APOE and atherosclerosis: It should be noted, however, that in 10–15% of Western-type diet-fed APOE*3-Leiden and APOE*3-Leiden.CETP mice, total cholesterol levels remain below the threshold of approximately 7 mM to develop atherosclerosis after a typical run-in period of 4 weeks (often referred to as ‘low-responders’ or ‘non-responders’), and are therefore not included for randomization in experiments (94, 95).