Endocrine Abstracts

Laminitis, an inflammatory condition of the sensitive and specialised architecture (the laminae) in the equine hoof, can be induced by over-ingestion of non-structural carbohydrates (NSC) from spring/summer pasture. Some equids that are predisposed to laminitis appear to share characteristics described in human patients with metabolic syndrome, such as vascular dysfunction, obesity, development of an inflammatory profile and insulin resistance. We investigated whether adipose tissue from laminitis prone equids (LP) functions differently from non-laminitis prone equids (NL), by examining gene expression (using a 44K equine expression microarray) in subcutaneous adipose tissue from healthy LP and NL (n=6 each group), obtained at two different times of the year (season: summer and winter) and following increased NSC consumption (dietary intervention: 7 days in the winter). Data were first analysed in GeneSpring and then the expression of 40 genes associated with insulin signalling compared between groups using a linear mixed model in SPSS statistics 20. Genes with a >1.5-fold difference and P<0.05 were considered significant. In addition, an oral glucose tolerance test (OGTT) was performed on each occasion. LP always had a significantly (P<0.05) increased insulin response to oral glucose (area under curve (AUCi)) compared to NL. After dietary intervention, AUCi was significantly increased in NL (P<0.05), but unchanged in LP. AKT3 and CBL were upregulated in LP compared to NL in the summer, whilst HK2 and INSL3 were downregulated. DOK2 and CBL (LP), INSL3 and PPP1CA (NL) were upregulated whilst INSR and IRS2 (NL and LP) were downregulated in summer compared with winter. SLC2A1 (LP) and FRS3 (NL) were upregulated by dietary intervention. An increase in secretion of insulin in LP was associated with a concurrent regulation of genes within the insulin signalling pathway. Short-term dietary intervention did not induce the same changes in insulin dynamics as did season.