CTRL and neoplasm: The chymotrypsin-like enzymatic activity, which is the catalytic portion of the ubiquitin-proteasome, was increased approximately 3.9-fold in group W, and despite having tumours, the foetuses from pregnant rats that received a leucine-rich diet (LW) showed a less-pronounced increase in the chymotrypsin-like activity compared to the rats in group W. These differences were near statistical significance (Figure 4A; P = 0.0803).