The elevated gut SCFAs, especially propionic acid, were accompanied by up-regulation of GPR41 and GPR43 and a parallel rise in the obesity-related hormones GLP-1 and PYY; a direct causal chain remains to be proven, mitigating the obesity and its associated metabolic disorders (Figure 6J). The gene discussed is PYY; the disease is obesity due to melanocortin 4 receptor deficiency.