Cyp1b1 expression in WT mice is not sensitive to the dietary fat content. In fact, more genes in male mice (560) are sensitive to the deletion of Cyp1b1 than to the increase in dietary fat (176). These Cyp1b1-deletion-sensitive genes resolve into three main groups that are, respectively, independent of dietary fat or are diet-selective (LFD or HFD). Surprisingly, only about 10 percent of genes that respond to HFD in WT mice exhibit suppression in Cyp1b1-ko mice (18), thus paralleling the changes in obesity. Many genes (75), however, respond similarly to Cyp1b1 deletion and to HFD in the WT mice, suggesting that these genes exhibit an enhanced sensitivity to dietary fat in Cyp1b1-ko mice. In the 36 week female mice, there are many fewer responses to Cyp1b1 deletion on the LFD, but the number of these responses increases on the HFD. Nevertheless, an appreciable number of highly expressed genes conserve their responses to Cyp1b1 deletion on both diets, suggesting their linkage to the core Cyp1b1-sensitive control processes. Many of these changes also reflect an extensive attenuation of expression differences between these
