title: Intake of low-dose leucine-rich essential amino acids stimulates muscle anabolism equivalently to bolus whey protein in older women at rest and after exercise.
abstract: Dysregulated anabolic responses to nutrition/exercise may contribute to sarcopenia; however, these characteristics are poorly defined in female populations. We determined the effects of two feeding regimes in older women (66 ± 2.5 yr; n = 8/group): bolus whey protein (WP-20 g) or novel low-dose leucine-enriched essential amino acids (EAA) [LEAA; 3 g (40% leucine)]. Using [(13)C6]phenylalanine infusions, we quantified muscle (MPS) and albumin (APS) protein synthesis at baseline and in response to both feeding (FED) and feeding plus exercise (FED-EX; 6 × 8 knee extensions at 75% 1-repetition maximum). We also quantified plasma insulin/AA concentrations, whole leg (LBF)/muscle microvascular blood flow (MBF), and muscle anabolic signaling by phosphoimmunoblotting. Plasma insulinemia and EAA/aemia were markedly greater after WP than LEAA (P < 0.001). Neither LEAA nor WP modified LBF in response to FED or FED-EX, whereas MBF increased to a similar extent in both groups only after FED-EX (P < 0.05). In response to FED, both WP and LEAA equally stimulated MPS 0-2 h (P < 0.05), abating thereafter (0-4 h, P > 0.05). In contrast, after FED-EX, MPS increased at 0-2 h and remained elevated at 0-4 h (P < 0.05) with both WP and LEAA. No anabolic signals quantifiably increased after FED, but p70 S6K1 Thr(389) increased after FED-EX (2 h, P < 0.05). APS increased similarly after WP and LEAA. Older women remain subtly responsive to nutrition ± exercise. Intriguingly though, bolus WP offers no trophic advantage over LEAA.
authors.affiliation: Medical Research Council/Arthritis Research United Kingdom Centre of Excellence for Musculoskeletal Ageing Research, University of Nottingham, Derby, United Kingdom; and.
authors.forename: Syed S I
authors.initials: SS
authors.lastname: Bukhari
authors.affiliation: Medical Research Council/Arthritis Research United Kingdom Centre of Excellence for Musculoskeletal Ageing Research, University of Nottingham, Derby, United Kingdom; and.
authors.forename: Bethan E
authors.initials: BE
authors.lastname: Phillips
authors.affiliation: Medical Research Council/Arthritis Research United Kingdom Centre of Excellence for Musculoskeletal Ageing Research, University of Nottingham, Derby, United Kingdom; and.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Wilkinson
authors.affiliation: Medical Research Council/Arthritis Research United Kingdom Centre of Excellence for Musculoskeletal Ageing Research, University of Nottingham, Derby, United Kingdom; and.
authors.forename: Marie C
authors.initials: MC
authors.lastname: Limb
authors.affiliation: Medical Research Council/Arthritis Research United Kingdom Centre of Excellence for Musculoskeletal Ageing Research, University of Nottingham, Derby, United Kingdom; and.
authors.forename: Debbie
authors.initials: D
authors.lastname: Rankin
authors.affiliation: Medical Research Council/Arthritis Research United Kingdom Centre of Excellence for Musculoskeletal Ageing Research, University of Nottingham, Derby, United Kingdom; and.
authors.forename: William K
authors.initials: WK
authors.lastname: Mitchell
authors.affiliation: Ajinomoto Company Incorporated, Tokyo, Japan.
authors.forename: Hisamine
authors.initials: H
authors.lastname: Kobayashi
authors.affiliation: Medical Research Council/Arthritis Research United Kingdom Centre of Excellence for Musculoskeletal Ageing Research, University of Nottingham, Derby, United Kingdom; and.
authors.forename: Paul L
authors.initials: PL
authors.lastname: Greenhaff
authors.affiliation: Medical Research Council/Arthritis Research United Kingdom Centre of Excellence for Musculoskeletal Ageing Research, University of Nottingham, Derby, United Kingdom; and.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Smith
authors.affiliation: Medical Research Council/Arthritis Research United Kingdom Centre of Excellence for Musculoskeletal Ageing Research, University of Nottingham, Derby, United Kingdom; and.
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Atherton
mesh_terms: D000368:Aged; D000601:Amino Acids, Essential / Q000008:administration & dosage* / Q000097:blood; D004032:Diet; D004044:Dietary Proteins / Q000008:administration & dosage*; D019587:Dietary Supplements; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D007328:Insulin / Q000097:blood; D007930:Leucine / Q000008:administration & dosage* / Q000097:blood; D008875:Middle Aged; D008894:Milk Proteins / Q000008:administration & dosage*; D009124:Muscle Proteins / Q000096:biosynthesis* / Q000187:drug effects; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism; D012146:Rest / Q000502:physiology*; D000067816:Whey Proteins
chemical_list: D000601:Amino Acids, Essential; D004044:Dietary Proteins; D007328:Insulin; D008894:Milk Proteins; D009124:Muscle Proteins; D000067816:Whey Proteins; D007930:Leucine
keywords: aging; amino acids; blood flow; exercise; protein synthesis; skeletal muscle