Relation of the insulin pathway to phosphatidylinositols. The insulin receptor resides in the cell membrane. When its β subunit is phosphorylated by the presence of insulin, insulin receptor substrates (IRSs) are activated. P13K docks to the IRSs, which then leads to phosphorylation of phosphatidylinositol, eventuating in inulin action. It is postulated that myo-inositol may increase insulin sensitivity by making more phosphatidylinositol available. PI3K, phosphatidyl inositol 3-kinase; PDK1, phosphoinositide-dependent kinase 1; PKB, protein kinase B. (Adapted with permission from Agarwal AK, Garg A. Congenital generalized lipodystrophy: significance of triglyceride biosynthetic pathways. Trends Endocrinol Metab 2003;14:214–221.)