GPBAR1 and obesity due to melanocortin 4 receptor deficiency: Bile acids (BAs) are products from hepatic cholesterol metabolism that help to absorb dietary lipids and vitamins.60 Primary bile acids (PBAs) and secondary bile acids (SBAs) are also involved in the activation of intestinal nuclear farnesoid X receptor (FXR) which has a crosstalk interaction with G protein-coupled bile acid receptor (TGR5).61,62 FXR is more involved in GLP-1 secretion, helping to improve glucose and insulin sensitivity, while TGR5 is more focused on the browning process, energy metabolism, and decreasing obesity in adipose tissue.63