Effects of oral phosphatidic acid feeding with or without whey protein on muscle protein synthesis and anabolic signaling in rodent skeletal muscle.
BACKGROUND
Phosphatidic 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).


METHODS
Overnight 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.


RESULTS
Compared 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).


CONCLUSIONS
Our 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.
School of Kinesiology, Auburn University, Auburn, AL USA.
C Brooks
CB
Mobley
Department of Comparative Biosciences, University of Wisconsin-Madison, Madison, WI USA.
Troy A
TA
Hornberger
School of Kinesiology, Auburn University, Auburn, AL USA.
Carlton D
CD
Fox
School of Kinesiology, Auburn University, Auburn, AL USA.
James C
JC
Healy
School of Kinesiology, Auburn University, Auburn, AL USA.
Brian S
BS
Ferguson
Department of Health Sciences and Human Performance, University of Tampa, Tampa, FL USA.
Ryan P
RP
Lowery
Department of Comparative Biosciences, University of Wisconsin-Madison, Madison, WI USA.
Rachel M
RM
McNally
4LIFE Research, LLC, Sandy, UT USA.
Christopher M
CM
Lockwood
Human Performance Laboratory, University of Central Florida, Orlando, FL USA.
Jeffrey R
JR
Stout
School of Kinesiology, Auburn University, Auburn, AL USA.
Andreas N
AN
Kavazis
Department of Health Sciences and Human Performance, University of Tampa, Tampa, FL USA.
Jacob M
JM
Wilson
School of Kinesiology, Auburn University, Auburn, AL USA.
Michael D
MD
Roberts
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D051275:Glucose Transporter Type 4 / Q000235:genetics / Q000378:metabolism; D008297:Male; D000076222:Mechanistic Target of Rapamycin Complex 1; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism; D009124:Muscle Proteins / Q000096:biosynthesis*; D018482:Muscle, Skeletal / Q000187:drug effects; D010712:Phosphatidic Acids / Q000008:administration & dosage*; D010766:Phosphorylation; D014176:Protein Biosynthesis / Q000187:drug effects*; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000235:genetics / Q000378:metabolism; D058570:TOR Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D000067816:Whey Proteins / Q000008:administration & dosage*
D001786:Blood Glucose; D051275:Glucose Transporter Type 4; D046912:Multiprotein Complexes; D009124:Muscle Proteins; D010712:Phosphatidic Acids; C495694:Slc2a4 protein, rat; D000067816:Whey Proteins; D000076222:Mechanistic Target of Rapamycin Complex 1; D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases