Indoles and kynurenines are known ligands of the AHR (37, 38, 72), whose prolonged activation has been associated with the development of metabolic syndrome (44, 45), disruption of circadian rhythms (73), altered glucose and lipid metabolism (45, 74, 75), and mitochondrial respiratory impairments (76–78). The gene discussed is AHR; the disease is metabolic syndrome.