Glucose regulates protein turnover and growth-related mechanisms in rainbow trout myogenic precursor cells

Authors: LATIMER, MARY - University Of Alabama; REID, ROSS - University Of Alabama; BIGGA, PEGGY - University Of Alabama; Cleveland, Beth

Submitted to: Comparative Biochemistry and Physiology - Part A: Molecular & Integrative Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/12/2019
Publication Date: 3/21/2019
Citation: Latimer, M., Reid, R., Bigga, P., Cleveland, B.M. 2019. Glucose regulates protein turnover and growth-related mechanisms in rainbow trout myogenic precursor cells. Comparative Biochemistry and Physiology - Part A: Molecular & Integrative Physiology. 232:91-97. https://doi.org/10.1016/j.cbpa.2019.03.010.
DOI: https://doi.org/10.1016/j.cbpa.2019.03.010

Interpretive Summary: Muscle growth in rainbow trout responds in a coordinated way to changes in both nutrient availability and composition. The nutrient profile of the trout diet contains additional carbohydrates when sustainable plant proteins are used and this can cause hyperglycemia. Although it is understood that glucose can indirectly regulate muscle growth through endocrine pathways involving insulin, it is unknown if glucose can directly regulate metabolic mechanisms. Therefore, the objective of this study was to determine the protein turnover and gene expression response in isolated rainbow trout muscle cells exposed to different glucose concentrations. Cells exposed to low glucose displayed slower rates of protein synthesis and exhibited a gene expression response, supporting that glucose is a direct regulator of mechanisms regulating protein accretion in muscle. These findings highlight the role of glucose as a metabolic regulator of muscle growth, indicating that diet effects on plasma glucose should be considered when evaluating new feed ingredients or formulations.

Technical Abstract: Rainbow trout have been termed glucose intolerant and are considered to be poor utilizers of glucose, despite having functional insulin receptors and glucose transporters. Following high carbohydrate meals rainbow trout are persistently hyperglycemic, which is likely due to low glucose utilization in periphery tissues including the muscle. Myogenic precursor cells (MPCs) treated in vitro with both insulin and IGF1 can increase glucose uptake as well as increase protein synthesis and decrease protein degradation. Given our understanding of glucose regulation in trout, we sought to understand how glucose concentrations affect protein synthesis, protein degradation and expression of genes associated with muscle growth and proteolysis in MPC's. We found that following 24 and 48 hrs of treatment with low glucose media, myoblasts had significant decreases in protein synthesis. Also, 48 and 72h low glucose treatments effected the expression of both mstn2a and igfbp5. These findings support that glucose is a direct regulator of protein synthesis and growth-related mechanisms in rainbow trout muscle.