Aging-induced differential gene expression in the 3 segments of the small intestine and the colon. (A) Differences in basal gene expression between 4- and 21-month-old mice were calculated for each of the 4 segments of the intestine. The number of genes showing over 2-fold differential gene expression observed under either low-fat or high-fat dietary conditions are presented in the figure. (B) A comparison of all genes showing differential expression in response aging in at least one of on the 4 segments of the intestine shows an overlap between the response under low-fat and high-fat conditions. (C) By comparing all aging-responsive genes under both low-fat and high-fat conditions a marked difference between the proximal, middle and distal part of the small intestine was observed. (D) In total, 124 genes were over 2-fold regulated in the small intestine in response to aging and 104 genes showed a differential aging response in the colon, 27 of these genes were differentially expressed in both segments.