NNMT and obesity due to melanocortin 4 receptor deficiency: Additionally, significant associations were observed between single nucleotide variants in the NNMT gene and energy metabolism, obesity, T2D, hyperlipidemia, and hypertension (Zhu et al., 2016; Zhou et al., 2017; Li et al., 2018; Guan et al., 2021; Liu et al., 2021).