ATP8B1 and obesity due to melanocortin 4 receptor deficiency: Our finding demonstrates that obese subjects have increased levels of ATP8A1 and ATP8B1 in visceral adipose tissue, compared with non-obese controls, and their positive correlation with obesity-related metabolic disorders gives new insights into the role that ATP8A1 and ATP8B1 may exert in human adipose tissue in obesity and may eventually lead to the definition of valuable obesity markers.