Mechanisms underlying insulin supported skeletal muscle growth

Abstract Text: Basic principles governing skeletal muscle growth and development, from a cellular point of view, have been realized for several decades. Skeletal muscle is marked by the capacity for rapid hypertrophy and increases in protein content. Ultimately, skeletal muscle growth is controlled by two basic means; myonuclear accumulation stemming from cellular proliferation and the balance between cellular protein synthesis and degradation. Each process underlies the rapid changes in lean tissue accretion evident during neonatal growth and are particularly sensitive to nutritional manipulation. Although multiple signals converge to alter skeletal muscle mass, postprandial changes in the anabolic hormone, insulin, link feed intake with enhanced rates of protein synthesis in the neonate. Indeed, a consequence of insulin-deficient states such as diabetes or malnutrition is a net loss of body protein. A prominent mechanism mediating the anabolic effect of insulin is the phosphatidylinositol 3-kinase (PI3K) mammalian target of rapamycin (mTOR) signaling pathway. Activation of mTOR leads to control of translation initiation via the phosphorylation of downstream targets. Modulation of this pathway by insulin, as well as other hormones and nutrients, accounts for enhanced protein synthesis leading to efficient lean tissue accretion and rapid skeletal muscle gain in the growing animal.

Keywords: Insulin, Skeletal muscle, Growth