Association of sustained supraphysiologic hyperinsulinemia and inflammatory signaling within the digital lamellae in light‐breed horses

• Published in: Journal of veterinary internal medicine Vol. 33; no. 3; pp. 1483 - 1492
• Main Authors: Watts, Mauria R., Hegedus, Olivia C., Eades, Susan C., Belknap, James K., Burns, Teresa A.
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01.05.2019; Wiley
• Subjects: Animals; CD163 antigen; Chemokines; Chemokines - genetics; Chemokines - metabolism; Conflicts of interest; Cytokines; Cytokines - genetics; Cytokines - metabolism; Deoxyribonucleic acid; DNA; Emigration; endocrinopathic; Epithelial cells; EQUID; equine metabolic syndrome; Foot Diseases - veterinary; Glucose Clamp Technique - veterinary; Hoof and Claw - metabolism; Hoof and Claw - pathology; Horse Diseases - pathology; Horses; Hyperinsulinemia; Hyperinsulinism - veterinary; Immunoblotting; Immunohistochemistry; immunology; Inflammation; Inflammation - veterinary; Insulin; Interleukin 1; Interleukin 11; Investigations; Kinases; Laboratories; Lamellae; Lamellar structure; laminitis; Ligands; MAP kinase; Metabolic disorders; Metabolic syndrome; Metastases; Nuclei (cytology); Polymerase chain reaction; Prospective Studies; Proteins; Sepsis; Signal Transduction; Stat1 protein; Stat3 protein; Transcription; Tumor necrosis factor-TNF; Tumor necrosis factor-α; Ohio; Indiana; United States > US; Indianapolis Indiana; equine metabolic syndrome; insulin; endocrinopathic; inflammation; immunology; laminitis
• ISSN: 0891-6640; 1939-1676
• DOI: 10.1111/jvim.15480

Background Hyperinsulinemia is associated with equine laminitis, and digital lamellar inflammation in equine metabolic syndrome‐associated laminitis (EMSAL) is modest when compared with sepsis‐associated laminitis. Objectives To characterize digital lamellar inflammation in horses in a euglycemic‐hyperinsulinemic clamp (EHC) model of laminitis. Animals Sixteen healthy adult Standardbred horses. Methods Prospective experimental study. Horses underwent EHC or saline infusion (CON) for 48 hours or until the onset of Obel grade 1 laminitis. Horses were euthanized, and digital lamellar tissue was collected and analyzed via polymerase chain reaction (pro‐inflammatory cytokine and chemokine genes—CXCL1, CXCL6, CXCL8, IL‐6, MCP‐1, MCP‐2, IL‐1β, IL11, cyclooxygenases 1 and 2, tumor necrosis factor alpha [TNF‐α], E‐selectin, and ICAM‐1), immunoblotting (phosphorylated and total signal transducer and activator of transcription 1 [STAT1], STAT3, and p38MAPK), and immunohistochemistry (markers of leukocyte infiltration: CD163, MAC387). Results Lamellar mRNA concentrations of IL‐1β, IL‐6, IL‐11, COX‐2, and E‐selectin were increased; the concentration of COX‐1 was decreased; and concentrations of CXCL1, CXCL6, MCP‐1, MCP‐2, IL‐8, TNF‐α and ICAM‐1 were not significantly different in the EHC group compared to the CON group (P ≤ .003). Lamellar concentrations of phosphorylated STAT proteins (P‐STAT1 [S727], P‐STAT1 [Y701], P‐STAT3 [S727], and P‐STAT3 [Y705]) were increased in the EHC group compared to the CON group, with phosphorylated STAT3 localizing to nuclei of lamellar basal epithelial cells. There was no change in the lamellar concentration of P‐p38 MAPK (T180/Y182), but the concentration of total p38 MAPK was decreased in the EHC samples. There was no evidence of notable lamellar leukocyte emigration. Conclusions and Clinical Importance These results establish a role for lamellar inflammatory signaling under conditions associated with EMSAL.