These studies do not indicate which organ(s) are responsible for these various measures of enhanced insulin action but given the central importance of skeletal muscle in contributing to the state of insulin resistance in animals and humans on a high fat diet [3, 11] and recognizing that AMPD1 is only highly expressed in skeletal muscle of humans and rodents [6], it points to changes in skeletal muscle metabolism as the most likely tissue to produce the observed changes in insulin and glucose metabolism in the whole animal. The gene discussed is INS; the disease is Insulin resistance.