Understanding the sensitivity of muscle protein synthesis to dairy protein in middle-aged men

Men have more muscle than women, but most studies evaluating sex differences in muscle protein metabolism have been unable to discern sexual dimorphism in basal muscle protein turnover rates in young and middle-aged adults. We hypothesized that the anabolic response to nutritional stimuli (i.e., amino acids and insulin) would be greater in young/middle-aged men than women. We therefore measured the rates of muscle protein synthesis (MPS) in 16 healthy individuals [8 men and 8 women, matched for age (mean ± SE: 37.7 ± 1.5 yr) and body mass index (25.2 ± 0.7 kg/m2)] after an overnight fast (plasma insulin ∼5 μU/ml and plasma phenylalanine ∼60 μM) and during a hyperinsulinemic-hyperaminoacidemic-euglycemic clamp (plasma insulin ∼28 μU/ml; plasma phenylalanine ∼110 μM; plasma glucose ∼5.4 mM). The rates of MPS were not different between men and women (ANOVA main effect for sex; P = 0.49). During the clamp, the rate of MPS increased by ∼50% ( P = 0.003) with no difference in the increases from basal values between men and women (+0.019 ± 0.004 vs. +0.018 ± 0.010%/h, respectively; P = 0.93). There were also no differences between men and women in the basal concentrations of muscle phosphorylated AktSer473, AktThr308, mTORSer2448, and p70s6kThr389 or in the hyperinsulinemia-hyperaminoacidemia-induced increases in phosphorylation of those signaling elements ( P ≥ 0.25). We conclude that there are no major differences in the rate of MPS and its intracellular control during basal conditions and during hyperinsulinemia-hyperaminoacidema between young and middle-aged adult men and women.

Download Full-text

Consumption of Milk Protein or Whey Protein Results in a Similar Increase in Muscle Protein Synthesis in Middle Aged Men

Nutrients ◽

10.3390/nu7105420 ◽

2015 ◽

Vol 7 (10) ◽

pp. 8685-8699 ◽

Cited By ~ 38

Author(s):

Cameron Mitchell ◽

Robin McGregor ◽

Randall D’Souza ◽

Eric Thorstensen ◽

James Markworth ◽

...

Keyword(s):

Protein Synthesis ◽

Whey Protein ◽

Milk Protein ◽

Muscle Protein ◽

Muscle Protein Synthesis ◽

Similar Increase ◽

Middle Aged

Download Full-text

Impact of dairy protein during limb immobilization and recovery on muscle size and protein synthesis; a randomized controlled trial

Journal of Applied Physiology ◽

10.1152/japplphysiol.00803.2017 ◽

2018 ◽

Vol 124 (3) ◽

pp. 717-728 ◽

Cited By ~ 16

Author(s):

Cameron J. Mitchell ◽

Randall F. D’Souza ◽

Sarah M. Mitchell ◽

Vandre C. Figueiredo ◽

Benjamin F. Miller ◽

...

Keyword(s):

Protein Synthesis ◽

Muscle Protein ◽

Muscle Protein Synthesis ◽

Controlled Trial ◽

Protein Supplementation ◽

Muscle Size ◽

Thigh Muscle ◽

Muscle Disuse ◽

And Function ◽

Dairy Protein

Muscle disuse results in the loss of muscular strength and size, due to an imbalance between protein synthesis (MPS) and breakdown (MPB). Protein ingestion stimulates MPS, although it is not established if protein is able to attenuate muscle loss with immobilization (IM) or influence the recovery consisting of ambulatory movement followed by resistance training (RT). Thirty men (49.9 ± 0.6 yr) underwent 14 days of unilateral leg IM, 14 days of ambulatory recovery (AR), and a further six RT sessions over 14 days. Participants were randomized to consume an additional 20 g of dairy protein or placebo with a meal during the intervention. Isometric knee extension strength was reduced following IM (−24.7 ± 2.7%), partially recovered with AR (−8.6 ± 2.6%), and fully recovered after RT (−0.6 ± 3.4%), with no effect of supplementation. Thigh muscle cross-sectional area decreased with IM (−4.1 ± 0.5%), partially recovered with AR (−2.1 ± 0.5%), and increased above baseline with RT (+2.2 ± 0.5%), with no treatment effect. Myofibrillar MPS, measured using deuterated water, was unaltered by IM, with no effect of protein. During AR, MPS was increased only with protein supplementation. Protein supplementation did not attenuate the loss of muscle size and function with disuse or potentiate recovery but enhanced myofibrillar MPS during AR. NEW & NOTEWORTHY Twenty grams of daily protein supplementation does not attenuate the loss of muscle size and function induced by 2 wk of muscle disuse or potentiate recovery in middle-age men. Average mitochondrial but not myofibrillar muscle protein synthesis was attenuated during immobilization with no effect of supplementation. Protein supplementation increased myofibrillar protein synthesis during a 2-wk period of ambulatory recovery following disuse but without group differences in phenotype recovery.

