Abstract
BackgroundPhosphatidic acid (PA) is a diacyl-glycerophospholipid that acts as a signaling molecule in numerous cellular processes. Recently, PA has been proposed to stimulate skeletal muscle protein accretion, but mechanistic studies are lacking. Furthermore, it is unknown whether co-ingesting PA with other leucine-containing ingredients can enhance intramuscular anabolic signaling mechanisms. Thus, the purpose of this study was to examine if oral PA feeding acutely increases anabolic signaling markers and muscle protein synthesis (MPS) in gastrocnemius with and without whey protein concentrate (WPC).MethodsOvernight fasted male Wistar rats (~250 g) were randomly assigned to four groups: control (CON, n = 6-13), PA (29 mg; n = 8), WPC (197 mg; n = 8), or PA + WPC (n = 8). Three hours post-feeding, gastrocnemius muscle was removed for markers of Akt-mTOR signaling, gene expression patterns related to skeletal muscle mass regulation and metabolism, and MPS analysis via the SUnSET method.ResultsCompared to CON rats, PA, WPC and PA + WPC resulted in a significant elevation in the phosphorylation of mTOR (Ser2481) and rps6 (Ser235/236) (p < 0.05) in the gastrocnemius though there were no differences between the supplemented groups. MPS levels in the gastrocnemius were significantly (p < 0.05) elevated in WPC versus CON rats, and tended to be elevated in PA versus CON rats (p = 0.08), though MPS was less in PA + WPC versus WPC rats (p < 0.05) in spite of robust increases in mTOR pathway activity markers in the former group. C2C12 myoblast data agreed with the in vivo data herein showing that PA increased MPS levels 51 % (p < 0.001) phosphorylated p70s6k (Thr389) levels 67 % (p < 0.001).ConclusionsOur results are the first in vivo evidence to demonstrate that PA tends to increases MPS 3 h post-feeding, though PA may delay WPC-mediated MPS kinetics within a 3 h post-feeding window.
Highlights
Phosphatidic acid (PA) is a diacyl-glycerophospholipid that acts as a signaling molecule in numerous cellular processes
Compared to CON, phosphorylated p-Mammalian target of rapamycin (mTOR) (Ser2481), which is a marker of mTOR autophosphorylation and activation [21], was approximately 2-fold higher in PA and PA + whey protein concentrate (WPC) rats (p < 0.05; Fig. 1b), though there was no difference in this marker between the latter two groups
WPC robustly increased muscle protein synthesis (MPS) levels compared to CON rats confirming our prior data
Summary
Phosphatidic acid (PA) is a diacyl-glycerophospholipid that acts as a signaling molecule in numerous cellular processes. While mTOR activation is complex, a simplistic overview of this process is as follows [2]: a) mTOR complex 1 (mTORC1), which is comprised of mTORRaptor- mLST8, can be activated by muscle contraction and nutritional factors; b) activated mTORC1 acts to phosphorylate and activate p70s6 kinase (p70s6k) while hyper-phosphorylating eukaryotic initiation factor 4E (eIF4E)-binding proteins (4EBP-1/2); c) activated p70s6k phosphorylates and activates ribosomal protein s6 (rps6), while hyperphosphorylated 4EBP1/2 become inactive facilitating ribosomal assembly; and d) activated rps further increases ribosomal assembly via enhanced 5’-cap-dependent messenger RNA (mRNA) translation of selective genes These aforementioned processes result in an elevation in skeletal muscle protein synthesis (MPS) and, if stimulated repetitively with resistance exercise and ample nutrition, lead to an increase in skeletal muscle accretion. Notwithstanding, and in spite of these divergent findings, there is ample in vitro evidence to suggest that PA increases mTORC1 signaling
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Journal of the International Society of Sports Nutrition
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
