Enhanced expression of genes involved in immune response and inflammation in the colon of aging mice. (A) Ingenuity Pathway Analysis was carried out on the genes showing at least 2-fold differential expression in the colon of aging mice. Ingenuity Pathway Analysis identified Immune response as the major regulated category. Functions within this category are shown that were significant with a p-value of at least 0.005 (−log p-value 2.3) and at least five genes differentially expressed between old and young mice in the LF group. (B) Although INFγ expression was below the threshold level of our microarray data a large number of INFγ-responsive genes showed over 2-fold up-regulation in aging mice. (C) Q-PCR analysis confirmed the up-regulation of the INFγ target genes IF44 and IF47 and showed in addition up-regulated expression of INFγ, TNFα and IL-1β but not of IL6 in 21-month-old mice. (D) Basal expression levels of various genes measured by microarray analysis and (E) total number of bacteria present in the lumen of the 4 segments of the intestine measured by 16S rRNA Q-PCR in old and young mice under low-fat and high-fat conditions. The mean values ± SE were presented, *p < 0.05.