Palmitate and oleate co-treatment increases myocellular protein content via impaired protein degradation.

OBJECTIVES: Protein balance is a crucial determinant of myocellular size and function. The effects of fatty acids on myocellular protein balance remain controversial. The aim of this study was to determine the direct effects of a mixed-species fatty acid environment on myocellular protein synthesis and degradation. METHODS: C2C12 myotubes were cultured in media containing equimolar (250 µM) palmitic acid and oleate (PO) or bovine serum albumin control for ≤72 h. Myocellular protein balance was determined via incorporation (synthesis) or release (degradation) of 3H-tyrosine after 24, 48, and 72 h of treatment. Expression of major proteolytic genes was measured by reverse transcription polymerase chain reaction. RESULTS: PO significantly increased myocellular protein content at 24, 48, and 72 h. Basal myocellular protein synthesis was unchanged by PO. However, PO significantly decreased basal rate of protein degradation at 24 h and this effect persisted throughout 72 h of treatment. Expression of the proteolytic genes Atrogin-1 (MAFbx), MuRF-1, LC3, and ATG4 B, was reduced during the 72 h PO. CONCLUSIONS: A mixed-species fatty acid environment increases myocellular protein content by decreasing the rate of protein degradation, which may be regulated at the level of gene transcription.