MTTP and fatty liver disease: Betaine attenuated HFD-induced hepatic steatosis and triglyceride accumulation in mice by alleviating the methylation of microsomal triglyceride transfer protein (MTTP) and peroxisomal proliferator-activated receptor alpha (PPARα) promoter in the liver (Wang et al., 2013; Wang et al., 2014), indicating the crucial relationship between DNA methylation and NAFLD development.