses). Both hypotheses were therefore accepted. CONCLUSIONS The Kaimanawa feral horse population demonstrated a broad range of foot abnormalities and we propose that one reason for the questionable foot health and conformation is lack of abrasive wearing by the environment. In comparison with other feral horse populations in Australia and America there may be less pressure on the natural selection of the foot of the Kaimanawa horses by the forgiving environment of the Kaimanawa Ranges. Contrary to popular belief, the feral horse foot type should not be used as an ideal model for the domestic horse foot.
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Affiliation(s)
- B A Hampson
- Australian Brumby Research Unit, School of Veterinary Science, The University of Queensland, St Lucia, Brisbane, Queensland, Australia.
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Milinovich GJ, Klieve AV, Pollitt CC, Trott DJ. Microbial events in the hindgut during carbohydrate-induced equine laminitis. Vet Clin North Am Equine Pract 2010; 26:79-94. [PMID: 20381737 DOI: 10.1016/j.cveq.2010.01.007] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Equine laminitis is the most serious foot disease of the horse, often resulting in death or euthanasia. Laminitis has long been recognized as an affliction of horses, as has the association of this condition with the ingestion of carbohydrates. Research into the pathophysiology of this condition has been facilitated by the development of reliable models for experimentally inducing laminitis, and DNA-based techniques for profiling complex microbiomes have dramatically increased the knowledge of the microbiology of this disease. Recent studies have provided substantial evidence showing equine hindgut streptococcal species to be the most likely causative agent. Although these studies are not definitive, they provide the foundations for future work to determine the source of laminitis trigger factors and their mechanisms of action.
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Affiliation(s)
- Gabriel J Milinovich
- Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, St Lucia, Queensland 4072, Australia.
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Abstract
In acute laminitis, the suspensory apparatus of the distal phalanx fails at the lamellar dermal/epidermal interface. A grading system for the histopathology of laminitis is based on the consistent pattern of histologic changes to the secondary epidermal lamellae, basal cells, and basement membrane that occur as carbohydrate-induced laminitis develops. The actual trigger factors of carbohydrate-induced laminitis remain unidentified.
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Affiliation(s)
- Christopher C Pollitt
- School of Veterinary Science, The University of Queensland, St Lucia, Brisbane, Queensland 4072, Australia.
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Abstract
The equine hoof capsule protects the softer, more sensitive, structures within. Failure of the connection between hoof and bone (suspensory apparatus of the distal phalanx or SADP) results in the crippling lameness of laminitis. Active basal cell proliferation occurs principally in tubular hoof and proximal and distal lamellae. The remaining lamellae are virtually non-proliferative and the hoof wall moves past the stationary distal phalanx, by controlled activation and inhibition of constituent proteases. The lamellar corium derives most of its blood supply from the branches of the terminal arch which perforate the distal phalanx. Valveless veins within the foot can be exploited clinically for retrograde venous therapy or contrast radiography (venography). The basement membrane (BM) forms the interface between the lamellar epidermis and the adjacent dermis and the plasma membrane of each lamellar basal cell is attached to the BM by numerous electron dense adhesion plaques or hemidesmosomes the ultimate attachment unit of the SADP. Laminitis destroys and dislocates the BM and its components and without an intact, functional BM, the structure and function of the lamellar epidermis is pathologically compromised. Transcription and activation of constituent proteases occurs in normal hoof lamellae but in increased amounts during laminitis.
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Affiliation(s)
- Christopher C Pollitt
- School of Veterinary Science, The University of Queensland, St Lucia, Brisbane, Queensland 4072, Australia.
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Abstract
Venography (retrograde venous angiography) is a relatively simple and practical method for vascular assessment of the digits in the standing horse. The technique is a useful adjunct to routine radiography. The clinical use of the laminitis venogram has resulted in a more comprehensive understanding of the collateral pathology associated with distal phalanx displacement and abnormal hoof growth. The effectiveness of therapeutic procedures such as hoof wall resection, coronary band grooving, deep digital flexor tenotomy, and therapeutic shoeing can be assessed by serial venography. This article discusses the venographic appearance during the transition from the clinically normal hoof to the severe chronic laminitis cases similar to those seen in practice.
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Affiliation(s)
- Gregory I Baldwin
- Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Slip Road, St Lucia, Queensland 4217, Australia.
