HMOX1 and injury: For example, in potassium chloride-induced hyperuricemic mice (172), arsenic-exposed mice (173, 174), and sodium fluoride-induced renal injury rat models (175), betaine exerts protective effects by regulating urate transporters, inhibiting oxidative stress, and modulating the Nrf-2/heme oxygenase-1 (HO-1) signaling axis (Figure 6B).