NFE2L2 and obesity due to melanocortin 4 receptor deficiency: Likewise, gene deficiency has been linked to steatohepatitis in mice [16,18,19,20,21,25,26], consistent with the effect of polymorphisms linked to the genes encoding NRF1 (NFE2L1) and NRF2 (NFE2L2) in people with obesity [28].