ATP8B1 and obesity due to melanocortin 4 receptor deficiency: Moreover, in order to determine the importance of obesity, sex, and selected miRs on the expression of P4-ATPase genes, we performed backward linear regression models including the expression of ATP8A1 as a dependent variable and obesity, sex, and the gene expression of miR-548b-5p and miR-4643 as independent variables; a second regression model included the expression of ATP8B1 as dependent variable and waist, sex, and miR-548b-5p and miR-4643 gene expressions as independent variables.