Results Expression levels of a total of 2016 genes were signifi cantly altered by fasting and or insulin neutralization when compared to fed Inhibitors,Modulators,Libraries controls based on an FDR adjusted p value 0. 05. Sixty nine percent of these genes showed a fold change |1. 5|. The majority of changes in expression employed to validate differential expression based on the microarray data. Eleven genes were selected based on fold change or biological functions of interest. Differential expression under fasting versus fed conditions was validated for all genes except pre B cell leukemia homeobox 3. Ten of the eleven genes were also differentially expressed in insulin neutralized compared to fed birds based on QPCR.

Genes that were differentially expressed in at least one pairwise comparison were clustered to visualize the si milarities between groups and to determine if insulin neutralized expression profiles were more similar to fasted or to fed status. As shown in Figure 2A, samples within each of the three experimental Inhibitors,Modulators,Libraries Drug_discovery groups clustered together. The dendrogram also showed that the fasting group was distant from fed and insulin neutralized groups, which were closer to each other. To further visualize relationships between treatments with regard to gene expression, distinct clusters of genes were extracted and submitted to gene set enrichment analysis to identify GO terms and pathways that were significantly overrepresented among genes contained in these clusters. Seven clusters repre sented four general patterns of similarities between treat ments.

Clusters 1, 3 and 4 consisted of genes with higher expression in fasting compared to both insulin neutralized and fed conditions, with insulin neutralized intermediate between fasted and fed. This set of genes was significantly enriched in GO terms related to protein and lipid catabolism and to cell signaling, including regulation of the Inhibitors,Modulators,Libraries stress sensitive NF��B cascade. These three clusters were also enriched in members of the KEGG path ways ubiquitin mediated proteolysis, sphingolipid meta bolism, PPAR signaling, fatty acid metabolism and the peroxisome. The rate limiting genes for fatty acid oxidation, along with fatty acid binding pro teins 5 and 6, are contained in these three clusters. Clusters 5 and 7 also contained genes with higher levels in fasted vs.

the other two groups, but with comparable expression levels between insulin neutralized Inhibitors,Modulators,Libraries and fed, and thus no clear effect of insulin loss. These two clusters were signifi were attributable to fasting, with 917 up regulated and 863 down regulated genes in fasted vs. fed adipose tis sue. Insulin neutralization altered expression of 92 genes, 72 of which were also differentially expressed with fasting. All genes that were affected by both treatments changed in the same direction.