SummaryReasons for performing study: There is a need to assess the laminar inflammatory response in a laminitis model that more closely resembles clinical cases of sepsis-related laminitis than the black walnut extract (BWE) model.

SummaryReasons for performing study: The pathophysiological events inhibited by prophylactic digital hypothermia that result in reduction of the severity of acute laminitis are unknown. Objectives: To determine if digital hypothermia inhibits lamellar inflammatory signalling during development of oligofructose (OF) induced laminitis. Methods: Fourteen Standardbred horses were given 10 g/kg bwt OF by nasogastric tube with one forelimb (CRYO) continuously cooled by immersion in ice and water and one forelimb (NON-RX) at ambient temperature. Lamellae were harvested prior to the onset of lameness (24 h post OF administration, DEV group, n = 7) or at the onset of lameness (OG1 group, n = 7). Lamellar mRNA was purified and cDNA produced for real time-quantitative PCR analysis of mRNA concentrations of cytokines (IL-6, IL-1b, IL-10), chemokines (CXCL1, CXCL6, CXCL8/IL-8, MCP-1, MCP-2), cell adhesion molecules (ICAM-1, E-selectin), COX-2 and 3 housekeeping genes. Data were analysed (NON-RX vs. CRYO, NON-RX vs. archived control [CON, n = 7] lamellar tissue) using nonparametric tests. Results: Compared with CON, the OG1 NON-RX had increased (P<0.05) lamellar mRNA concentrations of all measured mediators except IL-10, IL-1b and MCP-1/2, whereas only CXCL8 was increased (P<0.05) in DEV NON-RX. Within the OG1 group, CRYO limbs (compared with NON-RX) had decreased (P<0.05) mRNA concentrations of the majority of measured inflammatory mediators (no change in MCP-1 and IL-10). Within the DEV group, mRNA concentrations of CXCL-1, ICAM-1, IL-1b, CXCL8 and MCP-2 were decreased (P<0.05) and the anti-inflammatory cytokine IL-10 was increased (compared with NON-RX limbs; P<0.05). Conclusions: Digital hypothermia effectively blocked early lamellar inflammatory events likely to play an important role in lamellar injury including the expression of chemokines, proinflammatory cytokines, COX-2 and endothelial adhesion molecules. Potential relevance: This study demonstrates a potential mechanism by which hypothermia reduces the severity of acute laminitis, and may help identify molecular targets for future laminitis intervention.

These results support further investigation of mTORC1/RPS6 signalling as a potential therapeutic target(s) in EMSAL. The Summary is available in Chinese - see Supporting Information.

SummaryReasons for performing study: Hyperinsulinaemia has been implicated in the pathogenesis of laminitis; however, laminar cell types responding to insulin remain poorly characterised. Objectives: To identify laminar cell types expressing insulin receptor (IRc) and/or insulin-like growth factor-1 receptor (IGF-1R); and to evaluate the effect of dietary nonstructural carbohydrate (NSC) on their expression. Methods: Mixed-breed ponies (n = 22) received a conditioning hay chop diet (NSC~6%); following acclimation, ponies were stratified into lean (n = 11, body condition score [BCS] Յ4) or obese (n = 11, BCS Ն7) groups and each group further stratified to remain on the low NSC diet (n = 5 each for obese and lean) or receive a high NSC diet (total diet~42% NSC; n = 6 each for obese and lean) for 7 days. Laminar samples were collected at the end of the feeding protocol and stained immunohistochemically for IRc and IGF-1R. The number of IRc(+) cells was quantified; distribution of IGF-1R was qualitatively described. Laminar IRc content was assessed via immunoblotting. Results: The number of IRc(+) cells was greater in the laminae of high NSC ponies than low NSC ponies (P = 0.001); there was a positive correlation between the change in serum insulin concentration and number of IRc (+)