FFAR2 and obesity due to melanocortin 4 receptor deficiency: GPR43 knockout mice on a normal chow diet become obese compared with WT mice on the same diet, and mice with adipose-specific overexpression of GPR43 are lean, even on an HFD.97 However, obesity-protective effects in the adipose-specific GPR43 overexpression murine model are reversed when mice are given antibiotics, suggesting a role for the gut microbiome in mediating this effect.