Role of insulin in the regulation of protein synthesis

We have investigated the action of insulin on protein turnover in heart, skeletal muscle and liver. Protein turnover in heart is obviously important for the survival of the organism. Protein turnover in skeletal muscle is important because this tissue comprises approximately 45% of the body weight and provides the bulk of amino acids which become substrates for gluconeogenesis and, in diabetes, contribute to the hyperglycemic condition. Protein turnover in liver is important because this tissue also contributes amino acids for gluconeogenesis. In addition, most of the plasma proteins are synthesized in liver. To investigate protein turnover in these tissues, we have employed isolated perfused preparations of rat heart, skeletal muscle, and liver, as well as isolated liver cells. We have established the conditions and methodology for determining accurate rates of protein synthesis and degradation, and we have developed approaches for identifying the biochemical steps involved in the control of these pathways. The purpose of this lecture is to review our recent studies on the role of insulin in the control of protein synthesis.