NNMT and obesity due to melanocortin 4 receptor deficiency: NNMT expression has been shown to be negatively correlated with glucose transporter 4 (GLUT4) in adipose tissue [107], and NNMT expression was increased in ob/ob, db/db, and HFD-mice when compared to lean mice, whereas NNMT knockdown in white adipose tissue and liver protected against HFD-induced obesity via enhanced SIRT1 target gene expression and energy expenditure [107].