GLOSSARY

Insulin Receptor Signaling
Insulin receptor signaling begins when insulin binds its receptor and changes the activity of the receptor's intrinsic tyrosine kinase. Receptor phosphorylation and phosphorylation of adaptor proteins organize several downstream pathways.

A metabolic branch

IRS proteins connect the receptor to PI3K and Akt. In muscle and adipose tissue, this pathway supports movement of GLUT4-containing vesicles toward the cell surface. It also regulates glycogen synthesis and other aspects of nutrient handling.

Other outputs

Additional signaling routes contribute to gene regulation, growth and survival. The response varies among tissues, with hepatic effects including regulation of glucose production and storage.

During exercise recovery

Muscle contraction recruits glucose transport through partly distinct signaling mechanisms. Insulin action after activity interacts with this altered muscle state. A normal insulin concentration does not directly measure signaling effectiveness, and resistance can arise at several points between receptor binding and the final metabolic response.