Increased entry of amino acids from the blood. Amino acids are the building blocks of protein. Once inside the muscle most of them are sent to ribosomes where the manufacture of various muscle protein will take place. Overall Effects of Insulin on Muscle and Fat Decreased breakdown of existing muscle proteins into glucose. This effect of insulin along with each of the above is essential to the muscle's ability to grow and maintain itself.
Insufficient insulin causes the reverse of all of the above.
The severity of the reversal is proportional to the severity of the insulin deficiency. Glucose cannot be delivered to muscle cells so they lack quick fuel to do their work. Muscle cells then begin to convert glycogen stores to glucose but there is no new glycogen being formed. When glycogen stores get too low muscle cells turn to fat and protein as fuel sources but new amino acids cannot get into cells to replace the protein losses. The result is elevated blood glucose, loss of muscle mass, weight loss, weakness and fatigue.