title: The developmental and acute phases of insulin-induced laminitis involve minimal metalloproteinase activity.
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.
authors.affiliation: Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton, Queensland 4343, Australia. m.delaat@uq.edu.au
authors.forename: M A
authors.initials: MA
authors.lastname: de Laat
authors.forename: M T
authors.initials: MT
authors.lastname: Kyaw-Tanner
authors.forename: A R
authors.initials: AR
authors.lastname: Nourian
authors.forename: C M
authors.initials: CM
authors.lastname: McGowan
authors.forename: M N
authors.initials: MN
authors.lastname: Sillence
authors.forename: C C
authors.initials: CC
authors.lastname: Pollitt
mesh_terms: D051722:ADAM Proteins / Q000235:genetics / Q000378:metabolism; D000071121:ADAMTS4 Protein; D000208:Acute Disease; D000818:Animals; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D005534:Foot Diseases / Q000201:enzymology / Q000209:etiology / Q000235:genetics / Q000662:veterinary*; D015870:Gene Expression; D006724:Hoof and Claw / Q000201:enzymology; D006734:Horse Diseases / Q000201:enzymology* / Q000209:etiology* / Q000235:genetics; D006736:Horses; D006946:Hyperinsulinism / Q000150:complications / Q000662:veterinary; D053511:Matrix Metalloproteinase 14 / Q000235:genetics / Q000378:metabolism; D020778:Matrix Metalloproteinase 2 / Q000235:genetics / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000235:genetics / Q000378:metabolism; D020782:Matrix Metalloproteinases / Q000235:genetics* / Q000378:metabolism*; D011348:Procollagen N-Endopeptidase / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019717:Tissue Inhibitor of Metalloproteinase-3 / Q000235:genetics / Q000378:metabolism
chemical_list: D017931:DNA Primers; D012333:RNA, Messenger; D019717:Tissue Inhibitor of Metalloproteinase-3; D051722:ADAM Proteins; D020782:Matrix Metalloproteinases; D011348:Procollagen N-Endopeptidase; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9; D053511:Matrix Metalloproteinase 14; D000071121:ADAMTS4 Protein