Insulin-Sensitive Glucose Transport

Abstract

Publisher Summary This chapter discusses the effects and classification of insulin-sensitive glucose transport across the plasma membrane. The effects of insulin on cellular metabolism are diverse; some effects are chronic, others acute and complete within five–twenty minutes. The chronic effects of insulin include many complex processes, such as the stimulation of protein synthesis, cell growth and mitosis. The acute effects are also complex but may be classified into subgroups, presented in the chapter. The effects of insulin on these enzymes are consistent with the interpretation that the hormone promotes dephosphorylation of the enzymes. The effects of insulin on Type A enzymes are reversed by phosphorylation mediated by either cyclic adenosine monophosphate (cAMP)-dependent protein kinase or protein kinase C. The insulin-dependent stimulation of cAMP phosphodiesterase (Type B) is observable only in the presence of adenosine triphosphate (ATP), and the effect of the hormone on this enzyme is reversed in the absence of ATP. The effect of insulin on this enzyme is mimicked, rather than reversed, by the action of agents that increase the cellular concentration of cAMP. ATP is involved in both the insulin-dependent translocation of the glucose transport system and the reversal of the hormonal effect on the system in adipocytes.