Effect of PCSK9 on HDL cholesterol concentration in mice having a wild-type control, Ldlr KO or Apoe KO background. Fasting plasma samples were obtained from 3-month-old mice (n = 5 per genotype) fed a normal chow diet. HDL cholesterol concentrations were measured in mice that expressed normal endogenous PCSK9 (white control bars) or were deficient in PCSK9 (black bars). Data represent the mean ± SEM. ‡P < 0.0001.