IRS1 and diabetes mellitus: Whereas the transgenic/knock-out model offers an ideal way to identify a single gene or protein in the development of diabetes, which, for example, makes it easier to dissect the complex genetics network of diabetes genes implicated in insulin resistance (e.g. IRS-1,IRS-2, GLUT-4) [8–10] or in lipid and glucose metabolism(e.g. PPARs) [11].