title: Aging Is Accompanied by a Blunted Muscle Protein Synthetic Response to Protein Ingestion.
abstract: OBJECTIVE
  Progressive loss of skeletal muscle mass with aging (sarcopenia) forms a global health concern. It has been suggested that an impaired capacity to increase muscle protein synthesis rates in response to protein intake is a key contributor to sarcopenia. We assessed whether differences in post-absorptive and/or post-prandial muscle protein synthesis rates exist between large cohorts of healthy young and older men.
  
  
  METHODS
  We performed a cross-sectional, retrospective study comparing in vivo post-absorptive muscle protein synthesis rates determined with stable isotope methodologies between 34 healthy young (22±1 y) and 72 older (75±1 y) men, and post-prandial muscle protein synthesis rates between 35 healthy young (22±1 y) and 40 older (74±1 y) men.
  
  
  RESULTS
  Post-absorptive muscle protein synthesis rates did not differ significantly between the young and older group. Post-prandial muscle protein synthesis rates were 16% lower in the older subjects when compared with the young. Muscle protein synthesis rates were >3 fold more responsive to dietary protein ingestion in the young. Irrespective of age, there was a strong negative correlation between post-absorptive muscle protein synthesis rates and the increase in muscle protein synthesis rate following protein ingestion.
  
  
  CONCLUSIONS
  Aging is associated with the development of muscle anabolic inflexibility which represents a key physiological mechanism underpinning sarcopenia.
authors.affiliation: NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Centre, Maastricht, 6200 MD, The Netherlands.
authors.forename: Benjamin Toby
authors.initials: BT
authors.lastname: Wall
authors.affiliation: NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Centre, Maastricht, 6200 MD, The Netherlands.
authors.forename: Stefan H
authors.initials: SH
authors.lastname: Gorissen
authors.affiliation: NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Centre, Maastricht, 6200 MD, The Netherlands.
authors.forename: Bart
authors.initials: B
authors.lastname: Pennings
authors.affiliation: NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Centre, Maastricht, 6200 MD, The Netherlands.
authors.forename: René
authors.initials: R
authors.lastname: Koopman
authors.affiliation: NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Centre, Maastricht, 6200 MD, The Netherlands.
authors.forename: Bart B L
authors.initials: BB
authors.lastname: Groen
authors.affiliation: NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Centre, Maastricht, 6200 MD, The Netherlands.
authors.forename: Lex B
authors.initials: LB
authors.lastname: Verdijk
authors.affiliation: NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Centre, Maastricht, 6200 MD, The Netherlands.
authors.forename: Luc J C
authors.initials: LJ
authors.lastname: van Loon
mesh_terms: D000368:Aged; D000375:Aging; D003430:Cross-Sectional Studies; D004044:Dietary Proteins / Q000378:metabolism; D006801:Humans; D008297:Male; D009124:Muscle Proteins / Q000378:metabolism*; D019518:Postprandial Period; D014176:Protein Biosynthesis / Q000502:physiology*; D012189:Retrospective Studies; D055948:Sarcopenia / Q000378:metabolism / Q000473:pathology; D055815:Young Adult
chemical_list: D004044:Dietary Proteins; D009124:Muscle Proteins