Kumar V, Selby A, Rankin D, et al. Age-related differences in the dose-response relationship of muscle protein synthesis to resistance exercise in young and old men. J. Physiol. 587 (Pt 1): 211-7

University of Nottingham, School of Graduate Entry Medicine and Health, City Hospital, Uttoxeter Road, Derby, DE22 3DT, UK.
The Journal of Physiology (Impact Factor: 5.04). 11/2008; 587(Pt 1):211-7. DOI: 10.1113/jphysiol.2008.164483
Source: PubMed

ABSTRACT We investigated how myofibrillar protein synthesis (MPS) and muscle anabolic signalling were affected by resistance exercise at 20-90% of 1 repetition maximum (1 RM) in two groups (25 each) of post-absorptive, healthy, young (24 +/- 6 years) and old (70 +/- 5 years) men with identical body mass indices (24 +/- 2 kg m(-2)). We hypothesized that, in response to exercise, anabolic signalling molecule phosphorylation and MPS would be modified in a dose-dependant fashion, but to a lesser extent in older men. Vastus lateralis muscle was sampled before, immediately after, and 1, 2 and 4 h post-exercise. MPS was measured by incorporation of [1,2-(13)C] leucine (gas chromatography-combustion-mass spectrometry using plasma [1,2-(13)C]alpha-ketoisocaparoate as surrogate precursor); the phosphorylation of p70 ribosomal S6 kinase (p70s6K) and eukaryotic initiation factor 4E binding protein 1 (4EBP1) was measured using Western analysis with anti-phosphoantibodies. In each group, there was a sigmoidal dose-response relationship between MPS at 1-2 h post-exercise and exercise intensity, which was blunted (P < 0.05) in the older men. At all intensities, MPS fell in both groups to near-basal values by 2-4 h post-exercise. The phosphorylation of p70s6K and 4EBP1 at 60-90% 1 RM was blunted in older men. At 1 h post-exercise at 60-90% 1 RM, p70s6K phosphorylation predicted the rate of MPS at 1-2 h post-exercise in the young but not in the old. The results suggest that in the post-absorptive state: (i) MPS is dose dependant on intensity rising to a plateau at 60-90% 1 RM; (ii) older men show anabolic resistance of signalling and MPS to resistance exercise.

