GPBAR1 and obesity due to melanocortin 4 receptor deficiency: There have been several reports on the anti-obesity effects of limonoids; nomilin (10) and obacunone (11) are agonists of the bile acid-specific G protein-coupled receptor, TGR5, and are known to improve insulin resistance and increase energy expenditure by activating TGR5 in L cells of the small intestine and skeletal muscle [65,66,67].