NR1H4 and obesity due to melanocortin 4 receptor deficiency: FXR-deficient mice are resistant to obesity induced by a high-fat diet, and transferring their microbiota to germ-free wild-type mice reduces obesity and improves glucose tolerance, indicating that the gut microbiota promotes weight gain and hepatic steatosis in an FXR-dependent manner (Parséus et al., 2017).