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Hampson BA, Morton JM, Mills PC, Trotter MG, Lamb DW, Pollitt CC. Monitoring distances travelled by horses using GPS tracking collars. Aust Vet J 2010; 88:176-81. [DOI: 10.1111/j.1751-0813.2010.00564.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Keegan KG, Dent EV, Wilson DA, Janicek J, Kramer J, Lacarrubba A, Walsh DM, Cassells MW, Esther TM, Schiltz P, Frees KE, Wilhite CL, Clark JM, Pollitt CC, Shaw R, Norris T. Repeatability of subjective evaluation of lameness in horses. Equine Vet J 2010; 42:92-7. [PMID: 20156242 DOI: 10.2746/042516409x479568] [Citation(s) in RCA: 175] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
REASONS FOR PERFORMING STUDY Previous studies have suggested that agreement between equine veterinarians subjectively evaluating lameness in horses is low. These studies were limited to small numbers of horses, evaluating movement on the treadmill or to evaluating previously-recorded videotape. OBJECTIVES To estimate agreement between equine practitioners performing lameness evaluations in horses in the live, over ground setting. METHODS 131 mature horses were evaluated for lameness by 2-5 clinicians (mean 3.2) with a weighted-average of 18.7 years of experience. Clinicians graded each limb using the AAEP lameness scale by first watching the horse trot in a straight line only and then after full lameness evaluation. Agreement was estimated by calculation of Fleiss' (kappa). Evaluators agreed if they picked the same limb as lame or not lame regardless of the severity of perceived lameness. RESULTS After only evaluating the horse trot in a straight line clinicians agreed whether a limb was lame or not 76.6% of the time (kappa= 0.44). After full lameness evaluation clinicians agreed whether a limb was lame or not 72.9% of the time (kappa= 0.45). Agreement on forelimb lameness was slightly higher than on hindlimb lameness. When the mean AAEP lameness score was >1.5 clinicians agreed whether or not a limb was lame 93.1% of the time (kappa= 0.86), but when the mean score was < or = 1.5 they agreed 61.9% (kappa= 0.23) of the time. When given the task of picking whether or not the horse was lame and picking the worst limb after full lameness evaluation, clinicians agreed 51.6% (kappa= 0.37) of the time. CONCLUSIONS For horses with mild lameness subjective evaluation of lameness is not very reliable. POTENTIAL RELEVANCE A search for and the development of more objective and reliable methods of lameness evaluation is justified and should be encouraged and supported.
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Affiliation(s)
- K G Keegan
- Department of Veterinary Medicine and Surgery, University of Missouri, Columbia, Missouri 65211, USA
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Visser MB, Pollitt CC. Characterization of extracellular matrix macromolecules in primary cultures of equine keratinocytes. BMC Vet Res 2010; 6:16. [PMID: 20230631 PMCID: PMC2847556 DOI: 10.1186/1746-6148-6-16] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2009] [Accepted: 03/15/2010] [Indexed: 02/02/2023] Open
Abstract
Background Most research to date involving laminins and extracellular matrix protein function in both normal and pathological conditions involves in vitro culture of keratinocytes. Few methods are established to allow for prolonged propagation of keratinocytes from equine tissues, including the hoof lamellae. In this study we modified cell isolation and culture techniques to allow for proliferation and sub-culturing of equine lamellar keratinocytes. Additionally, the production and processing of extracellular matrix molecules by skin and lamellar keratinocytes were studied. Results Physical and proteolytic tissue separation in combination with media containing a calcium concentration of 0.6 mM in combination with additional media supplements proved optimal for proliferation and subculture of equine lamellar keratinocytes on collagen coated substratum. Immunofluorescence and immunoblotting studies confirmed that equine skin and lamellar keratinocytes produce Ln-332 in vitro and processing of this molecule follows that of other species. As well, matrix components including integrin alpha-6 (α6) and the hemidesmsome proteins, bullous pemphigoid antigen 1 (BP180) bullous pemphigoid antigen 2 (BP230) and plectin are also expressed. Conclusions Isolation of equine keratinocytes and study of the matrix and adhesion related molecules produced by them provides a valuable tool for future work in the veterinary field.
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Affiliation(s)
- Michelle B Visser
- The Australian Equine Laminitis Research Unit, School of Veterinary Science, University of Queensland, St Lucia, 4072, Australia.
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Nourian AR, Mills PC, Pollitt CC. Development of intraosseous infusion of the distal phalanx to access the foot lamellar circulation in the standing, conscious horse. Vet J 2010; 183:273-7. [DOI: 10.1016/j.tvjl.2009.05.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2009] [Revised: 04/06/2009] [Accepted: 05/04/2009] [Indexed: 10/20/2022]
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Abstract
REASONS FOR PERFORMING STUDY A previous preliminary study demonstrated the potential of distal limb cryotherapy (DLC) for preventing laminitis. Clinically, DLC must be effective for periods longer than 48 h and the preventive effect must extend beyond its discontinuation. OBJECTIVES To evaluate the effect of DLC, applied during the developmental phase of induced laminitis, on the severity of clinical laminitis and lamellar histopathology 7 days after dosing. METHODS Eighteen normal Standardbred horses were divided into 3 groups of 6. Continuous cryotherapy was applied for 72 h to the distal limbs of the first group. The second and third groups were administered laminitis inducing doses of oligofructose and 72 h of cryotherapy applied (immediately after dosing) to the second group. After clinical assessment all horses were subjected to euthanasia 7 days after dosing and hoof lamellar tissues were harvested and analysed. RESULTS In the laminitis induced horses clinical lameness and laminitis histopathology was significantly reduced in horses that underwent 72 h of DLC compared with untreated controls. Cryotherapy alone produced no significant lameness or other ill effect. CONCLUSIONS Continuous, medium- to long-term (72 h) cryotherapy applied to the distal limbs of horses safely and effectively ameliorates the clinical signs and pathology of acute laminitis. POTENTIAL RELEVANCE Pre-emptive distal limb cryotherapy is a practical method of ameliorating laminitis in ill horses at risk of developing the disease.
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Affiliation(s)
- A W Van Eps
- Australian Equine Laminitis Research Unit, School of Veterinary Science, Faculty of Natural Resources Agriculture and Veterinary Science, The University of Queensland, St. Lucia, Queensland 4072, Australia
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