Although obesity and T2DM are correlated with an increase in specific BA, such as 12α-hydroxylated BA or deoxycholic acid, the main issue lies with improper BA fluctuation before and after meals [122,123], where the expression of the two BA transporters in the liver, NTCP and ASBT, is reduced in obesity (thus, a surge of serum BA after meals is blunted in obese subjects) [123]. Here, SLC10A1 is linked to obesity due to melanocortin 4 receptor deficiency.