FGF21 and Insulin resistance: FGF21-KO mice were less insulin sensitive than WT mice with higher blood glucose concentrations at 15 min and 30 min after insulin injection (Figures 1g and h) and consistently, the ‘homeostasis model assessment' (HOMA-IR) index, which measures the degrees of insulin resistance, was also increased in FGF21-KO mice (Figure 1i).