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    • "However, there is still no consensus regarding the mechanisms that lead to the sexual dimorphism in muscle mass as well as muscle loss with aging. Several researchers reported that aging does not alter basal muscle protein synthesis in men (Cuthbertson et al., 2005; Kumar et al., 2009; Volpi et al., 2001) or women (Chevalier et al., 2011), and that basal muscle protein synthesis is not affected by sex in young or middle-aged adults (Dreyer et al., 2010; Fujita et al., 2007a; Jahn et al., 1999; Parise et al., 2001; Smith et al., 2009; West et al., 2012) despite the obvious differences in muscle size between men and women. Conversely, others asserted an apparent sexual dimorphism in obese older adults, with women having a surprisingly higher basal muscle protein synthesis rate than men (G.I. "
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    ABSTRACT: 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. Copyright © 2015. Published by Elsevier Inc.
    Experimental Gerontology 02/2015; 65. DOI:10.1016/j.exger.2015.02.015 · 3.49 Impact Factor
    • "soy) in young healthy males. Compared with young adults, the muscle protein synthesis response to resistance exercise [6] [7] and protein intake [8] may be blunted in older adults, resulting in higher protein doses (>20 g) being required to stimulate an increase [9]. The aim of the current study was to evaluate whether, when protein intake was at least 20 g at each meal, the consumption of a eucaloric high protein diet rich in dairy protein would provide greater increases in muscle strength, lean mass and physical function compared with either an isocaloric diet representative of the typical Australian dietary protein intake (i.e. "
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    ABSTRACT: Maintenance of muscle mass and strength into older age is critical to maintain health. The aim was to determine whether increased dairy or soy protein intake combined with resistance training enhanced strength gains in older adults. 179 healthy older adults (age 61.5 ± 7.4 yrs, BMI 27.6 ± 3.6 kg/m(2)) performed resistance training three times per week for 12 weeks and were randomized to one of three eucaloric dietary treatments which delivered >20 g of protein at each main meal or immediately after resistance training: high dairy protein (HP-D, >1.2 g of protein/kg body weight/d; ∼27 g/d dairy protein); high soy protein (HP-S, >1.2 g of protein/kg body weight/d; ∼27 g/d soy protein); usual protein intake (UP, <1.2 g of protein/kg body weight/d). Muscle strength, body composition, physical function and quality of life were assessed at baseline and 12 weeks. Treatments effects were analyzed using two-way ANOVA. 83 participants completed the intervention per protocol (HP-D = 34, HP-S = 26, UP = 23). Protein intake was higher in HP-D and HP-S compared with UP (HP-D 1.41 ± 0.14 g/kg/d, HP-S 1.42 ± 0.61 g/kg/d, UP 1.10 ± 0.10 g/kg/d; P < 0.001 treatment effect). Strength increased less in HP-S compared with HP-D and UP (HP-D 92.1 ± 40.8%, HP-S 63.0 ± 23.8%,UP 92.3 ± 35.4%; P = 0.002 treatment effect). Lean mass, physical function and mental health scores increased and fat mass decreased (P ≤ 0.006), with no treatment effect (P > 0.06). Increased soy protein intake attenuated gains in muscle strength during resistance training in older adults compared with increased intake of dairy protein or usual protein intake. Clinical Trial Registration: ACTRN12612000177853 Copyright © 2015 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.
    Clinical Nutrition 02/2015; DOI:10.1016/j.clnu.2015.01.018 · 4.48 Impact Factor
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    • "Akt phosphorylation , mTOR phosphorylation, and MHC mRNA expression did not appear to be altered by the resistance exercise protocol. The phosphorylation of p70S6k regulates several factors involved in translation initiation and protein synthesis (Goodman 2014), and the phosphorylated state of p70S6k has shown to be a proxy marker of myofibrillar protein synthesis rates (Kumar et al. 2009; West et al. 2010a) and exercise-induced hypertrophy (Baar and Esser 1999; Terzis et al. 2008; Mayhew et al. 2009; Mitchell et al. 2013). Following resistance exercise, rapid elevation of p70S6k phosphorylation has been observed in untrained and recreationally active men in both fed (Karlsson et al. 2004; Farnfield et al. 2009; Hulmi et al. 2009; "
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    ABSTRACT: Resistance exercise stimulates an increase in muscle protein synthesis regulated by intracellular anabolic signaling molecules in a mammalian/mechanistic target of rapamycin (mTOR)-dependent pathway. The purpose of this study was to investigate acute anabolic signaling responses in experienced, resistance-trained men, and to examine the association between myosin heavy chain (MHC) isoform composition and the magnitude of anabolic signaling. Eight resistance-trained men (24.9 ± 4.3 years; 91.2 ± 12.4 kg; 176.7 ± 8.0 cm; 13.3 ± 3.9 body fat %) performed a whole body, high-volume resistance exercise protocol (REX) and a control protocol (CTL) in a balanced, randomized order. Participants were provided a standardized breakfast, recovery drink, and meal during each protocol. Fine needle muscle biopsies were completed at baseline (BL), 2 h (2H) and 6 h post-exercise (6H). BL biopsies were analyzed for MHC isoform composition. Phosphorylation of proteins specific to the Akt/mTOR signaling pathway and MHC mRNA expression was quantified. Phosphorylation of p70S6k was significantly greater in REX compared to CTL at 2H (P = 0.04). MHC mRNA expression and other targets in the Akt/mTOR pathway were not significantly influenced by REX. The percentage of type IIX isoform was inversely correlated (P < 0.05) with type I and type IIA MHC mRNA expression (r = −0.69 to −0.93). Maximal strength was also observed to be inversely correlated (P < 0.05) with Type I and Type IIA MHC mRNA expression (r = −0.75 to −0.77) and p70S6k phosphorylation (r = −0.75). Results indicate that activation of p70S6k occurs within 2-h following REX in experienced, resistance-trained men. Further, results also suggest that highly trained, stronger individuals have an attenuated acute anabolic response.
    01/2015; 3(1). DOI:10.14814/phy2.12268
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