Control of muscle protein kinetics by acid-base balance

Abnormalities of acid-base balance accompany many pathological conditions. Acidosis is associated with several diseases such as chronic renal failure, diabetic ketosis, severe trauma and sepsis, and chronic obstructive respiratory disease, which are often associated with muscle wasting. There is evidence that acidosis can induce muscle protein catabolism and it could therefore be an important factor contributing to loss of muscle protein in these conditions. This review aims at outlining the effects of acid-base balance abnormalities on muscle protein metabolism, and will in particular summarize and evaluate the most recent studies on the impact of pH on control of muscle protein metabolism.

Acidosis has been shown to promote muscle protein catabolism by stimulating protein degradation and amino acid oxidation. This effect is achieved through up-regulation of the ubiquitin-proteasome pathway - one of the major enzyme systems for protein degradation. Recent studies in animals and humans have also shown that acidosis inhibits muscle protein synthesis. Little is known about the mechanisms by which acidosis depresses protein synthesis, or of the impact of alkalosis on protein metabolism.

Increasing evidence suggests that acidosis promotes muscle protein wasting by both increasing protein degradation and inhibiting protein synthesis. Correction of acidosis may therefore help to preserve muscle mass and improve the health of patients with pathological conditions associated with acidosis.