Insulin causes lipogenesis by all, EXCEPT:
Insulin increases the activity of PDH (Pyruvate dehydrogenase). Insulin increases the recruitment of GLUT to the surface of various cells and thus increases the uptake of insulin various cells. Insulin has got inhibitory effect on adenylyl cyclase activity and so cause dephosphorylation. Insulin increases the activity of acetyl CoA carboxylase activity and thus has got stimulatory effect on lipogenesis. Also Know: Pyruvate Dehydrogenase is also regulated by Acyl-CoA: Acyl-CoA causes an inhibition of pyruvate dehydrogenase by inhibiting the ATP-ADP exchange transpoer of the inner mitochondrial membrane, which leads to increased intramitochondrial (ATP)/(ADP) ratios and therefore to conversion of active to inactive pyruvate dehydrogenase, thus regulating the availability of acetyl-CoA for lipogenesis. Fuhermore, oxidation of acyl-CoA due to increased levels of free fatty acids may increase the ratios of (acetyl-CoA)/(CoA) and (NADH)/(NAD+) in mitochondria, inhibiting pyruvate dehydrogenase. Insulin Also Regulates Lipogenesis by Other Mechanisms: Insulin stimulates lipogenesis by several other mechanisms as well as by increasing acetyl-CoA carboxylase activity. It increases the transpo of glucose into the cell (eg, in adipose tissue), increasing the availability of both pyruvate for fatty acid synthesis and glycerol 3-phosphate for esterification of the newly formed fatty acids, and also conves the inactive form of pyruvate dehydrogenase to the active form in adipose tissue, but not in liver. Insulin also--by its ability to depress the level of intracellular cAMP--inhibits lipolysis in adipose tissue and reducing the concentration of plasma-free fatty acids and, therefore, long-chain acyl-CoA, which are inhibitors of lipogenesis. Ref: Botham K.M., Mayes P.A. (2011). Chapter 23. Biosynthesis of Fatty Acids & Eicosanoids. In D.A. Bender, K.M. Botham, P.A. Weil, P.J. Kennelly, R.K. Murray, V.W. Rodwell (Eds), Harper's Illustrated Biochemistry, 29e.
Increasing acetyl CoA carboxylase activity
Increasing the transpo of glucose into the cell
Inhibits PDH
Decreased intracellular cAMP level