In vitro acute effects of free fatty acids on protein degradation in young rat skeletal muscle

Abstract

Previous reports from literature have suggested that plasma free fatty acids (FFA) may reduce the rates of proteolysis, sparing muscle proteins in situations like fasting and diabetes. Here we investigated the acute effects of palmitic acid on total protein degradation and the activity of proteolytic pathways in rat skeletal muscle incubated in vitro. Soleus muscles were removed from Wistar male rats (70–80g) and incubated in Krebs‐Ringer buffer in the presence of palmitic acid (0,3–2,0mM) bound to albumin 1–2%. The rates of total proteolysis and proteolytic pathways were determined by release of tyrosine in the medium. The presence of palmitic acid (1,0mM) induced a clear reduction of total proteolysis (nmol Tyr/mg.2h) (0,340±0,014; 0,242±0,007; n=8), which was accompanied by a 50% reduction in the activity of calcium‐dependent proteolytic process. No changes in lysosomal and ATP‐Ub‐proteasome processes were observed. The inhibition of palmitic acid oxidation (50%) by etomoxir (75μM) and dichloroacetate (7mM) or the presence of 2‐bromopalmitate, a non‐metabolizable analog of fatty acids, did not alter the antiproteolytic effect observed. The present results show that palmitic acid exerts an acute inhibitory effect on total proteolysis by reducing the activity of calcium‐dependent pathway in rat skeletal muscle and this effect seems not depend on fatty acid oxidation.Financial Support: FAPESP and CNPq