GATA4 and obesity due to melanocortin 4 receptor deficiency: Interestingly, it has been previously shown that the expression of FXR and its downstream-regulated genes such as ASBT are upregulated in the GATA4 null mice jejunum [46], which suggests that GATA4 might regulate the altered expression of both ASBT and FXR along the proximal length of the small intestine in obesity.