10 - Diet and Protein Metabolism in Skeletal Muscle

Abstract

This chapter discusses the effect of dietary change on protein metabolism in skeletal muscle. In skeletal muscle, the contractile cell is essentially the individual fiber, and as there is little change in the number of fibers, apart from a modest increase in the immediate postnatal period, muscle growth results from fiber growth. As protein turnover in muscle is relatively slow, the growth component of protein synthesis accounts for a significant fraction of the total protein synthesis, and as a first approximation, the fall in RNA concentration with age may simply reflect the fall in the growth rate, that is, the rate of net protein synthesis. In malnourished rats and infants, the muscle connective tissue, and collagen content, can be very high. This seems to result from an insensitivity of collagen synthesis to malnutrition, as collagen can accumulate in skeletal muscle of malnourished rats at a rate that is similar to that in control animals whilst the accumulation of intracellular proteins is severely inhibited. In contrast to the connective tissue proteins, those of the contractile cell are very sensitive to dietary intake.