Author(s): NEWBOLD, J., GREYVENSTEIN, D., LEES, M.J., NUNES, E.A., DA COSTA, F.P., VILORIA, A.M., BAKER, E., SAMPAIO, M., CHAN, E., PHILLIPS, S.M., Institution: MCMASTER UNIVERSITY, Country: CANADA, Abstract-ID: 943

INTRODUCTION:
Load-induced skeletal muscle hypertrophy is thought to be regulated by subcellular protein interactions, specifically mechanistic target of rapamycin (mTOR)-lysosome colocalization and translocation to the cell periphery. However, evidence supporting this model is largely derived from studies examining the acute ~3 h period. This narrow window does not reflect typical daily feeding patterns consisting of multiple meals, which serve as subsequent anabolic stimuli over a 24-hour period. Therefore, current evidence provides an incomplete understanding of how subcellular protein complexes interact to drive changes in muscle protein synthesis over the course of an entire day. We compared post-exercise changes in subcellular protein interactions in males and females after consuming one large meal of protein a day (OMAD), or three smaller meals of protein (SPLIT) over a 24-hour period.
METHODS:
Healthy young males and females (n = 12 per group) were randomized to consume either one meal (OMAD) or three meals (SPLIT) comprising a total of 1.6 g/kg of protein/day, following a single bout of whole-body resistance exercise (RE). Skeletal muscle biopsies of the vastus lateralis were taken to examine subcellular protein complex interactions. Muscle sections were stained for mTOR complex 1, lysosomal associated membrane protein 2 (LAMP2), and laminin, then imaged and quantified. Pearson’s product-moment correlation coefficients were used to quantify interactions and are expressed as fold change from baseline.
RESULTS:
A significant group x time interaction (p < 0.01) was found for LAMP2-laminin colocalization. At 14.5h post-RE, LAMP2-laminin colocalization differed significantly between OMAD and SPLIT (p < 0.0001). Specifically, colocalization was significantly reduced from baseline in OMAD (p < 0.0001), whereas SPLIT did not differ from baseline (p = 0.991). No significant main effects of group or group x time interaction were detected for mTOR-LAMP2 colocalization (p = 0.326 and p = 0.369, respectively), or for mTOR-laminin colocalization (p = 0.768 and p = 0.225, respectively).
CONCLUSION:
Subcellular interactions between mTOR and the lysosome were subtly but differentially impacted by the SPLIT and OMAD feeding patterns. While previous work found mTOR-LAMP2 interactions to peak ~1-3 hours following anabolic stimuli, no significant changes were observed here, likely because our post-exercise/first meal biopsy occurred 4.5 hours after anabolic stimuli. Therefore, the window for significant changes in mTOR-LAMP2 and mTOR-laminin interactions may have been missed. Notably, a SPLIT feeding pattern seemed to better maintain the interaction between lysosomes and the cell periphery when compared with OMAD, possibly due to the influx of amino acids following the third meal. Thus, anabolism-associated lysosomal positioning at the cell border is affected by meal pattern and presumably amino acid availability, and may occur independently of detectable changes in mTOR localization.