Effect of age on basal muscle protein synthesis and mTORC1 signaling in a large cohort of young and older men and women.
The rate of muscle loss with aging is higher in men than women. However, women have smaller muscles throughout the adult life. Protein content is a major determinant of skeletal muscle size. This study was designed to determine if age and sex differentially impact basal muscle protein synthesis and mammalian/mechanistic target of rapamycin complex 1 (mTORC1) signaling. We performed a secondary data analysis on a cohort of 215 healthy, non-obese (BMI<30kg·m(-2)) young (18-40y; 74 men, 52 women) and older (60-87y; 57 men, 32 women) adults. The database contained information on physical characteristics, basal muscle protein fractional synthetic rate (FSR; n=215; stable isotope methodology) and mTORC1 signaling (n=125, Western blotting). FSR and mTORC1 signaling were measured at rest and after an overnight fast. mTORC1 and S6K1 phosphorylation were higher (p<0.05) in older subjects with no sex differences. However, there were no age or sex differences or interaction for muscle FSR (p>0.05). Body mass index, fat free mass, or body fat was not a significant covariate and did not influence the results. We conclude that age and sex do not influence basal muscle protein synthesis. However, basal mTORC1 hyperphosphorylation in the elderly may contribute to insulin resistance and the age-related anabolic resistance of skeletal muscle protein metabolism to nutrition and exercise.
Sealy Center on Aging, University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA.
Melissa M
MM
Markofski
Department of Nutrition and Metabolism, University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA; Division of Rehabilitation Sciences, University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA.
Jared M
JM
Dickinson
Division of Rehabilitation Sciences, University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA.
Micah J
MJ
Drummond
Sealy Center on Aging, University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA; Department of Nutrition and Metabolism, University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA; Division of Rehabilitation Sciences, University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA.
Christopher S
CS
Fry
Sealy Center on Aging, University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA; Division of Rehabilitation Sciences, University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA.
Satoshi
S
Fujita
Department of Nutrition and Metabolism, University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA; Division of Rehabilitation Sciences, University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA.
David M
DM
Gundermann
Division of Rehabilitation Sciences, University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA.
Erin L
EL
Glynn
Sealy Center on Aging, University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA; Department of Preventive Medicine and Community Health, University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA.
Kristofer
K
Jennings
Sealy Center on Aging, University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA; Department of Nutrition and Metabolism, University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA; Division of Rehabilitation Sciences, University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA.
Douglas
D
Paddon-Jones
Division of Rehabilitation Sciences, University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA.
Paul T
PT
Reidy
Sealy Center on Aging, University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA; Department of Internal Medicine, University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA.
Melinda
M
Sheffield-Moore
Sealy Center on Aging, University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA; Division of Rehabilitation Sciences, University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA.
Kyle L
KL
Timmerman
Sealy Center on Aging, University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA; Department of Nutrition and Metabolism, University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA; Division of Rehabilitation Sciences, University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA.
Blake B
BB
Rasmussen
Sealy Center on Aging, University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA; Department of Internal Medicine, University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA. Electronic address: evolpi@utmb.edu.
Elena
E
Volpi
D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D000076222:Mechanistic Target of Rapamycin Complex 1; D008875:Middle Aged; D046912:Multiprotein Complexes / Q000378:metabolism*; D009119:Muscle Contraction / Q000502:physiology; D009124:Muscle Proteins / Q000096:biosynthesis / Q000378:metabolism; D018482:Muscle, Skeletal / Q000502:physiology*; D010766:Phosphorylation / Q000502:physiology; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism*; D012737:Sex Factors; D015398:Signal Transduction / Q000502:physiology; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*
D046912:Multiprotein Complexes; D009124:Muscle Proteins; D000076222:Mechanistic Target of Rapamycin Complex 1; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases; C448901:ribosomal protein S6 kinase, 70kD, polypeptide 1
Aging; Gender; Protein metabolism; Sarcopenia; Stable isotopes; mTOR