Download Full-text

Effects of Whey Protein Isolate Ingestion on Muscle Protein Synthesis at Rest and After Resistance-exercise in Middle-aged Men: A Research Protocol

10.26685/urncst.231 ◽

2021 ◽

Vol 5 (4) ◽

Author(s):

David Zhao ◽

Parrish Evers

Keyword(s):

Protein Synthesis ◽

Resistance Exercise ◽

Whey Protein ◽

Muscle Protein ◽

Muscle Protein Synthesis ◽

Whey Protein Isolate ◽

Protein Isolate ◽

Research Protocol ◽

Middle Aged

Download Full-text

Higher Protein Intake Does Not Augment Muscle Protein Synthetic Responses During the Early Stages of Resistance Training in Middle-Aged Adults

Current Developments in Nutrition ◽

10.1093/cdn/nzab041_035 ◽

2021 ◽

Vol 5 (Supplement_2) ◽

pp. 520-520

Author(s):

Amadeo Salvador ◽

Colleen McKenna ◽

Kevin J.M. Paulussen ◽

Alexander Keeble ◽

Andrew Askow ◽

...

Keyword(s):

Protein Synthesis ◽

Resistance Training ◽

Dietary Protein ◽

Protein Intake ◽

Muscle Protein ◽

Muscle Protein Synthesis ◽

Protein Fractions ◽

Dietary Protein Intake ◽

Middle Aged ◽

Middle Aged Adults

Abstract Objectives Dietary protein intake augments muscle protein synthesis rates during acute recovery from resistance exercise training (RET) and can help offset age-related loss in muscle mass. Skeletal muscle tissue contains a variety of different protein pools such as myofibrillar (contractile), mitochondrial (substrate oxidation), and collagen (structural support) proteins that have been reported to have different contraction and nutrient sensitivities in controlled laboratory studies. However, no study has investigated the impact of dietary protein intake on the synthesis of these specific muscle proteins fractions during RET in a free-living setting. Therefore, we investigated the effect of dietary protein intake on daily muscle protein synthesis rates (PS) within the myofibrillar (MyoPS), mitochondrial (MitoPS), and collagen (CPS) protein fractions throughout the early phase (0 – 3 wks) of RET in middle-aged adults. Methods Twenty middle-aged adults (47 ± 1 y, BMI 28 ± 1 kg/m2, M = 12, F = 8) were stratified and randomized to consume either moderate (MOD; 1.06 ± 0.22 g/kg/d) or high (HI; 1.55 ± 0.25 g/kg/d) amounts of protein during a dietary counseling-controlled resistance training program. On day 0, participants ingested intermittent boluses of deuterated (2H) water followed by daily maintenance doses throughout the study period. Muscle biopsies were collected prior to and at weeks 1, 2, and 3 of the intervention to assess MyoPS, MitoPS, and CPS by LC/MS. Results MitoPS decreased at 0–3 wks when compared to 0–1 wks (P = 0.010, CI: −0.77 – −0.10%/d) regardless of group (HI: 0.64 ± 0.32%/d and MOD 0.86 ± 0.55%/d; P = 0.827). A similar decline was also observed for CPS (group P = 0.323; time P = 0.007). The MyoPS in the HI condition remained constant (0–1 wk: 0.81 ± 0.42%/d and 0–3 wks: 0.81 ± 0.72%/d, P = 1.0), but MOD decreased over time (0–1 wk: 1.35 ± 0.9%/d and 0–3 wks: 0.77 ± 0.43%/d, P = 0.023). Conclusions Our results demonstrated that additional protein intake above moderate amounts does not meaningfully potentiate the stimulation of longer-term muscle protein synthetic responses within the myofibrillar, mitochondrial, or collagen protein fractions during the early stages of a RET in middle-aged adults. Funding Sources Funded in part by the Beef Checkoff. AFS funded by CAPES Scholarship.

Download Full-text