Changes in adipose MRNA expression between previously laminitic ponies and nonlaminitic ponies in summer and winter

Reasons for performing study:

Some ponies are predisposed to recurrent pasture-associated laminitis, but the mechanisms underlying this remain unclear. Adipose tissue is a highly metabolically active tissue that secretes mediators which affect vascular function, insulin signalling and inflammation, all of which are potentially implicated in the pathogenesis of laminitis.

Objectives:

To determine whether the gene expression of adipose tissue from previously laminitic ponies (LP) differs from nonlaminitic ponies (NL).

Study design:

Subcutaneous adipose tissue was collected by biopsy from the neck region of healthy LP and NL (n = 6 each group) in the summer and winter.

Methods:

Gene expression was determined using a 44K equine expression microarray. Data were analysed using GeneSpring and Ingenuity Pathway Analysis. Genes with >2-fold difference, P<0.01 were considered significant using a t test to analyse group and/or season.

Results:

The most significant differences in global gene expression in adipose tissue were observed between summer and winter in both groups, with 244 (NL) and 174 (LP) genes differentially expressed. There was a significant difference between LP and NL groups in the summer (141 genes differentially expressed), whereas the 2 groups were more similar in the winter (40 genes differentially expressed). Eight of the top 10 upregulated genes and 3 of the top 5 canonical pathways that differed between LP and NL in the summer were associated with inflammation and/or immunity.

Conclusions:

Laminitic ponies appear to have a different adipose tissue gene expression profile to NL, particularly in the summer. Inflammatory genes and pathways were significantly upregulated in the LP group suggesting higher levels of inflammation or priming of inflammatory pathways which may contribute to a predisposition to laminitis