INS and metabolic syndrome: Lipotoxicity, characterized by a high concentration of non-esterified fatty acid and induced especially by palmitic acid in blood, aggravates not only insulin tolerance and beta cell function, but also whole body inflammation in type 2 diabetes and metabolic syndrome caused by obesity.(40) Therefore, C2C12 cells treated with palmitic acid were used in this study as a model of lipotoxicity and insulin resistance caused by obesity.