LEP and Hyperinsulinemia: Various leptin receptor knockout mouse lines, generated to investigate the role of leptin on β-cell function in vivo, have also produced conflicting results: LepR fl/flRIP-cre and LepRfl/fl Psdx1-cre mice are characterized by hyperinsulinemia (Covey et al., 2006; Morioka et al., 2007), whereas LepRflfl Ins1-cre mice do not exhibit hyperinsulinemia (Soedling et al., 2015).