The mechanism of insulin action

Insulin was isolated over 70 years ago, but the intracellular transduction of the insulin signal has not been elucidated. Significant progress has been made, particularly in the last 10 years, with the characterization of the insulin receptor and its intrinsic tyrosine kinase. However, no mechanism has been proposed that accounts for all the actions of insulin. Furthermore, all the mechanisms discussed in this brief overview contain major inadequacies. Despite these gaps in our knowledge, substantial evidence indicates that receptor tyrosine kinase activity is essential for insulin action and multiple pathways almost certainly participate. Hopefully, continued dissection of the signalling pathways will soon yield the mechanism of insulin action.