SLC4A4 and obesity due to melanocortin 4 receptor deficiency: Some studies have shown that SLC4A4 may be involved in the pathogenesis of obesity and also participate in immune infiltration (Li et al., 2015; Li et al., 2022), and the methylation of the solute carrier protein (SLC) gene has been closely related to BMI and waist circumference (Mendelson et al., 2017; Sayols-Baixeras et al., 2017).